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A tendril of oil from the Gulf of Mexico spill is "increasingly likely" to be captured over the next few days by the warm Loop Current, an extension of the Gulf Stream into the Gulf of Mexico, and could be pulled towards the Florida Straits and the rich coral reefs of the Florida Keys in eight to 10 days, a NOAA administrator said Tuesday.
The new development has prompted additional closures of fishing in federal waters that will go into effect at 6 p.m. today, increasing to 45,728 square miles, or 19 percent of the federal waters of the Gulf subject to fishing restrictions.
"That oil, if it gets into the Loop Current, will become very, very dilute and will be highly weathered," said Jane Lubchenco, a marine scientist who leads the federal agency overseeing ocean issues. "Its state will be in continuous change as it moves farther along. As it travels, it will become more highly weathered and more dilute.
"This is a time for awareness and preparation, but not overreaction," she said.
The tendril, described as a streamer of emulsified oil likely to contain tarballs, is sandwiched between the northern edge of the clockwise flowing loop current more than 100 miles south of Alabama and the Florida panhandle and a counter-clockwise eddy that is likely to draw some of the material north and west.
Lubchenco said modeling indicates that if oil does become entrained in the current and passes through the Florida Straits at the state's southern tip, it will be transported by the Gulf Stream up the East Coast, but little is likely to be washed ashore. Most should stay east of the coast, she said. The announcement came the same day that officials in Florida reported that tarballs had been spotted washing ashore in the Florida Keys. Lubchenco said they've been taken to a U.S. Coast Guard Marine Safety Laboratory in Connecticut for analysis.
She said that tarballs found earlier at several locations along the northern Gulf Coast included some whose oil was identified as coming from the BP well, and others that came from other sources. Lubchenco said NOAA is stepping up its efforts to track oil from the uncontrolled well, both through aerial observations by planes, helicopters and satellites, and with sensors that have been dropped into the ocean.
"I want to emphasize that the bulk of the oil is northwest of the Loop Current," Lubchenco said.
Methane-trapping ice of the kind that has frustrated the first attempt to contain oil gushing offshore of Louisiana may have been a root cause of the blowout that started the spill in the first place, according to University of California, Berkeley, professor Robert Bea, who has extensive access to BP p.l.c. documents on the incident. If methane hydrates are eventually implicated, the U.S. oil and gas industry would have to tread even more lightly as it pushes farther and farther offshore in search of energy. Drillers have long been wary of methane hydrates because they can pack a powerful punch. One liter of water ice that has trapped individual methane molecules in the "cages" of its crystal structure can release 168 liters of methane gas when the ice decomposes. Bea, who has 55 years of experience assessing risks in and around offshore operations, says "there was concern at this location for gas hydrates. We're out to the [water depth] where it ought to be there." The deeper the water, the greater the pressure, which when high enough can keep hydrates stable well below the sea floor. And there were signs that drillers did encounter hydrates. About a month before the blowout, a "kick" of gas pressure hit the well hard enough that the platform was shut down. "Something under high pressure was being encountered," says Bea—apparently both hydrates and gas on different occasions.
Workers from Halliburton who had just pumped cement into the well to temporarily seal it off were well aware of the potential hydrate hazards, says Bea. Halliburton just last year had developed strategies to avoid having the heat of curing cement decompose any nearby hydrates and trigger a kick, he says. A special foamy cement was used to seal the well this time. It was just after the seal was tested that natural gas drove through it, a malfunctioning blowout preventer, and a drill pipe full of seawater to ignite on the platform, killing 11 and eventually sinking it. "There are so many operations like this around the world," says Bea. "My hope is we'll use this disaster as an opportunity to take a step forward" in risk reduction.
What caused the worst mass extinction in Earth's history 251 million years ago? This event is one of the most catastrophic in life's history: the P/T extinction.
