Research activity information

• Apr. 2025, 文部科学省, 令和7年度科学技術分野の文部科学大臣表彰科学技術賞（研究部門）
• Aug. 2017, 日本気象学会 堀内賞
• Feb. 2016, 北海道大学, 教育総長賞奨励賞

• Antarctic Bottom Water in a changing climate
  Stephen R. Rintoul; Andrew L. Stewart; Gregory C. Johnson; Shenjie Zhou; Annie Foppert; Qian Li; Adele K. Morrison; Alessandro Silvano; Kathryn L. Gunn; Matthew H. England; Sohey Nihashi; Shigeru Aoki
  Nature Reviews Earth & Environment, Springer Science and Business Media LLC, 09 Dec. 2025
  Scientific journal
• Antarctic ice-shelf collapse in Holocene driven by meltwater release feedbacks
  Yusuke Suganuma; Takuya Itaki; Yuki Haneda; Kazuya Kusahara; Takashi Obase; Takeshige Ishiwa; Takayuki Omori; Minoru Ikehara; Robert McKay; Osamu Seki; Daisuke Hirano; Masakazu Fujii; Yuji Kato; Atsuko Amano; Yuki Tokuda; Hokuto Iwatani; Yoshiaki Suzuki; Motohiro Hirabayashi; Hiroyuki Matsuzaki; Takeyasu Yamagata; Masao Iwai; Kota Katsuki; Francisco J. Jimenez-Espejo; Hiroki Matsui; Koji Seike; Moto Kawamata; Naohisa Nishida; Masato Ito; Shin Sugiyama; Jun’ichi Okuno; Takanobu Sawagaki; Ayako Abe-Ouchi; Shigeru Aoki; Hideki Miura
  Nature Geoscience, 18, 12, 1216, 1223, Springer Science and Business Media LLC, 07 Nov. 2025
  Scientific journal, Abstract
  
  Circumpolar Deep Water inflow onto Antarctica’s continental shelves is a key driver of accelerated Antarctic Ice Sheet mass loss, both presently and during the last deglaciation. However, the mechanisms driving enhanced inflow and the resultant impact on large-scale ice-sheet retreat events are still not fully understood. Here we address this topic using marine sediment cores from Lützow–Holm Bay, East Antarctica, through analyses of sedimentary beryllium isotopes and complementary proxies. These records, when compared to inland mountain outcrop records, show that ice-shelf collapse and simultaneous inland ice-sheet thinning ~9,000 years ago were associated with enhanced Circumpolar Deep Water inflow and sea-level rise. A hierarchical modelling approach that combines climate and high-resolution ocean simulations suggests that freshwater discharge from adjacent Antarctic sectors into the Southern Ocean probably enhanced the regional inflow into submarine troughs in Lützow–Holm Bay between 10,000 and 9,000 years ago. We propose a feedback loop whereby meltwater from rapidly retreating Antarctic sectors since the Last Glacial Maximum enhanced stratification and Circumpolar Deep Water incursions onto adjacent shelves. Alongside relative sea-level rise, this meltwater feedback triggers further ice-shelf instability and enhances dynamic inland ice discharge, highlighting a mechanism relevant to future Antarctic Ice Sheet changes.
• Algal enrichment process for newly formed sea ice in the Dalton polynya off East Antarctica during the late summer–early autumn
  Keigo D. Takahashi; Masato Ito; Natsumi Nojiro; Daiki Nomura; Masayoshi Sano; Shigeru Aoki; Pat Wongpan; Guy D. Williams; Michiyo Yamamoto-Kawai; Takeshi Tamura; Masato Moteki; Toru Hirawake; Ryosuke Makabe
  Elem Sci Anth, 13, 1, University of California Press, 02 Jun. 2025
  Scientific journal, Newly formed sea ice can incorporate considerable amounts of organic matter including phytoplankton during its freezing and growth. This initial incorporation influences the standing stocks of ice algae, a fundamental component of high-latitude marine ecosystems. Physical incorporation via the accretion of frazil ice, instead of congelation growth, is considered to incorporate particles efficiently. However, for thin ice (<0.20 m thickness), information on the relationship between ice texture and particle incorporation is scarce. Here, we assessed sea-ice texture (proportion of frazil ice-origin layer), macronutrient concentrations, fraction of snow, and algal composition in Antarctic sea ice and their effects on the enrichment of algae into thin ice in terms of chlorophyll a (Chl a) and biogenic silica (BSi). Chl a and BSi concentrations of thin ice ranged over 0.2–11.6 µg L−1 and 0.5–11.1 µmol L−1, respectively, being significantly concentrated compared to seawater. BSi enrichment in thin ice correlated negatively with the proportion of frazil ice-origin layer, while no relationship was observed with Chl a enrichment. These results suggest that frazil ice could play a minor role in entraining algal cells under certain circumstances, possibly due to the low turbulence and wind speeds of the late summer–early autumn season dampening the interaction between frazil ice and phytoplankton. Algal composition data could suggest that ice algae from the previous winter’s sea ice were released and re-incorporated into the surrounding thin ice on its formation, given the high similarity in species composition observed between older ice and several thin ice samples. This mechanism potentially promotes algal enrichment without the accretion of frazil ice, as indicated by the maximum enrichment in thin ice which developed via congelation growth. Our results show that algal concentration in thin ice could be affected by the presence of old sea ice and hydrographic and meteorological conditions.
• Ocean Response Along the East Antarctic Coastal Margin to the Southern Ocean Annular Mode
  K. Mizobata; D. Hirano; K. Kusahara; S. Aoki; J. Inoue; S. Takao; R. Makabe
  Geophysical Research Letters, 52, e2024GL112914., Mar. 2025, [Peer-reviewed]
  English, Scientific journal
• Intense frazil ice production promotes high algal biomass in newly-formed sea ice
  Ito, M.; K. D. Takahashi; R. Makabe; D. Hirano; K. I. Ohshima; T. Tamura; S. Aoki
  Journal of Geophysical Research: Oceans, 130, 3, e2024JC021689, Mar. 2025, [Peer-reviewed]
  English, Scientific journal
• Hydrographic section along 55° E in the Indian and Southern oceans
  Katsuro Katsumata; Shigeru Aoki; Kay I. Ohshima; Michiyo Yamamoto-Kawai
  Ocean Science, 21, 1, 419, 436, Copernicus GmbH, 12 Feb. 2025, [Peer-reviewed]
  English, Scientific journal, Abstract. A hydrographic section along 55° E, south of 30° S, was visited from December 2019 to January 2020 as the first occupation under the Global Ocean Ship-based Hydrographic Investigations Program. The water column was measured from the sea surface to 10 dbar above the bottom with eddy-resolving station spacings and state-of-the-art accuracy. The upper profile was characterised by a conspicuous front between 42.5 and 43° S and a cold-core eddy at 39° S. The front was identified as the confluence of Subtropical and Subantarctic fronts. The Agulhas Return Current front was found at 41.6° S. When combined with the section north of 30° S observed in 2018, another subsurface front was found in dissolved oxygen around 28° S at depths of 1500 to 3000 dbar. In the eastern Weddell–Enderby Abyssal Plain, no obvious large-scale flow was observed at depths greater than 3000 dbar. We used transient tracers to estimate isopycnal diffusivity there to be 72±16 m2 s−1. Antarctic Bottom Water in the basin consisted of water masses originating from the Cape Darnley region (0 %–35 %) and Weddell Sea Deep Water (5 %–75 %) diluted by Lower Circumpolar Deep Water above. These snapshot observations not only confirm hydrographic features reported earlier in the Madagascar and Crozet basins, but also describe the diffusive nature of the deep to bottom circulation in the Weddell–Enderby Abyssal Plain.
• Revisiting circulation and water masses over the East Antarctic margin (80–150°E)
  Kaihe Yamazaki; Katsuro Katsumata; Daisuke Hirano; Daiki Nomura; Hiroko Sasaki; Hiroto Murase; Shigeru Aoki
  Progress in Oceanography, 103285, 103285, Elsevier BV, May 2024, [Peer-reviewed]
  Scientific journal
• Oceanographic factors determining the distribution of nutrients and primary production in the subpolar Southern Ocean
  Manami Tozawa; Daiki Nomura; Kaihe Yamazaki; Masaaki Kiuchi; Daisuke Hirano; Shigeru Aoki; Hiroko Sasaki; Hiroto Murase
  Progress in Oceanography, 103266, 103266, Elsevier BV, Apr. 2024, [Peer-reviewed]
  Scientific journal
• How Can Helicopters Help Us Determine the Health of Antarctica’s Oceans?
  Yoshihiro Nakayama; Pat Wongpan; Jamin S. Greenbaum; Kaihe Yamazaki; Shigeru Aoki
  Frontiers for Young Minds, 12, Frontiers Media SA, 27 Mar. 2024
  Scientific journal, In East Antarctica, warm ocean water travels toward the Totten Ice Shelf. This water melts and thins the ice shelf, and speeds up the rate at which ice moves into the sea, leading to sea-level rise. Scientists often get on board ships called icebreakers to study the ice and water in these regions. However, sea ice and icebergs are major obstacles to navigation and scientific operations. For example, American, Australian, and Japanese icebreakers tried but could only observe a small area where sea ice was more broken up. So, we used a helicopter to measure the ocean during one of our research expeditions. Helicopters can travel faster than icebreakers. They can fly over sea ice and icebergs, and trained workers can drop sensors into small gaps in the ice. In 6 days, we observed ocean temperatures at 67 sites, covering a large area that could not be studied before. We identified wide pathways of warm water flowing toward the Totten Ice Shelf.
• Radiolarian assemblages related to the ocean–ice interaction around the East Antarctic coast
  Mutsumi Iizuka; Takuya Itaki; Osamu Seki; Ryosuke Makabe; Motoha Ojima; Shigeru Aoki
  Journal of Micropalaeontology, 43, 1, 37, 53, Copernicus GmbH, 24 Jan. 2024, [Peer-reviewed]
  Scientific journal, Abstract. The Southern Ocean plays a central role in Earth's climate, ecology, and biogeochemical cycles. Therefore, understanding long-term changes in Southern Ocean water masses in the geologic past is essential for assessing the role of the Southern Ocean in the climate system. Radiolarian fossils are a useful tool to reconstruct the water masses of the Southern Ocean. However, the radiolarian assemblages in the high latitudes of the Southern Ocean (south of the polar front (PF)) are still poorly understood. In this paper, we report the radiolarian assemblages in surface marine sediment and plankton tow samples collected from the high latitudes south of the PF. In the surface sediments, four factors (named F1–F4) of the radiolarian assemblages were identified using Q-mode factor analysis, which are related to different water masses and hydrological conditions. F1 is related to the surface waters south of the southern boundary (SB) of the Antarctic Circumpolar Current (ACC), which are cooled by melting sea ice and ice sheets. F2 is associated with water masses north of the SB. A comparison with the vertical distribution of the radiolarian assemblages in plankton tow samples indicates that characteristic species are associated with the Circumpolar Deep Water (CDW) and surface waters north of the SB. F3 is associated with modified Circumpolar Deep Water (mCDW). The radiolarian assemblage of F4 does not seem specifically related to any of the water mass here analyzed. However, the species in this assemblage are typically dwells within ice shelf and/or sea ice edge environments. Radiolarian assemblages here identified and associated with water masses, and ice edge environments are useful to reconstruct the environment south of the PF in the geologic past.
• Observing Antarctic Bottom Water in the Southern Ocean
  Alessandro Silvano; Sarah Purkey; Arnold L. Gordon; Pasquale Castagno; Andrew L. Stewart; Stephen R. Rintoul; Annie Foppert; Kathryn L. Gunn; Laura Herraiz-Borreguero; Shigeru Aoki; Yoshihiro Nakayama; Alberto C. Naveira Garabato; Carl Spingys; Camille Hayatte Akhoudas; Jean-Baptiste Sallée; Casimir de Lavergne; E. Povl Abrahamsen; Andrew J. S. Meijers; Michael P. Meredith; Shenjie Zhou; Takeshi Tamura; Kaihe Yamazaki; Kay I. Ohshima; Pierpaolo Falco; Giorgio Budillon; Tore Hattermann; Markus A. Janout; Pedro Llanillo; Melissa M. Bowen; Elin Darelius; Svein Østerhus; Keith W. Nicholls; Craig Stevens; Denise Fernandez; Laura Cimoli; Stanley S. Jacobs; Adele K. Morrison; Andrew McC. Hogg; F. Alexander Haumann; Ali Mashayek; Zhaomin Wang; Rodrigo Kerr; Guy D. Williams; Won Sang Lee
  Frontiers in Marine Science, 10, Frontiers Media SA, 08 Dec. 2023, [Peer-reviewed]
  Scientific journal, Dense, cold waters formed on Antarctic continental shelves descend along the Antarctic continental margin, where they mix with other Southern Ocean waters to form Antarctic Bottom Water (AABW). AABW then spreads into the deepest parts of all major ocean basins, isolating heat and carbon from the atmosphere for centuries. Despite AABW’s key role in regulating Earth’s climate on long time scales and in recording Southern Ocean conditions, AABW remains poorly observed. This lack of observational data is mostly due to two factors. First, AABW originates on the Antarctic continental shelf and slope where in situ measurements are limited and ocean observations by satellites are hampered by persistent sea ice cover and long periods of darkness in winter. Second, north of the Antarctic continental slope, AABW is found below approximately 2 km depth, where in situ observations are also scarce and satellites cannot provide direct measurements. Here, we review progress made during the past decades in observing AABW. We describe 1) long-term monitoring obtained by moorings, by ship-based surveys, and beneath ice shelves through bore holes; 2) the recent development of autonomous observing tools in coastal Antarctic and deep ocean systems; and 3) alternative approaches including data assimilation models and satellite-derived proxies. The variety of approaches is beginning to transform our understanding of AABW, including its formation processes, temporal variability, and contribution to the lower limb of the global ocean meridional overturning circulation. In particular, these observations highlight the key role played by winds, sea ice, and the Antarctic Ice Sheet in AABW-related processes. We conclude by discussing future avenues for observing and understanding AABW, impressing the need for a sustained and coordinated observing system.
• Distribution of stable oxygen isotope in seawater and implication on freshwater cycle off the coast from Wilkes to George V Land, East Antarctica
  Shigeru Aoki; Kaihe Yamazaki; Daisuke Hirano; Daiki Nomura; Hiroto Murase
  Progress in Oceanography, 217, 103101, 103101, Elsevier BV, Sep. 2023, [Peer-reviewed]
  Scientific journal
• Modeling seasonal-to-decadal ocean-cryosphere interactions along the Sabrina Coast, East Antarctica
  Kazuya Kusahara; Daisuke Hirano; Masakazu Fujii; Alexander Fraser; Takeshi Tamura; Kohei Mizobata; Guy Williams; Shigeru Aoki
  Copernicus GmbH, 21 Aug. 2023, [Peer-reviewed]
  Abstract. The Totten Ice Shelf (TIS) and Moscow University Ice Shelf (MUIS), along the Sabrina Coast of Wilkes Land, are the floating seaward terminuses of the second-largest freshwater reservoir in the East Antarctic Ice Sheet. Being a marine ice sheet, it is vulnerable to the surrounding ocean conditions. Recent comprehensive oceanographic observations, including bathymetric measurements off the Sabrina Coast, have shed light on the widespread intrusion of warm modified Circumpolar Deep Water (mCDW) onto the continental shelf and the intense ice-ocean interaction beneath the TIS. However, the spatiotemporal coverage of the observation is very limited. Here, we use an ocean–sea ice–ice shelf model with updated bathymetry to better understand the regional ocean circulations and ocean-cryosphere interactions. The model successfully captured the widespread intrusions of mCDW, local sea-ice production and the ocean heat and volume transports into the TIS cavity, facilitating an examination of the overturning ocean circulation within the cavities and the resultant ice-shelf basal melting. We found notable differences in the temporal variability of ice-shelf basal melting across the two adjacent ice shelves of the TIS and the western part of the MUIS. Ocean heat transport by mCDW controls the low-frequency interannual-to-decadal variability in ice-ocean interactions, but the sea-ice production in the Dalton Polynya strongly modifies the signals, explaining the regional difference between the two ice shelves. The formation of a summertime eastward-flowing undercurrent beneath the westward-flowing Antarctic Slope Current is found to play an important role in the seasonal delivery of ocean heat to the continental shelf.
• Biogeochemical characteristics of brash sea ice and icebergs during summer and autumn in the Indian sector of the Southern Ocean
  Daiki Nomura; Reishi Sahashi; Keigo D. Takahashi; Ryosuke Makabe; Masato Ito; Manami Tozawa; Pat Wongpan; Ryo Matsuda; Masayoshi Sano; Michiyo Yamamoto-Kawai; Natsumi Nojiro; Aiko Tachibana; Norio Kurosawa; Masato Moteki; Takeshi Tamura; Shigeru Aoki; Hiroto Murase
  Progress in Oceanography, 214, 103023, 103023, Elsevier BV, Apr. 2023, [Peer-reviewed]
  Scientific journal
• Diffusion of Circumpolar Deep Water towards Antarctica
  Kaihe Yamazaki; Shigeru Aoki; Kohei Mizobata
  Journal of Geophysical Research: Oceans, 06 Feb. 2023, [Peer-reviewed]
  Scientific journal
• The biogeochemistry of zinc and cadmium in the Amundsen Sea, coastal Antarctica
  Hung-An Tian; Mathijs van Manen; Flora Wille; Jinyoung Jung; SangHoon Lee; Tae-Wan Kim; Shigeru Aoki; Charlotte Eich; Corina P.D. Brussaard; Gert-Jan Reichart; Tim M. Conway; Rob Middag
  Marine Chemistry, 249, 104223, 104223, Elsevier BV, Feb. 2023, [Peer-reviewed]
  Scientific journal
• On-Shelf Circulation of Warm Water Toward the Totten Ice Shelf, East Antarctica
  Hirano, D; T. Tamura; K. Kusahara; M. Fujii; K. Yamazaki; Y. Nakayama; K. Ono; T. Itaki; Y. Aoyama; D. Simizu; K. Mizobata; K. I. Ohshima; Y. Nogi; S. R. Rintoul; E. Wijk; J. S. Greenbaum; D. D. Blankenship; K. Saito; S. Aoki
  Nature Communications, 14, 4995, Springer Science and Business Media LLC, 2023, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
  English, Scientific journal, Abstract
  
