Fiammetta Straneo

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Heat and Freshwater Through The Labrador Sea

Like much of the subpolar region, the Labrador Sea experiences a net heat loss to the atmosphere. On a yearly average, this heat loss amounts to approximately 2GJ of net heat loss per square meter which has to be balanced by a supply of heat by the ocean circulation. This heat is advected into the Labrador Sea via its boundary currents, and supplied to the interior region (where the bulk of the dense water formation occurs) by eddies. Similarly, freshwater of Arctic origin is advected around the basin by the surface boundary currents and advected into the interior via instabilities/eddy fluxes. This freshwater is mixed vertically during convection, and partly removed with the export of the fresh, cold, dense Labrador Sea Water that is produced during convection.

To first order, for the ocean to be in steady state, one would expect the heat and freshwater transports through the Labrador Sea to balance on an annual basis. In practice, however, there occur large variations in the heat and freshwater transports through the basin which, in turn, affect the water column's stability and its ability to undergo deep convection.

The net seasonal cycle of heat and freshwater through the central Labrador Sea, and their interannual variations are examined using historical (1964-1974) and modern (1996-2000) data (see Figure). The historical data were collected at Ocean Weather Station Bravo in the central Labrador Sea, while the modern time series were constructed using profiling float data, mostly concentrated in the central region.

Note the shutdown of deep convection recorded from 1969 to 1972, resulting in an increase of heat and salt in the sub-surface waters.

Straneo, F., 2006: Heat and Freshwater Transport through the Central Labrador Sea.    J. Phys. Ocean.,36(4), 606-628.

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