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Current rates of climate change could trigger instability in a major Antarctic glacier, ultimately leading to more than 2m of sea-level rise.

This is the conclusion of a new study looking at the future of Totten Glacier, a significant glacier in Antarctica. Totten Glacier drains one of the world's largest areas of ice, on the East Antarctic Ice Sheet (EAIS).

By studying the history of Totten's advances and retreats, researchers have discovered that if climate change continues unabated, the glacier could cross a critical threshold within the next century, entering an irreversible period of very rapid retreat.

This would cause it to withdraw up to 300 kilometres inland in the following centuries and release vast quantities of water, contributing up to 2.9 metres to global sea-level rise.

The EAIS is currently thought to be relatively stable in the face of global warming compared with the much smaller ice sheet in West Antarctica, but Totten Glacier is bucking the trend by losing substantial amounts of ice. The new research reveals that Totten Glacier may be even more vulnerable than previously thought.

The study, by scientists from Imperial College London and institutions in Australia, the US, and New Zealand is >published in Nature. Last year, the team discovered that there is currently warm water circulating underneath a floating portion of the glacier that is causing more melting than might have been expected.

Their new research looks at the underlying geology of the glacier and reveals that if it retreats another 100-150 km, its front will be sitting on an unstable bed and this could trigger a period of rapid retreat for the glacier. This would cause it to withdraw nearly 300 km inland from its current front at the coast.

Retreating the full 300 km inland may take several hundred years, according to co-author Professor Martin Siegert, Co-Director of the Grantham Institute at Imperial College London. However, once the glacier crosses the threshold into the unstable region, the melting will be unstoppable -- at least until it has retreated to the point where the geology becomes more stable again.

"The evidence coming together is painting a picture of East Antarctica being much more vulnerable to a warming environment than we thought," he said. "This is something we should worry about. Totten Glacier is losing ice now, and the warm ocean water that is causing this loss has the potential to also push the glacier back to an unstable place."

"Totten Glacier is only one outlet for the ice of the East Antarctic Ice Sheet, but it could have a huge impact. The East Antarctic Ice Sheet is by far the largest mass of ice on Earth, so any small changes have a big influence globally."

To uncover the history of Totten Glacier's movements, the team looked at the sedimentary rocks below the glacier using airborne geophysical surveys. From the geological record, influenced by the erosion by ice above, they were able to understand the history of the glacier stretching back millions of years.

They found that the glacier has retreated more quickly over certain 'unstable' regions in the past. Based on this evidence, the scientists believe that when the glacier hits these regions again we will see the same pattern of rapid retreat.

Author: Hayley Dunning. | Source: Imperial College London [May 18, 2016]

Trekking across the high Canadian Arctic almost 20 years ago, Howie Scher had an unexpected encounter that helped fix the course of his career.

An undergraduate on a research expedition over summer break, Scher was part of a scientific group traveling deep into the Arctic Circle to collect basalt cores for paleomagnetic analysis. But as focused as the team was on finding rocks with magnetic minerals that can help establish where on Earth they had formed, it was stony deposits that had once been very much alive that really caught the team's collective eye.

"We stumbled across a fossil bone bed there," Scher says. "We were pulling out vertebrate fossils--crocodilians, turtles, bony fish--and when we got home we showed them to a paleontologist who told us it was a warm water assemblage. That was a great experience as a freshman in college, and it got me very interested in climate--just seeing how it had been so different in the past than what my experience was near the North Pole, trudging through the snow."

Now an associate professor at the University of South Carolina, Scher has made a career of climate science. He is part of an international team that recently published a report pinpointing the genesis of one of the cornerstones of the Earth's current climate system, the Antarctic Circumpolar Current.

A constant eastward flow of ocean water in the Southern Ocean encircling Antarctica, the Antarctic Circumpolar Current is akin to the Gulf Stream, the current that moves water through the Atlantic Ocean from the tip of Florida, along the east coast of North America, and, by extension into the North Atlantic Current, to the shores of western and northern Europe. The Gulf Stream's transport of warm southern waters northward is why many European countries have more temperate climates than would be expected purely from their latitudes (relatively mild London, for example, lies more than 500 miles further north than Toronto).

But if the Atlantic Circumpolar Current is something like the Gulf Stream, there's a notable difference: it's even bigger.