  The Totten Glacier in East Antarctica, with an ice volume equivalent to >3.5 m of global sea-level rise, is grounded below sea level and, therefore, vulnerable to ocean forcing. Here, we use bathymetric and oceanographic observations from previously unsampled parts of the Totten continental shelf to reveal on-shelf warm water pathways defined by deep topographic features. Access of warm water to the Totten Ice Shelf (TIS) cavity is facilitated by a deep shelf break, a broad and deep depression on the shelf, a cyclonic circulation that carries warm water to the inner shelf, and deep troughs that provide direct access to the TIS cavity. The temperature of the warmest water reaching the TIS cavity varies by ~0.8 °C on an interannual timescale. Numerical simulations constrained by the updated bathymetry demonstrate that the deep troughs play a critical role in regulating ocean heat transport to the TIS cavity and the subsequent basal melt of the ice shelf.
• The role of the Dotson Ice Shelf and Circumpolar Deep Water as driver and source of dissolved and particulate iron and manganese in the Amundsen Sea polynya, Southern Ocean
  Mathijs van Manen; Shigeru Aoki; Corina P.D. Brussaard; Tim M. Conway; Charlotte Eich; Loes J.A. Gerringa; Jinyoung Jung; Tae-Wan Kim; SangHoon Lee; Youngju Lee; Gert-Jan Reichart; Hung-An Tian; Flora Wille; Rob Middag
  Marine Chemistry, 246, 104161, 104161, Elsevier BV, Oct. 2022, [Peer-reviewed]
  Scientific journal
• Impacts of basal melting of the Totten Ice Shelf and biological productivity on marine biogeochemical components in Sabrina Coast, East Antarctica
  Tetsuya P. Tamura; Daiki Nomura; Daisuke Hirano; Takeshi Tamura; Masaaki Kiuchi; Gen Hashida; Ryosuke Makabe; Kazuya Ono; Shuki Ushio; Kaihe Yamazaki; Yoshihiro Nakayama; Keigo D. Takahashi; Hiroko Sasaki; Hiroto Murase; Shigeru Aoki
  Global Biogeochemical Cycles, American Geophysical Union (AGU), 13 Sep. 2022, [Peer-reviewed]
  Scientific journal, Abstract
  
  To clarify the impacts of basal melting of the Antarctic ice sheet and biological productivity on biogeochemical processes in Antarctic coastal waters, concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA), inorganic nutrients, chlorophyll a, and stable oxygen isotopic ratios (δ¹⁸O) were measured from the offshore slope to the ice front of the Totten Ice Shelf (TIS) during the spring/summer of 2018, 2019, and 2020. Modified Circumpolar Deep Water (mCDW) intruded onto the continental shelf off the TIS and flowed along bathymetric troughs into the TIS cavity, where it formed a buoyant mixture with glacial meltwater from the ice shelf base. Physical oceanographic processes mostly determined the distributions of DIC, TA, and nutrient concentrations. However, photosynthesis and dilution by meltwater from sea ice and the ice shelf base decreased DIC, TA, and nutrient concentrations in surface water near the ice front. These causes also reduced the CO₂ partial pressure in surface water by more than 100 μatm with respect to mCDW in austral summer of 2018 and 2020, and the surface water became a strong CO₂ sink for the atmosphere. Phytoplankton photosynthesis changed DIC and TA in a molar ratio of 106:16. Thus, CO₂ partial pressure decreased mostly as a result of photosynthesis while dilution by glacial and sea ice meltwater had a small effect. The nutrient consumption ratio suggested that photosynthesis was stimulated by iron in the water column, supplied to the surface layer via buoyancy‐driven upwelling and basal ice shelf meltwater in addition to sea ice meltwater.
• Interactive movements of outlet glacier tongue and landfast sea ice in Lützow-Holm Bay, East Antarctica, detected by ALOS-2/PALSAR-2 imagery
  Kazuki Nakamura; Shigeru Aoki; Tsutomu Yamanokuchi; Takeshi Tamura
  Science of Remote Sensing, 100064, 100064, Elsevier BV, Aug. 2022, [Peer-reviewed]
  Scientific journal
• Effects of Snow and Remineralization Processes on Nutrient Distributions in Multi‐Year Antarctic Landfast Sea Ice
  Reishi Sahashi; Daiki Nomura; Takenobu Toyota; Manami Tozawa; Masato Ito; Pat Wongpan; Kazuya Ono; Daisuke Simizu; Kazuhiro Naoki; Yuichi Nosaka; Takeshi Tamura; Shigeru Aoki; Shuki Ushio
  Journal of Geophysical Research: Oceans, 127, 7, American Geophysical Union (AGU), Jul. 2022, [Peer-reviewed]
  Scientific journal
• Warm surface waters increase Antarctic ice shelf melt and delay dense water formation
  Shigeru Aoki; Tomoki Takahashi; Kaihe Yamazaki; Daisuke Hirano; Kazuya Ono; Kazuya Kusahara; Takeshi Tamura; Guy D. Williams
  Communications Earth & Environment, 3, 1, Springer Science and Business Media LLC, Jun. 2022, [Peer-reviewed]
  Scientific journal, Abstract
  
  Melting ice shelves around Antarctica control the massive input of freshwater into the ocean and play an intricate role in global heat redistribution. The Amery Ice Shelf regulates wintertime sea-ice growth and dense shelf water formation. We investigated the role of warm Antarctic Surface Water in ice shelf melting and its impact on dense shelf water. Here we show that the coastal ocean in summer 2016/17 was almost sea-ice free, leading to higher surface water temperatures. The glacial meltwater fraction in surface water was the highest on record, hypothesised to be attributable to anomalous ice shelf melting. The excess heat and freshwater in early 2017 delayed the seasonal evolution of dense shelf water. Focused on ice shelf melting at depth, the importance and impacts of warming surface waters has been overlooked. In a warming climate, increased surface water heating will reduce coastal sea-ice production and potentially Antarctic Bottom Water formation.
• Shoaling of abyssal ventilation in the Eastern Indian Sector of the Southern Ocean
  Keishi Shimada; Yujiro Kitade; Shigeru Aoki; Kohei Mizobata; Lingqiao Cheng; Kunio T. Takahashi; Ryosuke Makabe; Jota Kanda; Tsuneo Odate
  Communications Earth & Environment, 3, 120, May 2022, [Peer-reviewed]
  English, Scientific journal
• Seasonal Variation and Governing Dynamics of the Mixed Layer in the Indian Sector of the Southern Ocean
  Matheus Ferreira Azevedo; Shigeru Aoki; Yujiro Kitade
  Journal of Geophysical Research: Oceans, 127, 4, American Geophysical Union (AGU), 04 Apr. 2022, [Peer-reviewed]
  Scientific journal
• Validation for Ice Flow Velocity Variations of Shirase Glacier Derived From PALSAR-2 Offset Tracking
  Kazuki Nakamura; Shigeru Aoki; Tsutomu Yamanokuchi; Takeshi Tamura; Koichiro Doi
  IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 15, 3269, 3281, Institute of Electrical and Electronics Engineers (IEEE), Apr. 2022, [Peer-reviewed]
  Scientific journal
• Helicopter-based ocean observations capture broad ocean heat intrusions towards the Totten Ice Shelf
  Nakayama, Y; J. S. Greenbaum; P. Wongpan; K. Yamazaki; T. Noguchi; D. Simizu; H. Kashiwase; D. D. Blankenship; T. Tamura; S. Aoki
  Geophysical Research Letters, 50, 17, in press, American Geophysical Union (AGU), 2022, [Peer-reviewed], ［Internationally co-authored］, [International Magazine]
  English, Scientific journal, Abstract
  
  The recent discovery of warm ocean water near the Totten Ice Shelf (TIS) has increased attention to the Sabrina Coast in East Antarctica. We report the result of 6‐day helicopter‐based observations conducted during the 61st Japanese Antarctic Research Expedition (JARE61), revealing warm ocean water (0.5–1°C) occupying a large previously unsampled area of the Sabrina Coast (116.5°E−120°E) below 550–600 m. Along the TIS front, we observe modified Circumpolar Deep Water (mCDW) well above freezing (∼−0.7°C), consistent with previous work. We identify glacial meltwater outflow from the TIS cavity west of 116°E. No signs of mCDW intrusions toward the Moscow University Ice Shelf cavity are observed; however, those observations were limited to only two shallow (∼330 m) profiles. We also highlight the advantages of helicopter‐based observations for accessibility, speed, maneuverability, and cost‐efficiency. The combination of ship‐ and helicopter‐based observations using the JARE61 approach will increase the potential of future polar oceanographic observations.
• Seasonal Variations and Drivers of Surface Ocean pCO2 in the Seasonal Ice Zone of the Eastern Indian Sector, Southern Ocean
  Manami Tozawa; Daiki Nomura; Shin ichiro Nakaoka; Masaaki Kiuchi; Kaihe Yamazaki; Daisuke Hirano; Shigeru Aoki; Hiroko Sasaki; Hiroto Murase
  Journal of Geophysical Research: Oceans, 127, 1, Jan. 2022, [Peer-reviewed]
  Scientific journal
• Thermohaline structure and circulation beneath the Langhovde Glacier ice shelf in East Antarctica
  Masahiro Minowa; Shin Sugiyama; Masato Ito; Shiori Yamane; Shigeru Aoki
  Nature Communications, 12, 1, Dec. 2021, [Peer-reviewed]
  Scientific journal
• Shoreward intrusion of oceanic surface waters alters physical and biological ocean structures on the Antarctic continental shelf during winter: Observations from instrumented seals
  Nobuo Kokubun; Yukiko Tanabe; Daisuke Hirano; Vigan Mensah; Takeshi Tamura; Shigeru Aoki; Akinori Takahashi
  Limnology and Oceanography, 66, 10, 3740, 3753, Oct. 2021, [Peer-reviewed]
  Scientific journal
• Tracing Circumpolar Deep Water and glacial meltwater using humic-like fluorescent dissolved organic matter in the Amundsen Sea, Antarctica
  Mi Hae Jeon; Jinyoung Jung; Mi Ok Park; Shigeru Aoki; Tae Wan Kim; Seung Kyu Kim
  Marine Chemistry, 235, 20 Sep. 2021, [Peer-reviewed]
  Scientific journal
• Antarctic Slope Current Modulates Ocean Heat Intrusions Towards Totten Glacier
  Yoshihiro Nakayama; Chad A. Greene; Fernando S. Paolo; Vigan Mensah; Hong Zhang; Haruhiko Kashiwase; Daisuke Simizu; Jamin S. Greenbaum; Donald D. Blankenship; Ayako Abe-Ouchi; Shigeru Aoki
  Geophysical Research Letters, 48, 17, 16 Sep. 2021, [Peer-reviewed]
  Scientific journal
• Poleward eddy-induced warm water transport across a shelf break off Totten Ice Shelf, East Antarctica
  Daisuke Hirano; Kohei Mizobata; Hiroko Sasaki; Hiroto Murase; Takeshi Tamura; Shigeru Aoki
  Communications Earth & Environment, 2, 1, Springer Science and Business Media LLC, 06 Aug. 2021, [Peer-reviewed]
  Scientific journal, Abstract
  