An asteroid or comet colliding with Earth? A greenhouse effect? Volcanic eruptions in Siberia? Or an entirely different culprit? Scientists have suggested many possible causes for this "Great Dying": severe volcanism, a nearby supernova, environmental changes wrought by the formation of a super-continent, the devastating impact of a large asteroid -- or some combination of these. Whatever happened during this period left no form of life undisturbed: No class or species was spared from devastation. Trees, plants, lizards, proto-mammals, insects, fish, mollusks, and microbes -- all were nearly wiped out. More than 9 in 10 marine species and 7 in 10 land species vanished. Life on our planet almost came to an end.
This catastrophe - marked in the geologic record as the Permian/Triassic boundary - occurred about 250 million years ago--and is not to be confused with the better-known Cretaceous-Tertiary (K/T) extinction that signaled the end of at least fifty percent of all species, including the dinosaurs, 65 million years ago. During this earlier cataclysmic period in Earth's history, known as "The Great Dying," up to 96 percent of marine species and about 70 percent of land species were wiped out. Scientists have not been able to determine what caused this cataclysm to life, although theories of asteroid impacts, climatic changes, and the greenhouse effect have all been suggested. Many paleontologists have been skeptical of the theory that an asteroid caused the extinction, since early studies of the fossil record suggested that the die-out happened gradually over millions of years -- not suddenly like a single, catastrophic event. But as their methods for dating the disappearance of species has improved, estimates of its duration have shrunk from millions of years to between 8,000 and 100,000 years--a very quick event in geological terms.
A Northwestern University chemical engineer believes the culprit may be an enormous explosion of methane (natural gas) erupting from the ocean depths. This explanation is closer to the inverse of an external impact, like an asteroid, and more like a disgorging of trapped energy that erupts from deep below the oceans. Such a global catastrophe has a more local precedent, as a similar eruption happened in Africa at Lake Nyos in 1986, killing 1700 people and rippling as far away as 25 kilometers.
Considerable methane fluxes to the atmosphere from hydrocarbon seeps in the Gulf of Mexico
Evan A. Solomon1, Miriam Kastner1, Ian R. MacDonald2 & Ira Leifer3 Abstract
The fluxes of the greenhouse gas methane from many individual sources to the atmosphere are not well constrained1. Marine geological sources may be significant2, but they are poorly quantified and are not included in the Intergovernmental Panel on Climate Change budget1. Previous results based on traditional indirect sampling techniques and modelling suggested bubble plumes emitted from marine seeps at depths greater than 200 m do not reach the surface mixed layer because of bubble dissolution and methane oxidation3, 4, 5. Here we report methane concentration and isotope-depth profiles from direct submersible sampling of deepwater (550–600 m) hydrocarbon plumes in the Gulf of Mexico. We show that bubble size, upwelling flows and the presence of surfactants inhibit bubble dissolution, and that methane oxidation is negligible. Consequently, methane concentrations in surface waters are up to 1,000 times saturation with respect to atmospheric equilibrium. We estimate that diffusive atmospheric methane fluxes from individual plumes are one to three orders of magnitude greater than estimates from shallow-water seeps6, 7, 8, greatly expanding the depth range from which methane seep emissions should be considered significant. Given the widespread occurrence of deepwater seeps, we suggest that current estimates of the global oceanic methane flux to the atmosphere1 may be too low.
Photosynthetic organisms produce complex organic molecules, which eventually sink to the seafloor. Once in the sediment, bacteria utilize dissolved oxygen, nitrate and sulfate to convert organic matter to new compounds, including carbon dioxide and acetate. From these simple compounds, other microbes generate carbon-13-depleted methane. The dissolved gas migrates vertically and horizontally via diffusion and fluid flow. Eventually, at sufficient gas concentrations and appropriate pressure and temperature conditions, gas hydrates can precipitate in pore space. Sediment burial over time slowly brings the solid hydrates to higher temperatures. At the base of the GHSZ, gas hydrates are no longer stable and dissociate to water and free methane bubbles. Much of this methane can then migrate upward through the sediments to recycle.
