Why is warming in the Arctic accelerating and where will this lead to?
Where does the extra heat go?
Global warming is causing Earth to heat up. As shown on the image below, by Nuccitelli et al., most heat goes into the oceans.
Warming of water in the Arctic Ocean
White arrows mark ice drift directions. Red arrows mark the transport path of warm Atlantic water entering the Arctic where it submerges under the cold, ice-covered surface layer. Robert Spielhagen (IFM-GEOMAR, Kiel)
Global warming is heating up the oceans big time. As above image shows, the global ocean heat content has been rising for many years.
Water flowing into the Arctic Ocean from the Atlantic Ocean is about 2°C warmer today than it has been for at least 2,000 years, according to a study published in Science. The current of warm water lies 50 metres below the surface, and can reach 6°C in summer — warm compared to Arctic surface waters, which can be -2°C.
At the same time, cold water and sea ice are driven out of the Arctic Ocean, along the edges of Greenland. The net result is a marked increase in the temperature of the water in the Arctic Ocean, especially the top layer of the water which causes the sea ice to melt.
The Arctic radiates comparatively less heat into space
Cold layers of air close to the surface make it difficult for infrared radiation to go out to space, according to a study published in Science. These layers do warm up, but warming of these layers is directed downwards, thus amplifying warming in the Arctic.
Surface air temperatures in the Arctic are rising rapidly
Anomalies for surface air temperatures are higher in the Arctic than anywhere else on Earth. This is illustrated by the interactive images and text in the box at the bottom of this post.
The increase in temperature anomalies appears to be an exponential rise. This is caused not only by the above-described impacts of cold air close to the surface, but also by feedback effects as further described below.
Feedbacks further accelerate warming in the Arctic
One such feedback is albedo change — retreat of Arctic sea ice results in less sunlight being reflected back into space, as further discussed in Albedo Change in the Arctic. Loss of Arctic sea ice is effectively doubling mankind's contribution to global warming. Increased absorption of the sun's rays is the equivalent of about 20 years of additional CO2 being added by man, Professor Peter Wadhams said in a recent BBC article.
One of the most threatening feedbacks is release of methane that are held in the currently frozen seabed. As the seabed warms up, it starts to release methane in what can be rather abrupt ways. Due to methane's high global warming potential, this can further accelerate local warming, triggering further methane releases, in a vicious circle that threatens to spiral into runaway global warming.
Push something and it moves a little. Push it a little more and it moves a little more. This is called a “linearity” response. But sometimes a little push can lead to something totally unexpected! This is called “nonlinearity” and, contrary to what one might think, nonlinearities are inherent in most systems - like our atmosphere, for example. In fact, abrupt and unexpected change happens at some point in most systems - we even have a saying for such unexpected outcomes: a tipping point.
Until recently, our atmosphere and oceans behaved like linear systems: incremental dumping of greenhouse gases into the atmosphere caused incremental changes, like rising temperatures and predictable rates of ice melt. But things are now changing unexpectedly fast – nonlinearity is kicking in! We only have to look at the rapidly vanishing arctic icecap for astonishing evidence.
A few years ago, I felt compelled to leave my previous pursuits in Engineering Physics (and chess master) to begin a PhD thesis focusing on abrupt climate change. I felt the planet’s climate was approaching several tipping points and analysis of Paleoclimatology records (tree rings, ice cores, ocean sediment, etc.) may provide evidence on what tipping points – nonlinearities – we might expect to see first (and maybe prevent).
Sadly, I’m late to the game. The rapidly disappearing Arctic icecap is a tipping point in motion. In all likelihood, statistically speaking, it’s gone, history. Within a few years when the ice disappears entirely, for the first time in 3 (or as many as 13) million years, hold on because our weather patterns will be drastically destabilized. Most folks in my field are still reluctant to acknowledge this 800 pound gorilla staring us right in the face.
Methane, an extremely potent greenhouse gas (105 times more efficient at trapping heat in the atmosphere than carbon dioxide over 20 years, see image left) is a product of ancient wetlands, locked in permafrost and ocean sediments for millions of years. Today, warming air and seawater causes methane to be released more quickly. In the ocean off Siberia, methane plumes greater than one kilometre in diameter have been observed. Shocking stuff in my business.
And other tipping points abound. If the melting Arctic icecap isn’t bad enough, how about persistent droughts turning the Amazon rainforest into dry savannah? Much of the forest would burn first, delivering the double whammy of massive carbon emissions and the loss of a vital carbon sink.
Or how about collapsing boreal forest ecosystems. In Canada, drought-stressed trees, not already under attack by mountain pine beetles and emerald ash borers, would surely burn in the new norm of arid heat waves.
