May 12, 2003
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Contents of this News Tip:
Hurricanes at the Equator: "Impossible Perfect Storm" Observed
ARLINGTON, Va.—Hurricanes cannot form near the equator, or so meteorology textbooks maintain. But a storm named Typhoon Vamei upended scientists' thinking when it swirled above the equator in the South China Sea near Singapore on December 27, 2001. It formed so close to the equator that its winds howled in both hemispheres.
New research funded by the National Science Foundation (NSF) and the U.S. Navy's Office of Naval Research reveals the unusual mechanism for the birth of such a storm.
Intense thunderstorms over expanses of warm ocean water roil the atmosphere. Earth's rotation spins these storms through the Coriolis Effect, a deflection that results in storms whirling counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
The quiescent region for this force (much like the "eye" of a hurricane) is at the equator, so researchers once believed nascent storms in this region could not build the power to start spinning. Before Typhoon Vamei (hurricanes are called typhoons when they form over the Pacific Ocean), no hurricane in recorded history had formed within 200 miles of the equator.
"Typhoon Vamei happened because of two interacting systems, a weak circulation that formed over Borneo and drifted into the southern tip of the South China Sea and remained there, and a strong and persistent northeast wind surge that turned as it crossed the equator and created a large background rotation," explained NSF-awardee C.P. Chang, a meteorologist at the Naval Postgraduate School in Monterey, Calif. Chang collaborated with meteorologists C.H. Liu from the Chinese Culture University and H.C. Kuo from the National Taiwan University, both sponsored by Taiwan's National Science Council.
"The mechanism we identified raises additional questions," remarked Chang. "Both the wind surge and the Borneo thunderstorms are common features of the winter monsoon. Why was an equatorial cyclone not observed before?"
From analyses of weather model and satellite data, the researchers found that the land-sea terrain in the equatorial South China Sea, while necessary for strengthening and turning the cross-equatorial wind surge, also places a time constraint on the confluence of events that occurred in December of 2001. Nonetheless, Vamei still wreaked havoc: U.S. Navy ships were damaged by the typhoon, and the southern Malay Peninsula was flooded by storm surges from its 87-mile-per-hour winds.
"When something like this happens—intense background winds wrapping around a weak disturbance that lingers over warm ocean waters—and that vortex starts to spin with no help from Earth's rotation, unlikely factors have come together," said Chang. "What you have then is just about 'the perfect storm.' The probability of a similar equatorial development is estimated to be once every 100 to 400 years, and it probably cannot happen outside the southern South China Sea." [Cheryl Dybas]
NSF Science Expert: Pam Stephens, email@example.com
NSF Principal Investigator: C. P. Chang, firstname.lastname@example.org
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Rapid Release of Sea-Floor Methane Caused Extreme Global Warming 55 Million Years Ago
ARLINGTON, Va.—Scientists have just returned from two months at sea aboard the oceanographic drill ship JOIDES Resolution where they studied the effects of a larger than expected methane release 55 million years ago that may have caused extreme global warming.
In March, the scientists traveled to a site near Walvis Ridge—an ancient submarine mountain chain off Africa—as part of the NSF-supported Ocean Drilling Program (ODP) Leg 208. The researchers searched for evidence of roughly 2,000 gigatons of methane they believe escaped into the ocean and atmosphere to cause the Paleocene-Eocene Thermal Maximum, an extreme global warming event that is unique in Earth history in both magnitude and rate of warming.
Sediments far below the seafloor hold clues to the cause of this warming. Evidence for the dissolution of methane was recorded in debris that settled, layer by layer, on the ocean floor over thousands of years.
Cores of sediment brought up from the study site suggested a significant amount of methane dissolution, said ODP scientist Jim Zachos of the University of California at Santa Cruz, perhaps twice the original estimate.
"It far exceeds what has been estimated by models, assuming a release of 2,000 gigatons of methane," added Dick Kroon of Vrije Universiteit Amsterdam, a fellow researcher aboard JOIDES Resolution.
The initial results also suggest that Earth's recovery to a "normal state" took as long as 100,000 years.
