Active faults more accessible to geologists

The October GSA TODAY science article, “Open-source archive of active faults for northwest South America,” by Gabriel Veloza and colleagues, is now online at www.geosociety.org/gsatoday/archive/22/10/. The article introduces the “Active Tectonics of the Andes Database,” which will provide more data to more geoscientists.

Understanding important aspects of how the Earth works — in this case, hazards associated with active seismic fault zones — is greatly improved by free and open access to the many types of spatial and geological data collected by geologists. While some geophysical data, such as that obtained from seismograms of earthquakes, have long been widely available in digital form, the geological information that is needed to better understand the long-term history and evolution of deformation in fault zones is often not widely or freely available.

The diverse range of geological data — rock types and ages, fault locations and orientations, slip-direction from faults, geometry of other features such as folds and bedding planes — are often difficult to compile and assemble into useful digital forms.

Some of the most important questions and issues that can be addressed with these digital compilations of geological data include comparison of the direction and velocity of surface displacement measured by Global Positioning System receivers (GPS) with the location, orientation, and type of fault zone observed in the geological data. While the GPS data provide excellent coverage of the modern-day surface motion associated with plate boundary zones, many faults and fault zones have longer-term histories of displacement. For example, many fault zones have geological records of large earthquakes that have long, and sometimes variable, recurrence rates that cannot be adequately studied using short-term data from GPS.

In order to really understand the seismic hazards associated with faults that have long-term slip histories, evidence from the geological record must be used. In the October 2012 issue of GSA Today, graduate students Gabriel Veloza and Richard Styron, and their faculty advisor, Michael Taylor, from the Dept. of Geology at the University of Kansas, and Andrés Mora from the Instituto Colombiano del Petroleo in Colombia, present a detailed digital compilation of active faults and other geological feature from the NW portion of South America.

Their work — the Active Tectonics of the Andes Database — includes the locations and associated geological information for more than 400 mapped faults in this region. The digital nature of these data allow modern mapping tools, including Google Earth, to depict these faults and to include other forms of data, such as GPS velocities, earthquake locations, and plate motion data. This new database will allow access by many other geoscientists and will promote a better understanding of the different seismic hazards in this region of South America. For example, comparison of fault zone locations and orientations with GPS-based displacements has led Veloza’s team to recognize several zones with different displacement behavior and relate these to changes in plate motions and plate boundary orientation.

Active faults more accessible to geologists

The October GSA TODAY science article, “Open-source archive of active faults for northwest South America,” by Gabriel Veloza and colleagues, is now online at www.geosociety.org/gsatoday/archive/22/10/. The article introduces the “Active Tectonics of the Andes Database,” which will provide more data to more geoscientists.

Understanding important aspects of how the Earth works — in this case, hazards associated with active seismic fault zones — is greatly improved by free and open access to the many types of spatial and geological data collected by geologists. While some geophysical data, such as that obtained from seismograms of earthquakes, have long been widely available in digital form, the geological information that is needed to better understand the long-term history and evolution of deformation in fault zones is often not widely or freely available.

The diverse range of geological data — rock types and ages, fault locations and orientations, slip-direction from faults, geometry of other features such as folds and bedding planes — are often difficult to compile and assemble into useful digital forms.

Some of the most important questions and issues that can be addressed with these digital compilations of geological data include comparison of the direction and velocity of surface displacement measured by Global Positioning System receivers (GPS) with the location, orientation, and type of fault zone observed in the geological data. While the GPS data provide excellent coverage of the modern-day surface motion associated with plate boundary zones, many faults and fault zones have longer-term histories of displacement. For example, many fault zones have geological records of large earthquakes that have long, and sometimes variable, recurrence rates that cannot be adequately studied using short-term data from GPS.

In order to really understand the seismic hazards associated with faults that have long-term slip histories, evidence from the geological record must be used. In the October 2012 issue of GSA Today, graduate students Gabriel Veloza and Richard Styron, and their faculty advisor, Michael Taylor, from the Dept. of Geology at the University of Kansas, and Andrés Mora from the Instituto Colombiano del Petroleo in Colombia, present a detailed digital compilation of active faults and other geological feature from the NW portion of South America.

Their work — the Active Tectonics of the Andes Database — includes the locations and associated geological information for more than 400 mapped faults in this region. The digital nature of these data allow modern mapping tools, including Google Earth, to depict these faults and to include other forms of data, such as GPS velocities, earthquake locations, and plate motion data. This new database will allow access by many other geoscientists and will promote a better understanding of the different seismic hazards in this region of South America. For example, comparison of fault zone locations and orientations with GPS-based displacements has led Veloza’s team to recognize several zones with different displacement behavior and relate these to changes in plate motions and plate boundary orientation.

