Norwegian Sea warm pulses during Dansgaard-Oeschger stadials: Zooming in on these anomalies over the 35-41 ka cal BP interval and their impacts on proximal European ice-sheet dynamics

作者：Wary Melanie^*; Eynaud Frederique; Rossignol Linda; Lapuyade Joanna; Gasparotto Marie Camille; Londeix Laurent; Malaize Bruno; Castera Marie Helene; Charlier Karine

来源：Quaternary Science Reviews, 2016, 151: 255-272.

DOI：10.1016/j.quascirev.2016.09.011

• Dansgaard-Oeschger events
• Heinrich events
• Trigger mechanism
• Sea ice
• Surface/subsurface hydrological conditions
• High resolution multiproxy approach

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during the 35 -41 ka cal BP interval covering three Dansgaard-Oeschger cycles and including Heinrich event 4, in a new unpublished marine record, i.e. the MD99-2285 core (62.69 degrees N; -3.57s degrees E).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 haloclirie 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.

• 出版日期2016-11-1