Source: Global Biogeochemical Cycles

Marine life plays a pivotal role in Earth’s carbon cycle. Phytoplankton at the base of the aquatic food web take up carbon dioxide from the atmosphere, convert it to organic carbon, and move it around as they become food for other organisms. Much of this carbon eventually returns to the atmosphere, but some ends up sequestered in the deep ocean via a process called carbon export.

Quantifying carbon export to the deep ocean is critical for understanding changes in Earth’s climate. Measurements in the Southern Ocean, a key region for global ocean circulation and a substantial carbon sink, are especially important but have been sparse, particularly in areas with sea ice that are difficult to access.

To address that gap, Liniger et al. used data from 212 autonomous, floating instruments known as Biogeochemical-Argo (BGC-Argo) floats to estimate carbon export across the Southern Ocean basin. These floats roam the upper 2,000 meters of the ocean, can travel beneath sea ice, and are equipped with sensors that measure physical and biogeochemical properties of seawater.

Though prior studies have used BGC-Argo data to estimate Southern Ocean carbon export, most focused on narrow regions or timescales and excluded sea ice–covered areas. The new analysis uses data collected between 2014 and 2022 by floats scattered across the entire ocean basin, including under sea ice. After developing a novel method to calculate carbon export using the floats’ measurements of sinking particulate organic carbon and dissolved oxygen change over time, the researchers estimated that about 2.69 billion tons of carbon sink to the deep sea each year in the Southern Ocean.

Their findings also suggest that carbon export varies significantly in different parts of the Southern Ocean, with only about 8% occurring in seasonally ice-covered areas. But the researchers say more investigation is needed to clarify the role of the highly active ecosystems in the sea ice zone, especially as climate change drives shifts in sea ice dynamics. (Global Biogeochemical Cycles, https://doi.org/10.1029/2024GB008193, 2025)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2025), Robotic floats quantify sinking carbon in the Southern Ocean, Eos, 106, https://doi.org/10.1029/2025EO250193. Published on 27 May 2025.

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Eos is welcoming June (that’s National Ocean Month in the United States) with a rhyming tradition of something old, something new, something borrowed, and something blue.

Our “something old” is the spectacularly upgraded, 60-years-young Alvin, probably the world’s most famous human-occupied deep-sea submersible. Alvin can now dive to 6,500 meters—a full 2,000 meters more than its previous limit—and explore 99% of the seafloor. Read all about it in “An Upgraded Alvin Puts New Ocean Depths Within Reach.”

“Something new” is the two-vehicle fleet of midsize remotely operated vehicles (mROVs) that will join the U.S. Academic Research Fleet. The mROVs will “fill the niche between large, work-class vehicles such as Jason and small vehicles used primarily for observation.”

“Something borrowed” is time on the JOIDES Resolution (JR), the legendary research vessel that retired last year. In this month’s opinion, three early-career researchers share what they learned, from sediment cores to transdisciplinary collaboration, as part of the JR’s final voyage.

Something blue? That’s the deep blue sea, of course. Dive in!

—Caryl-Sue Micalizio, Editor in Chief

Citation: Micalizio, C.-S. (2025), Submerged in science, Eos, 106, https://doi.org/10.1029/2025EO250199. Published on 22 June 2025.

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Boots On the Ground

Seen from above, the dozens of people trekking through the Rwenzori Mountains might have looked something like an ant farm branching across the landscape, said Klaus Thymann. The expedition into the range on the border between Uganda and the Democratic Republic of the Congo included Thymann, an environmental scientist; Heïdi Sevestre, a glaciologist at the Arctic Monitoring and Assessment Programme; guides from the Uganda Wildlife Authority (UWA); and—predominantly—interested community members there to help with logistics.

The group was there in August 2024 to survey ice on the range’s three tallest peaks and to create the first 3D model of the glaciers on Mount Stanley, whose apex, Margherita Peak, is the third highest in Africa at 5,109 meters (16,763 feet).

“It’s really a team work, and a very good one,” said Thymann, founder and director of Project Pressure, a nonprofit organization focused on environmental issues.

Their newly analyzed data confirmed that Mount Speke, the second-highest peak in the range, no longer hosts a glacier (only static ice) and that Mount Baker, the third highest, is practically ice free. The researchers found that the surface area of the Stanley Plateau glacier fell by 29.5% between 2020 and 2024.

“Glaciers worldwide are shrinking or disappearing, so that’s not a surprise,” Thymann said. “I think what is surprising is how rapid it’s going.”

Jim Russell, a climate scientist and geochemist at Brown University who was not involved in the research, has been making expeditions to the Rwenzori Mountains since 2006. He called these glaciers a “canary in a coal mine.”

“The recent retreat is really significant, and it’s illustrating substantial climate change is happening at high elevations,” he said.

Sleeping Bags, Licorice, and Drones

Aside from essentials, such as sleeping bags and licorice (“It’s all about the amount of flavor you can get with the least amount of volume,” Thymann explained), the crew carried an array of equipment, including a generator, fuel and cables for the generator, three drones, and GPS hardware.

“There’s no roads, there’s no helicopters, there’s not even a donkey,” Thymann said. “Everything has to be carried in, so that makes science challenging because the logistics are difficult.” With the weight of equipment and the need to acclimate to the elevation, it’s a 5-day trek from the entrance of Rwenzori Mountains National Park up through tropical, bamboo, and alpine forests to the Stanley Plateau.

Thymann led expeditions to the area in 2012, 2020, and 2022. In 2020, the team captured images of the plateau with consumer drones, then used photogrammetry to create a digital elevation model of the area.

When they returned in 2024, they went one step further. They used a surveying system to determine the precise GPS coordinates of eight points along the plateau, then set up a brightly colored target on each point. When they flew drones over the area to capture more than 850 photos, they could not only create a model but also anchor it to precise GPS coordinates. They also used the points to retroactively anchor the 2020 model. By comparing the two models, they determined the extent of ice loss on the plateau.

Sevestre, the glaciologist, also used ground-penetrating radar to determine the depth of the glaciers. “If you want to know volume, you have to know three dimensions. You have to know the x, the y, and then the z,” Thymann said. “Nobody knew the z, so nobody knew the depth.”

The researchers expect to publish more detailed findings, including glacier volume, in late 2025.

Russell said he was “amazed” the researchers were able to do this work in this remote area. Though there is no standard way of mapping glaciers, he added that the Rwenzori Mountains’ glaciers have historically been mapped simply by tracing the movement of their edges. The Project Pressure team is “not just tracing the lowest elevation of the glacier,” he said. “They’re also able to kind of see the sides, see how that’s shrinking, potentially see it thinning from the top.”

Protecting the Home of Gods

The dwindling of Rwenzori’s ice may be a bellwether of glaciers’ futures worldwide, but closer to home, its effects are already being felt.

The ice on the mountain range is the highest source of water for the River Nile and holds water that millions of Ugandans rely upon. Trekking tourism to Rwenzori Mountains National Park, a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site, also bolsters the local economy.

“This ice supports the people of the communities living around it, 100%,” said Masereka Solomon, a tour guide in Uganda who began working with Thymann in 2012. Solomon has lived in the area for 34 years—his whole life—and has watched the ice retreat firsthand. For him and other Bakonzo people who live in the foothills of the Rwenzori Mountains, the glaciers also hold a deep religious and cultural significance, as they believe that their gods live in the ice atop the mountains.

“We believe if we protect this mountain, if we fight hard to maintain the small ice, or the small glaciers that [remain], our gods will not be homeless,” Solomon said.

Thymann emphasized the role of the dozens of community members during the expeditions, from helping transport equipment up the mountain to spotting the drones and returning regularly to maintain time-lapse cameras. He and the other Project Pressure researchers analyze the data and share the results with UWA and locals.

He added that though the Bakonzo people understand that the retreating ice is caused by climate change, he hopes that this more detailed data can “empower” the community and that sharing these findings widely will raise awareness of Uganda’s shrinking glaciers.

—Emily Dieckman (@emfurd.bsky.social), Associate Editor

Citation: Dieckman, E. (2025), A new 3D map shows precipitous decline of Ugandan glaciers, Eos, 106, https://doi.org/10.1029/2025EO250126. Published on 3 April 2025.

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Boots On the Ground

In mid-January, a team of scientists were sailing aboard a research vessel in frigid Antarctic waters. They planned to investigate an unexplored section of the Bellingshausen Sea and the creatures that live there, but were stymied by more sea ice than they expected.

“We found ourselves restricted to a smaller area,” said Patricia Esquete, a marine biologist at the Universidade de Aveiro in Portugal and expedition co–chief scientist. “Instead of Bellingshausen Sea, we were restricted to the Ronne Entrance.” The team made the most of the situation, and their research vessel, Schmidt Ocean Institute’s R/V Falkor (too), settled in to conduct science operations in front of the ice shelf.

While checking satellite images of sea ice extent, they noticed that a crack had formed along the edge of the George VI ice shelf about 30 kilometers from their location. They jotted it down but didn’t worry about any dangers it posed. Such cracks can take weeks or months to fully force a break from the shelf and form an iceberg, Esquete explained.

