Selasa, 24 November 2020

A Floating Buoy Fleet Could Help Scientists Track Rising Seas - Eos

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As climate warms, thermal expansion of seawater and meltwater from ice over land that flows into the ocean both cause sea level rise, potentially threatening coastal communities and fragile coastal ecosystems. Rising sea levels therefore provide a way to measure climate change. Both local and global predictions of this rise rely on accurate sea level measurements.

Elipot proposes a new way to track sea level rise: a worldwide system of roving, satellite-tracked buoys. NOAA already maintains the Global Drifter Program, a fleet of freely drifting buoys, or surface drifters, that record ocean currents and other information, such as sea surface temperatures. These drifters are tracked by GPS to determine their 3D position on the surface of the ocean, but they transmit only their longitude and latitude to researchers, not their altitude, which could be used to estimate sea level, as Elipot suggests.

To obtain meaningful regional and global sea level information, surface drifters would need to be equipped with standardized and relatively accurate GPS receivers. According to Elipot’s simulations, an individual drifter’s daily random vertical error of 1.6 meters would be accurate enough to lead to an error of only 0.3 millimeter per year for global mean sea level decadal trend estimates. As buoys in this program generally last less than a year, equipping new buoys to transmit altitude measurements as they are deployed would mean the drifter fleet could begin reporting sea level data within a few years.

Global mean sea level is currently tracked using coastal tide gauges and satellite radar altimeters. The new research suggests that surface drifters would provide similar accuracy while extending the measurement range around the entire planet, rather than only near coasts or within the limited latitudes covered by reference altimeter satellites. (Geophysical Research Letters, https://doi.org/10.1029/2020GL091078, 2020)

—Elizabeth Thompson, Science Writer

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US, Russian Navies Get Into Brief Confrontation In Sea Of Japan - NPR

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The Russian navy's Admiral Vinogradov arrives for a five-day goodwill visit at the South Harbor of Manila in June 2018. The vessel was involved in an incident Tuesday in the Sea of Japan involving the USS John S. McCain. Eloisa Lopez/AFP via Getty Images hide caption

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The Russian navy's Admiral Vinogradov arrives for a five-day goodwill visit at the South Harbor of Manila in June 2018. The vessel was involved in an incident Tuesday in the Sea of Japan involving the USS John S. McCain.

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Russia says it caught a U.S. Navy ship illegally operating in Russian waters in the Sea of Japan and "chased off" the offending ship on Tuesday.

The area in question has been claimed by Russia as part of its territorial waters since 1984, but the U.S. does not recognize that claim.

The Admiral Vinogradov, a Russian destroyer, verbally warned the USS John S. McCain that it would be rammed if it didn't leave the area after it violated the boundary by more than a mile, according to Russia's Defense Ministry. The McCain, an Arleigh-Burke class destroyer, immediately returned to neutral waters after the warning, according to the Kremlin.

The John S. McCain (DDG-56) leaves a naval port in Busan, South Korea, in 2009. Jo Jung-ho/AP hide caption

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The John S. McCain (DDG-56) leaves a naval port in Busan, South Korea, in 2009.

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However, the U.S. is telling a different story. It says that the McCain "asserted navigational rights and freedoms in the vicinity of Peter the Great Bay in the Sea of Japan."

The 106-nautical mile closing line at the mouth of the bay is "inconsistent with the rules of international law as reflected in the Law of the Sea Convention," according to the Navy.

"This freedom of navigation operation upheld the rights, freedoms, and lawful uses of the sea recognized in international law by challenging Russia's excessive maritime claims," the Navy said in a statement.

Although not uncommon during the Cold War, the U.S. and Russian naval forces have had close encounters on the sea and air even in recent years. Russian ships and planes regularly challenge U.S. naval vessels.

Last year, the Admiral Vinogradov came within 50 to 100 feet of the USS Chancellorsville as the American ship was busy recovering a helicopter. The Chancellorsville had to take evasive action to avoid the Russian warship, the Navy says.