Rare great earthquake in April triggers large aftershocks all over the globe

<IMG SRC="/Images/427985608.jpg" WIDTH="350" HEIGHT="371" BORDER="0" ALT="Some 380 seconds into the greatest earthquake to rupture since 1960, the simulated dynamic Coulomb stress waves (red-blue) shed continuously off the 2004 M=9.2 Sumatra rupture front can be seen sweeping through the Andaman Sea, where faults remarkably shut down for the next five years. Earthquakes since 1964 are shown as black dots, and the Sunda trench along which the 1400-km-long earthquake occurred is the arcuate black line on the left (west). Sumatra is on the right, and Myanmar/Burma is at top. Sevilgen et al (Proc. Nat. Acad. Sci, 2012) find that despite the magnitude of thesedynamic stress waves, the much smaller permanent stresses account for the change in seismicity after the main shock.

This graphic accompanies the Sept. 3, 2012 article in Proceedings of the National Academy of Sciences by Volkan Sevilgen, Ross Stein and Fred Pollitz. – U.S. Geological Survey”>

Some 380 seconds into the greatest earthquake to rupture since 1960, the simulated dynamic Coulomb stress waves (red-blue) shed continuously off the 2004 M=9.2 Sumatra rupture front can be seen sweeping through the Andaman Sea, where faults remarkably shut down for the next five years. Earthquakes since 1964 are shown as black dots, and the Sunda trench along which the 1400-km-long earthquake occurred is the arcuate black line on the left (west). Sumatra is on the right, and Myanmar/Burma is at top. Sevilgen et al (Proc. Nat. Acad. Sci, 2012) find that despite the magnitude of thesedynamic stress waves, the much smaller permanent stresses account for the change in seismicity after the main shock.

This graphic accompanies the Sept. 3, 2012 article in Proceedings of the National Academy of Sciences by Volkan Sevilgen, Ross Stein and Fred Pollitz. – U.S. Geological Survey


Large earthquakes can alter seismicity patterns across the globe in very different ways, according to two new studies by U.S. Geological Survey seismologists. Both studies shed light on more than a decade of debate on the origin and prevalence of remotely triggered earthquakes. Until now, distant but damaging “aftershocks” have not been included in hazard assessments, yet in each study, changes in seismicity were predictable enough to be included in future evaluations of earthquake hazards.

In a study published in this week’s issue of “Nature,” USGS seismologist Fred Pollitz and colleagues analyzed the unprecedented increase in global seismic activity triggered by the Magnitude-8.6 East Indian Ocean quake of April 11, 2012, and in a recently published study in the “Proceedings of the National Academy of Sciences,” seismologist Volkan Sevilgen and his USGS colleagues investigated the near-cessation of seismic activity up to 250 miles away caused by the 2004 M9.2 Sumatra earthquake.

While aftershocks have traditionally been defined as those smaller earthquakes that happen after and nearby the main fault rupture, scientists now recognize that this definition is wrong. Instead, aftershocks are simply earthquakes of any size and location that would not have taken place had the main shock not struck.

“Earthquakes are immense forces of nature, involving complex rock physics and failure mechanisms occurring over time and space scales that cannot be recreated in a laboratory environment,” said USGS Director Marcia McNutt. “A large, unusual event such as the East Indian earthquake last April is a once-in-a-century opportunity to uncover first order responses of the planet to sudden changes in state of stress that bring us a little closer to understanding the mystery of earthquake generation.”

Global aftershock study: April 2012: East Indian Ocean quake triggers many distant quakes

An extraordinary number of earthquakes of M4.5 and greater were triggered worldwide in the six days after the M8.6 East Indian Ocean earthquake in April 2012. These large and potentially damaging quakes, occurring as far away as Mexico and Japan, were triggered within days of the passage of seismic waves from the main shock that generated stresses in Earth’s crust.

The East Indian Ocean event was the largest – by a factor of 10 – strike-slip earthquake ever recorded (the San Andreas is perhaps the most famous strike-slip fault). “Most great earthquakes occur along subduction zones and involve large vertical motions. No other recorded earthquake triggered as many large earthquakes elsewhere around the world as this one,” said Pollitz, “probably because strike-slip faults around the globe were more responsive to the seismic waves produced by a giant strike-slip temblor.”

Another clue in the six days of global aftershocks following the M8.6 quake is that the rate of global quakes during the preceding 6-12 days was extremely low. “Imagine an apple tree, with apples typically ripening and then falling at some steady rate,” Stein said. “If a week goes by without any falling, there will be more very ripe apples on the tree. Now shake the trunk, and many more than normal might drop.”

The authors emphasize that the week of global triggering seen after the East Indian Ocean quake has no bearing on the hypothesis advanced by others that the 2004 M9.2 Sumatra, 2010 M8.8 Maule, Chile, and 2011 M9.0 Tohoku, Japan, are related to each other. Instead, the effect of increased earthquakes lasted a week-not a decade.

Sumatra quake affects faults up to 250 miles away

While global triggering of large aftershocks appears very rare, regional triggering is common and important to understand for post-main shock emergency response and recovery. Sevilgen and his USGS colleagues studied the largest quake to strike in 40 years to understand just how great the reach is on aftershock occurrence. After the M9.2 earthquake in Sumatra in 2004, aftershocks larger than M4.5 ceased for five years along part of a distant series of linked faults known as the Andaman back arc fault system. Along a larger segment of the same system, the sideways-slipping transform earthquakes decreased by two-thirds, while the rate of rift events – earthquakes that happen on a spreading center – increased by 800 percent, according to Sevilgen and his colleagues at the USGS. These very large, but distant seismicity rate changes are unprecedented.

