Ancient Ocean on Mars

The European Space Agency's Mars Express has returned compelling evidence that the red planet once hosted an enormous ocean in its northern plains. The probe's radar detected sediments reminiscent of an ocean floor, within areas that have been suspected to be shorelines.

Jérémie Mouginot from the Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), the University of California in Irvine, and colleagues analysed more than two years of data from Mars Express' Marsis (Mars Advanced Radar for Subsurface and Ionosphere Sounding) radar.

The radar can penetrate deep into the planet's ground, and reveal the first 60 to 80 metres of the planet's subsurface. At these depths, the team found that the northern plains are covered in low-density material.

"We interpret these as sedimentary deposits, maybe ice-rich," says Mouginot. "It is a strong new indication that there was once an ocean here."

The notion of water on Mars and big ideas of oceans in the planet's ancient history are nothing new. But this research provides some of the best evidence yet that there were once large bodies of liquid water on Mars, and it is further proof that water played a role in martian geological history.

"Previous Mars Express results about water on Mars came from the study of images and mineralogical data, as well as atmospheric measurements," said Olivier Witasse, a Mars Express project scientist at the European Space Agency.

This data supports a proposed theory where Mars has had two oceans in its lifetime. One four billion years ago when warmer conditions prevailed, and another three billion years go when subsurface ice melted following a large impact.

This later ocean would have been very temporary. It would only have lasted about a million years or less, Mouginot estimates, and then the water would have either frozen back in place or turned into vapour and lifted gradually into the planet's weak atmosphere.

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"I don't think it could have stayed as an ocean long enough for life to form," Mouginot says.

A recent study from Imperial College London doesn't offer much good news for martian life-hunters, either. Soil analysis at the site of Nasa's Phoenix mission suggest that surface of Mars has dry as a bone for hundreds of millions of years, making it too hostile for any life to survive on the planet's surface

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Posted in: mars,ocean,space

Plan to Save the Oceans

The world has made lacklustre progress in meeting most of the commitments it made 20 years ago to safeguard the oceans, says a report. At the 1992 Earth Summit in Rio de Janeiro, Brazil, agreements were made on issues such as sustainable fisheries and aquaculture, capacity building, and biodiversity; later, the Johannesburg Summit in 2002 in South Africa set targets and timetables to achieve those goals.

But a report entitled Oceans at Rio+20 has rated both the effort and the achievements to date in protecting oceans and meeting these commitments as 'low to medium'. Meanwhile a separate, UN report says that at least 40 per cent of the global oceans are 'heavily affected' by human activities and that 60 per cent of the world's major marine ecosystems have been degraded or are being used unsustainably. It makes ten proposals for improvement. Oceans at Rio+20 calls for a string of actions, including more scientific research and capacity building in small island states, to try to tackle the problems. Read more Environment Clean Generations

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Posted in: africa,earth,ecosystems,environment clean generations,ocean

Tsunami Facts

What is a tsunami?

A tsunami is a series of ocean waves with very long wavelengths (typically hundreds of kilometres) caused by large-scale disturbances of the ocean, such as:

• earthquakes
• landslide
• volcanic eruptions
• explosions
• meteorites

These disturbances can either be from below (e.g. underwater earthquakes with large vertical displacements, submarine landslides) or from above (e.g. meteorite impacts).

Tsunami is a Japanese word with the English translation: "harbour wave". In the past, tsunamis have been referred to as "tidal waves" or "seismic sea waves".

 The term "tidal wave" is misleading; even though a tsunami's impact upon a coastline is dependent upon the tidal level at the time a tsunami strikes, tsunamis are unrelated to the tides. (Tides result from the gravitational influences of the moon, sun, and planets.) The term "seismic sea wave" is also misleading. "Seismic" implies an earthquake-related generation mechanism, but a tsunami can also be caused by a non-seismic event, such as a landslide or meteorite impact.

Tsunamis are also often confused with storm surges, even though they are quite different phenomena. A storm surge is a rapid rise in coastal sea-level caused by a significant meteorological event - these are often associated with tropical cyclones.

The physics of a tsunami

Tsunamis can have wavelengths ranging from 10 to 500 km and wave periods of up to an hour. As a result of their long wavelengths, tsunamis act as shallow-water waves. A wave becomes a shallow-water wave when the wavelength is very large compared to the water depth. Shallow-water waves move at a speed, c, that is dependent upon the water depth and is given by the formula:

where g is the acceleration due to gravity (= 9.8 m/s²) and H is the depth of water.

In the deep ocean, the typical water depth is around 4000 m, so a tsunami will therefore travel at around 200 m/s, or more than 700 km/h.

