NewScientist: Antarctic wind vortex is strongest for 1,000 years

The winds ripping around Antarctica. (Image: earth.nullschool.net)

by Michael Slezak, NewScientist, May 11, 2014 

Our greenhouse gas emissions are helping to spin up a giant vortex of winds around Antarctica.

Antarctica has been warming relatively slowly compared with the rest of the world. The explanation seems to be that the winds spinning clockwise around the continent have been getting stronger, preventing warm air from entering.

In a way, those winds have done us a favour by keeping warm air away from the South Pole. Otherwise it might be melting. But as this atmospheric maelstrom accelerates, it shrinks, leaving the most vulnerable parts of Antarctica out in the warm and dragging winter rain away from Western Australia.

In 2009, it seemed that the hole in the ozone layer above Antarctica was responsible for boosting the winds. Now Nerilie Abram from the Australian National University in Canberra and her colleagues have shown the ozone hole is only part of the story. Global warming is just as important.

Warming powers winds

The team reconstructed Antarctic temperatures over the past 1,000 years, using an ice core from James Ross Island near the Antarctic Peninsula. The temperatures correlated with how strong and tight the winds are, so they could construct a record of wind strength.

They found that the current strength of the winds is unprecedented over the past millennium. But the surge in strength started in the 1940s, decades before the ozone hole.

So Abram's team simulated the last millennium using 8 climate models, driven by actual greenhouse gas levels previously reconstructed from ice cores. All the models predicted that the winds would pick up by the 1940s, suggesting greenhouse gases were playing a role. That may be because the Northern Hemisphere is warming faster than the south – because it has more continents – creating a strong temperature gradient that boosts the winds.

Such historical data is vital, says Wenju Cai from the CSIRO, Australia's national research agency, in Melbourne. In as-yet-unpublished work, he estimates that ozone depletion has caused two-thirds of the impact on the Antarctic winds, with greenhouse gases responsible for the rest.

Futureshock

If greenhouse gases really are contributing to the winds, it changes our expectations for what will happen to the climate in Australia and Antarctica.

The ozone hole is expected to heal in the coming decades, and if it was the only factor controlling the winds they would weaken and expand. So Australia would get its rain back, while the western parts of Antarctica might get some more protection against warming.

However, Abram says rising global temperatures will counteract this weakening effect on the winds. That means Western Australia will stay dry and the western parts of Antarctica, stranded outside the winds, will keep melting.

Cai estimates that, on our current emissions pathway, the two factors will counteract each other until 2045, so the winds will stay constant. After that, without reducing our emissions, greenhouse gases will boost the winds further.

Journal reference: Nature Climate Change, DOI: 10.1038/NCLIMATE2235

http://www.newscientist.com/article/dn25547-antarctic-wind-vortex-is-strongest-for-1000-years.html#.U4I2Y_ldXX4

Australia: Wilder winds, less rain, as Roaring Forties become Furious Fifties

by Peter Hannam, Environment Editor, The Sydney Morning Herald, May 11, 2014

Photo: Fairfax Graphics

The Roaring Forties, the Southern Ocean winds which once bore European sailors to Australia and the East Indies, are becoming more like the Furious Fifties as climate change triggers a shift in key weather patterns poleward, an Australian-led team of scientists has found.

Using data derived from Antarctic ice cores and other sources, the researchers found Southern Ocean winds are now stronger than at any time in the past 1,000 years.

Greenhouse gases are what are causing the winds to intensify now and that’s really moving the system beyond the natural range,” said Nerilie Abram of the Australian National University’s Research School of Earth Sciences and lead author of the research, published on Monday in Nature Climate Change.

In the past half century, the westerly winds have quickened 10-15% and moved 2-5 degrees closer to the South Pole – meaning fewer storms are reaching as far north as Australia.

“That isn’t good news for farmers in the southern parts of Australia who are reliant on the winter winds that come out of the Southern Ocean,” Dr Abram said. Winter rainfall has dropped 20% in southwest Western Australia since the 1960s, with cool-season rain tallies also lower in Australia’s southeast.

The stronger winds also help resolve a climate-change conundrum – why Antarctica is not warming as fast as other continents and the Arctic. “Over a large part of Antarctica we don’t get much warming at all,” Dr Abram said. [This may be changing - temperature anomalies over Antarctica have become very significant this year.]

