We employ high-resolution, high-precision, helicopter-borne gravity observations of the Northern (NPI) and Southern Patagonia Icefields (SPI), South America, to infer ice thickness and bed topography using a three-dimensional model constrained by Fjord and lake bathymetry, and a land-ice mask. The results reveal thicker ice than the reflecting horizon of radar sounders, with 1 km deep ice for Glaciar San Rafael and Colonia (NPI) and 1.5 km deep ice for Glaciar Occidental (SPI). These bedrock troughs channelize fast motion of ice from the plateaus. Combining ice motion and thickness, we calculate balance accumulation levels of 3–6 m/yr water equivalent for the plateaus. Bed elevation remains below sea/lake level 15–20 km inland for Jorge Montt and O’Higgins, which favors retreat, and is at sea level for San Rafael, which halted its retreat. The results demonstrate the utility of airborne gravity surveys for providing critical data on ice volume, bed elevation, and balance accumulation of temperate ice masses.

We present surface mass balance simulations of the Southern Patagonia Icefield (SPI) driven by downscaled reanalysis data. The simulations were evaluated and interpreted using geodetic mass balances, measured point balances and a complete velocity field of the icefield for spring 2004. The high measured accumulation of snow of up to 15.4 m w.e. yrg'1 (meters water equivalent per year) as well as the high measured ablation of up to 11 m w.e. yrg'1 is reproduced by the model. The overall modeled surface mass balance was positive and increasing during 1975-2011. Subtracting the surface mass balance from geodetic balances, calving fluxes were inferred. Mass losses of the SPI due to calving were strongly increasing from 1975-2000 to 2000-2011 and higher than losses due to surface melt. Calving fluxes were inferred for the individual glacier catchments and compared to fluxes estimated from velocity data. Measurements of ice thickness and flow velocities at the glaciers' front and spatially distributed accumulation measurements can help to reduce the uncertainties of the different terms in the mass balance of the Southern Patagonia Icefield.

Interferometric synthetic-aperture radar data collected by ERS-1/2 and Radarsat-1 satellites show that Antarctic Peninsula glaciers sped up significantly following the collapse of Larsen B ice shelf in 2002. Hektoria, Green and Evans glaciers accelerated eightfold between 2000 and 2003 and decelerated moderately in 2003. Jorum and Crane glaciers accelerated twofold in early 2003 and threefold by the end of 2003. In contrast, Flask and Leppard glaciers, further south, did not accelerate as they are still buttressed by an ice shelf. The mass loss associated with the flow acceleration exceeds 27 km3 per year, and ice is thinning at rates of tens of meters per year. We attribute this abrupt evolution of the glaciers to the removal of the buttressing ice shelf. The magnitude of the glacier changes illustrates the importance of ice shelves on ice sheet mass balance and contribution to sea level change. Copyright 2004 by the American Geophysical Union.

Satellite radar interferometry data from 1995 to 2004, and airborne ice thickness data from 2002, reveal that the glaciers flowing into former Wordie Ice Shelf, West Antarctic Peninsula, discharge 6.8 ± 0.3 km3/yr of ice, which is 84 ± 30 percent larger than a snow accumulation of 3.7 ± 0.8 km3/yr over a 6,300 km2 drainage basin. Airborne and ICESat laser altimetry elevation data reveal glacier thinning at rates up to 2 m/yr. Fifty km from its ice front, Fleming Glacier flows 50 percent faster than it did in 1974 prior to the main collapse of Wordie Ice Shelf. We conclude that the glaciers accelerated following ice shelf removal, and have been thinning and losing mass to the ocean over the last decade. This and other observations suggest that the mass loss from the northern part of the Peninsula is not negligible at present. Copyright 2005 by the American Geophysical Union.

Recent aircraft and satellite laser altimeter surveys of the Amundsen Sea sector of West Antarctica show that local glaciers are discharging about 250 cubic kilometers of ice per year to the ocean, almost 60% more than is accumulated within their catchment basins. This discharge is sufficient to raise sea level by more than 0.2 millimeters per year. Glacier thinning rates near the coast during 2002-2003 are much larger than those observed during the 1990s. Most of these glaciers flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way.