Decades of data on world’s oceans reveal a troubling oxygen decline

Date: May 4, 2017

Source: Georgia Institute of Technology

Summary: The amount of dissolved oxygen contained in the water — an important measure of ocean health — has been declining for more than 20 years, reveals a new analysis of decades of data on oceans across the globe.

A new analysis of decades of data on oceans across the globe has revealed that the amount of dissolved oxygen contained in the water — an important measure of ocean health — has been declining for more than 20 years.

Canary in the kelp forest

The one-two punch of warming waters and ocean acidification is predisposing some marine animals to dissolving quickly under conditions already occurring off the Northern California coast, according to a study from the University of California, Davis.

In the study, published in the journal Proceedings of the Royal Society B: Biological Sciences, researchers at the UC Davis Bodega Marine Laboratory raised bryozoans, also known as “moss animals,” in seawater tanks and exposed them to various levels of water temperature, food and acidity.

The scientists found that when grown in warmer waters and then exposed to acidity, the bryozoans quickly began to dissolve. Large portions of their skeletons disappeared in as little as two months.

“We thought there would be some thinning or reduced mass,” said lead author Dan Swezey, a recent Ph.D. graduate in professor Eric Sanford’s lab at the UC Davis Bodega Marine Laboratory. “But whole features just dissolved practically before our eyes.”

SKELETONS KEY

Bryozoans are colonial animals, superficially similar to, but not related, to corals. They are abundant in California kelp forests and are calcareous, meaning they build their honeycomb-shaped skeletons from calcium carbonate.

The scientists found that when raised under warming conditions, bryozoans altered their chemical composition by building higher levels of magnesium into their skeletons, particularly if they were also eating less food. When exposed to acidic conditions already observed off coastal California, these changes predisposed the animals to dissolve.

The researchers consider bryozoans a canary in the coal mine for other marine animals that build calcareous skeletons containing magnesium. These include sea stars, sea urchins, calcifying algae and tube-building worms.

The authors do not know why the bryozoans added more magnesium to their skeletons under warmer temperatures. But they conclude that marine organisms with skeletons made of high-magnesium calcite may be especially susceptible to ocean acidification because this form of calcium carbonate dissolves more easily than others.

Bryozoans grow in connected colonies. During the experiments, the animals shut down parts of themselves when undergoing the stress of ocean acidification, redirecting their energy to new growth. This was somewhat like closing down units of a condominium complex while building new ones at the same time. But the moss animals could not outpace the dissolution.

“They were trying to grow but were dissolving at the same time,” Swezey said.

CALCIFIED ANIMALS INCREASINGLY VULNERABLE

The authors said the study underlines the increasing vulnerability of calcified animals to ocean acidification, which occurs as the ocean absorbs more atmospheric carbon emitted through the burning of fossil fuels.

During the spring and summer months, deep ocean water rich in carbon dioxide periodically wells up along the California coast when surface waters are pushed offshore by strong winds. These upwelling events also push nutrients to the surface to help support kelp forests and productive fisheries. However, this deep water tends to be more acidic.

Climate modeling shows that the trends of warming ocean temperatures, stronger winds and increasingly strong upwelling events are expected to continue in the coming years as carbon dioxide concentrations in the atmosphere increase. This indicates that acidic conditions will likely become more common, rather than episodic.

MARINE LIFE FACES MANY CHANGES AT ONCE

“Marine life is increasingly faced with many changes at once,” said co-author Sanford, a professor in the UC Davis Department of Evolution and Ecology. “For bryozoans, their response to warmer temperature makes them unexpectedly vulnerable to ocean acidification. The question now is whether other marine species might respond in a similar way.”

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The study’s other co-authors include Jessica Bean, Aaron Ninokawa, Tessa Hill, and Brian Gaylord from UC Davis. Bean is also affiliated with UC Berkeley.

