WAS THE WEST ANTARCTIC ICE SHEET THE ONLY SOURCE FOR ICE SHEET EXPANSIONS INTO THE ROSS SEA DURING THE EARLY NEOGENE? USING SEISMIC STRATIGRAPHY AND CORE TO TEST THE CRYOSPHERIC HISTORY INTERPRETATION OF ANDRILL

Cryosphere dynamics are fundamentally linked to climate and ocean circulation variations. Understanding the cryospheric response to past changes will allow for more robust predictions of current and future climatic variations. The most complete and direct records of global climate change and ice dynamics come of the Antarctic continental margin. The Ross Sea preserves an extensive record of Cenozoic glacial dynamics from both the East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheets (WAIS). The Ross Sea also has among the densest populations of sedimentologic cores and seismic profiles along the continental margin. The ANDRILL Program is the latest effort in resolving the details of climate change recorded in drill core from the western Ross Sea and suggests a dynamic WAIS prone to catastrophic collapse and influenced by orbital parameters.

We propose alternate models for glacial history in the Ross Sea. 1) Initial formation of WAIS and its advance into the Ross Sea during the Neogene. Its advance blocked the mouths of valleys that dissect TAM and buttressed early EAIS outlet glaciers, preventing contribution of EAIS into the Ross Sea until initial deglaciation of WAIS. As the WAIS began to retreat, from north to south, this allowed EAIS outlet glaciers, now free of the WAIS barrier, to surge onto the Ross Sea continental margin. However, as deglaciation progressed the outlet glaciers became unstable and then retreated back to the TAM. Once the Ross Sea became fully deglaciated, subsequent readvances of ice sheets into the Ross Sea incorporated EAIS outlet glaciers along the western margin. 2) EAIS has been present in the western Ross Sea since the onset of Cenozoic glaciation, with the earliest ice sheet advance beginning by at least the earliest Miocene, while WAIS influenced the central and eastern portions of the Ross Sea. 3) (hypothesized by the ANDRLL group) WAIS was the only ice sheet advancing and retreating across the Ross Sea continental margin, until sometime in the latest Neogene, when EAIS began contributing to the ice sheet dynamics in the western Ross Sea.

To test these new models we have conducted a comprehensive survey of the stratigraphy in the Ross Sea from legacy and recent single- and multi-channel seismic surveys and reexamined clast provenance from sediment cores in the western Ross Sea.