Public release date: 15-Jun-2012[ | E-mail |

Share ]
Contact: Mary Catherine Adams
mcadams@agu.org
202-777-7530
American Geophysical Union
The following highlights summarize research papers that have been recently
published in Geophysical Research Letters (GRL), and Journal of Geophysical
Research-Oceans (JGR-C).
In this release:
1. Measuring currents between North Atlantic and Nordic Seas
2. For first time, entire thermal infrared spectrum observed
3. Changing El Nino could reshape Pacific Ocean biology
4. Italian super-eruption larger than thought
5. Langmuir circulation inhibits near-surface water turbulence
6. Seasonal algae plays critical role in North Pacific carbon uptake
Anyone may read the scientific abstract for any already-published paper by
clicking on the link provided at the end of each Highlight. You can also read the
abstract by going to http://www.agu.org/pubs/search_options.shtml and inserting
into the search engine the full doi (digital object identifier), e.g.
10.1029/2012GL051269. The doi is found at the end of each Highlight below.
Journalists and public information officers (PIOs) at educational or scientific
institutions who are registered with AGU also may download papers cited in this
release by clicking on the links below. Instructions for members of the news
media, PIOs, and the public for downloading or ordering the full text of any
research paper summarized below are available at
http://www.agu.org/news/press/papers.shtml.
>
1. Measuring currents between North Atlantic and Nordic Seas
The fluxes of water from the North Atlantic to the Nordic Seas provide a measure
of the water that flows into and out of the global ocean as part of the meridional
overturning circulation. The meridional overturning circulation, which carries
warm water in the Atlantic from the tropics northward and brings cold dense
water back southward, is a key part of global ocean circulation and a strong
influence on climate; some research has suggested that the meridional overturning
circulation could slow down as the global climate warms. Using an acoustic
Doppler current profiler mounted in the high seas ferry Norrona to repeatedly
measure the currents in the Faroe-Shetland Channel and over the Iceland-Faroe
Ridge, Rossby and Flagg report on three years of weekly measurements that
provide a new, accurate measure of the exchange of water between the North
Atlantic to the Nordic Seas. The observations will be useful in understanding the
meridional overturning circulation.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051269, 2012
http://dx.doi.org/10.1029/2012GL051269
Title:
Direct measurement of volume flux in the Faroe-Shetland Channel and over the
Iceland-Faroe Ridge
Authors:
T. Rossby: Graduate School of Oceanography, University of Rhode Island,
Kingston, Rhode Island, USA;
C. N. Flagg: Marine Sciences, Stony Brook University, Stony Brook, New York,
USA.
2. For first time, entire thermal infrared spectrum observed
The driving mechanism of the greenhouse effect, and the underpinning of modern
anthropogenic warming, is the absorption, emission, and transmission of infrared
radiation by atmospheric gases. The heat-trapping ability of a gas depends on its
chemical composition, and each type of gas absorbs infrared radiation of different
energies. The amount of infrared radiation that escapes into space depends on the
net effect of the myriad gases in the atmosphere, with water vapor being the
primary gaseous absorber of infrared radiation. Water vapor absorbs a wide range
of infrared radiation, masking the effects of other gases. In fact, in many spectral
regions (or infrared radiation energy bands), water vapor is so strongly absorbing
that it makes testing the accuracy of infrared radiation absorption
parameterizations used in general circulation models difficult.
To surmount this obstacle, Turner et al. headed to a 5.3-kilometer (3.3-mile)
altitude site in the Atacama Desert in northern Chile, where the air is extremely
dry. Using a broad suite of spectroscopic equipment, they produce the first
ground-based measurement of the entire atmospheric infrared radiation absorption
spectrum-from 3.3 to 1000 micrometers-including spectral regions that are
usually obscured by strong water vapor absorption and emission. Though the data
collected will likely be valuable for a broad range of uses, the authors use their
measurements to verify the water vapor absorption parameterizations used in the
current generation of climate models.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051542, 2012
http://dx.doi.org/10.1029/2012GL051542
Title:
Ground-based high spectral resolution observations of the entire terrestrial
spectrum under extremely dry conditions
Authors:
D. D. Turner: National Severe Storms Laboratory, NOAA, Norman, Oklahoma,
USA;
E. J. Mlawer and J. S. Delamere: Atmospheric and Environmental Research, Inc.,
Lexington, Massachusetts, USA;
G. Bianchini and L. Palchetti: Istituto di Fisica Applicata "Nello Carrara, "
Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy;
M. P. Cadeddu: Argonne National Laboratory, Argonne, Illinois, USA;
S. Crewell and G. Maschwitz: Institut fur Geophysik und Meteorologie,
University of Cologne, Cologne, Germany;
R. O. Knuteson and D. C. Tobin: Space Science and Engineering Center,
University of Wisconsin-Madison, Madison, Wisconsin, USA;
M. Mlynzcak: NASA Langley Research Center, Hampton, Virginia, USA;
S. Paine: Smithsonian Astrophysical Observatory, Cambridge, Massachusetts,
USA.
