Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean: an eddy-resolving model study
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Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean: an eddy-resolving model study LI Qun1∗ , ZHANG Zhanhai1 , WU Huiding1,2 1 2
Polar Research Institute of China, State Oceanic Administration, Shanghai 200136, China National Marine Environmental Forecasting Center, State Oceanic Administration, Beijing 100081, China
Received 8 October 2011; accepted 3 May 2012 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2013
Abstract The dramatic decline of summer sea ice extent and thickness has been witnessed in the western Arctic Ocean in recent decades, which has motivated scientists to search for possible factors driving the sea ice variability. An eddy-resolving, ice-ocean coupled model covering the entire Arctic Ocean is implemented, with focus on the western Arctic Ocean. Special attention is paid to the summer Alaskan coastal current (ACC), which has a high temperature (up to 5◦ C or more) in the upper layer due to the solar radiation over the open water at the lower latitude. Downstream of the ACC after Barrow Point, a surface-intensified anticyclonic eddy is frequently generated and propagate towards the Canada Basin during the summer season when sea ice has retreated away from the coast. Such an eddy has a warm core, and its source is high-temperature ACC water. A typical warm-core eddy is traced. It is trapped just below summer sea ice melt water and has a thickness about 60 m. Temperature in the eddy core reaches 2–3◦ C, and most water inside the eddy has a temperature over 1◦ C. With a definition of the eddy boundary, an eddy heat is calculated, which can melt 1 600 km2 of 1 m thick sea ice under extreme conditions. Key words: eddy-resolving, anticyclonic eddy, sea ice, western Arctic Ocean, Alaskan coastal current Citation: Li Qun, Zhang Zhanhai, Wu Huiding. 2013. Interaction of an anticyclonic eddy with sea ice in the western Arctic Ocean: an eddy-resolving model study. Acta Oceanologica Sinica, 32(3): 54–62, doi: 10.1007/s13131-013-0289-1
in response to 0.5 W/m2 increases in AW ocean heat flux which implicated that AW warming helped precondition the polar ice cap for the extreme ice loss observed in recent years. On the other hand, heat contained in Pacific inflow from the Bering Strait has also strongly increased over recent decades (Woodgate et al., 2006). This has been speculated to play an important role in the decline of sea ice in the western Arctic Ocean. An observed flux increase between 2001 and 2004 was estimated to be capable of melting 640 000 km2 of 1 m thick ice, but fluxes in 2001 were the smallest (Woodgate et al., 2006). The subsequent analysis (Shimada et al., 2006) nevertheless revealed a link between ice loss and increases in the Pacific surface water (PSW) temperature in the Arctic Ocean, beginning in the late 1990s. This was concurrent with the onset of sharp sea ice reductions in the Chukchi and Beaufort Seas. Based on ice mass balance data, Perovich et al. (2008) demonstrated an extraordinary bottom melt of sea ice in the Beaufort
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