ScienceLine: Fishing “Down The Pricelist” Threatens Ocean Ecosystems
Overfishing has led Indian fisheries to rely on less marketable species for profit — a practice that could have severe ecological consequences
Would you consider purchasing starfish or sand dollars instead of lobster or snapper at your local supermarket? In India, shoppers have little choice. A steep population decline of commonly consumed species such as shrimp and grouper — from overfishing — has forced Indian fishermen to land a larger portion of less desirable varieties such as sardines and sea urchins, also referred to as bycatch. Although they used to discard it in the millions of tons, fishermen now sell bycatch for local consumption and poultry feed. And according to new research, Indian fisheries have become reliant on bycatch for turning a profit, a practice that could severely disrupt the entire offshore ecosystem where Indian vessels exhaustively trawl the waters.
Researchers examined changes in catches by Indian trawlers by interviewing fishermen in three locations and reconstructing trends in income, bycatch figures, and catch of marketable species over the past thirty years. The results revealed that the annual catch of more marketable species like shrimp and grouper has declined sharply in the past twenty years while the amount of bycatch sold has steadily increased. They also saw a steady rise in bycatch sales to India’s growing poultry industry, whose rapid expansion coincides with the country’s burgeoning affluence and consequential shift away from vegetarianism. As stocks of more commonly eaten species dwindle, the demand for bycatch from both local consumers and from the poultry industry has become critical to fisheries’ survival.
Aaron Savio Lobo, a Ph.D. candidate who studies ecology at Cambridge University in the U.K., was the lead author of the paper describing the research, which was published in August in the journal Conservation Letters. Bycatch commercialization is “definitely bad news” for the marine environment, Lobo said, with “profound implications” for the health of fish stocks. Fishers “scraping the sea floor and picking up whatever they can possibly get, from the tiniest bivalve shells to massive rays” could lead to “ecological catastrophe,” and may push marketable species beyond their ability to ever recover, Lobo warns.
William Cheung, a marine biologist at the University of East Anglia in the U.K., who was not part of the study, explained that the shift to bycatch targeting is referred to as “fishing down the food web,” or as in the case in India, fishing “down the price list.” As more desirable species become depleted, fishermen target cheaper and cheaper varieties “until we finally develop markets for jellyfish and plankton,” Cheung said. “I don’t think that would be a good way to go.” Moreover, Cheung explained, commercializing bycatch makes it even more difficult for originally targeted species to survive, since the incentive no longer exists for fishermen to move to a new location after marketable fish stocks have been exhausted. Fishers lingering on in a depleted area to collect bycatch leave no window of opportunity for population recovery of marketable species, as the next generation of juvenile fish is scooped up alongside the few remaining adults. As a result, Cheung concluded, fish stocks cannot fully recuperate and some species can even be driven to local extinction.
Lobo hopes his future research, which will concentrate on establishing bycatch figures, can further define the scope of the problem. If successful, his work could contribute to the design of strategies that would strike a balance between the livelihoods of fishermen and the survival of threatened species currently suffering the effects of overfishing. This would ultimately benefit the fishing industry through sustainable management of species populations, Lobo says.
But for now, Lobo says, no easy solution exists. “What are you going to do with all those fishermen? They pick up whatever they can possibly get, just to keep afloat.”
Wednesday, November 10, 2010
Sea Turtle Herpes Tumors Linked to Sewage?
National Graphic Daily News: Sea Turtle Herpes Tumors Linked to Sewage?
Rebecca Kessler
for National Geographic News
November 9, 2010
Tumors that have plagued green sea turtles worldwide for decades may be caused by pollution, a new study says.
Nitrogen-rich runoff from sewers and farms is fueling a rise in invasive seaweed that, when consumed by the reptiles, may trigger an otherwise dormant herpes virus. This virus in turn causes the often fatal growths.
The cauliflower-like tumors—which can sprout on a turtle's eyes, mouth, joints, and internal organs—have contributed to declines in the 4-foot-long (1.2-meter-long) turtles. Listed as endangered by the International Union for Conservation of Nature, green sea turtles are found in the world's tropical and subtropical waters. (See sea turtle pictures.)