The reason for the discrepancy is that cool air is being trapped over Antarctica, resulting in increased snowfall for some regions. However, areas exposed to stronger winds and warming seas, such as the Antarctic Peninsula, are heating up faster than anywhere else in the Southern Hemisphere.

“The West Antarctic Ice Sheet [adjacent  to the peninsula] is probably the bit of the Antarctic ice mass that we’ve been most concerned about for the longest time,” said Matthew England, from the University of NSW’s Climate Change Research Centre, and a co-author of the paper. If it all melted, that ice sheet could lift global sea levels by 4-5 metres, he said.

Professor England said the changes to atmospheric variability that see the band of westerly winds oscillate north or south – known in the Southern Hemisphere as the Southern Annular Mode – are driven roughly equally by the effect of rising greenhouse gases and the ozone hole.

The relative contribution, though, should alter as internationally agreed constraints on the use of chemicals that destroy the protective ozone layer take effect, potentially slowing the pick-up in wind speeds.

“Going forward, the greenhouse aspect will dominate as the ozone hole starts to repair and, of course, greenhouse gases are going terrifyingly upwards in their concentration,” he said.

Wenju Cai, an atmospheric scientist at the CSIRO who was not part of the research team, said the findings would assist the study of other key processes, such as whether the rate at which the Southern Ocean absorbs heat and carbon dioxide is changing.

The faster winds “may have a lot of influences that we do not know now,” Dr Cai said. “We may even solve some of the big issues that have been puzzling scientists for many, many years.”

http://www.smh.com.au/environment/weather/wilder-winds-less-rain-as-roaring-forties-become-furious-fifties-20140511-zr9b1.html

"Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus," by Matthew H. England et al., Nature Clim. Change (2014); doi: 10.1038/nclimate2106

Nature Climate Change, 4 (9 February 2014) 222–227; doi: 10.1038/nclimate2106

Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus

• Matthew H. England*, 
• Shayne McGregor,
• Paul Spence,
• Gerald A. Meehl,
• Axel Timmermann,
• Wenju Cai,
• Alex Sen Gupta,
• Michael J. McPhaden,
• Ariaan Purich and
• Agus Santoso

Abstract

Despite ongoing increases in atmospheric greenhouse gases, the Earth’s global average surface air temperature has remained more or less steady since 2001. A variety of mechanisms have been proposed to account for this slowdown in surface warming. A key component of the global hiatus that has been identified is cool eastern Pacific sea surface temperature, but it is unclear how the ocean has remained relatively cool there in spite of ongoing increases in radiative forcing. Here we show that a pronounced strengthening in Pacific trade winds over the past two decades—unprecedented in observations/reanalysis data and not captured by climate models—is sufficient to account for the cooling of the tropical Pacific and a substantial slowdown in surface warming through increased subsurface ocean heat uptake. The extra uptake has come about through increased subduction in the Pacific shallow overturning cells, enhancing heat convergence in the equatorial thermocline. At the same time, the accelerated trade winds have increased equatorial upwelling in the central and eastern Pacific, lowering sea surface temperature there, which drives further cooling in other regions. The net effect of these anomalous winds is a cooling in the 2012 global average surface air temperature of 0.1–0.2 °C, which can account for much of the hiatus in surface warming observed since 2001. This hiatus could persist for much of the present decade if the trade wind trends continue, however rapid warming is expected to resume once the anomalous wind trends abate. [Note to readers -- the winds have shifted from west to east, and a Kelvin wave is bringing very anomalously warm water to the eastern Pacific, with a probable El Nino forming in a few more months.]

At a glance

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Link: http://www.nature.com/nclimate/journal/v4/n3/full/nclimate2106.html

Trade winds drop 28% since 1970s and leave Hawaii drier and more humid

by AUDREY McAVOY Associated Press, Honalulu, June 3, 2013

Part of what makes living in Hawaii so pleasant is the gentle breeze. Arriving from the northeast, it's light enough that it is barely noticeable but strong enough to chase away the humidity.

It's a natural draw to the outdoors. It is not uncommon to show up at a house to find its residents relaxing out in the covered porch or in the car port, not their living room, and enjoying the cooling winds — and a cool drink.

Nowadays, experts say, these breezes, called trade winds, are declining, a drop that's slowly changing life across the islands.

The effects can be seen from the relatively minor, such as residents unaccustomed to the humidity complaining about the weather and having to use their fans and air conditioning more often, to the more consequential, including winds being too weak to blow away volcanic smog.

