A growing network of lakes on the Greenland ice sheet has been found to drain in a chain reaction that speeds up the flow of the ice sheet, threatening its stability.

Melting of Greenland ice sheet forms lakes that drain in summer [Credit: Timo Lieber]

Researchers from the UK, Norway, US and Sweden have used a combination of 3D computer modelling and real-world observations to show the previously unknown, yet profound dynamic consequences tied to a growing number of lakes forming on the Greenland ice sheet.

Lakes form on the surface of the Greenland ice sheet each summer as the weather warms. Many exist for weeks or months, but drain in just a few hours through more than a kilometre of ice, transferring huge quantities of water and heat to the base of the ice sheet. The affected areas include sensitive regions of the ice sheet interior where the impact on ice flow is potentially large.

Previously, it had been thought that these 'drainage events' were isolated incidents, but the new research, led by the University of Cambridge, shows that the lakes form a massive network and become increasingly interconnected as the weather warms. When one lake drains, the water quickly spreads under the ice sheet, which responds by flowing faster. The faster flow opens new fractures on the surface and these fractures act as conduits for the drainage of other lakes. This starts a chain reaction that can drain many other lakes, some as far as 80 kilometres away.

These cascading events -- including one case where 124 lakes drained in just five days -- can temporarily accelerate ice flow by as much as 400%, which makes the ice sheet less stable, and increases the rate of associated sea level rise. The results are reported in the journal Nature Communications.

The study demonstrates how forces within the ice sheet can change abruptly from one day to the next, causing solid ice to fracture suddenly. The model developed by the international team shows that lakes forming in stable areas of the ice sheet drain when fractures open in response to a high tensile shock force acting along drainage paths of water flowing beneath the ice sheet when other lakes drain far away.

Scientists abseil into large fracture produced by a drained lake on Greenland ice sheet [Credit: Samuel Doyle]

"This growing network of melt lakes, which currently extends more than 100 kilometres inland and reaches elevations as high a 2,000 metres above sea level, poses a threat for the long-term stability of the Greenland ice sheet," said lead author Dr Poul Christoffersen, from Cambridge's Scott Polar Research Institute. "This ice sheet, which covers 1.7 million square kilometres, was relatively stable 25 years ago, but now loses one billion tonnes of ice every day. This causes one millimetre of global sea level rise per year, a rate which is much faster than what was predicted only a few years ago."

The study departs from the current consensus that lakes forming at high elevations on the Greenland ice sheet have only a limited potential to influence the flow of ice sheet as climate warms. Whereas the latest report by Intergovernmental Panel on Climate Change concluded that surface meltwater, although abundant, does not impact the flow of the ice sheet, the study suggests that meltwater delivered to the base of the ice sheet through draining lakes in fact drives episodes of sustained acceleration extending much farther onto the interior of the ice sheet than previously thought.

"Transfer of water and heat from surface to the bed can escalate extremely rapidly due to a chain reaction," said Christoffersen. "In one case we found all but one of 59 observed lakes drained in a single cascading event. Most of the melt lakes drain in this dynamic way."

Although the delivery of small amounts of meltwater to the base of the ice sheet only increases the ice sheet's flow locally, the study shows that the response of the ice sheet can intensify through knock-on effects.

When a single lake drains, the ice flow temporarily accelerates along the path taken by water flowing along the bottom of the ice sheet. Lakes situated in stable basins along this path drain when the loss of friction along the bed temporarily transfers forces to the surface of the ice sheet, causing fractures to open up beneath other lakes, which then also drain.

"The transformation of forces within the ice sheet when lakes drain is sudden and dramatic," said co-author Dr Marion Bougamont, also from the Scott Polar Research Institute. "Lakes that drain in one area produce fractures that cause more lakes to drain somewhere elsewhere. It all adds up when you look at the pathways of water underneath the ice."

