The arctic flux study: A regional view of trace gas release

Fluxes of trace gases from northern ecosystems represent a highly uncertain and potentially significant component of the arctic land-atmosphere system, especially in the context of greenhouse-induced climate change. The initial goal of the Arctic Flux Study (a part of NSF's Arctic System Science Program) is a regional estimate of the present and future movement of materials between the land, atmosphere and ocean in the Kuparuk River basin in northern Alaska. We are measuring rates and controls of processes along a north-south transect running from the marshy coastal plain to mountain valleys. Important vertical fluxes under study are the release of CO2 and CH4 from soils and water, lateral fluxes are surface water, nutrients, and organic matter. A hierarchy of measurements allow the rates and understanding of processes to be scaled from plots to the landscape, regional, and circumarctic level. These include gas flux measurements in small chambers, measurements over larger areas by eddy correlation from small towers, and measurements at the landscape scale from airplane overflights. Experimental manipulations of carbon dioxide, soil moisture, nutrients and soil temperature from this and other studies give information on process controls. The distribution of plant communities has been described at several landscape-scale sites and a hierarchic GIS has been developed for the region at three scales (plot, landscape, region). Climate is measured at six sites and hydrological processes are being studied at each watershed scale. In the soils, measurements are being made of soil organic matter and active layer thickness and of availability of soil organic matter for microbial transformation into CO2 and CH4. Fluxes and process understanding have been incorporated into a hierarchy of models at different scales. These include models of regional climate nested in a GCM; of regional- and continental-scale plant productivity and carbon cycling including CO2 release under altered climates; watershed and regional models of hydrology; and surface energy budgets. After the first year of study the regional climate model has been successfully configured to the northern Alaska region We have also measured a large release of carbon dioxide from tundra soils in all but the coldest and wettest parts of the transect. The rates from eddy correlation towers (landscape level) agree closely with rates from chambers (plot level). Observations, experimental manipulations and modelling analyses result in the prediction that the combination of warmer and drier soils is responsible for the large CO2 release.