A simple model of the Arctic Ocean response to annular atmospheric modes

A dynamical mechanism is described that modulates the tilt of the sea-surface height and pycnocline depth between the central Arctic and the continental shelves. A simple analytical model is presented, forced with idealized zonal winds over an idealized, 2-layer, cylinder representing the Arctic Ocean. Ekman transports are linked to sea-surface and pycnocline tilt anomalies and basin-scale circulation in response to an annular wind anomaly. We compare the results to tide gauge data, as well as results from a more realistic numerical simulation and find that the model explains a major fraction of the interannual-to-decade scale sea-surface height anomalies at Arctic coastal tide gauges. The analytical model indicates, for example, that on the order of 10 cm of the observed rise of about 18 cm in coastal Arctic sea-surface height between about 1985 and 1993 was probably a response to increased Westerly winds associated with a strong positive phase of the Northern Annular Mode of atmospheric variability. The pycnocline depth anomaly time series from the model is used to calculate implied changes in the outflow of relatively fresh Polar Water to the North Atlantic. The comparisons indicate that the Ekman transport mechanism is important to changes in the export of buoyancy from the Arctic Ocean on seasonal, interannual, and decadal timescales.