The winds also help bring the rains, and their decline means less water. It's one reason officials are moving to restore the health of the mountainous forests that hold the state's water supply and encourage water conservation. Scholars are studying ways for farmers to plant crops differently.

It's not clear what's behind the shift in the winds.

"People always try to ask me: 'Is this caused by global warming?' But I have no idea," said University of Hawaii at Manoa meteorologist Pao-shin Chu, who began to wonder a few years ago about the winds becoming less steady and more intermittent.

Chu suggested a graduate student look into it. The resulting study, published last fall in the Journal of Geophysical Research, showed a decades-long decline, including a 28% drop in northeast trade wind days at Honolulu's airport since the early 1970s.

The scientists used wind data from four airports and four ocean buoys as well as statistical data analysis for their study. Now, they are working to project future trade winds using the most recent data from the Intergovernmental Panel on Climate Change, a scientific body of the United Nations.

Luke Evslin is already noticing the dip. The 28-year-old has paddled outrigger canoes — boats long used around the Pacific for fishing, travel and racing — for most of his life. In Hawaii, this means he rides waves generated by trade winds. These days, though, there are fewer waves to surf because the winds are arriving less often.

"You show up and the wind is blowing in the wrong direction. So instead of a 3-hour-45-minute race, it turns into a 5 ½-hour race," Evslin said. "So instead of testing your surfing ability, it's testing your endurance. It's a different type of paddling."

He's thinking he'll now have to start training for races in canals and rivers to better prepare for flat water conditions.

Sometimes the winds are too weak to blow away the volcanic smog, or vog, created by sulfur dioxide erupting from Kilauea volcano on the Big Island, leaving a white or brownish haze hanging over Honolulu. This aggravates asthma and other respiratory problems.

For now, Chu said the most important consequence will be declining rainfall and a drop in the water supply, particularly as Hawaii's population grows and uses more water.

Trade winds deliver rain to Hawaii when clouds carried from the northeast hit mountainous islands built by millions of years of volcanic eruptions. These rains, together with rainfall from winter storms, are the state's primary sources of water.

On Oahu, the rain feeds ground aquifers that supply water to about 950,000 people in Honolulu and surrounding towns.

Barry Usagawa, the water resources program administrator for Honolulu's water utility, said residents are reporting streams near their homes are flowing lower than before.

"What we don't know is if this is truly a downward trend or just the lower leg of a long-term cycle. Is it going to go back up?" he said. The utility has contracted Chu to develop rainfall forecasts to plan for the decades ahead.

The water utility is also encouraging people to fix leaks and buy appliances that use less water to reduce their water consumption. It's developing water recycling facilities so places like golf courses will be irrigated with recycled water. Desalinizing ocean water may also be an option, Usagawa said.

In the meantime, the utility supports efforts to improve the health of Oahu's forests so they can absorb as much rain as they get.

The Legislature this year approved a state budget with $8.5 million for watershed protection steps next fiscal year that include removing invasive weeds and keeping out pigs and other feral animals that dig up forest plants.

The drop in trade winds, along with a separate decline in winter Kona storms, is one reason parts of Hawaii are in drought. Maui, for example, just had the driest April on record.

To cope with the rainfall decline, University of Hawaii at Manoa agriculture professor Ali Fares said farmers can try to grow crops during the rainy reason and avoid months with more uncertainty about water availability.

Farmers could also plant more drought tolerant crops and irrigate when crops are under the most stress. "So many people only talk about drought when there's no water. But it's too late then. We have to talk about these before they happen," Fares said.

The trade wind decline may be too subtle to affect the state's biggest industry, tourism, and keep away any of the 8 million travelers who visit Hawaii each year. After all, even without trade winds, Hawaii's humidity is mild compared to Hong Kong or Tokyo. And the heat here is nothing compared to summer in Texas or Arizona.