Gas hydrates do not continually accumulate, however, because methane also escapes from sediment. In most places, methane moving up from depth encounters sulfate diffusing down from the seafloor. Microbes step in, using the methane and sulfate as food in an anaerobic process that typically occurs over a thin horizon within the upper 40 meters of sediment and produces bicarbonate ion and hydrogen sulfide. Seafloor vents also discharge methane into deep water at a few locations, notably where conduits bring gas-charged fluids up from below the GHSZ. At present day, aerobic oxidation by bacteria consumes most of this methane in the water column before it reaches the atmosphere.
In certain regards, gas hydrates and underlying free gas represent a major yet overlooked component of the global carbon cycle. Burial and degradation of organic carbon slowly contributes carbon to gas hydrate systems, while anaerobic microbial oxidation and seafloor venting slowly return carbon to the ocean. Gas hydrates may serve as a “capacitor,” however, with relatively steady carbon inputs but highly variable carbon outputs, depending on temperature and pressure throughout time. Consider, for example, a rise in seafloor temperatures along continental margins from 0 degrees Celsius to 5 degrees Celsius. This temperature increase would significantly shrink the GHSZ, destabilizing large amounts of gas hydrate into free-gas bubbles. Buildup of free gas within sediment might then cause local pressures to exceed those of overlying sediment — thus releasing methane from the seafloor through venting or sediment failure.
The capacitor concept brings some essential elements to discussions of gas hydrates and climate change. Perhaps most important to note is that widely accepted models for the global carbon cycle invariably omit gas hydrates and seafloor methane fluxes. These models remain accurate portrayals of carbon cycling when a small carbon input to gas hydrates roughly balances a small carbon output, which probably describes the present-day situation, but not necessarily the conditions of past time periods. Additionally, sedimentary strata suggest that organic carbon has accumulated in relatively cold deep waters (less than 15 degrees Celsius) throughout the geologic record. Thus, methane production and gas hydrates have likely been ubiquitous phenomena over time. Lastly, sea level has dropped and bottom-water temperature has warmed in the past, sometimes abruptly. Large amounts of carbon-13-depleted methane might escape the seafloor during these intervals, potentially leading to a warming in the atmosphere.
Substantial oxidation of methane in the ocean, however, would also affect the environment, principally by removing dissolved oxygen from seawater and dissolving carbonate on the seafloor. Thus, irrespective of whether methane burst into the atmosphere or ocean, the methane would ultimately convert to carbon dioxide, which would propagate throughout the ocean, atmosphere and terrestrial biomass. A massive release of carbon-13-depleted methane would, therefore, decrease the ratio of carbon-13 to carbon-12 across Earth’s surface — a ratio geologists can measure for different time periods in the past.
The juiciest disaster-movie scenario would be a release of enough methane to significantly change the atmospheric concentration, on a time scale that is fast compared with the lifetime of methane. This would generate a spike in methane concentration. For a scale of how much would be a large methane release, the amount of methane that would be required to equal the radiative forcing of doubled CO2 would be about ten times the present methane concentration. That would be disaster movie. Or, the difference between the worst case IPCC scenario and the best conceivable ‘alternative scenario’ by 2050 is only about 1 W/m2 mean radiative energy imbalance. A radiative forcing on that order from methane would probably make it impossible to remain below a ‘dangerous’ level of 2 deg above pre-industrial. I calculate here that it would take about 6 ppm of methane to get 1 W/m2 over present-day. A methane concentration of 6 ppm would be a disaster in the real world. The atmosphere currently contains about 3.5 Gton C as methane. An instantaneous release of 10 Gton C would kick us up past 6 ppm. This is probably an order of magnitude larger than any of the catastrophes that anyone has proposed. Landslides release maybe a gigaton and pockmark explosions considerably less. Permafrost hydrates are melting, but no one thinks they are going to explode all at once.
