Review: Impacts of permafrost degradation on inorganic chemistry of surface fresh water

Average atmospheric temperature has increased globally over the last decades and, as a response, the cryosphere is changing (Fountain et al., 2012). Permafrost, a component of the cryosphere, is widespread in the Arctic and Antarctica, and in cold mountains, including densely populated areas of the European Alps and Asian mountain ranges (Gruber, 2012). Permafrost interacts with climate (Walter Anthony et al., 2006; Schuur et al., 2015), hydrology (e.g., Liljedahl et al., 2016), ecosystems (Jorgenson et al., 2001; Vonk et al., 2015) and human systems (Nelson et al., 2002; Harris et al., 2009). Recent reviews have focused on the impacts of permafrost warming and degradation on river biogeochemistry (Frey and McClelland, 2009) and aquatic ecosystems (Vonk et al., 2015) in the Arctic. Notwithstanding, local and regional modifications of water hydrochemistry due to permafrost degradation have been reported from many locations, globally. Given the sparsity of data available, understanding and analysing permafrost degradation impacts on inorganic chemistry of surface fresh water will benefit from identifying common patterns in existing studies. The present review thus aims to distil insight gained across differing permafrost environments and configurations globally. Following a brief background section, we distinguish three typical example configurations of permafrost thaw. For those, we review impacts of permafrost degradation on major ions (e.g., Ca2+, Mg2+, SO42-, NO3-) and on trace elements (e.g., Ni, Mn, Al, Hg, Pb).