The study used high-resolution satellite images to confirm that fractures on the surface of the ice sheet open up when cascading lake drainage occurs. "This aspect of our work is quite worrying," said Christoffersen. "We found clear evidence of these crevasses at 1,800 metres above sea level and as far 135 kilometres inland from the ice margin. This is much farther inland than previously considered possible."

While complete loss of all ice in Greenland remains extremely unlikely this century, the highly dynamic manner in which the ice sheet responds to Earth's changing climate clearly underscores the urgent need for a global agreement that will reduce the emission of greenhouse gases.

Source: University of Cambridge [March 14, 2018]

Scientists have peered into the brain of a prehistoric creature that lived around 520 million years ago. Fifteen fossils of the ancient predator were recently discovered in Greenland, which had fortunately escaped the ravages of time and elements.

An artist's reconstruction of the 520-million-year-old Kerygmachela kierkegaardi depicts the ancient species as a formidable ocean predator [Credit: Nature Communications (2018)]

This allowed the creature’s nervous tissue to be fossilized, providing researchers with new insights into panarthropods' evolutionary developments. Panarthropods are an animal group that include creatures such as tardigrades or water bears, velvet worms and arthropods, such as insects.

“The findings shed light on the ancestral condition of the panarthropod brain and the origin of complex arthropod compound eyes. The new material, furthermore, provides novel information on the overall anatomy of Kerygmachela,” the researchers wrote in the new study, published in the journal Nature Communications.

The newly discovered fossils belonged to a now-extinct species called Kerygmachela kierkegaardi. The prehistoric creature swam across the Earth’s oceans during the Cambrian explosion — an era that saw the emergence of incredible and rapid diversity among life forms over a short period of time.

The ancient creature measured between one to ten inches and is flanked by 11 wrinkly flaps on both sides of the body. The predator also sported a round head and an elongated tail spine. United Kingdom-based paleontologist Jakob Vinther, who led the study along with Tae-Yoon Park of the Korea Polar Research Institute, told National Geographic the creature’s forward-facing appendages grabbed onto prey, “making lives miserable for other animals.”

The ancient creature measures between one to ten inches and is flanked by 11 wrinkly flaps on both sides of the body [Credit: Tae-Yoon Park/Nature Communications]

The new study challenges previous theories that claimed the common ancestor of all panarthropods had complex three-part brain. Instead, the researchers argue the new evidence indicated the common ancestor of panarthropods, as well as invertebrate panarthropods and vertebrates, did not have complex brains.

Researchers believe despite its simple brain, the Kerygmachela’s eyes were likely complex enough to form images. The ancient predator’s eyes likely mirror the smaller and much simpler eyes of modern-day tardigrades and velvet worms.

However, some scientists appear to be unconvinced of the new details.

“If they’re going to say that the brain of Kerygmachela is like that of a tardigrade, you have to be really, really careful,” Nicholas Strausfeld told National Geographic. “Because it might not be.”

“The discovery of the simple unipartite brain in stem-group euarthropods corroborates the ancestral simplicity of the panarthropod brain, and also suggests that the complex neural concentrations, such as tripartite brains in euarthropods and chordates, are the result of convergent adaptations,” the researchers concluded.

Author: India Aishani Ashok | Source: International Business Times [March 13, 2018]

It may not rank among the all-time greatest dramas, but the history of ice on Greenland has been a source of scientific controversy for more than a decade.

Iceberg off the coast of Greenland [Credit: Drew Avery/WikiCommons]

A study led by UCLA climate scientist Aradhna Tripati appears to put the debate to rest, with major implications for future research across a range of disciplines, from climate science to geology. The paper, which is published today in the journal Nature Communications, also sheds light on how global climate may change as people continue emitting greenhouse gases, revealing a potential tipping point: atmospheric carbon dioxide concentrations of 500 parts per million or more. Beyond that threshold, major ice sheets at both poles could melt significantly. Current levels are near 400 parts per million.

For years, the prevailing belief was that glaciers first appeared on Greenland between 5 million and 11 million years ago. Then, in 2005, Tripati authored a study suggesting the ice had been present there much earlier: about 35 to 40 million years ago.

