MID-TO-LATE HOLOCENE DIATOM RECORD OF PALEOCEANOGRAPHIC CONDITIONS, SABRINA COAST, EAST ANTARCTICA

Recent observations document the intrusion of modified circumpolar deep water (mCDW) on the Sabrina Coast shelf (East Antarctica), which has been linked to ice loss. This region, which is the site of the Totten Glacier, has a sea level equivalent of about 3.8 meters, leading to concern about its future stability and potential contribution to sea level rise. The aim of this study was to provide an oceanographic perspective on recent observations of basal melt and ice thinning that have been recorded in this region. We evaluated changes in diatom assemblage and abundance over the mid-to-late Holocene, in three multicores which were collected during the expedition IN2017_V01 from the Sabrina Coast continental rise, off East Antarctica. The cores were extruded on board, and later processed for quantitative diatom evaluation. Chronologic work indicates that one core extends back to ~6.3 ka, while the other two record changes over the past ~2.0-2.5 ka. Diatom assemblage data show the dominance of the open Southern Ocean diatom Fragilariopsis kerguelensis, along with a lesser contribution from typical sea ice associated species of Fragilariopsis, such as F. curta. In all three of the cores, the assemblage is remarkably consistent throughout, recording relatively stable oceanographic conditions over this time period, indicating little variability in overall sea ice extent. Despite little change in diatom assemblage, the abundances are highest at ~5.1 ka and decrease toward the present, suggesting a general decrease in ocean primary productivity over this time period. These data document relative stability through the mid-to-late Holocene. However, recent rapid basal melting of the Totten Glacier, recorded by satellite datasets, may be documented by higher resolution records from the continental shelf.