# Horgan2006Static

The grounding line along the Siple Coast was mapped by Horgan and Anandakrishnan (2006) by examining the region of high surface slope which connects relatively flat floating ice shelf to relatively flat fully-grounded ice. Here we create a plot of surface slope similar to their Figure 1.

## Requirements

This example requires the following:

## Plot background image

First, surface data are imported into Matlab via the bedmap2_data command, then magnitude of surface slope is calculated and plotted using the pcolorm function. Using the full 1 km resolution data set, plotting may take a whole minute on a modern laptop computer, whereas 2 km data should take about 15 seconds.

Start by importing surface elevation data:

```% Define a center location:
[centerlat,centerlon] = scarloc('siple coast');

% Import data and calculate surface slope:
[lat,lon,sfz] = bedmap2_data('surface',centerlat,centerlon,400);
```

## Turn surface elevation into surface slope

Use Matlab's gradient function to turn surface elevations into surface slopes. Note that we're dividing sfz by horizontal resolution in meters:

```[dhdx,dhdy] = gradient(sfz/1000); % divide by dx = dy = 1000 m
sfzslope = atand(hypot(dhdx,dhdy)); % surface slope in degrees
```

## Plot surface slope

Initialize a figure, use antmap to set up polar stereographic map axes, and use pcolorm to plot the surface:

```figure('position',[100 100 1000 900])
antmap
pcolorm(lat,lon,sfzslope)

% colorbar:
cb = colorbar;
ylabel(cb,'slope magnitude (deg)')
caxis([0 .5]);
``` ## Change formatting:

Use rgbmap to match the color scheme of Horgan and Anandakrishnan's figure. Then use antmap to overlay a graticule, mapzoom to zoom in, and scarlabel to label key locations:

```rgbmap('dark blue','light blue','canary','light red','white')

% Add a black grid and zoom to the region:
antmap('graticule','lats',-86:-79,'lons',180:10:230,'color','k')
mapzoom('siple coast','mapwidth',750,'inset','northwest','size',.2)

% Add text labels formatted as shown in Horgan and Anandakrishnan (2006):
places = {'Siple Dome','Whillans Ice Stream','Kamb Ice Stream',...
'Bindschadler Ice Stream','MacAyeal Ice Stream','Ross Ice Shelf',...
'Crary Ice Rise'};
scarlabel(places,'background','white')
``` ## Author Info

Chad Greene wrote this. Chad claims absolutely no credit for the data, the science, or the creative display shown above.