COG3

The overflow of 14C and 18O depleted water from the Nordic Seas during glacial termination

Abstract:

During the last glacial termination, the circulation of the North Atlantic underwent fundamental changes which had important consequences for global climate through the ocean’s role in heat redistribution and carbon cycling. Yet, uncertainty remains regarding circulation patterns within the deepwater formation regions of the Northeast Atlantic and Nordic Seas. Much of this uncertainty is centred on the cause of mid-depth low benthic δ18O recorded during Heinrich Stadial 1, and episodic incursions of an extremely 14C-depleted (i.e., poorly ventilated) water mass in the Northeast Atlantic. Existing proxy data are insufficient to resolve the cause of these ‘anomalies’ and models typically fail to reconstruct such variability, hindering our understanding of the mechanisms of glacial termination.

Through the development and application of a bottom water temperature proxy, in combination with new radiocarbon measurements from the deep Norwegian Sea, we are able to reconcile existing data sets. Our data suggest the development of an isolated glacial Arctic Ocean and deep Norwegian Sea, with 14C ventilation ages in excess of 7000 years, that episodically overflowed into the North Atlantic during the deglaciation, where it can be detected as a cold water mass with extremely low Δ14C and depleted δ18O. The inferred circulation pattern differs greatly from climate model predictions and alters our traditional understanding of the circulation of the high latitude North Atlantic and Arctic.