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Cavaleri L.,Institute of Marine Science
Journal of Geophysical Research: Oceans | Year: 2016

In this paper, a new methodology is proposed for the computation of Background Errors in wave data assimilation systems. Background errors define the spatial influence of an observation in the model domain. Since at present the directional wave spectrum is the fundamental variable of both state-of-the-art numerical models and most modern instrumentation, this is at the core of the proposed methodology. The advantage of the spectral approach is that the wave spectrum contains detailed information of the different wave systems and physical processes at work (e.g., wind-sea or swells). These systems have different origins and may be driven by different mechanisms, having therefore different spatial structures, length scales, and sensitivity to local wind conditions. The presented method enables making consistent and specific corrections to each component of the spectrum, in time and space. The innovations presented here require an integral look at the data assimilation algorithm for which a suitable scheme is also proposed. Examples of computed background errors are presented for shelf and oceanic basins showing the spatial structures of the different wave systems active in these areas. © 2015. American Geophysical Union. Source


McCulloch M.,University of Western Australia | Falter J.,University of Western Australia | Trotter J.,University of Western Australia | Montagna P.,Laboratoire Des Science Du Climat Et Of Lgenvironnement | And 2 more authors.
Nature Climate Change | Year: 2012

Rapidly rising levels of atmospheric CO 2 are not only causing ocean warming, but also lowering seawater pH hence the carbonate saturation state of the oceans, on which many marine organisms depend to calcify their skeletons. Using boron isotope systematics, we show how scleractinian corals up-regulate pH at their site of calcification such that internal changes are approximately one-half of those in ambient seawater. This species-dependent pH-buffering capacity enables aragonitic corals to raise the saturation state of their calcifying medium, thereby increasing calcification rates at little additional energy cost. Using a model of pH regulation combined with abiotic calcification, we show that the enhanced kinetics of calcification owing to higher temperatures has the potential to counter the effects of ocean acidification. Up-regulation of pH, however, is not ubiquitous among calcifying organisms; those lacking this ability are likely to undergo severe declines in calcification as CO 2 levels increase. The capacity to up-regulate pH is thus central to the resilience of calcifiers to ocean acidification, although the fate of zooxanthellate corals ultimately depends on the ability of both the photosymbionts and coral host to adapt to rapidly increasing ocean temperatures. © 2012 Macmillan Publishers Limited. All rights reserved. Source


News Article
Site: http://news.yahoo.com/green/

COCONUT ISLAND, Hawaii (AP) — Scientists at a research center on Hawaii's Coconut Island have embarked on an experiment to grow "super coral" that they hope can withstand the hotter and more acidic oceans that are expected with global warming. The quest to grow the hearty coral comes at a time when researchers are warning about the dire health of the world's reefs, which create habitats for marine life, protect shorelines and drive tourist economies. When coral is stressed by changing environmental conditions, it expels the symbiotic algae that live within it and the animal turns white or bright yellow, a process called bleaching, said Ruth Gates, director of the Institute of Marine Biology at the University of Hawaii. If the organisms are unable to recover from these bleaching events, especially when they recur over several consecutive years, the coral will die. Gates estimated that about 60 to 80 percent of the coral in Kaneohe Bay has bleached this year. "The bleaching has intensified and got much more serious," said Gates of the coral around the bay. Where they once looked for the bleached coral among the healthy, Gates said her team is now "looking for the healthy individuals in a sea of pale corals." Gates and her team are taking the coral to their center on the 29-acre isle, once a retreat for the rich and famous and home to television's Gilligan's Island, and slowly exposing them to slightly more stressful water. They bathe chunks of coral that they've already identified as having strong genes in water that mimics the warmer and more acidic oceans. They are also taking resilient strains and breeding them with one another, helping perpetuate those stronger traits. The theory they are testing is called assisted evolution, and while it has been used for thousands of years on other plants and animals, the concept has not been applied to coral living in the wild. "We've given them experiences that we think are going to raise their ability to survive stress," Gates said. She said they hope to see these corals, which will soon be transplanted into the bay, maintain their color, grow normally and then reproduce next summer. In early October, the National Oceanic and Atmospheric Administration said that coral reefs worldwide are experiencing bleaching, calling the event extensive and severe. "We may be looking at losing somewhere in the range of 10 to 20 percent of the coral reefs this year," NOAA coral reef watch coordinator Mark Eakin said when the report was released. "Hawaii is getting hit with the worst coral bleaching they have ever seen." And this is the second consecutive year Hawaii has experienced widespread bleaching. Scientists say some coral has already fallen victim to global warming. About 30 percent of the world's population has already perished as a result of above average ocean temperatures, El Nino's effects and acidification. Gates and her team understand the challenges of scalability and time. Having success locally does not necessarily mean they will be able to scale their project to address a massive, global marine crisis before much of the world's coral reefs are already gone. Tom Oliver, a marine biologist and team leader at NOAA's Coral Reef Ecosystem Division, said the project is scalable with the requisite amount of effort and funding. He said, "the question is not can they do it, it's can they do it fast enough?" Oliver said that many reef restoration projects struggle because of the cost and time involved with raising standard coral and planting it in the ocean. "Restoration needs to have brood stock that can handle the changing conditions on reefs," he said. Gates said more research needs to be done before they can begin to address scalability. In 2013, Gates and her Australian counterpart Dr. Madeleine van Oppen, who does coral research at the Australia Institute of Marine Science, won the $10,000 Paul G. Allen Ocean Challenge for their proposal to assist coral evolution. Allen's foundation then asked them for a proposal to fully fund the idea, which they eventually did with a $4 million grant in June. Allen, who co-founded Microsoft with Bill Gates, has various climate-related projects in his philanthropic portfolio.


