Abstract
Abstract. The northern and southern Patagonian ice fields (NPI and SPI) have been subject to accelerated retreat during the last decades, with considerable variability in magnitude and timing among individual glaciers. We derive spatially detailed maps of surface elevation change (SEC) of NPI and SPI from bistatic synthetic aperture radar (SAR) interferometry data of the Shuttle Radar Topography Mission (SRTM) and TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X) for two epochs, 2000–2012 and 2012–2016, and provide data on changes in surface elevation and ice volume for the individual glaciers and the ice fields at large. We apply advanced TanDEM-X processing techniques allowing us to cover 90 % and 95 % of the area of NPI and 97 % and 98 % of SPI for the two epochs, respectively. Particular attention is paid to precisely co-registering the digital elevation models (DEMs), accounting for possible effects of radar signal penetration through backscatter analysis and correcting for seasonality biases in case of deviations in repeat DEM coverage from full annual time spans. The results show a different temporal trend between the two ice fields and reveal a heterogeneous spatial pattern of SEC and mass balance caused by different sensitivities with respect to direct climatic forcing and ice flow dynamics of individual glaciers. The estimated volume change rates for NPI are -4.26±0.20 km3 a−1 for epoch 1 and -5.60±0.74 km3 a−1 for epoch 2, while for SPI these are -14.87±0.52 km3 a−1 for epoch 1 and -11.86±1.99 km3 a−1 for epoch 2. This corresponds for both ice fields to an eustatic sea level rise of 0.048±0.002 mm a−1 for epoch 1 and 0.043±0.005 mm a−1 for epoch 2. On SPI the spatial pattern of surface elevation change is more complex than on NPI and the temporal trend is less uniform. On terminus sections of the main calving glaciers of SPI, temporal variations in flow velocities are a main factor for differences in SEC between the two epochs. Striking differences are observed even on adjoining glaciers, such as Upsala Glacier, with decreasing mass losses associated with slowdown of flow velocity, contrasting with acceleration and increase in mass losses on Viedma Glacier.
Highlights
The northern and southern Patagonian ice fields (NPI and SPI) are the largest contiguous temperate ice bodies in midlatitudes of the Southern Hemisphere
surface elevation change rate (SECR) and volume change rate (VCR) are assembled in 50 m elevation bins using the surface of the 2012 TDM digital elevation models (DEMs) as reference
We report on a detailed study focussing on the climatesensitive northern and southern Patagonian ice fields, where high-resolution maps of surface elevation change were obtained for the epochs 2000–2012 and 2012–2016 from bistatic InSAR DEMs, allowing us to derive the total net mass balance of most of the glacier basins
Summary
The northern and southern Patagonian ice fields (NPI and SPI) are the largest contiguous temperate ice bodies in midlatitudes of the Southern Hemisphere. They stretch from 46.5 to 47.5◦ S and 48.3 to 51.6◦ S, respectively, along the main ridge of the southern Andes and cover areas of about 4000 and 13 000 km (Davies and Glasser, 2012). Because the ice fields are located on the only significant land mass between 45◦ S and Antarctica, they offer unique possibilities for studying the impact of changes in Southern Hemisphere westerly flow on glacier evolution and for inferring Holocene climate history from glacial evidence (Rasmussen et al, 2007; Lopez et al, 2010; Glasser et al, 2011; Davies and Glasser, 2012; Garreaud et al, 2013). Abdel Jaber et al.: SEC and mass balance of the Patagonian ice fields
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