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Dansgaard–Oeschger and Heinrich events constitute ones of the most enigmatic features of the last glacial period. Many studies have focused on their characteristic millennial climatic variability, testing atmospheric/cryospheric/oceanic couplings, but major uncertainties and discrepancies still remain. A new scenario, robustly supported by an approach coupling paleoreconstructions and freshwater hosing experiments simulating Heinrich-type perturbations, has recently emerged. Reconciling most of the up to now hypothesized theories, it suggests the occurrence of a regional seesaw between a cooled-down North Atlantic Ocean and warmed-up Nordic Seas during cold atmospheric phases, in relation to enhanced subsurface advection of warm Atlantic waters re-emerging in the Norwegian Sea. The associated ocean warming, thus reaching Nordic basins at a critical location beyond the Faeroe-Shetland sill, is proposed to be involved in the concomitant release of European icebergs. Here we further investigate this promising scenario over the 35–41 ka BP interval by (i) outlining its precise spatial pattern in a crucial area, i.e. the junction between the North Atlantic and the Norwegian Sea close to European ice-sheets, (ii) resolving its very fine temporal and regional evolution during critical transitions associated with the onset of warm advection, i.e. Greenland Interstadial to Greenland Stadial and Greenland Interstadial to Heinrich Stadial, and (iii) assessing its impact on the spatio-temporal dynamic of iceberg discharges from the European and Laurentide ice-sheets during cold stadial episodes especially including Heinrich event 4. [ABSTRACT FROM AUTHOR]

The last glacial millennial climatic events (i.e. Dansgaard-Oeschger and Heinrich events) constitute outstanding case studies of coupled atmosphere-ocean-cryosphere interactions. Here, we investigate the evolution of sea-surface and subsurface conditions, in terms of temperature, salinity and sea ice cover, at very high-resolution (mean resolution between 55 and 155 years depending on proxies) during the 35–41 ka cal BP interval covering three Dansgaard-Oeschger cycles and including Heinrich event 4, in a new unpublished marine record, i.e. the MD99-2285 core (62.69°N; -3.57s°E). We use a large panel of complementary tools, which notably includes dinocyst-derived sea-ice cover duration quantifications. The high temporal resolution and multiproxy approach of this work allows us to identify the sequence of processes and to assess ocean-cryosphere interactions occurring during these periodic ice-sheet collapse events. Our results evidence a paradoxical hydrological scheme where (i) Greenland interstadials are marked by a homogeneous and cold upper water column, with intensive winter sea ice formation and summer sea ice melting, and (ii) Greenland and Heinrich stadials are characterized by a very warm and low saline surface layer with iceberg calving and reduced sea ice formation, separated by a strong halocline from a less warm and saltier subsurface layer. Our work also suggests that this stadial surface/subsurface warming started before massive iceberg release, in relation with warm Atlantic water advection. These findings thus support the theory that upper ocean warming might have triggered European ice-sheet destabilization. Besides, previous paleoceanographic studies conducted along the Atlantic inflow pathways close to the edge of European ice-sheets suggest that such a feature might have occurred in this whole area. Nonetheless, additional high resolution paleoreconstructions are required to confirm such a regional scheme. [ABSTRACT FROM AUTHOR]