King penguins may be on the move very soon

More than 70 percent of the global King penguin population, currently forming colonies in Crozet, Kerguelen and Marion sub-Antarctic islands, may be nothing more than a memory in a matter of decades, as global warming will soon force the birds to move south, or disappear. This is the conclusion of a study published in the journal Nature Climate Change and performed by an international team of researchers.

More than 70 percent of the global King penguin population may be nothing more than a memory in a matter of decades,
 as global warming will soon force the birds to move south, or disappear [Credit: Robin Cristofari]

"The main issue is that there is only a handful of islands in the Southern Ocean and not all of them are suitable to sustain large breeding colonies" says Robin Cristofari, first author of the study, from the Institut Pluridisciplinaire Hubert Curien (IPHC/CNRS/University of Strasbourg) and the Centre Scientifique de Monaco (CSM).

King penguins are in fact picky animals: in order to form a colony where they can mate, lay eggs and rear chicks over a year, they need tolerable temperature all year round, no winter sea ice around the island, and smooth beach of sand or pebbles. But, above all, they need an abundant and reliable source of food close by to feed their chicks. For millennia, this seabird has relied on the Antarctic Polar Front, an upwelling front in the Southern Ocean concentrating enormous amounts of fish on a relatively small area.

Yet, due to climate change, this area is drifting south, away from the islands where most King penguins currently live. Parents are then forced to swim farther to find food, while their progeny is waiting, fasting longer and longer on the shore. This study predicts that, for most colonies, the length of the parents' trips to get food will soon exceed the resistance to starvation of their offspring, leading to massive King penguin crashes in population size, or, hopefully, relocation.

King penguins are picky animals [Credit: Celine LeBohec]

Using the information hidden away in the penguin's genome, the research team has reconstructed the changes in the worldwide King penguin population throughout the last 50,000 years, and discovered that past climatic changes, causing shifts in marine currents, sea-ice distribution and Antarctic Polar Front location, have always been linked to critical episodes for the King penguins. However, hope is not lost yet: King penguins have already survived such crises several times (the last time was 20 thousand years ago), and they may be particularly good at it.

"Extremely low values in indices of genetic differentiation told us that all colonies are connected by a continuous exchange of individuals," says Emiliano Trucchi formerly at the University of Vienna and now at the University of Ferrara, one of the coordinator of the study. "In other words, King penguins seem to be able to move around quite a lot to find the safest breeding locations when things turn grim."

But there is a major difference this time: for the first time in the history of penguins, human activities are leading to rapid and/or irreversible changes in the Earth system, and remote areas are no exception. In addition to the strongest impact of climate change in Polar Regions, Southern Ocean is now subject to industrial fishing, and penguins may soon have a very hard time fighting for their food.

Penguins form colonies in Crozet, Kerguelen and Marion sub-Antarctic islands [Credit: Celine LeBohec]

"There are still some islands further south where King penguins may retreat," notes Celine Le Bohec (IPHC/CNRS/University of Strasbourg and CSM), leader of the programme 137 of the French Polar Institut Paul-Emile Victor within which the study was initiated, "but the competition for breeding sites and for food will be harsh, especially with the other penguin species like the Chinstrap, Gentoo or Adelie penguins, even without the fisheries. It is difficult to predict the outcome, but there will surely be losses on the way. If we want to save anything, proactive and efficient conservation efforts but, above all, coordinated global action against global warming should start now."

Source: University of Vienna [February 26, 2018]

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Stagnation in the South Pacific

A team led by geochemist Dr. Katharina Pahnke from Oldenburg has discovered important evidence that the rise in atmospheric carbon dioxide levels at the end of the last ice age was triggered by changes in the Antarctic Ocean. The researchers from the University of Oldenburg's Institute for Chemistry and Biology of the Marine Environment (ICBM), the Max Planck Institute for Marine Microbiology in Bremen and the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) were able to demonstrate that the deep South Pacific was strongly stratified during the last ice age, and could thus have facilitated long-term, deep-sea storage of the greenhouse gas carbon dioxide (CO2). The study, which has now been published in the academic journal Science, also indicates that in the course of the warming following the end of the last ice age the mixing of the deep water masses increased, releasing stored CO2 and enhancing global warming.

Snapshot from aboard RV Polarstern [Credit: Mario Hoppmann]

The Southern Ocean plays an important role in climate events because CO2 can be absorbed from the atmosphere into the ocean. When increased amounts of dust are deposited in the seawater, microscopic algae multiply because the iron contained in the dust acts as a fertilizer. When these single celled algae die, they sink to the ocean floor, taking the sequestered carbon dioxide with them. To ensure long-term removal of the CO2 from the atmosphere, however, it must be stored in stable conditions in deep water over long periods of time.

In order to find out how water masses in the deep South Pacific have developed over the last 30,000 years, the team recovered sediment cores from water depths of between 3,000 and more than 4,000 metres during an expedition of the research vessel "Polarstern" to the South Pacific. The geochemists Dr. Chandranath Basak and Dr. Henning Fröllje of the ICBM - the two main authors of the study - extracted tiny teeth and other skeletal debris of fossil fish from the sediment to analyse their content of isotopes of the rare earth metal neodymium.

"Neodymium is particularly useful for identifying water masses of different origin," said Pahnke, the head of the Max Planck Research Group for Marine Isotope Geochemistry based at the ICBM and the Max Planck Institute for Marine Microbiology in Bremen, explaining that each layer of water has its own characteristic neodymium signature. The isotope ratios of this element vary depending on which ocean basin the water comes from. For instance, the coldest and therefore deepest water mass in the Southern Pacific forms on the continental shelf of Antarctica and carries a distinct neodymium signature. Overlying this mass is a layer that combines water from the North Atlantic, the South Pacific and the North Pacific and hence is marked by a different signature.

View from RV Polarstern while collecting sediment samples used in the study by Basak et al.
[Credit: Dr. Katharina Pahnke]

Using fish debris in deep-sea sediments, the researchers were able to trace the variations in neodymium concentrations at different depths over the course of time. The result: at the peak of the last ice age approximately 20,000 years ago, the neodymium signature of samples taken from depths below 4,000 metres was significantly lower than at lower depths. "The only explanation for such a pronounced difference is that there was no mixing of the water masses at that time," said Fröllje, who currently works at the University of Bremen. He and his colleagues concluded from this that the deep waters were strongly stratified during the glacial period.

As the climate in the southern hemisphere grew warmer towards the end of the last ice age around 18,000 years ago, the stratification of the water masses was broken up and neodymium values at different depths converged. "There was probably more mixing because the density of the water decreased as a result of the warming," Pahnke explained. This then led to the release of the carbon dioxide stored in deep waters.

For some time now climate researchers have been speculating on why fluctuations in atmospheric CO2 levels followed the same pattern as temperature in the southern hemisphere whereas the temperature in the north at times ran counter to these fluctuations. One theory is that certain processes in the Southern Ocean played an important role.

"With our analyses we have for the first time provided concrete evidence supporting the theory that there is a connection between the CO2 fluctuations and stratification in the Southern Ocean," said co-author of the study Dr. Frank Lamy of the AWI in Bremerhaven. The current study supports the hypothesis that the warming of the southern hemisphere broke up stable stratification in the Antarctic Ocean, resulting in the release of the carbon dioxide that was stored in these waters.

Source: Alfred Wegener Institute [February 22, 2018]

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Extinct lakes of the American desert west

The vestiges of lakes long extinct dot the landscape of the American desert west. These fossilized landforms provide clues of how dynamic climate has been over the past few million years.

Erosional Pleistocene shorelines in Surprise Valley, California, USA [Credit: Anne Egger]

Identification of ancient lake shoreline features began with early explorers of the continent. The first detailed studies were conducted by pioneering American geologists such as G.K. Gilbert and I.C. Russell in the late 1800s, who studied Lake Bonneville, now the remnant Great Salt Lake in Utah, and Lake Lahonton, located in northwestern Nevada.

Through this long history of studying fossil shorelines and lake sediments, we know that these lakes existed during two periods with distinct environmental conditions during the geologically recent past. The first was during ice age maxima, such as the last ice age, 14 to 30 thousand years ago, when global temperatures were 4 to 6 degrees colder and continental ice sheets expanded into the continental United States.

The second time period was about three million years ago during the middle of the Pliocene epoch--a global climate characterized by warmer temperatures and atmospheric CO2 levels roughly equivalent to today's values, which has led many scientists to view the Pliocene as a potential analogue for future climate change.

These observations lead to an important question, says the study's lead author, Daniel Ibarra, "Why are there lake systems under both colder and warmer climates, but not today?" Of particular interest, he says, is the presence of lakes under warmer conditions, which, under a "wet gets wetter, dry gets drier" paradigm, goes against projections of future warming.

Shorelines of Lake Bonneville along the Oquirrh Mountains, Utah, USA. (H.H. Nichols [artist] and G.K. Gilbert,
in Gilbert, 1884) [Credit: H.H. Nichols [artist] and G.K. Gilbert, in Gilbert, 1884. Public domain]

To answer this question, Ibarra and colleagues looked at the competing influences of temperature and precipitation, and how they combine to allow for the existence of lakes under these dual climate states.

The authors compiled evidence for, and created models of, lakes during both colder and warmer than modern periods of the Pliocene-Pleistocene (the last 5 million years). During colder glacial periods, they found that increased precipitation and decreased evaporation combined to form large lakes that occupied the inward draining basins in the western United States, particularly in northern Nevada and Utah.

Increased precipitation also drove the formation of lakes, particularly in southern Nevada and southern California during the warmer middle Pliocene, outpacing higher temperatures and evaporation rates during that time. This increase in precipitation during the middle Pliocene and dominantly southwestern distribution of lake deposits is similar to the pattern of precipitation during modern El Niño years, corroborating previous hypotheses for mean "El Niño-like" conditions during the mid-Pliocene.

The team's interdisciplinary approach explains the conditions driving lake systems in mid-latitude regions today and over the geologic past. Further, notes Ibarra, "This work illustrates the importance of understanding how the El Niño Southern Oscillation drives precipitation patterns in arid regions, which is important for future water resources planning for the western United States."

The study appears in the Geological Society of America Bulletin.

Source: Geological Society of America [February 22, 2018]

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First evidence of surprising ocean warming around Galápagos corals

The ocean around the Galápagos Islands has been warming since the 1970s, according to a new analysis of the natural temperature archives stored in coral reefs.

Diane Thompson (left), Roberto Pépolas (center) and Alexander Tudhope (right) use a hydraulic drill to take a core
from a Porites lobata coral head near Wolf Island in the Galápagos [Credit: Jenifer Suarez, Cole lab]

The finding surprised the University of Arizona-led research team, because the sparse instrumental records for sea surface temperature for that part of the eastern tropical Pacific Ocean did not show warming.

"People didn't know that the Galápagos or eastern Pacific was warming. People theorized or suggested it was cooling," said lead author Gloria Jimenez, a UA doctoral candidate in geosciences.

Scientists thought strong upwelling of colder deep waters spared the region from the warming seen in other parts of the Pacific, she said.

"My colleagues and I show that the ocean around the northern Galápagos Islands is warming and has been since the 1970s," Jimenez said. The research is part of her doctoral work.

Jimenez studied cores taken from coral heads in the uninhabited northern part of Galápagos National Park. The cores represented the years 1940 to 2010. Corals lay down seasonal growth layers that serve as a natural archive of ocean temperatures.

Her analysis revealed that from 1979 to 2010, regional ocean temperatures increased almost 0.4 degrees F (0.2 degrees C) per decade -- about 1.1 degrees F (0.6 degrees C) overall.

The very strong El Niño of 1982-83 temporarily warmed the surrounding ocean so much that most of the corals in the southern part of the Galápagos died, said co-author Julia Cole, who collected the coral cores while she was a faculty member at the UA.

She is concerned about ocean warming around the northern Galápagos and parts of the eastern tropical Pacific.

"Warming in this area is particularly disturbing, because it's the only place that reefs have persisted in the Galápagos. This suggests those reefs are more vulnerable than we thought," said Cole, who is now a professor of earth and environmental sciences at the University of Michigan.

Cores collected in 2010 from a Porites lobate coral near Wolf Island in Galapagos Islands. The core,
now broken into three pieces, is 3.5 inches (8.9 cm) in diameter [Credit: Julia Cole © 2010]

The research paper, "Northern Galápagos corals reveal twentieth century warming in the eastern tropical Pacific," by Jimenez, Cole and their co-authors, Diane M. Thompson of Boston University in Massachusetts and Alexander W. Tudhope of the University of Edinburgh in the UK, is published in Geophysical Research Letters.

The National Science Foundation, the UK Natural Environment Research Council and the Philanthropic Education Organization Fellowship funded the research.

For 30 years, Cole, a paleoclimatologist, has been studying climate change and the El Niño/ La Niña climate cycle.

In 1989 she went to the Galápagos hoping to use the natural climate archives stored in corals to develop a long-term record of El Niño, but found that none of the large, old corals others reported had survived the intense warming of the 1982-83 El Niño.

"We went from site to site -- and they were all gone," Cole said. "One of my co-workers said, 'There used to be corals here, and now all I see is sand.'"

Years later, she heard large corals were still alive near Wolf Island in the remote northern part of the Galápagos archipelago, so in 2010 she followed up on the tip with a team that included co-authors Tudhope and Thompson, then a UA graduate student.

The team members dove to the reef and took several cores from large, blobby dome-shaped Porites lobata corals using an underwater hydraulic drill powered by vegetable oil. The three-and-a-half-inch (8.9 cm) diameter cores ranged from two to three feet long and had annual bands 0.4 to 0.8 inches (1-2 cm) wide. Each core showed damage from when the coral stopped growing during the 1982-83 El Niño and then started growing again.

Jimenez used chemical analysis to tease temperature information out of two of those coral cores.

After removing two cores from this Porites lobata coral colony near Wolf Island in the Galápagos, the University of
Arizona-led team of researchers plugged the drill holes. The cement plugs help the coral grow over the holes
and keep out animals out of the holes [Credit: Diane Thompson © 2010]

Coral skeletons are made mostly of calcium carbonate. However, corals sometimes substitute the element strontium for the calcium. Corals substitute more strontium when the water is cold and less when the water is warm, so the strontium/calcium ratio of a bit of skeleton can reveal what the water temperature was when that piece of skeleton formed.

Jimenez used a little drill bit to take a tiny sample every millimeter for the length of each core. She took 10 to 20 samples from each annual band of each core and analyzed the samples for the strontium/calcium ratio using atomic emission spectrometry.

She then used that information to create a continuous record of the region's ocean temperature from 1940 to 2010.

Because the El Niño/ La Niña climate cycle generates large fluctuations in ocean temperatures around the Galápagos and in the eastern tropical Pacific, long-term changes can be hard to spot.

Jimenez wanted to determine whether the region's ocean temperature changed significantly from 1940 to 2010. Therefore she analyzed her Galápagos coral temperature chronologies alongside published coral temperature chronologies from islands farther north and west and instrumental sea surface temperature records from the southern Galápagos town of Puerto Ayora and the Peruvian coastal town of Puerto Chicama.

Jimenez said her research convinces her that the ocean around the Galápagos and much of the eastern tropical Pacific is warming. She's concerned about the effect of warming seas.

"The Galápagos National Park has been designated a World Heritage Site because it's a special and unique place," Jimenez said. "Losing the corals would be an enormous blow to the underwater biodiversity."

Jimenez's next project involves analyzing an eight-foot-long Galápagos coral core she collected in 2015 that goes back to about 1850.

Author: Mari N. Jensen | Source: University of Arizona [February 21, 2018]

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New study brings Antarctic ice loss into sharper focus

A NASA study based on an innovative technique for crunching torrents of satellite data provides the clearest picture yet of changes in Antarctic ice flow into the ocean. The findings confirm accelerating ice losses from the West Antarctic Ice Sheet and reveal surprisingly steady rates of flow from its much larger neighbor to the east.

The flow of Antarctic ice, derived from feature tracking of Landsat imagery
[Credit: NASA Earth Observatory]

The computer-vision technique crunched data from hundreds of thousands of NASA-U.S. Geological Survey Landsat satellite images to produce a high-precision picture of changes in ice-sheet motion.

The new work provides a baseline for future measurement of Antarctic ice changes and can be used to validate numerical ice sheet models that are necessary to make projections of sea level. It also opens the door to faster processing of massive amounts of data.

“We’re entering a new age,” said the study’s lead author, cryospheric researcher Alex Gardner of NASA’s Jet Propulsion Laboratory in Pasadena, California. “When I began working on this project three years ago, there was a single map of ice sheet flow that was made using data collected over 10 years, and it was revolutionary when it was published back in 2011. Now we can map ice flow over nearly the entire continent, every year. With these new data, we can begin to unravel the mechanisms by which the ice flow is speeding up or slowing down in response to changing environmental conditions.”

The innovative approach by Gardner and his international team of scientists largely confirms earlier findings, though with a few unexpected twists.

Among the most significant: a previously unmeasured acceleration of glacier flow into Antarctica’s Getz Ice Shelf, on the southwestern part of the continent -- likely a result of ice-shelf thinning.

Speeding up in the west, steady flow in the east

The research, published in the The Cryosphere, also identified the fastest speed-up of Antarctic glaciers during the seven-year study period. The glaciers feeding Marguerite Bay, on the western Antarctic Peninsula, increased their rate of flow by 1,300 to 2,600 feet (400 to 800 meters) per year, probably in response to ocean warming.

Perhaps the research team’s biggest discovery, however, was the steady flow of the East Antarctic Ice Sheet. During the study period, from 2008 to 2015, the sheet had essentially no change in its rate of ice discharge -- ice flow into the ocean. While previous research inferred a high level of stability for the ice sheet based on measurements of volume and gravitational change, the lack of any significant change in ice discharge had never been measured directly.

The study also confirmed that the flow of West Antarctica’s Thwaites and Pine Island glaciers into the ocean continues to accelerate, though the rate of acceleration is slowing.

In all, the study found an overall ice discharge for the Antarctic continent of 1,929 gigatons per year in 2015, with an uncertainty of plus or minus 40 gigatons. That represents an increase of 36 gigatons per year, plus or minus 15, since 2008. A gigaton is one billion tons.

The study found that ice flow from West Antarctica -- the Amundsen Sea sector, the Getz Ice Shelf and Marguerite Bay on the western Antarctic Peninsula -- accounted for 89 percent of the increase.

Computer vision

The science team developed software that processed hundreds of thousands of pairs of images of Antarctic glacier movement from Landsats 7 and 8, captured from 2013 to 2015.

These were compared to earlier radar satellite measurements of ice flow to reveal changes since 2008.

“We’re applying computer vision techniques that allow us to rapidly search for matching features between two images, revealing complex patterns of surface motion,” Gardner said.

Instead of researchers comparing small sets of very high-quality images from a limited region to look for subtle changes, the novelty of the new software is that it can track features across hundreds of thousands of images per year -- even those of varying quality or obscured by clouds -- over an entire continent.

“We can now automatically generate maps of ice flow annually -- a whole year -- to see what the whole continent is doing,” Gardner said.

The new Antarctic baseline should help ice sheet modelers better estimate the continent’s contribution to future sea level rise.

“We’ll be able to use this information to target field campaigns, and understand the processes causing these changes,” Gardner said. “Over the next decade, all this is going to lead to rapid improvement in our knowledge of how ice sheets respond to changes in ocean and atmospheric conditions, knowledge that will ultimately help to inform projections of sea level change.”

Author: Pat Brennan | Source: NASA [February 21, 2018]

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Land use change has warmed Earth's surface

Natural ecosystems play a crucial role in helping combat climate change, air pollution and soil erosion. A new study by a team of researchers from the Joint Research Centre, the European Commission's science and knowledge service, sheds light on another, less well-known aspect of how these ecosystems, and forests in particular, can protect our planet against global warming.

Changes to the way land is used is having a knock-on effect on temperatures
[Credit: European Commission Joint Research Centre]

The research team used satellite data to analyse changes in global vegetation cover from 2000 to 2015 and link these to changes in the surface energy balance. Modifying the vegetation cover alters the surface properties - such as the amount of heat dissipated by water evaporation and the level of radiation reflected back into space - which has a knock-on effect on local surface temperature. Their analysis reveals how recent land cover changes have ultimately made the planet warmer.

"We knew that forests have a role in regulating surface temperatures and that deforestation affects the climate, but this is the first global data-driven assessment that has enabled us to systematically map the biophysical mechanisms behind these processes", explains Gregory Duveiller, lead author of the study.

The study also looked beyond deforestation, analysing changes between different types of vegetation, from evergreen forests to savannas, shrublands, grasslands, croplands and wetlands. However, they found that the removal of tropical evergreen forest for agricultural expansion is the vegetation cover transition most responsible for local increases in surface temperature.

From a greenhouse gas perspective, the cutting of forests might only affect the global climate in the mid-to-long term. However, the scientists point out that local communities living in areas where the trees are cut will immediately be exposed to rising temperatures.

The findings are published in Nature Communications.

Source: European Commission Joint Research Centre [February 20, 2018]

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Research identifies 'evolutionary rescue' areas for animals threatened by climate change

As winters arrive later and snow melts earlier, the worldwide decrease in snow cover already may have dramatic impacts on animals that change coat colors with the seasons. An international scientific team led by University of Montana Professor L. Scott Mills has set out to discover whether adaptive evolution can rescue these animals in the face of rapidly changing climate.

Brown and white snowshoe hares on snow at a University of Montana research facility
[Credit: L.S. Mills research photos by Jaco and Lindsey Barnard]

Twenty-one species of mammals and birds rely on the ability to change their coat color from brown in summer to white in winter to avoid fatal encounters with predators, but in some parts of their range individuals forgo the white molt and remain brown in winter.

"Weasels in the southern U.S. and mountain hares in Ireland, for example, have evolved to remain brown year-round," Mills said. "This is a genetic adaptation to retain camouflage in areas where snow is intermittent or sparse."

Mills' group previously found that winter white snowshoe hares confronting snowless ground have higher mortality rates that could drive massive population declines as snow duration continues to decrease. Other scientists have pointed to coat-color mismatch against snowless ground as a cause for recent range decreases of hares, ptarmigan and other species.

Brown and white snowshoe hares on bare ground at a University of Montana research facility
[Credit: L.S. Mills research photos by Jaco and Lindsey Barnard]

In a new article in Science, Mills' team identified areas that could foster rapid "evolutionary rescue" of these species particularly vulnerable to climate change. The study describes how the international team mapped "polymorphic zones" for eight color-changing species, including hares, weasels and the Arctic fox. In these zones, both brown and white individuals coexist in winter.

"These areas hold the special sauce for rapid evolutionary rescue," Mills said. "Because they contain winter-brown individuals better adapted to shorter winters, these polymorphic populations are primed to promote rapid evolution toward being winter brown instead of white as climate changes."

The authors emphasize that these hotspots for evolutionary rescue are not magic fortresses that will prevent climate change effects on wild animals.

"Ultimately, the world must reduce carbon dioxide emissions or else the climate effects will overwhelm the ability of many species to adapt," co-author Eugenia Bragina said. "But by mapping these adaptive hotspots, we identify places where people could help foster evolutionary rescue in the short term by working to maintain large and connected wildlife populations."

Source: The University of Montana [February 15, 2018]

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Rapid evolution of a calcareous microalgae

When simulating future environmental conditions researchers face a problem: laboratory experiments are easy to control and to reproduce, but are insufficient to mimic the complexity of natural ecosystems. In contrast, experiments under real conditions in nature are much more complicated and difficult to control. Scientist of the GEOMAR Helmholtz Centre for Ocean Research Kiel have combined both approaches to investigate the response of a major plankton species to increasing ocean acidification.

Emiliania huxleyi cells in an electron microscopic picture
[Credit: Lennart Bach, GEOMAR]

The concentration of carbon dioxide (CO2) in the atmosphere increases continuously. As a consequence, an increasing amount of CO2 dissolves in the ocean, where it reacts to carbonic acid and acidifies the seawater. As ocean acidification progresses steadily, scientists aim to assess the implications of this process for marine ecosystems.

A team of researchers from the GEOMAR Helmholtz Centre for Ocean Research Kiel has for the first time examined the adaptability of the calcified alga Emiliania huxleyi to ocean acidification in a combination of laboratory and field experiments. "Some of the algae lineages in the experiment showed an extremely rapid change in their ecological fitness. We did not expect that to happen," says lead author Dr. Lennart Bach from GEOMAR. The study has been published recently in the international journal Nature Ecology and Evolution.

The current experiments were preceded by years of laboratory tests with Emiliania huxleyi at the GEOMAR in Kiel. Dr. Kai Lohbeck, co-author of the new study, had been keeping the algae under increased CO2 concentrations. Three years later, it became apparent that Emiliania huxleyi coped better with acidification than at the beginning of the experiment. "For us, that was a clear indication for the adaptability of the algae. But the experiment took place under laboratory conditions. Therefore, the question remained whether the evolutionary adaptation during an isolated lab experiment would bring an advantage also under natural conditions," says Lohbeck.

The opportunity to investigate this question emerged in the spring of 2013. The research group of Professor Ulf Riebesell conducted experiments with the Kiel Offshore Mesocosms in the framework of the collaborative project BIOACID (Biological Effects of Ocean Acidification) on the influence of ocean acidification on natural communities in Gullmarsfjord in Sweden. From the laboratory in Kiel, some of the already adapted algae cultures as well as the associated control groups were taken along to Sweden. There, they were added to the plankton communities which were acclimated to high CO2 levels in the field experiments.

"To our surprise, we found that the algae lineages that had already been adapted to ocean acidification in the lab did not cope any better at lower pH levels than the control groups that had never experienced acidification before," says Dr. Bach. An equally surprising finding: Although all algal lineages had the same ancestors, they differed significantly in their ability to compete in the natural plankton community after only three years. While some lineages proliferated rapidly, others tended to be excluded from the natural community, regardless of whether or not they were previously adapted to ocean acidification. "This demonstrates Emiliania huxleyi's ability to evolve rapidly," Bach resumes the results of the study.

Prof. Riebesell, co-author of the study and coordinator of the BIOACID project, sees this as an indication of how little we understand the long-term effects of ocean acidification: "The organisms' ability to adapt to new environmental conditions surprises us again and again. However, it does not change the fact that as ocean acidification progresses, many species will be unable to maintain their ecological niches. The loss of biodiversity is therefore inevitable."

Source: Helmholtz Centre for Ocean Research Kiel (GEOMAR) [February 14, 2018]

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Projecting the impacts of climate change

How might climate change affect the acidification of the world's oceans or air quality in China and India in the coming decades, and what climate policies could be effective in minimizing such impacts? To answer such questions, decision makers routinely rely on science-based projections of physical and economic impacts of climate change on selected regions and economic sectors. But the projections they obtain may not be as reliable or useful as they appear: Today's gold standard for climate impact assessments—model intercomparison projects (MIPs)—fall short in many ways.

Air pollution in Bangladesh and Northern India [Credit: Jacques Descloitres,
MODIS Rapid Response Team, NASA/GSFC]

MIPs, which use detailed climate and impact models to assess environmental and economic effects of different climate-change scenarios, require international coordination among multiple research groups, and use a rigid modeling structure with a fixed set of climate-change scenarios. This highly dispersed, inflexible modeling approach makes it difficult to produce consistent and timely climate impact assessments under changing economic and environmental policies. In addition, MIPs focus on a single economic sector at a time and do not represent feedbacks among sectors, thus degrading their ability to produce accurate projections of climate impacts and meaningful comparisons of those impacts across multiple sectors.

To overcome these drawbacks, researchers at the MIT Joint Program on the Science and Policy of Global Change propose an alternative method that only a handful of other groups are now pursuing: a self-consistent modeling framework to assess climate impacts across multiple regions and sectors. They describe the Joint Program's implementation of this method and provide illustrative examples in a new study published in Nature Communications.

The Joint Program method is essentially a next-generation Integrated Assessment Model (IAM). IAMs typically come in two forms—either as simple climate models coupled with algorithms that translate increases in average global surface temperature into environmental and economic damages known as the social cost of carbon; or as more detailed Earth-system models with continually improving representation of physical impacts, coupled with economic models. The Joint Program IAM integrates a geospatially resolved physical representation of climate impacts into a coupled human and Earth system modeling framework.

Developed over the past 26 years, the MIT Integrated Global System Modeling (IGSM) framework allows researchers to custom-design climate-change scenarios and assess climate impacts under those scenarios. For a given climate change scenario, they can use the framework to analyze the chain of physical changes at the regional and sectoral levels, and then estimate economic impacts at those levels.

"The IGSM framework makes it possible to do multisectoral climate impact assessment within a single modeling framework within a single group," says Erwan Monier, lead author of the study and a principal research scientist at the Joint Program. "It's responsive to changes in environmental policies, internally consistent, and much more flexible than multimodel international exercises."

In the study, Monier and his co-authors applied the IGSM framework to assess climate impacts under different climate-change scenarios—"Paris Forever," a scenario in which Paris Agreement pledges are carried out through 2030, and then maintained at that level through 2100; and "2C," a scenario with a global carbon tax-driven emissions reduction policy designed to cap global warming at 2 degrees Celsius by 2100. The assessments show that "Paris Forever" would lead to a wide range of projected climate impacts around the world, evidenced by different levels of ocean acidification, air quality, water scarcity, and agricultural productivity in different regions. The "2C" scenario, however, would mitigate a substantial portion of these impacts. The researchers also explored additional scenarios developed by Shell International regarding the potential development of low-carbon energy technologies.