"We do have the best weather in the planet. We really do," said Jerome Agrusa, a travel industry management professor at Hawaii Pacific University. "Once you leave to go visit somewhere else, you realize. I go away and I think: 'What did I go for?' "

http://abcnews.go.com/US/wireStory/trade-winds-drop-hawaii-muggy-19310499#.Ua1tdkAp9XF

Readers, a must-read: The Antarctic Half of the Global Thermohaline Circulation Is Faltering

byFishOutofWaterFollowforOcean Advocates,  Daily Kos, April 10, 2013

The sudden cooling of Europe, triggered by collapse of the global thermohaline circulation in the north Atlantic and the slowing of the Gulf Stream has been popularized by the movies and the media. The southern half of the global thermohaline circulation is as important to global climate but has not been popularized. The global oceans' coldest water, Antarctic bottom water forms in several key spots around Antarctica. The water is so cold and dense that it spreads out along the bottom all of the major ocean basins except the north Atlantic and Arctic. Multiple recent reports provide strong evidence that the formation of Antarctic bottom water has slowed dramatically in response to massive subsurface melting of ice shelves and glaciers. The meltwater is freshening a layer of water found between depths of 50 and 150 meters. This lightened layer is impeding the formation of Antarctic bottom water, causing the Antarctic half of the global thermohaline circulation to falter.

Update from the comments

I have been asked what's going to happen in response to the faltering of the thermohaline circulation around Antarctica. This post is based on a synthesis of very recent research reports. The key report, that found the layer of fresh water between 50 and 150 meters deep, was just published. Deward Hastings explained, in a comment, how disruptive this lens of freshened water could be to the earth's climate system and our models of it:

it IS complicated, and confusing

That lens of (relatively) fresh water that is forming around Antarctica is challenging, and changing, almost everything in global circulation patterns.  It freezes sooner (and at a higher temperature).  That shields the water from the wind, and reduces wind-driven mixing.  It reduces, perhaps to the point of stopping altogether, the present global ocean circulation patterns.  That in turn will change global atmospheric weather.

Nobody knows exactly what comes next.  We've never seen it happen, and our models, not terribly accurate in describing the world we know, are completely untested in the coming world that we don't know.

Without a constant flow of cold water from the poles the Abyss will warm . . . and without cold slowly rising from the Abyss the mid-ocean and ocean surface will warm (already happening).  That will lead to more evaporation (driving a different haline circulation in the tropics) and stronger tropical winds driving different surface currents and greater mixing.

Pretty much everything changes as a result . . . pretty much everywhere.  After it's all over some places will have it better and some worse.  While it's changing everywhere will be worse, because there is no way to know what to expect (except that it won't be what you've prepared for).

The best guesses we can make now about the effects of this melt layer are based on paleoclimatology research. Possible effects, based on paleoclimatology studies, are presented in the last few paragraphs. The results of these new studies will be challenging climate modelers for many years.

Sea ice extent has been increasing around Antarctica. In September 2012, while Arctic sea ice was at record low levels, Antarctic sea ice extent hit a record high. Climate skeptics jumped on the Antarctic record as evidence of cooling, while sea ice researchers blamed it on the wind.

Since the start of the satellite record, total Antarctic sea ice has increased by about 1% per decade. Whether the small overall increase in sea ice extent is a sign of meaningful change in the Antarctic is uncertain because ice extents in the Southern Hemisphere vary considerably from year to year and from place to place around the continent. Considered individually, only the Ross Sea sector had a significant positive trend, while sea ice extent has actually decreased in the Bellingshausen and Amundsen Seas. In short, Antarctic sea ice shows a small positive trend, but large scale variations make the trend very noisy.

NSIDC scientist Ted Scambos said, "Antarctica's changes—in winter, in the sea ice—are due more to wind than to warmth, because the warming does not take much of the sea ice area above the freezing point during winter. Instead, the winds that blow around the continent, the "westerlies," have gotten stronger in response to a stubbornly cold continent, and the warming ocean and land to the north."

Several recent reports, however, paint a more complex and disturbing picture where the intensifying winds are speeding up below surface currents bringing more above freezing water in contact with deep ice around Antarctica. Twenty of the ice shelves and many of the glaciers that feed them are melting from below.

Researchers used 4.5 million measurements made by a laser instrument mounted on NASA’s ICESat satellite to map the changing thickness of almost all the floating ice shelves around Antarctica, revealing the pattern of ice-shelf melt across the continent. Of the 54 ice shelves mapped, 20 are being melted by warm ocean currents, most of which are in West Antarctica.

Figure 2 | Antarctic ice-shelf ice-thickness change rate DT/Dt, 2003–2008.

Seaward of the ice shelves, estimated average sea-floor potential temperatures (in uC) from the World Ocean Circulation Experiment Southern Ocean Atlas (pink to blue) are overlaid on continental-shelf bathymetry (in metres)30 (greyscale, landward of the continental-shelf break, CSB) Grey circles show relative ice losses for ice-sheet drainage basins (outlined in grey) that lost mass between 1992 and 2006 (after ref. 2).

