Location: Recovery Lake “B”, 82° 48’ S, 18° 54’ E
Weather: All clear, -22 C, wind 12 kts

Yes, there really is liquid, unfrozen water under the ice sheet. This is due to two factors. First, the Earth is constantly giving off heat. If you've ever been in caves or mines under the surface of the Earth, you know that as you dig deeper, the temperature is higher. This heat enventually finds it's way to the surface, where it is lost into the atmosphere, or it can be trapped by things sitting on top of the Earth, like an ice sheet. The earth doesn't give off a lot of heat; it's only about 1/1000 as much as a normal incadenscent lightbulb. Second, ice is a pretty good insulator and traps that heat, essentially acting like a very thick blanket. If the ice is thin, then the heat from the Earth only warms up the ice a little bit; but if the ice is thick enough, the heat build up and melts the bottom part of the ice sheet. Large areas of Antarctica have thick enough ice to cause melting at the bottom.

So there is liquid water down at the bottom of the ice in some places. We can predict this from calculations, and we have observed it in several different boreholes drilled through the ice sheet. In places where the topography of the bedrock forms a basin, that water can collect and form lakes under the ice; these are called subglacial lakes. In other places, the water drains downhill, just as it would elsewhere. These lakes can be quite large - like the Recovery Lakes. In total, we have found about 150 lakes beneath the Antarctic ice sheet of various shapes and sizes. The Recovery Lakes are a group of 4 or 5 (or 6) subglacial lakes located at the start of the Recovery Ice Stream.

If the subglacial lake is large enough (like the Recovery Lakes) then the ice that flows over the lake floats, and makes the surface of the ice sheet there quite flat. It may seem unexpected that a 2.5 km thick ice sheet can float, but the area of the lake (about 30km wide and 80 km long) is much larger than the thickness of the ice and the ice floats, just like an ice cube in a glass of water. (Except that this is a really big ice cube and a really really big glass of water!) We can measure the elevation of the ice surface very accurately with satellites (such as NASA's IceSAT) that bounce a light pulse off the surface and measure how long it takes to come back. Subglacial lakes show up as broad flat spots on an otherwise lumpy ice sheet. It's hard to recognize subglacial lakes if you are standing on them; a broader view is really needed (which is why the traverses that went through this area in the 1960's did not notice them).

The Recovery Lakes were just discovered in the last few years and we are the first scientists to visit since their discovery. We have a lot to learn about them yet, but over the coming weeks, we hope to collect the data that will help us better understand them and the role they play in the Antarctic ice sheet.

A northerly breeze (from the right) sweeps the vast plain of Recovery Lake B.  The vehicle tracks break the surface wind, and thus the drifting snow is dropped and deposited in the tracks. Photo: Stein Trondstad.