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

Abstract:

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.