The North Atlantic was a key locus for circulation-driven abrupt climate change in the past and could
play a similar role in the future. Abrupt cold reversals, including the 8.2 ka event, punctuated the
otherwise warm early Holocene in the North Atlantic region and serve as useful paleo examples of rapid
climate change. In this work, we assess the cryospheric response to early Holocene climate history on
Baffin Island, Arctic Canada, using cosmogenic radionuclide dating of moraines. We present 39 new 10Be
ages from four sets of multi-crested early Holocene moraines deposited by cirque glaciers and ice cap
outlet glaciers, as well as erratic boulders along adjacent fiords to constrain the timing of regional
deglaciation. The age of one moraine is additionally constrained by in situ 14C measurements, which
confirm 10Be inheritance in some samples. All four moraines were deposited between ~9.2 and 8.0 ka,
and their average ages coincide with abrupt coolings at 9.3 and 8.2 ka that are recorded in Greenland ice
cores. Freshwater delivery to the North Atlantic that reduced the flux of warm Atlantic water into Baffin
Bay may explain brief intervals of glacier advance, although moraine formation cannot be definitively
tied to centennial-scale cold reversals. We thus explore other possible contributing factors, including ice
dynamics related to retreat of Laurentide Ice Sheet outlet glaciers. Using a numerical glacier model, we
show that the debuttressing effect of trunk valley deglaciation may have contributed to these morainebuilding
events. These new age constraints and process insights highlight the complex behavior of the
cryosphere during regional deglaciation and suggest that multiple abrupt cold reversalsdas well as
deglacial ice dynamicsdlikely played a role in early Holocene moraine formation on Baffin Island.
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Early Holocene ice retreat from Isle Royale in the Laurentian Great Lakes constrained with 10 Be exposure-age dating
Abstract. The timing of the Laurentide Ice Sheet's final retreat from North America's Laurentian Great Lakes is relevant to understanding regional meltwater routing, changing proglacial lake levels, and lake-bottom stratigraphy following the Last Glacial Maximum. Recessional moraines on Isle Royale, the largest island in Lake Superior, have been mapped but not directly dated. Here, we use the mean of 10 new 10Be exposure ages of glacial erratics from two recessional moraines (10.1 ± 1.1 ka, one standard deviation; excluding one anomalously young sample) to constrain the timing of Isle Royale's final deglaciation. This 10Be age is consistent with existing minimum-limiting 14C ages of basal organic sediment from two inland lakes on Isle Royale, a sediment core in Lake Superior southwest of the island, and an estimated deglaciation age of the younger of two subaqueous moraines between Isle Royale and Michigan's Keweenaw Peninsula. Relationships between Isle Royale's landform ages and Lake Superior bottom stratigraphy allow us to delineate the retreat of the Laurentide ice margin across and through Lake Superior in the early Holocene. We suggest that Laurentide ice was in contact with the southern shorelines of Lake Superior later than previously thought.
more » « less- Award ID(s):
- 1719249
- NSF-PAR ID:
- 10490173
- Publisher / Repository:
- Geochronology
- Date Published:
- Journal Name:
- Geochronology
- Volume:
- 5
- Issue:
- 2
- ISSN:
- 2628-3719
- Page Range / eLocation ID:
- 413 to 431
- 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/10.5194/gchron-5-413-2023
