melting ice sheet

The [thing] that I’m concerned about for Greenland is the black carbon. And when black carbon deposits on ice — something that’s very dark in color on something that’s very white — that then speeds up the melting of the Greenland ice sheet.

Jessica McCarty, an assistant professor of geography at Miami University in Ohio

Greenland Is Still Burning, But The Smoke May Be The Real Problem
Which cities will flood as ice melts?
A forecasting tool reveals which cities will be affected as different portions of the ice sheet melt, say scientists.

A forecasting tool reveals which cities will be affected as different portions of the ice sheet melt, say scientists.

It looks at the Earth’s spin and gravitational effects to predict how water will be “redistributed” globally.


When UN climate negotiators meet for summit talks this month, there will be a new figure on the table: 3C. Until now, global efforts such as the Paris climate agreement have tried to limit global warming to 2C above pre-industrial levels. However, with latest projections pointing to an increase of 3.2C by 2100, these goals seem to be slipping out of reach.

One of the biggest resulting threats to cities around the world is sea-level rise, caused by the expansion of water at higher temperatures and melting ice sheets on the north and south poles. Scientists at the non-profit organisation Climate Central estimate that 275 million people worldwide live in areas that will eventually be flooded at 3C of global warming.

The regional impact of these changes is highly uneven, with four out of five people affected living in Asia. Here are some the most vulnerable global cities in terms of the number of residents like to be flooded:

  • Shanghai, China:  17.5 million people to be flooded
  • Osaka, Japan: 5.2 million people affected

  • Alexandria, Egypt: 3 million people to be flooded

  • Miami, US:  2.7 million people to be flooded

  • Rio de Janeiro, Brazil:  1.8 million people to be flooded

Source:  The Guardian (3 November 2017)

The most recent report from the United Nations sponsored gathering of scientists known as the Intergovernmental Panel on Climate Change was released on the 27th of September 2013. Over 800 reviewers participated in its publication. Here’s a short summary of its major conclusions: Humans are responsible:

This won’t come as a shock to most people, but the IPCC have increased their level of certainty that the rise in global temperatures during the last half century is the result of anthropogenic processes. The confidence level has risen from 90% in 2007, to 95% now.

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Jeff Goodell, The Doomsday Glacier
In the farthest reaches of Antarctica, a nightmare scenario of crumbling ice – and rapidly rising seas – could spell disaster for a warming planet.

This is terrifying.

A few years ago, James Hansen, the godfather of global-warming science, told me that he believed the IPCC estimates were far too conservative and that the waters could rise as much as 10 feet by 2100. For Hansen, the past is prologue. Three million years ago, during the Pliocene Epoch, when the level of CO2 in the atmosphere was about the same as it is today, and temperatures were only slightly warmer, the seas were at least 20 feet higher. That suggests there is a lot of melting to come before the ice sheets reach a happy equilibrium. Mountain glaciers could contribute a little bit, as would the thermal expansion of the oceans as they warmed, but to get to more than 20 feet of sea-level rise, Greenland and Antarctica would both have to contribute in a big way.


But in recent years, things have gotten weird in Antarctica. The first alarming event was the sudden collapse, in 2002, of the Larsen B ice shelf, a vast chunk of ice on the Antarctic Peninsula. An ice shelf is like an enormous fingernail that grows off the end of a glacier where it meets the water. The glaciers behind the Larsen B, like many glaciers in both Antarctica and Greenland, are known as “marine-terminating glaciers,” because large portions of them lie below sea level. The collapse of ice shelves does not in itself contribute to sea-level rise, since they are already floating (just like ice melting in a glass doesn’t raise the level of liquid). But they perform an important role in buttressing, or restraining, the glaciers. After the Larsen B ice shelf vanished, the glaciers that had been behind it started flowing into the sea up to eight times faster than they had before. “It was like, ‘Oh, what is going on here?' ” says Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colorado. “It turns out glaciers are much more responsive than anyone thought.”