The study was supported by grants from the National Science Foundation and the University of California Multicampus Research Programs and Initiatives. Swezey was also supported by a NSF Graduate Research Fellowship.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

Originally posted: https://www.eurekalert.org/pub_releases/2017-04/uoc–cit041717.php

Video: Leading Fisheries Scientists Challenge Lenfest Research that Recommended Cutting Catch of Forage Fish

Clockwise from top left: Dr. Ray Hilborn, Dr. Ricardo O. Amoroso, and Dr. Carl J. Walters

WASHINGTON (NCFC) — April 3, 2017 — A new study by a team of respected fisheries scientists from around the globe is challenging previous forage fish research, most notably the 2012 Lenfest Oceans Program report “Little Fish, Big Impact,” which recommended leaving more forage fish in the water to be eaten by predators.

Dr. Ray Hilborn of the University of Washington was the lead author on the paper, which will be published later today in the peer-reviewed journal Fisheries Research. The study concludes that fishing of forage species likely has a lower impact on their predators than previously thought.

You can learn more about this important research right now by watching the seven-minute video below. In the video, Dr. Hilborn and two of the paper’s co-authors, Dr. Carl J. Walters and Dr. Ricardo O. Amoroso, discuss the paper’s findings, and their implications for forage fish management.

The Lenfest Oceans Program was established in 2004 by the Lenfest Foundation and is managed by the Pew Charitable Trusts

Look for further updates, and the complete research paper, from Saving Seafood’s National Coalition for Fishing Communities throughout the day.

Copyright © 2016 Saving Seafood

Figuring Out When and Why Squids Lost Their Shells

A 166-million-year-old fossil of an extinct relative of the squid. Credit Jonathan Jackson and ZoË Hughes/National History Museum of London

Shaped like a torpedo and about as swift, squids are jet-propelled underwater predators. Together with their nimble brethren, the octopus and cuttlefish, they make for an agile invertebrate armada.

But that was not always the case. Hundreds of millions of years ago, the ancestors of the tentacled trio were slow, heavily armored creatures, like the coil-shelled ammonites and the cone-shelled belemnites.

Alastair Tanner, a doctoral student at University of Bristol in England, wanted to better understand why those cephalopods lost their shells. But though both ammonites and the belemnites have left behind rich fossil records, their shell-less descendants have not.

So Mr. Tanner conducted a genetic analysis of 26 present day cephalopods, including the vampire squid, the golden cuttlefish and the southern blue-ringed octopus.

With the molecular clock technique, which allowed him to use DNA to map out the evolutionary history of the cephalopods, he found that today’s cuttlefish, squids and octopuses began to appear 160 to 100 million years ago, during the so-called Mesozoic Marine Revolution.

Mr. Tanner published his findings last week in the journal Proceedings of the Royal Society B: Biological Sciences.

During the revolution, underwater life underwent a rapid change, including a burst in fish diversity. Some predators became better suited for crushing shellfish, while some smaller fish became faster and more agile.

“There’s a continual arms race between the prey and the predators,” said Mr. Tanner. “The shells are getting smaller, and the squids are getting faster.”

The evolutionary pressures favored being nimble over being armored, and cephalopods started to lose their shells, according to Mr. Tanner. The adaptation allowed them to outcompete their shelled relatives for fast food, and they were able to better evade predators. They were also able to keep up with competitors seeking the same prey.

Today most cephalopods are squishy and shell-less. The biggest exception is the nautilus. But though there are more than 2,500 fossilized species of nautilus, today only a handful of species exist.

Squid and octopus species number around 300 each, and there are around 120 species of cuttlefish. The differences in number, compared with the nautilus, indicates the advantages that these cephalopods may have gained over their shelled relatives, according to Mr. Tanner.

“It became a much more successful strategy to be a really high metabolism, very rapid moving animal,” Mr. Tanner said, “and they evolved into these really quite amazing things we see today.”