"It's the largest ocean current today, and it's the only one that connects all the ocean basins," Scher says. "The Atlantic, Pacific and the Indian are huge oceans, but they're all bounded by continents; they have firm boundaries. The Southern Ocean, around Antarctica, is the only band of latitude where there's an ocean that goes continuously around the globe. Because of that, the winds that blow over the Southern Ocean are unimpeded by continental barriers.

"So the distance that the wind can blow over the ocean, which as oceanographers we call the 'fetch,' is infinite. And fetch is one of the things that determines how high the waves are, how much mixing goes on in the oceans, and ultimately what drives surface ocean currents. With infinite fetch, you can have a very strong ocean current, and because this particular band of ocean connects all of the world's oceans, it transports heat and salt and nutrients all around the world."

In a paper recently published in the journal Nature, Scher and his team make the case for just when this massive ocean current first started flowing. One straightforward obstacle in the distant past was the arrangement of continental masses. Antarctica and Australia were part of a single super-continent, Gondwana, and began to separate about 83 million years ago, so the Pacific and Indian Oceans couldn't have been in contact near the South Pole before then.

It was much later than the initial separation of Australia and Antarctica that deep ocean currents could flow between the two continents, though. Paleoceanographers have identified a transition, the opening of the Tasmanian gateway, a deep-water channel between Tasmania and Antarctica, as being a necessary part of any large-scale, sustained flow on the order of the Antarctic Circumpolar Current.

Using novel information about the separation of Antarctica and Australia, Scher and his team developed a tectonic model that showed that the Tasmanian gateway first developed at least 500 meters of depth some time between 35 and 32 million years ago.

From geochemical analyses of sediment core, however, they concluded that the channel opening to that depth wasn't enough to get the Antarctic Circumpolar Current flowing. The Pacific Ocean is in contact with much younger rock than the Indian Ocean, Scher says, which leads to a distinguishing concentration in each ocean of one isotope of neodymium that has a half-life longer than that of the solar system.

By measuring neodymium isotope compositions incorporated into fish teeth fossils in core samples, the team was able to establish that eastward current flow between the Pacific and Indian Oceans didn't begin until about 30 million years ago, some 2 to 5 million years after the Tasmanian gateway opened.

Taking both geophysical and geochemical data into account, they conclude that although the Tasmanian gateway was wide enough to accommodate a deep current, the gateway was located too far south to be in contact with the mid-latitude trade winds, which are the driving force for today's eastward-flowing Antarctic Circumpolar Current.

Instead, when the gateway first opened, water initially flowed westward, the opposite of that today, in keeping with the prevailing polar winds located at the more southern latitudes.

Only as both continents, and the gateway between the two, drifted northward on their tectonic plates over the next several million years did alignment with the trade winds come about. That reversed the current flow, to the east, and the Antarctic Circumpolar Current was born.

"It's the global mix-master of the oceans--that's a quote from Wally Broecker [of Columbia University's Lamont-Doherty Earth Observatory], and that's what it's been called by oceanographers for 50 years now," Scher says. "The Antarctic Circumpolar Current is the world's largest current today, it influences heat exchange and carbon exchange, and we really didn't know for how long it's been operating, which I call a major gap in our command of Earth history. It was a cool outcome."

Author: Steven Powell  | Source: University of South Carolina [August 25, 2015]

The world's largest canyon may lie under the Antarctic ice sheet, according to analysis of satellite data by a team of scientists, led by Durham University.

Although the discovery needs to be confirmed by direct measurements, the previously unknown canyon system is thought to be over 1,000km long and in places as much as 1km deep, comparable in depth to the Grand Canyon in USA, but many times longer.

The canyon system is made up of a chain of winding and linear features buried under several kilometres of ice in one of the last unexplored regions of the Earth's land surface: Princess Elizabeth Land (PEL) in East Antarctica. Very few measurements of the ice thickness have been carried out in this particular area of the Antarctic, which has led to scientists dubbing it one of Antarctica's two 'Poles of Ignorance'.

The researchers believe that the landscape beneath the ice sheet has probably been carved out by water and is either so ancient that it was there before the ice sheet grew or it was created by water flowing and eroding beneath the ice.