There is an event documented in sediments from 55 million years ago called the Paleocene Eocene Thermal Maximum, during which (allegedly) several thousand Gton C of methane was released to the atmosphere and ocean, driving 5° C warming of the intermediate depth ocean. It is not easy to constrain how quickly things happen so long ago, but the best guess is that the methane was released over perhaps a thousand years, i.e. not catastrophically [Zachos et al., 2001; Schmidt and Shindell, 2003].
The other possibility for our future is an increase in the year-in, year-out chronic rate of methane emission to the atmosphere. The ongoing release of methane is what supplies, and determines the concentration of, the ongoing concentration of methane in the atmosphere. Double the source, and you’d double the concentration, more or less. (A little more, actually, because the methane lifetime increases.) The methane is oxidized to CO2, another greenhouse gas that accumulates for hundreds of thousands of years, same as fossil fuel CO2 does. Models of chronic methane release often show that the accumulating CO2 contributes as much to warming as does the transient methane concentration. Anthropogenic methane sources, such as rice paddies, the fossil fuel industry, and livestock, have already more than doubled the methane concentration in the atmosphere from pre-industrial levels. Currently methane levels appear stable, but the reasons for this relatively recent phenomena are not yet clear. The amount of permafrost hydrate methane is not known very well, but it would not take too much methane, say 60 Gton C released over 100 years, to double atmospheric methane yet again. Peat deposits may be a comparable methane source to melting permafrost hydrate. When peat that has been frozen for thousands of years thaws, it still contains viable populations of methanotrophic bacteria [Rivkina et al., 2004] that begin to convert the peat into CO2 and CH4. It’s not too difficult to imagine 60 Gton C over 100 years from peat, either. Changes in methane production in existing wetlands and swamps due to changes in rainfall and temperature could also be important. Ocean hydrates have also been forecast to melt, but only slowly [Harvey and Huang, 1995]. Places to watch would seem to be the Arctic and the Gulf of Mexico.
So, in the end, not an obvious disaster-movie plot, but a potential positive feedback that could turn out to be the difference between success and failure in avoiding ‘dangerous’ anthropogenic climate change. That’s scary enough.
According to Moffett, the Davy Jones structure covers 20,000 acres and appears on seismic to be a classic four-way closure. That is telling, he says, because four-way traps are a common denominator among discoveries with at least 500 Bcfe of reserves both offshore on the Louisiana Shelf and onshore South Louisiana.
“There are a lot of four-way closures–more than two dozen of these big piles of sand on four-way closures–just to the north of the salt weld below the Shelf,” Moffett states. “Every one of those fields was drilled between the 1930s and 1960s.”
Jumping across the Shelf into deep water, Moffett says four-way closures are being discovered from Thunderhorse in Mississippi Canyon, to Tahiti and Knotty Head in Green Canyon, to the Lower Tertiary/Wilcox finds at Walker Ridge, Keathley Canyon and Alaminos Canyon. “We have a complete trend,” he holds. “There are now more than 40 of these giant four- and three-way closures against salt. We had all these discoveries onshore, and we now are seeing four-way closures in deep water.” Labeling the Miocene, Wilcox and Tuscaloosa as “big-ticket items,” Moffett reiterates that like the onshore and deep water, large structures with four-way closures below salt on the Shelf appear to cover enough area to hold major reserves. “When you are looking at multiple-Tcf reserves, these structures could flow 1 Bcf or more a day, and they are in the middle of Shelf infrastructure,” he says. “We are going back to the 1940s and ’50s, when this series of big four-way closures was drilled onshore. These ultradeep Shelf structures will get drilled, I can tell you that.” That is the good news. The bad news is that the prospects will have to be drilled with heavy-duty rigs and heavy mud weights, and logged and completed with HP/HT-rated equipment the likes of which the Gulf has never seen, Moffett goes on. “For example, conventional logging tools will not work with these temperatures and pressures,” he points out. “We probably spent three months trying to get good logs on Davy Jones.”
