Greenland ice sheet climate disequilibrium and committed sea-level rise

Abstract

Ice loss from the Greenland ice sheet is one of the largest sources of contemporary sea-level rise (SLR). While process-based models place timescales on Greenland’s deglaciation, their confidence is obscured by model shortcomings including imprecise atmospheric and oceanic couplings. Here, we present a complementary approach resolving ice sheet disequilibrium with climate constrained by satellite-derived bare-ice extent, tidewater sector ice flow discharge and surface mass balance data. We find that Greenland ice imbalance with the recent (2000–2019) climate commits at least 274 ± 68 mm SLR from 59 ± 15 × 103 km2 ice retreat, equivalent to 3.3 ± 0.9% volume loss, regardless of twenty-first-century climate pathways. This is a result of increasing mass turnover from precipitation, ice flow discharge and meltwater run-off. The high-melt year of 2012 applied in perpetuity yields an ice loss commitment of 782 ± 135 mm SLR, serving as an ominous prognosis for Greenland’s trajectory through a twenty-first century of warming.

Quantifying uncertainty in the temporal disposition of groundwater inundation under sea level rise projections

“…While the mapping of groundwater inundation is discussed in Morris et al (2018) and others, projecting this mapping into a risk framework has been missing from the literature. The distributed properties that support the risk maps of groundwater inundation in response to SLR extends the recent work of Merchán-Rivera et al (2022), which also applied a Bayesian framework to the creation of risk maps, but used spatially lumped hydraulic properties. The spatially distributed hydraulic properties adopted in this work enabled a detailed delineation of areas that is not possible using a spatially lumped parameterisation scheme.…”

The extreme yet transient nature of glacial erosion

“…1). This provides a direct analogue to the contemporary response and deglaciation of the Greenland ice sheet under abrupt 21 st century warming 57 . Record meltwater fluxes accessing the ice-bed interface due to anomalously warm and wet summers 58 , coupled with enhanced dynamics as interior Article https://doi.org/10.1038/s41467-022-35072-0 regions of the Greenland ice sheet transition to wet-bedded regimes, promote the mobilization of new, subglacial sequences of sediment 59,60 by more extensive and intense basal drainage, with resulting suspended loads suggesting erosion rates orders-ofmagnitude above the considered long-term norm 53,61 .…”

Comparison and Synthesis of Sea‐Level and Deep‐Sea Temperature Variations Over the Past 40 Million Years

“…Note that "slow" in "slow feedback" is a relative categorization given that certain mechanisms can substantially accelerate ice-volume changes to centennial (or even shorter) timescales, such as a positive feedback loop of melt-back to lower, warmer elevations that drives further melt (e.g., Levermann & Winkelmann, 2016) or ice-shelf-collapse related processes Pollard et al, 2015). With specific focus on processes that are accelerating mass loss in the Greenland ice sheet to centennial and even decadal timescales, Box et al (2022) listed: "tidewater glacier acceleration and destabilization by submarine melting (Khazendar et al, 2019a(Khazendar et al, , 2019bTruffer & Fahnestock, 2007;Wood et al, 2021); loss of floating ice shelves (Mouginot et al, 2015); accelerating interior motion from increased melt and rainfall (Doyle et al, 2015); enhanced basal thawing due to hydraulically released latent heat and viscous warming (Phillips et al, 2010); amplified surface melt run-off due to bio-albedo darkening (Stibal et al, 2017); and impermeable firn layers (MacFerrin et al, 2019) amplified by ice-sheet surface hypsometry (Mikkelsen et al., 2016;." In West Antarctica, sea-floor data indicate sustained pulses of very rapid Thwaites Glacier retreat (>2 km per day) within the past two centuries that are related to tidally modulated grounding-line migration (Graham et al, 2022).…”