But when the next batch of satellite images came through a few days later, the team was surprised to see that a 510-square-kilometer (209-square-mile) iceberg had broken off and was drifting along (and occasionally bumping against) the coast of the Antarctic Peninsula. The departure of the Chicago-sized iceberg, A-84, revealed a patch of polar seafloor that had been covered by ice for years, and possibly centuries.

“As soon as we realized that the iceberg had moved on and left that space for us to sample, we immediately decided to go there and see [what] the seafloor looks like under the ice,” Esquete said. When they arrived, they found a thriving ecosystem rivaling those in nutrient-rich open waters.

Luck and Daring

Before A-84 calved, the team was poised to document the biodiversity of a nearby deep-sea ecosystem, collect sediment samples, study underwater ocean dynamics, and create seafloor maps.

“A holy grail for oceanography is not only mapping the entirety of the deep seabed in high resolution in terms of its shape and structure, but also in terms of specifically what lives there and how,” said Dawn Wright, an oceanographer and chief scientist at Environmental Systems Research Institute (Esri) in Redlands, Calif., who was not involved with this expedition.

Sea ice impedes that goal: Research vessels can’t get too close to the ice shelf, and remotely operated vehicles (ROVs) and autonomous underwater vehicles can travel only so far from the ship to explore under the ice.

The procedures involved in securing funding and scheduling a ship can make seagoing research in the Antarctic a slow process, explained Joan Bernhard, a biological oceanographer at Woods Hole Oceanographic Institution in Massachusetts. Planning an expedition like the one in January can take years or even decades, with few exceptions.

Some expeditions have been able to mobilize when seafloor is newly exposed. After Larsen C calved in 2017, for example, research vessels arrived in the area about a year later—much faster than average. Changes at the surface take time to affect the seafloor, but even with such a quick response time, researchers still missed the opportunity to establish a precalving baseline.

After most calvings, “any newly exposed seafloor will have been subject to open-water conditions for years; currents could import alien species potentially impactful to indigenous taxa,” said Bernhard, who was not involved with the Falkor (too) expedition.

Iceberg A-84 calved on 13 January. Falkor (too) reached the newly exposed seafloor just 12 days later.

After relocating, the researchers conducted the same suite of science observations they had originally planned, just in the newly exposed location. Thanks to the quick pivot, the team was able to observe the area as if it were still covered by the ice—an “incredibly rare” opportunity, Bernhard said.

“In my view, nowhere has serendipity in ocean science proved more critical,” Wright said of the expedition. Operating in those conditions is hard enough, and it’s even tougher to be in the right place at the right time, she added.

Esquete acknowledged the expedition’s fortune. “Good luck played a huge role. We cannot deny that,” she said. “But there’s also value in daring to explore the unexplored.” The team would have missed the opportunity had they not already been exploring one of the most remote parts of the world.

Thriving Beneath the Ice

The researchers collected sediment samples, used lidar to create bathymetric maps, and studied the water column and ocean currents. They are still analyzing those data. They also deployed the ROV SuBastian to document the biodiversity of the deep sea and found a thriving ecosystem spanning the trophic web: corals, sponges, invertebrates, cephalopods, king crabs, and krill, as well as a few unknown species.

“I was excited to see what appeared to be meter-tall sponges, ‘giant’ pycnogonids (sea spiders), and large ophiuroids (brittle stars), all similar to those known from the McMurdo Sound region,” Bernhard said.

“What surprised me was the sheer variety of organisms that were found, as well as the huge sizes of some of the deep-sea sponges that had apparently been growing for hundreds of years under such harsh Antarctic conditions,” Wright said.

What’s more, the team found several species that filled discrete ecological niches, which suggested that the ice-covered ecosystem received a steady, high-level influx of nutrients and may have been there for a while, Esquete said.

“Basically, we found the same type of ecosystems that you can expect in that area of the Bellingshausen Sea,” Esquete said. But unlike the other areas the team studied, this ecosystem thrived “in an area that’s been permanently covered by ice for probably centuries.”

That in itself was surprising, she said. Most deep-sea ecosystems that aren’t covered by thick ice receive nutrients that trickle down from photosynthetic organisms near the surface. Scientists think that nutrients carried on deep-sea currents supply nutrients to benthic ecosystems where ice prevents top-down nutrient delivery.

“I was mildly surprised by the plethora of sea anemones on a boulder adjacent to a barrel sponge because all are filter feeders,” Bernhard said. “Such abundance implies currents are strong enough to transport sufficient organic matter to this area.”

A Future Without Ice

The Falkor (too) researchers returned to the mainland after weeks studying the newly discovered Bellingshausen habitat. They already hope for a return trip to investigate how that patch of seafloor changes now that its icy cover has drifted off. Nutrients trickling down from photosynthetic algae might now be available, but the ecosystem has already adapted to and thrived on a lower nutrient supply.

“Open-water conditions may imperil these ecosystems,” Bernhard said. “More settlement of organics to the seafloor…could cause an ecological imbalance.”

As climate change melts Antarctic ice, this ecosystem could be a bellwether for changes across polar ecosystems.

“The accelerating loss of polar ice that protects these ecosystems, including channeling of nutrient-rich currents to them, does not bode well for their vitality,” Wright said. “But there is so much that we just don’t know. The oceanographic community will be watching the results of this expedition as they become available with intense interest. It has direct bearing on the overall health of the planet.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2025), Thriving Antarctic ecosystem revealed by a departing iceberg, Eos, 106, https://doi.org/10.1029/2025EO250124. Published on 31 March 2025.

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Editors’ Highlights are summaries of recent papers by AGU’s journal editors.

Source: Journal of Geophysical Research: Earth Surface

Rock debris on glacier surfaces substantially modifies their behavior in comparison with climatically equivalent clean-ice glaciers. However, glacier-scale observations of the evolution of debris-covered glacier surfaces over multiple years and at the level of detail sufficient to explore these processes are rare.

Kraaijenbrink and Immerzeel [2025] present a unique dataset obtained from drone surveys of Langtang and Lirung Glaciers in the Nepal Himalaya between 2013 and 2018. The survey period includes the magnitude 7.8 2015 Gorkha earthquake, which caused a short-lived increase in velocity for Langtang Glacier and may have changed the glaciers’ internal structure.

The survey results are surprising, providing a first look at the complexity of processes that operate across the surfaces of debris-covered glaciers. The observed changes in glacier surface elevation, and hence ice volume, are highly spatially heterogeneous within and between years. However, when surface elevation change is considered over multiple years, and displacement by ice flow is accounted for, a different picture emerges, and the differences in mass balance and surface changes are reduced across and between the glaciers.  

Citation: Kraaijenbrink, P. D. A., & Immerzeel, W. W. (2025). Spatial and temporal variability of the surface mass balance of debris-covered glacier tongues. Journal of Geophysical Research: Earth Surface, 130, e2024JF007935. https://doi.org/10.1029/2024JF007935

—Ann Rowan, Editor-in-Chief, JGR: Earth Surface

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In a review of the status of U.S. ocean science, published in February, members of the National Academies of Sciences, Engineering, and Medicine emphasized the need to invest in ocean research equipment, echoing calls from the ocean science community that more funding and support are needed to maintain the United States’ position as a leader in ocean science.

“We have much work to do,” the authors wrote. “We need all hands on deck.”

Two new midsize remotely operated vehicles (mROVs), supported by awards from the U.S. National Science Foundation (NSF) and NOAA, will be part of that effort. The new submersibles will be used by scientists for undersea research in coastal and nearshore waters.

Design of the mROVs, led by the Woods Hole Oceanographic Institution (WHOI) and Greensea IQ, an ocean robotics company, has begun.

“We are eagerly anticipating the ability to support even more exciting science in some of the most challenging to access regions of the planet,” said Brian Midson, program director for Ship and Submersible Support at the National Science Foundation, in a statement.

Submersible Science

The current deep-submergence vehicles available to the U.S. scientific community as part of the Academic Research Fleet are operated by the National Deep Submergence Facility, a WHOI group funded by NSF, the Office of Naval Research, and NOAA. These vehicles include Jason, an ROV equipped with video and sampling equipment that is capable of submerging 6,500 meters (4 miles); Alvin, which can carry three people and also submerge to 6,500 meters (4 miles); and Sentry, which is used for autonomous mapping and imaging and can submerge 6,000 meters (3.7 miles).

The existing vehicles have played a “key role in advancing ocean science in the last decade,” according to the National Academies report. However, they are designed to operate on existing ships within the Academic Research Fleet, which can limit their research scope. And growing interest from researchers in using ROVs in coastal and nearshore waters revealed a need for additional, smaller ROVs, according to the report.

In 2022, a committee at the University-National Oceanographic Laboratory System, which oversees the operation of the U.S. Academic Fleet, also recommended funding a new midsize ROV. “An NDSF [National Deep Submergence Facility] mROV would bring increased capability and accessibility to American deep-submergence scientists,” the committee wrote.

“What is needed now are platforms that fill the niche between large, work-class vehicles such as Jason and small vehicles used primarily for observation,” said Andy Bowen, director of the National Deep Submergence Facility, in a statement.

