El Niño: Is 2014 the new 1997?

Every ten days, the NASA/French Space Agency Jason-2 satellite maps all the world’s oceans, monitoring changes in sea surface height, a measure of heat in the upper layers of the water.   Because our planet is more than 70% ocean, this information is crucial to global forecasts of weather and climate.

Lately, Jason-2 has seen something brewing in the Pacific—and it looks a lot like 1997.

“A pattern of sea surface heights and temperatures has formed that reminds me of the way the Pacific looked in the spring of 1997,” says Bill Patzert, a climatologist at NASA’s Jet Propulsion Laboratory. “That turned out to be the precursor of a big El Niño.”

A new ScienceCast video examines the evidence that an El Niño is developing in the Pacific.  Play it

“We can’t yet say for sure that an El Niño will develop in 2014, or how big it might be,” cautions Mike McPhaden of NOAA’s Pacific Environmental Research Laboratories in Seattle, “but the Jason-2 data support the El Niño Watch issued last month by NOAA.”

What Jason-2 has been seeing is a series of “Kelvin waves”—massive ripples in sea level that travel across the Pacific from Australia to South America.  Forecasters are paying close attention because these waves could be a herald of El Niño.

The two phenomena, Kelvin waves and El Niño, are linked by wind. Pacific trade winds blow from east to west, pushing sun-warmed surface waters toward Indonesia.  As a result, the sea level near Indonesia is normally 45 cm higher than it is near Ecuador.  Researchers call that area the “warm pool”—it is the largest reservoir of warm water on our planet.

Sometimes, however, trade winds falter for a few days or weeks, and some of that excess sea level   ripples back toward the Americas. “That’s a Kelvin wave,” says McPhaden. “It’s not unusual to see a couple every winter.”

El Niño happens when trade winds falter not just for days, but for many months. Then Kelvin waves    cross the Pacific like a caravan, raising sea level and leaving warmer equatorial waters in their wake.

On May 8th, the National Centers for Environmental Prediction forecasted a 65% chance of El Niño developing during the summer of 2014. More

“The El Niño of 1997/98 was a textbook example,” recalls Patzert. “At that time we were getting data from TOPEX/Poseidon, a predecessor of Jason-2.  Sea surface maps showed a whitish bump, indicating a sea level some 10 centimeters higher than usual, moving along the equator from Australia to South America.”

“The same pattern is repeating in 2014,” says McPhaden. “A series of Kelvin waves generated by localized west wind bursts in the western Pacific that began in mid-January 2014 are headed east. Excitement is building as a third weakening of the Pacific trade winds happened in mid-April.”

Ocean and atmospheric scientists at NOAA and NASA are carefully monitoring the Pacific trade winds. The tipping point for declaring a significant El Niño will be an even longer lasting, larger collapse in Pacific trade winds, possibly signaling a shift in weather all around our planet.

“It will become much clearer over the next two to three months whether these recent developments are the forerunner of a major El Niño—or any El Niño at all,” says McPhaden.

“Jason-2 is a marvelous Kelvin wave counter,” adds Patzert, “and it will tell the tale.”

West Antarctic Glaciers in Irreversible Decline

Over the years, as temperatures around the world have ratcheted upward, climate change researchers have kept a wary eye on one place perhaps more than any other:  The West Antarctic Ice Sheet, and particularly the fastest melting part of it, the glaciers that flow into the Amundsen Sea.

In that region, six glaciers hang in a precarious balance, partially supported by land, and partially floating in waters just offshore.  There’s enough water frozen in the ice sheet that feeds these icy giants to raise global sea levels by 4 feet—if they were to melt. That’s troubling because the glaciers are melting. Moreover, a new study finds that their decline appears to be unstoppable.

A new ScienceCast video lays out the evidence for irreversible decline of the West Antarctic glaciers. Play it

“We’ve passed the point of no return,” says Eric Rignot, a glaciologist working jointly at NASA’s Jet Propulsion Laboratory and the University of California, Irvine.  Rignot and colleagues have used 19 years of satellite radar data to map the fast-melting glaciers. In their paper, which has been accepted for publication in Geophysical Research Letters, they conclude that “this sector of West Antarctica is undergoing a marine ice sheet instability that will significantly contribute to sea level rise” in the centuries ahead.