One day, Alley was thinking about a problem that Dave Pollard, a colleague at Penn State, and Rob DeConto, a climate scientist at the University of Massachusetts, Amherst, had been having with their climate model. DeConto and Pollard had been collaborating for years to develop a sophisticated model to help them understand the impact of warming from fossil-fuel pollution on Greenland and Antarctica. Climate models are computer programs that try to capture fundamental physics of the natural world, such as, if the temperature warms one degree, how much will the seas around the world rise? It is not a simple question, and requires calculating everything from changes in how much sunlight the ice reflects to how much one degree of heat causes the Atlantic Ocean to expand. Models have gotten a lot better in the past few decades, but they still can’t simulate all the processes in the real world.

One way that scientists test how well a model might predict the future is by seeing how well it recreates the past. If you can run a model backward and it gets things right, then you can run it forward and trust that the results might be accurate. For years, DeConto and Pollard have been trying to get their model to re-create the Pliocene, the era 3 million years ago when the CO2 levels in the atmosphere were very close to what they are today, except the seas were 20 feet higher. But no matter what knobs they turned, they couldn’t get their model to melt the ice sheets fast enough to replicate what the geological record told them had happened. “We knew something was missing from the dynamics of our model,” DeConto tells me.

Alley suggested they plug in his new understanding of ice physics, including the structural integrity of the ice itself (or lack thereof), and “see what happens.” They did, and lo, their model worked. They were able to get the Pliocene melt just about right. In effect, they found the missing mechanism. Their model was now road-tested for accuracy.

The next thing that DeConto and Pollard did, of course, was run the model forward. What they found was that, in high-emissions scenarios – that is, the track we are on today – instead of virtually zero contribution to sea-level rise from Antarctica by 2100, they got more than three feet, most of it from West Antarctica. If you add in a fairly conservative estimate of the contribution to sea-level rise from Greenland in the same time frame, as well as expansion of the oceans, you get more than six feet – that’s double the high-end IPCC scenario.

For anyone living in Miami Beach or Brooklyn or Boston’s Back Bay or any other low-lying coastal neighborhood, the difference between three feet of sea-level rise by 2100 and six feet is the difference between a wet but livable city and a submerged city – billions of dollars worth of coastal real estate, not to mention the lives of the 145 million people who live less than three feet above sea level, many of them in poor nations like Bangladesh and Indonesia. The difference between three feet and six feet is the difference between a manageable coastal evacuation and a decades-long refugee disaster. For many Pacific island nations, it is the difference between survival and extinction.


In any case, the threat is clear. In a rational world, awareness of these risks would lead to deep and rapid cuts in carbon pollution to slow the warming, as well as investment in more research in West Antarctica to get a clearer understanding of what is going on. Instead, Americans elected a president who thinks climate change is a hoax, who is hellbent on burning more fossil fuels, who installs the CEO of the world’s largest oil company as secretary of state, who wants to slash climate-science funding and instead spend nearly $70 billion to build a wall at the Mexican border and another $54 billion to beef up the military.


In the end, no one can say exactly how much longer the West Antarctica glaciers will remain stable. “We just don’t know what the upper boundary is for how fast this can happen,” Alley says, sounding a bit spooked. “We are dealing with an event that no human has ever witnessed before. We have no analogue for this.” But it is clear that thanks to our 200-year-long fossil-fuel binge, the collapse of West Antarctica is already underway, and every Miami Beach condo owner and Bangladeshi farmer is living at the mercy of ice physics right now. Alley himself would never put it this way, but in West Antarctica, scientists have discovered the engine of catastrophe.
In Greenland, a once doubtful scientist witnesses climate change's troubling toll
Petermann glacier has lost huge ice islands since 2010, and Andreas Muenchow thinks another break is coming.

Half a decade before he took this trip to the farthest reaches of the north, Andreas Muenchow had his doubts about whether warming temperatures were causing one of the world’s great platforms of ice to melt and fall apart.

He even stood before Congress in 2010 and balked on whether climate change might have caused a mammoth chunk of ice, four times the size of Manhattan, to break off from this floating, 300-square-mile shelf. The University of Delaware oceanographer said he wasn’t sure. He needed more evidence.

But then the Petermann Ice Shelf lost another two Manhattans of ice in 2012, and Muenchow decided to see for himself, launching a project to study the ice shelf intensively.

He was back again in late August, no longer a skeptic. It was hard not to be a believer here at 81 degrees north latitude, where Greenland and Canada very nearly touch. The surface of the bumpy and misshapen ice was covered with pools and puddles, in some cases frozen over but with piercing blue water beneath. Streams carved through the vast shelf, swelling into larger ponds or even small lakes.

