Researcher Database

Daisuke Hirano
Institute of Low Temperature Science Water and Material Cycles
Assistant Professor

Researcher Profile and Settings

Affiliation

  • Institute of Low Temperature Science Water and Material Cycles

Job Title

    Assistant Professor

URL

Research funding number

  • 30790977

Research Areas

  • Earth and planetary science / Meteorology/Physical oceanography/Hydrology

Association Memberships

  • American Geophysical Union   THE OCEANOGRAPHIC SOCIETY OF JAPAN   

Research Activities

Published Papers

  • Favorable conditions for suspension freezing in an Arctic coastal polynya
    Masato Ito, Kay I. Ohshima, Yasushi Fukamachi, Daisuke Hirano, Andrew Mahoney, Joshua Jones, Toru Takatsuka, Hajo Eicken
    Journal of Geophysical Research: Oceans 124 2019/12 [Refereed][Not invited]
     Research paper (scientific journal)
  • Hirano Daisuke, Fukamachi Yasushi, Ohshima Kay I, Watanabe Eiji, Mahoney Andrew R., Eicken Hajo, Itoh Motoyo, Simizu Daisuke, Iwamoto Katsushi, Jones Joshua, Takatsuka Toru, Kikuchi Takashi, Tamura Takeshi
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 123 (8) 5688 - 5705 2169-9275 2018/08 [Refereed][Not invited]
  • Ryosuke Makabe, Atsushi Tanimura, Takeshi Tamura, Daisuke Hirano, Keishi Shimada, Fuminori Hashihama, Mitsuo Fukuchi,
    Polar Science 12 25 - 33 1873-9652 2017/06 [Refereed][Not invited]
     Research paper (scientific journal)
  • Journal of Geophysical Research: Oceans 21699275 2016/01 [Refereed][Not invited]
     Research paper (scientific journal) 
    © 2016. American Geophysical Union. The nature of the Barrow Coastal Polynya (BCP), which forms episodically off the Alaska coast in winter, is examined using mooring data, atmospheric reanalysis data, and satellite-derived sea-ice concentration and production data. We focus on oceanographic conditions such as water mass distribution and ocean current structure beneath the BCP. Two moorings were deployed off Barrow, Alaska in the northeastern Chukchi Sea from August 2009 to July 2010. For sea-ice season from December to May, a characteristic sequence of five events associated with the BCP has been identified; (1) dominant northeasterly wind parallel to the Barrow Canyon, with an offshore component off Barrow, (2) high sea-ice production, (3) upwelling of warm and saline Atlantic Water beneath the BCP, (4) strong up-canyon shear flow associated with displaced density surfaces due to the upwelling, and (5) sudden suppression of ice growth. A baroclinic current structure, established after the upwelling, caused enhanced vertical shear and corresponding vertical mixing. The mixing event and open water formation occurred simultaneously, once sea-ice production had stopped. Thus, mixing events accompanied by ocean heat flux from the upwelled warm water into the surface layer played an important role in formation/maintenance of the open water area (i.e., sensible heat polynya). The transition from a latent to a sensible heat polynya is well reproduced by a high-resolution pan-Arctic ice-ocean model. We propose that the BCP, previously considered to be a latent heat polynya, is a wind-driven hybrid latent and sensible heat polynya, with both features caused by the same northeasterly wind.
  • Daisuke Hirano, Daisuke Hirano, Yujiro Kitade, Kay I. Ohshima, Yasushi Fukamachi
    Journal of Geophysical Research C: Oceans 120 910 - 922 21699275 2015/02 [Refereed][Not invited]
     
    © 2014. American Geophysical Union. All Rights Reserved. The mixing process associated with modified Shelf Water (mSW) overflows that eventually mix to form Cape Darnley Bottom Water (CDBW) was investigated by hydrographic and microstructure observations off the Cape Darnley Polynya (CDP), East Antarctica, in January 2009. Closely spaced microstructure observations revealed that mSW properties varied considerably within a distance of ∼4 km across the shelf edge. Near the bottom, the rate of turbulent kinetic energy dissipation was enhanced to values greater than 10-7 W kg-1, and the vertical scale of the bottom boundary layer (BBL) was on the order of 10 m. The observed BBL around the shelf edge was characterized by strong vertical mixing with turbulent eddy diffusivities of ∼O(10-3-10-2) m2 s-1. A geostrophically balanced density current, which resulted from the presence of mSW over the continental shelf, is considered the primary energy source for the turbulent mixing in the BBL. This turbulent mixing transforms the overflowing mSW through mixing with ambient water masses, specifically with the overlying modified Circumpolar Deep Water. The BBL is also thought to partly contribute to the gradual descent of mSW down the continental slope through bottom Ekman transport. We conclude that turbulent mixing, primarily caused by a density current, plays an important role in CDBW formation, by modifying the mSW overflowing from the CDP.
  • 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 6 235 - 240 17520894 2013/03 [Refereed][Not invited]
     