In some parts of Hawaii, where green sea turtle strandings occur regularly, as many as 90 percent of stranded dead or dying turtles discovered have been afflicted with the disease, according to study leader Kyle Van Houtan, an ecologist with the National Oceanic and Atmospheric Administration's Pacific Islands Fisheries Science Center in Honolulu.
(Related pictures: "Millions of Sea Turtles Killed Accidentally?")
Wherever the turtle strandings occur, there is often evidence of sewage and invasive algae, Van Houtan said.
Until now, however, hard evidence that pollution factors into the turtles' disease has remained elusive, he noted.
Polluted Areas Are Turtle-Tumor Hot Spots
Van Houtan and colleagues analyzed human activities on land to calculate a "nitrogen footprint" for each watershed—an area that drains into a water body—on the Hawaiian islands of Oahu, the Big Island, and Maui (see map). The team also studied 28 years' worth of data on green sea turtle strandings on the islands.
Comparing the two data sets, the scientists found that diseased turtles strand more in areas with high nitrogen runoff from agriculture, sewers, and cities.
(See "Cocaine, Spices, Hormones Found in Drinking Water.")
These turtle-tumor hot spots are "the places that I wouldn't necessarily want to go surfing after a rain … because of the nasty stuff that would show up" in the ocean, Van Houtan added.
Nitrogen Awakens Herpes Viruses
The scientists don't think the nitrogen-loaded runoff causes tumors directly. Instead, there may be a chain of interactions that starts with a nitrogen-fed boom in nonnative seaweed, at least in Hawaii.
Nitrogen acts as a fertilizer in oceans, and is a main cause of oxygen-sucking algae blooms called dead zones.
Around the Hawaiian islands, several seaweed species were either accidentally introduced or deliberately harvested for food crops and later "escaped" cultivation and spread into the wild.
For instance, hookweed—native to the Mediterranean, the Caribbean, the Indian Ocean, and the Philippines—was introduced to Hawaii in 1974. Gorillo ogo and spiny seaweed came from the Pacific and Indian Oceans and Guam, respectively.
(Learn more about marine invasive species.)
The seaweed absorbs the extra nitrogen and converts it into an amino acid—the building block of protein—called arginine. When turtles eat the seaweed, arginine awakens dormant herpes viruses in the turtles' bodies that generate the tumors.
It's possible that nonnative seaweed in Hawaii is better than native seaweed species at converting nitrogen to arginine, Van Houtan noted.
And because Hawaiian green sea turtles now rely on the invasive seaweed for food, Van Houtan suspects the animals get dosed with tumor-triggering amino acids at every meal.
Turtle Tumors Have Other Causes?
Alonso Aguirre, a wildlife epidemiologist with the environmental nonprofit EcoHealth Alliance in New York, praised the study for confirming the link between pollution and sea turtle tumors.
But he also said that the tumors' cause may be more complicated.
The pollution-virus link is "a very simplistic pathway to explain the whole disease," Aguirre said, adding he suspects other factors, such as water temperature, and possibly additional viruses, are at play.
Regardless of exactly how the tumors form, Aguirre said the study shows that "the turtles … are telling us that something is happening to the oceans in a way that now, we have to pay attention."
Turtle-tumor research published September 29 in the journal PLoS ONE.
Rebecca Kessler
for National Geographic News
November 9, 2010
Tumors that have plagued green sea turtles worldwide for decades may be caused by pollution, a new study says.
Nitrogen-rich runoff from sewers and farms is fueling a rise in invasive seaweed that, when consumed by the reptiles, may trigger an otherwise dormant herpes virus. This virus in turn causes the often fatal growths.
The cauliflower-like tumors—which can sprout on a turtle's eyes, mouth, joints, and internal organs—have contributed to declines in the 4-foot-long (1.2-meter-long) turtles. Listed as endangered by the International Union for Conservation of Nature, green sea turtles are found in the world's tropical and subtropical waters. (See sea turtle pictures.)
In some parts of Hawaii, where green sea turtle strandings occur regularly, as many as 90 percent of stranded dead or dying turtles discovered have been afflicted with the disease, according to study leader Kyle Van Houtan, an ecologist with the National Oceanic and Atmospheric Administration's Pacific Islands Fisheries Science Center in Honolulu.
(Related pictures: "Millions of Sea Turtles Killed Accidentally?")
Wherever the turtle strandings occur, there is often evidence of sewage and invasive algae, Van Houtan said.
