Water isotopes( del18O or del D) preserved in high Alpine glaciers may provide temperatureproxy records complementary to those of polar ice cores, including a potentialextension of the 250a instrumental temperature series available for the Greater AlpineRegion. To minimize the influence of glacio-meteorological noise, which challengethe reconstruction of long-term temperature changes from Alpine ice core sites, amulti-core array established at Colle Gnifetti (Monte Rosa, 4450m a.s.l.) was supplementedby a new ice core to bedrock, specifically dedicated to the millennial timescale.The 62m core is shown to offer an outstanding small annual snow accumulation rate(11 cm water i.e. up to a factor of 2-4 lower than at previous cores), an accordinglyincreased distance of the 1000a horizon to bedrock at around 16 m and an approximately2m bottom section possibly older than 10.000a.Main features of the new del18O-record are discussed over last 1000a in view of constraintsarising from the implementable time resolution, dating uncertainties (up to+ 80a), the varying isotope/temperature relationship and the glaciological up streameffects. Overall, over last 250a common isotope variability is seen among the differentcores (though considerably differing by their depositional regime), with a fairlygood correspondence to the instrumental time series. Beyond that period, there is noclear sign of a LIA related cooling, but two striking periods of relative warm isotopetemperature around 1400 (+- 50a) and 900 (+- 100a) AD , with the latter, possiblyassociated with the medieval warming phenomenon.
AWI Organizations > Geosciences > Junior Research Group: LIMPICS
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL1-Processes and interactions in the polar climate system