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FLOW Paper published in Nature Communications (Apr. 2018)

Publicerad 2018-04-24

The paper ‘Warm summers during the Younger Dryas cold reversal’ by Schenk, Väliranta, Muschitiello, Tarasov, Heikkilä, Björck, Brandefelt, Johansson, Näslund and Wohlfarth has been published in Nature Communications.

The multidisciplinary author team presents the first global high resolution full-complexity Earth System Model simulations for climate instabilities at the transition from the last ice age to our current warm period. They find that the Fennoscandian Ice Sheet enforces strong atmospheric blocking of zonal flow leading to a fundamentally different large-scale flow pattern across Europe with warming summers in response to strong North Atlantic Ocean cooling. The model setup and boundary conditions, which incorporate ancient continental ice sheets, vertical isostatic land adjustments and 60-70 m lower sea-levels, were developed at KTH. The simulations are part of an ongoing cooperation within the Bolin Centre for Climate Research between Stockholm University and KTH Mechanics involving Frederik Schenk (former PostDoc at KTH, now researcher at Stockholm University), Jenny Brandefelt, (former researcher at KTH, now at SKB company) and Arne Johansson.

The study was funded by the Swedish Nuclear Fuel and Waste Management Company (SKB).

Abstract:

The Younger Dryas (YD) cold reversal interrupts the warming climate of the deglaciation with global climatic impacts. The sudden cooling is typically linked to an abrupt slowdown of the Atlantic Meridional Overturning Circulation (AMOC) in response to meltwater discharges from ice sheets. However, inconsistencies regarding the YD-response of European summer temperatures have cast doubt whether the concept provides a sufficient explanation. Here we present results from a high-resolution global climate simulation together with a new July temperature compilation based on plant indicator species and show that European summers remain warm during the YD. Our climate simulation provides robust physical evidence that atmospheric blocking of cold westerly winds over Fennoscandia is a key mechanism counteracting the cooling impact of an AMOC-slowdown during summer. Despite the persistence of short warm summers, the YD is dominated by a shift to a continental climate with extreme winter to spring cooling and short growing seasons.

Nature Communications 9, Article number: 1634 (2018) doi: 10.1038/s41467-018-04071-5

Innehållsansvarig:Ardeshir Hanifi
Tillhör: FLOW
Senast ändrad: 2018-04-24