Courtesy FundyAlong with wind and solar, harvesting power from tidal forces comes up a lot in discussions of alternative energy sources.
Was that a horrible sentence? I think it was. What I meant to say is this: we can generate electricity from tides, and lots of it. "Tidal power" is often brought up alongside solar power and wind power, but while I can easily picture windmills and solar panels, I'm not always sure what sort of device we'd use to harness the power in the tides.
This sort of device! For those of you too afraid to click on a strange link (who knows... I could be linking to an image like this!), the article depicts something that looks sort of like a thick, stubby windmill, with blades on its front and back. It's a tidal turbine, and at 74 feet tall and 130 tons it's the world's largest. It should be able to supply electricity to about 1,000 households. Pretty impressive.
Tidal turbines, apparently, are so productive because water is so much denser than water, and so it takes a lot more energy to move it. An ocean current moving at 5 knots (that's a little shy of 6 miles per hour, for the landlubbers) has more kinetic energy, for example, than wind moving at over 217 miles per hour.
At least according to that article, the United States and Great Britain each have enough tidal resources (areas where this kind of generator could be installed) to supply about 15% of their energy needs.
More info on the tidal turbine, which I am calling "the Kraken," because it's big, underwater, and will occupy your mind for only a very short time.
Since the Deepwater Horizon oil rig exploded on April 20th of this year, approximately 4.9 million barrels of oil have flowed into the waters of the Gulf of Mexico. In the intervening months, BP added 1.8 million gallons of petroleum-containing chemical dispersant to the oily waters. It is not yet clear what the effects of such a mix will be.
When oil is spilling into water, as it did for 114 days from BP’s blown out Macondo well, there are three options available for clearing it: skimming, burning, and dispersing. Skimming the oil is the safest and least environmentally-damaging option, but the skimmer equipment is expensive and slow to deploy. Burning can effectively remove oil from the water, but the process pollutes the air and sends a lot of heavy residue to the sea floor. For this spill, BP decided to rely substantially upon the use of chemical dispersants.
Chemical dispersants do not themselves remove oil from water, but bacteria that naturally live within the Gulf of Mexico do. The trouble is that the highly cohesive properties of oil mean that large slicks like this one in the Gulf present very little molecular surface area upon which the microbes can work. Thus, the dispersants, which work a bit like dish detergent, are used to break up the oil into smaller droplets and make it easier for bacteria to degrade.
In an attempt to keep oil off of Florida beaches and out of deltaic wetlands (and, some would say, out of the public eye), dispersants were applied in vast quantities and in unprecedented ways during the Gulf Coast cleanup effort. Not only was it sprayed from planes onto the surface of oil slicks, as is the traditional application, it was pumped 1.5 km below the ocean surface into the oil plume flowing from the broken wellhead. More than four million liters of dispersants were applied to surface waters offshore and 2.5 million at the site of the leak.
The long-term implications of this unprecedented use of dispersants are not known. The oil is now spread more widely than it would have been without the use of dispersants and the smaller particles are located throughout the water column. The worry is that the small, diffuse particles will be more easily taken up by marine organisms. "By breaking up oil slicks, you might reduce the number of acutely oiled pelicans and sea turtles," Doug Rader, chief ocean scientist for Environmental Defense Fund told Rolling Stone Magazine. But, adds Melanie Driscoll, a bird-conservation director with the National Audubon Society, “Are these birds better off in the long run than the heavily oiled birds? We don't know. We don't know yet about their survival rate weeks or months from now, or about their reproductive capacity in the future. Frankly, there are just a huge number of unknowns here – and that's what concerns me."
Courtesy US Fish & Wildlife Service
There is also concern that bacterial degradation of the dispersed oil is leaving behind large swaths of de-oxygenated water that is inhospitable to marine life. Larry McKinney, executive director of the Harte Research Institute of Gulf of Mexico Studies at Texas A & M University told Discovery News that the spill may have increased the size of the so-called “dead zone” of oxygen-starved water in the Gulf. The zone, which is caused by agricultural runoff flowing through the Mississippi River, is the largest it has been in twenty-five years. McKinney believes that increased microbial oil metabolism is the culprit.
