Arctic Sea Ice Loss Could Dry out California

Arctic sea ice loss of the magnitude expected in the next few decades could impact California’s rainfall and exacerbate future droughts, according to new research led by Lawrence Livermore National Laboratory (LLNL) scientists.

The dramatic loss of Arctic sea ice cover observed over the satellite era is expected to continue throughout the 21st century. Over the next few decades, the Arctic Ocean is projected to become ice-free during the summer. A new study by Ivana Cvijanovic and colleagues from LLNL and University of California, Berkeley shows that substantial loss of Arctic sea ice could have significant far-field effects, and is likely to impact the amount of precipitation California receives. The research appears in the Dec. 5 edition of Nature Communications(link is external).

The study identifies a new link between Arctic sea ice loss and the development of an atmospheric ridging system in the North Pacific. This atmospheric feature also played a central role in the 2012-2016 California drought and is known for steering precipitation-rich storms northward, into Alaska and Canada, and away from California. The team found that sea ice changes can lead to convection changes over the tropical Pacific. These convection changes can in turn drive the formation of an atmospheric ridge in the North Pacific, resulting in significant drying over California.

arctic sea ice
Schematics of the teleconnection through which Arctic sea-ice changes drive precipitation decrease over California. Arctic sea-ice loss induced high-latitude changes first propagate into tropics, triggering tropical circulation and convection responses. Decreased convection and decreased upper level divergence in the tropical Pacific then drive a northward propagating Rossby wavetrain, with anticyclonic flow forming in the North Pacific. This ridge is responsible for steering the wet tropical air masses away from California. Graphic by Kathy Seibert/LLNL

“On average, when considering the 20-year mean, we find a 10-15 percent decrease in California’s rainfall. However, some individual years could become much drier, and others wetter,” Cvijanovic said.

The study does not attribute the 2012-2016 drought to Arctic sea ice loss. However, the simulations indicate that the sea-ice driven precipitation changes resemble the global rainfall patterns observed during that drought, leaving the possibility that Arctic sea-ice loss could have played a role in the recent drought.

“The recent California drought appears to be a good illustration of what the sea-ice driven precipitation decline could look like,” she explained.

California’s winter precipitation has decreased over the last two decades, with the 2012-2016 drought being one of the most severe on record. The impacts of reduced rainfall have been intensified by high temperatures that have enhanced evaporation. Several studies suggest that recent Californian droughts have a manmade component arising from increased temperatures, with the likelihood of such warming-enhanced droughts expected to increase in the future.

“Our study identifies one more pathway by which human activities could affect the occurrence of future droughts over California — through human-induced Arctic sea ice decline,” Cvijanovic said. “While more research should be done, we should be aware that an increasing number of studies, including this one, suggest that the loss of Arctic sea ice cover is not only a problem for remote Arctic communities, but could affect millions of people worldwide. Arctic sea ice loss could affect us, right here in California.”

Other co-authors on the study include Benjamin Santer, Celine Bonfils, Donald Lucas and Susan Zimmerman from LLNL and John Chiang from the University of California, Berkeley.

The research is funded by Department of Energy (DOE) Office of Science. Cvijanovic and Bonfils were funded by the DOE Early Career Research Program Award and Lucas is funded by the DOE Office of Science through the SciDAC project on Multiscale Methods for Accurate, Efficient and Scale-Aware Models of the Earth System.

Source : Lawrence Livermore National Laboratory

Researchers Make Improbable Discovery of Deep-sea Coral Reefs in “Hostile” Pacific Ocean Depths

Scientists had long believed that the waters of the Central and Northeast Pacific Ocean were inhospitable to certain species of deep-sea corals, but a marine biologist’s discovery of an odd chain of reefs suggests there are mysteries about the development and durability of coral colonies yet to be uncovered.

Scientist Amy Baco-Taylor of Florida State University (FSU), in collaboration with researchers from Texas A&M University, found the reefs during an autonomous underwater vehicle survey of the seamounts of the Northwestern Hawaiian Islands.

In a paper published today in the journal Scientific Reports, Baco-Taylor and her team document the reefs. They also discuss possible explanations for the reefs’ appearance in areas considered hostile to large communities of scleractinia — small, stony corals that settle on the seabed and grow bony skeletons to protect their soft bodies.