The authors investigated two possible causes for the changes in remote seismicity rates: the dynamic stresses imparted by the main shock rupture, which best explain the global triggering in the April 2012 quake case; and the small but permanent stress changes, which best explain this one. The authors found that the main shock brought the transform fault segments about ¼ bar of pressure farther from static failure, and the rift segments about ¼ bar closer to static failure (for comparison, car tires are inflated with about 3 bars of pressure), which matches the seismic observations.

Why it matters

Incorporating the probability of aftershocks into the hazard assessment of an area is important because the damage of even a moderate aftershock sometimes exceeds that wrought by the main event. For example, a M6.3 aftershock five months after the M7.1 New Zealand earthquake in 2010 hit a more populated area, causing 181 deaths and tripling the insured property damage of the main event.

Rare great earthquake in April triggers large aftershocks all over the globe

<IMG SRC="/Images/427985608.jpg" WIDTH="350" HEIGHT="371" BORDER="0" ALT="Some 380 seconds into the greatest earthquake to rupture since 1960, the simulated dynamic Coulomb stress waves (red-blue) shed continuously off the 2004 M=9.2 Sumatra rupture front can be seen sweeping through the Andaman Sea, where faults remarkably shut down for the next five years. Earthquakes since 1964 are shown as black dots, and the Sunda trench along which the 1400-km-long earthquake occurred is the arcuate black line on the left (west). Sumatra is on the right, and Myanmar/Burma is at top. Sevilgen et al (Proc. Nat. Acad. Sci, 2012) find that despite the magnitude of thesedynamic stress waves, the much smaller permanent stresses account for the change in seismicity after the main shock.

This graphic accompanies the Sept. 3, 2012 article in Proceedings of the National Academy of Sciences by Volkan Sevilgen, Ross Stein and Fred Pollitz. – U.S. Geological Survey”>

Some 380 seconds into the greatest earthquake to rupture since 1960, the simulated dynamic Coulomb stress waves (red-blue) shed continuously off the 2004 M=9.2 Sumatra rupture front can be seen sweeping through the Andaman Sea, where faults remarkably shut down for the next five years. Earthquakes since 1964 are shown as black dots, and the Sunda trench along which the 1400-km-long earthquake occurred is the arcuate black line on the left (west). Sumatra is on the right, and Myanmar/Burma is at top. Sevilgen et al (Proc. Nat. Acad. Sci, 2012) find that despite the magnitude of thesedynamic stress waves, the much smaller permanent stresses account for the change in seismicity after the main shock.

This graphic accompanies the Sept. 3, 2012 article in Proceedings of the National Academy of Sciences by Volkan Sevilgen, Ross Stein and Fred Pollitz. – U.S. Geological Survey


Large earthquakes can alter seismicity patterns across the globe in very different ways, according to two new studies by U.S. Geological Survey seismologists. Both studies shed light on more than a decade of debate on the origin and prevalence of remotely triggered earthquakes. Until now, distant but damaging “aftershocks” have not been included in hazard assessments, yet in each study, changes in seismicity were predictable enough to be included in future evaluations of earthquake hazards.

In a study published in this week’s issue of “Nature,” USGS seismologist Fred Pollitz and colleagues analyzed the unprecedented increase in global seismic activity triggered by the Magnitude-8.6 East Indian Ocean quake of April 11, 2012, and in a recently published study in the “Proceedings of the National Academy of Sciences,” seismologist Volkan Sevilgen and his USGS colleagues investigated the near-cessation of seismic activity up to 250 miles away caused by the 2004 M9.2 Sumatra earthquake.

While aftershocks have traditionally been defined as those smaller earthquakes that happen after and nearby the main fault rupture, scientists now recognize that this definition is wrong. Instead, aftershocks are simply earthquakes of any size and location that would not have taken place had the main shock not struck.

“Earthquakes are immense forces of nature, involving complex rock physics and failure mechanisms occurring over time and space scales that cannot be recreated in a laboratory environment,” said USGS Director Marcia McNutt. “A large, unusual event such as the East Indian earthquake last April is a once-in-a-century opportunity to uncover first order responses of the planet to sudden changes in state of stress that bring us a little closer to understanding the mystery of earthquake generation.”

Global aftershock study: April 2012: East Indian Ocean quake triggers many distant quakes

An extraordinary number of earthquakes of M4.5 and greater were triggered worldwide in the six days after the M8.6 East Indian Ocean earthquake in April 2012. These large and potentially damaging quakes, occurring as far away as Mexico and Japan, were triggered within days of the passage of seismic waves from the main shock that generated stresses in Earth’s crust.

The East Indian Ocean event was the largest – by a factor of 10 – strike-slip earthquake ever recorded (the San Andreas is perhaps the most famous strike-slip fault). “Most great earthquakes occur along subduction zones and involve large vertical motions. No other recorded earthquake triggered as many large earthquakes elsewhere around the world as this one,” said Pollitz, “probably because strike-slip faults around the globe were more responsive to the seismic waves produced by a giant strike-slip temblor.”

