Lin, and 6 co-authors, reported in early 2021 that The most rapid global sea-level rise event of the last deglaciation, Meltwater Pulse 1A (MWP-1A), occurred ∼14,650 years ago. Considerable uncertainty regarding the sources of meltwater limits understanding of the relationship between MWP-1A and the concurrent fast-changing climate. Here we present a data-driven inversion approach, using a glacio-isostatic adjustment model to invert for the sources of MWP-1A via sea-level constraints from six geographically distributed sites.
The authors concluded that contributions from Antarctica, 1.3 m (0–5.9 m; 95% probability), Scandinavia, 4.6 m (3.2–6.4 m) and North America, 12.0 m (5.6–15.4 m), giving a global mean sea-level rise of 17.9 m (15.7–20.2 m) in 500 years. Only a North American dominant scenario successfully predicts the observed sea-level change across our six sites and an Antarctic dominant scenario is firmly refuted by Scottish isolation basin records. Our sea-level based results therefore reconcile with field-based ice-sheet reconstructions.
FYI:
Sea-Level Fingerprint Methods:
The sea-level fingerprint for each ice sheet is obtained by calculating the normalized global pattern of RSL change associated with melt from a specific ice sheet over a finite time interval. Because sea-level fingerprints are sensitive to the geometry of ice melt, the authors used realistic melt geometries across MWP-1A from two recent regional ice-sheet reconstructions of Lambeck et al., and the BRITICE-CHRONO project (with SCEAN1D scenario; S. Bradley, personal communication 2020) for the NAIS and SIS, respectively (Fig. 1a, c). The latter is constrained using geomorphological data compiled in Hughes et al. and Clark et al., and reconstructed using a plastic ice-sheet model. The authors also used some alternative NAIS and SIS melt geometries from ICE6G_C22, GLAC-1D10 and G1211 for the NAIS and PATTON2017 for the SIS to test the dependence of the inversion results on the assumed ice melt geometries. This leads to essentially unchanged inversion results (see Supplementary Table 3). For the AIS, due to the lack of geological constraints, the melt geometry across MWP-1A remains largely unknown.
Since East Antarctica is estimated to have contributed only ∼1 m to post-Last Glacial Maximum ESL rise, with this melt most likely to have occurred after MWP-1A78, any Antarctic contribution to MWP-1A is likely to have come from the West AIS. The authors generated the AIS sea-level fingerprint using the Last Glacial Maximum-to-present pattern of ice loss across West Antarctica adopted by the W12 ice model (Fig. 1b). Because all of the authors' six sea-level sites are far away from the AIS, their AIS sea-level fingerprint values are not sensitive to the assumed West AIS melt geometry.
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