Evolution of Denmark Strait overflow cyclones and their relationship to overflow surges

Almansi, Mattia ORCID:; Haine, Thomas; Gelderloos, Renske; Pickart, Robert. 2021 Evolution of Denmark Strait overflow cyclones and their relationship to overflow surges. In: European Geosciences Union General Assembly 2021, Online, 19-30 Apr 2021.

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Denmark Strait, the channel located between Greenland and Iceland, is a critical gateway between the Nordic Seas and the North Atlantic. Mesoscale features crossing the strait regularly enhance the volume transport of the Denmark Strait overflow. They interact with the dense water masses descending into the subpolar North Atlantic and therefore are important for the Atlantic Meridional Overturning Circulation. Using a realistic numerical model, we find new evidence of the causal relationship between overflow surges (i.e., mesoscale features associated with high-transport events) and overflow cyclones observed downstream. Most of the cyclones form at the Denmark Strait sill during overflow surges and, because of potential vorticity conservation and stretching of the water column, grow as they move equatorward. A fraction of the cyclones form downstream of the sill, when anticyclonic vortices formed during high-transport events start collapsing. Regardless of their formation mechanism, the cyclones weaken starting roughly 150 km downstream of the sill, and potential vorticity is only materially conserved during the growth phase.

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Date made live: 22 Apr 2021 10:11 +0 (UTC)

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