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Seafloor Volcano Pulses May Alter Climate
http://www.earth.columbia.edu/articles/view/3231[font face=Serif][font size=5]Seafloor Volcano Pulses May Alter Climate[/font]
[font size=4]New Data Show Strikingly Regular Patterns, From Weeks to Eons[/font]
2015-02-05
[font size=3]Vast ranges of volcanoes hidden under the oceans are presumed by scientists to be the gentle giants of the planet, oozing lava at slow, steady rates along mid-ocean ridges. But a new study shows that they flare up on strikingly regular cycles, ranging from two weeks to 100,000 years—and, that they erupt almost exclusively during the first six months of each year. The pulses—apparently tied to short- and long-term changes in earth’s orbit, and to sea levels--may help trigger natural climate swings. Scientists have already speculated that volcanic cycles on land emitting large amounts of carbon dioxide might influence climate; but up to now there was no evidence from submarine volcanoes. The findings suggest that models of earth’s natural climate dynamics, and by extension human-influenced climate change, may have to be adjusted. The study appears this week in the journal Geophysical Research Letters.
“People have ignored seafloor volcanoes on the idea that their influence is small—but that’s because they are assumed to be in a steady state, which they’re not,” said the study’s author, marine geophysicist Maya Tolstoy of Columbia University’s Lamont-Doherty Earth Observatory. “They respond to both very large forces, and to very small ones, and that tells us that we need to look at them much more closely.” A related study by a separate team this week in the journal Science bolsters Tolstoy’s case by showing similar long-term patterns of submarine volcanism in an Antarctic region Tolstoy did not study.
Volcanically active mid-ocean ridges crisscross earth’s seafloors like stitching on a baseball, stretching some 37,000 miles. They are the growing edges of giant tectonic plates; as lavas push out, they form new areas of seafloor, which comprise some 80 percent of the planet’s crust. Conventional wisdom holds that they erupt at a fairly constant rate--but Tolstoy finds that the ridges are actually now in a languid phase. Even at that, they produce maybe eight times more lava annually than land volcanoes. Due to the chemistry of their magmas, the carbon dioxide they are thought to emit is currently about the same as, or perhaps a little less than, from land volcanoes—about 88 million metric tons a year. But were the undersea chains to stir even a little bit more, their CO2 output would shoot up, says Tolstoy.
Some scientists think volcanoes may act in concert with Milankovitch cycles--repeating changes in the shape of earth’s solar orbit, and the tilt and direction of its axis—to produce suddenly seesawing hot and cold periods. The major one is a 100,000-year cycle in which the planet’s orbit around the sun changes from more or less an annual circle into an ellipse that annually brings it closer or farther from the sun. Recent ice ages seem to build up through most of the cycle; but then things suddenly warm back up near the orbit’s peak eccentricity. The causes are not clear.
…[/font][/font]
[font size=4]New Data Show Strikingly Regular Patterns, From Weeks to Eons[/font]
2015-02-05
[font size=3]Vast ranges of volcanoes hidden under the oceans are presumed by scientists to be the gentle giants of the planet, oozing lava at slow, steady rates along mid-ocean ridges. But a new study shows that they flare up on strikingly regular cycles, ranging from two weeks to 100,000 years—and, that they erupt almost exclusively during the first six months of each year. The pulses—apparently tied to short- and long-term changes in earth’s orbit, and to sea levels--may help trigger natural climate swings. Scientists have already speculated that volcanic cycles on land emitting large amounts of carbon dioxide might influence climate; but up to now there was no evidence from submarine volcanoes. The findings suggest that models of earth’s natural climate dynamics, and by extension human-influenced climate change, may have to be adjusted. The study appears this week in the journal Geophysical Research Letters.
“People have ignored seafloor volcanoes on the idea that their influence is small—but that’s because they are assumed to be in a steady state, which they’re not,” said the study’s author, marine geophysicist Maya Tolstoy of Columbia University’s Lamont-Doherty Earth Observatory. “They respond to both very large forces, and to very small ones, and that tells us that we need to look at them much more closely.” A related study by a separate team this week in the journal Science bolsters Tolstoy’s case by showing similar long-term patterns of submarine volcanism in an Antarctic region Tolstoy did not study.
