Machine learning helps map global ocean communities

On land, it’s fairly obvious where one ecological region ends and another begins, for instance at the boundary between a desert and savanna. In the ocean, much of life is microscopic and far more mobile, making it challenging for scientists to map the boundaries between ecologically distinct marine regions.

One way scientists delineate marine communities is through satellite images of chlorophyll, the green pigment produced by phytoplankton. Chlorophyll concentrations can indicate how rich or productive the underlying ecosystem might be in one region versus another. But chlorophyll maps can only give an idea of the total amount of life that might be present in a given region. Two regions with the same concentration of chlorophyll may in fact host very different combinations of plant and animal life.

“It’s like if you were to look at all the regions on land that don’t have a lot of biomass, that would include Antarctica and the Sahara, even though they have completely different ecological assemblages,” says Maike Sonnewald, a former postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences.

Now Sonnewald and her colleagues at MIT have developed an unsupervised machine-learning technique that automatically combs through a highly complicated set of global ocean data to find commonalities between marine locations, based on their ratios and interactions between multiple phytoplankton species. With their technique, the researchers found that the ocean can be split into over 100 types of “provinces” that are distinct in their ecological makeup. Any given location in the ocean would conceivably fit into one of these 100 ecological  provinces.

The researchers then looked for similarities between these 100 provinces, ultimately grouping them into 12 more general categories. From these “megaprovinces,” they were able to see that, while some had the same total amount of life within a region, they had very different community structures, or balances of animal and plant species. Sonnewald says capturing these ecological subtleties is essential to tracking the ocean’s health and productivity.

“Ecosystems are changing with climate change, and the community structure needs to be monitored to understand knock on effects on fisheries and the ocean’s capacity to draw down carbon dioxide,” Sonnewald says. “We can't fully understand these vital dynamics with conventional methods, that to date don’t include the ecology that’s there. But our method, combined with satellite data and other tools, could offer important progress.”

Sonnewald, who is now an associate research scholar at Princeton University and a visitor at the University of Washington, has reported the results today in the journal Science Advances. Her coauthors at MIT are Senior Research Scientist Stephanie Dutkiewitz, Principal Research Engineer Christopher Hill, and Research Scientist Gael Forget.

Rolling out a data ball

The team’s new machine learning technique, which they’ve named SAGE, for the Systematic AGgregated Eco-province method, is designed to take large, complicated datasets, and probabilistically project that data down to a simpler, lower-dimensional dataset.

“It’s like making cookies,” Sonnewald says. “You take this horrifically complicated ball of data and roll it out to reveal its elements.”

In particular, the researchers used a clustering algorithm that Sonnewald says is designed to “crawl along a dataset” and hone in on regions with a large density of points — a sign that these points share something in common. 

Sonnewald and her colleagues set this algorithm loose on ocean data from MIT’s Darwin Project, a three-dimensional model of the global ocean that combines a model of the ocean’s climate, including wind, current, and temperature patterns, with an ocean ecology model. That model includes 51 species of phytoplankton and the ways in which each species grows and interacts with each other as well as with the surrounding climate and available nutrients.

If one were to try and look through this very complicated, 51-layered space of data, for every available point in the ocean, to see which points share common traits, Sonnewald says the task would be “humanly intractable.” With the team’s unsupervised machine learning algorithm, such commonalities “begin to crystallize out a bit.”

This first “data cleaning” step in the team’s SAGE method was able to parse the global ocean into about 100 different ecological provinces, each with a distinct balance of species.

The researchers assigned each available location in the ocean model to one of the 100 provinces, and assigned a color to each province. They then generated a map of the global ocean, colorized by province type.  

“In the Southern Ocean around Antarctica, there’s burgundy and orange colors that are shaped how we expect them, in these zonal streaks that encircle Antarctica,” Sonnewald says. “Together with other features, this gives us a lot of confidence that our method works and makes sense, at least in the model.”

Ecologies unified

The team then looked for ways to further simplify the more than 100 provinces they identified, to see whether they could pick out commonalities even among these ecologically distinct regions.

“We started thinking about things like, how are groups of people distinguished from each other? How do we see how connected to each other we are? And we used this type of intuition to see if we could quantify how ecologically similar different provinces are,” Sonnewald says.

