EMERGE: European mountain lake ecosystems - regionalisation, diagnostics & socio-economic evaluation

• Unité de recherche: PCRD EU
• Numéro de projet: 99.0394-2
• Titre du projet anglais: EMERGE: European mountain lake ecosystems - regionalisation, diagnostics & socio-economic evaluation

Mots-clé (Anglais)

Mountain lakes; sediment traps; particles; ice model; lake surface temperatures

Autre Numéro de projet (Anglais)

EU project number: EVK1-1999-00032

Programme de recherche (Anglais)

EU-programme: 5. Frame Research Programme - 1.4a.2 Global change, climate and biodiversity

Description succincte (Anglais)

See abstract

Partenaires et organisations internationales (Anglais)

Coordinator: University College London (UK)

Résumé des résultats (Abstract) (Anglais)

Results of sediment traps measurements in two high mountain lakes (>2200 m a.s.l.) showed generally very low total particle fluxes with a mean of 62 mg m-2 d-l in Estany Redo (Spain) and of 4.8 mg m-2 d-l. in Gossenkollesee (Austria). For the fIrst time automated, micro processor driven sediment traps were successfully deployed in high mountain lakes. They allowed interval sampling at high time- resolution. Results of these measurements showed that particle fluxes in both lakes (although low) vary substantially durin¥ the year. Very low fluxes are observed during periods of ice cover. High fluxes (max. 650 mg m- d-l for Estany Redo; max. 16 mg m-2 d.l for Gossenkollesee) occur just after ice break-up and during summer.
SEM-image analyses showed that algal blooms (diatoms, chrysophytes) in the water column are mainly responsible for high flux rates, causing high organic carbon and biogenic silica (opal) concentrations in the suspended material. Indications of dust material have been observed in the traps of Lake Redo, when gypsum particles of the catchment are blown into the lake during ice-free periods in summer. Higher concentrations of Mn, Fe and S during ice-cover lead to the assumption of oxygen deficiency in the bottom water of the lakes.
Preliminary analysis of lake surface temperatures (LST) from high mountain lake districts across Europe indicates a high degree of spatial coherence within each lake district. LSTs in summer are highly correlated with equilibrium temperatures calculated from automatic weather station data, and the equilibrium temperatures are in turn governed largely by air temperature. This indicates that the use of empirical models based on altitude-dependent air temperature alone may suffice to upscale LSTs from individual lakes to lake districts.
The development of an ice module to be incorporated into an already existing physical lake model was continued by incorporating slush and snow-ice, so that the physical lake model with the new ice module is now capable of simulating temperature profiles and the thicknesses of snow, slush, snow-ice and clear ice layers. The model was applied with some success to Gossenkollesee (Tyrol). However, some problems concerned with the simulation of vertical mixing in the water column arose which may still need to be solved. Model results suggest that an air temperature shift of +4°C will result in a decrease in the duration of ice cover on Gossenkollesee by 40-50 days. The model was also employed to give a preliminary simulation of temperature profiles in Estany Red6 (Pyrenees).

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: 99.0394-2