Source: Florida State University
Posted by Jenny Griffin
A new study by a Florida State University biologist shows that bleaching events brought on by rising sea temperatures are having a detrimental long-term impact on coral.
Professor Don Levitan, chair of the Department of Biological Science, writes in the latest issue of Marine Ecology Progress Series that bleaching -- a process where high water temperatures or UV light stresses the coral to the point where it loses its symbiotic algal partner that provides the coral with color -- is also affecting the long-term fertility of the coral.
"Even corals that didn't bleach aren't reproducing at the levels they should," Levitan said.
Most corals reproduce by releasing sperm and eggs into the ocean during brief annual spawning events. The chance of sperm finding and fertilizing an egg depends on corals spawning in close proximity and in synchrony with each other.
In a study of the corals that build the major framework of Caribbean coral reefs, Levitan's team found that the species living in shallower water experienced near total reproductive failure, while the species living in deeper water was about half as likely to spawn.
"The remarkable finding from this study was that the reduction in spawning persisted for three additional years, long after the corals had regained their symbiotic partners and regained their normal appearance," Levitan said.
The worldwide decrease in coral abundance in combination with long-term reductions in spawning and reproduction following bleaching events put reef- building corals in a difficult situation. Eggs might be released, but never fertilized.
And that could have a major impact on the ecosystem at large.
Levitan's team has been studying coral that is just off the coast of Panama since 1996. And since then, those corals have been exposed to two bleaching events. On average, it takes coral three to four years to recover from bleaching.
"Even if we can fix what's killing these corals, it's going to be hard for coral populations to recover, because the surviving corals might not successfully produce enough offspring to repopulate reefs," he said.
The coral in that region is critical to building reefs, a crucial part of local ecosystems.
"There's a variety of reasons why people should care about this," Levitan said.
Coral reefs provide protection and shelter for many different species of fish. Without the reefs, certain fish are left homeless and without an area to reproduce. They also protect coastlines from large waves and flooding, a major issue in areas that are prone to tropical storms or hurricanes.
In the future, Levitan said his team would like to examine the quality of gamete production and also determine if corals that have already bleached are more or less likely to bleach again.
Levitan DR, Boudreau W, Jara J, Knowlton N (2014) Long-term reduced spawning in Orbicella coral species due to temperature stress. Mar Ecol Prog Ser 515:1-10 doi:10.3354/meps11063
New study shows significant differences between climate archives and climate models
Source: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
Posted by Jenny Griffin
Earth's climate appears to have been more variable over the past 7,000 years than often thought. This is the conclusion of a new study forthcoming online this week in the U.S. scientific journal Proceedings of the National Academy of Sciences (PNAS). In the study, scientists from the Potsdam-based Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, and Harvard University show that sea surface temperatures reconstructed from climate archives vary to a much greater extent on long time scales than simulated by climate models. The consequence: either the analysed climate archives supply inaccurate temperature signals, or the tested models underestimate the regional climate fluctuations in Earth's recent history.
In order to reconstruct climate history, it is necessary to study natural climate archives since, in terms of Earth's history, humankind has only very recently begun measuring the planet. There have been instrumental measurements of ocean temperatures for only around 150 years now. For periods prior to that, scientists have to rely on "proxies," i.e. indicators enabling indirect conclusions to be drawn about climate data from earlier times. Such climate archives generally refer to spatially limited areas and differ in their temporal resolution. They may also include significant "background noise."
"In our study we weren't interested in how warm the climate might have been at time X in a specific region. We wanted to retrospectively analyse how much the regional climate temporally varies over decades to millennia," explains Dr. Thomas Laepple from the Alfred Wegener Institute. "One of our biggest challenges was to make it possible to compare various measured data and climate archives from a wide variety of regions and filter out the natural noise that can greatly distort the signal of climate archives."
Laepple and his colleague Peter Huybers from Harvard University compared data from temperature measurements, corals and sediment cores originating from many different marine regions of the world. Climate data from modern corals date back no more than 400 years. They allow conclusions to be made about temperature changes over decades or centuries. Marine sediments may contain much older data, but generally only achieve a centennial or millennial resolution. Using different calibration and filtering processes, the two researchers succeeded in combining a wide variety of available data from temperature measurements and climate archives in such a way that they were able to compare the reconstructed sea surface temperature variations at different locations around the globe on different time scales over a period of 7,000 years.
"We initially determined that the natural variations of ocean temperatures are surprisingly large -- and the longer the periods we analysed, the greater the variations," was the initial conclusion of the two scientists. Then, in a second step, they studied around 20 climate models in over 100 test runs to ascertain how well the models can simulate these temperature variations. The result: measured and climate archive data closely correspond to model runs for periods of years. Toward longer timescales, however, discrepancies grow -- most significantly in tropical marine regions. On a millennial time scale, conventional climate models underestimated the variations of sea surface temperatures reconstructed from climate archives by a factor of 50.
