Reconstructions of the Laurentide Ice Sheet based on Quaternary sediment architecture and buried glacial channels on the Labrador Shelf

The Laurentide Ice Sheet (LIS) covered vast areas of North America during the Wisconsinan period. The melting of the LIS resulted in the release of a substantial volume of freshwater into the Labrador Sea, thereby affecting the strength of the Atlantic Meridional Overturning Circulation (AMOC), a critical component of the global climate system. Consequently, the investigation of the dynamics of the LIS provides a framework for predicting the melting of analogous ice sheets, such as the Greenland Ice Sheet, in the future. This study presents an updated Quaternary stratigraphy of the Labrador Shelf, based on 2D multi-channel seismic reflection data from three glacial cross-shelf troughs: Okak, Hopedale and Cartwright. Seven different seismic units are described and interpreted in terms of their origin and deposition processes. We observe de- and interglacial deposits between glacial till layers for the first time on the Labrador Shelf. Additionally, sets of incised channels at three different depth intervals have been discovered. The data gathered indicates that these channels are of subglacial origin. Finally, the observations are combined into a shelf evolution model consisting of eight stages and spanning two glacial-interglacial cycles. Our study demonstrates that the cross-shelf troughs of the Labrador Shelf were not fully excavated by the LIS during the Wisconsinan glaciation. Instead, deeper sediment layers contain evidence of older glacial-interglacial cycles. Consequently, the sedimentary succession can be used as an archive to reconstruct the dynamics of glaciations during Quaternary glacial-interglacial cycles.