Continue Reading.

As the globe continues to warm, the ice sheets — particularly over Greenland — will continue to melt. But the rate of melting, the consequences of the melt and the impacts that various processes will have are not only uncertain, they’re unprecedented. If the entire Greenland ice sheet melts, the sea level will rise by approximately 8 meters (26 feet), submerging huge amounts of coastal and low-lying areas around the world, including the majority of the state of Florida. Melting, sliding, percolation and runoff are all sources of uncertainty, and its a combination of modeling and monitoring that’s necessary to understand what’s happening.
—  Ethan Siegel at Medium. The First Climate Model Turns 50, And Predicted Global Warming Almost Perfectly
For those who still don’t believe in global warming, the science has had it right for half a century now.

Research shows ice sheets as large as Greenland’s melted fast in a warming climate

New research published in Science shows that climate warming reduced the mass of the Cordilleran Ice Sheet by half in as little as 500 years, indicating the Greenland Ice Sheet could have a similar fate.

The Cordilleran Ice Sheet covered large parts of North America during the Pleistocene - or Last Ice Age - and was similar in mass to the Greenland Ice Sheet. Previous research estimated that it covered much of western Canada as late as 12,500 years ago, but new data shows that large areas in the region were ice-free as early as 1,500 years earlier. This confirms that once ice sheets start to melt, they can do so very quickly.

The melting of the Cordilleran Ice Sheet likely caused about 20 feet of sea level rise and big changes in ocean temperature and circulation. Because cold water is denser than warm water, the water contained by ice sheets sinks when it melts, disrupting the “global conveyor belt” of ocean circulation and changing climate.

Researchers used geologic evidence and ice sheet models to construct a timeline of the Cordilleran’s advance and retreat. They mapped and dated moraines throughout western Canada using beryllium-10, a rare isotope of beryllium that is often used as a proxy for solar intensity. Measurements were made in Purdue University’s PRIME Lab, a research facility dedicated to accelerator mass spectrometry.

“We have one group of beryllium-10 measurements, which is 14,000 years old, and another group, which is 11,500 years old, and the difference in these ages is statistically significant,” said Marc Caffee, a professor of physics in Purdue’s College of Science and director of PRIME Lab. “The only way this would happen is if the ice in that area had completely gone away and then advanced.”

Around 14,000 years ago the Earth started warming, and the effects were significant - ice completely left the tops of the mountains in western Canada, and where there were ice sheets, they probably thinned a lot. About a thousand years later, the climate cooled again, and glaciers started to advance, then retreated as conditions warmed at the onset of the Holocene. If the Cordilleran Ice Sheet had still been there when the climate started cooling during a period known as the Younger Dryas, cirque and valley glaciers wouldn’t have advanced during that time. This indicates a rapid disappearance rather than a gradual melting of the ice sheet.

Reconstructing precise chronologies of past climate helps researchers establish cause and effect. Some have wondered whether the melting of the Cordilleran Ice Sheet caused the Younger Dryras cooling, but it’s unlikely; the cooling started too early for that to be true, according to the study. What caused the cooling is still up for debate.

Creating a timeline of glacial retreat also provides insight into how the first people got to North America. Current estimates place human migration to the south of the Cordilleran and Laurentide Ice Sheets between 14,600 and 18,000 years ago, but how they got there isn’t clear. Some say humans could have crossed through an opening between the ice sheets, but these new findings show that passage was likely closed until 13,400 years ago.

This paper should serve as motivation for further studies, said Caffee. Continental ice sheets don’t disappear in a simple, monolithic way - it’s an extremely complicated process. The more we know about the retreat of the Cordilleran Ice Sheet, the better we’ll be able to predict what’s to come for the Greenland Ice Sheet.

IMAGE….Unvegetated terminal moraine from Nahanni National Park, NWT, Canada dating to the end of the last ice age (about 13,800 years ago).
Photo by Brian Menounos, University of Northern British Columbia

Earth Expeditions Preview

A Closer Look at Our Home Planet

Our view from space shows our planet is changing, but to really understand the details of these changes and what they mean for our future, scientists need a closer look. Over the next six months, we’re taking you on a world tour as we kick off major new field research campaigns to study regions of critical change from land, sea and air.

