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. 2021 Apr 30;7(18):eabf7787.
doi: 10.1126/sciadv.abf7787. Print 2021 Apr.

Rapid postglacial rebound amplifies global sea level rise following West Antarctic Ice Sheet collapse

Linda Pan  1 , Evelyn M Powell  2 , Konstantin Latychev  2   3 , Jerry X Mitrovica  2 , Jessica R Creveling  4 , Natalya Gomez  5 , Mark J Hoggard  2   3 , Peter U Clark  4
Affiliations

Rapid postglacial rebound amplifies global sea level rise following West Antarctic Ice Sheet collapse

Linda Pan et al. Sci Adv. .

Abstract

Geodetic, seismic, and geological evidence indicates that West Antarctica is underlain by low-viscosity shallow mantle. Thus, as marine-based sectors of the West Antarctic Ice Sheet (WAIS) retreated during past interglacials, or will retreat in the future, exposed bedrock will rebound rapidly and flux meltwater out into the open ocean. Previous studies have suggested that this contribution to global mean sea level (GMSL) rise is small and occurs slowly. We challenge this notion using sea level predictions that incorporate both the outflux mechanism and complex three-dimensional viscoelastic mantle structure. In the case of the last interglacial, where the GMSL contribution from WAIS collapse is often cited as ~3 to 4 meters, the outflux mechanism contributes ~1 meter of additional GMSL change within ~1 thousand years of the collapse. Using a projection of future WAIS collapse, we also demonstrate that the outflux can substantially amplify GMSL rise estimates over the next century.

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Figures

Fig. 1
Fig. 1. Time series of GMSL after WAIS collapse.
(A) Evolution of GMSL for a simulation of sea level change driven by WAIS collapse in the scenario B2009 (see Introduction), as described in (10). Solid line: Prediction based on the 3D viscoelastic Earth model V3DSD summarized in Fig. 2 (A and B) and an instantaneous deglaciation. Shaded region: The range of the viscoelastic contribution to GMSL reproduced from (10) for the case of a collapse of WAIS over a 500-year time scale. (B) Evolution of GMSL for two simulations of sea level change driven by the PSU3D1 scenario of WAIS collapse (17), as shown in Fig. 2F, with changes in EAIS masked out. Solid line: Prediction based on the 3D viscoelastic Earth model V3DSD summarized in Fig. 2 (A and B) and an instantaneous deglaciation. Dashed-dotted line: Same as solid line, with the exception that a 2000-year deglaciation was adopted. The y axis in both panels begins at the GMSL computed without the contribution from uplift of exposed marine-based sectors for the associated collapse scenario [3.20 m for B2009 in (A) and 3.76 m for PSU3D1 in (B)].
Fig. 2
Fig. 2. 3D viscoelastic Earth models used in calculations.
(A) Elastic lithospheric thickness and (B) mean viscosity from the base of the lithosphere to 400-km depth across Antarctica and the Southern Ocean for the Earth model V3DSD used in the majority of results described in the main text. Labels EL and MBL indicate the location of Ellsworth Land and Marie Byrd Land, respectively. The symbols indicate the location of GPS sites in inferences of mantle viscosity by (49) in the southern Antarctic Peninsula (squares) and (1) in the Amundsen Sea Embayment (triangles). (C) Antarctic bedrock topography from Bedmap2 (35). (D and E) As in (A) and (B) but with the alternative 3D viscoelastic Earth model V3DRH discussed in Materials and Methods. (F) Final grounded ice configuration in the ice sheet simulation PSU3D1 (17), with the red line showing the initial ice extent.
Fig. 3
Fig. 3. Postglacial sea level change after WAIS collapse.
Snapshots of predicted sea level changes (A to D) 0, 500, 2000, and 4000 years after an instantaneous collapse of marine-based sectors of WAIS, based on the PSU3D1 scenario [(17); see Fig. 2F]. Calculations were performed using the 3D viscoelastic Earth model V3DSD summarized in Fig. 2 (A and B). The thin blue line on each frame shows the areal extent of ice that melts in the PSU3D1 ice sheet simulation [(17); see Fig. 2F].
Fig. 4
Fig. 4. Global sea level changes after WAIS collapse.
Predicted sea level changes (A) 0 and (B) 2 ka after an instantaneous collapse of marine-based sectors of WAIS based on the PSU3D1 scenario (Fig. 2F) (17) and computed using the 3D viscoelastic Earth model V3DSD summarized in Fig. 2 (A and B).
Fig. 5
Fig. 5. Sea level change at Eleuthera, Bahamas, in the far field of WAIS.
Solid line: Predicted sea level change at Eleuthera, Bahamas, in the far field of WAIS for the simulation based on the PSU3D1 melt scenario (Fig. 2F) (17) and the 3D viscoelastic Earth model V3DSD (Fig. 2, A and B). The dashed line is analogous to the solid line, with the exception that only ice above floatation before the deglaciation is melted, and no outflux of water from rebounding marine sectors of WAIS is permitted (in this case, the GMSL rise is 3.76 m across the entire simulation; see The sea level fingerprint of WAIS collapse).
Fig. 6
Fig. 6. Time series of GMSL after WAIS collapse for different Earth models and melt geometries.
(A) Evolution of GMSL for four simulations of sea level change driven by WAIS collapse scenario PSU3D1 (Fig. 2F) (17). Each simulation adopts a different viscoelastic Earth model. Solid, dashed, and dotted blue lines: Earth models V3DSD (Fig. 2, A and B), V3DSD+, and V3DSD–, respectively (see Sensitivity tests). Solid purple line: Earth model V3DRH (Fig. 2, D and E). (B) Evolution of GMSL due to uplift of marine-based sectors for five scenarios of WAIS collapse taken from (17), as labeled, and the 3D viscoelastic Earth model V3DSD (Fig. 2, A and B). The GMSL computed without the outflux mechanism (i.e., without uplift of exposed marine-based sectors) for each simulation is listed in the legend.
Fig. 7
Fig. 7. Projected GMSL change in response to AIS mass flux simulated with RCP 8.5 climate forcing.
(A and B) Ice geometry at the start and end of an ice sheet simulation forced by a high-emission (RCP 8.5) scenario with the PSU ice sheet model (36). The red line in (B) shows the perimeter of the ice in frame (A). (C) Solid line: Evolution of the total GMSL computed using this ice history and the 3D viscoelastic Earth model V3DSD (Fig. 2, A and B). Dashed line: GMSL rise when the outflux mechanism is not included. The inset focuses on the GMSL results within the period 2000–2100 CE.
Fig. 8
Fig. 8. Time series of GMSL after EAIS collapse.
Evolution of GMSL due to uplift of marine-based sectors for two scenarios of EAIS collapse taken from (17), as labeled, and the 3D viscoelastic Earth model V3DSD (Fig. 2, A and B). The GMSL computed without the outflux mechanism (i.e., without uplift of exposed marine-based sectors) for each simulation is listed in the legend. All mass changes within WAIS for the two melt scenarios are masked out.
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