On the Nature of Upwelling Storms in the Western Arctic

The characteristics of Pacific-born storms that cause upwelling along the Beaufort Sea continental slope are investigated using meteorological re-analysis fields. In fall 2002 a mooring array located near 152 W measured 11 significant upwelling events that brought warm and salty Atlantic water to shallow depths. Comparing the storms that caused these events to other Aleutian lows that did not induce upwelling, interesting trends emerged. Upwelling occurred most frequently when storms were located in a region near the eastern end of the Aleutian Island Arc and Alaskan Peninsula. Not only were these storms deep, but they generally had northward tending trajectories. While the steering flow aloft aided this northward progression, the occurrence of lee cyclogenesis due to the orography of Alaska seems to play a role as well in expanding the meridional influence of the storms. In late fall and early winter the upwelling diminished significantly at the array site. It is argued that this was due to two different upper- level blocking patterns, inhibiting the far field influence of the storms.