Dust in ice cores leads to new knowledge on the advancement of the ice before the ice age

By: Thomas Schmitt Attorney on October 03, 2019 / comment : 0 Climate Change, Earth Science, Greenland, Palaeoclimate, Palaeontology

Researchers from the section Physics of Ice, Climate and Earth (PICE) at the Niels Bohr Institute, University of Copenhagen, have succeeded in making a method to enlighten an otherwise dark period in climate history. Working with the ice core ReCap, drilled close to the coast in East Greenland, postdoc Marius Simonsen wondered why the dust particles from the interglacial period—the warmer period of time between the ice ages—were several times bigger than the dust particles from the ice age. His research led to the invention of a method able to map the advancement of the glaciers in cold periods and the melting in warmer periods. This data is important for the climate models we use to predict sea level rise. The result is now published in Nature Communications.

Credit: Hubertus Fischer/Alfred Wegener Institute

The larger particles of dust don't travel far—they come from East Greenland

Based on the hypothesis that the bigger dust particles in the ice couldn't have come from afar, the then Ph.D. student, Marius Simonsen, examined the dust at select locations on the coast of East Greenland close to the drill site. The chemical composition turned out to be similar to the larger particles in the ice. The smaller particles of dust caught in the ice, on the other hand, travel from Asia, blown to Greenland by dust storms.

In other words, the bigger particles of dust in the ice must mean presence of bare land close to the drill site. The ice is composed of annual layers, like the growth rings in a tree, so the distribution of large and small dust particles can be linked to the advancement and melting of the ice. Large particles mean bare land in the vicinity, small particles mean the land is covered in ice. The end of the ice age, where the ice cap is receding, is well explained scientifically, Marius Simonsen explains. "But it is very difficult to retrieve data on the period before the ice age. The ice is an extremely strong natural force, so it grinds away everything when advancing. But with the new method, we have data on the advancement of the ice. All of a sudden, we have a link to information on how quickly we enter an ice age, in a way we never used to have."

Gaining knowledge on Glacier reaction to atmospheric content of CO2 is crucial

It is important to know more about how glaciers react to changes in the atmosphere, and rather a lot is known on the composition of the atmosphere during the ice age. The results from the new method can now be used to compare the reaction in the masses of ice to changes in the atmospheric content of greenhouse gases like CO2.

Marius Simonsen says: "The glaciers receded at the beginning of the present interglacial, just like they do today because of climate change. The two scenarios are not entirely comparable, because there was much more inland ice then than now by the coast in East Greenland where the ice core is drilled. Never the less, the results are very interesting indeed when making climate models, because the models must be tested by comparison to reality. And in the new method we've acquired an anchor point in a period about which not much scientific knowledge existed." The method helps putting constraints on our knowledge on the influence of greenhouse gases on ice melting and, consequently, sea level.

The method can provide us with new information on how fast the glaciers recede

Helle Astrid Kjær, Assistant professor in PICE, says the objective of PICE now is to utilize the new method at other locations so we can gather more data on the changes of glaciers in the past. The researchers are already planning new drill sites in North East Greenland and Canada. It is very likely that advancement and melting of the ice there is different from East Greenland. "Perhaps, with the new method, we are able to see how fast the ice age came in from the north and moved south," Helle Astrid Kjær says.

It is a precondition for the feasibility of the method that bare land exists in the vicinity of the drill site, so dust particles can be found. This was the case during the last interglacial as the temperature then, app. 115,000 years ago, was up to 8 degrees C. warmer than today, according to a former study from the Niels Bohr Institute. Hence, the method will most likely be usable in North East Greenland and Canada. The researchers at the Niels Bohr Institute are already establishing new collaborations with Canadian researchers based on the new method.

Drilling of the ice core ReCap was supported by The Danish National Research Foundation, the American National Science Foundation, the German Alfred Wegener Institute and the European Union Horizon 2020 Research and Innovation Programme. The measurements of dust were supported by the EU funding ice2ice and Horizon 2020—TIPES.

Source: Niels Bohr Institute [October 03, 2019]

Greenland's growing 'ice slabs' intensify meltwater runoff into ocean

By: Thomas Schmitt Attorney on September 18, 2019 / comment : 0 Climate Change, Earth Science, Environment, Greenland, Natural Heritage

Thick, impenetrable ice slabs are expanding rapidly on the interior of Greenland's ice sheet, where the ice is normally porous and able to reabsorb meltwater. These slabs are instead sending meltwater spilling into the ocean, according to a new CIRES-led assessment, threatening to increase the country's contribution to sea level rise by as much as 2.9 inches by 2100.

Researchers Michael MacFerrin (left) and Horst Machguth (right) look over Sondre Stromfjord outside Kangerlussuaq, Greenland, where meltwater from the ice sheet runs into the ocean, 2013 [Credit: Karen Alley/CU Boulder/Wooster College]

Although runoff from ice slabs has added less than a millimeter to global sea levels so far, this contribution will grow substantially as ice slabs continue to expand in a warming climate, said Mike MacFerrin, a CIRES and University of Colorado Boulder researcher who led the new study, published in Nature.

"Even under moderate climate projections, ice slabs could double the size of the runoff zone by 2100," MacFerrin said. "Under higher emissions scenarios, the runoff zone nearly triples in size."

In 2000, Greenland's runoff zone--the region of the ice sheet where runoff contributes to sea level rise--was roughly the size of New Mexico. Between 2001 and 2013, ice slabs expanded the runoff zone by about 65,000 km2--that's an average pace of two American football fields a minute. By 2100, as Earth's temperatures continue to climb and ice slabs continue to grow, the runoff zone could expand by the size of Colorado under a moderate emissions scenario, the team found. That would raise seas by an extra quarter inch to just over an inch (7-33 mm).

Alex Crawford (left) and Mike MacFerrin (right) prepare to drive a snowmobile with ground-penetrating-radar to measure Greenland's ice slab extent in 2013 [Credit: Karen Alley/CU Boulder/Wooster College]

Under a higher emissions scenario, with greater release of greenhouse gases, the runoff zone could increase by the size of Texas, according to the new paper, contributing an extra half inch to nearly three inches (17-74 mm) of sea-level rise. The runoff estimates from ice slabs are in addition to other sources of sea-level rise from Greenland, such as calving icebergs.

