The Great London [Search results for Greenland] 

The ice sheet covering Greenland is four times bigger than California -- and holds enough water to raise global sea-level more than twenty feet if most of it were to melt. Today, sea levels are rising and the melting of Greenland is a major contributor. Understanding how fast this melting might proceed is a pressing question for policymakers and coastal communities.

To make predictions about the future of the ice sheet, scientists have tried to understand its past, hoping to glean what the ice was doing millions of years ago when the Earth was three or more degrees Fahrenheit warmer than it is now. But our understanding of the ice sheet's complex behavior before about 125,000 years ago has been fragmentary at best.

Now, two first-of-their-kind studies provide new insight into the deep history of the Greenland Ice Sheet, looking back millions of years farther than previous techniques allowed. However, the two studies present some strongly contrasting evidence about how Greenland's ice sheet may have responded to past climate change -- bringing new urgency to the need to understand if and how the giant ice sheet might dramatically accelerate its melt-off in the near future.

The two new studies were published in the journal Nature, including one led by University of Vermont geologist Paul Bierman.

Ice On the East

In >the first study Bierman and four colleagues -- from UVM, Boston College, Lawrence Livermore Laboratory, and Imperial College London -- examined deep cores of ocean-bottom mud containing bits of bedrock that eroded off of the east side of Greenland. Their results show that East Greenland has been actively scoured by glacial ice for much of the last 7.5 million years -- and indicate that the ice sheet on this eastern flank of the island has not completely melted for long, if at all, in the past several million years. This result is consistent with existing computer models.

Their field-based data also suggest that during major climate cool-downs in the past several million years, the ice sheet expanded into previously ice-free areas, "showing that the ice sheet in East Greenland responds to and tracks global climate change," Bierman says. "The melting we are seeing today may be out of the bounds of how the Greenland ice sheet has behaved for many millions of years."

Since the data the team collected only came from samples off the east side of Greenland, their results don't provide a definitive picture of the whole Greenland ice sheet. But their research, with support from the National Science Foundation, provides strong evidence that "an ice sheet has been in East Greenland pretty much continuously for seven million years," says Jeremy Shakun, a geologist at Boston College who co-led the new study. "It's been bouncing around and dynamic -- but it's been there nearly all the time."

Contrasting Results

The >other study in Nature -- led by Joerg Schaefer of Lamont-Doherty Earth Observatory and Columbia University, and colleagues -- looked at a small sample of bedrock from one location beneath the middle of the existing ice sheet and came to what appears to be a different conclusion: Greenland was nearly ice-free for at least 280,000 years during the middle Pleistocene -- about 1.1 million years ago. This possibility is in contrast to existing computer models.

"These results appear to be contradictory -- but they may not be," UVM's Bierman says. He notes that both studies have "some blurriness," he says, in what they are able to resolve about short-term changes and the size of the ancient ice sheet. "Their study is a bit like one needle in a haystack," he says, "and ours is like having the whole haystack, but not being sure how big it is."

That's because Schaefer and colleagues' data comes from a single point in the middle of Greenland, pointing to a range of possible scenarios of what happened in the past, including several that challenge the image of Greenland being continuously covered by an extensive ice sheet during the Pleistocene. In contrast, Bierman and colleagues' data provides a record of continuous ice sheet activity over eastern Greenland but can't distinguish whether this was because there was a remnant in East Greenland or whether the ice sheet remained over the whole island, fluctuating in size as the climate warmed and cooled over millions of years.

"It's quite possible that both of these records are right for different places," Bierman says. "Both of these studies apply a similar innovative technique and let us look much farther into the past than we have been able to before."

New Method

Both teams of scientists used, "a powerful new tool for Earth scientists," says Dylan Rood, a scientist at Imperial College London and a co-author on the Bierman-led study: isotopes within grains of quartz, produced when bedrock is bombarded by cosmic rays from space. The isotopes come into being when rock is at or near Earth's surface -- but not when it's buried under an overlying ice sheet. By looking at the ratio of two of these cosmic-ray-made elements -- aluminum-26 and beryllium-10 caught in crystals of quartz, and measured in an accelerator mass spectrometer -- the scientists were able to calculate how long the rocks in their samples had been exposed to the sky versus covered by ice.

