A Pan-Arctic Synthesis of Cold Season Carbon Emissions

Over the past several decades, surface air temperatures in the Arctic have increased at approximately twice the global rate, and climate models project that this rate of warming will continue through the century, with the greatest warming occurring during the winter months. Carbon emissions during the cold season (i.e., fall, winter and spring) are an important component of annual respiratory loss, yet there are large uncertainties in local and regional estimates of cold season carbon emissions. To address these uncertainties, we conducted a pan-Arctic synthesis of cold season CO2 emissions from northern high latitude terrestrial ecosystems. We compiled data from more than 70 studies from sites located throughout the permafrost region. We examined differences in cold season respiration among permafrost zones, biomes, and ecosystem types. We found that cold season CO2 emissions were positively related to mean annual air temperature, growing season precipitation, and NDVI. There were significant differences in CO2 emissions among permafrost zones: CO2 emissions were greatest in the sporadic zone compared to discontinuous and continuous zones, and were significantly lower in the continuous permafrost zone. There were also significant differences among landscape positions, with higher cold season CO2 emissions in upland compared to lowland ecosystems. Synthesized results of experimental studies showed that cold season CO2 emissions were significantly higher when soils were warmed and lower when vegetation was removed, demonstrating the sensitivity of carbon release to both rising temperatures and changes in vegetation cover in northern high latitudes. These results highlight the importance of including cold season respiration in current and future carbon estimates for the northern region, and suggest that as winter temperatures increase across the Arctic, cold season CO2 emissions may offset potential increases in plant productivity.