Publications by authors named "Sohey Nihashi"

2 Publications

  • Page 1 of 1

Estimation of sea-ice thickness and volume in the Sea of Okhotsk based on ICESat data.

Ann Glaciol 2018 Jul 5;59(76 Pt 2):101-111. Epub 2018 Apr 5.

Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo 060-0819, Japan.

Sea-ice thickness in the Sea of Okhotsk is estimated for 2004-2008 from ICESat derived freeboard under the assumption of hydrostatic balance. Total ice thickness including snow depth ( ) averaged over 2004-2008 is 95 cm. The interannual variability of is large; from 77.5 cm (2008) to 110.4 cm (2005). The mode of varies from 50-60 cm (2007 and 2008) to 70-80 cm (2005). Ice thickness derived from ICESat data is validated from a comparison with that observed by Electromagnetic Induction Instrument (EM) aboard the icebreaker near Hokkaido, Japan. Annual maps of reveal that the spatial distribution of is similar every year. Ice volume of 6.3 × 10 m is estimated from the ICESat derived and AMSR-E derived ice concentration. A comparison with ice area demonstrates that the ice volume cannot always be represented by the area solely, despite the fact that the area has been used as a proxy of the volume in the Sea of Okhotsk. The ice volume roughly corresponds to that of annual ice production in the major coastal polynyas estimated based on heat budget calculations. This also supports the validity of the estimation of sea-ice thickness and volume using ICESat data.
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July 2018

Evidence for ice-ocean albedo feedback in the Arctic Ocean shifting to a seasonal ice zone.

Sci Rep 2017 Aug 15;7(1):8170. Epub 2017 Aug 15.

International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, 99775-7340, USA.

Ice-albedo feedback due to the albedo contrast between water and ice is a major factor in seasonal sea ice retreat, and has received increasing attention with the Arctic Ocean shifting to a seasonal ice cover. However, quantitative evaluation of such feedbacks is still insufficient. Here we provide quantitative evidence that heat input through the open water fraction is the primary driver of seasonal and interannual variations in Arctic sea ice retreat. Analyses of satellite data (1979-2014) and a simplified ice-upper ocean coupled model reveal that divergent ice motion in the early melt season triggers large-scale feedback which subsequently amplifies summer sea ice anomalies. The magnitude of divergence controlling the feedback has doubled since 2000 due to a more mobile ice cover, which can partly explain the recent drastic ice reduction in the Arctic Ocean.
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August 2017