Russia's military said at the time that the two vessels were "heading in parallel directions" when the U.S. ship "impeded" its vessel.

In 2017, the McCain was involved in a collision with a tanker that killed 10 sailors.

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How Biden Should Handle the South China Sea Disputes - War on the Rocks

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The future of U.S.-Chinese relations may well hinge on disputes in a distant sea where the United States has no direct claims of sovereignty or unique maritime rights. The South China Sea is arguably at the crux of future U.S.-Chinese great-power relations. In addition to the critical Taiwan issue, the South China Sea is the arena where competing paradigms are clashing and the chance of war is more likely than anywhere else. While China views the South China Sea as the cornerstone on which to make its ambitions to become a superpower concrete, the United States sees the dispute as a key part of its security strategy and goal of strengthening alliances and strategic partnerships in the region. The incoming administration of President-elect Joe Biden  is unlikely to seek confrontation with China the way that President Donald Trump’s administration did. Yet, the new administration should seriously consider continuing some of the current U.S. strategies in the South China Sea, including strong support for Association of Southeast Asian Nations (ASEAN) states, strong condemnation of China’s illegal actions in the disputed sea, and support for disputants’ deterrence by denial capabilities. In any case, the administration should make it clear to China that the United States will not be leaving the region anytime soon.

U.S. Interests in the South China Sea

The U.S. government’s primary interests in the South China Sea are to maintain a free and open Indo-Pacific region and to deny China the ability to dominate the maritime arena. More specifically, the United States seeks to guarantee trade routes and free sea-lanes, strengthen defense ties with its allies and partners in the region, and balance China’s rising power. The official maritime objectives of the Department of Defense are to safeguard freedom of navigation for maritime vessels as recognized by the U.N. Convention on the Law of the Sea, deter conflict and coercion, and promote states to pursue international law. Until recently, the U.S. position had been deliberately ambiguous, taking no position on the validity of specific sovereignty claims. The U.S. government only expressed concern that China was not following the rules-based order set by the law of the sea. The United States had also done relatively little in response to the 2016 arbitration ruling in favor of the Philippines and against Chinese actions in the South Sea. This changed in July 2020 when U.S. Secretary of State Michael Pompeo announced his strong support of the ruling, chastising China’s claims as “completely unlawful,” and suggesting that the United States could come to the defense of the disputants if targeted by China.

The United States has responded to the South China Sea dispute and its growing rivalry with China in multiple ways. Starting with the Obama administration’s Asia pivot strategy in 2011, which was toughened by the Trump administration, the United States conducts freedom of navigation operations in the disputed waters, pursues multistate exercises in the region, places diplomatic pressure on China for its illegal construction and militarization of maritime features and the over-extensive nine-dash line claim, and pursues targeted economic sanctions on Chinese companies involved in the reclamation, building, and militarization of artificial islands. The 2017 National Security Strategy directly calls out China for its militarization of artificial islands seized by China, threatening the free flow of trade and sovereignty of other states, and undermining regional stability. The National Security Strategy explicitly states that the United States will “maintain a forward military presence capable of deterring and, if necessary, defeating any adversary,” with an implicit focus on China.

U.S. Strategies and Operations

The United States has carried out 23 freedom of navigation operations since October 2015, with frequency and intensity increasing each year. The official purposes of these operations are to challenge excessive maritime claims and to ensure freedom of navigation, but unofficially, they credibly signal resolve and U.S. capabilities while limiting the potential for military escalation. Although the United States justifies the operations strictly in the context of upholding a broader worldwide position on freedom of navigation, they indirectly serve as part of the U.S. deterrence strategy against China. From China’s perspective, even if freedom of navigation operations are conducted in all claimants’ waters, they are clearly targeted at China.

