Global Warming 2020

Global Warming News : Robot Sub Searches For Signs Of Melting 60 Km Into An Antarctic Ice Shelf Cavity

ScienceDaily (Mar. 18, 2009) — Autosub, a robot submarine built and developed by the UK’s National Oceanography Centre, Southampton, has successfully completed a high-risk campaign of six missions travelling under an Antarctic glacier.

Autosub has been exploring Pine Island Glacier, a floating extension of the West Antarctic ice sheet, using sonar scanners to map the seabed and the underside of the ice as it juts into the sea. Scientists hope to learn why the glacier has been thinning and accelerating over recent decades. Pine Island Glacier is in the Amundsen Sea, part of the South Pacific bordering West Antarctica. Changes in its flow have been observed since the early 1970s, and together with neighbouring glaciers it is currently contributing about 0.25 mm a year to global sea level rise.

Steve McPhail led the Autosub team during the ten-day survey. He said: “Autosub is a completely autonomous robot: there are no connecting wires with the ship and no pilot. Autosub has to avoid collisions with the jagged ice overhead and the unknown seabed below, and return to a pre–defined rendezvous point, where we crane it back onboard the ship.

“Adding to the problems are the sub zero water temperatures and the crushing pressures at 1000 m depth. All systems on the vehicle must work perfectly while under the ice or it would be lost. There is no hope of rescue 60 km in, with 500 metres of ice overhead.”

An international team of scientists led by Dr Adrian Jenkins of British Antarctic Survey and Stan Jacobs of the Lamont-Doherty Earth Observatory, Columbia University, New York on the American ship, the RVIB Nathaniel B Palmer, has been using the robot sub to investigate the underside of the ice and measure changes in salinity and temperature of the surrounding water.

After a test mission in unusually ice-free seas in front of the face of the glacier, they started with three 60km forays under the floating glacier and extended the length of missions to 110km round-trip. In all, a distance over 500km beneath the ice was studied.

Using its sonar, the Autosub picks its way through the water, while creating a three-dimensional map that the scientists will use to determine where and how the warmth of the ocean waters drives melting of the glacier base.

“There is still much work to be done on the processing of the data”, said Adrian Jenkins, “but the picture we should get of the ocean beneath the glacier will be unprecedented in its extent and detail. It should help us answer critical questions about the role played by the ocean in driving the ongoing thinning of the glacier.”

The lead US researcher on the project, Stan Jacobs, is studying the Pine Island Glacier with International Polar Year (IPY) funding from the National Science Foundation (NSF). One of the IPY research goals is to better understand the dynamics of the world’s massive ice sheets, including the massive West Antarctic Ice Sheet. If this were to melt completely global sea levels would rise significantly. The most recent report of the Intergovernmental Panel on Climate Change (IPCC) noted that because so little is understood about ice-sheet behaviour it is difficult to predict how ice sheets will contribute to sea level rise in a warming world. The behaviour of ice sheets the IPCC report said is one of the major uncertainties in predicting exactly how the warming of the global will affect human populations.

Complementing the Autosub exploration, other work during the 53-day NB Palmer cruise included setting out 15 moored instrument arrays to record the variability in ocean properties and circulation over the next two years, extensive profiling of ‘warm’ and melt-laden seawater, sampling the perennial sea ice and swath-mapping deep, glacially-scoured troughs on the sea floor.

Autosub is an AUV – Automated Underwater Vehicle, designed, developed and built at the National Oceanography Centre, Southampton with funding from the Natural Environment Research Council. Autosub has a maximum range of 400km and is powered by 5,000 ordinary D-cell batteries. The batteries are packed in bundles in pressure-tested housings. Either end of the seven-metre sub there are free-flooding areas where the payload of instruments are installed. It carries a multibeam sonar system that builds up a 3D map of the ice above and the seabed below.. It also carries precision instruments for measuring the salinity, temperature, and oxygen concentrations in the sea water within the ice cavity, which are vital to understanding the flow of water within the ice cavity and the rate of melting. Autosub is 7m long and weighs 3.5 tonnes. Travelling at 6km hour it is capable of diving up to 1600 m deep, and can operate for 72 hours (400 km) between battery changes.

