Highlights, including authors and their institutions
The following highlights summarize research papers that have been recentlypublished in Geophysical Research Letters (GRL), Journal of GeophysicalResearch - Solid Earth (JGR-B), Journal of Geophysical Research - Oceans(JGR-C), and Water Resources Research (WRR).
In this release:
1. The pros and cons of trading water: A case study in Australia
2. Linking typhoon tracks with rainfall patterns and flood timing
3. Novel observations of currents and drag generated by a tsunami
4. More water stored along major rivers during El Nino years
5. Model suggests Earth is undergoing true polar wander
6. High-speed imagery captures new sea spray formation mechanism
Anyone may read the scientific abstract for any already-published paper byclicking on the link provided at the end of each Highlight. You can also read theabstract by going to http://www.agu.org/pubs/search_options.shtml and insertinginto the search engine the full doi (digital object identifier), e.g.10.1029/2012WR012140. The doi is found at the end of each Highlight below.
Journalists and public information officers (PIOs) at educational or scientificinstitutions who are registered with AGU also may download papers cited in thisrelease by clicking on the links below. Instructions for members of the newsmedia, PIOs, and the public for downloading or ordering the full text of anyresearch paper summarized below are available athttp://www.agu.org/news/press/papers.shtml.
1. The pros and cons of trading water: A case study in Australia
Water is a commodity, and water rights can be freely traded in an open market.Proponents of the free market approach argue that it leads to the most efficientallocation of water resources, as it would for any other commodity. However,unlike some commodities, water is critical for human life, for many humanactivities, and for environmental resources. When such an essential commoditybecomes scarce, as frequently happens in Australia, a land prone to sudden anddramatic droughts, severe problems can occur quickly. In Australia's MurrayDarling Basin, the country's largest agricultural region, the government hadhistorically controlled the distribution of water rights. However, under thesecontrols, a selected few controlled a large share of the water. To resolve thisproblem of overallocation, a free market approach was put in place in the early1990s.
Crase et al. summarize the advantages and possible pitfalls of the free marketapproach in the Murray Darling Basin. They suggest that making water rightsavailable in an open market generally had positive outcomes for the region; theapproach released the state controls, which allocated water inefficiently, andcreated a situation in which supply and demand dictate price, and farmers seem torespond efficiently.
However, the authors note that the free market approach could lead to speculation,in which some people who have little practical use for water rights hoard them todrive up the price, leaving less water available for others who might need it. Inconclusion, the authors advocate the free market-based approach but caution thatsuch a system also has the potential to create economic, social, environmental,and ecological problems.
Source:Water Resources Research, doi:10.1029/2012WR012140, 2012http://dx.doi.org/10.1029/2012WR012140
Title:Enhancing agrienvironmental outcomes: Market-based approaches to water inAustralia's Murray-Darling Basin
Authors:Lin Crase and Sue O'Keefe: Centre for Water Policy and Management, La TrobeUniversity, Victoria, Australia;Yukio Kinoshita: Faculty of Agriculture, Iwate University, Morioka, Japan.
2. Linking typhoon tracks with rainfall patterns and flood timing
Being able to predict the timing and amount of flooding during and following ahurricane or typhoon would improve early warning and mitigation efforts.However, variable typhoon tracks and interaction between typhoons and variedlandscapes make flood prediction challenging.
Huang et al. investigated the detailed distribution of typhoon-induced rainfall overa mesoscale mountainous watershed located in eastern Taiwan, a region that isregularly affected by severe typhoons-losses associated with typhoons inTaiwan can reach $500 million per year. The researchers analyzed high-resolutionradar observations of 38 rainfall events during 2000-2010 in eastern Taiwan tostudy the relationship between typhoon track, rainfall patterns, and the timing ofpeak flooding.
On the basis of the statistical characteristics of these events, they identify threedifferent types of rainfall patterns. They find that the different types of rainfallpatterns are correlated with different typhoon tracks and linked flood peak timesto the rainfall types and typhoon tracks. For instance, the peak flood time for oneof their identified rainfall patterns - a pattern with an approximately north-northeast-south-southwest oriented rainfall belt across the downstream area of thewatershed they studied - was 3 hours earlier than peak flood time for otherrainfall patterns.
They suggest that the relationships are due to the typhoons' interaction with themountainous landscape in the region. Their study could lead to improved real-time flood warning systems in Taiwan and other typhoon-prone regions.
Source:Water Resources Research, doi:10.1029/2011WR011508, 2012http://dx.doi.org/10.1029/2011WR011508
Title:Linking typhoon tracks and spatial rainfall patterns for improving flood lead timepredictions over a mesoscale mountainous watershed
Authors:Jr-Chuan Huang, Jun-Yi Lee, and Tsung-Yu Lee: Department of Geography,National Taiwan University, Taipei, Taiwan;
Cheng-Ku Yu and Lin-Wen Cheng: Department of Atmospheric Sciences,Chinese Culture University, Taipei, Taiwan;
Shuh-Ji Kao: Research Center for Environmental Changes, Academia Sinica,Taipei, Taiwan, and State Key Laboratory of Marine Environmental Science,Xiamen University, Xiamen, China.
