Posts Tagged oceans

Feb 17 2017

Scientists: Major Oxygen Loss to Oceans Linked to Warming Climate

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

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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

 

Mar 28 2012

House Subcommittee Holds Hearing on the National Ocean Policy’s Effect on Fishing

California Capitol Hill Bulletin – March 22, 2012

The House Natural Resources Subcommittee on Fisheries, Wildlife, Oceans, and Insular Affairs met on Thursday, March 21, 2012 for an oversight hearing titled Empty Hooks: The National Ocean Policy is the Latest Threat to Access for Recreational and Commercial Fishermen. The Committee previously held a hearing on the National Ocean Policy on October 4, 2011.

Witnesses included: Captain Robert F. Zales, II, President, National Association of Charterboat Operators; Gary Zurn, Senior Vice President Marketing, Big Rock Sports, LLC; Terry Gibson, Principle, North Swell Media, LLC; George J. Mannina, Jr., Partner, Nossaman, LLC; and Justin LeBlanc, Federal Representative, United Charter Boats.

The President signed an executive order on July 19th, 2010 to adopt the final recommendations of the Interagency Ocean Policy Task Force, effectively instituting the new National Ocean Policy (the Policy). Over 140 federal laws and numerous agencies have jurisdiction over ocean resources. The aim of the Policy is to manage commerce and conservation of ocean resources through a “comprehensive and collaborative framework for the stewardship of the ocean, our coasts, and the Great Lakes that facilitates cohesive actions across the Federal Government, as well as participation of State, tribal, and local authorities, regional governance structures, nongovernmental organizations, the public, and the private sector.” The National Ocean Council, tasked with implementing the Policy, extended the public comment period on the draft National Ocean Policy Implementation Plan by one month through March 28, 2012. House Resources Committee Chair Doc Hastings (WA) had requested that the deadline be extended by 90 days, arguing “[t]he likelihood of deterring new investment and job creation is too great to rush the implementation of this questionable new federal bureaucracy.”

This week’s hearing focused on the effects of the Policy on commercial and recreational fishing. Issues discussed included:

 

  • Recreational and commercial fishing statistics, including that recreational fishing in 2009 produced sales impacts totaling $50 billion and value added impacts of $23 billion while providing over 327,000 jobs. Commercial Fishing provided over 1 million jobs, $116 billion in sales and $32 billion in income impacts.

 

  • The possible negative effect of the Policy on jobs directly and indirectly related to fishing.

 

  • The level of involvement of stakeholders in the advancement of the Policy, with concerns raised regarding the lack of fishery representatives on the Policy’s Regional Planning Bodies.

 

  • The current regulatory burdens on fishing (including no-fishing mandates), and whether the industry can absorb more regulation without serious consequence to its economic value.

 

  • The Policy’s lack of regulatory authority, but the concern that it may still add new and expanded regulations on already regulated industries and activities.

 

  • The impact of California’s expected finalization of a statewide effort that will place 15-20 percent of the state’s coastal waters off limits to fishing through a process called the Marine Life Protection Act Initiative (MLPA).

 

  • The benefits that can be realized because of the Policy’s new management framework, which will create a coordinated, regional system that breaks down barriers between different agencies and reduces the complicated regulatory bureaucracy currently governing the oceans.

 

Read the article on California Capital Hill Bulletin, or for more information visit NaturalResources.house.gov.