DOI: 10.15784/601484
title: Circum-Antarctic grounding-line sinuosity

description: The dataset here allows exploration of the causes and significance of Antarctic grounding-line sinuosity by coupling observations of contemporary Antarctic grounding lines and paleo-grounding lines expressed as ice-marginal landforms on the Ross Sea continental shelf. Modern grounding lines are derived from the MEaSUREs Version 2 Differential Satellite Radar Interferometry dataset with spatial resolutions of 25-120 m spanning February 1992 to December 2014 (Rignot et al., 2016; Mouginot et al., 2017). The boundaries of individual grounding lines representative of individual glacial catchments (n=664) were delineated by the inflection points of the shear strain rate, εxy (c.f Van der Veen et al., 2011). Sinuosity was calculated as the ratio of the true length, orthogonal to ice-flow direction, of the grounding lines and the straight line length between end-points and in units of km/km. Raster data were extracted at 1-km points along each grounding line; the mean was calculated for each grounding line and merged in a table with sinuosity data. A dataset of 6,275 paleo-grounding lines expressed as ice-marginal landforms on the deglaciated western Ross Sea continental shelf are used in this study, originally published by Simkins et al., 2018. The ice-marginal landforms were mapped from multibeam echo sounder data that was collected onboard the RVIB Nathaniel B. Palmer (NBP) 15-02 cruise using a Kongsberg EM122 operating in dual swath mode at 12 kHz frequency with 30-60% swath overlap (Cruise DOI: 10.7284/901477). The resulting bathymetry data was gridded at 20-40 m with decimeter vertical elevation resolution depending on water depth and sea-state. Sinuosity is calculated as a ratio of true (mapped) landform length, measured in the across paleo-ice flow direction at the crest of the landform, to the straight line distance between the mapped landform endpoints and in units of km/km. To compare modern and paleo-grounding lines, we use a consistent length scale by segmenting the grounding lines into 2-km sections for the two datasets (modern, n=12,966; paleo, n=5,832), even though this eliminates grounding lines that are less than 2-km long and thus results in 1 modern and 3,873 paleo-grounding lines removed. The full-length and 2-km segmented groundings lines are provided as shapefiles "InSAR_groundinglines_full" and "InSAR_groundinglines_2km", the paleo-grounding lines are provided as shapefiles "RossSea_icemarginal_full" and "RossSea_icemarginal_2km", and points marking modern grounding lines retreat from repeat InSAR surveys are provided as shapefile "InSAR_retreat_points", all stored together in a geodatabase named "Antarctic_groundinglines.gbd". Additional grounding line metrics, including length, sinuosity, bed roughness, and bed slope for modern and paleo-grounding lines, and height-above-buoyancy gradient, ice-flow velocity, presence of pinning points and ice shelves are provided for modern grounding lines. The published dataset was compiled and analyzed in the article "Controls on circum-Antarctic grounding-line sinuosity " by Simkins, L.M., Stearns, L.A., and Riverman, K.L, which will be submitted to a peer-review journal in November 2021. References Mouginot, J., B. Scheuchl, and E. Rignot. 2017. MEaSUREs Antarctic Boundaries for IPY 2007-2009 from Satellite Radar, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. Rignot, E., J. Mouginot, and B. Scheuchl. 2016. MEaSUREs Antarctic Grounding Line from Differential Satellite Radar Interferometry, Version 2. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. Simkins, L. M., Greenwood, S. L., & Anderson, J. B. (2018). Diagnosing ice sheet grounding line stability from landform morphology. The Cryosphere, 12(8), 2707-2726. Van der Veen, C. J., J. C. Plummer, & L. A. Stearns. (2011). Controls on the recent speed up of Jakobshavn Isbræ, West Greenland. Journal of Glaciology, 57(204), 770-782