Greenland's ice sheet is a complex quilt of frozen textures: melt lakes dot the surface, snow falls each winter, and old compacted snow slowly compresses into glacial ice. Over most of Greenland, the snow only partially melts each summer and later refreezes into thin ice disks or "lenses" just an inch or two thick, nestled within the compacted snow. Normally, meltwater can percolate downward and around ice lenses, refreezing in place without running off to sea.

But as extreme Arctic melting events become more frequent, those delicate ice layers expand and solidify into mammoth, 1- to 16-meter (3- to 50-foot) thick "slabs," creating an impermeable shell just beneath the surface. Meltwater can no longer percolate down into the ice sheet and instead flows downhill along the ice slabs, eventually into the ocean.

Mike MacFerrin (left) and Horst Machguth (right) analyze ice core samples drilled from the Greenland ice sheet in 2012 [Credit: Babis Charalampidis/Bavarian Academy of Sciences and Humanities, Germany (© 2012 Geological Survey of Denmark and Greenland)]

Such melt episodes are increasingly common in Greenland: In July of 2012, snow and ice melted from 97 percent of Greenland's ice sheet surface, an event not seen in the 33-year satellite record, according to the National Snow and Ice Data Center (NSIDC), part of CIRES and CU Boulder. This spring, which was particularly warm and sunny in Greenland, a record-setting 80 billion tons of Greenland ice melted.

MacFerrin and his colleagues accidentally discovered ice slabs in 2012, when they found large sections of solid ice in ice core samples, instead of the thin ice lenses they expected. They'd never seen anything like it before, MacFerrin said. Since the initial discovery, the team has investigated the ice slabs by driving snowmobiles across southwest Greenland, dragging ground-penetrating radars behind to map the extent of slabs. The scientists also harnessed NASA Icebridge data and climate models to understand how the slabs have expanded in recent decades, and to predict how they may continue to grow.

"As the climate continues to warm, these ice slabs will continue to grow and enhance other meltwater feedbacks," said Mahsa Moussavi, NSIDC researcher and a coauthor on the paper. "It's a snowball effect: more melting creates more ice slabs, which create more melting, which, creates again more ice slabs."


This process fundamentally alters the ice sheet's present and future hydrology. Arctic feedbacks like this are critical to understand because they show just how much, and how quickly, a warming climate can change Earth's most vulnerable regions.

"Interestingly, decades ago scientists hypothesized what meltwater in a warming climate could do to Greenland's snow layers, based on measurements and theory." said Horst Machguth, a researcher at the University of Fribourg, Switzerland, and second author on the paper. "Our results show that their hypotheses were close to what is playing out in Greenland today."

The climate mitigation path the world follows will determine how much the ice slabs will contribute to sea level in decades to come--from a couple millimeters to a few inches. "Humans have a choice about which way this goes," MacFerrin said.

Source: University of Colorado at Boulder [September 18, 2019]

Geoscientists discover mechanisms controlling Greenland ice sheet collapse

By: Thomas Schmitt Attorney on July 19, 2019 / comment : 0 Climate Change, Greenland, Natural Heritage, Oceans

Greenland's more than 860,000 square miles are largely covered with ice and glaciers, and its melting fuels as much as one-third of the sea level rise in Florida. That's why a team of University of South Florida geoscientists' new discovery of one of the mechanisms that allows Greenland's glaciers to collapse into the sea has special significance for the Sunshine State.

Clacier calving occuring on the Greenland Ice Sheet [Credit: Tim Dixon, PhD]

In research published in Nature Communications, a group of scientists led by USF Distinguished University Professor Tim Dixon, PhD, uncovered a process that can control the "calving" of glaciers - when large chunks of glacier ice collapse into the sea, forming icebergs like the one that sank the Titanic. The discovery by the team that included USF PhD student Surui Xie; David Holland, PhD, and Irena Vaková, PhD, at New York University (NYU) and NYU-Abu Dhabi Research Institute; and Denis Voytenko, PhD, formerly at NYU and now at Nielson Communications, will help the scientific community better model future Greenland ice loss and sea level rise.

Glacier calving is one of the more dramatic aspects of climate change. Depending on the height of the glacier, calving can be akin to an ice structure the size of a tall skyscraper falling into the sea. Dixon's team caught one such calving on video.

"Iceberg calving has been challenging to model," Dixon said. "One of the big unknowns in future sea level rise is how fast Greenland falls apart, and iceberg calving is one of the least understood mechanisms."

The team ventured to Greenland in the summer of 2016 to install a new radar system to better understand the process. In particular, they wanted to monitor formations known as pro-glacial "mélange" (from the French word for mixture), a combination of sea ice and icebergs in front of the glacier. The mélange can be tightly packed in the long, narrow fjords that front many of Greenland's glaciers that meet the sea.

Scientists have long known that mélange can impede glaciers as they move toward the sea, but they haven't had the data to fully understand the phenomenon.

Dr. Tim Dixon poses while on a research trip in Greenland [Credit: Tim Dixon, University of South Florida]

Dixon's team developed a new radar-based approach to precisely measure elevations of the mélange in front of Jakobshavn Glacier , a major outlet glacier on Greenland's west side. Using analytical techniques developed by Xie, the scientists measured the height of the mélange. The scientists found a thick mélange wedge pressed up against the glacier in late spring and early summer.

During this period, no icebergs calved, the scientists observed. Once the wedge thinned and melted by mid-summer, calving began in earnest.

"On the surface, this mélange is a subtle thing - it appears almost flat- but underwater, there are huge variations," Dixon said. "It's really the underwater part that is pinning the glacier back and preventing it from calving. By precisely measuring the surface elevations, we were able to get a handle on the much bigger sub-surface variations, which define mélange thickness."

Earlier this spring, NASA scientists reported Jakobshavn Glacier, which has been Greenland's fastest -thinning glacier for the last 20 years, was slowing in its movement toward the ocean in what appears to be a cyclical pattern of warming and cooling. But because Jakobshavn is still giving up more ice than it accumulates each year, its sheer size makes it an important factor in sea level rise, the NASA scientists maintain.

"Our study helps understand the calving process," Dixon said. "We are the first to discover that mélange isn't just some random pile of icebergs in front of the glacier. A mélange wedge can occasionally 'hold the door' and keep the glacier from calving."