Though Tripati's paper was published in Nature—one of the most-respected scientific journals—it was considered controversial. At the heart of the conflict was a simple question: Why weren't similar observations made by other studies? Because the findings were not in line with previous knowledge, the paper was regarded as an outlier.

Tripati, who was then a postdoctoral fellow, admits that her research, which was based on the chemistry of Pacific Ocean samples and what they implied about ancient seawater, was "a pretty indirect indicator." Still, she had confidence in the results. She, her students and other researchers conducted a series of studies using different climate indicators, and they kept reaching the same conclusion.

"Understanding the history of ice at both poles and how they respond to changing carbon dioxide levels is so important that, as we published these papers, controversy built up," said Tripati, who is a member of the UCLA Institute of the Environment and Sustainability. "We dug in and continued to try to understand what the history, in fact, was."

In 2014, Tripati sent Dennis Darby, an Arctic paleoclimate specialist at Old Dominion University who became her co-author on the new paper, promising samples taken from a site in the Greenland Sea where icebergs that broke off—a process known as "calving"—from glaciers on the island would have drifted by.

"As glaciers move across land, they incorporate pieces of sediment," Tripati said. "As glaciers produce icebergs and those icebergs drift through the ocean, those little fragments of rock get released as the ice melts. Each rock fragment has a unique chemistry. That chemistry is a fingerprint—each grain tells you something about where the ice came from."

Those samples are dated based on what fossils are present and their magnetic properties, allowing researchers to reconstruct where and when there was ice present on Greenland and other land masses in the Arctic, as well as when there was sea ice in the ocean.

Data visualization showing changes in Greenland’s ice sheet from 2003 to 2012. Rapidly thinning coastal regions are shown in green, blue and purple [Credit: NASA]

Tripati chose to send those new samples to Darby because he had published a study that corroborated her 2005 findings. Using a method he pioneered, Darby analyzed them without knowing what he was looking at, where it came from or how old it was—sort of like a blind taste test.

He found that the samples contained "very high matches" to east Greenland source sites, again confirming Tripati's earlier research. In fact, his analysis showed that large glaciers were present on Greenland even earlier: up to 47.1 million years ago. That was right at the beginning of the middle Eocene epoch, about 20 million years after dinosaurs went extinct.

Darby was also able to match ice from the samples to other locations across the Arctic region.

"That's important," Darby said. "It shows this was not just a local or regional effect in Greenland. It was something climatically induced on a much larger scale, a polar event."

With their new study, Tripati and Darby think the mystery is solved. Darby's technique was rigorously tested in a 2012 study and found to be accurate 98.5 percent of the time. They examined 100 sediment samples and fingerprinted the chemistry of more than 2,000 rock fragments.

Today's paper also contains revelations about how atmospheric conditions relate to the presence or absence of ice. In the years since that first freeze, ice formed and retreated from Greenland several times. The researchers found that ice was usually present when carbon dioxide levels were lower than 500 parts per million.

"What happens if carbon dioxide levels get sustained at 800 parts per million, where some carbon emissions scenarios have us going?" Tripati asked. "Greenland has a lot of ice. If it all melted, it could raise sea level globally by about 20 feet."

Ice comes and goes at both poles under those conditions, the study found. Tripati's research from 2016 that suggested massive ice shelves on Antarctica are also at risk of melting supports this.

Understanding tipping points is important because Earth's climate can change quickly, Darby said. He pointed to 10,000 years ago in Greenland, when temperatures rose 10 degrees Celsius in 10 years.

"Those thresholds need to be researched," Darby said. "They are largely ignored by climate scientists because these things happened way in the past. Many of them are sort of stuck in the past 50 years. And in that time, we don't see any big changes except in the past two decades, when we see very rapid changes that are concerning."

Tripati said that controversies are good for science in general, she said—it shows the scientific process is healthy. She recalled cat-sitting for renowned scientist Sir Nicholas Shackleton around the time she was conducting the early study.

