Abstract. We analysed volume change and mass balance of outlet glaciers on the northern Antarctic Peninsula over the periods 2011 to 2013 and 2013 to 2016, using high-resolution topographic data from the bistatic interferometric radar satellite mission TanDEM-X. Complementary to the geodetic method that applies DEM differencing, we computed the net mass balance of the main outlet glaciers using the mass budget method, accounting for the difference between the surface mass balance (SMB) and the discharge of ice into an ocean or ice shelf. The SMB values are based on output of the regional climate model RACMO version 2.3p2. To study glacier flow and retrieve ice discharge we generated time series of ice velocity from data from different satellite radar sensors, with radar images of the satellites TerraSAR-X and TanDEM-X as the main source. The study area comprises tributaries to the Larsen A, Larsen Inlet and Prince Gustav Channel embayments (region A), the glaciers calving into the Larsen B embayment (region B) and the glaciers draining into the remnant part of the Larsen B ice shelf in Scar Inlet (region C). The glaciers of region A, where the buttressing ice shelf disintegrated in 1995, and of region B (ice shelf break-up in 2002) show continuing losses in ice mass, with significant reduction of losses after 2013. The mass balance numbers for the grounded glacier area of region A are −3.98 ± 0.33 Gt a−1 from 2011 to 2013 and −2.38 ± 0.18 Gt a−1 from 2013 to 2016. The corresponding numbers for region B are −5.75 ± 0.45 and −2.32 ± 0.25 Gt a−1. The mass balance in region C during the two periods was slightly negative, at −0.54 ± 0.38 Gt a−1 and −0.58 ± 0.25 Gt a−1. The main share in the overall mass losses of the region was contributed by two glaciers: Drygalski Glacier contributing 61 % to the mass deficit of region A, and Hektoria and Green glaciers accounting for 67 % to the mass deficit of region B. Hektoria and Green glaciers accelerated significantly in 2010–2011, triggering elevation losses up to 19.5 m a−1 on the lower terminus during the period 2011 to 2013 and resulting in a mass balance of −3.88 Gt a−1. Slowdown of calving velocities and reduced calving fluxes in 2013 to 2016 coincided with years in which ice mélange and sea ice cover persisted in proglacial fjords and bays during summer.
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.
Abstract. We analyzed volume change and mass balance of outlet glaciers on the northern Antarctic Peninsula over the periods 2011 to 2013 and 2013 to 2016, using high resolution topographic data of the bistatic interferometric radar satellite mission TanDEM-X. Complementary to the geodetic method applying DEM differencing, we computed the net mass balance of the main outlet glaciers by the input/output method, accounting for the difference between the surface mass balance (SMB) and the discharge of ice into an ocean or ice shelf. The SMB values are based on output of the regional climate model RACMO Version 2.3p2. For studying glacier flow and retrieving ice discharge we generated time series of ice velocity from data of different satellite radar sensor, with radar images of the satellites TerraSAR-X and TanDEM-X as main source. The study area comprises tributaries to the Larsen-A, Larsen Inlet, and Prince-Gustav-Channel embayments (region A), the glaciers calving into Larsen B embayment (region B), and the glaciers draining into the remnant part of Larsen B ice shelf in SCAR Inlet (region C). The glaciers of region A, where the buttressing ice shelf disintegrated in 1995, and of region B (ice shelf break-up in 2002) show continuing losses in ice mass, with significant reduction of losses after 2013. The mass balance numbers for grounded glacier area of the region A are Bn = −3.98 ± 0.33 Gt a-1 during 2011 to 2013 and Bn = −2.38 ± 0.18 Gt a-1 during 2013 to 2016. The corresponding numbers for region B are Bn = −5.75 ± 0.45 Gt a-1 and Bn = −2.32 ± 0.25 Gt a-1. The mass losses in region C during the two periods were modest, Bn = −0.54 ± 0.38 Gt a-1, respectively Bn = −0.58 ± 0.25 Gt a-1. The main share in the overall mass losses of the region were contributed by two glaciers: Drygalski Glacier contributing 61 % to the mass deficit of region A, and Hektoria and Green glaciers accounting for 67 % to the mass deficit of region B. Hektoria and Green glaciers accelerated significantly in 2010/2011, triggering elevation losses up to 19.5 m a-1 on the lower terminus and a rate of mass depletion of 3.88 Gt a-1 during the period 2011 to 2013. Slowdown of calving velocities and reduced calving fluxes in 2013 to 2016 coincided with years when the sea ice cover in front of the glaciers persisted during summer.
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