  Ice mass loss in the Wilkes Land sector of East Antarctica and the Amundsen and Bellingshausen Sea sectors of West Antarctica has contributed to a rise in sea levels over several decades. The massive continental ice behind the Totten Ice Shelf, equivalent to a few meters of sea-level rise, is grounded well below sea level and therefore, potentially vulnerable to oceanic heat. Here, we present analyses of comprehensive hydrographic observations at the continental slope and shelf break regions off Totten Ice Shelf. We provide robust evidence that the relatively warm Circumpolar Deep Water that originates at intermediate depths in the Antarctic Circumpolar Current is transported efficiently towards the shelf break by multiple cyclonic eddies. We propose that these semi-permanent cyclonic circulations play a critical role in transporting the available ocean heat towards Totten Ice Shelf, and melting it from underneath, thus eventually influencing the global climate.
• Multidecadal poleward shift of the southern boundary of the Antarctic Circumpolar Current off East Antarctica
  Kaihe Yamazaki; Shigeru Aoki; Katsuro Katsumata; Daisuke Hirano; Yoshihiro Nakayama
  SCIENCE ADVANCES, 7, 24, Jun. 2021, [Peer-reviewed]
  English, Scientific journal
• The Effect of Basal Melting of the Shirase Glacier Tongue on the CO2 System in Lützow-Holm Bay, East Antarctica
  Masaaki Kiuchi; Daiki Nomura; Daisuke Hirano; Takeshi Tamura; Gen Hashida; Shuki Ushio; Daisuke Simizu; Kazuya Ono; Shigeru Aoki
  Journal of Geophysical Research: Biogeosciences, 126, 5, May 2021, [Peer-reviewed]
  Scientific journal
• Reversal of freshening trend of Antarctic Bottom Water in the Australian-Antarctic Basin during 2010s
  S. Aoki; K. Yamazaki; D. Hirano; K. Katsumata; K. Shimada; Y. Kitade; H. Sasaki; H. Murase
  Scientific Reports, 10, 1, 01 Dec. 2020, [Peer-reviewed]
  Scientific journal
• Using under-ice hyperspectral transmittance to determine land-fast sea-ice algal biomass in Saroma-ko Lagoon, Hokkaido, Japan
  Pat Wongpan; Daiki Nomura; Takenobu Toyota; Tomonori Tanikawa; Klaus M. Meiners; Tomomi Ishino; Tetsuya P. Tamura; Manami Tozawa; Yuichi Nosaka; Toru Hirawake; Atsushi Ooki; Shigeru Aoki
  Annals of Glaciology, 61, 83, 454, 463, 24 Sep. 2020, [Peer-reviewed]
  English, Scientific journal
• Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica
  Daisuke Hirano; Takeshi Tamura; Kazuya Kusahara; Kay I. Ohshima; Keith W. Nicholls; Shuki Ushio; Daisuke Simizu; Kazuya Ono; Masakazu Fujii; Yoshifumi Nogi; Shigeru Aoki
  Nature Communications, 11, 1, 24 Aug. 2020, [Peer-reviewed]
  Scientific journal
• Freshening of Antarctic Bottom Water Off Cape Darnley, East Antarctica
  S. Aoki; K. Katsumata; M. Hamaguchi; A. Noda; Y. Kitade; K. Shimada; D. Hirano; D. Simizu; Y. Aoyama; K. Doi; Y. Nogi
  Journal of Geophysical Research: Oceans, 125, 8, 01 Aug. 2020, [Peer-reviewed]
  Scientific journal
• Structure of the Subpolar Gyre in the Australian-Antarctic Basin Derived From Argo Floats
  Kaihe Yamazaki; Shigeru Aoki; Keishi Shimada; Taiyo Kobayashi; Yujiro Kitade
  Journal of Geophysical Research: Oceans, 125, 8, 01 Aug. 2020, [Peer-reviewed]
  English, Scientific journal
• The Cyclonic Eddy Train in the Indian Ocean Sector of the Southern Ocean as Revealed by Satellite Radar Altimeters and In Situ Measurements
  K. Mizobata; K. Shimada; S. Aoki; Y. Kitade
  Journal of Geophysical Research: Oceans, 125, 6, 01 Jun. 2020, [Peer-reviewed]
  Scientific journal
• Continuous winter oceanic profiling in the Cape Darnley Polynya, East Antarctica
  Shigeru Aoki; Kazuya Ono; Daisuke Hirano; Takeshi Tamura
  Journal of Oceanography, 76, 5, 365, 372, 25 May 2020, [Peer-reviewed]
  English, Scientific journal
• Vertical distribution of water mass properties under the influence of subglacial discharge in Bowdoin Fjord, northwestern Greenland
  Yoshihiko Ohashi; Shigeru Aoki; Yoshimasa Matsumura; Shin Sugiyama; Naoya Kanna; Daiki Sakakibara
  Ocean Science, 16, 3, 545, 564, 04 May 2020, [Peer-reviewed]
  Scientific journal
• Saroma-ko Lagoon observations for sea ice physico-chemistry and ecosystems 2019 (SLOPE2019)
  Daiki Nomura; Pat Wongpan; Takenobu Toyota; Tomonori Tanikawa; Yusuke Kawaguchi; Takashi Ono; Tomomi Ishino; Manami Tozawa; Tetsuya P. Tamura; Itsuka S. Yabe; Eun Yae Son; Frederic Vivier; Antonio Lourenco; Marion Lebrun; Yuichi Nosaka; Toru Hirawake; Atsushi Ooki; Shigeru Aoki; Brent Else; Francois Fripiat; Jun Inoue; Martin Vancoppenolle
  Bulletin of Glaciological Research, 38, 1, 12, 2020, [Peer-reviewed]
  Scientific journal
• Fluctuations of the Ice Flow Velocity of Shirase Glacier and its Surrounding Landfast Ice Displacement in East Antarctica Derived from alos-2/Palsar-2 Image Correlation
  Kazuki Nakamura; Shigeru Aoki; Tsutomu Yamanokuchi; Takeshi Tamura; Shuki Ushio; Koichiro Doi
  International Geoscience and Remote Sensing Symposium (IGARSS), 4172, 4174, Jul. 2019, [Peer-reviewed]
  International conference proceedings
• Recent research results and future project in the Antarctic Ocean by Umitaka-Maru research group for physical oceanography
  Yujiro Kitade; Keishi Shimada; Shigeru Aoki; Kay I. Ohshima
  Oceanography Challenges to Future Earth: Human and Natural Impacts on our Seas, 123, 135, 15 Feb. 2019, [Peer-reviewed]
  In book
• Freshening by glacial meltwater enhances melting of ice shelves and reduces formation of Antarctic Bottom Water
  Alessandro Silvano; Stephen Rich Rintoul; Beatriz Peña-Molino; William Richard Hobbs; Esmee Van Wijk; Shigeru Aoki; Takeshi Tamura; Guy Darvall Williams
  Science Advances, 4, 4, Apr. 2018, [Peer-reviewed]
  English, Scientific journal
• Influence of Sea Ice Crack Formation on the Spatial Distribution of Nutrients and Microalgae in Flooded Antarctic Multiyear Ice
  Daiki Nomura; Shigeru Aoki; Daisuke Simizu; Takahiro Iida
  Journal of Geophysical Research: Oceans, 123, 2, 939, 951, Feb. 2018, [Peer-reviewed]
  Scientific journal
• Changes in water properties and flow regime on the continental shelf off the Adélie/George V Land coast, East Antarctica, after glacier tongue calving
  S. Aoki; R. Kobayashi; S. R. Rintoul; T. Tamura; K. Kusahara
  Journal of Geophysical Research: Oceans, 122, 8, 6277, 6294, Aug. 2017, [Peer-reviewed]
  Scientific journal
• Breakup of land-fast sea ice in Lützow-Holm Bay, East Antarctica, and its teleconnection to tropical Pacific sea surface temperatures
  S. Aoki
  Geophysical Research Letters, 44, 7, 3219, 3227, Apr. 2017, [Peer-reviewed]
  Scientific journal
• Modeling ocean-cryosphere interactions off adélie and George V Land, East Antarctica
  Kazuya Kusahara; Hiroyasu Hasumi; Alexander D. Fraser; Shigeru Aoki; Keishi Shimada; Guy D. Williams; Robert Massom; Takeshi Tamura
  Journal of Climate, 30, 1, 163, 188, 2017, [Peer-reviewed]
  Scientific journal
• Creation of a gridded dataset for the southern ocean with a topographic constraint scheme
  Keishi Shimada; Shigeru Aoki; Kay I. Ohshima
  Journal of Atmospheric and Oceanic Technology, 34, 3, 511, 532, 2017, [Peer-reviewed]
  English, Scientific journal
• Oceanic fronts and jets around Japan: A review
  Shinichiro Kida; Humio Mitsudera; Shigeru Aoki; Xinyu Guo; Shin Ichi Ito; Fumiaki Kobashi; Nobumasa Komori; Atsushi Kubokawa; Toru Miyama; Ryosuke Morie; Hisashi Nakamura; Tomohiro Nakamura; Hideyuki Nakano; Hajime Nishigaki; Masami Nonaka; Hideharu Sasaki; Yoshi N. Sasaki; Toshio Suga; Shusaku Sugimoto; Bunmei Taguchi; Koutarou Takaya; Tomoki Tozuka; Hiroyuki Tsujino; Norihisa Usui
  Hot Spots in the Climate System: New Developments in the Extratropical Ocean-Atmosphere Interaction Research, 1, 30, 01 Jan. 2016, [Peer-reviewed]
  In book
• Atlantic-Pacific asymmetry of subsurface temperature change and frontal response of the antarctic circumpolar current for the recent three decades
  Shigeru Aoki; Genta Mizuta; Hideharu Sasaki; Yoshikazu Sasai; Stephen R. Rintoul; Nathaniel L. Bindoff
  Hot Spots in the Climate System: New Developments in the Extratropical Ocean-Atmosphere Interaction Research, 157, 170, 01 Jan. 2016, [Peer-reviewed]
  In book
• Spatial and temporal variations in high turbidity surface water off the Thule region, northwestern Greenland
  Yoshihiko Ohashi; Takahiro Iida; Shin Sugiyama; Shigeru Aoki
  Polar Science, 10, 3, 270, 277, 2016, [Peer-reviewed]
  English, Scientific journal
• Atlantic–Pacific asymmetry of subsurface temperature change and frontal response of the Antarctic Circumpolar Current for the recent three decades
  Shigeru Aoki; Genta Mizuta; Hideharu Sasaki; Yoshikazu Sasai; Stephen R. Rintoul; Nathaniel L. Bindoff
  Journal of Oceanography, 71, 5, 623, 636, 29 Oct. 2015, [Peer-reviewed]
  English, Scientific journal
• Multidecadal warming of Antarctic waters
  Sunke Schmidtko; Karen J. Heywood; Andrew F. Thompson; Shigeru Aoki
  Science, 346, 6214, 1227, 1231, 05 Dec. 2014, [Peer-reviewed]
  Scientific journal
• Active water exchange and life near the grounding line of an Antarctic outlet glacier
  Shin Sugiyama; Takanobu Sawagaki; Takehiro Fukuda; Shigeru Aoki
  EARTH AND PLANETARY SCIENCE LETTERS, 399, 52, 60, Aug. 2014, [Peer-reviewed]
  English, Scientific journal
• Antarctic bottom water production from the Vincennes Bay Polynya, East Antarctica
  Yujiro Kitade; Keishi Shimada; Takeshi Tamura; Guy D. Williams; Shigeru Aoki; Yasushi Fukamachi; Fabien Roquet; Mark Hindell; Shuki Ushio; Kay I. Ohshima
  Geophysical Research Letters, 41, 10, 3528, 3534, 28 May 2014, [Peer-reviewed]
  Scientific journal
• Observations: Ocean
  Rhein, M; S.R. Rintoul; S. Aoki; E. Campos; D. Chambers; R. A. Feely; S. Gulev; G. C. Johnson; S. A. Josey; A. Kostianoy; C. Mauritzen; D. Roemmich; L. D. Talley; F. Wang
  Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, 255, 316, Cambridge University Press, Jan. 2014, [Peer-reviewed]
  In book
• Use of L-band SAR data for monitoring of ice sheet marginal zone on East Antarctica
  Tsutomu Yamanokuchi; Koichiro Doi; Kazuki Nakamura; Shigeru Aoki; Kazuo Shibuya
  Proceedings of the European Conference on Synthetic Aperture Radar, EUSAR, Proceedings of the European Conference on Synthetic Aperture Radar, EUSAR, 102, 105, 2014, [Peer-reviewed]
  International conference proceedings
• Distribution of oxygen isotope ratio of precipitation in the Atlantic-Indian sectors of the Southern Ocean
  Kayo Nakamura; Shigeru Aoki; Kei Yoshimura; Naoyuki Kurita
  Scientific Online Letters on the Atmosphere, 10, 1, 154, 157, 2014, [Peer-reviewed]
  English, Scientific journal
• Widespread freshening in the Seasonal Ice Zone near 140°E off the Adélie Land Coast, Antarctica, from 1994 to 2012
  S. Aoki; Y. Kitade; K. Shimada; K. I. Ohshima; T. Tamura; C. C. Bajish; M. Moteki; S. R. Rintoul
  Journal of Geophysical Research: Oceans, 118, 11, 6046, 6063, Nov. 2013, [Peer-reviewed]
  Scientific journal
• Antarctic Bottom Water production by intense sea-ice formation in the Cape Darnley polynya
  Kay I. Ohshima; Yasushi Fukamachi; Guy D. Williams; Sohey Nihashi; Fabien Roquet; Yujiro Kitade; Takeshi Tamura; Daisuke Hirano; Laura Herraiz-Borreguero; Iain Field; Mark Hindell; Shigeru Aoki; Masaaki Wakatsuchi
  Nature Geoscience, 6, 3, 235, 240, Mar. 2013, [Peer-reviewed]
  English, Scientific journal
• Quasi-decadal circumpolar variability of antarctic sea ice
  C. C. Bajish; S. Aoki; B. Taguchi; N. Komori; S. J. Kim
  Scientific Online Letters on the Atmosphere, 9, 1, 32, 35, 2013, [Peer-reviewed]
  Scientific journal
• Monitoring of the changes of glacier and ice sheet on polar region by L-band SAR data
  Tsutomu Yamanokuchi; Koichiro Doi; Kazuki Nakamura; Shigeru Aoki; Kazuo Shibuya
  Conference Proceedings of 2013 Asia-Pacific Conference on Synthetic Aperture Radar, APSAR 2013, 198, 201, 2013, [Peer-reviewed]
  International conference proceedings
• Influence of Ross Sea Bottom Water changes on the warming and freshening of the Antarctic Bottom Water in the Australian-Antarctic Basin
  K. Shimada; S. Aoki; K. I. Ohshima; S. R. Rintoul
  Ocean Science, 8, 4, 419, 432, 2012, [Peer-reviewed]
  Scientific journal
• Incorporation of nitrogen compounds into sea ice from atmospheric deposition
  Daiki Nomura; Andrew McMinn; Hiroshi Hattori; Shigeru Aoki; Mitsuo Fukuchi
  Marine Chemistry, 127, 1-4, 90, 99, 20 Dec. 2011, [Peer-reviewed]
  Scientific journal
• Monitoring of east Antarctic marginal zone using ALOS/PALSAR data
  Tsutomu Yamanokuchi; Kazuo Shibuya; Koichiro Doi; Shigeru Aoki
  2011 3rd International Asia-Pacific Conference on Synthetic Aperture Radar, APSAR 2011, 554, 557, 2011, [Peer-reviewed]
  International conference proceedings
• The cyclonic circulation in the Australian-Antarctic basin simulated by an eddy-resolving general circulation model
  Shigeru Aoki; Yoshikazu Sasai; Hideharu Sasaki; Humio Mitsudera; Guy D. Williams
  Ocean Dynamics, 60, 3, 743, 757, Jun. 2010, [Peer-reviewed]
  English, Scientific journal
• Surface oceanography of BROKE-West, along the Antarctic margin of the south-west Indian Ocean (30 - 80^{{ring operator}} E)
  G. D. Williams; S. Nicol; S. Aoki; A. J.S. Meijers; N. L. Bindoff; Y. Iijima; S. J. Marsland; A. Klocker
  Deep-Sea Research Part II: Topical Studies in Oceanography, 57, 9-10, 738, 757, May 2010, [Peer-reviewed]
  Scientific journal
• Strong export of Antarctic Bottom Water east of the Kerguelen plateau
  Y. Fukamachi; S. R. Rintoul; J. A. Church; S. Aoki; S. Sokolov; M. A. Rosenberg; M. Wakatsuchi
  Nature Geoscience, 3, 5, 327, 331, May 2010, [Peer-reviewed]
  English, Scientific journal
• Antarctic bottom water from the adélie and George v Land Coast, East Antarctica (140-149°E)
  G. D. Williams; S. Aoki; S. S. Jacobs; S. R. Rintoul; T. Tamura; N. L. Bindoff
  Journal of Geophysical Research: Oceans, 115, 4, Apr. 2010, [Peer-reviewed]
  Scientific journal
• State of the antarctic and southern ocean climate system
  P. A. Mayewski; M. P. Meredith; C. P. Summerhayes; J. Turner; A. Worby; P. J. Barrett; G. Casassa; N. A.N. Bertler; T. Bracegirdle; A. C. Naveira Garabato; D. Bromwich; H. Campbell; G. S. Hamilton; W. B. Lyons; K. A. Maasch; S. Aoki; C. Xiao; Tas Van Ommen
  Reviews of Geophysics, 47, 1, Mar. 2009
• The Southern Annular Mode and opposite-phased Basin Mode of the Southern Ocean circulation
  Yuji Iijima; Shigeru Aoki; Kunio Kutsuwada
  Journal of Oceanography, 65, 1, 53, 60, 2009, [Peer-reviewed]
  English, Scientific journal
• Deep western boundary current and southern frontal systems of the Antarctic Circumpolar Current southeast of the Kerguelen Plateau
  Shigeru Aoki; Nobuhiro Fujii; Shuki Ushio; Yasushi Yoshikawa; Shuichi Watanabe; Genta Mizuta; Yasushi Fukamachi; Masaaki Wakatsuchi
  Journal of Geophysical Research: Oceans, 113, 8, 08 Aug. 2008, [Peer-reviewed]
  English, Scientific journal
• Development of grounding line database using ers-1/2 data by insar technique
  Tsutomu Yamanokuchi; Koichiro Doi; Kazuo Shibuya; Shigeru Aoki
  International Geoscience and Remote Sensing Symposium (IGARSS), 4, 1, 2008, [Peer-reviewed]
  International conference proceedings
• Formation regions of Subantarctic Mode Water detected by OFES and Argo profiling floats
  Shigeru Aoki; Mieko Hariyama; Humio Mitsudera; Hideharu Sasaki; Yoshikazu Sasai
  Geophysical Research Letters, 34, 10, 28 May 2007, [Peer-reviewed]
  English, Scientific journal
• A series of cyclonic eddies in the Antarctic Divergence off Adélie Coast
  Shigeru Aoki; Daisuke Fukai; Toru Hirawake; Shuki Ushio; Stephen R. Rintoul; Hiroshi Hasumoto; Takashi Ishimaru; Hideharu Sasaki; Takashi Kagimoto; Yoshikazu Sasai; Humio Mitsudera
  Journal of Geophysical Research: Oceans, 112, 5, 08 May 2007, [Peer-reviewed]
  Scientific journal
• Observations of small-scale disturbances of the Subantarctic Front south of Australia
  Shigeru Aoki; Kazunori Akitomo
  Deep-Sea Research Part I: Oceanographic Research Papers, 54, 3, 320, 339, Mar. 2007, [Peer-reviewed]
  Scientific journal
• Frontal positions and mixed layer evolution in the seasonal ice zone along 140°E in 2001/02
  Shigeru Aoki; Stephen R. Rintoul; Hiroshi Hasumoto; Hideki Kinoshita
  Polar Bioscience, 20, 1, 20, Dec. 2006, [Peer-reviewed]
  Scientific journal
• Freshening of the Adélie land bottom water near 140 °E
  Shigeru Aoki; Stephen R. Rintoul; Shuki Ushio; Shuichi Watanabe; Nathaniel L. Bindoff
  Geophysical Research Letters, 32, 23, 1, 4, 16 Dec. 2005, [Peer-reviewed]
  Scientific journal
• Inter-annual variability of chlorophyll and sea-ice in the Antarctic Divergence region: an attempt to derive their quantitative relationship
  T Hirawake; S Kudoh; S Aoki; T Odate; M Fukuchi
  INTERNATIONAL JOURNAL OF REMOTE SENSING, 26, 10, 2035, 2044, May 2005, [Peer-reviewed]
  English, Scientific journal
• Interdecadal water mass changes in the Southern Ocean between 30°E and 160°E
  Shigeru Aoki; Nathaniel L. Bindoff; John A. Church
  Geophysical Research Letters, 32, 7, 1, 5, Apr. 2005, [Peer-reviewed]
  Scientific journal
• Characteristics of sea ice thickness and snow depth distributions of the land-fast ice during summer in Lützow-Holmbukta, Antarctica, revealed from ship-based observations
  Shotaro Uto; Haruhito Shimoda; Koh Izumiyama; Shuki Ushio; Shigeru Aoki; Gen Hashida; Hiroyuki Wakabayashi; Fumihiko Nishio
  Antarctic Record, 48, 3, 165, 179, Nov. 2004, [Peer-reviewed]
  Scientific journal
• Combined utilization of GPS and bottom pressure gauge in landfast ice region around Antarctica
  S. Aoki; K. Shibuya; K. Doi
  Ocean '04 - MTS/IEEE Techno-Ocean '04: Bridges across the Oceans - Conference Proceedings, 3, 1644, 1648, 2004, [Peer-reviewed]
  International conference proceedings
• Seasonal and spatial variations of iceberg drift off Dronning Maud Land, Antartica, detected by satellite scatterometers
  Shigeru Aoki
  Journal of Oceanography, 59, 5, 629, 635, Oct. 2003, [Peer-reviewed]
  Scientific journal
• Eddies revealed by SeaWiFS ocean color images in the Antarctic Divergence zone near 140°E
  Toru Hirawake; Sakae Kudoh; Shigeru Aoki; Stephen R. Rintoul
  Geophysical Research Letters, 30, 9, 01 May 2003, [Peer-reviewed]
  Scientific journal
• Sea level variation in seismic normal mode band observed with on-ice GPS and on-hand SG at Syowa Station, Antarctica
  Kazunari Nawa; Naoki Suda; Shigeru Aoki; Kazuo Shibuya; Tadahiro Sato; Yoshio Fukao
  Geophysical Research Letters, 30, 7, 55, 1, Apr. 2003, [Peer-reviewed]
  Scientific journal
• Multidecadal warming of subsurface temperature in the Indian sector of the Southern Ocean
  Shigeru Aoki; Miwako Yoritaka; Akihiro Masuyama
  Journal of Geophysical Research: Oceans, 108, 4, Apr. 2003, [Peer-reviewed]
  Scientific journal
• Tidal observations on floating ice using a single GPS receiver
  Matt King; Shigeru Aoki
  Geophysical Research Letters, 30, 3, 01 Feb. 2003, [Peer-reviewed]
  Scientific journal
• Coherent sea level response to the Antarctic Oscillation
  Shigeru Aoki
  Geophysical Research Letters, 29, 20, 11, 1, 15 Oct. 2002, [Peer-reviewed]
  Scientific journal
• Sea surface height determination by GPS in sea ice region of Lutzow-Holm Bay, Antarctica
  Doi Koichiro; Seo Noritsune; Aoki Shigeru; Shibuya Kazuo
  Polar geoscience, 15, 104, 111, National Institute of Polar Research, Oct. 2002
  English, Global Positioning System (GPS) measurements were conducted at five sites on sea ice in Liitzow-Holm Bay, Antarctica We deteimined sea surface height (SSH) at each point aftei correcting for ocean tides, atmospheric pressuie and vertical distance from sea surface to ice suiface The overall erroi of the obtained SSH is estimated as smaller than 10cm We also obtained sea surface dynamic height (SSDT) by subtiacting synthetic geoidal height from the observed SSH The obtained SSDT values show good agreement with those calculated from the fine resolution Antaictic model (FRAM) After taking tempoial variations ot SSH into consideration the values took higher values at the southern end of the bay than at the northern end of the bay This spatial feature corresponds to the southward increase of SSDT across the continental slope
• Evaluation of seasonal sea level variation at Syowa Station, Antarctica, using GPS observations
  Shigeru Aoki; Kazuo Shibuya; Akihiro Masuyama; Taku Ozawa; Koichiro Doi
  Journal of Oceanography, 58, 3, 519, 523, 2002, [Peer-reviewed]
  Scientific journal
• Ocean Tide Observed with Differential GPS Technique in Lützow-Holm Bay, Antarctica
  Shigeru Aoki; Taku Ozawa; Kazuo Shibuya; Akihiro Masuyama
  Journal of the Geodetic Society of Japan, 47, 1, 181, 186, 2001, [Peer-reviewed]
  Scientific journal
• Observations of water temperature and salinity in Ongul Strait, Antarctica, in 1998 and investigations of their intraseasonal, seasonal, and interannual variations
  Aoki Shigeru; Hashida Gen
  Polar meteorology and glaciology, 14, 68, 77, National Institute of Polar Research, Nov. 2000
  English, Water temperature and salinity variations were observed below fast ice in Ongul Strait, Antarctica, in 1998. Vertical profiles of temperature and salinity were obtained with a conductivity-temperature-depth profiler, and temperature and salinity were continuously observed with moored sensors. Intraseasonal variations were observed in both fields. Especially, temperature variation of about 0.05℃ was apparent on the time scale of about one month near the thermocline depth. Seasonal variations of temperature and salinity were similar to those observed in 1982-1983 and 1990-1991. However, the temporally averaged temperature and salinity for 1998 showed differences from those for previous years; temperature was higher in 1998 than in 1982-1983 and 1990-1991 at middle to deep layers, and salinity was intermediate between 1982 (more saline) and 1990-1991 (fresher) throughout the water column.
• GPS observation of the sea level variation in Lutzow-Holm Bay, Antarctica
  Shigeru Aoki; Taku Ozawa; Koichiro Doi; Kazuo Shibuya
  Geophysical Research Letters, 27, 15, 2285, 2288, 01 Aug. 2000, [Peer-reviewed]
  Scientific journal
• Installation and operation of PRARE tracking antenna at Syowa Station, Antarctica
  Kazuo Shibuya; Masaki Kanao; Toshihiro Higashi; Shigeru Aoki
  Antarctic Record, 44, 1, 14, 24, Mar. 2000, [Peer-reviewed]
  Scientific journal
• Precise determination of geoid height and free-air gravity anomaly at Syowa Station, Antarctica
  Kazuo Shibuya; Koichiro Doi; Shigeru Aoki
  Earth, Planets and Space, 51, 3, 159, 168, 1999, [Peer-reviewed]
  Scientific journal
• Trends and interannual variability of surface layer temperature in the Indian sector of the Southern Ocean observed by Japanese Antarctic Research Expeditions
  Shigeru Aoki
  Journal of Oceanography, 53, 6, 623, 631, Dec. 1997, [Peer-reviewed]
  Scientific journal
• SAR data processing for interferometry using a personal computer
  Makoto Omura; Katsuaki Koike; Koichiro Doi; Shigeru Aoki
  International Geoscience and Remote Sensing Symposium (IGARSS), 4, 1582, 1584, 1997, [Peer-reviewed]
  International conference proceedings
• Eddy activities of the surface layer in the western North Pacific detected by satellite altimeter and radiometer
  Shigeru Aoki; Shiro Imawaki
  Journal of Oceanography, 52, 4, 457, 474, Aug. 1996, [Peer-reviewed]
  Scientific journal
• Baroclinic disturbances propagating westward in the Kuroshio extension region as seen by a satellite altimeter and radiometers
  S. Aoki; S. Imawaki; K. Ichikawa
  Journal of Geophysical Research, 100, C1, 839, 855, 1995, [Peer-reviewed]
  Scientific journal

