Thursday, January 10, 2013

Brine time!

It’s been a busy few weeks here in Antarctica, which is why there have been so few posts lately! I’ve been working with my team—up to 9 other outstanding scientists—which has kept me running around all day getting the junior team members trained up so they can work on the water tracks and buried ice projects, and helping the senior team members implement their own field experiments. With so many big and small projects going on up and down the whole length of Taylor Valley, it’s been hard to find a minute to post!

So, what have we been up to?

The team has been trying to figure out how much water and how much salt is moving though the ground here in Taylor Valley. Groundwater is a big part of the total water budget in the valley, but nobody knows for sure how much there is—that’s what we’re here to figure out. The organisms living in the soil in the Taylor Valley ecosystem, from the smallest microbe to the biggest nematode (okay, nematodes aren’t that big, really), rely on groundwater to survive. These organisms also rely on the groundwater to bring them food—in the form of nutrients—but are also at risk of being pickled if too much salt gets into the groundwater. The soil here is VERY salty—so much so that crusts of salt show up on the ground, looking like frost on the ground on a winter’s day at home. Because salt dissolves in water, we’ve been trying to follow the water and follow the salt. When groundwater and soil salts combine, you get a salty liquid, sometimes called a brine (if you’ve brined your Thanksgiving turkey by soaking it in salt water, you’ve experienced a piece of what it’s like to work here).

All the brown you see in these satellite images is the cold dirt of Taylor Valley. Green dots are where our camps are. 

We’ve been moving through Taylor Valley over the last few weeks, bouncing from camp to camp every few days. It feels like we’re bunch of roadies following a band on tour, except we’re following the brine (“The Brine” would actually be a pretty good name for a band). So far, we’ve visited New Harbor (a beautiful camp on the frozen coast of the Ross Sea), Lake Hoare (my old home away from home next to the Canada Glacier), and Lake Bonney (the furthest field camp from the sea).

At each camp, we’ve been trying to tap into the salty brines that flow through the ground. We track them by following the salt crusts they leave at the surface and by looking for lines of wet soil that point downhill. Water flows downhill, even when it flows through the soil, so dark lines of dirt mean water movement below! These groundwater flow lines are called “water tracks.”

A water track--can you dig it? The water flowing downhill wicks up and darkens the soil. Stolen shamelessly from Becky Ball's Polar Soils blog. 

To tap the brine, we’ve been hammering in pipes into the dirt that have lots of holes in them—like a kitchen strainer. These pipes are called piezometers. Groundwater flows into the piezometers and we can stick in a tube to suck it up into our sampling bottles. It’s like sticking a straw into the Earth. The water we get out can be analyzed by the members of our team to find out what kinds of salts are in the water (this tells us where they water came from), how long the water has been in the ground, and how much biological activity has occurred in the water).

We’ve also been trying to monitor what the water tracks have been doing using a bunch of different technologies. Chris Thomas, a team member from Oregon State University, and Becky Ball, a team member from Arizona State University, have been measuring how carbon dioxide (CO2) moves into and out of the water track, as the creates living in the ground breath. Brendan Hermalyn, a team member from the University of Hawaii has been using infrared cameras (that measure the temperature of the whole landscape) to determine how the water tracks heat up and cool down. Because the water tracks are dark in color, they absorb a lot of sunlight—but because they’re wet, they cool by evaporation (the same way sweating cools you off). We’re trying to figure out how these processes interact to make water tracks suitable for the critters that live in them. Jay Dickson has been working on recording flow in the water tracks using time lapse photography—a process similar to the one I used last year to look for water tracks on Mars! And Alex Rytel, a recent grad from Ohio State University, has been helping me measure the electrical conductivity of the landscape. Wet, salty soils are very good conductors, whereas dry soils are electrical insulators. By looking for the physical fingerprint of water tracks, we can see how they move brines through the soil.

As you can tell, we’ve been very busy! Tomorrow, it’s off to our next camp at Lake Hoare. Time to get packing! 

No comments:

Post a Comment