The Quest for Buried Ice Layers!

Last summer, just before IGERT cohort 3 journeyed up to Summit Camp, the Greenland ice sheet experienced extensive surface melting. Much of the top layer of snow melted and dripped through the snow near the surface. But of course in the cold weather, it didn’t remain as water for very long! This water refroze in the snow, forming flat layers of ice which are connected to one another by vertical columns of ice (see the picture below for an idea of what this looks like). Since last summer, it has snowed quite a bit at Summit, so now the ice layers and the columns that connect them are buried. We would like to know what this ice layer looks like and how many of these ice columns formed in areas around Summit Camp. Now don’t get me wrong, I love digging a good snow pit, but unfortunately, we can’t dig up miles of snow. What we would like is to see what’s under the snow without having to break our backs.

A view inside of our snow pit. I am pointing to the vertical ice column which is right beneath an ice layer that extends all the way across the snow pit. (Photo: Jim Lever)

Using ground penetrating radar (GPR), we can look down below us and “see” the layers of snow upon which we stand. We can also see when there is something different in the snow, like ice which is visible because it has a much higher density.  In our first week, we have spent some time getting the radar system running and testing it out by setting it in a sled and pulling it behind as we walk. One question lingered – is the radar “seeing” what we would see in real life? For that, we had to dig! We dug up a snow pit to see just how prominent the ice layer actually is and to determine if we could see any vertical ice columns. Sure enough, both the ice layer and even a vertical column were easy to find in the snow pit!

Walking off into the distance with the ground penetrating radar in tow. (Photo: Jim Lever)

Though pulling sleds wasn’t so bad, I would sometimes sink nearly to my knees in snow drifts which made keeping a constant walking pace tough. Enter Cool Robot – an autonomous robot (designed right at Dartmouth’s Thayer School of Engineering and wired up by IGERTeer Ben Walker!) that can follow preset directions and drive itself in nice, well-paced patterns across the snow while towing the radar system. We set up a square grid for the robot to follow that was 50 meters on each side. The robot is light and reliable – not sinking into the snow, keeping a constant pace and following our directions within about a meter of the set path. So I’ll admit, Cool Robot has me beat by far in the ability to run a GPR survey. But hey, at least I know not to run straight into the flag markers all around camp! : )

Cool Robot crushing the competition in quality of GPR surveys! (Photo: Jim Lever)

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IGERTs Greenland Field Season Begins!

The first of the IGERTs are up in Greenland as the 2013 field season begins. Ben Walker and I (IGERT cohort 4s) are up at Summit Station in Greenland for the next three and a half weeks with Dr. Jim Lever from CRREL and Alison Morlock (a recent Thayer MS graduate – congrats!). We will be working with the Cool Robot – a solar powered robot that is designed to carry instruments across polar ice sheets for scientific research. I have a few different projects that I’ll be working on up here, and the science is just getting started!

Spectacular view out of the window of the LC-130 cargo plane! My best guess at a location is Northern Canada!

We had a great trip from Scotia up to Kangerlussuaq on Monday, and only a night in Kanger before heading up to Summit. We still took the time to take a walk around Kanger and up to Lake Ferguson. After the unfortunate washout of the bridge last summer, construction of the bridge across the river in town is moving along, but it is still not complete. We were able to take a route around and over to the lake. We were surprised to find that there was still ice on the lake!

There was still ice covering most of Lake Ferguson!

We received a very warm welcome from the crews at Kanger and at Summit, and we are so thankful of all they have done for us already! The rest of the week has been spent acclimatizing to the altitude, unpacking and testing out gear and making plans for the rest of our trip. More updates to come!

View of Summit Camp at bedtime

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The Promised Phosphorus Blog

I’ve been promising a blog post about phosphorus in Taylor Valley, so here goes.  At this point in the season, we’re a little frantic processing samples, packaging up boxes of soil and rock to send home, returning all of our gear, and cleaning the lab.  But I’ll find the time to write this post, since it’s something I’m invested in.

So why are we interested in phosphorus in the first place?  Phosphorus is a limiting nutrient in many ecosystems, but the Taylor Valley lake basins are some of the most phosphorus deficient systems in the world.  Understanding how phosphorus enters the Taylor Valley system and becomes available to organisms is thus critical to understanding the controls on life in this extreme environment.

In addition to general phosphorus deficiency throughout most of the valley, there is also an interesting and well-established phosphorus gradient up the valley.  Down in the lowest-elevation Fryxell basin, there is a relative abundance of phosphorus compared to the higher elevation Hoare and Bonney basins.  Why does this gradient exist?  Multiple ideas have been proposed: perhaps it is due differences in climate, age of the soils, or till type from which the soil has formed.  This last explanation – that the composition of the till determines the amount of phosphorus available – is one that seems to fit best with the data.  And it is this claim that I hope to address with the samples that I have collected this season.

Even within the Fryxell basin there are different colors of till. How do different till types impact the soil geochemistry?

If the till type results in such a strong phosphorus gradient, then the till in the Fryxell basin must be significantly different from the till covering the rest of the valley.  Indeed, the Ross Sea till that covers the Fryxell basin contains kenyte, an unusual phosphorus-rich volcanic rock originating from Mt. Erebus, the volcano that dominates Ross Island.  The Taylor till found throughout the rest of the valley, on the other hand, contains no kenyte. Is Mt. Erebus responsible for providing the Fryxell basin with its higher levels of phosphorus?  Using the rock and soil samples I’ve collected, we hope to use isotopic signatures to differentiate apatite (the most common phosphorus-bearing mineral) that stems directly from Mt. Erebus from apatite stemming from other rock types.

A kenyte boulder found near Lake Fryxell. The boulder likely comes from Mt. Erebus, on Ross Island.

We are not only interested in how apatite gets into the Taylor Valley system; we are also curious about its fate.  How do microorganisms interact with the apatite in the soil?  Are microorganisms responsible for releasing phosphorus from the apatite?  As a start, we’ve set up a little experiment (involving soil sausages) that will stay out in the field until next season.  The sausages are tubes full of soil, apatite grains, and glass beads (used as controls), cleverly held together with red clips.  The semi-permeable tubing we used will allow the environment to interact with what’s inside the sausages while keeping everything nicely contained for retrieval next year.  When we collect the apatite grains next year, we hope to be able to see evidence of how the grains have been altered by microorganisms.  We’ll look for organisms on the grains themselves, as well as signs that the microbes have been eating away at the mineral.

Ross and I put together the apatite soil incubations.

On Friday, Eric and I went out to F6 camp to bury the sausages.  We picked a location near Von Guerard stream – a wet soil but a stable location.  We buried the soil incubations five centimeters below the surface, marking them with tags and recording the exact location.  Next year we’ll return to dig them up.  I hope both that they are intact, and that they give us more insight into the ways in which phosphorus moves throughout the Taylor Valley system.

An apatite soil incubation buried in the ground.

Next step?  Packaging up my samples to be shipped back to Dartmouth, and figuring out how to process them once we’re all back in Hanover.

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