Greenland Surface Strain Rates & Stresses

These datasets  available via Ghub are 2D principal strain rates and principal stresses across the surface of the Greenland Ice Sheet.We started with representative surface velocities over a 20-year period (Joughin et al., 2016). We smoothed the velocities with a 1 km × 1 km boxcar filter, which carries through many high-strain-rate features. We propagated errors in the velocity observations through this filter and then calculated the two horizontal principal strain rates by taking centered spatial derivatives of the smoothed velocities.  We calculated the errors in these strain rates following basic error propagation principles.The equations for principal strain rates and their errors can be found as Equations 1-4 in Poinar & Andrews (2021), "Challenges in predicting Greenland supraglacial lake drainages at the regional scale", The Cryosphere, 15, 1455–1483, doi:10.5194/tc-15-1455-2021.Finally, we also convert surface strain rates into surface stresses using Glen's flow law.  See attachment pdf "Stresses from Strain Rates" for formulas.Update: Finer-res version, 26 November 2023A 250 m resolution version is now available, although the strain rates should NOT be interpreted finer than a scale of ~1 ice thickness (~1 km).This version uses the Savitzky-Golay filter for smoothing and differentiation, as described in the the attached .m file, following work by Brent Minchew, doi:10.1017/jog.2018.47.  Processes controlling the downstream evolution of ice rheology in glacier shear margins: case study on Rutford Ice Stream, West Antarctica.  Minchew, Meyer, Robel, Gudmundsson, and Simons, 2018.Update: Stresses with uncertainties, 27 March 2024The principal stresses (as well as the principal strain rates) now come with uncertainties propagated through.ReferencesJoughin, I., Smith, B. E., Howat, I., and Scambos, T. (2016). "MEaSUREs Multi-year Greenland Ice Sheet Velocity Mosaic, Version 1", NASA National Snow and Ice Data Center Distributed Active Archive Center, doi:10.5067/QUA5Q9SVMSJG.  NSIDC-0670.Poinar & Andrews (2021), "Challenges in predicting Greenland supraglacial lake drainages at the regional scale", The Cryosphere, 15, 1455–1483, doi:10.5194/tc-15-1455-2021.