# isice documentation

The isice function returns logical true for all grounded ice and ice shelves according to MEaSURES Antarctic Boundaries for IPY 2007-2009 from Satellite Radar, Version 2. This is the logical NOT of the isopenocean function.

The Antarctic Boundaries dataset is described on the NSIDC site here. An overview of the tools in this AMT plugin can be found here.

## Syntax

```tf = isice(lati,loni)
tf = isice(xi,yi)```

## Description

tf = isice(lati,loni) returns true for all geo locations (lati,loni) identified as grounded ice or ice shelf in the Mask_Antactica_v2.tif (sic) dataset.

tf = isice(xi,yi) returns true for all locations identified as grounded ice in Mask_Antactica_v2.tif (sic), where input coordinates are automatically determined to be polar stereographic (true lat 71 S) meters if their values exceed the normal lat,lon range.

## Example: Mask a gravity dataset:

This example uses a Gravity Plugin for AMT to load some example data, but I'll show you how you can follow along without loading that dataset. Whether you have the gravity plugin or not, begin by creating a 300 km wide grid centered on PIG, at 0.25 km resolution:

```[lat,lon] = psgrid('pine island glacier',300,0.25);
```

If you have the gravity plugin, interpolate gravity values to the grid like this:

```FA = gravity_interp(lat,lon,'free air');
```

If you don't have the gravity plugin you can simply use random data like this:

`FA = rand(1201);`

Use isice to find out which parts of the dataset are over the ice sheet:

```ice = isice(lat,lon);
```

Mask-out all non-grounded ice (use the tilde for NOT) by setting it to NaN:

```FA(~ice) = NaN;
```

Because isice returns the logical not of isopenocean, we could have accomplished the step above by setting all isopenocean values to NaN, like this; it's just a matter of personal preference:

```FA(isopenocean(lat,lon)) = NaN;
```

Plot the gravity data corresponding to the ice sheet:

```pcolorps(lat,lon,FA)
axis tight
```

For context, overlay a red grounding line and a black coastline:

```antbounds('gl','r')
antbounds('coast','k')
```

## Citing this dataset

If you use this dataset, please cite the following:

• The dataset: Mouginot, J., B. Scheuchl, and E. Rignot. 2017. MEaSUREs Antarctic Boundaries for IPY 2007-2009 from Satellite Radar, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. http://dx.doi.org/10.5067/AXE4121732AD.
• 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), November 2016. Updated May 2017.