"He said to me 'When you discover something surprising, remember that it's OK to be wrong, but ideally you should be the person to find out. Always try to prove yourself wrong instead of trying to prove yourself right,' " Tripati recalled.

"I think that's excellent advice. With this study, I didn't know what we were going to find. If it didn't work out, fine—we could have written a paper that definitively said 'no evidence for this.' And then we're on the right side of science."

The process also underscored the importance of including diverse perspectives in science, Tripati said. Last summer she launched the UCLA Center for Diverse Leadership in Science—the first initiative of its kind devoted to including people of all backgrounds in environmental science. Dogma that endured for decades can shift dramatically if the scientific community is inclusive and welcomes new perspectives, she said. Inclusion and social belonging will foster diversity, and research shows that leads to more creative approaches and ideas, fueling innovation and scientific breakthroughs.

Tripati and Darby both hope today's findings inspire future research to better understand what will happen to Earth's climate, species and human communities if we continue on our current carbon emissions trajectory.

They also hope it will inform policies aimed at preventing a climate catastrophe—particularly efforts to reduce carbon emissions, Darby said.

"We need to start looking at what we're doing," Darby said. "Some people stick their heads in the sand because they think we'll come up with technology to save us at the last minute. But that's provided we don't hit one of these thresholds first."

Author: David Colgan | Source: University of California, Los Angeles [March 13, 2018]

Spring is arriving earlier, but how much earlier? The answer depends on where on Earth you find yourself, according to a study led by the University of California, Davis.

Spring is springing earlier at northern latitudes, such as in Greenland, than it is at lower latitudes [Credit: Eric Post/UC Davis]

The study, published in Nature’s online journal Scientific Reports, found that for every 10 degrees north from the equator you move, spring arrives about four days earlier than it did a decade ago. This northward increase in the rate of springtime advance is roughly three times greater than what previous studies have indicated.

For example, at southern to mid latitudes such as Los Angeles, New Orleans or Dallas, the study suggests spring might be arriving a mere one day earlier than it did a decade ago. Farther north, in Seattle, Chicago or Washington D.C., it might be arriving four days earlier. And if you live in the Arctic, it might be arriving as much as 16 days earlier.

“This study verifies observations that have been circulating in the scientific community and popular reports for years,” said lead author Eric Post, a fellow of the John Muir Institute and polar ecologist in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Yes, spring is arriving earlier, and the Arctic is experiencing greater advances of spring than lower latitudes. What our study adds is that we connect such differences to more rapid springtime warming at higher latitudes.”

Cottongrass blows in the Greenland wind [Credit: Eric Post/UC Davis]

Accelerated spring 
                                         
The study is the most comprehensive analysis to date of springtime advance, or phenology, as you move north with latitude. Such signs include birds migrating, flowers blooming, amphibians calling and the emergence of leaves.

The researchers analyzed 743 previously published estimates of the rate of springtime advance from studies spanning 86 years across the Northern Hemisphere, as well as rates of springtime warming over the same range of years and latitude. Even after accounting for differences in the length, time and location of those previous studies, the relationship between earlier springs and higher latitudes was strong.

A nest holding the eggs of northern wheatears rests on branches in Greenland. These birds are long-distance migrants, overwintering in sub-Saharan Africa and breeding in the Arctic. With earlier springs happening faster at higher but not lower latitudes, the birds may find themselves "late for dinner" if the insects they flew north to feast upon have already emerged [Credit: Eric Post/UC Davis]

Unknowns for birds, migratory species

Springtime provides important biological cues for many plant and animal species, and it is unclear how an accelerated spring could play out for these species across the planet.

The study notes that impacts to migratory birds are a potential concern. Many birds move from tropical zones to higher latitudes, such as the Arctic, to breed.

“Whatever cues they’re relying on to move northward for spring might not be reliable predictors of food availability once they get there if the onset of spring at these higher latitudes is amplified by future warming,” Post said. “The springtime emergence of the plants and insects they’ll eat when they arrive is happening faster than the changes at the lower latitudes those birds are departing from.”