“I’ve been exploring the deep sea around the Hawaiian Archipelago since 1998, and have seen enough to know that the presence of the reefs at these depths was definitely unexpected,” Baco-Taylor said.

Some ocean areas, such as the North Atlantic and South Pacific, are particularly fertile habitats for deep-sea scleractinian reefs, but a combination of factors led scientists to believe that finding these coral colonies was exceedingly unlikely in the deep waters of the North Pacific.

The North Pacific‘s low level of aragonite, an essential mineral in the formation of scleractinian skeletal structures, makes it difficult for the coral polyps to develop their rugged skeletons.

In addition, North Pacific carbonate dissolution rates, a measure of the pace at which carbonate substances such as coral skeletons dissolve, exceed those of the more amenable North Atlantic by a factor of two.

In other words, said Baco-Taylor, the reefs simply should not exist in the North Pacific.

“Even if the corals could overcome low aragonite saturation and build up robust skeletons, there are areas on the reefs that are just exposed skeleton, and those should be dissolving,” Baco-Taylor said. “We shouldn’t be finding an accumulation of reefs.”

The researchers suggest potential reasons for the improbable success of these hardy reefs. Among them, higher concentrations of chlorophyll in the areas of reef growth suggest that an abundance of food may provide the excess energy needed for calcification in waters with low aragonite saturation.

But that doesn’t tell the whole story.

It doesn’t explain “the unusual depths of the reefs, or why, moving to the northwest along the seamounts, they get shallower,” Baco-Taylor said. “There’s still a mystery as to why these reefs are here.”

The unexpected discovery of the reefs has prompted some scientists to reconsider the effects of ocean acidification on vulnerable coral colonies. At a time when stories about the wholesale demise of reefs around the world are sparking alarm, these findings may offer a glimmer of hope.

“These results show that the effects of ocean acidification on deep-water corals may not be as severe as predicted,” said David Garrison, a program director in the National Science Foundation’s Division of Ocean Sciences, which funded the research. “What accounts for the resilience of these corals on seamounts in the Pacific, however, remains to be determined.”

The reefs occur primarily outside the protected Papahanamoukuakea Marine National Monument, which means they exist in areas where destructive trawling is permitted and active.

Researcher Nicole Morgan of FSU, also a co-author of the paper, said that locating the survivalist reefs is crucial because it gives scientists a chance to preserve them.

“We want to know where these habitats are so that we can protect them,” Morgan said. “We don’t want important fisheries to collapse, which often happens when reefs disappear.”

The discovery of the puzzling reefs shows that there are still gaps in scientists’ understanding of the deep sea. The success of hypothesis-driven exploration, like the kind that produced these findings, demonstrates the importance of continuing to strike out into the unknown, said Baco-Taylor.

“These results highlight the importance of doing research in unexplored areas, or ‘exploration science,’ as we like to call it,” said Brendan Roark of Texas A&M University, project co-principal investigator with Baco-Taylor.

If there are additional similar reefs sprinkled across the Northwestern Hawaiian seamounts, Baco-Taylor wants to find them. Further study of these reefs could reveal important information about how they might endure in a time of climbing carbon dioxide levels and increasing ocean acidification.

“If more of these reefs are there, that would run counter to what ocean acidification and carbonate chemistry dictate,” Baco-Taylor said.

“It leaves us with some big questions: Is there something we’re not understanding? How is the existence of these reefs possible?”

Source : National Science Foundation

Discovery of Industrial Chemicals 10 Km below Sea Surface ‘Disturbing’

The discovery of extremely high levels of pollution at the bottom of two of the Earth’s deepest oceanic trenches is a disturbing development that highlights the far-reaching impact of human activities, according to UNSW marine ecologist Dr Katherine Dafforn.

A study by an international team of researchers published today in the journal Nature Ecology and Evolution found that tiny marine crustaceans collected from up to 10 kilometres below the ocean surface contained levels of persistent organic pollutants similar to those in in highly industrialised areas.

In a commentary on the study published in the journal, Dr Dafforn noted that “We still know more about the surface of the moon than that of the ocean floor”.

She says the researchers had for the first time “provided clear evidence that the deep ocean, rather than being remote, is highly connected to surface waters and has been exposed to significant concentrations of human-made pollutants”.