Cavaleri L.,Institute of Marine Science | Fox-Kemper B.,University of Colorado at Boulder | Hemer M.,Center for Australian Weather and Climate Research | Hemer M.,CSIRO
Bulletin of the American Meteorological Society | Year: 2012

The Earth climate system contains a vast range of processes and feedbacks, so it is natural to focus first on the dominant ones, for example, those dominating planetary heat and carbon budgets. However, these basic processes have been modeled with increasing accuracy since the days of Arrhenius (1896a,b). Nowadays, we seek to improve representation and quantify the uncertainty of many more processes. Quite often dominant processes modulate the subdominant, and vice versa, with a whole cascade of reciprocal actions and feedbacks. This last point, feedback, is where difficulties arise, particularly if it occurs within interactions spanning multiple scales. Then practical difficulties of measuring the relevant interactions or the excessive computer power required for simulation limit our development of theoretical and quantitative assessment of how important these feedbacks may be. In this situation, we take a shortcut and use a parameterization that summarizes one, or several, processes into a simplified algorithm. Progress, bias analysis, and experience tell us how much further we need to go to have more accurate and reliable results. Today it is obvious that the atmosphere and ocean are heavily interacting-enormous quantities of heat, energy, water vapor, and carbon dioxide are exchanged each instant through their boundary layers. After the overall radiation balance, these exchange processes are the next priority in providing predictions of the climate system from seasons to centuries. The role of these exchanges is clear, in that the heat capacity of only a few meters of the ocean equals that of the whole atmosphere, and the carbon reservoir of the ocean dwarfs all but the lithosphere. However, having in mind the scale of the planet, it is natural to look at the problem on a large scale. Waves are small in comparison, a tiny distributed detail. However, it is a beautiful example of the little process modulating the overall large-scale behavior. Granted that some of the small-scale processes do affect the large-scale ones, the question is how much they affect the climate. One point of view is that the climate is established by the overall budget of incoming and outgoing radiation. Even if this is the case, two aspects need to be pointed out. First, the distribution of temperature and other parameters will vary based on small-scale processes rather than overall balances, and such distributions and their variations are relevant to humans even if they only slightly affect the global energy balance. Second, as climate is progressively changing through natural and anthropogenic changes, we live in a permanent transient situation. Only application of our best physical principles, rather than empirical parameterizations, can be robust in the face of a changing climate. Science has been slow to appreciate the extent of the interaction between ocean and the atmosphere. It took even longer to understand how these exchanges are modulated by the characteristics of the surface that separates the two phases. Here, we have tried to emphasize how sea state, particularly during wave-breaking conditions and when waves are not equilibrated with the wind, strongly modulates many of the processes that have a direct influence on climate. We still do not grasp the whole physics nor an accurate measure of the degree to which the mean state and climate feedbacks are affected by these modulations, but having an idea of where we want to go is certainly a good start. Many groups worldwide are attempting to quantify these effects of waves on climate in observations, models, and theory, and we celebrate their accomplishments and look forward to their discoveries. We need to carry on, understanding more and more the physics of the thin layer of fluid that, in the immensity of space, surrounds the planet that is our home. © 2012 American Meteorological Society. Source


News Article
Site: http://phys.org/biology-news/

The research, from the University's Institute of Marine Science, led by Master's student Lucy van Oosterom and including Dr Craig Radford and Professors John Montgomery and Andrew Jeffs, is the first direct evidence that fish communicate to maintain group cohesion. While scientists have known fish send messages to each other for mating purposes or to defend territory, this is the first time research has proved they also use contact calls to keep together. The research team used captive wild Bigeyes (Pempheris adspersa) in the study, a species commonly found along New Zealand's north-east coast. Bigeyes are generally nocturnal, retreating to caves during the day and foraging at night in loosely-knit shoals. Previous work by Dr Radford has shown Bigeyes have a distinctive 'pop' call with an estimated maximum range of 31.6m. This vocal behaviour, coupled with relatively sensitive hearing organs, led researchers to assume Bigeyes communicated in groups but up to now the evidence has been anecdotal. Using underwater hydrophones, a GoPro camera and an MP3 player, the researchers collected almost 100 fish from the Leigh coast north of Auckland and put them in saltwater tanks at Leigh Marine Laboratory. In experiments carried out over five months, they played two types of sound to the captive fish: one of the normal reef environment at Leigh where the fish live, and another recording of Bigeye vocalisations. When the sound recordings were played, the Bigeyes increased their own calling rates by more than five times in order to maintain contact over and above the background noise. They also swam closer together. When there were no sound, the fish swam further apart. "This study means that fish are now the oldest vertebrate group in which this behaviour has been observed and that has interesting implications for our understanding of evolutionary behaviour among vertebrates," Ms van Oosterom says. Explore further: Fish talk to each other, researcher finds More information: L. van Oosterom et al. Evidence for contact calls in fish: conspecific vocalisations and ambient soundscape influence group cohesion in a nocturnal species, Scientific Reports (2016). DOI: 10.1038/srep19098

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