Until now, however, hard evidence that pollution factors into the turtles' disease has remained elusive, he noted.
Polluted Areas Are Turtle-Tumor Hot Spots
Van Houtan and colleagues analyzed human activities on land to calculate a "nitrogen footprint" for each watershed—an area that drains into a water body—on the Hawaiian islands of Oahu, the Big Island, and Maui (see map). The team also studied 28 years' worth of data on green sea turtle strandings on the islands.
Comparing the two data sets, the scientists found that diseased turtles strand more in areas with high nitrogen runoff from agriculture, sewers, and cities.
(See "Cocaine, Spices, Hormones Found in Drinking Water.")
These turtle-tumor hot spots are "the places that I wouldn't necessarily want to go surfing after a rain … because of the nasty stuff that would show up" in the ocean, Van Houtan added.
Nitrogen Awakens Herpes Viruses
The scientists don't think the nitrogen-loaded runoff causes tumors directly. Instead, there may be a chain of interactions that starts with a nitrogen-fed boom in nonnative seaweed, at least in Hawaii.
Nitrogen acts as a fertilizer in oceans, and is a main cause of oxygen-sucking algae blooms called dead zones.
Around the Hawaiian islands, several seaweed species were either accidentally introduced or deliberately harvested for food crops and later "escaped" cultivation and spread into the wild.
For instance, hookweed—native to the Mediterranean, the Caribbean, the Indian Ocean, and the Philippines—was introduced to Hawaii in 1974. Gorillo ogo and spiny seaweed came from the Pacific and Indian Oceans and Guam, respectively.
(Learn more about marine invasive species.)
The seaweed absorbs the extra nitrogen and converts it into an amino acid—the building block of protein—called arginine. When turtles eat the seaweed, arginine awakens dormant herpes viruses in the turtles' bodies that generate the tumors.
It's possible that nonnative seaweed in Hawaii is better than native seaweed species at converting nitrogen to arginine, Van Houtan noted.
And because Hawaiian green sea turtles now rely on the invasive seaweed for food, Van Houtan suspects the animals get dosed with tumor-triggering amino acids at every meal.
Turtle Tumors Have Other Causes?
Alonso Aguirre, a wildlife epidemiologist with the environmental nonprofit EcoHealth Alliance in New York, praised the study for confirming the link between pollution and sea turtle tumors.
But he also said that the tumors' cause may be more complicated.
The pollution-virus link is "a very simplistic pathway to explain the whole disease," Aguirre said, adding he suspects other factors, such as water temperature, and possibly additional viruses, are at play.
Regardless of exactly how the tumors form, Aguirre said the study shows that "the turtles … are telling us that something is happening to the oceans in a way that now, we have to pay attention."
Turtle-tumor research published September 29 in the journal PLoS ONE.
Research: Thinning Ozone Could Be Leaving Whales Sunburned; 'Exposure To Strong Sun Is Damaging'
Underwater Times: Research: Thinning Ozone Could Be Leaving Whales Sunburned; 'Exposure To Strong Sun Is Damaging'
LONDON, England -- Whales exhibit skin damage consistent with acute sunburn in humans, and it seems to be getting worse over time, reveals research published this week in Proceedings of the Royal Society B.
Scientists from the Zoological Society of London (ZSL), Queen Mary, University of London and CICIMAR, studied blue whales, fin whales and sperm whales in the Gulf of California to determine the effect of rising levels of ultraviolet radiation (UVR) on their health.
For a number of years scientists have observed blisters on the skin of whales. Now, using high-quality photos to give accurate counts of the blisters and analysing areas of damage in skin samples, this research has found that the three species of whale exhibit skin damage that is commonly associated with acute sunburn in humans.
Notably, the scientists also found that signs of sun damage were more severe in the paler-skinned blue whales, compared with the darker-skinned fin whales, and that in blue whales the symptoms of sunburn seem to be getting worse during the three years the study took place.
The UV index for the Gulf of California fluctuates between high and extremely high throughout the year. Lead author, Laura Martinez–Levasseur from ZSL and Queen Mary, says, "Whales need to come to the surface to breathe air, to socialise and to feed their young, meaning that they are frequently exposed to the full force of the sun.
