Study hints that ancient Earth made its own water — geologically

A new study is helping to answer a longstanding question that has recently moved to the forefront of earth science: Did our planet make its own water through geologic processes, or did water come to us via icy comets from the far reaches of the solar system?

The answer is likely “both,” according to researchers at The Ohio State University– and the same amount of water that currently fills the Pacific Ocean could be buried deep inside the planet right now.

At the American Geophysical Union (AGU) meeting on Wednesday, Dec. 17, they report the discovery of a previously unknown geochemical pathway by which the Earth can sequester water in its interior for billions of years and still release small amounts to the surface via plate tectonics, feeding our oceans from within.

In trying to understand the formation of the early Earth, some researchers have suggested that the planet was dry and inhospitable to life until icy comets pelted the earth and deposited water on the surface.

Wendy Panero, associate professor of earth sciences at Ohio State, and doctoral student Jeff Pigott are pursuing a different hypothesis: that Earth was formed with entire oceans of water in its interior, and has been continuously supplying water to the surface via plate tectonics ever since.

Researchers have long accepted that the mantle contains some water, but how much water is a mystery. And, if some geological mechanism has been supplying water to the surface all this time, wouldn’t the mantle have run out of water by now?

Because there’s no way to directly study deep mantle rocks, Panero and Pigott are probing the question with high-pressure physics experiments and computer calculations.

“When we look into the origins of water on Earth, what we’re really asking is, why are we so different than all the other planets?” Panero said. “In this solar system, Earth is unique because we have liquid water on the surface. We’re also the only planet with active plate tectonics. Maybe this water in the mantle is key to plate tectonics, and that’s part of what makes Earth habitable.”

Central to the study is the idea that rocks that appear dry to the human eye can actually contain water–in the form of hydrogen atoms trapped inside natural voids and crystal defects. Oxygen is plentiful in minerals, so when a mineral contains some hydrogen, certain chemical reactions can free the hydrogen to bond with the oxygen and make water.

Stray atoms of hydrogen could make up only a tiny fraction of mantle rock, the researchers explained. Given that the mantle is more than 80 percent of the planet’s total volume, however, those stray atoms add up to a lot of potential water.

In a lab at Ohio State, the researchers compress different minerals that are common to the mantle and subject them to high pressures and temperatures using a diamond anvil cell–a device that squeezes a tiny sample of material between two diamonds and heats it with a laser–to simulate conditions in the deep Earth. They examine how the minerals’ crystal structures change as they are compressed, and use that information to gauge the minerals’ relative capacities for storing hydrogen. Then, they extend their experimental results using computer calculations to uncover the geochemical processes that would enable these minerals to rise through the mantle to the surface–a necessary condition for water to escape into the oceans.

In a paper now submitted to a peer-reviewed academic journal, they reported their recent tests of the mineral bridgmanite, a high-pressure form of olivine. While bridgmanite is the most abundant mineral in the lower mantle, they found that it contains too little hydrogen to play an important role in Earth’s water supply.

Another research group recently found that ringwoodite, another form of olivine, does contain enough hydrogen to make it a good candidate for deep-earth water storage. So Panero and Pigott focused their study on the depth where ringwoodite is found–a place 325-500 miles below the surface that researchers call the “transition zone”–as the most likely region that can hold a planet’s worth of water. From there, the same convection of mantle rock that produces plate tectonics could carry the water to the surface.

One problem: If all the water in ringwoodite is continually drained to the surface via plate tectonics, how could the planet hold any in reserve?

For the research presented at AGU, Panero and Pigott performed new computer calculations of the geochemistry in the lowest portion of the mantle, some 500 miles deep and more. There, another mineral, garnet, emerged as a likely water-carrier–a go-between that could deliver some of the water from ringwoodite down into the otherwise dry lower mantle.

If this scenario is accurate, the Earth may today hold half as much water in its depths as is currently flowing in oceans on the surface, Panero said–an amount that would approximately equal the volume of the Pacific Ocean. This water is continuously cycled through the transition zone as a result of plate tectonics.

“One way to look at this research is that we’re putting constraints on the amount of water that could be down there,” Pigott added.

Panero called the complex relationship between plate tectonics and surface water “one of the great mysteries in the geosciences.” But this new study supports researchers’ growing suspicion that mantle convection somehow regulates the amount of water in the oceans. It also vastly expands the timeline for Earth’s water cycle.

“If all of the Earth’s water is on the surface, that gives us one interpretation of the water cycle, where we can think of water cycling from oceans into the atmosphere and into the groundwater over millions of years,” she said. “But if mantle circulation is also part of the water cycle, the total cycle time for our planet’s water has to be billions of years.”

Study hints that ancient Earth made its own water — geologically

A new study is helping to answer a longstanding question that has recently moved to the forefront of earth science: Did our planet make its own water through geologic processes, or did water come to us via icy comets from the far reaches of the solar system?

The answer is likely “both,” according to researchers at The Ohio State University– and the same amount of water that currently fills the Pacific Ocean could be buried deep inside the planet right now.

At the American Geophysical Union (AGU) meeting on Wednesday, Dec. 17, they report the discovery of a previously unknown geochemical pathway by which the Earth can sequester water in its interior for billions of years and still release small amounts to the surface via plate tectonics, feeding our oceans from within.

In trying to understand the formation of the early Earth, some researchers have suggested that the planet was dry and inhospitable to life until icy comets pelted the earth and deposited water on the surface.

Wendy Panero, associate professor of earth sciences at Ohio State, and doctoral student Jeff Pigott are pursuing a different hypothesis: that Earth was formed with entire oceans of water in its interior, and has been continuously supplying water to the surface via plate tectonics ever since.

