Synthesizing historical records to constrain and understand Great Sea Ice Anomalies

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Arctic sea ice is not just a passive indicator of climate change, but also an active agent of change. Interactions between sea ice, oceans, and the atmosphere affect the global climate system in ways that are not yet fully understood. This project focuses on understanding how sudden changes in the export of sea ice (Great Sea Ice Anomalies or GSIAs) from the Arctic Ocean through Fram Strait (between Svalbard and Greenland) and along the East Greenland Current can have far-reaching and long-lasting effects in the subpolar North Atlantic. For example, in the 1960s and 1970s, a large and abrupt influx of sea ice and freshwater from the Arctic Ocean led to a strong anomaly in the salinity of the northern Atlantic Ocean (what has become known as the Great Salinity Anomaly). There are indications that such GSIA events have occurred in the past, but the frequency, intensity, and causes of such events are not yet understood. The research team is assembling data from historical and cultural records dating back to 1600 to identify potential anomalies and combining these results with advanced modelling results to understand potential triggers of GSIAs and how their occurrence affects the North Atlantic. This study will investigate abrupt GSIAs in the Atlantic Arctic using multiple lines of evidence based on data from long observational time series, historical, and proxy records of sea ice spanning several centuries in the waters near southwestern Greenland, northern Iceland, and the western Nordic Seas. These data will provide an empirical foundation required to assess the occurrence and origins of GSIAs and explore three hypotheses: (1) GSIAs of decadal to multidecadal duration are recurrent events, with the (sub)decadal sea ice anomaly leading to the 1960–70s salinity anomaly being a moderate realization; (2) GSIAs can be initiated spontaneously from natural internal climate-system variability alone; and (3) sea ice anomalies east of Greenland and multidecadal variability in Atlantic Ocean sea-surface temperatures are coupled bidirectionally. The research will provide the first-ever consistent catalog of GSIAs and improve our fundamental understanding of how abrupt changes in sea ice in the Atlantic Arctic occur. The research will provide important historical perspectives and contribute to a better understanding of changes in the Arctic system. This research has broad scientific importance because abrupt changes in sea ice export may influence ocean circulation and temperatures, marine ecosystems, and climate across the northern North Atlantic.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.