For tsunamis that are generated by underwater earthquakes, the amplitude (i.e wave height) of the tsunami is determined by the amount by which the sea-floor is displaced. Similarly, the wavelength and period of the tsunami are determined by the size and shape of the underwater disturbance.

As well as travelling at high speeds, tsunamis can also travel large distances with limited energy losses. As the tsunami propagates across the ocean, the wave crests can undergo refraction (bending), which is caused by segments of the wave moving at different speeds as the water depth along the wave crest varies.

What happens to a tsunami as it approaches land?

As a tsunami leaves the deep water of the open-ocean and travels into the shallower water near the coast, it transforms. If you read the "The physics of a tsunami" section, you will know that a tsunami travels at a speed that is related to the water depth - hence, as the water depth decreases, the tsunami slows. The tsunami's energy flux, which is dependent on both its wave speed and wave height, remains nearly constant.

Consequently, as the tsunami's speed diminishes, its height grows. This is called shoaling. Because of this shoaling effect, a tsunami that is unnoticeable at sea, may grow to be several metres or more in height near the coast.

The increase of the tsunami's waveheight as it enters shallow water is given by:

where h_s and h_d are waveheights in shallow and deep water and H_s and H_d are the depths of the shallow and deep water. So a tsunami with a height of 1 m in the open ocean where the water depth is 4000m would have a waveheight of 4 to 5 m in water of depth 10 m.

Just like other water waves, tsunamis begin to lose energy as they rush onshore - part of the wave energy is reflected offshore, while the shoreward-propagating wave energy is dissipated through bottom friction and turbulence. Despite these losses, tsunamis still reach the coast with tremendous amounts of energy. Depending on whether the first part of the tsunami to reach the shore is a crest or a trough, it may appear as a rapidly rising or falling tide.

Local bathymetry may also cause the tsunami to appear as a series of breaking waves.

Tsunamis have great erosion potential, stripping beaches of sand that may have taken years to accumulate and undermining trees and other coastal vegetation. Capable of inundating, or flooding, hundreds of metres inland past the typical high-water level, the fast-moving water associated with the inundating tsunami can crush homes and other coastal structures. Tsunamis may reach a maximum vertical height onshore above sea level, often called a run-up height, of tens of metres.

How are tsunamis measured or observed?

In the deep ocean, a tsunami has a small amplitude (less than 1 metre) but very long wavelength (hundreds of kilometres). This means that the slope, or steepness of the wave is very small, so it is practically undetectable to the human eye. However, there are ocean observing instruments that are able to detect tsunamis.

Tide Gauges

Tide gauges measure the height of the sea-surface and are primarily used for measuring tide levels. Most of the tide gauges operated by the Bureau of Meteorology's National Tidal Centre are SEAFRAME stations (Sea Level Fine Resolution Acoustic Measuring Equipment). These consist of an acoustic sensor connected to a vertical tube open at the lower end which is in the water.

The acoustic sensor emits a sound pulse which travels from the top of the tube down to the water surface, and is then reflected back up the tube. The distance to the water level can then be calculated using the travel time of the pulse. This system filters out small-scale effects like wind-waves and has the capacity to measure sea-level changes within 1mm accuracy.

The tide gauge at Cocos Island observed the tsunami on December 26th 2004 as it passed by the island, as shown in these observations made during December.

Satellites

Satellite altimeters measure the height of the ocean surface directly by the use of electro-magnetic pulses. These are sent down to the ocean surface from the satellite and the height of the ocean surface can be determined by knowing the speed of the pulse, the location of the satellite and measuring the time that the pulse takes to return to the satellite.

One problem with this kind of satellite data is that it can be very sparse - some satellites only pass over a particular location about once a month, so you would be lucky to spot a tsunami since they travel so quickly. However, during the Indian Ocean tsunami of December 26th 2004, the Jason satellite altimeter happened to be in the right place at the right time.

The picture below shows the height of the sea surface (in blue) measured by the Jason satellite two hours after the initial earthquake hit the region southeast of Sumatra (shown in red) on December 26, 2004. The data were taken by a radar altimeter on board the satellite along a track traversing the Indian Ocean when the tsunami waves had just filled the entire Bay of Bengal. The data shown are the differences in sea surface height from previous observations made along the same track 20-30 days before the earthquake, showing the signals of the tsunami.