Researchers have long accepted that the mantle contains some water, but how much water is a mystery. And, if some geological mechanism has been supplying water to the surface all this time, wouldn’t the mantle have run out of water by now?

Because there’s no way to directly study deep mantle rocks, Panero and Pigott are probing the question with high-pressure physics experiments and computer calculations.

“When we look into the origins of water on Earth, what we’re really asking is, why are we so different than all the other planets?” Panero said. “In this solar system, Earth is unique because we have liquid water on the surface. We’re also the only planet with active plate tectonics. Maybe this water in the mantle is key to plate tectonics, and that’s part of what makes Earth habitable.”

Central to the study is the idea that rocks that appear dry to the human eye can actually contain water–in the form of hydrogen atoms trapped inside natural voids and crystal defects. Oxygen is plentiful in minerals, so when a mineral contains some hydrogen, certain chemical reactions can free the hydrogen to bond with the oxygen and make water.

Stray atoms of hydrogen could make up only a tiny fraction of mantle rock, the researchers explained. Given that the mantle is more than 80 percent of the planet’s total volume, however, those stray atoms add up to a lot of potential water.

In a lab at Ohio State, the researchers compress different minerals that are common to the mantle and subject them to high pressures and temperatures using a diamond anvil cell–a device that squeezes a tiny sample of material between two diamonds and heats it with a laser–to simulate conditions in the deep Earth. They examine how the minerals’ crystal structures change as they are compressed, and use that information to gauge the minerals’ relative capacities for storing hydrogen. Then, they extend their experimental results using computer calculations to uncover the geochemical processes that would enable these minerals to rise through the mantle to the surface–a necessary condition for water to escape into the oceans.

In a paper now submitted to a peer-reviewed academic journal, they reported their recent tests of the mineral bridgmanite, a high-pressure form of olivine. While bridgmanite is the most abundant mineral in the lower mantle, they found that it contains too little hydrogen to play an important role in Earth’s water supply.

Another research group recently found that ringwoodite, another form of olivine, does contain enough hydrogen to make it a good candidate for deep-earth water storage. So Panero and Pigott focused their study on the depth where ringwoodite is found–a place 325-500 miles below the surface that researchers call the “transition zone”–as the most likely region that can hold a planet’s worth of water. From there, the same convection of mantle rock that produces plate tectonics could carry the water to the surface.

One problem: If all the water in ringwoodite is continually drained to the surface via plate tectonics, how could the planet hold any in reserve?

For the research presented at AGU, Panero and Pigott performed new computer calculations of the geochemistry in the lowest portion of the mantle, some 500 miles deep and more. There, another mineral, garnet, emerged as a likely water-carrier–a go-between that could deliver some of the water from ringwoodite down into the otherwise dry lower mantle.

If this scenario is accurate, the Earth may today hold half as much water in its depths as is currently flowing in oceans on the surface, Panero said–an amount that would approximately equal the volume of the Pacific Ocean. This water is continuously cycled through the transition zone as a result of plate tectonics.

“One way to look at this research is that we’re putting constraints on the amount of water that could be down there,” Pigott added.

Panero called the complex relationship between plate tectonics and surface water “one of the great mysteries in the geosciences.” But this new study supports researchers’ growing suspicion that mantle convection somehow regulates the amount of water in the oceans. It also vastly expands the timeline for Earth’s water cycle.

“If all of the Earth’s water is on the surface, that gives us one interpretation of the water cycle, where we can think of water cycling from oceans into the atmosphere and into the groundwater over millions of years,” she said. “But if mantle circulation is also part of the water cycle, the total cycle time for our planet’s water has to be billions of years.”

Hidden movements of Greenland Ice Sheet, runoff revealed

For years NASA has tracked changes in the massive Greenland Ice Sheet. This week scientists using NASA data released the most detailed picture ever of how the ice sheet moves toward the sea and new insights into the hidden plumbing of melt water flowing under the snowy surface.

The results of these studies are expected to improve predictions of the future of the entire Greenland ice sheet and its contribution to sea level rise as researchers revamp their computer models of how the ice sheet reacts to a warming climate.

“With the help of NASA satellite and airborne remote sensing instruments, the Greenland Ice Sheet is finally yielding its secrets,” said Tom Wagner, program scientist for NASA’s cryosphere program in Washington. “These studies represent new leaps in our knowledge of how the ice sheet is losing ice. It turns out the ice sheet is a lot more complex than we ever thought.”

University at Buffalo geophysicist Beata Csatho led an international team that produced the first comprehensive study of how the ice sheet is losing mass based on NASA satellite and airborne data at nearly 100,000 locations across Greenland. The study found that the ice sheet shed about 243 gigatons of ice per year from 2003-09, which agrees with other studies using different techniques. The study was published today in the Proceedings of the National Academy of Sciences.

The study suggests that current ice sheet modeling is too simplistic to accurately predict the future contribution of the Greenland ice sheet to sea level rise, and that current models may underestimate ice loss in the near future.

The project was a massive undertaking, using satellite and aerial data from NASA’s ICESat spacecraft, which measured the elevation of the ice sheet starting in 2003, and the Operation IceBridge field campaign that has flown annually since 2009. Additional airborne data from 1993-2008, collected by NASA’s Program for Arctic Regional Climate Assessment, were also included to extend the timeline of the study.

Current computer simulations of the Greenland Ice Sheet use the activity of four well-studied glaciers — Jakobshavn, Helheim, Kangerlussuaq and Petermann — to forecast how the entire ice sheet will dump ice into the oceans. The new research shows that activity at these four locations may not be representative of what is happening with glaciers across the ice sheet. In fact, glaciers undergo patterns of thinning and thickening that current climate change simulations fail to address, Csatho says.

