Record-breaking drill (523 Meters) through Antarctic ice

 Uncovering 23 Million years of climate secrets by record-breaking Antarctic drill 

An international team featuring faculty at Binghamton University, State University of New York has drilled the longest ever sediment core from under an ice sheet, providing a record stretching back millions of years which will help climate scientists forecast the fate of the ice sheet in our world. “To our knowledge, the longest sediment cores previously drilled under an ice sheet are less than 10 m, “ said Molly Patterson, co-chief scientist and associate professor of earth sciences at Binghamton University. “We exceeded our target of 200 m, and undertook this 700 km from the nearest base, this is Antarctic frontier science.” Scientists recovered a 228-meter Antarctic sediment core showing past ice-sheet retreat during warm periods above 2°C. Deep beneath Antarctica’s ice, a geological archive which could reshape predictions of future sea-level rise. Working roughly 700 km's from the closest Antarctic research stations, the team drilled through 523 meters of solid ice at Crary Ice Rise, located along the edge of the West Antarctic Ice Sheet. Beneath the ice, they recovered a 228-meter-long core made up of layered mud and rock. These sediments preserve a long record of environmental change during earlier warm phases in Earth’s history, offering crucial evidence for estimating how quickly ice in the region could melt as the planet warms.

The sediment core holds an archive of past environmental conditions at the site from warmer periods in Earth’s history, vital information for climate scientists to determine how much and how fast the ice sheet will melt in the future under our warming climate. The 228 m of ancient mud and rock was drilled from under 523 m of ice. The vast West Antarctic Ice Sheet holds enough ice to raise global sea levels by 4-5 m if it were to melt completely. Satellite observations over recent decades show the ice sheet is losing mass at an accelerating rate, but there is uncertainty around the temperature increase which could trigger rapid loss of ice. Up until now, ice sheet modellers have relied on geological records obtained next to the ice sheet, below floating ice shelves, sea ice and in the open Ross Sea and Southern Ocean.  If the West Antarctic Ice Sheet were to collapse entirely, scientists estimate that global sea levels would climb by four to five meters. Until now, predictions about how the ice sheet might react to additional warming have relied largely on satellite data and sediment records gathered near the ice margin, beneath floating ice shelves, within sea ice and across the Ross Sea and Southern Ocean. The newly recovered core was drilled as part of the international SWAIS2C project (Sensitivity of the West Antarctic Ice Sheet to 2°C). It was collected at Crary Ice Rise, an ice dome anchored at the inner edge of the Ross Ice Shelf. Unlike previous records, this core provides direct and detailed evidence of how the ice sheet’s margin behaved during earlier warm intervals.

The new sediment core, recovered by the SWAIS2C project, provides a direct and comprehensive record of how this margin of the ice sheet has behaved in the past warm periods. “This record will give us critical insights about how the West Antarctic Ice Sheet and Ross Ice Shelf is likely to respond to temperatures above 2°C. Initial indications are that the layers of sediment in the core span the past 23 million years, including time periods when Earth’s global average temperatures were significantly higher than 2°C above pre-industrial,” said co-chief scientist Huw Horgan (Te Herenga Waka – Victoria University of Wellington, New Zealand, ETH Zurich and WSL, Switzerland). Preliminary dating of the sediment carried out in the field was based on identification of tiny fossils of marine organisms found in some of the layers. A wider team of scientists from the 10 countries collaborating in the SWAIS2C project will apply a range of techniques to refine and confirm the age of the records. The researchers recovered the sediment core at a drilling site in West Antarctica, located around 700 km's from the nearest support station (Scott Base, New Zealand). Fragments of shells and the remains of light-dependent marine organisms indicate that the area was once covered by open ocean rather than ice. Scientists have long suspected that this region experienced earlier periods of open water, suggesting partial or even complete retreat of the Ross Ice Shelf and the possible collapse of parts of the West Antarctic Ice Sheet. Pinpointing exactly when these retreats occurred, and identifying the environmental conditions that triggered them, is now a primary goal for the SWAIS2C research team, according to Patterson.