Source: University of South Florida [July 19, 2019]

Climate change threatens Greenland's archaeological sites: study

By: Thomas Schmitt Attorney on July 11, 2019 / comment : 0 Archaeology, Climate Change, Greenland, Heritage

In Greenland, climate change isn't just a danger to ecosystems but also a threat to history, as global warming is affecting archaeological remains, according to a study published Thursday.

Students and scientists investigate materials found at the Norse site Iffiartarfik [Credit: Roberto Fortuna, National Museum of Denmark]

There are more than 180,000 archaeological sites across the Arctic, some dating back thousands of years, and previously these were protected by the characteristics of the soil.

"Because the degradation rate is directly controlled by the soil temperature and moisture content, rising air temperatures and changes in precipitation during the frost-free season may lead to a loss of organic key elements such as archaeological wood, bone and ancient DNA," the report, published in the scientific journal Scientific Reports, stated.

The team behind the study, led by Jorgen Hollesen, has been examining seven different sites around the vast Arctic territory's capital Nuuk, since 2016.

In addition to organic elements, such as hair, feathers, shells and traces of flesh, some of the sites contain the ruins of Viking settlements.

Greenland's many kitchen middens sites consist of several layers of bones, worn-out tools and other items that the prehistoric people considered to be garbage [Credit: Roberto Fortuna, National Museum of Denmark]

Projections used in the study, which are based on different warming scenarios, predict that average temperature could increase by up to 2.6 degrees Celsius (4.7 degrees Fahrenheit), leading to "higher soil temperatures, a longer thaw season, and increased microbial activity within the organic layers".

"Our results show that 30 to 70 percent of the archaeological fraction of organic carbon (OC) could disappear within the next 80 years," Hollesen told AFP.

This means that these remains, some of which provide a unique insight into the lives of the first inhabitants of Greenland from around 2,500 BC, are at risk.

When comparing their findings with previous surveys of the sites they found evidence of degradation already ongoing.

One of the finds was this hand-carved bone point [Credit: Roberto Fortuna National Museum of Denmark]

"At some sites we did not find any intact bones or pieces of wood, suggesting that these have disintegrated within the last decades," Hollesen said.

Hollesen added that remains of organic material are being broken down by microbes, but their activity could be slowed down if precipitation increased.

"More rainfall would be good and less rainfall, bad," he said explaining that "if the organic layers remain wet less oxygen will be available for the microbes that degrade the organic materials".

In other Arctic regions, such as Alaska, hundreds of ancient artifacts have recently emerged as the permafrost, the layer of earth that is frozen all year, thaws due to rising temperatures.

Source: AFP [July 11, 2019]

Researchers discover ice is sliding toward edges off Greenland Ice Sheet

By: Thomas Schmitt Attorney on July 10, 2019 / comment : 0 Climate Change, Environment, Greenland, Natural Heritage

Ice on the Greenland Ice Sheet doesn't just melt. The ice actually slides rapidly across its bed toward the ice sheet's edges. As a result, because ice motion is from sliding as opposed to ice deformation, ice is being moved to the high-melt marginal zones more rapidly than previously thought.

Neil Humphrey (left), a University of Wyoming professor of geology and geophysics, and Nathan Maier, a UW geology Ph.D. student, pose on the Greenland Ice Sheet during 2017 field research [Credit: Neil Humphrey]

Neil Humphrey, a University of Wyoming professor of geology and geophysics, and Nathan Maier, a UW geology Ph.D. student from Morristown, N.J., headed a recent research group that discovered that you do not need beds with till or mud, which acts as a lubricant, to have high rates of sliding. Rather, they discovered that it is over hard bedrock where ice slides more rapidly. Additionally, the ice slides over the bedrock much more than previous theories predicted of how ice on the Greenland Ice Sheet moves.

"That's the kicker. The Greenland Ice Sheet is happily sliding over a surface that theory says it shouldn't be able to rapidly slide over," Humphrey says. "What's important is that, because of this, you get a lot of ice to the oceans or low altitudes where it can melt really fast. It's like a lump of molasses sliding off the continent. It just doesn't melt. It slides toward the ocean."

"Our measurements of sliding-dominated flow over a hard bed in a slow-moving region were quite surprising because people don't typically associate these regions with high sliding," Maier adds. "Generally, people associate lots of sliding motion with regions that have soft beds (mud) or exceptionally high-sliding velocities, such as ice streams. Yet, in this relatively boring region, we found the highest fraction of sliding measured to date."

Maier was lead author and Humphrey was a co-author of the paper, titled "Sliding Dominates Slow-Flowing Margin Regions, Greenland Ice Sheet," that was published in Science Advances. The peer-reviewed, multidisciplinary open-access scientific journal includes all areas of science, including the life sciences, physical sciences, social sciences, computer sciences and environmental sciences.

Other contributors to the paper were Joel Harper, an associate professor of geosciences, and Toby Meierbachtol, an assistant professor, both from the University of Montana. The paper represents work conducted on the Greenland Ice Sheet from 2014-16.

The researchers installed 212 tilt sensors within a network of boreholes drilled into the ice bed. The tilt sensors allow for observation of ice deformation and sliding movement. Humphrey uses a large drill he designed, which he describes as "a very large truck washer" that puts out high-pressure steam with a large drill nozzle and hydraulic hose. He says it is "the fastest ice drill in the world" and can drill 5,000 feet into the Greenland Ice Sheet in eight hours.

"Most of our work is truly arcane," Humphrey says. "We're boring holes through the ice sheet, but we don't even collect ice cores."

Modeling constrained by detailed tilt observations made along the basal interface of the ice suggests that the high sliding is due to a slippery bed, where sparsely spaced bedrock bumps provide limited resistance to sliding. Estimates of sliding speed are typically based on the residual between observed surface velocity and modeled ice deformational velocity.

"We don't have a good theory for this type of sliding," Humphrey explains. "But the data from this paper will allow us to work on an improved theory."

Maier agrees, saying their work should help improve the accuracy of ice sheet models as they try to predict future mass loss from Greenland.

"There has been some debate as to whether ice flow along the edges of Greenland should be considered mostly deformation or mostly sliding," Maier says. "This has to do with uncertainty of trying to calculate deformation motion using surface measurements alone. Our direct measurements of sliding- dominated motion, along with sliding measurements made by other research teams in Greenland, make a pretty compelling argument that no matter where you go along the edges of Greenland, you are likely to have a lot of sliding."

