Abstract
Palaeo data suggest that Greenland must have been largely ice free during Marine Isotope Stage 11 (MIS-11). However, regional summer insolation anomalies were modest during this time compared to MIS-5e, when the Greenland ice sheet likely lost less volume. Thus it remains unclear how such conditions led to an almost complete disappearance of the ice sheet. Here we use transient climate–ice sheet simulations to simultaneously constrain estimates of regional temperature anomalies and Greenland’s contribution to the MIS-11 sea-level highstand. We find that Greenland contributed 6.1 m (3.9–7.0 m, 95% credible interval) to sea level, ∼7 kyr after the peak in regional summer temperature anomalies of 2.8 °C (2.1–3.4 °C). The moderate warming produced a mean rate of mass loss in sea-level equivalent of only around 0.4 m per kyr, which means the long duration of MIS-11 interglacial conditions around Greenland was a necessary condition for the ice sheet to disappear almost completely.
Highlights
Palaeo data suggest that Greenland must have been largely ice free during Marine Isotope Stage 11 (MIS-11)
The application of the palaeo constraints to the icesheet extent (DYE-3 and southern Greenland ice free, GRIP ice covered), limits the magnitude and duration of summer temperature anomalies to a range that reflects the fact that temperatures needed to be high enough for a long enough period of time to melt ice away from southern Greenland, but not high enough to melt the ice sheet completely (Fig. 1)
We estimate that the peak MIS-11 regional summer temperature anomaly was 2.8 °C (2.1–3.4 °C, 95% credible interval) relative to present day, with a duration of positive regional summer temperature anomalies of 16.1 kyr (14.3–17.3 kyr)
Summary
Palaeo data suggest that Greenland must have been largely ice free during Marine Isotope Stage 11 (MIS-11). Regional summer insolation anomalies were modest during this time compared to MIS-5e, when the Greenland ice sheet likely lost less volume. Ancient DNA has been identified in the silt beneath the DYE-3 ice core pertaining to several boreal forest species including Alder, Spruce and Pine, as well as that of some insects[2] The existence of such material, most likely local in origin, indicates that most or all of southern Greenland, and the DYE-3 location, was ice free for a period of time. Analysis of cosmogenic elements in the soil beneath the ice sheet shows that the glacial landscape there has been preserved over the last few million years[6]
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