As a step toward building better models of sea level rise, the research team divided Greenland’s 242 glaciers into 7 major groups based on their behavior from 2003-09.

“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

The team also identified areas of rapid shrinkage in southeast Greenland that today’s models don’t acknowledge. This leads Csatho to believe that the ice sheet could lose ice faster in the future than today’s simulations would suggest.

In separate studies presented today at the American Geophysical Union annual meeting in San Francisco, scientists using data from Operation IceBridge found permanent bodies of liquid water in the porous, partially compacted firn layer just below the surface of the ice sheet. Lora Koenig at the National Snow and Ice Data Center in Boulder, Colorado, and Rick Forster at the University of Utah in Salt Lake City, found signatures of near-surface liquid water using ice-penetrating radar.

Across wide areas of Greenland, water can remain liquid, hiding in layers of snow just below the surface, even through cold, harsh winters, researchers are finding. The discoveries by the teams led by Koenig and Forster mean that scientists seeking to understand the future of the Greenland ice sheet need to account for relatively warm liquid water retained in the ice.

Although the total volume of water is small compared to overall melting in Greenland, the presence of liquid water throughout the year could help kick off melt in the spring and summer. “More year-round water means more heat is available to warm the ice,” Koenig said.

Koenig and her colleagues found that sub-surface liquid water are common on the western edges of the Greenland Ice Sheet. At roughly the same time, Forster used similar ground-based radars to find a large aquifer in southeastern Greenland. These studies show that liquid water can persist near the surface around the perimeter of the ice sheet year round.

Another researcher participating in the briefing found that near-surface layers can also contain masses of solid ice that can lead to flooding events. Michael MacFerrin, a scientist at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, and colleagues studying radar data from IceBridge and surface based instruments found near surface patches of ice known as ice lenses more than 25 miles farther inland than previously recorded.

Ice lenses form when firn collects surface meltwater like a sponge. When this shallow ice melts, as was seen during July 2012, they can release large amounts of water that can lead to flooding. Warm summers and resulting increased surface melt in recent years have likely caused ice lenses to grow thicker and spread farther inland. “This represents a rapid feedback mechanism. If current trends continue, the flooding will get worse,” MacFerrin said.




Video
Click on this image to view the .mp4 video
This animation (from March 2014) portrays the changes occurring in the surface elevation of the Greenland Ice Sheet since 2003 in three drainage areas: the southeast, the northeast and the Jakobshavn regions. In each region, the time advances to show the accumulated change in elevation, 2003-2012.

Downloadable video: http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4022 – NASA SVS NASA’s Goddard Space Flight Center

Hidden movements of Greenland Ice Sheet, runoff revealed

For years NASA has tracked changes in the massive Greenland Ice Sheet. This week scientists using NASA data released the most detailed picture ever of how the ice sheet moves toward the sea and new insights into the hidden plumbing of melt water flowing under the snowy surface.

The results of these studies are expected to improve predictions of the future of the entire Greenland ice sheet and its contribution to sea level rise as researchers revamp their computer models of how the ice sheet reacts to a warming climate.

“With the help of NASA satellite and airborne remote sensing instruments, the Greenland Ice Sheet is finally yielding its secrets,” said Tom Wagner, program scientist for NASA’s cryosphere program in Washington. “These studies represent new leaps in our knowledge of how the ice sheet is losing ice. It turns out the ice sheet is a lot more complex than we ever thought.”

University at Buffalo geophysicist Beata Csatho led an international team that produced the first comprehensive study of how the ice sheet is losing mass based on NASA satellite and airborne data at nearly 100,000 locations across Greenland. The study found that the ice sheet shed about 243 gigatons of ice per year from 2003-09, which agrees with other studies using different techniques. The study was published today in the Proceedings of the National Academy of Sciences.

The study suggests that current ice sheet modeling is too simplistic to accurately predict the future contribution of the Greenland ice sheet to sea level rise, and that current models may underestimate ice loss in the near future.

The project was a massive undertaking, using satellite and aerial data from NASA’s ICESat spacecraft, which measured the elevation of the ice sheet starting in 2003, and the Operation IceBridge field campaign that has flown annually since 2009. Additional airborne data from 1993-2008, collected by NASA’s Program for Arctic Regional Climate Assessment, were also included to extend the timeline of the study.

Current computer simulations of the Greenland Ice Sheet use the activity of four well-studied glaciers — Jakobshavn, Helheim, Kangerlussuaq and Petermann — to forecast how the entire ice sheet will dump ice into the oceans. The new research shows that activity at these four locations may not be representative of what is happening with glaciers across the ice sheet. In fact, glaciers undergo patterns of thinning and thickening that current climate change simulations fail to address, Csatho says.

As a step toward building better models of sea level rise, the research team divided Greenland’s 242 glaciers into 7 major groups based on their behavior from 2003-09.

“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

The team also identified areas of rapid shrinkage in southeast Greenland that today’s models don’t acknowledge. This leads Csatho to believe that the ice sheet could lose ice faster in the future than today’s simulations would suggest.

In separate studies presented today at the American Geophysical Union annual meeting in San Francisco, scientists using data from Operation IceBridge found permanent bodies of liquid water in the porous, partially compacted firn layer just below the surface of the ice sheet. Lora Koenig at the National Snow and Ice Data Center in Boulder, Colorado, and Rick Forster at the University of Utah in Salt Lake City, found signatures of near-surface liquid water using ice-penetrating radar.