3. Changing El Nino could reshape Pacific Ocean biology
Over the past few decades, the scientific understanding of El Nino has grown
increasingly complex. Traditionally viewed as a periodic warming focused largely
in the eastern equatorial Pacific Ocean, El Nino is associated with reduced
productivity in South American fisheries and changing temperature, pressure, and
rainfall patterns around the world. In the 1990s, however, researchers started to
notice a new kind of El Nino, one where anomalous ocean temperatures were
concentrated mainly in the central equatorial Pacific Ocean. This previously
unknown mode of variability, now termed the Central Pacific (CP) El Nino, in
contrast to the classical Eastern Pacific (EP) El Nino, has increased in frequency
and intensity over the past 30 years. Some scientists expect CP El Ninos to
become the dominant El Nino variant in response to global warming, so
understanding their differing effects is a pressing concern.
Comparing the major 1997-98 EP and 2009-10 CP El Nino events, Gierach et al.
determined the effect of each on surface ocean biology. Using a satellite-based
proxy measurement for phytoplankton biomass, they find that the EP event
brought about a strong decrease in both eastern and central Pacific biomass. The
CP event ties to a larger decline in central Pacific phytoplankton biomass but has
little effect on eastern Pacific activity. They find that during the CP event, strong
westerly winds brought warm nutrient-depleted waters to the central Pacific from
the west. For the EP El Nino, westerly winds weakened upwelling and vertical
mixing in the eastern Pacific, inhibiting the supply of nutrients from the
subsurface ocean. In both cases, a reduction in nutrient supply caused a drop in
productivity in the near-surface tropical waters. The authors suggest that a shift to
more frequent CP El Ninos in the future could alter ecosystem dynamics in the
equatorial Pacific Ocean, enhancing productivity in the eastern basin while
reducing it in the central basin.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051103, 2012
http://dx.doi.org/10.1029/2012GL051103
Title:
Biological response to the 1997-98 and 2009-10 El Nino events in the equatorial
Pacific Ocean
Authors:
Michelle M. Gierach and Tong Lee: Jet Propulsion Laboratory, California
Institute of Technology, Pasadena, California, USA;
Daniela Turk: Department of Oceanography, Dalhousie University, Halifax, Nova
Scotia, Canada and Lamont-Doherty Earth Observatory, Earth Institute at
Columbia University, Palisades, New York, USA;
Michael J. McPhaden: Pacific Marine Environmental Laboratory, NOAA, Seattle,
Washington, USA.
4. Italian super-eruption larger than thought
Recent research suggested that the super-eruption of the Campi Flegrei caldera
volcano in southern Italy about 40,000 years ago may have played a part in
wiping out, or forcing the migration of, the Neanderthal and modern human
populations in the eastern Mediterranean regions that were covered in ash. Now a
new modeling study by Costa et al. suggests that this eruption may have been
even larger than previously thought. This Campi Flegrei eruption produced a
widespread ash layer known as Campanian Ignimbrite (CI). Using ash thickness
measurements collected at 115 sites and a three-dimensional ash dispersal model,
the authors find that the CI super-eruption would have spread 250-300 cubic
kilometers (60-72 cubic miles) of ash across a 3.7-million-square-kilometer (1.4-
million-square-mile) region-2 to 3 times previous ash volume estimates.
The updated values stem from a new method of modeling what the wind would
have been like during the eruption. Traditionally, models assume a consistent
wind field for the entire duration of an eruption. The authors, however,
incorporate wind fields into the model that are based on 15 years of recent
measurements, using the modern wind field that best accounts for the ash deposit
measurements.
