Terrestrial Carbon Cycle
The Arctic continues to warm at a rate that is currently twice as fast as the global average (see essay on Surface Air Temperature). Warming is causing normally frozen ground (permafrost) to thaw, exposing significant quantities of organic soil carbon to decomposition by soil microbes (Romanovsky et al. 2010, Romanovsky et al. 2012). This permafrost carbon is the remnants of plants, animals, and microbes accumulated in frozen soil over hundreds to thousands of years (Schuur et al. 2008). The northern permafrost zone holds twice as much carbon as currently in the atmosphere (Schuur et al. 2015, Hugelius et al. 2014, Tarnocai et al. 2009, Zimov et al. 2006). Release of just a fraction of this frozen carbon pool, as the greenhouse gases carbon dioxide and methane, into the atmosphere would dramatically increase the rate of future global climate warming (Schuur et al. 2013).
This report details recent advances in quantifying the amount of organic carbon stored in permafrost zone soils and recent trends (1970-2010) in the exchange of carbon between tundra ecosystems and the atmosphere. These data are the most recent comprehensive data synthesis across individual sites.