South Greenland ice-sheet collapse during Marine Isotope Stage 11

Abstract

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, implying substantial mass loss from the Greenland ice sheet (GIS). There are, however, no model simulations and only limited proxy data to constrain the magnitude of the GIS response to climate change during this 'super interglacial', thus confounding efforts to assess climate/ice-sheet threshold behaviour and associated sea-level rise. 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 as a result of near-complete deglaciation of south Greenland. Comparison with ice-sheet configurations from numerical models suggests that the GIS lost about 4.5 to 6 metres of sea-level-equivalent volume during MIS 11. This is evidence for late-Quaternary GIS collapse after it crossed a climate/ice-sheet stability threshold that may have been no more than several degrees above pre-industrial temperatures.

Sea-level rise due to polar ice-sheet mass loss during past warm periods

“…A cessation of ice-sheet eroded sediment discharge and IRD suggests ice-margin retreat from the southern Greenland coast (46), whereas continued IRD deposition in the northeast demonstrates the persistence of marine-terminating ice over northeastern Greenland (47). Comparison of these constraints with ice-sheet models suggests that the GrIS could have contributed 4.5-6 m to GMSL rise above present (46).…”

“…Given lags in the climate system, simple correlation between such climate parameters can be misleading because the extremes may not be synchronous over a 10-kyr long interglacial period. Peak temperatures attained during previous warm periods may also be dependent upon the length of the interglacial period (41,46), suggesting that warm periods lasting several kyr may not represent equilibrium conditions for the climate-cryosphere system. Moreover, ice sheets in different hemispheres may not respond in phase.…”

“…Comparison of these constraints with ice-sheet models suggests that the GrIS could have contributed 4.5-6 m to GMSL rise above present (46). Higher GMSL estimates thus require an Antarctic contribution, but few geologic constraints on AIS history exist for MIS 11 (48).…”

“…Two approaches show great promise for identifying and quantifying the contribution of individual ice sheets that retreated during previous warm periods: geochemical provenance in marine sediments (20,46,67) and sea-level fingerprinting (103). Existing evidence points to southern Greenland as the most susceptible sector of the GrIS to warmer-than-present temperatures (46,67), although some models predict retreat in the north and others in the south.…”

Ice sheet model dependency of the simulated Greenland Ice Sheet in the mid-Pliocene

“…Palaeoclimatic studies of proxy records (NEEM Community Members, 2013) and numerical modeling (Cuffey and Marshall, 2000;Otto-Bliesner et al, 2006;van de Berg et al, 2011;Colville et al, 2011;Helsen et al, 2013;Reyes et al, 2014) of the past few interglacials confirm that GrIS has a large sensitivity to high-latitude warming. The midPiacenzian (Dowsett et al, 2010a) or Pliocene warm period (between 3.264 and 3.025 Ma) has been identified as a potential past climate of high commonality to projected future warming (Haywood et al, 2011a), with higher than modern surface temperatures and with boundary conditions and forcings similar to today (e.g., Pagani et al, 2009;Seki et al, 2010).…”