Another clue in the six days of global aftershocks following the M8.6 quake is that the rate of global quakes during the preceding 6-12 days was extremely low. “Imagine an apple tree, with apples typically ripening and then falling at some steady rate,” Stein said. “If a week goes by without any falling, there will be more very ripe apples on the tree. Now shake the trunk, and many more than normal might drop.”

The authors emphasize that the week of global triggering seen after the East Indian Ocean quake has no bearing on the hypothesis advanced by others that the 2004 M9.2 Sumatra, 2010 M8.8 Maule, Chile, and 2011 M9.0 Tohoku, Japan, are related to each other. Instead, the effect of increased earthquakes lasted a week-not a decade.

Sumatra quake affects faults up to 250 miles away

While global triggering of large aftershocks appears very rare, regional triggering is common and important to understand for post-main shock emergency response and recovery. Sevilgen and his USGS colleagues studied the largest quake to strike in 40 years to understand just how great the reach is on aftershock occurrence. After the M9.2 earthquake in Sumatra in 2004, aftershocks larger than M4.5 ceased for five years along part of a distant series of linked faults known as the Andaman back arc fault system. Along a larger segment of the same system, the sideways-slipping transform earthquakes decreased by two-thirds, while the rate of rift events – earthquakes that happen on a spreading center – increased by 800 percent, according to Sevilgen and his colleagues at the USGS. These very large, but distant seismicity rate changes are unprecedented.

The authors investigated two possible causes for the changes in remote seismicity rates: the dynamic stresses imparted by the main shock rupture, which best explain the global triggering in the April 2012 quake case; and the small but permanent stress changes, which best explain this one. The authors found that the main shock brought the transform fault segments about ¼ bar of pressure farther from static failure, and the rift segments about ¼ bar closer to static failure (for comparison, car tires are inflated with about 3 bars of pressure), which matches the seismic observations.

Why it matters

Incorporating the probability of aftershocks into the hazard assessment of an area is important because the damage of even a moderate aftershock sometimes exceeds that wrought by the main event. For example, a M6.3 aftershock five months after the M7.1 New Zealand earthquake in 2010 hit a more populated area, causing 181 deaths and tripling the insured property damage of the main event.

Large bacterial population colonized land 2.75 billion years ago

A drill core from the 2.5 billion-year-old Mount McRae Shale formation in Western Australia, which originally was fine-grained ocean sediment, shows high concentrations of sulfide and molybdenum. That supports the idea that most of the sulfate came from land, likely freed by microbial activity on rocks. Some data for the research came from the Mount McRae formation. -  Roger Buick/U. of Washington
A drill core from the 2.5 billion-year-old Mount McRae Shale formation in Western Australia, which originally was fine-grained ocean sediment, shows high concentrations of sulfide and molybdenum. That supports the idea that most of the sulfate came from land, likely freed by microbial activity on rocks. Some data for the research came from the Mount McRae formation. – Roger Buick/U. of Washington

There is evidence that some microbial life had migrated from the Earth’s oceans to land by 2.75 billion years ago, though many scientists believe such land-based life was limited because the ozone layer that shields against ultraviolet radiation did not form until hundreds of millions years later.

But new research from the University of Washington suggests that early microbes might have been widespread on land, producing oxygen and weathering pyrite, an iron sulfide mineral, which released sulfur and molybdenum into the oceans.

“This shows that life didn’t just exist in a few little places on land. It was important on a global scale because it was enhancing the flow of sulfate from land into the ocean,” said Eva Stüeken, a UW doctoral student in Earth and space sciences.

In turn, the influx of sulfur probably enhanced the spread of life in the oceans, said Stüeken, who is the lead author of a paper presenting the research published Sunday (Sept. 23) in Nature Geoscience. The work also will be part of her doctoral dissertation.

Sulfur could have been released into sea water by other processes, including volcanic activity. But evidence that molybdenum was being released at the same time suggests that both substances were being liberated as bacteria slowly disintegrated continental rocks, she said.

If that is the case, it likely means the land-based microbes were producing oxygen well in advance of what geologists refer to as the “Great Oxidation Event” about 2.4 billion years ago that initiated the oxygen-rich atmosphere that fostered life as we know it.

In fact, the added sulfur might have allowed marine microbes to consume methane, which could have set the stage for atmospheric oxygenation. Before that occurred, it is likely large amounts of oxygen were destroyed by reacting with methane that rose from the ocean into the air.

“It supports the theory that oxygen was being produced for several hundred million years before the Great Oxidation Event. It just took time for it to reach higher concentrations in the atmosphere,” Stüeken said.

The research examined data on sulfur levels in 1,194 samples from marine sediment formations dating from before the Cambrian period began about 542 million years ago. The processes by which sulfur can be added or removed are understood well enough to detect biological contributions, the researchers said.

The data came from numerous research projects during the last several decades, but in most cases those observations were just a small part of much larger studies. In an effort to provide consistent interpretation, Stüeken combed the research record for data that came from similar types of sedimentary rock and similar environments.

“The data has been out there for a long time, but people have ignored it because it is hard to interpret when it is not part of a large database,” she said.

