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"The question is not whether sea ice loss is affecting the large-scale atmospheric circulation...it's how can it not?"
That was the take-home message from Dr. Jennifer Francis of Rutgers University, in her talk "Does Arctic Amplification Fuel Extreme Weather in Mid-Latitudes?", presented at last week's American Geophysical Union meeting in San Francisco. Dr. Francis presented new research in review for publication, which shows that Arctic sea ice loss may significantly affect the upper-level atmospheric circulation, slowing its winds and increasing its tendency to make contorted high-amplitude loops.
High-amplitude loops in the upper level wind pattern (and associated jet stream) increases the probability of persistent weather patterns in the Northern Hemisphere, potentially leading to extreme weather due to longer-duration cold spells, snow events, heat waves, flooding events, and drought conditions.
Summertime Arctic sea ice loss: 40% since 1980
The Arctic has seen a stunning amount of sea ice loss in recent years, due to melting and unfavorable winds that have pushed large amounts of ice out of the region. Forty percent of the sea ice was missing in September 2007, compared to September of 1980. This is an area equivalent to about 44% of the contiguous U.S., or 71% of the non-Russian portion of Europe. Such a large area of open water is bound to cause significant impacts on weather patterns, due to the huge amount of heat and moisture that escapes from the exposed ocean into the atmosphere over a multi-month period following the summer melt.
Arctic sea ice loss can slow down jet stream winds
Dr. Francis looked at surface and upper level data from 1948 - 2010, and discovered that the extra heat in the Arctic in fall and winter over the past decade had caused the Arctic atmosphere between the surface and 500 mb (about 18,000 feet or 5,600 meters) to expand. As a result, the difference in temperature between the Arctic (60 - 80°N) and the mid-latitudes (30 - 50°N) fell significantly. It is this difference in temperature that drives the powerful jet stream winds that control much of our weather. The speed of fall and winter west-to-east upper-level winds at 500 mb circling the North Pole decreased by 20% over the past decade, compared to the period 1948 - 2000, in response to the extra warmth in the Arctic. This slow-down of the upper-level winds circling the pole has been linked to a Hot Arctic-Cold Continents pattern that brought cold, snowy winters to the Eastern U.S. and Western Europe during 2009 - 2010 and 2010 - 2011.
Arctic sea ice loss may increase the amplitude of jet stream troughs and ridges
The jet stream generally blows from west to east over the northern mid-latitudes, with an average position over the central U.S. in winter and southern Canada in summer. The jet stream marks the boundary between cold polar air to the north and warm subtropical air to the south, and is the path along which rain and snow-bearing low pressure systems ride. Instead of blowing straight west-to-east, the jet stream often contorts itself into a wave-like pattern. Where the jet stream bulges northwards into a ridge of high pressure, warm air flows far to the north. Where the jet loops to the south into a trough of low pressure, cold air spills southwards. The more extreme these loops to the north and south are--the amplitude of the jet stream--the slower the waves move eastward, and consequently, the more persistent the weather conditions tend to be. A high-amplitude jet stream pattern (more than 1000 miles or 1610 km in distance between the bottom of a trough and the peak of a ridge) is likely to bring abnormally high temperatures to the region under its ridge, and very cold temperatures and heavy precipitation underneath its trough. The mathematics governing atmospheric motions requires that higher-amplitude flow patterns move more slowly. Thus, any change to the atmosphere that increases the amplitude of the wave pattern will make it move more slowly, increasing the length of time extreme weather conditions persist.
Dr. Francis discovered that during the early 1960s, a natural pattern in the atmosphere called the Arctic Oscillation increased the amplitude of the winter jet stream pattern over North America and the North Atlantic by more than 100 miles, increasing the potential for long-lasting weather conditions. The amplitude of the winter jet fell over 100 miles (161 km) during the late 1960s, remained roughly constant during the 1970s - 1990s, then increased by over 100 miles again during the 2000s. This latest increase in wave amplitude did not appear to be connected to the Arctic Oscillation, but did appear to be connected to the heating up of the Arctic due to sea ice loss.
A warmer Arctic allows ridges of high pressure to build farther to the north. Since temperatures farther to the south near the bases of the troughs are not changing much by comparison, the result is that the amplitude of the jet stream grows as the ridges of high pressure push farther to the north. Thus it is possible that Arctic sea ice loss and the associated increases in jet stream amplitude could be partially responsible for some of the recent unusual extreme weather patterns observed in the Northern Hemisphere.
http://www.wunderground.com/blog/JeffMa ... rynum=2003
Published on Wednesday, January 23, 2013 by Common Dreams
Melting Glaciers in Andes Could Spell Continental Water Crisis in South America
Climate change is driving 'unprecedented' shrinking of crucial resource
- Jon Queally, staff writer
The great glaciers of South America are disappearing at rates never seen in modern times and the continents fresh water supply is at serious risk if the trend continues, says a new study.