To do this, the team applied techniques from graph theory to represent all 100 provinces in a single graph, according to biomass — a measure that’s analogous to the amount of chlorophyll produced in a region. They chose to group the 100 provinces into 12 general categories, or “megaprovinces.” When they compared these megaprovinces, they found that those that had a similar biomass were composed of very different biological species.

“For instance, provinces D and K have almost the same amount of biomass, but when we look deeper, K has diatoms and hardly any prokaryotes, while D has hardly any diatoms, and a lot of prokaryotes. But from a satellite, they could look the same,” Sonnewald says. “So our method could start the process of adding the ecological information to bulk chlorophyll measures, and ultimately aid observations.”

The team has developed an online widget that researchers can use to find other similarities among the 100 provinces. In their paper, Sonnewald’s colleagues chose to group the provinces into 12 categories. But others may want to divide the provinces into more groups, and drill down into the data to see what traits are shared among these groups.

Sonnewald is sharing the tool with oceanographers who want to identify precisely where regions of a particular ecological makeup are located, so they could, for example, send ships to sample in those regions, and not in others where the balance of species might be slightly different.

“Instead of guiding sampling with tools based on bulk chlorophyll, and guessing where the interesting ecology could be found with this method, you can surgically go in and say, ‘this is what the model says you might find here,’” Sonnewald says. “Knowing what species assemblages are where, for things like ocean science and global fisheries, is really powerful.”

This research was funded, in part, by NASA and the Jet Propulsion Laboratory.

from MIT News - Oceanography and ocean engineering https://ift.tt/3diQTVu

Read More

Search-and-rescue algorithm identifies hidden “traps” in ocean waters

The ocean is a messy and turbulent space, where winds and weather kick up waves in all directions. When an object or person goes missing at sea, the complex, constantly changing conditions of the ocean can confound and delay critical search-and-rescue operations.

Now researchers at MIT, the Swiss Federal Institute of Technology (ETH), the Woods Hole Oceanographic Institution (WHOI), and Virginia Tech have developed a technique that they hope will help first responders quickly zero in on regions of the sea where missing objects or people are likely to be.

The technique is a new algorithm that analyzes ocean conditions such as the strength and direction of ocean currents, surface winds, and waves , and identifies in real-time the most attracting regions of the ocean where floating objects are likely to converge.

The team demonstrated the technique in several field experiments in which they deployed drifters and human-shaped manikins in various locations in the ocean. They found that over the course of a few hours, the objects migrated to the regions that the algorithm predicted would be strongly attracting, based on the present ocean conditions.

The algorithm can be applied to existing models of ocean conditions in a way that allows rescue teams to quickly uncover hidden “traps” where the ocean may be steering missing people at a given time.

“This new tool we’ve provided can be run on various models to see where these traps are predicted to be, and thus the most likely locations for a stranded vessel or missing person,” says Thomas Peacock, professor of mechanical engineering at MIT. “This method uses data in a way that it hasn’t been used before, so it provides first responders with a new perspective.”

Peacock and Pierre Lermusiaux, also a professor of mechanical engineering at MIT, who oversaw the project, and their colleagues report their results in a study published today in the journal Nature Communications. Their coauthors are lead author Mattia Serra and corresponding author George Haller of ETH Zurich, Irina Rypina and Anthony Kirincich of WHOI, Shane Ross of Virginia Tech, Arthur Allen of the U.S. Coast Guard, and Pratik Sathe of the University of California at Los Angeles.

Hidden traps

Today’s search-and-rescue operations combine weather forecasts with models of both ocean dynamics and the ways in which objects can drift through the ocean, to map out a search plan, or regions where teams should concentrate their search.

But the ocean is a complicated space of unsteady, ever-changing flow patterns. Coupled with the fact that a missing person has likely been continuously floating through this unsteady flow field for some time, Peacock and his colleagues say that significant errors can accumulate in predicting where to look first, when using a simple approach that directly predicts the trajectories of a few drifting objects.

