The Mars Dust Cycle: Investigating the Effects of Radiatively Active Water Ice Clouds on Surface Stresses and Dust Lifting Potential with the NASA Ames Mars General Circulation Model

NASA Technical Reports Server (NTRS)

Kahre, Melinda A.; Hollingsworth, Jeffery

2012-01-01

The dust cycle is a critically important component of Mars' current climate system. Dust is present in the atmosphere of Mars year-round but the dust loading varies with season in a generally repeatable manner. Dust has a significant influence on the thermal structure of the atmosphere and thus greatly affects atmospheric circulation. The dust cycle is the most difficult of the three climate cycles (CO2, water, and dust) to model realistically with general circulation models. Until recently, numerical modeling investigations of the dust cycle have typically not included the effects of couplings to the water cycle through cloud formation. In the Martian atmosphere, dust particles likely provide the seed nuclei for heterogeneous nucleation of water ice clouds. As ice coats atmospheric dust grains, the newly formed cloud particles exhibit different physical and radiative characteristics. Thus, the coupling between the dust and water cycles likely affects the distributions of dust, water vapor and water ice, and thus atmospheric heating and cooling and the resulting circulations. We use the NASA Ames Mars GCM to investigate the effects of radiatively active water ice clouds on surface stress and the potential for dust lifting. The model includes a state-of-the-art water ice cloud microphysics package and a radiative transfer scheme that accounts for the radiative effects of CO2 gas, dust, and water ice clouds. We focus on simulations that are radiatively forced by a prescribed dust map, and we compare simulations that do and do not include radiatively active clouds. Preliminary results suggest that the magnitude and spatial patterns of surface stress (and thus dust lifting potential) are substantial influenced by the radiative effects of water ice clouds.

The climate of Mars

NASA Astrophysics Data System (ADS)

Haberle, R. M.

1986-05-01

The composition of the primitive Martian atmosphere and its development into the present environment are described. The primitive atmosphere consisted of water vapor, carbon dioxide, and nitrogen released from rocks; the greenhouse effect which maintained the surface temperature above the frost point of water is examined. Volcanic activity reduced the greenhouse effect and along with CO2 removal from the atmosphere caused a lowering of the planet temperature. The global circulation patterns on earth and Mars are compared; the similarities in the circulation patterns and Mars' seasonal variations are studied. The carbon dioxide and water cycles on Mars are analyzed; the carbon dioxide cycle determines seasonal variations in surface pressure and the behavior of the water cycle. The behavior of the atmospheric dust and the relationship between the seasonal dust cycle and Hadley circulation are investigated. The periodic variations in the three orbital parameters of Mars, which affect the climate by changing the seasonal and latitudinal distribution of incoming solar energy are discussed

Surface water subduction during a downwelling event in a semienclosed bay

NASA Astrophysics Data System (ADS)

Barton, E. D.; Torres, R.; Figueiras, F. G.; Gilcoto, M.; Largier, J.

2016-09-01

The Ría de Vigo is a bay strongly influenced by upwelling-downwelling cycles along the adjacent coast of NW Iberia. Moored and ship-board observations during September 2006 showed that subduction, initially associated with an estuarine circulation, strengthened when a strong downwelling circulation, resulting from northward wind over the coastal ocean, was generated in the outer Ría causing ambient waters to be advected outward in the lower layer. Incoming surface waters confined the estuarine circulation to the shallow interior and displaced isopleths downward through the water column at ˜10 m d-1. As the estuarine circulation retreated inward, strong flow convergence developed between middle and inner ria in the layer above 15 m, while divergence developed beneath. The convergence increased through the period of downwelling-favorable wind at a rate consistent with the observed isopleth displacement velocities. The coefficient of turbulent diffusion Kt, from a microstructure profiler, indicated that mixing was strong in the estuarine circulation and subsequently in the downwelling zone, where localized instabilities and temperature-salinity inversions were observed. During the downwelling, concentrations of phytoplankton, including potentially harmful species, increased, especially in the middle and inner ria, as a result of inward advection, subduction, and the ability of the dinoflagellates to maintain their position in the water column by swimming. In the course of the 5 day event, the water mass of all but the innermost Ría was flushed completely and replaced by waters originating in the coastally trapped poleward flow along the Atlantic coastline.