"These examples showcase the responsiveness, consistency and multisectoral capability of our approach, which we believe represents a promising direction for the climate impact modeling community," says Sergey Paltsev, a co-author of the study and deputy director of the MIT Joint Program, as well as a senior research scientist at the MIT Energy Initiative and the MIT Center for Energy and Environmental Policy Research. "Unlike traditional IAMs and MIPs, the improved coupled human-Earth system models like the IGSM framework enable researchers to design new emissions scenarios in a matter of months rather than years, avoid inconsistencies among different model components and scenarios, and analyze multiple sectors all at once."

Author: Mark Dwortzan | Source: Massachusetts Institute of Technology [February 14, 2018]

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Twenty-five years of satellite data confirm rising sea levels

Global sea level rise is not cruising along at a steady 3 mm per year, it's accelerating a little every year, like a driver merging onto a highway, according to a powerful new assessment led by CIRES Fellow Steve Nerem. He and his colleagues harnessed 25 years of satellite data to calculate that the rate is increasing by about 0.08 mm/year every year -- which could mean an annual rate of sea level rise of 10 mm/year, or even more, by 2100.

A family of sea-level-measuring satellites [Credit: NASA]

"This acceleration, driven mainly by accelerated melting in Greenland and Antarctica, has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate -- to more than 60 cm instead of about 30." said Nerem, who is also a professor of Aerospace Engineering Sciences at the University of Colorado Boulder. "And this is almost certainly a conservative estimate," he added. "Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."

If the oceans continue to change at this pace, sea level will rise 65cm (26 inches) by 2100 -- enough to cause significant problems for coastal cities, according to the new assessment by Nerem and several colleagues from CU Boulder, the University of South Florida, NASA Goddard Space Flight Center, Old Dominion University, and the National Center for Atmospheric Research. The team, driven to understand and better predict Earth's response to a warming world, published their work in the journal Proceedings of the National Academy of Sciences.

Rising concentrations of greenhouse gases in Earth's atmosphere increase the temperature of air and water, which causes sea level to rise in two ways. First, warmer water expands, and this "thermal expansion" of the oceans has contributed about half of the 7 cm of global mean sea level rise we've seen over the last 25 years, Nerem said. Second, melting land ice flows into the ocean, also increasing sea level across the globe.

The satellite record (blue line) was adjusted first to remove the effects of the 1991 Pinatubo eruption (red line)
and then to remove the influence of El Niño and La Niña (green line) [Credit: Nerem et al./PNAS]

These increases were measured using satellite altimeter measurements since 1992, including the U.S./European TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 satellite missions. But detecting acceleration is challenging, even in such a long record. Episodes like volcanic eruptions can create variability: the eruption of Mount Pinatubo in 1991 decreased global mean sea level just before the Topex/Poseidon satellite launch, for example. In addition, global sea level can fluctuate due to climate patterns such as El Niños and La Niñas (the opposing phases of the El Niño Southern Oscillation, or ENSO) which influence ocean temperature and global precipitation patterns.

So Nerem and his team used climate models to account for the volcanic effects and other datasets to determine the ENSO effects, ultimately uncovering the underlying sea-level rate and acceleration over the last quarter century. They also used data from the GRACE satellite gravity mission to determine that the acceleration is largely being driven by melting ice in Greenland and Antarctica.

The team also used tide gauge data to assess potential errors in the altimeter estimate. "The tide gauge measurements are essential for determining the uncertainty in the GMSL (global mean sea level) acceleration estimate," said co-author Gary Mitchum, USF College of Marine Science. "They provide the only assessments of the satellite instruments from the ground." Others have used tide gauge data to measure GMSL acceleration, but scientists have struggled to pull out other important details from tide-gauge data, such as changes in the last couple of decades due to more active ice sheet melt.

"This study highlights the important role that can be played by satellite records in validating climate model projections," said co-author John Fasullo, a climate scientist at the National Center for Atmospheric Research. "It also demonstrates the importance of climate models in interpreting satellite records, such as in our work where they allow us to estimate the background effects of the 1991 eruption of Mount Pinatubo on global sea level."

Although this research is impactful, the authors consider their findings to be just a first step. The 25-year record is just long enough to provide an initial detection of acceleration -- the results will become more robust as the Jason-3 and subsequent altimetry satellites lengthen the time series.

Ultimately, the research is important because it provides a data-driven assessment of how sea level has been changing, and this assessment largely agrees with projections using independent methods. Future research will focus on refining the results in this study with longer time series, and extending the results to regional sea level, so they can better predict what will happen in your backyard.

Source: University of Colorado at Boulder [February 13, 2018]

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