McMurdo Weather

After 4 days at station working in the lab, we were supposed to be going back to the field today. But we have yet another bad-weather day that won't allow us to fly! So this is a good time to blog about weather in McMurdo.

We are in a polar desert. That means that there is very little precipitation, just like deserts in the U.S. But this is a polar desert, which means it is very cold, not hot like deserts in the U.S. We do get storms here, but they are mostly made up of wind and clouds and involve only a little bit of precipitation. The little bit of precipitation we get comes as snow, and most of it returns to the air before it melts into liquid water on the ground (that's called sublimation). So, it occasionally snows in the dry valleys, but when it does, it usually only looks like this for a few hours before it disappears.
Right now, we have a snow system over us. In this radar image, you can see where I am right now at McMurdo Station (at the "You Are Here" arrow). There's a big bunch of clouds right over us and the dry valleys where we're trying to go! There's not a whole lot of snow coming down. There's just a dusting on the ground, but it really restricts visibility, especially over the ice. Here is a picture looking out of our lab window across McMurdo Sound on a normal, sunny day. You can see all the way across the ice to the Trans-Antarctic Mountains and the dry valleys where we do our research.

And here's a view out of our window today.

You can't see very far! And since the ice is white and the view ahead is white, helicopter pilots can't see the difference between the ground and the sky, which makes it unsafe to fly. We've had more snow than usual this summer. I've heard from people here earlier than me this spring that at one point there were eight inches of snow on the ground in the dry valleys! That means there's more moisture on the ground from the little bit of the snow that melts, and the soils are wetter than normal. Since the soils are so water-limited, that can change a lot!

Though it's too dangerous to fly, and it's cold and there are snow flurries, it is still not truly bad weather. This area can get far worse storms that include really strong winds and white-out conditions. The strongest and most dangerous type of weather is called a "herbie". Herbies are very strong windstorms coming from the south that bring along a lot of blown snow and very cold wind chills. They can come without much warning, and people will suddenly find themselves with no visibility and dangerously low temperatures. Luckily, they are not very common, and I haven't been here for a herbie yet. I have been here for a different type of windstorm called a katabatic wind. This occurs when cold air from the south gets pushed up higher in elevation to go over a mountain (like the Trans-Antarctic Mountains). Normally, cold air sits lower on the ground and warm air rises higher, because warm air is less dense. When cold air gets forced higher due to a mountain, it'll eventually reach the top of the mountain and then rush back down to the ground on the other side. It rushes down because it gets pushed down by the warm air waiting for it on the other side and squeezed into a smaller space of a valley. This can cause huge, fast gusts of wind that rush down the valleys where we work. We've seen tents be blown away before, and at times entire buildings have been blown apart. These happen most in the winter when there is a lot of cold air coming from the south, but there are occasionally katabatics in the summers, too.

To manage safety during these different types of weather, we use a rating system that restricts activity for people on base. Condition 3 means the weather is fine, and people can move about normally. Condition 2 means stronger winds and colder temperatures, and you have to receive permission to leave the base. Condition 1 means the weather has gotten really bad, and you're not allowed to leave the building or vehicle that you're currently in. So if it turns to Condition 1, you'd better hope you're in the Galley so you can have something to eat while you wait! We can find out what Condition we're in using these electronic notices posted around station, as well as colored lights that are mounted on the outside of the buildings.Even though the weather right now is bad and it's snowing, it's still Condition 3. We can move around base, we just can't fly. Our weather service on base is predicting snow for the next several days, so it's not looking good to get back into the field!

Our Group is Complete!

Our other two group members, Ross and Julia, arrived yesterday in Antarctica. Our group is now complete! We've been very busy working in the lab, but we plan to head back to the field on Monday. That's all the news for now!

Back at the Lab

Jen and I finally made it back to McMurdo Station! We got stuck at Fryxell camp for a couple of days. The weather over McMurdo was bad, so the helicopters couldn't leave to pick us up. But, the weather in the dry valleys was very nice, so it was a nice place to be stuck. It's good to be back in town, though, because we have to process all of those samples we took to start getting some data! Since we were a day and a half behind, it's been a very busy couple of days (but at least we had a chance to shower and put on clean clothes for the first time in 8 days).

There are a lot of chemical and physical properties we measure on our soil samples. Some of them get done here at McMurdo, and some wait until we get home. One of the basic things we measure here on our soil samples is soil moisture. We want to know how much water is in the soil. Knowing how much water is in the soil tells us how much might be available for organisms living in the soil that need water. (It also helps us standardize all of the other measurements we make. If we express the amount of nutrients per gram of dry soil, it's standardized among all of the different soils we measure, rather than changing based on the amount of water in each sample if we expressed it per gram "fresh" soil.) We measure soil moisture by simply weighing a subsample of the soil, placing it in an oven at 105°C, then weighing it again after 24 hours. The weight lost was water that evaporated from the soil. Jenn and I both have weighed a lot of samples to measure moisture over the past two days.
I also started working on the moss samples I took. To measure the nutrients in the moss, I first have to rinse away all of the soil that's mixed up with the moss. I have to do that using a microscope so that I can see that all of the little pebbles have been rinsed away.