Read the original post: https://www.nytimes.com/

Scientists: Major Oxygen Loss to Oceans Linked to Warming Climate

— Posted with permission of SEAFOODNEWS.COM. Please do not republish without their permission. —

Copyright © 2017 Seafoodnews.com

SEAFOODNEWS.COM [Washington Post] by By Chris Mooney – February 16, 2017

A large research synthesis, published in one of the world’s most influential scientific journals, has detected a decline in the amount of dissolved oxygen in oceans around the world — a long-predicted result of climate change that could have severe consequences for marine organisms if it continues.

The paper, published Wednesday in the journal Nature by oceanographer Sunke Schmidtko and two colleagues from the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, found a decline of more than 2 percent in ocean oxygen content worldwide between 1960 and 2010. The loss, however, showed up in some ocean basins more than others. The largest overall volume of oxygen was lost in the largest ocean — the Pacific — but as a percentage, the decline was sharpest in the Arctic Ocean, a region facing Earth’s most stark climate change.

The loss of ocean oxygen “has been assumed from models, and there have been lots of regional analysis that have shown local decline, but it has never been shown on the global scale, and never for the deep ocean,” said Schmidtko, who conducted the research with Lothar Stramma and Martin Visbeck, also of GEOMAR.

Ocean oxygen is vital to marine organisms, but also very delicate — unlike in the atmosphere, where gases mix together thoroughly, in the ocean that is far harder to accomplish, Schmidtko explained. Moreover, he added, just 1 percent of all the Earth’s available oxygen mixes into the ocean; the vast majority remains in the air.

Climate change models predict the oceans will lose oxygen because of several factors. Most obvious is simply that warmer water holds less dissolved gases, including oxygen. “It’s the same reason we keep our sparkling drinks pretty cold,” Schmidtko said.

But another factor is the growing stratification of ocean waters. Oxygen enters the ocean at its surface, from the atmosphere and from the photosynthetic activity of marine microorganisms. But as that upper layer warms up, the oxygen-rich waters are less likely to mix down into cooler layers of the ocean because the warm waters are less dense and do not sink as readily.

“When the upper ocean warms, less water gets down deep, and so therefore, the oxygen supply to the deep ocean is shut down or significantly reduced,” Schmidtko said.

The new study represents a synthesis of literally “millions” of separate ocean measurements over time, according to GEOMAR. The authors then used interpolation techniques for areas of the ocean where they lacked measurements.

The resulting study attributes less than 15 percent of the total oxygen loss to sheer warmer temperatures, which create less solubility. The rest was attributed to other factors, such as a lack of mixing.

Matthew Long, an oceanographer from the National Center for Atmospheric Research who has published on ocean oxygen loss, said he considers the new results “robust” and a “major advance in synthesizing observations to examine oxygen trends on a global scale.”

Long was not involved in the current work, but his research had previously demonstrated that ocean oxygen loss was expected to occur and that it should soon be possible to demonstrate that in the real world through measurements, despite the complexities involved in studying the global ocean and deducing trends about it.

That’s just what the new study has done.

“Natural variations have obscured our ability to definitively detect this signal in observations,” Long said in an email. “In this study, however, Schmidtko et al. synthesize all available observations to show a global-scale decline in oxygen that conforms to the patterns we expect from human-driven climate warming. They do not make a definitive attribution statement, but the data are consistent with and strongly suggestive of human-driven warming as a root cause of the oxygen decline.

“It is alarming to see this signal begin to emerge clearly in the observational data,” he added.

“Schmidtko and colleagues’ findings should ring yet more alarm bells about the consequences of global warming,” added Denis Gilbert, a researcher with the Maurice Lamontagne Institute at Fisheries and Oceans Canada in Quebec, in an accompanying commentary on the study also published in Nature.

Because oxygen in the global ocean is not evenly distributed, the 2 percent overall decline means there is a much larger decline in some areas of the ocean than others.

Moreover, the ocean already contains so-called oxygen minimum zones, generally found in the middle depths. The great fear is that their expansion upward, into habitats where fish and other organism thrive, will reduce the available habitat for marine organisms.