The dispersants that were used on the Macondo BP oil spill were developed by Exxon in the 1970s and are sold under the name Corexit. By volume, Corexit 9500 is largely composed of petroleum distillates, solvents known to be animal carcinogens. But, as marine biologist Jane Lubchenco, director of the National Oceanic and Atmospheric Administration, expressed at a press conference on May 12, the use of these dispersants was viewed as “a trade-off decision to lessen the overall environmental impact.”
What exactly that trade-off will be is unclear. In the wake of its widespread use, questions developed about the toxicity of Corexit and other dispersants in combination with oil. Last week, the EPA released a study on the acute toxicity of dispersants alone, oil alone, and dispersants in combination with oil. The results of the study suggest that the toxicity of the dispersant-oil mixture is similar to that of oil alone and is more toxic than dispersant alone; the long-term health effects of the dispersant breakdown products however are entirely unknown.
A hard yank of the rusty metal door of the Acme Commercial Processing Facility outside of Port Angeles, Washington leads visitors down a white and green linoleum corridor to dark room dripping with condensation. Inside is a bank of twenty refrigerator-like machines whirring in unison day and night to preserve over 120 bushels of cones—Douglas-fir, grand fir, western red cedar, and western hemlock—for their eventual time the sun.
Courtesy National Park ServiceThe cones, together with seeds and cuttings of more than 80 plant species native to Olympic National Park, have been collected over the course of several years as part of a plan to re-vegetate 268 square miles of land currently sitting beneath nearly sixteen billion gallons of water and 18 million cubic yards of sediment.
The land is located at the bottom of the Mills and Aldwell reservoirs, impoundments on the Elwha River that developed in the wake of the erection the Elwha and Glines Canyon Dams in the early 1900s. In a little less than one year, the process of removing the dams, and revealing land long drowned underneath billions of gallons of water, will begin.
The Elwha and Glines Canyon Dams were built nearly 100 years ago when entrepreneur Thomas Aldwell saw the potential for power within the steep hills surrounding the Elwha River. Interested in harnessing that power, Aldwell formed the Olympic Power and Development Company and drew up plans to build the105-foot Elwha hydroelectric dam. Construction on the dam began in 1910 and by 1913 it was supplying energy to pulp mills in Port Angeles. By 1927,with the need for energy within Port Angeles continuing to increase, Aldwell’s company erected the 210-foot Glines Canyon dam eight miles upstream.
Courtesy National Park ServiceThe Elwha is a rocky river that originates 4500 ft above sea level in the snowfields of the Olympic Mountains and cascades north through temperate forests to discharge its waters five miles west of Port Angeles into the Strait of Juan de Fuca. Before construction of the dams, the river’s 45-mile main channel and over 100 miles of tributaries had been host to runs of ten native anadromous salmon and trout.
Courtesy National Park Service
Today, changes to the river that developed in the wake of dam construction have conspired to reduce salmon populations by more than 100-fold. Since erection of the dams, migrating salmon have been confined to the lowermost 4.9 miles of river. Sediment that travels down river from the watershed’s mountains has been trapped behind the dams and available spawning habitat has decreased as a result. Diseases, parasites and fish mortality have increased concomitantly with river temperatures. In sum, native salmon populations have declined from approximately 400,000 to fewer than 3,000 individuals today. The diminished stocks are currently maintained primarily through hatchery production.
In the late 1960’s and early 1970’s the Elwha and Glines Canyon Dams were subject to licensing procedures by the Federal Energy Regulatory Commission (FERC). During the review, questions arose about the legal and philosophical conflicts involved in operating dams within a national park. Opposition to the dams mounted during the 70’s and 80’s and, in response to pressure from the Lower Elwha S’Klallam Tribe and sixteen area conservation groups, Congress considered the case of the Elwha River. In 1992 the Elwha River Ecosystem and Fisheries Restoration Act was passed.
The act mandated full restoration of the Elwha River ecosystem and its native anadromous fish, but did not specify the actions necessary to achieve “full restoration”. Instead, the Department of Interior was directed to study and evaluate alternative restoration scenarios, including the removal of one or both dams. By 1994, the National Park Service, the U.S. Fish and Wildlife Service, the U.S. Bureau of Reclamation, the Bureau of Indian Affairs, and the Lower Elwha S’Klallam Tribe released a joint study concluding that the best action for river and fish restoration would be removal of both dams.
