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#446034 - 09/07/12 09:06 AM Half of the polar ice cap is missing
Marty Online   happy
Extraordinary melting of sea ice in the Arctic this summer has shattered the all-time low sea ice extent record set in September 2007, and sea ice continues to decline far below what has ever been observed. The new sea ice record was set on August 26, a full three weeks before the usual end of the melting season, according to the National Snow and Ice Data Center. Every major scientific institution that tracks Arctic sea ice agrees that new records for low ice area, extent, and volume have been set. These organizations include the University of Washington Polar Science Center (a new record for low ice volume), the Nansen Environmental & Remote Sensing Center in Norway, and the University of Illinois Cryosphere Today. A comprehensive collection of sea ice graphs shows the full story. Satellite records of sea ice extent date back to 1979, though a 2011 study by Kinnard et al. shows that the Arctic hasn't seen a melt like this for at least 1,450 years (see a more detailed article on this over at skepticalscience.com.) The latest September 5, 2012 extent of 3.5 million square kilometers is approximately a 50% reduction in the area of Arctic covered by sea ice, compared to the average from 1979 - 2000. The ice continues to melt, and has not reached the low for this year yet.

Figure 1. A sunny, slushy day at the North Pole on September 1, 2012. Webcam image courtesy of the North Pole Environmental Observatory.

Figure 2. Sea ice extent on September 5, 2012, showed that half of the polar ice cap was missing, compared to the average from 1979 - 2000. Image credit: National Snow and Ice Data Center.

Why the Arctic sea ice is important
Arctic sea ice is an important component of the global climate system. The polar ice caps help to regulate global temperature by reflecting sunlight back into space. White snow and ice at the poles reflects sunlight, but dark ocean absorbs it. Replacing bright sea ice with dark ocean is a recipe for more and faster global warming. The Autumn air temperature over the Arctic has increased by 4 - 6°F in the past decade, and we could already be seeing the impacts of this warming in the mid-latitudes, by an increase in extreme weather events. Another non-trivial impact of the absence of sea ice is increased melting in Greenland. We already saw an unprecedented melting event in Greenland this year, and as warming continues, the likelihood of these events increase.

Figure 3. August set a new record for lowest Arctic sea ice extent. Image credit: National Snow and Ice Data Center.

Figure 4. Arctic sea ice death spiral as plotted by Jim Pettit using data from the Japan Aerospace Exploration Agency.

Huge storm pummels Alaska
A massive low pressure system with a central pressure of 970 mb swept through Alaska on Tuesday, generating hurricane-force wind gusts near Anchorage, Alaska that knocked out power to 55,000 homes. Mighty Alaskan storms like this are common in winter, but rare in summer and early fall. The National Weather Service in Anchorage said in their Wednesday forecast discussion that the forecast wind speeds from this storm were incredibly strong for this time of year--four to six standard anomalies above normal. A four-standard anomaly event occurs once every 43 years, and a five-standard anomaly event is a 1-in-4800 year event. However, a meteorologist I heard from who lives in the Anchorage area characterized the wind damage that actually occurred as a 1-in-10 year event. A few maximum wind gusts recorded on Tuesday during the storm:

McHugh Creek (Turnagain Arm)... ... ..88 mph
Paradise Valley (Potter Marsh)... ... 75 mph
Upper Hillside (1400 ft)... ... ... ... 70 mph
Anchorage port... ... ... ... ... ... ... .63 mph

The storm has weakened to a central pressure of 988 mb today, and is located just north of Alaska. The storm is predicted to bring strong winds of 25 - 35 mph and large waves to the edge of the record-thin and record-small Arctic ice cap, and may add to the unprecedented decline in Arctic sea ice being observed this summer.

Figure 5. An unusually strong storm formed off the coast of Alaska on August 5 and tracked into the center of the Arctic Ocean, where it slowly dissipated over the next several days. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this natural-color mosaic image on Aug. 6, 2012. The center of the storm at that date was located in the middle of the Arctic Ocean. Image credit: NASA.

Arctic storms may be increasing due to climate change
This week's Alaskan storm is the second unusually strong low pressure system to affect the Arctic in the past month. On August 4 - 8, a mighty storm with a central pressure of 963 mb raged through the Arctic, bringing strong winds that helped scatter and break up Arctic sea ice. According to a detailed post at NASA Earth Observatory, that storm was in the top 3 percent for strongest storms ever recorded north of 70 degrees latitude. A study of long-term Arctic cyclone trends authored by a team led by John Walsh and Xiangdong Zhang of the University of Alaska Fairbanks found that number and intensity of Arctic cyclones has increased during the second half of the twentieth century, particularly during the summer. Dr. Zhang explained that climate change has caused sea ice to retreat markedly in recent decades and has also warmed Arctic Ocean temperatures. Such changes may be providing more energy and moisture to support cyclone development and persistence. The strong storms of this week and a month ago would have had far less impact on the ice just a decade ago, when the sea ice was much thicker and more extensive.