Although not visible to the naked eye, the subglacial landscape can be identified in the surface of the ice sheet.

Faint traces of the canyons were observed using satellite imagery and small sections of the canyons were then found using radio-echo sounding data, whereby radio waves are sent through the ice to map the shape of the rock beneath it. These are very large features which appear to reach from the interior of Princess Elizabeth Land to the coast around the Vestfold Hills and the West Ice Shelf.

The canyons may be connected to a previously undiscovered subglacial lake as the ice surface above the lake shares characteristics with those of large subglacial lakes previously identified. The data suggests the area of the lake could cover up to 1250km², more than 80 times as big as Lake Windermere in the English Lake District.

An airborne survey taking targeted radio-echo sounding measurements over the whole buried landscape is now underway with the aim of unambiguously confirming the existence and size of the canyon and lake system, with results due later in 2016.

Lead researcher, Dr Stewart Jamieson, from the Department of Geography at Durham University in the UK, said: "Our analysis provides the first evidence that a huge canyon and a possible lake are present beneath the ice in Princess Elizabeth Land. It's astonishing to think that such large features could have avoided detection for so long.

"This is a region of the Earth that is bigger than the UK and yet we still know little about what lies beneath the ice. In fact, the bed of Antarctica is less well known than the surface of Mars. If we can gain better knowledge of the buried landscape we will be better equipped to understand how the ice sheet responds to changes in climate."

Co-Author Dr Neil Ross from Newcastle University in the UK, said: "Antarctic scientists have long recognised that because the way ice flows, the landscape beneath the ice sheet was subtly reflected in the topography of the ice sheet surface. Despite this, these vast deep canyons and potential large lake had been overlooked entirely.

"Our identification of this landscape has only been possible through the recent acquisition, compilation and open availability of satellite data by many different organisations (e.g. NASA, ESA and the US National Snow and Ice Data Center), to whom we are very grateful, and because of some serendipitous reconnaissance radio-echo sounding data acquired over the canyons by the ICECAP project during past Antarctic field seasons."

Co-Author Professor Martin Siegert, from the Grantham Institute at Imperial College London, UK, said: "Discovering a gigantic new chasm that dwarfs the Grand Canyon is a tantalising prospect. Geoscientists on Antarctica are carrying out experiments to confirm what we think we are seeing from the initial data, and we hope to announce our findings at a meeting of the ICECAP2 collaboration, at Imperial, later in 2016.

"Our international collaboration of US, UK, Indian, Australian and Chinese scientists are pushing back the frontiers of discovery on Antarctica like nowhere else on earth. But the stability of this understudied continent is threatened by global warming, so all the countries of the world now must rapidly reduce their greenhouse gas emissions and limit the damaging effects of climate change."

>The research is >published in >Geology>.

Source: Durham University [January 13, 2016]

Planetary scientists have discovered pieces of opal in a meteorite found in Antarctica, a result that demonstrates that meteorites delivered water ice to asteroids early in the history of the solar system. Led by Professor Hilary Downes of Birkbeck College London, the team announce their results at the National Astronomy Meeting in Nottingham on Monday 27 June.

Opal, familiar on Earth as a precious stone used in jewellery, is made up of silica (the major component of sand) with up to 30% water in its structure, and has not yet been identified on the surface of any asteroid. Before the new work, opal had only once been found in a meteorite, as a handful of tiny crystals in a meteorite from Mars.

Downes and her team studied the meteorite, named EET 83309, an object made up of thousands and broken pieces of rock and minerals, meaning that it originally came from the broken up surface, or regolith, of an asteroid. Results from other teams show that while the meteorite was still part of the asteroid, it was exposed to radiation from the Sun, the so-called solar wind, and from other cosmic sources. Asteroids lack the protection of an atmosphere, so radiation hits their surfaces all the time.

EET 83309 has fragments of many other kinds of meteorite embedded in it, showing that there were many impacts on the surface of the parent asteroid, bringing pieces of rock from elsewhere in the solar system. Downes believes one of these impacts brought water ice to the surface of the asteroid, allowing the opal to form.

She comments: "The pieces of opal we have found are either broken fragments or they are replacing other minerals. Our evidence shows that the opal formed before the meteorite was blasted off from the surface of the parent asteroid and sent into space, eventually to land on Earth in Antarctica."