On the basis of their updated estimates, the authors calculate that up to 450
million kilograms (990 million pounds) of sulfur dioxide would have been spread
into the atmosphere, driving down temperatures by 1-2 degrees Celsius (1.8-3.6
degrees Fahrenheit) for 2 to 3 years. Further, sulfur dioxide and chloride
emissions would have triggered acidic rains, and fluorine-laden ash would have
become incorporated into plant matter, potentially inducing fluorosis, replete with
eye, tooth, and organ damage, in animal populations.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051605, 2012
http://dx.doi.org/10.1029/2012GL051605
Title:
Quantifying volcanic ash dispersal and impact of the Campanian Ignimbrite
super-eruption
Authors:
A. Costa: Environmental Systems Science Centre, University of Reading,
Reading, UK and Istituto Nazionale di Geofisica e Vulcanologia, sezione
"Osservatorio Vesuviano," Napoli, Italy;
A. Folch: Barcelona Supercomputing Center - Centro Nacional de
Supercomputacion, Barcelona, Spain;
G. Macedonio and R. Isaia: Istituto Nazionale di Geofisica e Vulcanologia,
sezione "Osservatorio Vesuviano," Napoli, Italy;
B. Giaccio: Istituto di Geologia Ambientale e Geoingegneria, CNR, Rome, Italy;
V. C. Smith: Research Laboratory for Archaeology and the History of Art,
University of Oxford, Oxford, UK.
5. Langmuir circulation inhibits near-surface water turbulence
In the surface ocean, breaking waves are a major source of air bubbles and
turbulent kinetic energy. During the presence of a consistent surface wind, these
wave-generated bubbles, along with other surface material like seaweed or foam,
can be drawn into long rows along the surface. Driving this organization is
Langmuir circulation, a phenomenon in which the wind and waves cause surface
waters to rotate helically, moving like a wire wrapped around a pole in the
windward direction. These spiral currents oscillate between left-handed and right-
handed rotations, such that in some places the surface waters are pushed together
and in others they are pulled apart. Researchers have previously found that at sites
of convergence the bubbles produced by breaking waves are pushed to depths of
15 meters (49 feet) or more, with important implications for air-sea gas mixing
and other processes.
Of interest to Gemmrich, however, is whether Langmuir circulation-induced
convergence also affects near-surface turbulent kinetic energy, the other product
of breaking waves. Using measurements taken from aboard the R/P Floating
Instrument Platform, a unique ship designed to deliberately flood itself to turn
into a stable floating research station, the author finds that Langmuir circulation
convergence zones suppressed turbulence in the near-surface ocean. The author
suggests that in convergence zones the wave-generated bubbles that had been
forced to depth would rise at varying rates, with large bubbles rising faster than
small bubbles. This would cause the ocean waters to become stratified by air
fraction. This stable stratification would, in turn, inhibit turbulence close to the
surface. The results suggest that in a convergence zone, buoyant particles
originating from a surface source-such as oil from a tanker spill-would get
trapped in the near-surface waters rather than be mixed to depth, the opposite of
what would have been previously assumed.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051691, 2012
http://dx.doi.org/10.1029/2012GL051691
Title:
Bubble-induced turbulence suppression in Langmuir circulation
Authors:
Johannes Gemmrich: Department of Physics and Astronomy, University of
Victoria, Victoria, British Columbia, Canada.
6. Seasonal algae plays critical role in North Pacific carbon uptake
The role of the North Pacific Ocean as a net carbon sink may prove to be more
precarious than previously thought as researchers work to isolate the contributions
of biological and physical processes to air-sea gas exchange. Scientists have long
known that physical processes, such as the seasonally changing solubility of
carbon dioxide in seawater, combine with a biological pump driven by seasonal
shifts in phytoplankton growth to control the carbon dioxide flux in the region. A
dearth of on-site evidence regarding biological pump function, however, has
prevented researchers from assessing the relative importance of either mechanism
to known carbon uptake rates. From data collected during four cruises from 2003
to 2008, Juranek et al. determined the strength of the biological pump, finding that
for the northern Pacific Ocean it was strong enough to counteract solubility
induced outgassing in summer, turning a net source region into a carbon sink.
