Sensitivity of the North Atlantic climate to Greenland Ice Sheet melting during the Last Interglacial

Abstract

Abstract.During the Last Interglacial (LIG;∼130 000 yr BP), part of the Greenland Ice Sheet (GIS) melted due to a warmer than present-day climate. However, the impact of this melting on the LIG climate in the North Atlantic region is relatively unknown. Using the LOVE-CLIM Earth system model of intermediate complexity, we have systematically tested the sensitivity of the LIG climate to increased freshwater runoff from the GIS. In addition, experiments have been performed to investigate the impact of an idealized reduction of both surface elevation and extent of the GIS on the LIG climate. Based on changes in the maximum sea-ice cover and the strength of the overturning circulation, three regimes have been identified, which are characterized by a specific pattern of surface temperature change in the North Atlantic region. By comparing the simulated deep ocean circulation with proxy-based reconstructions, the most realistic simulated climate could be discerned. The resulting climate is characterized by a shutdown of deep convection and a subsequent ∼4 • C cooling in the Labrador Sea. Furthermore, a cooling of ∼1 • C over the North Atlantic Ocean between 40 • N and 70 • N is seen. The prescribed reduction in surface elevation and extent of the GIS results in a local warming of up to 4 • C and amplifies the freshwater-forced reduction in deep convection and the resultant cooling in the Nordic Seas. A further comparison of simulated summer temperatures with both continental and oceanic proxy records reveals that the partial melting of the GIS during the LIG could have delayed maximum summer temperatures in the western part of the North Atlantic region relative to the insolation maximum.

Impact of meltwater on high-latitude early Last Interglacial climate

“…Govin et al (2012) considered the melting of the Greenland ice sheet and its influence on surface temperatures and NADW formation at 126 ka and showed a slowdown of the AMOC along with reduced SSTs in the North Atlantic, but the timing of the cooling from the new data synthesis of Capron et al (2014) predates conditions at 126 ka. Similar work by Bakker et al (2012) and OttoBliesner et al (2006) showed that melting of the Greenland ice sheet resulted in a reduction in the AMOC strength and cooling in the vicinity of the Labrador Sea. Goelzer et Figure 2.…”

“…As a result of this range in response of AMOC collapse to freshwater input, we perform an analysis of the response of the high-latitude regions to varying amounts of freshwater forcing in the North Atlantic to test the sensitivity of the model under 130 ka forcing conditions. This is similar to the study of Bakker et al (2012), which looked at the sensitivity of the AMOC to Greenland ice-sheet melt during the LIG using a climate model of intermediate complexity. Figure 9 shows the model summer North Atlantic temperature response (averaged over the locations for which Capron et al, 2014, provide temperature records) for freshwater input, varying from 0 to 1 Sv compared with the average NH temperature anomaly from the Capron et al (2014) dataset (horizontal dashed line).…”

Last interglacial model–data mismatch of thermal maximum temperatures partially explained

“…Several transient modelling experiments and proxy-based temperature reconstructions for both the present interglacial (PIG) and the LIG have shown that there are large regional differences in the timing of interglacial maximum warmth, of the order of several thousands of years (Renssen et al, 2009Bakker et al, 2012;Govin et al, 2012;Langebroek and Nisancioglu, 2014). These temporal differences result from latitudinal and seasonal differences in the evolution of the orbital forcing, from the thermal inertia of the oceans and from a variety of feedbacks in the climate system, such as the presence of remnant ice sheets from the preceding deglaciation, changes in sea-ice cover, vegetation, meridional overturning strength and monsoon dynamics.…”

“…The last interglacial period (LIG; ∼ 130-116 thousand years before present [ka]) receives increasing attention because of the potential to constrain the impact of climate feedbacks such as increased melt rates of the major ice sheets in warm climates (Otto-Bliesner et al, 2006;Bakker et al, 2012Bakker et al, , 2013Stone et al, 2013) and to evaluate climate model performance for a warmer than present-day climate (Otto-Bliesner et al, 2006Lunt et al, 2013;MassonDelmotte et al, 2013). To facilitate the model-data comparisons that are crucial in the evaluation of climate model performance, a number of compilations of reconstructed maximum LIG temperatures have been produced (e.g.…”

The Holocene thermal maximum in the Nordic Seas: the impact of Greenland Ice Sheet melt and other forcings in a coupled atmosphere–sea-ice–ocean model

“…sum of excess precipitation and snow melt), which is then evenly distributed over 10 major runoff points (c.f. Bakker et al, 2012) for locations of river outflow points.…”