Sea ice in the Scotia Sea

Making a simple animation of satellite data

I’m currently making slides for a presentation at a conference later this month. I will be showing data from a cruise in the Southern Ocean in Jan-Feb 2013 on the RRS James Clark Ross (as part of the UK Ocean Acidification research programme). To help set the scene, I made this simple animation of the fraction of the ocean surface covered by sea ice (imaginatively named the ‘sea ice fraction’) during that cruise:

As you can see, we managed to miss most of the sea ice, which was unfortunate (though hitting it wasn’t the main point of the cruise). You can see this is partly because of its retreat from the east, as summer progresses.

How was it made?

I used MATLAB and GIMP to make the animation. The process to first order went something like this:

1. In MATLAB, load the sea ice data (provided for me by Sally Thorpe of the British Antarctic Survey) into a 3D matrix, where rows/columns are latitude/longitude, and each ‘sheet’ in the 3rd dimension is 1 day
2. Load the cruise track as vectors of latitude, longitude and date
3. Set up the figure for just 1 day of data (any day)
4. Use a for loop to generate a figure for each day of data, with the saveas() function in the loop to save a separate image each time
5. In GIMP, ‘open as layers’ all of the saved images
6. Export from GIMP as a .gif, selecting the appropriate animation options in the pop-up

The whole thing took about an hour, with the longest part being step 3 (although steps 1 & 2 could take much longer if the data is not in a MATLAB-friendly format). So this seems to be a time-efficient way to produce a figure that’s a little more eye-catching than the static slides that seem to be the norm at conferences in my field of research.