Removing the dams from their place within the river involves more than simply eliminating the tons of concrete, enormous steel tubes, and spillway gates that comprise the dams’ structures. More than 80 years of restricted water and sediment flow in the river has resulted in the build-up of approximately 18 million cubic yards of sediment behind the dams. As easy as it might be to simply blast the dams out, releasing all the sediment in one pulse would devastate downstream and coastal habitats. Geomorphologists working on the project needed to find a way to control the downstream movement of sediment during and after dam removal.
Thirteen of the eighteen million cubic yards of sediment within the river lie behind the 210-foot Glines Canyon Dam. To study sediment movement in the wake of dam removal, researchers from the National Center for Earth-surface Dynamics constructed a physical model of the dam and surrounding watershed to test alternative removal scenarios.
Above are a series of stills from the sediment transport experiments conducted at NCED by Chris Bromely.
The agreed upon strategy, developed through analysis of the physical model studies in conjunction with mathematical models, involves gradually drawing-down the Mills reservoir using an outlet pipe to move water downstream. As the water level drops, demolition crews will cut and remove 7.5-foot sections of the dam starting from the top. Once the level of the dam has reached the level of the sediment layer sitting behind the dam, demolition crews will use controlled blasting to clear the remainder of the dam (see the really neat demolition illustration video from the National Park Service and Interactive Earth).
Removal of Elwha and Glines Canyon dams will be the largest dam removal project in U.S. history, one that is considered an unprecedented learning opportunity be scientists who study rivers and their associated ecosystems. Tim Randle, manager of the sedimentation and river-hydraulics group of the Bureau of Reclamation’s technical-service center in Denver, organized a recent trip to the site for engineers, fisheries scientists, biologists, geomorphologists, and a botanist to consider what can be learned from this extraordinary project. "It's the first time anyone has done a staged, step-by-step dam removal of this scale," Randle told the Seattle Times. “It's the largest controlled release of sediment ever in North America.”
The scientists plan to study what actually happens to all the mobile sediment once the dams are removed. They will investigate how salmon re-colonize the river once fish are again able to reach spawning grounds above the dams. They will research the re-vegetation of the hundreds of acres of exposed river banks and reservoir bottoms that will emerge as the Aldwell and Mills reservoirs drain, but they have nothing quite like this scenario upon which to base their expectations. Joshua Chenoweth, a botanist with Olympic National Park, likens the re-vegetation to that which occurred in the wake of the Mount St. Helens eruption of 1980. “At least there were buried roots at Mount St. Helens,” he told the Times, “We have nothing. This is the first time anyone has tried anything like this. The scale is unprecedented.”
The possibilities for renewal though, seem almost as vast as the wilderness itself. Bushel after bushel of those fir, cedar and hemlock cones still sit quiescent within the dark of cold storage at the Acme Commercial Processing Facility. In a matter of years the sun will shine upon the cones and on land long lost underneath billions of gallons of water. Native salmon and trout may be industriously swimming past.
4.9 million barrels of oil, where did it go?
“It’s becoming a very elusive bunch of oil for us to find” – National Incident Commander Thad Allen
The federal government released a report last Wednesday claiming that about 75% of the more than 4.9 million barrels of oil spewed from BP’s blown out Macondo well has “evaporated or otherwise been contained.”
After reading which I thought: “...?..”
Really? Where did the oil go? The oil really evaporated?
The chart suggests that about one quarter of the oil that spilled from the well remains in the water, on shore, or in sand and sediments. One quarter of the oil is said to have evaporated or dissolved in the water, and the rest has been dispersed or collected (more on dispersion later).
OK…but, again, really evaporated? And why hasn’t all of the oil met the same fate? Why did some of the oil evaporate while some dissolved, and still other bits formed tar balls and washed ashore?
The answer, it seems, is that, according to Oil in the Sea III, a report published by the National Academy of Sciences, oil is a mixture of hundreds of compounds--including benzene, toluene, and heavy metals--the composition of which varies from source to source and over time. The hours-long journey that the oil makes from the well head to the ocean surface causes the oil to fractionate into its component chemicals, leading the heavier compounds to drift to the ocean bottom while the lighter compounds rise to the ocean surface.