Across wide areas of Greenland, water can remain liquid, hiding in layers of snow just below the surface, even through cold, harsh winters, researchers are finding. The discoveries by the teams led by Koenig and Forster mean that scientists seeking to understand the future of the Greenland ice sheet need to account for relatively warm liquid water retained in the ice.

Although the total volume of water is small compared to overall melting in Greenland, the presence of liquid water throughout the year could help kick off melt in the spring and summer. “More year-round water means more heat is available to warm the ice,” Koenig said.

Koenig and her colleagues found that sub-surface liquid water are common on the western edges of the Greenland Ice Sheet. At roughly the same time, Forster used similar ground-based radars to find a large aquifer in southeastern Greenland. These studies show that liquid water can persist near the surface around the perimeter of the ice sheet year round.

Another researcher participating in the briefing found that near-surface layers can also contain masses of solid ice that can lead to flooding events. Michael MacFerrin, a scientist at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, and colleagues studying radar data from IceBridge and surface based instruments found near surface patches of ice known as ice lenses more than 25 miles farther inland than previously recorded.

Ice lenses form when firn collects surface meltwater like a sponge. When this shallow ice melts, as was seen during July 2012, they can release large amounts of water that can lead to flooding. Warm summers and resulting increased surface melt in recent years have likely caused ice lenses to grow thicker and spread farther inland. “This represents a rapid feedback mechanism. If current trends continue, the flooding will get worse,” MacFerrin said.




Video
Click on this image to view the .mp4 video
This animation (from March 2014) portrays the changes occurring in the surface elevation of the Greenland Ice Sheet since 2003 in three drainage areas: the southeast, the northeast and the Jakobshavn regions. In each region, the time advances to show the accumulated change in elevation, 2003-2012.

Downloadable video: http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4022 – NASA SVS NASA’s Goddard Space Flight Center

Massive study provides first detailed look at how Greenland’s ice is vanishing

The surface of the Greenland Ice Sheet. A new study uses NASA data to provide the first detailed reconstruction of how the ice sheet and its many glaciers are changing. The research was led by University at Buffalo geologist Beata Csatho. -  Beata Csatho
The surface of the Greenland Ice Sheet. A new study uses NASA data to provide the first detailed reconstruction of how the ice sheet and its many glaciers are changing. The research was led by University at Buffalo geologist Beata Csatho. – Beata Csatho

The Greenland Ice Sheet is the second-largest body of ice on Earth. It covers an area about five times the size of New York State and Kansas combined, and if it melts completely, oceans could rise by 20 feet. Coastal communities from Florida to Bangladesh would suffer extensive damage.

Now, a new study is revealing just how little we understand this northern behemoth.

Led by geophysicist Beata Csatho, PhD, an associate professor of geology at the University at Buffalo, the research provides what the authors think is the first comprehensive picture of how Greenland’s ice is vanishing. It suggests that current ice sheet modeling studies are too simplistic to accurately predict the future contributions of the entire Greenland Ice Sheet to sea level rise, and that Greenland may lose ice more rapidly in the near future than previously thought.

“The great importance of our data is that for the first time, we have a comprehensive picture of how all of Greenland’s glaciers have changed over the past decade,” Csatho says.

“This information is crucial for developing and validating numerical models that predict how the ice sheet may change and contribute to global sea level over the next few hundred years,” says Cornelis J. van der Veen, PhD, professor in the Department of Geography at the University of Kansas, who played a key role in interpreting glaciological changes.

The project was a massive undertaking, using satellite and aerial data from NASA’s ICESat spacecraft and Operation IceBridge field campaign to reconstruct how the height of the Greenland Ice Sheet changed at nearly 100,000 locations from 1993 to 2012.

Ice loss takes place in a complex manner, with the ice sheet both melting and calving ice into the ocean.
The study had two major findings:

  • First, the scientists were able to provide new estimates of annual ice loss at high spatial resolution (see below).

  • Second, the research revealed that current models fail to accurately capture how the entire Greenland Ice Sheet is changing and contributing to rising oceans.

The second point is crucial to climate change modelers.

Today’s simulations use the activity of four well-studied glaciers — Jakobshavn, Helheim, Kangerlussuaq and Petermann — to forecast how the entire ice sheet will dump ice into the oceans.

But the new research shows that activity at these four locations may not be representative of what is happening with glaciers across the ice sheet. In fact, glaciers undergo patterns of thinning and thickening that current climate change simulations fail to address, Csatho says.

“There are 242 outlet glaciers wider than 1.5 km on the Greenland Ice Sheet, and what we see is that their behavior is complex in space and time,” Csatho says. “The local climate and geological conditions, the local hydrology — all of these factors have an effect. The current models do not address this complexity.”

The team identified areas of rapid shrinkage in southeast Greenland that today’s models don’t acknowledge. This leads Csatho to believe that the ice sheet could lose ice faster in the future than today’s simulations would suggest.

The results will be published on Dec. 15 in the Proceedings of the National Academy of Sciences, and the study and all information in this press release are embargoed until 3 p.m. Eastern Time that day.

Photos, data visualizations and video are available by contacting Charlotte Hsu at the University at Buffalo at chsu22@buffalo.edu.

How much ice is the Greenland Ice Sheet losing?

To analyze how the height of the ice sheet was changing, Csatho and UB research professor and photogrammetrist Anton Schenk, PhD, developed a computational technique called Surface Elevation Reconstruction And Change detection to fuse together data from NASA satellite and aerial missions.

The analysis found that the Greenland Ice Sheet lost about 243 metric gigatons of ice annually — equivalent to about 277 cubic kilometers of ice per year — from 2003-09, the period for which the team had the most comprehensive data. This loss is estimated to have added about 0.68 millimeters of water to the oceans annually.

The figures are averages, and ice loss varied from year to year, and from region to region.

