Air-sea interactions and water mass transformation during a katabatic
storm in the Irminger Sea
Abstract
We use a global 5-km resolution model to analyse the air-sea
interactions during a katabatic storm in the Irminger Sea originating
from the Ammassalik valleys. Katabatic storms have not yet been resolved
in global climate models, raising the question of whether and how they
modify water masses in the Irminger Sea. Our results show that dense
water forms along the boundary current and on the shelf during the
katabatic storm due to the heat loss caused by the high wind speeds and
the strong temperature contrast. The dense water contributes to the
North Atlantic Deep Water and thus to the Atlantic Meridional
Overturning Circulation (AMOC). The katabatic storm triggers a polar
low, which in turn amplifies the near-surface wind speed in a positive
feedback, in addition to acceleration from a breaking mountain wave.
Resolving katabatic storms in global models is therefore important for
the formation of dense water in the Irminger Sea, which is relevant to
the AMOC, and for the large-scale atmospheric circulation by triggering
polar lows.