Coupled ice sheet–climate modeling under glacial and pre-industrial boundary conditions

Abstract

Abstract. In the standard Paleoclimate Modelling Intercomparison Project (PMIP) experiments, the Last Glacial Maximum (LGM) is modeled in quasi-equilibrium with atmosphere-ocean-vegetation general circulation models (AOVGCMs) with prescribed ice sheets. This can lead to inconsistencies between the modeled climate and ice sheets. One way to avoid this problem would be to model the ice sheets explicitly. Here, we present the first results from coupled ice sheet-climate simulations for the pre-industrial times and the LGM.Our setup consists of the AOVGCM ECHAM5/MPIOM/LPJ bidirectionally coupled with the Parallel Ice Sheet Model (PISM) covering the Northern Hemisphere. The results of the pre-industrial and LGM simulations agree reasonably well with reconstructions and observations. This shows that the model system adequately represents large, non-linear climate perturbations.A large part of the drainage of the ice sheets occurs in ice streams. Most modeled ice stream systems show recurring surges as internal oscillations. The Hudson Strait Ice Stream surges with an ice volume equivalent to about 5 m sea level and a recurrence interval of about 7000 yr. This is in agreement with basic expectations for Heinrich events. Under LGM boundary conditions, different ice sheet configurations imply different locations of deep water formation.

The effect of greenhouse gas concentrations and ice sheets on the glacial AMOC in a coupled climate model

“…The warming did not occur in simulations using the ICE-4G ice sheets (Justino et al, 2005;Kim, 2004) but it was present in simulations using the ICE-5G ice sheets (Pausata et al, 2011). Ziemen et al (2014) found that different ice-sheet configurations had a large impact on deep-water formation patterns in the North Atlantic and thus also on regional heat budgets and surface temperatures.…”

An ice sheet model of reduced complexity for paleoclimate studies

“…The LGM uc ensemble accumulates ice in the North American part of the Bering Strait, whereas the ice in the LGM bs ensemble and ICE-5G reconstruction is in this part not that distinct. Ziemen et al (2014) attribute the overestimated accumulation in this region to the missing albedo variation in their model and moisture blocking of the atmospheric forcing. The land around the New Siberian Islands is covered by a small ice sheet in both ensembles, while this area is ice-free in the LGM ICE-5G reconstruction.…”

Views on grand research challenges for Quaternary geology, geomorphology and environments

“…The calibration and refining of Earth System models (ESM) to boundary conditions of past periods in the Quaternary is an ongoing effort to improve the predictive capabilities for future climate simulations (cf. Schmidt et al, 2014;Ziemen et al, 2014;Moberg et al, 2015). The integration of Quaternary proxy climatic data with ESMs on the global and the regional scale is needed to provide insight into non-linear response of climate dynamics on various spatial scales, for areas affected by monsoonal systems, and varying modes of ocean circulation, like the El Nino Southern Oscillation or the North Atlantic Oscillation.…”