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In some ways, drilling into Antarctica’s ancient ice is easier than interpreting it. Today, more than 2 years after presenting the discovery of the world’s oldest ice core, scientists have published an analysis of the 2.7-million-year-old sample. One surprising finding: Air bubbles from 1.5 million years ago—from a time before the planet’s ice age cycles suddenly doubled in length—contain lower than expected levels of carbon dioxide (CO2), a possible clue to the shift in the ice age cycle. The CO2 levels are “amazingly low,” says Yige Zhang, a paleoclimatologist at Texas A&M University in College Station. He adds that the study, published today in Nature, is “quite interesting” because it reports the first direct measurements of atmospheric gases from that mysterious time. Some 2.6 million years ago, Earth entered a time known as the Pleistocene, which saw the planet swing in and out of deep periods of glaciation at regular 40,000-year intervals. About 1 million years ago, during what’s called the Mid-Pleistocene transition, these ice age cycles went from occurring every 40,000 years to 100,000 years. (The most recent ice age ended 11,000 years ago.) Scientists have long known that tiny changes in Earth’s orbit, called Milankovitch cycles, drive the planet in and out of these ice ages. But nothing changed in orbital patterns 1 million years ago that would have driven the “flip.” Some scientists suspect that overall CO2 levels were higher in the 40,000-year world, but declined over time and cooled the planet, eventually reaching a point where Earth transitioned into deeper, longer freezes every 100,000 years. One way to check that theory would be to examine samples of Earth’s atmosphere from before the flip. But before the discovery of the new ice core, the oldest greenhouse gases one could measure were in trapped bubbles in ice dating to about 800,000 years ago. To reach further back in time, a team of scientists targeted so-called “blue ice” near Antarctica’s surface in the Allan Hills. Here, ancient ice flows have exhumed the oldest ice from the deep. Old ice layers are driven up from below, while wind strips away snow and younger ice. Paul Mayewski, a glaciologist at the University of Maine in Orono, suspected such ice could be ancient, and Michael Bender, a geochemist at Princeton University, developed a way to date chunks of ice directly from trace amounts of argon and potassium gases they contain. In 2015, a team led by John Higgins, a Princeton geochemist, excavated the record-setting core. At first, the oldest ice seemed to contain startling levels of CO2, several times the 407 parts per million (ppm) we see today, says Yuzhen Yan, the Princeton geochemist who led the new study. Further analysis, however, revealed the bubbles had been contaminated by CO2 percolating from beneath the ice, likely released by microbes. That meant the team had to toss out data from many of the oldest samples—a reflection of their conscientiousness, says Bärbel Hönisch, a geochemist at Columbia University. “The authors had to do a lot of work to convince themselves of what they’re actually seeing.” When the team looked at CO2 levels from 1.5 million years ago, they found them on average quite similar to the postflip world, swinging between 204 and 289 ppm, depending on whether the world was in an ice age or not. “It’s surprising,” Yan says, given broad evidence that the world was warmer in the early Pleistocene, before the ice ages grew deeper. “The educated guess is you’d have higher CO2 to achieve that. But that’s not something we see.” That means that something other than a long-term CO2 decline was likely driving the cooling, says Peter Clark, a glaciologist at Oregon State University in Corvallis. One such driver could be the cumulative buildup of ice across the Northern Hemisphere; more ice would leave the world more arid, for example, allowing iron-rich dust to fertilize ocean microbes, encouraging them to absorb more CO2 from the atmosphere during glacial times. Clark has long advanced a hypothesis that repeated glaciations gradually scoured away soil and other loose grit that would have prevented ice from “sticking” to bedrock. Once that grit was gone, the anchored ice sheets could thicken and grow to a tipping point, sending the planet into 100,000-year cycles. Other subtleties in the ice’s CO2 levels point to other possible mechanisms. When the planet transitioned to 100,000-year ice ages, for example, levels of CO2 dropped on average 24 ppm lower during glacial periods compared with similar events in the previous era. That suggests the world was quite sensitive to CO2 and could have “flipped” thanks to something like a small disruption in the currents that drive carbon storage in the ocean—perhaps caused by ice sheet growth or something else, Hönisch says. Given its limitations, including a small amount of material collected by a narrow drill, the Allan Hills core is unlikely to settle debate on the ice age transition. However, its data are helping calibrate other, indirect methods of measuring ancient CO2, like using isotopic shifts in single-celled foraminifera fossils. As those methods have improved, their estimates have lined up with the new findings. “It’s a wonderful confirmation that the proxies are really working,” Hönisch says. Meanwhile, the team hasn’t stopped its exploration of the blue ice. “It’s conceivable that there’s ice as old, or even older, out there,” Yan says. Next month, a team led by Higgins will arrive in Antarctica to hunt for it. And this time, they’re bringing a bigger drill. source: https://www.sciencemag.org/news/2019/10/world-s-oldest-ice-core-could-solve-mystery-flipped-ice-age-cycles