The North Pacific is split into three sections: an anticyclonic subtropical gyre, a
cyclonic subarctic gyre, and a transition zone sandwiched between. Superimposed
on these largely stationary features, the transition zone chlorophyll front (TZCF)
travels from 30 degrees North in winter to 40 degrees North in summer. Using
dissolved gas concentration and isotope ratio detections, satellite measurements of
chlorophyll concentrations, and other data sources, the authors map the oxygen
and carbon dioxide budgets of the different North Pacific regions. They find that
in the TZCF, biological productivity was 2-4 times higher than in adjacent
regions. This spike was driven by the confluence of enhanced ocean mixing,
increased nutrient availability, and a change in the TZCF's algal ecosystem
composition. Owing to the newly realized power of the biological pump, the
authors suggest that understanding how North Pacific algal populations could be
affected by changing climate or hydrological conditions is a pressing concern.
Source:
Journal of Geophysical Research-Oceans, doi:10.1029/2011JC007450, 2012
http://dx.doi.org/10.1029/2011JC007450
Title:
Biological production in the NE Pacific and its influence on air-sea CO2 flux:
Evidence from dissolved oxygen isotopes and O2/Ar
Authors:
L. W. Juranek: College of Earth, Ocean, and Atmospheric Sciences, Oregon State
University, Corvallis, Oregon, USA;
P. D. Quay and D. Lockwood: School of Oceanography, University of
Washington, Seattle, Washington, USA;
R. A. Feely: NOAA Pacific Marine Environmental Laboratory, Seattle,
Washington, USA;
D. M. Karl and M. J. Church: School of Ocean and Earth Science and
Technology, University of Hawai'i at Manoa, Honolulu, Hawaii, USA.
###
Contact:
Mary Catherine Adams
Phone (direct): +1 202 777 7530
Email: mcadams@agu.org
![[ Back to EurekAlert! ]](http://www.eurekalert.org/images/back2e.gif)
[ | E-mail |

Share ]
?
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
Public release date: 15-Jun-2012[ | E-mail |

Share ]
Contact: Mary Catherine Adams
mcadams@agu.org
202-777-7530
American Geophysical Union
The following highlights summarize research papers that have been recently
published in Geophysical Research Letters (GRL), and Journal of Geophysical
Research-Oceans (JGR-C).
In this release:
1. Measuring currents between North Atlantic and Nordic Seas
2. For first time, entire thermal infrared spectrum observed
3. Changing El Nino could reshape Pacific Ocean biology
4. Italian super-eruption larger than thought
5. Langmuir circulation inhibits near-surface water turbulence
6. Seasonal algae plays critical role in North Pacific carbon uptake
Anyone may read the scientific abstract for any already-published paper by
clicking on the link provided at the end of each Highlight. You can also read the
abstract by going to http://www.agu.org/pubs/search_options.shtml and inserting
into the search engine the full doi (digital object identifier), e.g.
10.1029/2012GL051269. The doi is found at the end of each Highlight below.
Journalists and public information officers (PIOs) at educational or scientific
institutions who are registered with AGU also may download papers cited in this
release by clicking on the links below. Instructions for members of the news
media, PIOs, and the public for downloading or ordering the full text of any
research paper summarized below are available at
http://www.agu.org/news/press/papers.shtml.
>
1. Measuring currents between North Atlantic and Nordic Seas
The fluxes of water from the North Atlantic to the Nordic Seas provide a measure
of the water that flows into and out of the global ocean as part of the meridional
overturning circulation. The meridional overturning circulation, which carries
warm water in the Atlantic from the tropics northward and brings cold dense
water back southward, is a key part of global ocean circulation and a strong
influence on climate; some research has suggested that the meridional overturning
circulation could slow down as the global climate warms. Using an acoustic
Doppler current profiler mounted in the high seas ferry Norrona to repeatedly
measure the currents in the Faroe-Shetland Channel and over the Iceland-Faroe
Ridge, Rossby and Flagg report on three years of weekly measurements that
provide a new, accurate measure of the exchange of water between the North
Atlantic to the Nordic Seas. The observations will be useful in understanding the
meridional overturning circulation.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051269, 2012
http://dx.doi.org/10.1029/2012GL051269
Title:
Direct measurement of volume flux in the Faroe-Shetland Channel and over the
Iceland-Faroe Ridge
Authors:
T. Rossby: Graduate School of Oceanography, University of Rhode Island,
Kingston, Rhode Island, USA;
C. N. Flagg: Marine Sciences, Stony Brook University, Stony Brook, New York,
USA.