Instead, the team developed a method to interpret the ocean’s complex flows using advanced, data-driven ocean modeling and prediction systems. They used a novel “Eulerian” approach, in contrast to more commonly used “Lagrangian” approaches — mathematical techniques that involve integrating snapshots of the ocean velocity due to waves and currents to slowly generate an uncertain trajectory for where a missing person or object may have been carried.

The new Eulerian approach uses the most reliable velocity forecast snapshots, close to the point where a missing person or object was last seen, and quickly uncovers the most attracting regions of the ocean at a given time. These Eulerian predictions are then continuously updated when the next batch of updated velocity information becomes available.

The team has named their approach TRAPS, for its goal of identifying TRansient Attracting Profiles, or short-lived regions where water may converge and be likely to pull objects or people. The method is based on a recent mathematical theory,

developed by Serra and Haller at ETH Zurich, to uncover hidden attracting structures in highly unsteady flow data.

“We were a bit skeptical whether a mathematical theory like this would work out on a ship, in real time,” Haller says. “We were all pleasantly surprised to see how well it repeatedly did.”

“We can think of these ‘traps’ as moving magnets, attracting a set of coins thrown on a table. The Lagrangian trajectories of coins are very uncertain, yet the strongest Eulerian magnets predict the coin positions over short times,” Serra says.

“The key thing is, the traps may not have any signature in the ocean current field,” Peacock adds. “If you do this processing for the traps, they might pop up in very different places from where you’re seeing the ocean current projecting where you might go. So you have to do this other level of processing to pull out these structures. They’re not immediately visible.”

Out at sea

Led by WHOI sea-going experts, the researchers tested the TRAPS approach in several experiments out at sea. “As with any new theoretical technique, it is important to test how well it works in the real ocean,” Rypina says.

In 2017 and 2018, the team sailed a small research vessel several hours out off the coast of Martha’s Vineyard, where they deployed at various locations, an array of small round buoys, and manikins.

“These objects tend to travel differently relative to the ocean because different shapes feel the wind and currents differently,” Peacock says. “Even so, the traps are so strongly attracting and robust to uncertainties that they should overcome these differences and pull everything onto them.”

The team ran their modeling and prediction systems, forecasting the ocean’s behavior and currents, and used the TRAPS algorithm to map out strongly attracting regions over the course of the experiment. The researchers let the objects drift freely with the currents for a few hours, and recorded their positions via GPS trackers, before retrieving the objects at the end of the day.

“With the GPS trackers, we could see where everything was going, in real-time,” Peacock says. “So we laid out this initial, widespread pattern of the drifters, and saw that, in the end, they converged on these traps.”

The researchers are planning to share the TRAPS method with first responders such as the U.S. Coast Guard, as a way to speed up search-and-rescue algorithms, and potentially save many more people lost at sea.

“People like Coast Guard are constantly running simulations and models of what the ocean currents are doing at any particular time and they’re updating them with the best data that inform that model,” Peacock says. “Using this method, they can have knowledge right now of where the traps currently are, with the data they have available. So if there’s an accident in the last hour, they can immediately look and see where the sea traps are. That’s important for when there’s a limited time window in which they have to respond, in hopes of a successful outcome.”

This research was primarily funded by the National Science Foundation’s Hazards SEES program, with additional support from the Office of Naval Research and the German National Science Foundation.

from MIT News - Oceanography and ocean engineering https://ift.tt/3grSRVx

Read More

Towable sensor free-falls to measure vertical slices of ocean conditions

The motion of the ocean is often thought of in horizontal terms, for instance in the powerful currents that sweep around the planet, or the waves that ride in and out along a coastline. But there is also plenty of vertical motion, particularly in the open seas, where water from the deep can rise up, bringing nutrients to the upper ocean, while surface waters sink, sending dead organisms, along with oxygen and carbon, to the deep interior.

Oceanographers use instruments to characterize the vertical mixing of the ocean’s waters and the biological communities that live there. But these tools are limited in their ability to capture small-scale features, such as the up- and down-welling of water and organisms over a small, kilometer-wide ocean region. Such features are essential for understanding the makeup of marine life that exists in a given volume of the ocean (such as in a fishery), as well as the amount of carbon that the ocean can absorb and sequester away.

