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Abstract. The northern sector of the Greenland Ice Sheet is considered to beparticularly susceptible to ice mass loss arising from increased glacierdischarge in the coming decades. However, the past extent and dynamics ofoutlet glaciers in this region, and hence their vulnerability to climatechange, are poorly documented. In the summer of 2019, the Swedish icebreakerOden entered the previously unchartered waters of Sherard Osborn Fjord, whereRyder Glacier drains approximately 2 % of Greenland's ice sheet into theLincoln Sea. Here we reconstruct the Holocene dynamics of Ryder Glacier andits ice tongue by combining radiocarbon dating with sedimentary faciesanalyses along a 45 km transect of marine sediment cores collected betweenthe modern ice tongue margin and the mouth of the fjord. The resultsillustrate that Ryder Glacier retreated from a grounded position at thefjord mouth during the Early Holocene (> 10.7±0.4 ka cal BP) and receded more than 120 km to the end of Sherard Osborn Fjord by theMiddle Holocene (6.3±0.3 ka cal BP), likely becoming completelyland-based. A re-advance of Ryder Glacier occurred in the Late Holocene,becoming marine-based around 3.9±0.4 ka cal BP. An ice tongue,similar in extent to its current position was established in the LateHolocene (between 3.6±0.4 and 2.9±0.4 ka cal BP) andextended to its maximum historical position near the fjord mouth around 0.9±0.3 ka cal BP. Laminated, clast-poor sediments were deposited duringthe entire retreat and regrowth phases, suggesting the persistence of an icetongue that only collapsed when the glacier retreated behind a prominenttopographic high at the landward end of the fjord. Sherard Osborn Fjordnarrows inland, is constrained by steep-sided cliffs, contains a number ofbathymetric pinning points that also shield the modern ice tongue andgrounding zone from warm Atlantic waters, and has a shallowing inlandsub-ice topography. These features are conducive to glacier stability andcan explain the persistence of Ryder's ice tongue while the glacier remainedmarine-based. However, the physiography of the fjord did not halt thedramatic retreat of Ryder Glacier under the relatively mild changes inclimate forcing during the Holocene. Presently, Ryder Glacier is groundedmore than 40 km seaward of its inferred position during the Middle Holocene,highlighting the potential for substantial retreat in response to ongoingclimate change.
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Holocene glacial activity in B arilari B ay, west A ntarctic P eninsula, tracked by magnetic mineral assemblages: L inking ice, ocean, and atmosphere
Abstract We investigate the origin and fate of lithogenic sediments using magnetic mineral assemblages in Barilari Bay, west Antarctic Peninsula (AP) from sediment cores recovered during the Larsen Ice Shelf System, Antarctica (LARISSA) NBP10‐01 cruise. To quantify and reconstruct Holocene changes in covarying magnetic mineral assemblages, we adopt an unsupervised mathematical unmixing strategy and apply it to measurements of magnetic susceptibility as a function of increasing temperature. Comparisons of the unmixed end‐members with magnetic observations of northwestern AP bedrock and the spatial distribution of magnetic mineral assemblages within the fjord, allow us to identify source regions, including signatures for “inner bay,” “outer bay,” and “northwestern AP” sources. We find strong evidence that supports the establishment of a late Holocene ice shelf in the fjord coeval with the Little Ice Age. Additionally, we present new evidence for late Holocene sensitivity to conditions akin to positive mean Southern Annual Mode states for western AP glaciers at their advanced Neoglacial positions.
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- PAR ID:
- 10530114
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Journal Name:
- Geochemistry, Geophysics, Geosystems
- Volume:
- 17
- Issue:
- 11
- ISSN:
- 1525-2027
- Page Range / eLocation ID:
- 4553 to 4565
- Subject(s) / Keyword(s):
- Antarctic Peninsula Barilari Bay Environmental Magnetism Iron oxides Provenance
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/2016GC006627