In July 2020, the United States sent two aircraft carrier strike groups — the Nimitz and Ronald Reagan — to conduct freedom of navigation operations and naval drills in the South China Sea, which were conducted at the same time as Chinese naval exercises in disputed waters. The U.S. Navy has also conducted several joint military exercises and carrier group transits with allies and security partners in the region, through or near the South China Sea. In 2019 alone, the United States conducted 85 military exercises — including Balikatan conducted with the Philippines, Singapore, and Thailand, and Rim of the Pacific, the largest international maritime exercise, involving the armed forces of 10 states, including Japan, South Korea, Thailand, Malaysia, Indonesia, and Singapore, and until a couple of years ago, China, before it was kicked out.

The combined U.S. strategy of freedom of navigation operations, promotion of a rules-based order, military exercises, and support for allies and strategic partners in the region are designed to send a clear signal to China that the United States will continue to maintain its military presence in the region as well as to support its regional allies and security partners. These current strategies are all necessary, but not sufficient. China continues to flout international law, pursue low-level coercive actions against the Philippines, Vietnam, Malaysia, Taiwan, and Indonesia, and challenge the U.S. military presence in the region. China does all this through anti-access/area denial (A2/AD) strategy, and more recently, power projection. Most importantly, both the Obama and Trump administrations have been unwilling to actively deter China from seizing and militarizing many maritime features that China has built into artificial islands or outposts in the South China Sea due to the fear of military engagement. The United States is understandably unwilling to engage militarily with China, but this caution also holds back America’s ability to effectively signal full resolve for the U.S. intolerance of China’s actions in the South China Sea.

Strategy Options for the Next Presidential Administration

The most important U.S. objective in the South China Sea is to counter China’s territorial and maritime claims. The Trump administration’s more overt and aggressive position against China has effectively deterred China from seizing more maritime features, but this deterrence did not effectively prevent further militarization of the artificial islands that it controls. In the past four years, the Chinese have deployed surface-to-air (HQ-9B) missile systems and anti-ship cruise missile (YJ-12B and YJ-62) systems and positioned an increasing number of Shenyang J-11 fighters and Xian H-6 bombers on several artificial islands that China controls. This militarization provides China with extended reach into the Pacific, within target range of U.S. territories and bases. The Biden administration will have to consider how to deter through denial Chinese targeting of U.S. ships and bases and further Chinese reach into the Pacific. Rather than threatening severe punishment, deterrence by denial makes actions infeasible or unlikely to succeed. Such deterrence would ideally deny further Chinese seizures of maritime features and prevent building up of ones already acquired, particularly Scarborough Shoal, located in the Philippines Exclusive Economic Zone. It is critical to meet this objective because China’s long-term goal is to acquire effective control of most or all of the maritime features in the South China Sea. This strategy will have to involve increasing resources for the Indo-Pacific Command and matching the intentions laid out by successive secretaries of defense.

Support for Southeast Asian States

The United States needs to clearly signal strong support of Southeast Asian states, both those involved in the dispute and other members of ASEAN, all of whom are being wooed economically by China. China’s intention is to persuade these states to bandwagon with China instead of balancing against China on the side of the United States. Already, a handful of ASEAN member states are ardently pro-Chinese — including Cambodia, which appears to be allowing China to build a base on its territory — or leaning toward China, including the Philippines under President Rodrigo Duterte. If China can effectively persuade states in Southeast Asia that the United States is not credibly willing to support them, the United States could risk these states moving into China’s sphere of influence. Despite sustained military presence, stated alliance commitments, and partnership support, the Trump administration’s record of support for these states is weak. The Biden administration should be explicit and forthcoming in its support to bolster regional security partners in their own military capabilities, many of which are dated and insufficient to defend against Chinese actions in the South China Sea. The United States could provide more reasonably priced military transfers to these states, such as surveillance drones, sea mines, land-based anti-ship missiles, fast attack missile boats, and mobile air defense. The recent announcement by the Trump administration of plans to sell Harpoon missile systems to Taiwan exemplifies such potential military transfers in the region.