The two new mROVs are meant to operate with smaller crews and with a smaller footprint than the existing deep-submergence vehicles. They’ll be able to reach depths of 4,000 meters (2.5 miles). Equipment such as cameras, lights, manipulator arms, sensors, and samplers will be added as needed, depending on mission requirements. The new mROVs will free up the ROV Jason, in particular, to prioritize science that requires the larger ROV, Midson said in the statement.

The two mROVs are designed to be used with three under-construction Regional Class Research Vessels intended for scientific missions in the coastal and nearshore waters of the Atlantic, Pacific, and Gulf of Mexico.

Sea trials for the mROVs are expected to start in 2026, according to an NSF spokesperson. They are planned to be available for use by the scientific community in 2027. One mROV will be operated by WHOI’s National Deep Submergence Facility, and the other will be operated by the University of Southern Mississippi as part of the NOAA Ocean Exploration Cooperative Institute.

Deep-Sea Investigations

The mROV that the University of Southern Mississippi will operate is planned to support a project that aims to restore seafloor habitats in the Gulf of Mexico damaged by the Deepwater Horizon oil spill in 2010.

“This ROV is going to be instrumental to the restoration effort,” said Leila Hamdan, a marine microbial biologist and associate vice president for research for coastal operations at the University of Southern Mississippi, in a statement.

The new mROVs will also help scientists better understand the “vastly unexplored” deep ocean, which contains mineral resources such as polymetallic nodules and supports important fisheries, an NSF spokesperson said in an email.

“The mROVs themselves are only the tip of the iceberg,” Bowen said in the WHOI statement. “The mROV concept advances exploration and understanding and we’re excited to be expanding our impact through this unique new program.”

Despite funding uncertainties, both projects are expected to move forward as planned, according to NSF and NOAA. However, NOAA public affairs officer Theo Stein wrote in an email that the agency “can’t speculate on the effects of the recent terminations or how that may or may not affect certain programs,” referring to recent mass layoffs of NOAA employees.

—Grace van Deelen (@gvd.bsky.social), Staff Writer

12 March 2025: This article was updated to correct Leila Hamdan’s title.

Citation: van Deelen, G. (2025), Two ROVs to join the U.S. Academic Research Fleet, Eos, 106, https://doi.org/10.1029/2025EO250098. Published on 11 March 2025.

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The deepest regions of Earth’s oceans, known as the abyssal and hadal zones, lie at least as far under the water’s surface as Mount Rainier’s peak rises above the land surface. These great depths of 4,000 or more meters make up one of Earth’s least explored frontiers and are home to some of its most extreme environments and habitats.

The conditions in these regions—immense pressures, cold temperatures, and the total lack of sunlight—shape the physical, chemical, and geological phenomena that occur there in ways both predictable and surprising [e.g., Marlow et al., 2021]. They also support unique life-forms that—far removed from the sunlit world above—thrive on alternative energy sources such as hydrothermal vents, seeps, and whale falls.

This part of the ocean remains largely unexplored because of the technical challenges of reaching such depths. However, potential discoveries within abyssal and hadal regions—such as dark oxygen, critical mineral resources, pressure-adapted extremophilic organisms, distinct ecosystems, archaeological sites (e.g., submerged human artifacts, including shipwrecks), and otherwise unknown landscapes—reinforce their allure. Remotely operated and autonomous vehicles offer valuable access to these regions, but there is no substitute for direct human observation: The situational awareness and targeted, delicate sampling that human-occupied vehicles (HOVs) enable are unique capabilities.

Yet the small number of vehicles capable of reaching abyssal and hadal depths—and the even smaller subset that can safely carry humans—limits the ability to explore them.

A key tool for this exploration is the deep submergence vehicle Alvin, the world’s longest-operating and most productive human-occupied deep-sea submersible, with more than 5,000 dives completed over 60 years of operation. Alvin recently underwent a significant upgrade, allowing it to reach depths of up to 6,500 meters—surpassing its previous limit of 4,500 meters.

The upgrade and a capstone science verification expedition (SVE) represent more than a decade of planning, scientific and engineering input, and technological development that have opened new possibilities for deep-sea research. With Alvin, researchers now have access to roughly 99% of the ocean floor (Figure 1), enabling in-person observations and data collection in regions that were previously unreachable by the submersible.

Exploring the Deep Ocean Directly

Direct exploration is crucial for understanding deep-ocean environments. Pilots and observers inside an HOV can see the area around them, intuitively perceive distances, and feel the movement of the thrusters and robotic arms when they collect samples. These sensory inputs help them understand spatial relationships among features as well as water currents and the condition of specimens as they are being collected.

In addition, because a human-occupied submersible is not connected to a surface ship by a cable, it is a versatile and nimble exploration tool. An HOV can change direction more quickly than a remotely operated vehicle, without requiring a ship move, and it can explore steeper, more complex areas without encountering the constraints of a tether and a surface vessel, albeit usually with shorter dive times.

Such exploration is especially needed, for example, to provide baseline information that allows us to evaluate whether—and, if so, how—human-induced global changes are affecting deep ecosystems at different depths. Such effects are already pronounced in most ocean environments closer to the surface.

Alvin is owned by the U.S. Navy and certified under the Navy’s Submarine Safety Program (SUBSAFE) protocol but is part of the National Science Foundation’s National Deep Submergence Facility (NDSF) hosted at the Woods Hole Oceanographic Institution (WHOI). Operated by WHOI since its commissioning in 1964 and used by many research organizations, Alvin has long been at the forefront of deep-sea exploration. It can conduct a variety of logistical and scientific tasks, notably, transporting observers to study sites, conducting mapping and photographic surveys, and collecting samples using its robotic arms.

Throughout its lifetime, Alvin has undergone numerous upgrades to remain a state-of-the-art research platform. The most recent upgrade included outfitting it with a new, larger personnel sphere with better ergonomics and improved visibility, as well as improved thrusters and a more advanced command-and-control system. New high-definition imaging systems and faster data acquisition capabilities were also installed, as were enhanced inertial navigation capabilities enabling very accurate tracking from the surface to seafloor, even at great depth, and a new science interface that enables rapid integration of routine and novel sensors for in-sub viewing.

The 2022 Science Verification Expedition

In summer 2022, a diverse team of scientists—led in part by researchers from WHOI and the University of Rhode Island Graduate School of Oceanography (URI-GSO)—put Alvin and its upgraded systems to the test in real-world conditions during its first SVE following the upgrade [Soule et al., 2022]. Team members represented a wide range of disciplines, career stages, and personal backgrounds, and the expedition included a major milestone in U.S. deep-sea science: Alvin’s first dives below 6,000 meters.

All told, the expedition involved six successful dives in the Puerto Rico Trench to nearly 6,400-meter depth and nine along the Mid-Cayman Rise to nearly 6,100-meter depth (Figure 2). These areas, chosen for their extreme depths and diverse conditions, provided rigorous proving grounds for Alvin’s new systems and offered opportunities to study underexplored regions.

During the dives, scientists explored various geological features, including fault lines, landslides, outcrops of ancient oceanic crust, young volcanic features, and active hydrothermal vent systems. The crew also deployed complementary tools, such as a CTD (conductivity, temperature, depth) profiler, as well as an autonomous sampling lander [Muir et al., 2021] that enhanced Alvin’s observational and sampling capabilities down to 8,000-meter depth.

The 2022 expedition yielded several significant scientific observations that have contributed to our understanding of Earth’s geological history and processes that shape the ocean floor. On the Mid-Cayman Rise, researchers aboard Alvin discovered the world’s deepest-known very young (<1–2 decades) submarine volcanic eruption site at 6,000 meters deep [Rubin et al., 2023], an important finding for understanding the effect of high ambient pressure and low temperature on eruption mechanisms.

These researchers also characterized high-grade metamorphic rocks in multiple locations and collected samples at the Von Damm and Beebe active hydrothermal vents [German et al., 2010], which have distinct faunal communities (Figure 3). In addition, the science team recovered the first samples of the active microbial communities living within the vent chimneys, offering insights into life in these extreme environments.

In the Puerto Rico Trench, Alvin’s dives uncovered well-preserved geological structures on steep rock faces, including samples of intrusive oceanic crust [e.g., Rubin et al., 2022] thought to be as much as 100 million years old [Klein et al., 2017]. The site is well suited for systematic follow-on studies of spatiotemporal variations that occur during crustal accretion and alteration at the slow-spreading Mid-Atlantic Ridge. The team also documented behavioral adaptations of deep-dwelling isopods in response to the recent appearance of Sargassum in the Caribbean Sea [Peoples et al., 2024], a remarkable adaptation in the deep ocean to a modern ecological change in the surface waters.

The scientists and Alvin operations team of pilots and engineers on the SVE, over the course of these dives, confirmed the upgraded Alvin’s readiness for abyssal and hadal explorations. Indeed, the submersible’s new capabilities, including enhanced imaging, improved maneuverability, and upgraded navigational tracking, proved essential for the success of the mission.