Maier says this is important to the future of Greenland because it means the ice sheet can move mass around efficiently and, thus, respond rapidly to a changing climate.

Similarly, Maier says changes in ice motion due to a warming climate also will result in thickening and thinning along the edges of the ice sheet. Because ice can be moved around efficiently due to high rates of sliding, changes in melting can occur rapidly.

The sliding ice does two things, Humphrey says. First, it allows the ice to slide into the ocean and make icebergs, which then float away. Two, the ice slides into lower, warmer climate, where it can melt faster.

While it may sound dire, Humphrey notes the entire Greenland Ice Sheet is 5,000 to 10,000 feet thick.

"In a really big melt year, the ice sheet might melt a few feet. It means Greenland is going to be there another 10,000 years," Humphrey says. "So, it's not the catastrophe the media is overhyping."

Humphrey has been working in Greenland for the past 30 years and says the Greenland Ice Sheet has only melted 10 feet during that time span.

Source: University of Wyoming [July 10, 2019]

Researchers discover more than 50 lakes beneath the Greenland Ice Sheet

By: Thomas Schmitt Attorney on June 26, 2019 / comment : 0 Earth Science, Ecosystems, Environment, Greenland, Natural Heritage

Researchers have discovered 56 previously uncharted subglacial lakes beneath the Greenland Ice Sheet bringing the total known number of lakes to 60. Although these lakes are typically smaller than similar lakes in Antarctica, their discovery demonstrates that lakes beneath the Greenland Ice Sheet are much more common than previously thought.

Researchers have discovered 56 previously uncharted subglacial lakes beneath the Greenland Ice Sheet bringing the total known number of lakes to 60. Although these lakes are typically smaller than similar lakes in Antarctica, their discovery demonstrates that lakes  beneath the Greenland Ice Sheet are much more common than previously thought [Credit: Dr Andrew Sole, University of Sheffield]

The Greenland Ice Sheet covers an area approximately seven times the size of the UK, is in places more than three kilometres thick and currently plays an important role in rising global sea levels.

Subglacial lakes are bodies of water that form beneath ice masses. Meltwater is derived from the pressure of the thick overlying ice, heat generated by the flow of the ice, geothermal heat retained in the Earth, or water on the surface of the ice that drains to the bed. This water can become trapped in depressions or due to variations in ice thickness.

Knowledge of these new lakes helps form a much fuller picture of where water occurs and how it drains under the ice sheet, which influences how the ice sheet will likely respond dynamically to rising temperatures.

Published in Nature Communications this week, their paper, "Distribution and dynamics of Greenland subglacial lakes", provides the first ice-sheet wide inventory of subglacial lakes beneath the Greenland Ice Sheet.

By analysing more than 500,000 km of airborne radio echo sounding data, which provide images of the bed of the Greenland Ice Sheet, researchers from the Universities of Lancaster, Sheffield and Stanford identified 54 subglacial lakes, as well as a further two using ice-surface elevation changes.

Surface meltwater in Greenland [Credit: Winnie Chu, Stanford University]

Lead author Jade Bowling of the Lancaster Environment Centre, Lancaster University, said: "Researchers have a good understanding of Antarctic subglacial lakes, which can fill and drain and cause overlying ice to flow quicker. However, until now little was known about subglacial lake distribution and behaviour beneath the Greenland Ice Sheet. This study has for the first time allowed us to start to build up a picture of where lakes form under the Greenland Ice Sheet. This is important for determining their influence on the wider subglacial hydrological system and ice-flow dynamics, and improving our understanding of the ice sheet's basal thermal state."

The newly discovered lakes range from 0.2-5.9 km in length and the majority were found beneath relatively slow moving ice away from the largely frozen bed of the ice sheet interior and seemed to be relatively stable.

However, in the future as the climate warms, surface meltwater will form lakes and streams at higher elevations on the ice sheet surface, and the drainage of this water to the bed could cause these subglacial lakes to drain and therefore become active. Closer to the margin where water already regularly gets to the bed, the researchers saw some evidence for lake activity, with two new subglacial lakes observed to drain and then refill.

Dr. Stephen J. Livingstone, Senior Lecturer in Physical Geography, University of Sheffield, said: "The lakes we have identified tend to cluster in eastern Greenland where the bed is rough and can therefore readily trap and store meltwater and in northern Greenland, where we suggest the lakes indicate a patchwork of frozen and thawed bed conditions. These lakes could provide important targets for direct exploration to look for evidence of extreme life and to sample the sediments deposited in the lake that preserve a record of environmental change."

Source: Lancaster University [June 26, 2019]

Study predicts more long-term sea level rise from Greenland ice

By: Thomas Schmitt Attorney on June 19, 2019 / comment : 0 Arctic, Climate Change, Earth Science, Environment, Greenland, Natural Heritage

Greenland's melting ice sheet could generate more sea level rise than previously thought if greenhouse gas emissions continue to increase and warm the atmosphere at their current rate, according to a new modeling study. The study, which used data from NASA's Operation IceBridge airborne campaign, was published in Science Advances. In the next 200 years, the ice sheet model shows that melting at the present rate could contribute 19 to 63 inches to global sea level rise, said the team led by scientists at the Geophysical Institute at the University of Alaska Fairbanks. These numbers are at least 80 percent higher than previous estimates, which forecasted up to 35 inches of sea level rise from Greenland's ice.

The researchers ran their model 1500 times, testing a variety of land, ice, ocean and atmospheric variables to see how they affected ice melt rate - including three possible future climate scenarios (from left to right: low, medium, and high emissions out to the year 2300) [Credit: NASA/Cindy Starr]

The team ran the model 500 times out to the year 3000 for each of three possible future climate scenarios, adjusting key land, ice, ocean and atmospheric variables to test their effects on ice melt rate. The three climate scenarios depend on the amount of greenhouse gas emissions in the atmosphere in coming years. In the scenario with no reduction of emissions, the study found that the entire Greenland Ice Sheet will likely melt in a millennium, causing 17 to 23 feet of sea level rise.

In the scenario where emissions are stabilized by the end of the century rather than continue to increase, the model shows ice loss falling to 26-57 percent of total mass by 3000. Drastically limiting emissions so they begin to decline by the end of the century could limit ice loss to 8-25 percent. This scenario would produce up to six feet of sea level rise in the next millennium, according to the study.

