Drilling for Insight in Antarctica

23 October 2007 | 04:58 Code : 15731 Geoscience events
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In the relative warmth of an Antarctic spring, when the coastal temperature....

  In the relative warmth of an Antarctic spring, when the coastal temperature rises to the freezing point, a 60-ton drilling platform is towed sledgelike to its operating site across floating sea ice. No more than 25 feet of ice separate the rig and the chill, hypersaline waters of McMurdo Sound. Fifteen hundred feet below the ice is the sea floor, and below that, layers of rock built of millennia of sedimentary deposits. The rig is the heartbeat of a scientific enterprise. And, with the help of Apple technology, its drill cores will yield insights into the changing climate of our planet. This is the Southern McMurdo Sound Project (SMS), the second Antarctic data-gathering project for ANDRILL (ANtarctic geologic DRILLing), a scientific initiative funded by Germany, Italy, New Zealand and the United States. ANDRILL is focused on uncovering the geologic history of the Antarctic continent. Its findings have meaning for every one of us. Antarctica, bigger than Europe, bigger than Australia, bigger than the U.S., stores a huge percentage of the earth’s fresh water in its coast-to-coast freezer. The oceans meet here, and the dense, cold water that flows from under Antarctica’s ice sheets creates currents that affect water movement and weather patterns around the earth. Melting ice in Antarctica raises sea levels worldwide. What happens here affects us all. Sea levels are currently rising at a rate of a tenth of an inch per year. These and other environmental phenomena, including changes in atmospheric gases and global temperature levels, are taken by most scientists as unmistakable indications that the earth is warming. The International Polar Year (2007-2009), of which ANDRILL is a part, is a collaborative effort by scientists to examine the geologic history of the Polar Regions and their current behavior to provide perspective on these changes. “We’re trying to recover the geologic record of ice shelf and ice sheet behavior in Antarctica,” says ANDRILL staff scientist Dr. Richard Levy. “We really have very little evidence of how the ice sheet behaved in the past. We want to know how the ice shelf and the ice system have responded to climate changes over the last 15-20 million years. To do that we have to drill through the ice and get to the sediment layers that are preserved in the basins that surround the continent.” The Southern McMurdo Sound Project will be ANDRILL’s second Antarctic drilling project. It will apply the same technology and methods as the first ANDRILL expedition — the McMurdo Ice Shelf Project (MIS), begun late in 2006 and completed early in 2007. MIS drilled to 4200 feet below the seafloor, starting with wider diameter pipe (the riser), then using successively smaller drill pipes inside the larger pipes, deploying a total of 20,000 feet of pipe. The team drilled 20 feet at a time, pulling up a 3.5-inch-diameter core in the first stage — a half-hour procedure — and drilled again. At greater depths, where they used smaller-diameter pipe, they pulled longer, narrower cores — roughly 30 feet long and 1.5 to 2.0 inches in diameter. Curators at the drill site washed the cores and cut them to three-foot lengths. The cores were then transported to McMurdo Station, where they were sliced in half longitudinally and protected with PVC liners. One half was boxed and archived; the other went to the sedimentology room. Each was marked to show the top end and the depth at which it was cut. Cores were scanned with a high-resolution camera. The digital image data was fed into a Corewall core-analysis system that included an Intel-based Mac Pro workstation and two 30-inch Apple Cinema Displays in an 8-megapixel tiled configuration. Corelyzer, a visualization tool that is part of the Corewall software suite, enabled ANDRILL scientists to enlarge images of the cores from their original diameters (1.5 to 3.5 inches) up to 30-inch diameters and make annotations. “I think Corelyzer is considered a major breakthrough for scientists who need to look at visualizations of drill cores,” says Dr. Jason Leigh, Director of the Electronic Visualization Laboratory (EVL), where Corewall was developed. “Formerly, they would split the cores, take pictures of them, and pretty much never touch or see the core again — and they couldn’t look at the imagery at full resolution either. We enable them to see those cores again as they were first obtained and do much more with them.”