Since the SVE, Alvin has returned to its regular operational cadence, completing more than 100 dives per year. These dives have included expeditions back to long-term study sites on the East Pacific Rise—where researchers, aided by the autonomous underwater vehicle Sentry, discovered a new off-axis hydrothermal vent site (D. Fornari, personal communication, 2024)—and in the Guaymas Basin, where scientists found dramatically changed hydrothermal venting at a previously known site (M. Joye, personal communication, 2024). A subsequent series of deep science dives in 2024 reached nearly 5,000 meters in the Aleutian Trench, where polychaete-populated seeps were observed to provide habitat for a host of organisms such as hydroids, foraminifera, bacteria, and folliculinids, including possibly new species discoveries (L. Levin, personal communication, 2024).

Alvin’s Legacy and Future

The deep ocean is a place where high hydrostatic pressure influences biological adaptation, geological processes like volcanism, and chemical phenomena such as mineral and ore formation. Throughout its history, Alvin—the most active research submersible in the world and the only U.S. HOV capable of reaching such extreme depths—has contributed to numerous scientific discoveries related to these processes, as well as to explorations of shipwrecks and unknown deep-sea environs.

Alvin’s notable contributions to deep-sea exploration include, among many others, the first discoveries of submarine hydrothermal vents (on the Galapagos Spreading Center in 1977) and black smokers (at 21°N on the East Pacific Rise in 1979), the discovery of methane seeps along the Florida Escarpment in 1984, Bob Ballard’s famous 1986 dive to the Titanic, and the first exploration of the unique Lost City hydrothermal field in 2000.

Alvin has also supported U.S. leadership in deep-ocean exploration and motivated the work of more than 14,000 personnel. Continuing through the SVE in 2022, it has been a major part of each of our own dive histories, for example, contributing indelibly to our research and careers.

The SVE didn’t involve just established scientists, however. As part of an emphasis on equity, diversity, and inclusion within the scientific community, it also included 11 early-career scientists, most of whom were diving in Alvin for the first time. These scientists offered their expertise in geology, microbiology, biology, hydrothermal activity, and resource mapping, and they hailed from oceanographic institutions, large research universities, and smaller teaching colleges, as well as from the Cayman Islands government. The continuing focus on inclusivity in future expeditions will help to foster a welcoming environment for the next generation of researchers using Alvin to expand our understanding of deep-sea biological, geological, and chemical processes.

Alvin’s upgraded capabilities will offer these scientists opportunities to study such processes in greater detail, contributing to knowledge of how life and Earth itself have evolved under extreme conditions. They will also help to provide vital understanding and insights into how human activities are increasingly affecting environments, including deep-ocean ecosystems, supporting comprehensive assessments of global change and how we might manage these regions. As we continue to push the boundaries of human exploration ever deeper in the ocean, Alvin remains a critical tool and a symbol of enduring curiosity and commitment to understanding the world beneath the waves.

Acknowledgments

Alvin is a U.S. Navy–owned asset certified under the Navy’s SUBSAFE protocol with support from the Naval Sea Systems Command (NAVSEA). The recent Alvin upgrade was supported primarily by the National Science Foundation with additional support from the Office of Naval Research. K.H.R. is the associate dean of research at URI-GSO and has completed more than 30 HOV dives. A.P.M.M. is an associate scientist at WHOI and the current chief scientist of deep submergence at NDSF. S.A.S. is a professor of oceanography at URI-GSO, director of the Ocean Exploration Cooperative Institute, and former NDSF chief scientist.

References

German, C. R., et al. (2010), Diverse styles of submarine venting on the ultraslow spreading Mid-Cayman Rise, Proc. Natl. Acad. Sci. U. S. A., 107(32), 14,020—14,025, https://doi.org/10.1073/pnas.1009205107.

Klein, F., et al. (2017), Mid-ocean ridge serpentinite in the Puerto Rico Trench: From seafloor spreading to subduction, J. Petrol., 58(9), 1,729–1,754, https://doi.org/10.1093/petrology/egx071.

Marlow, J. J., et al. (2021), New opportunities and untapped scientific potential in the abyssal ocean, Front. Mar. Sci., 8, 798943, https://doi.org/10.3389/fmars.2021.798943.

Muir, L., et al. (2021), The Deep Autonomous Profiler (DAP), a platform for hadal profiling and water sample collection, J. Atmos. Oceanic Technol., 38(10), 1,833–1,845.

Peoples, L. M., et al. (2024), A deep-sea isopod that consumes Sargassum sinking from the ocean’s surface, Proc. R. Soc. B, 291(2030), 20240823, https://doi.org/10.1098/rspb.2024.0823.

Rubin, K., et al. (2022), Classic oceanic crustal section recovered by Alvin submersible divers from the Puerto Rico Trench north wall, Abstract OS25B-05 presented at 2022 Fall Meeting, AGU, Chicago, Ill., 12–16 Dec., https://doi.org/10.5281/zenodo.13930734.

Rubin, K., et al. (2023), Young submarine lava flow identified at 6 km depth on the Mid Cayman Rise, Abstract 928 presented at IAVCEI 2023 Scientific Assembly, Int. Assoc. of Volcanol. and Chem. of the Earth’s Inter., Rotorua, New Zealand, 30 Jan. to 3 Feb., zenodo.org/records/13930806.

Soule, S. A., A. Michel, and Alvin Science Verification Team (2022), An upgraded HOV Alvin for abyssal and hadal science, Abstract OS25B-04 presented at 2022 Fall Meeting, AGU, Chicago, Ill., 12–16 Dec.

Author Information

Kenna Harmony Rubin (kenna.rubin@uri.edu), Graduate School of Oceanography, University of Rhode Island, Narragansett; Anna P. M. Michel, Woods Hole Oceanographic Institution, Woods Hole, Mass.; and S. Adam Soule, Graduate School of Oceanography, University of Rhode Island, Narragansett

Citation: Rubin, K. H., A. P. M. Michel, and S. A. Soule (2025), An upgraded Alvin puts new ocean depths within reach, Eos, 106, https://doi.org/10.1029/2025EO250037. Published on 31 January 2025.

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Source: Geochemistry, Geophysics, Geosystems

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

一艘远程控制的研究船从Hunga火山（以前称为Hunga Tonga-Hunga Ha ‘apai）两年前爆发后留下的巨大火山口内收集了首批综合测量数据。

2022年1月，汤加火山在水下喷发，向大气中喷射了20公里（12英里）的火山灰和气体，并在海底形成了一个850米（半英里）深的火山口。得益于全球监测系统的综合网络，火山喷发对海洋上空的影响已经得到了很好的研究。但后勤方面的困难和持续的危险使得调查火山喷发后的水下情况变得更加困难。

Walker和de Ronde提出了一种解决方案：在16,000公里（10,000英里）之外的地方，由远程操作员驾驶无人驾驶船。

在一项新研究中，他们分享了2022年夏天在火山口上方进行的三次任务的结果。这艘研究船由英国的技术人员操作，配备了多波束声纳来绘制火山口的地图，并使用仪器来测量火山口的温度、浑浊度和内部水的化学成分等特征。

研究人员发现，火山喷发7个月后，火山口内有火山灰羽流和持续喷发的证据，以及单独的二氧化碳脱气区域，表明该地点仍然活跃。他们报告说，较高的火山口边缘将大部分羽流困在火山口内，有少量通过两个缺口逸出，这可能会影响该地区的生态恢复。目前还不清楚羽流是火山活动还是热液活动造成的，还是两者兼而有之。

该任务成功地使用远程控制工具对活跃的海底火山口进行全面采样，凸显了无人任务在这些潜在危险环境中收集数据的价值。此外，他们认为，尽管没有证据表明火山表面有活动，但在火山上发现了持续存在的喷发和脱气的证据，这凸显了水下探测任务的重要性，比如监测海洋活火山的水下探测任务，这些任务应该应用到其他地方。(Geochemistry, Geophysics, Geosystems, https://doi.org/10.1029/2024GC011685, 2024)

—科学撰稿人Nathaniel Scharping (@nathanielscharp)

This translation was made by Wiley. 本文翻译由Wiley提供。

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Source: Geochemistry, Geophysics, Geosystems

A translation of this article was made by Wiley. 本文由Wiley提供翻译稿。

A remotely controlled research vessel has gathered some of the first comprehensive measurements from within the massive crater left by the Hunga volcano (formerly known as Hunga Tonga-Hunga Ha‘apai) after it erupted 2 years ago.

The underwater eruption of the Tongan volcano in January 2022 sent a plume of ash and gas 20 kilometers (12 miles) into the atmosphere and excavated a crater 850 meters (half a mile) deep on the ocean floor. The eruption’s effects above the ocean have been well studied, thanks to comprehensive networks of global monitoring systems. But logistical difficulties and ongoing danger made it harder to investigate underwater conditions following the eruption.

Walker and de Ronde present one solution: an uncrewed vessel piloted by remote operators 16,000 kilometers (10,000 miles) away.

In new research, they share results from three missions over the crater undertaken in summer 2022. The research vessel, operated by technicians in the United Kingdom, was equipped with multibeam sonar for mapping the crater and instruments to measure characteristics including temperature, turbidity (cloudiness), and the chemistry of the water within.

