Earliest Holocene south Greenland ice sheet retreat within its late Holocene extent

Abstract

Early Holocene summer warmth drove dramatic Greenland ice sheet (GIS) retreat. Subsequent insolation-driven cooling caused GIS margin readvance to late Holocene maxima, from which ice margins are now retreating. We use 10 Be surface exposure ages from four locations between 69.4°N and 61.2°N to date when in the early Holocene south to west GIS margins retreated to within these late Holocene maximum extents. We find that this occurred at 11.1 ± 0.2 ka to 10.6 ± 0.5 ka in south Greenland, significantly earlier than previous estimates, and 6.8 ± 0.1 ka to 7.9 ± 0.1 ka in southwest to west Greenland, consistent with existing 10 Be ages. At least in south Greenland, these 10Be ages likely provide a minimum constraint for when on a multicentury timescale summer temperatures after the last deglaciation warmed above late Holocene temperatures in the early Holocene. Current south Greenland ice margin retreat suggests that south Greenland may have now warmed to or above earliest Holocene summer temperatures.

The PMIP4 contribution to CMIP6 – Part 2: Two interglacials, scientific objective and experimental design for Holocene and Last Interglacial simulations

“…While the presence of a relic of the Laurentide ice sheet may be the origin of modeldata mismatches in the climate of eastern North America (Wohlfahrt et al, 2004), the effect is local and small. Cosmogenic surface exposure ages and threshold lake records (Carlson et al, 2014;Larsen et al, 2015;Sinclair et al, 2016) also suggest that by 6 ka, the Greenland ice sheet was similar in extent to present. The ice-sheet distribution and elevations, land-sea mask, continental topography and oceanic bathymetry should all be prescribed as the same as in piControl in the midHolocene simulation (Table 1).…”

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

“…Only a few meters of ice-sheet loss occurred between ~7 and ~2 ka (82,83), which is thought to be dominated by loss from the AIS (84,85). Field data and ice-sheet models suggest that the GrIS was smaller than present during the early to middle Holocene thermal optimum (9.5-5.5 ka) (86,87), and began to readvance during the cooler Neoglacial period (<5 ka), reaching its maximum extent in many places during the Little Ice Age and causing a GMSL lowering of <0.2 m (88).…”

“…2i) that reflect ice-sheet loss and coupled atmosphere-ocean variability (95). Late-Holocene ice-margin reconstructions for the AIS suggest little change (84,85,96), while those for the GrIS suggest general advance (86)(87)(88). The clearest signal in geological and long tide gauge records is the transition from low rates of change during the last ~2 ka (order tenths of mm yr -1 ) to modern rates (order mm yr -1 ) in the late 19 th to early 20 th centuries, although the spatial manifestation of this change is variable (1, 81).…”

The Greenland Ice Sheet during the last glacial cycle: Current ice loss and contribution to sea-level rise from a palaeoclimatic perspective

“…Even in areas where moraine ridges are completely lacking it is possible to build a deglacial chronology by combining ages obtained from exposure dating of bedrock surfaces and radiocarbon dates of terrestrial deposits (e.g. Hughes et al, 2012;Carlson et al, 2014;Dyke et al, 2014;Winsor, 2014).…”

“…It was the period when the ice margin first retreated onto land after the LGM along most of the Greenland coast, and in many areas it retreated all the way to its present position and beyond (Hughes et al, 2012;Larsen et al, 2014;Carlson et al, 2014;Dyke et al, 2014;Winsor, 2014;Winsor et al, 2015).…”