Changing pattern of ice flow and mass balance for glaciers discharging into the Larsen A and B embayments, Antarctic Peninsula, 2011 to 2016

Abstract

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.

Evolving Instability of the Scar Inlet Ice Shelf based on Sequential Landsat Images Spanning 2005–2018

“…More recently, Chen et al [6] found that the surface elevation of the SIIS decreased at a rate of −0.07 m/year from 1992 to 2010; surface elevation was more stable after 2002 (as the LBIS retreated), and its ice area in 2015 was slightly larger than its ice area in 2009. Rott et al [29] found that the ice flow velocities for the Flask and Leppard Glaciers exhibited only modest changes after 2011 but still remained higher than velocities measured before 2002. In addition, Borstad et al [30] used assimilated observations in a constitutive framework to reproduce the evolution of the 2002 LBIS collapse and concluded that the weakening and fracturing of the ice shelf reduced its buttressing effect.…”

“…Wuite et al [21] also observed several major rifts in the SIIS using advanced synthetic aperture radar (ASAR) images captured on 28 January 2004 and suggested that the 2002 collapse of the LBIS was an important factor affecting the instability of the SIIS. Flask and Leppard Glaciers exhibited moderate mass loss, while the smaller glaciers of the SIIS approached equilibrium [29]. Fast ice, also called landfast ice, is sea ice that is "fastened" to the coastline, to the sea floor along shoals, or to grounded icebergs.…”

“…Thus, it is meaningful and useful to monitor the long time series evolution and understand the changing mechanism of the remnant section of LBIS after its disintegration. Several detailed analyses of ice front retreat, surface features, and velocities of the SIIS and its tributary prior to 2016 were presented by Khazendar et al, Wuite et al,and Rott et al [20,21,29]. Here, we build upon and provide a continuum framework for the previous work, assimilated and analyzed long-term observations of ice front positions, surface features, and ice flow velocities for the SIIS based on sequential Landsat satellite images spanning 2005-2018, thereby providing a constant change in the frontal position and surface features both in time and space across 14 years and extending the time series to cover ice flow velocities up to 2018.…”

Answer to RC1

“…plying the ScanSAR technique to four sub-swaths featuring horizontal and vertical co-polarization (HH, VV, VV, HH) and look angles between 30 to 56 • . The large number of interwoven acquisitions at higher latitudes contributed to both absolute and relative accuracy as well as to reducing voids: the nine ascending and nine descending datatakes covering the Patagonian ice fields (Seal and Rogez, 2000) are listed in Table S3. The performance of SRTM, among others, was assessed by Rodriguez et al (2005), Brown et al (2005), Carabajal and Harding (2006), and Wendleder et al (2016).…”

Detailed quantification of glacier elevation and mass changes in South Georgia

“…While there are several studies reporting glacier mass changes of the Antarctic ice sheet (e.g. Shepherd et al 2018, Rignot et al 2019, the Antarctic Peninsula (Rott et al 2014, Rott et al 2018 and Patagonia (e.g. Malz et al 2018, less is known about the glaciers located on the sub-Antarctic islands and the potential impacts of atmospheric warming on their retreat during the 20th and 21st centuries.…”