Now researchers at MIT and the Woods Hole Oceanographic Institution (WHOI) have engineered a lightweight instrument that measures both physical and biological features of the vertical ocean over small, kilometer-wide patches. The “ocean profiler,” named EcoCTD, is about the size of a waist-high model rocket and can be dropped off the back of a moving ship. As it free-falls through the water, its sensors measure physical features, such as temperature and salinity, as well as biological properties, such as the optical scattering of chlorophyll, the green pigment of phytoplankton.

“With EcoCTD, we can see small-scale areas of fast vertical motion, where nutrients could be supplied to the surface, and where chlorophyll is carried downward, which tells you this could also be a carbon pathway. That’s something you would otherwise miss with existing technology,” says Mara Freilich, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences and the MIT-WHOI Joint Program in Oceanography/Applied Ocean Sciences and Engineering.

Freilich and her colleagues have published their results today in the Journal of Atmospheric and Oceanic Technology. The paper’s co-authors are J. Thomas Farrar, Benjamin Hodges, Tom Lanagan, and Amala Mahadevan of WHOI, and Andrew Baron of Dynamic System Analysis, in Nova Scotia. The lead author is Mathieu Dever of WHOI and RBR, a developer of ocean sensors based in Ottawa.

Ocean synergy

Oceanographers use a number of methods to measure the physical properties of the ocean. Some of the more powerful, high-resolution instruments used are known as CTDs, for their ability to measure the ocean’s conductivity, temperature, and depth. CTDs are typically bulky, as they contain multiple sensors as well as components that collect water and biological samples. Conventional CTDs require a ship to stop as scientists lower the instrument into the water, sometimes via a crane system. The ship has to stay put as the instrument collects measurements and water samples, and can only get back underway after the instrument is hauled back onboard.

Physical oceanographers who do not study ocean biology, and therefore do not need to collect water samples, can sometimes use “UCTDs” — underway versions of CTDs, without the bulky water sampling components, that can be towed as a ship is underway. These instruments can sample quickly since they do not require a crane or a ship to stop as they are dropped.

Freilich and her team looked to design a version of a UCTD that could also incorporate biological sensors, all in a small, lightweight, towable package, that would also keep the ship moving on course as it gathered its vertical measurements.

“It seemed there could be straightforward synergy between these existing instruments, to design an instrument that captures physical and biological information, and could do this underway as well,” Freilich says.

“Reaching the dark ocean”

The core of the EcoCTD is the RBR Concerto Logger, a sensor that measures the temperature of the water, as well as the conductivity, which is a proxy for the ocean’s salinity. The profiler also includes a lead collar that provides enough weight to enable the instrument to free-fall through the water at about 3 meters per second — a rate that takes the instrument down to about 500 meters below the surface in about two minutes.

“At 500 meters, we’re reaching the upper twilight zone,” Freilich says. “The euphotic zone is where there’s enough light in the ocean for photosynthesis, and that’s at about 100 to 200 meters in most places. So we’re reaching the dark ocean.”

Another sensor, the EcoPuck, is unique to other UCTDs in that it measures the ocean’s biological properties. Specifically, it is a small, puck-shaped bio-optical sensor that emits two wavelengths of light — red and blue. The sensor captures any change in these lights as they scatter back and as chlorophyll-containing phytoplankton fluoresce in response to the light. If the red light received resembles a certain wavelength characteristic of chlorophyll, scientists can deduce the presence of phytoplankton at a given depth. Variations in red and blue light scattered back to the sensor can indicate other matter in the water, such as sediments or dead cells — a measure of the amount of carbon at various depths.

The EcoCTD includes another sensor unique to UCTDs — the Rinko III Do, which measures the oxygen concentration in water, which can give scientists an estimate of how much oxygen is being taken up by any microbial communities living at a given depth and parcel of water.

Finally, the entire instrument is encased in a tube of aluminum and designed to attach via a long line to a winch at the back of a ship. As the ship is moving, a team can drop the instrument overboard and use the winch to pay the line out at a rate that the instrument drops straight down, even as the ship moves away. After about two minutes, once it has reached a depth of about 500 meters, the team cranks the winch to pull the instrument back up, at a rate that the  instrument catches up to the ship within 12 minutes. The crew can then drop the instrument again, this time at some distance from their last dropoff point.

“The nice thing is, by the time we go to the next cast, we’re 500 meters away from where we were the first time, so we’re exactly where we want to sample next,” Freilich says.

They tested the EcoCTD on two cruises in 2018 and 2019, one to the Mediterranean and the other in the Atlantic, and in both cases were able to collect both physical and biological data at a higher resolution than existing CTDs.

“The ecoCTD is capturing these ocean characteristics at a gold-standard quality with much more convenience and versatility,” Freilich says.

The team will further refine their design, and hopes that their high-resolution, easily-deployable, and more efficient alternative may be adapted by both scientists to monitor the ocean’s small-scale responses to climate change, as well as fisheries that want to keep track of a certain region’s biological productivity.  

This research was funded in part by the U.S. Office of Naval Research.

from MIT News - Oceanography and ocean engineering https://ift.tt/2LJGFBp

Read More

Melting glaciers cool the Southern Ocean

Tucked away at the very bottom of the globe surrounding Antarctica, the Southern Ocean has never been easy to study. Its challenging conditions have placed it out of reach to all but the most intrepid explorers. For climate modelers, however, the surface waters of the Southern Ocean provide a different kind of challenge: It doesn’t behave the way they predict it would. “It is colder and fresher than the models expected,” says Craig Rye, a postdoc in the group of Cecil and Ida Green Professor of Oceanography John Marshall within MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).

In recent decades, as the world warms, the Southern Ocean’s surface temperature has cooled, allowing the amount of ice that crystallizes on the surface each winter to grow. This is not what climate models anticipated, and a recent study accepted in Geophysical Research Letters attempts to disentangle that discrepancy. “This paper is motivated by a disagreement between what should be happening according to simulations and what we observe,” says Rye, the lead author of the paper who is currently working remotely from NASA’s Goddard Institute for Space Studies, or GISS, in New York City.

“This is a big conundrum in the climate community,” says Marshall, a co-author on the paper along with Maxwell Kelley, Gary Russell, Gavin A. Schmidt, and Larissa S. Nazarenko of GISS; James Hansen of Columbia University’s Earth Institute; and Yavor Kostov of the University of Exeter. There are 30 or so climate models used to foresee what the world might look like as the climate changes. According to Marshall, models don’t match the recent observations of surface temperature in the Southern Ocean, leaving scientists with a question that Rye, Marshall, and their colleagues intend to answer: how can the Southern Ocean cool when the rest of the Earth is warming?

This isn’t the first time Marshall has investigated the Southern Ocean and its climate trends. In 2016, Marshall and Yavor Kostov PhD ’16 published a paper exploring two possible influences driving the observed ocean trends: greenhouse gas emissions, and westerly winds — strengthened by expansion of the Antarctic ozone hole — blowing cold water northward from the continent. Both explained some of the cooling in the Southern Ocean, but not all of it. “We ended that paper saying there must be something else,” says Marshall.

That something else could be meltwater released from thawing glaciers. Rye has probed the influence of glacial melt in the Southern Ocean before, looking at its effect on sea surface height during his PhD at the University of Southampton in the UK. “Since then, I’ve been interested in the potential for glacial melt playing a role in Southern Ocean climate trends,” says Rye.

The group’s recent paper uses a series of “perturbation” experiments carried out with the GISS global climate model where they abruptly introduce a fixed increase in melt water around Antarctica and then record how the model responds. The researchers then apply the model’s response to a previous climate state to estimate how the climate should react to the observed forcing. The results are then compared to the observational record, to see if a factor is missing. This method is called hindcasting.

Marshall likens perturbation experiments to walking into a room and being confronted with an object you don’t recognize. “You might give it a gentle whack to see what it’s made of,” says Marshall. Perturbation experiments, he explains, are like whacking the model with inputs, such as glacial melt, greenhouse gas emissions, and wind, to uncover the relative importance of these factors on observed climate trends.