Perhaps the Greenland ice sheet will be the ultimate smoking gun. It contains enough water to raise global sea level by seven metres. With melt rates doubling every few years, knowing what I know, I can honestly say I am gravely concerned. Many models predict Greenland’s ice sheet will be ‘ok’ for another 3 centuries, but as I wrote in my last blog, you can officially pitch those models out the window.
Unlike our ancestors, humanity has a shot at stopping this – that is, if we throw everything we have at it. But we need to urgently focus on doing two things: radically reduce carbon emissions and prevent further warming of the Arctic Ocean; and keep as much methane locked underground as possible (we have the technology to do this today).
We have officially entered the realm of unknown-unknowns; the nonlinearity zone.
The question is will politicians reach the tipping point of reason?
Posted with author's permission. Earlier posted at Sierra Club Canada. Paul Beckwith is a PhD student with the laboratory for paleoclimatology and climatology, department of geography, University of Ottawa.
About 5 million years ago continental drift pushed North and South America together, creating the Isthmus of Panama where the Central American Seaway ocean passage had previously existed. The Pacific and Atlantic were no longer connected, drastically altering global ocean currents and atmospheric circulation patterns. As the Atlantic Gulf Stream strengthened, it carried vast amounts of moisture into the northern regions. The Arctic eventually cooled and it’s estimated sea ice cover has existed continuously in the Arctic Ocean for 3 million years, possibly for as long as 13 million years.
Slow cycling between cold and warm periods occurred on Earth many times due to the planet's changing orbit, tilt, and position relative to the sun. This caused the sea ice to wax and wane in size but it always persisted, never vanishing. Not any longer. The sea ice will disappear for longer and longer periods over the coming years until it is finally gone for good, likely within a decade.
The world will be a different place - just like the world from 3, or even 13, million years ago. No longer will the bright white parasol on the top of the world reflect sunlight and keep the Arctic cool. Dark seawater will absorb light and rapid Arctic warming will quickly decrease temperature gradients between the pole and equator. Jet streams will slow down, meander and change tracks. Storms will change in location, intensity, frequency, and speed and everything that humans know about weather and seasons for growing food will be obsolete. Everything.
Higher global temperatures will cause more evaporation, putting more water vapor into the atmosphere. Condensing into clouds, huge amounts of heat will be released, fueling even larger and more frequent storms.
Throw out the models that project disturbing climate effects in 2100. They're happening now! Already we're seeing rising sea levels from the massive and accelerating Greenland ice melt. The rapid warming of southern oceans is melting and destabilizing Antarctic ice from below, causing enormous chunks to break off (we’ve all seen them on TV). And big increases in Arctic temperatures mean terrestrial permafrost is melting and the now-warmer continental shelf sea floor is releasing increasing amounts of methane gas, a potent climate change gas.
Why is the sea ice getting hammered? Feedback loops. Unknown unknowns
NASA images showing the difference between sea ice cover between 1980 and 2012.
A very rare cyclone churned up the entire Arctic region for over a week in early August, destroying 20% of the ice area by breaking it into tiny chunks, melting it, or spitting it into the Atlantic. Cold fresh surface water from melted sea ice mixed with warm salty water from a 500 metre depth! Totally unexpected. A few more cyclones with similar intensity could have eliminated the entire remaining ice cover. Thankfully that didn't happen. What did happen was Hurricane Leslie tracked northward and passed over Iceland as a large storm. It barely missed the Arctic this time. Had the storm tracked 500 to 600 kilometres westward, Leslie would have churned up the west coast of Greenland and penetrated directly into the Arctic Ocean basin.
We dodged a bullet, at least this year. This luck will surely run out. What can we do about this? How about getting our politicians to listen to climatologists, for starters.
Posted with author's permission. Earlier posted at Sierra Club Canada. Paul Beckwith is a PhD student with the laboratory for paleoclimatology and climatology, department of geography, University of Ottawa.
Andrew Glikson, earth and paleo-climate scientist at Australian National University
The linear nature of global warming trends projected by the IPCC since 1990 and as late as 2007 (see Figure 1) has given the public and policy makers an impression there is plenty of time for economies to convert from carbon-emitting industries to non-polluting utilities.
Paleo-climate records suggest otherwise. They display abrupt shifts in the atmosphere/ocean/cryosphere system, as manifest in the ice core records of the last 800,000 years. This suggests high sensitivity of the climate system to moderate changes in radiative forcing, whether triggered by changes in solar radiation energy or the thermal properties of greenhouse gases or aerosols. In some instances these shifts have happened over periods as short as centuries to decades, and even over a few years.
Figure 1: Global surface temperature rise trajectories for the 21st century under varying carbon emission scenarios portrayed by the IPCC AR4 2007. A2 represents the business-as-usual scenario consistent with currently rising global emissions. IPCC Examples of abrupt climate shifts are the 1470 years-long Dansgaard-Oeschger intra-glacial cycles, which were triggered by solar signals amplified by ocean currents, and the “younger dryas” cold interval, which occured when interglacial peaks resulted in extensive melting of ice and cooling of large ocean regions by melt water.