Picture courtesy of NASA/JPL-Caltech

The DART System

In 1995 the National Oceanic and Atmospheric Administration (NOAA) began developing the Deep-ocean Assessment and Reporting of Tsunamis (DART) system. An array of stations is currently deployed in the Pacific Ocean. These stations give detailed information about tsunamis while they are still far off shore. Each station consists of a sea-bed bottom pressure recorder which detects the passage of a tsunami. (The pressure of the water column is related to the height of the sea-surface) .

The data is then transmitted to a surface buoy via sonar. The surface buoy then radios the information to the Pacific Tsunami Warning Center (PTWC) via satellite. The bottom pressure recorder lasts for two years while the surface buoy is replaced every year. The system has considerably improved the forecasting and warning of tsunamis in the Pacific.

The Indian Ocean tsunami of 26th December 2004

An undersea earthquake in the Indian Ocean on 26th December 2004 produced a tsunami that caused one of the biggest natural disasters in modern history. Over 200,000 people are known to have lost their lives.

The waves devastated the shores of parts of Indonesia, Sri Lanka, India, Thailand and other countries with waves reported up to 15 m high, reaching as far as Somalia on the east coast of Africa, 4500 km west of the epicentre. Refraction and diffraction of the waves meant that the impact of the tsunami was noticed around the world and sea-level monitoring stations in places such as Brazil and Queensland also felt the effect of the tsunami.

This animation (10.4Mb) was produced by scientists in the Bureau of Meteorology's National Tidal Centre. A numerical model was used to replicate the generation and propagation of the tsunami and it shows how the waves propagated around the world's ocean basins.

The earthquake took place at about 1am UTC (8am local time) in the Indian Ocean off the western coast of northern Sumatra. With a magnitude of 9.0 on the Richter scale, it was the largest since the 1964 earthquake off Alaska and equal fourth largest since 1900, when accurate global seismographic record-keeping began.

The epicentre of the earthquake was located about 250 km south-southeast of the Indonesian city of Banda Aceh. It was a rare megathrust earthquake and occurred on the interface of the India and Burma tectonic plates.

This was caused by the release of stresses that develop as the India plate subducts beneath the overriding Burma plate. A megathrust earthquake is where one tectonic plate slips beneath another, causing vertical motion of the plates. This large vertical displacement of the sea-floor generated the devastating tsunami, which caused damage over such a large area around the Indian Ocean.

The earthquake was also unusually large in geographical extent. An estimated 1200 km of faultline slipped about 15 m along the subduction zone over a period of several minutes. Because the 1,200 km of faultline affected by the quake was in a nearly north-south orientation, the greatest strength of the waves was in an east-west direction. Bangladesh, which lies at the northern end of the Bay of Bengal, had very few casualties despite being a populous low-lying country.

Due to the distances involved, the tsunami took anywhere from fifteen minutes to seven hours (for Somalia) to reach the various coastlines. (See this travel time map). The northern regions of the Indonesian island of Sumatra were hit very quickly, while Sri Lanka and the east coast of India were hit roughly two hours later. Thailand was also struck about two hours later, despite being closer to the epicentre, because the tsunami travelled more slowly in the shallow Andaman Sea off its western coast.

On its arrival on shore, the height of the tsunami varied greatly, depending on its distance and direction from the epicentre and other factors such as the local bathymetry. Reports have the height ranging form 2-3 m at the African coast (Kenya) up to 10-15 m at Sumatra, the region closest to the epicentre.

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Posted in: caltech,earth,earthquake,environment clean generations,ocean,tsunami,tsunami facts,water,wave

First Comet Found with Ocean-Like Water

New evidence supports the theory that comets delivered a significant portion of Earth's oceans, which scientists believe formed about 8 million years after the planet itself.

Astronomers have found a new cosmic source for the same kind of water that appeared on Earth billions of years ago and created the oceans. The findings may help explain how Earth's surface ended up covered in water. 

New measurements from the Herschel Space Observatory show that comet Hartley 2, which comes from the distant Kuiper Belt, contains water with the same chemical signature as Earth's oceans. This remote region of the solar system, some 30 to 50 times as far away as the distance between Earth and the sun, is home to icy, rocky bodies including Pluto, other dwarf planets and innumerable comets. 

"Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early Earth," said Dariusz Lis, senior research associate in physics at the California Institute of Technology in Pasadena and co-author of a new paper in the journal Nature, published online today, Oct. 5. "This finding substantially expands the reservoir of Earth ocean-like water in the solar system to now include icy bodies originating in the Kuiper Belt."

Scientists theorize Earth started out hot and dry, so that water critical for life must have been delivered millions of years later by asteroid and comet impacts. Until now, none of the comets previously studied contained water like Earth's. However, Herschel's observations of Hartley 2, the first in-depth look at water in a comet from the Kuiper Belt, paint a different picture. 

