Tomographic data obtained during early 1989 in the Greenland Sea have been analyzed at 4--8 hour resolution to give the range-averaged vertical temperature evolution in the upper 500 m for a 106 km path. The tomographic inversions used both ray travel time data and normal mode group velocity data in order to maximize near-surface resolution. Two major events are apparent in the results. The first is the warming of a cold (-1.9 ¿C) 100 m thick surface layer, and the second, 10 days later, is the cooling of a relatively warm (-0.9 ¿C) subsurface layer between 300 m and 500 m depth. This warm subsurface layer is a critical source of salinity and buoyancy for deep convection. The surface layer warming is consistent with a mixed layer deepening over a portion of the path, bringing up water from below. Special Sensor Microwave Imager (SSM/I) ice data indicate that the local ice field disappears 3--4 days after the surface warming. The cooling of the warm 300 m to 500 m layer is also consistent with a vertical process. There is no ice cover at this time, and so surface heat fluxes are large. A northerly wind event occurs at the onset of the cooling of the 300--500 m layer, suggesting that wind-induced mixing may have played a role in initiating the process. There is evidence of southward flow advecting warm water into the area both before and after the two events studied in detail here. ¿ 1997 American Geophysical Union