Since China should continue to operate, supply, and defend the artificial islands that it built, the United States should provide support to its allies and security partners in the region that would help to frustrate the ease of Chinese movement in the South China Sea. Although several Chinese controlled islands are already built and militarized, without logistical support, the remote outposts could be considered “dead wood.” Therefore, increased deterrence by denial can slow down China’s ability to resupply the artificial islands it controls. A 2017 assessment of regional military capabilities argues that in the long run, China will be unable to enforce its maritime claims in the South and East China Seas if its neighbors are able to engage in A2/AD strategies against China and the United States is able to bolster and support such efforts. This assessment suggests that China’s neighbors could have better naval capabilities than perceived. Specifically, on the southern (Indonesian and Malaysian) and western (Vietnamese) borders of the sea, Southeast Asian states have achieved A2/AD capabilities that can deny China’s ability to command sea and air in the disputed waters. These states already have some denial capabilities that include warships armed with anti-ship missiles, aerial capabilities, and submarines that together would help deter Chinese air and sea command of these parts of the disputed seas. Extending these capabilities with U.S. support and further joint exercises with these states could better deter China’s enforcement of its maritime claims and control of maritime features, and challenge China’s consolidation of its control and command of the disputed sea. Although the maritime features controlled by China are unlikely to be overturned, the United States and its partners can work to prevent further militarization and acquisitions if they recalibrate and extend deterrence in the region.

Stronger Support from U.S. Allies

U.S. allies Japan, Australia, and India — members of the Quadrilateral Security Dialogue — as well as South Korea, France, and the United Kingdom, should continue to play an increasing role in deterrence of Chinese expansionism jointly with the United States, militarily, politically, and economically. U.S. allies could participate in multinational deployments to international waters in the South China Sea beyond freedom of navigation operations, particularly in joint operations and exercises with disputants challenged by China. These allies should also consider increasing military and economic support for Southeast Asian states to help U.S. efforts to ensure balancing against China, and not bandwagoning with China. As members of the Quad, Japan and Australia have stepped up, while South Korea and other allies could and should follow suit.

Up to this point, U.S. strategies have partially deterred China’s continued militarization and expansionism in the South China Sea and broader Pacific region. The Biden administration should continue to credibly and assertively deter China’s strategies in the South China Sea in several ways.  These means include continued freedom of navigation operations and joint military exercises, stronger and more credible support for Southeast Asian states, consistent and greater involvement by U.S. allies to balance China’s rise, increased training for war fighting scenarios, and targeted sanctions on Chinese companies that are involved in the building or militarization of the artificial islands, or surveying in the waters of the South China Sea. The United States should be willing to follow through with the costly signals of resolve and deterrence, being prepared for some risky engagement with Chinese vessels. The Biden administration should seriously follow through on the intentions of the Obama administration’s Asia pivot, but also consider continuing some of the Trump administration’s actions. Neutralizing Chinese domination of the South China Sea deserves to be the highest priority for the next presidential administration.

Krista E. Wiegand is Director of the Global Security Program at the Howard H. Baker Jr. Center for Public Policy and Associate Professor of Political Science at the University of Tennessee. She is a specialist in territorial and maritime disputes, maritime law, and East Asian security.

Image: Nicholas V. Huynh

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November 24, 2020 at 03:48PM
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Senin, 23 November 2020

Sea Level Watcher Takes Flight - nasa.gov

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A joint U.S.-European satellite, built to monitor global sea levels, lifted off on a SpaceX Falcon 9 rocket from Vandenberg Air Force Base just after 9 a.m. Pacific Time on November 21, 2020. About the size of a small pickup truck, Sentinel-6 Michael Freilich will extend a nearly 30-year continuous dataset on sea surface height.

The satellite’s principal instrument is a radar altimeter, which monitors the height and shape of the ocean’s peaks and valleys—known to scientists as ocean surface topography. Radar altimeters continually send out pulses of radio waves (microwaves) that bounce off the surface of the ocean and reflect back toward the satellite. The instrument calculates the time it takes for the signal to return, while also tracking the precise location of the satellite in space. From this, scientists can derive the height of the sea surface directly underneath the satellite.