This illustration shows the locations of various classes of comets in the Solar System, relative to the orbits of the planets. The left panel shows the inner Solar System along with the orbit of Jupiter-Family comet Hartley 2. The central panel shows a larger portion of the Solar System beyond the orbit of Jupiter, as well as the Kuiper Belt, one of the two main reservoirs of comets in the solar system. The right panel shows the Oort Cloud, the other main reservoir of comets located well beyond the outer solar system. Credit: ESA/AOES Medialab 

Herschel peered into the comet's coma, or thin, gaseous atmosphere. The coma develops as frozen materials inside a comet vaporize while on approach to the sun. This glowing envelope surrounds the comet's "icy dirtball"-like core and streams behind the object in a characteristic tail. Herschel detected the signature of vaporized water in this coma and, to the surprise of the scientists, Hartley 2 possessed half as much "heavy water" as other comets analyzed to date. In heavy water, one of the two normal hydrogen atoms has been replaced by the heavy hydrogen isotope known as deuterium. The ratio between heavy water and light, or regular, water in Hartley 2 is the same as the water on Earth's surface. The amount of heavy water in a comet is related to the environment where the comet formed.

By tracking the path of Hartley 2 as it swoops into Earth's neighborhood in the inner solar system every six-and-a-`half years, astronomers know that it comes from the Kuiper Belt. The five comets besides Hartley 2 whose heavy-water-to-regular-water ratios have been obtained all come from an even more distant region in the solar system called the Oort Cloud. This swarm of bodies, 10,000 times farther afield than the Kuiper Belt, is the wellspring for most documented comets.  

Using the Herschel Space Observatory, astronomers have discovered that comet Hartley 2 possesses a ratio of "heavy water" to light, or normal, water that matches what's found in Earth's oceans. Image credit: NASA/JPL-Caltech

Given the higher ratios of heavy water seen in Oort Cloud comets compared to Earth's oceans, astronomers had concluded that the contribution by comets to Earth's total water volume stood at approximately 10 percent. Asteroids, which are found mostly in a band between Mars and Jupiter but occasionally stray into Earth's vicinity, looked like the major depositors. The new results, however, point to Kuiper Belt comets having performed a previously underappreciated service in bearing water to Earth. 

How these objects ever came to possess the telltale oceanic water is puzzling. Astronomers had expected Kuiper Belt comets to have even more heavy water than Oort Cloud comets because the latter are thought to have formed closer to the sun than those in the Kuiper Belt. Therefore, Oort Cloud bodies should have had less frozen heavy water locked in them prior to their ejection to the fringes as the solar system evolved.

"Our study indicates that our understanding of the distribution of the lightest elements and their isotopes, as well as the dynamics of the early solar system, is incomplete," said co-author Geoffrey Blake, professor of planetary science and chemistry at Caltech. "In the early solar system, comets and asteroids must have been moving all over the place, and it appears that some of them crash-landed on our planet and made our oceans."

 by "environment clean generations"

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Posted in: comet,ocean,Oort cloud,space,sun

How Low Can Life Go?

• The byproducts of rock-eating microbes have been found pouring out of a hole in the sea floor
• The unidentified microbe that live in the rocks could be widespread in the oceans.
• How much these subterranean, submarine microbes contribute to the global carbon budget is still unknown. 

There is a thriving realm of mysterious microbes of potential importance to the global carbon budget hidden beneath the sea floor near where the Earth's crust is being pulled apart, according to new evidence from deep-sea explorers.

In the frigid depths of the Juan de Fuca tectonic plate off the coast of the Pacific Northwest, warm water moving through the sea floor near the plate edges has been found loaded with dissolved organic matter with a telltale carbon signature that could have only come from microbes in the rocks.

The warm waters were captured as they poured from an old bore-hole and into the freezing waters, and were double-checked for contamination by comparing them to waters obtained from sterile, specially made samplers that were driven into the sea floor.

"It looks like a massive fire hose," said Matthew McCarthy of the University of California at Santa Cruz, referring to the pressurized, 80-degree Fahrenheit groundwater spewing from the old hole in the sea bottom. McCarthy is one of the authors of a paper about the secrets of that groundwater, being published in the January issue of the journal Nature Geoscience.

The goal of the work, McCarthy explained, was to irrefutably show that the waters from the hole were representative of what lies much deeper, rather than just contaminated by the human activities that drilled the hole.

"If there was ever any contamination, it was long gone," McCarthy said of he and his colleagues conclusions.