    The formation of Antarctic Bottom Water-the cold, dense water that occupies the abyssal layer of the global ocean-is a key process in global ocean circulation. This water mass is formed as dense shelf water sinks to depth. Three regions around Antarctica where this process takes place have been previously documented. The presence of another source has been identified in hydrographic and tracer data, although the site of formation is not well constrained. Here we document the formation of dense shelf water in the Cape Darnley polynya (65°-69°E) and its subsequent transformation into bottom water using data from moorings and instrumented elephant seals (Mirounga leonina). Unlike the previously identified sources of Antarctic Bottom Water, which require the presence of an ice shelf or a large storage volume, bottom water production at the Cape Darnley polynya is driven primarily by the flux of salt released by sea-ice formation. We estimate that about 0.3-0.7 × 106 m3 s-1 of dense shelf water produced by the Cape Darnley polynya is transformed into Antarctic Bottom Water. The transformation of this water mass, which we term Cape Darnley Bottom Water, accounts for 6-13% of the circumpolar total. Copyright © 2013 Macmillan Publishers Limited.
  • Kazuo Amakasu, Atsushi Ono, Daisuke Hirano, Masato Moteki, Takashi Ishimaru
    Polar Science 5 187 - 194 18739652 2011/08 [Not refereed][Not invited]
     
    From January to February 2008 the training research vessel TRV Umitaka Maru conducted a comprehensive oceanographic survey of the waters around the 140°E meridian off Adélie Land as part of the Collaborative East Antarctic Marine Census (CEAMARC) project. The acoustic component of this survey was conducted using a scientific echosounder operating at 38 and 70 kHz to estimate the distribution and density of Antarctic krill (Euphausia superba) and ice krill (E. crystallorophias). In addition, the relationship between the vertical distribution of Antarctic krill and the water temperature structure along the 140°E meridian was investigated. Antarctic krill were distributed in the waters of the continental slope at 65-66°S and the maximum value of the mean areal density ρ in 1 nautical mile (nmi) intervals was 4344 inds. m-2. Ice krill were distributed in the neritic waters of the continental shelf to the south of the 66°S and the maximum ρ in 1 nmi intervals was 23,669 inds. m-2. Along the 140°E meridian, Antarctic krill were mainly distributed at the water temperatures below 0.5 °C. Although they were mostly distributed shallower than approximately 100 m, dense aggregations at approximately 180-200 m were also observed, which coincided with a depression of the water temperature structure. © 2011 Elsevier B.V. and NIPR.
  • Philippe Koubbi, Philippe Koubbi, Percy Alexander Hulley, Patrice Pruvost, Pauline Henri, Pauline Henri, Jean Philippe Labat, Jean Philippe Labat, Victoria Wadley, Daisuke Hirano, Masato Moteki
    Polar Science 5 195 - 210 18739652 2011/08 [Refereed][Not invited]
     
    The pelagic fish community of the Dumont d'Urville Sea (East Antarctica) was investigated during the 2008 austral-summer using IYGPT (International Young Gadoid Pelagic Trawl) samples taken in different depth layers from the surface to 1000 m. The aim of this paper is to describe the mesopelagic fish community and its size distribution. The family Myctophidae dominated the mesopelagic ichthyofauna, while bathylagids were abundant in deeper hauls. Bathylagids. , Cyclothone spp., Gymnoscopelus opisthopterus, Electrona antarctica, Protomyctophum bolini, and Krefftichthys anderssoni were the most abundant taxa in the samples and showed size stratification with depth. Community and size structuring appear to be influenced by the hydrology and by the proximity of the continental margin, as well as a relationship to the circulation of the Modified Circumpolar Deep Water. © 2011 Elsevier B.V. and NIPR.
  • Atsushi Ono, Masato Moteki, Kazuo Amakasu, Ryoji Toda, Naho Horimoto, Daisuke Hirano, Takashi Ishimaru, Graham W. Hosie
    Polar Science 5 146 - 165 18739652 2011/08 [Refereed][Not invited]
     