The updated model more accurately represents the flow of outlet glaciers, the river-like bodies of ice that connect to the ocean. Outlet glaciers play a key role in how ice sheets melt, but previous models lacked the data to adequately represent their complex flow patterns. The study found that melting outlet glaciers could account for up to 40 percent of the ice mass lost from Greenland in the next 200 years.

By incorporating ice thickness data from IceBridge and identifying sources of statistical uncertainty within the model, the study creates a more accurate picture of how human-generated greenhouse gas emissions and a warming climate may affect Greenland in the future.

A clearer picture

Capturing the changing flow and speed of outlet glacier melt makes the updated ice sheet model more accurate than previous models, according to the authors. As ocean waters have warmed over the past 20 years, they have melted the floating ice that shielded the outlet glaciers from their rising temperatures. As a result, the outlet glaciers flow faster, melt and get thinner, with the lowering surface of the ice sheet exposing new ice to warm air and melting as well.

Ilulissat, known as 'the city of icebergs' sits adjacent to Greenland's Ilulissat Glacier, which flows into the Atlantic Ocean. Such outlet glaciers lead ice sheet loss in Greenland. New research shows that if this loss continues at its current rate,  it could result in an ice-free Greenland by the year 3000 and 24 feet of global sea level rise [Credit: Martin Truffer]

"Once we had access to satellite observations, we were able to capture the surface velocity of the whole Greenland Ice Sheet and see how that ice flows. We recognized that some outlet glaciers flow very fast -- orders of magnitude faster than the interior of the ice sheet," said lead author Andy Aschwanden, a research associate professor at the University of Alaska Fairbanks' Geophysical Institute.

IceBridge's detailed ice thickness measurements helped the team to be the first to model these areas where outlet glaciers are affected by warmer ocean waters, as well as to model more of the complex feedbacks and processes influencing ice loss than previously possible. They examined the importance of factors like underwater melting, large ice chunks breaking off of glaciers, changing snowfall rates and rising air temperatures. They also examined factors that could slow down ice loss, like the movement of Earth's surface "bouncing back" from the weight of ice that is no longer there.

"At the end of the day, glaciers flow downhill," Aschwanden said. "That's very simplified, but if you don't know where downhill is, the model can never do a good job. So the most important contributor to understanding ice flow is knowing how thick the ice is."

Each of the three emissions scenarios used in the study produced different patterns of ice retreat across Greenland. The least severe scenario showed the ice retreating in the west and north, while the moderate scenario showed ice retreat around the island, except for in the highest elevation areas. The most severe scenario, in which emissions continue to increase at their present rate, showed more than half of the model runs losing more than 99 percent of the ice sheet by 3000.

These maps of Greenland show ice losses under two 'representative concentration pathways' of greenhouse gases  in Earth's atmosphere from present day to the year 3000. The RCPs, adopted by the Intergovernmental Panel on Climate Change, reflect higher (8.5) and lower (2.6) greenhouse gas concentrations associated with different levels of emissions from human use of fossil fuels. Currently, the planet is on the higher pathway [Credit: UAF Geophysical Institute]

At its thickest point, the Greenland Ice Sheet currently stands more than 10,000 feet above sea level. It rises high enough into the atmosphere to alter the weather around it, as mountains do. Today, this weather pattern generates almost enough snowfall to compensate for the amount of naturally melting ice each year. In the future, however, melting and flow will thin the interior, lowering it into a layer of the atmosphere that lacks the conditions necessary for sufficient replenishing snowfall.

"In the warmer climate, glaciers have lost the regions where more snow falls than melts in the summer, which is where new ice is formed," said Mark Fahnestock, research professor at the Geophysical Institute and the study's second author. "They're like lumps of ice in an open cooler that are melting away, and no one is putting any more ice into the cooler."

The team stressed that despite the need for ongoing research on exactly how glaciers will move and melt in response to warming temperatures, all of the model runs show that the next few decades will be pivotal in the ice sheet's future outcome.

"If we continue as usual, Greenland will melt," Aschwanden said. "What we are doing right now in terms of emissions, in the very near future, will have a big long-term impact on the Greenland Ice Sheet, and by extension, if it melts, to sea level and human society."

Bridging the data gap

The model runs were performed on high-performance supercomputers at NASA's Ames Research Center and the University of Alaska Fairbanks (UAF) using the Parallel Ice Sheet Model (PISM), an open-source model developed at UAF and the Potsdam Institute for Climate Impact Research. NASA also provided funding support for the study. While other ice sheet models could perform the simulations they did, the team said, PISM is unique for its high resolution and low computational cost.

NASA's Operation IceBridge is the world's largest airborne survey of polar land and sea ice. Using an array of aircraft and scientific instruments, IceBridge has collected data between the end of the first Ice, Cloud and Land Elevation Satellite (ICESat) mission in 2010 and the second, ICESat-2, which launched in 2018. It has measured the height of the ice below its flight path as well as the bedrock under the ice sheets.

"NASA's space and airborne campaigns, like IceBridge, have fundamentally transformed our ability to try and make a model mimic the changes to the ice sheet," Fahnestock said. "The technology that allows improved imaging of the glacier bed is like a better pair of glasses allowing us to see more clearly. Only NASA had an aircraft with the instruments and technology we needed and could go where we needed to go."

Author: Jessica Merzdorf | Source: NASA's Goddard Space Flight Center [June 19, 2019]

Arctic could face another scorching annus horribilis

By: Thomas Schmitt Attorney on June 19, 2019 / comment : 0 Arctic, Climate Change, Greenland, Natural Heritage

Scientists say 2019 could be another annus horribilis for the Arctic with record temperatures already registered in Greenland—a giant melting icicle that threatens to submerge the world's coastal areas one day.

Sled dogs wade through standing water on the sea ice during an expedition in northwestern Greenland, whose ice sheet may have completely melted within the next millennium if greenhouse gas emissions continue at their current rate, a study has found [Credit: Steffen Olsen/AFP]

"It's possible that we could break the records set in 2012 for both lowest Arctic sea ice extent ... and for record high Greenland ice sheet melt," warned Ruth Mottram, a climatologist at the Danish Meteorological Institute (DMI).

"It is very much dependent on weather conditions this year."

A striking photograph of the early ice melt taken last week by a DMI scientist in northwestern Greenland has gone viral.

