Arctic sea ice variability during the last half century

Observational data and modeling results are analyzed to describe changes in the Arctic sea ice cover during the last half century. Accelerated melt of sea ice cover is reported during the late 1990s and 2000s both based on satellite observations of sea ice extent and model simulations of sea ice thickness. The observed and modeled changes are in qualitative agreement but model results imply higher rate of ice thickness decline compared to sea ice extent. Possible causes of variability in sea ice cover include increased surface air temperatures, changes in atmospheric circulation and changes in the absorption of incoming radiative flux. However, atmospheric forcings, such as the Arctic Oscillation (AO), explain less than half of the total variance in Arctic sea ice cover. Model results analyzed in the Greenland Sea as well as observations in the western Arctic Ocean indicate that oceanic forcing might be an important overlooked factor in driving recent sea ice melt. The main oceanic processes relevant to variability of sea ice cover include advection of heat and melting of sea ice in marginal ice zones and at the ice-ocean interface downstream of the warm water paths. Such changes have potential significant ramifications to the entire pan-Arctic region, including the physical environment, regional ecosystems, native communities, and use of the region for commercial exploration and transportation. Continued studies including in situ and remote sensing observations and modeling are critical to advancing the knowledge of Arctic climate change and predicting scenarios of future change.