Holocene paleoclimatic variability from South Orkney Plateau, West Antarctica

Abstract

Comprehensive analyses of a 5.3-m gravity core retrieved from the South Orkney Plateau in West Antarctica yield a record of past climatic and oceanographic changes during the last 8,700 years. Light grayish olive diatomaceous silt and mud are predominant throughout the core. The age for the core sediment was determined by AMS radiocarbon dating for organic matter in the sediment. The core was divided into two parts at 3.5m (4,900 cal yr B.P.) based on total organic carbon content(TOC), CaCO3 content and biogenic silica content(BSi). Lower part is characterized by variable TOC and higher CaCO3, and upper part by higher TOC and lower CaCO3. BSi varies similar to TOC in the lower part, but it does not correlate with TOC in the upper part. These characteristics imply that study area was under the influence of Scotia Sea Water prior to 4.9 ka and of Weddell Sea Water later. High concentration of open water diatom species and subpolar form of Eucampia antarctica in the lower part also suggests less winter sea ice during early Holocene. Cooling at 4.9 ka marks the onset of Neoglacial condition in the South Orkney Plateau and it accompanied northward shift of Weddell-Scotia frontal system.