While researching oceanographic moorings and a weather station, Steffen Olsen snapped a picture of his sled dogs pushing through a fjord, the sea ice submerged under several centimetres (inches) of meltwater.

Under a bright blue sky, with a snow-free mountain in the background, the dogs appear to be walking on water.

"The picture is striking ... because it really visualises how the Arctic is changing," Mottram told AFP.

Locals who accompanied Olsen's expedition "didn't expect the sea ice to start melting that early. They usually take that route because the ice is very thick, but they had to turn back because the water was deeper and deeper and they couldn't" advance, she said.

On June 12, the day before the photograph was taken, the closest weather station, in Qaanaaq, registered temperatures of 17.3 degrees Celsius (63.1 Fahrenheit), just 0.3 points lower than the record set on June 30, 2012.

"There was a dry winter and then recently (there has been) warm air, clear skies and sun—all preconditions for an early melting," Mottram explained.

As the atmosphere heats up, the phenomenon is expected to accelerate, changing the way of life for the local population—who will see shorter hunting seasons on the ice, on which they depend for their survival—as well as an altered ecosystem.

The number of polar bears in the Arctic has decreased by around 40 percent in the past decade due the shrinking ice, according to the US Geological Survey.

Narwhals—whales with a large unicorn-like tusk, found in the Arctic—are seeing their natural ice shelter from their main predator, killer whales, dwindle.

Melting permafrost in the Arctic [Credit: Sophie Ramis/AFP]

The melting sea ice is one thing. But it is the melting of the ice sheet and glaciers that has a direct impact on rising sea levels worldwide.

Greenland's "Summit Station", located at an altitude of 3,000 metres (9,843 feet), on April 30 recorded the warmest temperature in its history, at minus 1.2 degrees Celsius, according to DMI.

On June 17, Greenland lost 3.7 billion tonnes of ice in a single day, DMI said.

Since early June, 37 billion tonnes of ice have melted, Xavier Fettweis, a climatologist at the University of Liege, wrote on Twitter.

"It becomes more and more likely that a record of mass loss will be broken for the month of June in 2019," he wrote.

Also worrying is how early in the year the ice is melting.

Danish meteorologists announced the ice melting season had begun at the start of May, almost a month earlier than usual.

The ice melt has only begun before early May once—in 2016—since data began being registered in 1980.

"The start of the melt season occurs on the first of three consecutive days where more than five percent of the ice sheet has melted at the surface," said scientist Peter Langen on the site polarportal.dk, which collects data from several Danish scientific institutions in the Arctic.

Greenland's ice melt contributes around 0.7 millimetres per year to rising sea levels, an amount that could increase further if the ice melt continues at the current rate.

Since 1972, Greenland's melting glaciers have contributed to a 13.7 millimetre increase in sea levels.

A study published in April in the Proceedings of the National Academy of Sciences showed that Greenland's ice loss since the 1980s has accelerated dramatically since the 2000s, and especially since 2010.

The ice is melting six times faster now than in the 1980s. And the forecasts are alarming.

In 2014, the UN Intergovernmental Panel on Climate Change (IPCC) predicted in its worst-case scenario that by the end of the 21st century, sea levels would be almost one metre higher than what they were between 1986 and 2005.

Author: Camille Bas-Wohlert | Source: AFP [June 19, 2019]

New evidence shows rapid response in the West Greenland landscape to Arctic climate shifts

By: Thomas Schmitt Attorney on June 18, 2019 / comment : 0 Arctic, Climate Change, Environment, Greenland, Natural Heritage

New evidence shows that Arctic ecosystems undergo rapid, strong and pervasive environmental changes in response to climate shifts, even those of moderate magnitude, according to an international research team led by the University of Maine.

Understanding how ecosystems in the West Greenland respond to abrupt climate change is central to predicting and managing potentially disruptive environmental change [Credit: Sergi Pla-Rabes]

Links between abrupt climate change and environmental response have long been considered delayed or dampened by internal ecosystem dynamics, or only strong in large magnitude climate shifts. The research team, led by Jasmine Saros, associate director of the UMaine Climate Change Institute, found evidence of a "surprisingly tight coupling" of environmental responses in an Arctic ecosystem experiencing rapid climate change.

Using more than 40 years of weather data and paleoecological reconstructions, the 20-member team quantified rapid environmental responses to recent abrupt climate change in West Greenland. They found that after 1994, mean June air temperatures were 2.2 degrees C higher and mean winter precipitation doubled to 40 millimeters. Since 2006, mean July air temperatures shifted 1.1 degree C higher.

The "nearly synchronous" environmental response to those high-latitude abrupt climate shifts included increased ice sheet discharge and dust, and advanced plant phenology. In lakes, there was earlier ice-out and greater diversity of algal functional traits.

The new evidence underscores the highly responsive nature of Arctic ecosystems to abrupt transitions -- and the strength of climate forcing, according to the team, which published its findings in the journal Environmental Research Letters.

Understanding how ecosystems respond to abrupt climate change is central to predicting and managing potentially disruptive environmental shifts, says Saros, one of seven UMaine professors who have been conducting research in the Arctic in recent years.

"We present evidence that climate shifts of even moderate magnitude can rapidly force strong, pervasive environmental changes across a high-latitude system," says Saros. "Prior research on ecological response to abrupt climate change suggested delayed or dampened ecosystem responses. In the Arctic, however, we found that nonlinear environmental responses occurred with or shortly after documented climate shifts in 1994 and 2006."

Source: University of Maine [June 18, 2019]

Phytoplankton decline coincides with warming temperatures over the last 150 years

By: Thomas Schmitt Attorney on May 07, 2019 / comment : 0 Climate Change, Earth Science, Ecosystems, Greenland, Natural Heritage, Wildlife

Virtually all marine life depends on the productivity of phytoplankton — microscopic organisms that work tirelessly at the ocean’s surface to absorb the carbon dioxide that gets dissolved into the upper ocean from the atmosphere.

Matt Osman, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, overlooking a frozen Baffin Bay to the west, Nuussuaq Peninsula Ice Cap, west Greenland [Credit: Luke Trusel/Rowan University]

Through photosynthesis, these microbes break down carbon dioxide into oxygen, some of which ultimately gets released back to the atmosphere, and organic carbon, which they store until they themselves are consumed. This plankton-derived carbon fuels the rest of the marine food web, from the tiniest shrimp to giant sea turtles and humpback whales.