Large bacterial population colonized land 2.75 billion years ago

A drill core from the 2.5 billion-year-old Mount McRae Shale formation in Western Australia, which originally was fine-grained ocean sediment, shows high concentrations of sulfide and molybdenum. That supports the idea that most of the sulfate came from land, likely freed by microbial activity on rocks. Some data for the research came from the Mount McRae formation. -  Roger Buick/U. of Washington
A drill core from the 2.5 billion-year-old Mount McRae Shale formation in Western Australia, which originally was fine-grained ocean sediment, shows high concentrations of sulfide and molybdenum. That supports the idea that most of the sulfate came from land, likely freed by microbial activity on rocks. Some data for the research came from the Mount McRae formation. – Roger Buick/U. of Washington

There is evidence that some microbial life had migrated from the Earth’s oceans to land by 2.75 billion years ago, though many scientists believe such land-based life was limited because the ozone layer that shields against ultraviolet radiation did not form until hundreds of millions years later.

But new research from the University of Washington suggests that early microbes might have been widespread on land, producing oxygen and weathering pyrite, an iron sulfide mineral, which released sulfur and molybdenum into the oceans.

“This shows that life didn’t just exist in a few little places on land. It was important on a global scale because it was enhancing the flow of sulfate from land into the ocean,” said Eva Stüeken, a UW doctoral student in Earth and space sciences.

In turn, the influx of sulfur probably enhanced the spread of life in the oceans, said Stüeken, who is the lead author of a paper presenting the research published Sunday (Sept. 23) in Nature Geoscience. The work also will be part of her doctoral dissertation.

Sulfur could have been released into sea water by other processes, including volcanic activity. But evidence that molybdenum was being released at the same time suggests that both substances were being liberated as bacteria slowly disintegrated continental rocks, she said.

If that is the case, it likely means the land-based microbes were producing oxygen well in advance of what geologists refer to as the “Great Oxidation Event” about 2.4 billion years ago that initiated the oxygen-rich atmosphere that fostered life as we know it.

In fact, the added sulfur might have allowed marine microbes to consume methane, which could have set the stage for atmospheric oxygenation. Before that occurred, it is likely large amounts of oxygen were destroyed by reacting with methane that rose from the ocean into the air.

“It supports the theory that oxygen was being produced for several hundred million years before the Great Oxidation Event. It just took time for it to reach higher concentrations in the atmosphere,” Stüeken said.

The research examined data on sulfur levels in 1,194 samples from marine sediment formations dating from before the Cambrian period began about 542 million years ago. The processes by which sulfur can be added or removed are understood well enough to detect biological contributions, the researchers said.

The data came from numerous research projects during the last several decades, but in most cases those observations were just a small part of much larger studies. In an effort to provide consistent interpretation, Stüeken combed the research record for data that came from similar types of sedimentary rock and similar environments.

“The data has been out there for a long time, but people have ignored it because it is hard to interpret when it is not part of a large database,” she said.

Gas outlets off Spitsbergen are no new phenomenon

Frequent storms and sub-zero temperatures – nature drove the marine researchers that were assessing gas outlets on the sea bed off the coast of Spitsbergen for four and a half weeks to their limits. Nevertheless the participants were very pleased when they returned: “We were able to gather many samples and data in the affected area. With the submersible JAGO we even managed to form an impression of the sea bed and the gas vents” summarized the chief scientist Professor Dr. Christian Berndt from GEOMAR | Helmholtz Centre for Ocean Research Kiel.

The reason for the expedition was the supposition that ice-like methane hydrates stored in the sea bed were dissolving due to rising water temperatures. “Methane hydrate is only stable at very low temperatures and under very high pressure. The gas outlets off Spitsbergen lie approximately at a depth which marks the border between stability and dissolution. Therefore we presumed that a measurable rise in water temperature in the Arctic could dissolve the hydrates from the top downwards” explained Professor Berndt. Methane could then be released into the water or even into the atmosphere, where it would act as a much stronger greenhouse gas than CO2.

In fact, what the researchers found in the area offers a much more differentiated picture. Above all the fear that the gas emanation is a consequence of the current rising sea temperature does not seem to apply. At least some of the gas outlets have been active for longer. Carbonate deposits, which form when microorganisms convert the escaping methane, were found on the vents. “At numerous emergences we found deposits that might already be hundreds of years old. This estimation is indeed only based on the size of the samples and empirical values as to how fast such deposits grow. On any account, the methane sources must be older” says Professor Berndt. The exact age of the carbonates will be determined from samples in GEOMAR’s laboratories.

“Details will only be known in a few months when the data has been analysed; however the observed gas emanations are probably not caused by human influence” says Berndt. There are two other possible explanations instead: Either they are symptoms of a long term temperature rise or they show a seasonal process where gas hydrates continuously melt and reform.

Another interesting observation made on the expedition, was that a very active microbial community that consumes the methane has established itself on the sea bed. “We were able to detect high concentrations of hydrogen sulphide, which is an indication of methane consuming microbes in the sea bed, and, with the help of JAGO, discovered typical biocoenoses that we recognised from other, older methane outlets” explained microbiologist Professor Dr. Tina Treude from GEOMAR, who also took part in the expedition. “Methane consuming microbes grow only slowly in the sea bed, thus their high activity indicates that the methane has not just recently begun effervescing.”

