In order to utilise Equilibrium Line Altitudes in a regional European analysis of YD glaciation and climate, the first requirement is that the glacier mapping, reconstructions and palaeo-climate extrapolations are all uniform in their approach. Therefore the first aim of this project is to develop a robust data set by applying a consistent methodology to key sites for which YD moraines have been identified and dated.
The glaciologists participating in this project will discuss and together develop a uniform methodology which will be applied to all YD dated moraines across the study region.
GLAYDE study areas
The size of a glacier is fundamentally controlled by the interplay between accumulation (precipitation) and ablation (temperature), with both being equal at the Equilibrium Line Altitude (ELA).
Empirical relationships have been derived which link precipitation and temperature at the ELA and can be used to derive quantitative estimates of palaeoclimate from the evidence of YD glaciers preserved in the geomorphological record.
The second aim of the project is to analyse the synchroneity of the YD glacial advance.
Some direct and many indirect dates, based on either cosmogenic radionuclides, 14C and OSL techniques, are available, but a systematic revision of them is needed. This is important because dating techniques evolve over time, and different publications, even when applying the same dating technique, use different production rates, calibration statistics etc. Therefore, the geochronologists will establish a uniform methodology and where necessary, re-calculate dates.
All dates will be consolidated onto a common timescale to enable correlation across the study area.
Finally, the pan-European YD climate will be analysed in terms of both its spatial and temporal variability, and the results will be used to test and tune atmospheric and climatic models.
The chronology and ELA-climate data will elucidate the synchronicity of glacier maxima and synoptic-scale weather patterns across the region. For example, the steep present-day west-east ELA gradient along the Alps reflects the location of the Polar Frontal Jet Stream (PFJS) to the north which guides the general track of mid latitude depressions.
The data will test the hypothesised lower W-E precipitation gradient during the YD which would indicate that the PFJS was located further south than at present, likely along the northern flank of the Alps. The combined ELA-climate and chronological data will be compared against output from ECHAM3 and ECHAM4 atmospheric general circulation models (13), and the HIRHAM regional climate model to evaluate the model results and the applied forcing scenarios.
New transient experiments with LOVECLIM (a coupled atmosphere-ocean-vegetation model) will allow assessment of key process during the rapid initial cooling and abrupt warming of the YD eg location of the PFJS and sea ice formation.