A new study shows that increased heat from Arctic rivers is melting sea ice in the Arctic Ocean and warming the atmosphere. The study published this week in Science Advances was led by the Japan Agency for Marine-Earth Science and Technology, with contributing authors in the United States, United Arab Emirates, Finland and Canada. According to the research, major Arctic rivers contribute significantly more heat to the Arctic Ocean than they did in 1980. River heat is responsible for up to 10% of the total sea ice loss that occurred from 1980 to 2015 over the shelf region of the Arctic Ocean. That melt is equivalent to about 120,000 square miles of 1-meter thick ice. "If Alaska were covered by 1-meter thick ice, 20% of Alaska would be gone," explained Igor Polyakov, co-author and oceanographer at the University of Alaska Fairbanks' International Arctic Research Center and Finnish Meteorological Institute. Rivers have the greatest impact during spring breakup. The warming water dumps into the ice-covered Arctic Ocean and spreads below the ice, decaying it. Once the sea ice melts, the warm water begins heating the atmosphere. The research found that much more river heat energy enters the atmosphere than melts ice or heats the ocean. Since air is mobile, this means river heat can affect areas of the Arctic far from river deltas. The impacts were most pronounced in the Siberian Arctic, where several large rivers flow onto the relatively shallow shelf region extending nearly 1,000 miles offshore. Canada's Mackenzie River is the only river large enough to contribute substantially to sea ice melt near Alaska, but the state's smaller rivers are also a source of heat. Polyakov expects that rising global air temperatures will continue to warm Arctic rivers in the future. As rivers heat up, more heat will flow into the Arctic Ocean, melting more sea ice and accelerating Arctic warming. Rivers are just one of many heat sources now warming the Arctic Ocean. The entire Arctic system is in an extremely anomalous state as global air temperatures rise and warm Atlantic and Pacific water enters the region, decaying sea ice even in the middle of winter. All these components work together, causing positive feedback loops that speed up warming in the Arctic. "It's very alarming because all these changes are accelerating," said Polyakov. "The rapid changes are just incredible in the last decade or so." Authors of the paper include Hotaek Park, Eiji Watanabe, Youngwook Kim, Igor Polyakov, Kazuhiro Oshima, Xiangdong Zhang, John S. Kimball and Daqing Yang. source: https://www.sciencedaily.com/releases/2020/11/201107133922.htm

The International Maritime Organization (IMO) has issued a resolution for maritime cyber-risk management, effective January 2021. IMO Resolution MSC.428(98) affirms that maritime operators need to address cyber threats that risk the integrity and availability of technology systems. GPS/GNSS signal jamming and spoofing expose the vulnerabilities of PNT-reliant systems. The single point of failure in the signals used to synchronize military operations or determine a vessel’s location leaves maritime systems open to attack. With resilient PNT, maritime and naval vessels can rely on trusted data. Remote Operations at Sea. In September, Orolia participated in a Remotely Operated Service at Sea (ROSS) demonstration where an unmanned vessel was tele-operated from more than 800 kilometers (500 miles) away. With its SecureSync Interference Detection and Mitigation (IDM) suite, Orolia provided the project’s PNT cybersecurity package and delivered precise, reliable data for the control center to pilot the vessel from afar. The IDM suite includes GNSS threat detection and mitigation, as well as the option to include encrypted and alternative signals for use in GNSS-denied environments. After this successful demonstration, SeaOwl Group, the company leading the ROSS project, obtained the first remotely operated vessel navigation license in France. Diving Deep. Atomic clocks and oscillators are useful for underwater operations where RF signals are unavailable to provide accurate PNT data. Precision timing technologies, such as Orolia’s Spectratime mRO-50 oscillator, ensure stable timing for navigation systems through radar. They support missions such as: stabilizing and synchronizing sensor measurement data collection for autonomous underwater vehicles (AUVs) providing holdover to maintain precise positioning on submarines during extended periods of GNSS signal denial generating precise frequencies with low phase noise and less burden on radio receiver architecture, such as search-and-rescue control centers operating with low power consumption and increasing the reliability of radio reception. Resilient PNT is essential at sea, from military missions and commercial freight shipping to port management, search and rescue, research and fishing operations. Jamming and spoofing detection, threat mitigation, and alternative PNT sources configured in multiple layers of protection can ensure continuous operations, even in compromised environments. In shallow or deep-water environments, Orolia’s portfolio includes critical infrastructure support for naval command-and-control centers, essential GNSS vulnerability testing and services, and wearable solutions that fit in the palm of a hand. source: https://www.gpsworld.com/resilient-pnt-critical-to-maritime-advancement/