Author: Kat Kerlin | Source: UC Davis [March 02, 2018]

On the basis of a unique global comparison of data from core samples extracted from the ocean floor and the polar ice sheets, AWI researchers have now demonstrated that, though climate changes have indeed decreased around the globe from glacial to interglacial periods, the difference is by no means as pronounced as previously assumed. Until now, it was believed that glacial periods were characterised by extreme temperature variability, while interglacial periods were relatively stable. The researchers publish their findings advanced online in the journal Nature.

Drilling an Antarctic ice core [Credit: Martin Leonhardt]

If you want to know how the climate will change in the future, you need to look at the past. By looking at the climate changes that took place thousands of years ago, we can improve predictions for future climate. Comparing layers in the ice-core samples and ocean sediments has allowed researchers to deduce e.g. how the average temperature on Earth has changed over time, and also how great the variability was. From the height of the last glacial period 21,000 years ago to our current interglacial period, the Earth has warmed by an average of five degrees Celsius. In view of future global warming, it's vital for today's global population to know whether temperatures will rise steadily, or whether there will be sudden, major fluctuations. The frequency of extreme events represents an essential benchmark for climate change adaptation measures, since, when it comes to flood protection, transport and building materials, we need to be prepared for the worst-case scenario, and not just for "average" changes.

Climate researchers from the Helmholtz Young Investigators Group ECUS at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) in Potsdam have now investigated how temperature variability changed as the Earth warmed from the last glacial period to the current interglacial period. To date it has been assumed that temperatures varied greatly during the last glacial, while the current interglacial was largely characterised by small temperature variations. This interpretation was based on water isotope data from central Greenland ice cores.

Sampling locations [Credit: Kira Rehfeld]

The team, led by Dr Kira Rehfeld and Dr Thomas Laepple, compared the Greenland data with that from sediments collected in several ocean regions around the globe, as well as from ice-core samples gathered in the Antarctic. They demonstrate that the phenomenon of major temperature fluctuations during glacial periods has by no means manifested uniformly worldwide, but has instead varied from region to region. For instance, in the Tropics the temperature variations were three times as intense as today at the height of the last glacial, whereas the ice cores from Greenland indicate variations that were 70 times as intense. "The ice cores from Greenland are without a doubt an important key to understanding the climate of the past. That being said, our study confirms that the conclusions regarding Greenland aren't always representative of the entire world," explains Young Investigators Group leader Laepple, who also heads the ERC-funded Young Investigators Group SPACE.

The achievement of first author Kira Rehfeld and her colleagues: they have for the first time gathered and compared data from diverse climate archives and a total of 99 research sites. In the climate research community, ice cores are generally considered the gold standard, because their layers are highly consistent, unlike sediment layers from the seafloor, which are frequently marred by tectonic shifts, currents or marine organisms. The AWI researchers have devised mathematical methods that allow them to estimate the uncertainties and potential sources of error while assessing various paleoclimate archives, and to take these factors into account in their analyses. "As such, we can compare the sediment samples with the ice cores for various epochs in the planet's history," says Laepple.

Detail of an Antarctic ice core from 2668 meters depth [Credit: Sepp Kipfstuhl]

The more intensive variations during glacial periods are due to the greater difference in temperature between the ice-covered polar regions and the Tropics, which produced a more dynamic exchange of warm and cold air masses. "If we then follow that idea to its logical conclusion, it tells us the variations will continue to lessen as global warming progresses," says Rehfeld -- simply because the difference in temperature between the warming North and the Tropics will decline. "However, our data covers timeframes spanning centuries and millennia -- we can't zoom in on just a handful of years, which means we can only draw indirect conclusions regarding the extreme events that shape weather," explains climate researcher Rehfeld, who is currently pursuing research with the British Antarctic Survey (BAS).

