Sunday, January 10, 2010

Snowfall in the Dry Valleys

I've spent the past five days in the dry valleys. As you've heard, we were weather-delayed getting out there. Then weather delayed my team from meeting me there. Then, my team got stuck there with me and couldn't get back to McMurdo. There was a lot of snow!

That snow doesn't stick around long. We don't have to wait for warm temperatures to melt the snow in order to see it disappear. In the dry valleys, the air is so dry that the snow will sublimate: turn directly from solid (snow) to gas (water vapor) and disappear from our view. On Thursday morning, there was a little over an inch of snow on the ground, but it all disappeared that day even though the air temperature never got above freezing.

These are all photos of roughly the same scene behind our hut at F6, looking north at the Kukri Hills. Here it is at 9:00 in the morning with an inch of snow, while it was still snowing a little bit. You can't even see the mountains because the clouds are so low:

And at noon:

And at 2:30 in the afternoon:

And at 6:00 pm:

And 7:30 pm:

And by midnight, it was gone:

Similarly, another group here has a camera set up in a different valley, called Wright Valley, and are taking time-lapse photos of one particular area. You can see snow come and go over the course of hours! Click here to see it on YouTube.

We think that most of the snow turns into water vapor, but some of it does melt. That extra moisture in the soil will be really important for the organisms living in the soil that are usually water-deprived. To find out how much moisture was getting added, we decided to take soil samples under the snow as it was ablating. Every few hours, we scraped away the snow and took soil samples from the surface (0-2 cm into the ground) and just below the surface (2-5 cm into the ground). We'll measure the soil moisture of those soil samples to see how much water melts into the ground from the snow and whether it ever trickles down to lower depths in the soil.

Now that we're finally all back in the lab at McMurdo (but barely, we almost got stuck at Marble Point, the helicopter fueling station, for the night!), I spent the day weighing out samples for soil moisture. Tomorrow, I will know how much the moisture was influenced by the snow, and how quickly it disappeared!

Tomorrow, I'm heading to the field with Julia, Zach, and Bishwo to sample and treat the stoichiometry plots that are at Lake Bonney. It is supposed to be a day trip, though, so there shouldn't be any getting stuck.

1 comment:

  1. Here are my answers to some questions from my friends at Thetford Elementary School:

    Q: When you were at Lake Bonney putting the solutions into the soil, can you ever put too much in? We know you double check what you are putting in but do you ever put too much of something in? too much nitrogen or carbon....
    A: We put on a very specific amount. Each plot gets 5.6 liters of water that contains a certain amount of carbon, nitrogen, or phosphorus. When I'm pouring from the carboy into the pour jug, I pour until I reach a line that marks 5.6 L. The person I'm pouring for tells me when I reach the line (it's just hard to hear Zach say "you're good" in the video). We want to know how much each plot gets so we can track that given amount as it moves through the soil, so we have to be very exact!

    Q: How long do you have to wait until you see some reaction in the soil from adding the solutions?
    A: We see some reactions immediately. At Fryxell, I already know that there is more respiration (CO2 flux) when carbon and nitrogen are added together than in all of the other plots. But, for some measurements, we will have to wait years to see a reaction. Organisms grow very slowly here, and it could be years before we see a change in their numbers. That is why we plan to run the experiment for a long time.

    Q: How deep in the soil are those organisms?
    A: In Antarctica, organisms are generally in the top 10 cm of soil. They have to stay higher up in the soil where they can get the little bit of moisture and nutrients are, but they can't be on the very top of the soil because they'd be exposed to the cold wind. So we generally find soil organisms between 1 and 10 cm deep. In other places, like Vermont, though, organisms can be much, much deeper in the soil.

    Q: Since so much of the snow turns into water vapor, how much snow actually sticks and accumulates?
    A: Snow doesn't stick and accumulate in the dry valleys. It falls, then disappears within hours. So, almost all of the snow that falls turns into vapor, but a little bit of it melts and adds water to the soil. I don't know yet how much melts and how much turns to vapor. That's what I was trying to measure during the snow storm, and I don't have the answer yet!

    Q: Did we hear music in the background while you were vidiotaping your research? Do you listen to music while you work?
    A: Of course! I have an MP3 player that is attached to a speaker that is home-made from an Altoids tin. It works off of one AA battery and has pretty good sound for the fact that it's an Altoid tin! It's called the FED (the "field entertainment device"). Music makes work go much faster!

    Q: What time do you get up in the morning?
    A: I usually wake up at 7 A.M. I'm not a morning person, so I don't like to get up any earlier than that. I go right to breakfast, and am at work by 7:30 or 8:00.