Ice-dynamic projections of the Greenland ice sheet in response to atmospheric and oceanic warming

Abstract

Abstract. Continuing global warming will have a strong impact on the Greenland ice sheet in the coming centuries. During the last decade (2000–2010), both increased melt-water runoff and enhanced ice discharge from calving glaciers have contributed 0.6 ± 0.1 mm yr−1 to global sea-level rise, with a relative contribution of 60 and 40% respectively. Here we use a higher-order ice flow model, spun up to present day, to simulate future ice volume changes driven by both atmospheric and oceanic temperature changes. For these projections, the flow model accounts for runoff-induced basal lubrication and ocean warming-induced discharge increase at the marine margins. For a suite of 10 atmosphere and ocean general circulation models and four representative concentration pathway scenarios, the projected sea-level rise between 2000 and 2100 lies in the range of +1.4 to +16.6 cm. For two low emission scenarios, the projections are conducted up to 2300. Ice loss rates are found to abate for the most favourable scenario where the warming peaks in this century, allowing the ice sheet to maintain a geometry close to the present-day state. For the other moderate scenario, loss rates remain at a constant level over 300 years. In any scenario, volume loss is predominantly caused by increased surface melting as the contribution from enhanced ice discharge decreases over time and is self-limited by thinning and retreat of the marine margin, reducing the ice–ocean contact area. As confirmed by other studies, we find that the effect of enhanced basal lubrication on the volume evolution is negligible on centennial timescales. Our projections show that the observed rates of volume change over the last decades cannot simply be extrapolated over the 21st century on account of a different balance of processes causing ice loss over time. Our results also indicate that the largest source of uncertainty arises from the surface mass balance and the underlying climate change projections, not from ice dynamics.

Recent Progress in Understanding and Projecting Regional and Global Mean Sea Level Change

“…The consequent mass loss, of which ∼40 % is from ice discharge, contributes 0.62 mm year −1 to GMSL rise, similar to observations (section BGreenland Ice Sheet^), giving confidence in the ice sheet model. With forcing from an ensemble of ten CMIP5 AOGCMs under the four RCP scenarios, Fürst et al [104] found the contributions to GMSL rise by 2100 relative to 2000 range from 0.04±0.02 m (1 std. dev.)…”

“…Fürst et al [104] forced an ice sheet model that accounts for basal lubrication and ocean thermal forcing of ice discharge with reanalysis data over the period 2005-2010. The consequent mass loss, of which ∼40 % is from ice discharge, contributes 0.62 mm year −1 to GMSL rise, similar to observations (section BGreenland Ice Sheet^), giving confidence in the ice sheet model.…”

Impact of ice sheet meltwater fluxes on the climate evolution at the onset of the Last Interglacial

“…Huybrechts, 1990;Letréguilly et al, 1991;Zweck and Huybrechts, 2005;Greve et al, 2011). For the GrIS the forcing record was created following Fürst et al (2015). We combine a synthesised Greenland δ 18 O record derived from Antarctica Dome C using a bipolar seesaw model (Barker et al, 2011) with the NEEM temperature reconstruction (NEEM community members, 2013) between 128.44 and 120 kyr BP.…”

The sensitivity of the Greenland Ice Sheet to glacial–interglacial oceanic forcing

“…On average, the GrIS contributed to 0.47 ± 0.23 mm a −1 of sea-level rise from 1991 to 2015 (van den Broeke et al, 2016), with an accelerated rate of 0.89 ± 0.09 mm a −1 from 2010 to 2014 (Yi et al, 2015). In the future, the GrIS is expected to continue losing mass, contributing to a sea-level rise relative to the 20th century between 90 and 280 mm by 2100 in the worst-case scenario (RCP8.5) IPCC, 2013;Clark et al, 2015;Fürst et al, 2015). This accelerated ice loss is due to a combination of increased surface melting and enhanced ice discharge from marine-terminating glaciers to the ocean (van den .…”

“…Various numerical models have been used to simulate current submarine melt rates (Jenkins, 2011;Rignot et al, 2016;Sciascia et al, 2013;Xu et al, 2012Xu et al, , 2013 and dynamic retreat Vieli and Nick, 2011) of the GrIS marine-terminating glaciers, as well as ice-dynamic future projections of the whole GrIS (Fürst et al, 2015;Nowicki et al, 2013), due to changes in the oceanic temperatures. However, how this thermal forcing affected the past GrIS configuration has not been explored from a modelling perspective so far.…”