Characteristics and climate impacts of sea ice in the glacial North Atlantic

North Atlantic sea ice displacements are thought to play an important role in the abrupt Dansgaard-Oeschger (D-O) cycles of the last glacial period. This model study investigates sea ice variability in glacial climates to help provide constraints on its involvement in D-O cycles. Sea ice variability in a coupled climate model simulation of the Last Glacial Maximum (21 ka) is concentrated in the winter season, with large year to year differences in the ice cover of the Nordic Seas and western North Atlantic. Experiments performed with an atmospheric general circulation model indicate that Greenland surface climate is more sensitive to Nordic Seas ice perturbations than to western North Atlantic ice perturbations. Nordic Seas ice retreat causes 10 C of winter warming and a 50% increase in snow accumulation at Greenland Summit, in qualitative agreement with observations of the cold-to-warm (stadial-to-interstadial) transitions of D-O cycles; concomitant ice retreat in the western North Atlantic has little additional effect. The results suggest that winter sea ice displacements in the Nordic Seas are important for creating the observed climate signals associated with D-O cycles in the Greenland ice cores.