The gulf stream is slowing
The powerful ocean current that bathes Britain and northern Europe in warm waters from the tropics has weakened dramatically in recent years, a consequence of global warming that could trigger more severe winters and cooler summers across the region, scientists warn today.
Researchers on a scientific expedition in the Atlantic Ocean measured the strength of the current between Africa and the east coast of America and found that the circulation has slowed by 30% since a previous expedition 12 years ago.
The current, which drives the Gulf Stream, delivers the equivalent of 1m power stations-worth of energy to northern Europe, propping up temperatures by 10C in some regions. The researchers found that the circulation has weakened by 6m tonnes of water a second. Previous expeditions to check the current flow in 1957, 1981 and 1992 found only minor changes in its strength, although a slowing was picked up in a further expedition in 1998.
The current is essentially a huge oceanic conveyor belt that transports heat from equatorial regions towards the Arctic circle. Warm surface water coming up from the tropics gives off heat as it moves north until eventually, it cools so much in northern waters that it sinks and circulates back to the south. There it warms again, rises and heads back north. The constant sinking in the north and rising in the south drives the conveyor.
Global warming weakens the circulation because increased meltwater from Greenland and the Arctic icesheets along with greater river run-off from Russia pour into the northern Atlantic and make it less saline which in turn makes it harder for the cooler water to sink, in effect slowing down the engine that drives the current. Thermal expansion of ocean water will double the increase from glacial melting and runoff from rivers and streams that empty in reaching the ocean.
The researchers measured the strength of the current at a latitude of 25 degrees N and found that the volume of cold, deep water returning south had dropped by 30%. At the same time, they measured a 30% increase in the amount of surface water peeling off early from the main northward current, suggesting far less was continuing up to Britain and the rest of Europe. According to climate modelers, the drop in temperature caused by a slowing of the Atlantic current will, in the long term, be swamped by a more general warming of the atmosphere.
Saturday, March 13, 2010
Friday, March 12, 2010
Climate Change, Time to deal With It
Global warming has become perhaps the most complicated issue facing world leaders. On the one hand, warnings from the scientific community are becoming louder, as an increasing body of science points to rising dangers from the ongoing buildup of human-related greenhouse gases — produced mainly by the burning of fossil fuels and forests. On the other, the technological, economic and political issues that have to be resolved before a concerted worldwide effort to reduce emissions can begin have gotten no simpler, particularly in the face of a global economic slowdown.
At the heart of the debate is a momentous tussle between rich and poor countries over who steps up first and who pays most for changed energy menus. People worldwide must come to the realization that we will have to pay now or later but we will pay in the end and the cost to the economies of the world will suffer greater the longer we wait.
96 percent of the worlds glaciers are shrinking.
The continued retreat of glaciers will have a number of different quantitative impacts. In areas that are heavily dependent on water runoff from glaciers that melt during the warmer summer months, a continuation of the current retreat will eventually deplete the glacial ice and substantially reduce or eliminate runoff. A reduction in runoff will affect the ability to irrigate crops and will reduce summer stream flows necessary to keep dams and reservoirs replenished. This situation is particularly acute for irrigation in South America, where numerous artificial lakes are filled almost exclusively by glacial melt. Central Asian countries have also been historically dependent on the seasonal glacier melt water for irrigation and drinking supplies. In Norway, the Alps, and the Pacific Northwest of North America, glacier runoff is important for hydropower.
Pine Island glacier in Antarctic is being depleted at the rate of 16 meters per year loss of ice depth Larson ice shelves a and b are already gone with Larson B being the size of Rhode Island
The recent collapse of Wordie Ice Shelf, Prince Gustav Ice Shelf, Mueller Ice Shelf, Jones Ice Shelf, Larsen-A and Larsen-B Ice Shelf on the Antarctic Peninsula has raised awareness of how dynamic ice shelf systems are. Jones ice Shelf had an area of 35 km2 in the 1970s but by 2008 it had disappeared.
Wordie Ice Shelf has gone from an area of 1500 square kilometers in 1950 to 140 km2 in 2000.
Prince Gustav Ice Shelf has gone from an area of 1600 km2 to 11 km2 in 2008.
After their loss the reduced buttressing of feeder glaciers has allowed the expected speed-up of inland ice masses after shelf ice break-up.
. The Wilkins Ice Shelf is another ice shelf that has suffered substantial retreat. The ice shelf had an area of 16,000 km2 (6,200 sq mi) in 1998 when 1,000 km2 (390 sq mi) was lost.
In 2007 and 2008 significant rifting developed and led to the loss of another 1,400 km2 (540 sq mi) of area.
Studies show of 244 glaciers on the peninsula, 212 have retreated an average of 600 m (2,000 ft) from where they were when first measured in 1953.
The greatest retreat was seen in Sjogren Glacier, which is now 13 km (8.1 mi) further inland than where it was in 1953. There are 32 glaciers that were measured to have advanced; however, these glaciers showed only a modest advance averaging 300 m (980 ft) per glacier, which is significantly smaller than the massive retreat observed.
Arctic arches that contain sea ice from escaping into the Pacific at the Bering Strait and the Atlantic at the Nords strait have failed to stop the doubling of ice released into the oceans with real possibilities of further diluting salt water and effecting ocean currents.
Geophysical Research Letters, used satellites and buoys to show that winds since 2000 had pushed huge amounts of thick old ice out of the Arctic basin past Greenland. The thin floes that formed on the resulting open water melted quicker or could be shuffled together by winds and similarly expelled. The pace of change has far exceeded what had been estimated by almost all the simulations used to envision how the Arctic will respond to rising concentrations of greenhouse gases linked to Global warming. Proponents of cuts in greenhouse gases cited the meltdown as proof that human activities are propelling a slide toward climate calamity.
