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During the last deglaciation, collapse of the saddle between the North American Cordilleran and Laurentide ice sheets led to rapid ice-sheet mass loss and separation, with meltwater discharge contributing to deglacial sea level rise. We directly date ice-sheet separation at the end of the saddle collapse using 64 10Be exposure ages along an ~1200-km transect of the ice-sheet suture zone. Collapse began in the south by 15.4 ± 0.4 ka and ended by 13.8 ± 0.1 ka at ~56◦N. Ice-sheet model simulations consistent with the 10Be ages find that the saddle collapse contributed 6.2–7.2 m to global mean sea-level rise from ~15.5 ka to ~14.0 ka, or approximately one third of global mean sea-level rise over this period. We determine 3.1–3.6 m of the saddle collapse meltwater was released during Meltwater Pulse 1A ~14.6-14.3 ka, constituting 20–40% of this meltwater pulse’s volume. Because the separation of the Cordilleran and Laurentide ice sheets occurred over 1–2 millennia, the associated release of meltwater during the saddle collapse supplied a smaller contribution to the magnitude of Meltwater Pulse 1A than has been recently proposed.
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This content will become publicly available on December 14, 2026
K'/Ar Provenance Analysis of Bermuda Rise Sediment during Termination I
The formation of North Atlantic Deep Water (NADW) is an important component of the Atlantic Meridional Overturning Circulation’s redistribution of solar heat to the northern latitudes, and is sensitive to salinity perturbations in its source locations. Fresh glacial meltwater lowers the density of seawater, potentially influencing affect the strength and position of the density-driven overturning circulation. During Heinrich Stadial 1, the Laurentide Ice Sheet retreated rapidly from its maximum southeastern extent during the Last Glacial Maximum, sending icebergs and meltwater into the western North Atlantic. The Bermuda Rise is located in the deep western subtropical North Atlantic, where Antarctic Bottom Water mixes with newly formed NADW. Sediment proxy records from the Bermuda Rise have demonstrated that the strength of the NADW varied with abrupt deglacial climate changes (e.g., McManus et al., 2004, Nature). This study seeks to explore the influence of meltwater pulses from the Laurentide and Greenland ice sheets on NADW during the last deglaciation through the lens of the transport and deposition of silt and clay by deep ocean currents. We present a detailed record of fine-grained sediment provenance across the deglaciation using K’/Ar ages from Bermuda Rise Core KNR191-CDH13 (33 41.2 N, 57 36.9 W, 4583 m). The K’/Ar ages are based on measured 40Ar* (radiogenic product of 40K) and an assumed K concentration of 2% (The 40Ar* measurements are rapid and simple, allowing the development of high resolution records. Initial results from deglacial sediments on Bermuda Rise display values within the range of K’/Ar ages documented by previous studies of iceberg deposition from the North Atlantic, from ~400 to 1,200 Ma (e.g., Jantschik and Huon,1992, Eclogae geol. Helv.; Hemming et al., 2002, Chem. Geol.).
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- Award ID(s):
- 2442513
- PAR ID:
- 10649973
- Publisher / Repository:
- American Geophysical Union
- Date Published:
- Format(s):
- Medium: X
- Location:
- New Orleans, LA
- Sponsoring Org:
- National Science Foundation
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