Volcanically active mid-ocean ridges crisscross earth’s seafloors like stitching on a baseball, stretching some 37,000 miles. They are the growing edges of giant tectonic plates; as lavas push out, they form new areas of seafloor, which comprise some 80 percent of the planet’s crust. Conventional wisdom holds that they erupt at a fairly constant rate--but Tolstoy finds that the ridges are actually now in a languid phase. Even at that, they produce maybe eight times more lava annually than land volcanoes. Due to the chemistry of their magmas, the carbon dioxide they are thought to emit is currently about the same as, or perhaps a little less than, from land volcanoes—about 88 million metric tons a year. But were the undersea chains to stir even a little bit more, their CO2 output would shoot up, says Tolstoy.
Some scientists think volcanoes may act in concert with Milankovitch cycles--repeating changes in the shape of earth’s solar orbit, and the tilt and direction of its axis—to produce suddenly seesawing hot and cold periods. The major one is a 100,000-year cycle in which the planet’s orbit around the sun changes from more or less an annual circle into an ellipse that annually brings it closer or farther from the sun. Recent ice ages seem to build up through most of the cycle; but then things suddenly warm back up near the orbit’s peak eccentricity. The causes are not clear.
…[/font][/font]
http://news.agu.org/press-release/unseen-volcanoes-may-play-role-in-earths-long-term-climate/
[font face=Serif][font size=5]Unseen volcanoes may play role in Earth’s long-term climate[/font]
5 February 2015
[font size=3]WASHINGTON, D.C. – The intensity of volcanic activity at deeply submerged mid-ocean ridges waxes and wanes on a roughly 100,000-year cycle, according to a new study that might help explain poorly understood variations in Earth’s climate that occur on approximately the same timetable.
Cyclical variations in Earth’s tilt and orbit–occurring at 23,000-, 41,000- and 100,000-year intervals–are known to strongly influence our planet’s long-term climate. They are associated with the coming and going of ice ages that also takes place about every 100,000 years.
In particular, changes in the roundness of Earth’s orbit around the Sun unfold on approximately the same 100,000 year cycle as the planet’s global swings between icy and temperate conditions. But, the variation in solar radiation reaching Earth due to temporarily larger and smaller distances between our planet and the Sun can’t fully explain the magnitude of the climatic shifts.
The new research finds evidence in the profile of sea-floor elevation that volcanic activity at mid-ocean ridges, where molten rock emerges from Earth’s interior and creates new planetary crust, coincides with these 100,000-year changes in Earth’s orbit and climate. Given that volcanic eruptions release the climate-altering gas carbon-dioxide, significant emissions of the gas might take place during upswings of undersea volcanic activity, potentially affecting the climate at 100,000-year intervals.
…[/font][/font]
5 February 2015
[font size=3]WASHINGTON, D.C. – The intensity of volcanic activity at deeply submerged mid-ocean ridges waxes and wanes on a roughly 100,000-year cycle, according to a new study that might help explain poorly understood variations in Earth’s climate that occur on approximately the same timetable.
Cyclical variations in Earth’s tilt and orbit–occurring at 23,000-, 41,000- and 100,000-year intervals–are known to strongly influence our planet’s long-term climate. They are associated with the coming and going of ice ages that also takes place about every 100,000 years.
In particular, changes in the roundness of Earth’s orbit around the Sun unfold on approximately the same 100,000 year cycle as the planet’s global swings between icy and temperate conditions. But, the variation in solar radiation reaching Earth due to temporarily larger and smaller distances between our planet and the Sun can’t fully explain the magnitude of the climatic shifts.
The new research finds evidence in the profile of sea-floor elevation that volcanic activity at mid-ocean ridges, where molten rock emerges from Earth’s interior and creates new planetary crust, coincides with these 100,000-year changes in Earth’s orbit and climate. Given that volcanic eruptions release the climate-altering gas carbon-dioxide, significant emissions of the gas might take place during upswings of undersea volcanic activity, potentially affecting the climate at 100,000-year intervals.
…[/font][/font]
