Posted by: sioglac | Jan 7, 2013

My science in Antarctica: maintaining GPS

I explained what took a bulk of my time last season, but still haven’t shown you pictures of what I do for my science when I’m down in Antarctica. That seems silly. And by showing you pictures of what I did last year, you’ll see what I’m going to do for the next month! Killing two birds with one stone here… Without further ado:

We have 23 permanent GPS installations across the lower ice plain of the Whillans Ice Stream. I made a map of where they are with big red dots for the WISSARD webpage. It looks like this:

WISforWeb

GPS stations are the red dots. The drill location for WISSARD is the green star. According to my colleague Sasha, subglacial water flows from left to right along the blue lines. I trust him. Tick marks are 10km (~6.2 miles) in both directions.

We drive on snowmobiles from red dot to red dot to check each GPS station individually and to download the past year of data. Here’s what our skidoos look like:

P1000577

BRP Skandic, with kinematic GPS unit mounted on the rear. A machine with which I am intimately familiar. Those are my big driving mittens. Yes I have driving mittens.

The first and most important thing we do when we park at a GPS station is check the physical infrastructure. There are two major things that go wrong. The first is the strong Antarctic winds can wreak havoc on anything in its way. This is what our GPS station closest to the drill site looked last year:

P1000388

The wind snapped the ~1/4 inch metal wind turbine mount. There was a light breeze this day and the turbine was just clanging against the metal post when we got there. Not a noise I was expected in Antarctica

Here’s the other major issue we deal with:

P1000461

A GPS station after 3 years

After 2-3 years, a GPS station can be completely buried on the Whillans Ice Stream. When we find this, we have to dig the whole thing out. This includes 4-8 3-foot long metal anchors that were buried under the snow when the unit was first set up. These anchors can be up to 6 or 7 feet below the surface and are frozen in the ice, so they need to be dug out entirely (as in you can’t just find where it is then yank the cable attached to it). We also have to dig out the large grey box that houses the GPS unit itself. Oh there are 4-10 car batteries in there too. Because of its dark grey color, the box heats up in the Antarctic sun, melting surrounding snow. The outcome is that this box, multiple feet below the surface and containing hundreds of pounds of batteries, can be encased in a few inches are hard, refrozen ice. Not the most fun thing to deal with. Here’s what the scene looks like after an hour or two of digging:

P1000507

Shovel in one of the anchor pits for scale. Finding exactly where the anchor is below ground isn’t easy. We still have to dig the main box out too.

After everything is dug out, we pull out the solar panels and GPS antenna and “redeploy” the site on the surface:

P1000517

Fresh GPS install. This should be good to go for 3 years or so.

Now that the station is accessible, we can download the data and update any software that needs it (the easy part!):

P1000494

Inside the grey box. The yellow thing is the GPS unit itself. If you look closely, you can actually see the data copying onto the computer.

We double check everything is on and working, then we’re off to the next station, which can be up to 30 miles away. Easy as 1, 2, 3, right?? I guess no one ever said that maintaining the largest on-ice network of GPS stations in the world would be easy. (For those that will argue about that claim, I will note POLENET is on rock, not ice.)

Just for fun, here’s another picture of GPS work I did last year:

P1000696

Most Antarctic vets see this picture and think it’s a runway. It’s not. This is what it looks like after Lucas and I drove for 12 hours continuously across the flexure zone of the Whillans Ice Stream (deemed the 12 hour experiment. Whether its a geophysical experiment or a sociological one, I have yet to determine). I named it the Whillans Highway. This should probably in Google Street View.

All this fun with GPS couldn’t be done without the help of the fantastic people at UNAVCO, so a big thank you to them.

Last but not least, I get back home to the US and process the data:

SLWlakehistory

Continuing to monitor subglacial lake water levels. My advisor Helen discovered “active” subglacial lakes using ICESat data (the blue line) and I am continuing to monitor what the lakes are doing with GPS data. We now have 10 years of data for Subglacial Lake Whillans

slm20082012

Subglacial Lake Mercer lake level since 2008. We think the lake might have flooded this past year! It is VERY exciting that we might have a high resolution dataset documenting it.

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Responses

  1. […] New Zealand for a few days, get stuck in McMurdo a week or three, fly to the Whillans Ice Stream, drive over 1000 miles on a snow machine, dig some holes, collect some data, come home. It’s been three years of that. Each year, I […]


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