"The increase in skin damage seen in blue whales is a matter of concern, but at this stage it is not clear what is causing this increase. A likely candidate is rising UVR as a result of either ozone depletion, or a change in the level of cloud cover."
Co-author Professor Edel O'Toole, from Queen Mary, says, "As we would expect to see in humans, the whale species that spent more 'time in the sun' suffered greater sun damage. We predict that whales will experience more severe sun damage if ultraviolet radiation continues to increase."
The next phase of the research will look at the expression of genes involved in the production of skin pigmentation and DNA damage repair and try to gain a greater understanding of the consequences of sun damage in whales.
Lead author Dr Karina Acevedo-Whitehouse, from ZSL says, "We have shown that exposure to strong sun is damaging to whales' skin. We now need to understand the knock-on effects and whether whales are able to respond quickly to increasing radiation by enhancing their natural sun-protection mechanisms."
LONDON, England -- Whales exhibit skin damage consistent with acute sunburn in humans, and it seems to be getting worse over time, reveals research published this week in Proceedings of the Royal Society B.
Scientists from the Zoological Society of London (ZSL), Queen Mary, University of London and CICIMAR, studied blue whales, fin whales and sperm whales in the Gulf of California to determine the effect of rising levels of ultraviolet radiation (UVR) on their health.
For a number of years scientists have observed blisters on the skin of whales. Now, using high-quality photos to give accurate counts of the blisters and analysing areas of damage in skin samples, this research has found that the three species of whale exhibit skin damage that is commonly associated with acute sunburn in humans.
Notably, the scientists also found that signs of sun damage were more severe in the paler-skinned blue whales, compared with the darker-skinned fin whales, and that in blue whales the symptoms of sunburn seem to be getting worse during the three years the study took place.
The UV index for the Gulf of California fluctuates between high and extremely high throughout the year. Lead author, Laura Martinez–Levasseur from ZSL and Queen Mary, says, "Whales need to come to the surface to breathe air, to socialise and to feed their young, meaning that they are frequently exposed to the full force of the sun.
"The increase in skin damage seen in blue whales is a matter of concern, but at this stage it is not clear what is causing this increase. A likely candidate is rising UVR as a result of either ozone depletion, or a change in the level of cloud cover."
Co-author Professor Edel O'Toole, from Queen Mary, says, "As we would expect to see in humans, the whale species that spent more 'time in the sun' suffered greater sun damage. We predict that whales will experience more severe sun damage if ultraviolet radiation continues to increase."
The next phase of the research will look at the expression of genes involved in the production of skin pigmentation and DNA damage repair and try to gain a greater understanding of the consequences of sun damage in whales.
Lead author Dr Karina Acevedo-Whitehouse, from ZSL says, "We have shown that exposure to strong sun is damaging to whales' skin. We now need to understand the knock-on effects and whether whales are able to respond quickly to increasing radiation by enhancing their natural sun-protection mechanisms."
Saturday, November 6, 2010
Scripps plays role in national research of sea trash
Sign On San Diego: Scripps plays role in national research of sea trash
Researchers at the Scripps Institution of Oceanography in La Jolla will count plastic particles that were collected during an October voyage by scientists studying the impact of debris on marine creatures and humans.
Those on the expedition - sponsored by the National Oceanic and Atmospheric Administration - found the plastic and other items in the "great Pacific garbage patch." The Texas-sized mass of floating objects in north Pacific Ocean has attracted interest from researchers worldwide, including some in Indonesia who joined the NOAA voyage.
Scientists from Scripps, based at the University of California San Diego, have done their own research on the vortex of plastic and have talked about plans to search for plastic in the South Pacific Ocean. The northern gyre has included everything from detergent bottles to toothbrushes, though most of the items are microscopic.
Besides plastic, scientists on the October trip collected samples of plankton, small organisms that may have consumed plastic bits. The effort was intended to fill gaps in data from parts of the Pacific Ocean, such as the stretch between Guam and Hawaii.
"We need samples in these areas to better describe the diversity and distribution of plankton, so we may detect changes and better understand the plankton communities," said Michael Ford, a chief NOAA scientist.
After Scripps tallies the plastic pieces, NOAA scientists in Seattle will test them for chemicals such as the pesticide DDT and BPA, a substance used to make plastics. Both are considered harmful to living organisms.
