“…The increasing thickness of the active layer has been indicated by many observations in permafrost regions at high latitudes and altitudes (Brown et al, 2000;Frauenfeld et al, 2004;Zhang et al, 2005;Fyodorov-Davydov et al, 2008;Wu et al, 2010;Zhao et al, 2010;Callaghan et al, 2011;Liu et al, 2014a, b;Stocker et al, 2014). Less research has focused on SFG areas Frauenfeld et al, 2004;Frauenfeld and Zhang, 2011;Wang et al, 2015), although the near-surface soil freezethaw status has been investigated using satellite passive microwave remote sensing (Zhang and Armstrong, 2001;Zhang et al, 2003Zhang et al, , 2004Li et al, 2008;Jin et al, 2015). Peng et al (2016b) analyzed the response of soil freeze-thaw states to climate change across China, based on observational data.…”