The last glacial termination (when large-scale melting of ice occurred between about 18,000 to 11,000 years ago) is attributed to transient solar pulsations of 40–60 Watt/m2 affecting mid-northern latitudes. This led to a ~6.5+/-1.5 Watt/m2 rise in mean global atmospheric energy level, which meant a mean global temperature rise of ~5.0+/-1.0 degrees Celsius and sea level rise of 120 meters (see Figure 2).
Figure 2: Comparison between radiative forcing levels of (1) the Pliocene (~400 ppm CO2; T ~ 2-3 degrees C; Sea level 25+/-12 meters higher than pre-industrial); (2) the last Glacial Termination (~6.5+/-1.5 Watt/m2; ~5.0+/-1.0 degrees C; SL rise 120 meters) and (3) Anthropogenic 1750-2007 warming (1.66 Watt/m2 + 1.35 Watt/m2 – the latter currently masked by sulphur aerosols). Modified after Hansen et al 2008 As shown in Figure 2, anthropogenic carbon emission and land clearing since 1750 have raised the atmospheric energy level by +1.66 Watt/m2. Once the masking effect of industrial sulphur aerosols is taken into account. This totals ~3.0 Watt/m2, namely near half the radiative forcing associated with the last glacial termination.
Compounding the major rise in radiative forcing over the last ~260 years is the rate of greenhouse gas (GHG) rise. This has averaged ~0.5ppm CO2 per year since 1750. That’s more than 40 times the rate during the last glacial termination, which was 0.012ppm CO2 per year. The current CO2 rise rate – 2ppm a year – is the fastest recorded for the Cainozoic (the period since 65 million years ago) (see Figure 3).
Figure 3: Relations between CO2 rise rates and mean global temperature rise rates during warming periods, including the Paleocene-Eocene Thermal Maximum, Oligocene, Miocene, glacial terminations, Dansgaard-Oeschger (D-O) cycles and the post-1750 period. Glikson We have seen this scale and rate of radiative forcing, in particular since the 1970s, expressed by intensification of the hydrological cycle, heat waves and hurricanes around the globe. It imparts a new meaning to the otherwise little-defined term, “tipping point”.
Between 1900 and 2000, the ratio of observed to expected extremes in monthly mean temperatures has risen from ~1.0 to ~3.5. From about 1970 the Power Dissipation Index (which combines storm intensity, duration, and frequency) of North Atlantic storms increased from ~1.0 to ~2.7-5.5 in accord with tropical sea surface temperatures which rose by about 1.0 degree Celsius.
The ostensibly large number of recent extreme weather events has triggered intensive discussions, both in- and outside the scientific community, on whether they are related to global warming. Here, we review the evidence and argue that for some types of extreme — notably heat waves, but also precipitation extremes — there is now strong evidence linking specific events or an increase in their numbers to the human influence on climate. For other types of extreme, such as storms, the available evidence is less conclusive, but based on observed trends and basic physical concepts it is nevertheless plausible to expect an increase.
Hansen et al analysed the distribution of anomalous weather events relative to the 1951–1980 base line, displaying a shift toward extreme heat events (see Figure 4). The authors observe:
hot extreme[s], which covered much less than 1% of Earth’s surface during the base period (1951-1980), now typically [cover] about 10% of the land area. It follows that we can state, with a high degree of confidence, that extreme anomalies such as those in Texas and Oklahoma in 2011 and Moscow in 2010 were a consequence of global warming because their likelihood in the absence of global warming was exceedingly small.
Figure 4: Hansen et al 2012 calculate the seasonal mean and standard deviation at each grid point for this period, and then normalize the departures from the mean, obtaining a Gaussian bell-shaped distribution. They plot a histogram of the values from successive decades, getting a sense for how much the climate of each decade departed from that of the initial baseline period. The shift in the mean of the histogram is an indication of the global mean shift in temperature, and the change in spread gives an indication of how regional events would rank with respect to the baseline period. Hansen et al The consequences for the biosphere of accelerating climate change are discussed by Baronsky et al in the following terms:
Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence.
Climates found at present on 10–48% of the planet are projected to disappear within a century, and climates that contemporary organisms have never experienced are likely to cover 12–39% of Earth. The mean global temperature by 2070 (or possibly a few decades earlier) will be higher than it has been since the human species evolved.
At 400ppm CO2, potential climate conditions have reached levels which last existed in the peak Pliocene epoch (5.3-2.6 million years ago). Given an increase in extreme weather events under conditions of +0.8C, an even higher rate of extreme events is expected under conditions of +2.0C currently shielded by industrially emitted sulphur aerosols.
