Diachronous retreat of the Greenland ice sheet during the last deglaciation

Abstract

a b s t r a c tThe last deglaciation is the most recent interval of large-scale climate change that drove the Greenland ice sheet from continental shelf to within its present extent. Here, we use a database of 645 published 10 Be ages from Greenland to document the spatial and temporal patterns of retreat of the Greenland ice sheet during the last deglaciation. Following initial retreat of its marine margins, most land-based deglaciation occurred in Greenland following the end of the Younger Dryas cold period (12.9e11.7 ka). However, deglaciation in east Greenland peaked significantly earlier (13.0e11.5 ka) than that in south Greenland (11.0e10 ka) or west Greenland (10.5e7.0 ka). The terrestrial deglaciation of east and south Greenland coincide with adjacent ocean warming. 14 C ages and a recent ice-sheet model reconstruction do not capture this progression of terrestrial deglacial ages from east to west Greenland, showing deglaciation occurring later than observed in 10 Be ages. This model-data misfit likely reflects the absence of realistic ice-ocean interactions. We suggest that oceanic changes may have played an important role in driving the spatial-temporal ice-retreat pattern evident in the 10 Be data.

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).…”

Greenland‐Wide Seasonal Temperatures During the Last Deglaciation

“…Its past extent is recorded in glacial landforms such as moraines (e.g., Denton et al, 2005;Funder et al, 2011;Kelly et al, 2008;Levy et al, 2016;Rinterknecht et al, 2014;Young et al, 2013) and most precisely reconstructed using exposure dating techniques (e.g., Carlson et al, 2014;Corbett et al, 2011;Hughes et al, 2012;Kelley et al, 2013;Larsen et al, 2014;Sinclair et al, 2016;Young et al, 2013). Its past extent is recorded in glacial landforms such as moraines (e.g., Denton et al, 2005;Funder et al, 2011;Kelly et al, 2008;Levy et al, 2016;Rinterknecht et al, 2014;Young et al, 2013) and most precisely reconstructed using exposure dating techniques (e.g., Carlson et al, 2014;Corbett et al, 2011;Hughes et al, 2012;Kelley et al, 2013;Larsen et al, 2014;Sinclair et al, 2016;Young et al, 2013).…”

Implementation of higher-order vertical finite elements in ISSM v4.13. for improved ice sheet flow modeling over paleoclimate timescales

“…Currently, analysis of ice sheet modeling experiments focusing on the past behavior of the GrIS are being complemented with rich paleoclimate data constraining features of the past ice sheet behavior (Larsen et al, 2015;Young and Briner, 2015;Sinclair et al, 2016). Where shallow ice models might be limited in their ability to simulate the marginal behavior of the GrIS through the exclusion of higher-order stress terms and an inability to run on a high-resolution mesh, BP models may 395 become more appropriate for such comparisons in the future.…”

“…This approach was improved through increased data coverage during later studies (Simpson et al, (2009); Lecavalier et al, 2014), highlighting the practical usage of paleoclimate proxies in ice sheet modeling efforts. Recently, ice sheet modeling results of the last deglaciation and Holocene have been compared with terrestrial records 60 that capture changes in the ice sheet margin position (Larsen et al, 2015;Young and Briner, 2015;Sinclair et al, 2016). Because these comparisons are still relatively nascent, large model-data discrepancies do exist in some locations between the modeled margin and the margin derived from the proxy evidence, particularly in areas along the ice sheet margin where fast flow dominates.…”

“…Because these comparisons are still relatively nascent, large model-data discrepancies do exist in some locations between the modeled margin and the margin derived from the proxy evidence, particularly in areas along the ice sheet margin where fast flow dominates. Some reasons for the model-data discrepancies include the use of a relatively coarse (10km or greater) grid and use of the shallow ice 65 approximation (SIA; Hutter, 1983;Sinclair et al, 2016). Because the SIA was mainly developed for modeling the interior flow of ice sheets where the ice flow is dominated by vertical shear, it ignores membrane stresses (longitudinal and lateral drag) that are predominant closer to the GrIS margin (Hutter, 1983), and can lead to large thickness errors in these regions (Bueler et al, 2005).…”