Atlantic Ocean Circulation and Climate: The Current View From the Geological Record

NASA Astrophysics Data System (ADS)

Curry, W.

2006-12-01

Several recent advances in our understanding of past ocean circulation come from geological reconstructions using deep sea sediment proxies of water mass structure and flow. Put together, the observations suggest that the Atlantic Ocean during the last glacial period (21,000 years ago) was very different from today. Geochemical tracers document a shoaling of North Atlantic Deep Water and a much greater volume of deep waters with an Antarctic origin. Sedimentary pore water profiles have detected a reversal in the salinity gradient between northern and southern deep water sources. Uranium-series decay products in North Atlantic sediments indicate that the southward transport of North Atlantic Deep Water was as much as 30-40% reduced from today's transport. Ocean-margin density reconstructions are consistent with a one third reduction in transport through the Florida Straits. A reversed cross-basin density gradient in the South Atlantic calls for a different intermediate water circulation in the South Atlantic. The glacial Atlantic circulation appears to be best explained by a reduced influence of North Atlantic deep water sources and much greater influence of Antarctic deep water sources. More recent changes in Atlantic circulation have been much more modest. During the Little Ice Age (LIA - a much smaller cooling event about 200 to 600 years ago), transport of the Florida Current was reduced by about 10%, significant but a much smaller reduction than observed during the glacial period. There is little evidence for a change in the distribution or geochemistry of the water masses during the LIA. For both climate events (the glacial and the LIA) reduced Florida Current transport was accompanied by increased salinity of its surface waters, linking changes in ocean circulation to large scale changes in surface water hydrology. A feedback between the circulation of the Atlantic Ocean and the climate of the tropics has been proposed before and also seen in some coupled climate models: variations in the temperature gradients in the Atlantic basin affect the position of the Intertropical Convergence Zone and alter evaporation and precipitation patterns in the tropics. The salinity anomalies caused by these atmospheric shifts eventually are transported back to high latitudes by ocean circulation (Vellinga and Wu, 2004). Several recent geological reconstructions appear to observe such a coupling on centennial and millennial time scales.

Global Ocean Circulation in Thermohaline Coordinates and Small-scale and Mesoscale mixing: An Inverse Estimate.

NASA Astrophysics Data System (ADS)

Groeskamp, S.; Zika, J. D.; McDougall, T. J.; Sloyan, B.

2016-02-01

I will present results of a new inverse technique that infers small-scale turbulent diffusivities and mesoscale eddy diffusivities from an ocean climatology of Salinity (S) and Temperature (T) in combination with surface freshwater and heat fluxes.First, the ocean circulation is represented in (S,T) coordinates, by the diathermohaline streamfunction. Framing the ocean circulation in (S,T) coordinates, isolates the component of the circulation that is directly related to water-mass transformation.Because water-mass transformation is directly related to fluxes of salt and heat, this framework allows for the formulation of an inverse method in which the diathermohaline streamfunction is balanced with known air-sea forcing and unknown mixing. When applying this inverse method to observations, we obtain observationally based estimates for both the streamfunction and the mixing. The results reveal new information about the component of the global ocean circulation due to water-mass transformation and its relation to surface freshwater and heat fluxes and small-scale and mesoscale mixing. The results provide global constraints on spatially varying patterns of diffusivities, in order to obtain a realistic overturning circulation. We find that mesoscale isopycnal mixing is much smaller than expected. These results are important for our understanding of the relation between global ocean circulation and mixing and may lead to improved parameterisations in numerical ocean models.

Exchange of Laptev Sea and Arctic Ocean halocline waters in response to atmospheric forcing

NASA Astrophysics Data System (ADS)

Bauch, D.; Dmitrenko, I. A.; Wegner, C.; HöLemann, J.; Kirillov, S. A.; Timokhov, L. A.; Kassens, H.

