This will be the first in a short series of posts which will attempt to overlay published bathymetry and grounding line data on recent Sentinel-1 satellite images.
I will start with the bathymetry map found in Millan 2017 "Bathymetry of the Amundsen Sea Embayment sector of West Antarctica from Operation IceBridge gravity and other data"
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL072071The first image below is box (b) "Thwaites/Haynes" from figure 2.
The second is the matching Sentinel-1 "Extra Wide Mode" image from October 16, as processed by Polar View.
The third is the bathymetry overlaid over the satellite image at 50% opacity. Grounding line positions are red (year 1996), ice front positions (year 2008) are yellow. Bed elevation is color coded from light blue to dark blue (−1400 m), with light contours every 100 m and thick contours every 400 m (300, 700, 1100 m) although the light contour lines are very faint in the overlay.
The next step will be to update the grounding lines from Milillo 2019 "Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica"
https://advances.sciencemag.org/content/5/1/eaau3433For those that are interested, here is the process that I used to generate these images. Anyone with minor proficiency in GIMP or any similar image processing software (Photoshop, etc.) should be able to duplicate this and verify my results.
Start by downloading this Sentinel-1 image from Polar View (available for 30 days):
https://www.polarview.aq/images/105_S1jpgfull/S1B_EW_GRDM_1SSH_20191016T041914_9DC8_S_1.final.jpgIf you wish to use another image, make sure that the full rectangle, 100 to 110 degrees West and 74 to 75 degrees South is visible. Your scaling numbers may vary slightly from the ones below.
Download Figure 2 from Millan 2017 (link above) using the "Open in Figure Viewer" link then "Save Image as..."
I opened the satellite image in GIMP first and then "Open as Layers..." Figure 2. (It only works in that order because the satellite image is larger.)
I measured the 100 to 110 degrees West and 74 to 75 degrees South rectangle in both images and estimated that I needed to scale the satellite image down by a factor of 4.46. (I confess that this calculation was non-trivial, but the results were surprisingly good.) I scaled the image from 14060x14406 to 3152x3230.
Then I just reduced the opacity of the top layer to 50% and lined up the corners of the rectangle. It was not off by more than a pixel so I was happy. Finally I cropped to image to the edges of the black box (b) and saved it.
Let me know if you have any problems duplicating this.