Possible provenance of IRD by tracing late Eocene Antarctic iceberg melting using a high-resolution ocean model

Abstract. The Eocene–Oligocene transition (EOT) is characterised by the inception of the large-scale Antarctic ice sheet. However, evidence of earlier glaciation during the Eocene has been found, including the presence of ice-rafted debris (IRD) at Ocean Drilling Program (ODP) Leg 113 Site 696 on the South Orkney Microcontinent (SOM) (Carter et al., 2017). This suggests marine-terminating glaciers should have been present in the southern Weddell Sea region during the late Eocene, generating sufficiently large icebergs to the South Orkney Microcontinent to survive the high Eocene ocean temperatures. Here, we use Lagrangian iceberg tracing in a high-resolution eddy-resolving ocean model of the late Eocene (Nooteboom et al., 2022) to show that icebergs released from offshore the present-day Filchner Ice Shelf region and Dronning Maud Land could reach the South Orkney Microcontinent during the late Eocene. The high melt rates under the Eocene warm climate require a minimum initial iceberg mass on the order of 100 Mt and an iceberg thickness of several tens of metres to be able to reach the South Orkney Microcontinent. Although this places the iceberg mass at the larger end of the present-day range of common iceberg masses around Antarctica, the minimum estimates are not unfeasible; hence, the present study confirms previous findings suggesting glaciation and iceberg calving were possible in the late Eocene.