Maximum Southwest Greenland Ice Sheet Recession in the Early Holocene

Abstract

Establishing the timing of maximum Holocene warmth in the Arctic is critical for understanding global climate system response to external forcing. In Greenland, challenges in obtaining climate records that span the full Holocene have hampered efforts to robustly identify when the Holocene Thermal Maximum occurred. Reconstructing land‐based ice sheet history can fill this gap because these ice sheet regions respond sensitively to summer temperature. We synthesize new and published 10Be and 14C ages from southwest Greenland to map Greenland ice sheet margin positions from 12 to 7 ka and calculate retreat rates from 12 to 0 ka. We found that maximum Greenland ice sheet recession occurred between ~10.4 and 9.1 ka. Our reconstruction suggests that summer air temperatures in southwest Greenland were highest from ~10.4 to 9.1 ka, providing support for an early regional Holocene Thermal Maximum. These results can serve as benchmarks for comparison with ice sheet and climate model simulations.

The worst is yet to come for the Greenland ice sheet

“…Briner and colleagues take this approach. The authors show that their estimates for the Holocene are in good agreement with recently published geol ogical reconstructions of Holocene ice-margin positions in WSW Greenland 7 .…”

Reconstructing Arctic Precipitation Seasonality Using Aquatic Leaf Wax δ2H in Lakes With Contrasting Residence Times

“…Ice sheet model simulations suggest several kilometers of retreat of the 585 southwestern margin of the Greenland Ice Sheet during the middle Holocene (Lecavalier et al, 2014;Simpson et al, 2009;Tarasov & Peltier, 2003). Direct measurements of the western Greenland Ice 587 Sheet margin extent, however, show only minor Holocene retreat, around 1 to 10 kilometers behind the present margin (Håkansson et al, 2014;Lesnek et al, 2020;Ruskeeniemi et al, 2018;Young & Briner, 2015). An ice sheet flow line model matched to tightly constrained Holocene ice sheet margin extents near Kangerlussuaq (Lesnek et al, 2020;Young et al, 2020) shows that winter precipitation may have 591 been 0.2 to 0.4 meters water equivalent (25 to 40%) greater than 20 th century values to offset middle Holocene ablation (Fig.…”

Millennial-scale migration of the frozen/melted basal boundary, western Greenland ice sheet

“…Because the outer flanks of western GrIS contain numerous deep and steep-sided subglacial troughs, we focus our investigation on a single flowline transect so that we can employ high time/space resolution in our model. Our transient model includes higher order stresses, a well-informed paleoclimate (Buizert and others, 2018; Downs and others, 2020), thermally active bedrock, and honors previously published records of terminus retreat (Briner and others, 2016; Lesnek and others, 2020; Young and others, 2020). We track the constitutive components of the basal heat budget during the transient simulation to isolate the energy sources and sinks associated with the migration of frozen/melted bed conditions.…”

“…Detailed chronologies of Holocene ice margin retreat have been established for this sector of the ice sheet based on glacial geologic evidence with 10 Be and 14 C age dating (Briner and others, 2016; Lesnek and others, 2020; Young and others, 2020). The ice margin retreated most rapidly during the first half of the last 11 ka.…”