The authors found evidence of ash plumes and ongoing venting within the crater 7 months after the eruption, as well as separate areas of carbon dioxide degassing, indicating the site remained active. The high crater rim was trapping much of the plume within the crater, with small amounts escaping through two breaches, which could affect ecological recovery in the area, they report. It’s not yet clear whether the plume was due to volcanic or hydrothermal activity or some combination of the two.

The mission’s success in using a remotely controlled vehicle to conduct comprehensive sampling of an active submarine volcanic crater highlights the value of uncrewed missions for gathering data in these potentially dangerous environments. Additionally, finding persistent evidence of venting and degassing at the volcano, despite little evidence of activity on the surface, underlines the importance of underwater missions such as these for monitoring active volcanoes in the oceans, and such missions should be applied elsewhere, they argue. (Geochemistry, Geophysics, Geosystems, https://doi.org/10.1029/2024GC011685, 2024)

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2024), Exploring an underwater volcano from 16,000 kilometers away, Eos, 105, https://doi.org/10.1029/2024EO240408. Published on 12 September 2024.

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17 October 2024: This article has been updated to add context and references about earlier developments of spectroscopy technologies for underwater exploration.

The deep ocean continues to be our local frontier. We have charted the Moon, Mars, and even Venus in more detail than we have our own ocean floor. For example, whereas the seafloor is mapped to a resolution of about 5 kilometers globally [Sandwell et al., 2014] and about 25% is now mapped to roughly 100-meter resolution, the Moon’s entire surface was recently mapped to roughly 2-meter resolution [Fortezzo et al., 2020]. Apart from the shortage of detailed bathymetry, much remains unknown about the composition, structure, dynamics, biology, and other aspects of the seafloor.

Characterizing the ocean floor requires overcoming myriad engineering and technical challenges. The average depth to the seafloor is 3,682 meters, for example: No light penetrates, hydrostatic pressure reaches roughly 370 times atmospheric pressure, and temperatures drop to about 4°C [e.g., Ramirez-Llodra et al., 2010; Liu et al., 2021, 2022]. The lack of light complicates navigation and visual observations for both crewed and remotely operated vehicles (ROVs), and the pressure and cold can be punishing for sensitive instruments.

In 2023, scientists—including us—tested underwater exploration technology designed to overcome such challenges. From 16 May to 13 June, the team traveled to Kingman Reef and Palmyra Atoll, about halfway between the Hawaiian Islands and American Samoa, an isolated and little-explored area. There, we mounted the In-situ Vent Analysis Divebot for Exobiology Research, or InVADER, onto an ROV and sent it down deep to collect first-of-their-kind observations. This instrument can quickly analyze the composition of seawater as well as of seafloor rocks, sediments, and organisms, gathering data as fast as the ROV moves and allowing for efficient surveys of large areas.

The InVADER project embraces the concept of bringing the lab to sites of interest instead of taking snapshots of the field by collecting samples to be analyzed in the laboratory. In this way, the technology supports novel explorations and characterization of the ocean floor. It also may represent a prototype for systems that could one day explore the oceans of icy moons such as Enceladus and Europa, which scientists have identified as sites that may potentially harbor life.

Laser Spectroscopy Under the Sea

InVADER comprises an integrated imaging and spectroscopy payload that includes Raman and laser-induced native fluorescence (LINF) technologies. Raman and LINF measurements are made by directing light from a dual-laser system that emits light at green and ultraviolet (UV) wavelengths at a target of interest. Raman spectroscopy involves detecting changes in the energy of the light that is scattered back from the target, and LINF involves detecting fluorescence emitted by the target as electrons excited by the laser return to their ground state.

These techniques are commonly used to identify minerals and molecules in a variety of applications, including in geochemistry and medicine. But they have not been used to their full potential for exploring the deep ocean, where they can enable in situ real-time measurements of minerals, organics, and dissolved ions on the seafloor and in the water column. The spring 2023 deployment of InVADER built on earlier investigations and ROV deployments of both short-path and long-path (i.e., standoff, or spectroscopy at a distance) spectroscopy technologies used for underwater exploration [e.g., Brewer et al., 2004, 2019; White et al., 2006; Zhang et al., 2011, 2012].

Some of this prior underwater work included deploying a Raman probe that emitted and received light near target surfaces [e.g., Zhang et al., 2017]. This approach allows detection of relatively strong signals, whereas typical standoff Raman measurements must detect signals that get weaker with distance from the target. However, standoff Raman enables scientists to make measurements remotely and to explore environments and samples that are out of reach of the ROV carrying the instrumentation, an incredibly powerful feature.

The idea behind InVADER’s bespoke and cost-effective design—to combine stand-off Raman and luminescence spectroscopy and have it operate at relatively long distances from target materials—is meant to both enhance capabilities for taking detailed in situ real-time measurements and to enable data collection over larger areas than was possible with earlier systems.

Carrying out standoff Raman and fluorescence measurements in the deep sea is no easy task. As the laser light travels through the water column, it is partially absorbed before it reaches the sample. It also encounters particulate debris in the water, which can scatter the light and produce fluorescent signals that impede measurements. Furthermore, movement of the ROV platform during measurements can lead to signal degradation. In situ standoff measurements thus have lower signal-to-noise ratios and higher background fluorescence.

Before sending InVADER—the product of a multi-institution partnership—into the deep sea, we tested its performance and viability for field deployment using a laboratory setup at Impossible Sensing, a small start-up based in St. Louis that focuses on developing remote sensing technology for extreme environments. The setup allowed us to experiment with firing InVADER to target a series of mineral and organic standards in air and in different water compositions at distances of up to 7 meters.

Performing the testing involved overcoming a few unconventional challenges. For example, when InVADER arrived at Impossible Sensing’s headquarters—at the time located in an aging former church building—and was first turned on, a neighborhood-wide power outage occurred. (It’s unclear whether this outage was a coincidence or perhaps resulted from InVADER’s substantial electrical demands.) Thankfully, the outage caused no damage, although it forced adjustments in the laboratory setup to avoid repeat occurrences. A tilt in the building’s floor also proved challenging, and it took a while to account for the tilt and align InVADER’s laser correctly.

With these issues worked out, subsequent testing of InVADER in and out of the water necessitated changing the optical focusing distance and optimizing InVADER’s signal-to-noise ratio for different conditions. All told, it took a few months to achieve readiness for deployment in the field.

Bringing the Lab to the Field

In May 2023, we set out from Hawaii on cruise NA149 of the E/V Nautilus. We deployed the InVADER laser divebot on six of 16 dives by the ROV Hercules, with deployment depths ranging from 1,087 to 3,111 meters [Wagner et al., 2024]. Prior to each dive, we mapped the seafloor with multibeam sonar to locate target areas for our study.

We chose the top of an unnamed guyot—a flat-topped seamount—1,226 meters below the surface as the target of the first dive (Figure 1). To verify InVADER’s performance as it descended, we collected Raman and LINF spectra of seawater every 50 meters down to a depth of 300 meters and then every 100 meters below that.

Some of the first spectra collected showed a strong water signal and indicated the presence of marine snow (organic carbon descending through the water column) as well as sulfate. These results confirmed that the Raman and fluorescence lasers were functioning as expected underwater. Subsequent spectra showed decreasing organic carbon with increasing depth, again in agreement with expectations.

During the remaining five dives, we achieved a series of engineering and scientific accomplishments important for validating InVADER’s flexibility and usefulness for underwater exploration. For example, when the original calibration target for the green and UV lasers proved insufficient under the cold temperatures and extended durations of the deployments, we developed a new calibration target on the fly using high-density polyethylene that worked under the harsh deployment conditions. Similarly, we made engineering adjustments to correct for electronics issues resulting from the low temperatures. We also tested the focusing distance of the lasers from 3 to 10 meters and found 4 meters to be the best standoff distance for collecting optimal spectra.

We detected enhanced fluorescence from seawater with increasing depth on InVADER’s third dive, a trend that may be attributable to increasing salinity. These measurements were particularly striking and initially unexpected. Fluorescence was suggested previously as a way to measure salinity in situ, but that approach has not been demonstrated [Simis et al., 2012; Stirchak et al., 2019]. Follow-up measurements in the laboratory will allow us to further resolve and understand our observations of fluorescence enhancement.

Following comprehensive depth profiling of the water column, the team turned its attention to exploring the ocean floor up the slope of another local guyot (Figure 2). Features detected by InVADER’s instruments appeared to be consistent with microcrystalline quartz and, intermittently, pigments and organic signals from sponges and detrital material. The ability to collect these observations while in motion holds large promise not only for fundamental exploration of the seafloor but also for future endeavors in economic mineralogy surveys and baseline environmental characterizations.

Future Explorations on Earth and Other Ocean Worlds

The 2023 deployment of InVADER showcased the ability of this technology to expedite retrieval and interpretation of information on mineralogy, water column chemistry, and organic materials in the ocean. Broader use of the technology in the future has the potential to produce large data sets of standoff observations in the field and to enable long-term monitoring of biogeochemical changes in challenging deep-sea environments. It could also inform and guide sample collection efforts and robustly document settings where samples are retrieved.

