Archive for the ‘atmospheric circulation’ Category

Atmospheric circulation determines extent of arctic sea ice

08/25/2009

“During the first half of August, Arctic ice extent declined more slowly than during the same period in 2007 and 2008. The slower decline is primarily due to a recent atmospheric circulation pattern, which transported ice toward the Siberian coast and discouraged export of ice out of the Arctic Ocean. It is now unlikely that 2009 will see a record low extent …

Ice motion changes in August

A recent atmospheric circulation pattern, which led to a change in ice motion, caused the ice loss rate to slow down significantly in the first two weeks of August. As discussed in the August 4 post, during much of June and July, a strong Beaufort Sea high-pressure pattern promoted winds that helped push ice out of the Siberian coastal seas, and also brought clear skies and warm temperatures that helped induce melt.

Toward the end of July, the atmospheric pattern changed. Averaged over the past two weeks, a high-pressure system has been centered over the Barents Sea, with low pressure centered over the Laptev Sea. In accordance with Buys Ballot’s Law, this pattern led to winds that redirected the motion of the ice cover, pushing the ice edge outward toward the Siberian coast and discouraging ice from exiting the Arctic Ocean through Fram Strait.

The Northwest Passage and Northern Sea Route

So far this year, neither the Northwest Passage nor the Northern Sea Route has opened. The Northern Sea Route appears likely to open soon, but ice still clogs many of the channels in the Northwest Passage.

Whether or not the navigational passages through the Arctic Ocean will open in a given summer depends on atmospheric circulation and ice thickness. For example, although 2007 was a record low extent in the Arctic and the Northwest Passage was nearly completely open, the Northern Sea Route was still choked with ice because of a circulation pattern that pushed a tongue of ice against the Siberian coast. Recent research by Stephen Howell at the University of Waterloo in Canada shows that whether the Northwest Passage clears depends less on how much melt occurs, and more on whether multi-year sea ice is pushed into the channels. Counterintuitively, as the ice cover thins, ice may flow more easily into the channels, preventing the Northwest Passage from regularly opening in coming decades.

Comment on atmospheric circulation patterns

James Overland of the NOAA Pacific Marine Environmental Laboratory in Seattle, Washington has taken a close look at patterns of atmospheric circulation in recent summers. Overland notes that the periods June through August 2007 and June and July 2009 both saw an unusual atmospheric pattern of sea level pressure, with higher pressure on the Alaskan side of the Arctic and lower pressure on the Eurasian side. This pressure difference brought warm air into the central Arctic and transported sea ice towards the Atlantic. Historically, such a pattern is a rare event—before 2007, it only occurred twice in 30 years. Normally there is little difference in pressure across the Arctic during summer, and winds are slack.” “A change in ice motion slows seasonal decline” Prior post here

Atmospheric circulation determines extent of arctic sea ice

08/25/2009

“During the first half of August, Arctic ice extent declined more slowly than during the same period in 2007 and 2008. The slower decline is primarily due to a recent atmospheric circulation pattern, which transported ice toward the Siberian coast and discouraged export of ice out of the Arctic Ocean. It is now unlikely that 2009 will see a record low extent …

Ice motion changes in August

A recent atmospheric circulation pattern, which led to a change in ice motion, caused the ice loss rate to slow down significantly in the first two weeks of August. As discussed in the August 4 post, during much of June and July, a strong Beaufort Sea high-pressure pattern promoted winds that helped push ice out of the Siberian coastal seas, and also brought clear skies and warm temperatures that helped induce melt.

Toward the end of July, the atmospheric pattern changed. Averaged over the past two weeks, a high-pressure system has been centered over the Barents Sea, with low pressure centered over the Laptev Sea. In accordance with Buys Ballot’s Law, this pattern led to winds that redirected the motion of the ice cover, pushing the ice edge outward toward the Siberian coast and discouraging ice from exiting the Arctic Ocean through Fram Strait.

The Northwest Passage and Northern Sea Route

So far this year, neither the Northwest Passage nor the Northern Sea Route has opened. The Northern Sea Route appears likely to open soon, but ice still clogs many of the channels in the Northwest Passage.

Whether or not the navigational passages through the Arctic Ocean will open in a given summer depends on atmospheric circulation and ice thickness. For example, although 2007 was a record low extent in the Arctic and the Northwest Passage was nearly completely open, the Northern Sea Route was still choked with ice because of a circulation pattern that pushed a tongue of ice against the Siberian coast. Recent research by Stephen Howell at the University of Waterloo in Canada shows that whether the Northwest Passage clears depends less on how much melt occurs, and more on whether multi-year sea ice is pushed into the channels. Counterintuitively, as the ice cover thins, ice may flow more easily into the channels, preventing the Northwest Passage from regularly opening in coming decades.

