Contrasting evidence of Holocene ice margin retreat, south-western Greenland

• Published in: Journal of Quaternary Science
• Main Authors: Levy, L. B., Larsen, N. K., Davidson, T. A., Strunk, A., Olsen, J., Jeppesen, E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Glacier fluctuations; Greenland Ice Sheet; Holocene; Isua; Lake sediment records; glacier; Godthåbsfjord; Greenland; Ice Sheet
• Online Access: https://pure.au.dk/portal/da/publications/contrasting-evidence-of-holocene-ice-margin-retreat-southwestern-greenland(cb60d763-ca8d-4a54-9bab-95775dd05a36).html; https://doi.org/10.1002/jqs.2957

Constraining the Greenland Ice Sheet's (GrIS) response to Holocene climate change provides calibrations for ice sheet models that hindcast past ice margin fluctuations. Ice sheet models predict enhanced ice retreat in south-western Greenland during the middle Holocene; however, few geological observations corroborating the extensive retreat are available. We present new data from lake sediment cores from the Isua region, south-western Greenland, which provide constraints on Holocene fluctuations of the GrIS margins. Our data indicate that the main GrIS margin was 30km west of its present-day extent by ∼5.7k cal a BP and had retreated to within 3km of its present-day margin by ∼4.6k cal a BP; with subsequent re-advances by ∼1.8 and at ∼1.7, ∼1.3 and ∼0.5k cal a BP. Times of ice retreat are coeval with increasing temperatures in western Greenland, suggesting that temperature was a dominant factor in ice retreat. The late retreat at Isua is in contrast to the early retreat observed in the Godthåbsfjord area and is probably related to the lack of fjords extending to the present Isua ice margin. Our data are not consistent with current ice sheet models that overestimate the middle Holocene ice retreat in the Isua region of south-western Greenland.