A key concept in the Rignot study is the “grounding line”—the dividing line between land and water underneath a glacier.  Because virtually all melting occurs where the glaciers’ undersides touch the ocean, pinpointing the grounding line is crucial for estimating melt rates.

The problem is, grounding lines are buried under thousands of feet of glacial ice. “It’s challenging for a human observer to figure out where they are,” Rignot explains. “There’s nothing obvious that sticks out on the surface to say, ‘This is where the glacier goes afloat.’”

To find the hidden grounding lines, they examined radar images of the glaciers made by the European Space Agency’s Earth Remote Sensing satellites from 1992 to 2011. Glaciers flex in response to tides.  By analyzing the flexing motions, they were able to trace the grounding lines.

This led to a key discovery.  In all the glaciers they studied, grounding lines were rapidly retreating away from the sea.

Click on the image to view more animations related to this story.More

“In this sector, we are seeing retreat rates that we don’t see anywhere else on Earth,'” Rignot says. Smith Glacier’s line moved the fastest, retreating 22 miles upstream. The other lines retreated from 6 to 19 miles.

As the glaciers melt and lose weight, they float off the land where they used to sit.  Water gets underneath the glacier and pushes the grounding line inland. This, in turn, reduces friction between the glacier and its bed.  The glacier speeds up, stretches out and thins, which drives the grounding line to retreat farther inland. 

This is a “positive feedback loop” that leads to out of control melting.

The only natural factor that can slow or stop this process is a “pinning point” in the bedrock — a bump or projection that snags the glacier from underneath and keeps it from sliding toward the sea. To investigate this possibility, the researchers made a novel map of the bed beneath the glaciers using radar and other data from satellites and NASA’s airborne IceBridge mission. The map revealed that the glaciers had already floated off many of their small pinning points.

In short, there seems to be no turning back. 

“At current melt rates,” concludes Rignot, “these glaciers will be ‘history’ within a few hundred years.”

Warming World Shrinks Salamanders

In ancient mythology, salamanders could withstand fire. In modern times, though, just a small warming has been enough to dramatically change them—and perhaps threaten their future. Salamanders in the southern Appalachian Mountains of Tennessee, North Carolina, and Virginia have gotten smaller over the past 50 years due to increasing temperatures in their habitats, a new study has concluded. It’s the first confirmation that climate change can alter body size, a connection that had only been hypothesized in the past, and one of the fastest studied responses to changing temperatures on record.

“This is helping us understand yet another way in which climate change could play out,” says ecologist Michael Adams of the U.S. Geological Survey in Corvallis, Oregon, who was not involved in the new work. “In this case, we’re learning how it can change the life history of an organism.”

Over the past decade, scientists have documented several population declines in amphibians, including salamanders. But the causes of these declines have been hard to work out; some are due to disease, others to habitat loss or invasive species. Karen Lips, a biologist at the University of Maryland, College Park, wanted to determine what was behind dropping numbers of Plethodontidae, or lungless salamanders, across the eastern United States. The Appalachians are home to more salamander species than any place on Earth, many unique to the area. The Plethodontidae, the most numerous, represent a large and diverse family of salamanders that all respire through their skin. The salamanders play a key role in the ecosystems of the mountains, consuming insects that are too tiny for most other vertebrates.

Lips and her colleagues analyzed more than 9000 salamanders from a dozen different Plethodontidae species, some from museum specimens collected as early as 1950 and others from 85 current locations across the southern Appalachians. Although they didn’t find widespread evidence of disease, they did notice another trend: The salamanders had gotten smaller. Salamanders collected after 1980 were 8% smaller than those from decades past. The trend was most significant in places that had seen the largest shifts in climate during that time: low elevations with an increase in temperature and a decrease in rain, the team reports online today in Global Change Biology. On average, the salamanders shrunk by 1% per generation.

Lungless salamanders, Lips explains, are highly sensitive to changes in their surrounding environment because of the way they breathe through their skin. When the temperature rises, their body speeds up. Using computer modeling, Lips’ collaborators showed that temperature increases in the areas of the Appalachians that have warmed over the past 50 years could speed the salamanders’ metabolisms by more than 7%.