This month, another group of researchers will embark on a separate journey that also will involve plastic pollution in the ocean.
Experts from the Santa Monica-based 5 Gyres Institute will sail from Rio de Janeiro to Cape Town, South Africa, to show "you can't cross an ocean today without finding plastic pollution," said Anna Cummins, an institute co-founder.
Members of that team also hope to study whether the plastic poses harm to marine life.
Researchers at the Scripps Institution of Oceanography in La Jolla will count plastic particles that were collected during an October voyage by scientists studying the impact of debris on marine creatures and humans.
Those on the expedition - sponsored by the National Oceanic and Atmospheric Administration - found the plastic and other items in the "great Pacific garbage patch." The Texas-sized mass of floating objects in north Pacific Ocean has attracted interest from researchers worldwide, including some in Indonesia who joined the NOAA voyage.
Scientists from Scripps, based at the University of California San Diego, have done their own research on the vortex of plastic and have talked about plans to search for plastic in the South Pacific Ocean. The northern gyre has included everything from detergent bottles to toothbrushes, though most of the items are microscopic.
Besides plastic, scientists on the October trip collected samples of plankton, small organisms that may have consumed plastic bits. The effort was intended to fill gaps in data from parts of the Pacific Ocean, such as the stretch between Guam and Hawaii.
"We need samples in these areas to better describe the diversity and distribution of plankton, so we may detect changes and better understand the plankton communities," said Michael Ford, a chief NOAA scientist.
After Scripps tallies the plastic pieces, NOAA scientists in Seattle will test them for chemicals such as the pesticide DDT and BPA, a substance used to make plastics. Both are considered harmful to living organisms.
This month, another group of researchers will embark on a separate journey that also will involve plastic pollution in the ocean.
Experts from the Santa Monica-based 5 Gyres Institute will sail from Rio de Janeiro to Cape Town, South Africa, to show "you can't cross an ocean today without finding plastic pollution," said Anna Cummins, an institute co-founder.
Members of that team also hope to study whether the plastic poses harm to marine life.
'Urgent change required' over fishing policy
BBC: North East, Orkney & Shetland News: 'Urgent change required' over fishing policy
Scotland's seas are a "graveyard for the EU's attempt at management", an independent panel has claimed.
The Future of Fisheries Management was set up by the Scottish government to look at ways of safeguarding fish stocks and fishing communities.
It has recommended a more regional approach to managing stocks, rather than having catches dictated by Brussels.
The inquiry panel also called on industry leaders to get more involved.
Cabinet Secretary for Rural Affairs and the Environment Richard Lochhead established the group last year to look into the future of fisheries management in Scotland.
Urgent change
It was headed up by Alan Campbell CBE, the former chief executive of Aberdeenshire Council and Grampian Regional Council.
He said: "A major recommendation of the inquiry panel is that we need to move to a more regional management structure of the Common Fisheries Policy (CFP).
Continue reading the main story
“
Start Quote
We will now work to study the report in detail and see how we can incorporate its findings into achieving a fishing industry that remains profitable and successful into the future”
End Quote
Richard Lochhead
Fisheries minister
"It is only in this way that we see these European regulations being more relevant, understandable and respected by Scotland's fishermen.
"Furthermore, the embarrassment of discards - which achieve nothing except the wasteful reduction of stocks - must stop being an inevitable outcome of CFP regulations."
He said during the next 10 years the Scottish industry was likely to face greater uncertainty than at any time since the early 1980s.
"That's why real change is now urgent," he added.
Mr Lochhead said: "This timely and powerful report will make a substantial contribution to the immediate debate on the future of EU fisheries policy and the long-term future of our fishing communities.
"Importantly, the report delivers a clarion call for the radical overhaul of EU fishing policy given the damage inflicted in recent decades by the Common Fisheries Policy.
"It rightly refers to Scotland's seas as the 'graveyard for the EU's attempt at management'."
'Wide-ranging'
Liberal Democrat Fisheries spokesman Liam McArthur congratulated the team for its analysis of the "complex challenges" facing the fishing industry.
"The recommendations they make are wide-ranging," he said.
"In many cases, they will make for uncomfortable reading not just for fishermen and ministers, but for all those with an interest and involvement in the sector."
Peter Peacock, Labour MSP for Highlands and Islands, said the report would be a useful contribution to shaping the future of fisheries management in Scotland.