As the team drilled down through the layers of sediment deep below the ice sheet, pulling up the core in lengths up to 3 m long, the researchers examined the sediment for tell-tale indications of the environmental conditions under which it was deposited. They encountered a wide variety of sediment types from fine-grained muds through to firmer gravels with larger rocks embedded within. “We saw a lot of variability. Some of the sediment was typical of deposits that occur under an ice sheet, like we have at Crary Ice Rise today,” said Patterson. “But we also saw material that’s more typical of an open ocean, an ice shelf floating over ocean, or an ice-shelf margin with icebergs calving off,” Recovering the sediment core represents both a scientific milestone and a major engineering accomplishment. The 29-member team of scientists, drillers, engineers, and polar specialists faced significant uncertainty from the outset. Two previous drilling attempts had failed due to technical difficulties. The challenge was considerable, as no project had previously extracted such a deep geological record from beneath an ice sheet at such a remote location. The team operated continuously in rotating shifts, using a specially built drilling system. They first melted a 523 m deep hole through the ice with a hot water drill. More than 1300 m of ‘riser’ and ‘drill string’ pipe was then lowered to reach the sediment below. Each recovered section of core was carefully logged, photographed, x-rayed, and sampled for further study.

Open ocean conditions were indicated by the presence of shell fragments and the remains of marine organisms which require light to survive, implying the lack of ice above. Although it is already thought that there has been open ocean in this region in the past, indicating partial or total retreat of the Ross Ice Shelf, and potential collapse of the West Antarctic Ice Sheet, there is uncertainty about which time periods this occurred in. “This new record provides sequences of environmental conditions through time, and ground truths the presence of open ocean in this region. In addition to pinning down the time when this occurred and the corresponding global temperature, analysis will help us quantify the environmental factors that drove the ice sheet retreat, such as determining what the ocean temperatures were at that time,” said Patterson. Initial age estimates were made at the drilling site by identifying microscopic fossils from marine organisms preserved in several sediment layers. Researchers from 10 countries will now carry out more detailed analyses to confirm and refine the timeline. As drilling progressed deeper below the ice sheet, the team extracted sections of core measuring up to 3 meters at a time. The sediments showed remarkable diversity, ranging from fine mud to compact gravel containing larger embedded rocks. “We saw a lot of variability. Some of the sediment was typical of deposits that occur under an ice sheet like we have at Crary Ice Rise today. But we also saw material that’s more typical of an open ocean, an ice shelf floating over ocean, or an ice-shelf margin with icebergs calving off,” says Co-Chief Scientist Molly Patterson.

The team of 29 scientists, drillers, engineers and polar specialists living in tents on the snow at Crary Ice Rise knew that success was not guaranteed. This was not unexpected, no one has ever drilled geological records this deep under an ice sheet and so far away from any main base of resources. This work was supported by logistical contributions from two national Antarctic programs. Antarctica New Zealand provided the traverse capability to tow the custom-designed drilling system and field supplies 1100km across the Ross Ice Shelf. This team then established and operated the remote field camp through a nearly 10-week season. The National Science Foundation’s United States Antarctic Program also provided critical airlift and other logistical support. Weather presented a significant challenge, with the drillers’ and scientists’ flights into camp delayed by weeks due to freezing fog at the site. “It was a great feeling when that first core came up, but then you start worrying about the next core and the next core after that. So, it’s stressful right up until the end. We’re thrilled to have learned from our previous challenges and to have successfully retrieved this geological record that will help the world prepare for the impacts of climate change,” says Horgan. Looking ahead, the team plans to build on this success. “Our multi-disciplinary international team is already collaborating to unravel the climate secrets hidden in the core. With our drilling system having been put to the test under these tough Antarctic conditions and passing with flying colors, we’re looking ahead to plan future drilling to continue our mission to learn more about the sensitivity of the West Antarctic Ice Sheet to global warming,” says Horgan.

By drilling more than 500 meters down through the ice sheet, the researchers were able to retrieve a sediment core over 200 meters in length from the deposits beneath the ice. For two months, a team of researchers from ten countries lived and worked in a remote field camp in West Antarctica. Their efforts have culminated in the recovery of a remarkable record of past climate preserved in the sediments beneath the ice. To access the elusive sediment, the team had to first use a hot-water drill to melt a hole through 523 m of ice, then lowered more than 1300 m of ‘riser’ and ‘drill string’ pipe down the hole. Once the core was pulled up, the scientists described, photographed and x-rayed the tubes of sediment, and took samples. The team worked in shifts around the clock to make the best use of limited time on site. The core has been transported back to Scott Base and will soon make its way to New Zealand. Samples will then be sent to SWAIS2C scientists around the world for further analysis to be used in future.