You can follow the Earth Expeditions on Facebook, Twitter and their Blog.

Take a look at the eight campaigns we will explore:

CORAL (Coral Reef Airborne Laboratory)

This three-year CORAL mission will use advanced airborne instruments and in-water measurements to survey a portion of the world’s coral reefs. The mission will assess the conditions of these threatened ecosystems to better understand their relation to the environment, including physical, chemical and human factors. With a new understanding of reef condition, the future of this global ecosystem can be predicted.

OMG (Oceans Melting Greenland)

Oceans Melting Greenland (OMG) mission will pave the way for improved estimates of sea level rise by addressing the question: To what extent are the oceans melting Greenland’s ice from below? This mission will observe changing water temperatures and glaciers that reach the ocean around all of Greenland from 2015 to 2020. This year, the OMG mission will fly over the periphery of Greenland to take measurements of the heights and extents of Greenland’s coastal glaciers that reach the ocean and release expendable sensors to measure the temperature and salinity of coastal waters. The OMG field campaign will gather data that will help scientists both understand how the oceans are joining with the atmosphere in melting the vast ice sheet and to predict the extent and timing of the resulting sea level rise.

NAAMES (North Atlantic Aerosols and Marine Ecosystems Study)

About half the carbon dioxide emitted into Earth’s atmosphere each year ends up in the ocean, and plankton absorb a lot of it. The NAAMES mission studies the world’s largest plankton bloom and how it gives rise to small organic particles that leave the ocean and end up in the atmosphere, ultimately influencing clouds and climate. This mission will be taking measurements from both ship and aircraft in the North Atlantic. 

KORUS-AQ (Korea U.S.-Air Quality)

Air quality is a significant environmental concern around the world. Scientists are developing new ways to untangle the different factors that contribute to poor air quality. KORUS-AQ is a joint field study between NASA and the Republic of Korea to advance the ability to monitor air pollution from space. The campaign will assess air quality across urban, rural and coastal South Korea using observations from aircraft, ground sites, ships and satellites to test air quality models and remote sensing methods. Findings from this study will help develop observing systems using models and data to improve air quality assessments for decision makers.

ABoVE (Arctic Boreal Vulnerability Experiment)

The ABoVE mission covers 2.5 million square miles of tundra, forests, permafrost and lakes in Alaska and Northwestern Canada. Scientists from the mission are using satellites and aircraft to study this formidable terrain as it changes in a warming climate. Teams of researchers will also go out into the field to gather additional data. The mission will investigate questions about the role of climate in wildfires, thawing permafrost, wildlife migration habits, insect outbreaks and more.

ATom (Atmospheric Tomography)

The ATom mission takes flight through Earth’s atmosphere to understand how short-lived greenhouse gases like ozone and methane contribute to climate change. In late July through August 2016, a suite of instruments aboard our DC-8 flying laboratory will be hopping down the Pacific Ocean from Alaska to the southern tip of South America. It will then travel north up the Atlantic to Greenland to measure more than 200 gases and particles in the air and their interactions all around the world.

ORACLES (Observations of Clouds above Aerosols and their Interactions)

Southern Africa produces almost a third of the world’s vegetative burning, which sends smoke particles up into the atmosphere, where they eventually mix with stratocumulus clouds over the southeastern Atlantic Ocean. Little is known about how these particles impact the clouds, which play a key role in both regional and global surface temperatures and precipitation. The ORACLES mission is a five-year ground and air campaign aimed at better understanding their interactions and improve on current climate models.

ACT-America (Atmospheric Carbon and Transport – America)

The ACT-America mission will conduct five airborne campaigns across three regions in the eastern United States to study the transport of atmospheric carbon. This region serves as an ideal study area for its productive biosphere, agricultural activity, gas and oil extraction and consumption, dynamic seasonally varying weather patterns and the most extensive carbon cycle and meteorological observing networks on Earth. Using space borne, airborne and ground-based measurements, this mission will enable more accurate and precise estimates for climate management and prediction by studying sources and sinks of greenhouse gases, which act as a thermal blanket for Earth.