>Paul Bierman, a geologist at the University of Vermont and his colleagues --f rom UVM, Boston College, 
>Lawrence Livermore Laboratory, and Imperial College London--wanted to develop a better understanding 
>of the ancient history of the huge ice sheet that covers Greenland, like this portion of the ice sheet shown from 
>a helicopter on a Bierman-led expedition there. The team studied deep cores of ocean-bottom mud containing 
>bits of bedrock that eroded off of the east side of Greenland. Their results show that East Greenland has been 
>actively scoured by glacial ice for much of the last 7.5 million years--and indicate that the ice sheet on the 
>eastern flank of the island has not completely melted for long, if at all, in the past several million years. Their 
>field-based data also suggest that during major climate cool-downs in the past several million years, the ice sheet 
>expanded into previously ice-free areas, "showing that the ice sheet in East Greenland responds to and tracks
> global climate change," Bierman says. "The melting we are seeing today may be out of the bounds of how 
>the Greenland ice sheet has behaved for many millions of years." [Credit: Joshua Brown/UVM]
This isotope technique has been used for several decades for measuring land-based erosion, but this is its first application to ocean core samples, said Lee Corbett, a postdoctoral researcher at UVM and co-author with Bierman. "This has never been attempted with marine sediments," she says. Their results overcome a basic problem of trying to discern the deep history of ice from bedrock: every time an ice sheet retreats and then grows back, it scours away the bedrock and the isotope record of its own past. "It's hard to discern an ice sheet's cycles on land because it destroys the evidence," she says, "but it dumps that evidence in the oceans, archived in layers on the bottom."

Now Corbett, Shakun, and others are applying this isotope technique to additional cores taken from around the coast of Greenland to get a more complete and in-focus picture of the whole ice sheet's long history. And they have already applied the new isotope technique far beyond Greenland -- particularly in exploring the much larger, more mysterious ice sheets covering Antarctica.

"These two apparently conflicting -- but not necessarily conflicting -- studies in Nature really force the issue that we don't know enough about how ice sheets work over deep time," Bierman says. "We must recognize the importance of advancing polar science to understand how our world works. And, right now, because we're pumping huge plumes of greenhouse gases into the atmosphere, we really need to know how our world works."

The dynamics of Antarctica's giant ice sheet is full of questions and the disastrous potential. "But there's enough sea-level rise tied-up in Greenland alone to put a lot of cities and long stretches of coastline underwater," says Paul Bierman, "including Donald Trump's property in Florida."

Source: University of Vermont [December 07, 2016]

An ancient basin hidden beneath the Greenland ice sheet, discovered by researchers at the University of Bristol, may help explain the location, size and velocity of Jakobshavn Isbræ, Greenland's fastest flowing outlet glacier.

The research also provides an insight into what past river drainage looked like in Greenland, and what it could look like in the future as the ice sheet retreats.

Michael Cooper and colleagues from Bristol's School of Geographical Sciences and Cabot Institute, and Imperial College London, studied the bedrock in Greenland using data collected mainly by NASA (through Operation Ice Bridge), as well as various researchers from the UK and Germany, over several decades. This data is collected by aircraft using ice penetrating radar, which bounces back off the bedrock underneath the ice (as ice is mostly transparent to radio waves at certain frequencies).

Mr Cooper said: "The drainage basin we discovered shows signs of being carved by ancient rivers, prior to the extensive glaciation of Greenland (i.e. before the Greenland Ice Sheet existed), rather than being carved by the movement of ice itself. It has been remarkably well preserved – and has not been eroded away by successive glaciations. The channel network has never been seen before by humans – it was last uncovered around 3.8 million years ago."

The size of the drainage basin the team discovered is very large, at around 450,000 km2, and accounts for about 20 per cent of the total land area of Greenland (including islands).

This is comparable to the size of the Ohio River drainage basin, which is the largest tributary of the Mississippi. The channels the team mapped could more appropriately be called 'canyons', with relative depths of around 1,400 metres in places, and nearly 12km wide, all hidden underneath the ice.

