Rapid Cooling and Increased Storminess Triggered by Freshwater in the North Atlantic

Oltmanns, Marilena, Karstensen, Johannes, Moore, G. W. K. and Josey, S. A. (2020) Rapid Cooling and Increased Storminess Triggered by Freshwater in the North Atlantic Geophysical Research Letters, 47 (14). Art.Nr. e2020GL087207. DOI 10.1029/2020GL087207.

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Abstract

Recent winters have been unique due to the rapid and extreme cooling of the subpolar North Atlantic. Here, we present a novel view on its causes and consequences. Combining in-situ observations with remote sensing and atmospheric reanalysis data, we show that increased freshening of the subpolar region gives rise to a faster surface cooling in fall and winter. Large freshwater events, in particular, result in pronounced cold anomalies with sharp temperature gradients that promote an enhanced storminess. The storms reinforce the cooling by driving stronger heat losses and modulating the surface flow. Consistent with this mechanism, past freshwater events have been followed by cold anomalies in winter of approximately −2°C and increases in the North Atlantic Oscillation index of up to ∼0.6 within 3 years. We expect that future freshwater discharges into the North Atlantic will amplify the cold anomaly and trigger an enhanced wintertime storminess with far-reaching climatic implications.

Document Type: Article
Keywords: atmosphere ocean interactions; climate variability; freshwater; North Atlantic Ocean
Research affiliation: NOC
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
DOI etc.: 10.1029/2020GL087207
ISSN: 0094-8276
Related URLs:
Projects: Blue-Action, AtlantOS, RACE, ARGO Program
Date Deposited: 03 Aug 2020 08:49
Last Modified: 03 Aug 2020 08:49
URI: http://eprints.uni-kiel.de/id/eprint/50249

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