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 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.

Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica

“…Furthermore, glaciological investigations assessing the impact of ice shelf loss on glaciers along the Antarctic Peninsula provide important insights into the preservation of ice, albeit on a smaller scale. The 2002 Larsen B ice shelf collapse led to many of the tributary glaciers abruptly changing from a convex to a concave profile (cross-section) (40), with relict ice left isolated on the upper flanks of the valleys (41). These scenarios are consistent with extensive grounding line retreat across the inner shelf of the Weddell Sea and associated substantial ice loss across the wider WSE (29).…”

“…The 2002 Larsen B ice shelf collapse led to many of the tributary glaciers abruptly changing from a convex to a concave profile (40), with relict ice left isolated on the upper flanks of the valleys (41). Under a scenario of extreme ice surface lowering arising from ocean warming during the early LIG, the ice at Patriot Hills preserves a record of glacier flow in the overdeepened Horseshoe Valley up to the moment when the Filcher-Ronne Ice Shelf collapsed, after which the sequence likely remained isolated for multiple millennia until the ice surface had risen sufficiently to reincorporate the isolated ice into the glacier sometime during late MIS 5.…”

Reduced ice mass loss and three-dimensional viscoelastic deformation in northern Antarctic Peninsula inferred from GPS

“…We consider vertical and, for the first time in the NAP, horizontal displacement fields from three continuous GPS stations. We update the ice loading history used by Nield et al (2014) with a high-resolution ice loading history from Rott et al (2018) as input to a viscoelastic solid earth model to compare with observations, and arrive at new constraints on NAP solid Earth rheology.…”

“…We use the ice history described in Nield et al (2014) as input to the viscoelastic modelling for phase X: 1995.5-2011.5 (divided into linear rates over 1995. 5-2001.0; 2001.0-2006.0; 2006.0-2011.5) and a new ice loading history taken from Rott et al (2018) for phase Y: 2011.5-2018.0. The new ice loading model is derived from the surface elevation change (SEC) data described in Rott et al (2018).…”

Ice flow velocity as a sensitive indicator of glacier state

“…satellite radar interferometry (e.g. Rignot and Kanagaratnam, 2006;Moon et al, 2012, Hogg et al, 2017, Rott et al, 2017 and show that changing patterns of ice flow velocity play an important role in the reaction of polar glacier systems to climate change. Feature Tracking and DinSAR both do not reveal full 3D velocity information and need additional assumptions.…”