• 南極海と地球の気候
  青木茂, 極地, 58, 1, 3, 6, Mar. 2022
• Horizontal diffusion due to medium-scale eddies in Meridional Ocean Circulation of Southern Ocean
  北出裕二郎; 溝端浩平; 嶋田啓資; 青木茂; 内田裕, 日本地球惑星科学連合大会予稿集(Web), 2022, 2022
• 大気海洋雪氷系における大洋・半球スケールの鉛直結合変動
  中村尚; 行本誠史; 小寺邦彦; 水田亮; 青木茂; 小川史明; 西井和晃; 宮坂貴文; 吉田聡; 宮本歩; 岡島悟; 田口文明; 野中正見; 升永竜介; 村崎万代, 気象研究ノート「気候系のHotspot：中緯度大気海洋相互作用研究の新展開」, 244, 244, 245, 277, Oct. 2021
  日本気象学会, Japanese
• 南極の海に探る地球の未来
  青木茂, 東陽テクニカルマガジン, 30, 2, 5, Sep. 2020
• 第61次南極地域観測隊の計画概要
  青木茂, 極地, 56, 79, 88, Mar. 2020
• Temporal variation of the Antarctic Bottom Water revealed by the mooring measurements off the Vincennes Bay
  溝端浩平; 北出裕二郎; 嶋田啓資; 平野大輔; 松村義正; CHENG Lingqiao; 青木茂; 田村岳史, 日本地球惑星科学連合大会予稿集(Web), 2020, 2020
• トッテン棚氷近傍海域における暖水分布
  平野大輔; 田村岳史; 溝端浩平; 伊藤優人; 山崎開平; 國府陽一郎; 木内政彰; 村瀬弘人; 佐々木裕子; 青木茂, 日本海洋学会大会講演要旨集, 2019, 2019
• 南大洋子午面循環の直接測流と定量評価を目指した係留観測
  北出裕二郎; 溝端浩平; 渡部和帆; CHEN Linquiao; GUO Gaopin; 青木茂; 牛尾収輝; 嶋田啓資; 大島慶一郎, 日本地球惑星科学連合大会予稿集(Web), 2019, 2019
• Development of monitoring buoy system for polar oceans-field experiment in the Okhotsk Sea-
  青木茂; 市川雅明; 市川雅明; 小野数也; 深町康; 深町康; 深町康; 大島慶一郎; 大島慶一郎; 中川敏彦; 小林研吾; 小竹正人; 小竹正人; 小澤知史, 海洋理工学会誌(Web), 25, 1, 29‐34(J‐STAGE), 2019
  Japanese
• 南大洋における観測からみた海洋長期変動
  青木茂, 低温科学, 76, 25, 31, Mar. 2018
• 南大洋における大気・海洋結合系の長期変動に関する観測的研究 ―2017年度堀内賞受賞記念講演―
  青木茂, 天気, 65, 6, 27, 33, 2018
• Temporal variations in the flow velocity for Shirase Glacier in Antarctica over a 20-year period
  中村 和樹; 山之口 勤; 青木 茂; 土井 浩一郎; 澁谷 和雄, Journal of the Japanese Society of Snow and Ice, 79, 1, 3, 15, Jan. 2017
  日本雪氷学会, Japanese
• Modeling subglacial meltwater plumes and associated sediment transport
  松村 義正; 大橋 良彦; 青木 茂; 杉山 慎, 低温科学, 75, 77, 84, 2017
  グリーンランド氷床の表面融解水は，氷河を貫通するムーランを通過して岩盤に到達し，陸上の堆積物を懸濁物質として取り込みながら氷河末端で海洋に流出する．淡水である融解水は海水より軽いため直ちに湧昇し，氷河末端で高濁度の融解水プルームを形成してフィヨルド内の鉛直循環を駆動する．本研究では粒子追跡法を組み込んだ非静力学海洋モデルによる理想化シミュレーションによってこの高濁度水プルームを再現し，特にフィヨルド内の懸濁物質輸送過程について解析した．The surface meltwater of the Greenland ice sheet is drained through englacial channels called moulins that reachthe bedrock, and hence it contains substantial amounts of terrestrial sediments. The meltwater runoff from marineterminatingglaciers form an upwelling turbid plume at the glacier front and drives overturning circulation in the fjord.We perform idealized numerical experiments on the turbid meltwater plume and associated sediment transport byusing a non-hydrostatic ocean model coupled with a Lagrangian particle tracking system that simulates the dynamicsof suspended sediments., 低温科学第75巻編集委員会, Japanese
• ビンセネス湾沖における巨大係留系による長期観測
  北出裕二郎; 嶋田啓資; 溝端浩平; 青木茂; 田村岳史; 千手智晴; 深町康; 大島慶一郎, 日本海洋学会大会講演要旨集, 2017, 2017
• Effects from ocean and atmosphere on ice-front position of tidewater glaciers, northwest Greenland
  箕輪昌紘; 箕輪昌紘; 杉山慎; 澤柿教伸; 津滝俊; 榊原大貴; 榊原大貴; 大橋良彦; 大橋良彦; 青木茂, 雪氷研究大会講演要旨集(Web), 2016, 2016
• 豪州南極海盆における南極底層水の急速かつ持続的な低塩分化
  嶋田啓資; 北出裕二郎; 溝端浩平; 青木茂; 大島慶一郎; 田村岳史; 小達恒夫, 日本地球惑星科学連合大会予稿集(Web), 2016, 2016
• Effects from ocean and atmosphere on ice-front position of tidewater glaciers, northwest Greenland
  Minowa Masahiro; Sugiyama Shin; Sawagaki Takanobu; Tsutaki Shun; Sakakibara Daiki; Ohashi Yoshihiko; Aoki Shigeru, Summaries of JSSI and JSSE Joint Conference on Snow and Ice Research, 2016, 0, 29, 29, 2016
  The Japanese Society of Snow and Ice / Japan Society for Snow Engineering, Japanese
• 2. Recent Changes in Polar Oceans and Roles of Global Freshwater Cycle(Polar Regions: Key Regions for the Changing Climate (A Report on the Symposium of the 2011 Spring Assembly of the Meteorological Society of Japan))
  AOKI Shigeru, 天気, 60, 11, 888, 892, 2013
  日本気象学会, Japanese
• Meridional distribution and seasonal variation of stable oxygen isotope ratio of precipitation in the Southern Ocean
  Nakamura Kayo; Aoki Shigeru; Toyota Takenobu; Aoyama Yuichi, Antarctic record, 54, 2, 190, 202, Jul. 2010
  National Institute of Polar Research, Japanese
• 観測から見た南極底層水の変質と氷床融解の影響把握
  青木茂, 月刊海洋, 号外54, 142, 150, Jun. 2010
• 未知の南極底層水生成域の発見と今後の観測に向けて―ケープダンレープロジェクト―
  大島慶一郎; 深町康; 青木茂; 清水大輔; 田村岳史; 牛尾収輝; 橋田元; 北出裕二郎; 若土正暁, 月刊海洋 総特集「南大洋の深層水形成と海氷過程」, 54、12-20, 2010
• 南極陸棚斜面横断東経115度ラインにおける酸素安定同位体比分布
  青木茂, 九州大学応用力学研究所所報, 135, 89, 93, Sep. 2008
• 干渉SAR処理を用いた南極接地線(grounding line)の精密決定
  山之口勤; 土井浩一郎; 澁谷和雄; 青木茂, 九州大学応用力学研究所所報, 135, 95, 99, Sep. 2008
• 南極を学び、地球を知る－北海道大学 国際南極大学カリキュラムの取り組み―
  青木茂, 大阪国際サイエンスクラブ会報, 217, 4, 6, Jul. 2008
• しらせ海上気象観測データから見た110°E 線の亜南極フロント上における大気の海洋に対する応答
  飯島裕司; 青木茂; 谷本陽一, 月刊海洋, 49, 66, 73, Jan. 2008
• Characteristics of Sea lce Thickness and Snow Depth Distributions of Land-fast lce During Summer in Lutzow-Holmbukta, Antarctica, Revealed from Ship-based Observations(Summaries of Papers Published by Staff of National Maritime Research Institute at Outside Organizations)
  宇都 正太郎; 下田 春人; 泉山 耕; 牛尾 収輝; 青木 茂; 橋田 元; 若林 裕之; 西尾 文彦, 海上技術安全研究所報告, 5, 2, 261, 261, 2005
  海上技術安全研究所, Japanese
• JARE-43 Tangaroa marine science cruise report (Physical oceanography)
  Shigeru Aoki; Toshihiko Sato, Antarctic Record, 48, 3, 204, 218, Nov. 2004
• 南極の海と淡水循環
  青木茂, 細氷, 50, 2, 9, Jan. 2004
• 南極海ダイナミクス 気候変動の鍵を握る南極底層水
  青木茂, ILLUME, 31, 16, 4, 21, Jan. 2004
• Oceanographic Data in Lutzow-Holm Bay from July 1998 to December 1998 (JARE-39)
  Shigeru AOKI; Gen HASHIDA, JARE data reports. Oceanography = JARE data reports. Oceanography, 22, 1, 18, Mar. 2001
  English
• 南極域の海面変動と地殻変動-観測の現状と課題-
  青木茂, 月刊地球, 35, 149, 156, 2001
• Changes of Climate System in the Southern Ocean
  AOKI Shigeru, Journal of the Japan Institute of Energy, 79, 11, 1050, 1053, Nov. 2000
  日本エネルギ-学会, Japanese
• 衛星観測データに基づく西部北太平洋の中規模擾乱の研究
  青木茂; 今脇資郎, 九州大学応用力学研究所所報, 76, 103, 122, Sep. 1994
• 海面高度計データと現場海洋観測によるジオイド・モデルの改良
  市川香; 青木茂; 今脇資郎, 月刊地球, 186, 616, 621, Jan. 1994
• 衛星海面高度計と放射温度計で検出された黒潮続流の擾乱
  青木茂; 今脇資郎; 市川香, 九州大学応用力学研究所所報, 75, 47, 67, May 1993
• Westward propagation of sea surface anomalies in the western North Pacific as seen by the altimeter and radiometer
  Aoki, S; S. Imawaki; K. Ichikawa, Proceedings of the PORSEC-'92 in Okinawa, 273, 278, Aug. 1992