Rigs with the mechanical capacities to safely drill ultradeep wells are another issue. “You need a derrick with a hook load capacity of at least 2 million pounds to set the intermediate casing string between 16,000 and 18,000 feet. We have two of the three rigs in the Gulf with sufficient hook load capacity to drill these wells (Rowan’s Mississippi and Ralph Coffman jackups),” Moffett reports. “We have a commitment on the third rig (also owned by Rowan), and will put it to work later this year. If the ultradeep play catches on like we think, a lot of contractors will be upgrading their rigs.”
Minerals Management Service (MMS) geological reviews of exploration and development plans and applications for permit to drill on Gulf of Mexico OCS leases include a discussion of possible abnormal pressure zones. Geopressure is defined as the situation where pore fluid pressure exceeds normal hydrostatic pressure (Fertl, 1976; Dutta, 1987). This onset of moderate overpressure in continental shelf deltaic sediment occurs where pore pressures are equivalent to 12.5 pound per gallon (ppg) mud weights. In deep water, however, the fracture gradient and shallow casing shoe tests are lower, and the onset of even mild overpressures of 9.5 to 12.0 ppg contributes to many drilling problems such as shallow water flow. Burial rates, geothermal gradients, compaction, and diagenetic reactions are the primary factors affecting the occurrence of geopressure (Law et al., 1998). In deep-water wells, the large seawater column also results in greater depths to abnormal pressure, so depths below the mud line (bml) or sea floor were used in this study in place of vertical subsea depths. Geological factors that control the deposition of turbidite systems, sequence stratigraphy, major faults, unconformities, and salt also affect pore pressure. In complexly faulted structures, formation pressures may be compartmentalized and may vary between different sands.
We analyzed predicted and actual pore pressures, sedimentation rates, and formation temperatures in the deep-water Gulf of Mexico and prepared trend maps of the occurrence of geopressure for this province. The top of geopressure was defined as the depth at which pore-pressure equivalent mud weights, referenced to kelly bushing elevation, exceeded 12.5 ppg. The wells in this study are located in four deep-water sections that include, from east to west, Viosca Knoll/ Mississippi Canyon/Atwater Valley, Green Canyon, Garden Banks, and East Breaks/Alaminos Canyon. The upper slope (less than 1000 m of water) in Mississippi Canyon has a thicker Pliocene section with a shallower top of geopressure, an average of about 6950 ft (2118 m) bml, than the deeper water parts of this area. In deeper water, the average top of geopressure occurs in the Miocene at about 10,700 ft (3261 m) bml. In the younger Pliocene-Pleistocene section to the west in Green Canyon, Garden Banks, and East Breaks, the average top of geopressure occurs at about 8700 ft (2652 m) bml. In the deeper water sections in Green Canyon, Garden Banks, and Alaminos Canyon to the south and southeast, however, the top of geopressure occurs in the Miocene at an average depth of about 11,200 ft (3414 m) bml. Throughout the deep-water Gulf of Mexico, as shown in Figure 2, it appears that older and more compacted strata have a deeper top of geopressure than occurs in younger strata.
Except for the northeastern corner of Mississippi Canyon, the thermal gradient in the eastern study area is lower than that of deep-water areas to the west, generally about 1.05oF/100 ft (0.58oC/30.5 m). The thermal gradient falls from an average of 1.25oF/100 ft (0.69oC/30.5 m) in East Breaks to about 1.0oF/100 ft (0.555oC/30.5 m) in Garden Banks, and in Green Canyon the temperature gradient appears to decrease from 1.3 to 0.8oF/100 ft (from 0.72 to 0.44oC/30.5 m) to the southeast with greater water depths. These observations suggest that lower thermal gradients may correspond to a deeper top of geopressure...
Many of the serious and costly drilling problems in deep water are related to the pore-pressure/fracture gradient relationship. Other pressure-related hazards, such as shallow water flow, require better predrill identification and quantification of overpressured problem sands. In many Gulf of Mexico frontier deep-water areas, a lack of offset wells mandates better pressure models that incorporate all available geological data. Operations geologists and geophysicists in the MMS are working with deep-water operators to establish databases and methodologies that will improve industry’s success in dealing with deep-water geohazards well into the new millennium.
