Heinrich event iceberg flux, melting, and ocean circulation in the North Atlantic

Lead PI: Jerry F. McManus

Unit Affiliation: Geochemistry, Lamont-Doherty Earth Observatory (LDEO)

September 2016 - August 2019
Atlantic Ocean
Project Type: Research

DESCRIPTION: This project generally aims to generate high-resolution data on a suite of deep-sea sediment cores from the North Atlantic Ocean and to conduct a comparison of the results with conceptual and computer models for the episodic production of major iceberg discharges. The researchers aim to produce a spatially systematic dataset of the concentration, provenance and flux of ice-rafted debris (IRD), derived from the North American Laurentide Ice Sheet (LIS) in an array of sites extending from west to east across the subpolar ocean, and south to the subtropics. These data will be used to test hypotheses regarding the genesis and subsequent distribution of melting icebergs associated with the Heinrich events of the last glaciation and to provide insights into the interactions of cryosphere and ocean circulation. The catastrophic iceberg discharge (Heinrich) events that punctuated the last ice age were among the largest known interactions of the Earth's cryosphere, ocean, and climate. Although there is continued debate about their causes and consequences, in at least a subset of the events, the evidence is consistent with their likely influence on the salinity and stability of the subpolar Atlantic, significant weakening of the Atlantic meridional overturning circulation (AMOC), cooling of the northern hemisphere, warming of the southern hemisphere, and shifts in the global hydrological cycle and large-scale atmospheric circulation and composition. Yet deposits associated with two of the six events originally identified during the last glaciation have very different sedimentary characteristics in the eastern subpolar North Atlantic, where they have most commonly been compared. This poses a problem for any single mechanism proposed to explain the events, requiring exceptions or contrasting explanations for different events. The Broader Impacts involve advancing understanding of the cryosphere, ocean, and climate system. The project will support an early career postdoctoral researcher and several undergraduates in the research. Research participants will take part in a research cruise to recover new sediments as part of a collaborative effort that is aligned with the goals of international efforts to understand the Coupled North Atlantic-Arctic System. The Broader Impacts also involve outreach through collaboration with for New York City public high school teachers and students. Members of the project will participate in the biennial Lamont-Doherty Earth Observatory Open House which draws thousands of visitors of all ages to the campus.