Indeed, now the researchers have evidence of what is probably a vast volume of lava rocks going down to unknown depths which are loaded with microbes. Those microbes make their living by using reactions on the surface of basalt rocks that have been erupted over the millennia on the seafloor.

The microbes belong to a group called called chemo-litho-autotrophs that live without any connection to the more common Earth ecosystems which are dependent on sunlight.

Such microbial ecosystems could be widespread in the oceans. If they are, they could play an important and unknown role in the cycling of carbon in the deep seas, said McCarthy.

"If these kinds of reactions are happening at Juan de Fuca, chances they are happening at other places are very high," agreed researcher Katrina Edwards of the University of Southern California. "The potential is pretty widespread."

So far the actual identities of the microbes is unknown, said McCarthy. "Our data don't tell you about the microbes that made it," he said.

Although some microbes have been found, it's not clear they are the source of the dissolved organic carbon in the water.

As for how it fits into the Earth's carbon budget, that's still unknown, says Edwards. She likes to visualize the carbon budget as being made of many carbon cycles that are like gears of different sizes and turning at different speeds.

 

"This one is moving slowly and we don't know how big it is," she said of the deep sea, chemo-litho-autotroph carbon cycle.

One thing that will help to begin defining its size will be more work on other seafloor spreading centers. Edwards and her team are planning just that, with a new observatory slated to be installed on the Mid-Atlantic Ridge in late 2011.

by "environment clean generations"

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Posted in: chemo-litho-autotrophs,dead sea,life,microbes,ocean,water

Dust Level High

There is twice as much desert dust in the atmosphere now than a century ago. Particles of dust in the air affect climate and ocean ecology. A better understanding of changing dust levels should help scientists make more accurate climate predictions. 

The amount of dust in the atmosphere has doubled over most of the planet since the last century, finds a new study.

As wind blows through the world's deserts, it whisks dust up into the air and down into the oceans and can significantly affect climate and the environment in all sorts of ways. 

Understanding the changing patterns of dirt particles in the atmosphere could help scientists improve the accuracy of climate predictions. Tracing swirls of dust to their roots could also lead to better land management practices that might mitigate the flow of dust from Earth to sky and sea.

But first, researchers need to figure out why dust levels are rising in the first place. 

"We don't know," said Natalie Mahowald, an atmospheric scientist at Cornell University in Ithaca, N.Y. "It's probably a combination of agriculture and pasture-usage as well as climate change because a lot of regions are getting drier, and that would increase desert dust."

"We put big uncertainty bars on everything," she added. "We need more data."

Climate researchers have spent a lot of time worrying about the effects of particles that human actions release into the atmosphere. Known as anthropomorphic aerosols, these include sulfates from coal-fired power plants and nitrogen oxides from automobile exhaust. 

Mahowald is more interested in desert dust, which can also affect climate in a number of ways. For one thing, particles of soil that are suspended in the air alter the way the atmosphere absorbs and reflects energy from the sun. Dust also changes the properties of clouds, which play a big role in climate patterns. Overall, rising levels of dust tend to cool the atmosphere down.

Dust also affects the chemistry of the oceans. That's because dust contains iron, which boosts growth of plankton, allowing the oceans to pull a little more carbon out of the air. 

To piece together a history of Earth's blowing dust, Mahowald and colleagues compiled a wealth of published data, which included analyses of layered ice cores and sediment samples taken from more than a dozen sites around the world. Most of these cores held specks of dust that had blown in from somewhere else. 

In ice cores from Antarctica, for example, scientists identified soil from South America. Lake sediments in Colorado's San Juan Mountains contained soil particles originally from the Mojave Desert in California, 1,000 kilometers (600 miles) away. Each layer was dated so the researchers could tell how the levels of blowing dust changed over time. 

For the 100-year span from about 1900 to 2000, levels of dust fluctuated quite a bit and patterns differed in different regions, the researchers reported in the journal Atmospheric Chemistry and Physics. Overall, though, levels of dust around the globe doubled everywhere except above North America, where levels dropped a little bit. 

By comparing dusty periods with periods that weren't so dusty, the researchers were able to show that dusty skies lead to lower temperatures -- masking some of the warming effects of greenhouse gasses. As dust accumulates in the air, it also affects clouds enough to move storms away from desert areas, possibly propelling droughts that, in turn, lead to even more dust. 

In the oceans, dust boosts productivity and sucks up more carbon from the air, which can also cool the climate. But that may be offset by erosion and the loss of plant cover on land.

In satellite images of Earth, you can see three obvious colors, said Joseph Prospero, an atmospheric scientist at the University of Miami in Florida: The blue of oceans, the white of clouds and the brown of massive desert dust storms. 

