Direct evidence for thinning and retreat of the southernmost Greenland ice sheet during the Younger Dryas

During the last deglaciation, North Atlantic climate abruptly warmed at the Bølling (∼14.7 ka), cooled into the Younger Dryas (∼12.9 ka) and abruptly warmed again into the Holocene (∼11.7 ka). While these events are defined by Greenland ice cores, there is still considerable uncertainty on Greenland...

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Bibliographic Details
Published in:Quaternary Science Reviews
Main Authors: Carlson, AE, Reyes, A, Gusterson, E, Axford, Y, Wilcken, KM, Rood, DH
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier 2021
Subjects:
Science & Technology
Physical Sciences
Geography
Physical
Geosciences
Multidisciplinary
Physical Geography
Geology
Pleistocene
Glaciation
Paleoclimatology
Greenland
Cosmogenic isotopes
NORTH-ATLANTIC
GLACIAL ICE
CLIMATE
DEGLACIATION
BE-10
SOUTH
SHELF
Paleontology
04 Earth Sciences
21 History and Archaeology
Greenland ice cores
Ice Sheet
North Atlantic
Online Access:http://hdl.handle.net/10044/1/93503
https://doi.org/10.1016/j.quascirev.2021.107105
Description
Summary:During the last deglaciation, North Atlantic climate abruptly warmed at the Bølling (∼14.7 ka), cooled into the Younger Dryas (∼12.9 ka) and abruptly warmed again into the Holocene (∼11.7 ka). While these events are defined by Greenland ice cores, there is still considerable uncertainty on Greenland ice-sheet margin responses to abrupt climate change. To refine the ice sheet's deglacial history, we present new cosmogenic nuclide surface exposure ages from boulders on bedrock at five sites in southernmost Greenland fjords located midway between the coast and inland ice margin. We find ice-sheet thinning below three local topographic highs at 12.7 ± 0.3 ka (n = 3), 13.1 ± 0.4 ka (n = 1, 2 outliers), and 12.3 ± 0.2 ka (n = 3), with up-fjord retreat at 12.5 ± 0.3 ka (n = 3) and 12.7 ± 0.2 ka (n = 4) based on two sites just above the mid-fjord marine limit. These mid-fjord 10Be ages therefore show southernmost Greenland ice-sheet thinning and retreat during the Younger Dryas. We hypothesize that this thinning and retreat was a response to ocean warming prior to the Holocene and/or summer shortwave radiative forcing during the Younger Dryas due to peak boreal summer insolation. Our results also support a previously hypothesized winter bias in proxy records of Younger Dryas atmospheric cooling, since a large summer cooling during the Younger Dryas could have counteracted the effects of ocean warming and direct radiative forcing, inhibiting ice-sheet retreat.

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