He called on the government to step up efforts to protect the interests of Scottish fleets.
Dr Mireille Thom, marine policy officer at WWF Scotland said the report made it clear that the industry faced an "uncertain future" without additional steps at home and abroad.
Scotland's seas are a "graveyard for the EU's attempt at management", an independent panel has claimed.
The Future of Fisheries Management was set up by the Scottish government to look at ways of safeguarding fish stocks and fishing communities.
It has recommended a more regional approach to managing stocks, rather than having catches dictated by Brussels.
The inquiry panel also called on industry leaders to get more involved.
Cabinet Secretary for Rural Affairs and the Environment Richard Lochhead established the group last year to look into the future of fisheries management in Scotland.
Urgent change
It was headed up by Alan Campbell CBE, the former chief executive of Aberdeenshire Council and Grampian Regional Council.
He said: "A major recommendation of the inquiry panel is that we need to move to a more regional management structure of the Common Fisheries Policy (CFP).
Continue reading the main story
“
Start Quote
We will now work to study the report in detail and see how we can incorporate its findings into achieving a fishing industry that remains profitable and successful into the future”
End Quote
Richard Lochhead
Fisheries minister
"It is only in this way that we see these European regulations being more relevant, understandable and respected by Scotland's fishermen.
"Furthermore, the embarrassment of discards - which achieve nothing except the wasteful reduction of stocks - must stop being an inevitable outcome of CFP regulations."
He said during the next 10 years the Scottish industry was likely to face greater uncertainty than at any time since the early 1980s.
"That's why real change is now urgent," he added.
Mr Lochhead said: "This timely and powerful report will make a substantial contribution to the immediate debate on the future of EU fisheries policy and the long-term future of our fishing communities.
"Importantly, the report delivers a clarion call for the radical overhaul of EU fishing policy given the damage inflicted in recent decades by the Common Fisheries Policy.
"It rightly refers to Scotland's seas as the 'graveyard for the EU's attempt at management'."
'Wide-ranging'
Liberal Democrat Fisheries spokesman Liam McArthur congratulated the team for its analysis of the "complex challenges" facing the fishing industry.
"The recommendations they make are wide-ranging," he said.
"In many cases, they will make for uncomfortable reading not just for fishermen and ministers, but for all those with an interest and involvement in the sector."
Peter Peacock, Labour MSP for Highlands and Islands, said the report would be a useful contribution to shaping the future of fisheries management in Scotland.
He called on the government to step up efforts to protect the interests of Scottish fleets.
Dr Mireille Thom, marine policy officer at WWF Scotland said the report made it clear that the industry faced an "uncertain future" without additional steps at home and abroad.
Thursday, November 4, 2010
Study: Melt Water Flowing Through Ice Sheets Accelerates Warming, Could Speed Up Ice Flow
Underwater Times: Study: Melt Water Flowing Through Ice Sheets Accelerates Warming, Could Speed Up Ice Flow
BOULDER, Colorado -- Melt water flowing through ice sheets via crevasses, fractures and large drains called moulins can carry warmth into ice sheet interiors, greatly accelerating the thermal response of an ice sheet to climate change, according to a new study involving the University of Colorado at Boulder.
The new study showed ice sheets like the Greenland Ice Sheet can respond to such warming on the order of decades rather than the centuries projected by conventional thermal models. Ice flows more readily as it warms, so a warming climate can increase ice flows on ice sheets much faster than previously thought, said the study authors.
"We are finding that once such water flow is initiated through a new section of ice sheet, it can warm rather significantly and quickly, sometimes in just 10 years, " said lead author Thomas Phillips, a research scientist with Cooperative Institute for Research in Environmental Sciences. CIRES is a joint institute between CU-Boulder and the National Oceanic and Atmospheric Administration.
Phillips, along with CU-Boulder civil, environmental and architectural engineering Professor Harihar Rajaram and CIRES Director Konrad Steffen described their results in a paper published online this week in Geophysical Research Letters.
Conventional thermal models of ice sheets do not factor in the presence of water within the ice sheet as a warming agent, but instead use models that primarily consider ice-sheet heating by warmer air on the ice sheet surface. In water's absence, ice warms slowly in response to the increased surface temperatures from climate change, often requiring centuries to millennia to happen.