As well as being an interesting discovery of great size, the channel network and basin was instrumental in influencing the flow of ice from the deep interior to the margin, both now and over several glacial cycles, as well as influencing the location and speed of the Jakobshavn ice stream.

The study is published in >Geophysical Research Letters.

Source: University of Bristol [June 14, 2016]

The traditional diet of Greenland natives — the Inuit — is held up as an example of how high levels of omega-3 fatty acids can counterbalance the bad health effects of a high-fat diet, but a new study hints that what’s true for the Inuit may not be true for everyone else.

The study, which appears in the Sept. 18 issue of the journal Science, shows that the Inuit and their Siberian ancestors have special mutations in genes involved in fat metabolism. The mutations help them partly counteract the effects of a diet high in marine mammal fat, mostly from seals and whales that eat fish with high levels of omega-3 polyunsaturated fatty acids.

Those genetic mutations, found in nearly 100 percent of the Inuit, are found in a mere 2 percent of Europeans and 15 percent of Han Chinese, which means that these groups would synthesize omega-3 polyunsaturated fatty acids differently from the Inuit.

“The original focus on fish oil and omega-3s came from studies of Inuit. On their traditional diet, rich in fat from marine mammals, Inuit seemed quite healthy with a low incidence of cardiovascular disease, so fish oil must be protective,” said project leader Rasmus Nielsen, a UC Berkeley professor of integrative biology. “We’ve now found that they have unique genetic adaptations to this diet, so you cannot extrapolate from them to other populations. A diet that is healthy for the Inuit may not necessarily be good for the rest of us.”

These genetic mutations in the Inuit have more widespread effects. They lower “bad” LDL cholesterol and fasting insulin levels, presumably protecting against cardiovascular disease and diabetes. They also have a significant effect on height, because growth is in part regulated by a person’s fatty acid profile. The researchers found that the mutations causing shorter height in the Inuit are also associated with shorter height in Europeans.

“The mutations we found in the Inuit have profound physiological effects, changing the whole profile of fatty acids in the body, plus it reduces their height by 2 centimeters: nearly an inch,” said Ida Moltke, a University of Copenhagen associate professor of bioinformatics who is joint first author on the study. “Height is controlled by many genes, but this mutation has one of the strongest effects on height ever found by geneticists.”

Personalized diets

Nielsen noted that this is some of the clearest evidence to date that human populations are actually adapted to particular diets; that is, they differ in the way they physiologically respond to diets. Just as genome sequencing can lead to personalized medicine tailored to an individual’s specific set of genes, so too may a person’s genome dictate a personalized diet.

“People ask themselves whether they should be on a Stone Age diet, for example. The response may well depend on their genome,” Nielsen said.

Nielsen and his colleagues at UC Berkeley and in Greenland and Denmark came to their conclusions after analyzing the genomes of 191 Greenlanders with a low admixture of European genes (less than 5 percent) and comparing them to the genomes of 60 Europeans and 44 Han Chinese. They looked for mutations occurring in a large percentage of Inuit individuals but in few or no other groups, which indicates that the mutation spread throughout the Inuit because it was somehow useful to their survival while not essential in other groups.

One cluster of mutations — in genes that code for enzymes that desaturate carbon-carbon bonds in fatty acids — stood out strongly, said Anders Albrechtsen, an associate professor of bioinformatics at the University of Copenhagen and a joint project leader. Fatty acids are the fat in our diet, and occur in saturated, polyunsaturated and unsaturated forms, depending on whether the molecules’ carbon atoms are linked together with no, some or all double bonds. Saturated fats are considered bad because they raise levels of cholesterol in the blood and lower the “good” high-density lipoproteins (HDL), all of which leads to plaque formation and clogged arteries. Diets rich in polyunsaturated and unsaturated fats are linked to lower heart disease. Desaturase enzymes convert dietary fatty acids into fatty acids stored and metabolized by the body.

The mutations common in the Inuit, once known as Eskimos, decrease the production of both omega-3 and omega-6 polyunsaturated fatty acids, presumably to account for the high amount of these fatty acids coming from the diet. Changing production of one fatty acid affects all fatty acids, however, since they regulate one another in a complex way, Albrechtsen said.