In their hindcasting, they estimate what would have happened to a pre-industrial Southern Ocean (before anthropogenic climate change) if up to 750 gigatons of meltwater were added each year. That quantity of 750 gigatons of meltwater is estimated from observations of both floating ice shelves and the ice sheet that lies over land above sea level. A single gigaton of water is very large — it can fill 400,000 Olympic swimming pools, meaning 750 gigatons of meltwater is equivalent to pouring water from 300 million Olympic swimming pools into the ocean every year.

When this increase in glacial melt was added to the model, it led to sea surface cooling, decreases in salinity, and expansion of sea ice coverage that are consistent with observed trends in the Southern Ocean during the last few decades. Their model results suggest that meltwater may account for the majority of previously misunderstood Southern Ocean cooling.

The model shows that a warming climate may be driving, in a counterintuitive way, more sea ice by increasing the rate of melting of Antarctica’s glaciers. According to Marshall, the paper may solve the disconnect between what was expected and what was observed in the Southern Ocean, and answers the conundrum he and Kostov pointed to in 2016. “The missing process could be glacial melt.”

Research like Rye’s and Marshall’s help project the future state of Earth’s climate and guide society’s decisions on how to prepare for that future. By hindcasting the Southern Ocean’s climate trends, they and their colleagues have identified another process, which must be incorporated into climate models. “What we’ve tried to do is ground this model in the historical record,” says Marshall. Now the group can probe the GISS model response with further “what if?” glacial melt scenarios to explore what might be in store for the Southern Ocean.

from MIT News - Oceanography and ocean engineering https://ift.tt/2zGkycy

Read More

Protecting seafarers and the global supply chain during Covid-19

The offshore and shipping industries are grappling with unique challenges in the face of the Covid-19 pandemic. The virus’ rapid spread on ships like the Diamond Princess and USS Theodore Roosevelt highlighted the health risks that the 1.2 million workers currently at sea face. Travel restrictions and closed borders offer an additional challenge by not only disrupting the global supply chain, but preventing scheduled crew changeovers from taking place.

To address these issues, the UN Global Compact Action Platform for Sustainable Ocean Business recently released recommendations developed by their Covid-19 Task Force. Thomas Peacock, professor of mechanical engineering, is a member of the task force, along with representatives from professional societies, international agencies, industry, nonprofits, and academia.

According to the UN, 90 percent of traded goods are transported via shipping. On a typical day, there are 50,000 vessels at sea, making a total of 4 million ports of call annually. Meanwhile, offshore platforms supply one third of the world’s oil and gas.

“The shipping and offshore industries are the heart of the global supply chains,” explains Peacock. “Governments need to take a unified approach to not only avoid disruptions to the international supply chain, but to protect the health of seafarers.”

Peacock has conducted research at sea for 15 years on global-class research vessels and aboard local coastal vessels all over the world — from the South China Sea to the Arctic. Peacock was originally connected to the UN Global Compact through the MIT Policy Lab at the Center for International Studies for his extensive work in deep-sea mining.

As Covid-19 began its global spread, the UN Global Compact focused on the associated challenges. They drafted a plan to operate in phases, or “short sprints.” “The goal of this first ‘short sprint’ has been to identify the most pressing issues and try and deal with them first,” adds Peacock.

The result is a list of 14 recommendations that help “ensure the continuing safe and efficient function of ocean-related supply chains during the Covid-19 pandemic.” One main theme that emerges from these recommendations is that in order to protect both seafarers and the global supply chain, a unified international response will be vital.

Ensuring the health and safety of seafarers

After the plight of cruise ships and news broke about the Covid-19 cases aboard the USS Roosevelt, concerns about the impact the pandemic may have on seafarers increased. “The USS Roosevelt will have world-class medical capabilities on board,” explains Peacock. “If that level of offshore vessel faced challenges coping with a Covid outbreak, you can appreciate the challenges facing a commercial shipping fleet.”

The most pressing issue the shipping industry will face in the next few weeks relates to the changeover of crew onboard that typically takes places each month. The crew on shipping vessels rotate over a certain period of time — usually a few months. Each month, roughly 100,000 seafarers change over, with crew members who have been at sea relieved by a new set of crew members once they arrive in port. At present, new data from the International Chamber of Shipping suggest the current number is at 150,000.

