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

Abstract

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.