Oxygen-isotope (δ18O) evidence of Holocene hydrological changes at Signy Island, maritime Antarctica

Abstract

A record of Holocene hydrological changes has been produced from variations in oxygen-isotope composition (δ18O) preserved in freshwater lake sediments from maritime Antarctica. Small amounts (<5%) of authigenic carbonate have been extracted from a non-marl sediment core from Sombre Lake, Signy Island (60°43'S, 45°38'W). Oxygen-isotope and particle-size analysis provide a sensitive record of hydrological events in the lake arising from local and regional climate phenomena. The climate affects δ18O through snowpack volume and glacier activity in the catchment, lakewater temperatures, the input versus evaporation balance and the duration of seasonal lake ice cover. The most depleted (negative) δ18O values are associated with influxes of meltwater at times of glacier advance or retreat. Enriched (positive) δ18O values occur during more arid, warmer conditions with longer periods of open water in summer. This isotope record can be used to determine century-scale to decadal variability in air circulation and moisture origin. Strong similarities with other Holo cene proxy records from the Weddell Sea and Antarctic Peninsula Region are apparent, including the mid-Holocene climate optimum followed by the Neoglacial and, most recently, late twentieth-century climatic warming. The oxygen-isotope record from Sombre Lake illustrates the importance of remote islands in contribu ting to our understanding of teleconnections in atmospheric and oceanographic circulation, sea-ice extent, air temperatures and precipitation in the Southern Ocean.