• 海の温暖化 : 変わりゆく海と人間活動の影響
  日本海洋学会, 第2.3.1節
  朝倉書店, Jul. 2017, 9784254161304, viii, 154p, 巻頭図版 [8] p, Japanese, [Contributor]
• 低温環境の科学事典
  青木茂, 第5章、第9章
  朝倉書店, Jul. 2016, 9784254963922, 1 online resource (xii, 411p, 図版 [8] p), Japanese, [Contributor]
• Handbook of low temperature science
  北海道大学低温科学研究所
  丸善出版, Oct. 2015, 9784621089644, xvii, 383p, Japanese, [Contributor]
• 地球温暖化 : そのメカニズムと不確実性
  日本気象学会地球環境問題委員会; 日本気象学会, 6.6章、6.7章
  朝倉書店, Dec. 2014, 9784254161267, iv, 162p, 図版 [8] p, Japanese, [Contributor]
• 南極海ダイナミクスをめぐる地球の不思議
  青木 茂
  シーアンドアール研究所, Jun. 2013, 9784863547162, 255p, Japanese
• 南極海－氷の海の生態系－
  青木茂, 第4章 ロス海で環境異変は起きているのか？
  東海大学出版会, Jan. 2013, 9784486018896, [Contributor]

• Oceanographic and geophysical observations off Sabrina Coast, East Antarctica, in 2019/2020
  S.Aoki; T.Tamura; Y.Nakayama; K.Ono; P.Wongpan; K.Yamazaki; T.Itaki; Y.Tokuda; S.Sasaki; D.Hirano; Y.Aoyama
  JpGU-AGU 2020, 13 Jul. 2020
  [Invited]
• Roles of warm and cold sea water pumps along the coast of East Antarctica
  Shigeru Aoki
  The 1st GRAntarctic International Symposium, 03 Dec. 2018
  [Invited]
• 南大洋における大気・海洋結合系の長期変動に関する観測的研究
  青木茂
  日本気象学会2017年度堀内賞受賞記念講演, 31 Oct. 2017
  [Invited]
• Research of Oceain-ice BOundary InTeraction adn Change around Antarctica (ROBOTICA): A strategy to explore ice-ocean interactions in East Antarctica
  Shigeru Aoki; Takeshi Tamura
  AOGS 2017, 11 Aug. 2017
  [Invited]
• 南極大陸棚域における淡水供給 -その空間分布と近年の変化-
  青木茂
  Japan Geoscience Union Meeting 2014, 02 May 2014
  [Invited]
• 近年の極域海洋変動と淡水循環の役割
  青木茂
  日本気象学会2011年春季大会シンポジウム「変動する地球気候の鍵‐南極・北極‐」, 20 May 2011
  [Invited]
• Recent freshening of the Antarctic Bottom Water in the Australian-Antarctic basin
  Shigeru Aoki
  EGU General Assembly 2007, 16 Apr. 2007
  [Invited]
• Interdecadal water-mass changes in the;Indian sector of the;Southern Ocean;heir impacts on;sea level rise
  Aoki, S; N.L. Bindoff; J.A. Church
  IAMAS 2005, 05 Aug. 2005
  [Invited]
• 南極海ダイナミクス -気候変動の鍵を握る南極底層水-
  青木茂
  第19回電熱大会, 25 Nov. 2004
  [Invited]
• Large-scale variations of sea level in the Southern Ocean
  Shigeru Aoki
  Asia Oceania Geoscience Society, 1st meeting, 05 Jul. 2004
  [Invited]
• Observations of annular variations of the Southern Ocean
  Shigeru Aoki
  Southern Ocean Week 2003, 10 Sep. 2003
  [Invited]
• Oceanic response to the Antarctic Oscillation
  Shigeru Aoki
  IUGG 2003, 02 Jul. 2003
  [Invited]