Current trends in the frequency and intensity of extreme weather events are evident globally (see Figure 5). In the USA, the number of meteorological, hydrological and climatological events rose from about 20-40 per year during 1980-1988, to about 40-80 per year during 1989-2005, to between 70-100 per year after 2006, consistent with global rise in the frequency of extreme weather events.
Figure 5: Global frequency of natural disaster impacts and associated human and economic losses from the 1970s to 1990s. World Meteorological Organization, 2006 http://www.nrcan.gc.ca/earth-sciences/climate-change/community-adaptation/assessments/378 James Hansen states:
There is still time to act and avoid a worsening climate, but we are wasting precious time. We can solve the challenge of climate change with a gradually rising fee on carbon collected from fossil-fuel companies, with 100% of the money rebated to all legal residents on a per capita basis. This would stimulate innovations and create a robust clean-energy economy with millions of new jobs. It is a simple, honest and effective solution.
New solar technologies promise to provide a large part of the answer. Time is of the essence.
Andrew Glikson is Honorary Professor at the Geothermal Energy Centre of Excellence, The University of Queensland, and a Visiting Fellow at the Australian National University.
The PLA National Defense University (Chinese: ä¸å›½äººæ°‘解放军国防大å¦) is a state university administered by the PLA. It is the top education institution for military education in China.
The university located in Beijing under the leadership of PLA Central Committee. The current President of the university is Prof. Lt. Gen Wang Xibin.
It was formed in 1985 with the merger of parts of the PLA Military Academy, the PLA Political Academy and the PLA Logistics Academy. It is claimed to be "China's equivalent of West Point
The black rectangle on this map shows the general region where Paull and his collaborators have been studying methane releases in the Beaufort Sea. The smaller red rectangle indicates the edge of the continental shelf and continental slope where they will conduct research during t heir current expedition. These areas are shown in greater detail in the maps below. Base image: Google Maps
Chasing gas bubbles in the Beaufort Sea
In the remote, ice-shrouded Beaufort Sea, methane (the main component of natural gas) has been bubbling out of the seafloor for thousands of years. MBARI geologist Charlie Paull and his colleagues at the Geological Survey of Canada are trying to figure out where this gas is coming from, how fast it is bubbling out of the sediments, and how it affects the shape and stability of the seafloor. Although Paull has been studying this phenomenon for a decade, his research has taken on new urgency in recent years, as the area is being eyed for oil and gas exploration.
In late September 2012, Paull and his fellow researchers will spend two weeks in the Beaufort Sea on board the Canadian Coast Guard ship Sir Wilfred Laurier, collecting seafloor sediment, mapping the seafloor using sonar, installing an instrument that will "listen" for undersea gas releases, and using a brand new undersea robot to observe seafloor features and collect gas samples.
This will be Paull's third Beaufort Sea expedition. As in previous expeditions, he will be working closely with Scott Dallimore of Natural Resources Canada's Geological Survey of Canada and Humfrey Melling of Fisheries and Oceans Canada's Institute of Ocean Sciences.
Over time, the focus of the team's research has moved farther offshore, into deeper water. Their second expedition in 2010 looked at diffuse gas venting along the seaward edge of the continental shelf. The 2012 expedition will focus on three large gas-venting structures on the continental slope, at depths of 290 to 790 meters (950 to 2,600 feet).
The Beaufort Sea, north of Canada's Yukon and Northwest Territories, is a hostile environment by any definition of the term. It is covered with ice for much of the year. Historically, only from mid-July to October has a narrow strip of open water appeared within about 50 to 100 kilometers (30 to 60 miles) of the coast. Even at this time of year, winds often howl at 40 knots and temperatures can drop well below freezing at night. Researchers must allow extra time for contingencies such dodging pack ice and having to shovel snow off the deck of the research vessel.
Average annual air temperatures along the coast of the Beaufort Sea are well below freezing. Thus deeper soils remain permanently frozen throughout the year, forming what is called permafrost. Around the Beaufort Sea, permafrost extends more than 600 meters (about 2,000 feet) below the ground.
Permafrost also exists in the sediments underlying the continental shelf of Beaufort Sea. This permafrost is a relict of the last ice age, when sea level was as much as 120 meters lower than today. At that time, areas that are now covered with seawater were exposed to the frigid Arctic air.
As sea-level rose over the last 10,000 years, it flooded the continental shelf with seawater. Although the water in the Beaufort Sea is cold—about minus 1.5 degrees Centigrade—it is still much warmer than the air, which averages minus 15 degrees C. Thus, as the ocean rose, it is gradually warmed up the permafrost beneath the continental shelf, causing it to melt.
Quite a bit of methane, the main component of "natural gas," is trapped within the permafrost. As the permafrost melts, it releases this methane, which may seep up through the sediments and into the overlying ocean water.
The deeper sediments of the Beaufort Sea also contain abundant layers of methane hydrate—an ice-like mixture of water and natural gas. As the seafloor has warmed, these hydrates have also begun to decompose, releasing additional methane gas into the surrounding sediment.
These maps show the area to be studied during the current expedition. The lower map shows the continental shelf and continental slope of the Beaufort Sea. The upper image shows detailed seafloor bathymetry of a portion of the continental slope that will be studied during the current cruise, as well as the three seafloor mounds that the researchers will explore using their new ROV. Lower image modified from Google Maps. Upper image: Natural Resources Canada.
A tantalizing glimpse
A 2010 expedition by Paull and his colleagues provided a tantalizing glimpse of how much methane is present on the continental shelf of the Beaufort Sea. Using a remotely operated vehicle (ROV) with video camera to explore the shelf edge, they found white mats of methane-loving bacteria almost everywhere. They also videotaped what turned out to be methane bubbles emerging from many of these mats. Based on these observations, as well as the contents of sediment cores collected by the Geological Survey of Canada, the researchers concluded that the shelf edge is an area of "widespread diffuse venting" and that "methane permeates the shelf edge sediments in this region."
During 2010, the research team also conducted ROV dives on a shallow underwater mound called Kopanoar PLF. At the top of this mound they discovered "vigorous and continuous gas venting" that released clouds of bubbles and sediment into the water. In one ROV dive, the researchers saw something no one had ever seen before—a plume of gas bubbles that moved rapidly along the sea floor, apparently following a crack in the sediment that was in the process of being forced open by the pressure of the gas coming up from below.
The researchers also studied several deeper PLFs during the 2010 expedition. They dropped core tubes into the tops of these mounds. When the cores were lifted back onto the ship, the sediments inside fizzed and bubbled for up to an hour. The sediment was chock full of methane hydrates. Paull said, "We knew that there was a lot of gas venting going on down there, and now we have good reasons to believe that methane hydrates are present within the surface sediments. But our ROV couldn't dive deep enough, so we weren't able to go down and see what these areas actually looked like." That's one reason the team is heading back to the Arctic in 2012.
For the 2012 expedition, the team will continue its strategy of following the topography to study areas of gas venting in the Beaufort Sea. They plan to focus on three circular, flat-topped mounds on the continental slope. The researchers believe that these pingo-like features form at the tops of "chimneys" or conduits where methane is seeping up from sediments hundreds of meters below the seafloor.
During his previous cruises, Paull used a small ROV that could dive only about 120 meters below the surface. However, the mounds on the continental slope are in about 300 to 800 meters of water. So MBARI engineers Dale Graves and Alana Sherman designed and built an entirely new ROV just for this expedition. The new ROV is small, portable, agile, relatively inexpensive, and can dive to 1,000 meters. It can also be launched and operated by just two people (for the 2012 expedition, those two people will be Graves and Sherman).
Amazingly, the new mini-ROV went from initial design to final field tests in only 15 months. But the vehicle's simple yet elegant design reflects Graves' decades of experience designing ROVs and underwater control systems. "It was a fun project for me," Graves said. "A dream come true. We designed it from scratch with a budget of just $75,000, not including labor. We mostly reused parts from MBARI's older ROVs, and built the rest in house. MBARI's electrical and mechanical technicians and machinists worked on it in between their other projects."
In addition to a state-of-the-art high-definition video camera, the ROV carries a special system for collecting methane gas bubbles. This is not as easy as it sounds, because the methane gas has a tendency to turn back into solid methane hydrate, which blocks the flow of any additional methane gas into the system. The new ROV's gas collection system includes a built-in heater to melt the hydrates and keep the gas flowing.
In addition to collecting samples of gas, the ROV will be used to look for communities of tubeworms or clams that typically grow around seafloor methane seeps. Paull said, "Nobody has ever found a living chemosynthetic biological community in the Arctic proper. But I think we have a good chance of finding them at the tops of these structures."
Although the researchers have begun to understand where the gas in the Beaufort Sea is coming from, many other questions remain. One of the big questions the researchers are trying to answer is whether the three gas chimney structures on the continental slope are related to the gas venting systems in shallower water, on the continental shelf. As Paull put it, "Are they independent gas-venting structures that just happen to be together, or are they all part of the same system?"
Another important question is how all this methane gas affects the stability of the seafloor. When methane hydrates warm up and release methane gas, the gas takes up much more space than the solid hydrate, putting pressure on the surrounding sediments. Similarly, the decomposition of either methane hydrate or permafrost can reduce the mechanical strength of the surrounding sediment. Either process could make the seafloor more susceptible to submarine landslides.
Undersea landslides are common along the continental slope of the Beaufort Sea, but researchers do not yet know when or how they form. However, decomposing methane hydrates are believed to have triggered major landslides in other deep-sea areas. Such landslides could potentially destabilize oil platforms, pipelines, or other equipment on the seafloor, and have the potential to generate tsunamis.
If there is time during the 2012 cruise, the researchers hope to perform ROV dives on one or more underwater-landslides. In Fall 2013, when the team returns to the Beaufort Sea for a fourth time, these features will become the primary focus. During that expedition, the team also hopes to use one of MBARI's autonomous underwater vehicles (AUVs) to make very detailed maps of the shelf edge, the underwater landslides, and areas where methane is bubbling out of the seafloor.
Oil and gas companies have known for decades that deep oil and natural gas deposits exist in the sediments below the continental slope of the Beaufort Sea. With the warming of the Arctic and the retreat of sea ice, these hydrocarbons have become more accessible. However, it remains to be seen whether they can be extracted safely, economically, and without excessive environmental damage. Thus, the team's research will not only provide new insights into previously unknown geological processes, but will also provide important information for decision-makers involved in oil and gas permitting. For more information on this article, please contact MBARI.
Sept. 23, 2012 – A University of Utah study suggests something amazing: Periodic changes in winds 15 to 30 miles high in the stratosphere influence the seas by striking a vulnerable “Achilles heel” in the North Atlantic and changing mile-deep ocean circulation patterns, which in turn affect Earth’s climate.
“We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate,” says Thomas Reichler, senior author of the study published online Sunday, Sept. 23 in the journal Nature Geoscience.
Simplified artist’s conception showing how changes in polar vortex winds high in the stratosphere can influence the North Atlantic to cause changes in the global conveyor belt of ocean circulation. Credit: Thomas Reichler, University of Utah.
Scientists already knew that events in the stratosphere, 6 miles to 30 miles above Earth, affect what happens below in the troposphere, the part of the atmosphere from Earth’s surface up to 6 miles or about 32,800 feet. Weather occurs in the troposphere.
Researchers also knew that global circulation patterns in the oceans – patterns caused mostly by variations in water temperature and saltiness – affect global climate.
“It is not new that the stratosphere impacts the troposphere,” says Reichler, an associate professor of atmospheric sciences at the University of Utah. “It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean.”
Funded by the University of Utah, Reichler conducted the study with University of Utah atmospheric sciences doctoral student Junsu Kim, and with atmospheric scientist Elisa Manzini and oceanographer Jürgen Kröger, both with the Max Planck Institute for Meteorology in Hamburg, Germany.
Stratospheric Winds and Sea Circulation Show Similar Rhythms
Reichler and colleagues used weather observations and 4,000 years worth of supercomputer simulations of weather to show a surprising association between decade-scale, periodic changes in stratospheric wind patterns known as the polar vortex, and similar rhythmic changes in deep-sea circulation patterns. The changes are:
– “Stratospheric sudden warming” events occur when temperatures rise and 80-mph “polar vortex” winds encircling the Artic suddenly weaken or even change direction. These winds extend from 15 miles elevation in the stratosphere up beyond the top of the stratosphere at 30 miles. The changes last for up to 60 days, allowing time for their effects to propagate down through the atmosphere to the ocean.
– Changes in the speed of the Atlantic circulation pattern – known as Atlantic Meridional Overturning Circulation – that influences the world’s oceans because it acts like a conveyor belt moving water around the planet.
Sometimes, both events happen several years in a row in one decade, and then none occur in the next decade. So incorporating this decade-scale effect of the stratosphere on the sea into supercomputer climate simulations or “models” is important in forecasting decade-to-decade climate changes that are distinct from global warming, Reichler says.
“If we as humans modify the stratosphere, it may – through the chain of events we demonstrate in this study – also impact the ocean circulation,” he says. “Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate.”
A Vulnerable Soft Spot in the North Atlantic
“The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide,” Reichler says. “In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough – and thus dense enough – so the water starts sinking.”
It is Earth’s most important region of seawater downwelling, he adds. That sinking of cold, salty water “drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans.”
Reichler continues: “This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them.”
Because of that sensitivity, Reichler calls the sea south of Greenland “the Achilles heel of the North Atlantic.”
From Stratosphere to the Sea
In winter, the stratospheric Arctic polar vortex whirls counterclockwise around the North Pole, with the strongest, 80-mph winds at about 60 degrees north latitude. They are stronger than jet stream winds, which are less than 70 mph in the troposphere below. But every two years on average, the stratospheric air suddenly is disrupted and the vortex gets warmer and weaker, and sometimes even shifts direction to clockwise.
“These are catastrophic rearrangements of circulation in the stratosphere,” and the weaker or reversed polar vortex persists up to two months, Reichler says. “Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface.”
Reichler’s study ventured into new territory by asking if changes in stratospheric polar vortex winds impart heat or cold to the sea, and how that affects the sea.
It already was known that that these stratospheric wind changes affect the North Atlantic Oscillation – a pattern of low atmospheric pressure centered over Greenland and high pressure over the Azores to the south. The pattern can reverse or oscillate.
