Evaluation of existing and new methods of tracking glacier terminus change

Several different methodologies have previously been employed in the tracking of glacier terminus change, though a systematic comparison of these has not been undertaken. The frequent application of single methods to multiple glaciers over large geographical areas such as Greenland, raises the question of whether individual methodologies are robust. In this study we evaluate three existing methodologies that have been widely used to track terminus change (the centre-line, bow and box methods) against a full range of idealized glaciological scenarios and six examples of real glaciers. We also evaluate two new methodologies that aim to reduce measurement error compared with the existing methodologies. The first is a modification to the box method that can account for termini retreating through fjords that change orientation (termed the curvilinear box method), while the second determines the average terminus position relative to the glacier centre line using an inverse distance weighting extrapolation (termed the extrapolated centre-line method). No single method tested achieved complete accuracy for all scenarios, though the extrapolated centre-line method was able to successfully account for variable fjord orientation, width and terminus geometry with the least error.