Von Guerard Stream

I wanted to take a little time to tell you about the streams here in the McMurdo Dry Valleys. I should start by saying that they are not your typical streams. They originate from glaciers that heat up from the sun and melt during the short, austral summers. The streams drain into lakes which are frozen year-round.



Even though the air temperatures are often below freezing, there is plenty of energy from the sun to melt the glaciers. Most of the time the streamflow is little more than a trickle, but during warm summers they can really rip! By tracking the amount of water flowing through the streams we can determine how much the glaciers are melting.


Lost Seal Stream, above, starts at the Commonwealth Glacier and ends at Lake Fryxell.


Many of the streams have a peak stream flow every day, what I refer to as a "flood pulse" or diurnal flow pattern. Here's a video of a diurnal flow event at Von Guerard stream, just outside of camp:
http://picasaweb.google.com/lh/photo/4Dh86LphsLwfmXpm5OEX_A?feat=directlink

Garwood Stream, located in Garwood Valley, has changed a lot recently. A few years ago an unusually warm summer generated really high flows. The stream banks are sandy and very unstable and collapsed from the high flows:A section of the Garwood River now flows below ground, and you can see giant boulders frozen into the exposed permafrost.

Dry Valley streams are dynamic and unpredictable, which make them interesting places to study ecosystems. I'm constantly amazed by the ability of life to exist in such harsh places (humans excluded, of course).