Those images, Prospero said, clearly show that dust is a major player that needs to play a more significant role in climate models as one of a multitude of fluctuating and complicated factors. 

"When climate changes, you get a tremendous amount of variability in dust output," he said. "There is a strong possible loop where the climate becomes drier and windier causing more dust, and more dust affects radiation, so it feeds back on climate."

"There is a lot of uncertainty about how that works," he added. "That's why we focus on dust."

 by "environment clean generations"

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Posted in: air,desert,drought,dust,earth,Mahowald,ocean,particles,satellite

Ocenas Could Rise 2 Meters by 2100

 A warmer Arctic will mean rising sea levels of between 3.0 to 5.3 feet by 2100. Even the low end of this range would have devastating consequences for coastal cities and densely-populated, low-lying deltas.
Higher seas would literally cover some small island nations, ruin vast expanses of land and boost the intensity of deadly storms. 

            Warming in the Arctic occurring at twice the global average is on track to lift sea levels by up to 5.3 feet (1.6 meters) by 2100, a far steeper jump than predicted a few years ago, a consortium of scientists reported Tuesday.

            Melting ice and snow has accounted for 40 percent of recent increases in ocean levels and are likely to play an even larger role in future, according to the Oslo-based Arctic Monitoring and Assessment Project (AMAP).

            "Global sea level is projected to rise 3.0 to 5.3 feet (0.9 to 1.6 meters ) by 2100, and the loss from Arctic glaciers, ice caps and the Greenland Ice Sheet will make a substantial contribution to this," AMAP said in a report.

             Even the low end of this range would have devastating consequences for coastal cities and densely-populated, low-lying deltas in Bangladesh, Vietnam, China and many other countries, scientists have warned.

Higher seas would literally cover some small island nations, ruin vast expanses of land used to grow food, and boost the intensity of deadly hurricanes and other extreme weather events.

             In early 2007, the UN's Intergovernmental Panel on Climate Change (IPCC) said the world's oceans would creep up 18 to 59 centimeters (7 to 23 inches) by century's end.

But the panel's landmark report did not include the potential impact of melting ice, especially from the massive Greenland Ice Sheet, which alone holds enough frozen water to push up sea levels by at least five metres (16 feet).

            The new study shows that the past six years have been the warmest period ever recorded for the Arctic, and that summer temperatures were higher in the past few decades than at any time in the last 2,000 years.

           "The changes that are emerging in the Arctic are very strong, dramatic even," said Mark Serreze, director of the U.S. National Snow and Ice Data Center in Boulder, Colorado, and a contributor to the report.

             "But this is not entirely a surprise.

We have known for decades that, as climate change takes hold, it is the Arctic where you are going to see it first, and where it is going to be pronounced," he said by phone.

The report forecasts that the Arctic Ocean, within three or four decades, will likely become nearly ice free during the summer months.

              Three of the last four years have seen polar sea ice shrinking to its smallest area since satellite images became available, with a record low in 2007 of 4.13 million square kilometres (1.56 million square miles).

The report also highlights new evidence that changes in Arctic snow and ice conditions may actually be accelerating the warming process.

              "The fact that highly reflective snow and ice surfaces are diminishing means that darker land or ocean surfaces are absorbing more of the sun's energy, warming the Earth's surface and the air above," the researchers said.

              Rather than being bounced back into space by white surfaces, in other words, the sun's heat is trapped inside the atmosphere. The study identified eight of these so-called natural "feedback mechanisms" that have become both symptom and cause of climate change.

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Posted in: ocean,rise,temperature

Plastic Ocean

 

The most plastic at the surface of the western Atlantic centers off of Atlanta and stretches from Virginia to Cuba. The number of plastic pieces in that area has not changed in more than 20 years. It's a mystery where all our extra plastic is going, raising concerns for the environment and health. 

             The concentration of plastic bits floating on the surface of the Atlantic has held steady for more than 20 years, found a new study, even as people use and discard ever-increasing amounts of plastic.

With growing concerns about plastic in the environment, the surprising new finding raises questions about where all that stuff is ending up. 

            “We know that the global production of plastic has increased at a very high rate, and we know that plastics in the waste stream have also increased over time,” said Kara Lavender, an oceanographer at the Sea Education Association in Woods Hole, Mass. 

             “We infer that plastic in the ocean is most likely increasing,” she added. “So how come we’re not seeing increasing amounts of plastic in areas where the plastic is accumulating? That’s the mystery.”

Although massive garbage patches have drawn lots of attention lately to plastic in the oceans, few studies have looked at exactly how much is out there and where it’s going. Lavender realized she had the perfect data set just waiting to be analyzed.