Destabilization of methane hydrates: a risk analysis
A Report Prepared for the German Advisory Council on Global Change
Department of the Geophysical Sciences
University of Chicago
A huge reservoir of carbon resides as methane in clathrate deposits on the sea floor and associated with permafrost soils. On geologic time scales of thousands of years and longer, this reservoir seems precarious, because the hydrate ice floats in water, and melts at Earth surface conditions. Eventually the hydrates could release as much carbon as we release from fossil fuels. On an anthropogenic time scale of the coming century, however, estimates of methane release from hydrates are generally small relative to the climate forcing from fossil fuel CO2 release. The risk of climate impact in the coming century from the methane hydrate reservoir is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from decomposition of melting peat deposits.
Major landslides such as the Storegga slide off the coast of Norway could have released at most a gigaton of C as methane to the atmosphere. The potential climate perturbation from a release this size is smaller, although of opposite sign and somewhat longer lived, than the climate impact from a major volcanic eruption.
The nightmare scenario would be the catastrophic release of some large fraction of the enormous methane hydrate reservoir, but no one has proposed a mechanism by which this could take place. (my note: apparently no one thought anyone was crazy enough to punch a hole in they couldn't plug in a high pressure methane deposit) The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C from hydrates, but the time scale of the release appears to have been thousands of years, i.e. a chronic release rather than a catastrophic. Anthropogenic warming may drive a chronic, ongoing release of methane that would raise the steady-state concentration of methane in the atmosphere, and contribute another source of CO2, which accumulates to impact climate for hundreds of thousands of years.
Several simulations have found a greater climate impact from the accumulating CO2 than from the transient atmospheric methane...
CO2 is the dominant anthropogenic greenhouse gas in the atmosphere, because the anthropogenic perturbation to the CO2 concentration is much larger than the anthropogenic change in CH4. However, the higher concentration of CO2 means that on a per-molecule basis, CO2 is a less potent greenhouse gas than CH4 by about a factor of 24 [Wuebbles and Hayhoe, 2002]. Figure 1 shows the radiative impact of changes in CO2
and CH4 concentrations. The most significant practical distinction between the gases is that CO2 is more concentrated in the atmosphere than is methane. For this reason, the strongest absorption bands of CO2 already absorb most of the outgoing longwave light from the ground. An increase in CO2 concentration tends to make the absorption bands a bit wider, but they cannot get any more intense. Methane is less concentrated than CO2,
and its absorption bands less saturated, so a single molecule of additional methane has a larger impact on the radiation balance than a molecule of CO2, by about a factor of 24 [Wuebbles and Hayhoe, 2002]. The radiative impact of CH4 follows the concentration to roughly the 1/3 power, while the CO2 impact follows the log of the concentration. To get an idea of the scale, we note that a doubling of methane from present-day concentration
would be equivalent to 60 ppm increase in CO2 from present-day, and 10 times present methane would be equivalent to about a doubling of CO2.
Once methane is released to the oxic, sunlit atmosphere, it oxidizes to CO2 on a time scale of about 8 years. Ultimately, the oxidizing power comes from O2, but the reactive compound OH is a necessary intermediate, following the reaction
CH4 + OH -> CH3 + H2O
where CH3 produced is a reactive radical compound, quickly reacting with water vapor and other gases to form ultimately CO2. OH is produced by photolysis, the absorption of light energy by the severing of a chemical bond. Ozone photolyzes in the troposphere to yield OH, as does H2O2 and NO2. In the absence of sunlight, such as in ice cores, no OH is produced, and CH4 and O2 are able to coexist with negligible reaction for hundreds of thousands of years.