Apart from its technological and scientific abilities, a major highlight of the InVADER program is that it leverages and aligns with efforts of multiple U.S. federal agencies to map and explore the ocean, increase ocean literacy, and characterize the ocean seafloor. It is also an example of an effective collaboration among research institutions and the private sector that supports small businesses.

The recent InVADER deployment further highlights the potential science return from using such a payload in planetary exploration campaigns on other ocean worlds, such as Enceladus or Europa. These places are thought to have oceans of water below their icy crusts that could harbor the chemical building blocks of life, or even life itself, and are high on scientists’ lists of desired destinations for future robotic exploration. InVADER-like technology could help determine exactly what minerals, molecules, and other materials are present in these extraterrestrial oceans. To be sure, further development would be needed to adapt the instrumentation for space travel and the extreme conditions of other worlds. But InVADER’s success so far suggests it could be a promising starting point for this development.

What’s next for InVADER? Within the next few years, the platform will explore black smoker hydrothermal vents. These tantalizing targets support a wide diversity of organisms and are often regarded as oases of life in the deep sea. They are also dynamic structures that are sensitive to geologic activity (e.g., underwater volcanic eruptions), and they may have been important sites for the origins of prebiotic chemistry on early Earth.

Planned developments to continue advancing InVADER include taking it deeper into the ocean to test its performance under increasingly extreme conditions and incorporating colocated laser induced breakdown spectroscopy (LIBS) with its Raman and fluorescence capabilities. The addition of LIBS will allow InVADER to measure simultaneously the mineralogical and elemental makeup of target materials, including rocks and organic compounds, providing richer and more complete pictures of the materials’ compositions.

With these ongoing efforts, we anticipate that InVADER will help reveal additional insights about Earth’s own local frontier and, one day, about frontiers beyond our planet.

Acknowledgments

The InVADER project is funded by NASA Planetary Science and Technology from Analog Research (PSTAR) grant 80NSSC18K1651. NOAA’s Ocean Exploration Cooperative Institute (OECI) and the Bureau of Ocean Energy Management’s Marine Minerals Program provided additional funds to develop and deploy the technology. The Ocean Exploration Trust’s NA149 expedition was funded by NOAA Ocean Exploration via OECI. Parts of this work were additionally supported by NASA Habitable Worlds grant 80NSSC20K0228 to L.M.B. and R.E.P. and carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology. This endeavor is accomplished with collaboration between several institutions and partnerships working closely together over a number of years. We thank all of the scientists and engineers of Impossible Sensing LLC, NASA JPL, SETI Institute, the University of Washington’s Applied Physics Laboratory, NOAA Ocean Exploration via the University of Southern Mississippi and the Ocean Exploration Institute, the Bureau of Ocean Energy Management’s Marine Minerals Program, the University of Southern California, the State University of New York at Stony Brook, the University of Southampton, the University of Hawaii, the Lunar and Planetary Institute, the Oak Crest Institute of Science, Citrus College, Honeybee Robotics, the Geological Survey of Belgium, and the crew of the Ocean Exploration Trust’s E/V Nautilus. The authors also want to acknowledge and honor the contributions to the InVADER mission of Jan Amend, professor of Earth and biological sciences at the University of Southern California, who unexpectedly passed away earlier this year. He was an exceptionally valuable member of the InVADER team, and his death was an incredibly large loss to the marine biology, oceanography, and geobiology communities both in the United States and across the globe. We send our condolences to Jan Amend’s family, close ones, and all those who had the honor of working with him.

References

Brewer, P. G., et al. (2004), Development of a laser Raman spectrometer for deep-ocean science, Deep-Sea Res. I, 51, 739–753, https://doi.org/10.1016/j.dsr.2003.11.005.

Brewer, P. G., E. T. Peltzer, and P. M. Walz (2019), How much H₂O is there in the ocean? The structure of water in sea water, J. Geophys. Res. Oceans, 124, 212–226, https://doi.org/10.1029/2018JC014457.

Fortezzo, C. M., P. D. Spudis, and S. L. Harrel (2020), Release of the digital unified global geologic map of the Moon at 1:5,000,000-scale, paper presented at 51st Lunar and Planetary Science Conference, Lunar and Planet. Inst, The Woodlands, Texas, https://www.hou.usra.edu/meetings/lpsc2020/pdf/2760.pdf.

Liu, Q., et al. (2021), Development of an easy-to-operate underwater Raman system for deep-sea cold seep and hydrothermal vent in situ detection, Sensors, 21(15), 5090, https://doi.org/10.3390/s21155090.

Liu, Q., et al. (2022), Underwater Raman microscopy—A novel in situ tool for deep-sea microscale target studies, Front. Mar. Sci., 9, https://doi.org/10.3389/fmars.2022.1018042.

Ramirez-Llodra, E., et al. (2010), Megabenthic diversity patterns and community structure of the Blanes submarine canyon and adjacent slope in the northwestern Mediterranean: A human overprint?, Mar. Ecol., 31, 167–182, https://doi.org/10.1111/j.1439-0485.2009.00336.x.

Sandwell, D. T., et al. (2014), New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure, Science, 346, 65–67, https://doi.org/10.1126/science.1258213.

Simis, S. G. H., et al. (2012), Optimization of variable fluorescence measurements of phytoplankton communities with cyanobacteria, Photosynthesis Res., 112, 13–30, https://doi.org/10.1007/s11120-012-9729-6.

Stirchak, L. T., et al. (2019), Differences in photochemistry between seawater and freshwater for two natural organic matter samples, Environ. Sci. Processes Impacts, 21, 28–39, https://doi.org/10.1039/C8EM00431E.

Wagner, D. (Ed.) (2024), The Ocean Exploration Trust 2023 field season, Ocean Exploration Trust, 94 pp., https://doi.org/10.62878/vud148.

White et al. (2006), In situ Raman analyses of deep-sea hydrothermal and cold seep systems (Gorda Ridge and Hydrate Ridge), Geochem. Geophys. Geosyst., 7, Q05023, https://doi.org/10.1029/2005GC001204.

Zhang, X., et al. (2011), In situ Raman-based measurements of high dissolved methane concentrations in hydrate-rich ocean sediments, Geophys. Res. Lett., 38, L08605, https://doi.org/10.1029/2011GL047141.

Zhang, X., et al. (2012), A review of advances in deep-ocean Raman spectroscopy, Appl. Spectrosc., 66, 237–249, https://doi.org/10.1366/11-06539.

Zhang, X., et al. (2017), Development of a new deep-sea hybrid Raman insertion probe and its application to the geochemistry of hydrothermal vent and cold seep fluids, Deep Sea Res., Part I, 123, 1–12, https://doi.org/10.1016/j.dsr.2017.02.005.

Author Information

Anastasia G. Yanchilina (ayanchil@caltech.edu), Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena; Laura E. Rodriguez, Lunar and Planetary Institute, Houston; Roy Price, Stony Brook University, Stony Brook, N.Y.; Laura M. Barge, NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena; and Pablo Sobron, Impossible Sensing LLC, St. Louis

Citation: Yanchilina, A. G., L. E. Rodriguez, R. Price, L. M. Barge, and P. Sobron (2024), Sensing remote realms of the deep ocean on Earth—and beyond, Eos, 105, https://doi.org/10.1029/2024EO240375. Published on 29 August 2024.

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This is an authorized translation of an Eos article. Dies ist eine autorisierte Übersetzung eines Eos artikels.

Wälder haben eine komplexe Beziehung zum Klimawandel. Einerseits absorbieren sie Kohlenstoff aus der Atmosphäre, ja sie vermehren sich sogar in wechselndem Klima. Andererseits leiden sie oft unter größerem Hitzestress, was ihre Kapazität als Kohlenstoffsenken und ihre Resilienz gegen Trockenheit beeinträchtigt. Mit rund 10,5 Mio. Euro von der Deutschen Forschungsgemeinschaft werden Forschende in Europa jetzt Wälder mit neuartigen Sensoren ausrüsten, um die Auswirkung von Klimaveränderungen auf Waldgebiete besser zu verstehen.

Durch die Kombination von Forstwissenschaft mit dem Internet der Dinge (Internet of Things, IoT), mit Technik, Drohnen und anderen Instrumenten will EcoSense versuchen, den Auswirkungen des Klimawandels auf die Wechselbeziehungen zwischen Pflanzen, Boden und der Atmosphäre auf den Grund zu gehen. Diese Wechselbeziehungen hängen ab von den jeweiligen Arten, Standorten und Gehölzsammlungen, d. h. eine Ansammlung von Bäumen in einem Wald, die in Bezug auf Alter, Größe, Verteilung und andere Faktoren relativ homogen ist. Die Initiative EcoSense schließt an Untersuchungen wie den sogenannten „Wired Forest“ oder „verkabelten Wald“ der Harvard University an.

Das Projekt wird einem Umriss zufolge gezielt abiotische und biotische Prozesse im Kohlenstoff- und Wasseraustausch des Waldes und die Reaktion des Ökosystems auf Stressoren in der Umwelt untersuchen und damit die Vorhersage prozessbasierter Veränderungen in der Funktionsweise und Nachhaltigkeit ermöglichen. Echtzeitdaten aus dem Sensorennetzwerk werden an eine Datenbank übermittelt, wo dann Analysen und Deep-Learning-Simulationsmodelle für kurz- und mittelfristige Vorhersagen erstellt werden.