Colleagues from Bremen, Switzerland, Great Britain and Norway worked alongside marine scientists from GEOMAR and from the Cluster of Excellence “The Future Ocean”. “The study of the gas outlets in the Norwegian Sea is a good example for combined European research” stressed Professor Berndt. Hence German scientists recovered an ocean floor observatory, installed by the British research vessel James Clark Ross a year ago during a joint expedition of the National Oceanography Centre Southampton and the Institut français de recherche pour l’exploitation de la mer (Ifremer). “Understanding the ocean as a system is a challenge that only works in international co-operations” emphasized Berndt. The analysis of the gathered data will also be carried out internationally.

Gas outlets off Spitsbergen are no new phenomenon

Frequent storms and sub-zero temperatures – nature drove the marine researchers that were assessing gas outlets on the sea bed off the coast of Spitsbergen for four and a half weeks to their limits. Nevertheless the participants were very pleased when they returned: “We were able to gather many samples and data in the affected area. With the submersible JAGO we even managed to form an impression of the sea bed and the gas vents” summarized the chief scientist Professor Dr. Christian Berndt from GEOMAR | Helmholtz Centre for Ocean Research Kiel.

The reason for the expedition was the supposition that ice-like methane hydrates stored in the sea bed were dissolving due to rising water temperatures. “Methane hydrate is only stable at very low temperatures and under very high pressure. The gas outlets off Spitsbergen lie approximately at a depth which marks the border between stability and dissolution. Therefore we presumed that a measurable rise in water temperature in the Arctic could dissolve the hydrates from the top downwards” explained Professor Berndt. Methane could then be released into the water or even into the atmosphere, where it would act as a much stronger greenhouse gas than CO2.

In fact, what the researchers found in the area offers a much more differentiated picture. Above all the fear that the gas emanation is a consequence of the current rising sea temperature does not seem to apply. At least some of the gas outlets have been active for longer. Carbonate deposits, which form when microorganisms convert the escaping methane, were found on the vents. “At numerous emergences we found deposits that might already be hundreds of years old. This estimation is indeed only based on the size of the samples and empirical values as to how fast such deposits grow. On any account, the methane sources must be older” says Professor Berndt. The exact age of the carbonates will be determined from samples in GEOMAR’s laboratories.

“Details will only be known in a few months when the data has been analysed; however the observed gas emanations are probably not caused by human influence” says Berndt. There are two other possible explanations instead: Either they are symptoms of a long term temperature rise or they show a seasonal process where gas hydrates continuously melt and reform.

Another interesting observation made on the expedition, was that a very active microbial community that consumes the methane has established itself on the sea bed. “We were able to detect high concentrations of hydrogen sulphide, which is an indication of methane consuming microbes in the sea bed, and, with the help of JAGO, discovered typical biocoenoses that we recognised from other, older methane outlets” explained microbiologist Professor Dr. Tina Treude from GEOMAR, who also took part in the expedition. “Methane consuming microbes grow only slowly in the sea bed, thus their high activity indicates that the methane has not just recently begun effervescing.”

Colleagues from Bremen, Switzerland, Great Britain and Norway worked alongside marine scientists from GEOMAR and from the Cluster of Excellence “The Future Ocean”. “The study of the gas outlets in the Norwegian Sea is a good example for combined European research” stressed Professor Berndt. Hence German scientists recovered an ocean floor observatory, installed by the British research vessel James Clark Ross a year ago during a joint expedition of the National Oceanography Centre Southampton and the Institut français de recherche pour l’exploitation de la mer (Ifremer). “Understanding the ocean as a system is a challenge that only works in international co-operations” emphasized Berndt. The analysis of the gathered data will also be carried out internationally.

Stratosphere targets deep sea to shape climate

Thomas Reichler, a University of Utah atmospheric scientist, led a new study showing that changes in winds 15- to 30-miles high in the stratosphere can influence seawater circulation a mile or more deep in the ocean. He says this effect should be taken into account in forecasting climate change distinct from global warming. -  Lee J. Siegel, University of Utah.
Thomas Reichler, a University of Utah atmospheric scientist, led a new study showing that changes in winds 15- to 30-miles high in the stratosphere can influence seawater circulation a mile or more deep in the ocean. He says this effect should be taken into account in forecasting climate change distinct from global warming. – Lee J. Siegel, University of Utah.

A University of Utah study suggests something amazing: Periodic changes in winds 15 to 30 miles high in the stratosphere influence the seas by striking a vulnerable “Achilles heel” in the North Atlantic and changing mile-deep ocean circulation patterns, which in turn affect Earth’s climate.

“We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate,” says Thomas Reichler, senior author of the study published online Sunday, Sept. 23 in the journal Nature Geoscience.

Scientists already knew that events in the stratosphere, 6 miles to 30 miles above Earth, affect what happens below in the troposphere, the part of the atmosphere from Earth’s surface up to 6 miles or about 32,800 feet. Weather occurs in the troposphere.