Comment on atmospheric circulation patterns

James Overland of the NOAA Pacific Marine Environmental Laboratory in Seattle, Washington has taken a close look at patterns of atmospheric circulation in recent summers. Overland notes that the periods June through August 2007 and June and July 2009 both saw an unusual atmospheric pattern of sea level pressure, with higher pressure on the Alaskan side of the Arctic and lower pressure on the Eurasian side. This pressure difference brought warm air into the central Arctic and transported sea ice towards the Atlantic. Historically, such a pattern is a rare event—before 2007, it only occurred twice in 30 years. Normally there is little difference in pressure across the Arctic during summer, and winds are slack.” “A change in ice motion slows seasonal decline” Prior post here

Arctic sea ice does not melt in place, it is pushed out of the arctic by winds and currents

04/14/2009


“One of the common misconceptions pushed in the media is that Arctic sea ice simply “melts in place”. …

[But] this NASA JPL study that suggests winds may play a key role in pushing Arctic sea ice into lower latitudes where it melts. The author suggests winds may be the dominant factor in the 2007 record low ice extent:

Nghiem said the rapid decline in winter perennial ice the past two years was caused by unusual winds. “Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic,” he said. When that sea ice reached lower latitudes, it rapidly melted in the warmer waters.

Interestingly we can now watch this actually happen thanks to an animation of AMSER-E satellite 89Ghz sounder images … available here as a flash video or here as an AVI file (highest quality 7.3 MB)

What is interesting about this video is that you can watch sea ice being flushed out of the Arctic sea and pushed along Greenland’s east coast [top center], where it then finds its way into warmer waters and melts. Also note how in the lower right, in the Beaufort sea, older multiyear ice gets fractured and broken up as winds and currents stress it.” “Watching the 2007 historic low sea ice flow out of the Arctic Sea

Arctic sea ice does not melt in place, it is pushed out of the arctic by winds and currents

04/14/2009


“One of the common misconceptions pushed in the media is that Arctic sea ice simply “melts in place”. …

[But] this NASA JPL study that suggests winds may play a key role in pushing Arctic sea ice into lower latitudes where it melts. The author suggests winds may be the dominant factor in the 2007 record low ice extent:

Nghiem said the rapid decline in winter perennial ice the past two years was caused by unusual winds. “Unusual atmospheric conditions set up wind patterns that compressed the sea ice, loaded it into the Transpolar Drift Stream and then sped its flow out of the Arctic,” he said. When that sea ice reached lower latitudes, it rapidly melted in the warmer waters.

Interestingly we can now watch this actually happen thanks to an animation of AMSER-E satellite 89Ghz sounder images … available here as a flash video or here as an AVI file (highest quality 7.3 MB)

What is interesting about this video is that you can watch sea ice being flushed out of the Arctic sea and pushed along Greenland’s east coast [top center], where it then finds its way into warmer waters and melts. Also note how in the lower right, in the Beaufort sea, older multiyear ice gets fractured and broken up as winds and currents stress it.” “Watching the 2007 historic low sea ice flow out of the Arctic Sea

A look back from 2058

12/23/2008

“The early 20th century experienced cooling temperatures that had some scientists concerned about a return to ice age conditions. Then, from about 1920 through 1940, a shift to warmer weather had scientists fretting about the dramatic warming. The decade of the 1930s remains the warmest in the relatively short US temperature history as does the year 1934. Then concerns about global warming faded as patterns again shifted around 1940 and global cooling prevailed. As glaciers and polar ice expanded, concerns grew among some scientists that coal burning added particulates to the atmosphere that blocked incoming solar radiation to reduce global temperatures.

However, just as concerns peaked about a possible human-induced new ice age, another natural warm cycle began. During the last few decades of the 20th century, Earth experienced a natural warming cycle related to normal shifts in oceanic and atmospheric circulations and solar cycles. Nevertheless, some scientists became alarmed about increasing global temperatures, dubbing this warming episode “global warming” and, noting an upward trend in atmospheric carbon dioxide, presumed it to come from human activity. These scientists ignored historic climate trends and leapt at a theory, “anthropogenic global warming” (AGW), that tried to explain global warming as catastrophic to the planet’s future and caused by humans burning fossil fuels! …

Then as the 21st century began, Earth’s climate managed to grab the headlines from the scientists. Once again the forces that create short-term climate variability worked to switch back to a cold phase. Ocean and atmospheric circulations moved to cold phase and solar activity dropped to an unusually low level that promised to be of extended duration. These factors led to a prolonged cooling trend whose effects are still being played out at this date!

As global cooling replaced warming, the flawed AGW theory was rejected in favor of more research into natural climate variability and planning so humans could adapt to climate change. …

Humanity learned a valuable lesson in humility as it’s understanding of natural climate change matured and we became better prepared for inevitable climate changes.” “How Humans Dealt With Climate Change – A look back from 2058

A look back from 2058

12/23/2008

“The early 20th century experienced cooling temperatures that had some scientists concerned about a return to ice age conditions. Then, from about 1920 through 1940, a shift to warmer weather had scientists fretting about the dramatic warming. The decade of the 1930s remains the warmest in the relatively short US temperature history as does the year 1934. Then concerns about global warming faded as patterns again shifted around 1940 and global cooling prevailed. As glaciers and polar ice expanded, concerns grew among some scientists that coal burning added particulates to the atmosphere that blocked incoming solar radiation to reduce global temperatures.