„Klimawandel wirkt sich bereits gewaltig auf Waldökosysteme aus. Wir sehen bereits vermehrtes Bäumesterben weltweit“, sagte Christiane Werner, Professorin für Ökosystemphysiologie am Institut für Geo- und Umweltwissenschaften der Universität Freiburg, und verwies auf die Auswirkungen für die Bäume während der Trockenheit 2018 in Europa. „Zurzeit haben wir gute Modelle, die das Funktionieren des Ökosystems insgesamt unter nicht gestressten Bedingungen vorhersagen können, aber wir verstehen nicht, wann und warum Klimaextreme wie Hitzewellen oder Dürren einzelne Bäume oder Waldabschnitte über ihre Kipppunkte hinaus treiben.“

Internet der Walddinge

Das Forschungsteam wird mehrere Hektar Hügellandschaft im Schwarzwald, auf denen reine Buchenstände, reine Fichtenstände und Mischwald wachsen, mit Instrumenten ausrüsten. Klimabedingte Veränderungen im Wald haben möglicherweise weiterreichende Folgen; die Wälder sind für die Wirtschaft und den Fremdenverkehr in Deutschland wichtig, der Schwarzwald ist schließlich berühmt für seine alten Bauernhäuser und Kuckucksuhren, seinen Schinken und die gleichnamige Torte.

Das Toolkit von EcoSense wird sich voraussichtlich aus Kohlendioxid- (CO₂) -Sensoren, Drohnen mit Kameras und anderen Instrumenten zusammensetzen. Zunächst wird das Team handelsübliche Instrumente verwenden und sie dann ab 2024 mit neu entwickelten Mikrosensoren, die zum Teil energieautonom sein werden, ersetzen, erklärt Ulrike Wallrabe, Professorin am Institut für Mikrosystemtechnik an der Universität Freiburg.

„Wir wollen Wasserströmungen, Kohlendioxid-Isotopendiskriminierung und flüchtige organische Verbindungen und Stressmarker, in erster Linie die photosynthetische Effizienz durch Chlorophyll-Fluoreszenz vom Boden bis hinauf in die Atmosphäre messen“, sagte Wallrabe. „Das Sensornetzwerk wird aus neuen, kompakten und nach Möglichkeit energieautonomen Sensoren bestehen, die im Rahmen des Projekts entwickelt werden sollen.“

Nach Auffassung von Daniel Kneeshaw, Wald- und Klimawandelforscher an der Universität von Quebec in Montreal und nicht an EcoSense beteiligt, untersucht das Projekt interessante Parameter, die für eine breite Vielfalt von Forschenden nützlich sein könnten.

„Wie die Forschenden nahelegen, kann das, was auf Zellniveau passiert, auf höheren Skalen immense Auswirkungen über weite Gebiete haben“, sagte Kneeshaw und wollte zugleich wissen, wie die Daten von EcoSense nach oben und unten skaliert werden. „Ein besseres Verständnis der Mechanismen wird uns helfen, besser auf künftige Veränderungen vorbereitet zu sein. Wenn wir Netzwerke dieser Art auf der ganzen Welt haben und Wissenschaftler:innen der einzelnen Netzwerke [darüber] reden, bekommen wir noch solidere Ergebnisse und Interpretationen.“

Das Projekt EcoSense wird voraussichtlich 2023 mit der Veröffentlichung von Studien beginnen, einige daran beteiligte Gruppen haben jedoch bereits erste Ergebnisse bekannt gegeben. So publizierte beispielsweise eine Gruppe um Werner einen wissenschaftlichen Artikel über ein kabelloses, autonomes Chlorophyll-Fluorometer, das die Effizienz der Phytosynthese in Pflanzen misst. Mit einer Reichweite von 10 Kilometern kann dieses neuartige Instrument irgendwo an einem Baum befestigt werden, braucht wenig Strom und ist relativ kostengünstig.

Zusätzlich zur Finanzierung für die ersten 4 Jahre hat EcoSense die Option, zweimal um je 4 Jahre zu verlängern, sodass eine Langzeitperspektive gewonnen werden kann. Die Forschenden haben hohe Erwartungen, dass sie damit bedeutende Ergebnisse erzielen werden.

„Unsere Besonderheit liegt in der einmaligen Verknüpfung von Ökosystemforschung mit Mikrosystemtechnik. Verteilte autonome Sensoren und ihre Prinzipien werden der Ökosystemforschung neue Türen öffnen“, sagte Werner. „Wir werden eine bisher nie dagewesene Skalenabdeckung erreichen: sowohl räumlich, vom Blatt bis zum Wald, als auch in zeitlicher Dimension, von Minuten bis zu Jahren, von Prozessen und Interaktionen, die Kohlenstoff- und Wasserströmungen steuern, einschließlich Stressmarkern wie flüchtige organische Verbindungen und Chlorophyll-Fluoreszenz.“

—Tim Hornyak (@robotopia), wissenschaftlicher Autor

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Britney Schmidt grew up in southern Arizona, but she now seeks out decidedly chillier climes. She frequents such places as Antarctica, Greenland, and Canada’s Northwest Territories to learn about the icy worlds of our outer solar system. Her work is an amalgam of engineering, planetary science, astrobiology, robotics, and polar oceanography.

“I like to focus on everything,” Schmidt said. “That multidisciplinary approach is, to me, really exciting.”

Schmidt became a scientist almost by accident. “Nobody in my family is a scientist or an academic,” she said. In college, Schmidt was having trouble deciding on a major and on a whim took an introductory astronomy class. It captivated her, and she remembered being astounded when she learned that some of the moons of Jupiter and Saturn contain oceans hidden under thick layers of ice. “I had my mind blown,” she said.

Today Schmidt is an Earth and planetary scientist at Cornell University in Ithaca, N.Y. She’s still fascinated by ice-covered oceans, and she builds instruments such as submersibles that she and her team use in polar regions. It’s exciting to think that similar technology might one day be used to explore a distant world like Jupiter’s moon Europa, she said.

There are closer-to-home motivations for her work, too, Schmidt said. The effects of climate change in polar regions are acute, and she and her colleagues are working to better understand some of those fragile landscapes before they disappear. “Being in these places that are so powerful and so delicate is really overwhelming,” she said.

—Katherine Kornei (@KatherineKornei), Science Writer

This profile is part of a special series in our August 2024 issue on science careers.

Citation: Kornei, K. (2024), Britney Schmidt: Following the ice, Eos, 105, https://doi.org/10.1029/2024EO240329. Published on 25 July 2024.

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With its spectacular geology entirely unobscured by tall vegetation, Svalbard is one of the best places in the world to study rock formations. But the High Arctic Norwegian archipelago is constantly reshaped by fast-moving glaciers and landslides that hide geological information. Researchers are racing to catalog Svalbard’s landscape for students and future research.

Digital outcrop models (DOMs) are created by stitching together thousands of overlapping photographs of a rock outcrop into a three-dimensional image. The advent of low-cost drones, which can be programmed to fly automated grid patterns and take photographs of the ground from different angles, has made DOMs easier to create, allowing geologists to study outcrops from the comfort of an office computer. That’s particularly useful in Svalbard, which is plunged into darkness during the winter months.

“We only have half a year of light to work with,” explained Peter Betlem of the University Centre in Svalbard (UNIS). Betlem is the digital data lead for a project that has been archiving DOMs of Svalbard’s outcrops and making them publicly available through an online portal called Svalbox. The work was recently published in Geosphere.

Venturing into rarely visited parts of the archipelago by boat, the team has so far modeled 135 outcrops, including the famous Festningen outcrop—a 7-kilometer-long cliff of layered sediments deposited over 400 million years.

Svalbox was initially developed for teaching purposes, Betlem said. “We have students who come in the dark season and are not able to see the rocks.” Using DOMs, “we can allow them to look at the outcrop from different angles and absorb the information,” he said. “Then, when we go into the field, the outcrop is not new to them.” But the digital outcrops are increasingly contributing to ongoing research into carbon capture and storage on the Norwegian Continental Shelf.

DOMs give researchers a perspective that’s hard to get from the ground, Betlem said. “Many times, you cannot see the faults, the structures, and the way the sediments are deposited. Having this view from the air and looking at the same outcrop from different angles is really beneficial.”

Documenting a Changing Landscape

Ice floes frequently alter Svalbard’s outcrops. “We have a lot of surging glaciers,” marine geoscientist and study coauthor Nil Rodés explained. “So the geomorphology of the island is changing very quickly.”

“Many of the sites we’ve been to have been eroded by glaciers,” Betlem said. “They are no longer there.”

And climate change, Rodés said, is hitting Svalbard hard because melting permafrost causes landslides that sometimes bury outcrops. “One of the goals is to collect a virtual model of how the outcrop was at the time of the data collection, in case you lose that information.”