The melting from below is creating a layer of relatively fresh water 50-150 meters below the surface around Antarctica. This layer of light fresh water is floating above a  salty layer below. When ice forms at the surface in the Antarctic winter, it creates cold dense salty water that tends to sink to the bottom, forming bottom water. However, this layer of light melt water is tending to block the water in the top 50 meters from sinking. The area of Antarctic sea ice has expanded because the layer of cold water has stayed on top and expanded outwards instead of sinking. Melting from below has created 2 stratified cold layers in the top 150 meters.

Note the bright pink area in the top 25 meters between 65° and 70° S. This top layer is becoming more saline. Brine is rejected from ice when sea ice forms. It isn't sinking because it is ponding above a freshening layer located at depths between 50 and 150 meters.

The freshened water column around Antarctica has become more stable between depths of 100 and 150 meters. This increasing stability is impeding the formation of Antarctic bottom water. Water that does sink is freshened through incorporation of glacial melt water.

Figure 3.  Austral winter half-year (April–September) zonal mean trends (1985–2010) of observed salinity, vertical density gradient and potential temperature, in the Southern Ocean. a, Salinity. b, Vertical density gradient. c, Potential temperature. Contours indicate the 1985–2010 mean state (psu; kg m^-4, °C). Colouring (bright or faint) indicates whether the trend is significant (yes or no) at p<0:1 65="" 70="" a="" according="" analysis="" and="" based="" between="" brine="" due="" en3="" font="" forms.="" from="" ice="" in="" increase="" is="" likely="" met="" most="" near-surface="" observations.="" observations="" ocean="" office="" on="" rejection="" salinity="" sea="" situ="" sub-surface="" t-test.="" taken="" the="" to="" two-sided="" were="" when="" which="">

Analysis of potential temperatures, which are temperatures adjusted for the effects of increasing pressure with depth, shows the surface water in the top hundred meters is cooling over a vast area from 40°-80° S, while the water in that vast area below 150 meters is warming.

These results show a trend towards reversal of vertical motions around Antarctica. Intermediate water is welling up around Antarctic melting ice from below, creating a freshened layer. Strengthening winds are blowing the cold surface water away from Antarctica. Bottom water formation, caused by the sinking of cold salty water formed by brine rejection, is declining.

The results of this study are confirmed by a detailed study of anthropogenic tracers in the Weddell sea.   Chlorofluorocarbon (CFC) observations showed increasing average ages of the deep water in the sea from 1984–2010. The average age increased because because bottom water formation, and outflow from the Weddell sea, declined.

...we find that all deep water masses in the Weddell Sea have been continually growing older and getting less ventilated during the last 27 years. The decline of the ventilation rate of Weddell Sea Bottom Water (WSBW) and Weddell Sea Deep Water (WSDW) along the Prime Meridian is in the order of 15–21%; the Warm Deep Water (WDW) ventilation rate declined much faster by 33%. About 88–94% of the age increase in WSBW near its source regions (1.8–2.4 years per year) is explained by the age increase of WDW (4.5 years per year). As a consequence of the aging, the anthropogenic Carbon increase in the deep and bottom water formed in the Weddell Sea slowed down by 14–21% over the period of observations.

The decline in Antarctic bottom water formation, combined with the southward expansion of warm subtropical water in the south Pacific and south Indian oceans has led to the rapid heating of intermediate and deep ocean water in the southern hemisphere.

Figure: Ocean Heat Content from 0 to 300 meters (grey), 700 m (blue), and total depth (violet) from ORAS4, as represented by its 5 ensemble members. The time series show monthly anomalies smoothed with a 12-month running mean, with respect to the 1958–1965 base period. Hatching extends over the range of the ensemble members and hence the spread gives a measure of the uncertainty as represented by ORAS4 (which does not cover all sources of uncertainty). The vertical colored bars indicate a two year interval following the volcanic eruptions with a 6 month lead (owing to the 12-month running mean), and the 1997–98 El Niño event again with 6 months on either side. On lower right, the linear slope for a set of global heating rates (W/m2) is given.

A new study of ocean warming has just been published in Geophysical Research Letters by Balmaseda, Trenberth, and Källén (2013).  There are several important conclusions which can be drawn from this paper.

• Completely contrary to the popular contrarian myth, global warming has accelerated, with more overall global warming in the past 15 years than the prior 15 years.  This is because about 90% of overall global warming goes into heating the oceans, and the oceans have been warming dramatically.

