The role of inland ice dynamics in controlling the variable maximum extent of the Laurentide Ice Sheet off southeastern Baffin Island

Abstract

Reconstructions of the maximum extent and dynamics of the Laurentide Ice Sheet (LIS) during the Last Glacial Maximum (LGM) are needed for understanding how marine-based ice sheets will respond to modern climate change. The partitioning of ice masses and the location of dominant ice flows within the LIS are broadly known at regional scales, but their influence on the marine-based maximum extent of the ice sheet remains poorly constrained. Here, we provide evidence for the maximal extent of the LIS margin during the LGM in the Broughton and Merchants cross-shelf troughs off southeastern Baffin Island based on newly acquired sea floor geomorphology data. Grounding-zone wedges (GZWs), moraines and ice-stream bedforms within the Merchants cross-shelf trough delimit the maximum extent of the LIS in this sector to near the mouth of the modern fjords. Two lateral moraines, mega-scale glacial lineations (MSGLs), and iceberg scours also indicate the presence of an ice shelf extending beyond the former grounding line. In Broughton Trough, the maximum extent of the LIS is interpreted from the distribution of MSGLs and iceberg scours. The presence of sticky spots near the shelf edge may have played a role in subglacial flow and thus glacier behaviour. The difference in ice extent between the two nearby troughs is attributed to partitioning of the LIS between ice flowing from the Penny Ice Cap into Broughton Trough and ice from local alpine glaciers flowing into Merchants Trough. In addition, the presence of a dominant ice flow south of the Cumberland Peninsula may have drained ice masses of Cumberland Peninsula towards the south and caused minimal expansion in Merchants Trough to the north. These results provide a clearer understanding of the relationship between ice-sheet extent along continental margins and inland ice dynamics.