But the Greenland ice sheet is not one solid, smooth mass of ice. As the ice flows towards the coast, grating on bedrock, crevasses and new fractures form in the upper 100 feet of the ice sheet. Melt water flowing through these openings can create "ice caves" and networks of "pipes" that can carry water through the ice and spreading warmth, the authors concluded.
To quantify the influence of melt water, the scientists modeled what would happen to the ice sheet temperature if water flowed through it for eight weeks every summer -- about the length of the active melt season. The result was a significantly faster-than-expected increase in ice sheet warming, which could take place on the order of years to decades depending on the spacing of crevasses and other "pipes" that bring warmer water into the ice sheet in summer.
"The key difference between our model and previous models is that we include heat exchange between water flowing through the ice sheet and the ice," said Rajaram.
Several factors contributed to the warming and resulting acceleration of ice flow, including the fact that flowing water into the ice sheets can stay in liquid form even through the winter, slowing seasonal cooling. In addition, warmer ice sheets are more susceptible to increases of water flow, including the basal lubrication of ice that allows ice to flow more readily on bedrock.
A third factor is melt water cascading downward into the ice, which warms the surrounding ice. In this process the water can refreeze, creating additional cracks in the more vulnerable warm ice, according to the study.
Taken together, the interactions between water, temperature, and ice velocity spell even more rapid changes to ice sheets in a changing climate than currently anticipated, the authors concluded. After comparing observed temperature profiles from Greenland with the new model described in the paper, the authors concluded the observations were unexplainable unless they accounted for warming.
"The fact that the ice temperatures warm rather quickly is really the key piece that's been overlooked in models currently being used to determine how Greenland responds to climate warming," Steffen said. "However, this process is not the 'death knell' for the ice sheet. Even under such conditions, it would still take thousands of years for the Greenland ice sheet to disappear, Steffen said.
BOULDER, Colorado -- Melt water flowing through ice sheets via crevasses, fractures and large drains called moulins can carry warmth into ice sheet interiors, greatly accelerating the thermal response of an ice sheet to climate change, according to a new study involving the University of Colorado at Boulder.
The new study showed ice sheets like the Greenland Ice Sheet can respond to such warming on the order of decades rather than the centuries projected by conventional thermal models. Ice flows more readily as it warms, so a warming climate can increase ice flows on ice sheets much faster than previously thought, said the study authors.
"We are finding that once such water flow is initiated through a new section of ice sheet, it can warm rather significantly and quickly, sometimes in just 10 years, " said lead author Thomas Phillips, a research scientist with Cooperative Institute for Research in Environmental Sciences. CIRES is a joint institute between CU-Boulder and the National Oceanic and Atmospheric Administration.
Phillips, along with CU-Boulder civil, environmental and architectural engineering Professor Harihar Rajaram and CIRES Director Konrad Steffen described their results in a paper published online this week in Geophysical Research Letters.
Conventional thermal models of ice sheets do not factor in the presence of water within the ice sheet as a warming agent, but instead use models that primarily consider ice-sheet heating by warmer air on the ice sheet surface. In water's absence, ice warms slowly in response to the increased surface temperatures from climate change, often requiring centuries to millennia to happen.
But the Greenland ice sheet is not one solid, smooth mass of ice. As the ice flows towards the coast, grating on bedrock, crevasses and new fractures form in the upper 100 feet of the ice sheet. Melt water flowing through these openings can create "ice caves" and networks of "pipes" that can carry water through the ice and spreading warmth, the authors concluded.
To quantify the influence of melt water, the scientists modeled what would happen to the ice sheet temperature if water flowed through it for eight weeks every summer -- about the length of the active melt season. The result was a significantly faster-than-expected increase in ice sheet warming, which could take place on the order of years to decades depending on the spacing of crevasses and other "pipes" that bring warmer water into the ice sheet in summer.
"The key difference between our model and previous models is that we include heat exchange between water flowing through the ice sheet and the ice," said Rajaram.
Several factors contributed to the warming and resulting acceleration of ice flow, including the fact that flowing water into the ice sheets can stay in liquid form even through the winter, slowing seasonal cooling. In addition, warmer ice sheets are more susceptible to increases of water flow, including the basal lubrication of ice that allows ice to flow more readily on bedrock.
