The Eurasian arctic drainage is a vast area that constitutes over 10 percent of the global land mass. Much of this region is either boreal forest or tundra, both of which are fragile ecosystems that have undergone considerable change over the last half century. The presence of permafrost and modest relief impedes the subsurface drainage of water and makes lakes and wetlands a dominant feature throughout the region. Most global carbon budgets have concluded that the boreal forest portion of the region is a net sink of as much as 0.5 Pg/year of carbon, while the tundra area is nearly in balance. However, these estimates may be considerably in error, as they account at best approximately for the contribution of methane emissions from wetlands. Methane emissions are sensitive to temperature, which has shown marked increases over the last half century, and is projected to continue to warm as the global climate changes. Furthermore, while the extent of wetlands within the region may be increasing, most estimates are based on coarse resolution (typically 1 km) satellite data, which tend to lead to substantial underestimates (by factors of two or more) of "minority" land cover classes, like wetlands.This investigation will address the overarching science question: How have changes in lake and wetland extent in northern Eurasia over the last half-century affected the region's carbon balance, and how are changes in lakes and wetlands over the region likely to affect its carbon balance over the next century? We will employ high resolution SAR data in combination with in situ data to test and evaluate new lake and wetland, and permafrost dynamics models within the Variable Infiltration Capacity (VIC) macroscale hydrology model. The VIC model will be linked with a dynamic terrestrial carbon model, and with a lake and wetland methane model. Evaluation of the carbon and methane models will be performed with respect to large area estimates of carbon production and sequestration based on a combination of extrapolation of direct measurements, inverse modeling methods, and other modeling studies. Using the extended VIC construct, we will attempt to reconstruct the time history of terrestrial carbon and methane balances over the arctic Eurasia drainage, and, using a range of climate scenarios, to interpret how these balances might change over the next century.