    The distribution and community structure of euphausiids and the population structure of Euphausia superba were investigated mainly along 140°E off Adélie Land in the Indian Ocean sector of the Southern Ocean during the austral summers of 2003, 2005 and 2008. Euphausiids were collected from six discrete depth layers, primarily between 0 and 2000 m, using an RMT 8 net. Euphausia frigida and Euphausia triacantha mainly occurred north of the Southern Boundary of the Antarctic Circumpolar Current (SB) whereas E. superba was distributed south of the SB, and occurred abundantly in the continental slope area where Antarctic Winter Water was observed. E. frigida and E. triacantha occurred in the upper 200 m during the night whereas they were mainly found below 200 m during the daytime. Cluster analysis on stations suggested that the SB is an important biological boundary for euphausiid communities. The population structure of E. superba in 2003 was different from that of 2005 and 2008. While large mature individuals dominated in 2003, small immature krill (juveniles and subadult males) were more abundant in 2005 and 2008. Further sea-ice extension in the preceding winter in 2005 and 2008 likely provided favourable conditions for spawning and survival. A cluster analysis based on similarity of the maturity stages of E. superba revealed that mature males and gravid females (stage IIIC-E) were mainly distributed in the offshore area and mesopelagic zone, while juveniles and subadult males were found in the epipelagic zone of the continental slope area. Therefore, it is considered that E. superba migrates to the offshore area and mesopelagic zone as it grows. © 2011 Elsevier B.V. and NIPR.
  • Philippe Koubbi, Philippe Koubbi, Catherine Ozouf-Costaz, Anne Goarant, Anne Goarant, Masato Moteki, Percy Alexander Hulley, Romain Causse, Agnès Dettai, Guy Duhamel, Patrice Pruvost, Eric Tavernier, Alexandra L. Post, Robin J. Beaman, Stephen R. Rintoul, Toru Hirawake, Daisuke Hirano, Takashi Ishimaru, Martin Riddle, Graham Hosie
    Polar Science 4 115 - 133 18739652 2010/08 [Refereed][Not invited]
     
    Ecoregions are defined in terms of community structure as a function of abiotic or even anthropogenic forcing. They are meso-scale structures defined as the potential habitat of a species or the predicted communities geographic extent. We assume that they can be more easily defined for long-lived species, such as benthos or neritic fish, in the marine environment. Uncertainties exist for the pelagic realm because of its higher variability, plus little is known about the meso- and bathypelagic zones. A changing environment and modification of habitats will probably drive new communities from plankton to fish or top predators. We need baseline studies, such as those of the Census of Antarctic Marine Life, and databases like SCAR-MarBIN as tools for integrating all of these observations. Our objective is to understand the biodiversity patterns in the Southern Ocean and how these might change through time. © 2010 Elsevier B.V.
  • Daisuke Hirano, Yujiro Kitade, Hideki Nagashima, Masaji Matsuyama
    Journal of Oceanography 66 95 - 104 09168370 2010/01 [Refereed][Not invited]
     
    The strength of mixing due to turbulence in the Antarctic Slope Front (ASF) region was investigated using CTD (conductivity-temperature-depth profilers) observations and direct measurements of turbulence conducted off Adélie Land, East Antarctica along 140°E from the 12th-14th February, 2005. The strongest horizontal gradient of the ASF was located below 300 m depth near the 1000 m isobath. The turbulent measurements revealed that the energy dissipation rate frequently exceeded 10-8 Wkg-1 on the continental shelf and upper slope regions. Turbulent diffusivities near the shelf break were higher than 10-3 m2s-1. Near the ASF the average turbulent heat flux was 5.7 Wm-2 and 1.1 Wm-2 across the temperature minimum layer to 250 m and from 300 to 600 m, respectively. The distribution of the high dissipation rate was consistently explained by the characteristic curve of the M2 internal wave emanating from the shelf break and continental slope. The water mass observed in the ASF below 300 m in the continental slope comprised Modified Circumpolar Deep Water and low salinity Shelf Water originating from either the upper layer of the Adélie Depression or the Adélie Bank, and produced by boundary mixing near the shelf break. © Springer Science+Business Media B.V. 2010.

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