• 大学院共通授業科目（教育プログラム）：南極学, 2024年, 修士課程, 大学院共通科目
• 大学院共通授業科目（教育プログラム）：南極学, 2024年, 修士課程, 大学院共通科目
• 極域海洋学特論, 2024年, 修士課程, 環境科学院
• 大気海洋解析法特論, 2024年, 修士課程, 環境科学院
• 一般教育演習(ﾌﾚｯｼｭﾏﾝｾﾐﾅｰ), 2024年, 学士課程, 全学教育

• 海洋理工学会
• 日本海洋学会

• 雪や氷の融解は海洋の生物生産と二酸化炭素吸収にどのような影響を与えるのか？
  科学研究費助成事業
  01 Apr. 2025 - 31 Mar. 2029
  野村 大樹; 漢那 直也; 藤原 周; 青木 茂; 渡邉 英嗣
  日本学術振興会, 基盤研究(A), 北海道大学, 25H00679
• Antarctic ice sheet-ocean interactions in the era of global warming
  Grants-in-Aid for Scientific Research
  01 Apr. 2024 - 31 Mar. 2029
  平野 大輔; 溝端 浩平; 草原 和弥; 青木 茂; 小野 数也
  Japan Society for the Promotion of Science, Grant-in-Aid for Transformative Research Areas (A), National Institute of Polar Research, 24H02340
• Global Antarctic Science: connecting the chain of changing huge ice sheet and global environments
  Grants-in-Aid for Scientific Research
  01 Apr. 2024 - 31 Mar. 2029
  青木 茂
  Japan Society for the Promotion of Science, Grant-in-Aid for Transformative Research Areas (A), 24A402
• グローバル南極学：大変化する氷床と地球環境の連鎖をつなぐ
  科学研究費助成事業
  01 Apr. 2024 - 31 Mar. 2029
  青木 茂
  日本学術振興会, 学術変革領域研究(A), 北海道大学, 24H02339
• Resilience of the Antarctic Treaty System under the Anthropocene
  Grants-in-Aid for Scientific Research
  09 Jul. 2021 - 31 Mar. 2026
  柴田 明穂; 原田 尚美; 青木 茂; 木村 ひとみ; 稲垣 治; 來田 真依子
  本研究は、地球システムと人類社会システムが一体化する人新世の下での法学研究の先駆として、国際法制度のレジリエンスのあり方を、法学的知見と地球科学を中心とした自然科学的知見を連携させた社会自然科学的手法を駆使して分析し、新たな国際法学術体系を開拓する。そのモデルケースとして、人新世的痕跡が著しい南極地域を管理する南極条約体制(ATS)を題材として、地球科学からの知見を踏まえて100年先の南極の姿を構想しながら、ATSがそのレジリエンスを発揮し強化しうる国際法学的知見を提示する。
  
