Hydrological evolution of a shallow lake in the semiarid Fuegian steppe,southern Argentina,during the last ~7000 years based on multiproxy data

Abstract

The climate in southern Patagonia is heavily influenced by the Southern Westerly Winds (SWW). Therefore, climate reconstructions from this region are valuable for our understanding of the temporal dynamics in the atmospheric circulation of the Southern Hemisphere. In this study a sedimentary record from the shallow lake Laguna Amalia – located in the semiarid Fuegian steppe of Tierra del Fuego (53°S) – was used to study how the hydroclimate in this region has changed over the last ~7100 years. Our interpretations rely on a combination of pollen, diatoms, total organic carbon, carbonates, lithology and sediment accumulation rate, together with geomorphological features of the landscape. We conclude that before 6700 cal BP Laguna Amalia was a permanent water body. Around 6700 cal BP the climate becomes drier in response to stronger SWW, and from around 6000 cal BP the lake entered a semi-permanent state with variable salinity and prolonged drier periods. Between 3000 and 600 cal BP Laguna Amalia becomes a more permanent freshwater lake with only shorter periods with desiccation. For the last 600 years the climate has again become drier, and the lake is currently experiencing seasonal desiccation. These hydroclimatic changes can largely be attributed to the variable influence of the SWW, with weaker SWW allowing the advection of moist air masses from the east into northern Tierra del Fuego.