Arctic sea ice and freshwater in the East Greenland Current during the Deglacial

The oceans play a crucial role in transporting heat and moisture from the equator to the poles. Observations show that the input of freshwater in polar regions from melting glaciers and sea ice has already contributed to weakening ocean circulation. However, our understanding of these processes is limited by the length of observational records; examining previous periods of change can aid this understanding. This project focuses on the Younger Dryas (11.7-12.9 ka), a cold period that abruptly interrupted the Earth’s warming climate during deglaciation. The cause of this cooling is debated, but a leading hypothesis is that freshwater input from glacial lakes to the North Atlantic Ocean slowed ocean circulation. Alternatively, computer models indicate that sea ice export from the Arctic Ocean, traveling along the east coast of Greenland, could have been responsible for triggering the Younger Dryas. Yet, there are currently limited palaeoceanographic data from this region to evaluate this alternate hypothesis. To address this data gap, this project will utilize existing marine sediment cores to reconstruct sea ice and freshwater changes during the Younger Dryas. This research will provide quantitative data to understand what triggered an abrupt slowdown of ocean circulation that resulted in prominent cooling of the Northern Hemisphere. The results will lead to a better understanding of the sensitivity of ocean circulation to the input of freshwater from sea ice export and melt, important for evaluating the potential impact of future melt water release from the Arctic. Additionally, this project was conceived and will be led by a postdoctoral researcher, with support from two established principal investigators. Thus, an early career researcher will develop leadership and supervisory skills, essential to professional development. This project addresses the hypothesis that ‘The Younger Dryas was initiated by the export of Arctic sea ice and freshwater carried by the East Greenland Current’. We will leverage existing marine sediment cores collected from the eastern coast of Greenland. Sea ice and salinity dynamics will be inferred from stable isotope measurements on planktic foraminifera and algal lipids, as well as from sea-ice biomarkers, lipid-based sea-surface temperature reconstructions, sedimentological analyses, and radiocarbon dating. Results will be synthesized with existing data to the north (Fram Strait and the Arctic Ocean) and south (Denmark Strait and the northern North Atlantic), in the context of existing model results, to examine the role sea ice and freshwater played in triggering the Younger Dryas. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.