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Atlantic heat constrains Arctic sea ice extent
26 June 2012
University of Bergen
The Arctic sea ice cover is a sensitive indicator of climate variability and change. Researchers from the Bjerknes Centre in Bergen, Norway, have for the first time quantified how Atlantic heat influences the sea ice extent in the Barents Sea, where the retreat in Arctic winter sea ice is the most pronounced.
The winter sea ice extent in the Barents Sea has gradually decreased during the last three decades, and the annual mean sea ice area was reduced by about 50% during the last decade (1998-2008). A new study reported in Journal of Climate by researchers from the Bjerknes Centre for Climate Research (University of Bergen, Uni Research, and Institute of Marine Research), shows that interannual variability and long-term decrease in sea ice cover reflect changes in the inflow of Atlantic water.
This warm water flows northward off the Norwegian coast and into the Barents Sea as an extension of the Gulf Stream. Measurements from the south-western Barents Sea and results from a numerical ocean model reveal that increased heat transport (a product of changes in temperature and current speed) associated with Atlantic water leads to a larger area with no wintertime freezing.
Most of the sea ice retreat is thus not ice that has melted - this sea ice never froze - and is therefore a fundamentally different process than the observed summer sea ice retreat in the central Arctic.
Map of the Barents Sea showing mean winter sea ice concentration between 1979 and 2010 (colormap) and main paths of Atlantic water (red arrows). Winter ice extent (15% concentration) during the 1980s (solid line), 1990s (dashed) and 2000s (dash-dotted) is also shown.
Annual (July-June) observed (1980-2010) and modelled (1949-2007) sea ice area and trends.
Ice-covered sea off the coast of Svalbard, at the entrance to the Barents Sea. Photo: Marius Årthun