However, just as concerns peaked about a possible human-induced new ice age, another natural warm cycle began. During the last few decades of the 20th century, Earth experienced a natural warming cycle related to normal shifts in oceanic and atmospheric circulations and solar cycles. Nevertheless, some scientists became alarmed about increasing global temperatures, dubbing this warming episode “global warming” and, noting an upward trend in atmospheric carbon dioxide, presumed it to come from human activity. These scientists ignored historic climate trends and leapt at a theory, “anthropogenic global warming” (AGW), that tried to explain global warming as catastrophic to the planet’s future and caused by humans burning fossil fuels! …

Then as the 21st century began, Earth’s climate managed to grab the headlines from the scientists. Once again the forces that create short-term climate variability worked to switch back to a cold phase. Ocean and atmospheric circulations moved to cold phase and solar activity dropped to an unusually low level that promised to be of extended duration. These factors led to a prolonged cooling trend whose effects are still being played out at this date!

As global cooling replaced warming, the flawed AGW theory was rejected in favor of more research into natural climate variability and planning so humans could adapt to climate change. …

Humanity learned a valuable lesson in humility as it’s understanding of natural climate change matured and we became better prepared for inevitable climate changes.” “How Humans Dealt With Climate Change – A look back from 2058

Scare tactics in Oregon: it's all based on models

12/16/2008

“If global warming continues unabated, summer temperatures in the Rogue River Valley could rise up to 15 degrees by 2080, making the weather in the southern Oregon valley similar to Sacramento’s, Oregon researchers said in a report released today. …

The report, drafted by the University of Oregon’s Climate Leadership Initiative and the Ashland-based National Center for Conservation Science & Policy, is the first of four that will try to boil down climate change predictions to a regional scale in southern Oregon.” “Climate change could hit Rogue Valley hard

From the report link above: “The project began by downscaling three climate models (CSIRO, MIROC, and Hadley) and incorporating a global vegetation change model (MC1) used by the Intergovernmental Panel on Climate Change. A panel of scientists and land managers then assessed the likely risks posed by changing climate [model] conditions to natural systems and made recommendations for increasing the capacity of ecosystems and species to withstand and adapt to those [virtual] stressors. In turn, a panel of policy experts used the [virtual] information provided by the scientists to assess the likely risks to economic, built, and human systems within the Rogue Basin posed by [virtual] climate change and recommended ways to increase resistance and resiliency of those systems.”

Scare tactics in Oregon: it’s all based on models

12/16/2008

“If global warming continues unabated, summer temperatures in the Rogue River Valley could rise up to 15 degrees by 2080, making the weather in the southern Oregon valley similar to Sacramento’s, Oregon researchers said in a report released today. …

The report, drafted by the University of Oregon’s Climate Leadership Initiative and the Ashland-based National Center for Conservation Science & Policy, is the first of four that will try to boil down climate change predictions to a regional scale in southern Oregon.” “Climate change could hit Rogue Valley hard

From the report link above: “The project began by downscaling three climate models (CSIRO, MIROC, and Hadley) and incorporating a global vegetation change model (MC1) used by the Intergovernmental Panel on Climate Change. A panel of scientists and land managers then assessed the likely risks posed by changing climate [model] conditions to natural systems and made recommendations for increasing the capacity of ecosystems and species to withstand and adapt to those [virtual] stressors. In turn, a panel of policy experts used the [virtual] information provided by the scientists to assess the likely risks to economic, built, and human systems within the Rogue Basin posed by [virtual] climate change and recommended ways to increase resistance and resiliency of those systems.”

A new cause for enviros to get excited about?

11/19/2008

“Generating wind power at sea may disturb ocean currents and marine ecosystems, according to a new study. …

Extracting energy from wind changes regional air currents, which can in turn affect how the nearby ocean circulates, according to Goran Brostrom of the Norwegian Meteorological Institute in Oslo. …

Still, Dvorak pointed out Brostrom’s study raises a point no one in the wind power industry had yet considered.

“People have looked at the climate effects of wind farms on land, but this is the first to bring up the question of ocean currents,” he said. “This is something we should be looking at.”” “Offshore wind power could alter ocean currents

A new cause for enviros to get excited about?

11/19/2008

“Generating wind power at sea may disturb ocean currents and marine ecosystems, according to a new study. …

Extracting energy from wind changes regional air currents, which can in turn affect how the nearby ocean circulates, according to Goran Brostrom of the Norwegian Meteorological Institute in Oslo. …

Still, Dvorak pointed out Brostrom’s study raises a point no one in the wind power industry had yet considered.

“People have looked at the climate effects of wind farms on land, but this is the first to bring up the question of ocean currents,” he said. “This is something we should be looking at.”” “Offshore wind power could alter ocean currents