Interannual sea-level variations in the Scotia-Maine region in the 1990s

The TOPEX/Poseidon altimeter data over the period from 1992 to 1999 have been analyzed to examine interannual sea-level variability in the Scotia-Maine region (defined as the outer Laurentian Channel, the Scotian Shelf, the Gulf of Maine, and the northern Middle Atlantic Bight). A modified orthogonal response analysis is used to simultaneously remove the annual cycle and residual tides (including the semi-annual cycle). Altimetric data reveal significant interannual sea-level variability of magnitude 5-10 cm over the shelves in the 1990s, falling to the lowest level in 1994, rising to the highest level in 1997-1998, and falling again. The second sea-level decrease shows an overall equatorward propagation. These results are generally consistent with those detected from detrended coastal tide-gauge data at Halifax, Nova Scotia. The interannual sea-level variability is thought to be forced by fluctuations of the Gulf Stream position, which seems to be related to the North Atlantic Oscillation, and the baroclinic Labrador Current transport.