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!

Tuesday, October 21, 2014

Painting Antarctica

Look familiar? NSF Office of Polar Programs Artist and Writer Program laureate, Lily Simonson, has just concluded a gallery show in Los Angeles featuring paintings of Garwood and Taylor Valley. 

Check out our science + art talk, "Exploring Antarctica: New Frontiers of Art and Science" here

Monday, February 17, 2014

Climate Change in Two Graphs (and a lot of Facebook posts)

I've been having an interesting discussion of climate change and climate education on a friend's Facebook page, and thought it might make more sense to move the conversation over here. The blog format is a little more conducive to long-format discussions than other social media.

The chat began with a question about why Bill Nye would engage in public debates with creationists or would debate climate change on the Sunday magazine shows. It definitely gives the non-scientific camp a chance to present their views as legitimate, which is a serious concern given the snake oil they are peddling. But my hope for the debates (and maybe Bill Nye's, too) is that these public "debates" will reach viewers who might ascribe to a creationist viewpoint or a climate change denial opinion just because they live in a family or a community that has denied them access to accurate information. I think we take for granted the free an unfettered access to accurate science reportingupdates on medical studies, andfree venues for the exchange of ideas. It might be that folks who have been sequestered from that kind of information will tune in to see "their" side talk, but will have the candle of critical thought lit by "the other side." Any scientist will tell you, a little bit of doubt is a wonderful thing.

This led to a discussion of climate change and how we know what we know. Differences of opinion were raised. Some folks had heard different things from different people. Others felt that whatever the facts of climate change are, that stewardship of the planet was most important. In order to help share information with the first group and to help empower the the positive sentiment of the second group, I thought I'd post what I think are the two most important graphs for explaining what is known and what isn't known about climate change. You could save them to your phone so you have them on hand to share whenever (J. Tuzo Wilson, the father of plate tectonics, is claimed to have carried around a little plate model with him in his wallet to show anyone who'd give him the time--he must have been a hit at dinner parties).

The first graph is the data plot:

This is from Shaun Marcott's 2013 Science paper. The graph shows temperature anomaly (with error bars that show the statistical range of potential uncertainty around the measurements) during the Holocene (the last 11,300 or so years) in the blue, black, and orange lines. Temperature anomaly is how much warmer or colder a year's temperature is from a specified long-term average. You read this graph from left (ancient) to right (modern). See that big spike at the end? That's climate change. What's cool about the graph is that it's derived from 73 different kinds of measurements of past climate, and breaks down warming by latitude and region (that's what they mean by "stack"--it's a lot of data stacked together). Something serious is happening to our planet!

Now, no one who lived 11,300 years ago (in a cave) is still around to tell us how things were, so we rely on temperature records encoded in tree rings, corals, cave stalactites, etc. to measure the temperature in the past. These slow-growing, temperature-dependent natural phenomena are called "proxies." Folks shouldn't distrust proxies just because they are complicated or involve chemistry and math. Anyone who's ever had a strep throat test come back positive might still be alive thanks to proxies. We can't see strep cells with our own eyes, but doctors have devised chemical tests that can detect the presence of strep antigens and then change color (something we can detect) if they're there. The same level of care goes into devising climate proxies. We can't see temperature in the chemical zonation of a stalactite with our bare eyes, but we can measure the ratio of oxygen isotopes in it with sensitive tools to detect the changes different air temperatures caused to the composition of the rock over time. By measuring lots of these temperature-dependent phenomena over time, it's possible to reconstruct the history of past climate around the world. It's like sifting through thousands of newspaper weather reports from ancient history. Each proxy says "on this date, right here, it was this temperature."

The second image is the model that helps explain what forces are driving the data. The term "model" can be confusing sometimes. For most people a model means "a small version of something that doesn't do everything the big one does." A model airplane looks like a plane, but doesn't fly you to London. J. Tuzo Wilson's plate tectonics model was cardboard and couldn't possibly capture everything that's going on in the Earth's crust.

A climate model is different. A climate model is a collection of equations (mostly drawn from thermodynamics--the scientific laws of how heat moves through the universe) that describe the physics of the climate system. It's like the engineering model of the computer or phone you're probably reading this post on. Engineers combined the known behavior of semiconductor chips, resistors, LEDs, etc. into a system so that they could predict how electricity and binary code would move through the complex parts of the computer to display the desired information. Now, your phone doesn't know what you're going to say next (in the same way the output of a climate model isn't prescribed), but the components of the phone are capable of capturing your voice, digitizing it, and transmitting it in a coherent way. 

The climate models have components that describe how heat and water and sunlight combine to make our planet tick. A computer solves these calculations step-wise so that physical laws (conservation of mass, conservation of energy, etc.) are obeyed. What comes out is a dynamic view of how our climate responds to forcings. Forcings are things like changes in solar intensity, or injection of volcanic ash into the atmosphere, etc. that cause changes to the climate. By analogy, heat from the stove burner is a forcing in the stove-teakettle system. Turn up the heat (change the forcing) and the system responds: the teakettle heats up.

So what's in this amazing figure from the IPCC? The map shows for each continent and the global ocean the observed temperature anomaly (black line), the climate model output for the same time period with only natural forcings (blue bars--it's the range of a lot of models), and the climate models that include anthropogenic CO2 and other emissions (methane, soot, etc.).  

What's amazing about this picture is that it shows that scientists around the world cannot explain changes to our climate if they only consider natural forcings. To explain what our planet is doing, you have to include human activity. That's what scientists mean when they say things like "More than half of the observed increase in average surface temperature from 1951 to 2010 is very likely [90-100% probability] due to the observed anthropogenic increase in [greenhouse gas] concentrations." It's not that we want global warming to happen, it's not that we feel guilty and want to pin the blame on humanity. It's that the only explanation for the observed facts that fits is that humans are playing a huge role in changing our planet. 

So there you have it--what's going on, and why it appears to be going on in two graphs. It's scary, awesome data. What people do with the results is up to them. My advice: learn to adapt. The world is changing around us whether we like it or not. Better to learn to be happy and wealthy and productive in a changing world. But if folks want to ignore the observations and the best explanations for why change is occurring, that's fine too. Like their Holocene ancestors, folks are allowed to live in a cave. I'd just suggest living in a cave well above sea level. 

PS--here's the 2013 update of that amazing figure: