Atlantic heat constrains Arctic sea ice extent

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.