The Greenland glaciers that cover the island contain enough water to raise sea level twenty feet, or seven meters. It was once thought (and that was only six years ago) that the glaciers would be self-sustaining even in a warming world because of size and so on. We now know that not only are the edges melting fast, but the surface melt is seeping through the ice to lubricate the junction between the glacier and the rock underneath. This is the unexpected factor that has turned scientific attention onto this escalating problem. When this happens much of this mountain of water will flow into the sea. Already twenty-one of the great glacial masses are moving seawards eight times faster than ten years ago and disintegrating three times faster than in the preceding five years. The Greenland, Alaskan and West Antarctic ice sheets together hold about 25% of the fresh water on the planet. The effects of the collapse of either ice sheet would be huge. Once you lost one of these ice sheets, there's no putting it back for thousands of years, if ever.
If they disintegrate, sea level could rise nearly 20 meters, possibly in only one decade. This would swamp most cities and ports, as well a much of the best agricultural land.
At the heart of the debate is a momentous tussle between rich and poor countries over who steps up first and who pays most for changed energy menus. People worldwide must come to the realization that we will have to pay now or later but we will pay in the end and the cost to the economies of the world will suffer greater the longer we wait.
96 percent of the worlds glaciers are shrinking.
The continued retreat of glaciers will have a number of different quantitative impacts. In areas that are heavily dependent on water runoff from glaciers that melt during the warmer summer months, a continuation of the current retreat will eventually deplete the glacial ice and substantially reduce or eliminate runoff. A reduction in runoff will affect the ability to irrigate crops and will reduce summer stream flows necessary to keep dams and reservoirs replenished. This situation is particularly acute for irrigation in South America, where numerous artificial lakes are filled almost exclusively by glacial melt. Central Asian countries have also been historically dependent on the seasonal glacier melt water for irrigation and drinking supplies. In Norway, the Alps, and the Pacific Northwest of North America, glacier runoff is important for hydropower.
Pine Island glacier in Antarctic is being depleted at the rate of 16 meters per year loss of ice depth Larson ice shelves a and b are already gone with Larson B being the size of Rhode Island
The recent collapse of Wordie Ice Shelf, Prince Gustav Ice Shelf, Mueller Ice Shelf, Jones Ice Shelf, Larsen-A and Larsen-B Ice Shelf on the Antarctic Peninsula has raised awareness of how dynamic ice shelf systems are. Jones ice Shelf had an area of 35 km2 in the 1970s but by 2008 it had disappeared.
Wordie Ice Shelf has gone from an area of 1500 square kilometers in 1950 to 140 km2 in 2000.
Prince Gustav Ice Shelf has gone from an area of 1600 km2 to 11 km2 in 2008.
After their loss the reduced buttressing of feeder glaciers has allowed the expected speed-up of inland ice masses after shelf ice break-up.
. The Wilkins Ice Shelf is another ice shelf that has suffered substantial retreat. The ice shelf had an area of 16,000 km2 (6,200 sq mi) in 1998 when 1,000 km2 (390 sq mi) was lost.
In 2007 and 2008 significant rifting developed and led to the loss of another 1,400 km2 (540 sq mi) of area.
Studies show of 244 glaciers on the peninsula, 212 have retreated an average of 600 m (2,000 ft) from where they were when first measured in 1953.
The greatest retreat was seen in Sjogren Glacier, which is now 13 km (8.1 mi) further inland than where it was in 1953. There are 32 glaciers that were measured to have advanced; however, these glaciers showed only a modest advance averaging 300 m (980 ft) per glacier, which is significantly smaller than the massive retreat observed.
Arctic arches that contain sea ice from escaping into the Pacific at the Bering Strait and the Atlantic at the Nords strait have failed to stop the doubling of ice released into the oceans with real possibilities of further diluting salt water and effecting ocean currents.
Geophysical Research Letters, used satellites and buoys to show that winds since 2000 had pushed huge amounts of thick old ice out of the Arctic basin past Greenland. The thin floes that formed on the resulting open water melted quicker or could be shuffled together by winds and similarly expelled. The pace of change has far exceeded what had been estimated by almost all the simulations used to envision how the Arctic will respond to rising concentrations of greenhouse gases linked to Global warming. Proponents of cuts in greenhouse gases cited the meltdown as proof that human activities are propelling a slide toward climate calamity.
The Greenland glaciers that cover the island contain enough water to raise sea level twenty feet, or seven meters. It was once thought (and that was only six years ago) that the glaciers would be self-sustaining even in a warming world because of size and so on. We now know that not only are the edges melting fast, but the surface melt is seeping through the ice to lubricate the junction between the glacier and the rock underneath. This is the unexpected factor that has turned scientific attention onto this escalating problem. When this happens much of this mountain of water will flow into the sea. Already twenty-one of the great glacial masses are moving seawards eight times faster than ten years ago and disintegrating three times faster than in the preceding five years. The Greenland, Alaskan and West Antarctic ice sheets together hold about 25% of the fresh water on the planet. The effects of the collapse of either ice sheet would be huge. Once you lost one of these ice sheets, there's no putting it back for thousands of years, if ever.
If they disintegrate, sea level could rise nearly 20 meters, possibly in only one decade. This would swamp most cities and ports, as well a much of the best agricultural land.
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