2. For first time, entire thermal infrared spectrum observed
The driving mechanism of the greenhouse effect, and the underpinning of modern
anthropogenic warming, is the absorption, emission, and transmission of infrared
radiation by atmospheric gases. The heat-trapping ability of a gas depends on its
chemical composition, and each type of gas absorbs infrared radiation of different
energies. The amount of infrared radiation that escapes into space depends on the
net effect of the myriad gases in the atmosphere, with water vapor being the
primary gaseous absorber of infrared radiation. Water vapor absorbs a wide range
of infrared radiation, masking the effects of other gases. In fact, in many spectral
regions (or infrared radiation energy bands), water vapor is so strongly absorbing
that it makes testing the accuracy of infrared radiation absorption
parameterizations used in general circulation models difficult.
To surmount this obstacle, Turner et al. headed to a 5.3-kilometer (3.3-mile)
altitude site in the Atacama Desert in northern Chile, where the air is extremely
dry. Using a broad suite of spectroscopic equipment, they produce the first
ground-based measurement of the entire atmospheric infrared radiation absorption
spectrum-from 3.3 to 1000 micrometers-including spectral regions that are
usually obscured by strong water vapor absorption and emission. Though the data
collected will likely be valuable for a broad range of uses, the authors use their
measurements to verify the water vapor absorption parameterizations used in the
current generation of climate models.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051542, 2012
http://dx.doi.org/10.1029/2012GL051542
Title:
Ground-based high spectral resolution observations of the entire terrestrial
spectrum under extremely dry conditions
Authors:
D. D. Turner: National Severe Storms Laboratory, NOAA, Norman, Oklahoma,
USA;
E. J. Mlawer and J. S. Delamere: Atmospheric and Environmental Research, Inc.,
Lexington, Massachusetts, USA;
G. Bianchini and L. Palchetti: Istituto di Fisica Applicata "Nello Carrara, "
Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy;
M. P. Cadeddu: Argonne National Laboratory, Argonne, Illinois, USA;
S. Crewell and G. Maschwitz: Institut fur Geophysik und Meteorologie,
University of Cologne, Cologne, Germany;
R. O. Knuteson and D. C. Tobin: Space Science and Engineering Center,
University of Wisconsin-Madison, Madison, Wisconsin, USA;
M. Mlynzcak: NASA Langley Research Center, Hampton, Virginia, USA;
S. Paine: Smithsonian Astrophysical Observatory, Cambridge, Massachusetts,
USA.
3. Changing El Nino could reshape Pacific Ocean biology
Over the past few decades, the scientific understanding of El Nino has grown
increasingly complex. Traditionally viewed as a periodic warming focused largely
in the eastern equatorial Pacific Ocean, El Nino is associated with reduced
productivity in South American fisheries and changing temperature, pressure, and
rainfall patterns around the world. In the 1990s, however, researchers started to
notice a new kind of El Nino, one where anomalous ocean temperatures were
concentrated mainly in the central equatorial Pacific Ocean. This previously
unknown mode of variability, now termed the Central Pacific (CP) El Nino, in
contrast to the classical Eastern Pacific (EP) El Nino, has increased in frequency
and intensity over the past 30 years. Some scientists expect CP El Ninos to
become the dominant El Nino variant in response to global warming, so
understanding their differing effects is a pressing concern.
