Melting Greenland icesheet affects ocean + Squishy robot fingers + Twilight zone fish

Melting Greenland ice sheet may affect global ocean circulation, future climate: University of South Florida and international scientists find influx of freshwater could disrupt the Atlantic Meridional Overturning Circulation, an important component of global ocean circulation

RELEASE: Scientists from the University of South Florida, along with colleagues in Canada and the Netherlands, have determined that the influx of fresh water from the Greenland ice sheet is "freshening" the North Atlantic Ocean and could disrupt the Atlantic Meridional Overturning Circulation (AMOC), an important component of global ocean circulation that could have a global effect. Researchers say it could impact the future climate in places such as portions of Europe and North America.

Their study on the influence of freshwater influx on Labrador Sea convection and Atlantic circulation is published in a new issue of the journal Nature Communications.

"We derived a new estimate of recent freshwater flux from Greenland using updated GRACE satellite data," said USF professor Tim Dixon. "The data suggest that the influx of freshwater from Greenland is accelerating, and has changed the Labrador Sea in ways that could lead to a weakening of the AMOC."

Freshwater flux from Greenland is composed of melt runoff from ice and tundra runoff as well as ice discharge ("calving" of icebergs). The amount of freshwater flux from Greenland was relatively stable from the late 1970's to the mid 1990's, and then began to increase. Increased freshwater flux could weaken the AMOC, resulting in a number of consequences, both local and global, said the researchers.

"Focused freshwater flux into the Labrador Sea has the potential to increase the buoyancy of surface waters and reduce formation of dense, deep water that helps drive the overturning circulation," said co-author Don Chambers , USF College of Marine Science associate professor.

How much of the enhanced freshwater flux actually winds up in the Labrador Sea?

Because of the clockwise nature of ocean circulation around Greenland, most of the freshwater increase, up to 70 percent, is being driven toward the Labrador Sea, magnifying its impact and increasing the possibility of significant effects on the AMOC, said Qian Yang, the paper's first author and a PhD student at USF whose dissertation, in part, includes this research.

According to the researchers, not only are changes in the AMOC difficult to measure, it's also difficult to separate natural climatic variation from climate changes induced by human activity.

The potential consequences of a weakened AMOC include changes in climate.

"The AMOC transports a large amount of heat into the North Atlantic where it is given up to the atmosphere and helps regulate the climate in Europe and North America. The major effect of a slowing AMOC is expected to be cooler winters and summers around the North Atlantic, and small regional increases in sea level on the North American coast," explained Chambers.

According to Dixon, the global impacts are less certain, but potentially more consequential.

"The AMOC and Gulf Stream are part of a complex global ocean circulation system that is still not completely understood," said Dixon. "If human activities are starting to impact this system, it is a worrying sign that the scale of human impacts on the climate system may be reaching a critical point."

Continued long-term observation is required to understand the impact of the freshwater influx.

"This shows the need to continue to look at different components of the climate system, including the ice sheets and oceans, in an integrated sense," concluded Paul Myers, study co-author and Professor of Oceanography at the University of Alberta.

'Squishy' robot fingers aid deep sea exploration: Researchers successfully demonstrate soft robotic grippers able to collect underwater specimens

EXCERPT: During a 2014 talk on his exploration of deep-sea coral reefs, Baruch College marine biologist David Gruber showed a video of clunky robotic hands collecting fragile specimens of coral and sponges from the ocean floor. Harvard engineer and roboticist Robert J. Wood was in the audience -- the two scientists were being recognized as Emerging Explorers by the National Geographic Society -- and a lightbulb went off.

"They were using rigid Jaws of Life-type grippers designed for the oil and gas industry that were totally overpowered and were destroying things," Wood recalls. "It immediately clicked that there was a soft robotics solution that may be viable."

In the months that followed, the pair collaborated to design, fabricate, and test soft robotic grippers for deep-sea collection of fragile biological specimens. Their recent expedition to the Gulf of Eilat in the northern Red Sea, a unique marine ecosystem that houses one of the world's largest and most diverse coral reefs, marked the first use of soft robotics for the non-destructive sampling of fauna from the ocean floor.

The new technology could enhance researchers' ability to collect samples from largely unexplored habitats thousands of feet beneath the ocean surface, areas that scientists believe are biodiversity hot spots teeming with unknown life. The soft grippers also could be useful in underwater archaeology.

As described in a paper published today in the journal Soft Robotics, the team successfully developed two types of grippers, and in the process demonstrated a new fabrication technique that allows for the rapid creation of soft actuators.

Gruber, associate professor of biology and environmental science at Baruch College of the City University of New York, and research associate with the American Museum of Natural History, explores deep ocean ecosystems, with a particular focus on organisms that display bioluminescent and biofluorescent traits. (Bioluminescent animals produce their own light; biofluorescent animals absorb light and re-emit it as a different color.)