Once at the surface, the lighter hydrocarbons, also known as light ends, are more prone to evaporation than are the heavier components. Rough seas, high wind, and high temperatures increase the rate of evaporation and the proportion of oil lost this way. The warm, turmultuous water of the gulf has therefore promoted evaporation of the lighter fractions of the spilled oil.
Some of the “hundreds of compounds” in oil are water soluble and dissolve into the surrounding water, a process that occurs more quickly when the oil is finely dispersed. The more soluble compounds turn out to also be the light aromatic hydrocarbons. Thus, the processes of evaporation and dissolution are lumped into one pie of the chart.
What about the 16% of the oil that has “naturally dispersed”? Like with dissolution and evaporation, the character of the oil and the state of the sea influence how much oil is naturally dispersed. Waves and turbulence at the sea surface can promote natural dispersion, causing an oil slick to break up into droplets which then become mixed into the upper levels of the water column. Dissolution, biodegradation, and sedimentation are more likely when the oil remains suspended in the water as droplets. Again, light, low viscosity oil is most prone to natural dispersion.
So the oil that has dissolved or dispersed (naturally or chemically) is not really gone. It is still in the water, it just can't be seen.
Also, unfortunately, some researchers remain wary that oil that has disappeared from the water's surface will reappear onshore in the future, as happened with the 1979 Ixtoc I oil spill. Larry McKinney, director of the Harte Institute for Gulf of Mexico Studies at Texas A&M, Corpus Christi, told Discovery News that dispersants similar to those used on the BP spill were used to break up the Ixtoc oil, which later washed ashore onto Texas beaches. McKinney is worried that the same thing will happen with this spill. "BP used a lot of dispersant and the oil went someplace," he said.
I am quite curious about the use of chemical dispersants with this spill and the microbes that are doing the degradation, so I am writing a post about it. If you are curious too, check out Petroleum to clean up petroleum? on the Buzz blog.
One last thing:
According to the New York Times, reaction to the report (and its associated chart) has been varied among scientists specializing in the issues it raises. In fact, Samantha Joye, a marine scientist at the University of Georgia told the Times that a lot of the report’s content is “based on modeling and extrapolation and very generous assumptions.” She said that the report would have been “torpedoed into a billion pieces” if it had been put out by an academic scientist.
On the other hand, Edward B. Overton of Louisiana State University said that the report might have underestimated the amount of oil that has effectively left the Gulf. See the Times for a full examination of the debate and the applicability of modeling for predicting the amount of oil that remains.
Apparently, massive earthquakes (reaching magnitudes of 7.0 and 8.0) struck Middle America between December 1911 and February 1812. (The largest of those quakes caused the Mississippi River to flow backwards temporarily!)
The area of the quakes, New Madrid Missouri, isn’t located at the intersection of tectonic plates, so why did earthquakes of such magnitude strike there?
Courtesy National Center for Earth-surface Dynamics (NCED)Well, a paper recently published in the journal Nature suggests that the earthquakes were due to the actions of our beloved mighty Mississippi River.
The idea is that the Mississippi rapidly eroded tons of soil—39 feet of sediment from the river basin—at the end of the last ice age (around 16,000 years ago). That “quite dramatic” erosion (which occurred over a period of 6,000 years, but I guess is considered “rapid” in geological time) set in motion the events that would lead to the New Madrid quakes, as Roy Van Arsdale, a geologist and co-author of the study told msnbc.
Courtesy National Center for Earth-surface Dynamics (NCED)Van Arsdale and fellow authors suggest that the erosion of the sediment released a lot of weight from the Earth’s surface, causing it to buckle just like a stick that is bent from both ends. Imagine bending a stick in your mind, and you will see that in the middle, bending part of the stick, the top part curves upward and is stretched. The bottom part is compressed. In the case of the Earh's crust, the stretching creates faults, or cracks, in the crust. The study's authors suggest that the faults failed in 1811 and unleashed the Earthquakes of New Madrid.
So there you have it, earthquakes in the middle of the country (which is apparently the the country's most earthquake-prone region outside California! Who knew?!) caused by our old familiar mighty Mississippi.
A new record hail stone fell on 23 July 2010 near Vivian SD!
It is 8-inch in diameter hail stone and weighs 1.9375 pounds.
