The first estimation of Fleuve Manche palaeoriver discharge during the last deglaciation: Evidence for Fennoscandian ice sheet meltwater flow in the English Channel ca 20?18 ka ago

The Fleuve Manche (English Channel) palaeoriver represents the largest river system that drained the European continent during Pleistocene lowstands, particularly during the Elsterian (Marine Isotope Stage 12) and Saalian Drenthe (MIS 6) glaciations when extensive ice advances into the North Sea area forced the central European rivers to flow southwards to the Bay of Biscay (NE Atlantic). Numerous long piston cores and high-resolution acoustic data from the northern Bay of Biscay have been correlated using a well-constrained chronostratigraphical framework, and for the first time allow the estimation of the discharge of the Fleuve Manche palaeoriver at the end of the last glacial period (i.e. Weichselian). Our results, discussed in the light of relationships between river loads and drainage area characteristics, strongly suggest that the Bay of Biscay collected sediment-laden meltwater from the Northern European lowlands and the southern part of the Fennoscandian ice sheet at the end of the last glacial period and particularly during the paroxysmal phase of the European deglaciation ca 20?18 ka ago. This demonstrates that the Fleuve Manche drainage area at that time was equivalent to those dating from the major Elsterian and Saalian Drenthe glaciations. Based on our data, we propose a revision of the palaeogeographical and palaeoglaciological evolution of the North Sea area while showing that the British and Fennoscandian ice sheets entered the North Sea basin until ca 18 ka initiating isostatic adjustment of the basin. This allowed the North Sea fluvial system to flow southwards through the Dover Strait. Finally, we discuss the Fleuve Manche freshwater discharge during the maximum European ice sheet retreat ca 18 ka. The estimated discharge at this time appears important and sufficiently sustained to possibly contribute to the profound destabilisation of the thermohaline circulation recognised in the North Atlantic from ca 18 to 16 ka.