Using atmospheric observations to quantify annual biogenic carbon dioxide fluxes on the Alaska North Slope

Abstract. The continued warming of the Arctic could release vast stores carbon into atmosphere from high-latitude ecosystems, especially thawing permafrost. Increasing uptake dioxide (CO2) by vegetation during longer growing seasons may partially offset such carbon. However, evidence significant net annual site-level observations and model simulations across tundra ecosystems has been inconclusive. To address this knowledge gap, we combined top-down atmospheric CO2 concentration enhancements aircraft a tall tower, which integrate ecosystem exchange over large regions, with bottom-up observed fluxes environments found that Alaska North Slope is not consistent source nor sink to (ranging ?6 +6 Tg C yr?1 for 2012–2017). Our analysis suggests biogenic unfrozen terrestrial soils, likely inland waters, early cold season (September–December) are major factors in determining balance Slope, implying strong sensitivity rapidly freeze-up period. At regional level, find no previously reported late-cold-season (January–April) emissions study Despite importance cold-season total, interannual variability flux driven fluxes. During season, also highly sensitive distribution types throughout Slope. This shows quantification characterization year-round heterogeneous aquatic using both important accurately project Earth system response future warming.