Yesterday, our colleagues from Colorado State arrived from the U.S. So, the lab has become very busy! Tomorrow, the other two group members from Dartmouth are scheduled to arrive, and then our group will be complete! So will 2009!

Getting Our Feet Wet to Sample Moss

Most people think of Antarctica as being a big, barren land with no animals or plants living on it. That is not true! In fact, there are plants growing in Antarctica, even here in the dry valleys. You just have to look very closely to be able to see them, because they are small! The only plants we have in the dry valleys are several species of moss. They grow very slowly and are generally found only in small patches.

Moss has a lot of challenges to face to grow in the dry valleys. It's very dry here, so they cannot get much water to grow. The only time water is plentiful is during the 14 weeks of the year when the meltwater streams are flowing, and that water is only available if you're right next to the stream. Sunlight is also a problem. During the winter there's no sunlight for photosynthesis, but during the summer the sun can be so intense that it can actually damage plants. So, it takes a very hardy plant to be able to grow here! Most of the time you do not find moss that is lush and green, because it's usually too cold, too dry, or there's too much sun damage. Sometimes, though, you find moss that was recently uncovered by the water or a rock, and it is green and happy.

But, moss is the only above-ground life in the dry valleys. All of the other organisms live in the soil, not on it. So, moss are in a way like the redwood forests of the Antarctic Dry Valleys! They are one of the few sources of food for soil organisms. When mosses die, they decompose in the soil, just like plants in warmer climates. The carbon and nutrients released from mosses when they decompose are probably a very important part of the soil food web.

We want to learn more about moss's role in the carbon and nutrient cycles in the dry valleys, so one of our projects is to find out where they are getting their nutrients. Mosses grow in the soil like other plants, but are always very close to water. Are their nutrients coming from the soil or the water? Do mosses take up all of the available nutrients, or just some? We're trying to find out by taking from each location a moss sample, soil sample, stream water sample, and groundwater sample. (Groundwater on the edge of a stream can be very different from the stream water, and is more likely the water being used by moss when stream flow is low, which is most of the time!) We will measure the ratio of carbon, nitrogen and phosphorus in the moss tissue and see if it reflects the ratio in the soil or the water. If the ratio (called "stoichiometry") of the moss is more like that of the water than the soil, that would suggest that the nutrient source is the water. We've visited many of the streams and wet areas around Lake Fryxell and taken moss, soil, and water samples. You can see the patch of moss at the base of the rock that my backpack is on. Jenn is in Lost Seal Stream taking a sample of stream water. She pulls the water up into a giant syringe, then snaps a filter onto the end of the syringe and sloooooowly squirts the water through the filter to remove all of the sediment. If you click on the photo to make it bigger, you can see that between my backpack and Jenn is my setup for collecting groundwater. We use a miniature well system called a piezometer. I insert a long tube into the ground using stiff wire, then attach a hand-powered vacuum pump onto the end of it to suck water out from below the stream bed into a flask. The water comes out very, very silty so I will have to filter it using a more powerful setup back at the lab. You can see a groundwater sample on the rock next to my backpack (it's the bottle with the orange label).

We've visited several streams to do sampling like this so far. Each stream that flows into Lake Fryxell has a different ratio of nutrients. If the nutrient content of moss changes the same way that the streams change, this would be a clue that nutrients are coming from the stream and that mosses use all the nutrients that are available. If the nutrient content of the moss doesn't change with the stream and soil, this would be a clue that the mosses only take up a certain amount of nutrients no matter what is available. That would suggest that their role in nutrient cycling is more stable and less likely to change if nutrient availability changes.

This is one of the projects that Jenn and I have been working on this field this past week. We are trying to return to McMurdo Station tonight to process our samples and get ready for the next field project, but the weather is bad and the helicopters can't come get us! Hopefully we will get home tonight or tomorrow morning.

Merry Christmas

Merry Christmas from Lake Hoare, Taylor Valley, Antarctica!

Before we left F6 to come to Lake Hoare, Santa and his elves came to visit us by helicopter. They brought us a giant box of "freshies": fresh vegetables, fruit, and homemade cookies and bread! We aren't normally able to get a lot of freshies down here, especially in the field, so it was a very wonderful treat!
We arrived at Lake Hoare and were set to work decorating. We decorated Christmas cookies, put up the Christmas tree, and made a gingerbread house.
Then, we had a big family dinner! There are scientists from many different projects gathered here, so there were 15 people for dinner. After dinner, we played the "gift game" by the Christmas tree. I got a cool, new water bottle! Now, in Antarctica, it is the day after Christmas, and it is time to get back to work! We'll be hiking over the glacier to Lake Fryxell camp to sample mosses along some of the streams.