• As suspected, much of the 'missing heat' Kevin Trenberth previously talked about has been found in the deep oceans.  Consistent with the results of Nuccitelli et al. (2012), this study finds that 30% of the ocean warming over the past decade has occurred in the deeper oceans below 700 meters, which they note is unprecedented over at least the past half century.

As the earth has warmed in response to the effects of increasing levels of greenhouse gases the southern subtropical belt in the oceans and atmosphere has expanded, tightening the rings of winds and ocean currents around Antarctica. Enormous volumes of warm subtropical water have been added to the southern ocean at depths greater than 300 meters (greater than approximately 1000 feet).

Observed temperature trends in the Indian Ocean present complex patterns that cannot be explained by surface heating alone. The heat storage has apparently increased more in the southern part than in the northern part of the Indian Ocean (Levitus et al. 2005), although this result may be biased by the sparse data coverage, particularly in the south (Harrison & Carson 2007). The strongest warming is found near the subtropical front and extends as deep as 800 m; it is not directly linked to surface heating but rather due to a southward shift of the oceanic gyre circulation and associated thermal structure (Alory et al. 2007).

Another recent detailed study of the water properties of the southern ocean has independently determined that the southern branch of the global thermohaline circulation has slowed dramatically, contributing to a large uptake of heat by the deep southern ocean.

A statistically significant reduction in Antarctic Bottom Water (AABW) volume is quantified between the 1980s and 2000s within the Southern Ocean and along the bottom-most, southern branches of the Meridional Overturning Circulation (MOC). AABW has warmed globally during that time, contributing roughly 10% of the recent total ocean heat uptake. This warming implies a global-scale contraction of AABW.

Rates of change in AABW-related circulation are estimated in most of the world’s deep
ocean basins by finding average rates of volume loss or gain below cold, deep potential temperature (θ) surfaces using all available repeated hydrographic sections. The
Southern Ocean is losing water below θ = 0 °C at a rate of -8.2 (±2.6) × 106 m3 s-1.

The budget calculations and global contraction pattern are consistent with a global scale slowdown of the bottom, southern limb of the MOC.

The slowdown of the southern branch of the thermohaline circulation and the cooling of the surface waters close to Antarctica are enhancing the thermal gradient from the tropics to the pole, speeding up the winds in the Southern Hemisphere. These increases in wind speeds are likely increasing the flow of water from the Pacific to the Atlantic ocean, enhancing the northward flow of water, salt and heat from the south to the north Atlantic. Moreover, the southward movement of the subtropical front allows more flow of the Agulhas current around the south African capes from the Indian ocean to the south Atlantic.

Thus, increased melting of Arctic sea ice may be related to declines in Antarctic bottom water formation. Likewise, the cool Pacific, warm Atlantic pattern causing increased U.S. droughts and storminess in the north Atlantic may be tied to these changes in ocean circulation patterns. Paleoclimate studies have consistently shown oscillations between Antarctic and north Atlantic bottom water formation and between relative coolness around Antarctica and north Atlantic warmth.

The Arctic melt down that is far exceeding model predictions is connected to the slow down in Antarctic bottom water formation. Climate modelers will be challenged to model the connections and the details. The cooling waters around Antarctica, while apparently good news, are not. The rapid melting of the Arctic will be enhanced.

http://www.dailykos.com/story/2013/04/10/1200602/-The-Antarctic-Half-of-the-Global-Thermohaline-Circulation-Is-Faltering

Peter Sinclair: More from the "never before have we seen" scene -- 2 million cords of wood blown down in Wisconsin in July by a severe thunderstorm

from Peter Sinclair's Climate Denial Crock of the Week



Wisconsin Journal-Sentinel:

During nearly 50 years in the logging business, Max Ericson has seen trees – lots of them – blown down by the wind. What took place this summer in parts of Wisconsin’s North Woods, though, shocked him.

“I’ve never seen our forests so devastated as they are now,” said Ericson, owner of Ericson Logging in Minong. “It’s going to impact the timber industry for a least a couple generations.”

Across a swath of northwestern Wisconsin, an estimated 2 million cords of wood – $160 million worth by one estimate – are on the ground, blown down during a severe thunderstorm in July.

“We’ve had blow-downs before, just nothing this size,” said Henry Schienebeck, a third-generation logger and executive director of the Great Lakes Timber Professionals Association in Rhinelander. 