2009-05-01

Combined δ18O/salinity data reveal a distinctive water mass generated during winter sea ice formation which is found predominantly in the coastal polynya region of the southern Laptev Sea. Export of the brine-enriched bottom water shows interannual variability in correlation with atmospheric conditions. Summer anticyclonic circulation is favoring an offshore transport of river water at the surface as well as a pronounced signal of brine-enriched waters at about 50 m water depth at the shelf break. Summer cyclonic atmospheric circulation favors onshore or an eastward, alongshore water transport, and at the shelf break the river water fraction is reduced and the pronounced brine signal is missing, while on the middle Laptev Sea shelf, brine-enriched waters are found in high proportions. Residence times of bottom and subsurface waters on the shelf may thereby vary considerably: an export of shelf waters to the Arctic Ocean halocline might be shut down or strongly reduced during "onshore" cyclonic atmospheric circulation, while with "offshore" anticyclonic atmospheric circulation, brine waters are exported and residence times may be as short as 1 year only.

Effects of a Circulating-water Garment and Forced-air Warming on Body Heat Content and Core Temperature

PubMed Central

Taguchi, Akiko; Ratnaraj, Jebadurai; Kabon, Barbara; Sharma, Neeru; Lenhardt, Rainer; Sessler, Daniel I.

2005-01-01

Background: Forced-air warming is sometimes unable to maintain perioperative normothermia. We therefore compared heat transfer, regional heat distribution, and core rewarming of forced-air warming with a novel circulating-water garment. Methods: Nine volunteers were each evaluated on two randomly ordered study days. They were anesthetized and cooled to a core temperature near 34°C. The volunteers were subsequently warmed for 2.5 hours with either a circulating-water garment or forced-air cover. Overall, heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Average arm and leg (peripheral) tissue temperatures were determined from 18 intramuscular needle thermocouples, 15 skin thermal flux transducers, and “deep” arm and foot thermometers. Results: Heat production (≈ 60 kcal/h) and loss (≈45 kcal/h) were similar with each treatment before warming. The increase in heat transfer across anterior portions of the skin surface was similar with each warming system (≈65 kcal/h). Forced-air warming had no effect on posterior heat transfer whereas circulating-water transferred 21 ± 9 kcal/h through the posterior skin surface after a half hour of warming. Over 2.5 h, circulating-water thus increased body heat content 56% more than forced air. Core temperatures thus increased faster than with circulating water than forced air, especially during the first hour, with the result that core temperature was 1.1 ± 0.7°C greater after 2.5 h (P < 0.001). Peripheral tissue heat content increased twice as much as core heat content with each device, but the core-to-peripheral tissue temperature gradient remained positive throughout the study. Conclusions: The circulating-water system transferred more heat than forced air, with the difference resulting largely from posterior heating. Circulating water rewarmed patients 0.4°C/h faster than forced air. A substantial peripheral-to-core tissue-temperature gradient with each device indicated that peripheral tissues insulated the core, thus slowing heat transfer. PMID:15114200

Comet assay and micronucleus test in circulating erythrocytes of Cyprinus carpio specimens exposed in situ to lake waters treated with disinfectants for potabilization.

PubMed

Buschini, A; Martino, A; Gustavino, B; Monfrinotti, M; Poli, P; Rossi, C; Santoro, M; Dörr, A J M; Rizzoni, M

2004-02-14

The detection of a possible genotoxic effect of surface water treated with disinfectants for potabilization is the aim of the present work. The Comet assay and the micronucleus test were applied in circulating erythrocytes of Cyprinus carpio. Young specimens (20-30 g) were exposed in experimental basins, built within the potabilization plant of Castiglione del Lago (Perugia, Italy). In this plant the water of the Trasimeno Lake is treated and disinfected for potabilization before it is distributed to the people in the net of drinkable water. A continuous flow of water at a constant rate was supplied to basins; the water was continuously treated at a constant concentration with one of the three tested disinfectants (sodium hypochlorite, peracetic acid and chloride dioxide), one control basin being supplied with untreated water. Three sampling campaigns were performed: October 2000, February 2001 and June 2001. Repeated blood samplings through intracardiac punctures allowed to follow the same fish populations after different exposure times: before introduction of the disinfectant, and 10 or 20 days afterwards. An additional blood sampling was performed 3 h after addition of the disinfectant in other, simultaneously exposed, fish populations. Genotoxic damage was shown in fish exposed to water disinfected with sodium hypochlorite and chloride dioxide. The Comet assay showed an immediate response, i.e. DNA damage that was induced directly in circulating erythrocytes, whereas micronuclei reached their highest frequencies at later sampling times, when a genotoxic damage in stem cells of the cephalic kidney is expressed in circulating erythrocytes. The quality of the untreated surface water seems to be the most important parameter for the long-term DNA damage in circulating erythrocytes.

