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Lonnie Thompson, a distinguished professor at the Ohio State University's School of Earth Sciences, is seen here cutting an ice core extracted from the Guliya Ice Cap in Tibet’s Kunlun Mountains in 2015. Photo by Giuliano Bertagna/Byrd Polar and Climate Research Center.The history of life is written in the fossil record. Through studying skeletons, footprints, and other preserved remains, scientists uncover new information about ancient organisms. But when it comes to studying past climates, things are different. Unlike dinosaurs or mastodons, climate leaves no bones behind or tracks to follow. However, clues to past weather conditions can still be discovered — you just need to know where to search for them.
A significant source of evidence comes from glacial ice across the globe. Glaciers form where snow accumulates without melting, and over time, the weight of new snow layers compresses the older snow crystals. This pressure fuses them into a solid, rock-like sheet of ice. Eventually, this forms a glacier, made up of these compacted layers, with the oldest layers resting at the bottom.
Scientists often refer to glacial ice as a natural annual record. Each new layer that forms traps tiny bubbles of air, and by studying these bubbles, researchers can learn about the levels of greenhouse gases in the atmosphere at the time the ice solidified. Additionally, volcanic ash can become trapped in the ice, revealing the timing of ancient eruptions. Ice can also provide clues about prehistoric wind strengths and the global temperatures from past eras.
Researchers extract valuable data from glaciers by drilling. Using mechanical or thermal drills, a team can retrieve long vertical ice columns called "ice cores." These cores can vary in length, with some measuring just over 328 feet (100 meters), while others stretch more than 2 miles (3.2 kilometers). After extraction, the cores are broken into smaller pieces, placed in metal cylinders, and stored in chilled laboratories for further analysis.
One of the benefits of studying glaciers is their annual layering system, which allows scientists to estimate the age of ice core segments by counting these layers. Another method for dating ice is through radiometric techniques.
The widespread presence of glaciers is also beneficial to researchers; glaciers exist on every continent except Australia. However, most of the ice cores recovered so far have come from Greenland or Antarctica. That said, scientists are not overlooking glaciers elsewhere. In December, a significant ice core from the Tibetan Plateau was announced, providing crucial historical data.
The Ohio State University recently shared updates from a joint expedition led by scientists from its Byrd Polar and Climate Research Center (BPCRC) and the Chinese Institute of Tibetan Plateau Research. The mission, which took place in September and October 2015, involved an international team traveling to the Guliya Ice Cap in Tibet's Kunlun Mountains, with 6 tons (5.4 metric tons) of equipment flown in from the U.S. for the journey.
The team's mission was to drill new ice cores to deepen our understanding of the glacial history of western Tibet. By studying the past, they aim to predict the uncertain future of the region.
Over 1.4 billion people depend on the 46,000 glaciers that cover the Tibetan Plateau, a region known as 'the third pole.' Climate change has raised concerns about the region's long-term stability. A 2012 study published in Nature revealed that most of Tibet's glaciers have shrunk over the past three decades, and the melting ice from the highlands has been a major contributor to rising global sea levels.
The international research team successfully retrieved five ice cores from Guliya, with the longest one setting a new record. Stretching over 1,000 feet (304.8 meters), it is almost twice as tall as the Washington Monument. More remarkably, the deepest layers of this core date back around 600,000 years ago, marking it as the oldest ice core found outside Earth's polar regions.
In comparison, some glacial ice from Antarctica is much older; a core taken in 2015 was about 2.7 million years old. However, this does not diminish the significance of the Tibetan cores. It is rare for humanity to uncover such well-preserved climate history spanning 600,000 years.
The addition of these new ice cores to the global collection will be invaluable for future research. By examining cores from various parts of the world, scientists can determine whether weather trends in the past were global or specific to regions. For example, a comparison of Tibetan and European ice cores in the early 2010s revealed that while Europe experienced a brief warm period in medieval times, central Asia most likely didn't.
Over the next few months, scientists from China and the United States will conduct a detailed chemical analysis on the newly discovered ice cores.
A common myth about woolly mammoths is that their preserved remains have been found within glaciers. This is not true. All known mammoth carcasses were actually discovered buried in permafrost (frozen soil), not inside glacial ice.
