Situated at the southern margin of the hemispheric westerly wind belt and immediately north of the Antarctic Polar Frontal zone, Tierra del Fuego is well-positioned to monitor coupled changes in the ocean-atmosphere system of the high southern latitudes. Here we describe a Holocene paleoclimate record from sediment cores obtained from Lago Fagnano, a large lake in southern Tierra del Fuego at 55°S, to investigate past changes in climate related to these two important features of the global climate system. We use an AMS radiocarbon chronology for the last 8000yr based on pollen concentrates, thereby avoiding contamination from bedrock-derived lignite. Our chronology is consistent with a tephrochronologic age date for deposits from the middle Holocene Volcán Hudson eruption. Combining bulk organic isotopic (δ13C and δ15N) and elemental (C and N) parameters with physical sediment properties allows us to better understand sediment provenance and transport mechanisms and to interpret Holocene climate and tectonic change during the last 8000yr. Co-variability and long-term trends in C/N ratio, carbon accumulation rate, and magnetic susceptibility reflect an overall Holocene increase in the delivery of terrestrial organic and lithogenic material to the deep eastern basin. We attribute this variability to westerly wind-derived precipitation. Increased wind strength and precipitation in the late Holocene drives the Nothofagus forest eastward and enhances run-off and terrigenous inputs to the lake. Superimposed on the long-term trend are a series of abrupt 9 negative departures in C/N ratio, which constrain the presence of seismically-driven mass flow events in the record. We identify an increase in bulk δ13C between 7000 and 5000calyr BP that we attribute to enhanced aquatic productivity driven by warmer summer temperatures. The Lago Fagnano δ13C record shows similarities with Holocene records of sea surface temperature from the mid-latitude Chilean continental shelf and Antarctic air temperatures from the Taylor Dome ice core record in East Antarctica. Mid-Holocene warming occurred simultaneously across the Antarctic Frontal Zone, and in particular, in locations currently influenced by the Antarctic Circumpolar Current.
Bibliographical noteFunding Information:
We would like to thank the scientific and general staff at the Centro Austral de Investigaciones Científicas (CADIC) in Ushuaia, Argentina for their continued help and support during this project. We thank Captains Jorge Ebling and Rafael Quezada for their assistance with R/V Neecho operations. In addition, we thank Steffen Saustrup and Mark Wiederspahn of the Institute for Geophysics for their technical assistance in the field. Funding for this research was provided by a U.S. National Science Foundation (NSF) SGER grant to RBD, Swiss NSF awards ( 10 200021-100668/1 and 200020-111928/1 ) to DA, and a National Geographic Society grant ( CRE12 7705-04 ) to JAA. C. Moy gratefully acknowledges support from a U.S. Dept. of Energy Global Change Education Program Graduate Fellowship , a Kerry Kelts Award from the Limnogeology Division of the Geological Society of America , and a Stanford University McGee grant UTIG Contribution Number #2330.
Copyright 2011 Elsevier B.V., All rights reserved.
- Holocene paleoclimate
- Southern Hemisphere westerly winds
- Stable isotopes
- Tierra del Fuego