The goal of this project is to improve process-based understanding of marine-terminating ice sheet retreat by studying the inception of deglaciation along the western margin of the Greenland Ice Sheet (GIS) and the coeval evolution of Baffin Bay oceanography. At the end of the last ice age, about 20,000 years ago, the western GIS margin extended farther into Baffin Bay, hundreds of kilometers west of its present position. By 10,000 years ago, the ice margin had largely retreated to within the current coastline. It is unclear if a warming atmosphere, a warming ocean, or some combination of the two is responsible for the retreat. Sediments studied along the West Greenland margin as part of this project will establish regional variations in the timing, magnitude, and rate of GIS retreat during the deglaciation. The relative timing of GIS changes and ocean warming, recorded in the same sediments, will improve our understanding of the behavior of large ice sheets in the past and future. The project broader impacts include support for a postdoctoral researcher, three graduate students, and undergraduate researchers. In addition, the project will support production of an outreach film based on the proposed research expedition. The project also will facilitate development of an upper-level undergraduate course focused on the deglaciation. To accomplish this goal, an oceanographic expedition will study four West Greenland trough mouth fan systems (where the GIS deposited large volumes of sediment when it extended offshore) using seafloor and sub-seafloor imaging techniques and by collecting sediment cores spanning the end of the last ice age to present. Biological, magnetic, geochemical, and physical properties from the sediment records will be used to test the primary hypothesis; that increasing ocean temperature at the base of marine terminating glaciers is a major driver of ice-sheet instability. The project will establish: 1) the timing and extent of warm Atlantic water incursion along the west Greenland margin; 2) the phasing of ice margin retreat and ocean change; and 3) the influence of regional geology, geomorphology, and ice dynamics on ice-margin retreat. Early career leadership (supported by senior mentors) is at the heart of this project with three US-based assistant professors and one post-doctoral researcher directing shipboard operations and spearheading the post-expedition science. Half of the sea-going science party will be graduate and undergraduate students. Acquisition of the first US-based sediment cores from Baffin Bay and archival of the cores and data in US facilities and databases will provide diverse high-latitude research opportunities to the NSF community, ensuring the continuing legacy of this project.

This collaboration between Hatfield (University of Florida, 2112536), Walczak (Oregon State University, 2112498), Klotsko (University of North Carolina at Wilmington, 2112529), Reilly (University of California-San Diego Scripps, 2112542) and Jennings (University of Colorado at Boulder, 2112547) will improve process-based understanding of marine-terminating ice sheet retreat by studying the inception of deglaciation along the western margin of the Greenland Ice Sheet (GIS) and the coeval evolution of Baffin Bay oceanography. During the summer of 2023 a team of 22 scientific participants will conduct sampling onboard the R/V Armstrong on the West Greenland slope and shelf in Baffin Bay and the Labrador Sea. The aim of the project is to study the spatial and temporal characterization of the past history of the West Greenland Current and the west Greenland Ice Sheet since the last glacial maximum with a focus on four Trough Mouth Fan (TMF) systems and their fine grained hemipelagic deposits to their north. Studies will include sub-bottom geophysical surveys, sediment coring, and water sampling for paleo-proxy calibration. Cargo will board the Armstrong in Woods Hole, MA, USA and disembark in Reykjavik, Iceland. Shipment to Woods Hole and from Reykjavik will be arranged by the Marine Sediment Sampling (MARSSAM) group at Oregon State University. Some representative samples will be unloaded and transported home with the science party. Twenty US-based Science Personnel and two Greenlandic-based Science personal will board the Armstrong in Nuuk (Godthaab), Greenland and disembark in Reykjavik, Iceland. Participants will travel to/from Greenland/Iceland via commercial air.

All other logistics will be organized by the researchers and paid through their grants.