MIS3 to late Holocene Palaeo-ice Thickness Constraints of Glacier Viedma, Hielo Patagonico Sur, Southern South America

Southern South America 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 palaeo-behavior. In order to unravel the nature of the SWW over the last glacial cycle, a tighter grid of sensitive palaeo-proxies in the region is required. The work presented here is based on the palaeo-glaciology of the Viedma outlet (49°S, 72°W), the second largest glacier draining the Hielo Patagonico Sur (HPS). This locality corresponds to the present day center of the precipitation bearing SWW in southern South America, which are a key factor in maintaining the HPS. Any variation in SWW strength or location has a direct impact on glacial expansion in the region, hence palaeo-glacial geometries can provide key insights into SWW dynamics. Palaeo-ice surface, thickness and thinning rates spanning MIS3 to the late Holocene are presented based on 16 Be-10 exposure ages along three vertical transects covering the accumulation and ablation areas of glacier Viedma. Results indicate a maximum ice thickness over MIS3, a thickening over the Antarctic Cold Reversal (ACR), which overprinted the vertical expression of the LGM, and progressive ice surface lowering from the middle to the late Holocene. The palaeo-climatic implications will be discussed, particularly with focus on SWW positioning and behavior.