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Abstract. Sometime during the middle to late Holocene (8.2 ka to ∼ 1850–1900 CE), the Greenland Ice Sheet (GrIS) was smaller than its currentconfiguration. Determining the exact dimensions of the Holocene ice-sheetminimum and the duration that the ice margin rested inboard of its currentposition remains challenging. Contemporary retreat of the GrIS from itshistorical maximum extent in southwestern Greenland is exposing a landscapethat holds clues regarding the configuration and timing of past ice-sheetminima. To quantify the duration of the time the GrIS margin was near itsmodern extent we develop a new technique for Greenland that utilizes in situcosmogenic 10Be–14C–26Al in bedrock samples that have becomeice-free only in the last few decades due to the retreating ice-sheet margin atKangiata Nunaata Sermia (n=12 sites, 36 measurements; KNS), southwest Greenland. To maximizethe utility of this approach, we refine the deglaciation history of the regionwith stand-alone 10Be measurements (n=49) and traditional 14C agesfrom sedimentary deposits contained in proglacial–threshold lakes. We combineour reconstructed ice-margin history in the KNS region with additionalgeologic records from southwestern Greenland and recent model simulations ofGrIS change to constrain the timing of the GrIS minimum in southwestGreenland and the magnitude of Holocene inland GrIS retreat, as well as to explore theregional climate history influencing Holocene ice-sheet behavior. Our10Be–14C–26Al measurements reveal that (1) KNS retreated behindits modern margin just before 10 ka, but it likely stabilized near thepresent GrIS margin for several thousand years before retreating fartherinland, and (2) pre-Holocene 10Be detected in several of our sample sitesis most easily explained by several thousand years of surface exposure duringthe last interglaciation. Moreover, our new results indicate that the minimumextent of the GrIS likely occurred after ∼5 ka, and the GrISmargin may have approached its eventual historical maximum extent as early as∼2 ka. Recent simulations of GrIS change are able to match thegeologic record of ice-sheet change in regions dominated by surface massbalance, but they produce a poorer model–data fit in areas influenced by oceanicand dynamic processes. Simulations that achieve the best model–data fitsuggest that inland retreat of the ice margin driven by early to middleHolocene warmth may have been mitigated by increased precipitation. Triple10Be–14C–26Al measurements in recently deglaciated bedrockprovide a new tool to help decipher the duration of smaller-than-present iceover multiple timescales. Modern retreat of the GrIS margin in southwestGreenland is revealing a bedrock landscape that was also exposed during themigration of the GrIS margin towards its Holocene minimum extent, but it has yetto tap into a landscape that remained ice-covered throughout the entireHolocene.
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Deglaciation of the Prudhoe Dome in northwestern Greenland in response to Holocene warming
Projections of future sea-level rise benefit from understanding the response of past ice sheets to warming during past Quaternary interglacials. Constraints on the extent of inland Greenland Ice Sheet retreat during the Middle Holocene (~8–4 thousand years before present) are limited because geological records of a smaller-than-modern phase largely remain beneath the modern ice sheet. We drilled through 509 metres of firn and ice at Prudhoe Dome, northwestern Greenland, to obtain sub-ice material yielding direct evidence for the response of the northwest Greenland ice sheet to Holocene warmth. Here we present infrared stimulated luminescence measurements from sub-ice sediments that indicate that the ground below the summit was exposed to sunlight 7.1 ± 1.1 thousand years ago. This proposed complete deglaciation of Prudhoe Dome, coeval to reduced extent at other ice caps across northern Greenland, is consistent with interglacial-only δ18O values from the Prudhoe Dome ice column and ice depth–age modelling. Our results point to a substantial response of the northwest Greenland ice sheet to early Holocene warming, estimated to be +3–5 °C from palaeoclimate data. This range of summer temperatures is similar to projections of warming by 2100 CE.
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- PAR ID:
- 10662770
- Publisher / Repository:
- Nature Geoscience
- Date Published:
- Journal Name:
- Nature Geoscience
- ISSN:
- 1752-0894
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41561-025-01889-9