              For nearly 40 years, the Sea Education Association (SEA) has been taking college students on educational semesters at sea. As part of the program, students have sampled surface waters by dragging a one meter-wide mesh net behind their live-aboard ship.

             The net, which catches anything bigger than one-third of a millimeter wide, has been dragged throughout the western Atlantic, from Newfoundland to the southern Caribbean. When it comes back onboard after sampling a nautical mile, SEA students use tweezers to pick through the plankton, jellies, tiny fish and occasional tar balls. 

             Within the gooey brown mush, they count and record every single piece of plastic. For the new study, Lavender and colleagues compiled 22 years' worth of those numbers. 

            One of the work’s major findings, published this week in the journal Science, was to show for the first time that the highest concentration of plastic in the western Atlantic is centered in a region offshore at about the latitude of Atlanta. The bulk of the waste stretches from Virginia to Cuba.

            To the surprise of Lavender and her colleagues, the study also showed no overall change in the amount of plastic snared from 1986 to 2008, even though they assume more plastic is making its way into the ocean.

            “I expected to see the line go right up,” she said. “It took us a good year to decide, no, we have not seen an increase, no matter how you slice it.”

Where is all the missing plastic? 

          One theory is that it’s breaking down into really tiny pieces that the nets can’t catch. Another possibility is that it’s sinking below the surface, either because tiny organisms are growing on it and weighing it down, or because birds, fish and other animals are eating it and excreting it. 

             Or maybe the plastic is getting incorporated into tissues of animals that mistake it for food.

Each scenario offers consequences to be concerned about. When animals eat plastic, they can damage their insides, become malnourished, or consume chemical pollutants, which tend to stick to plastic like a sponge. These pollutants may then work their way through the food chain all the way up to people. 

              When drifting plastic becomes homes for colonizing organisms like barnacles, they can become vehicles for invasive species, added University of Hawaii oceanographer David Karl, whose recent work has shown that plastic is like the bottom of a boat -- an easy target for ocean slime.

               Degenerating plastics also release chemicals with unknown consequences.

“Plastic is a chemical compound that does not naturally occur in nature,” Lavender said. “We could be altering the chemistry of the ocean.”

              Of course, the findings could also be good news, Karl said. Maybe the plastic is simply washing back up onto shore. Or maybe people are being more careful with trash disposal and recycling, and less plastic is getting into the ocean, though he admitted that was a hard scenario to believe.

             “This may be another unplanned experiment of humankind,” Karl said. “Since the 1950s, we’ve been putting plastic into the ocean. Now we’re trying to figure out where it’s gone and what it’s done and what the impact is ecologically.”

  

   by "environment clean generations"

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Ocenas Getting Warmer

     The global marine environment is getting warmer, more acidic, and low on oxygen and all are consequences of human activity. Ocean health has declined further and faster than dire forecasts only a few years ago. 

              Pollution and global warming are pushing the world's oceans to the brink of a mass extinction of marine life unseen for tens of millions of years, a consortium of scientists warned Monday. 

  

              Dying coral reefs, biodiversity ravaged by invasive species, expanding open-water "dead zones," toxic algae blooms, the massive depletion of big fish stocks -- all are accelerating, they said in a report compiled during an April meeting in Oxford of 27 of the world's top ocean experts. 

              Sponsored by the International Programme on the State of the Ocean (IPSO), the review of recent science found that ocean health has declined further and faster than dire forecasts only a few years ago. 

             These symptoms, moreover, could be the harbinger of wider disruptions in the interlocking web of biological and chemical interactions that scientists now call the Earth system. All five mass extinctions of life on the planet, reaching back more than 500 million years, were preceded by many of the same conditions now afflicted the ocean environment, they said. 

            "The results are shocking," said Alex Rogers, an Oxford professor who heads IPSO and co-authored the report. "We are looking at consequences for humankind that will impact in our lifetime." 

          Three main drivers are sickening the global marine environment, and all are a direct consequence of human activity: global warming, acidification and a dwindling oxygen level, a condition known as hypoxia. 

          Up to now, these and other impacts have been studied mainly in isolation. Only recently have scientists began to understand how these forces interact. 

         "We have underestimated the overall risks, and that the whole of marine degradation is greater than the sum of its parts," Rogers said. "That degradation is now happening at a faster rate than predicted." 

            Indeed, the pace of change is tracking or has surpassed the worst-case scenarios laid out by the UN Intergovernmental Panel on Climate Change (IPCC) in its landmark 2007 report, according to the new assessment. The chain reaction leading to increased acidification of the oceans begins with a massive influx of carbon into Earth's climate system. 

