Reconstructing glacier-based climates of LGM Europe and Russia – Part 1: Numerical modelling and validation methods

Abstract

Abstract. The mountain environments of mid-latitude Europe and Arctic Russia contain widespread evidence of LateQuaternary glaciers that have been attributed to the Last Glacial Maximum (LGM). This glacial-geological record has yet to be used to quantitatively reconstruct the LGM climate of these regions. Here we describe a simple glacier-climate model that can be used to derive regional temperature and precipitation information from a known glacier distribution. The model was tested against the present day distribution of glaciers in Europe. The model is capable of adequately predicting the spatial distribution, snowline and equilibrium line altitude climate of glaciers in the Alps, Scandinavia, Caucasus and Pyrenees Mountains. This verification demonstrated that the model can be used to investigate former climates such as the LGM. Reconstructions of LGM climates from proxy evidence are an important method of assessing retrospective general circulation model (GCM) simulations.LGM palaeoclimate reconstructions from glacial-geological evidence would be of particular benefit to investigations in Europe and Russia, where to date only fossil pollen data have been used to assess continental-scale GCM simulations.

Reconstructing glacier-based climates of LGM Europe and Russia – Part 3: Comparison with previous climate reconstructions

“…www.clim-past.net/4/265/2008/ Allen et al, 2007a). Note the axes on the temperature anomaly graphs have been inverted, the diagonal line is the 1:1 line; any data point plotting above the 1:1 line indicates the glacial-geological temperature anomaly is larger than the HadCM3 temperature anomaly for that region and vice versa for data points plotting below the 1:1 line.…”

“…1. The range of results (indicated by the minimum and maximum error bars) represents the variability in model climate caused by the use of a suite of lapse rates to downscale the climate onto the glacier surface (this is explained in Allen et al, 2007a). Note the axes on the temperature anomaly graphs have been inverted, the diagonal line is the 1:1 line; any data point plotting above the 1:1 line indicates the glacial-geological temperature anomaly is larger than the HadCM3 temperature anomaly for that region and vice versa for data points plotting below the 1:1 line.…”

“…For example, if the 21 k climate was correct but the 0 k climate was too cold LGM temperature anomalies would be underestimated. Using the glacier-climate model (Allen et al, 2007a), World Glacier Inventory (WGI) (National Snow and Ice Data Center, 1999) dataset of present day glaciers, and LGM glacialgeological evidence it is possible to test the compatibility of HadCM3 (or other GCMs) 0 k and 21lk absolute climates with the cryosphere of these different time periods. The 0 k and 21 k climates were assessed by using the extrapolated climate (described in Sect.…”

“…LGM climate anomalies were reconstructed from a present day climate baseline described by the CRU2.0 ∼20 km resolution climate dataset (New et al, 2002) which had been verified against the present day cryosphere of Europe (Allen et al, 2007a). The model assumes that the glacier extents in Ehlers and Gibbard (2004) are correct, and that their extents were reached at the same time.…”

Using the surface profiles of modern ice masses to inform palaeo-glacier reconstructions

“…Ballantyne, 1989;Stansell et al, 2007) and alongside other palaeo-environmental datasets (e.g. Mark et al, 2005); if extensive, they may also be used to test general circulation models (Allen et al, 2008).…”