Pedrazas Micaela N, Cardenas M Bayani, Demir Cansu, Watson Jeffery A, Connolly Craig T, McClelland James W
Department of Geological Sciences, The University of Texas at Austin, Austin, TX 78712, USA.
Marine Science Institute, The University of Texas at Austin, Austin, TX 78373, USA.
Sci Adv. 2020 Oct 23;6(43). doi: 10.1126/sciadv.abb5083. Print 2020 Oct.
Relict permafrost is ubiquitous throughout the Arctic coastal shelf, but little is known about it near shore. The presence and thawing of subsea permafrost are vital information because permafrost stores an atmosphere's worth of carbon and protects against coastal erosion. Through electrical resistivity imaging across a lagoon on the Alaska Beaufort Sea coast in summer, we found that the subsurface is not ice-bonded down to ~20 m continually from within the lagoon, across the beach, and underneath an ice-wedge polygon on the tundra. This contrasts with the broadly held idea of a gently sloping ice-bonded permafrost table extending from land to offshore. The extensive unfrozen zone is a marine talik connected to on-land cryopeg. This zone is a potential source and conduit for water and dissolved organic matter, is vulnerable to physical degradation, and is liable to changes in biogeochemical processes that affect carbon cycling and climate feedbacks.
残留多年冻土在整个北极沿海大陆架普遍存在，但近岸地区的情况却鲜为人知。海底多年冻土的存在和解冻是至关重要的信息，因为多年冻土储存着相当于大气中碳含量的碳，并能防止海岸侵蚀。通过在夏季对阿拉斯加波弗特海海岸一个泻湖进行电阻率成像，我们发现，从泻湖内部、穿过海滩到冻原上的一个冰楔多边形下方，地下约20米深处并非一直被冰胶结。这与普遍认为的从陆地到近海延伸着一个平缓倾斜的冰胶结多年冻土台的观点形成了对比。这个广阔的未冻结区域是一个与陆地冻土层相连的海相融区。该区域是水和溶解有机物的潜在来源和通道，易受物理破坏，并且可能会发生影响碳循环和气候反馈的生物地球化学过程变化。
