Slow retreat of a land based sector of the West Greenland Ice Sheet during the Holocene Thermal Maximum: evidence from threshold lakes at Paakitsoq

10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland

“…Reconstructions of land-terminating ice margins elsewhere in western and southern Greenland also reveal ice margin stability in the early Holocene followed by minimum extent during the latter portion of the Holocene (e.g., Larsen et al, 2011Larsen et al, , 2015. In particular, the ice margin at Paakitsoq (80 km south of our field site) was reconstructed to have been relatively stable between~7.9 and 5.4 ka, followed by its minimum extent between 5.4 and 0.24 ka Håkansson et al, 2014). Based on a synthesis of geologic data like ours, Young and Briner (2015) suggested that the minimum extent of the western GrIS was experienced between~4 and~2 ka.…”

“…The heterogeneous response of GrIS is also highlighted by how the Drygalski Moraines represent multiple cycles of advance and retreat and/or stillstands spanning from~8.6 to <7.6 ka, as opposed to the Fjord Stade Moraine record characterized by a more simple sequence of two moraine crests coinciding with the 9.3 and 8.2 ka events. This difference in timing and moraine deposition may be a function of a lagged response of the Nuussuaq Lobe to climate perturbations, such as early Holocene Laurentide Ice Sheet meltwater events (Jennings et al, 2015). If so, the Drygalski Moraines may represent the cumulative effect of climate on the millennial scale as opposed to the discrete climate events archived by the Fjord Stade Moraines in response to decadal-to centennial-scale climate forcing.…”

“…While isotope records from central GrIS ice cores generally follow high-latitude summertime insolation and indicate an early-Holocene thermal maximum followed by steady cooling in the subsequent Holocene (e.g., Vinther et al, 2006), other records, primarily from coastal areas around Greenland (e.g. Axford et al, 2013;Perner et al, 2013;Jennings et al, 2014), reveal a middle-Holocene thermal maximum (Fig. 7).…”

“…7). Increased meltwater discharge into Baffin Bay and the North Atlantic Ocean from thinning ice sheets during the early Holocene (e.g., Jennings et al, 2015) has been invoked to explain the delayed timing of the Holocene thermal maximum in parts of Greenland (e.g., Kaplan and Wolfe, 2006;Renssen et al, 2009). .…”

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

“…Threshold lakes record periods when the ice sheet was large enough to feed meltwater into the lake's catchment (e.g. Kaplan et al, 2002;Briner et al, 2010Briner et al, , 2013Håkansson et al, 2014;Larsen et al, 2011Larsen et al, , 2015. If this threshold is located behind the present-day ice margin, i.e.…”