Part of the Pastoruri glacier is seen atop Peru's Cordillera Blanca, or "White Mountain Range." The largest glacier chain in the tropics, the range is melting fast. Climate change could melt the Andean glaciers away altogether in coming years, says the new study. (Photo: AP File)
Driven by global climate change, the report—published in the online academic journal Crysophere—shows that the Andean glaciers have shrunk anywhere from 30% to 50% since the 1970s.
"Glacier retreat in the tropical Andes over the last three decades is unprecedented," said Antoine Rabatel, the lead author of the study and a scientist with the Laboratory for Glaciology and Environmental Geophysics in Grenoble, France.
"Because the maximum thickness of these small, low-altitude glaciers rarely exceeds 40 meters, with such an annual loss they will probably completely disappear within the coming decades," Rabatel added.
If that happens, warned scientists, millions of people who depend on the glaciers to feed mountain streams and replenish water reserves would be at catastrophic risk.
And the Carbon Brief adds:
Retreating glaciers aren't just a visible indication of climate change - there are practical consequences, too. Another author of the new study, Alvaro Soruco, says the Andean glaciers are an important source of fresh water for nearby populations:
"Glaciers provide about 15 per cent of the La Paz water supply throughout the year, increasing to about 27 per cent during the dry season."
Rabatel explained to Carbon Brief today that as well as domestic consumption, the supply of water from mountain glaciers is important for agriculture and hydropower. So water shortages could become more problematic for local communities if the ice melt doesn't stop soon.
Successive studies show that glaciers are melting in response to climate change. But there are still relatively few studies like this one, with data spanning several decades. Such research is invaluable to climate scientists looking to get an idea of the full impact of rising temperatures are having on the world's glaciers - and what to expect in the future.
Greenland ice cores reveal warm climate of the past
2013-01-22
The climate graph shows the temperature from the previous warm interglacial period, the Eemian (left) throughout the entire ice age to present time. The blue colours indicate ice from a cold period, the red colour is ice from a warm period and yellow and green is from the climate period in between. The new results show that during the Eemian period 130,000 to 115,000 thousand years ago the climate in Greenland was around 8 degrees C warmer than today. The top shows a graph of ice sheet surface temperature and altitude. In the beginning of the Eemian, 128,000 years ago, the ice sheet in northwest Greenland was 200 meters higher than today, but during the warm Eemian period the ice mass regressed, so 122,000 years before now the surface had sunk to a level of 130 meters below the current level. During the rest of the Eemian the ice sheet remained stable at the same level with an ice thickness of 2,400 meters. Credit: Niels Bohr Institute
In the period between 130,000 and 115,000 years ago, Earth’s climate was warmer than today. But how much warmer was it and what did the warming do to global sea levels? – as we face global warming in the future, the answer to these questions is becoming very important. New research from the NEEM ice core drilling project in Greenland shows that the period was warmer than previously thought. The international research project is led by researchers from the Niels Bohr Institute and the very important results are published in the prestigious scientific journal, Nature.
In the last million years the Earth’s climate has alternated between ice ages lasting about 100,000 years and interglacial periods of 10,000 to 15,000 years. The new results from the NEEM ice core drilling project in northwest Greenland, led by the Niels Bohr Institute at the University of Copenhagen show that the climate in Greenland was around 8 degrees C warmer than today during the last interglacial period, the Eemian period, 130,000 to 115,000 thousand years ago.
Ocean Acidification In Washington’s Waters: Why Washington Needs To Act
This morning on Daybreak, Bill Dewey from Taylor Shellfish was on the show talking about Ocean Acidification and the risk it poses to Washington’s marine environment, economy and cultural resources.
..Massive die-offs of oyster larvae at Pacific Northwest hatcheries between 2005 and 2009 were due to low pH seawater entering the hatcheries. ..
The West Coast is currently facing severe acidification and the problem is expected to get worse in the coming decades.
West Coast shellfish producers are now experiencing levels of acidity that were not expected for decades.
Along the West Coast and within Puget Sound, scientists have documented levels of acidity up to three times greater than the average in the oceans.
Given the current rate of global carbon dioxide emissions, the average acidity of the global surface ocean is on pace to increase by about 150 percent (relative to pre-industrial levels) by the latter half of this century. ..
Ben D wrote:Well this study really highlights the possibility that the world may have a lot of warming ahead, but not because of humans.
one of the authors in Nature.com
“The good news is that Greenland is not as sensitive to climate warming as we thought,” says Dahl-Jensen. “The bad news is that if Greenland’s ice sheet did not disappear during the Eemian, Antarctica must have been responsible for a significant part of the sea-level rise,” she adds. These two ice sheets, the world’s biggest, have been stable for most of the current interglacial period.