In shallower waters, meanwhile, the development of ocean “hypoxic” areas, or so-called “dead zones,” may also be influenced in part by declining oxygen content overall.

On top of all of that, declining ocean oxygen can also worsen global warming in a feedback loop. In or near low oxygen areas of the oceans, microorganisms tend to produce nitrous oxide, a greenhouse gas, Gilbert writes. Thus the new study “implies that production rates and efflux to the atmosphere of nitrous oxide … will probably have increased.”

The new study underscores once again that some of the most profound consequences of climate change are occurring in the oceans, rather than on land. In recent years, incursions of warm ocean water have caused large die-offs of coral reefs, and in some cases, kelp forests as well. Meanwhile, warmer oceans have also begun to destabilize glaciers in Greenland and Antarctica, and as they melt, these glaciers freshen the ocean waters and potentially change the nature of their circulation.

When it comes to ocean deoxygenation, as climate change continues, this trend should also increase — studies suggest a loss of up to 7 percent of the ocean’s oxygen by 2100. At the end of the current paper, the researchers are blunt about the consequences of a continuing loss of oceanic oxygen.

“Far-reaching implications for marine ecosystems and fisheries can be expected,” they write.

Copyright © 2016 Seafoodnews.com

Ocean acidification to hit West Coast Dungeness crab fishery, new assessment shows

The acidification of the ocean expected as seawater absorbs increasing amounts of carbon dioxide from the atmosphere will reverberate through the West Coast’s marine food web, but not necessarily in the ways you might expect, new research shows.

Dungeness crabs, for example, will likely suffer as their food sources decline. Dungeness crab fisheries valued at about $220 million annually may face a strong downturn over the next 50 years, according to the research published Jan. 12 in the journal Global Change Biology. But pteropods and copepods, tiny marine organisms with shells that are vulnerable to acidification, will likely experience only a slight overall decline because they are prolific enough to offset much of the impact, the study found.

Dungeness crab.jkirkhart35/Flickr

Marine mammals and seabirds are less likely to be affected by ocean acidification, the study found.

“What stands out is that some groups you’d expect to do poorly don’t necessarily do so badly – that’s probably the most important takeaway here,” saidKristin Marshall, lead author of the study who pursued the research as a postdoctoral researcher at the University of Washington and NOAA Fisheries’ Northwest Fisheries Science Center. “This is a testament in part to the system’s resilience to these projected impacts. That’s sort of the silver lining of what we found.”

While previous studies have examined the vulnerability of particular species to acidification in laboratories, this is among the first to model the effects across an entire ecosystem and estimate the impacts on commercial fisheries.

“The real challenge is to go from experiments on what happens to individual animals in the lab over a matter of weeks, to try to capture the effects on the whole population and understand how vulnerable it really is,” said Isaac Kaplan, a research scientist at NOAA Fisheries’ Northwest Fisheries Science Center in Seattle.

The research used sophisticated models of the California Current ecosystem off the Pacific Coast to assess the impacts of a projected 0.2 unit decline in the pH of seawater in the next 50 years, which equates to a 55 percent increase in acidity. The California Current is considered especially vulnerable to acidification because the upwelling of deep, nutrient-rich water low in pH already influences the West Coast through certain parts of the year.

The ocean absorbs about one-third of carbon dioxide released into the atmosphere from the burning of fossil fuels, which has led to a 0.1 unit drop in pH since the mid-1700s.

The research built on an earlier effort by NOAA scientists Shallin Busch and Paul McElhanythat quantified the sensitivity of various species to acidification, as originally reported in 393 separate papers. In a novel approach, Busch and McElhany weighed the evidence for each species based on its reported sensitivity in the laboratory, relevance to the California Current and agreement between studies.

