Oceanic δ 13 C Fingerprints Caused by Laurentice Ice Sheet Discharges: Model‐Data Comparison During Heinrich Event 4

Abstract This study investigates the sensitivity of the oceanic circulation and of the dissolved inorganic carbon to ice discharge events from the Laurentide ice sheet (LIS), using an isotope‐enabled and coupled climate–ice sheet model, and observations. The ice discharges are triggered by either reduced friction at the ice sheet‐bedrock interface or increased oceanic melt rates in the Hudson Strait ice stream region. The simulated decreases in both scenarios, following freshwater release and the weakening of the Atlantic Meridional Overturning Circulation. The best agreement with the observed anomalies is achieved with large ice volume loss, by reducing ice sheet basal friction. In our model, the freshwater discharges from the LIS need to be amplified to better represent the observed changes. The LIS alone does not seem able to explain the observed oceanic variations, which may indicate that additional processes are required to account for these changes.