ArcGIS Living Atlas

Breathing Earth: Arctic Sea Ice

Here are five minutes of just straight up chill-zone time:

It is based on the simple Breathing Earth animation, the GIF that just keeps giving. But this version includes aggregate Arctic sea ice extents. Here’s how to make it in ArcGIS Pro

The basemap comes from the NASA Visible Earth set of monthly cloud-free image mosaics. You can find them here, though they’ll have to be georeferenced. Alternatively, you can download handy spatial-aware geoTIF files from this resource.

Here they are added to a Pro layout, and given a North Pole Orthographic projection…to look all globe-y.

NASA imagery in ArcGIS Pro, with North Pole Orthographic projection

Because Pro tries to optimize the appearance of imagery, we’ll have to re-set some visual parameters so the images appear consistently from month to month. In this case I’ve changed the “resampling type” (how to render large images when zoomed out) to “cubic” so it appears smooth and jaggy-free, we set the stretch to “none” so that the original brightness levels of the image are retained (again, very important when showing a series of images, so they don’t appear to dance in brightness), the “gamma” we reset to 1, and set the “no data” background color of the image to black rather than transparent.

Re-configuring image settings to their native condition, rather than auto-optimized.

You aren’t stuck with the earth rotated like that, too. We can open the map properties and rotate it. This rotation of -155 degrees puts Europe and Siberia on the left and North America on the right; it’s just an aesthetic choice that looked good to me.

Maps can be easily rotated in an ArcGIS Pro layout

Now we are ready for some Sea Ice data. Living Atlas has a very helpful collection of sea ice resources, including the Sea Ice Aware app, that lets you explore this dat in a more controlled fashion. We’ll be using the Arctic Sea Ice extents layer, made available by the folks at the National Snow and Ice Data Center.

Sea Ice Extent data

Hundreds of polygons, spanning decades, each with year and month attributes, stack up on each other. If we set each polygon to be white and 95% transparent, the stacking contributes to an opaque mass with feathered edges where sea ice is less frequent.

Sea ice extents

To visually disambiguate sea ice with terrestrial ice, we can change its color to something cool and bright. We’ve also given the polygons two semi-transparent boundaries, each with a randomized wave effect to break up the ice edges.

Sea ice with semitransparent blue symbology

In order to bring in a bit of the underlying arctic bathymetry from the base image, we can use the “Hard Light” blend mode. The result is a more vibrant ice field.

Sea ice with a blend mode

To provide a visual reference of coastlines, and just to make the land/sea edge pop a bit more in the basemap, we’ve added a global oceans polygon layer, and symbolozed it with a thin white border, and a couple thicker semi-transparent borders in an earthy color.

Coastal boundaries are added

In order to help the sea ice appear as the prominent visual element of this map, it’s time to de-saturate the imagery a bit. Here is a trick to desaturate any map: add a global background polygon to the top of the image layers…

Global background rectangle covers the whole map

…and give it a “Color” blend mode. This has the effect of making the underlying map appear grayscale…

Making the imagery grayscale with the color blend mode.

…but we want just a bit of color to come through, so it’s just a matter of giving the global rectangle some transparency. 30% transparency makes the imagery look 70% desaturated. Neat trick, huh? Blend modes are just absolute magic.

Partially desaturated imagery

We now have a pretty stark edge to our map. It would be nice if it looked more en-thing-ified. We can hack in an atmospheric effect super easily, and it can make a…world…of difference. Here’s how. Insert a rectangle, and draw it to fit the edge of the layout…

Inserting a rectangle graphic around the layout

…and instead of a black border and no fill, give it no border and a circle gradient fill. You can play with the transparency and colors of the gradient, but the goal is a nice fuzzy atmospheric ring.

Creating an atmospheric effect with a circle gradient and transparency

Of course you should always sign your work and cite your sources.

Insert text to sign and credit data sources.

At this point we’re ready to start making month-specific views of the map. With only one of the month basemaps active, we opened up the Definition Query form for the sea ice layer and filtered it to show only the ice polygons corresponding to the visible basemap (without deleting the data or selecting-by-attribute and making duplicate layers).

Filter using a definition query.

Lastly, it helps with a 12-month looping animation to provide a small visual indication of progress. Here we’ve inserted 12 point graphics and styled them as minimal little circles.

Insert circles to serve as a time legend

And we can evenly distribute the graphics in the layout.

Evenly distribute graphics in a layout

And make the fill a bit bolder for the month that corresponds to the basemap and ice month. In this case, December. This we’ll do manually for each exported month image.

Change the graphic to indicate current month.

You can use the powerful animation features to export an animation of these 12 months, but in this case, since we have manual graphics to update, it’s easiest to simply export 12 distinct images and stitch them together in whatever animation tool (or website) works best.

Exporting layout as an image

The result, is a happily looping seasonal animation of sea ice.

Happy Earth Day Mapping! John Nelson

About the author

I have far too much fun looking for ways to understand and present data visually, hopefully driving product strategy and engaging users. I work in the ArcGIS Living Atlas team at Esri, pushing and pulling data in all sorts of absurd ways and then sharing the process. I also design user experiences for maps and apps. When I'm not doing those things, I'm chasing around toddlers and wrangling chickens, and generally getting into other ad-hoc adventures. Life is good. You might also like these Styles for ArcGIS Pro: esriurl.com/nelsonstyles

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