"This is more evidence that meteorites and asteroids can carry large amounts of water ice. Although we rightly worry about the consequences of the impact of large asteroid, billions of years ago they may have brought the water to the Earth and helped it become the world teeming with life that we live in today."

The team used different techniques to analyse the opal and check its composition. They see convincing evidence that it is extra-terrestrial in origin, and did not form while the meteorite was sitting in the Antarctic ice. For example, using the NanoSims instrument at the Open University, they can see that although the opal has interacted to some extent with water in the Antarctic, the isotopes (different forms of the same element) match the other minerals in the original meteorite.

Source: Royal Astronomical Society [June 28, 2016]

The human-dominated geological epoch known as the Anthropocene probably began around the year 1610, with an unusual drop in atmospheric carbon dioxide and the irreversible exchange of species between the New and Old Worlds, according to new research published today in Nature.

Previous epochs began and ended due to factors including meteorite strikes, sustained volcanic eruptions and the shifting of the continents. Human actions are now changing the planet, but are we really a geological force of nature driving Earth into a new epoch that will last millions of years?

Scientists at UCL have concluded that humans have become a geological power and suggest that human actions have produced a new geological epoch.

Defining an epoch requires two main criteria to be met. Long-lasting changes to the Earth must be documented. Scientists must also pinpoint and date a global environmental change that has been captured in natural material, such as rocks, ancient ice or sediment from the ocean floor. Such a marker -- like the chemical signature left by the meteorite strike that wiped out the dinosaurs -- is called a golden spike.

The study authors systematically compared the major environmental impacts of human activity over the past 50,000 years against these two formal requirements. Just two dates met the criteria: 1610, when the collision of the New and Old Worlds a century earlier was first felt globally; and 1964, associated with the fallout from nuclear weapons tests. The researchers conclude that 1610 is the stronger candidate.

The scientists say the 1492 arrival of Europeans in the Americas, and subsequent global trade, moved species to new continents and oceans, resulting in a global re-ordering of life on Earth. This rapid, repeated, cross-ocean exchange of species is without precedent in Earth's history.

They argue that the joining of the two hemispheres is an unambiguous event after which the impacts of human activity became global and set Earth on a new trajectory. The first fossil pollen of maize, a Latin American species, appears in marine sediment in Europe in 1600, becoming common over subsequent centuries. This irreversible exchange of species satisfies the first criteria for dating an epoch -- long-term changes to Earth.

The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right -- as Earth-changing as a meteorite strike

The researchers also found a golden spike that can be dated to the same time: a pronounced dip in atmospheric carbon dioxide centred on 1610 and captured in Antarctic ice-core records. The drop occurred as a direct result of the arrival of Europeans in the Americas. Colonisation of the New World led to the deaths of about 50 million indigenous people, most within a few decades of the 16th century due to smallpox. The abrupt near-cessation of farming across the continent and the subsequent re-growth of Latin American forests and other vegetation removed enough carbon dioxide from the atmosphere to produce a drop in CO2. Thus, the second requirement of a golden spike marker is met.

The researchers have named the 1610 dip in carbon dioxide the 'Orbis Spike'. They chose the Latin word for 'world' because this golden spike was caused by once-disconnected peoples becoming globally linked.

Lead author, Dr Simon Lewis (UCL Geography and University of Leeds), said: "In a hundred thousand years scientists will look at the environmental record and know something remarkable happened in the second half of the second millennium. They will be in no doubt that these global changes to Earth were caused by their own species. Today we can say when those changes began and why. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right -- as Earth-changing as a meteorite strike."

He added: "Historically, the collision of the Old and New Worlds marks the beginning of the modern world. Many historians regard agricultural imports into Europe from the vast new lands of the Americas, alongside the availability of coal, as the two essential precursors of the Industrial Revolution, which in turn unleashed further waves of global environmental changes. Geologically, this boundary also marks Earth's last globally synchronous cool moment before the onset of the long-term global warmth of the Anthropocene."

The authors also considered the merits of dating the Anthropocene to 1964, which saw a peak in radioactive fallout following nuclear weapons testing. This marker is seen in many geological deposits, and by the 1960s human impact on the Earth was large. However, the researchers note that while nuclear war could dramatically alter Earth, so far it has not. While the fallout from nuclear bomb tests is a very good marker, the testing of nuclear weapons has not been -- in geological terms -- an Earth-changing event.

