Terminus position time series: Helheim and Kangerdlugssuaq glaciers, Greenland

Both glaciers terminate at tidewater in deep fjords. Calving front positions for each glacier are derived from ~daily resolution satellite images collected by the MODIS (MODerate resolution Imaging Spectroradiometer) sensors onboard the Terra and Aqua satellites.

We use the MOD02QKM product which has a 250 m spatial resolution and is constructed from MODIS bands 1–2 in the visible part of the spectrum. Usable images are available for cloud-free days during periods of solar illumination, corresponding to near-daily coverage between 1 May and 31 October each year, and ~weekly coverage for the remainder of the year. Each terminus position was manually digitized according to the procedure described by Moon and Joughin (2008; Journal of Geophysical Research-Earth Surface) in which the calving terminus closes a polygon bounded on the sides by parallel lines approximating the lateral margins, and at the upglacier end by an arbitrary line well inland of the minimum observed terminus position.