The millennial-scale duration of summer warmth during interglacial periods may have a stronger influence on Greenland Ice Sheet (GIS) retreat than the maximum summer temperature, a study finds. If climate change continues unchecked, melting of the GIS is predicted to increase global sea level by up to 33 cm by 2100. However, such projections remain uncertain due to eroded terrestrial sedimentary records, which have obscured the effects of past climate conditions on GIS retreat. Allison Cluett and Elizabeth Thomas analyzed the hydrogen isotopic composition of terrestrial biomarkers deposited in marine sediments approximately 280 km south of Greenland during the six interglacial periods of the past 600,000 years. Extremely warm summers occurred when the GIS was relatively large, during a relatively brief period of the last interglacial, namely Marine Isotope Stage 5e, approximately 130,000--115,000 years ago. By contrast, the ice sheet was likely substantially reduced in response to moderate summer warmth sustained for more than 10,000 years during the super-interglacial Marine Isotope Stage 11, approximately 425,000--375,000 years ago. According to the authors, persistently high summer temperatures, which are likely to continue if greenhouse gas emissions are not reduced, will probably be more harmful to the long-term stability of the ice sheet than a brief period of exceptional summer heat.
Article #2020-22916: "Summer warmth of the past six interglacials on Greenland," by Allison Cluett and Elizabeth Thomas
MEDIA CONTACT: Allison Cluett, State University of New York, Buffalo, NY; tel: 631-258-0624; email: aacluett@buffalo.edu
###
Proceedings of the National Academy of Sciences