The implication of the short lifetime of methane in the atmosphere is that the concentration of methane at any given time is determined by the rate of methane emission over the past few decades. If emission is steady with time, then the steady-state atmospheric concentration can be calculated as
Inventory [mol] = Emission flux [mol/year] / Atmospheric lifetime [years]
One unknown in this equation is how strongly the methane lifetime may depend on the methane source flux. If the methane oxidation rate were strictly limited by the supply rate of OH, then the lifetime should increase linearly as methane increased, and the steady-state concentration would increase as the emission flux squared. The concentration of OH, and hence the lifetime of methane, could also be affected by anthropogenic emissions of combustion products such as the nitrogen oxides NOx, hydrocarbons, and carbon monoxide. The large anthopogenic changes in the concentrations of these compounds in the atmosphere appear to have cancelled each other out, however, so that the OH concentration, and the methane lifetime, seem to largely unaffected [Wang and Jacob, 1998].
The other aspect of methane concentration behavior in the atmosphere is the response to a spike of methane emission. If the methane is released on a time scale that is short compared to the atmospheric lifetime, the resulting methane concentration in the atmosphere follows a time-trajectory, and can reach much higher values than typical steady-state values. We will refer to this as a “catastrophic” methane release, as opposed to a “chronic” release. In the case of an instantaneous release, the concentration of methane increases instantaneously, and decays back to a long-term mean concentration on an e-folding time scale of the atmospheric lifetime, currently 8 years. The record of methane recorded in an ice core represents a time-average of longer duration than the atmospheric lifetime, so that the maximum concentration reached just after an emission event would be smoothed out. The current inventory of methane in the atmosphere is about 3 Gton C. Therefore, the release of 1 Gton of methane catastrophically to the atmosphere would raise the methane concentration by 33%. 10 Gton C would triple atmospheric methane.
US oil spill in Loop Current 'heading for Florida'
PARIS (AFP) – The Gulf of Mexico oil spill has entered the Loop Current, a powerful conveyor belt that flows clockwise around the Gulf towards Florida, the European Space Agency said Wednesday.
Scientists monitoring the massive slick via ESA satellites say that oil has for the first time hit the current and is likely to reach Florida within six days.
"We have visible proof that at least oil from the surface of the water has reached the current," said Bertrand Chapron, a scientist at the French Research Institute for Exploitation of the Sea.
A satellite image from May 18 shows a long tendril of the spill extending down into the Loop Current, which will drag it south towards coral reefs in the Florida Keys.
"It is likely to reach Florida within six days," Chapron said.
Using several European satellites, European scientists have tracked the spill's progress across the surface of the Gulf over the last two weeks, monitoring the proximity of the oil to the current.
But once it enters the deep and intense Loop Current, they warned, turbulent waters will accelerate the mixing of oil and water.
"This might remove the oil film on the surface and prevent us from tracking it with satellites, but the pollution is likely to affect the coral reef marine ecosystem," said Fabrice Collard of CLS, a subsidiary of France's National Centre for Space Studies.
It's time to revisit this subject. NOAA and BP are still saying the spill rate is 210,000 gallons (5,000 barrels) per day, despite plenty of evidence to the contrary. Many in the media continue to uncritically accept this estimate.
Why is it important to get this number right? This is about more than just liability, or PR. You can bet that our future response capacity is going to be overhauled and retooled based on this spill. If we low-ball the spill amount and rate, we run the risk of designing an inadequate new spill-response system that is doomed to fail the next time something this big occurs.
A couple of thoughts:
1) Are we really being asked to believe that the spill-response capability of one of the world's biggest oil companies AND the United States Coast Guard has been totally overwhelmed by a spill of just 210,000 gallons per day? That's a big spill, but not nearly as big as could reasonably be anticipated. Plenty of wells in the Gulf produce more than that under controlled flow-rate conditions; plenty of tankers plying our waters hold millions of gallons of oil.
2) BP claims the siphon they've inserted into the end of the damaged riser pipe is diverting 84, 000 gallons (2,000 barrels) of oil per day from the main leak to a tanker at the surface. That is good news indeed. But it's worth remembering that for nearly a week BP stated the total spill rate was only 1,000 barrels per day.
