A NOTE ON SEASONAL CYCLES OF TEMPERATURE AND SALINITY IN THE UPPER WATERS OF THE GREENLAND SEA GYRE FROM HISTORICAL DATA

Monthly climatologies of temperature and salinity for two regions in the Greenland Sea are created by combining historical archives of hydrographic stations with observations from recent cruises. The first region corresponds to the gyre center, where deepwater formation occurs and a large bay forms in the winter ice pack (''Nordbukta''), and the second region lies directly to the south, in the area usually covered by an ice tongue (''Odden'') in February and March. Surface temperature responds primarily to local surface heat fluxes, consistently warming in the summer to about 4 degrees C and cooling in the fall to the freezing point. Interannual variability appears to be greater for salinity than for temperature. This, coupled with the sparse data coverage, makes it more difficult to define a seasonal salinity cycle. However, in July and August, surface salinity in both regions appears to decrease drastically, with freshening being more pronounced in the southern region. In the fall this mixed-layer fresh anomaly is removed, probably by brine rejection due to the local formation of ice and its subsequent removal by northerly winds. Eventually, ice formation causes the surface waters to overturn and entrain the warmer water below, inhibiting further ice formation. The fresh anomaly is smaller in the gyre center than in the Odden region, so that ice formation will end there earlier, resulting in the appearance of a bay to the north of an ice tongue. Since the disappearance of ice is a necessary precursor to mixing deeper than about 100 m, this suggests that large areal changes in ice cover may be used as a proxy for identifying the strength and onset of deep convection.