Threshold for Greenland ice sheet collapse

Researchers reconstruct the climate near southern Greenland during late Pleistocene interglacials. The complete melting of the Greenland Ice Sheet (GIS) could contribute up to 7 m of global sea-level rise. Understanding the GIS response to past interglacial periods could help determine its response to future warming, but climate records around Greenland during past interglacials are sparse. Nil Irvali, Ulysses Ninnemann, and colleagues used data on multiple temperature proxies from marine microfossils to reconstruct sea surface temperatures (SSTs) at a site off southern Greenland during 4 interglacial periods, spanning the past 450,000 years. SSTs were as warm or warmer than at present during all 4 previous interglacials, with mean summer SSTs ranging from 7-11 °C, compared with the modern value of 7.7 °C. Sediment records suggest that the most complete deglaciation of southern Greenland occurred during one of these interglacials that was only slightly warmer than the present, whereas ice persisted on southern Greenland during the warmest interglacials. However, during the period with the strongest deglaciation, temperatures exceeded present levels longer than for any of the other interglacials, suggesting that the duration of warming influences the fate of the GIS. The results suggest that the warming threshold for significant GIS retreat could be less than 1 °C above the present, within the range of projected values for this century, according to the authors.

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Article #19-11902: “A low climate threshold for south Greenland Ice Sheet demise during the Late Pleistocene,” by Nil Irvali

et al

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MEDIA CONTACT: Nil Irvali, University of Bergen, NORWAY; tel: +47-45663073; e-mail:

[email protected]

; Ulysses Ninnemann, University of Bergen, NORWAY; e-mail:

[email protected]