"Fundamentally, there are only two explanations," says Thomas Laepple. "Either the climate archives do not provide reliable temperature data, or the climate models underestimate the variability of the climate. Or both may be true to some extent." The results are based on a number of independent climate archives, as well as instrumental records, and hold up whilst applying a wide range of correction methods, which leads Laepple to believe that the problem lies more with the models.
"We seem to have to revise upward predictions of how much climate can regionally vary," suggests Thomas Laepple, based on his findings. "Given the huge amount of greenhouse gases released into the atmosphere, we can be sure that it is getting warmer globally. But the range of changes we are headed for could well be larger than we have generally expected." This has to do with the fact that the natural variations in combination with the warming trend always point in both directions: over a period of decades or a hundred years temperatures in a particular region may rise to a lesser or greater degree than present-day climate models generally forecast.
Since this is a central issue for the forecasting of future climatic conditions on Earth, for about a year now the physicist in Potsdam has been heading an interdisciplinary research group that focuses specifically on this topic. It is called "ECUS -- Estimating climate variability by quantifying proxy uncertainty and synthesizing information across archives."
According to Laepple: "We are in the middle of an experiment that we cannot reverse, but which we still don't understand well enough to make clear statements at the regional level on longer time scales. Unfortunately, we will just have to continue to live with this uncertainty for some time."
T. Laepple, P. Huybers. Ocean surface temperature variability: Large model-data differences at decadal and longer periods. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1412077111
Salinity and temperature records from corals in a remote Pacific island in Kiribati show the ocean has warmed over the last sixty years and has set up the conditions for stronger El Niño weather events.
Source: Australian National University
Posted by Jenny Griffin
The ocean is warming steadily and setting up the conditions for stronger El Niño weather events, a new study has shown.
A team of US, Australian, and Canadian researchers sampled corals from a remote island in Kiribati to build a 60-year record of ocean surface temperature and salinity.
“The trend is unmistakeable, the ocean’s primed for more El Niño events,” says lead-author Dr Jessica Carilli, now based at the University of Massachusetts, Boston.
Team member Dr Helen McGregor from the Research School of Earth Sciences at The Australian National University said the change in El Niño patterns could have a major impact on Australia’s weather.
“During an El Niño event warm waters to the north of Australia move eastward, taking their rainfall with them,” she said.
“This changes the pattern of Australia’s rainfall and droughts significantly.”
El Niños occurs irregularly every two to seven years and have often coincided with severe droughts in Queensland and New South Wales. The current conditions show that a weak El Niño has brought warmer and drier conditions to Australia for late 2014.
The team focused on regional differences in sea temperatures that generate the circulating winds known as the Walker Circulation, which drive the trade winds that bring moisture across the Pacific Ocean to the north of Australia.
The island from which the corals were sampled, Butaritari, was chosen for its location at one end of the Walker Circulation.
The team extracted a core from a Porites coral on the outer part of the atoll which showed a clear layer structure that, like tree rings, told the seasonal life story of the coral.
“This coral quietly laid down an excellent record of the ocean conditions at that location,” Dr McGregor said.
“It greatly complements direct measurements of the ocean temperatures made by humans throughout the 60 year period, filling in the inconsistencies and gaps.”
The team used the amounts of the chemicals strontium, calcium and oxygen in the coral to work out the ocean’s salinity and temperature.
Jessica E. Carilli, Helen V. McGregor, Jessica J. Gaudry, Simon D. Donner, Michael K. Gagan, Samantha Stevenson, Henri Wong, David Fink. Equatorial Pacific coral geochemical records show recent weakening of the Walker Circulation. Paleoceanography, 2014; DOI: 10.1002/2014PA002683
Source: University of Hawaii ‑ SOEST
Posted by Jenny Griffin
"This summer has seen the highest global mean sea surface temperatures ever recorded since their systematic measuring started. Temperatures even exceed those of the record-breaking 1998 El Niño year," says Axel Timmermann, climate scientist and professor, studying variability of the global climate system at the International Pacific Research Center, University of Hawaii at Manoa.
From 2000-2013 the global ocean surface temperature rise paused, in spite of increasing greenhouse gas concentrations. This period, referred to as the Global Warming Hiatus, raised a lot of public and scientific interest. However, as of April 2014 ocean warming has picked up speed again, according to Timmermann's analysis of ocean temperature datasets.
"The 2014 global ocean warming is mostly due to the North Pacific, which has warmed far beyond any recorded value (see Figure 1a on this page, above) and has shifted hurricane tracks, weakened trade winds, and produced coral bleaching in the Hawaiian Islands," explains Timmermann.
He describes the events leading up to this upswing as follows: Sea-surface temperatures started to rise unusually quickly in the extratropical North Pacific already in January 2014. A few months later, in April and May, westerly winds pushed a huge amount of very warm water usually stored in the western Pacific along the equator to the eastern Pacific. This warm water has spread along the North American Pacific coast, releasing into the atmosphere enormous amounts of heat--heat that had been locked up in the Western tropical Pacific for nearly a decade.
"Record-breaking greenhouse gas concentrations and anomalously weak North Pacific summer trade winds, which usually cool the ocean surface, have contributed further to the rise in sea surface temperatures. The warm temperatures now extend in a wide swath from just north of Papua New Guinea to the Gulf of Alaska (see Figure 1b on this page, above)," says Timmermann.
The current record-breaking temperatures indicate that the 14-year-long pause in ocean warming has come to an end.
Source: NOAA Headquarters
Posted by Jenny Griffin
Warming water temperatures due to climate change could expand the range of many native species of tropical fish, including the invasive and poisonous lionfish, according to a study of 40 species along rocky and artificial reefs off North Carolina by researchers from NOAA and the University of North Carolina-Wilmington.
The findings, reported for the first time, were published in the September issue of Marine Ecology Progress Series.
“The results will allow us to better understand how the fish communities might shift under different climate change scenarios and provide the type of environmental data to inform future decisions relating to the management and siting of protected areas,” said Paula Whitfield, a research ecologist at NOAA’s National Centers for Coastal Ocean Science (NCCOS) and lead author of the study.
The North Carolina reefs lie within the temperate-tropical transition zone, where historically, both temperate and tropical species live, at their respective range limits. However, water temperatures in the zone are becoming more tropical, making it an important place to detect climate changes and its impacts.
The researchers first made these discoveries during an ecological study of the marine communities on the North Carolina reefs. Findings from this earlier study showed similar shifts of climate change induced shifts in algal populations.
Researchers combined year-round bottom water temperature data with 2006-2010 fish community surveys in water depths from 15 to 150 feet off the coast of North Carolina. The study revealed that the fish community was primarily tropical in the deeper areas surveyed, from 122 to 150 feet, with a winter mean temperature of 21 °C (69.8 °F). However, many of these native tropical fishes, usually abundant in shallow, somewhat cooler reefs, tended to remain in the deeper, warmer water, suggesting that temperature is a main factor in controlling their distribution.
“Globally, fish communities are becoming more tropical as a result of warming temperatures, as fish move to follow their optimal temperature range.,” said Whitfield. “Along the North Carolina coast, warming water temperatures may allow the expansion of tropical fish species, such as lionfish, into areas that were previously uninhabitable due to cold winter temperatures. The temperature thresholds collected in this study will allow us to detect and to estimate fish community changes related to water temperature.”
“This kind of monitoring data set is quite rare because it combines multi-year quantitative fish density data with continuous bottom water temperature data from the same location,” said Jonathan A. Hare, NOAA Fisheries research oceanographer and a co-author on the study.
Similarly, the distribution of the venomous Indo-Pacific lionfish (Pterois volitans), a species new to the Atlantic since 2000, was restricted to water depths deeper than 87 feet where the average water temperature was higher than 15.2°C (approximately 59.4 °F). As the more shallow waters warm, lionfish may expand their range, since they seem to be attracted to areas with a warmer minimum temperature. Although lionfish only arrived in North Carolina in 2000 they were the most common species observed in water depths from 122 to 150 feet in this study.
Since their first sighting off the Florida east coast, in the late 1980s, lionfish have spread throughout the western North Atlantic including the Gulf of Mexico and Caribbean. They are considered a major threat to Atlantic reefs by reducing reef fish recruitment and biomass, and have been implicated in cascading impacts such as decreased coral cover on coral reefs. To date, cold winter bottom temperatures are the only factor found to control their distribution on a large scale.
PE Whitfield, RC Muñoz, CA Buckel, BP Degan, DW Freshwater, JA Hare. Native fish community structure and Indo-Pacific lionfish Pterois volitans densities along a depth-temperature gradient in Onslow Bay, North Carolina, USA. Marine Ecology Progress Series, 2014; 509: 241 DOI: 10.3354/meps10882
Source: United States Geological Survey
Posted by Jenny Griffin
Late-summer water temperatures near the Florida Keys were warmer by nearly 2 degrees Fahrenheit in the last several decades compared to a century earlier, according to a new study by the U.S. Geological Survey.
Researchers indicate that the warmer water temperatures are stressing corals and increasing the number of bleaching events, where corals become white resulting from a loss of their symbiotic algae. The corals can starve to death if the condition is prolonged.
"Our analysis shows that corals in the study areas are now regularly experiencing temperatures above 84 F during July, August and September; average temperatures that were seldom reached 120 years ago," said Ilsa Kuffner, a USGS research marine biologist and the study's lead author. "When corals are exposed to water temperatures above 84 F they grow more slowly and, during extended exposure periods, can stop growing altogether or die."
The new analysis compares water temperatures during two time periods a century apart at two of Florida's historic offshore lighthouses -- Fowey Rocks Lighthouse, off Miami, and Carysfort Reef Lighthouse, off Key Largo, Florida. The first period included data from 1879 to 1912, while the second period spanned from 1991 to 2012. Temperatures at a third area, a reef off Islamorada, Florida, were also monitored from 1975 to 2007.
"What's interesting is that the temperature increase observed during this recent 32-year period was as large as that measured at the lighthouses spanning 120 years," said Kuffner. "This makes it likely the warming observed at the lighthouses has actually occurred since the 1970s."
The study indicates that August is consistently the month when Florida's ocean temperatures peak. In the analysis of recent decades, average temperatures for August have been at or very close to 86 F. At Fowey Lighthouse from 1879 to 1912, the average August temperature was just 84.2 F. Temperatures this August at the same location, though not included in the study, averaged 87 F.
Coral bleaching is currently underway in the Florida Keys, highlighting the real-time impact that warmer ocean temperatures are having on reefs. Corals can recover from bleaching if the waters cool down within a few weeks, but mortality usually ensues if corals remain bleached longer than a month or two.
Ilsa B. Kuffner, Barbara H. Lidz, J. Harold Hudson, Jeffrey S. Anderson. A Century of Ocean Warming on Florida Keys Coral Reefs: Historic In Situ Observations. Estuaries and Coasts, 2014; DOI: 10.1007/s12237-014-9875-5
Posted by Jenny Griffin
In a world warmed by rising atmospheric greenhouse gas concentrations, precipitation patterns are going to change because of two factors: one, warmer air can hold more water; and two, changing atmospheric circulation patterns will shift where rain falls. According to previous model research, mid- to high-latitude precipitation is expected to increase by as much as 50%. Yet the reasons why models predict this are hard to tease out.
Using a series of highly idealized model runs, Lu et al. found that ocean warming should cause atmospheric precipitation bands to shift toward the poles. The changes in atmospheric circulation brought on by a warming ocean should cause an increase in the intensity and frequency of extreme precipitation events at mid- and high-latitudes, and a reduction in the same near the equator. The changes would mean that, for high-latitude regions, now-rare storms would become much more common.
The authors tested the effect of ocean warming on atmospheric circulation and precipitation using a highly idealized "aquaplanet" model, a representation of the Earth that was just sea and sky, but no land. They ran the model at a range of spatial resolutions and found that the changes in precipitation that stem from changing circulation patterns may possibly outweigh changes that derive from other factors.
Jian Lu, L. Ruby Leung, Qing Yang, Gang Chen, William D. Collins, Fuyu Li, Z. Jason Hou, Xuelei Feng. The robust dynamical contribution to precipitation extremes in idealized warming simulations across model resolutions. Geophysical Research Letters, 2014; 41 (8): 2971 DOI: 10.1002/2014GL059532
Source: University of New South Wales Australia Newsroom
Posted by Jenny Griffin
The migration of tropical fish as a result of ocean warming poses a serious threat to the temperate areas they invade, because they overgraze on kelp forests and seagrass meadows, a new study concludes.
The harmful impact of tropical fish is most evident in southern Japanese waters and the eastern Mediterranean, where there have been dramatic declines in kelps.
There is also emerging evidence in Australia and the US that the spread of tropical fish towards the poles is causing damage in the areas they enter.
"The tropicalisation of temperate marine areas is a new phenomenon of global significance that has arisen because of climate change," says study lead author, Dr Adriana Verges, of UNSW Australia.
"Increases in the number of plant-eating tropical fish can profoundly alter ecosystems and lead to barren reefs, affecting the biodiversity of these regions, with significant economic and management impacts."
The study is published in the journal Proceedings of the Royal Society B.
As the oceans have warmed and the climate has changed, hotspots are developing in regions where the currents that transport warm tropical waters towards the poles are strengthening.
Increased flow of the East Australian Current, for example, has meant waters south-east of the continent are warming at two to three times the global average. Tropical fish are now common in Sydney Harbour during the summer months.
Japan, the east coast of the US, northern Brazil and south eastern Africa are also strongly influenced by coastal currents that transport warm tropical waters.
"In tropical regions, a wide diversity of plant-eating fish perform the vital role of keeping reefs free of large seaweeds, allowing corals to flourish. But when they intrude into temperate waters they pose a significant threat to these habitats. They can directly overgraze algal forests as well as prevent the recovery of algae that have been damaged for other reasons," says Dr Verges.
Tropical fish expanding their ranges into temperate areas include unicornfish, parrotfish, and rabbitfish.
The study authors include researchers from Australia, the US, Spain, Singapore, the UK and Japan.
More than 40 per cent of the kelp and algal beds have disappeared since the 1990s, a phenomenon known in Japan as isoyake. Tropical species including rabbitfish and parrotfish appear to be mainly responsible.
Although these fish have been present for a long time, their annual grazing rates have increased dramatically as ocean temperatures in winter have risen. Corals now dominate the ecosystem in many locations. The changes have led to the collapse of the abalone fishery.
Tropical fish moved into the eastern Mediterranean from the Red Sea after the opening of the Suez Canal. In recent decades, rabbitfish numbers have increased, resulting in hundreds of kilometres of deforested areas and a 40 per cent decrease in the variety of marine species.
As the Mediterranean warms the rabbitfish are expanding their range westward, putting other shallow ecosystems at risk.
There has been a more than 20-fold increase in the number of parrotfish in the Gulf of Mexico – a species which consumes seagrass at five times the rate of native grazers. The number of plant-eating green turtles and manatees has also increased.
In Western Australia, emerging evidence suggests that increases in the number of tropical fish are preventing the recovery of kelp forest damaged by a heat wave in 2011.
In eastern Australia, kelp has disappeared from numerous reefs in the past 5 years and Dr Verges' research suggests intense grazing by tropical fish on the kelp preceded this.
Vergés A, Steinberg PD, Hay ME, Poore AG, Campbell AH, Ballesteros E, Heck KL, Booth D, Coleman MA, Feary D, Figueira W, Langlois T, Marzinelli EM, Mizerek T, Mumby PJ, Nakamura Y, Roughan M, van Sebille E, Sen Gupta A, Smale DA, Tomas F, Wernberg T, Wilson SK (In press, accepted 4/06/14) The tropicalisation of temperate marine ecosystems: climate-mediated changes in herbivory and community phase shifts. Proceedings of the Royal Society B.
A quick glance at a world precipitation map shows that most tropical rain falls in the Northern Hemisphere. The Palmyra Atoll, at 6 degrees north, gets 175 inches of rain a year, while an equal distance on the opposite side of the equator gets only 45 inches. Scientists long believed that this was a quirk of the Earth's geometry – that the ocean basins tilting diagonally while the planet spins pushed tropical rain bands north of the equator. But a new University of Washington study shows that the pattern arises from ocean currents originating from the poles, thousands of miles away.
The findings, published 20 October 2013 in Nature Geoscience, explain a fundamental feature of the planet's climate, and show that icy waters affect seasonal rains that are crucial for growing crops in such places as Africa's Sahel region and southern India.
In general, hotter places are wetter because hot air rises and moisture precipitates out.
"It rains more in the Northern Hemisphere because it's warmer," said corresponding author Dargan Frierson, a UW associate professor of atmospheric sciences. "The question is: What makes the Northern Hemisphere warmer? And we've found that it's the ocean circulation."
Frierson and his co-authors first used detailed measurements from NASA's Clouds and Earth's Radiant Energy System, or CERES, satellites to show that sunlight actually provides more heat to the Southern Hemisphere – and so, by atmospheric radiation alone, the Southern Hemisphere should be the soggier one.
After using other observations to calculate the ocean heat transport, the authors next used computer models to show the key role of the huge conveyor-belt current that sinks near Greenland, travels along the ocean bottom to Antarctica, and then rises and flows north along the surface. Eliminating this current flips the tropical rain bands to the south.
The reason is that as the water moves north over many decades it gradually heats up, carrying some 400 trillion (that's four with 14 zeroes after it) watts of power across the equator.
For many years, slanting ocean basins have been the accepted reason for the asymmetry in tropical rainfall.
"But at the same time, a lot of people didn't really believe that explanation because it's kind of a complicated argument. For such a major feature there's usually a simpler explanation," Frierson said.
The ocean current they found to be responsible was made famous in the 2004 movie "The Day After Tomorrow," in which the premise was that the overturning circulation shut down and New York froze over. While a sudden shutdown like in the movie won't happen, a gradual slowing – which the recent United Nations report said was "very likely" by 2100 – could shift tropical rains south, the study suggests, as it probably has in the past.
The slowdown of the currents is predicted because increasing rain and freshwater in the North Atlantic would make the water less dense and less prone to sinking.
"This is really just another part of a big, growing body of evidence that's come out in the last 10 or 15 years showing how important high latitudes are for other parts of the world," Frierson said.
Frierson's earlier work shows how the changing temperature balance between hemispheres influences tropical rainfall. A recent study by Frierson and collaborators looked at how pollution from the industrial revolution blocked sunlight to the Northern Hemisphere in the 1970s and '80s and shifted tropical rains to the south.
"A lot of the changes in the recent past have been due to air pollution," Frierson said. "The future will depend on air pollution and global warming, as well as ocean circulation changes. That makes tropical rainfall particularly hard to predict."
Dargan M. W. Frierson, Yen-Ting Hwang, Neven S. Fučkar, Richard Seager, Sarah M. Kang, Aaron Donohoe, Elizabeth A. Maroon, Xiaojuan Liu, David S. Battisti. Contribution of ocean overturning circulation to tropical rainfall peak in the Northern Hemisphere. Nature Geoscience, 2013; DOI: 10.1038/ngeo1987
We all know the feeling, it's a hot summer afternoon and you have no appetite and don't want to do anything apart from lay on the couch. A team of researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University has shown that ocean warming may make some large reef fish feel the same way.
Researcher Dr Jacob Johansen said that fish rely on swimming for almost all activities necessary for survival, including hunting for food and finding mates. “However, global warming may reduce the swimming ability of many fish species, and have major impacts on their ability to grow and reproduce,” he said.
Dr Johansen said that research aimed at understanding the impact of global warming on the commercially important fish species, coral trout, revealed that increasing ocean temperatures may cause large fish to become lethargic, spending more time resting on the bottom and less time swimming in search for food or reproductive opportunities.
He said that the study he and his colleagues had undertaken showed that even when individuals do muster up enough energy to swim around, they swim at a much slower rate. This lower activity is likely to directly impact their ability to catch food, or visit spawning sites.
“The loss of swimming performance and reduced ability to maintain important activities, like moving to a spawning site to reproduce, could have major implications for the future distribution and abundance of these species,” Dr Johansen said.
Professor Morgan Pratchett said that the changes to activity patterns and swimming speeds “may directly influence where we will find these species in the future and how many we are able to fish sustainably.” But all is not lost, Dr Johansen said, as there was some evidence that coral trout may be able to adapt to increasing temperatures.
“Populations from the northern region of the Great Barrier Reef were a little better than southern populations at tolerating these conditions,” he said.
“Coral trout is one of the most important fisheries in the South-East Pacific. If we want to keep this fishery in the future, it is critical that we understand how global warming may impact the species. This will allow us to develop management plans that will help to keep the species, and its fisheries, healthy.”
The research team, which comprises Dr Vanessa Messmer, Dr Darren Coker, and Dr Andrew Hoey, along with Professor Pratchett and Dr Johansen, are planning further experiments to clarify the ability of coral trout to adapt to the rapid changes caused by global warming or if they may be forced to relocate to cooler more southerly waters.
Their paper 'Increasing ocean temperatures reduce activity patterns of a large commercially important coral reef fish' by J.L. Johansen, V. Messmer, D.J. Coker, A.S. Hoey and M.S. Pratchett is published online in the Nov 2013 issue of the journal Global Change Biology (DOI:10.1111/gcb.12452).
The intermediate waters of the Pacific Ocean are absorbing heat 15 times faster over the past 60 years than in the past 10,000
Some climate change skeptics have pointed out that global atmospheric temperatures have been stable, or even declined slightly, over the past decade. They claim it's a sign that global warming has either ceased, slowed down or is not caused by human activity.
So, where did all that heat that we're supposedly producing go?
Climate scientists say it went into the ocean, which over the past 60 years has acted as a buffer against global warming. However, a new study led by Rutgers' Yair Rosenthal shows that the ocean is now absorbing heat 15 times faster than it has over the previous 10,000 years. Although the increased heat absorption by the ocean may give scientists and policymakers more time to deal with the issue of climate change, Rosenthal says the problem is real and must be addressed.
“We may have underestimated the efficiency of the oceans as a storehouse for heat and energy,” Rosenthal said. “It may buy us some time – how much time, I don't really know – to come to terms with climate change. But it's not going to stop climate change.”
Rosenthal, a professor of marine and coastal sciences in Rutgers' School of Environmental and Biological Sciences; Braddock Linsley of Columbia University's Lamont-Doherty Earth Observatory; and Delia W. Oppo of the Woods Hole Oceanographic Institution in Woods Hole, Massachusetts, used the shells of tiny single-celled, bottom-dwelling foraminifera found in sediment cores to reconstruct the Pacific Ocean's heat content over the last 10,000 years. Their paper has been published in Science.
The heat content of the ocean had been measured before, but only instrumentally, and only back to the mid-20th century.
Their research was undertaken on marine sediment collected from the seas surrounding Indonesia, where the waters of the Pacific and Indian oceans overlap. The researchers measured the ratio of magnesium to calcium in the shells of a particular species of foraminifera, Hyalinea balthica. The warmer the waters when the organism calcified, the greater the magnesium to calcium ratio.
The shell chemistry of these tiny creatures provides a record of intermediate water temperatures going back 10,000 years, not only in the part of the Pacific where they were collected but from the higher latitudes in the Pacific as well. That's because the intermediate water in the western Pacific – depths between 450 and 1,000 meters – consists of water that once was near the surface in the northern and southern Pacific. The waters became saltier and colder over time and sank, then flowed very slowly toward the equator and through the passages between islands in Indonesia.
“Our work showed that intermediate waters in the Pacific had been cooling steadily from about 10,000 years ago" said Linsley. This places the recent warming of Pacific intermediate waters in temporal context. The trend has now reversed in a big way and the deep ocean is warming.”
