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Below the surface

“What we see is only a fractional part of what it really is” – While I’m pretty sure this quote wasn’t written about Antarctica, it certainly is applicable. Here’s a glimpse below the surface.

Are you wondering what on earth you’re looking at? Well you can bring your complaints to me because I actually made this plot the other week as part of my research. We are looking at data collected by an airborne radar survey (data provided by NASA Operation Ice Bridge). This image shows us a slice through the ice sheet, allowing us to see more than 4 km (2.5 miles) down below the surface. In fact, this image even shows a lake (yes unfrozen water!) below the ice sheet. This is called Lake Vostok and it is comparable in size to North America’s Lake Ontario yet completely hidden below the surface of the ice. Without imaging below the surface, we would never know that unfrozen lakes exist below ice sheets. Can you find the lake in the image.

The red line traces the surface of the ice and the blue line traces the bottom of the ice sheet. See where the blue line dips down and then gets very flat? That is the lake surface (below the ice sheet). And how do we know it is not frozen? Reflectivity of water is much higher than ice and the radar detects very high reflectivity values over this area. How does a radar make this image of the subsurface?… to be continued next time.

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