Scientists read Antarctic mud for climate change insight
A four-inch core sample is a chapter of ancient history in which a Neanderthal amoeba or a worm can thicken the plot for researchers.
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The team must rush to finish its work. Fifteen miles from McMurdo, the drill rig rumbles atop 28 feet of floating ice. Its shaft churns through the ice and then 1,300 feet of seawater below to reach the seabed, where it gradually chews a 3,600-foot hole. Drillers must extract that entire section of core within eight weeks – while the weather is warm enough for outdoor work, but before summer temperatures make the ice too slushy to support the 40-ton drill rig.Skip to next paragraph
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The drill turns 24/7, as do the two shifts of geologists analyzing each day's core, 90 feet of which is delivered by helicopter at 10 p.m.
At 2 a.m. sunlight streams horizontally through the windows of the core lab. Christopher Fielding, the University of Nebraska geologist who heads the vampire shift here, motions toward a section of core that alternates paper-thin layers of gray and white stone – layers of mud that solidified long ago. "We've had a lot of nice things to look at," he says, "but this is particularly nice."
When these mud layers formed, Antarctica must have had less ice than it does now – otherwise such delicate layers would have been scrambled by the piles of stones that coastal glaciers dump into the sea. They represent only a short chapter – a few thousand years out of millions – but they're sure to provoke "a feeding frenzy" in the morning, says Dr. Fielding, as people debate how to study them further.
One table over, another section of tonight's core traverses a different period of history. Pebbles lay suspended like chunks of fruit in a Jell-O salad, trapped in the gray background of the core exactly where they fell into the mud millions of years ago.
"Every single stone is recorded in color," says Fielding. "She's up to about 60,000 so far."
The color Dr. Sandroni chooses for each pebble signifies the type of rock: red for granite, blue for sandstone, white for pumice, and so on. These rocks traveled to the ocean inside glaciers and icebergs, and by matching them to rocks in different parts of present-day Antarctica, she can tell where the rocks came from.
It's fascinating to watch her draw stone number 60,001 in red – not just the science, but also the sheer monotony with which discovery unfolds. Sandroni, undeterred, has already tuned out the conversation.
Just then Sandra Passchier, a sedimentologist from Montclair State University in New Jersey, points out something special in another section: embedded in stone, two conjoined circles of white, each the size of a pencil eraser. They are the cross section of a fossil shell called a foram.
"They're single-celled organisms related to amoebas," she says. "They have these little feet that they stick out of their shell to feed."
"I haven't seen any that big before," says Fielding as he gazes at the wonder. It's a single cell large enough to see – a Neanderthal amoeba.
These surprises are part of the fun of looking at cores. A core is a blind stab into the past: a four-inch aperture through which to view an entire epoch of history. That narrow gaze is sure to overlook some prizes – like a rare specimen that the drill misses an inch to the left.
But then come moments of serendipity, says Fielding: "You're always surprised when you find a large, well-preserved fossil. The chances of hitting a complete mollusk in a four-inch cylinder drilled into the seafloor are pretty slim. And we've had some beautiful fossils."
Each fossil presents an opportunity; not a eureka moment, but at least a chance to reconstruct an ancient environment by identifying the species that lived there.
The process begins in Antarctica at 2 in the morning, and will continue as pieces of the core are picked apart, in labs around the world, for years to come.