The Tenth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Thu. 5 Dec. / 2F Auditorium , National Institute of Polar Researc

Daisuke Hirano

Hiroko Sasaki

Hiroto Murase

Kaihe Yamazaki

Koh Yoichiro

Kohei Mizobata

Masaaki Kiuchi

Masato Ito

Shigeru Aoki

Takeshi Tamura

National Institute of Polar Research Repository

  Offshore-origin warm water inflows toward Totten Ice Shelf, East Antarctica  Daisuke Hirano1, Kohei Mizobata2, Takeshi Tamura3, Masato Ito1, Kaihe Yamazaki1, Koh Yoichiro1, Masaaki Kiuchi4, Hiroto Murase2, Hiroko Sasaki5, Shigeru Aoki1 1Institute of Low Temperature Science, Hokkaido University 2Tokyo University of Marine Science and Technology, 3National Institute of Polar Research, 4Faculty of Fisheries Sciences, Hokkaido University, 5National Research Institute of Far Seas Fisheries    The Antarctic ice sheet is the largest freshwater reservoir on the Earth surface. Mass loss from the Antarctic ice sheet results directly in global sea-level rise and Southern Ocean freshening. Recent observational and modeling studies have demonstrated that ice shelf basal melting, resulting from the inflow of warm water onto the Antarctic continental shelf, plays a key role in the ice sheet’s mass balance. In recent decades, warm ocean-cryosphere interaction in the Amundsen and Bellingshausen Seas (ABS) has received a great deal of attention. In contrast, East Antarctic continental shelves are primarily occupied by “cold waters” (Schmidtko et al., 2014), with ice shelves typically having cold ice cavities. An exception is Totten Ice Shelf (TIS) which experiences the highest basal melt rates in East Antarctica (>10 m/yr) comparable with those for the ABS ice shelves. Although comprehensive hydrographic observations from ice front to continental shelf and slope regions are indispensable for understanding ice-ocean interaction beneath the TIS, so far, the observations in these regions are quite sparse. The only one observation has been done by Australia in January 2015 and has revealed relatively warm, modified CDW inflows into TIS cavity (Rintoul et al., 2016; Silvano et al., 2017).   In this talk, we show the characteristics of offshore-origin warm water distribution at the TIS ice front and continental slope regions, using the hydrographic data obtained by Icebreaker Shirase in March 2018 (59th Japanese Antarctic Research Expedition) and R/V Kaiyo-maru in February 2019 (multidisciplinary ecosystem survey in the eastern Indian sector of the Antarctic with a focus on Antarctic krill, Fisheries Agency). The offshore-origin modified Circumpolar Deep Water (mCDW, up to 0.3oC) is found in deep glacial troughs near the TIS ice front, which is ~0.7oC warmer than that observed at the almost same position in January 2015 (Rintoul et al., 2016). This suggests a seasonal or interannual variation in inflowing ocean heat flux into TIS cavity. Along the continental slope, warmer mCDW (>1oC) lies at subsurface layer (~500 dbar), and particularly warm cores (1.2-1.4oC) is found around the eastern limb of cyclonic eddies, indicating a possible role of cyclonic eddies on a poleward transport of offshore warm water. Various processes from offshore to ice front regions would consequently result in the variations in the ocean heat flux into TIS cavity (i.e., the magnitude of basal melting) with various time scales.    References Rintoul, S. R., et al. (2016), Ocean heat drives rapid basal melt of the Totten Ice Shelf, Sci Adv, 2(12), e1601610, doi:10.1126/sciadv.1601610. Schmidtko, S., K. J. Heywood, A. F. Thompson, & S. Aoki (2014), Multidecadal warming of Antarctic waters, Science, 346(6214), 1227-1231, doi:10.1126/science.1256117. Silvano, A., S. R. Rintoul, B. Pena-Molino, & G. D. Williams (2017), Distribution of water masses and meltwater on the continental shelf near the Totten and Moscow University ice shelves, Journal of Geophysical Research-Oceans, 122(3), 2050-2068, doi:10.1002/2016jc012115.  

Offshore-origin warm water inflows toward Totten Ice Shelf, East Antarctica

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Offshore-origin warm water inflows toward Totten Ice Shelf, East Antarctica

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