HR: 0830h
AN: B11D-0718    [PDF]
TI: How the Winter Arctic Oscillation influences Spring Terrestrial Carbon Fluxes in the Northern Hemisphere
AU: * Schaefer, K
EM: kevin@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371 United States
AU: Denning, A
EM: denning@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371 United States
AU: Leonard, O
EM: owen@atmos.colostate.edu
AF: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371 United States
AB: We explored how the winter Arctic Oscillation (AO) influences spring carbon fluxes from the terrestrial biosphere in the Northern Hemisphere. We used the Simple Biosphere model, Version 2 (SiB2) using the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis and the NCEP reanalysis as input to estimate terrestrial Gross Primary Production (GPP) and respiration fluxes for the 1980s and 1990s. The AO influences winter temperatures and precipitation throughout the mid- and high- northern latitudes. The winter AO signal persists into spring and early summer as snow cover and soil temperature anomalies. Temperature correlations with the winter AO peak at later lags at deeper soil depths as temperature anomalies penetrate into the soil over a period of several months. Shallow soil layer temperatures respond quickly to atmospheric forcing, so the correlations start strong and drop off within 3-4 months. The deepest soil layers do not respond to winter AO temperature anomalies until April and May, and can persist throughout the summer and even into the next winter. As a temperature anomaly descends through the soil, it's influence on respiration declines since most of the soil carbon available for respiration lies near the surface. The influence of winter AO on respiration tapers off by April and May, when winter temperature anomalies have sunk below most of the soil carbon. Spring Gross Primary Productivity (GPP) depends primarily on the timing of snowmelt: reduced snow cover and warmer temperatures indicate early snowmelt and budburst and thus increased GPP. Throughout Eurasia, the date of snowmelt and spring GPP correlate strongly with the winter AO, indicating winter AO temperature and precipitation anomalies influence the timing of spring.
DE: 0315 Biosphere/atmosphere interactions
DE: 1030 Geochemical cycles (0330)
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting