Huge 20-Year Build up of Arctic Fresh Water May Flood North Atlantic & Stall Gulf Stream

by FishOutOfWater, DailyKos, December 13, 2016



"Figure 3 Time series of freshwater content in different layers of the Beaufort Gyre region. Blue bars depict total liquid freshwater content. Black bars show freshwater content in sea ice. Yellow bars – freshwater content in the mixed layer, red bars – in the Pacific and green bars – in the Atlantic water layer. Freshwater content is shown in thousand cubic kilometers. Upper left bars shows total annual freshwater flux into the Arctic Ocean from all rivers; green and black small bars show errors in liquid and sea ice freshwater content estimates. All freshwater contents are calculated relative to 34.8 reference water salinity." The build up in volume from 2002 to 2015 is about the volume of Lake Michigan which stores 4,918 cubic km of water.

Huge volumes of fresh water have been building up over the past 20 years in the Arctic waters north of Alaska. A volume the size of Lake Michigan built up from 2003 through the end of 2015. Before the 1990s, there were regular cycles of fresh water build up and release within decades as periods of high pressure north of Alaska were followed by periods of stormy weather. Scientists suspect that over the past 20 years large amounts of melt water from Greenland’s glaciers have changed the dynamics of the North Atlantic ocean and the Arctic atmosphere. Since the 1990s, a dome of high pressure has persisted in the Beaufort sea and the anticyclonic winds have pumped fresh water towards the high’s center building up a mound of relatively fresh water over a huge area north of Alaska. The primary source of the fresh water is rivers that flow into the Arctic. Over the past several decades, sea ice melting has added about 20%  to the increase of fresh water in the Beaufort sea.

The freshwater content of the Beaufort gyre  increased by a volume the size of lake Michigan from the 1970s to 2008.

A major 2008 report by a team of scientists led by Wood’s Hole oceanographer Andrey Proshutinsky found an increase of 5000 km3 of fresh water from the 1970s to 2008. www.whoi.edu/…

From 2008 to 2015 an additional 2000 km3 was added so the total increase in fresh water is 7,000km3. The total volume of the world’s second largest lake by volume, Lake Michigan, is just under 5,000km3.

Preliminary data from the BGOS 2008 cruise indicate that the FWCL in the BG continued to rise in 2008 and reached 21,000 km3– a historical maximum from all available years of observations. Compared to 1970s climatology (the pre-90s decade with the most extensive data coverage, (Figure 1) there has been a FWCL increase in the BG of approximately 5,000 km3. This is comparable with the volume of fresh water annually delivered to the Arctic Ocean by rivers and through Bering Strait (5700 km3 per year, Serreze et al., [2006]).

The freshwater layer in the Beaufort sea deepened by 3 meters - about 10 feet from 2003 to 2007. Because the Beaufort gyre covers a large area, this is a huge volume of fresh water. Anticyclonic winds associated with persistent high pressure in 2007 caused Siberian and North American river water and water from a record melt of sea ice in 2007 to flow into this Arctic sea north of Alaska.

The persistent anticyclonic Beaufort high pressure builds up a mound of water under it because the direction of a mass of water moves to the right of the wind  direction in the northern hemisphere because  the rotation of the earth gives the water spin. See this post at Neven’s sea ice blog by an Arctic oceanographer for details. neven1.typepad.com/...

On the other hand, cyclonic rotation associated with low pressure areas causes water to well up from below the center of the low. Thus  years of high pressure followed by  years of storminess cause moderate periodic surges of fresh water from the Arctic to the north Atlantic ocean. It was like the Arctic breathed in fresh water then breathed it out in a period of a decade or less. The largest observed freshwater surge called the “Great Salinity Anomaly” happened in the early 1970’s.

The Great Salinity anomaly was one of the likely causes of the brutal American winters of the 1970s. Fresh water tends to float over denser warm salty Gulf Stream water in sub-Arctic seas of the north Atlantic. This keeps the warm salty water from releasing its heat to the atmosphere and sinking thousands of feet into the deep Atlantic. This disruption of the thermohaline circulation is popularly called slowing down the Gulf Stream. The deep overturning circulation brings Gulf Stream water to the subarctic seas, warming Europe and north America. When deep water formation slows brutal winters tend to follow.  This effect, combined with the reflective effects of growing levels of sulfuric acid pollution over the north Atlantic in the 1960s and 1970s caused cold north American and European winters  in those decades. This cool period that broke up the trend of greenhouse gas caused global warming that has been ongoing since the turn of the twentieth century has been intentionally misinterpreted by climate change deniers to confuse politicians and the public about climate change.

Winters were miserably cold in Minnesota and the central and eastern U.S. in the 1970s.

Last spring, following the extremely abrupt collapse of the winter polar vortex in a sudden stratospheric warming a very intense Beaufort high developed driving more fresh water into the gyre. The strong high pressure in the sunny spring months melted out the ice early. Midwinter high pressure under dark skies is favorable for ice growth but under the bright long sunny days of May the ice melted and the water took up enormous amounts of heat. That warm water then opened up the ice plugged channels between the islands of northernmost Canada. If high pressure breaks down now the thick plugs of multi-year ice that used to block the channels won’t be there to impede the fresh water from draining out to the north Atlantic. The largest channels have a thin ice cover.

Arctic scientists fear that a large volume of the stored fresh water could be rapidly released, drastically impacting the northern hemisphere’s weather. earthobservatory.nasa.gov/...

As I said back in my first blog entry, one of the key objectives of the expedition was to produce an up-to-date assessment of the freshwater content of the Beaufort Gyre. Based on a preliminary analysis of the data collected on this cruise, my colleagues reckon the total freshwater content of the Gyre could be at a record high. A chemical analysis of the ocean surface suggests that sea ice melt contributed around 20 percent of the fresh water mixed up within the surface waters, compared to around 80 percent from Canadian and Russian rivers flowing into the Arctic. The sea ice contribution was thought to be neutral a few decades ago, but the ice is now melting more than it’s growing, as we clearly witnessed, causing an imbalance. The wind circulation is also important in driving the ocean circulation that sucks in fresher surface waters into the Gyre (see an earlier blog of mine for more details).

Why does this all matter? Well, some scientists posited that the Beaufort Gyre oscillates between periods of spinning up and sucking in freshwater, and spinning down and releasing fresh water. A kind of breathing, if you like. The Gyre has been spinning up and sucking in fresh water for a few decades now (2008 saw a big increase) and we keep waiting, with similarly bated breath, for this trend to reverse. If the Gyre does reverse (breathe out), the Arctic Ocean will likely dump a load of fresh water into the Atlantic Ocean (as we think it did in the 1970s), which could cause some big impacts on weather patterns across the Northern Hemisphere. We’re not expecting a scene out of The Day After Tomorrow, but we’re not entirely sure what could happen either.

This dark half of the Arctic year has been by far the warmest to date on record and storms have repeatedly slammed the sea ice to record lows while pulling in heat from both the Atlantic and Pacific oceans. If this stormy weather continues, the fresh water dome will break down and the fresh water rapidly drain towards the north Atlantic through the channels of the Canadian archipelago and through the Fram strait east of northern Greenland.

The weather forecast for the next 10 days by the European model is insane. Deep lows will pull massive amounts of heat into the Arctic, which will keep sea ice extent and volume at record low levels for the date and will work to spin down the currents that keep the dome fresh water in the Beaufort sea.

5 day ECMWF weather forecast shows storms entering the Arctic from both the Atlantic and Pacific. The winds will bring enormous amounts of atmospheric heat, taken from the Atlantic and Pacific oceans, into the Arctic.

The weather pattern developing in the Arctic is the pattern that has drained the fresh water form the Beaufort gyre in the past. Extremely deep lows are moving from the Atlantic into the Arctic. Low pressure is dominating the region from the Atlantic’s subarctic seas to the Arctic ocean. If this pattern continues through this winter, a volume of fresh water greater than lake Michigan could be set in motion towards the north Atlantic and the overturning circulation could stall when the light fresh water caps the Labrador sea. This could cause the Gulf Stream itself to slow while heat would build up in tropical oceans.

Extreme low pressure is forecast by the ECMWF model to cover the Arctic and north Atlantic in 7 days.

Scientists and Arctic observers are shocked by this year’s extraordinarily warm Arctic weather but the sudden release of fresh water to the Atlantic could cause a sudden shift to much colder winter weather towards the end of the decade. This is a very unpredictable situation, but Greenland ice cores show that rapid, extreme climate oscillations may be triggered by north Atlantic salinity cycles. www.atmosp.physics.utoronto.ca/…

We may be entering a period of extreme climate chaos.

http://www.dailykos.com/story/2016/12/13/1610344/-Huge-20-Year-Build-up-of-Arctic-Fresh-Water-May-Flood-North-Atlantic-Stall-Gulf-Stream

RUSSIAN RIVER WATER UNEXPECTED CULPRIT BEHIND ARCTIC FRESHENING

by Sandra Hines, UW Today, January 4, 2012

A hemisphere-wide phenomenon – and not just regional forces – has caused record-breaking amounts of freshwater to accumulate in the Arctic's Beaufort Sea.



Frigid freshwater flowing into the Arctic Ocean from three of Russia's mighty rivers was diverted hundreds of miles to a completely different part of the ocean in response to a decades-long shift in atmospheric pressure associated with the phenomenon called the Arctic Oscillation, according to findings published in the January 5, 2012, issue of Nature.

The new findings show that a low pressure pattern created by the Arctic Oscillation from 2005 to 2008 drew Russian river water away from the Eurasian Basin, between Russia and Greenland, and into the Beaufort Sea, a part of the Canada Basin bordered by the United States and Canada. It was like adding 10 feet (3 meters) of freshwater over the central part of the Beaufort Sea.

“Knowing the pathways of freshwater in the upper ocean is important to understanding global climate because of freshwater's role in protecting sea ice – it can help create a barrier between the ice and warmer ocean water below – and its role in global ocean circulation. Too much freshwater exiting the Arctic would inhibit the interplay of cold water from the poles and warm water from the tropics,” said Jamie Morison, an oceanographer with the University of Washington's Applied Physics Laboratory and lead author of the Nature paper.

Red arrows show the new path of Russian river water into the Canada Basin. The previous freshwater pathway – across the Eurasian Basin toward Greenland and the Atlantic – was altered by atmospheric conditions created by the Arctic Oscillation. Credit: University of Washington

Morison and his six co-authors from the UW and NASA's Jet Propulsion Laboratory are the first to detect this freshwater pathway and its connection to the Arctic Oscillation. The work is based on water samples gathered in the field combined with satellite oceanography possible for the first time with data from NASA satellites known as ICESat and GRACE.

“Changes in the volume and extent of Arctic sea ice in recent years have focused attention on the impacts of melting ice,” said co-author Ron Kwok, senior research scientist with the Jet Propulsion Laboratory in Pasadena, Calif. “The combined GRACE and ICESat data allow us to now examine the impacts of widespread changes in ocean circulation.”

Red arrows show the new path of Russian river water into the Canada Basin. The previous freshwater pathway – across the Eurasian Basin toward Greenland and the Atlantic – was altered by atmospheric conditions created by the Arctic Oscillation. Credit: University of Washington

Taken as a whole, the salinity of the Arctic Ocean is similar to the past, but the change in the freshwater pathway means the Eurasian Basin has gotten more saline while the Canada Basin has gotten fresher.

“The freshening on the Canadian side of the Arctic over the last few years represents a redistribution of freshwater, there does not seem to be a net freshening of the ocean,” Kwok said.

In the Eurasian Basin, the change means less freshwater enters the layer known as the cold halocline and could be contributing to declines in ice in that part of the Arctic, Morison said. The cold halocline normally sits like a barrier between ice and warm water that comes into the Arctic from the Atlantic Ocean. Without salt the icy cold freshwater is lighter, which is why it is able to float over the warm water.

In the Beaufort Sea, the water is the freshest its been in 50 years of record keeping, he said. The new findings show that only a tiny fraction is from melting ice and the vast majority is Eurasian river water.

The Beaufort Sea stores a significant amount of freshwater from a number of sources, especially when an atmospheric condition known as the Beaufort High causes winds to spin the water in a clockwise gyre. When the winds are weaker or spin in the opposite direction, freshwater is released back into the rest of the Arctic Ocean, and from there to the worlds oceans. Some scientists have said a strengthening of the Beaufort High is the primary cause of freshening, but the paper says salinity began to decline in the early 1990s, a time when the Beaufort High relaxed and the Arctic Oscillation increased.

“We discovered a pathway that allows freshwater to feed the Beaufort gyre,” Kwok said. “The Beaufort High is important but so are the broader-scale effects of the Arctic Oscillation.”

“A number of people have come up with ways of looking at regional forces at work in the Arctic,” Morison said, “To better understand changes in sea ice and the Arctic overall we need to look more broadly at the hemisphere-wide Arctic Oscillation, its effects on circulation of the Arctic Ocean and how global warming might enhance those effects.”

In coming years if the Arctic Oscillation stops perpetuating that low pressure, the freshwater pathway should switch back.

Morison and the co-authors argue that, compared to prior years, the Arctic Oscillation has been in its current state for the last 20 years. For example, the changes detected in response to the Arctic Oscillation between 2005 and 2008 are very similar to freshening seen in the early 1990s, Morison said.

Discerning the track of freshwater from Eurasian rivers would have been impossible without the ICESat and GRACE satellites, Kwok and Morison agree. With satellite measurements of ocean height and bottom pressures, the researchers could separate the changes in mass from changes in density – or freshwater content – of the water column.