Changes Brought by Permafrost Melt

We've been in the field for a couple days now taking soil samples. One of the projects we've been working on is to study the effects of permafrost melt water seeps on soil chemistry.

Beneath the soil in the dry valleys there is permafrost. Permafrost is permanently-frozen ground. Beneath the surface, the temperatures are so cold that the water associated with the soil is always frozen, making the soil in the permafrost a frozen block. In the Lake Fryxell basin, where we are, the permafrost starts about 30 cm (about 1 foot) beneath the soil. When the ground gets warm enough, the permafrost can start to melt, and that water moves up through the soil and appears on the surface as a wet patch like this:
As that water moves up through the soil, there are a lot of ions, including nutrients, that get dissolved and move up through the soil with the water. We want to know how much nutrients are moving in the soil profile with that water and how much that changes soil nutrient cycling overall. To study that, we have to dig a lot of soil pits. That's what Jenn is doing in this photo. We dig pits both inside and outside the seep patches to see how their soil nutrients differ.In the pits, we take soil samples from the wall of the pit along the depth of the soil profile. That way we can measure the ion concentrations in each layer.
Last season was a particularly warm year, so there were a LOT o f permafrost seep patches all over the Fryxell basin. We dug many pits and found that nutrients were much more abundant in the seep patches than dry soil, especially at the top near the surface. With more ions and nutrients in them, the seep patches are a very different habitat for soil organisms than what would normally exist in dry soil. That is why we're interested in studying the seep patches. Nutrient cycles could change a lot when permafrost melts, because more nutrients become available and there's more water for organisms to use while they process the nutrients.

This year we're digging more pits and taking similar samples, but we're specifically interested in the sulfur cycle this time. We found that the ion sulfate (SO4) is very abundant in seep patches, but not at the very bottom of the soil pit near the melting permafrost. Other scientists have found that there are a lot of bacteria at the bottom of soil pits near the permafrost that use sulfate instead of oxygen to breathe. These are called "sulfate-reducing bacteria" and they live all over the world. We think that maybe permafrost melting releases a lot of sulfate, but near the bottom layer the sulfate is used up by the sulfate-reducing bacteria. Other scientists have also found that some of the bacteria in the dry valleys use a very old metabolic pathway for sulfate reduction, and we are looking to see if this metabolic pathway is being used by sulfate-reducing bacteria near the permafrost, and how much their activity can change the soil sulfur cycle when permafrost melts. It requires a lot of digging! So far we have sampled 7 soil pits.

Now we have moved camps, and we're now sitting on Lake Hoare. We will be doing some field work here, as well as enjoying the Christmas holiday with our friends from other science groups. It should be a good two days here on Lake Hoare!

Finally in the Field

We finally made it out to our first field site in the Dry Valleys. We were supposed to have left yesterday, but the weather was too bad for the helicopters to fly. Today, though, the weather was decent enough to get us out in the morning, and here we are in Taylor Valley!

We do our field work in the dry valleys. These are the valleys in the Trans-Antarctic Mountains that dissect the continent. The presence of the mountains prevent the ice sheet from moving into the valleys, so they are de-glaciated. It is a desert, so there is not enough snow to maintain ice cover on the ground. There is only about 2% of the continent that is not covered in ice, and the dry valleys are a large part of that 2%. Here is a map of the main area of the McMurdo Dry Valleys:
We do most of our work in Taylor Valley. There are three lakes in Taylor Valley, and right now we are on the eastern-most lake, Lake Fryxell, at F-6 Camp. The lakes are covered in an ice cap, but there is liquid water beneath it. That thin strip of white coming in from the left side of the photo is part of Lake Fryxell. These lakes are fed by glacial meltwater streams. That's Commonwealth Glacier in the background, and there are several streams from it that flow into Fryxell. So, there is liquid water in the dry valleys, but only in certain places. If you're not near a lake, stream, or glacier, there's not a lot of water for you to use.

The soil in the dry valleys is very rocky and sandy. Most of the soil comes from rocks that were left by the glaciers that once covered the area a long time ago. So, not all of the soil originates from inside Taylor Valley. Some of it comes from the volcano across McMurdo Sound. Some of it comes from further inland on the continent.

Since we're a day behind, we immediately started doing field work when we were dropped off by the helicopter. So, I'm pretty worn out and it's late at night. I'll blog more about what we're working on tomorrow, after I've had some rest!