Climate modellers had previously postulated the mechanism of reduced variability under warmer climatic conditions in 2014. Yet with their analysis, Rehfeld, Laepple and colleagues are the first to reinforce this theory with global climate data from the past. The AWI researchers describe their next endeavour as follows: "We plan to investigate in detail the changes in short-term variations in the past and their relation to long-term climate changes. To do so, we need reliable climate archives, and to improve our understanding of how they work." Increasing the accuracy to a level at which paleo-archives can also reflect extreme events will likely be one of the greatest challenges for the years to come.

Source: Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research [February 05, 2018]

Greenland's ice sheet is becoming smaller and smaller. The melting takes place with increased strength and at a speed that no models have previously predicted.

Several glaciers flow into the area of Young Sound where researchers have shown that heat from the Earth's interior warms up the bottom water of the fjord [Credit: Mikael Sejr]

Today, in the journal Scientific Reports, researchers from the Arctic Research Centre, Aarhus University, and the Greenland Institute of Natural Resources present results that, for the first time, show that the deep bottom water of the north-eastern Greenland fjords is being warmed up by heat gradually lost from the Earth's interior. And the researchers point out that this heat loss triggers the sliding of glaciers from the ice sheet towards the sea.

Icelandic conditions

"North-East Greenland has several hot springs where the water becomes up to 60 degrees warm and, like Iceland, the area has abundant underground geothermal activity," explains Professor Soren Rysgaard, who headed the investigations.

Although it may be biting cold over the water, heat from the Earth's interior is transported to the bottom water of Young Sound, North-East Greenland [Credit: Wieter Boone]

For more than ten years, the researchers have measured the temperature and salinity in the fjord Young Sound, located at Daneborg, north of Scoresbysund, which has many hot springs, and south of the glacier Nioghalvfjerdsfjorden, which melts rapidly and is connected to the North-East Greenland Ice Stream (NEGIS).

By focusing on an isolated basin in the fjord with a depth range between 200 and 340 m, the researchers have measured how the deep water is heated over a ten-year period. Based on the extensive data, researchers have estimated that the loss of heat from the Earth's interior to the fjord is about 100 MW m-2. This corresponds to a 2 megawatt wind turbine sending electricity to a large heater at the bottom of the fjord all year round.

Heat from the Earth's interior - an important influence

It is not easy to measure the geothermal heat flux -- heat emanating from the Earth's interior -- below a glacier, but within the area there are several large glaciers connected directly to the ice sheet. If the Earth releases heat to a fjord, heat also seeps up to the bottom part of the glaciers. This means that the glaciers melt from below and thus slide more easily over the terrain on which they sit when moving to the sea.

Sampling in Young Sound in spring where the sea ice still lies as a solid lid on the fjord [Credit: Soren Rysgaard]

"It is a combination of higher temperatures in the air and the sea, precipitation from above, local dynamics of the ice sheet and heat loss from the Earth's interior that determines the mass loss from the Greenland ice sheet," explains Soren Rysgaard.

"There is no doubt that the heat from the Earth's interior affects the movement of the ice, and we expect that a similar heat seepage takes place below a major part of the ice cap in the north-eastern corner of Greenland," says Soren Rysgaard.

The researchers expect that the new discoveries will improve the models of ice sheet dynamics, allowing better predictions of the stability of the Greenland ice sheet, its melting and the resulting global water rise.

Source: Aarhus University [Janaury 22, 2018]

The discovery of the 3.7 billion-year-old fossil pushes back earliest life on Earth by 220 million years, raising chances that Mars once had life, when both planets were similar.

Alister Doyle Rueters 8-30-16

OSLO, Aug 31 - The earliest fossil evidence of life on Earth has been found in rocks 3.7 billion years old in Greenland, raising chances of life on Mars aeons ago when both planets were similarly desolate, scientists said on Wednesday....

“This indicates the Earth was no longer some sort of hell 3.7 billion years ago,” lead author Allen Nutman, of the University of Wollongong, told Reuters of the findings that were published in the journal Nature.

“It was a place where life could flourish.” ...
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