This synthesis by Busch and McElhany identified 10 groups of species with highest vulnerability to acidification. Marshall and colleagues incorporated this into the ecosystem model to examine how acidification will play out in nature. The study particularly examined the effects on commercially important species including Dungeness crab; groundfish such as rockfish, sole and hake; and coastal pelagic fish such as sardines and anchovy over the period from 2013 to 2063.

The study modeled the potential risks of ocean acidification (under a future decrease in pH) on the West Coast marine food web and fisheries over 50 years, from 2013 to 2063. NOAA Fisheries

“This was basically a vulnerability assessment to sharpen our view of where the effects are likely to be the greatest and what we should be most concerned about in terms of how the system will respond,” said Tim Essington, a UW professor of aquatic and fishery sciences and a co-author of the research.

The study provides a foundation for further research into the most affected species, he said.

Although earlier studies have shown that Dungeness crab larvae is vulnerable to acidification, the assessment found that the species declined largely in response to declines in its prey – including bivalves such as clams and other bottom-dwelling invertebrate species.

Since Dungeness crab is one of the most valuable fisheries on the West Coast, its decline would have some of the most severe economic effects, according to the research. Groundfish such as petrale sole, Dover sole and deep-dwelling rockfish are also expected to decline due to acidification, according to the assessment. However, fisheries for those species are much less valuable so the economic impact would not be as large.

Coastal pelagic fish were only slightly affected.

“Dungeness crab is a bigger economic story than groundfish,” Kaplan said. “There are winners and losers, but the magnitude of the impact depends on how important the species is economically.”

The research was funded by the NOAA Ocean Acidification Program and the National Centers for Coastal Ocean Science. Marshall was supported by a National Research Council fellowship.

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For more information, contact Marshall at kmarsh2@uw.edu and Kaplan atisaac.kaplan@noaa.gov 206-302-2446.

This piece was adapted from a Northwest Fisheries Science Center news release.

Squid boats dot Malibu coast: Roughly 40,157 tons of squid caught this season

Squid boats are seen from Malibu’s Zuma Beach on a recent January evening. Suzanne Guldimann/22nd Century Media

Almost every night this winter, bright lights have appeared off the coast of Malibu.

It’s an eerie sight on a foggy evening, suggesting something unearthly or supernatural, but the only thing these ghostly lights portend is the presence of Doryteuthis opalescens, the common market squid.

It’s a good omen for California’s seafood industry. Market squid is one of California’s largest commercial fisheries, and tons of frozen California calamari are shipped all over the world each year. However, the species had almost entirely disappeared from Southern California waters last year. The absence of squid is being blamed on El Niño.

California Department of Fish and Wildlife environmental scientist Laura Ryley studies squid.

“Market squid was very limited in Southern California last year,” she told The Malibu Surfside News. 

Ryley explained that the squid are thought to react to the warmer water generated by El Niño, migrating further north in search of the right water temperature and conditions for spawning.

“The commercial fishery was landing squid in Eureka and off the coast of Oregon last year,” Ryley said.

She added that the management plan for the species implemented in 2005 provides an opportunity for scientists to gather data on the size, sex and abundance of the species. That data show that market squid generally have the ability to recover swiftly after an El Niño event.

“The patterns in the past show the squid are still able to reproduce and that they bounce back quickly,” she said.

While concerns are being raised over the potential impact of prolonged ocean warming on the species, the return of more normal temperature conditions in the Pacific this winter appears to have signaled the return of the squid. 

An abundance of cephalopods isn’t just an auspicious sign for the fishing industry. It may mean fewer problems for local sea lion and elephant seal populations, which have experienced mass stranding events blamed in part on the same warm water that impacted the squid and other key prey species like Pacific sardines and mackerel.

“I’ve heard that market squid isn’t the sea lion’s favorite, but they will eat it,” Ryley said. “It’s an important food for other species as well. Salmonids eat them. So do sea birds.”

The California Department of Fish and Wildlife’s management plan for the market squid fishery limits the seasonal catch to 118,000 tons per season. The season opens April 1 each year, and runs until the limit is met or until March 31, whichever comes first.

