An atmospheric circulation model is used to show that a reduction in sea ice extent in the North Atlantic produces a climatic response consistent with abrupt changes in temperature and snow accumulation recorded in Greenland during the Dansgaard-Oeschger (D-O) events of the last glacial period. The model simulations exhibit warming that is especially pronounced in winter and an accumulation increase that occurs primarily in summer, though the fractional accumulation increase is greater in winter. The seasonality of the combined temperature and accumulation changes is also consistent with the oxygen isotope signal, explaining why estimates of the magnitude of D-O warming from oxygen isotopes are damped relative to direct estimates. Mechanisms for driving such displacements of sea ice could be changes in ocean thermohaline circulation (OTC) or rearrangements of the tropical atmosphere-ocean system.