Because the oscillating pressure patterns are located above the ocean downwelling area near Greenland, the question is whether that pattern affects the downwelling and, in turn, the global oceanic circulation conveyor belt.
The study’s computer simulations show a decadal on-off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the North Atlantic and changes in sea circulation more than one mile beneath the waves. Observations are consistent with the pattern revealed in computer simulations.
Observations and Simulations of the Stratosphere-to-Sea Link
In the 1980s and 2000s, a series of stratospheric sudden warming events weakened polar vortex winds. During the 1990s, the polar vortex remained strong.
Reichler and colleagues used published worldwide ocean observations from a dozen research groups to reconstruct behavior of the conveyor belt ocean circulation during the same 30-year period.
“The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic,” Reichler says.
To reduce uncertainties about the observations, the researchers used computers to simulate 4,000 years worth of atmosphere and ocean circulation.
“The computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events,” Reichler says.
To further verify the findings, the researchers combined 18 atmosphere and ocean models into one big simulation, and “we see very similar outcomes.”
The study suggests there is “a significant stratospheric impact on the ocean,” the researchers write. “Recurring stratospheric vortex events create long-lived perturbations at the ocean surface, which penetrate into the deeper ocean and trigger multidecadal variability in its circulation. This leads to the remarkable fact that signals that emanate from the stratosphere cross the entire atmosphere-ocean system.”
Below is part of a recent interview published by Voice of Russia - click here for the full report. Editorial note: We anxiously await further findings from the research team as to what the source is of these releases, when the methane was formed and by how much these releases are likely to increase over the years.
Methane emission in the Arctic – a possible key to the global warming
Russian scientists have discovered more than 200 sources of methane emissions in the Arctic, particularly in the north of the Laptev Sea. Two of the methane fields exceed 1 kilometer in diameter, said Igor Semiletov, expedition head aboard the Viktor Buinitsky research vessel. Methane emissions in the Arctic have been observed before and are explained by bacterial activity. Head of the ecology department at Moscow State University, Dmitry Zamolodchikov, spoke about the possible consequences in an exclusive interview with the Voice of Russia.
How would you comment on this discovery by Russian scientists?
Different examples of methane emissions in Arctic coastal regions and in the tundra systems have been observed over the last 20 or 30 years. There is really nothing surprising about this. Because, first of all, we are talking about frozen substances and cold conditions in the coastal area, in addition to the water pressure, all of which make perfect conditions for so called gas hydrates. That is a bond between methane and water, which looks like snow, and is fairly unstable. Gas hydrates can quite easily break and can cause, correspondingly, methane emissions. Methane emerges as a result of bacteria activity in an environment with little oxygen which decomposes organic substances. The tundra has a humid climate, meaning it has the perfect conditions for the methane-producing bacteria. In that sense tundra is the source of methane and these bacteria are active in this region. In other words the Arctic has many mechanisms for production of natural methane. There are many mechanisms that conserve methane, for example gas hydrates. Many of those mechanisms are broken at higher temperatures. Therefore, in some cases, mass emissions of methane can be observed.
In the Youtube video below, Professor Peter Wadhams, Professor of Ocean Physics and Head of the Polar Ocean Physics Group of the University of Cambridge and one of the world's top sea-ice experts, joins The Big Picture, a show with Thom Hartmann filmed live and broadcast from the RT America studios in Washington DC.
Professor Wadhams warns that the Arctic sea ice looks set to be completely melted in just a few years. Professor Wadhams adds that action is needed that includes not only emissions cuts, but also geoengineering methods.
It was a Skype connection, so the sound quality was not optimal, but Peter Carter has improved this in the version below. Anyway, the message is important enough to be watched closely and to be further shared and discussed.
As the Arctic sea ice retreats, an ever smaller area remains in summer. Snow cover on the ice reflects between 80% and 90% of sunlight, while the dark ocean without ice cover reflects only 7% of the light, explains Stephen Hudson of the Norwegian Polar Institute. As the sea ice cover decreases, less solar radiation is reflected away from the surface of the Earth in a feedback effect that causes more heat to be absorbed and consequently melting to occur faster still.
The image below shows the retreat in September 2012 to date, compared with 7 other recent years.
The image below further illustrates the rate at which Arctic sea ice is declining, and thus losing its reflectivity.
Image produced by Peter Carter based on NSIDC images, showing the now exposed permafrost areas that extend from the continents into the shallow parts of the Arctic Ocean.
NASA images showing the difference between sea ice cover between 1980 and 2012.
NSIDC have already made a preliminary call that September 16 was the date that sea ice extent was at its minimum in the year 2012.
Volume is something else and the record low hasn't been called yet. Nonetheless, it's interesting to look at where the trend might point at, once a value for 2012 has been added into the picture. On the interactive graph below, data for September 2nd have been added.
