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These datasets 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.

Unfortunately, the text editor does not support equations.  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.

 

 

References

Joughin, 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.

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