Lips’ team hasn’t yet confirmed the mechanism by which the change in body size has occurred, although she hypothesizes that it’s driven by the salamanders’ metabolisms. “If it’s a little bit warmer, the animal is going to burn through its calories much faster,” Lips says. If availability of extra calories or extra time to forage is limited, the salamanders will grow to a smaller adult size due to this increased calorie burn. And smaller salamanders, she says, lay fewer eggs and are more susceptible to predators. “In general, bigger is better for these guys,” Lips says.

The scientists haven’t yet confirmed that the salamanders’ smaller size is behind the documented population declines, though they are confident that climate change is what’s driving the shrinkage in body size.

Joseph Milanovich, an ecologist at Loyola University Chicago in Illinois, says that an ability to alter their body size could be what has allowed salamanders to survive previous temperature fluctuations. “These organisms have been on Earth for hundreds of millions of years,” he notes. “They’ve been through climate warming and cooling cycles before.” So the flexibility to alter their metabolism and body size may be an adaptation that’s arisen throughout these cycles. But that doesn’t mean that their current decrease in size will allow them to survive the faster pace of climate change that’s occurring now, Milanovich says.

Lips and her colleagues next plan to study how the change in body size affects the lungless salamanders’ interactions with each other and other species. The change in size, she says, could have broader effects on the Appalachian forest habitats they live in due to their key role in the food chain.

“These guys are really important in the food web of the forest,” Lips says. “They are extremely abundant and they play an important role in nutrient cycling by eating bugs and converting those into food for birds and mammals.” So understanding how salamanders respond to climate change is likely one piece of the larger story of how entire ecosystems respond, she says.

Back to life after 1,500 years

Researchers from the British Antarctic Survey and Reading University have demonstrated that, after over 1,500 years frozen in Antarctic ice, moss can come back to life and continue to grow. For the first time, this vital part of the ecosystem in both polar regions has been shown to have the ability to survive century to millennial scale ice ages. This provides exciting new insight into the survival of life on Earth. The team, reporting inCurrent Biology this week, observed moss regeneration after at least 1,530 years frozen in permafrost. This is the first study to show such long-term survival in any plant; similar timescales have only been seen before in bacteria. Mosses are known to survive environmental extremes in the short-term with previous evidence confirming up to a 20 year timescale for survival. Their potential to survive much longer timescales had not previously been examined.

Mosses are an important part of the biology of both polar regions. They are the dominant plants over large areas and are a major storer of fixed carbon, especially in the north.

Co-author Professor Peter Convey from the British Antarctic Survey explains: “What mosses do in the ecosystem is far more important than we would generally realise when we look at a moss on a wall here for instance. Understanding what controls their growth and distribution, particularly in a fast-changing part of the world such as the Antarctic Peninsula region, is therefore of much wider significance.”

The team took cores of moss from deep in a frozen moss bank in the Antarctic. This moss would already have been at least decades old when it was first frozen. They sliced the frozen moss cores very carefully, keeping them free from contamination, and placed them in an incubator at a normal growth temperature and light level. After only a few weeks, the moss began to grow. Using carbon dating, the team identified the moss to be at least 1,530 years of age, and possibly even older, at the depth where the new growth was seen.

According to Professor Convey: “This experiment shows that multi-cellular organisms, plants in this case, can survive over far longer timescales than previously thought. These mosses, a key part of the ecosystem, could survive century to millennial periods of ice advance, such as the Little Ice Age in Europe.

“If they can survive in this way, then recolonisation following an ice age, once the ice retreats, would be a lot easier than migrating trans-oceanic distances from warmer regions. It also maintains diversity in an area that would otherwise be wiped clean of life by the ice advance.

“Although it would be a big jump from the current finding, this does raise the possibility of complex life forms surviving even longer periods once encased in permafrost or ice.”

Source: British Antarctic Survey

Southern Ocean iron cycle gives new insight into climate change

An international team of researchers analyzed the available data taken from all previous studies of the Southern Ocean, together with satellite images taken of the area, to quantify the amount of iron supplied to the surface waters of the Southern Ocean. They found that deep winter mixing, a seasonal process which carries colder and deeper, nutrient-rich water to the surface, plays the most important role in transporting iron to the surface. The iron is then able to stimulate phytoplankton growth which supports the ocean’s carbon cycle and the aquatic food chain

They were also able to determine that following the winter iron surge, a recycling process is necessary to support biological activity during the spring and summer seasons.