As travel bans and restrictions were put in place across the world in March and April, the typical crew changeover that would have occurred in mid-April was put on hold. Crew members currently at sea had their contracts extended. Additionally, repair work and inspections have been delayed. With many of the travel restrictions still in place, a solution for May is urgently needed.

“There comes a point when you have to switch people out from the ship, get new people on board, and make any necessary repairs to vessels and offshore platforms,” says Peacock. “And so, unless appropriate action is taken, there could be major challenges pending regarding the May crew changeovers.” He adds, “It is also important to recognize the selfless contribution that many  seafarers have made in dealing with the situation throughout April by remaining at sea.”

One of the solutions the UN Global Compact Task Force recommends is classifying seafarers as “key workers” and deeming shipping and offshore activities an “essential service.” Doing so would help ensure the freedom of movement necessary to protect seafarers’ health and minimize impact to the global supply chain.

An international approach

Response to the spread of Covid-19 has varied widely across different countries. From quarantine measures to contact tracing and travel bans, government intervention has differed at the national, state, and local level. But when it comes to ocean supply chains, according to the UN Global Compact recommendations, a unified international approach is essential.

“If there are different rules and protocols in one country compared to another, this inevitably brings challenges,” explains Peacock. “As much as possible, there needs to be a unified approach and leading agencies such as the IMO, the ILO, the WHO, and many others have been working incredibly hard to develop protocols and recommendations.”

To help shape this international approach, the UN Global Compact Task Force has recommended the establishment of an Ocean Supply Chain Task Force in pursuit of “holistic and harmonized global cooperation and coordination to ensure the safety and integrity of ocean-related global supply chains.”

Another element that will need to be consistent across borders according to the UN Global Compact Task Force includes the certification and classification procedures

“Shipping relies on certification and classification programs that everyone has to abide by to be able operate,” adds Peacock. “Those take time to reassess, but there must be pragmatism in making certain allowances in light of this global pandemic.”

The recommendations outlined by the UN Global Compact Task Force serve as a first step toward addressing the threats Covid-19 brings to both the safety of those at sea and the integrity of the global supply chains. The task force will continue meeting to draft additional recommendations in the hopes that governments will work together and take an international approach.

from MIT News - Oceanography and ocean engineering https://ift.tt/3fKmvVV

Read More

3 Questions: Harnessing wave power to rebuild islands

Many island nations, including the Maldives in the Indian Ocean, are facing an existential threat as a result of a rising sea level induced by global climate change. A group of MIT researchers led by Skylar Tibbits, an associate professor of design research in the Department of Architecture, is testing ways of harnessing nature’s own forces to help maintain and rebuild threatened islands and coastlines.

Some 40 percent of the world’s population lives in coastal areas that are threated by sea level rise over the coming decades, yet there are few proven measures for countering the threat. Some suggest building barrier walls, dredging coastlines to rebuild beaches, or building floating cities to escape the inevitable, but the search for better approaches continues.

The MIT group was invited by Invena, a group in the Maldives who had seen the researchers’ work on self-assembly and self-organization and wanted to collaborate on solutions to address sea-level rise. The resulting project has now shown promising initial results, with a foot and a half of localized sand accumulation deposited in just four months. MIT News asked Tibbits to describe the new approach and its potential.

Q: People have been trying to modify and control the movement of sand for centuries. What was the inspiration for this new and different approach to rebuilding beaches and shorelines?

A: When we first visited the Maldives, we were taken to a local sandbar that had just formed. It was incredible to see the size of the sandbar, about 100 meters long and 20 meters wide, and the quantity of sand, over 1 meter deep, that was built completely on its own, in just a matter of months. We came to understand that these sandbars appear and disappear at different times of the year based on the forces of the ocean and underwater bathymetry. Local historians told us about how they would collaborate with the ocean, growing vegetation to expand their islands or morph their shape. These natural and collaborative approaches to growing land mass through sand self-organization came in stark contrast to the human dredging of sand from the deep ocean, which is also used for island reclamation. In the same amount of time that it takes to dredge an island, which takes months, we watched three different sandbars form themselves, through satellite imagery.