             Oceans act as a massive sponge, soaking up more than a quarter of the CO2 humans pump into the atmosphere. But when the sponge becomes too saturated, it can disrupt the delicately balanced ecosystems on which marine life -- and ultimately all life on Earth -- depends. 

             "The rate at which carbon is being absorbed is already far greater now than during the last globally significant extinction of marine species 55 million years ago," when some 50 percent of deep-sea life was wiped out, the report said. 

              

        That event, called the Paleocene-Eocene Thermal Maximum, or PETM, may be an ancient dress rehearsal for future climate change that could be even more abrupt and more damaging, some scientists fear. 

       Pollution has also taken a heavy toll, rendering the oceans less resilient to climate change. 

        Runoff from nitrogen-rich fertilizer, killer microbes, and hormone-disrupting chemicals, for example, have all contributed to the mass die-off of corals, crucial not just for marine ecosystems but a lifeline for hundreds of millions of people too.

The harvesting up to 90 percent of some species of big fish and sharks, meanwhile, has hugely disrupted food chains throughout the ocean, leading to explosive and imbalanced growth of algae, jellyfish and other "opportunistic" flora and fauna. 

                  "We now face losing marine species and entire marine ecosystems, such as coral reefs, within a single generation," said Daniel Laffoley, head of the International Union for Conservation of Nature's (IUCN) World Commission on Protected Areas, and co-author of the report.

                  "And we are also probably the last generation that has enough time to deal with the problems," he told AFP by phone. 

     

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A Tsunami

 

A tsunami is a series of ocean waves that sends surges of water, sometimes reaching heights of over 100 feet (30.5 meters), onto land. These walls of water can cause widespread destruction when they crash ashore.

                  These awe-inspiring waves are typically caused by large, undersea earthquakes at tectonic plate boundaries. When the ocean floor at a plate boundary rises or falls suddenly it displaces the water above it and launches the rolling waves that will become a tsunami.

         Most tsunamis, about 80 percent, happen within the Pacific Ocean’s “Ring of Fire,” a geologically active area where tectonic shifts make volcanoes and earthquakes common.

Tsunamis may also be caused by underwater landslides or volcanic eruptions. They may even be launched, as they frequently were in Earth’s ancient past, by the impact of a large meteorite plunging into an ocean.

         Tsunamis race across the sea at up to 500 miles (805 kilometers) an hour—about as fast as a jet airplane. At that pace they can cross the entire expanse of the Pacific Ocean in less than a day. And their long wavelengths mean they lose very little energy along the way.

         Occur most frequently in the Pacific and East Indies. One of the largest tsunami:
In the Atlantic Ocean, the earthquake of November 1, 1755 that hit Lisbon
The wave reached a height of 7 feet from the normal level, affecting coastal areas including the Netherlands.

           
         According database NOOA (National Oceanic and Atmospheric Administration), there are:

     

              2400 tsunami sources:  -81% Pacific Ocean,

                                                  -9% Mediterranean Sea

                                                  -7% Atlantic Ocean

                                                  -2% Black Sea

                                                  -1% Indian Ocean

              7,000 locations where tsunamis can trigger:

                                                

                                                 -89% Pacific Ocean

                                                 -6% Atlantic Ocean

                                                 -3% Mediterranean Sea

                                                 -2% Indian Ocean

  

           Causes of tsunamis:

                     landslides - events: 64; 4,6%; total dead: 14661

                     earthquakes - events: 1171; 82,3%; total dead: 390929

                     volcanic eruptions - events: 65; 4,6%; total dead: 51643

                     unknown - events: 121; 8,5%; total dead: 5364

                TOTAL: events: 1422; 100%; total dead: 462597


           A tsunami can deliver: 
                  - destruction of life, damage of all sorts, spread of diseases, destruction of particular ecosystems.


           We can reduce the energy of a tsunami by - development of offshore breakwaters, that can produce preventive breaking of the waves, prevent invasion of water in urban areas.

 
            In deep ocean, tsunami waves may appear only a foot or so high. But as they approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do, which causes them to rise precipitously.

                A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. This retreating of sea water is an important warning sign of a tsunami, because the wave’s crest and its enormous volume of water typically hit shore five minutes or so later. Recognizing this phenomenon can save lives.

               A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore. People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable locations.

                Some tsunamis do not appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas.

The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea. Similar systems are proposed to protect coastal areas worldwide.

         Video below shows a tsunami provoked by a testing submerged hydrogen bomb:

                    

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