MOLAR: Measuring and modelling the dynamic response of remote mountain lake ecosystems to environmental change

• Unité de recherche: PCRD EU
• Numéro de projet: 95.0518-1
• Titre du projet anglais: MOLAR: Measuring and modelling the dynamic response of remote mountain lake ecosystems to environmental change

Mots-clé (Anglais)

Climate; mountain lakes; limnology; palaeolimnology; palaeoecology

Autre Numéro de projet (Anglais)

EU project number: ENV4-CT95-0007

Programme de recherche (Anglais)

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

Description succincte (Anglais)

See abstract

Résumé des résultats (Abstract) (Anglais)

An investigation of the timing of ice break-up of various lakes in the Northern Hemisphere showed that the effects of the North Atlantic Oscillation and other large-scale climatic phenomena can be easily detected. Because spring ice break-up triggers many ecologically important physical, chemical, and biological processes, the detection of large-scale climate forcing signals in the timing of ice break-up implies that the ecology of individual lakes may be linked to climate on a very large scale. In view of the dominant role played by ice cover in controlling physical, chemical, and biological processes in high mountain lakes this result is of high relevance.
A model was developed to simulate the effect of local topography on solar radiation incident on mountain lakes. This model was applied successfully to Hagelseewli, our Swiss MOLAR site, as well as to other MOLAR lakes. Physical modelling of the water column was successful during the open-water phase, but the modelling of ice cover presents problems.
Thermistor measurements conducted in a Hagelseewli and a series of neighbouring lakes during the summer season showed that the short-term structure of summer lake surface water temperature (LSWT) in a suite of lakes at different altitudes is essentially the same as that of air temperature over a large altitudinal gradient. LSWTs tend to exceed corresponding air temperatures by 3-5 K. They decrease approximately linearly with altitude, allowing an LSWT 'lapse rate' to be defined that is slightly greater than that of air temperature. Diel variations in LSWT are large, implying that individual manual water temperature measurements are unlikely to be representative. Local factors such as topographic shading, partial ice cover and meltwater inflows affect LSWTs, but not air temperatures, possibly resulting in severe distortion of the relationship between the two.
Analyses of fossil remains in short sediment cores that date back to the Middle Ages show the impact of Little Ice Age climatic cooling on the planktonic and benthic organisms in Hagelseewli.

Références bases de données (Anglais)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 95.0518-1