“To me its pretty spectacular that you have these satellites zipping around hundreds of kilometers above the Earth and they give us a number about salinity that's very close to what we get from lowering little sampling bottles into the ocean,” Morison said.

Other co-authors are Cecilia Peralta-Ferriz with the UWs School of Oceanography and Matt Alkire, Ignatius Rigor, Roger Andersen and Mike Steele, all with the UWs Applied Physics Laboratory. The work was funded by the National Science Foundation and NASA. For more information: Morison, 206-543-1394 (office), 206-310-5307 (cell), morison@apl.washington.edu and Kwok, contact via Alan Buis, 818-354-0474, alan.d.buis@jpl.nasa.gov

Top Image: Julian Olden and graduate student Thomas Pool weigh invasive carp from an Arizona stream. Credit: Olden Lab

http://depts.washington.edu/coenv/freshwater/2012/01/russian-river-water-unexpected-culprit-behind-arctic-freshening-with-video/

NASA: Arctic Melt Season Lengthening 5 days per decade

from NASA, April 1, 2014

A new study by researchers from the National Snow and Ice Data Center (NSIDC) and NASA shows that the length of the melt season for Arctic sea ice is growing by several days each decade. An earlier start to the melt season is allowing the Arctic Ocean to absorb enough additional solar radiation in some places to melt as much as four feet of the Arctic ice cap’s thickness.

"The Arctic is warming and this is causing the melt season to last longer," said Julienne Stroeve, a senior scientist at NSIDC, Boulder and lead author of the new study, which has been accepted for publication in Geophysical Research Letters. "The lengthening of the melt season is allowing for more of the sun’s energy to get stored in the ocean and increase ice melt during the summer, overall weakening the sea ice cover."

A short video summarizes new findings about Arctic sea ice and warming oceans.  Play it!

Arctic sea ice has been in sharp decline during the last four decades. The sea ice cover is shrinking and thinning, making scientists think an ice-free Arctic Ocean during the summer might be reached this century. The seven lowest September sea ice extents in the satellite record have all occurred in the past seven years.

To study the evolution of sea ice melt onset and freeze-up dates from 1979 to the present day, Stroeve’s team used passive microwave data from NASA’s Nimbus-7 Scanning Multichannel Microwave Radiometer, and the Special Sensor Microwave/Imager and the Special Sensor Microwave Imager and Sounder carried onboard Defense Meteorological Satellite Program spacecraft. When ice and snow begin to melt, the presence of water causes spikes in the microwave radiation that the snow grains emit, which these sensors can detect.

Results show that although the melt season is lengthening at both ends, with an earlier melt onset in the spring and a later freeze-up in the fall, the predominant phenomenon extending the melting is the later start of the freeze season. Some areas, such as the Beaufort and Chukchi Seas, are freezing up between 6 and 11 days later per decade. Although melt onset variations are smaller, the timing of the beginning of the melt season has a larger impact on the amount of solar radiation absorbed by the ocean, because its timing coincides with when the sun is higher and brighter in the Arctic sky.

Despite large regional variations in the beginning and end of the melt season, the Arctic melt season has lengthened on average by 5 days per decade from 1979 to 2013.

Visit nasa.gov for more information about this research

Credits:

Production editor: Dr. Tony Phillips | Credit: Science@NASA

http://science.nasa.gov/science-news/science-at-nasa/2014/01apr_arcticice/

"Effects of Mackenzie River discharge and bathymetry on sea ice in the Beaufort Sea," by S. V. Nghiem et al., GRL (2014); doi: 10.1002/2013GL058956

Geophysical Research Letters, (10 February 2014); doi: 10.1002/2013GL058956

Effects of Mackenzie River discharge and bathymetry on sea ice in the Beaufort Sea

1. S. V. Nghiem^1,*, 
2. D. K. Hall², 
3. I. G. Rigor³,
4. P. Li¹ and 
5. G. Neumann¹

Abstract

Mackenzie River discharge and bathymetry effects on sea ice in the Beaufort Sea are examined in 2012 when Arctic sea ice extent hit a record low. Satellite-derived sea surface temperature revealed warmer waters closer to river mouths. By 5 July 2012, Mackenzie warm waters occupied most of an open water area about 316,000 km². Surface temperature in a common open water area increased by 6.5 °C between 14 June and 5 July 2012, before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the Mackenzie Delta. In 2012, melting by warm river waters was especially effective when the strong Beaufort Gyre fragmented sea ice into unconsolidated floes. The Mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the Arctic Ocean, constituting a stark contrast to the Antarctic that has no such rivers to affect sea ice.

http://onlinelibrary.wiley.com/doi/10.1002/2013GL058956/abstract

Warm-water discharge into Beaufort Sea from Mackenzie River corresponds to melting Arctic sea ice

Warm rivers play role in Arctic sea ice melt

These images show sea surface temperatures of the Beaufort Sea where Canada's Mackenzie River discharges into the Arctic Ocean, as measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra spacecraft.  Photo: NASA. Click on image to enlarge.

ScienceDaily, March 5, 2014

The heat from warm river waters draining into the Arctic Ocean is contributing to the melting of Arctic sea ice each summer, a new NASA study finds.

A research team led by Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperature of the waters discharging from a Canadian river into the icy Beaufort Sea during the summer of 2012. They observed a sudden influx of warm river waters into the sea that rapidly warmed the surface layers of the ocean, enhancing the melting of sea ice. A paper describing the study is now published online in the journal Geophysical Research Letters.

This Arctic process contrasts starkly with those that occur in Antarctica, a frozen continent without any large rivers. The sea ice cover in the Southern Ocean surrounding Antarctica has been relatively stable, while Arctic sea ice has been declining rapidly over the past decade.

"River discharge is a key factor contributing to the high sensitivity of Arctic sea ice to climate change," said Nghiem. "We found that rivers are effective conveyers of heat across immense watersheds in the Northern Hemisphere. These watersheds undergo continental warming in summertime, unleashing an enormous amount of energy into the Arctic Ocean, and enhancing sea ice melt. You don't have this in Antarctica."

The team said the impacts of these warm river waters are increasing due to three factors. First, the overall volume of water discharged from rivers into the Arctic Ocean has increased. Second, rivers are getting warmer as their watersheds (drainage basins) heat up. And third, Arctic sea ice cover is becoming thinner and more fragmented, making it more vulnerable to rapid melt. In addition, as river heating contributes to earlier and greater loss of the Arctic's reflective sea ice cover in summer, the amount of solar heat absorbed into the ocean increases, causing even more sea ice to melt.

To demonstrate the extensive intrusion of warm Arctic river waters onto the Arctic sea surface, the team selected the Mackenzie River in western Canada. They chose the summer of 2012 because that year holds the record for the smallest total extent of sea ice measured across the Arctic in the more than 30 years that satellites have been making observations.

The researchers used data from satellite microwave sensors to examine the extent of sea ice in the study area from 1979 to 2012 and compared it to reports of Mackenzie River discharge. "Within this period, we found the record largest extent of open water in the Beaufort Sea occurred in 1998, which corresponds to the year of record high discharge from the river," noted co-author Ignatius Rigor of the University of Washington in Seattle.

The team analyzed data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra satellite to examine sea ice patterns and sea surface temperatures in the Beaufort Sea. They observed that on June 14, 2012, a stretch of landfast sea ice (sea ice that is stuck to the coastline) formed a barrier that held the river discharge close to its delta. After the river water broke through the ice barrier, sometime between June 14 and July 5, the team saw that the average surface temperature of the area of open water increased by 11.7 degrees Fahrenheit (6.5 degrees Celsius).

"When the Mackenzie River's water is held back behind the sea ice barrier, it accumulates and gets warmer later in the summer," said Nghiem. "So when it breaks through the barrier, it's like a strong surge, unleashing warmer waters into the Arctic Ocean that are very effective at melting sea ice. Without this ice barrier, the warm river waters would trickle out little by little, and there would be more time for the heat to dissipate to the atmosphere and to the cooler, deeper ocean."

"If you have an ice cube and drop a few water droplets on it, you're not going to see rapid melt," said co-author Dorothy Hall of NASA's Goddard Space Flight Center in Greenbelt, Md. "But if you pour a pitcher of warm water on the ice cube, it will appear to get smaller before your eyes. When warm river water surges onto sea ice, the ice melts rapidly."

Nghiem's team has linked this sea ice barrier, which forms recurrently and persistently in this area, to the physical characteristics of the shallow ocean continental shelf, and concludes the seafloor plays a role in delaying river discharge by holding the barrier in place along the shore of the Mackenzie delta.

The team estimated the heating power carried by the discharge of the 72 rivers in North America, Europe and Asia that flow into the Arctic Ocean. Based on published research of their average annual river discharge, and assuming an average summer river water temperature of around 41 degrees Fahrenheit (5 degrees Celsius), they calculated that the rivers are carrying as much heat into the Arctic Ocean each year as all of the electric energy used by the state of California in 50 years at today's consumption rate.

While MODIS can accurately measure sea surface temperature where rivers discharge warm waters into the Arctic Ocean, researchers currently lack reliable field measurements of subsurface temperatures across the mouths of river channels. Nghiem said more studies are needed to establish water temperature readings in Arctic-draining rivers to further understand their contribution to sea ice melt.

NASA monitors Earth's vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better understand how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

For more information about NASA's Earth science activities in 2014, visit: http://www.nasa.gov/earthrightnow . For information on the latest NASA Earth science findings, visit: http://www.nasa.gov/earth .

---

Story Source:

The above story is based on materials provided by NASA/Jet Propulsion Laboratory. The original article was written by Maria-Jose Vinas. Note: Materials may be edited for content and length.

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Journal Reference:

1. S. V. Nghiem, D. K. Hall, I. G. Rigor, P. Li, G. Neumann. Effects of Mackenzie River discharge and bathymetry on sea ice in the Beaufort Sea. Geophysical Research Letters, 2014; DOI: 10.1002/2013GL058956

http://www.sciencedaily.com/releases/2014/03/140305134019.htm

Tipping point for polar ice cap may have come in 2012

by Yereth Rosen, Alaska Dispatch, October 16, 2013

The dramatic reduction of Arctic sea ice witnessed from 2007 to 2012 is now considered by some scientists to be a "persistent and permanent feature of the summer Arctic environment." Kathryn Hansen/NASA photo

This year may have granted a slight reprieve for vanishing Arctic sea ice, but evidence gathered to date shows that summer shrinkage will likely continue its downward spiral in future years, according to a new paper published in the Oct. 4 edition of the journal Geography Compass. 

The paper, by Kent State University doctoral candidate Thomas Ballinger and Jeffrey Rogers, a geography professor at Ohio State University, synthesizes information about weather, ocean currents and ice conditions in the Beaufort and Chukchi seas between 2007 through 2012, a six-year period of severe melt. Conditions in those seas appear to have changed for good, the paper says.

“Dramatic reduction in late summer sea ice on these seas occurring in 2007 and subsequent years now appears to be a persistent and permanent feature of the summer Arctic environment,” it says.

Perfect storm for vanishing ice

RELATED: 

Arctic ice melting rapidly, but some 'signs' are false alarms

The paper describes how, in the biggest ice-loss years, weather and ocean patterns aligned into almost a perfect storm to erase large amounts of ice.

That happened in 2007, when a Beaufort Sea high-pressure system persisted all summer, instead of being limited to short spurts, as is typical, Ballinger said in a telephone interview.

The year “was really remarkable” because there was still a lot of thicker multiyear ice around then, he said. Persistent high pressure brought clear skies, though, and intense solar radiation melted ice and was absorbed by the widened stretches of open ocean, where it amplified its effects, he said. That and other factors hammered the 2007 ice, he said. “It really cleared out a lot of that thicker ice,” he said.

Subsequent years showed large ice losses in the Beaufort and Chukchi, though not as bad as 2007. Then last year, the persistent Beaufort Sea high struck with a vengeance, followed by a strong cyclone in August. That helped break up fragile single-year ice that replaced multi-year ice lost in 2007, he said. The result was the lowest Arctic ice cover on record.

Thanks to the weaker nature of the ice, a record low would have been reached in 2012, even without the August cyclone, some scientists argue.

Interplay of sea ice and weather 

Scientists for years have studied the interplay between Arctic sea-ice dynamics and Arctic weather, as well as the impact on long-term climate beyond the Arctic. 

But any connection between the Arctic ice loss and specific weather events in southern latitudes is a complicated question, Ballinger said. “The link between the ice loss and any particular storm event is kind of hard to match up,” he said.

One recent study suggests sea-ice loss is a culprit in the nation’s biggest weather disaster of 2012. The study, published in the March edition of the journal Oceanography, is titled “Superstorm Sandy: A Series of Unfortunate Events?” 

Another study, published by the American Meteorological Society, ties Arctic sea-ice loss to a prediction of more extreme winter-weather events in northern Eurasia. 

Contact Yereth Rosen at yereth(at)alaskadispatch.com 

http://www.alaskadispatch.com/article/20131016/tipping-point-polar-ice-cap-may-have-come-2012

Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre, Nature Geoscience 5 (2012); doi: 10.1038/NGEO1379

Nature Geoscience 5 (January 22, 2012)  DOI: 10.1038/NGEO1379


Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre


Katharine A. Giles*, Seymour W. Laxon, Andy L. Ridout, Duncan J.Wingham and Sheldon Bacon

Abstract

The Arctic Ocean’s freshwater budget comprises contributions from river runoff, precipitation, evaporation, sea-ice and exchanges with the North Pacific and Atlantic1. More than 70,000 km3 of freshwater2 are stored in the upper layer of the Arctic Ocean, leading to low salinities in upper layer Arctic sea water, separated by a strong halocline from warm, saline water beneath. Spatially and temporally limited observations show that the Arctic Ocean’s freshwater content has increased over the past few decades, predominantly in the west3–5. Models suggest that wind-driven convergence drives freshwater accumulation6. Here we use continuous satellite measurements between 1995 and 2010 to show that the dome in sea surface height associated with the western Arctic Beaufort Gyre has been steepening, indicating spin-up of the gyre. We find that the trend in wind field curl—a measure of spatial gradients in the wind that lead to water convergence or divergence—exhibits a corresponding spatial pattern, suggesting that wind-driven convergence controls freshwater variability. We estimate an increase in freshwater storage of 8,000 +/- 2,000 km3 in the western Arctic Ocean, in line with hydrographic observations4,5, and conclude that a reversal in the wind field could lead to a spin-down of the Beaufort Gyre, and release of this freshwater to the Arctic Ocean.

Introduction

The Canada Basin contains the largest proportion of the Arctic Ocean's freshwater with the majority located in the Beaufort Gyre2 (Fig. 1a), a permanent anti-cyclonic circulation system. Comparisons between the Beaufort Gyre climatology, derived from winter data collected between 1950 and 1989, and an aerial hydrographic survey from March- April 2008 containing 64 station locations over 560,000 km2, indicate that the Beaufort Gyre freshwater content has increased by 8,500 km3 (ref. 4; the uncertainty was not estimated).  A similar increase of 8,400 +/- 2,000 km3 was found over the whole Arctic Ocean from analysis of conductivity temperature depth (CTD) and Expendable CTD observations from ships, submarines and ice drifting stations between the 1990s and 2006- 2008 (ref. 5), with the results also 'hinting'5 at a shift and expansion of the Gyre. However, as sampling is biased towards summer months, only observations between July and September were used5. Simultaneously, the combined analysis of hydrographic data collected between 1990 and 2008 and a coupled sea- ice- ocean general circulation model indicates that freshwater export through Davis Strait reduced by  50%, comparable to the observed increase in storage (Holliday, unpublished data). To use these snapshots of freshwater change to understand its variability and governing physics, models must be employed to put them into context. The wind exerts a frictional force on the ocean surface and the ocean surface waters respond to balance this force with the Coriolis force. This motion is termed Ekman transport. Variations in the magnitude and direction of the wind cause spatial gradients in the Ekman transport, and water to accumulate or dissipate, changing the sea surface height (SSH) and depth of the halocline. The resulting vertical velocity of the SSH or halocline is termed Ekman pumping. Modelling experiments suggest that freshwater is accumulated in the Beaufort Gyre during anticyclonic regimes and forced to the Arctic Ocean margins during cyclonic regimes, where it may then be released to the North Atlantic6. Therefore, the storage of freshwater in the Beaufort Gyre is predicted to vary with the wind stress curl. This is supported by data collected between 2003 and 2007 at two moorings in the Beaufort Sea that show an increase in the freshwater content and a strong negative wind stress curl over the same period3.

"Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre" by Katharine A. Giles et al., Nature Geoscience 5 (2012)

Nature Geoscience 5 (2012)  

194–197; doi:

10.1038/ngeo1379

Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre

Katharine A. Giles*,

Seymour W. Laxon,

Andy L. Ridout,

Duncan J. Wingham and

 Sheldon Bacon

Received

March 1, 2011; accepted December 29, 2011; published online January 22, 2012.

Abstract

The Arctic Ocean’s freshwater budget comprises contributions from river runoff, precipitation, evaporation, sea-ice and exchanges with the North Pacific and Atlantic¹. More than 70,000 km³ of freshwater² are stored in the upper layer of the Arctic Ocean, leading to low salinities in upper-layer Arctic sea water, separated by a strong halocline from warm, saline water beneath. Spatially and temporally limited observations show that the Arctic Ocean’s freshwater content has increased over the past few decades, predominantly in the west^3,4, 5. Models suggest that wind-driven convergence drives freshwater accumulation⁶. Here we use continuous satellite measurements between 1995 and 2010 to show that the dome in sea surface height associated with the western Arctic Beaufort Gyre has been steepening, indicating spin-up of the gyre. We find that the trend in wind field curl—a measure of spatial gradients in the wind that lead to water convergence or divergence—exhibits a corresponding spatial pattern, suggesting that wind-driven convergence controls freshwater variability. We estimate an increase in freshwater storage of 8,000±2,000 km³ in the western Arctic Ocean, in line with hydrographic observations^4, 5, and conclude that a reversal in the wind field could lead to a spin-down of the Beaufort Gyre, and release of this freshwater to the Arctic Ocean.

http://www.nature.com/ngeo/journal/v5/n3/abs/ngeo1379.html

Arctic Ocean freshwater bulge detected

By Jonathan AmosScience correspondent, BBC News, 23 January 2012

UK scientists have detected a huge dome of fresh water that is developing in the western Arctic Ocean.The bulge is some 8,000 cubic km in size and has risen by about 15cm since 2002. The team thinks it may be the result of strong winds whipping up a great clockwise current in the northern polar region called the Beaufort Gyre.

This would force the water together, raising sea surface height, the group tells the journal Nature Geoscience.

"In the western Arctic, the Beaufort Gyre is driven by a permanent anti-cyclonic wind circulation. It drives the water, forcing it to pile up in the centre of gyre, and this domes the sea surface," explained lead author Dr Katharine Giles from the Centre for Polar Observation and Modelling (CPOM) at University College London.

Arctic summers have seen a decline in both ice extent and thickness

"In our data, we see the trend being biggest in the centre of the gyre and less around the edges," she told BBC News.

Dr Giles and colleagues made their discovery using radar satellites belonging to theEuropean Space Agency (Esa).

These spacecraft can measure sea-surface height even when there is widespread ice cover because they are adept at picking out the cracks, or leads, that frequently appear in the frozen floes.

The data (1995-2010) indicates a significant swelling of water in the Beaufort Gyre, particularly since the early part of the 2000s. The rising trend has been running at 2cm per year.

Model prediction

A lot of research from buoys and other in-situ sampling had already indicated that water in this region of the Arctic had been freshening.

This fresh water is coming in large part from the rivers running off the Eurasian (Russian) side of the Arctic basin.

Winds and currents have transported this fresh water around the ocean until it has been pulled into the gyre. The volume currently held in the circulation probably represents about 10% of all the fresh water in the Arctic.

Of interest to future observations is what might happen if the anticyclonic winds, which have been whipping up the bulge, change behaviour.

"What we seen occurring is precisely what the climate models had predicted," said Dr Giles.

"When you have clockwise rotation - the fresh water is stored. If the wind goes the other way - and that has happened in the past - then the fresh water can be pushed to the margins of the Arctic Ocean.

"If the spin-up starts to spin down, the fresh water could be released. It could go to the rest of the Arctic Ocean or even leave the Arctic Ocean."

If the fresh water were to enter the North Atlantic in large volumes, the concern would be that it might disturb the currents that have such a great influence on European weather patterns. These currents draw warm waters up from the tropics, maintaining milder temperatures in winter than would ordinarily be expected at northern European latitudes.

Cracks, or leads, in the ice provide vertical surfaces against which the wind can push

The creation of the Beaufort Gyre bulge is not a continuous development throughout the 15-year data-set, and only becomes a dominant feature in the latter half of the study period.

This may indicate a change in the relationship between the wind and the ocean in the Arctic brought about by the recent rapid decline in sea-ice cover, the CPOM team argues in its Nature Geoscience paper.

It is possible that the wind is now imparting momentum to the water in ways that were not possible when the sea-ice was thicker and more extensive.

"The ice is now much freer to move around," said Dr Giles.

Cryosat-2: Esa's newest radar satellite is dedicated to studying the polar regions

"So, as the wind acts on the ice, it's able to pull the water around with it. Depending on how ridged the surface of ice is or how smooth the bottom of the ice is - this will all affect the drag on the water. If you have more leads, this also might provide more vertical ice surfaces for the wind to blow against."

One consequence of less sea-ice in the region is the possibility that winds could now initiate greater mixing of the different layers in the Arctic Ocean.

Scientists are aware that there is a lot of warm water at depth.

At present, this deep water's energy is unable to influence the sea-ice because of a buffer of colder, less dense water lying between it and the floes above.

But if this warm water were made to well up because of wind-driven changes at the surface, it could further accelerate the loss of seasonal ice cover.

The CPOM team is now investigating the likelihood of this happening with Cryosat-2, Esa's first radar satellite dedicated to the study of the polar regions.

"We now have the means to measure not only the ice thickness but also to monitor how the ocean under the ice is changing," says Dr Seymour Laxon, director of CPOM and co-author of the study, "and with CryoSat-2, we can now do so over the entire Arctic Ocean."

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter

http://www.bbc.co.uk/news/science-environment-16657122