The beginning of the Industrial Revolution, in the late 18th century, has most commonly been suggested as the start of the Anthropocene. This linked a clear turning point in human history, and the rise of atmospheric carbon dioxide from fossil fuel use is a long-term global environmental change of critical importance. However, the researchers did not find a golden spike at that time because most effects were local, while the global exponential rise in carbon dioxide was too smooth an increase to form a precisely dated marker.

The authors' new paper ends by highlighting some implications of formally defining the Anthropocene.

Co-author, geologist Professor Mark Maslin (UCL Geography) said: "A more wide-spread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth will have implications for our philosophical, social, economic and political views of our environment. But we should not despair, because the power that humans wield is unlike any other force of nature, it is reflexive and therefore can be used, withdrawn or modified. The first stage of solving our damaging relationship with our environment is recognising it."

An official decision on whether to formally recognise the Anthropocene, including when it began, will be initiated by a recommendation of the Anthropocene Working Group of the Subcommission of Quaternary Stratigraphy, due in 2016.

Source: University College London [March 11, 2015]

The arrival of intense cold similar to the one raged during the “Little Ice Age”, which froze the world during the XVII century and in the beginning of the XVIII century, is expected in the years 2030–2040.

These conclusions were presented by Prof. V. Zharkova (Northumbria University) during the National Astronomy Meeting in Llandudno in Wales by the international group of scientists, which also includes Dr Helen Popova of the Skobeltsyn Institute of Nuclear Physics and of the Faculty of Physics of the Lomonosov Moscow State University, professor Simon Shepherd of Bradford University (UK) and Dr Sergei Zharkov of Hull University (UK).

It is known, that the Sun has its own magnetic field, the amplitude and spatial configuration of which vary with time. The formation and decay of strong magnetic fields in the solar atmosphere results in the changes of electromagnetic radiation from the Sun, of the intensity of plasma flows coming from the Sun, and the number of sunspots on the Sun’s surface. The study of changes in the number of sunspots on the Sun’s surface has a cyclic structure vary in every 11 years that is also imposed on the Earth environment as the analysis of carbon-14, beryllium-10 and other isotopes in glaciers and in the trees showed.

There are several cycles with different periods and properties, while the 11-year cycle, the 90-year cycle are the best known of them. The 11-year cycle appears as a cyclical reduction in stains on the surface of the Sun every 11 years. Its 90-year variation is associated with periodic reduction in the number of spots in the 11-year cycle in the 50-25%. In 17th century though there was a prolonged of the solar activity called the Maunder minimum, which lasted roughly from 1645 to 1700. During this period, there were only about 50 sunspots instead of the usual 40-50 thousand sunspots. Analysis of solar radiation showed that its maxima and minima almost coincide with the maxima and minima in the number of spots.

In the current study published in 3 peer-reviewed papers the researchers analyzed a total background magnetic field from full disk magnetograms for three cycles of solar activity (21-23) by applying the so-called “principal component analysis”, which allows to reduce the data dimensionality and noise and to identify waves with the largest contribution to the observational data. This method can be compared with the decomposition of white light on the rainbow prism detecting the waves of different frequencies. As a result, the researchers developed a new method of analysis, which helped to uncover, that the magnetic waves in the Sun are generated in pairs, with the main pair covering 40% of variance of the data (Zharkova et al, 2012, MNRAS). The principal component pair is responsible for the variations of a dipole field of the Sun, which is changing its polarity from pole to pole during 11 year solar activity.

The magnetic waves travel from the opposite hemisphere to the Northern hemisphere (odd cycles) or to Southern hemisphere (even cycles), with the phase shift between the waves increasing with a cycle number. The waves interacts with each other in the hemisphere where they have maximum (Northern for odd cycles and Southern for even ones). These two components are assumed to originate in two different layers in the solar interior (inner and outer) with close, but not equal, frequencies and a variable phase shift (Popova et al, 2013, AnnGeo).

