ALPCLIM: Environmental and climate records from high elevation alpine glaciers

• Research unit: EU RFP
• Project number: 97.0349-3

Key words (English)

Climate change; ice cores; Alps

Alternative project number (English)

EU project number: ENV4-CT97-0639

Research programs (English)

EU-programme: 4. Frame Research Programme - 3.1 Environment

Short description (English)

See abstract

Partners and International Organizations (English)

Coordinator: Ruprecht-Karls-Univ. Heidelberg (D)

Abstract (English)

Reasearch in the past one and a half year (an extension of 6 months was agreed upon by the EU- officials) was threefold: (i) high resolution measurements of methane and nitrous oxide on Colle Gnifetti ice; (ii) methane and nitrous oxide on Jungfraujoch and Piz Corvatsch ice; and (iii) carbon isotope measurements on very small ice samples. The purpose of the high resolution methane and nitrous oxide analysis is to learn more about the higher scatter observed in Alpine ice cores. Therefore, we measured 15 samples along one bag. One ice sample covered significantly less than one year, at least for the ice. The analysed air is of course still a mean of about a decade due to its residence time in the fim column and its age widening through the enclosure process. Within such a small time window the trace gas concentrations should stay constant. However, we experienced variations up to 150ppb for methane and 20 ppb for N2O. Interestingly, a different behaviour with the measured gas content is obtained for methane and N2O, respectively. There are several explanations possible for this finding including winter-summer density differences, melt event frequency and variable shearing forcing within the ice due to flow dynamics.
In order to further investigate the very high trace gas concentration measurements found at the base of Alpine ice cores, we retrieved ice from the Jungfraujoch as well as from Piz Corvatsch. For both locations, ice from very near the bottom was taken. Measurements show as expected very high methane and nitrous oxide values, which range from 1 to 100 times today's atmospheric values. The gas content in this ice is very low with 8-23 ml STP/kg ice. No correlation of trace gas values with the gas content is observed. However, a significant correlation between methane and nitrous oxide is present. Most interestingly, the slopes of these correlations are opposite in sign for Jungfraujoch and Piz Corvatsch. This indicates that there is more than one process involved in modifying the gas content and gas composition of basal ice.
Isotope composition measurements of carbon dioxide is a useful tool to distinguish between potential production paths of the observed excess CO2. Excess CO2 is the difference between the observed and the expected free atmospheric concentration level for the corresponding time. Already a few &13C measurements (we obtained very low values) clearly documented that this excess CO2 most probably originates from organic material, which is slowly oxidised to CO2. What kind of oxidation path is taken is unknown up to now. Bacteriological oxidation seems to be most probable.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0349-3