“…These can be categorized into invasive (in situ on-ice measurements) and non-invasive (remote-sensing) methods. Remote-sensing methods include passive microwave radiometry (Kaleschke and others, 2012; Nakata and others, 2018), helicopter-based electromagnetic (EM) induction system (Haas and others, 2009; Hunkeler and others, 2016), ice freeboard measurements from Cryosat-2 radar altimeter (Laxon and others, 2013; Yi and others, 2019), ICESat laser altimeter (Kwok and Rothrock, 2009; Nihashi and others, 2018), upward-looking sonar (ULS) (Hudson, 1990; Kwok, 2018), Global Navigation Satellite Systems-Reflectometry (GNSS-R) (Li and others, 2017) and Ground-Penetrating Radar (GPR) (Matsumoto and others, 2018). While other remote-sensing methods are either swath-limited (e.g.…”