Environmental Report on the Northwest Pacific for the Marine Seismic System (MSS)

DTIC Science & Technology

1980-12-01

Kuroshio Cur rent is I oca t ed. F. Surface Currents Surface current circulation in the Northwest Pacific consists of the eastward-flowing warm water...overlying surface waters back to early late Miocene time. Prior to this, and through the Oligocene , the seamount was buried beneath a nearly equally

Decadal variability of tropical tropopause temperature and its relationship to the Pacific Decadal Oscillation.

PubMed

Wang, Wuke; Matthes, Katja; Omrani, Nour-Eddine; Latif, Mojib

2016-07-12

Tropopause temperatures (TPTs) control the amount of stratospheric water vapour, which influences chemistry, radiation and circulation in the stratosphere, and is also an important driver of surface climate. Decadal variability and long-term trends in tropical TPTs as well as stratospheric water vapour are largely unknown. Here, we present for the first time evidence, from reanalysis and state-of-the-art climate model simulations, of a link between decadal variability in tropical TPTs and the Pacific Decadal Oscillation (PDO). The negative phase of the PDO is associated with anomalously cold sea surface temperatures (SSTs) in the tropical east and central Pacific, which enhance the zonal SST gradient across the equatorial Pacific. The latter drives a stronger Walker Circulation and a weaker Hadley Circulation, which leads to less convection and subsequently a warmer tropopause over the central equatorial Pacific. Over the North Pacific, positive sea level pressure anomalies occur, which damp vertical wave propagation into the stratosphere. This in turn slows the Brewer-Dobson circulation, and hence warms the tropical tropopause, enabling more water vapour to enter the stratosphere. The reverse chain of events holds for the positive phase of the PDO. Such ocean-troposphere-stratosphere interactions may provide an important feedback on the Earth's global surface temperature.

Decadal variability of tropical tropopause temperature and its relationship to the Pacific Decadal Oscillation

PubMed Central

Wang, Wuke; Matthes, Katja; Omrani, Nour-Eddine; Latif, Mojib

2016-01-01

Tropopause temperatures (TPTs) control the amount of stratospheric water vapour, which influences chemistry, radiation and circulation in the stratosphere, and is also an important driver of surface climate. Decadal variability and long-term trends in tropical TPTs as well as stratospheric water vapour are largely unknown. Here, we present for the first time evidence, from reanalysis and state-of-the-art climate model simulations, of a link between decadal variability in tropical TPTs and the Pacific Decadal Oscillation (PDO). The negative phase of the PDO is associated with anomalously cold sea surface temperatures (SSTs) in the tropical east and central Pacific, which enhance the zonal SST gradient across the equatorial Pacific. The latter drives a stronger Walker Circulation and a weaker Hadley Circulation, which leads to less convection and subsequently a warmer tropopause over the central equatorial Pacific. Over the North Pacific, positive sea level pressure anomalies occur, which damp vertical wave propagation into the stratosphere. This in turn slows the Brewer-Dobson circulation, and hence warms the tropical tropopause, enabling more water vapour to enter the stratosphere. The reverse chain of events holds for the positive phase of the PDO. Such ocean-troposphere-stratosphere interactions may provide an important feedback on the Earth’s global surface temperature. PMID:27404090

Importance of ocean salinity for climate and habitability

PubMed Central

Cullum, Jodie; Stevens, David P.; Joshi, Manoj M.

