PREVIOUS PAGE: MARTIN FROGER SILVA vaguely fruit-like or floral scent — not nearly as harsh as other solvents like acetone, but still bothersome. At the Allan Hills, our camp didn’t have washing machines or bathing facilities, which meant that we wore the same layers of wool and fleece under our heavy overalls and coats for days or weeks on end. Fortunately, we had protective drill suits to cover our clothes, and boots that would not degrade when they came into contact with the drill fluid. This field mission was actually the first time we used the Shallow Wet Drill and the Estisol it requires. Previously, cores in the Allan Hills were dry drilled, a relatively easy and fuss-free method with minimal setup required. But compressed air in the bubbles in the ice can crack and badly fracture the cores while they’re being cut, contaminating the contents with modern air. COLDEX proposed to test whether fluid drilling would result in better ice core quality and commissioned this new drill from the NSF Ice Drilling Program for this season. This year’s goal wasn’t to find older ice than before, but to bring back better ice. The improved core quality made all the extra effort worth it. We started drilling this particular borehole dry, waiting to add fluid until core quality started to degrade. One day in mid-December, at about 115 meters deep, the last core of the day came up as complete rubble, unusable for scientific analysis. The next day we filled the borehole about halfway with Estisol and immediately began drilling beautiful, perfect cores, proving that wet drilling would work in a blue ice area. Still, despite drilling up to 20 meters a day, we were running out of time. In addition to drilling ice, our field team was also responsible for collecting data on the depth and movement of the ice sheet itself. We couldn’t take measurements until we were finished; otherwise the electricity from the generator-powered drill would interfere with radar measurements. We were scheduled to return to McMurdo Station on Jan. 11. We needed to speed things up and finish by Christmas in order to leave enough time for the other projects. ON DEC. 16, we had split the team into two shifts, with the goal of drilling about 16 hours a day until we reached bedrock. I volunteered for the night shift, figuring that bedtime was arbitrary when you had 24 hours of sunlight a day. An Li, a graduate student from the University of Washington who led the geophysics work on our field team, was the other core handler on the night shift. Andrew Haala and Dusty Brunner, engineers from the NSF Ice Drilling Program at the University of Wisconsin, rounded out our team. The first shift included OSU postdocs Romilly Harris Stuart and Ivo Strawson, Martin Froger Silva from the University of Minnesota, and drillers Elizabeth Morton and Jay Johnson. Each day, they headed out to the drill UNLIKE THE other international teams, COLDEX focuses on blue ice areas. These cover less than 1% of Antarctica and are found mainly at the margins of the East Antarctic ice sheet. Here, ice flow to the sea is interrupted by mountains, especially the Transantarctic Mountain Range.At these barriers, ancient ice once buried deep under the ice sheet resurfaces, and harsh katabatic winds scour away the younger ice on top. What’s left appears blue due to millions of years of compression. Recent COLDEX field seasons to blue ice areas have yielded ice far older than other oldest ice projects less than 200 meters below the surface. Unlike areas where deep ice cores are drilled, the Allan Hills have large amounts of ice from the Pliocene epoch (2.5 to 5.3 million years ago) and even before that. During the 2024-25 field season, COLDEX set a record, drilling a core with ice more than 6 million years old at its bottom. But there are disadvantages to working in a blue ice area. The same ice flow patterns that result in the retention of such old ice make the ice very difficult to work with. It has traveled hundreds of kilometers and has folded and thinned unevenly. John Higgins, a professor at Princeton University and the science lead for this COLDEX project, likes to compare the ice core records from deep continuous cores to “pages in a book, because you can read them in order and they tell a continuous story.” Data from Allan Hills ice cores, however, are more like snapshots jumbled up in a loose box of photos, with some of photos missing altogether. Because of this, we can’t assume that deeper ice is older than the shallower ice. COLDEX scientists determine the age back in the lab by analyzing argon gas isotopes trapped in bubbles in the cores.They’ve discovered that in one area of the Allan Hills, there’s a layer of much younger ice sandwiched in between two 3-million-year- old layers. Careful handling in the field — and detailed analysis in the laboratory — is required to accurately interpret data from these cores. EACH TIME THE DRILL pulls up another meter of ice, drill fluid drains out of the core barrel onto a sloped drip tray, which funnels it into a bucket. The fluid can be filtered to remove ice chips and then reused. The core handlers — wearing nitrile gloves over our wool glove liners to keep our hands dry, but not quite warm enough — vacuum the surface of the core to remove as much of the Estisol fluid from the surface as possible. The handlers then measure and log the core; label, photograph and bag it; and carefully place it in a large, insulated box, packed with snow, for storage and transport. These boxes can hold nine of the meter-long cores and, when full, weigh up to 200 pounds. In between drilling, the handlers try to warm up with thick gloves, hand warmers and a lot of dancing around. Whenever Estisol splashes onto any of our regular clothing, the smell follows us around for days. It has a 44 OregonStater.org GREENHOUSE GAS DATA FROM BACK THEN WILL HELP US UNDERSTAND HOW OUR CLIMATE COULD CHANGE IN THE NEAR FUTURE. PREVIOUS PAGE The Shallow Wet Drill tent where the team drilled the deepest core ever drilled in a blue ice area.
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