T91 Holocene Climate Change: Seasonal Variability to Centennial Trends II

Tuesday, 6 November 2001
1:30 PM - 5:30 PM

LARGE HOLOCENE EXCURSIONS IN BIOLOGIC PRODUCTIVITY AND TERRIGENOUS PROVENANCE IN A HIGH-RESOLUTION SEDIMENT RECORD FROM THE PALMER DEEP, WEST ANTARCTICA

Paper number: T91-6
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

The Antarctic Peninsula is highly sensitive to climate change. To assess Holocene climate variability in this region, the Ocean Drilling Program recovered ~50 m of laminated sediments from the Palmer Deep. This sequence comprises the first high-resolution, continuous, Holocene sediment record from the Antarctic margin and is also the only ultra-high resolution ODP record in the Southern Hemisphere. We analyzed Si, Al, Ti, P, Ba, biogenic opal, organic C and N, and organic delta13C and delta15N every 2.5 to 10 cm (~8 – 50 years.). Each of these proxies responds to a large climatic forcing initiated between 4500 and 7000 years B.P. Biogenic opal, Corg, and P accumulation rates double ~2,000 years B.P., reaching a maximum ~5,500 to 7,000 years B.P. Opal concentrations are less variable, indicating biosiliceous production increased during the mid-Holocene. 13C/12C in bulk organic matter are high (with values similar to ice-edge bloom products) ~4500 to 7000 years B.P., signifying stronger diatom bloom events during the mid-Holocene. Prior to ~3000 years B.P., delta15N was lower for ~2,000 years, resulting from less complete utilization of photic zone nitrate. The Al/Ti ratio indicates a change in terrigenous composition ~3500 years B.P. suggesting a change in source, weathering style and/or intensity. All tracers of productivity and terrigenous provenance exhibit significant variance at periods of ~400, 200, 140, and 70 years. Although the mechanisms forcing mid-Holocene enhancements in productivity and terrigenous supply remain unclear, candidates include greater glacial and sea-ice freshwater influences, reduced wind shear, or changing oceanographic frontal positions. A possible external forcing parameter is solar irradiance, possibly mediated through variability in the polar vortex.