Sentinel-6 Michael Freilich will continue a sea level record that began in 1992 with the TOPEX/Poseidon satellite and continued with Jason-1 (2001), OSTM/Jason-2 (2008), and Jason-3 (2016). Together, these satellites have provided long-term, precise measurements of sea level height while tracking the rate at which our oceans are rising in response to global warming. Sentinel-6 Michael Freilich will eventually pass the baton to its twin, Sentinel-6B, scheduled for launch in 2025.

“Together, these satellites will let us keep measuring global sea levels for another full decade,” said Josh Willis, the NASA Project Scientist for the mission and an ocean scientist at NASA’s Jet Propulsion Laboratory. “It is the first time we have been able to launch one of these while its predecessor is still young. Jason-3 is still within its design life, and that is a big deal for us because to keep the record accurate when it gets handed off from one satellite to the next, we really need them overlap so we can cross-calibrate.”

The time-lapse video above shows the plume of exhaust from the Falcon 9 in the 25 minutes after the rocket launched from California. The images were acquired with the Advanced Baseline Imager (band 2/red) on GOES-17. The satellite is operated by the National Oceanic and Atmospheric Administration (NOAA), and NASA helps develop and launch the GOES series.

The spacecraft is named in honor of Michael Freilich, the former director of NASA’s Earth Science Division and a leader in advancing ocean observations from space. Freilich retired in 2019 and passed away on August 5, 2020. His close family and friends attended the launch of the satellite that now carries his name.

“Michael was a tireless force in Earth sciences. Climate change and sea level rise know no national borders, and he championed international collaboration to confront the challenge,” said Josef Aschbacher, the director of Earth observation programmes for the European Space Agency (ESA). “It is fitting that a satellite in his name will continue the ‘gold standard’ of sea level measurements for the next half-decade.”

“The Earth is changing, and this satellite will help deepen our understanding of how,” said Karen St. Germain, director of NASA’s Earth Science Division. “Changing Earth processes are affecting sea level globally, but the impact on local communities varies widely. International collaboration is critical to both understanding these changes and informing coastal communities around the world.”

After arriving in orbit, the spacecraft separated from the rocket’s second stage and unfolded its twin sets of solar arrays. Ground controllers successfully acquired the satellite's signal, and initial telemetry reports showed the spacecraft is in good health. Sentinel-6 Michael Freilich will now undergo a series of exhaustive checks and calibrations before it starts collecting science data in a few months.

The initial orbit of Sentinel-6 Michael Freilich is about 20 kilometers (12 miles) lower than its ultimate operational orbit of 1,336 kilometers (830 miles). In about a month, the satellite will receive commands to raise its orbit, trailing Jason-3 by about 30 seconds. Mission scientists and engineers will then spend about a year cross-calibrating the data collected by the two satellites. Sentinel-6 Michael Freilich will then take over as the primary sea level satellite and Jason-3 will provide a supporting role until the end of its mission. Scientific instruments on both satellites will also make atmospheric measurements that can be used to complement climate models and help meteorologists make better weather forecasts.

Sentinel-6 Michael Freilich and Sentinel-6B compose the Sentinel-6/Jason-CS (Continuity of Service) mission developed in partnership with ESA, NASA, and NOAA. NASA JPL is contributing three science instruments to each Sentinel-6 satellite: the Advanced Microwave Radiometer for Climate, the Global Navigation Satellite System—Radio Occultation, and the Laser Retroreflector Array. NASA is also contributing launch services, ground systems and data support, and support for the U.S. component of the international Ocean Surface Topography Science Team.

To learn more about sea surface height and the long international collaboration to study it, read Taking a Measure of Sea Level Rise: Ocean Altimetry.

To learn more about Sentinel-6 Michael Freilich, visit the mission home pages at the European Space Agency, NASA, the European Union’s Copernicus program, and EUMETSAT.

Looking for data related to sea level rise? The Sea Level Change Data Pathfinder on NASA’s Earthdata site highlights tools used by researchers to study ocean altimetry, including the Integrated Multi-Mission Ocean Altimeter Data for Climate Research.

