Modeling of the northern hemisphere ice sheets during the last glacial cycle and glaciological sensitivity

Abstract

[1] We present a new three-dimensional thermomechanically coupled ice sheet model of the northern hemisphere to reconstruct the Quaternary ice sheets during the last glacial cycle. The model includes basal sliding, internally calculated surface mass balance, glacial isostasy, and a treatment for marine calving. The time dependent forcing consists of temperature and precipitation anomalies from the United Kingdom Meteorological Office (UKMO) General Circulation Model scaled to the Greenland Ice Core Project (GRIP) ice core d18 O record. Model parameters were chosen to best match geomorphological inferences on Last Glacial Maximum extent and global eustatic sea level change. For our standard run we find a maximum ice volume of 57 Â 10 6 km 3 at 18.5 ka cal BP. This corresponds to a eustatic sea level lowering of 110 m after correction for hydro-isostatic displacement and anomalous ice resulting from defects in the specified boundary conditions of the Paleoclimate Model Intercomparison Project (PMIP) for which the UKMO GCM results were generated. Of this 110 m, 82 m was stored in the North American ice sheet and 25 m in the Eurasian ice sheet. We determine the qualitative and quantitative response of the model from a comprehensive sensitivity study in which 11 important parameters were varied over their respective ranges of uncertainty. Model outputs comparable to the observational record were explored in detail as a linear function along the axes of parameter space of the reference model. The method reveals the dominance of climate uncertainty when modeling the Last Glacial Maximum configuration of the northern hemisphere ice sheets, but also highlights the role of ice rheology and basal processes for ice sheet thickness, and glacial isostasy and calving for the timing of maximum ice volume.Citation: Zweck, C., and P. Huybrechts (2005), Modeling of the northern hemisphere ice sheets during the last glacial cycle and glaciological sensitivity,

Warm Nordic Seas delayed glacial inception in Scandinavia

“…Numerical ice sheet modeling could improve the understanding of this period but most studies focus on the primary inception regions over North America and western Siberia (Marshall and Clarke, 1999;Zweck and Huybrechts, 2005;Calov et al, 2005a;Kubatzki et al, 2006;Charbit et al, 2007;Peyaud et al, 2007). This is probably due to the lack of constraints on timing and extent of ice from data, but also because the steep Scandinavian topography and variable climate are a challenge for the realistic representation of glaciers.…”

Dominant Northern Hemisphere climate control over millennial-scale glacial sea-level variability

“…Thus, the magnitude of millennial-scale temperature changes is comparable with that induced by orbital forcing, and it has been so far unexplained why these abrupt climate changes did not exert a strong impact on the mass balance of ice sheets. Indeed, results of experiments with climate-ice sheet models show a considerable negative change in mass balance of the NH ice sheets with the transition from stadial to interstadial conditions and a substantial interstadial freshwater output (Zweck and Huybrechts, 2005) ranging from several meters to several tens of meters of sea-level rise (e.g., Charbit et al, 2002;Schmittner et al 2002). An experiment with the CLIM-BER-2 model (Fig.…”

Modelling the Early Weichselian Eurasian Ice Sheets: role of ice shelves and influence of ice-dammed lakes

“…This model features ice shelves as well as grounded ice and allows us to test different assumptions for the glaciation of this area. In contrast to previous studies using a calving parameter to determine the limit of grounded ice (Zweck and Huybrechts, 2005;Siegert et al, 2001), we applied for the first time a model of grounded and floating ice to a whole northern ice sheet.…”