Source: Global Warming News, Climate Change, Greenhouse Effect information at sciencedaily.com

Global Warming News : Ozone: New Simulation Shows Consequences Of A World Without Earth’s Natural Sunscreen

The year is 2065. Nearly two-thirds of Earth’s ozone is gone — not just over the poles, but everywhere. The infamous ozone hole over Antarctica, first discovered in the 1980s, is a year-round fixture, with a twin over the North Pole. The ultraviolet (UV) radiation falling on mid-latitude cities like Washington, D.C., is strong enough to cause sunburn in just five minutes. DNA-mutating UV radiation is up 650 percent, with likely harmful effects on plants, animals and human skin cancer rates.

Such is the world we would have inherited if 193 nations had not agreed to ban ozone-depleting substances, according to atmospheric chemists at NASA’s Goddard Space Flight Center, Greenbelt, Md., Johns Hopkins University, Baltimore, and the Netherlands Environmental Assessment Agency, Bilthoven.

Led by Goddard scientist Paul Newman, the team simulated “what might have been” if chlorofluorocarbons (CFCs) and similar chemicals were not banned through the treaty known as the Montreal Protocol. The simulation used a comprehensive model that included atmospheric chemical effects, wind changes, and radiation changes. The analysis has been published online in the journal Atmospheric Chemistry and Physics.

“Ozone science and monitoring has improved over the past two decades, and we have moved to a phase where we need to be accountable,” said Newman, who is co-chair of the United Nations Environment Programme’s Scientific Assessment Panel to review the state of the ozone layer and the environmental impact of ozone regulation. “We are at the point where we have to ask: Were we right about ozone? Did the Montreal Protocol work? What kind of world was avoided by phasing out ozone-depleting substances?”

Ozone is Earth’s natural sunscreen, absorbing and blocking most of the incoming UV radiation from the sun and protecting life from DNA-damaging radiation. The gas is naturally created and replenished by a photochemical reaction in the upper atmosphere where UV rays break oxygen molecules (O2) into individual atoms that then recombine into three-part molecules (O3). As it is moved around the globe by upper level winds, ozone is slowly depleted by naturally occurring atmospheric gases. It is a system in natural balance.

But chlorofluorocarbons — invented in 1928 as refrigerants and as inert carriers for chemical sprays — upset that balance. Researchers discovered in the 1970s and 1980s that while CFCs are inert at Earth’s surface, they are quite reactive in the stratosphere (10 to 50 kilometers altitude, or 6 to 31 miles), where roughly 90 percent of the planet’s ozone accumulates. UV radiation causes CFCs and similar bromine compounds in the stratosphere to break up into elemental chlorine and bromine that readily destroy ozone molecules. Worst of all, such ozone depleting substances can reside for several decades in the stratosphere before breaking down.

In the 1980s, ozone-depleting substances opened a wintertime “hole” over Antarctica and opened the eyes of the world to the effects of human activity on the atmosphere. By 1987, the World Meteorological Organization and United Nations Environment Program had brought together scientists, diplomats, environmental advocates, governments, industry representatives, and non-governmental organizations to forge an agreement to phase out the chemicals. In January 1989, the Montreal Protocol went into force, the first-ever international agreement on regulation of chemical pollutants.

“The regulation of ozone depleting substances was based upon the evidence gathered by the science community and the consent of industry and government leaders,” Newman noted. “The regulation pre-supposed that a lack of action would lead to severe ozone depletion, with consequent severe increases of solar UV radiation levels at the Earth’s surface.”

In the new analysis, Newman and colleagues “set out to predict ozone losses as if nothing had been done to stop them.” Their “world avoided” simulation took months of computer time to process.

The team started with the Goddard Earth Observing System Chemistry-Climate Model (GEOS-CCM), an earth system model of atmospheric circulation that accounts for variations in solar energy, atmospheric chemical reactions, temperature variations and winds, and other elements of global climate change. For instance, the new model accounts for how changes in the stratosphere influence changes in the troposphere (the air masses near Earth’s surface). Ozone losses change the temperature in different parts of the atmosphere, and those changes promote or suppress chemical reactions.

The researchers then increased the emission of CFCs and similar compounds by 3 percent per year, a rate about half the growth rate for the early 1970s. Then they let the simulated world evolve from 1975 to 2065.

By the simulated year 2020, 17 percent of all ozone is depleted globally, as assessed by a drop in Dobson Units (DU), the unit of measurement used to quantify a given concentration of ozone. An ozone hole starts to form each year over the Arctic, which was once a place of prodigious ozone levels.