We started to realize that the amount of energy, time, money, labor, and destruction of the marine environment that is caused by dredging could likely be stopped if we could understand why sandbars form naturally and tap into this natural phenomenon of self-organization. The goal of our lab and field experiments is to test hypotheses on why sandbars form, and translate those into mechanisms for promoting their accumulation in strategic locations.

By collaborating with the natural forces of the ocean we believe we can promote the self-organization of sand structures to grow islands and rebuild beaches. We believe this is a sustainable approach to the problem that can eventually be scaled to many coastal areas around the world, just as forest management is used to help strengthen and protect forests from uncontrolled fires or overgrowth.

Q: Can you describe how this system works, and how it harnesses the energy of the waves to build up the sand in the places where it's needed?

A: Together with our collaborators in the Maldives, we are designing, testing, building, and deploying submersible devices that, based simply on their geometry in relationship to the ocean waves and currents, promote sand accumulation in specific areas. In our first field experiment we built bladders out of heavy-duty canvas, sewn together into the precise ramp geometries. With our second field experiment, we took the best designs from hundreds of lab experiments and had them fabricated from a geotextile membrane. In both experiments we filled the bladders with sand to weigh them down and then submerged them underwater. For our next field experiment we are building bladders that have internal chambers that act like a ballast in a submarine, allowing the bladder to sink or float and to be quickly moved or deployed. Each experiment is attempting to make the fabrication and installation process as simple and scalable as possible.

The simplest mechanism that we are testing is a ramp-like geometry that sits on the ocean floor and rises vertically to the surface of the water. To the best of our understanding, what we are seeing is that as the water flows over the top of the ramp it creates turbulence on the other side, mixing the sand and water and then creating sediment transport. The sand begins to accumulate on the backside of the ramp, continually piling on top of itself. We have tested many other geometries that attempt to minimize wrap-around effects, or focus the accumulation in specific areas, and we are continuing to search for optimal geometries. In many ways, these behave like natural depth variations, reef structures, or volcanic formations and may function similarly in promoting sand accumulation. Our goal is to create adaptable versions of these geometries which can be easily moved, reoriented, or deployed whenever seasons change or storms are increasing.

Since 2018 we have been conducting experiments in our lab at MIT in collaboration with Taylor Perron in [the Department of] Earth, Atmospheric and Planetary Sciences. We have built two wave tanks where we are testing a variety of wave conditions, sand behaviors, and geometries to promote accumulation. The goal is to align our lab experiments and models with real-world conditions specific to the two predominant seasons in the Maldives. We have done hundreds of tank experiments so far and are using these studies to gain intuition and insight into what mechanisms result in the greatest sand accumulation. The best of these lab experiments is then translated to field experiments twice a year.

Q: How were you able to detect and quantify the effects of your experiment, and what are your plans for continuing and expanding this project?

A: We have collected satellite imagery, drone footage, and physical measurements ever since installing our first field experiment in February 2019 and our second field experiment in October / November 2019. The satellite images and drone footage give us a visual indication of sand accumulation; however, it is challenging to quantify the amount of sand from those images. So we rely heavily on physical depth measurements. We have a series of coordinates that we send to our collaborators in the Maldives who then take a boat or jet ski out to those coordinates and take depth measurements. We then compare these measurements with our previous measurements, considering the day/time and relationship to the tide height.

With our latest field experiment, we have been collecting imagery and physical measurements to analyze the sand accumulation. We are now seeing roughly a half meter (about 20 inches) of new sand accumulation over an area of approximately 20 meters by 30 meters, since November. That is about 300 cubic meters of sand accumulation, in roughly four months. We see these as promising early results that are part of a much longer-term initiative where we aim to continue to test these approaches in the Maldives and various other locations around the world.

We have recently been awarded a National Geographic Exploration grant and plan to go back to the Maldives for two more field installations later this year and in 2021. Our long-term goal is to create a system of submersible structures that can adapt to the dynamic weather conditions to naturally grow and rebuild coastlines. We aim to scale this approach and tailor it to many locations around the world to help rebuild and stabilize heavily populated coastlines and vulnerable island nations.

from MIT News - Oceanography and ocean engineering https://ift.tt/2zopRwZ

Read More