MATLAB Examples

# gmb_data documentation

gmb_data loads gravimetric mass balance data from TU-Dresden (Groh & Horwath 2016).

## Syntax

```[lat,lon,t,dm] = gmb_data
[x,y,t,dm] = gmb_data('xy')```

## Description

[lat,lon,t,dm,A] = gmb_data loads grids of lat, lon, time t, change in ice mass dm, and grid cell area A.

[x,y,t,dm,A] = gmb_data('xy') as above, but for ps71 (EPSG:3031) x,y coordinates in meters.

## Requirements

Before you can use this function, you must download the ~36 MB AIS_GMB_grid.nc file from TU-Dresden here.

## Example

In this example we look at the seasonal cycle of Antarctic mass balance. Let's compare the average April mass balance to average October mass balance. Start by loading the data:

```[lat,lon,t,dm] = gmb_data; ```

For this example we'll ignore linear trends and just compare all April values to all October values. To do so, figure out which timestamps correspond to which months.

```% Get the month of each timestep: [year,month,day] = datevec(t); % logical indices of all april and october months: april = month==4; october = month==10; % average April and average October mass balances: dm_april = mean(dm(:,:,april),3); dm_october = mean(dm(:,:,october),3); ```

Now plot the difference between April and October mass balances. I'm using pcolorps from Antarctic Mapping Tools and the colormap from cmocean (Thyng et al., 2016).

```% Plot the difference: pcolorps(lat,lon,dm_october-dm_april) axis tight off cb = colorbar; ylabel(cb,'Typical April-October mass balance (kg/m^2)') cmocean('-curl','pivot') ```

## Citing this dataset

If this function is useful to you, please cite the following:

• Antarctic Mapping Tools: Greene, C. A., Gwyther, D. E., & Blankenship, D. D. Antarctic Mapping Tools for Matlab. Computers & Geosciences. 104 (2017) pp.151-157. doi:10.1016/j.cageo.2016.08.003.

## Author Info

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