Thus, while it’s not clear which specific gene or genes within the cluster is responsible for the alteration in fatty acid metabolism, he said that “when you change the genes that are involved in fatty acid synthesis, you change the whole conversation among fatty acids, and that has a lot of downstream effects.”

Adaptation to Ice Age living

The mutations seem to be at least 20,000 years old, and may have helped many groups of humans adapt to high-meat, high-fat, hunter-gatherer diets from large land and marine mammals high in certain types of omega-3 and omega-6 fatty acids, said Matteo Fumagalli, a researcher at University College London, who is joint first author of the study. They may have arisen among the original Siberians, who have lived in the Arctic for more than 20,000 years and arrived in Greenland when Inuit settled there about 1,000 years ago.

“We think it is a quite old selection that may have helped humans adapt to the environment during the last Ice Age, but the selection is far stronger in the Inuit than anywhere else,” said Fumagalli. “It’s fascinating that Greenlanders have a unique genetic makeup that lets them better use their traditional food sources.”

The researchers discovered another common mutation in a gene that is involved in the differentiation of brown, subcutaneous fat cells and brite fat cells, the latter of which generate heat. This may also have helped the Inuit adapt to a cold environment.

Author: Robert Sanders | Source: University of California, Berkeley [September 18, 2015]

The build-up and subsequent release of warm, stagnant water from the deep Arctic Ocean and Nordic Seas played a role in ending the last Ice Age within the Arctic region, according to new research led by a UCL scientist.

The study, published today in Science, examined how the circulation of the ocean north of Iceland -- the combined Arctic Ocean and Nordic Seas, called the Arctic Mediterranean -- changed since the end of the last Ice Age (~20,000-30,000 years ago).

Today, the ocean is cooled by the atmosphere during winter, producing large volumes of dense water that sink and flush through the deep Arctic Mediterranean. However, in contrast to the vigorous circulation of today, the research found that during the last Ice Age, the deep Arctic Mediterranean became like a giant stagnant pond, with deep waters not being replenished for up to 10,000 years.

This is thought to have been caused by the thick and extensive layer of sea ice and fresh water that covered much of the Arctic Mediterranean during the Ice Age, preventing the atmosphere from cooling and densifying the underlying ocean.

Dr David Thornalley (UCL Geography) said: "As well as being stagnant, these deep waters were also warm. Sitting around at the bottom of the ocean, they slowly accumulated geothermal heat from the seafloor, until a critical point was reached when the ocean became unstable.

"Suddenly, the heat previously stored in the deep Arctic Mediterranean was released to the upper ocean. The timing of this event coincides with the occurrence of evidence for a massive release of meltwater into the Nordic Seas. We hypothesize that this input of melt water was caused by the release of deep ocean heat, which melted icebergs, sea-ice and surrounding marine-terminating ice sheets."

This study highlights the important impact that changes in ocean circulation can have on climate, due to the ocean's capacity to redistribute vast quantities of heat around the globe. For example, scientists are currently concerned that ongoing changes in ocean circulation may result in warmer subsurface water that will cause enhanced melting and retreat of certain ice sheets in Greenland and Antarctica.

Dr Thornalley added: "To help predict the role of the ocean in future climate change, it is useful to investigate how ocean circulation changed in the past and what the associated climate effects were."

In this study, researchers from UCL, Woods Hole Oceanographic Institute and other partner institutions analysed the composition of calcite shells of small single-celled organisms (called foraminifera) that are found in ocean floor sediment. The shells of these organisms record the chemistry of the deep ocean at the time they were living, enabling the researchers to reconstruct past changes in ocean circulation.

By measuring the radiocarbon content of these shells, the research team was able to determine how rapidly deep water was being formed in the Arctic Mediterranean. A number of different techniques were then used to constrain past temperature changes, including measuring the ratio of magnesium and calcium, and the arrangement of isotopes of carbon and oxygen within the calcite shells of the foraminifera, both of which vary according to the temperature of the water in which the foraminifera grew.

A warmer, deep Arctic Mediterranean during glacial times has been suggested in previous studies, too. As summarised by co-author Dr Henning Bauch (GEOMAR/Germany) "It is good to see that new, independent proxy data would give strong support now to these former hypotheses."

Source: University College London [August 13, 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]