3. Novel observations of currents and drag generated by a tsunami
Tsunamis cause damage even after they have traveled thousands of kilometersfrom their sources, and much of the damage is through generation of local strongcurrents. Even though wave heights of tsunamis that have traveled long distancesare no greater than those of local tides or waves, tsunamis modify currents,resulting in unusually strong pulses of mixing, transport, and seiching (standingwaves in enclosed water bodies). Seiching is common and is the most destructivehazard, particularly along narrow bays and harbors.
In a new description of currents and sediment transport associated with a tsunami,Lacy et al. studied water height, currents, and suspended sediment concentrationsin the Monterey Bay, California, where a tsunami set off by a magnitude 8.8earthquake off the coast of Chile on 27 February 2010 arrived approximately 14hours later, causing strong seiching. Studying vertical velocity profiles of thetsunami waves reaching the inner shelf at Monterey Bay, the authors show thatthe friction from the shelf bed vastly affected the tsunami currents, and the beddrag coefficient varied with time. The observation is contrary to assumptionsbehind the common practice of using depth-averaged models to simulate tsunamisin the near-shore region.
The authors find that in the 10-meter (32.8-foot) deep study sites in the MontereyBay area, the largest tsunami wave vastly increased sediment transport toward theshore. On the other hand, the strong currents that lasted for several days followingthe seiche enhanced sediment transport along the shore. The tsunami generatedshear stress strong enough to entrain the sandy seafloor of the study site. Such in-depth understanding of the vertical structure of tsunami currents, and theirinteraction with the seafloor, is critical for improving the prediction of the passageof tsunamis across the inner shelf.
Source:Journal of Geophysical Research-Oceans, doi:10.1029/2012JC007954, 2012http://dx.doi.org/10.1029/2012JC007954
Title:Currents, drag, and sediment transport induced by a tsunami thawing
Authors:Jessica R. Lacy and David M. Rubin: U.S. Geological Survey, Pacific ScienceCenter, Santa Cruz, California, USA;
Daniel Buscombe: School of Marine Science and Engineering, University ofPlymouth, Plymouth, UK.
4. More water stored along major rivers during El Nino years
El Nino-Southern Oscillation (ENSO) - the semiperiodic climate eventassociated with warming sea surface temperatures off the coast of Peru - notonly disrupts atmospheric circulations, dramatically altering weather patternsacross the globe, but also may be determining the amount of fresh water stored oncontinents in tropical rainforests, according to a new study.
Phillips et al. used more than seven years of satellite-based observations of freshwater content of continents from the Gravity Recovery and Climate Experiment(GRACE) to show that between 2003 and 2010 the amount of fresh water storedon land (in terms of rain water, river water, lake, ground water, and snow)between the 15-degree north and 15-degree south latitudes depends on El Nino-Southern Oscillation. The authors also find that the effect of ENSO is strongest onland areas adjacent to the Pacific Ocean. The maximum increase in the amount ofstored fresh water on land was observed during El Nino years along major rivervalleys in the Borneo region of southeast Asia, the Amazon, the Congo, and theYangzte and Met Cong in China.
The authors suggest that these findings are not surprising given thatmeteorological conditions within 15 degrees north and 15 degrees south aresensitive to the location of the intertropical convergence zone (ITCZ) - a zone oflow pressure that brings heavy convective rainfall along the tropics; its location issensitive to the same ocean temperatures and atmospheric circulation patterns thatENSO disrupts. The authors feel confident that as more data become available, itwould be possible to predict water storage in other regions of the world,particularly in the Arctic region, where their preliminary study suggests that iceloss could be associated with El Nino events.
Source:Geophysical Research Letters, doi:10.1029/2012GL052495, 2012http://dx.doi.org/10.1029/2012GL052495
Title:The influence of ENSO on global terrestrial water storage using GRACE
Authors:T. Phillips: Department of Aerospace Engineering, University of Colorado atBoulder, Boulder, Colorado, USA, Colorado Center for Astrodynamics Research,University of Colorado at Boulder, Boulder, Colorado, USA, and Earth SystemObservation Center, University of Colorado at Boulder, Boulder, Colorado, USA;
R. S. Nerem: Department of Aerospace Engineering, University of Colorado atBoulder, Boulder, Colorado, USA, Colorado Center for Astrodynamics Research,University of Colorado at Boulder, Boulder, Colorado, USA, and CooperativeInstitute for Research in Environmental Science, University of Colorado atBoulder, Boulder, Colorado, USA;
Baylor Fox-Kemper: Cooperative Institute for Research in EnvironmentalScience, University of Colorado at Boulder, Boulder, Colorado, USA, andDepartment of Atmospheric and Ocean Sciences, University of Colorado atBoulder, Boulder, Colorado, USA;
J. S. Famiglietti: Center for Hydrologic Modeling, University of California,Irvine, California, USA, and Department of Earth System Science, University ofCalifornia, Irvine, California, USA;
B. Rajagopalan: Cooperative Institute for Research in Environmental Science,University of Colorado at Boulder, Boulder, Colorado, USA, and Department ofCivil, Environmental and Architectural Engineering, University of Colorado atBoulder, Boulder, Colorado, USA.
