Iceberg discharges of the last glacial period driven by oceanic circulation changes

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Proxy data reveal the existence of episodes of increased deposition of ice-rafted detritus in the North Atlantic Ocean during the last glacial period interpreted as massive iceberg discharges from the Laurentide Ice Sheet. Although these have long been attributed to self-sustained ice sheet oscillations, growing evidence of the crucial role that the ocean plays both for past and future behavior of the cryosphere suggests a climatic control of these ice surges. Here, we present simulations of the last glacial period carried out with a hybrid ice sheet–ice shelf model forced by an oceanic warming index derived from proxy data that accounts for the impact of past ocean circulation changes on ocean temperatures. The model generates a time series of iceberg discharge that closely agrees with ice-rafted debris records over the past 80 ka, indicating that oceanic circulation variations were responsible for the enigmatic ice purges of the last ice age.
© PNAS. We thank A. Ganopolski for helpful discussions. This work was funded by the Spanish Ministry of Science and Innovation under the CGL08-06558-C02-01 project. The research leading to these results has also received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under Grant 243908, “Past4Future. Climate change - Learning from the past climate”. A.R. is supported by the Marie Curie 7th Framework Programme.