Granted, when making projections, it's good to have sophisticated models. I don't claim to have used those, but I've got a good eye and by the looks of it, sea ice will be gone in September 2014.
This NASA satellite image shows how the Arctic sea ice extent, on Sept. 16, 2012, compares to the average minimum extent over the past 30 years (in yellow). Credit: NASA/Goddard Scientific Visualization Studio.
Arctic sea ice cover likely melted to its minimum extent for the year on September 16, says the National Snow and Ice Data Center (NSIDC), adding the note that this number is preliminary—changing weather conditions could still push the ice extent lower.
Sea ice extent—defined by NSIDC as the total area covered by at least 15 percent of ice—fell to 3.41 million square kilometers (1.32 million square miles), now the lowest summer minimum extent in the 33-year satellite record.
NSIDC adds that this minimum is 49% below the 1979 to 2000 average, as illustrated by the table below.
Table 1. Previous minimum Arctic sea ice extents
YEAR
MINIMUM ICE EXTENT
DATE
IN MILLIONS OF SQUARE KILOMETERS
IN MILLIONS OF SQUARE MILES
2007
4.17
1.61
September 18
2008
4.59
1.77
September 20
2009
5.13
1.98
September 13
2010
4.63
1.79
September 21
2011
4.33
1.67
September 11
2012
3.41
1.32
September 16
1979 to 2000 average
6.70
2.59
September 13
1979 to 2010 average
6.14
2.37
September 15
NSIDC adds that the six lowest seasonal minimum ice extents in the satellite record have all occurred in the last six years (2007 to 2012). In contrast to 2007, when climatic conditions (winds, clouds, air temperatures) favored summer ice loss, this year’s conditions were not as extreme. Summer temperatures across the Arctic were warmer than average, but cooler than in 2007. The most notable event was a very strong storm centered over the central Arctic Ocean in early August. It is likely that the primary reason for the large loss of ice this summer is that the ice cover has continued to thin and become more dominated by seasonal ice. This thinner ice was more prone to be broken up and melted by weather events, such as the strong low pressure system just mentioned. The storm sped up the loss of the thin ice that appears to have been already on the verge of melting completely.
NASA says that this year, a powerful cyclone formed off the coast of Alaska and moved on August 5 to the center of the Arctic Ocean, where it churned the weakened ice cover for several days. The storm cut off a large section of sea ice north of the Chukchi Sea and pushed it south to warmer waters that made it melt entirely. It also broke vast extensions of ice into smaller pieces more likely to melt.
“The storm definitely seems to have played a role in this year's unusually large retreat of the ice”, said Claire Parkinson, a climate scientist at NASA Goddard Space Flight Center, Greenbelt, Md. “But that exact same storm, had it occurred decades ago when the ice was thicker and more extensive, likely wouldn't have had as prominent an impact, because the ice wasn't as vulnerable then as it is now.”
In the press release, NSIDC lead scientist Ted Scambos said that thinning ice, along with early loss of snow, are rapidly warming the Arctic. “But a wider impact may come from the increased heat and moisture the warmer Arctic is adding to the climate system,” he said. “This will gradually affect climate in the areas where we live,” he added. “We have a less polar pole—and so there will be more variations and extremes.”
The image below, from Arctic Sea Ice Blog, shows Arctic sea ice observations (in red) against the backdrop of models used in IPCC AR4 (2007) for projection of sea ice up to the year 2100.
The image below, from NSIDC sea ice news, shows the observed September sea ice extent for 1952-2011 (black line) against a backdrop of projections used by IPCC AR4 (blue) as well as proposed for use in IPCC AR5 (red).
Note: The record low value for 2012 still has to be added on this image. Credit: NSIDC, Stroeve et al.
The image shows that the recently observed decline in sea ice extent is steeper than the CMIP3 models with a “business as usual” SRESA1B greenhouse gas emissions scenario (blue line), as used by the IPCC in AR4.
It is also steeper than the more recent CMIP5 models using a RCP 4.5 scenario (pink line) that are proposed to be used by the IPCC in AR5.
RCP 4.5 is a scenario in which the global temperature rise would would soon exceed 2 degrees Celsius. Since the Arctic experiences accelerated warming, such a scenario would clearly be catastrophic. Looking at sea ice volume, rather than extent, would show this even more clearly.
Above animation shows the 2012 time-series of ice extent using sea ice concentration data from the DMSP SSMI/S satellite sensor. The black area represents the daily average (median) sea ice extent over the 1979-2000 time period. Layered over top of that are the daily satellite measurements from January 1 to September 14, 2012. Published September 17, 2012 by NOAA Visualizations.
By comparison, this is more than the land and inland waters covered by the United States (or Canada, or China, for that matter). It is also more than the 9,826,630 square km (3,794,080 sq mi) covered by the United States when all its land, inland waters, the Great Lakes, coastal waters and territorial waters are included.
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