Why are today’s projections of sea level rise flawed, and how can we fix them?

Glaciers don’t just gradually lose mass when the temperature rises. That’s one reason it’s difficult to predict their response to global warming.

In the study, scientists found that some of Greenland’s glaciers thickened even when the temperature rose. Others exhibited accelerated thinning. Some displayed both thinning and thickening, with sudden reversals.

As a step toward building better models of sea level rise, the research team divided Greenland’s 242 glaciers into 7 major groups based on their behavior from 2003-09.

“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

In a new project, she and colleagues are investigating why different glaciers respond differently to warming. Factors could include the temperature of the surrounding ocean; the level of friction between a glacier and the bedrock below; the amount of water under a glacier; and the geometry of the fjord.

“The physics of these processes are not well understood,” Csatho says.

The NASA missions: A colossal undertaking

The study combined data from various NASA missions, including:

  • NASA’s Ice, Cloud and Land Elevation Satellite (ICESat), which measured the ice sheet’s elevation multiple times a year at each of the nearly 100,000 locations from 2003-09.

  • NASA’s, massive aerial survey that employs highly specialized research aircrafts to collect data at less frequent intervals than ICESat. These missions began measuring the Greenland Ice Sheet’s elevation in 1993. Operation IceBridge was started in 2009 to bridge the time between ICESat-1 and ICESat-2, and will continue until at least 2017, when NASA’s next generation ICESat-2 satellite is expected to come online.

Csatho says the new study shows why careful monitoring is critical: Given the complex nature of glacier behavior, good data is crucial to building better models.

Collaborators

Besides Csatho, Schenk and van der Veen, the project included additional researchers from the University at Buffalo, Utrecht University in The Netherlands, the Technical University of Denmark and Florida Atlantic University.

Massive study provides first detailed look at how Greenland’s ice is vanishing

The surface of the Greenland Ice Sheet. A new study uses NASA data to provide the first detailed reconstruction of how the ice sheet and its many glaciers are changing. The research was led by University at Buffalo geologist Beata Csatho. -  Beata Csatho
The surface of the Greenland Ice Sheet. A new study uses NASA data to provide the first detailed reconstruction of how the ice sheet and its many glaciers are changing. The research was led by University at Buffalo geologist Beata Csatho. – Beata Csatho

The Greenland Ice Sheet is the second-largest body of ice on Earth. It covers an area about five times the size of New York State and Kansas combined, and if it melts completely, oceans could rise by 20 feet. Coastal communities from Florida to Bangladesh would suffer extensive damage.

Now, a new study is revealing just how little we understand this northern behemoth.

Led by geophysicist Beata Csatho, PhD, an associate professor of geology at the University at Buffalo, the research provides what the authors think is the first comprehensive picture of how Greenland’s ice is vanishing. It suggests that current ice sheet modeling studies are too simplistic to accurately predict the future contributions of the entire Greenland Ice Sheet to sea level rise, and that Greenland may lose ice more rapidly in the near future than previously thought.

“The great importance of our data is that for the first time, we have a comprehensive picture of how all of Greenland’s glaciers have changed over the past decade,” Csatho says.

“This information is crucial for developing and validating numerical models that predict how the ice sheet may change and contribute to global sea level over the next few hundred years,” says Cornelis J. van der Veen, PhD, professor in the Department of Geography at the University of Kansas, who played a key role in interpreting glaciological changes.

The project was a massive undertaking, using satellite and aerial data from NASA’s ICESat spacecraft and Operation IceBridge field campaign to reconstruct how the height of the Greenland Ice Sheet changed at nearly 100,000 locations from 1993 to 2012.

Ice loss takes place in a complex manner, with the ice sheet both melting and calving ice into the ocean.
The study had two major findings:

  • First, the scientists were able to provide new estimates of annual ice loss at high spatial resolution (see below).

  • Second, the research revealed that current models fail to accurately capture how the entire Greenland Ice Sheet is changing and contributing to rising oceans.

The second point is crucial to climate change modelers.

Today’s simulations use the activity of four well-studied glaciers — Jakobshavn, Helheim, Kangerlussuaq and Petermann — to forecast how the entire ice sheet will dump ice into the oceans.

But the new research shows that activity at these four locations may not be representative of what is happening with glaciers across the ice sheet. In fact, glaciers undergo patterns of thinning and thickening that current climate change simulations fail to address, Csatho says.

“There are 242 outlet glaciers wider than 1.5 km on the Greenland Ice Sheet, and what we see is that their behavior is complex in space and time,” Csatho says. “The local climate and geological conditions, the local hydrology — all of these factors have an effect. The current models do not address this complexity.”

The team identified areas of rapid shrinkage in southeast Greenland that today’s models don’t acknowledge. This leads Csatho to believe that the ice sheet could lose ice faster in the future than today’s simulations would suggest.

The results will be published on Dec. 15 in the Proceedings of the National Academy of Sciences, and the study and all information in this press release are embargoed until 3 p.m. Eastern Time that day.

Photos, data visualizations and video are available by contacting Charlotte Hsu at the University at Buffalo at chsu22@buffalo.edu.

How much ice is the Greenland Ice Sheet losing?

To analyze how the height of the ice sheet was changing, Csatho and UB research professor and photogrammetrist Anton Schenk, PhD, developed a computational technique called Surface Elevation Reconstruction And Change detection to fuse together data from NASA satellite and aerial missions.

The analysis found that the Greenland Ice Sheet lost about 243 metric gigatons of ice annually — equivalent to about 277 cubic kilometers of ice per year — from 2003-09, the period for which the team had the most comprehensive data. This loss is estimated to have added about 0.68 millimeters of water to the oceans annually.

