Upwelling of Atlantic water along the Canadian Beaufort Sea continental slope: favourable atmospheric conditions, seasonal, and interannual variations

The role of wind forcing on the vertical displacement of the –1°C isotherm and 33.8 isohaline depths was examined based on snapshots of historical (1950-2013) temperature and salinity vertical profiles along the Mackenzie continental slope (Canadian Beaufort Sea). We find that upwelling is correlated with along-slope northeast winds during both ice-free and ice-covered conditions, although the wind impact is more efficient during open water conditions. The single most important factor responsible for vertical displacements of isopycnals is sustained wind forcing that can last for several weeks and even longer. The upwelling/downwelling events are discussed in the context of the interplay between two regional centers of action – the Beaufort High (BH) and Aleutian Low (AL) - that control the wind pattern over the southern Beaufort Sea. The probability of upwelling-favourable wind occurrence is closely related to the sea-level pressure difference between these two centers, as well as their geographical positions. The combined effect of both centers expressed as the sea level pressure differences highly correlated (+0.68/+0.66 for summer/winter) with occurrences of upwelling-favourable NE winds over the Mackenzie slope, although Beaufort High plays more important role. We also diagnosed the predominant upwelling-favourable conditions over the Mackenzie slope in the recent decade associated with the summertime amplification of the Beaufort High. The upwelling-favourable NE wind occurrences also demonstrate the significant but low (-0.30) correlation with Arctic Oscillation index during both summer and winter seasons, whereas the high correlation with North Pacific index (-0.52) is obtained only for ice-covered period.