Four decades of Antarctic Ice Sheet mass balance from 1979-2017

Abstract

We use updated drainage inventory, ice thickness, and ice velocity data to calculate the grounding line ice discharge of 176 basins draining the Antarctic Ice Sheet from 1979 to 2017. We compare the results with a surface mass balance model to deduce the ice sheet mass balance. The total mass loss increased from 40 ± 9 Gt/y in 1979-1990 to 50 ± 14 Gt/y in 1989-2000, 166 ± 18 Gt/y in 1999-2009, and 252 ± 26 Gt/y in 2009-2017. In 2009-2017, the mass loss was dominated by the Amundsen/Bellingshausen Sea sectors, in West Antarctica (159 ± 8 Gt/y), Wilkes Land, in East Antarctica (51 ± 13 Gt/y), and West and Northeast Peninsula (42 ± 5 Gt/y). The contribution to sea-level rise from Antarctica averaged 3.6 ± 0.5 mm per decade with a cumulative 14.0 ± 2.0 mm since 1979, including 6.9 ± 0.6 mm from West Antarctica, 4.4 ± 0.9 mm from East Antarctica, and 2.5 ± 0.4 mm from the Peninsula (i.e., East Antarctica is a major participant in the mass loss). During the entire period, the mass loss concentrated in areas closest to warm, salty, subsurface, circumpolar deep water (CDW), that is, consistent with enhanced polar westerlies pushing CDW toward Antarctica to melt its floating ice shelves, destabilize the glaciers, and raise sea level.

Keywords: Antarctica; climate change; glaciology; remote sensing; sea-level rise.

Fig. 1.

(A) Ice speed of the Antarctic Ice Sheet derived from multisensor data for the time period 2014–2016 (11) with 18 subregions A–K (black thin lines) delineated from surface slope and ice flow direction data (SI Appendix, Fig. S3). (B) Change in flow speed from the time period 2007–2008 to 2014–2015 color-coded from blue (deceleration) to red (acceleration). Grey areas have no data. (C) Basin names for subregions and ocean temperature at 310-m depth from the Southern Ocean State Estimate (SOSE) (12) color-coded from cold (blue) to warm (red). White areas in the ocean are shallower than 310 m depth. (D) Bed topography between 0 and 1,100 m depth, with SLE of each basin in centimeters of SLE (1, 13). (E) Change in grounding line ice discharge, D, for 1979–2017 for the 18 major subregions in billions of tons per year with percentage change in speed color-coded from red (acceleration) to blue (deceleration) and circle radius proportional to change. (F) Total change in mass of major basins color-coded from blue (gain) to red (loss) for 1979–2017 with circle radius proportional to the absolute mass balance.

Fig. 2.

Ice mass balance of Antarctica using the component method (SMB, on grounded ice minus ice discharge, D, at the grounding line) for (A) 1979–1990, (B) 1989–2000, (C) 1999–2009, and (D) 2009–2017. The size of the circle is proportional to the absolute magnitude of the anomaly in D (dD = ${\mathrm{S}\mathrm{M}\mathrm{B}}_{1979-2008}$ − D) or SMB (dSMB = SMB − ${\mathrm{S}\mathrm{M}\mathrm{B}}_{1979-2008}$). The color of the circle indicates loss in dD (dark red) or dSMB (light red) versus gain in dD (dark blue) or dSMB (light blue) in billions of tons (${\mathrm{10}}^{12}$ kg) per year. Dark color refers to dD; light color refers to dSMB. Plots show totals for Antarctica, Antarctic Peninsula, West Antarctica, and East Antarctica. Background is the total mass balance spread into the drainage basins color-coded from red (loss) to blue (gain).

Fig. 3.

Time series of cumulative anomalies in SMB (blue), ice discharge (D, red), and total mass (M, purple) with error bars in billions of tons for (A) West Antarctica, (B) East Antarctica; (C) Antarctic Peninsula), and (D) Antarctica, with mean mass loss in billions of tons per year and an acceleration in billions of tons per year per decade for the time period 1979 to 2017. The balance discharge is ${\mathrm{S}\mathrm{M}\mathrm{B}}_{1979-2008}$. Note that the total mass change, M = SMB − D, does not depend on ${\mathrm{S}\mathrm{M}\mathrm{B}}_{1979-2008}$.