EMPIRICAL ICE THICKNESS CONSTRAINTS FROM THE CERRO FITZ ROY MASSIF, SOUTHERN PATAGONIA, ARGENTINA

Southern Patagonia is the only landmass intersecting the southern westerly winds (SWW), which critically shape southern hemispheric and global climate. At present palaeo-climatic datasets stretching the 3000 km of SWW influence are in latitudinal disagreement suggesting a complex picture of SWW paleo-behaviour. In order to unravel the nature of the SWW fluctuations over the last glacial cycle, a tighter grid of palaeo-proxy studies in the region is required.

The work presented here is based on three mountain valleys in close proximity to the Fitz Roy massive (49°S, 72°W), which is located just east of the southern Patagonian Ice Field. At this site the Patagonian cordillera provides a topographic barrier to the SWW, hence the dominant limiting factor for glacier expansion on the lee side is precipitation.

Palaeo-ice surface, thickness and thinning rates spanning MIS3 to Termination I are presented based on 18 Be-10 exposure ages along three vertical transects over ~700m of relief. The results indicate a maximum ice thickness over MIS3 with progressive ice-lowering over MIS2 and small scale thickening at the end of the globally defined LGM. The palaeo-climatic implications will be discussed particularly with focus on SWW positioning and behaviour.