This season got off to a slow start but is accelerating. As of Dec. 30, 2016, the total landings of market squid were 40,157.6 tons.

That’s in sharp contrast to 2013, the last big year for squid, when the quota for the season was reached by early November, according to NOAA Fisheries data, but a major increase from 2014 and 2015, when the numbers plummeted in Southern California.

In the Malibu area, autumn and winter are the peak time for commercial squid fishing. The shallow waters along the Malibu coast are usually a prime location for squid, which migrate to the shallow, sandy, near-shore area in the fall to spawn.

Special light boats equipped with high wattage bulbs attract the squid, which are caught using either seine or scoop nets. The lights are supposed to be shielded to reduce the impact on migratory birds and coastal residents, but compliance isn’t 100 percent yet.

The Monterey Bay Aquarium’s Seafood Watch program rates market squid as a “good alternative” for sustainability, but most of the California catch is frozen and shipped to Asia. 

“The American market prefers squid with a thicker mantle,” Ryley said. 

Market squid rarely grow to be more than 10 inches in length. They are short-lived; 9-10 months is usually the maximum life span, and they spawn just once, at the end of their lives.

Squid can only be caught on weekdays from the U.S.-Mexico border to the California-Oregon border. From noon Friday to noon Sunday the squid are given a “break.”

“The thinking behind that is to give them a time for uninterrupted spawning,” Ryley explained.

Squid fishing is permitted all along the Malibu coast, even within the boundaries of the Point Dume State Marine Conservation Area, located off the coast of Zuma and Lechuza beaches. Only Point Dume State Marine Reserve (Paradise Cove to Westward Beach) is off limits.

With more than half the season’s limit still swimming around in the Pacific, it’s a safe bet that the unearthly green and pink glow of the squid boats will continue to light up Malibu’s coast, drawing the curiosity of more than just squid.

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Read the original post: http://www.malibusurfsidenews.com/

Scientists: Global Ocean Circulation Could Be More Vulnerable to Shutdown Than We Thought

— Posted with permission of SEAFOODNEWS.COM. Please do not republish without their permission. —

Copyright © 2017 Seafoodnews.com

SEAFOODNEWS.COM [The Washington Post] by Chelsea Harvey – January 5, 2017

Intense future climate change could have a far different impact on the world than current models predict, suggests a thought-provoking new study just out in the journal Science Advances. If atmospheric carbon dioxide concentrations were to double in the future, it finds, a major ocean current — one that helps regulate climate and weather patterns all over the world — could collapse. And that could paint a very different picture of the future than what we’ve assumed so far.

The Atlantic meridional overturning circulation, or AMOC, is often described as a large oceanic conveyor belt. It’s a system of water currents that transports warm water northward from the Atlantic toward the Arctic, contributing to the mild climate conditions found in places like Western Europe. In the Northern Atlantic, the northward flowing surface water eventually cools and sinks down toward the bottom of the ocean, and another current brings that cooler water back down south again. The whole process is part of a much larger system of overturning currents that circulates all over the world, from pole to pole.

But some scientists have begun to worry that the AMOC isn’t accurately represented in current climate models. They say that many models portray the current as being more stable than real-life observations suggest it actually is. Recent studies have suggested that the AMOC is weakening, although there’s some scientific debate about how much of this has been caused by human activities and how much by natural variations.

Nevertheless, the authors of the new study point out, many climate models assume a fairly stable AMOC — and that could be affecting the predictions they make for how the ocean will change under future climate change. And because overturning circulation patterns have such a significant effect on climate and weather all over the world, this could have big implications for all kinds of other climate-related projections as well.

“This is a very common and well-known issue in climate models,” said the new study’s lead author, Wei Liu, a postdoctoral associate at Yale University, who conducted the work while at the University of California at San Diego. “I wanted to see, if I use a corrected model, how this will affect the future climate change.”

