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Seaways across Antarctica could open in 1000 years
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Warmer world may split Antarctica AS ANTARCTICA melts, seaways will open up across the western side of the continent, linking marine communities that have long been isolated from one another. That’s according to David Vaughan of the British Antarctic Survey in Cambridge, UK, and colleagues, who have worked out where these seaways opened up during Antarctica’s warmer past – and where they are likely to form again if melting continues. Without its icy cover, much of west Antarctica would lie beneath sea level, partly because the ice has weighed down the continent. If, when Earth’s climate was warmer, Antarctica lost significant quantities of ice, areas of the ice sheet may have become thin and buoyant enough to float above the rocky continent. Seawater would then have flooded beneath the ice and created narrow channels across the continent between chunks of rock that retained their icy caps.
Red dwarfs throw new light on alien life SMALL and cool they may be, but red dwarfs, the most common kind of stars, are more likely to support life than we thought. Far-off icy planets that orbit these stars could still be warm enough to contain liquid water because of the way snow and ice absorb their near-infrared light. Alien-hunting astronomers tend to look for planets in the “habitable zone”, the range of distances from a star where temperatures are balmy enough for water to be in liquid form
Vaughan suspects that the channels would have been visible from the air, as the floating ice would quickly have broken up. The team used radar data to measure the depth of Antarctica’s rock and the thickness of the ice
Channels Channels through through the the ice ice
As Antarctica melts, narrow seaways may open up across As Antarctica melts, narrow seaways may open up across the west Antarctic Peninsula the west Antarctic Peninsula Ice above sea level Extent of today’s ice shelves Ice below sea level Ice above sea level Extent of today’s ice shelves Ice below sea level
Suggested Suggested openings of openings of seaways seaways
SOURCE: SOURCE: AGU AGU AND AND GEOCHEMICAL GEOCHEMICAL SOCIETY SOCIETY
Michael Marshall
sheet resting above it, and used this to work out which icy areas will be first to thin to the point that they would detach from the rock below. They identified a number of routes that are likely to have opened up across west Antarctica in the past (see map, below). To find evidence for their theory, Vaughan’s team turned to the animals living in the seas around Antarctica. They focused on bryozoans, marine filter
WEST ANTARCTIC PENINSULA WEST ANTARCTIC PENINSULA
but not so hot that it boils off. Red dwarfs are cooler than stars like our sun, so their habitable zones were thought to be smaller. This should make any planet’s gravitational tugs on the star stronger and habitable worlds easier to spot – if there are any. Red dwarfs tend to flare up, scorching any nearby planets. Those far enough away to be safe, meanwhile, could be too cold. Now, climate scientist Manoj Joshi of the University of Reading, UK, and Robert Haberle of NASA’s Ames Research Centre in California have discovered how red dwarfs could warm far-off planets. Ice and snow reflect 50 to 80 per cent of visible light so the ice on Earth
bounces most sunlight back to space, and stays frozen. Compared with our sun, red dwarfs shine less in visible wavelengths, and brighter in the near-infrared, which ice and snow soak up. “If there’s ice or snow on the ground, more of the radiation that hits the surface will be absorbed,” Joshi says. “Which means that you’d expect it to be a lot hotter than it would be otherwise.” Joshi and Haberle took spectral data for two red dwarfs known to have exoplanets, Gliese 436 and
“Snow on those worlds is half as shiny, and the outer edge of their habitable zone is further out”
feeders which spend their adult lives attached to rocks but move around as larvae. Communities on either side of the west Antarctic Peninsula share significantly more species in common than would be expected given the thousands of kilometres of coastline that separates them. This suggests there were once oceanic shortcuts across the peninsula itself, roughly where the team suspected the seaways to have been (Geochemistry, Geophysics, Geosystems, DOI: 10.1029/2011GC003688). “This is a great use of careful, fundamental science to extract important information from subtle clues,” says Richard Alley of Penn State University in University Park. Vaughan says the bryozoan data cannot tell us when the seaways last opened. Genetic testing of animals living at each end of the routes could help put a date on it, which in turn would tell us how likely the channels are to reopen and how vulnerable the west Antarctic ice sheet is to climate change. However, although parts of the sheet are already disappearing, Vaughan estimates that with the current rate of ice loss, even the most easily opened seaway is unlikely to reappear for around 900 years. n
GJ 1214. They found that an icy planet would reflect 10 to 40 per cent of the light it receives from that star. Effectively, snow on those worlds is half as shiny, and the outer edge of their habitable zone is 10 to 30 per cent further out from those stars than thought. “You’ve got more area, more chance of getting a planet in the habitable zone,” Joshi says. The work will be published in Astrobiology. Does the result bring any known exoplanets in from “too cold” to “just right”? Not just yet. Although exoplanet Gliese 581d is a possibility, Sara Seager at the Massachusetts Institute of Technology points out that this planet is not thought to have much ice. Lisa Grossman n 5 November 2011 | NewScientist | 9
Warmer world may split Antarctica AS ANTARCTICA melts, seaways will open up across the western side of the continent, linking marine communities that have long been isolated from one another. That’s according to David Vaughan of the British Antarctic Survey in Cambridge, UK, and colleagues, who have worked out where these seaways opened up during Antarctica’s warmer past – and where they are likely to form again if melting continues. Without its icy cover, much of west Antarctica would lie beneath sea level, partly because the ice has weighed down the continent. If, when Earth’s climate was warmer, Antarctica lost significant quantities of ice, areas of the ice sheet may have become thin and buoyant enough to float above the rocky continent. Seawater would then have flooded beneath the ice and created narrow channels across the continent between chunks of rock that retained their icy caps.
