Sunday, December 21, 2014

Mud Hunting 2.0

We’re on weather hold at McMurdo, waiting for some snow to clear, which is the perfect time to write a quick post.

What’s the Cold Dirt team up to this year? We’re here in the McMurdo Dry Valleys again trying to learn more about shallow groundwater. Because it’s so cold in Antarctic (-18˚C is the average temperature in this part of the world), most of the ground is frozen all the time. This frozen ground is called permafrost. But in the summer, temperatures climb up to freezing, or even a little bit above. When that happens, the warm surface of the soil starts to thaw. The ground thaws and ice in it melts down to a depth of 30-60 cm (about 1-2 feet). This is called the “active layer” among permafrost geologists because it is where freeze-thaw activity occurs.

When the active layer forms, the near-surface hydrological system starts to spin up. Water melted from ground ice, snow banks, and even sucked into the soil from thirsty salts starts to flow downhill. The water fills up the space between the ground surface and the frozen soil down below (called the ice table), making streaks of wet, muddy soil we call “water tracks.” Water tracks are like underground streams that connect the tops of the valleys to the ponds and lakes at the bottom of the valleys.

Water tracks in lower Taylor Valley. Snow melts and water flows downhill. Even in Antarctica.

This mud isn’t just fun for making mud pies, it’s actually very important for understanding how the ecosystem here functions and how it fits in to the bigger global climate system. Water tracks carry water and nutrients (like carbon and nitrogen) to microbes, algal mats, and invertebrates in the soils. These organisms may be far from streams and lakes and would be cut off from food and water without the underground plumbing system provided by water tracks. As a result, there’s actually quite a bit of soil carbon (living and dead microorganisms and nematode worms) that builds up in water tracks. Water tracks provide an organizing principle to the soil biological community here in the Dry Valleys, marking of places that are wet enough, food-rich-enough, but not too salty to live in.

Water tracks also give us an idea of what Antarctica might have been like 15-30 million years ago, when large parts of it were not coveredin ice sheets. If Antarctica was cold, but not quite so cold as today, large ice-free areas may have been crisscrossed by networks of water tracks. This shallow groundwater system might have been enough to support large communities of plants, microbes, and some organisms like insects and small invertebrates. If so, Antarctica may have looked much like the high Arctic today. Carbon preserved from this comparably warm portion of Antarctic history may be stored beneath the ice sheets today.  

Saturday, December 13, 2014

A decade of Antarctic science

The 2014-2015 field season is about to begin for the Cold Dirt team—we’re sitting in Sydney at the moment, waiting for our flight to Christchurch, New Zealand, and then down to McMurdo Station on Tuesday.

Before I get into the science next post, though, I wanted to mention that this is a special field season for me. I first was sent to Antarctica as a graduate student in 2004 to work as a field assistant for Dr. David Marchant at Boston University. I was bit by the Antarctic science bug that year, and have been back every year (but one) since then. Ten years is a long time to be working in one place, but the natural laboratory of Antarctica really is a place like no other. It’s a place where we can learn about the ancient past or the rapidly-changing present. It’s a landscape that transports us to other planets and distant moons. But most importantly, even though it is often out of sight and out of mind, Antarctica is a keystone in Earth’s climate system, its oceans, and its geology. Research in this far away place gives us a chance to take the Earth’s pulse and to understand our place in it better.

So stay tuned! This year will feature more science, more mud, and more peeks into the scientific enterprise in Antarctica!