The scientists managed to derive the analytical formula, describing the evolution of these two waves and calculated the summary curve which was linked to the variations of sunspot numbers, the original proxy of solar activity, if one used the modulus of the summary curve (Shepherd et al, 2014, ApJ). By using this formula the scientists made first the prediction of magnetic activity in the cycle 24, which gave 97% accuracy in comparison with the principal components derived from the observations.

Inspired by this success, the authors extended the prediction of these two magnetic waves to the next two cycle 25 and 26 and discovered that the waves become fully separated into the opposite hemispheres in cycle 26 and thus have little chance of interacting and producing sunspot numbers. This will lead to a sharp decline in solar activity in years 2030 – 2040 comparable with the conditions existed previously during the Maunder minimum in the XVII century when there were only about 50-70 sunspots observed instead of the usual 40-50 thousand expected.

The new reduction of the solar activity will lead to reduction of the solar irradiance by 3W/m^2 according to Lean (1997). This resulted in significant cooling of Earth and very severe winters and cold summers. “Several studies have shown that the Maunder Minimum coincided with the coldest phase of global cooling, which was called “the Little Ice Age”. During this period there were very cold winters in Europe and North America. In the days of the Maunder minimum the water in the river Thames and the Danube River froze, the Moscow River was covered by ice every six months, snow lay on some plains year round and Greenland was covered by glaciers” – says Dr Helen Popova, who developed a unique physical-mathematical model of the evolution of the magnetic activity of the sun and used it to gain the patterns of occurrence of global minima of solar activity and gave them a physical interpretation.

If the similar reduction will be observed during the upcoming Maunder minimum this can lead to the similar cooling of the Earth atmosphere. According to Dr Helen Popova, if the existing theories about the impact of solar activity on the climate are true, then this minimum will lead to a significant cooling, similar to the one occurred during the Maunder minimum.

However, only the time will show soon enough (within the next 5-15 years) if this will happen.

“Given that our future minimum will last for at least three solar cycles, which is about 30 years, it is possible, that the lowering of the temperature will not be as deep as during the Maunder minimum. But we will have to examine it in detail. We keep in touch with climatologists from different countries. We plan to work in this direction”, — Dr Helen Popova said.

The notion that solar activity affects the climate, appeared long ago. It is known, for example, that a change in the total quantity of the electromagnetic radiation by only 1% can result in a noticeable change in the temperature distribution and air flow all over the Earth. Ultraviolet rays cause photochemical effect, which leads to the formation of ozone at the altitude of 30-40 km. The flow of ultraviolet rays increases sharply during chromospheric flares in the Sun. Ozone, which absorbs the sun’s rays well enough, is being heated and it affects the air currents in the lower layers of the atmosphere and, consequently, the weather. Powerful emission of corpuscles, which can reach the Earth’s surface, arise periodically during the high solar activity. They can move in complex trajectories, causing aurorae, geomagnetic storms and disturbances of radio communication.

By increasing the flow of particles in the lower atmospheric layers air flows of meridional direction enhance: warm currents from the south with even greater energy rush in the high latitudes and cold currents, carrying arctic air, penetrate deeper into the south. In addition, the solar activity affects the intensity of fluxes of galactic cosmic rays. The minimum activity streams become more intense, which also affects the chemical processes in the Earth’s atmosphere

The study of deuterium in the Antarctic showed that there were five global warmings and four Ice Ages for the past 400 thousand years. The increase in the volcanic activity comes after the Ice Age and it leads to the greenhouse gas emissions. The magnetic field of the Sun grows, what means that the flux of cosmic rays decreases, increasing the number of clouds and leading to the warming again. Next comes the reverse process, where the magnetic field of the Sun decreases, the intensity of cosmic ray rises, reducing the clouds and making the atmosphere cool again. This process comes with some delay.

Dr Helen Popova responds cautiously, while speaking about the human influence on climate.

“There is no strong evidence, that global warming is caused by human activity. The study of deuterium in the Antarctic showed that there were five global warmings and four Ice Ages for the past 400 thousand years. People first appeared on the Earth about 60 thousand years ago. However, even if human activities influence the climate, we can say, that the Sun with the new minimum gives humanity more time or a second chance to reduce their industrial emissions and to prepare, when the Sun will return to normal activity”, — Dr Helen Popova summarized.

Source: Lomonosov Moscow State University [July 17, 2015]