By 2040, global ozone concentrations fall below 220 DU, the same levels that currently comprise the “hole” over Antarctica. (In 1974, globally averaged ozone was 315 DU.) The UV index in mid-latitude cities reaches 15 around noon on a clear summer day (a UV index of 10 is considered extreme today.), giving a perceptible sunburn in about 10 minutes. Over Antarctica, the ozone hole becomes a year-round fixture.

In the 2050s, something strange happens in the modeled world: Ozone levels in the stratosphere over the tropics collapse to near zero in a process similar to the one that creates the Antarctic ozone hole.

By the end of the model run in 2065, global ozone drops to 110 DU, a 67 percent drop from the 1970s. Year-round polar values hover between 50 and 100 DU (down from 300-500 in 1960). The intensity of UV radiation at Earth’s surface doubles; at certain shorter wavelengths, intensity rises by as much as 10,000 times. Skin cancer-causing radiation soars.

“Our world avoided calculation goes a little beyond what I thought would happen,” said Goddard scientist and study co-author Richard Stolarski, who was among the pioneers of atmospheric ozone chemistry in the 1970s. “The quantities may not be absolutely correct, but the basic results clearly indicate what could have happened to the atmosphere. And models sometimes show you something you weren’t expecting, like the precipitous drop in the tropics.”

“We simulated a world avoided,” said Newman, “and it’s a world we should be glad we avoided.”

The real world of CFC regulation has been somewhat kinder. Production of ozone-depleting substances was mostly halted about 15 years ago, though their abundance is only beginning to decline because the chemicals can reside in the atmosphere for 50 to 100 years. The peak abundance of CFCs in the atmosphere occurred around 2000, and has decreased by roughly 4 percent to date.

Stratospheric ozone has been depleted by 5 to 6 percent at middle latitudes, but has somewhat rebounded in recent years. The largest recorded Antarctic ozone hole was recorded in 2006.

“I didn’t think that the Montreal Protocol would work as well as it has, but I was pretty naive about the politics,” Stolarski added. “The Montreal Protocol is a remarkable international agreement that should be studied by those involved with global warming and the attempts to reach international agreement on that topic.”

Source: Global Warming News, Greenhouse Effect, Climate Change information at sciencedaily.com

Global Warming News : Major Losses For Caribbean Reef Fish In Last 15 Years

ScienceDaily (Mar. 20, 2009) — By combining data from 48 studies of coral reefs from around the Caribbean, researchers have found that fish densities that have been stable for decades have given way to significant declines since 1995.

“We were most surprised to discover that this decrease is evident for both large-bodied species targeted by fisheries as well as small-bodied species that are not fished,” said Michelle Paddack of Simon Fraser University in Canada. “This suggests that overfishing is probably not the only cause.”

Rather, they suggest that the recent declines may be explained by drastic losses in coral cover and other changes in coral reef habitats that have occurred in the Caribbean over the past 30 years. Those changes are the result of many factors, including warming ocean temperatures, coral diseases, and a rise in sedimentation and pollution from coastal development. Overfishing has also led to declines of many fish species, and now seems to also be removing those that are important for keeping the reefs free of algae.

“All of these factors are stressing the reefs and making them less able to recover from disturbances such as hurricanes, which also seem to be occurring more frequently,” Paddack said.

Scientists had previously documented historical declines in the abundance of large Caribbean reef fishes that probably reflect centuries of overexploitation. However, effects of recent degradation of reef habitats on reef fish had not been established before now.

In the new study, the research team compiled data on reef fish densities from 48 studies representing 318 reefs across the Caribbean from 1955 to 2007. Their analysis found that overall reef fish density has been declining significantly for more than a decade, at rates that are consistent across all sub-regions of the Caribbean basin. Specifically, they show losses in fish density of 2.7 to 6 percent per year.

Paddack said her study, which involved a very large team of scientists from around the globe, should serve as a call to action.

“If we want to have coral reefs in our future, we must ensure that we reduce damage to these ecosystems,” she said. “On a personal level, this may mean not buying wild-caught aquarium fish and corals, not eating reef fish species that are declining, taking care not to anchor on reefs, and reducing our carbon emissions to help control climate change. But importantly, we need to let lawmakers and resource managers know that we care about these ecosystems and we need to push for changes in how they are managed.”

The study appears online on March 19th in Current Biology, a Cell Press publication.

Source: Global Warming, Climate Change, Greenhouse Effect information at sciencedaily.com