3) Scientists analyzing video of that main leak, apparently shot on May 11 and released by BP on May 12, have estimated the flow rate from that leak to be anywhere from 20,000 to 100,000 barrels per day. This makes SkyTruth's 1.1 million gallon (26,500 barrel) per day estimate, based on our measurements of the oil slick as observed on satellite images and mapped by the Coast Guard, look fairly conservative. And it doesn't even include the additional 15-20% coming from the secondary leak. That means BP's siphoning effort is only capturing, at best, about 10% of the flow. This video of the main leak, shot on May 17 after the siphon was inserted and apparently working, shows the plume of oil continuing to spew into the Gulf; it hardly looks abated.
4) Speaking of which: video shot on May 15 and 16 has just been released showing the secondary leak, where the riser pipe is kinked and bent about 90 degrees a few feet above the blowout preventer stack. Unlike the short, blurry clip of the main leak, this video is several minutes long and quite sharp.
New underwater video released by BP showed oil and gas erupting under pressure in large, dark clouds from its crippled blowout preventer on the ocean floor. The leaks resembled a geyser on land.
BP and the Coast Guard have said about 210,000 gallons of oil a day is gushing from the well, but professors who have watched the video and others say they believe the amount is much higher.
Steve Wereley, a mechanical engineer at Purdue University in Indiana, said he is sticking with his estimate that 3.9 million gallons a day is spewing from two leaks.
His estimate of the amount leaked to date, which he calls conservative and says has a margin of error of plus or minus 20 percent, is 126 million gallons – or more than 11 times the total leaked from the Exxon Valdez disaster in 1989. The official estimate is closer to 6 million gallons. Another researcher, Timothy Crone of Columbia University's Lamont-Doherty Earth Observatory, said the latest video suggested a leak of at least 840,000 to 4.2 million gallons a day, though poor video quality made it difficult to come up with an accurate figure.
Government agencies have set up a task force to focus on how much oil is spilling, but BP America President Lamar McKay said under questioning at Wednesday's House hearing that officials still don't know which estimates are correct.
"It's theoretically possible," that the larger estimates are accurate, he said. "But I don't think anyone who's been working on this thinks it's that high."
BP has tried several unsuccessful methods to contain the oil, but earlier this week managed to insert a tube into one of the leaks and says that as of Wednesday it was sucking 126,000 gallons a day to the surface.
Methane is the major component of natural gas, about 87% by volume. At room temperature and standard pressure, methane is a colorless, odorless gas; the smell characteristic of natural gas as used in homes is an artificial safety measure caused by the addition of an odorant, often methanethiol or ethanethiol. Methane has a boiling point of −161 °C at a pressure of one atmosphere. As a gas it is flammable only over a narrow range of concentrations (5–15%) in air. Liquid methane does not burn unless subjected to high pressure (normally 4–5 atmospheres).
Methane is created near the Earth's surface, primarily in soils, rivers/seas and in animal innards. It is carried into the stratosphere by rising air in the tropics. Uncontrolled build-up of methane in the atmosphere is naturally checked — although human influence can upset this natural regulation — by methane's reaction with hydroxyl radicals formed from singlet oxygen atoms and with water vapor.
Methane in the Earth's atmosphere is an important greenhouse gas with a global warming potential of 25 compared to CO2 over a 100-year period (although accepted figures probably represents an underestimate). This means that a methane emission will have 25 times the impact on temperature of a carbon dioxide emission of the same mass over the following 100 years. Methane has a large effect for a brief period (a net lifetime of 8.4 years in the atmosphere), whereas carbon dioxide has a small effect for a long period (over 100 years). Because of this difference in effect and time period, the global warming potential of methane over a 20 year time period is 72. The Earth's methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases. Usually, excess methane from landfills and other natural producers of methane is burned so CO2 is released into the atmosphere instead of methane, because methane is such a more effective greenhouse gas. Recently, methane emitted from coal mines has been successfully utilized to generate electricity.
Arctic methane release from permafrost and clathrates is an expected consequence of global warming.