NASA Earth Observatory video by Joshua Stevens, using GOES 17 data from NOAA and the National Centers for Environmental Information (NCEI). Photographs courtesy of SpaceX. Story assembled from NASA and ESA press releases by Mike Carlowicz.

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Destroyer USS Donald Cook Now Operating in the Black Sea - USNI News - USNI News

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The Arleigh Burke-class guided-missile destroyer USS Donald Cook (DDG-75) conducts a personnel transfer in Souda Bay, Greece, Nov. 17, 2020. U.S. Navy Photo

Destroyer USS Donald Cook (DDG-75) moved into the Black Sea on Monday, U.S. 6th Fleet announced.

The Arleigh Burke-class destroyer’s arrival in the Black Sea marks the seventh trip for an American warship to the waters this year, the service said in a news release.

“Operating in the Black Sea signifies our commitment to partners and allies in the region,” Cmdr. Kelley Jones, Donald Cook’s commanding officer, said in a statement. “It is an important diplomatic mission, and Donald Cook has enjoyed the hospitality of Black Sea countries many times before.”

Donald Cook’s transit comes after Egyptian ships headed to the Black Sea last week to perform exercises with the Russian navy, according to a report in Al-Ahram, Egypt’s government-owned newspaper.

“The joint maritime drill Friendship Bridge 3 is one of the most important joint exercises between Egypt and Russia to transfer and exchange experiences between the armed forces of both countries,” reads a statement from Egypt’s army, as reported by the state-run newspaper.

In September, USS Roosevelt (DDG-80) sailed into the Black Sea to perform drills with the Ukrainian navy, USNI News previously reported. Roosevelt’s transit marked the sixth trip this year for an American warship into the waters.

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Shift in atmospheric rivers could affect Antarctic sea ice, glaciers - Science Daily

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Weather systems responsible for transporting moisture from the tropics to temperate regions in the Southern Hemisphere have been gradually shifting toward the South Pole for the past 40 years, a trend which could lead to increased rates of ice melt in Antarctica, according to new research.

Atmospheric rivers are long, narrow jets of air that carry huge amounts of water vapor from the tropics to Earth's continents and polar regions. The new study finds atmospheric rivers in the Southern Hemisphere are shifting due in part to ozone depletion, greenhouse gas emissions and natural variations in sea surface temperature.

This shift of atmospheric rivers may affect moisture and heat transported into Antarctica, said Weiming Ma, an atmospheric scientist at UCLA and lead author of the new study published in the AGU journal Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

"The most important implication of our finding is that due to this shift, more atmospheric rivers are expected to make landfall over Antarctica, which will have effects on the surrounding sea ice and glaciers on the continent," Ma said.

A River from Thin Air

Atmospheric rivers form when warm, turbulent air from the tropics encounter cold fronts in mid-latitude regions. The narrow band between these two competing air masses grows thick with condensed water vapor as temperatures drop in the region of saturated air.

Sometimes measuring thousands of kilometers in length, these cloud systems can contribute up to 60% of the annual precipitation in some regions, such as California, Chile and western Europe.

In the past, scientists have used simulations to predict the future occurrence of atmospheric rivers over western Europe, showing that these weather patterns are likely to become more common under a warming climate. However, since their direction and movement are determined in large part by Earth's jet streams, and as the westerly jet is expected to shift toward the North Pole in future climate models, researchers predict that atmospheric rivers will likely move poleward as well.

But the new study found atmospheric rivers in the Southern Hemisphere have already been following this trend, steadily creeping toward the South Pole for at least the last four decades. Using simulations based on multiple models and datasets spanning back to 1979, the researchers looked for broad trends and potential mechanisms that might explain observed patterns.

A Cloudy Outlook

According to modeling results from the new study, at least part of the observed trend can be explained by increases in greenhouse gas emissions and ozone depletion over Antarctica and their corresponding effect on temperature gradients between the equator and South Pole; however, the shift also appears to be driven by natural, long-term changes in sea surface temperatures.