Liu and colleagues from the UC-San Diego and the University of Wisconsin at Madison took a commonly used climate model and corrected for what they considered to be the AMOC stability bias. Then they ran an experiment to see how the correction would affect the model’s projections under future climate change. They instantaneously doubled the atmospheric carbon dioxide concentration from present-day levels in both the corrected and uncorrected models, and then they let both models run for hundreds of simulated years.

The differences were striking. In the uncorrected climate model, the AMOC weakens for a while, but eventually recovers. In the corrected model, however, the AMOC continues to weaken and after 300 years, it collapses altogether.

In a commentary also published today in RealClimate, Stefan Rahmstorf, an oceans physics expert at the Potsdam Institute for Climate Impact Research, explained how such a collapse could occur when the AMOC gets too weak.

“Freshwater continually flows into the northern Atlantic through precipitation, rivers and ice-melting,” he wrote. “But supply of salty waters from the south, through the Gulf Stream System, balances this. If however the current slows, there is less salt supply, and the surface ocean gets less salty.”

Because freshwater is less dense than salty water, this process can lead to a kind of stratification, in which the lighter freshwater gets stuck on the surface of the ocean and can’t sink to the bottom when it reaches the cooler north. When this happens, the overturning process that drives the current back down south again can’t occur.

“There is a critical point when this becomes an unstoppable vicious circle,” Rahmstorf wrote. “This is one of the classic tipping points in the climate system.”

The resulting climate consequences, compared to the uncorrected model, are also dramatic. Without the usual transport of warm water into the north, the corrected model predicts a marked cooling over the northern Atlantic, including in the United Kingdom, Iceland and northwestern Europe, as well as in the Arctic, where sea ice begins to expand.

Because the AMOC is part of a larger global conveyor system, which ferries warm and cold currents between the equator and both poles, the model predicts disruptions in other parts of the world as well. Without cold water moving back down south again, the corrected model indicates a stronger warming pattern south of the equator than what’s predicted by the uncorrected model, causing a polarization in precipitation patterns over the Americas — more rain for places like northeastern Brazil and less rain for Central America. The model also predicts a greater reduction in sea ice for the Antarctic.

All this doesn’t necessarily mean that everything we thought we knew about the future climate is wrong. For one thing, most modern climate projections focus on the next few decades or so, noted Thomas Haine, an expert on ocean circulation at Johns Hopkins University. And within 50 years or so, both the uncorrected and corrected models in the new study produce similar results. It is only after that, under extreme warming, that the current shifts.

Liu also cautioned that certain aspects of the experiment can’t exactly be considered realistic — for instance, instantaneously doubling the atmospheric carbon dioxide concentration. Current climate efforts are aimed at keeping us from ever getting to such a point — but even if we did, the process would happen gradually, not overnight. So the model’s outcome might have been different if the researchers had adopted a more realistic scenario.

Haine also suggested that the correction in the new study may have actually been a bit too strong, compared to actual observations — in other words, the modeled AMOC is “probably more unstable than the real system,” he said.

Rahmstorf also pointed out this issue in his commentary — but he added that the climate model used also did not account for an influx of meltwater from Greenland under future climate change, an event that recent research suggests could substantially speed the AMOC’s weakening.

“With unmitigated emissions . . . the Gulf Stream System weakens on average by 37 percent by the year 2300 without Greenland melt,” he notes. “With Greenland meltwater this doubles to 74 percent. And a few months ago, a study with a high-resolution ocean model appeared, suggesting that the meltwater from Greenland is likely to weaken the AMOC considerably within a few decades.”

The fact that current models don’t take this melting into account is further support for the idea that scientists have been underestimating the risk of a future AMOC collapse, he suggested.

According to Liu, the new study serves to make a point about the dramatic effects that can occur when corrections are made in climate models, as well as the AMOC’s major role in the global climate. By tweaking a climate model to make it more consistent with real-life observations, very different outcomes may be observed, Liu noted.

