DOI: 10.7280/d1xt4g
title: Melt rates in the kilometer-size grounding zone of Petermann Glacier, Greenland before and during a retreat

description: Warming of the ocean waters surrounding Greenland plays a major role in
 driving glacier retreat and the contribution of glaciers to sea level
 rise. The melt rate at the junction of the ocean with grounded ice—or
 grounding line—is, however, not well known. Here, we employ a time series
 of satellite radar interferometry data from the German TanDEM-X mission,
 the Italian COSMO-SkyMed constellation, and the Finnish ICEYE
 constellation to document the grounding line migration and basal melt
 rates of Petermann Glacier, a major marine-based glacier of Northwest
 Greenland. We find that the grounding line migrates at tidal frequencies
 over a kilometer-wide (2 to 6 km) grounding zone, which is one order of
 magnitude larger than expected for grounding lines on a rigid bed. The
 highest ice shelf melt rates are recorded within the grounding zone with
 values from 60 ± 13 to 80 ± 15 m/y along laterally confined channels. As
 the grounding line retreated by 3.8 km in 2016 to 2022, it carved a cavity
 about 204 m in height where melt rates increased from 40 ± 11 m/y in 2016
 to 2019 to 60 ± 15 m/y in 2020 to 2021. In 2022, the cavity remained open
 during the entire tidal cycle. Such high melt rates concentrated in
 kilometer-wide grounding zones contrast with the traditional plume model
 of grounding line melt which predicts zero melt. High rates of simulated
 basal melting in grounded glacier ice in numerical models will increase
 the glacier sensitivity to ocean warming and potentially double
 projections of sea level rise.
description: This dataset supplements the manuscript "Melt rates in the
 kilometer-size grounding zone of Petermann Glacier, Greenland before and
 during a retreat." by Ciracì, E., Rignot, E., Scheuchl, B., Tolpekin,
 V., Wollersheim, M., An, L., Milillo, P., Bueso-Bello, J. L., Rizzoli, P.,
 Dini, L. (2023), Proceedings of the National Academy of Sciences, Vol. 120
 No. 20 e2220924120.
description: # Melt rates in the kilometer-size grounding zone of Petermann Glacier,
 Greenland before and during a retreat Fields 1-6 unchanged with regards to
 April 2022 Version.  Added the following fields: 7\. P1M1_Bed1_Shade.tif:
 Shaded relief bathymetry derived from GBMF gravity data. Coordinate
 Reference System: EPSG:4326. Resolution: 500 m. Data format: GeoTIFF. Data
 type: Byte. 8\. P1M1_Bed1.tif: Bathymetry (bed elevation in meters above
 mean sea level) derived from GBMF gravity data acquired in 2020.
 Coordinate Reference System: EPSG:4326. Resolution: 500 m. Data format:
 GeoTIFF. Data type: Float32. ## Ciraci\_Rignot\_et\_al\_2022\_README.md -
 Original Version April 2023 ### Repository Content: 1\.
 tandem-x_dem_calibrated_wrt_amsl_EPSG-3413_res-150.zip:
 2011-06-09_tdemx_mosaic.tiff: TanDEM-X Digital Elevation Model organized
 by year (2011), month (06), day(09). Time period 2011-06-09 to
 2021-12-01.Elevation is in meters above mean seal level. Coordinate
 Reference System: EPSG:3413. Resolution: 150 m. Data format: GeoTIFF. Data
 type: Float32. NoData value: -9999.
 petermann_tandemx_dem_mosaics_index.shp; Index of the source TanDEM-X
 Digital Elevation Models (DEMs). The area covered by each DEM is
 represented as a polygon. Data format: ESRI shapefile format; Coordinate
 Reference System: EPSG:3413. 2\. melt_rate_maps.zip: Long-term average ice
 shelf basal melt rate maps for periods 2011-2015, 2016-2019, and 2020-2021
 calculated in a Lagrangian Framework and expressed in meters per year.