"We found evidence for cooling over the equatorial Pacific and the Southern Ocean, which is caused by a pattern called the inter-decadal Pacific Oscillation," said Ma. "This is a natural pattern that takes place over multiple decades and one that isn't driven by human activity."

These cooler patterns in sea surface temperature pull the westerly jet stream further south, pushing atmospheric rivers along with them. It's unclear exactly how this might affect rain and snowfall patterns over South America, but it seems likely that portions of Antarctica will experience increased rates of ice melt as a result, according to the researchers.

"Global sea level change depends critically on the fate of the Antarctic ice sheet, and that ice is impacted by how many atmospheric rivers hit Antarctica and how strong they are," said Marty Ralph, the director for the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography, who was not involved in the new study.

While atmospheric rivers over East Antarctica have been associated with increased snowfall accumulation in some years, they seem to have the opposite effect on the other side of the continent. According to research published in 2019 that used a similar dataset, an average of only 12 atmospheric rivers a year make their way across the western portion of Antarctica, yet they contribute up to 40% of the summer ice melt in some areas and appear to be responsible for the majority of ice melt in winter and in high-elevation glaciers.

Large ice melts in West Antarctica are still fairly rare, occurring only a few times each decade. However, scientists warn that increasing temperatures due to global climate warming and the shifting occurrence of atmospheric rivers in the southern hemisphere will likely cause the frequency and severity of those melting events to increase in the near future.

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Largest aggregation of fishes in abyssal deep sea - Science Daily

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The largest aggregation of fishes ever recorded in the abyssal deep sea was discovered by a team of oceanographers from the University of Hawai'i at Manoa (UH, USA), Monterey Bay Aquarium Research Institute (MBARI, USA) and the National Oceanography Centre (NOC, UK). Their findings were published recently in Deep-Sea Research.

"Our observations truly surprised us," said Astrid Leitner, lead author on the study, who conducted this work as graduate researcher in the UH Manoa School of Ocean and Earth Science and Technology (SOEST). "We had never seen reports of such high numbers of fishes in the sparsely-populated, food-limited deep-sea."

The researchers, including Leitner, Jennifer Durden (NOC) and professors Jeffrey Drazen (Leitner's doctoral research advisor) and Craig Smith, made the observation on an expedition to the Clarion Clipperton Zone (CCZ). The CCZ is a large region stretching nearly from Hawai'i to Mexico, which is being explored for deep sea mining of nodules containing metals such as copper, cobalt, zinc and manganese.

Abyssal seamounts, deep underwater mountains whose summits are 9,800 ft (3,000 m) below the sea surface, dot the deep seascape and are some of the least explored habitats on the planet. During the expedition, the research team sampled three of these seamounts and their surrounding plains as part of an effort to establish an ecological baseline prior to extraction activities.

On the summit of one of the three previously unmapped and completely unexplored seamounts, the team captured on video a swarm of 115 cutthroat eels (Family Synaphobranchidae) at a small bait package containing about two pounds (1 kg) of mackerel. A few eels were caught in a baited trap and identified to be of the species Ilyophis arx, a poorly known species with fewer than 10 specimens in fish collections worldwide.

These eels were observed at the top of all of the seamounts, but not on the surrounding abyssal plain. The findings provide evidence for an abyssal seamount effect (where these mountains can support much higher numbers of animals than other surrounding habitats), and also indicate these eels are likely to be seamount specialists.

After returning from the expedition, the team determined they had documented the highest number of fishes ever been recorded at one time in the abyssal ocean -- almost double the previous record.

"If this phenomenon is not just isolated to these two seamounts in the CCZ, the implications on deep sea ecology could be widespread," said Leitner, who is now a postdoctoral researcher at the Monterey Bay Aquarium Research Institute. "Our findings highlight how much there is still left to discover in the deep sea, and how much we all might lose if we do not manage mining appropriately."

Story Source:

Materials provided by University of Hawaii at Manoa. Original written by Marcie Grabowski. Note: Content may be edited for style and length.

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