第九届青年地学论坛

Numerous ice streams of the late Pleistocene Laurentide ice sheet (LIS) operated on the eastern Canadian continental margin during the last glacial cycle. The iconic largest Hudson Strait ice stream supplied enormous sediment and meltwater draining the interior of the LIS, resulting in development of Hatton trough-mouth fan. However, the ice-rafting through the Hudson Strait received worldwide attention due to the discovery of Heinrich layers in the North Atlantic during the last glacial cycle. The climatic impact of H-layers is the weakening of the AMOC by ice-rafted meltwater that disturbed the delicate salt balance at the sites of deep-water formation. As a result, the AMOC weakening is hypothesized as the instigator of the Northern Hemisphere cooling, as recorded in paleo-proxies. A new hypothesis appears to challenge this three-decade-old paradigm, suggesting that Hudson Strait ice stream was ice-free during MIS 3 (59 - 29 ka) and that the provenance of H-layers lies elsewhere. We used multi-beam swath bathymetry, seismic profiles, oxygen isotope stratigraphy, and geochemistry of 21 sediment cores data to make an attempt to refute the Hudson Strait ice-free hypothesis. Over the MIS 1–3 period, which was widely represented by cores, ice was grounded in the Hatton Basin and on the upper slope only immediately before H3. Older and younger H events had most likely a floating ice shelf in Hatton Basin, and sedimentation was dominated by the retreat of that ice shelf to Resolution Island. Distal cores show no systematic difference between the H1–top H3 and base H3–H5 intervals. Given the supply of carbonate detritus of consistent composition back to at least H5, any MIS 3 deglaciation of Hudson Bay would require improbably high growth rates of ice sheets in the center of the continent, unsupported by the current ice sheet and climate models.

Hudson Strait ice stream,MIS 3 ice-free,Heinrich layers,Laurentide ice-sheet,AMOC,trough-mouth fan