Late Pleistocene Laurentide-source iceberg outbursts in the western Arctic Ocean

Abstract

The source, amount, and trajectory of icebergs discharged into the western Arctic Ocean provide essential clues to Arctic ice sheet development and its feedback on Atlantic meridional overturning circulation (AMOC). Nd and Sr isotopes, ice-rafted debris, and mineral components were used to trace the icebergs that were first discharged into the western Arctic Ocean and then exported to the North Atlantic Ocean. The records indicated that the iceberg outburst (large-scale iceberg export via the Fram Strait) since the Late Pleistocene does not entirely depend on the iceberg discharge from the Laurentide ice sheet (LIS), which is mainly the result of multi-source ice interactions over the western Arctic Ocean. In marine isotope stage 5 (MIS5) and the MIS3a (39–29 ka), the LIS did not reach its maximum extent, discharging its most massive icebergs into the western Arctic Ocean. However, most icebergs were trapped in the western Arctic Ocean, instead of being exported to the North Atlantic Ocean. Different scenarios occurred in the MIS4 and MIS2, when the East Siberian ice sheet (ESIS) emerged and icebergs in the western Arctic Ocean began to accumulate robustly. Ice streams from the LIS or Eurasian ice sheet (EAIS) were finally deflected and pushed to the Fram Strait by the ice streams from the ESIS. The ESIS expansion may thus play a more positive role than the LIS-iceberg discharge in triggering Laurentide-source iceberg outbursts in the western Arctic Ocean. Our findings shed new light on the origin of icebergs in the North Atlantic Ocean and mechanisms of AMOC instability.