Towards improved estimation of carbon balance in a low-Arctic mire: a micrometeorological eddy covariance approach to methane flux characterization.

The climate is warming. The Arctic regions of the world have been shown to be warming at a rate faster than any other region on earth. These high northern latitude regions may play a critical role in determining the global impacts of climatic change because they cover a significant proportion of the earth's surface in the northern hermisphere and act as a major carbon sink, currently storing some 11% of the earth's carbon, locked away in the organic soils and peat of Arctic tundra and extensive mire sytems that are representative of these Arctic regions. Thus it is vital that we better understand the factors that currently determine the balance, and exchange of carbon between land surface and atmosphere so as to better predict the likely consequences of continued warming of the Arctic. However, these high latitude regions remain data sparse, not only in terms of spatial coverage of data, but perhaps as, or more, importantly, in terms of temporal coverage, with still relatively few data sets available spanning extended periods of the annual cycle. This is particularly the case in terms of carbon in the form of methane. Methane is a powerful greenhouse gas that accounts for about 20% of the increase in global radiative forcing since the pre-industrial era. Wetlands play an important dual role in the global carbon cycle, being both the largest natural methane source and a large net carbon sink (that is that it locks away more carbon dioxide from the atmosphere than it releases to it). About 30% of global wetlands are located in northern Eurasia; many throughout the Arctic and sub-Arctic regions. Quantifying the potential impacts of global warming, and any positive feedback, requires models that represent the landscape through both space and through time. Such models must be underpinned by ecosystem studies that will provide the data necessary to achieve adequate representation of landscape processes and how they vary through space and time. The present proposal, linking ecosystem scientists at Durham and Stirling having expertise in measurement of methane concurrently at a range of spatial scales, with micrometeorological and modelling expertise at Edinburgh, seeks to provide such key data related to methane flux from an Arctic mire in N Finland, so as to obtain estimates of carbon sinks and sources at the regional scale of northern Finland. We propose to use the understanding gained, and the models developed, to better predict potential future regional methane fluxes. The approach we will undertake is that of methane measurement by the eddy covariance technique (a chamberless technique for measuring methane across a portion of a landscape without using artificial chamber approaches which, by their very use, impact upon the vegetation/soils being sampled). The technique allows in integration of fluxes from the various vegetation and soil assemblages that characterise the heterogeneous surface of Arctic mire ecosystems. The key advantage here is a continous record of CH4 flux between land surface and atmosphere for an extended period (ca. 4 week campaigns at different times of the year, in this instance). Key strengths of the current proposal are: the commitment of personnel and equipment for extended periods to allow methane flux measurements to be made without the unwanted, confounding inter-annual variation that has been encountered in some previous studies; and the particularly high added value that it offers because it builds directly upon, and is complemented by, ongoing NERC-funded research.