Summer warmth of the past six interglacials on Greenland

Abstract

Significance Recurring glacial retreat and advance eroded most sedimentary records of pre-Holocene interglacials around Greenland, hindering development of long terrestrial paleoclimate records and leading to questions about what climate conditions caused past Greenland Ice Sheet (GrIS) retreat. We infer changes in summer temperature on Greenland from terrestrial biomarkers preserved in marine sediments through the past six interglacials. We find that exceptionally warm summers occurred during MIS5e when the GrIS remained relatively large, in contrast with moderate warmth through MIS11, when the GrIS was likely substantially reduced. Our results suggest that sustained summer warmth, a likely future if anthropogenic carbon emissions are not dramatically reduced, will be more detrimental to future stability of the GrIS than a brief period of exceptional warmth. The relative warmth of mid-to-late Pleistocene interglacials on Greenland has remained unknown, leading to debates about the regional climate forcing that caused past retreat of the Greenland Ice Sheet (GrIS). We analyze the hydrogen isotopic composition of terrestrial biomarkers in Labrador Sea sediments through interglacials of the past 600,000 y to infer millennial-scale summer warmth on southern Greenland. Here, we reconstruct exceptionally warm summers in Marine Isotope Stage (MIS) 5e, concurrent with strong Northern Hemisphere summer insolation. In contrast, “superinterglacial” MIS11 demonstrated only moderate warmth, sustained throughout a prolonged interval of elevated atmospheric carbon dioxide. Strong inferred GrIS retreat during MIS11 relative to MIS5e suggests an indirect relationship between maximum summer temperature and cumulative interglacial mass loss, indicating strong GrIS sensitivity to duration of regional warmth and elevated atmospheric carbon dioxide.