A Combined Paleo-Proxy and Modeling Study of Abrupt Climate Change in the Tropical Atlantic and Its Relation to Atlantic Meridional Overturning Circulation Variability

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Both coupled climate model simulations and instrumental data analyses indicate that variability in the large scale circulation of the Atlantic Ocean (also called the Atlantic meridional overturning circulation, or AMOC) may be tightly coupled to tropical North Atlantic and subsurface temperature variability through both atmospheric and oceanic processes. While a slowdown of the AMOC results in an atmospheric-induced surface cooling in the entire tropical North Atlantic, the subsurface experiences an even larger warming due to rapid reorganizations of ocean circulation patterns. As a result, recent modeling studies and observational data point to the subsurface of the western tropical North Atlantic as the most sensitive Tropical Atlantic region to respond to AMOC variability.This study, co-led by a paleoceanographer and a climate modeler from Texas A & M University, combines proxy reconstructions of sea surface and subsurface temperature and salinity with climate model simulations to identify and understand teleconnections between ocean circulation, high latitude variability, and tropical Atlantic climate. Specifically, the researchers will use a time slice approach to investigate the evolution of vertical temperature and salinity change in the western Tropical North Atlantic linked directly to atmospheric and ocean circulation changes during three of the most significant events of the last deglaciation (Heinrich Event 1, the Bolling-Allerod, and the Younger Dryas). They will also test the fidelity of model results by generating similar proxy records for the past 60,000 years. Overall they seek to test the hypothesis that cold periods on the high-latitude North Atlantic correspond to intense subsurface warming in the western tropical North Atlantic, suggesting that western tropical North Atlantic subsurface temperature change is a sensitive indicator of AMOC variability. This research will improve understanding of the interplay between ocean circulation and climate change, and could potentially improve predictive capability of tropical Atlantic climate variability. Funding supports two graduate students and fosters greater collaboration between two communities of researchers.