The paper titled 'Pacific Ocean Heat Content During the Past 10,000 Years' was published in Science (DOI: 10.1126/science.1240837) and can be accessed at the following link:
A new study offers an explanation for the extraordinary run of wet summers experienced by Britain and northwest Europe between 2007 and 2012. The study found that loss of Arctic sea ice shifts the jet stream further south than normal resulting in increased rain during the summer in northwest Europe.
Dr James Screen from the University of Exeter used a computer model to investigate how the dramatic retreat of Arctic sea ice influences the European summer climate. He found that the pattern of rainfall predicted by the model closely resembles the rainfall pattern of recent summers. The study is published in the journal Environmental Research Letters.
Dr Screen said: "The results of the computer model suggest that melting Arctic sea ice causes a change in the position of the jet stream and this could help to explain the recent wet summers we have seen."
“The study suggests that loss of sea ice not only has an effect on the environment and wildlife of the Arctic region but has far reaching consequences for people living in Europe and beyond.”
Jet streams are currents of strong winds high in the atmosphere – around the height at which aeroplanes fly. These winds steer weather systems and their rain. Normally in summer the jet stream lies between Scotland and Iceland and weather systems pass north of Britain. When the jet stream shifts south in summer, it brings unseasonable wet weather to Britain and northwest Europe causing havoc for tourism and farming.
The model suggests that while summer rainfall increases in northwest Europe, Mediterranean regions will receive less rain. The effects are not limited to Europe - weather systems as far as North America could also be influenced.
The annual average extent of Arctic sea ice is currently declining at about half a million square kilometres per decade – equivalent to about twice the area of the UK. The study compared weather patterns during low sea ice conditions as seen in recent years to weather patterns during high sea ice conditions typical of the late 1970s. The model did not use estimates of how much sea ice there will be in the future, and so this study cannot predict future weather. The results do suggest however that if sea ice loss continues as it has over recent decades, the risk of wet summers may increase.
Other studies have suggested that recent ocean warming of the North Atlantic could also be responsible for more summer rain in northwest Europe. It is likely that several other factors, combined with the impact of melting Arctic sea ice, explain the recent run of wet summers.
The next step is to use estimates of future sea ice loss to make predictions of how further melting could influence summer rainfall in Europe in the years to come.
The paper is published in Environmental Research Letters and is available via open access at the following link: http://iopscience.iop.org/1748-9326/8/4/044015/article
Parts of pacific warming 15 times faster than in past 10,000 years
A recent slowdown in global warming has led some skeptics to renew their claims that industrial carbon emissions are not causing a century-long rise in Earth's surface temperatures. But rather than letting humans off the hook, a new study in the leading journal Science adds support to the idea that the oceans are taking up some of the excess heat, at least for the moment. In a reconstruction of Pacific Ocean temperatures in the last 10,000 years, researchers have found that its middle depths have warmed 15 times faster in the last 60 years than they did during apparent natural warming cycles in the previous 10,000.
"We're experimenting by putting all this heat in the ocean without quite knowing how it's going to come back out and affect climate," said study coauthor Braddock Linsley, a climate scientist at Columbia University's Lamont-Doherty Earth Observatory. "It's not so much the magnitude of the change, but the rate of change."
In its latest report, released in September, the UN's Intergovernmental Panel on Climate Change (IPCC) noted the recent slowdown in the rate of global warming. While global temperatures rose by about one-fifth of a degree Fahrenheit per decade from the 1950s through 1990s, warming slowed to just half that rate after the record hot year of 1998. The IPCC has attributed the pause to natural climate fluctuations caused by volcanic eruptions, changes in solar intensity, and the movement of heat through the ocean. Many scientists note that 1998 was an exceptionally hot year even by modern standards, and so any average rise using it as a starting point would downplay the longer-term warming trend.
The IPCC scientists agree that much of the heat that humans have put into the atmosphere since the 1970s through greenhouse gas emissions probably has been absorbed by the ocean. However, the findings in Science put this idea into a long-term context, and suggest that the oceans may be storing even more of the effects of human emissions than scientists have so far realized. "We may have underestimated the efficiency of the oceans as a storehouse for heat and energy," said study lead author, Yair Rosenthal, a climate scientist at Rutgers University. "It may buy us some time – how much time, I don't really know. But it's not going to stop climate change."
Ocean heat is typically measured from buoys dispersed throughout the ocean, and with instruments lowered from ships, with reliable records at least in some places going back to the 1960s. To look back farther in time, scientists have developed ways to analyze the chemistry of ancient marine life to reconstruct the climates in which they lived. In a 2003 expedition to Indonesia, the researchers collected cores of sediment from the seas where water from the Pacific flows into the Indian Ocean. By measuring the levels of magnesium to calcium in the shells of Hyalinea balthica, a one-celled organism buried in those sediments, the researchers estimated the temperature of the middle-depth waters where H. Balthica lived, from about 1,500 to 3,000 feet down. The temperature record there reflects middle-depth temperatures throughout the western Pacific, the researchers say, since the waters around Indonesia originate from the mid-depths of the North and South Pacific.