The team is making their models, along with the associated raw photographs, additional data, and metadata, available for anyone, using open-source repositories including Zenodo and the Norwegian National e-Infrastructure for Research Data.

The project comes at a time when scientists are seeing the value of their work beyond just the single paper they write and are trying to get their own DOMs out to the world, said Clare Bond, an Earth scientist at the University of Aberdeen who was among the first to research the use of drone-based virtual outcrops. “I think we’re still really at the nub of these kinds of databases becoming standard.” Bond is not directly involved in the Svalbox project.

Svalbox is “a pilot project for the rest of the world. It’s signing the path for the future,” said Stefano Tavani, a geologist with the University of Naples Federico II who has worked extensively with DOMs but is not involved in the Svalbox project. Though the process of building a DOM is well established, the amount of raw data that goes into them means making them available to the world is impractical, he pointed out. Once the data are archived, the cost of server maintenance becomes prohibitive.

“There are some public repositories,” Tavani said, “but you cannot access the entire data set, just the final model—frequently downsized.” The Svalbox team, he explained, is “building an environment to share all the data.”

For Betlem, making these publicly funded data sets available on an open-source platform is about providing opportunities for collaboration and making sure they will be available for researchers to use indefinitely. “What typically happens, when you make these resources available but keep the source code or the source imagery to yourself, is that when your career ends, the source material ends as well.

“I’m not going to live forever. I’m probably not going to be in academia forever,” Betlem said. Svalbox is available open source “to make sure that someone doesn’t have to reinvent the wheel and go out and collect all the same data again.”

—Bill Morris, Science Writer

Citation: Morris, B. (2023), Digitally preserving Svalbard’s fragile geology, Eos, 104, https://doi.org/10.1029/2023EO230398. Published on 18 October 2023.

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Editors’ Highlights are summaries of recent papers by AGU’s journal editors.

Source: Geochemistry, Geophysics, Geosystems

Volcanoes are highly dynamic, time-variable systems that pose major local and regional hazards as well as long-term effects on climate. Many remote volcanoes are poorly monitored and acquiring time-series data on their gas emissions has been a challenge for existing resources and technologies.

As a complement to traditional ground-based and satellite-based methods, McCormick Kilbride et al. [2023] demonstrate a pioneering use of unmanned aerial vehicles (drones) to monitor volcanic gas emissions at Bagana Volcano in Papua New Guinea. Its remote location and variable activity have posed a challenge for quantifying its emissions and forecasting eruption hazard. Although ground-based and satellite instruments have been able to monitor SO₂, they are not able to determine CO₂ fluxes. The drone, on the other hand, by flying directly through the gas plume and determining the local CO₂/SO₂ ratio, provides the additional constraint needed to quantify net CO₂ emission from the volcano. This approach is important for monitoring of inaccessible volcanoes and for constraining the global volcanic CO₂ flux.

Citation: McCormick Kilbride, B. T., Nicholson, E. J., Wood, K. T., Wilkes, T. C., Schipper, C. I., Mulina, K., et al. (2023). Temporal variability in gas emissions at Bagana volcano revealed by aerial, ground, and satellite observations. Geochemistry, Geophysics, Geosystems, 24, e2022GC010786. https://doi.org/10.1029/2022GC010786

—Paul Asimow, Editor, G-Cubed

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Thwaites Glacier, infamous for its potentially outsized contribution to sea level rise, recently got its close-up. Researchers maneuvered a robot under Thwaites’s floating ice shelf and collected data about the Antarctic glacier’s so-called grounding line—the region where its ice first lifts off solid land. The new results revealed that enhanced melting occurs in places where Thwaites’s underbelly is particularly sloped and that water stratification helps to inhibit melting overall.

Reuniting with the Robots

In October 2019, Britney Schmidt, an Earth and planetary scientist then at the Georgia Institute of Technology in Atlanta, and her collaborators embarked on a multiday journey by plane to McMurdo Station, a research base in Antarctica operated by the United States. There, they met up with colleagues, tried their best to acclimate to the perpetual daylight of polar summer, and reunited with two very precious pieces of cargo.

The researchers had brought with them a pair of 3.5-meter-long robots. Known as Icefins, each bright yellow, pencil-shaped submersible was kitted out with instruments ranging from cameras to sonar to temperature and salinity sensors. Icefin is like a robotic oceanographer, said Schmidt, who led the sub’s development and is now at Cornell University in Ithaca, N.Y.

The submersible’s long, thin profile makes it well suited for maneuvering under ice, which is why Schmidt and her colleagues went to Antarctica to study Thwaites, a Florida-sized expanse of ice in West Antarctica that’s recently been melting at an alarming rate. The unstable nature of Thwaites, paired with its sheer volume—the water contained within it would raise global sea level by more than half a meter—has made it the target of a massive research effort that includes the project that brought Schmidt and her collaborators to Antarctica: the Melting at Thwaites grounding zone and its control on sea level (MELT) project.

After spending several months thoroughly testing the two Icefins on the McMurdo Ice Shelf, Schmidt and some of her colleagues departed for Thwaites with one of the robots in tow. Working in temperatures as low as −30°C, the researchers set up camp on the eastern part of the glacier’s ice shelf, roughly 2,000 kilometers (1,200 miles) from McMurdo. Their home away from home consisted of a line of brightly colored pyramidal tents—so-called Scott tents, named for the explorer Robert Falcon Scott—for sleeping in, a larger tent that could hold the entire group for meals and socializing, a drilling rig, and a dome-shaped tent that doubled as a scientific control room.

Like Hot Water Through Ice

Shortly after the New Year, the team began drilling. Using hot water, they bored through the full thickness of Thwaites’s ice shelf—587 meters (0.4 mile)—until they reached water. That process took roughly 24 hours. Schmidt and her colleagues then carefully lowered the Icefin down with just centimeters to spare around the robot. Roughly an hour later, when the Icefin’s sensors indicated that it had entered the Amundsen Sea, the team turned the robot toward the continent to seek uncharted territory.

For glaciers such as Thwaites that terminate in the ocean, some of their bulk rests on land, and some floats on the water. The transition is known as the grounding zone or grounding line. “That’s a really important place because it’s the place where the ice hits the water for the first time,” Schmidt said. Even water that’s only a few degrees above freezing can transfer enough heat to ice to kick-start melting, she explained.

But accessing the grounding line is notoriously tough—a glacier’s floating portion can extend for tens or even hundreds of kilometers beyond the grounding line, so exploring from the ocean side often isn’t practical. “It’s one of the hardest places to go look,” said Alastair Graham, a marine geophysicist at the University of South Florida who was not involved in the new research. Graham and his colleagues have studied how Thwaites’s grounding line has shifted position over time by analyzing the imprints it’s left behind in the seafloor.

“Until Thwaites, we had no data from the grounding line of any major glacier,” Schmidt said. “We were trying to get the very first data from this environment.”

Right up to the Edge

After maneuvering Icefin inland for a little over a kilometer (0.6 mile), the MELT team sent the robot to within a few centimeters of Thwaites’s grounding line. They discovered that the ice in the region was heavily scalloped and pitted with crevasses up to tens of meters deep. That was a big surprise, Graham said, because ice shelves long have been thought to be flat or gracefully sloping. “If you look at people’s drawings of grounding zones, they rarely have crevasses.”

The team furthermore found that ice at the grounding line was melting at different rates: Steeply sloped ice faces such as crevasse walls tended to melt much more rapidly than flatter ice faces. Only about 10% of Thwaites’s base is steeply sloped, but those regions account for 27% of ice loss, Schmidt and her colleagues reported in a paper published last month in Nature.

That difference likely arises because of water stratification, the researchers concluded. Colder, fresher water tends to linger above warmer, saltier water near the undersides of glaciers. Flatter ice faces are therefore mostly bathed in colder water, but steeply sloped ice faces are exposed to both colder and warmer waters.

Icefin also measured stronger water currents in crevasses, which might also play a role in transferring heat to the ice, the team suggested. That’s because stronger currents can disrupt water stratification. “You can imagine pouring your milk into your coffee and stirring it and seeing the billows and filaments,” said MELT team member Peter Davis, a physical oceanographer with the British Antarctic Survey in Cambridge, U.K. That mixing essentially removes the insulating layer of cold water that normally lingers near a glacier, explained Davis.

However, Davis and his colleagues calculated that overall, the underside of Thwaites is melting far less rapidly than predicted by models. That might sound like good news, Davis said, but the fact remains that the glacier is still retreating. “What this shows us is that the retreat is being driven by a lower rate of melting than perhaps we expected.” That observation sends scientists back to the drawing board, so to speak, to better understand what’s primarily responsible for Thwaites’s observed retreat, he said. Davis and his colleagues also reported their results last month in Nature.

It will be interesting to continue to monitor Thwaites, Graham said. There’s a chance that the glacier’s lower melt rate will translate into slower retreat in the future, he added, and Thwaites is definitely a glacier to watch. “I don’t think we should leave it alone.”

—Katherine Kornei (@KatherineKornei), Science Writer

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Citation: Kornei, K. (2023), “Icefin” investigates a glacial underbelly, Eos, 104, https://doi.org/10.1029/2023EO230101. Published on 15 March 2023.

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