A few highlights of the late glacial and deglacial history of Baffin Bay and the Labrador Sea

English Abstract:

Recent works, based on gravimetric data (e.g., Paulsen et al., GIJ 2007) provide new insights into the isostatic response of the northeastern American lithosphere to glacial loading and unloading. They point to a multidome Last Glacial Maximum (LGM) Laurentide Ice Sheet (LIS), with ice-divides over Keewatin, New-Quebec and the Foxe Basin-Baffin Land area, feeding large-scale ice streams (Stokes and Tarasov, GRL 2014). Similarly, recent studies of marine cores raised from Baffin Bay and the Labrador Sea led to reconstruct near steady-streaming interrupted by high amplitude, but out of phase surges along the NE LIS margin (cf. carbonate events from Hudson Strait and Baffin Bay; Simon et al., JQS 2014). These studies also point to the potential role of glacio- isostatic re-equilibrium and advection of warm, sub-surface waters in the NW North Atlantic sector, for the triggering of large ice surges, notably those off Hudson Strait. These findings might also imply a slightly lesser LIS-LGM volume than previously assumed (~ 70 m of "eustatic" sea level). However, a compilation of all available information on the isotopic composition of the LIS-ice suggests slightly less negative oxygen isotope composition than the currently assumed mean value (i.e., ~ -25‰ vs - 30‰, vs VSMOW). As a consequence, the overall ice-ocean mass transfer isotopic budgets between the LGM and the Present might require some re-examination. Nevertheless, the reconstruction of paleo-density gradients in the northern North Atlantic marginal basins since the LGM indicates a late attainment of full interglacial conditions, with a "modern-like" Atlantic Meridional Overturning inception at ~ 7.5 (Labrador Sea) and ~ 6.5 BP (western Nordic Seas), but fully emplaced since the mid-late Holocene transition only.