2016-01-01

Modeling studies of terrestrial extrasolar planetary climates are now including the effects of ocean circulation due to a recognition of the importance of oceans for climate; indeed, the peak equator-pole ocean heat transport on Earth peaks at almost half that of the atmosphere. However, such studies have made the assumption that fundamental oceanic properties, such as salinity, temperature, and depth, are similar to Earth. This assumption results in Earth-like circulations: a meridional overturning with warm water moving poleward at the surface, being cooled, sinking at high latitudes, and traveling equatorward at depth. Here it is shown that an exoplanetary ocean with a different salinity can circulate in the opposite direction: an equatorward flow of polar water at the surface, sinking in the tropics, and filling the deep ocean with warm water. This alternative flow regime results in a dramatic warming in the polar regions, demonstrated here using both a conceptual model and an ocean general circulation model. These results highlight the importance of ocean salinity for exoplanetary climate and consequent habitability and the need for its consideration in future studies. PMID:27044090

Importance of ocean salinity for climate and habitability.

PubMed

Cullum, Jodie; Stevens, David P; Joshi, Manoj M

2016-04-19

Modeling studies of terrestrial extrasolar planetary climates are now including the effects of ocean circulation due to a recognition of the importance of oceans for climate; indeed, the peak equator-pole ocean heat transport on Earth peaks at almost half that of the atmosphere. However, such studies have made the assumption that fundamental oceanic properties, such as salinity, temperature, and depth, are similar to Earth. This assumption results in Earth-like circulations: a meridional overturning with warm water moving poleward at the surface, being cooled, sinking at high latitudes, and traveling equatorward at depth. Here it is shown that an exoplanetary ocean with a different salinity can circulate in the opposite direction: an equatorward flow of polar water at the surface, sinking in the tropics, and filling the deep ocean with warm water. This alternative flow regime results in a dramatic warming in the polar regions, demonstrated here using both a conceptual model and an ocean general circulation model. These results highlight the importance of ocean salinity for exoplanetary climate and consequent habitability and the need for its consideration in future studies.

Seasonal surface circulation, temperature, and salinity in Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Musgrave, David L.; Halverson, Mark J.; Scott Pegau, W.

2013-02-01

Salinity, temperature, and depth profiles from 1973 to 2010 were used to construct a seasonal climatology of surface temperature, surface salinity, mixed layer depth (MLD), potential energy of mixing, and surface geostrophic circulation in Prince William Sound (PWS) and the adjacent Gulf of Alaska. Surface salinity is greatest in winter and least in summer due to the influence of increased freshwater runoff in summer. It is generally lowest in the northwest and highest in the Gulf of Alaska. The surface temperature is lowest in the winter and highest in the summer when surface heating is greatest, with little spatial variability across the Sound. The MLD is deepest in winter (9-27 m) and shallowest in summer (4-5 m). The work by winds was estimated from meteorological buoy data in central PWS and compared to the potential energy of mixing of the upper water column. The potential depth to which winds mix the upper water column was generally consistent with the MLD. The surface geostrophic circulation in the central Sound has: a southerly flow in the western central Sound in the winter; a closed, weak anticyclonic cell in spring; a closed, cyclonic cell in the summer; an open, cyclonic circulation in the fall. In the western passages, a southerly flow occurs in spring, summer, and fall. These results have important implications for oil spill response in PWS, the use of oil dispersants, and for comparison to numerical studies.

Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events

PubMed Central

Incarbona, Alessandro; Martrat, Belen; Mortyn, P. Graham; Sprovieri, Mario; Ziveri, Patrizia; Gogou, Alexandra; Jordà, Gabriel; Xoplaki, Elena; Luterbacher, Juerg; Langone, Leonardo; Marino, Gianluca; Rodríguez-Sanz, Laura; Triantaphyllou, Maria; Di Stefano, Enrico; Grimalt, Joan O.; Tranchida, Giorgio; Sprovieri, Rodolfo; Mazzola, Salvatore

2016-01-01

The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales. PMID:27412622

Effect of PEG and water-soluble chitosan coating on moxifloxacin-loaded PLGA long-circulating nanoparticles.

