South Greenland ice-sheet collapse during Marine Isotope Stage 11

• Published in: Nature (London) 2014-06, Vol.510 (7506), p.525-528
• Main Authors: Reyes, Alberto V., Carlson, Anders E., Beard, Brian L., Hatfield, Robert G., Stoner, Joseph S., Winsor, Kelsey, Welke, Bethany, Ullman, David J.
• Format: Article
• Language: English
• Subjects: 704/106/2738; 704/106/413; 704/2151/209; Climate change; Confidence intervals; Deglaciation; Environmental aspects; Environmental assessment; Glacial erosion; Humanities and Social Sciences; Ice; Ice sheets; Icebergs; Isotopes; letter; Mathematical models; multidisciplinary; Neodymium; Permafrost; Precambrian; Quaternary; Science; Sea level; Sediment transport; Strontium; Surface-ice melting
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature13456

The isotopic composition of glacial sediment discharged into the ocean from south Greenland is used to identify a major reduction in the amount of that sediment derived from erosion of Greenland’s Precambrian bedrock, probably indicating the cessation of subglacial erosion and sediment transport during Marine Isotope Stage 11 as a result of the almost complete deglaciation of south Greenland. Historic collapse of the Greenland ice sheet There is remarkably little geological evidence from which to determine the magnitude of the retreat of the Greenland ice sheet during past interglaciations, which in turn limits our ability to estimate its future contributions to sea-level rise in a warming world. Alberto Reyes et al . now provide isotopic evidence from an ocean sediment core from the nearby Labrador Sea that suggests that the bulk of the southern Greenland ice sheet collapsed during the Marine Isotope Stage 11 'super interglacial' about 400,000 years ago. The authors comment that this ice-sheet collapse occurred in response to climate conditions that are within the range of those anticipated by the end of the twenty-first century. Varying levels of boreal summer insolation and associated Earth system feedbacks led to differing climate and ice-sheet states during late-Quaternary interglaciations. In particular, Marine Isotope Stage (MIS) 11 was an exceptionally long interglaciation and potentially had a global mean sea level 6 to 13 metres above the present level around 410,000 to 400,000 years ago 1 , 2 , implying substantial mass loss from the Greenland ice sheet (GIS). There are, however, no model simulations and only limited proxy data 3 , 4 to constrain the magnitude of the GIS response to climate change during this ‘super interglacial’ 5 , thus confounding efforts to assess climate/ice-sheet threshold behaviour 6 , 7 and associated sea-level rise 1 , 2 . Here we show that the south GIS was drastically smaller during MIS 11 than it is now, with only a small residual ice dome over southernmost Greenland. We use the strontium–neodymium–lead isotopic composition of proglacial sediment discharged from south Greenland to constrain the provenance of terrigenous silt deposited on the Eirik Drift, a sedimentary deposit off the south Greenland margin. We identify a major reduction in sediment input derived from south Greenland’s Precambrian bedrock terranes, probably reflecting the cessation of subglacial erosion and sediment transport 8 as a result of near-com