The amount of wood on the ground is about what the state’s loggers usually cut in a year, Schienebeck said.

“If a tornado hits, a tornado is a half-mile to a mile wide and two to three miles long,” Ericson said. “Then it lifts and it’s done.

“This went on for miles.”

The huge number of trees in northern Wisconsin makes the region vulnerable to severe thunderstorm winds, and timber blow-downs occur often in the area.

“But not to this degree,” said Rick Hluchan, a meteorologist at the National Weather Service forecast office in Duluth, Minn., which provides forecast coverage for northwestern Wisconsin. “It’s been awhile since we’ve had winds this bad.”

Weather Service meteorologists used a combination of radar images and damage surveys done from the air and on the ground to determine that wind gusts in the storm were greater than 100 mph.

[Readers, in 2005, a 3-day straight-line wind storm in the Amazon rainforest knocked down one-half a billion trees -- yup, you read correctly -- half a billion!]

http://climatecrocks.com/2011/09/05/more-from-the-never-before-have-we-seen-so-much-never-before-seen-scene/

"Evidence for strengthening of the tropical Pacific Ocean surface wind speed during 1979–2001," by Gen Li & Baohua Ren, Theoretical and Applied Climatology, DOI: 10.1007/s00704-011-0463-3

Theoretical and Applied Climatology, DOI: 10.1007/s00704-011-0463-3

Evidence for strengthening of the tropical Pacific Ocean surface wind speed during 1979–2001

Gen Li and Baohua Ren

Abstract

Using multiple surface wind speed (SWS) data sets and trend empirical orthogonal function analysis, we have explored the trend in SWS associated with the large-scale tropical Pacific atmospheric circulation for the period 1979–2001. The present research provides a robust evidence of strengthening of the tropical Pacific Ocean SWS during this period and the magnitude is generally in line with the finding of Wentz et al. The strengthening in SWS is closely associated with the so-called La Niña-like sea surface temperature (SST) trend pattern rather than the changes in the ENSO, ENSO Modoki, or PDO. The present results, together with those from some recent climate model simulations, suggest that global warming forcing may have caused an intensification of SWS in the tropical Pacific Ocean by inducing the La Niña-like SST trend pattern due to ocean dynamics. Meanwhile, the strengthening in the tropical Pacific Ocean surface trade winds may also feedback to enhance the La Niña-like SST trend pattern under the positive wind-upwelling dynamic feedback mechanism.

http://www.springerlink.com/content/03252652v0156240/

John Bruno, Skeptical Science: More wind, bigger waves, changing marine ecosystems (wave height, wind and "storminess" have been increasing at sea and along the coasts over the last several decades, at least in non-tropical regions)

More wind, bigger waves, changing marine ecosystems

by John Bruno, Skeptical Science, April 13, 2011

There has been lots of science and even more debate about how anthropogenic climate change will alter the frequency and intensity of cyclonic storms. But you don't hear much about how ocean wind and waves in general are changing and how this might impact marine ecosystems. Some new work is beginning to address this important topic.   

Lets start with the physical changes.

A paper recently published in ScienceExpress (Young et al. 2011) reports that ocean wind and waves increased substantially over the last two and a half decades. The authors used satellite altimeter measurements to test for trends in wave height from 1985 to 2008 and wind speed from 1991 to 2008. There was a positive trend in average wind speed and wave height, especially at higher latitudes (note the weaker trends in equatorial regions are not statistically significant): 

Figure. 1. Colour contour plots of mean trend (% per year). Wind speed is shown at the top and wave height at the bottom. From Young et al. (2011). 

The change in significant wave height is more pronounced when you look at the 99 percentile (the very biggest waves):

Fig 2. Colour contour plots of the 99th percentile trend (% per year). Wind speed is shown at the top and wave height at the bottom. From Figure 3 in Young et al. (2011). 

The Young et al. (2011) study mirrors a number of smaller scale studies based on more direct measurements or estimates of wave height trends. For example, Bromirski et al. (2003) used tide gage data from San Francisco to assess "meteorologically forced nontide residuals" (NTR), i.e., ‘‘storminess’’ from 1858 to 2000 along the central california coast. They found an increase of both degree and duration since 1950, consistent with other local and regional studies:

Figure 3. (b) Cumulative extreme NTR (exceeding the 98th percentile level of 11.5 cm for the entire hourly NTR time series) during winter months (Dec–Mar), with its 5-yr running mean (red line). Least squares trend estimates for the entire winter record and since 1948 (dashed lines). (c) Cumulative extreme winter hours (blue line) and events (red line). Dashed blue line indicates less than 90% of the hourly data were available, indicating that these periods may be underestimated. Times of strong, moderately strong, and very strong El Ninos (Quinn & Neal 1987) are indicated by green dots. From Figure 6 in Bromirski et al. (2003).