A third factor is melt water cascading downward into the ice, which warms the surrounding ice. In this process the water can refreeze, creating additional cracks in the more vulnerable warm ice, according to the study.
Taken together, the interactions between water, temperature, and ice velocity spell even more rapid changes to ice sheets in a changing climate than currently anticipated, the authors concluded. After comparing observed temperature profiles from Greenland with the new model described in the paper, the authors concluded the observations were unexplainable unless they accounted for warming.
"The fact that the ice temperatures warm rather quickly is really the key piece that's been overlooked in models currently being used to determine how Greenland responds to climate warming," Steffen said. "However, this process is not the 'death knell' for the ice sheet. Even under such conditions, it would still take thousands of years for the Greenland ice sheet to disappear, Steffen said.
Wednesday, November 3, 2010
From whaler to whales' saviour
Brisbane Times: From whaler to whales' saviour
A FORMER Norwegian whaling ship, docked in Melbourne this week, has been transformed into an anti-whaling specialist by the Sea Shepherd activists.
The 52-metre Bob Barker, coated in the activists' signature black paint and named after the former US game show host who helped Sea Shepherd buy the ship, will open to the public on Saturday as the activists prepare for their seventh battle against Japan's whaling fleet in the Southern Ocean.
Sea Shepherd's Australian co-ordinator Gillian Forbes said the ship was given a free berth by the City of Melbourne's Docklands Waterways Unit after the activists won support from state Labor MP Nathan Murphy and Lord Mayor Robert Doyle.
Advertisement: Story continues below A City of Melbourne spokesperson said Sea Shepherd ships had received free berths several times before.
Ship manager Andrea Gordon would not reveal the anti-whaling tactics Sea Shepherd is planning for the December to March whaling season. But she defended its past controversial use of butyric acid, which Japanese whalers said had injured their crews. ''It was essentially rotten butter; Sea Shepherd is very proud that we have not injured anyone and we always make sure we're a safe and non-violent organisation,'' she said.
''We expect we will have some additional tactics this year - you'll have to wait and find out.'' Ms Gordon was more forthcoming about the latest weapon; a high-speed, multi-hull vessel. ''The new interceptor … looks like something out of Batman. It will be able to go faster than the harpoon ships, so it will be very useful in finding the whaling fleet.''
Futuristic craft Ady Gil was spectacularly destroyed after clashing with whaling ship Shonan Maru No. 2, but its replacement is twice the size.
The Bob Barker will leave for Hobart in less than two weeks to join two other Sea Shepherd ships for the next anti-whaling campaign in Antarctica.
A FORMER Norwegian whaling ship, docked in Melbourne this week, has been transformed into an anti-whaling specialist by the Sea Shepherd activists.
The 52-metre Bob Barker, coated in the activists' signature black paint and named after the former US game show host who helped Sea Shepherd buy the ship, will open to the public on Saturday as the activists prepare for their seventh battle against Japan's whaling fleet in the Southern Ocean.
Sea Shepherd's Australian co-ordinator Gillian Forbes said the ship was given a free berth by the City of Melbourne's Docklands Waterways Unit after the activists won support from state Labor MP Nathan Murphy and Lord Mayor Robert Doyle.
Advertisement: Story continues below A City of Melbourne spokesperson said Sea Shepherd ships had received free berths several times before.
Ship manager Andrea Gordon would not reveal the anti-whaling tactics Sea Shepherd is planning for the December to March whaling season. But she defended its past controversial use of butyric acid, which Japanese whalers said had injured their crews. ''It was essentially rotten butter; Sea Shepherd is very proud that we have not injured anyone and we always make sure we're a safe and non-violent organisation,'' she said.
''We expect we will have some additional tactics this year - you'll have to wait and find out.'' Ms Gordon was more forthcoming about the latest weapon; a high-speed, multi-hull vessel. ''The new interceptor … looks like something out of Batman. It will be able to go faster than the harpoon ships, so it will be very useful in finding the whaling fleet.''
Futuristic craft Ady Gil was spectacularly destroyed after clashing with whaling ship Shonan Maru No. 2, but its replacement is twice the size.
The Bob Barker will leave for Hobart in less than two weeks to join two other Sea Shepherd ships for the next anti-whaling campaign in Antarctica.
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