Circulation and Convection in the Irminger Sea

Kjetil Våge, Ph.D., 2010
Robert Pickart, Advisor

Aspects of the circulation and convection in the Irminger Sea are investigated using a variety of
in-situ, satellite, and atmospheric reanalysis products.

Westerly Greenland tip jet events are intense, small-scale wind phenomena located east of Cape
Farewell. A climatology of such events was used to investigate their evolution and mechanism of
generation. It is argued that the tip jet arises from the interplay of the synoptic-scale flow evolution and the perturbing effects of Greenland’s topography upon the flow.
The Irminger Gyre is a narrow, cyclonic recirculation confined to the southwest Irminger Sea.
The mean strength of the circulation between 1991 and 2007 was 6.8 ± 1.8 Sv. It intensified at
a rate of 4.3 Sv per decade over the observed period. The temporal evolution of the LSW layer
thickness across the Irminger Basin suggests that local convection formed LSW during the early
1990s within the Irminger Gyre. In contrast, LSW appeared outside of the gyre with a time lag of
2-3 years, consistent with transit from a remote source in the Labrador Sea.

In thewinter of 2007-08 deep convection returned to both the Labrador and Irminger seas following years of shallow overturning. The reasons why it happened are elucidated.