The Greenland Sea Ocean Acoustic Tomography Experiment was conducted during 1988--89, as one component of the international Greenland Sea Project, to study deep water formation and the response of the gyre to variations in wind stress and ice cover. Six acoustic transceivers moored in an array 200-km across transmitted to one another at four hour intervals. Near the end of February, 1989, a sub-surface temperature maximum at several hundred meters depth disappeared over a surprisingly large area of the central Greenladn Sea. While the water column was modified to about 1000 m depth over much of the gyre, the surface remained colder than the deeper water, contrary to what might be expected from simple models of convective renewal. ¿ American Geophysical Union 1993