But since temperatures began to soar a couple of decades ago, Greenland and Antarctica have been shedding ice fast. Between 1992 and 2011, they lost around 2,700 billion and 1,350 billion tonnes of ice, respectively — enough to raise sea levels by about 0.6 millimetres per year3. Scientists think that by 2100, the global sea level may have risen by 0.5–1.2 metres above current levels.
Although ice loss is currently greatest in Greenland, that could change: some parts of Antarctica are warming almost twice as fast as previously believed4, and glaciers in western Antarctica have retreated at a worrying rate in the past few decades5. Furthermore, Eemian sea-level rise seems to have proceeded in drastic jumps, rather than gradually6, suggesting that the ongoing sea-level rise could accelerate.
wintler2 wrote:Ben D wrote:Well this study really highlights the possibility that the world may have a lot of warming ahead, but not because of humans.
No it doesn't.
In the period between 130,000 and 115,000 years ago, Earth’s climate was warmer than today. But how much warmer was it and what did the warming do to global sea levels? – as we face global warming in the future, the answer to these questions is becoming very important.
Ben D wrote:wintler2 wrote:Ben D wrote:Well this study really highlights the possibility that the world may have a lot of warming ahead, but not because of humans.
No it doesn't.
How then do you address this understanding reached by the researchers that we face more global warming going into the future of this Holocene period based on the findings that in the Eemian period of 130,000 to 115,000 years ago, planet Earth was warmer than today?In the period between 130,000 and 115,000 years ago, Earth’s climate was warmer than today. But how much warmer was it and what did the warming do to global sea levels? – as we face global warming in the future, the answer to these questions is becoming very important.
Such surface melting has occurred very rarely in the last 5,000 years, but the team observed such a melting during the summer of 2012 when they were in Greenland.
..
“We were completely shocked by the warm surface temperatures at the NEEM camp in July 2012,” says Professor Dorthe Dahl-Jensen. “It was even raining and just like in the Eemian, the meltwater formed refrozen layers of ice under the surface. Although it was an extreme event the current warming over Greenland makes surface melting more likely and the warming that is predicted to occur over the next 50-100 years will potentially have Eemian-like climatic conditions,” she believes.
wintler2 wrote:Ben D wrote:wintler2 wrote:Ben D wrote:Well this study really highlights the possibility that the world may have a lot of warming ahead, but not because of humans.
No it doesn't.
How then do you address this understanding reached by the researchers that we face more global warming going into the future of this Holocene period based on the findings that in the Eemian period of 130,000 to 115,000 years ago, planet Earth was warmer than today?In the period between 130,000 and 115,000 years ago, Earth’s climate was warmer than today. But how much warmer was it and what did the warming do to global sea levels? – as we face global warming in the future, the answer to these questions is becoming very important.
Your quote doesn't support your claim, where do the researchers predict "that we face more global warming going into the future of this Holocene period based on the findings that in the Eemian period of 130,000 to 115,000 years ago, planet Earth was warmer than today"? Does not follow in itself, i'll bet cash you can't show the authors saying it.
Ben D wrote:Explain to me where and why you disagree with my deconstruction of the quote?
How then do you address this understanding reached by the researchers that we face more global warming going into the future of this Holocene period based on the findings that in the Eemian period of 130,000 to 115,000 years ago, planet Earth was warmer than today?
wintler2 wrote:Ben D wrote:Explain to me where and why you disagree with my deconstruction of the quote?
You didn't deconstruct it, you mangled it. Your words again:How then do you address this understanding reached by the researchers that we face more global warming going into the future of this Holocene period based on the findings that in the Eemian period of 130,000 to 115,000 years ago, planet Earth was warmer than today?
The underlined bit doesn't make sense to me - how does research on glacial depth since the Eemian predict future warming? It suggests alot about likely Greenland glacier responses to warming, which is not the same thing at all.
In the period between 130,000 and 115,000 years ago, Earth’s climate was warmer than today. But how much warmer was it and what did the warming do to global sea levels? – as we face global warming in the future, the answer to these questions is becoming very important.
wintler2 wrote:Of course it is 'possible', what is more useful is what is likely in given conditions. The conditions in the Eemian were quite different to today, hence the predictive power of greenland glacier observation is limited and simple correlation just plain wrong. Note that i have no problem with the article, thx for bringing it, i just don't get your "future warming .. based on .. Eemian observations", which is entirely your own construction.
In the period between 130,000 and 115,000 years ago, Earth’s climate was warmer than today. But how much warmer was it and what did the warming do to global sea levels? – as we face global warming in the future, the answer to these questions is becoming very important.
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