Comparing the major 1997-98 EP and 2009-10 CP El Nino events, Gierach et al.
determined the effect of each on surface ocean biology. Using a satellite-based
proxy measurement for phytoplankton biomass, they find that the EP event
brought about a strong decrease in both eastern and central Pacific biomass. The
CP event ties to a larger decline in central Pacific phytoplankton biomass but has
little effect on eastern Pacific activity. They find that during the CP event, strong
westerly winds brought warm nutrient-depleted waters to the central Pacific from
the west. For the EP El Nino, westerly winds weakened upwelling and vertical
mixing in the eastern Pacific, inhibiting the supply of nutrients from the
subsurface ocean. In both cases, a reduction in nutrient supply caused a drop in
productivity in the near-surface tropical waters. The authors suggest that a shift to
more frequent CP El Ninos in the future could alter ecosystem dynamics in the
equatorial Pacific Ocean, enhancing productivity in the eastern basin while
reducing it in the central basin.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051103, 2012
http://dx.doi.org/10.1029/2012GL051103
Title:
Biological response to the 1997-98 and 2009-10 El Nino events in the equatorial
Pacific Ocean
Authors:
Michelle M. Gierach and Tong Lee: Jet Propulsion Laboratory, California
Institute of Technology, Pasadena, California, USA;
Daniela Turk: Department of Oceanography, Dalhousie University, Halifax, Nova
Scotia, Canada and Lamont-Doherty Earth Observatory, Earth Institute at
Columbia University, Palisades, New York, USA;
Michael J. McPhaden: Pacific Marine Environmental Laboratory, NOAA, Seattle,
Washington, USA.
4. Italian super-eruption larger than thought
Recent research suggested that the super-eruption of the Campi Flegrei caldera
volcano in southern Italy about 40,000 years ago may have played a part in
wiping out, or forcing the migration of, the Neanderthal and modern human
populations in the eastern Mediterranean regions that were covered in ash. Now a
new modeling study by Costa et al. suggests that this eruption may have been
even larger than previously thought. This Campi Flegrei eruption produced a
widespread ash layer known as Campanian Ignimbrite (CI). Using ash thickness
measurements collected at 115 sites and a three-dimensional ash dispersal model,
the authors find that the CI super-eruption would have spread 250-300 cubic
kilometers (60-72 cubic miles) of ash across a 3.7-million-square-kilometer (1.4-
million-square-mile) region-2 to 3 times previous ash volume estimates.
The updated values stem from a new method of modeling what the wind would
have been like during the eruption. Traditionally, models assume a consistent
wind field for the entire duration of an eruption. The authors, however,
incorporate wind fields into the model that are based on 15 years of recent
measurements, using the modern wind field that best accounts for the ash deposit
measurements.
On the basis of their updated estimates, the authors calculate that up to 450
million kilograms (990 million pounds) of sulfur dioxide would have been spread
into the atmosphere, driving down temperatures by 1-2 degrees Celsius (1.8-3.6
degrees Fahrenheit) for 2 to 3 years. Further, sulfur dioxide and chloride
emissions would have triggered acidic rains, and fluorine-laden ash would have
become incorporated into plant matter, potentially inducing fluorosis, replete with
eye, tooth, and organ damage, in animal populations.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051605, 2012
http://dx.doi.org/10.1029/2012GL051605
Title:
Quantifying volcanic ash dispersal and impact of the Campanian Ignimbrite
super-eruption
Authors:
A. Costa: Environmental Systems Science Centre, University of Reading,
Reading, UK and Istituto Nazionale di Geofisica e Vulcanologia, sezione
"Osservatorio Vesuviano," Napoli, Italy;
A. Folch: Barcelona Supercomputing Center - Centro Nacional de
Supercomputacion, Barcelona, Spain;
G. Macedonio and R. Isaia: Istituto Nazionale di Geofisica e Vulcanologia,
sezione "Osservatorio Vesuviano," Napoli, Italy;
B. Giaccio: Istituto di Geologia Ambientale e Geoingegneria, CNR, Rome, Italy;
V. C. Smith: Research Laboratory for Archaeology and the History of Art,
University of Oxford, Oxford, UK.
5. Langmuir circulation inhibits near-surface water turbulence
In the surface ocean, breaking waves are a major source of air bubbles and
turbulent kinetic energy. During the presence of a consistent surface wind, these
wave-generated bubbles, along with other surface material like seaweed or foam,
can be drawn into long rows along the surface. Driving this organization is
Langmuir circulation, a phenomenon in which the wind and waves cause surface
waters to rotate helically, moving like a wire wrapped around a pole in the
windward direction. These spiral currents oscillate between left-handed and right-
handed rotations, such that in some places the surface waters are pushed together
and in others they are pulled apart. Researchers have previously found that at sites
of convergence the bubbles produced by breaking waves are pushed to depths of
15 meters (49 feet) or more, with important implications for air-sea gas mixing
and other processes.
