Late Quaternary variations of the southern westerly wind belt and its influences on aquatic ecosystems and glacier extend within the southernmost Andes

Abstract

The southern tip of South America is year-round influenced by the southern westerly wind belt (SWW) causing extremely high precipitation along the Chilean coast and the Andes south of 33°S with maximum values of 3000 to >10 000 mm/year within the SWW core between 49 to 55°S which is unique for temperate regions on the global scale. Due to this key position within the global atmospheric and oceanic framework we have investigated a large number of Late Quaternary climate archives during the last decade including fjord and lake sediments, peats, stalagmites and tree rings. To improve our proxy understanding in these various archives, climate as well as hydrological monitoring stations were operated since 1999. Here we present one-year monitoring data, which document the short term variability of climate and thermohaline conditions and related fertility in the fjord surface water. In this context we also analysed the interplay between palaeo-precipitation and related freshening of surface water (low nitrate and phosphate) and the terrestrial nutrient supply to the fjords during the last 5 ka BP using new salinity and productivity proxies of a fjord sediment core. Lake sediment cores and a stalagmite record document high chemical denudation rates, and metal leaching occurs on a weakly buffered granitoid basement and areas covered by acidic peaty soils. The partly climate-controlled changes in the iron and trace metal mobility have profound implications for both terrestrial and aquatic ecosystems. Based on the investigated archives we also reviewed SWW changes and regional temperature variations during the past 30 ka BP and their implication for Glacial and Holocene glacier advances.