This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Changes in the magnitude and seasonality of Arctic summer vegetation production over the past several decades have been documented. These changes will likely accelerate and have consequences for the entire Arctic terrestrial system, in particular energy and element budgets, and will also feed back to marine and atmospheric systems. This project will characterize the seasonal linkages between the land surface greenness and a suite of land, atmosphere, and ocean characteristics, focusing on the Beringia/Beaufort Sea, where there have been strong positive increases in the Normalized Difference Vegetation Index (NDVI) over the past 25 years, and the west-central Arctic Eurasia region , where the NDVI trends have been slightly negative. The following questions will be addressed: (1) What are the spatial and temporal variabilities in the seasonality of various arctic system components (sea-ice concentration and thickness, ocean and land surface temperatures, ocean heat fluxes, snow cover, and vegetation as specified by the NDVI? Specifically, how do these vary zonally and meridionally in the circumpolar Arctic? (2) What role do the atmosphere and ocean circulation patterns play in controlling the seasonality of land temperatures and vegetation production? (3) How do changes in the seasonality of these arctic system components affect vegetation growth and carbon sequestration? Using both satellite and in situ data sets, this project will document the seasonal (daily to monthly timescales) of the tundra and marine climate systems at a regional scale throughout the Arctic. Reanalysis data sets will be employed to describe local circulation characteristics. A pan-arctic ice-ocean model will be used to describe ocean circulation patterns relevant for tundra vegetation, with the application of statistical analyses to investigate mechanisms of ocean-atmosphere-land relationships. A vegetation change model (ArcVeg) will analyze the consequences of land temperature changes for carbon production along climate, disturbance, and soil gradients. This model will be enhanced for seasonality studies, including transition to a daily time step, and will allow the examination of effects of seasonality changes on the carbon accumulated by different functional plant types and into different plant tissue types.