Remember to follow the Earth Expeditions on Facebook, Twitter and their Blog.

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Drone Glider Finds Swirling Undersea Storms That Help Melt Ice Sheets

Using the undersea gliders above, scientists have uncovered swirling submarine storms that move hot and cold water around near Antarctic ice sheets.

Setting the six-foot-long properless vehicles loose in the Weddell Sea west of Antarctica, an international team of researchers hoped to collect data about how much these submarine eddies impact polar ice melt.

The gliders move down through the water column by pumping water in; they rise back toward the surface by pumping water out. Using this simple principle, they dive up to 3,280 feet below the ocean’s surface to collect temperature, salinity, pressure and oxygen readings at different depths. When the vehicle surfaces periodically through its two-month cruise, it transmits the data it has collected back to the mother ship.

Using this information, the scientists learned that giant invisible eddies spinning off of currents swirl the ocean’s water around, transporting warmer water at lower depths toward the ice.

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** Synopsis: Research by planetary scientists at Brown University finds that periodic melting of ice sheets on a cold early Mars would have created enough water to carve the ancient valleys and lakebeds seen on the planet today. **

For scientists trying to understand what ancient Mars might have been like, the red planet sends some mixed signals. Water-carved valleys and lakebeds leave little doubt that water once flowed on the surface. But climate models for early Mars suggest average temperatures around the globe stayed well below freezing.

A recent study led by Brown University geologists offers a potential bridge between the “warm and wet” story told by Martian geology and the “cold and icy” past suggested by atmospheric models. The study shows that it’s plausible, even if Mars was generally frozen over, that peak daily temperatures in summer might sneak above freezing just enough to cause melting at the edges of glaciers. That meltwater, produced in relatively small amounts year after year, could have been enough to carve the features observed on the planet today, the researchers conclude.

The study is published online in the journal Icarus. Ashley Palumbo, a Ph.D. student at Brown, led the work with Jim Head, a professor in Brown’s Department of Earth, Environmental and Planetary Science, and Robin Wordsworth, a professor in Harvard’s School of Engineering and Applied Sciences.

Palumbo says the research was inspired by climate dynamics found here on Earth.

“We see this in the Antarctic Dry Valleys, where seasonal temperature variation is sufficient to form and sustain lakes even though mean annual temperature is well below freezing,” Palumbo said. “We wanted to see if something similar might be possible for ancient Mars.”

The researchers started with a state-of-the-art climate model for Mars – one that assumes an ancient atmosphere composed largely of carbon dioxide (as it is today). The model generally produces a cold and icy early Mars, partly because the Sun’s energy output is thought to have been much weaker early in solar system history. The researchers ran the model for a broad parameter space for variables that may have been important around 4 billion years ago when the iconic valley networks on the planet’s southern highlands were formed.

While scientists generally agree that the Martian atmosphere was thicker in the past, it’s not clear just how thick it actually was. Likewise, while most researchers agree that the atmosphere was mostly carbon dioxide, there may have been small amounts of other greenhouse gases present. So Palumbo and her colleagues ran the model with various plausible atmospheric thicknesses and extra amounts of greenhouse warming.

It’s also not known exactly what the variations in Mars’ orbit might have been like 4 billion years ago, so the researchers tested a range of plausible orbital scenarios. They tested different degrees of axis tilt, which influences how much sunlight the planet’s upper and lower latitudes receive, as well as different degrees of eccentricity – the extent to which the planet’s orbit around the Sun deviates from a circle, which can amplify seasonal temperature changes.

The model produced scenarios in which ice covered the region near the location of the valley networks. And while the planet’s mean annual temperature in those scenarios stayed well below freezing, the model produced peak summertime temperatures in the southern highlands that rose above freezing.

In order for this mechanism to possibly explain the valley networks, it must produce the correct volume of water in the time duration of valley network formation, and the water must run off on the surface at rates comparable to those required for valley network incision. A few years ago, Head and Eliot Rosenberg, an undergraduate at Brown at the time who has since graduated, published an estimate of the minimum amount of water required to carve the largest of the valleys.

Using that as a guide, along with estimates of necessary runoff rates and the duration of valley network formation from other studies, Palumbo showed that model runs in which the Martian orbit was highly eccentric did indeed meet these criteria. That degree of eccentricity required is well within the range of possible orbits for Mars 4 billion years ago, Palumbo says.

