Fig. 1: Helheim Glacier and ice mélange.
From: Seasonal changes of mélange thickness coincide with Greenland calving dynamics
a Terrestrial laser scanner (TLS) measured elevation map overlain on a Sentinel-1 HV image (both acquired on 30 Nov 2019). The white line across the fjord indicates the glacier front location. The white triangle indicates the TLS location. The upper left inset shows the location of Helheim Glacier in Greenland. The image is in polar stereographic projection (EPSG: 3413). b Terminus position relative to 1 Sep 2019, where the positive sign indicates terminus advance. Blue dots denote the averaged mélange elevation within 1 km of the terminus, Z0. We mark the time period during which a calving event occurs by a red-shade rectangle. Four vertical black lines mark the dates for the TLS-measured elevation data presented in (c–f), which corresponds to 30 Nov 2019, 3 Jan 2020, 30 Mar 2020, and 31 May 2020, respectively. Solid black lines mark the dates with terminus advances, and dashed black lines mark the dates with terminus retreats. c–f Surface elevation profiles for the mélange displayed as density plots (1510–1859 data points in total); the color bar denotes the number of data points that have the same elevation and distance from terminus values. For any specific distance from terminus, we find the elevation value that has the maximum number of data points. Solid blue lines connect these elevation values along the distance from terminus as the representative mélange elevation profiles. Major calving occurred on 2 Jan 2020 and 28 May 2020 led to noticeable mélange thinning on 3 Jan (d) and 31 May (f). g–j The TLS-measured mélange surface elevation map from 7 Jul to 18 Jul 2020. Dashed white lines indicate positions of the terminus before calving. Solid white lines indicate positions of the terminus after calving. Dates on the images show the acquisition dates for TLS data and times are in UTC. TLS scans are overlain on Sentinel-2 images acquired around the same dates. Mélange thinning was observed from 7 Jul to 14 Jul 2020, followed by a major calving event occurred between 14 Jul and 15 Jul 2020.
