Last Interglacial climate and sea-level evolution from a coupled ice sheet-climate model

Abstract

Abstract. As the most recent warm period in Earth’s history with a sea-level stand higher than present, the Last Interglacial period (~130 to 115 kyr BP) is often considered a prime example to study the impact of a warmer climate on the two polar ice sheets remaining today. Here we simulate the Last Interglacial climate, ice sheet and sea-level evolution with the Earth system model of intermediate complexity LOVECLIM v.1.3, which includes dynamic and fully-coupled components representing the atmosphere, the ocean and sea ice, the terrestrial biosphere and the Greenland and Antarctic ice sheets. In this set-up, sea-level evolution and climate-ice sheet interactions are modelled in a consistent framework. Surface mass balance changes are the dominant forcing for the Greenland ice sheet, which shows a peak sea-level contribution of 1.4 m at 123 kyr BP in the reference experiment. Our results indicate that ice sheet-climate feedbacks play an important role to amplify climate and sea-level changes in the Northern Hemisphere. The sensitivity of the Greenland ice sheet to surface temperature changes considerably increases when interactive albedo changes are considered. Southern Hemisphere polar and sub-polar ocean warming is limited throughout the Last Interglacial and surface and sub-shelf melting exerts only a minor control on the Antarctic sea-level contribution with a peak of 4.4 m at 125 kyr BP. Retreat of the Antarctic ice sheet at the onset of the LIG is mainly forced by rising sea-level and reduced ice shelf viscosity as the surface temperature increases. Global sea level shows a peak of 5.3 m at 124.5 kyr BP, which includes a minor contribution of 0.35 m from oceanic thermal expansion. Neither the individual contributions nor the total modelled sea-level stand show multi millennial time scale variations as indicated by some reconstructions.

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

“…When assuming a maximum contribution from glaciers (0.42 ± 0.11) and an additional estimate for thermal expansion of the ocean (0.4 ± 0.3) as given by Masson-Delmotte et al (2013), the assumed ice sheet evolution in our setup reproduces well the average sea-level contribution between 125 and 120 kyr BP from the best estimate of Kopp et al (2009), but it does not represent the multi-peak structure of global sea-level contribution during the LIG as suggested by Kopp et al (2009Kopp et al ( , 2013. More details about the ice sheet and sea-level evolution can be found in a companion paper (Goelzer et al, 2016) that specifically deals with the sea-level contribution of the ice sheets during the LIG in a fully coupled model setup.…”

“…Nevertheless, any modelling approach will ultimately be confronted with the same problem of scarce data for model validation during that period. The exclusion of climate feedbacks on ice sheet evolution of our present one-way coupled modelling approach is a general limitation, which we have addressed in a separate study with a fully coupled model setup (Goelzer et al, 2016).…”

Long‐term projections of sea‐level rise from ice sheets

“…For these reasons, it is essential that models used to predict the future are also able to not only accurately capture the present‐day state of the GIS and AIS and their recent changes, but are also able to reproduce past ice sheet geometries that are consistent with palaeoenvironmental proxy records. Geological and palaeoenvironmental data have been used to parameterize and/or evaluate simulations of key intervals of the past such as the Last Glacial Maximum (LGM, 25–18 ka BP) (Briggs & Tarasov, ; N. Golledge et al, ), the Last Interglaciation (LIG, 130–115 ka BP) (Goelzer, Huybrechts, Loutre, & Fichefet, ), and interglacials of the Pliocene (5–3 Ma BP) (Gasson, DeConto, & Pollard, ; N. R. Golledge, Thomas, et al, ; Pollard & DeConto, ). Of these three periods, however, only the LGM and Pliocene provide sufficient ice‐proximal geological data for inferences to be made regarding changes in the extent, thickness, or volume of the former ice sheets; empirical constraints on ice sheet configuration during the LIG are extremely sparse for both Antarctica and for Greenland.…”

“…The remaining is attributed to thermal expansion of the ocean and melting of glaciers and ice caps. During the LIG, Antarctica is thought to have lost 3–5 m sea‐level‐equivalent (SLE) ice volume and Greenland less than 2 m (Clark et al, ; Dahl‐Jensen et al, ; Dutton et al, ; Goelzer et al, ), with additions of around 0.4 m each coming from thermal expansion of the ocean and from melting of glaciers and ice caps (Masson‐Delmotte et al, ). This total reflects the “very likely” range of 6–9 m from probabilistic assessments of LIG GMSL (Kopp, Simons, Mitrovica, Maloof, & Oppenheimer, ; Kopp, Simons, Mitrovica, Maloof, & Oppenheimer, ), but few ice sheet modeling experiments have been able to reproduce these inferred ice sheet changes.…”

“…This is especially true for the AIS where several studies have only been able to trigger substantial ice loss with ocean temperatures far higher than those simulated by climate models for the period (DeConto & Pollard, ; Sutter, Gierz, Grosfeld, Thoma, & Lohmann, ). However, (Goelzer et al, ) simulated both ice sheets in a fully coupled climate–ice sheet model framework and found maximum contributions to sea level of 1.4 and 4.4 m from the GIS and AIS, respectively, with loss from the latter primarily occurring in response to sea‐level forcing. Differences in timing of ice loss from the two ice sheets meant that peak‐modeled sea level of 5.3 m above present occurred at 124.5 ka BP, including a contribution of 0.35 m from ocean thermal expansion.…”