MATLAB Examples

Data included in this toolbox are from the Centre for Polar Observation and Modelling Data Portal, retrieved April 18, 2108.

Citation: Konrad, Shepherd, Gilbert, Hogg, McMillan, Muir, and Slater: Net retreat of Antarctic glacier grounding lines, Nature Geoscience, 11, 258-262, 2018, https://doi.org/10.1038/s41561-018-0082-z

Syntax

```[lat,lon,vgl] = konradgl

Description

[lat,lon,vgl] = konradgl returns the lat, lon, and rate of grounding line migration (m/yr).

[x,y,vgl] = konradgl('xy') converts lat and lon to polar stereographic meters (standard parallel 71 S).

[...,delta_vgl] = konradgl(...) also returns measurement uncertainty (m/yr).

To load all the Konrad et al. 2018 grounding line data, just type this:

```[lat,lon,vgl,vgl_uncertainty] = konradgl; ```

Eliminate low-confidence data

A measures of vgl uncertainty is provided. Here's how you might remove all data where uncertainty exceeds 23 m per year (thus eliminating 10% of the raw dataset)

```% Find the bad data points: bad = vgl_uncertainty>23; % Remove the bad data points: lat(bad) = []; lon(bad) = []; vgl(bad) = []; ```

Plot grounding line migration

Here we'll use scatterps to plot grounding line migration. For added context and visual impact, I'm also using a cmocean colormap (Thyng et al., 2016), Zwally's ice basins, and an underlay of the MODIS Mosaic of Antarctica.

```basinsps('grounded','k') % optional, black outlines of ice basins scatterps(lat,lon,25,vgl,'filled') caxis([-300 100]) % sets color axis limits cmocean('-balance','pivot') % optional, sets cmocean colormap. axis tight off % remove empty space, remove tick labels ```

That's looks like the data in the paper. Now let's zoom in on the action:

```mapzoomps('amundsen sea','mapwidth',1000) modismoaps('contrast','low') % places a MODIS MOA image on the bottom of the stack scalebarps('color','w') cb = colorbar; ylabel(cb,'grounding line migration (m/yr)') ```

Note: I flipped the colormap relative to Konrad's version because I like to let warm colors be associated with ice melt.

Citing these datasets:

If you use these datasets, please be sure to cite the following:

GROUNDING LINE DATA: Konrad, Shepherd, Gilbert, Hogg, McMillan, Muir, and Slater: Net retreat of Antarctic glacier grounding lines, Nature Geoscience, 11, 258-262, 2018, https://doi.org/10.1038/s41561-018-0082-z

ANTARCTIC MAPPING TOOLS: Greene, C.A., Gwyther, D.E. and Blankenship, D.D., 2017. Antarctic Mapping Tools for Matlab. Computers & Geosciences. http://dx.doi.org/10.1016/j.cageo.2016.08.003

CMOCEAN COLORMAPS IN THE EXAMPLE ABOVE: Thyng, K.M., C.A. Greene, R.D. Hetland, H.M. Zimmerle, and S.F. DiMarco. 2016. True colors of oceanography: Guidelines for effective and accurate colormap selection. Oceanography 29(3):9?13. http://dx.doi.org/10.5670/oceanog.2016.66.

Author Info

This function and supporting documentation were written by Chad A. Greene of the University of Texas Institute for Geophysics (UTIG), April 2018.