|
|
|
|
|
|
|
|
CGC-01 General contributions to climate change
|
|
|
|
Climate forcing in tierra del fuego since the LGM
|
|
|
|
Nicolas Waldmann, The University of Geneva (Switzerland)
Cristina Recasens, The University of Geneva (Switzerland)
Daniel Ariztegui, The University of Geneva (Switzerland)
Flavio Anselmetti, Swiss Federal Institute of Aquatic Science and Technology (Eawag) (Switzerland)
James Austin Jr., University of Texas at Austin (United States)
Andrea Coronato, Centro Austral de Investigaciones Cientificas-CADIC (Argentina)
Christopher Moy, Stanford University (United States)
Robert Dunbar, Stanford University (United States)
|
|
|
|
Recent advances in the chronology and the environmental significance of Antarctic ice-core records point towards a larger heterogeneity than previously thought. Thus, realistic inter-hemispheric correlations rely in the development of a tight array of well constrained records with a dense latitudinal coverage. Climatic records from southernmost Patagonia are hence critical corner-stones to link these Antarctic paleoclimatic archives with their South American counterparts. At 55°S on the Island of Tierra del Fuego, Lago Fagnano is located in one of the most substantially and extensively glaciated regions of southernmost South America during the Late Pleistocene. This elongated lake is the largest (∼110 km long) and southernmost non-ice covered water body in the world. The island's present climate is under the strong influence of the westerly winds and the Antarctic Oscillation (AAO) forcing.
Existing on-shore geomorphological reconstructions combined with new lacustrine subsurface data, allowed us to better constrain the magnitude and chronology of the Fagnano glacier fluctuations since the LGM. The former Fagnano glacier flowed eastwards from the Darwin Cordillera fed by more than 50 tributary glaciers. The glacier spread over the low ranges and lowlands through three different lobes and was drained by four main outwash basins directly into the Atlantic Ocean. During the maximum ice-expansion, the ice-covered area was ca. 4000 km2 with a maximum length of ca. 132 km. A set of submerged frontal moraines covered by lacustrine infilling identified in the seismic survey suggests occasional eastward re-advances of the paleo-glacier within the overall westward deglaciation pattern. These re-advances may correspond to cold events such as the Antarctic Cold Reversal (ACR), the Huelmo-Mascardi Cold Event (HMCE) and/or the Younger Dryas Chronozone (YDC). The ongoing development of a robust age model blended with a multi-proxy dataset will potentially clarify remining controversial issues dealing with the geographical extension and chronology of these cold episodes during the last deglaciation.
A multi-proxy study of selected cores retrieved from the deepest part of the lacustrine basin allows characterizing the Holocene sedimentary record. Detailed petrophysical, sedimentological and geochemical investigations of a continuous laminated sequence reveal fluctuations in major and trace elements, as well as organic-content, suggesting an apparent cyclicity. Preliminary radiocarbon dating suggests an annual character of these laminae. The statistical treatment of results from image-analyses of these laminated sections shows a frequency of changes that can be attributed to a strong influence of both the AAO and the Southern Westerlies.
These results provide a unique dataset that can be compared with other marine and continental archives to improve our understanding of the forcing mechanisms behind climate change in the Southern Hemisphere.
|
|
|
|
|
|
|
|
|