Of interest to Gemmrich, however, is whether Langmuir circulation-induced
convergence also affects near-surface turbulent kinetic energy, the other product
of breaking waves. Using measurements taken from aboard the R/P Floating
Instrument Platform, a unique ship designed to deliberately flood itself to turn
into a stable floating research station, the author finds that Langmuir circulation
convergence zones suppressed turbulence in the near-surface ocean. The author
suggests that in convergence zones the wave-generated bubbles that had been
forced to depth would rise at varying rates, with large bubbles rising faster than
small bubbles. This would cause the ocean waters to become stratified by air
fraction. This stable stratification would, in turn, inhibit turbulence close to the
surface. The results suggest that in a convergence zone, buoyant particles
originating from a surface source-such as oil from a tanker spill-would get
trapped in the near-surface waters rather than be mixed to depth, the opposite of
what would have been previously assumed.
Source:
Geophysical Research Letters, doi:10.1029/2012GL051691, 2012
http://dx.doi.org/10.1029/2012GL051691
Title:
Bubble-induced turbulence suppression in Langmuir circulation
Authors:
Johannes Gemmrich: Department of Physics and Astronomy, University of
Victoria, Victoria, British Columbia, Canada.
6. Seasonal algae plays critical role in North Pacific carbon uptake
The role of the North Pacific Ocean as a net carbon sink may prove to be more
precarious than previously thought as researchers work to isolate the contributions
of biological and physical processes to air-sea gas exchange. Scientists have long
known that physical processes, such as the seasonally changing solubility of
carbon dioxide in seawater, combine with a biological pump driven by seasonal
shifts in phytoplankton growth to control the carbon dioxide flux in the region. A
dearth of on-site evidence regarding biological pump function, however, has
prevented researchers from assessing the relative importance of either mechanism
to known carbon uptake rates. From data collected during four cruises from 2003
to 2008, Juranek et al. determined the strength of the biological pump, finding that
for the northern Pacific Ocean it was strong enough to counteract solubility
induced outgassing in summer, turning a net source region into a carbon sink.
The North Pacific is split into three sections: an anticyclonic subtropical gyre, a
cyclonic subarctic gyre, and a transition zone sandwiched between. Superimposed
on these largely stationary features, the transition zone chlorophyll front (TZCF)
travels from 30 degrees North in winter to 40 degrees North in summer. Using
dissolved gas concentration and isotope ratio detections, satellite measurements of
chlorophyll concentrations, and other data sources, the authors map the oxygen
and carbon dioxide budgets of the different North Pacific regions. They find that
in the TZCF, biological productivity was 2-4 times higher than in adjacent
regions. This spike was driven by the confluence of enhanced ocean mixing,
increased nutrient availability, and a change in the TZCF's algal ecosystem
composition. Owing to the newly realized power of the biological pump, the
authors suggest that understanding how North Pacific algal populations could be
affected by changing climate or hydrological conditions is a pressing concern.
Source:
Journal of Geophysical Research-Oceans, doi:10.1029/2011JC007450, 2012
http://dx.doi.org/10.1029/2011JC007450
Title:
Biological production in the NE Pacific and its influence on air-sea CO2 flux:
Evidence from dissolved oxygen isotopes and O2/Ar
Authors:
L. W. Juranek: College of Earth, Ocean, and Atmospheric Sciences, Oregon State
University, Corvallis, Oregon, USA;
P. D. Quay and D. Lockwood: School of Oceanography, University of
Washington, Seattle, Washington, USA;
R. A. Feely: NOAA Pacific Marine Environmental Laboratory, Seattle,
Washington, USA;
D. M. Karl and M. J. Church: School of Ocean and Earth Science and
Technology, University of Hawai'i at Manoa, Honolulu, Hawaii, USA.
###
Contact:
Mary Catherine Adams
Phone (direct): +1 202 777 7530
Email: mcadams@agu.org
![[ Back to EurekAlert! ]](http://www.eurekalert.org/images/back2e.gif)
[ | E-mail |

Share ]
?
AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.
steve jobs fbi file suge knight obama birth control mortgage settlement macauly culkin joe namath stefon diggs