 Coordinate Reference System: EPSG:3413. Resolution: 150 m. Data format:
 GeoTIFF. Data type: Float32. NoData value: -9999 3\. lagrangian_est.zip:
 Organized by year, month, day, ice shelf basal melt values obtained from
 each DEM pair used in the study expressed in meters per year. Coordinate
 Reference System: EPSG:3413. Resolution: 150 m. Data format: GeoTIFF. Data
 type: Float32. NoData value: -9999 4\. dhdt_maps.zip: Two digital maps of
 changes in ice surface elevation calculated between 2011-06-09 and
 2015-12-31; and between 2016-01-01 and 2021-12-01. Coordinate Reference
 System: EPSG:3413. Resolution: 150 m. Data format: GeoTIFF. Data type:
 Float32. NoData value: -9999 5\. petermann_grounding_lines_1996-2022.zip:
 Grounding lines of Petermann Glacier derived from DInSAR data between 1996
 and 2022. Data format: ESRI shapefile. Coordinate Reference System:
 EPSG:3413. Years: 1996 to 2022. 6\. petermann_grounding_zones.zip:
 Grounding zone shape files of Petermann Glacier derived from DInSAR data
 between 1996 and 2022. Data format: ESRI shapefile format. Coordinate
 Reference System: EPSG:3413. Years: 2011-2015, 2016-2017, 2020-2021 ###
 Conversion of Elevation Data from WGS84 to Height Above Mean Sea Level
 (HAMSL) Convert TanDEM-X data from elevation above the WGS84 Standard
 Ellipsoid into elevation above the mean sea level. This conversion is
 required to apply the Lagrangian Approach which assumes an ice shelf in
 hydrostatic equilibrium. Following Shean et al. 2019, the corrected ice
 surface elevation above sea level is calculated as follows: H = He − Hg −
 (MDT + Htide + hIBE ) Where: . He -&gt; DEM elevation above the WGS84
 ellipsoid; . Hg -&gt; the EIGEN-6C4 geoid offset; . MDT -&gt; Ocean Mean
 Dynamic Topography; . Htide -&gt; Tide elevations above the average sea
 level; . hIBE -&gt; Inverse Barometer Effect on sea level height. \- Hg -
 EEIGEN-6C4 geoid offset. For more details, see Förste et al. 2014. \- The
 Ocean Mean Dynamic Topography is distributed by AVISO and available here:
 \-
 [https://www.aviso.altimetry.fr/en/data/products/auxiliary-products/mdt.html](https://www.aviso.altimetry.fr/en/data/products/auxiliary-products/mdt.html) \- for more details, see Mulet et al. 2021. \- Tide Elevation at the time-tag associated with each TanDEM-X dem is estimates by employing outputs from the Arctic Ocean Tidal Inverse Model, 5km (AOTIM-5). See the project website for more details: \- [https://www.esr.org/research/polar-tide-models/list-of-polar-tide-models/aotim-5](https://www.esr.org/research/polar-tide-models/list-of-polar-tide-models/aotim-5) \- see also: Padman et al. 2004 \- The model solutions are extracted by employing the PyTMD module by Tyler Sutterley. Below, the link to the project home page on GitHub: \- [https://github.com/tsutterley/pyTMD](https://github.com/tsutterley/pyTMD) \- for more details, see Sutterley et al. 2019. \- The Inverse Barometer Correction is calculated by employing hourly estimates of Mean Sea Level Pressure provided by the ECMWF ERA5 Reanalysis: \- [https://www.ecmwf.int/en/forecasts/datasets/reanalysis-datasets/era5](https://www.ecmwf.int/en/forecasts/datasets/reanalysis-datasets/era5) \- for more details, see Hersbach et al. 2020. ### References Förste, Ch, S. Bruinsma, O. Abrikosov, J. Lemoine, T. Schaller, H. Götze, and G. Balmino. "EIGEN-6C4." The latest combined global gravity field model including GOCE data up to degree and order 2190 (2014). Mulet, Sandrine, Marie-Hélène Rio, Hélène Etienne, Camilia Artana, Mathilde Cancet, Gérald Dibarboure, Hui Feng et al. "The new CNES-CLS18 global mean dynamic topography." Ocean Science 17, no. 3 (2021): 789-808. Padman, L., and S. Erofeeva. "A barotropic inverse tidal model for the Arctic Ocean." Geophysical Research Letters 31, no. 2 (2004). Sutterley, Tyler C., Thorsten Markus, Thomas A. Neumann, Michiel van den Broeke, J. Melchior van Wessem, and Stefan RM Ligtenberg. "Antarctic ice shelf thickness change from multimission lidar mapping." The Cryosphere 13, no. 7 (2019): 1801-1817. Hersbach, Hans, Bill Bell, Paul Berrisford, Shoji Hirahara, András Horányi, Joaquín Muñoz‐Sabater, Julien Nicolas et al. "The ERA5 global reanalysis." Quarterly Journal of the Royal Meteorological Society 146, no. 730 (2020): 1999-2049.