The figures are averages, and ice loss varied from year to year, and from region to region.

Why are today’s projections of sea level rise flawed, and how can we fix them?

Glaciers don’t just gradually lose mass when the temperature rises. That’s one reason it’s difficult to predict their response to global warming.

In the study, scientists found that some of Greenland’s glaciers thickened even when the temperature rose. Others exhibited accelerated thinning. Some displayed both thinning and thickening, with sudden reversals.

As a step toward building better models of sea level rise, the research team divided Greenland’s 242 glaciers into 7 major groups based on their behavior from 2003-09.

“Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

In a new project, she and colleagues are investigating why different glaciers respond differently to warming. Factors could include the temperature of the surrounding ocean; the level of friction between a glacier and the bedrock below; the amount of water under a glacier; and the geometry of the fjord.

“The physics of these processes are not well understood,” Csatho says.

The NASA missions: A colossal undertaking

The study combined data from various NASA missions, including:

  • NASA’s Ice, Cloud and Land Elevation Satellite (ICESat), which measured the ice sheet’s elevation multiple times a year at each of the nearly 100,000 locations from 2003-09.

  • NASA’s, massive aerial survey that employs highly specialized research aircrafts to collect data at less frequent intervals than ICESat. These missions began measuring the Greenland Ice Sheet’s elevation in 1993. Operation IceBridge was started in 2009 to bridge the time between ICESat-1 and ICESat-2, and will continue until at least 2017, when NASA’s next generation ICESat-2 satellite is expected to come online.

Csatho says the new study shows why careful monitoring is critical: Given the complex nature of glacier behavior, good data is crucial to building better models.

Collaborators

Besides Csatho, Schenk and van der Veen, the project included additional researchers from the University at Buffalo, Utrecht University in The Netherlands, the Technical University of Denmark and Florida Atlantic University.

Research links soil mineral surfaces to key atmospheric processes

Pictured are, from left, are David Bish, Melissa Donaldson and Jonathan Raff. -  Indiana University
Pictured are, from left, are David Bish, Melissa Donaldson and Jonathan Raff. – Indiana University

Research by Indiana University scientists finds that soil may be a significant and underappreciated source of nitrous acid, a chemical that plays a pivotal role in atmospheric processes such as the formation of smog and determining the lifetime of greenhouse gases.

The study shows for the first time that the surface acidity of common minerals found in soil determines whether the gas nitrous acid will be released into the atmosphere. The finding could contribute to improved models for understanding and controlling air pollution, a significant public health concern.

“We find that the surfaces of minerals in the soil can be much more acidic than the overall pH of the soil would suggest,” said Jonathan Raff, assistant professor in the School of Public and Environmental Affairs and Department of Chemistry. “It’s the acidity of the soil minerals that acts as a knob or a control lever, and that determines whether nitrous acid outgasses from soil or remains as nitrite.”

The article, “Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid,” will be published this week in the journal Proceedings of the National Academy of Sciences. Melissa A. Donaldson, a Ph.D. student in the School of Public and Environmental Affairs, is the lead author. Co-authors are Raff and David L. Bish, the Haydn Murray Chair of Applied Clay Mineralogy in the Department of Geological Sciences.

Nitrous acid, or HONO, plays a key role in regulating atmospheric processes. Sunlight causes it to break down into nitric oxide and the hydroxyl radical, OH. The latter controls the atmospheric lifetime of gases important to air quality and climate change and initiates the chemistry leading to the formation of ground-level ozone, a primary component of smog.

Scientists have known about the nitrous acid’s role in air pollution for 40 years, but they haven’t fully understood how it is produced and destroyed or how it interacts with other substances, because HONO is unstable and difficult to measure.

“Only in the last 10 years have we had the technology to study nitrous acid under environmentally relevant conditions,” Raff said.

Recent studies have shown nitrous acid to be emitted from soil in many locations. But this was unexpected because, according to basic chemistry, the reactions that release nitrous acid should take place only in extremely acidic soils, typically found in rain forests or the taiga of North America and Eurasia.

The standard method to determine the acidity of soil is to mix bulk soil with water and measure the overall pH. But the IU researchers show that the crucial factor is not overall pH but the acidity at the surface of soil minerals, especially iron oxides and aluminum oxides. At the molecular level, the water adsorbed directly to these minerals is unusually acidic and facilitates the conversion of nitrite in the soil to nitrous acid, which then volatilizes.

“With the traditional approach of calculating soil pH, we were severely underestimating nitrous acid emissions from soil,” Raff said. “I think the source is going to turn out to be more important than was previously imagined.”

The research was carried out using soil from a farm field near Columbus, Ind. But aluminum and iron oxides are ubiquitous in soil, and the researchers say the results suggest that about 70 percent of Earth’s soils could be sources of nitrous acid.

Ultimately, the research will contribute to a better understanding of how nitrous acid is produced and how it affects atmospheric processes. That in turn will improve the computer models used by the U.S. Environmental Protection Agency and other regulatory agencies to control air pollution, which the World Health Organization estimates contributes to 7 million premature deaths annually.

“With improved models, policymakers can make better judgments about the costs and benefits of regulations,” Raff said. “If we don’t get the chemistry right, we’re not going to get the right answers to our policy questions regarding air pollution.”

Research links soil mineral surfaces to key atmospheric processes

Pictured are, from left, are David Bish, Melissa Donaldson and Jonathan Raff. -  Indiana University
Pictured are, from left, are David Bish, Melissa Donaldson and Jonathan Raff. – Indiana University

Research by Indiana University scientists finds that soil may be a significant and underappreciated source of nitrous acid, a chemical that plays a pivotal role in atmospheric processes such as the formation of smog and determining the lifetime of greenhouse gases.

