Posted by: sioglac | Nov 26, 2011

So why are we going to the Whillans Ice Stream?

I assume each and everyone one of you has been wondering, “Why does Matt get to play around in Antarctica for two months?” A lazy Sunday means I’m gonna tell you ALL about science. Isn’t that exciting?

Before I delve into the Whillans Ice Stream, I suppose it would be wise to take a step back and tell you what an ice stream is. You can read Wikipedia for a slightly longer version, but an ice stream is basically a chunk of fast moving ice. I like to compare how ice moves in an ice sheet to how water moves in North America. Streams start as small drips of water, growing bigger and faster as they work their way to the oceans. Similarly, ice in Antarctica starts as slow-moving ice on the interior of the ice sheet, coalescing into large, fast ice streams and draining into the Southern Ocean. Previous studies have determined that about 90% of the Antarctic ice sheet is drained by ice streams, so they are pretty critical to understanding the interactions between Antarctica and the global oceans. Using radar data, scientists map the speed continent-wide, making really cool (and colorful!) maps:

Although the scale doesn’t show it, at the bottom of some of these ice streams, the ice is moving far faster than 250 meters per year. We’re talking multiple kilometers per year. On the order of 30 feet per DAY. That white box is the Siple Coast (named for explorer [and dapper dresser], Paul Siple). I could be wrong, but I believe America’s fascination for the Siple Coast began in the late 1950s with the International Geophysical Year. You might know the IGY for launching Sputnik 1. I consider that small beans compared to the massive amount of Antarctic work that was started. Anyway, the Siple Coast consists of five ice streams, originally named Ice Streams A, B, C, D, and E. They have since been renamed to Mercer, Whillans, Kamb, Bindschadler, and MacAyeal Ice Streams in honor of prominent Antarctic scientists. There are 5 ice streams on the Siple Coast, but only four streaks of blue on the map above because Kamb Ice Stream actually stopped moving quickly about 150 years ago.

Scientists from the United States have been studying the Whillans Ice Stream since the 1960s, which by Antarctic standards is an eternity. So one of the reasons to study the Whillans Ice Stream is that it has an exceptionally long dataset to give context to our measurements. Whillans is also interesting because the ice moves in a unique way: twice a day it will lurch forward about 2 feet in the span of 30 minutes and barely move the rest of the day. We call this type of motion stick-slip. These “slip” events radiate energy just like an earthquake, which can be detected with seismometers. One of the ways we study Whillans ice motion is by putting seismometers out on the ice and just listening (called “passive seismics”).

Then in 2007, my advisor noticed strange surface elevation measurements near the end of the Whillans Ice Stream:

The actual surface of the ice was moving up and down by almost 30 feet over a short (less than a year) timescale. She attributed these inflation and deflation signals as water movement beneath the ice. There is very little melting on the surface of the ice in Antarctica because it is so cold, but ice is very good at insulating (that’s why survival trenches keep you warm at night), so the ice near the bottom is not subject to the cold surface temperatures. Underneath the ~2500 feet of the ice here, the ice is sliding over the bedrock, generating heat from friction. Along with the internal heat from the Earth, it’s just warm enough to melt the ice near the bottom.

This subglacial water was pooling in discreet lakes and then draining rapidly over the course of a few months. Subglacial lakes were long established phenomena, but they were thought to be isolated, topographically controlled features, which were interesting mostly from a biological perspective. These new dynamic, seemingly connected lakes proved that the subglacial water system (or the “plumbing”) was far more complex than we realized. With the glaciology, geochemical, microbiological, and oceanography communities all interested in these subglacial lakes, the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project was born.

The project has two main parts: extensive geophysical surveying followed by drilling into Subglacial Lake Whillans to sample the water. This field season (and the last) were both entirely geophysical surveying. We use ice-penetrating radar, “active” seismics (meaning we create seismic signals and record them moving through ice), and GPS to map how the ice moves and what the ice column and rocks beneath the ice look like. I work on the GPS data, which are distributed throughout the downstream portion of the ice stream:

Ignore the jargon on the map… I just wanted to give you a sense where our GPS units are. Because we learn more about the system every year and the GPS installations are moving downstream by about 400 meters between field seasons, we move them around a bit. The map above is our GPS plan for this year. The small ticks are 1 kilometer apart, so you can judge distances.

Hopefully, that gives you a bit of background on why we go where we go. I plan on forcing the scientists on our team to guest blog about what they are interested and the methods they use, which should enlighten you even more.

Now, coffee time.

 

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Responses

  1. Will you get your drinking water just from melting snow? Does it need to be purified? Also how does the water system at Mcmurdo work? Where does the water come from? What happens to the waste water (and other waste)?

    • We “make” water out in the field, so yes, we just melt snow. No purification necessary. Water at McMurdo is reverse osmosis of seawater– very energy intensive, but we don’t want to melt the entire ice sheet so we can shower, right? Grey water is sent through the purification system and released back into the ocean. All other waste is shipped out.

  2. […] now that you have some idea of why we’re going to the Whillans Ice Stream, maybe it’s about time I tell you more specifically what we’re doing while we’re […]

  3. […] Lake Whillans: You can read much more in depth about SLW at the WISSARD website or in my abbreviated explanation from last field season. This lake is different from Ellsworth and Vostok in that water is moving in […]

  4. […] my time in McMurdo Station, Antarctica, waiting for a plane to come whisk me away to the beautiful Whillans Ice Stream and I guess I never gave you any updates since then. Well whisk me away it did. Team GPS then had […]


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