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

• Main Authors: Cronauer, SL, Briner, JP, Kelley, SE, Zimmerman, SRH, Morlighem, M
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2016
• Subjects: Cosmogenic nuclide exposure dating; Greenland Ice Sheet; Proglacial-threshold lake; Holocene; Earth Sciences; History and Archaeology; Paleontology; Drygalski; Greenland; Nuussuaq; Ice Sheet
• Online Access: https://escholarship.org/uc/item/3fs4m51t

We reconstruct the history of the Greenland Ice Sheet margin on the Nuussuaq Peninsula in central West Greenland through the Holocene using lake sediment analysis and cosmogenic 10Be exposure dating of the prominent Drygalski Moraines. Erratics perched on bedrock outboard of the Drygalski Moraines constrain local deglaciation to ∼9.9±0.6ka (n=2). Three Drygalski Moraine crests yield mean 10Be ages of 8.6±0.4ka (n=2), 8.5±0.2ka (n=3), and 7.6±0.1ka (n=2) from outer to inner. Perched erratics between the inner two moraines average 7.8±0.1ka (n=2) and are consistent with the moraine ages. Sediments from a proglacial lake with a catchment area extending an estimated 2km beneath (inland of) the present ice sheet terminus constrain an ice sheet minimum extent from 5.4ka to 0.6ka. The moraine chronology paired with the lake sediment stratigraphy reveals that the ice margin likely remained within ∼2km of its present position from ∼9.9 to 5.4ka. This unexpected early Holocene stability, preceded by rapid ice retreat and followed by minimum ice extent between ∼5.4 and 0.6ka, contrasts with many records of early Holocene warmth and the Northern Hemisphere summer insolation maximum. We suggest ice margin stability may instead be tied to adjacent ocean temperatures, which reached an optimum in the middle Holocene.