Variability of sea-ice conditions in the Fram Strait over the past 30,000 years

Abstract

Sea ice is a critical component of the climate and oceanographic system in the North Atlantic Ocean. A biomarker record reveals millennial-scale and glacial–interglacial fluctuations in sea-ice coverage in the northernmost Atlantic Ocean over the past 30,000 years. Sea ice is a critical component of the climate system: variations in sea-ice cover affect the albedo of polar regions, and also the rate of deepwater formation1,2. Changes in the sea-ice cover of the North Atlantic Ocean are thought to have been related to abrupt climate changes throughout the last glacial termination3, but reconstructions of sea-ice conditions are rare. Here we use the sedimentary abundance of the IP25 and brassicasterol biomarkers, produced by sea-ice-associated diatoms and open-water phytoplankton, respectively, to generate a record of sea-ice conditions in the northernmost Atlantic Ocean for the past 30,000 years. Our reconstruction shows that a stationary margin between sea-ice cover and the open ocean existed during the Last Glacial, although perennial sea-ice cover prevailed for most of the Last Glacial Maximum. An early warming about 14,000 years ago was associated with ice-free conditions; however, seasonal sea ice was present throughout the Holocene. We find temporal links between our record of sea ice and reconstructions of the amount of relatively warm Atlantic water advected into the Nordic Seas4,5. We therefore conclude that changes in sea-ice conditions are linked to regional and global climate anomalies and oceanographic circulation in the North Atlantic.