Oceanographer, Dr Alessandro Tagliabue, from the University’s School of Environmental Sciences, said: “We combined all available iron data, matched them with physical data from autonomous profiling floats and used the latest satellite estimates of biological iron demand to explore how iron is supplied to the phytoplankton in the Southern Ocean.

“This is important because iron limits biological productivity and air to sea CO2 exchange in this region. We found unique aspects to the iron cycle and how it is supplied by physical processes, making it distinct to other nutrients.

“This means that the Southern Ocean’s nutrient supply would be affected by changes to the climate system (such as winds and freshwater input) differently to other areas of the ocean.

“We need to understand these unique aspects so that they can be used to better inform global climate predictions.”

Dr Jean-Baptiste Sallée, from the Centre National de la Recherche Scientifique and the British Antarctic Survey, said: “We are really excited to make this discovery because until now we didn’t know the physical processes allowing iron to reach the ocean surface and maintain biological activity. The combination of strong winds and intense heat loss in winter strongly mixes the ocean surface and the mixing reaches deep iron reservoir.”

The Southern Ocean comprises the southernmost waters of the world oceans that encircle Antarctica. Researchers have long known the region is crucial in the uptake of atmospheric CO2 and that biological processes in the Southern Ocean influence the global ocean system via northward flowing currents.

Source: University of Liverpool

Number of days without rain to dramatically increase in some world regions

By the end of the 21st century, some parts of the world can expect as many as 30 more days a year without precipitation, according to a new study by Scripps Institution of Oceanography, UC San Diego researchers. Ongoing climate change caused by human influences will alter the nature of how rain and snow falls; areas that are prone to dry conditions will receive their precipitation in narrower windows of time. Computer model projections of future conditions analyzed by the Scripps team indicate that regions such as the Amazon, Central America, Indonesia, and all Mediterranean climate regions around the world will likely see the greatest increase in the number of “dry days” per year, going without rain for as many as 30 days more every year. California, with its Mediterranean climate, is likely to have five to ten more dry days per year.

This analysis advances a trend in climate science to understand climate change on the level of daily weather and on finer geographic scales.

“Changes in intensity of precipitation events and duration of intervals between those events will have direct effects on vegetation and soil moisture,” said Stephen Jackson, director of the U.S. Department of the Interior Southwest Climate Science Center, which co-funded the study. “(Study lead author Suraj) Polade and colleagues provide analyses that will be of considerable value to natural resource managers in climate adaptation and planning. Their study represents an important milestone in improving ecological and hydrological forecasting under climate change.”

Polade, a postdoctoral researcher at Scripps, said that one of the implications of this finding is that annual rainfall could become less reliable in drying regions as annual averages will be calculated over a smaller number of days. The 28 models used by the team showed agreement in many parts of the world on the change in the number of dry days those regions will receive. They were in less agreement about how intense rain or snow will be when it does fall, although there is general consensus among models that the most extreme precipitation will become more frequent. Climate models agreed even less on how the conflicting daily changes affect annual mean rainfall.

“Looking at changes in the number of dry days per year is a new way of understanding how climate change will affect us that goes beyond just annual or seasonal mean precipitation changes, and allows us to better adapt to and mitigate the impacts of local hydrological changes,” said Polade, a postdoctoral researcher who works with Scripps climate scientists Dan Cayan, David Pierce, Alexander Gershunov, and Michael Dettinger, who are co-authors of the study.

In regions like the American Southwest, where precipitation is historically infrequent and where a couple of storms more or fewer can make a wet or a dry year, annual water accumulation varies greatly. A decrease in precipitation frequency translates into even more year-to-year variability in fresh water resources for the Southwest.

“These profound and clearly projected changes make physical and statistical sense, but they are invisible when looking at long-term trends in average climate projections,” Gershunov said.

Other regions of the world, most of which are climatologically wet, are projected to receive more frequent precipitation. Most such regions are not on land or are largely uninhabited, the equatorial Pacific Ocean and the Arctic prominent among them.

The authors suggest that follow-up studies should emphasize more fine-scale analyses of dry day occurrences and work towards understanding the myriad regional factors that influence precipitation.

“Climate models have improved greatly in the last 10 years, which allows us to look in detail at the simulation of daily weather rather than just monthly averages,” said Pierce.

Source: University of California – San Diego