Taken together, Palumbo says, the results offer a potential means of reconciling the geological evidence for flowing water on early Mars with the atmospheric evidence for a cold and icy planet.

“This work adds a plausible hypothesis to explain the way in which liquid water could have formed on early Mars, in a manner similar to the seasonal melting that produces the streams and lakes we observe during our field work in the Antarctic McMurdo Dry Valleys,” Head said. “We are currently exploring additional candidate warming mechanisms, including volcanism and impact cratering, that might also contribute to melting of a cold and icy early Mars.”

So while the work doesn’t close the “cold and icy” versus “warm and wet” debate, it does make the case that a mostly frozen early Mars was a distinct possibility.

IMAGE….Extensive valley networks spidering through the southern highlands of Mars suggest that the planet was once warmer and wetter, but new research shows that water could still have flowed intermittently on a cold and icy early Mars.NASA/JPL-Caltech/Arizona State University

Iceland volcanoes may erupt more with global warming

We just posted on the pulses of volcanism that result from the cycle between glacial and interglacial eras caused by the redistribution of the weight of water between land and ocean as sea levels and ice sheets wax and wane in inverse proportion (see These changes are linked to wobbles in the planet’s orbit around the sun and their effects on climate and sedimentation patterns (for a clear explanation of these wobbles, see our past post on astronomical rocks at Evidence recently obtained using GPS receivers placed around Iceland has provided us with a wonderful example of the phenomenon.

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I should add that the inevitable West Antarctic Ice Sheet melt and sea level rise reported this week is just one of the many likely, if not nearly certain effects of our warming planet and changing climate, including generally warmer oceans, numerous other melts and subsequent sea level rises, increasingly powerful coastal storms and deadly flooding, inland droughts, shifting of arable farmland, numerous extinctions, coral reef die-offs and the subsequent disruption of ecosystems and food webs.

The ice sheet and sea level rise are just the most obvious and most inevitable change yet. It shines a light on how far past the point of no return we are for some of this stuff. Not all of it, but some of it. Naturally, that sounds scary, as it should, because it IS scary. 

In no way is it the only climate issue we should pay attention to. But I’d just be happy if everyone would actually pay attention.

It’s All Over: Melting of Western Antarctic Ice Sheet Unstoppable, NASA Says

For the past few years climate scientists have been warning that Earth is nearing a tipping point, a juncture after which damage is irreversible and there’s no turning back. Two scientific teams have found that this is now happening in a section of the Western Antarctic ice sheet in a melt that can raise sea level by 10 feet or more, making many coastal cities uninhabitable within just a few hundred years.

Great Lakes, North America

Three of North America’s five Great Lakes are pictured in this Envisat image: Lake Huron (left), Lake Ontario (right) and lake Erie (bottom).

About 100 000 years ago, a major ice sheet formed over most of Canada and part of the US. As the ice sheet formed, giant glaciers flowed into the land carving out valleys and levelling mountains.

Some 14 000 years ago, higher temperatures began to melt the ice sheet, and meltwater filled the small and large holes left by the glaciers. Many of these holes today still contain water and form the thousands of lakes of the central USA and Canada. The biggest remnants of this process are the Great Lakes.

Covering an area of over 244 000 sq km and containing about 22 600 cubic km of water, together the Great Lakes form the largest connected area of fresh, surface water on Earth. The only place where more fresh water is contained is in the polar ice caps.

They have played an important role in North America’s economic development by providing a transportation system between the agricultural and mining regions on the western shores with the market centres on the East Coast. The ability to ship materials such as coal, iron and ore also gave rise to the steel and automobile industries in the area. Detroit – nicknamed ‘Motor City’ – is located on the Detroit River (lower left).

This image was acquired on 6 March 2010. Snow cover is evident across the land, and we can see ice build-up along some of the lakes’ edges.

A green algal bloom is also visible in Lake Erie. These toxic blooms have been a problem for the lake in recent years. Caused by heightened levels of phosphorus – found in fertilisers and common household products – finding its way into the water, these blooms have increased the size of the lake’s low-oxygen ‘dead zone’.

Image credit: ESA