So, the picture emerging from the complete scientific body of evidence is that wave height, wind and "storminess" have been increasing at sea and along the coasts over the last several decades, at least in non-tropical regions. Although in some cases the record is fairly long (for direct physical measurements), it isn't really long enough to strongly attribute these changes to ACC. Furthermore, predicting changes in mid-latitude or "extra-tropical" storms (such as would have been measured in the Bromirski et al. study) is tricky. But regardless of the cause, why should we care? 

One reason is that by impacting habitat-forming "foundation" species, physical disturbance, especially by waves, plays a hugely important role in structuring coastal marine communities. For example, Byrnes et al. (2011) just published a paper that assessed how changes in the frequency of coastal storms would affect kelp forest communities off of the central California coast.

Giant kelp (Macrocystis pyrifera) are the "foundation species" of the California kelp forest communities. This species creates the biotic structure that thousands of other organisms depend on. Other examples of marine foundation species are corals, oysters, seagrasses and mangroves. Trees are a great terrestrial example. Due to their size, foundation species are often susceptible to physical disturbances, such as waves, that can dislodge and remove them. 

The authors used structural equation modeling (SEM) to statistically relate the impacts of storms on kelp forest community structure (i.e., in situ measurements of invertebrate species richness, kelp cover, fish abundance, etc., collected with SCUBA by the Santa Barbara coastal LTER). They also compared the predictions of the SEM (depicted in Figure 4) with the effects of experimental kelp removal (from 2,000 m² plots!) on kelp forest communities. The SEM and the experimental manipulation both found that decreased kelp cover leads to a decrease in the diversity and complexity of kelp forest food webs. 

If large storms remain at their current annual frequency (roughly one major kelp-removing storm every 3.5 years), periodic storms help maintain the complexity of kelp forest food webs. However, if large storms increase in annual frequency and begin to occur year after year, kelp forest food webs become less diverse and complex as species go locally extinct. The loss of complexity occurs primarily due to decreases in the diversity and complexity of higher trophic levels. Our findings demonstrate that shifts in climate-driven disturbances that affect foundation species are likely to have impacts that cascade through entire ecosystems. 

Figure 4. Path diagrams showing how algal, sessile invertebrate, and mobile species richness are associated with winter wave disturbance from storms and the abundance of kelp in the past year. Results are from a fitted structural equation model that adequately reproduces the observed covariance matrix. Solid paths are statistically different from 0 at P 0.05. Dashed paths are not. Path widths are proportional to standardized regression coefficients (shown next to each path). For clarity, some path coefficients are included in variable boxes rather than being drawn directly on the diagram. From Figure 4 in Byrnes et al. (2011). 

Countless studies have investigated/documented the impacts of storms and other physical disturbances on kelp and many other marine foundation species. The effects are not always negative; a moderate level of disturbance can help maintain the diversity of foundation species and of community inhabitants by preventing competitively dominant species from excluding their neighbors (via the monopolization of resources) and by maintaining a "patch mosaic" of microhabitats that promotes diversity. 

One novel aspect of this work, in addition to combining a field manipulation with a statistical data-crunching approach, was the focus on the entire food web rather than just one trophic level. Yet this study builds on decades of work indicating how sensitive coastal communities are to intense disturbances. If storms, wind and waves are causally linked with ACC and do continue to increase, I think there is little question that we will see direct effects on marine ecosystems and the services they provide to people.  

Beyond that, you could imagine a variety of other ecological and socioeconomic impacts of increased ocean wind, waves and storminess. For one, this could result in more ocean mixing and less stratification, thereby enhancing primary production (by supplying more nutrients for phytoplankton in generally nutrient-poor surface waters). You might also expect greater coastal erosion (which is compounded by sea level rise) and effects on shipping, ocean oil refineries, wind farms, etc.

Ocean winds are not exactly the first thing you think about when the topic of climate change comes up. Yet if they do continue to increase, the knock on effects will be large and costly. Yet another reason I like to call it "Ocean Change" rather than "Climate Change." 

http://www.skepticalscience.com/more_wind_and_waves.html