Researchers also knew that global circulation patterns in the oceans – patterns caused mostly by variations in water temperature and saltiness – affect global climate.

“It is not new that the stratosphere impacts the troposphere,” says Reichler, an associate professor of atmospheric sciences at the University of Utah. “It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean.”

Funded by the University of Utah, Reichler conducted the study with University of Utah atmospheric sciences doctoral student Junsu Kim, and with atmospheric scientist Elisa Manzini and oceanographer Jürgen Kröger, both with the Max Planck Institute for Meteorology in Hamburg, Germany.

Stratospheric Winds and Sea Circulation Show Similar Rhythms


Reichler and colleagues used weather observations and 4,000 years worth of supercomputer simulations of weather to show a surprising association between decade-scale, periodic changes in stratospheric wind patterns known as the polar vortex, and similar rhythmic changes in deep-sea circulation patterns. The changes are:

– “Stratospheric sudden warming” events occur when temperatures rise and 80-mph “polar vortex” winds encircling the Artic suddenly weaken or even change direction. These winds extend from 15 miles elevation in the stratosphere up beyond the top of the stratosphere at 30 miles. The changes last for up to 60 days, allowing time for their effects to propagate down through the atmosphere to the ocean.

– Changes in the speed of the Atlantic circulation pattern – known as Atlantic Meridional Overturning Circulation – that influences the world’s oceans because it acts like a conveyor belt moving water around the planet.

Sometimes, both events happen several years in a row in one decade, and then none occur in the next decade. So incorporating this decade-scale effect of the stratosphere on the sea into supercomputer climate simulations or “models” is important in forecasting decade-to-decade climate changes that are distinct from global warming, Reichler says.

“If we as humans modify the stratosphere, it may – through the chain of events we demonstrate in this study – also impact the ocean circulation,” he says. “Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate.”

A Vulnerable Soft Spot in the North Atlantic


“The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide,” Reichler says. “In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough – and thus dense enough – so the water starts sinking.”

It is Earth’s most important region of seawater downwelling, he adds. That sinking of cold, salty water “drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans.”

Reichler continues: “This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them.”

Because of that sensitivity, Reichler calls the sea south of Greenland “the Achilles heel of the North Atlantic.”

From Stratosphere to the Sea


In winter, the stratospheric Arctic polar vortex whirls counterclockwise around the North Pole, with the strongest, 80-mph winds at about 60 degrees north latitude. They are stronger than jet stream winds, which are less than 70 mph in the troposphere below.But every two years on average, the stratospheric air suddenly is disrupted and the vortex gets warmer and weaker, and sometimes even shifts direction to clockwise.

“These are catastrophic rearrangements of circulation in the stratosphere,” and the weaker or reversed polar vortex persists up to two months, Reichler says. “Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface.”

Reichler’s study ventured into new territory by asking if changes in stratospheric polar vortex winds impart heat or cold to the sea, and how that affects the sea.

It already was known that that these stratospheric wind changes affect the North Atlantic Oscillation – a pattern of low atmospheric pressure centered over Greenland and high pressure over the Azores to the south. The pattern can reverse or oscillate.

Because the oscillating pressure patterns are located above the ocean downwelling area near Greenland, the question is whether that pattern affects the downwelling and, in turn, the global oceanic circulation conveyor belt.

The study’s computer simulations show a decadal on-off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the North Atlantic and changes in sea circulation more than one mile beneath the waves. Observations are consistent with the pattern revealed in computer simulations.

Observations and Simulations of the Stratosphere-to-Sea Link


In the 1980s and 2000s, a series of stratospheric sudden warming events weakened polar vortex winds. During the 1990s, the polar vortex remained strong.

Reichler and colleagues used published worldwide ocean observations from a dozen research groups to reconstruct behavior of the conveyor belt ocean circulation during the same 30-year period.

“The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic,” Reichler says.

To reduce uncertainties about the observations, the researchers used computers to simulate 4,000 years worth of atmosphere and ocean circulation.

“The computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events,” Reichler says.

To further verify the findings, the researchers combined 18 atmosphere and ocean models into one big simulation, and “we see very similar outcomes.”

The study suggests there is “a significant stratospheric impact on the ocean,” the researchers write. “Recurring stratospheric vortex events create long-lived perturbations at the ocean surface, which penetrate into the deeper ocean and trigger multidecadal variability in its circulation. This leads to the remarkable fact that signals that emanate from the stratosphere cross the entire atmosphere-ocean system.”

Stratosphere targets deep sea to shape climate

Thomas Reichler, a University of Utah atmospheric scientist, led a new study showing that changes in winds 15- to 30-miles high in the stratosphere can influence seawater circulation a mile or more deep in the ocean. He says this effect should be taken into account in forecasting climate change distinct from global warming. -  Lee J. Siegel, University of Utah.
Thomas Reichler, a University of Utah atmospheric scientist, led a new study showing that changes in winds 15- to 30-miles high in the stratosphere can influence seawater circulation a mile or more deep in the ocean. He says this effect should be taken into account in forecasting climate change distinct from global warming. – Lee J. Siegel, University of Utah.