She adds: “Their results are disturbing. Concentrations of PCBs (polychlorinated biphenyls) and PBDEs (polybrominated diphenyl ethers) in these tiny crustaceans were 50 times greater than in crabs from a highly polluted river system in China.

“This is significant since the trenches are many miles away from any industrial source and suggests that the delivery of these pollutants occurs over long distances, despite regulations since the 1970s.”

The researchers, led by Dr Alan Jamieson of the University of Aberdeen in Scotland, used deep-sea landers to collect the scavenging amphipod crustaceans from the depths of the Mariana Trench in the North Pacific Ocean and the Kermadec Trench in the South Pacific Ocean.

They suggest the pollutants most likely found their way to the trenches through contaminated plastic debris and carrion sinking to the bottom of the ocean, where they were then consumed by the amphipods.

PCBs and PBDEs are commonly used as dielectric fluids and flame retardants, respectively. These chemicals accumulate in fatty tissue and are highly detrimental to the health of organisms, due to their endocrine-disrupting properties and impact on the immune system.

“The toxic effects of these pollutants and their potential to biomagnify up the food chain still need to be tested,” Dr Dafforn writes. “These knowledge gaps can be addressed through ecotoxicological testing to investigate lethal and sublethal effects.”

pollution
Image courtesy of Nature Ecology & Evolution

Chilling Climate Revelations from the Last Ice Age

About 14,000 years ago, the southwest United States was lush and green, home to saber-toothed cats and mammoths. Meanwhile, the Pacific Northwest was mostly grassland.

That all changed as the last ice age was ending. Climate changes might be expected with the melt of a global freeze, but what’s surprising is how quickly climate and rainfall patterns changed. According to research published Nov. 22, the collapse of an ice sheet in what is now western Canada triggered a reorganization of the jet stream over the course of about 100 years — a blink of an eye in geological time.

Previous research showed that these changes had occurred, but didn’t address why or the speed at which they happened, said Juan Lora, lead author of the paper and a UCLA postdoctoral fellow.

“Basically, in a human lifetime the climate changed dramatically,” Lora said. “There was a very steady and stable configuration for tens of thousands of years until this moment, and then it suddenly changed to the climate we have now.”

The jet stream shifted north by nearly 500 miles, taking moisture and rainfall from the Pacific with it. That transformed the Pacific Northwest from grassland to the grand forests we now have, while what was once a lush, green Southwest U.S. dried up and became mostly desert. Large animals that relied on that lush ecosystem such as mammoths and saber-toothed cats went extinct over the next few thousand years, leaving behind only fossils and bones in places like the La Brea Tar Pits in Los Angeles.

So how do these findings relate to today’s man-made climate change?

“We know that the jet stream is changing, but the change seems to be a bit more gradual,” Lora said. “The point we’re making is that ice distribution has a very direct effect on the climate of the larger region.”

While we might not see a shift of the same magnitude, parts of the world could see relatively rapid changes as ice melts in polar regions from global warming. Large geographic features like glaciers, Arctic sea ice and ocean temperatures are all major drivers of weather patterns. This study demonstrates that major changes in ice and temperatures could cause abrupt effects farther away.

Co-author Aradhna Tripati, a professor with UCLA’s Institute of the Environment and Sustainability who initiated the study, echoed this concern. She pointed to recent news that Arctic air temperatures are 38 degrees warmer than usual for this time of year, preventing the usual formation of sea ice.

“It’s not just climate change in the Arctic that can affect us here and that we’re worrying about,” Tripati said. “Climate change elsewhere — whether it’s overseas in Europe, China or even Antarctica — can also affect us.”

To reach their conclusions, Tripati and Lora looked at data on past rainfall patterns, lake sediments, ice cores, the chemistry of deposits from caves and fossils from plants. They compared that evidence to computer climate model simulations of what might have happened. These records helped tell the story of the rapid climate shift.

They also serve as an important check on the uncertainty of climate models — the main tools scientists and policy makers use to predict future climate outcomes.

“Observations of past climate can be incredibly useful as a tool for verifying that a climate model’s projections are accurate,” Tripati said. “We need to start picking apart which individual models are doing a great job and why, and maybe even eliminate models that aren’t doing as well.”

Rapid changes in weather patterns would have major effects on the West Coast of North America, where food, water and energy systems are often stretched to capacity to support the tens of millions living in the region.

Daniel Swain, author of the California Weather Blog and a UCLA postdoctoral fellow, said the findings are particularly interesting in the context of California’s ongoing drought.

“This paper presents compelling evidence that atmospheric conditions over the North Pacific can shift abruptly and dramatically in response to incremental changes in the broader Earth system,” Swain said. “It serves as a reminder that the Earth system is full of complex and non-linear interactions — which can sometimes lead to climate surprises.”

Heatwaves in the Ocean – a Risk to Ecosystems?

Did you know that heatwaves not only occur on land, but also in the sea? We all remember the record-breaking European heatwave in summer of 2003: forests burned, rivers dried up and more than ten thousand people in Europe died as a result of the extremely high temperatures. [1] The marine environment – and in particular the organisms – also suffer from heat stress. Two exceptional heatwaves in the ocean during the past few years have alarmed us scientists. Humans will also feel their consequences in the long term.

Heatwaves in the Northeast Pacific…

An unusually long-lasting warm water bubble – nicknamed ‘The Blob’ – spread across the surface of the Northeast Pacific from winter 2013/2014 to the end of 2015. [2] The warm water bubble at times measured up to 1,600 kilometres in diameter and had water temperatures of more than 3 degrees Celsius above the long-term average. Because warm surface water has a lower density than the cold deep water, the exchange of nutrient-rich deep water with warm surface water was reduced, especially along the west coast of North America. This had far-reaching consequences for marine organisms and ecosystems: the growth of phytoplankton decreased due to the reduced supply of nutrients, and some zooplankton and fish species migrated from the warm and nutrient-poor water to cooler regions. By contrast, researchers found pygmy killer whales in the North Pacific for much longer than usual: this tropical whale species is usually observed 2,500 kilometres further south.

… and on the west coast of Australia

ecosystems
A kelp forest of brown algae. (Image: Ethan Daniels/Shutterstock)

A stronger but shorter heatwave hit Australia‘s west coast at the turn of the year 2010/2011, with sea temperatures of up to 6 degrees Celsius above normal levels for that time of year. The seabed along the coast of Western Australia is known for its high concentration of brown algae. These marine ‘kelp forests’ have similar functions as terrestrial forests: they provide habitat and food resource to numerous species; in particular a large number of fish. Australian researchers demonstrated that most of the kelp forest stocks rapidly disappeared during this heatwave. [3] In total, an area of 1,000 square kilometres of kelp forest was lost – this corresponds to twice the size of Lake Constance. Today, algae stocks haven‘t recovered yet. Instead, a new ecosystem with tropical fish and seaweeds has developed.

Risks for marine ecosystems?

We have known for some time that extreme weather and climate events on land, such as heatwaves, shape the structure of biological systems and affect their biogeochemical functions and the services they provide for society in a fundamental manner. It is also known that heatwaves affect a number of biological systems, including humans, more strongly than slower changes in the average temperature. This has to do with the fact that such extreme events push organisms and ecosystems to their limits of their resilience and beyond, potentially causing dramatic and irreversible changes.

The two extreme events in the North Pacific and along the west coast of Australia detailed us for the first time that marine heatwaves can also lead to a number of unprecedented ecological and socioeconomic consequences. For example, it revealed that a large number of fish moved to colder northern waters. Escaping to cooler ocean depths is often not an option because deeper depths lack sunlight, oxygen and plants for food. This may ultimately lead to losses for both the fishing and tourism sectors.

Looking ahead

As the world‘s oceans continue to warm, marine heatwaves are likely to become more frequent and intense. Observations and model simulations also demonstrate that other factors such as ocean acidification and deoxygenation are putting additional stress on marine organisms and ecosystems (see also this post in the Klimablog).

Until recently, climate models were unable to accurately represent the relevant physical and biogeochemical processes to simulate extreme events in the ocean and predict future changes. The uncertainties in future projections, particularly at the regional scale, were simply too large. [4] New model simulations linking the global carbon and oxygen cycle with high-resolution physical processes now enable us to make quantitative predictions about the frequency, strength and spatial distribution of future extreme events in the ocean for the first time. And this is precisely what my scientific research focuses on. But in order to better understand the impact of these extreme events on individual organisms or entire ecosystems and their socioeconomic services, interdisciplinary collaborations are urgently needed. Research on understanding such events is only just beginning.

Ocean Warming and Acidification Impact on Calcareous Phytoplankton

Two new studies recently published in Limnology & Oceanography and Biogeosciences report that ocean warming may exacerbate the impacts of ocean acidification on calcareous phytoplankton, and its evolutionary success and physiological performance will be hampered.

The oceans have absorbed more than a quarter of the human-made carbon dioxide (CO2) in the last century, changing the chemistry of the ocean and resulting in ‘ocean acidification’. A rise in average temperatures is also warming the sea surface. The risks posed by warming and acidification are expected to become more acute in the next decades, as CO2 emissions into the atmosphere are increasing.

Coccolithophores is a very abundant calcifying phytoplankton group which plays a major role in the biogeochemical cycle and in the regulation of the global climate. These tiny algae which measure less than one hundredth of a millimeter “form the basis of the aquatic trophic chain, and through calcification and photosynthesis coccolithophores regulate atmospheric and oceanic CO2 levels”, says Dr Patrizia Ziveri, ICREA researcher at ICTA-UAB and author of the study. The effects of acidification – and in particular warming – are rarely considered for the organism itself, and there is very little knowledge on how warming and acidification combined may affect the physiological performance or evolutionary success of coccolithophores.

Therefore, it was the aim of the team to investigate not only how temperature affects the impact of acidification on the cocolithophores, but also on the sinking rate and coccolithophores morphogenesis. A culture experiment was conducted on Mediterranean Sea and North Pacific Ocean strains of Emiliania huxleyi, the most abundant coccolitophore species.

Using scanning electron microscope (SEM) imaging, the researchers show in their study that there will be an increase in the percentage of malformed and incomplete coccoliths in a warmer and more acidified ocean. This will hamper the evolutionary success of these calcifiers and their role in regulating atmospheric carbon.

Since coccolithophores need to stay in the photic zone of the oceans, their sinking velocity affects their survival rate. Nothing is known about the response of coccolithophores to acidification and warming in terms of sinking rate, because it had been impossible to estimate sinking rate in the framework of a typical laboratory experiment. The team used a novel approach to calculate sinking rate from cell-architecture and showed that an increase in temperature will lead to an increase in sinking rate. Hence, the faster sinking for the organism itself has an impact on future global carbon cycling and therewith on atmospheric levels of CO2 and global climate.

Fukushima radioactivity diluted in the Pacific makes tracing ocean currents possible

Very little is known about ocean currents and generally about dynamics in the oceans. But radioactivity released into the Pacific by the Fukushima nuclear accident, which was quickly diluted to harmless levels, has allowed scientists to trace the ocean’s currents.

The JRC’s expertise in nuclear measurements was instrumental in detecting and quantifying the radioactivity of sea-water samples. The study was carried out with a team of researchers from two Japanese Universities, following a campaign of sampling and measuring anthropogenic radionuclides in the North Pacific. It allowed natural processes using radionuclides as tracers to be studied.

The most important oceanographic conclusion from the study is that most of the surface water transported to the east towards the USA is submerged to a depth of 400 m near to the International Date Line and then turns towards south-west. This movement of the currents was not known prior to this study and will have an impact on e.g. computer models calculating global warming.

The accident in the Fukushima Dai-ichi nuclear power plant in March 2011 led to the release of huge amounts of radioactivity into the Pacific Ocean. During 2011 and 2012, Japanese scientists collected some 800 water samples and about 80 samples of plankton and suspended particles. In collaboration with the JRC, the samples were analysed, revealing very low levels of radioactivity. To measure such low radiation, the samples were placed deep (225m) underground to avoid interference from cosmic rays in the sensitive instruments.

Three radionuclides from Fukushima were detected in the samples from the Pacific: Caesium-134 (134Cs, half-life: 2.1 years), Caesium-137 (137Cs, half-life: 30 years) and the Silver isotope 110mAg (half-life 0.68 years). The zoo-plankton contained higher amounts of radiocaesium than particulate matter as it consumes organic matter and thereby accumulates caesium. The study of plankton is useful to understand the uptake in the food chain and estimate impact on biosystems of future releases. The measurements of the plankton showed that in all sampling locations the level of radiocaesium was in the order of 30 mBq/g (May/June, 2011) whilst only those samples collected up to 70 km from Fukushima (near to the epicentre of the earthquake) had measurable amounts of 110mAg.

California drought patterns becoming more common

Atmospheric patterns associated with droughts in California have occurred more frequently in recent decades, Stanford scientists say.

In new research published online this week in Science Advances, a team of researchers led by Stanford scientist Noah Diffenbaughanalyzed the occurrence of large-scale atmospheric circulation patterns that have occurred during California’s historical precipitation and temperature extremes.

“The current record-breaking drought in California has arisen from both extremely low precipitation and extremely warm temperature,” said Diffenbaugh, an associate professor of Earth system science at Stanford School of Earth, Energy & Environmental Sciences and a senior fellow at Stanford Woods Institute for the Environment. “In this new study, we find clear evidence that atmospheric patterns that look like what we’ve seen during this extreme drought have in fact become more common in recent decades.”

In the new study, Stanford graduate student Daniel Swain and co-authors investigated whether atmospheric pressure patterns similar to those that occurred during California’s historically driest, wettest, warmest and coolest years have occurred with different frequency in recent decades compared with earlier in California’s history. The study focused on the northeastern Pacific Ocean and far western North America, encompassing the winter “storm track” region from which the vast majority of California precipitation originates.

The researchers used historical climate data from U.S. government archives to investigate changes during California’s October to May “rainy season.” They identified the specific North Pacific atmospheric patterns associated with the most extreme temperature and precipitation seasons between 1949 and 2015. Their analysis revealed a significant increase in the occurrence of atmospheric patterns associated with certain precipitation and temperature extremes over the 67-year period.

In particular, the Stanford scientists found robust increases in the occurrence of atmospheric patterns resembling what has occurred during the latter half of California’s ongoing multi-year drought.

“California’s driest and warmest years are almost always associated with some sort of persistent high pressure region, which can deflect the Pacific storm track away from California,” said Swain, the study’s first author and a graduate student in Diffenbaugh’s lab. “Since California depends on a relatively small number of heavy precipitation events to make up the bulk of its annual total, missing out on even one or two of these can have significant implications for water availability.”

Blocking ridges are regions of high atmospheric pressure that disrupt typical wind patterns in the atmosphere. Scientists concluded that one such persistent ridge pattern – which Swain named the Ridiculously Resilient Ridge – was diverting winter storms northward and preventing them from reaching California during the state’s drought. In 2014, the Stanford researchers published findings that showed that the increasing occurrence of extremely high atmospheric pressure over this same part of the Northeastern Pacific is “very likely” linked to global warming.

The group next wanted to investigate whether the particular spatial pattern associated with the Triple-R has become more common – a question not asked in the original 2014 study. The new study provides a more direct answer to this question.

“We found that this specific extreme ridge pattern associated with the ongoing California drought has increased in recent decades,” Swain said.

Despite the fact that the number of very dry atmospheric patterns in California has increased in recent decades, the number of very wet atmospheric patterns hasn’t declined.

“We’re seeing an increase in certain atmospheric patterns that have historically resulted in extremely dry conditions, and yet that’s apparently not occurring at the expense of patterns that have historically been associated with extremely wet patterns,” Swain said. “We’re not necessarily shifting toward perpetually lower precipitation conditions in California – even though the risk of drought is increasing.”

That might sound contradictory, but it’s not, the scientists said. Imagine looking at a 10-year period and finding that two of the years are wet, two are dry and the rest experienced precipitation close to the long-term average. Now imagine another decade with three very dry years, three very wet years and only four years with near-average precipitation.

“What seems to be happening is that we’re having fewer ‘average’ years, and instead we’re seeing more extremes on both sides,” Swain said. ” “This means that California is indeed experiencing more warm and dry periods, punctuated by wet conditions.”

Funding for the research was provided by the National Science Foundation, the Switzer Foundation, the ARCS Foundation, the U.S. Department of Energy and a G.J. Lieberman Fellowship from Stanford University.