5. Model suggests Earth is undergoing true polar wander
At various points throughout Earth's history, the planet's solid exterior has driftedabout in relation to the planetary rotation axis. This solid body drift, which isknown as "true polar wander," results in a wholesale shift in the orientation ofEarth's landmasses and is different from the motion of individual tectonic plates("tectonic drift") or of the magnetic pole ("apparent polar wander").
Sorting out when, in which direction, and at what rate the Earth's solid exteriorhas rotated in this way depends on having a stable frame of reference to whichobservations of relative motion can be compared. To develop such a frame,researchers rely on hot spots, regions of recurrent volcanism that are known toproduce long, largely linear island chains - such as the Hawaiian islands - asan overlying tectonic plate passes overhead. Hot spots are fed by magma plumesfrom the deep mantle and hence tend to be long-lived and relatively stable. Hotspots have long been used to understand the motion of tectonic plates.
Traditionally, scientists have treated hot spots as completely static features. Butby allowing hot spots' positions to slowly drift, Doubrovine et al. produced amodel of a stable reference frame that better matched observations of hot spottracks - the path drawn by each hot spot's island chain. Based on their newreference frame, which they consider accurate for the past 120 million years, theauthors identify four possible instances of true polar wander, including two inwhich the solid Earth traveled back and forth by nearly 9 degrees from 90 to 40million years ago. Further, they suggest that for the past 40 million years theEarth's solid outer layers have been slowly rotating at a rate of 0.2 degrees everymillion years.
Source:Journal of Geophysical Research - Solid Earth, doi:10.1029/2011JB009072,2012http://dx.doi.org/10.1029/2011JB009072
Title:Absolute plate motions in a reference frame defined by moving hot spots in thePacific, Atlantic and Indian oceans
Authors:Pavel V. Doubrovine: Physics of Geological Processes, University of Oslo,Norway and Center for Advanced Study, Norwegian Academy of Science andLetters, Oslo, Norway;
Bernhard Steinberger: Helmholtz Center Potsdam, GFZ German Research Centerfor Geosciences, Potsdam, Germany, Physics of Geological Processes, Universityof Oslo, Norway, and Center for Advanced Study, Norwegian Academy ofScience and Letters, Oslo, Norway;
Trond H. Torsvik: Physics of Geological Processes, University of Oslo, Norway,Center for Advanced Study, Norwegian Academy of Science and Letters, Oslo,Norway, Center for Geodynamics, Geological Survey of Norway, and School ofGeosciences, University of Witwatersrand, South Africa.
6. High-speed imagery captures new sea spray formation mechanism
When strong winds blow over ocean waves, small droplets of sea spray rise intothe air, enhancing the exchange of heat, mass, and energy between the air and thesea. How effective sea spray is at mediating each of these dynamics depends onthe rate at which droplets are created and the drop size distribution of the mist.Unfortunately, research has been limited by a dearth of observational evidencethat could explain the details of sea spray generation, including understanding thedrop size distribution or the effects of different wind speeds. Previous researchwith high-speed cameras aiming to capture the moment of drop formation waslimited by camera resolutions too low to see all but the largest drops.
Updating this previous line of work with improved technology, Veron et al.measured the formation of freshwater sea spray in a wave tank that also hadcontrollable wind. The authors tested three different wind speeds: 31.3, 41.2, and47.1 meters per second (70, 92.2, and 105.3 miles per hour), which equates totropical storm strength winds up to a category 1 hurricane on the Saffir-Simpsonscale. They used two different cameras: a high-speed camera that captured 1,000frames per second and allowed them to observe spray-forming dynamics, and ahigh-resolution camera that let them observe droplets as small as 140micrometers (0.006 inches). The authors find a higher abundance of large drops, those above amillimeter (0.04 inches) in diameter, than is expected by theoretical work. Further, they alsoidentify a novel spray formation mechanism whereby strong winds cause a thinsheet of water from the crest of a wave to fill up like a balloon and burst in aspray of droplets, a mechanism which they suggest may be applicable only forhurricane force winds.
Source:Geophysical Research Letters, doi:10.1029/2012GL052603, 2012http://dx.doi.org/10.1029/2012GL052603
Title:Sea spray spume droplet production in high wind speeds
Authors:F. Veron, E. L. Harrison, and J. A. Mueller: School of Marine Science and Policy,University of Delaware, Newark, Delaware, USA;
C. Hopkins: School of Earth and Atmospheric Sciences, Georgia Institute ofTechnology, Atlanta, Georgia, USA.
Source: American Geophysical Union