Though the climate of the last 10,000 years has been thought to be relatively stable, the researchers found that the Pacific intermediate depths have generally been cooling during that time, though with various ups and downs. From about 7,000 years ago until the start of the Medieval Warm Period in northern Europe, at about 1100, the water cooled gradually, by almost 1 degree C, or almost 2 degrees F. The rate of cooling then picked up during the so-called Little Ice Age that followed, dropping another 1 degree C, or 2 degrees F, until about 1600. The authors attribute the cooling from 7,000 years ago until the Medieval Warm Period to changes in Earth's orientation toward the sun, which affected how much sunlight fell on both poles. In 1600 or so, temperatures started gradually going back up. Then, over the last 60 years, water column temperatures, averaged from the surface to 2,200 feet, increased 0.18 degrees C, or .32 degrees F. That might seem small in the scheme of things, but it's a rate of warming 15 times faster than at any period in the last 10,000 years, said Linsley.
One explanation for the recent slowdown in global warming is that a prolonged La Niña-like cooling of eastern Pacific surface waters has helped to offset the global rise in temperatures from greenhouse gases. In a study in the journal Nature in August, climate modelers at the Scripps Institution of Oceanography showed that La Niña cooling in the Pacific seemed to suppress global average temperatures during northern hemisphere winters but allowed temperatures to rise during northern hemisphere summers, explaining last year's record U.S. heat wave and the ongoing loss of Arctic sea ice.
When the La Niña cycle switches, and the Pacific reverts to a warmer than usual El Niño phase, global temperatures may likely shoot up again, along with the rate of warming. "With global warming you don't see a gradual warming from one year to the next," said Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research in Boulder, Colo., who was not involved in the research. "It's more like a staircase. You trot along with nothing much happening for 10 years and then suddenly you have a jump and things never go back to the previous level again."
The study's long-term perspective suggests that the recent pause in global warming may just reflect random variations in heat going between atmosphere and ocean, with little long-term importance, says Drew Shindell, a climate scientist with joint appointments at Columbia's Earth Institute and the NASA Goddard Institute for Space Studies, and a lead author on the latest IPCC report. "Surface temperature is only one indicator of climate change,&quot; he said. &quot;Looking at the total energy stored by the climate system or multiple indicators--glacier melting, water vapor in the atmosphere, snow cover, and so on—may be more useful than looking at surface temperature alone."
The study, "Pacific Ocean Heat Content During the Past 10,000 Years," is available from the authors, or Science, firstname.lastname@example.org.
Meteorologists often use information about warm and cold fronts to determine whether a tornado will occur in a particular area. Now, a University of Missouri researcher has found that the temperature of the Pacific Ocean could help scientists predict the type and location of tornado activity in the U.S.
Laurel McCoy, an atmospheric science graduate student at the MU School of Natural Resources, and Tony Lupo, professor and chair of atmospheric science in the College of Agriculture, Food and Natural Resources, surveyed 56,457 tornado-like events from 1950 to 2011. They found that when surface sea temperatures were warmer than average, the U.S. experienced 20.3 percent more tornados that were rated EF-2 to EF-5 on the Enhanced Fuijta (EF) scale. (The EF scale rates the strength of tornados based on the damage they cause. The scale has six category rankings from zero to five.)
McCoy and Lupo found that the tornados that occurred when surface sea temperatures were above average were usually located to the west and north of tornado alley, an area in the Midwestern part of the U.S. that experiences more tornados than any other area. McCoy also found that when sea surface temperatures were cooler, more tornadoes tracked from southern states, like Alabama, into Tennessee, Illinois and Indiana.
"Differences in sea temperatures influence the route of the jet stream as it passes over the Pacific and, eventually, to the United States," McCoy said. "Tornado-producing storms usually are triggered by, and will follow, the jet stream. This helps explain why we found a rise in the number of tornados and a change in their location when sea temperatures fluctuated."
In the study, McCoy and Lupo examined the relationship between tornadoes and a climate phenomenon called the Pacific Decadal Oscillation (PDO). PDO phases, which were discovered in the mid-1990s, are long-term temperature trends that can last up to 30 years. According to NASA scientists, the current PDO phase has just entered into a 'cool' state.
"PDO cool phases are characterized by a cool wedge of lower than normal sea-surface ocean temperatures in the eastern Pacific and a warm horseshoe pattern of higher than normal sea-surface temperatures extending into the north, west and southern Pacific," McCoy said. "In the warm phase, which lasted from 1977 to 1999, the west Pacific Ocean became cool and the wedge in the east was warm."
In 2011, more than 550 deaths occurred as a result of tornadoes, resulting in more than $28 billion in property damage, according to the U.S. National Oceanic and Atmospheric Administration. McCoy says that with her findings, officials may be able to save lives in the future.
"Now that we know the effects of PDO cool and warm phases, weather forecasters have another tool to predict dangerous storms and inform the public of impending weather conditions," McCoy said.