The study shows for the first time that the surface acidity of common minerals found in soil determines whether the gas nitrous acid will be released into the atmosphere. The finding could contribute to improved models for understanding and controlling air pollution, a significant public health concern.

“We find that the surfaces of minerals in the soil can be much more acidic than the overall pH of the soil would suggest,” said Jonathan Raff, assistant professor in the School of Public and Environmental Affairs and Department of Chemistry. “It’s the acidity of the soil minerals that acts as a knob or a control lever, and that determines whether nitrous acid outgasses from soil or remains as nitrite.”

The article, “Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid,” will be published this week in the journal Proceedings of the National Academy of Sciences. Melissa A. Donaldson, a Ph.D. student in the School of Public and Environmental Affairs, is the lead author. Co-authors are Raff and David L. Bish, the Haydn Murray Chair of Applied Clay Mineralogy in the Department of Geological Sciences.

Nitrous acid, or HONO, plays a key role in regulating atmospheric processes. Sunlight causes it to break down into nitric oxide and the hydroxyl radical, OH. The latter controls the atmospheric lifetime of gases important to air quality and climate change and initiates the chemistry leading to the formation of ground-level ozone, a primary component of smog.

Scientists have known about the nitrous acid’s role in air pollution for 40 years, but they haven’t fully understood how it is produced and destroyed or how it interacts with other substances, because HONO is unstable and difficult to measure.

“Only in the last 10 years have we had the technology to study nitrous acid under environmentally relevant conditions,” Raff said.

Recent studies have shown nitrous acid to be emitted from soil in many locations. But this was unexpected because, according to basic chemistry, the reactions that release nitrous acid should take place only in extremely acidic soils, typically found in rain forests or the taiga of North America and Eurasia.

The standard method to determine the acidity of soil is to mix bulk soil with water and measure the overall pH. But the IU researchers show that the crucial factor is not overall pH but the acidity at the surface of soil minerals, especially iron oxides and aluminum oxides. At the molecular level, the water adsorbed directly to these minerals is unusually acidic and facilitates the conversion of nitrite in the soil to nitrous acid, which then volatilizes.

“With the traditional approach of calculating soil pH, we were severely underestimating nitrous acid emissions from soil,” Raff said. “I think the source is going to turn out to be more important than was previously imagined.”

The research was carried out using soil from a farm field near Columbus, Ind. But aluminum and iron oxides are ubiquitous in soil, and the researchers say the results suggest that about 70 percent of Earth’s soils could be sources of nitrous acid.

Ultimately, the research will contribute to a better understanding of how nitrous acid is produced and how it affects atmospheric processes. That in turn will improve the computer models used by the U.S. Environmental Protection Agency and other regulatory agencies to control air pollution, which the World Health Organization estimates contributes to 7 million premature deaths annually.

“With improved models, policymakers can make better judgments about the costs and benefits of regulations,” Raff said. “If we don’t get the chemistry right, we’re not going to get the right answers to our policy questions regarding air pollution.”

Migrating ‘supraglacial’ lakes could trigger future Greenland ice loss

Supraglacial lakes on the Greenland ice sheet can be seen as dark blue specks in the center and to the right of this satellite image. -  USGS/NASA Landsat
Supraglacial lakes on the Greenland ice sheet can be seen as dark blue specks in the center and to the right of this satellite image. – USGS/NASA Landsat

Predictions of Greenland ice loss and its impact on rising sea levels may have been greatly underestimated, according to scientists at the University of Leeds.

The finding follows a new study, which is published today in Nature Climate Change, in which the future distribution of lakes that form on the ice sheet surface from melted snow and ice – called supraglacial lakes – have been simulated for the first time.

Previously, the impact of supraglacial lakes on Greenland ice loss had been assumed to be small, but the new research has shown that they will migrate farther inland over the next half century, potentially altering the ice sheet flow in dramatic ways.

Dr Amber Leeson from the School of Earth and Environment and a member of the Centre for Polar Observation and Modelling (CPOM) team, who led the study, said: “Supraglacial lakes can increase the speed at which the ice sheet melts and flows, and our research shows that by 2060 the area of Greenland covered by them will double.”

Supraglacial lakes are darker than ice, so they absorb more of the Sun’s heat, which leads to increased melting. When the lakes reach a critical size, they drain through ice fractures, allowing water to reach the ice sheet base which causes it to slide more quickly into the oceans. These changes can also trigger further melting.

Dr Leeson explained: “When you pour pancake batter into a pan, if it rushes quickly to the edges of the pan, you end up with a thin pancake. It’s similar to what happens with ice sheets: the faster it flows, the thinner it will be.

“When the ice sheet is thinner, it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would have been if it were thicker, increasing the size of the melt zone around the edge of the ice sheet.”

Until now, supraglacial lakes have formed at low elevations around the coastline of Greenland, in a band that is roughly 100 km wide. At higher elevations, today’s climate is just too cold for lakes to form.

In the study, the scientists used observations of the ice sheet from the Environmental Remote Sensing satellites operated by the European Space Agency and estimates of future ice melting drawn from a climate model to drive simulations of how meltwater will flow and pool on the ice surface to form supraglacial lakes.

Since the 1970s, the band in which supraglacial lakes can form on Greenland has crept 56km further inland. From the results of the new study, the researchers predict that, as Arctic temperatures rise, supraglacial lakes will spread much farther inland – up to 110 km by 2060 – doubling the area of Greenland that they cover today.

Dr Leeson said: “The location of these new lakes is important; they will be far enough inland so that water leaking from them will not drain into the oceans as effectively as it does from today’s lakes that are near to the coastline and connected to a network of drainage channels.”

