Collapse of a marine-based ice stream during the early Younger Dryas chronozone, western Canadian Arctic

Abstract

New geophysical surveys and sediment cores constrain past dynamics of the Amundsen Gulf ice stream of the northwest Laurentide Ice Sheet (LIS), Arctic Canada, during the last glacial episode. An ice-rafted debris (IRD) unit and its stratigraphic relationship to former grounding lines record the withdrawal of the ∼60,000 km2 marine-based ice stream. Calibrated (cal.) radiocarbon ages from the IRD unit and from ice-contact raised marine sediments indicate that the ice stream retreated ∼250 km over a few centuries or less during the early Younger Dryas, ca. 12.80 ± 0.15 cal. kyr B.P. Despite a likely cooler paleoclimate, ice-marginal recession occurred at rates of at least 1 km/yr, triggered by grounding line retreat from a bathymetric sill and by a concomitant increase in calving margin length. Sediment cores from the adjacent continental slope confirm that the IRD-rich unit was also deposited in the Beaufort Sea as a chronostratigraphic marker bed. Such new evidence for widespread ice rafting establishes Amundsen Gulf as a discrete source area for early Younger Dryas sediment in the Arctic Ocean, including Fram Strait (between Greenland and Svalbard). The timing and scale of iceberg discharges show that Amundsen Gulf was a major conduit for fresh water to the Arctic Ocean during the Pleistocene-Holocene transition.

Isotopic Fingerprints of Ice‐Rafted Debris Offer New Constraints on Middle to Late Quaternary Arctic Circulation and Glacial History

“…These samples feature overall strongly unradiogenic εNd, as low as −22.9 in the prominent pink‐white layer PW2 assigned to MIS5d, probably indicating glacial discharge from the LIS interior (Canadian Shield; Patchett et al, 1999). This interpretation is consistent with the collapse pattern reconstructed for the NW LIS sector from glacial geological data (Lakeman et al, 2018; Stokes et al, 2009). PW carbonate layers with the North American signature occur as far from the Laurentide margin as the Mendeleev ridge (Core PS72/340; Figure 1), thus corroborating prominent ice‐collapse events (Bazhenova et al, 2017).…”

Sediment Provenance Changes in the Western Arctic Ocean in Response to Ice Rafting, Sea Level, and Oceanic Circulation Variations Since the Last Deglaciation

“…Major purge from the M'Clure and Amundsen Gulf ice stream was previously suggested by isotope data (Hillaire‐Marcel et al, ; Maccali et al, ), paleogeography study (Stokes et al, ), and numerical model (Tarasov & Peltier, ) between 13 and 12.7 ka cal BP and may have played a role in the slowdown of the Atlantic Meridional Overturning Circulation at the onset of the Younger Drays (Condron & Winsor, ). Overall, our results support the hypothesis that large meltwater and iceberg discharges from the Lake Agassiz outburst and Amundsen Gulf ice stream were likely to have triggered the Younger Dryas cooling by inhibiting deep water formation in the subpolar North Atlantic and weakening the strength of the Atlantic Meridional Overturning Circulation (Condron & Winsor, ; Hillaire‐Marcel et al, ; Lakeman et al, ; Maccali et al, ; Not & Hillaire‐Marcel, ; Tarasov & Peltier, ).…”

“…(b) Localization of cores 05JPC and 02PC (this study) as well as cores 56PC (Lakeman et al, ), 750PC (Scott et al, ), ARA2B‐A1 (Yamamoto et al, ), ARA2B‐1B (Stein et al, ), and core 06JPC (Ortiz et al, ). References used for the geochemical and mineralogical database are listed in Table S2 (mineralogical data: Andrews et al, ; Belt et al, ; Darby et al, ; Gamboa et al, ; Gamboa, ; Lakeman et al, ; Stein et al, ; geochemical data: Astakhov et al, ; Gamboa et al, ; Gordeev et al, ; Holemann et al, ; Rachold, ; Rachold et al, ; Savenko et al, ). BG = Beaufort Gyre; TPD = Transpolar Drift.…”

Leveraging the Rapid Retreat of the Amundsen Gulf Ice Stream 13,000 Years Ago to Reveal Insight Into North American Deglaciation

“…Evidence for the timing and rapid retreat of the Amundsen Gulf Ice Stream at 12.8 ka (Lakeman et al, ) motivates our model investigation of North American deglacial ice histories because ice sheet dynamics depend on bedrock topography. This topography is, in turn, controlled by the history of previous ice cover.…”

“…(b) Histogram showing the number of simulations (of 1,000 total) predicting specific ranges of grounding line retreat after 500 years. The dotted red line is the total grounding line retreat of the Amundsen Gulf Ice Stream reported byLakeman et al (2018); reaching this retreat extent with our model runs requires 300 years or longer.…”