Preprints
https://doi.org/10.5194/wcd-2023-1
https://doi.org/10.5194/wcd-2023-1
 
24 Jan 2023
24 Jan 2023
Status: this preprint is currently under review for the journal WCD.

European summer weather linked to North Atlantic freshwater events in preceding years

Marilena Oltmanns1, N. Penny Holliday1, James Screen2, Ben I. Moat1, Simon A. Josey1, D. Gwyn Evans1, and Sheldon Bacon1 Marilena Oltmanns et al.
  • 1National Oceanography Centre, Southampton, UK
  • 2University of Exeter, Exeter, UK

Abstract. Amplified Arctic ice loss in recent decades has been linked to increased occurrence of extreme mid-latitude weather. The underlying mechanisms remain elusive, however. One potential link occurs through the ocean as the loss of sea ice and glacial ice leads to increased freshwater fluxes into the North Atlantic. Thus, in this study, we examine the extent to which North Atlantic freshwater anomalies constrain the subsequent ocean-atmosphere evolution and assess their implications for European summer weather. Combining remote sensing, atmospheric reanalyses and model simulations, we show that stronger freshwater anomalies are associated with sharper sea surface temperature gradients over the North Atlantic in winter, destabilising the overlying atmosphere and inducing a northward shift in the North Atlantic Current. In turn, the jet stream over the North Atlantic is deflected northward in the following summers, leading to warmer and drier weather over Europe. Our results suggest that growing freshwater fluxes into the North Atlantic will increase the risk of heat waves and droughts over the coming decades, and could yield enhanced predictability of European summer weather, months to years in advance.

Marilena Oltmanns et al.

Status: open (until 09 Mar 2023)

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Marilena Oltmanns et al.

Marilena Oltmanns et al.

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Short summary
The Arctic is currently warming twice as fast as the global average. This results in enhanced melting and thus freshwater releases into the North Atlantic. Using a combination of observations and models, we show that atmosphere-ocean feedbacks initiated by freshwater releases into the North Atlantic lead to warmer and drier weather over Europe in subsequent summers. The existence of this dynamical link suggests that European summer weather can be predicted months to years in advance.