  
  採択通知後の約7ヶ月の本年度の研究は、引き続きコロナ禍の影響により海外研究者との研究交流はほぼストップし、オンラインによる研究メンバーとの意見交換と研究基盤形成（電子書籍等の購入）が中心となった。それら研究基盤を活用して、Oxford Handbook of International Environmental Lawに、国際法における信義誠実原則の機能を検討する論文を掲載することができた。コロナ禍においても、2021年11月に、南極研究科学委員会(SCAR)人文社会科学常設委員会の年次研究大会を神戸大学主催にてハイブリッド形式で開催し、本研究に関連する研究報告及び対面での意見交換が出来たことは有益であった。その成果としてZia Madani氏との共著論文を発表し、フェローとして研究支援してくれたオスロ大学ポスドクのYelena Yermakova氏とAntarctic Science誌における特別号企画を進められたことは重要である。
  Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Pioneering), Kobe University, 21K18124
• 氷床融解と深層循環の揺らぎをつなぐ－東南極亜寒帯循環から沿岸への輸送過程ー
  科学研究費助成事業
  05 Apr. 2021 - 31 Mar. 2026
  青木 茂; 草原 和弥; 平野 大輔; 松村 義正
  南極沿岸海洋は地球の海水位変動と海洋深層循環の鍵を握る。近年加速する南極氷床の流出・融解には、沿岸大陸棚上のホットスポットにおける熱輸送が重要な役割を果たしている。また、ホットスポットでの氷床融解は十年規模で変動し、沿岸コールドスポットから深海底へ沈み込む底層水に指摘されていた低塩化傾向はここ数年で逆転したことも明らかになりつつある。本研究課題では、南極氷床への熱供給メカニズムとその時間的な変動を解明するため、理解の遅れたウェッデル循環東端のコスモノート海を中心に、沿岸ホットスポットへの熱供給プロセスを現場船舶観測により明らかにする。海洋観測データの解析から、ここ30年ほどでトッテン沖では外洋の熱源が大陸棚に近づきつつあることが分かった。こうした熱の輸送経路として、沖合の時計回り循環と南極斜面流の重要性が明らかになった。またコスモノート海では、沖合から大陸棚上への熱供給パスの存在も分かった。我々が強みをもつ氷床融解水のトレーサーである酸素同位体比の国際共同観測網を主導し、氷床から海洋への融解水流出の実態とその十年規模変動を周極的に把握することを目指す。コールドスポットであるケープダンレー沖の解析では、夏季の表層高温と棚氷融解のリンクが明らかになった。数値実験の併用により、底層水形成のタイミングを送らせる働きをすることが見出され、将来の気候では表層水起源の南極氷床融解が海洋深層循環変化につながる可能性が示唆された。
  日本学術振興会, 基盤研究(A), 北海道大学, 21H04918
• Ice front processes and evolution mechanisms of calving glaciers -comparison between lake- and ocean terminating glaciers-
  Grants-in-Aid for Scientific Research
  01 Apr. 2020 - 31 Mar. 2025
  杉山 慎; 菅 浩伸; 古屋 正人; 青木 茂
  前年度に引き続き、2021年度もCOVID-19の影響を受けて、チリおよびアルゼンチンでの氷河観測が実施できない状況となった。そこで当初の計画を一部変更して、南極における野外観測を実施すると共に、人工衛星データを使った解析に力を入れた。その結果、南極のカービング氷河における重要な観測データが得られた他、既存のデータと衛星データの解析で論文出版と学会発表の成果が挙がった。
  (1) 野外観測： 2021年12月から2022年1月にかけて、南極ラングホブデ氷河で熱水掘削を含む観測を実施して、カービング氷河の底面観測に成功した。当初計画とは異なる地域、異なる手法による観測であるが、氷河氷床と海洋の相互作用解明につながる重要なデータが得られたと考えている。このほか、パタゴニアでの氷河・氷河湖・海洋調査に向けて、観測機器の調査と準備を行った。特にマルチビームソナーを使った観測に関して、専門業者への観測委託の検討が進んだ。
  (2) データ解析： 過去にチリ・グレイ氷河の前縁湖で測定した水温と流速データを解析して、氷河排水が氷河湖の水温季節変動に与える影響を明らかにした。また人工衛星データの解析によって、パタゴニア西部グレーベ湖で2020年に起きた急激な水位低下を発見した。詳しい解析の結果、この現象が近年では世界最大の氷河湖排水イベントであることが判明した。
  (3) 論文出版・学会発表：グレイ湖で測定した通年の水温変化をNature Communications誌に出版した他、氷河湖排水イベントをCommunications Earth & Environment誌に投稿中。COVID-19の影響で海外における学会発表は困難となり、国内での学会で成果を発表した。
  (4) 研究会合：10月にオスロ大学の研究者とオンラインでワークショップを開催した他、研究チームでの小規模な会合を適宜開催した。
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 20H00186
• Challenges for unexplored frontiers
  Grants-in-Aid for Scientific Research
  30 Jun. 2017 - 31 Mar. 2022
  野木 義史; 吉田 弘; 沖野 郷子; 巻 俊宏; 青山 雄一; 青木 茂; 末吉 哲雄; 田村 岳史
  本研究課題は、ロボット技術等の無人観測技術を、未探査領域である南極沿岸の海氷域と沿岸域に適用することで、新たなデータ取得を目指すものである。
  2019年度に、全体の会合を3回(2019年4/25, 10/10および2020年3/30(TV会議))開催し、現況や今後の方針等について議論した。また、AUV(Autonomous Underwater Vehicle)の専門的な検討を行うサブワーキンググループの会合も適宜実施し、AUV試験および試験結果に基づく改良点等の検討を行った。以下、2019年度に実施した概要を示す。
  前年度にAUVのほぼ全体的な組み上げを終了したAUVの試験を中心に実施し、調整や修正等を進めた。水槽実験や実際の海での試験に加え、特に冬期の北海道紋別港において、氷下海洋域での試験を行い、修正および調整を実施し、今後の改良点を整理した。さらにAUV回収のために、小型の遠隔操縦ロボット（ROV）の基本的な組立を実施、回収機構の設計を行った。南極沿岸浅海域海底地形調査用の小型ROVも基本的な組立を行い、水槽等で試験を行うい、さらに北海道サロマ湖において氷下での試験観測を実施し、概ね良好な結果を得た。また、AUV探査を行う予定である南極周辺の既存海底地形データの収集と整理を継続するとともに、AUV搭載マルチビーム測深機データの解析手法の検討を行った。
  南極ケープダンレー沖に設置した時系列データを衛星回線で送信する係留式ブイシステムについては回収を行った。一部システムに不具合等があり、原因解明を進めている。
  大陸域での観測では、固定翼・回転翼UAVを用い、昭和基地上空での空撮データを実施し、これまでのデータとともに昭和基地の表面地形図を作成および精度評価を継続した。さらに、固体班と連携し、積雪による地殻変動や重力変化の評価も継続した。また、氷河・棚氷の融解量把握のため白瀬氷河上において、氷河氷厚レーダーApRES(Autonomous phase-sensitive Radio-Echo Sounder) の観測も継続した。
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), National Institute of Polar Research, 17H06322
• Direct estimation of glacial ice meltwater discharge onto the Antarctic continental shelf using oxygen isotope measurement
  Grants-in-Aid for Scientific Research
  01 Apr. 2017 - 31 Mar. 2022
  Aoki Shigeru
  To investigate the effect of Antarctic glacial melt on the global sea level rise and overturning circulation, we established an international observational array of oxygen isotope ratio, a special tracer which is indispensable in estimating the freshwater sources, and examined glacial meltwater fraction directly in the surrounding ocean. We identified regions of high meltwater fraction. Off Adelie Land Coast we detected an increase of meltwater fraction after the calving event of the glacial tongue after 2010. After mid-2010s, we observed a reversal of the long-term freshening tendency of the bottom layer in the Australian-Antarctic Basin, which could be attributed to a decrease in meltwater discharge in the West Antarctica. We detected poleward shift of the overall oceanic structure over the recent three decades in the same basin, which contributed to a comprehensive understanding of the spatio-temporal changes of the circum-Antarctic shelf ocean.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 17H01615
• Integrated bio-physical study of multi-decadal variability of Antarctic land-fast sea ice breakup
  Grants-in-Aid for Scientific Research
  09 Nov. 2018 - 31 Mar. 2021
  青木 茂; WONGPAN PAT
  沿岸域に発達する定着海氷は極域の熱や物質循環に重要な役割をもつ。特に南極域では、氷河・氷床の流動を抑制する働きや生態系の生息環境の維持など、海洋海氷-氷床相互作用における重要な役割が近年注目を集めており、その物理・生物学的な特性の把握が望まれている。本研究では、これまで申請者がロス海現場観測に基づき開発した放射計による海氷厚および海氷中植物存在量の定式化をベースに、これを他の氷海域に適用して比較検討することで、より汎用性のある氷厚や生物生産量の定式化をめざす。まず、この観測に使用する光学系測器を中心とした観測システムを構築する。これらをもちいて現場海氷でもちいることで実際のスペクトル分布をうると同時に、他の直接的観測手法をもちいて実際の海氷の氷厚・積雪と植物存在量を同時に測定し、これらを比較することで、この関係性の定式化を目指す。
  本研究では、光学観測により海氷の物理―生物特性を測定する現場観測システムを構築し、このシステムを北海道サロマ湖定着氷域での集中海氷観測に適用した。これにより、海氷下連続スペクトル測定で正規化したスペクトル変化指数とアイスアルジーの生物量との関係を求めた。物理パラメータと生物量との間には一定の関係性が得られたが、その関係性はこれまで極域において先行研究が求めたものとは異なることが分かった。また、同観測システムを南極リュツォホルム湾およびトッテン氷河沖海域の多年氷域において運用し、サロマ湖で行った観測と同様にして物理パラメータと生物量との関係性を調べた。この結果をこれまでの他の定着氷域で得られた結果と統合することで、グローバルに適用可能な定式化を行った。加えて、南極リュツオホルム湾定着氷域でこれまで実施されてきた観測成果に基づき、十年規模変動の実態と植物存在量との変化の関係についての関係性を議論した。
  Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 18F18794
• Thermohaline and material circulation originating from coastal polynyas
  Grants-in-Aid for Scientific Research
  01 Apr. 2017 - 31 Mar. 2020
  OHSHIMA Keiichiro
  In the Antarctic, Arctic, and Okhotsk coastal polynyas, underwater frazil ice formation occurs down to a depth of ～100m under strong cooling, revealed by the detailed analysis of mooring data. This active underwater frazil ice formation results in much higher ice production than previously thought. In such polynyas, winter mixing often reaches to the ocean bottom. Thus, the bottom sediments dispersed by the strong bottom current can be brought up to near the surface and finally incorporated into sea ice (suspension freezing). This process is a possible mechanism of iron supply to sea ice, which melts in spring and causes phytoplankton bloom. We have developed a new algorithm of satellite passive microwave for detection of frazil ice and estimation of thin ice thickness, using the mooring data as validation data. This provides better estimation of sea ice production for global coastal polynyas, linked with deep/intermediate water formation.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 17H01157
• Development of high-buoyancy real-time monitoring float system in ice-covered oceans
  Grants-in-Aid for Scientific Research
  01 Apr. 2016 - 31 Mar. 2019
  Aoki Shigeru; ONO kazuya
  To develop a new autonomous profiler float to realize a time-series observation of water column in sea-ice covered continental shelf regions, we designed the system and investigated the operational details under high-current environment. A tethered-type float, which is capable of higher buoyancy, was designed, and it turned out to be significantly large for a realistic operational circumstance. Experimental operation by a tethered float with weaker buoyancy was conducted and successfully obtained profiles for more than 8 months. Although current speed was not large during the experiment, profiling completion rate was less than 50%, which shows an existence of limitation factor other than horizontal current intensity. Instead, a winch-driven float was introduced and an experiment was successfully started. With further comparisons among different realization, efficient monitoring of ice-covered ocean is expected.
  Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 16K12574
• Basic research on the prediction of changing for the Deep Global Circulation related with warming and freshening of Antarctic Bottom Water
  Grants-in-Aid for Scientific Research
  01 Apr. 2015 - 31 Mar. 2019
  KITADE YUJIRO; Azevedo Matheus; WATANABE Kazuho; SHIMADA Keishi
  As a result of Global warming, warming and freshening of the Antarctic Bottom Water (AABW) has been observed around Antarctica in recent years. In this study, we conducted basic research aiming to elucidate the mechanism by which the AABW is altered, and to clarify how the deep general circulation changes in the future. Ocean observation in the Southern Ocean along 110E and deployment and recovery of long-term moorings were continuously carried out for about one month in January every year for four years. As a result, we clarified the seasonal variation characteristics of intrusion depth in the formation of AABW and the main mechanism of material transport in the meridional direction. Furthermore, the influence of Antarctic ice sheet molten water on the alteration of AABW was evaluated. In addition, as a monitoring technique of medium-scale eddy that contribute as a key to meridional circulation, a correction algorithm was developed for satellite sea level data in the sea ice area.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Tokyo University of Marine Science and Technology, 15H01726
• Quantifying and investigating the causes of freshwater content change in the Southern Ocean overturning
  Grants-in-Aid for Scientific Research
  01 Apr. 2013 - 31 Mar. 2017
  AOKI Shigeru
  The Antarctic continental shelf is an important region in that it provides very dense water, which is one of the sources of Antarctic Bottom Water (AABW) that fills the global abyssal ocean. Recently freshening of AABW is reported and the causes are suspected to be on the Antarctic margin. This study aims to clarify the changes in oceanic properties in the Antarctic margin, especially based on in-situ hydrographic surveys including a noble tracer to detect continental ice melt component. For the Ross Sea shelf, the observed freshening corresponded to the basal warming in the West Antarctic shelf. For Adelie Depression off Adelie Land coast, both sea ice production and land-ice melt could change the shelf water properties, which can affect the properties of bottom water. Hence it was proposed that ice condition changes can affect the overturning circulation originated in the south.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 25281001
• A new picture of Antarctic Bottom Water and deep water circulation, linked with sea-ice production
  Grants-in-Aid for Scientific Research
  01 Apr. 2013 - 31 Mar. 2017
  OHSHIMA KEIICHIRO; USHIO SHUKI; TAMURA TAKESHI; TAKAHASHI AKINORI; NIHASHI SOHEY; FRASER ALEXANDER; WILLIAMS GUY; SATO TATSURU
  Formation of Antarctic Bottom Water (AABW) caused by high sea-ice production in coastal polynyas is detailed mainly for the East Antarctica. For the Cape Darnley polynya, the second highest ice production area in the Southern Ocean, the high ice production process through underwater frazil ice formation, and mixing/modification processes of dense water into AABW are clarified by mooring observations. For the Mertz polynya, which was the third ice production area, the ice production has decreased by as much as 50%, due to the glacier tongue calving, resulting in a significant decrease in AABW production. Formation of AABW is also suggested around the polynyas in Prydz Bay and Vincennes Bay in the East Antarctica. The balance between the polynya ice production (positive effect) and melting ice shelves (negative effect) is likely a key factor for the AABW formation.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 25241001
• Development of real-time monitoring buoy system of ocean environment in ice-covered regions
  Grants-in-Aid for Scientific Research
  01 Apr. 2013 - 31 Mar. 2016
  Aoki Shigeru; ONO Kazuya; ICHIKAWA Masaaki
  Based on state-of-the-art technologies like buoyancy control and satellite communication, this study aims to develop a tethered-buoy system for monitoring vertical profiles of oceanic environmental variables, which can be available in the ice-covered oceans. Field experiments of a prototype buoy were conducted for the total period of seven months off Shiretoko, Okhotsk Sea. The sensor buoy worked successfully for the programmed operations such as ascending/descending motions, controlling parking depths, data transfer through satellite system, endurance over half year period, and stop ascending near the surface in the ice covered condition. Current measurements clarified the limit of ambient current speed that allows a buoy to ascend to the surface. With these conditions surveyed and confirmed, we have established the technological basis for further variable conditions in the real ice oceans.
  Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, 25550002
• A basic study on evaluation of effects on the global deep circulation caused by freshening of Antarctic surface water
  Grants-in-Aid for Scientific Research
  01 Apr. 2011 - 31 Mar. 2015
  KITADE YUJIRO; TAMURA Takeshi; MIZOBATA Kohei; SHIMADA Keishi
  Freshening of Antarctic Bottom Water (AABW) associated with freshening of sea surface water has been reported in recent years. In order to evaluate the effects of freshening of AABW to the Global deep circulation, hydrographic observations, long term mooring observations and turbulence measurements were carried out around 110 E and 140 E in January of 2012 to 2015. We found Bottom Water originating from the Vincennes Bay Polynya (VBBW) in the first time. Our observation also showed that the VBBW has spread into the upper part of AABW in Australia-Antarctica Basin. Freshening of Bottom water was also indicated off the Vincennes Bay region. Especially, the data obtained in January of 2014 showed that the VBBW has a potential to sink down to the ocean floor when the water density of surrounding AABW was reduced by freshening and warming.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo University of Marine Science and Technology, 23310003
• Vertically-Coupled Variability in the Atmosphere, Ocean and Cryosphere Associated with the Asian Monsoon
  Grants-in-Aid for Scientific Research
  01 Apr. 2010 - 31 Mar. 2015
  NAKAMURA HISASHI; AOKI Shigeru; YUKIMOTO Seiji; TAKAYA Koutarou; MIYAMA Toru; KOMORI Nobumasa; YOSHIDA Akira; ENOMOTO Takeshi; SANPE Takeaki; KAMAHORI Hirotaka; TAGUCHI Bunmei; MIZUTA Ryo; MURASAKI Kazuyo; KOSAKA Yu; NISHII Kazuaki
  Over the last five years, the “Hot Spot Project” on extratropical air-sea interaction has conducted comprehensive research, providing a number of pieces of evidence that extratropical ocean, especially the warm Kuroshio and its Extension east of Japan and an associated frontal sea-surface temperature gradient with the cool Oyashio, can actively influence the overlying atmosphere. One of the main focuses of this group (A03-8) is the East Asian winter monsoon variability, which we find to be a manifestation of modulated seasonal evolution of planetary waves. The particular tropospheric blocking anticyclone that acts to enhance the monsoon is found to cool the Arctic stratosphere. We also demonstrate that decadal variability of the oceanic frontal zone east of Japan can not only modulate the boundary layer locally but also force a basin-scale atmospheric anomaly.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), The University of Tokyo, 22106009
• Is the region off Cape Darnley a main source of Antarctic Bottom Water?
  Grants-in-Aid for Scientific Research
  01 Apr. 2011 - 31 Mar. 2014
  FUKAMACHI Yasushi; AOKI Shigeru; MATSUMURA Yoshimasa; SHIMIZU Daisuke
  Combining time-series oceanic data obtained by moorings off the Cape Darnley in the Indian Sector of the Southern Ocean during 2008-09 with concurrent sea-ice data obtained by satellite remote sensing and hydrographic data obtained by instrumented seals, we have quantitatively shown that this region is the one of the main sources of Antarctic Bottom Water (AABW) due to intense sea-ice production in a coastal polynya. Namely, this region is the fourth AABW source region after the Weddell and Ross Seas and the region off Adélie Land. Unlike in the other three source regions, this region is the main AABW source solely due to intense sea-ice production without any of large continental shelf, ice shelf, and large depression.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 23340135
• Estimations of freshening of Antarctic Bottom Water by international observation network and effect of glacial melt water
  Grants-in-Aid for Scientific Research
  2009 - 2012
  AOKI Shigeru; FUKAMACHI Yasushi; SHIMADA Keishi
  We established an international ocean observation network in the Australian-Antarctic Basin, Southern Ocean, with implementing stable oxygen isotope measurements as the standard method and compared the results with the previous hydrographic observations. Freshening tendency of the Antarctic Bottom Water in this basin was estimated. Analysis revealed that the major cause of this freshening is the freshening of the bottom water, flowing into this basin from the east, and its reduction of the flow rate. With this observation network, the baseline structure of stable oxygen isotope was constructed to infer causes of future oceanic change.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 21310002