A sea ice decline double-whammy
The monster Arctic storms like we've seen this year have sped up the rate of sea ice loss, but increased water temperatures and air temperatures due to human-caused global warming are the dominant reasons for the record melting of the Arctic sea ice. A July 2012 study by Day et al. found that the most influential of the possible natural influences on sea ice loss was the Atlantic Multi-decadal Oscillation (AMO). The AMO has two phases, negative (cold) and positive (warm), which impact Arctic sea ice. The negative phase tends to create sea surface temperatures in the far north Atlantic that are colder than average. In this study, the AMO only accounted for 5% - 31% of the observed September sea ice decline since 1979. The scientists concluded that given the lack of evidence that natural forces were controlling sea ice fluctuations, the majority of sea ice decline we've seen during the 1953 - 2010 period was due to human causes.

#446494 - 09/13/12 07:56 AM Re: Half of the polar ice cap is missing [Re: Marty]
Marty Online   happy

Arctic Ice Melt Could Mean More Extreme Winters For U.S. And Europe

From Climate Central:

The record loss of Arctic sea ice this summer will echo throughout the weather patterns affecting the U.S. and Europe this winter, climate scientists said on Wednesday, since added heat in the Arctic influences the jet stream and may make extreme weather and climate events more likely.

The “astounding” loss of sea ice this year is adding a huge amount of heat to the Arctic Ocean and the atmosphere, said Jennifer Francis, an atmospheric scientist at Rutgers University in New Jersey. “It’s like having a new energy source for the atmosphere.” Francis was one of three scientists on a conference call Wednesday to discuss the ramifications of sea ice loss for areas outside the Arctic. The call was hosted by Climate Nexus.

arctic sea ice

The extent of Arctic sea ice on Aug. 26, 2012, the day the sea ice dipped to its smallest extent ever recorded in more than three decades of satellite measurements. The line on the image shows the average minimum extent from the period covering 1979-2010. Click on the image for a larger version. Credit: NASA/JPL.

On August 26, Arctic sea ice extent broke the record low set in 2007, and it has continued to decline since, dropping below 1.5 million square miles. That represents a 45 percent reduction in the area covered by sea ice compared to the 1980s and 1990s, according to the National Snow and Ice Data Center (NSIDC), and may be unprecedented in human history. The extent of sea ice that melted so far this year is equivalent to the size of Canada and Alaska combined.

The loss of sea ice initiates a feedback loop known as Arctic amplification. As sea ice melts, it exposes darker ocean waters to incoming solar radiation. The ocean then absorbs far more energy than had been the case when the brightly colored sea ice was present, and this increases water and air temperatures, thereby melting even more sea ice.

Peter Wadhams, the head of the polar ocean physics group at the University of Cambridge in the U.K., told BBC News on September 6 that the added heat from sea ice loss is equivalent to the warming from 20 years of carbon dioxide emissions. Carbon dioxide is the main greenhouse gas that is causing manmade global warming.

During the fall, when the sun sets once again and the Arctic Ocean begins to refreeze, the heat in the ocean gets released back into the atmosphere. Since the jet stream, which is a corridor of strong winds at upper levels of the atmosphere that generally blows from west to east across the northern mid-latitudes, is powered by the temperature difference between the Arctic and areas farther south, any alteration of that temperature difference is bound to alter the jet stream — with potentially profound implications. It just so happens that the jet stream steers day-to-day weather systems.

Francis published a study last year in which she showed that Arctic warming might already be causing the jet stream to become more amplified in a north-south direction. In other words, the fall and winter jet stream may be getting wavier. A more topsy-turvy jet stream can yield more extreme weather events, Francis said, because weather and climate extremes are often associated with large undulations in the jet stream that can take a long time to dissipate.

“We know that certain types of extreme weather events are related to weather that takes a long time to change,” Francis said.

While there are indications that the jet stream is slowing and may be more prone to making huge dips, or “troughs,” scientists have a limited ability to pinpoint how this will play out in the coming winter season.

“The locations of those waves really depends on other factors,” Francis said, such as El Niño and a natural climate pattern known as the Arctic Oscillation. “I can only say that it’s probably going to be a very interesting winter,” she said.

Francis’ work has linked Arctic warming to the unusually cold and snowy winters of 2009-10 and 2010-11, during which the U.S. East Coast and parts of Europe were pummeled by fierce winter storms and experienced cooler-than-average conditions. The winter of 2011-12 was much milder, by comparison, but Francis said it, too, was consistent with her research. Not all meteorologists agree on the Arctic connection theory, but that may change with time.

Jim Overland, an oceanographer at NOAA's Pacific Marine Environmental Laboratory, said the inconsistency of the past three winters doesn’t mean the Arctic connection hypothesis is invalid.

“People like direct causality, [the notion that] if you lose the ice every year it will cause the same effect,” Overland said. But the chaotic nature of the atmosphere means that all that scientists can say with a high degree of confidence is that “the number of [extreme] events somewhere are destined to increase” as a result of rapid Arctic climate change, Overland said.

Huffington Post

#456224 - 01/24/13 04:06 PM Re: Half of the polar ice cap is missing [Re: Marty]
PhilL Offline
Sudden stratospheric warming events are also becoming more common. These events are the primary cause for the extreme winters in the northern US and are connected with the loss of Arctic sea ice.

One of these events began on January 6th and what has been a mild winter so far has become very cold in the eastern US. And instead of the cold ending in mid-February, as usual, this year the cold may continue into March.

Tides, Quizzes

#456233 - 01/24/13 09:14 PM Re: Half of the polar ice cap is missing [Re: Marty]
Yet the Antarctic has more ice than before. The earth changes far more than the global warming activists will admit or, for that matter, understand.


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