“Besides viewing the raw core and the high-res enlarged images,” says Levy, “our scientists are able to use Corelyzer to integrate into the on-screen display physical properties such as sonic velocity, magnetic susceptibility, and density curves. You can actually fly up and down the core, and look at those data on the Mac in real time. “We might see an interval that looks fairly homogeneous, but notice that its physical properties change. Why? We can use the 30-inch screens to identify the interval, go back and look at the raw core, and come back to the screen. So we can interact between the technology and the raw core to help refine and adjust our descriptions. “One of our scientists has the job of describing the rock fragments he sees in the core. Where do these sediments come from? Can they help us learn where the glaciers that are dumping at this site have been picking up material? So Corelyzer helps us reconstruct paleoglacial activity.” In the evenings, the ANDRILL sedimentologists on the MIS expedition took other scientists on a tour of the day’s cores. The scientists sat at the Cinema Display screens to identify sections of the raw cores they wanted to sample for laboratory analysis. Core sections containing volcanic ash were dated radiometrically. Other sections were dated by biostratigraphy – the distribution of fossils. “At this point we’re able to date the top 600 meters to be about 5 million years and younger,” says Levy. As someone has said, there isn’t a lot of tech support in Antarctica. The stability of the Mac platform was of major importance to the scientists who used it constantly during the ANDRILL MIS expedition. “We took down a Mac Pro with two 30-inch Apple Cinema displays,” says Josh Reed, IT and Data Manager for the MIS project. “We also brought a PC, but it wasn’t as stable with Corelyzer as the Mac. There were crashes and it was pretty frustrating.” “What we’ve noticed,” says Jason Leigh of EVL, “is that the geoscience community treats technology like these tiled displays as an instrument, not a computer they want something they can turn on and use, and that’s it. That’s where I think Apple is significant here, because it’s a trusted vendor, producing very stable technology that geoscientists like using anyway.”That is true of Richard Levy, an ANDRILL paleontologist and biostratigrapher who confesses to being a Mac person. “I also believe that Megan Berg, who designed our excellent web site, was born in front of a Mac,” says Levy. “She made me switch from PowerPoint to Keynote the other day.”What we’re seeing from the body of results of climate research worldwide,” says Levy, “is that if you go back in time some five million years you will see a period when the earth was 2-3 degrees warmer than it is today. That was a natural occurrence, with no impact from humans. Looking at the natural cyclicity, we should be heading into a glacial period, starting to cool again. Instead, the earth is warming.” Many scientists see a clear correlation between today’s rising temperatures and human activity.“We know that atmospheric carbon dioxide levels during past natural warm cycles were about 300 parts per million (PPM),” says Levy. “But we’re currently pushing the CO2 level up to 380 or 400 PPM, which is unprecedented over the last 400,000 to 500,000 years, even all the way back some 15 million years ago. Some models predict that CO2 may rise to 900 PPM over the next one to two hundred years. And if that does cause warming, we would expect to see Earth begin to behave as it did naturally thirty five million years ago when ice sheets first formed on Antarctica. The difference is that human activity appears to be contributing to climate warming.” Findings from the 2006-2007 ANDRILL expedition indicate one thing clearly: projected warming of the earth’s climate will likely impact the current stable state of the Ross Ice Shelf. If as part of the current warming trend, the Ross Ice Shelf collapses – a distinct possibility – that could mean the loss of the West Antarctic Ice Sheet. And that, says Levy, could mean a sea level rise of up to 20 feet. The loss of the sea ice and the ice shelf, and the related impact on the formation of the cold, dense water beneath them will have a profound effect on the way oceans circulate and affect climate. How soon and how quickly could all this happen? Nobody knows. But ANDRILL, and the many other studies that are part of the International Polar Year, may ultimately tell us much more about it.

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