R. A. Fernandez¹, J. B. Anderson², J. S. Wellner³, R. L. Minzoni^2
1UT Institute for Geophysics
²Rice University
³University of Houston

Abstract
Erosion rates (Er) have been estimated for temperate glaciers in a number of middle latitude mountain ranges based mainly on modern observations (last few decades) of sediment fluxes (Harbor, 1992, 1993; Harbor and Warburton, 1993; Hallet et al., 1996). Recent studies of these temperate systems have shown that short term Er (<decadal) are not representative of long-term (centennial, millennial or million-year time scales) trends (Delmas et al., 2009; Koppes et al., 2009; Fernandez et al., 2011). However, at longer than millennial time-scales erosion rates seem to decrease until reaching values similar to thermochronology exhumation rates. At high latitudes (especially in the southern hemisphere), the scarcity of data impede an estimation of the magnitude of time- spatial variability of Er. At stake is a better understanding of the role of polar glaciers in the coupling between climate and tectonics, as well as their influence on mountain building and exhumation processes.

Using sediment fluxes calculated from sediment volumes accumulated in fjords, we estimate sediment yields (Y) and associated erosion rates (Er) for millennial time scales across a broad latitudinal transect from central Patagonia (46°S) to the Antarctic Peninsula (65°S). We show that erosion rates (Er) from the subpolar glaciers of northern AP (e.g. at Maxwell Bay, Herbert Sound etc.), ~10-1-100 mm/yr, are similar to published results from southern Patagonia temperate glaciers (Fernandez, 2011) and subpolar glaciers from Svalbard (Elverhoi, 1995, 1998), whereas Er values are an order of magnitude less for southern AP polar glaciers (e.g. Lapeyrere and Anvord bays), ~10-2 mm/yr, which is in the same order of magnitude of million year timescale erosion rates (Smith et al., 2010) but lower than estimated exhumations rates for the western AP (Guenthner et al., 2010). The pattern of thermochronology ages (Thompson et al., 2010; Guenthner et al., 2010), and the values of 103 and 106 years timescales erosion rates from our study, indicate that long-term glacial erosion decreases significantly its efficiency with latitude, implying that long-term glacial cover acts as a protective blanket, hindering erosion and allowing mountain growth as previously suggested by other researchers.Geological (tectonics, lithological), climatic (temperature, precipitation) and temporal controls on the observed Er patterns will be discussed.