• Global mapping and monitoring of sea ice production
  Grants-in-Aid for Scientific Research
  2008 - 2012
  OHSHIMA Keiichiro; EBUCHI Naoto; AOKI Shigeru; FUKAMACHI Yasushi; TOYOTA Takenobu; MATSUMURA Yoshimasa; KITADE Yujiro; TATEYAMA Kazutaka; NIHASHI Sohey; ONO Kazuya; ENOMOTO Hiroyuki; KIMURA Noriaki; TAMURA Takeshi
  Saline water rejected during sea ice formation drive the global overturning circulation. We have developed an algorithm to estimate and provide global mapping of sea ice production from satellite data for the first time. High ice production process in coastal polynyas has been clarified by mooring observations with validation of the algorithm. We have revealed that the region off Cape Darnley is the missing formation area of Antarctic Bottom Water with the second highest ice production in the Antarctica. We have also clarified the strong linkage between variabilities of sea ice production and bottom/intermediate water in the Antarctic Ocean and Okhotsk Sea and suggested weakening of the overturning in these oceans.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (S), Hokkaido University, 20221001
• 斜面下降流による南極底層水の混合過程の研究
  科学研究費助成事業
  2007 - 2009
  青木 茂; WILLIAMS Guv Darvall; WILLIAMS Guy Darvall
  南極底層水は世界で最も高密度の水塊であり、深層大循環の主要な構成要素である。南極底層水は、主として沿岸陸棚域での冷却・海氷生成により生じた高密度陸棚水が、沖側の高温高塩分水を取り込みつつ陸棚斜面を流れ下ることで形成される。オーストラリア・南極海盆では、ロス海から西向きに流れてきた底層水に対して、アデリー海谷上を中心とするポリニア起源の高密度陸棚水が陸棚斜面上を下降して加わることによって、低温・低塩の底層水が生じると考えられてきた。このアデリーランド沖における斜面下降流の詳細な特性を把握するため、2001年1月と2004年10月に実施された船舶観測のデータを解析した。その結果、従来言われていたアデリー海谷からの下降流に加えて、より東側に位置するメルツ海谷からの二次的な下降流の存在が新たに明らかになった。この下降流はメルツ海谷上の低塩陸棚水に起因すると考えられる。ただし、底層水の水塊変質に及ぼす影響はアデリー海谷からの下降流に比べて小さい。1998年の係留系の連続データの解析とあわせて、主として冬季の下降流イベントにより、ロス海に起因するやや高温な性質が低温側へ断続的に変質することが分かった。これらにより、アデリー海谷より上流側のメルツ海谷からの下降流も南極底層水の低温・低塩化に関与していることが示された。このメルツ海谷上の高密度水形成の原因を調べるため、海氷生産の役割について検討した。人工衛星観測に基づく海氷生成量との比較から、メルツポリニアでの海氷生産は、係留データから見積もられる海水の密度との間に強い相関をもつことが分かった。人工衛星観測の結果は、マックロバートソンランド沖など東南極沿岸の随所でメルツポリニアに匹敵する海氷生産量を示している。このことは、より広域にわたって海洋底層まで達する下降流が生じている可能性を示唆するものである。
  日本学術振興会, 特別研究員奨励費, 北海道大学, 07F07772
• Assessment of freshening of Antarctic Bottom Waters andchanges in fresh water cycle by stable oxygen isotope analysis
  Grants-in-Aid for Scientific Research
  2005 - 2008
  AOKI Shigeru; TOYOTA Takenobu
  南極海沿岸の四割に及ぶ領域で南極底層水・沿岸陸棚水の特性変化の実態を把握し、あわせて酸素同位体比解析のための資料の収集とそれによる変動原因の考察を行った。南極底層水は全般的に低塩化しつつある。ロス海では特に顕著で、陸棚水の低塩化と関連している可能性があるが、酸素同位体比解析により氷床融解の影響が示唆された。酸素同位体比は底層水の生成源の推定にも有効であった。インド洋区における起源淡水として降雪と陸氷の分析を実施したところ、平均的には両者は十分区別可能で、本手法の有効性が示された。
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 17510001
• Quantitative evaluations of ocean circulation and meridional themohaline transport in the Indian sector of Antarctic
  Grants-in-Aid for Scientific Research
  2005 - 2007
  WAKATSUCHI Masaaki; OHSHIMA Keiichiro; AOKI Shigeru; FUKAMACHI Yasushi; USHIO Shuki
  The purpose of this study is to make an analysis of our observational data in which the seasonal variability of volume transport for the northward flowing Antarctic Bottom Water in the Indian sector of the Antarctic could be successfully obtained for the first time. We have done the deployment of the current-mooring systems at 8 stations off the southeastern coast of the Kerguelen Plateau for two years from February 2003 to January 2005, as an international joint project together with CSIRO in Australia. Our primary data analyses have shown that this region has completely reverse current direction over the continental shelf slope and the far offshore; the former is northwestward flow while the latter is southeastward flow. Therefore, the water circulation system in this region is approximately composed of the northward flow as a western boundary current and southward flow due to the cyclonic recirculation.
  In this study, we have also derived the sea-ice thickness distribution in the coastal polynyas where are the formation areas of the Antarctic Bottom Water, using the SSMI microwave data. From the data analyses and heat-budget calculation, we also have successfully made the mapping of the amount of sea-ice production in the coastal polynyas. According to our study, the area of the largest amount of sea-ice production in the Antarctic is Ross Sea. However, the amount of the sea-ice production in the coastal polynyas of the Ross Sea decreases about 30% during the period from 1990's to 2000's; this may lead to the recent trend of the freshening of the Antarctic Bottom Water.
  Although we did not yet make all the data analyses, we will propose water circulation system in the Indian Ocean sector of the Antarctic quantitatively, in the nearfuture.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 17340138
• Validation of the GRACE-derived gravity variations in the Antarctic region
  Grants-in-Aid for Scientific Research
  2004 - 2006
  SHIBUYA Kazou; TANIGUCHI Makoto; AOKI Shigeru; FUKUDA Yoichi
  Our research aims at detecting gravity variations related with atmosphere-ocean-ice sheet change in the Antarctic region, and interpreting GRACE-satellite derived gravity variations together with the ground-truth geodetic validation data. From the analysis of 1999-2003 VLBI epoch campaign data, crustal uplift rate at Syowa Station was estimated as 4.6±2.2 mm/yr (Fukuzaki et al., 2005). This value is close to the DORIS result of 3.6±0.2 mm/yr by Amalvict et al. (2007), but is somewhat larger than the GPS result (1.4±0.2 mm/yr ; Ohzono et al., 2006) observed in the outcrop area of Lutzow-Holm Bay. The repeated absolute gravity measurements at Syowa Station revealed gravity decrease of-0.27 μGal/yr (Fukuda et al., 2006), and these space geodesy and precise gravimetry data are key factors to constrain glacial isostatic adjustment model as indicated by Makinen et al. (2007). Konishi et al. (2007) treated 17 years' onboard Shirase ship-gravimeter data with a unified drift correction model, and the obtained gravity anomalies will be used to improve static regional gravity field by joint Japan-Germany airborne geophysics surveys. This in turn will give us more precise and detailed dynamic gravity variations. As for new devices, OBPs deployed at (66°51'S, 37°49'E, 4600m sea depth) recorded sea-level change associated with the tsunami from the 2004 December 26 Sumatra Earthquake, and its loading effect to the SG and the STS was estimated by Nawa et al. (2007). It was shown that the residual OBP sea-level amplitudes after subtraction of tidal constituents have variations which are in phase with the GRACE monthly gravity variations. The seepage meter installed at the sea bottom of 800m in Lutzow-Holm Bay by JARE-46 recorded the value of 10^<-8> to 10^<-6> m/s, indicating the value of similar magnitude obtained in mid-latitudes. These two devices showed effectiveness of applicability in understanding water mass variations in the Antarctic region.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), National Institute of Polar Research, 16310015
• 海洋の南極振動とその気候変動における役割の解明
  科学研究費助成事業
  2003 - 2004
  青木 茂
  南半球の大気変動では、大気再解析データや大気-海洋結合モデルの結果から、南極大陸上と低緯度側とが逆位相で変動する南極振動(AAO)モードが卓越していることが明らかになってきた。こうした大気変動は数十日規模から数十年規模にわたって卓越している。南極海洋においても、これに対応した大規模な変動の存在が予想される。
  季節内周期帯においては、南極沿岸の水位がコヒーレントに変動することが示された。南極振動の指標であるAAOインデックスと沿岸水位変動は、季節内変動の振幅がともに冬に強い傾向を示す。一方、人工衛星海面高度計により求めた外洋域での水位変動については、AAOインデックスに対する回帰係数は沿岸における値に比べて一桁小さく、応答が南極沿岸域に集中していることを示している。九州大学応用力学研究所と共同で行った再解析データ(ERA40)を用いたモデル実験やGCM(ECCO)によって再現された季節内順圧変動を解析すると、南極振動に対応して、沿岸から水深3000m程度の陸棚斜面上まで同期したコヒーレントな変動が良く再現されていることが分かった。この変動の位相は沿岸で実際に観測された海水位変動のものと一致し、順圧応答の卓越性を示している。
  次いで十年規模以上の周期帯について、主として日本南極観測のデータに基づいて、インド洋区における水塊変動および力学的高度変動を調べた。亜南極前線以北では表層等密度面上において低塩・低温化傾向が観測された。これは気温の上昇や降水の増加と調和的であると同時に、西風の強化による高緯度からの低塩分水の輸送とも整合的である。この特徴が周極的であるとすれば、観測されているここ20-30年間におけるAAOの強化が関係している可能性が考えられる。今後は現象の周極性を確認すると同時に、底層における水塊変化や大陸斜面域における水塊混合過程とその径年的変化の影響を調べる必要がある。
  日本学術振興会, 若手研究(B), 北海道大学, 15710017
• Clarification of Antarctic Bottom Water circulation in the Indian sector of Antarctic, particularly direct observation of its meridionall volume transport
  Grants-in-Aid for Scientific Research
  2002 - 2004
  WAKATSUCHI Masaaki; OSHIMA Keiichiro; AOKI Shigeru; NAGASHIMA Hideki; USHIO Shuki; WATANABE Shunichi
  The Southern Ocean plays an important role on global climate through the directl heat and mass connections with Pacific Ocean, Atlantic Ocean and Indian Ocean. Especially, it is well known that the Antarctic Ocean is the largest seasonal sea ice zone in the world and produces the Antarctic Bottom Water (AABW) which is one of sources for general deep ocean circulation. In spite of its importance in earth sciences, there is very few direct observation for the meridional volume transport of AABW and its seasonal variations. It is widely believed that the AABW is produced in three coastal regions in the Weddell Sea, Ross Sea and off the Adelie coast. Recently, observational plans on the AABW formation are preceeded to have in the Weddell and Ross Seas by US and Europian oceanographers.
  The purpose of this study is to quantitatively evaluate the meridional volume transport of AABW (hereafter called to the Adelie AABW) which should be produced in the coastal polynyas off the Adelie coast by direct observations through a joint program with CSIRO in Australia. A recent result of numerical simulation on global ocean circulation suggests that the Adelie AABW may be the important source of Pacific and Indian Ocean deep water. We have deployed mooring systems with about 30 current meters and CT meters at 8 stations east of the Kerguelen Plateau for two years from February 2003 to February 2005, to observe the meridional volume transport of Adelie AABW as a werstern boundary current and its seasonal variations. We could successfully recover all the current and CT instrument mooring systems. We have now numerous valuable data. Since we fortunately could obtain a new research fund on ou study of the Adelie AABW formation, we are planning to progress analyzes of numerous and valuable data and would like to evaluate the meridional heat and volume transport of the Adelie AABW and its seasonal variability quantitatively.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 14403006
• Study on long-term variability of Antarctic marine environments
  Grants-in-Aid for Scientific Research
  1999 - 2001
  FUKUCHI Mitsuo; HIRAWAKE Toru; AOKI Shigeru; ODATE Tsuneo; TANIGUCHI Akira; TANIMURA Atsushi
  Variability of Antarctic marine environments is thought to be greatly related to the global environmental change. The Japanese Antarctic Research Expedition (JARE) has been conducting the routine observations on marine environments in the Indian sector of the Antarctic Ocean. The present project focuses on the long-term variability of marine environments in this sector based on the data accumulated by the JARE observations as well as those by the foreign countries from this sector. We have firstly discovered the long-term tendency of increasing in water temperature in upper layer of the Indian sector. Also. the standing stock of surface phytoplankton fluctuated greatly year to year. Zooplankton variability was analyzed based on data collected by the CPR method (Continuous Plankton recorder). The CPR samplings were carried out jointly with the ANARE program (Australian National Antarctic Research Expedition) and is now accepted as a good method for long-term monitoring program among the international society. Variability of nutrient salts is an important component to link the physical and biological variability. Surface silicate concentration in the Indian sector distributes heterogeneously, namely silicate rich water and silicate poor water locate side by side. The pattern of heterogeneous distribution is closely related to the recently discovered phenomena of ACW (Antarctic Circumpolar Wave), which is thought to closely link to the atmospheric oscillation. In order to understand the relation between the long-term variability and ACW phenomena. the process oriented information is necessary. To acquire such information, the international joint program of time-series observation was carried out in 2001/2002 summer season. Four research vessels were employed to repeat the core measurements, which are important parameters to analyze the long-term variability. Full coverage of summer season from November to March was firstly accomplished. Throughout the process of data analysis of long-term variability as well as time series observation, the basis of international collaboration for the multi and inter disciplinary approach has been constructed. This fundamental structure is essential for furth er development of the long-term data analysis.
  Japan Society for the Promotion of Science, Grant-in-Aid for Special Purposes, National Institute of Polar Research, 11800009
• Generation of digital elevation model in remote locations using satellite SAR interferometry and the model evaluation
  Grants-in-Aid for Scientific Research
  1997 - 2000
  AOKI Shigeru; OZAWA Taku; SHIBUYA Kazuo
  The primary goal of this study is to generate a digital elevation model (DEM) using satellite SAR interferometry for remote regions where ground observations are difficult, and is to evaluate them with independent methods.
  A DEM of the ice sheets around Lutzow-Holm Bay, where the Japanese wintering station is located, was generated with the satellite SAR three-pass method. Comparisons with the state-of-the-art global DEM showed improvement in its accuracy up to an order, using ground observations including GPS results as references. On the other hand, a few problems in the generation process were clearly identified.
  To derive a groundling line precisely, which forms the boundary between grounded ice sheet and floating ice shelf, the SAR interferometry was applied to Baudouin Ice Shelf to the west of Lutzow-Holm Bay. The grounding line was clearly identified and tracked from the spatial difference in fringes. The derived vertical displacement was consistent with the one which was inferred from a ocean tide model with inverse barometer effect.
  To establish and evaluate the methods of ground observations for the rapidly moving objects, GPS observations were conducted between the points on fast sea ice and on ground rocks. Simultaneous observations confirmed that the GPS can detect the vertical displacement of sea ice in an accuracy of 1-2 cm.
  As above, this study established the availability of the SAR interferometry to DEM generation for remote locations. Combined application with the effective GPS ground observations will enable much precise monitoring of the whole ice-covered area.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), National Institute of Polar Research, 09640512
• Ocean and earth dynamics study by TOPEX/POSEIDON altimeter
  Grants-in-Aid for Scientific Research
  1996 - 1997
  IMAWAKI Shiro; KOBLINSKY C.J.; OOE Masatugu; KUBOTA Masahisa; KAWAMURA Hiroshi; FUKUDA Yoichi
  Micro-wave radar altimeters on board satellites can measure the sea surface hight globally with accuracy of a few centimeters, and are considered to be very useful for studies of dynamics both of the oceans and solid earth. In the present study, cooperative works between physical oceanographers and solid earth geophysicists have been intended. The program sent the Principal Investigator and nine Co-Investigators to TOPEX/POSEIDON Science Working Team meetings held in England in 1996 and in France in 1997, in order to exchange information about international satellite altimetry studies. Scientific meetings were held in Tokyo in 1996 and 1997, in order to discuss about altimetry data processing and analyzes. For those meetings, four scientists of Australia, the United States and France were invited in order to stimulate international cooperation. Through those activities, following results have been obtained : (1) A long time series of transport of the Kuroshio south of Japan was obtained by combined use of satellite altimetry data with in situ oceanographic data ; (2) Features of surface circulations of the whole North Pacific were also revealed through combined use of altimetry data with in situ oceanographic data ; (3) The scheme has been developed to assimilate the altimetrly data to numerical models of the oceans ; (4) A precise global tide model was obtained from altimetry data ; (5) A high-resolution global map of gravity anomaly was obtained through the release of altimetry data during the GEOSAT Geodetic Mission, which has been unclassified recently ; and (6) A high-precision geoid map was obtained for the seas around Japan by combined use of altimetry data with in situ gravity anomaly data.
  Japan Society for the Promotion of Science, Grant-in-Aid for international Scientific Research, KYUSHU UNIVERSITY, 08044094
• 衛星海面高度計データを用いた全球における絶対海面力学高度場と流速場の推定と評価
  科学研究費助成事業
  1996 - 1996
  青木 茂
  人工衛星海面高度計のデータから海面高度の時間変動成分の時系列を作成し、別に求めた海面力学高度の時間平均場と組み合わせることにより、全球における絶対的な海面力学高度場を求めた。平均海面高度場(海面流速場についても同様)として、気候学的な密度場に基づいて求めた平均場(以下、気候学平均場)と、最新のジオイドモデルを用いた平均場(以下、ポテンシャル平均場)を作成した。気候学平均場については、Teagueら(1991)の1000db準拠のもの、World Ocean Atlas94の1000db・2500db準拠のものを用い、ポテンシャル平均場についてはTOPEX/POSEIDON-JGM3モデルを用いた。時間平均場の精度を評価するため、海面高度の格子点データから求めた平均流速場について、ドリフタ-ブイの軌跡から求められた平均海面流速場との比較を行った。その東西流速については、南北20°C以内の低緯度域と南大洋において両者間の差が大きい。低緯度域では、気候学平均場を用いた方が差が小さい。地衡流を考えた場合、ジオイドの誤差の影響は低緯度ほど相対的に大きく現れる。南大洋では、東西流速についてはポテンシャル平均場の方が差が小さく、ポテンシャル平均場の方がよい精度を与える可能性を示唆している。また、気候学平均場についても、1000db準拠のものより2500db準拠のものの方が差が小さく、全球について一律の無流面を仮定することが適当でないことを示唆している。南大洋における流速場の性質を詳しく調べるため、3年間のアルゴスブイデータと絶対流速場との比較を行った。東向き流速については、系統的にドリフタ-ブイの方が非常に速い場合が多く、フロントに伴う強い流れが再現されていないことが分かる。現実の東西流速を十分に表現するためには、緯度方向に密な平均場の精度の向上が必要である。
  日本学術振興会, 奨励研究(A), 国立極地研究所, 08740382