Reconstructing the last interglacial at Summit, Greenland: Insights from GISP2

Abstract

The Eemian (last interglacial, 130-115 ka) was likely the warmest of all interglacials of the last 800 ka, with summer Arctic temperatures 3-5°C above present. Here, we present improved Eemian climate records from central Greenland, reconstructed from the base of the Greenland Ice Sheet Project 2 (GISP2) ice core. Our record comes from clean, stratigraphically disturbed, and isotopically warm ice from 2,750 to 3,040 m depth. N of N 2 , and total air content for samples dating discontinuously from 128 to 115 ka indicate a warming of ∼6°C between 127-121 ka, and a similar elevation history between GISP2 and NEEM. The reconstructed climate and elevation histories are compared with an ensemble of coupled climate-ice-sheet model simulations of the Greenland ice sheet. Those most consistent with the reconstructed temperatures indicate that the Greenland ice sheet contributed 5.1 m (4.1-6.2 m, 95% credible interval) to global eustatic sea level toward the end of the Eemian. Greenland likely did not contribute to anomalously high sea levels at ∼127 ka, or to a rapid jump in sea level at ∼120 ka. However, several unexplained discrepancies remain between the inferred and simulated histories of temperature and accumulation rate at GISP2 and NEEM, as well as between the climatic reconstructions themselves.Greenland ice sheet | last interglacial | ice cores | sea level rise D uring the last interglacial (Eemian, 130-115 ka), Arctic summer temperatures were 3-5°C warmer than today (1), and peak global eustatic sea level was likely 6-9 m higher than the present (2). In the next century, due to anthropogenic emissions of greenhouse gases, we face a similar temperature scenario with 2-6°C of northern hemispheric polar warming (3), and a likely initial sea level rise (by 2100) of 0.3-1.0 m (4), with higher, but uncertain, levels beyond. Certainly there are important differences between the warming and sea level change observed during the last climatic warm period and future projections, notably the rate at which warming is expected to occur and its spatial pattern. Nevertheless, the Eemian history of the Greenland ice sheet (GrIS) serves as an essential test bed for understanding changes in ice sheets and sea level rise in response to rising global temperatures.Ice sheet modeling studies have estimated a wide range of GrIS contributions to sea level during the Eemian, with simulations producing 0.4-5.5 m of equivalent sea level rise above the present datum (5).

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

“…Even with considerable uncertainty due to uncertain spatial pattern of the warming, which modifies this simple reasoning, it is clear that the peak sea-level contribution from the GrIS has to occur late during the LIG. This argument is confirmed by our model results and in line with conclusions recently drawn by Yau et al (2016) based on data from another Greenland ice core and modelling. Based on the same argument, there is no evidence in the reconstructed NEEM temperature evolution suggesting a regrowth or substantial pause of melting of the GrIS any time during the LIG.…”

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

“…for Stone et al, 2013). Also, the timing at which the peak of deglaciation occurs, which spans between 122.3 and 121.6 ka BP in all the simulations, agrees with the timing proposed in many previous studies (Calov et al, 2015;Langebroek and Nisancioglu, 2016;Robinson et al, 2011;Stone et al, 2013;Yau et al, 2016). The time at which the peak of the Eemian occurs in our experiments depends partly on the timing of the atmospheric temperature peak and partly on the duration of the post-glacial rebound, which controls the intrusion of warm waters into the GrIS bays enhancing the ocean-driven retreat.…”

The sensitivity of the Greenland ice sheet to glacial-interglacial oceanic forcing

“…(2013)). Also, the timing at which the peak of deglaciation occurs, which spans between 122.5 and 121.5 ka BP in all the simulations, agrees with the timing proposed in many previous studies (Calov et al, 2015;Langebroek and Nisancioglu, 2016;Robinson et al, 2011;Stone et al, 2013;Yau et al, 2016). GrIS configuration.…”