Now, scientists at MIT, Woods Hole Oceanographic Institution (WHOI), and elsewhere have found evidence that phytoplankton’s productivity is declining steadily in the North Atlantic, one of the world’s most productive marine basins.

In a paper appearing this week in the journal Nature, the researchers report that phytoplankton’s productivity in this important region has gone down around 10 percent since the mid-19th century and the start of the Industrial era. This decline coincides with steadily rising surface temperatures over the same period of time.

Matthew Osman, the paper’s lead author and a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences and the MIT/WHOI Joint Program in Oceanography, says there are indications that phytoplankton’s productivity may decline further as temperatures continue to rise as a result of human-induced climate change.

“It’s a significant enough decine that we should be concerned,” Osman says. “The amount of productivity in the oceans roughly scales with how much phytoplankton you have. So this translates to 10 percent of the marine food base in this region that’s been lost over the industrial era. If we have a growing population but a decreasing food base, at some point we’re likely going to feel the effects of that decline.”

Drilling through “pancakes” of ice

Osman and his colleagues looked for trends in phytoplankton’s productivity using the molecular compound methanesulfonic acid, or MSA. When phytoplankton expand into large blooms, certain microbes emit dimethylsulfide, or DMS, an aerosol that is lofted into the atmosphere and eventually breaks down as either sulfate aerosol, or MSA, which is then deposited on sea or land surfaces by winds.

Ice core field camp on a clear spring evening, Disko Island Ice Cap, west Greenland [Credit: Luke Trusel/Rowan University]

“Unlike sulfate, which can have many sources in the atmosphere, it was recognized about 30 years ago that MSA had a very unique aspect to it, which is that it’s only derived from DMS, which in turn is only derived from these phytoplankton blooms,” Osman says. “So any MSA you measure, you can be confident has only one unique source — phytoplankton.”

In the North Atlantic, phytoplankton likely produced MSA that was deposited to the north, including across Greenland. The researchers measured MSA in Greenland ice cores — in this case using 100- to 200-meter-long columns of snow and ice that represent layers of past snowfall events preserved over hundreds of years.

“They’re basically sedimentary layers of ice that have been stacked on top of each other over centuries, like pancakes,” Osman says.

The team analyzed 12 ice cores in all, each collected from a different location on the Greenland ice sheet by various groups from the 1980s to the present. Osman and his advisor Sarah Das, an associate scientist at WHOI and co-author on the paper, collected one of the cores during an expedition in April 2015.

“The conditions can be really harsh,” Osman says. “It’s minus 30 degrees Celsius, windy, and there are often whiteout conditions in a snowstorm, where it’s difficult to differentiate the sky from the ice sheet itself.”

Iceberg in Disko Bay, west Greenland [Credit: Luke Trusel/Rowan University]

The team was nevertheless able to extract, meter by meter, a 100-meter-long core, using a giant drill that was delivered to the team’s location via a small ski-equipped airplane. They immediately archived each ice core segment in a heavily insulated cold storage box, then flew the boxes on “cold deck flights” — aircraft with ambient conditions of around minus 20 degrees Celsius. Once the planes touched down, freezer trucks transported the ice cores to the scientists’ ice core laboratories.

“The whole process of how one safely transports a 100-meter section of ice from Greenland, kept at minus-20-degree conditions,  back to the United States is a massive undertaking,” Osman says.

Cascading effects

The team incorporated the expertise of researchers at various labs around the world in analyzing each of the 12 ice cores for MSA. Across all 12 records, they observed a conspicuous decline in MSA concentrations, beginning in the mid-19th century, around the start of the Industrial era when the widescale production of greenhouse gases began. This decline in MSA is directly related to a decline in phytoplankton productivity in the North Atlantic.

“This is the first time we’ve collectively used these ice core MSA records from all across Greenland,  and they show this coherent signal. We see a long-term decline that originates around the same time as when we started perturbing the climate system with industrial-scale greenhouse-gas emissions,” Osman says. “The North Atlantic is such a productive area, and there’s a huge multinational fisheries economy related to this productivity. Any changes at the base of this food chain will have cascading effects that we’ll ultimately feel at our dinner tables.”

Retrieving an ice core section from the drill barrel during a west Greenland snowstorm, west Greenland Ice Sheet [Credit: Sarah Das/WHOI]

The multicentury decline in phytoplankton productivity appears to coincide not only with concurrent long-term warming temperatures; it also shows synchronous variations on decadal time-scales with the large-scale ocean circulation pattern known as the Atlantic Meridional Overturning Circulation, or AMOC. This circulation pattern typically acts to mix layers of the deep ocean with the surface, allowing the exchange of much-needed nutrients on which phytoplankton feed.

In recent years, scientists have found evidence that AMOC is weakening, a process that is still not well-understood but may be due in part to warming temperatures increasing the melting of Greenland’s ice. This ice melt has added an influx of less-dense freshwater to the North Atlantic, which acts to stratify, or separate its layers, much like oil and water, preventing nutrients in the deep from upwelling to the surface. This warming-induced weakening of the ocean circulation could be what is driving phytoplankton’s decline. As the atmosphere warms the upper ocean in general, this could also further the ocean’s stratification, worsening phytoplankton’s productivity.

“It’s a one-two punch,” Osman says. “It’s not good news, but the upshot to this is that we can no longer claim ignorance. We have evidence that this is happening, and that’s the first step you inherently have to take toward fixing the problem, however we do that.”

Author: Jennifer Chu | Source: Massachusetts Institute of Technology [May 07, 2019]

Researchers calculate decades of 'scary' Greenland ice melting

By: Thomas Schmitt Attorney on April 22, 2019 / comment : 0 Climate Change, Earth Science, Environment, Greenland, Natural Heritage

Measuring melting ice is a fairly precise business in 2019—thanks to satellites, weather stations and sophisticated climate models.

Satellites are used to measure ice loss in Greenland [Credit: Jeff Schmaltz/AFP]

By the 1990s and 2000s, scientists were able to make pretty good estimates, although work from previous decades was unreliable due to less advanced technology.

Now, researchers have recalculated the amount of ice lost in Greenland since 1972, the year the first Landsat satellites entered orbit to regularly photograph the Danish territory.