“I would say that it is reasonably well-accepted that a current generation of climate models [is] missing the essential physics in representing the AMOC,” said Haine. And he added that the new study “points to the need to fix these biases in the climate models.”

Peggy Parker, Science and Sustainability Editor
SeafoodNews.com 1-781-861-1441
Editorial Email: Editor@seafood.com
Reporter’s Email: peggyparker@seafood.com

Copyright © 2017 Seafoodnews.com

Download/Watch: NASA ThermohalineConveyor.mp4 | 81MB

Millions of Sardines Cloud San Diego Coast

A large sardine shoal showed up off the coast of California.

View original article/video: http://abcnews.go.com/

NOAA research links human-caused CO2 emissions to dissolving sea snail shells off U.S. West Coast

November 22, 2016 – For the first time, NOAA and partner scientists have connected the concentration of human-caused carbon dioxide in waters off the U.S. Pacific coast to the dissolving of shells of microscopic marine sea snails called pteropods.

Commercially valuable fish such as salmon, sablefish and rock sole make the pteropod a major part of their diet.

“This is the first time we’ve been able to tease out the percentage of human-caused carbon dioxide from natural carbon dioxide along a large portion of the West Coast and link it directly to pteropod shell dissolution,” said Richard Feely, a NOAA senior scientist who led the research appearing in Estuarine, Coastal and Shelf Science. “Our research shows that humans are increasing the acidification of U.S. West Coast coastal waters, making it more difficult for marine species to build strong shells.”

The global ocean has soaked up one-third of human-caused CO2 emissions since the start of the Industrial Era. While this reduces the amount of this greenhouse gas in the atmosphere, it comes at a cost to the ocean. CO2 absorbed by seawater increases its acidity, reducing carbonate ions, which are building blocks used by shellfish to grow their shells.

 (NOAA)

The pteropod, a sea snail the size of the head of a pin, is found in the Pacific Ocean. It has been the focus of research in recent years because its shell is affected by how much CO2 is in seawater and it may be an indicator of ocean acidification affecting the larger marine ecosystem.

A key piece of the new research was determining how much human CO2  emissions have added to naturally occurring CO2 in seawater off the U.S. West Coast. Using several decades of measurements from the Pacific Ocean taken through the U.S. Global Ocean Carbon and Repeat Hydrography Programoffsite link and new data from four NOAA West Coast research cruises conducted between 2007 and 2013, the research team developed a method to estimate additional CO2 from human-caused emissions since the start of the Industrial Era as compared to CO2 from natural sources.

The analysis shows that concentrations of human-caused CO2 are greatest in shallow waters where the atmosphere gives up large amounts of its CO2 to the sea. The researchers also estimated that CO2 concentrations from fossil fuel emissions make up as much as 60 percent of the CO2 that enriches most West Coast nearshore surface waters. But the concentrations dropped as they measured deeper. It drops to 21 percent in deeper waters of 328 feet or 100 meters, and falls even lower to about 18 percent in waters below 656 feet or 200 meters. Concentrations vary depending on location and seasons as well.

Once researchers created a detailed map of the human-generated CO2 concentrations, they  looked at how pteropod shells fared in areas with varying seawater CO2 concentrations. They found more than 50 percent of pteropod shells collected from coastal waters with the high CO2 concentrations were severely dissolved. An estimated 10 to 35 percent of pteropods taken from offshore waters showed shell damage when examined under a scanning electron microscope.

“We estimate that since pre-industrial times, pteropod shell dissolution has increased 20 to 25 percent on average in waters along the U.S. West Coast,” said Nina Bednaršek of the University of Washington. Earlier research by Bednaršek and others has shown that shell dissolution affects pteropod swimming ability and may hamper their ability to protect themselves from predators.

“This new research suggests we need a better understanding of how changes in pteropods may be affecting other species in the food chain, especially commercially valuable species such as salmon, sablefish, and rock sole that feed on pteropods,” Bednaršek added.

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