The old record heaviest U.S. hailstone was a 1.67-pound found near Coffeyville, KS on Sep. 3, 1970. The old record for the largest diameter hailstone was 7 inches found in Aurora, NE on June 22, 2003. This Aurora, NE hailstone still holds the U.S. record for circumference: 18.75 inches. The Vivian, SD hailstone circumference was only 18.5".
Hail is precipitation in the form of large balls or lumps of ice. Hailstones begin as small ice particles that grow primarily by accretion. The production of large hail requires a strong updraft that is tilted and an abundant supply of supercooled water. Because strong updrafts are required to generate large hailstones, it is not surprising to observe that hail is not randomly distributed in a thunderstorm; instead it occurs in regions near the strong updraft. Supercell thunderstorms, in which the strongest updrafts are created with help from the mesocyclone, often produce the largest hail.
Eventually, though, the weight of the hailstone overcomes the strength of the updraft, and it falls to earth. The curtain of hailstones that falls below the cloud base is called the hailshaft. These regions are often said to appear green to observers on the ground, although recent research suggests that heavy rain as well as hail can create this optical phenomenon. As the storm moves, it generates a hailswath, a section of ground covered with hail.
Hailstorms can severely damage crops, automobiles, and roofs. Sometimes the swath can be so big you can see it on the ground from a satellite
Whether you've been following the Deepwater Horizon (BP) oil spill or not, if you like theater, have I got a show for you!
A friend turned me on to Macondo playing at the Guthrie theater through this weekend (last show is Sunday, Aug. 1st at 1:00pm). The play is A Guthrie Experience for Actors in Training production, so tickets are only $10/each. I've posted the Guthrie's description of the play below, but if you want more information or to reserve your tickets, click here.
"Macondo is a place of myth, a place where oil spills under and over water, creating a chain reaction that devastates human lives and animal habitats. It is also the name of the ruptured BP undersea oil field and oil well responsible for the current Gulf of Mexico spill. The gods awake from their slumber and intervene in this dramatically unfolding story that currently weaves itself through the fabric of our lives."
The National Research Council’s conceptual framework which will guide the development of next generation standards for science education has just been released (today) for public comment.
Tropical Storm Alex, which formed over the northwestern Caribbean Sea out of a westward-moving tropical wave on Friday and Saturday (June 26 and27), emerged overnight into the Bay of Campeche from the Yucatan Peninsula. Since emerging from that landmass as a tropical depression (signifying sustained winds weaker than 35 knots), it has strengthened back to Tropical Storm status. Current forecasts place it as a hurricane — possibly major — near the northern Mexico Gulf Coast later this week.
Courtesy National Center for Earth-surface DynamicsThe Mississippi River has turned out to be a big, muddy, silent hero in the fight to save Louisiana's wetlands from the oil spill.
It turns out that many scientists believe that the flow of fresh water from the Mississippi River into the Gulf of Mexico has thus far kept the oil slick offshore and out of wetlands.
Guerry Holm, a researcher with the National Center for Earth-surface Dynamics (NCED) tells me that the flow of the Mississippi River has been at a relatively high stage for the past two months and that the river's high volume of freshwater has acted as a hydrologic barrier, keeping oil from moving into the Mississippi Delta wetlands from the sea. Holms is now studying how two river characteristics—the slope of the water surface from the river delta to the sea and the time it takes water to move through a wetland to the sea—help mitigate oil contamination of the wetlands.
Holm is collaborating on the research with NCED Principal Investigator Robert Twilley, who is also busy addressing an immediate concern: the flow of the Mississippi tends to drop seasonally, starting in June. If that happens and Mississippi water flow into the delta decreases, Twilley, Holm, and others worry that oil will reach more of the wetlands sooner.
To address these concerns, some area scientists are proposing to shift the flow of water between the Mississippi and a river in Louisiana it feeds called the Atchafalaya. Twilley supports the idea: "We've been in conversation with U.S. Army Corps of Engineers and the state [of Louisiana] about how to manage the river as a protection system," Twilley reports.
Unfortunately, the river flow adjustments may be difficult to accomplish for political reasons. The diversion structure used to control flow between the Mississippi and Atchafalaya Rivers is controlled by Congress. Earlier proposals to send more water down the Mississippi have been met with resistance.