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Temperature Related Isotope Records from Alpine Ice Cores: Reality or Fiction?

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Bohleber, P. , Wagenbach, D. , Böhm, R. and Schöner, W. (2009): Temperature Related Isotope Records from Alpine Ice Cores: Reality or Fiction? , MOCA09, 19-29th July, Montréal, Canada. .
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Abstract:

The variabilty of water isotopes (delta-O18 or delta-D) preserved in Alpine glaciers may provide mid-latitude temperature records supplementing respective proxy information from other archives. However, concerning long term records (i.e. exceeding 100 years) the limited glacier depth of suitable Alpine drill sites requires a relatively low accumulation rate. As a result, depositional noise is found to strongly challenge the interpretation of these isotope records in terms of net temperature change. Here we present results from our multi core array at the low accumulation Colle Gnifetti (CG) site (4450m asl, Swiss-Italian Alps) dedicated to assess the potential of long term ice core isotope records for paleoclimate reconstruction. To do so, a specific CG relevant temperature time series is synthesized from the high elevation stations of the instrumental HISTALP network considering among others the accumulation bias towards growing seasons. Within the last century (where dating and homogenity problems do not matter) dedicated time series analysis reveals a common signal in the decadal components of the temperature record and isotope records of four ice cores. Throughout the entire 250 year instrumental period, exceptions occur within the early instrumental period, as well as an unexpectedly high isotope-temperature sensitivity. An inter-core correspondence in the temperature related decadal trends can be revealed for two cores throughout the last 500 years. On a tentative basis, we discuss the delta O18-record of a new CG ice core dedicated to last 1000 years in view of constraints arising from varying time resolution, dating uncertainties and systematic glaciological up-stream effects.

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