CL29

Arctic and subarctic ocean circulation and climate change - natural and anthropogenic forcing
Co-Conveners: A. Kuijpers , J.H. Jungclaus , M.-A. Sicre 
Oral Programme
 / Tue, 21 Apr, 13:30–15:00  / Room 14
Poster Programme
 / Attendance Tue, 21 Apr, 17:30–19:00  / Halls X/Y
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The Arctic climate at present is showing signs of rapid change. Satellite data show that sea ice cover over the Arctic Ocean is decreasing, on average by 2-3 % per decade. The Arctic perennial ice cover has declined as much as 9.2 % from 1978 to 2000. Over the past two decades surface temperature at latitudes higher than 60° N has increased at an average rate of 0.5 °C per decade. The cold halocline layer insulating the ice from the warm Atlantic water below has thinned and disappeared in some areas. Oceanographic data indicate warming and increased extent of Atlantic-derived waters in the Arctic Ocean at 200-900 m depth, which seems consistent with greater inflow of Atlantic waters forced by change to the positive mode of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO) .
The West Spitsbergen Current (WSC) is the major pathway for warm and saline Atlantic water to enter the Arctic Ocean. The heat transport has a significant influence on the hydrographic conditions in the Arctic Ocean and on water mass modifications in the Nordic Seas, and to some extent the overflow into the North Atlantic. However, the geological history of exchange of waters and energy between the lower latitudes of the North Atlantic and the Pacific, and the Arctic Ocean is relatively poorly constrained. This session aims to assess and elucidate both the timing and variability of the warm and saline water inflow and cold and fresh water outflow from the Arctic Ocean in modern and geologic time scales.