Geochemists speculate that the methane escaped from sea-floor clathrates, methane-trapping ice-crystals that are distributed in sediments on the outer edges of continental margins worldwide. For reasons that remain unknown, the clathrates suddenly began to decompose on a massive scale at the time of the Paleocene-Eocene Thermal Maximum, increasing the amount of methane in the atmosphere and oceans.
The rapid release of so much methane, and the methane's oxidation to carbon dioxide, would have significantly altered ocean chemistry, and ultimately the atmosphere and global climate. The process appears to have lasted for a period of 40,000 years, scientists say, warming Earth by more than five degrees Celsius.
"We suspect the melting of clathrates and subsequent rapid release of methane was initiated by a gradual warming that pushed the climate system across a threshold," said Zachos. Once started, the release of methane and the resultant warming likely fueled the release of more methane, a phenomenon of concern for future global climate change, he added.
ODP is an international partnership of scientists and research institutions organized to study the evolution and structure of the Earth. It is funded by NSF with substantial contributions from international partners. [Cheryl Dybas]
NSF Science Expert: Bruce Malfait, email@example.com
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New DNA Probe Becomes Learning Tool for Undergraduates
ARLINGTON, Va.—Cutting-edge laboratory techniques and undergraduate chemistry courses do not always go hand in hand. However, last fall, chemistry majors at Georgia Tech were able to create and use a DNA probe that has only recently been described in a major journal. The technique, part of a research program to develop new sensor materials, introduces students to a number of sophisticated laboratory techniques.
Mira Josowicz, principal research scientist in Georgia Tech's School of Chemistry and Biochemistry, helped develop the DNA technique and uses it in her advanced chemistry laboratory, a "capstone class" required for all chemistry majors. Josowicz and Jiri Janata, Eminent Scholar of the Georgia Research Alliance in the School of Chemistry and Biochemistry, published the technique in the January Journal of the American Chemical Society.
"During the course, the students are introduced to many new techniques they haven't confronted during their studies," Josowicz said. "The experiment can vary many parameters, so there are always surprises. It's really new research each time for the students as well as for me."
DNA comprises two intertwined strands of bases, and each base in one strand is matched with its complement in the other strand. Taking advantage of DNA's natural preference to exist as intertwined strands, a DNA probe uses one single-stranded length of amino acids to detect the presence of the complementary strand that is under investigation.
The students start with standard platinum electrodes and deposit a layer of a material called polypyrrole. Polypyrrole is a "conducting polymer," one of a class of versatile materials whose electronic properties can be exploited in electric circuits, sensors and batteries.
In this case, the sensors use electric current to control the flow of negatively charged ions into and out of the polymer. Various techniques have used this behavior and DNA's negative charge to create sensors that detect the presence of matching DNA. However, previous methods have chemically bonded the single-stranded DNA within the polymer film and risk damaging the strands. Damaged DNA strands will not bind correctly with their complements.
In Josowicz's and Janata's technique, which originated from a master's thesis project by Liz Thompson, a second, non-conducting polymer layer is deposited on the polypyrrole. The second polymer's molecules have negatively charged appendages, and positively charged magnesium ions are used to link the probe DNA strands to these appendages. The DNA strands hinder the exchange of negatively charged chloride ions with the polypyrrole. The students measure the "electronic signature" of this effect when voltage is applied to the prepared electrode.
Next, the prepared electrode is dipped into a buffer solution containing possible matching DNA strands. If complementary DNA strands are present, they bind to the DNA strands on the electrode, increasing the negative charge on the polypyrrole surface. As a result, the flow of chloride ions is hindered even further, which causes a corresponding change in the electronic signature. Non-complementary DNA strands produce no change in the signature.
"In the course of this work the students perform and learn electrochemical experiments and ultraviolet spectrometry of DNA," Janata said. "Because every DNA they are given behaves slightly differently, there is always an element of exciting 'unknown' behavior for the students." [David Hart]
NSF Media Contact: David Hart, 703-292-8070, firstname.lastname@example.org
NSF Program Officer: Steven L. Bernasek, 609-258-4986, email@example.com
NSF Principal Investigator: Jiri Janata, 404-894-4828, firstname.lastname@example.org
and co-PI Mira Josowicz, 404-894-4032, email@example.com
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