DOI: 10.7280/d1tx1f
title: Physical processes controlling the rifting of Larsen C Ice Shelf, Antarctica, prior to the calving of iceberg A68 in 2017

description: The sudden propagation of a major pre-existing rift (full-thickness crack)
 in late 2016 on the Larsen C Ice Shelf, Antarctica lead to the calving of
 tabular iceberg A68 in July 2017, one of the largest icebergs on record,
 posing a threat for the stability of the remainder of the ice shelf. As
 for other ice shelves, the physical processes that led to the activation
 of the A68 rift and controlled its propagation have not been elucidated.
  Here, we model the response of the ice shelf stress balance to
 ice shelf thinning and to thinning of the ice mélange encased in
 pre-existing rifts. We find that  ice shelf thinning does not
 re-activate the rifts; it heals them. In contrast, thinning of the mélange
 directly controls the opening rate of the rift, with an above-linear
 dependence on thinning. The simulations indicate that a thinning of the
 ice mélange by 10-20 m is a sufficient condition to re-activate the rifts
 and trigger a large calving event, thereby establishing a direct link
 between climate forcing and ice shelf retreat that has not been used in
 ice sheet models. Rift activation may explain the early initiation of ice
 shelf retreat many years prior to hydro-fracture caused by the ponding of
 melt water at the ice shelf surface, hence for a smaller amount of climate
 warming.   
description: The dataset used to run the JPL/UCI Ice Sheet and Sea Level Model
 (ISSM) (Version of the development trunk, 22904, available at
 issm.jpl.nasa.gov upon request) includes:  1) runme.m:
 Matlab script use for the modeling: all routines and steps (pre and post
 processing as well as simulation runs) to carry out all the model
 runs. 2) firn.mat: a firn layer from the SeaRISE
 Antarctica5km_shelves_v1.0 experiment development data set at
 http://websrv.cs.umt.edu/isis/index.php/Present_Day_Antarctica
 3) vel_final_2014-07-01_2015-06-31_LC.nc: A velocity map from
 Sentinel 1-a interferometry SAR data  from Mouginot et al, 2017 in netcdf
 format. The netcdf contains several variables: CNT (number of points
 averaged to get result), errx (error in velocity along x-axis), erry (same
 for y-axis, stdx (standard deviation of velocity along x-axis), stdy (same
 for y-axis), vx (velocity along x-axis in meters per year), vy (same for
 y-axis), lat (latitude of each point in the grid), lon (same for
 longitude). The projection is EPSG:3031 - WGS 84 / Antarctic Polar
 Stereographic.  4) TDX_ANTPEN450m_msl_v18july2017.tif:
 A TanDEMx 50-m resolution Digital Elevation Model (surface elevation above
 mean sea level) from Rizzoli et al, 2017 in geotif format. The projection
 is EPSG:3031 - WGS 84 / Antarctic Polar Stereographic. Elevation in
 meters.  5) Rift2014_Passive.* and Rift2014_Active.*:
 ESRI Shapefiles for active and passive rits on Larsen C. Projection
 is EPSG:3031 - WGS 84 / Antarctic Polar Stereographic. 
 6)
 s1a-ew-grd-hh-20170727t002304-20170727t002404-017649-01d8bc-001.tiff: A
 Sentinel S1a Extended Width image in ground range from 2017-7-27 in
 geotiff format. Projection is EPSG:4326 - WGS 84 - Geographic.