Red dwarfs throw new light on alien life SMALL and cool they may be, but red dwarfs, the most common kind of stars, are more likely to support life than we thought. Far-off icy planets that orbit these stars could still be warm enough to contain liquid water because of the way snow and ice absorb their near-infrared light. Alien-hunting astronomers tend to look for planets in the “habitable zone”, the range of distances from a star where temperatures are balmy enough for water to be in liquid form
Vaughan suspects that the channels would have been visible from the air, as the floating ice would quickly have broken up. The team used radar data to measure the depth of Antarctica’s rock and the thickness of the ice
Channels Channels through through the the ice ice
As Antarctica melts, narrow seaways may open up across As Antarctica melts, narrow seaways may open up across the west Antarctic Peninsula the west Antarctic Peninsula Ice above sea level Extent of today’s ice shelves Ice below sea level Ice above sea level Extent of today’s ice shelves Ice below sea level
Suggested Suggested openings of openings of seaways seaways
SOURCE: SOURCE: AGU AGU AND AND GEOCHEMICAL GEOCHEMICAL SOCIETY SOCIETY
Michael Marshall
sheet resting above it, and used this to work out which icy areas will be first to thin to the point that they would detach from the rock below. They identified a number of routes that are likely to have opened up across west Antarctica in the past (see map, below). To find evidence for their theory, Vaughan’s team turned to the animals living in the seas around Antarctica. They focused on bryozoans, marine filter
WEST ANTARCTIC PENINSULA WEST ANTARCTIC PENINSULA
but not so hot that it boils off. Red dwarfs are cooler than stars like our sun, so their habitable zones were thought to be smaller. This should make any planet’s gravitational tugs on the star stronger and habitable worlds easier to spot – if there are any. Red dwarfs tend to flare up, scorching any nearby planets. Those far enough away to be safe, meanwhile, could be too cold. Now, climate scientist Manoj Joshi of the University of Reading, UK, and Robert Haberle of NASA’s Ames Research Centre in California have discovered how red dwarfs could warm far-off planets. Ice and snow reflect 50 to 80 per cent of visible light so the ice on Earth
bounces most sunlight back to space, and stays frozen. Compared with our sun, red dwarfs shine less in visible wavelengths, and brighter in the near-infrared, which ice and snow soak up. “If there’s ice or snow on the ground, more of the radiation that hits the surface will be absorbed,” Joshi says. “Which means that you’d expect it to be a lot hotter than it would be otherwise.” Joshi and Haberle took spectral data for two red dwarfs known to have exoplanets, Gliese 436 and
“Snow on those worlds is half as shiny, and the outer edge of their habitable zone is further out”
feeders which spend their adult lives attached to rocks but move around as larvae. Communities on either side of the west Antarctic Peninsula share significantly more species in common than would be expected given the thousands of kilometres of coastline that separates them. This suggests there were once oceanic shortcuts across the peninsula itself, roughly where the team suspected the seaways to have been (Geochemistry, Geophysics, Geosystems, DOI: 10.1029/2011GC003688). “This is a great use of careful, fundamental science to extract important information from subtle clues,” says Richard Alley of Penn State University in University Park. Vaughan says the bryozoan data cannot tell us when the seaways last opened. Genetic testing of animals living at each end of the routes could help put a date on it, which in turn would tell us how likely the channels are to reopen and how vulnerable the west Antarctic ice sheet is to climate change. However, although parts of the sheet are already disappearing, Vaughan estimates that with the current rate of ice loss, even the most easily opened seaway is unlikely to reappear for around 900 years. n
GJ 1214. They found that an icy planet would reflect 10 to 40 per cent of the light it receives from that star. Effectively, snow on those worlds is half as shiny, and the outer edge of their habitable zone is 10 to 30 per cent further out from those stars than thought. “You’ve got more area, more chance of getting a planet in the habitable zone,” Joshi says. The work will be published in Astrobiology. Does the result bring any known exoplanets in from “too cold” to “just right”? Not just yet. Although exoplanet Gliese 581d is a possibility, Sara Seager at the Massachusetts Institute of Technology points out that this planet is not thought to have much ice. Lisa Grossman n 5 November 2011 | NewScientist | 9