"When you look at several decades, it is best to sit back in your chair before looking at the results, because it is a bit scary to see how fast it is changing," said French glaciologist Eric Rignot, of the University of California at Irvine.

Rignot co-authored the study, published in the Proceedings of the National Academy of Sciences,with colleagues in California, Grenoble, Utrecht and Copenhagen.

"It's also something that affects the four corners of Greenland, not just the warmer parts in the south," he said.

Ice melting six times faster

Glaciologists use three methods to measure ice melting.

Firstly, satellites measure altitude with a laser: if a glacier melts, the satellite picks up its reduced height.

A second technique involves measuring variations in gravity, as ice loss can be detected through a decrease in gravitational pull. This method has been available since 2002 using NASA satellites.

Thirdly, scientists have developed so-called mass balance models, which compare mass accumulated (rain and snow) with mass lost (ice river discharges) to calculate what is left.

The Zachariae Glacier on Greenland's east coast is seen in a photograph taken by a NASA satellite [Credit: AFP]

These models, confirmed with field measurements, have become very reliable since the 2000s, according to Rignot—boasting a five to seven percent margin of error, compared to 100 percent a few decades ago.

The research team used these models to "go back in time" and reconstruct Greenland's ice levels in the 1970s and 1980s.

The limited data available for this period—medium-quality satellite photos, aerial photos, ice cores and other observations—helped refine them.

"We added a little bit of history that did not exist," said Rignot.

The results: during the 1970s, Greenland accumulated 47 gigatonnes of ice per year, on average. Then, it lost an equivalent volume in the 1980s.

The melting continued at that rate in the 1990s, before a sharp acceleration in the 2000s (187 Gt/year) and even more since 2010 (286 Gt/year).

Ice is melting six times faster than in the 1980s, researchers estimate—and Greenland's glaciers alone have contributed to a 13.7 millimeter rise in sea levels since 1972, they believe.

"This is an excellent piece of work by a well-established research group using novel methods to extract more information from the available data", said Colin Summerhayes, of the Scott Polar Research Institute in Cambridge.

As with a similar study carried out by the same team on Antarctica, the new study affords a longer term view of the rapid ice melt being observed in Greenland in recent years.

"This new data better enables us to put recent, dramatic, changes to Greenland's contribution to global sea level rise into a longer-term context—the ice loss we've seen in the last eight years is as much as was lost in the preceding four decades," said Amber Leeson, a lecturer in Environmental Data Science at Lancaster University.

Author: Ivan Couronne | Source: AFP [April 22, 2019]

North Atlantic warming hole impacts jet stream

By: Thomas Schmitt Attorney on April 15, 2019 / comment : 0 Climate Change, Earth Science, Environment, Greenland, Natural Heritage, Oceans

The North Atlantic warming hole (NAWH), a region of reduced warming located in the North Atlantic Ocean, significantly affects the North Atlantic jet stream in climate simulations of the future, according to a team of researchers.

Floating iceberg in Labrador Sea south of Greenland [Credit: Melissa Gervais/Penn State]

Sea surface temperatures (SST) are projected to increase in most of the world's oceans as the result of global climate change. However, within an area of rotating ocean currents just south of Greenland an anomaly exists where colder sea-surface temperatures were documented in both global climate-model projections and in observations.

"It's called a hole because there is a lack of warming," said Melissa Gervais, assistant professor of meteorology and atmospheric science, Penn State, who used the Community Earth System model (CESM) to investigate the impact of the NAWH on atmospheric circulation and midlatitude jets. "We found that this region of the ocean is a really important place for forcing the jet stream that goes across the North Atlantic Ocean."

Development of the NAWH is linked to a slowdown of the Atlantic Meridional Overturning Circulation, a large system of ocean currents that carry warm water from the tropics northwards into the North Atlantic, and is thought to be caused by an influx of fresh water coming from melting Arctic sea ice.

Previous research by Gervais and her team demonstrated that this increase in fresh water to the ocean changes circulation patterns and leads to surface cooling.

"With more Arctic sea ice melting, more fresh water flows into the Labrador Sea, which leads to a reduction in deep convection," said Gervais who also is an Institute for CyberScience co-hire. "That changes the ocean circulation, allowing it to cool in that region south of Greenland."

Floating iceberg in Labrador Sea south of Greenland [Credit: Melissa Gervais/Penn State]

This cooling pattern, relative to global average SST increase, is predicted to become greater and more apparent relative to the internal ocean variability as the 21st century progresses.

"These changes in SST patterns occur as the result of changes in ocean circulation and could have a significant impact on atmospheric circulation and the North Atlantic storm track in the future," said Gervais.

Jet streams, high altitude currents of wind flowing above the Earth, transport air masses and drive weather patterns. The relationship between climate change and jet streams is complex and understanding the potential impact of climate change on jet streams is crucial for understanding changes in weather patterns and storm tracks.

"With climate change we have some ideas about how the jets are going to change. In general, we expect to see a poleward shift and eastward elongation of the jet," said Gervais. "Right now, it's sort of a tug of war between impacts of the tropics and impacts of the arctic. So those two things are competing to shift where the jet is located."

Most climate models seem to agree that the Pacific jet stream is going to shift poleward but there is a lot of variability in predictions for the Atlantic, said Gervais.

The Greenland coast taken from the Knorr WHOI research vessel [Credit: Melissa Gervais/Penn State]

To investigate how the development of the NAWH impacts the jet stream, the team conducted a series of large-ensemble, atmospheric model experiments in the CESM with prescribed SST and sea ice levels over three different time periods.

"We ran three simulations," said Gervais. "One with current warming-hole conditions; one where the ocean temperature was increased to fill in the warming hole; and one where its size was twice as deep, to simulate more freshwater from melting ice sheets."

Their results indicate that the NAWH plays an important role in midlatitude atmospheric circulation changes in the model's future climate simulations.

"We found that it's really quite important for that region," said Gervais. "The NAWH seems to be elongating the jet even further and shifting it a little bit north. Instead of just thinking about how the tropics and arctic amplification are influencing the jet, we now also need to think about how this warming hole is going to influence the jet. These local changes in the North Atlantic jet are of a similar magnitude to the full climate-change response in the region, indicating that the North Atlantic warming hole could be an important additional factor in the tug of war on midlatitude circulation, that has received little attention."

The researchers published their findings in the Journal of Climate.

Source: Pennsylvania State University [April 15, 2019]