When he wants to visit a coral reef below the maximum depth that human divers can tolerate, Gruber must rely on a remotely operated vehicle (ROV). But there's a problem: The standard-issue robotic "hands" of underwater ROVs are ill-suited to collecting delicate coral, sponge and other samples. That's because the equipment was designed for undersea construction and to install and repair submerged pipelines.

Manipulating and grasping fragile organisms from the sea floor requires something that can mimic the dexterity and soft touch of a human diver's hand. Wood, Charles River Professor of Engineering and Applied Sciences at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and founding core faculty member of the Wyss Institute for Biologically Inspired Engineering at Harvard University, recognized that soft robotics is tailor-made for the task.

Design, fabrication and grasping vegetables

Wood and Wyss Institute mechanical engineer Kevin Galloway set about designing two types of hands to replace the ROV's factory-furnished metal gripper, each capable of gently recovering objects of different sizes and shapes. One, inspired by the coiling action of a boa constrictor, can access tight spaces and clutch small and irregular-shaped objects. The other, a bellows-style model, features opposing pairs of bending actuators.

To facilitate rapid in-field modification and repair, the team emphasized simple construction, inexpensive materials and a modular design. This meant they could try multiple configurations and make them in quantity. Harvard's Office of Technology Development has filed a patent application on the team's method for the manufacture of bellows-type soft actuators. The method is scalable, opening up a wide range of commercial, biomedical and industrial applications for this type of actuator.

The biggest design challenge, Wood said, was a lack of precise specifications. They weren't designing a robotic arm to repetitively attach doors to car bodies in an auto assembly plant. The team had no way of knowing the size, shape, or stiffness of the objects they would be sampling on the ocean floor. To approximate likely specimens, they visited the produce aisle and brought back an assortment of vegetables -- celery, radishes, carrots and bok choy -- tied them to a metal grate, and dropped them into a test tank at the University of Rhode Island. After exhaustive tank tests, the devices were put through their paces at depths greater than 800 meters off the Rhode Island coast.

Field testing took the team to Israel's Gulf of Eilat in the northern Red Sea in May 2015. There they conducted more than a dozen dives ranging from 100 to 170 meters (558 feet -- or as deep as the Washington Monument is tall). Most dives involved "catch-and-release" maneuvers to test system performance. But they did manipulate the grippers to retrieve samples of delicate (and relatively abundant) red soft coral, as well as difficult-to-snag coral whips, bringing them to the surface undamaged in the ROV's cargo tray.

Next steps

Simply collecting hard-to-harvest samples isn't the end game. Researchers like Gruber hope to apply these techniques to conduct in situ measurement of organisms, and eventually, gene expression and transcriptomic analysis. Conducting this work on the seabed floor rather than bringing samples to the surface, means that organisms are not exposed to stress from changes in temperature, pressure, and light and there is less disturbance to the reef system.

On the robotics side, Wood has a list of performance enhancements he hopes to pursue. Current-generation ROVs rely exclusively on visual feedback -- a live video feed from an onboard camera -- but he'd like to add tactile feedback, applying his lab's expertise in soft sensors to let an operator actually "feel" what the gripper is touching. He is also interested in experimenting with bilateral, rather than single-arm manipulation to achieve improved dexterity. Finally, the team wants to go deeper -- literally. During the Red Sea dives, the system operated at depths under 200 meters. They envision conducting field work in unexplored worlds 6,000 meters below the surface.

'Twilight zone' fish swim silently with forked tails

RELEASE: An international team of researchers has identified a way to predict which reef fish can live across a greater range of depths, increasing their chances of surviving natural disasters such as cyclones and coral bleaching.

Study lead author, Dr Tom Bridge from the ARC Centre of Excellence for Coral Reef Studies at James Cook University, says the research, published in the journal Proceedings of the Royal Society B, found that tail shape can help predict if a fish is likely to exist across a range of water depths.

"We found that the 'caudal fin aspect ratio', which measures the shape of the fishes tail, is the best predictor of which fish can live in a range of deep and shallow reefs." Dr Bridge says.

"In other words, fishes with more forked tails are significantly more likely to be found in both shallow and deep habitats than species with more rounded tails."

Dr Bridge says it's not known exactly why this is the case, though it's suspected that the forked tail allows fish to swim more 'silently'.

"The capacity for 'stealth swimming' is particularly important in deeper habitats, where light irradiance and wave energy are low and species rely on sensing changes in water pressure to capture prey and avoid predators."

Coral reefs are typically thought to occur in shallow, sun-lit waters, but new technology is revealing that reefs in the ocean's 'twilight zone', 50-150 m deep, support diverse and unique communities.

However conditions on these deep reefs can be challenging for coral reef fishes, with low light, high pressure, and low temperatures.

Study co-author Dr Osmar Luiz from Macquarie University says species that can survive in the twilight zone may be less susceptible to population declines and extinction.

"Identifying which species can occur over a broad depth range is important for understanding which fish are more vulnerable to local population declines and extinction, particularly from disturbances such as cyclones and coral bleaching events."

The researchers say the next step is to understand exactly what it is about the forked tails that provides fishes such an advantage in deeper water.

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