“In contrast, water draining from lakes farther inland could lubricate the ice more effectively, causing it to speed up.”

Ice losses from Greenland had been expected to contribute 22cm to global sea-level rise by 2100. However, the models used to make this projection did not account for changes in the distribution of supraglacial lakes, which Dr Leeson’s study reveals will be considerable.

If new lakes trigger further increases in ice melting and flow, then Greenland’s future ice losses and its contribution to global sea-level rise have been underestimated.

The Director of CPOM, Professor Andrew Shepherd, who is also from the School of Earth and Environment at the University of Leeds and is a co-author of the study, said: “Because ice losses from Greenland are a key signal of global climate change, it’s important that we consider all factors that could affect the rate at which it will lose ice as climate warms.

“Our findings will help to improve the next generation of ice sheet models, so that we can have greater confidence in projections of future sea-level rise. In the meantime, we will continue to monitor changes in the ice sheet losses using satellite measurements.”

Further information:


The study was funded by the Natural Environment Research Council (NERC) through their support of the Centre for Polar Observation and Modelling and the National Centre for Earth Observation.

The research paper, Supraglacial lakes on the Greenland ice sheet advance inland under warming climate, is published in Nature Climate Change on 15 December 2014.

Dr Amber Leeson and Professor Andrew Shepherd are available for interview. Please contact the University of Leeds Press Office on 0113 343 4031 or email pressoffice@leeds.ac.uk

Migrating ‘supraglacial’ lakes could trigger future Greenland ice loss

Supraglacial lakes on the Greenland ice sheet can be seen as dark blue specks in the center and to the right of this satellite image. -  USGS/NASA Landsat
Supraglacial lakes on the Greenland ice sheet can be seen as dark blue specks in the center and to the right of this satellite image. – USGS/NASA Landsat

Predictions of Greenland ice loss and its impact on rising sea levels may have been greatly underestimated, according to scientists at the University of Leeds.

The finding follows a new study, which is published today in Nature Climate Change, in which the future distribution of lakes that form on the ice sheet surface from melted snow and ice – called supraglacial lakes – have been simulated for the first time.

Previously, the impact of supraglacial lakes on Greenland ice loss had been assumed to be small, but the new research has shown that they will migrate farther inland over the next half century, potentially altering the ice sheet flow in dramatic ways.

Dr Amber Leeson from the School of Earth and Environment and a member of the Centre for Polar Observation and Modelling (CPOM) team, who led the study, said: “Supraglacial lakes can increase the speed at which the ice sheet melts and flows, and our research shows that by 2060 the area of Greenland covered by them will double.”

Supraglacial lakes are darker than ice, so they absorb more of the Sun’s heat, which leads to increased melting. When the lakes reach a critical size, they drain through ice fractures, allowing water to reach the ice sheet base which causes it to slide more quickly into the oceans. These changes can also trigger further melting.

Dr Leeson explained: “When you pour pancake batter into a pan, if it rushes quickly to the edges of the pan, you end up with a thin pancake. It’s similar to what happens with ice sheets: the faster it flows, the thinner it will be.

“When the ice sheet is thinner, it is at a slightly lower elevation and at the mercy of warmer air temperatures than it would have been if it were thicker, increasing the size of the melt zone around the edge of the ice sheet.”

Until now, supraglacial lakes have formed at low elevations around the coastline of Greenland, in a band that is roughly 100 km wide. At higher elevations, today’s climate is just too cold for lakes to form.

In the study, the scientists used observations of the ice sheet from the Environmental Remote Sensing satellites operated by the European Space Agency and estimates of future ice melting drawn from a climate model to drive simulations of how meltwater will flow and pool on the ice surface to form supraglacial lakes.

Since the 1970s, the band in which supraglacial lakes can form on Greenland has crept 56km further inland. From the results of the new study, the researchers predict that, as Arctic temperatures rise, supraglacial lakes will spread much farther inland – up to 110 km by 2060 – doubling the area of Greenland that they cover today.

Dr Leeson said: “The location of these new lakes is important; they will be far enough inland so that water leaking from them will not drain into the oceans as effectively as it does from today’s lakes that are near to the coastline and connected to a network of drainage channels.”

“In contrast, water draining from lakes farther inland could lubricate the ice more effectively, causing it to speed up.”

Ice losses from Greenland had been expected to contribute 22cm to global sea-level rise by 2100. However, the models used to make this projection did not account for changes in the distribution of supraglacial lakes, which Dr Leeson’s study reveals will be considerable.

If new lakes trigger further increases in ice melting and flow, then Greenland’s future ice losses and its contribution to global sea-level rise have been underestimated.

The Director of CPOM, Professor Andrew Shepherd, who is also from the School of Earth and Environment at the University of Leeds and is a co-author of the study, said: “Because ice losses from Greenland are a key signal of global climate change, it’s important that we consider all factors that could affect the rate at which it will lose ice as climate warms.

“Our findings will help to improve the next generation of ice sheet models, so that we can have greater confidence in projections of future sea-level rise. In the meantime, we will continue to monitor changes in the ice sheet losses using satellite measurements.”

Further information:


The study was funded by the Natural Environment Research Council (NERC) through their support of the Centre for Polar Observation and Modelling and the National Centre for Earth Observation.

The research paper, Supraglacial lakes on the Greenland ice sheet advance inland under warming climate, is published in Nature Climate Change on 15 December 2014.

Dr Amber Leeson and Professor Andrew Shepherd are available for interview. Please contact the University of Leeds Press Office on 0113 343 4031 or email pressoffice@leeds.ac.uk