A University of Utah study suggests something amazing: Periodic changes in winds 15 to 30 miles high in the stratosphere influence the seas by striking a vulnerable “Achilles heel” in the North Atlantic and changing mile-deep ocean circulation patterns, which in turn affect Earth’s climate.

“We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate,” says Thomas Reichler, senior author of the study published online Sunday, Sept. 23 in the journal Nature Geoscience.

Scientists already knew that events in the stratosphere, 6 miles to 30 miles above Earth, affect what happens below in the troposphere, the part of the atmosphere from Earth’s surface up to 6 miles or about 32,800 feet. Weather occurs in the troposphere.

Researchers also knew that global circulation patterns in the oceans – patterns caused mostly by variations in water temperature and saltiness – affect global climate.

“It is not new that the stratosphere impacts the troposphere,” says Reichler, an associate professor of atmospheric sciences at the University of Utah. “It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean.”

Funded by the University of Utah, Reichler conducted the study with University of Utah atmospheric sciences doctoral student Junsu Kim, and with atmospheric scientist Elisa Manzini and oceanographer Jürgen Kröger, both with the Max Planck Institute for Meteorology in Hamburg, Germany.

Stratospheric Winds and Sea Circulation Show Similar Rhythms


Reichler and colleagues used weather observations and 4,000 years worth of supercomputer simulations of weather to show a surprising association between decade-scale, periodic changes in stratospheric wind patterns known as the polar vortex, and similar rhythmic changes in deep-sea circulation patterns. The changes are:

– “Stratospheric sudden warming” events occur when temperatures rise and 80-mph “polar vortex” winds encircling the Artic suddenly weaken or even change direction. These winds extend from 15 miles elevation in the stratosphere up beyond the top of the stratosphere at 30 miles. The changes last for up to 60 days, allowing time for their effects to propagate down through the atmosphere to the ocean.

– Changes in the speed of the Atlantic circulation pattern – known as Atlantic Meridional Overturning Circulation – that influences the world’s oceans because it acts like a conveyor belt moving water around the planet.

Sometimes, both events happen several years in a row in one decade, and then none occur in the next decade. So incorporating this decade-scale effect of the stratosphere on the sea into supercomputer climate simulations or “models” is important in forecasting decade-to-decade climate changes that are distinct from global warming, Reichler says.

“If we as humans modify the stratosphere, it may – through the chain of events we demonstrate in this study – also impact the ocean circulation,” he says. “Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate.”

A Vulnerable Soft Spot in the North Atlantic


“The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide,” Reichler says. “In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough – and thus dense enough – so the water starts sinking.”

It is Earth’s most important region of seawater downwelling, he adds. That sinking of cold, salty water “drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans.”

Reichler continues: “This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them.”

Because of that sensitivity, Reichler calls the sea south of Greenland “the Achilles heel of the North Atlantic.”

From Stratosphere to the Sea


In winter, the stratospheric Arctic polar vortex whirls counterclockwise around the North Pole, with the strongest, 80-mph winds at about 60 degrees north latitude. They are stronger than jet stream winds, which are less than 70 mph in the troposphere below.But every two years on average, the stratospheric air suddenly is disrupted and the vortex gets warmer and weaker, and sometimes even shifts direction to clockwise.

“These are catastrophic rearrangements of circulation in the stratosphere,” and the weaker or reversed polar vortex persists up to two months, Reichler says. “Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface.”

Reichler’s study ventured into new territory by asking if changes in stratospheric polar vortex winds impart heat or cold to the sea, and how that affects the sea.

It already was known that that these stratospheric wind changes affect the North Atlantic Oscillation – a pattern of low atmospheric pressure centered over Greenland and high pressure over the Azores to the south. The pattern can reverse or oscillate.

Because the oscillating pressure patterns are located above the ocean downwelling area near Greenland, the question is whether that pattern affects the downwelling and, in turn, the global oceanic circulation conveyor belt.

The study’s computer simulations show a decadal on-off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the North Atlantic and changes in sea circulation more than one mile beneath the waves. Observations are consistent with the pattern revealed in computer simulations.

Observations and Simulations of the Stratosphere-to-Sea Link


In the 1980s and 2000s, a series of stratospheric sudden warming events weakened polar vortex winds. During the 1990s, the polar vortex remained strong.

Reichler and colleagues used published worldwide ocean observations from a dozen research groups to reconstruct behavior of the conveyor belt ocean circulation during the same 30-year period.

“The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic,” Reichler says.

To reduce uncertainties about the observations, the researchers used computers to simulate 4,000 years worth of atmosphere and ocean circulation.

“The computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events,” Reichler says.

To further verify the findings, the researchers combined 18 atmosphere and ocean models into one big simulation, and “we see very similar outcomes.”

The study suggests there is “a significant stratospheric impact on the ocean,” the researchers write. “Recurring stratospheric vortex events create long-lived perturbations at the ocean surface, which penetrate into the deeper ocean and trigger multidecadal variability in its circulation. This leads to the remarkable fact that signals that emanate from the stratosphere cross the entire atmosphere-ocean system.”