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Message  jerome gaillardet le Jeu 18 Avr - 8:48

Voici un projet de recherche proposé par les équipes du GET, LHYGES, BIOEMCO, Institut de la Forêt de Sukachev (Krasnoiarsk), soumis à l'ANR.

L'objectif du projet est de proposer un modèle hydrogéochimique du carbone et des dés éléments associés en contexte de permafrost continu en s'appuyant sur des mesures de terrain avec une forte résolution spatiale et temporelle et de la modélisation mécanistique.

Despite the existence of several pioneering studies, the knowledge of the effect of permafrost on functioning of arctic ecosystems remains limited. It is still impossible to predict, on the quantitative level, the response of the runoff and flux of chemical elements, to the decrease in the permafrost thickness, the increase in the active layer depth (unfrozen soil surface horizon), the increase in precipitation, plant biomass and primary productivity induced by climate warming. The PERMAFROST-THAW project addresses these issues via concerted and multidisciplinary study of three large Siberian watersheds draining Central Siberian Plateau and located within continuous and discontinuous permafrost zone, along a gradient of latitude, climate and vegetation density on the basaltic rocks of very similar lithology. Within each of these three large watersheds, we will select and instrument a small-size (< 50 km²) watershed exhibiting both south- and north-facing slopes. This choice implies the strategy of “substituting space for time” in addressing, in the most straightforward way, the combined effect of temperature raise, soil thaw and vegetation productivity increase on carbon and related element transport from the land to the ocean.

The main two goals of the present project are (i) to provide new and crucially important data for quantitative prediction of the direction and magnitude of dissolved and suspended matter flux change in the regions of high latitudes under the on-going climate warming and (ii) to constrain new hydrogeochemical models of carbon and related elements transport capable to operate in permafrost-bearing environments based on quantitative calibration of element pools and fluxes assessed from highly seasonally and spatially resolved natural observations and mechanistic modelling.
The originality of the project consists in quantifying, for the first time: 1) the specific hydrological regime of continuous permafrost developed under forest (and not previously studied tundra) vegetation; and 2) the stocks and fluxes of both carbon and trace elements, the latter being tightly linked to DOC via organo-mineral colloids. The project attempts to simulate the climate warming using a well selected latitude/climate/permafrost profile thus substituting “space for time” and allowing for separating the variables which is impossible based on available studies of other transects.
To this end, we will address both the “inorganic” and “organic” geochemistry of boreal ecosystems of variable permafrost depth and active layer thickness using a combination of bulk chemical, stable and radiogenic isotopic, and experimental physico-chemical measurements along with structural and molecular organic matter characterization of carefully selected pilot sites in Central Siberia. Three highly complementary French teams of geochemists and hydrologists together with Russian expert teams of Siberian permafrost and vegetation will be using state-of-the-art stable isotopic techniques, trace element speciation and spectroscopic observations, thermophysical measurements and experimental and numerical approaches. This should allow quantifying the relation between the fluxes and speciation of chemical elements in fluids and soils and the thickness of the permafrost and vegetation activity. This knowledge will be used to elaborate a quantitative and predictive model of Siberian ecosystem development under progressive warming of climate, thawing of permafrost and increase in vegetation coverage. The proposed project will be grounded on well established long-term relationships with Russian partner, recently reinforced by the creation of the GDRI CAR-WET-SIB and the Franco-Siberian Research Center for climate change and environmental science.

Institut de la Forêt de Sukachev (Krasnoiarsk)
Géosciences Environnement Toulouse
LHyGes (Strasbourg)

jerome gaillardet

Messages : 5
Date d'inscription : 08/03/2013

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