Ancient Permafrost and a Future, Warmer Arctic

摘要

Areas of permafrost are subdivided into continuous (>90% frozen ground), discontinuous (>50%), and sporadic (<50%) permafrost zones (Fig. 1A). Permafrost outside the continuous permafrost zone is particularly vulnerable to future climate change because it is near the melting point and because the depth of frozen ground is typically thin (a few to tens of meters). Permafrost in northwest North America warmed in the late 20th century (1), and numerical models predict widespread and severe permafrost degradation under 21st-century climate-warming scenarios (2), with potential for con-comitantreleaseofstored carbon (3).