PubMed

Mustafa, Sanaul; Devi, V Kusum; Pai, Roopa S

2017-02-01

Moxifloxacin (MOX) is a Mycobacterium tuberculosis DNA gyrase inhibitor. Due to its intense hydrophilicity, MOX is cleared from the body within 24 h and required for repetitive doses which may then result in hepatotoxicity and acquisition of MOX resistant-TB, related with its use. To overcome the aforementioned limitations, the current study aimed to develop PLGA nanoparticles (PLGA NPs), to act as an efficient carrier for controlled delivery of MOX. To achieve a substantial extension in blood circulation, a combined design, affixation of polyethylene glycol (PEG) to MOX-PLGA NPs and adsorption of water-soluble chitosan (WSC) (cationic deacetylated chitin) to particle surface, was rose for surface modification of NPs. Surface modified NPs (MOX-PEG-WSC NPs) were prepared to provide controlled delivery and circulate in the bloodstream for an extended period of time, thus minimizing dosing frequency. In vivo pharmacokinetic and in vivo biodistribution following oral administration were investigated. NP surface charge was closed to neutral +4.76 mV and significantly affected by the WSC coating. MOX-PEG-WSC NPs presented striking prolongation in blood circulation, reduced protein binding, and long-drawn-out the blood circulation half-life with resultant reduced liver sequestration vis-à-vis MOX-PLGA NPs. The studies, therefore, indicate the successful formulation development of MOX-PEG-WSC NPs that showed sustained release behavior from nanoparticles which indicates low frequency of dosing.

Slow and Steady: Ocean Circulation. The Influence of Sea Surface Height on Ocean Currents

NASA Technical Reports Server (NTRS)

Haekkinen, Sirpa

2000-01-01

The study of ocean circulation is vital to understanding how our climate works. The movement of the ocean is closely linked to the progression of atmospheric motion. Winds close to sea level add momentum to ocean surface currents. At the same time, heat that is stored and transported by the ocean warms the atmosphere above and alters air pressure distribution. Therefore, any attempt to model climate variation accurately must include reliable calculations of ocean circulation. Unlike movement of the atmosphere, movement of the ocean's waters takes place mostly near the surface. The major patterns of surface circulation form gigantic circular cells known as gyres. They are categorized according to their general location-equatorial, subtropical, subpolar, and polar-and may run across an entire ocean. The smaller-scale cell of ocean circulation is known' as an eddy. Eddies are much more common than gyres and much more difficult to track in computer simulations of ocean currents.

Seasonal Water Transport in the Atmosphere of Mars: Applications of a Mars General Circulation Model Using Mars Global Surveyor Data

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

1999-01-01

This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. We present below a summary of progress made during the duration of this JRI. The focus of this JRI has been to investigate seasonal water vapor transport in the atmosphere of Mars and its effects on the planet's present climate. To this end, the primary task has been to adapt a new dynamical processor for the adiabatic tendencies of the atmospheric circulation into the NASA Ames Mars general circulation model (MGCM). Using identical boundary and initial conditions, several comparative tests between the new and old MGCMs have been performed and the nature of the simulated circulations have been diagnosed. With confidence that the updated version of the Ames MGCM produces quite similar mean and eddy circulation statistics, the new climate model is well poised as a tool to pursue fundamental questions related to the spatial and seasonal variations of atmospheric water vapor on Mars, and to explore exchanges of water with non-atmospheric reservoirs and transport within its atmosphere. In particular, the role of surface sources and sinks can be explored, the range of water-vapor saturation altitudes can be investigated, and plausible precipitation mechanisms can be studied, for a range of atmospheric dust loadings. Such future investigations can contribute to a comprehensive study of surface inventories, exchange mechanisms, and the relative importance of atmospheric transport Mars' water cycle. A listing of presentations made and manuscripts submitted during the course of this project is provided.

Seasonal Water Transport in the Atmosphere of Mars: Applications of a Mars General Circulation Model Using Mars Global Surveyor Data

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

1999-01-01

This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. We present below a summary of progress made during the duration of this JRI. The focus of this JRI has been to investigate seasonal water vapor transport in the atmosphere of Mars and its effects on the planet's present climate. To this end, the primary task has been to adapt a new dynamical processor for the adiabatic tendencies of the atmospheric circulation into the NASA Ames Mars general circulation model (MGCM). Using identical boundary and initial conditions, several comparative tests between the new and old MGCMs have been performed and the nature of the simulated circulations have been diagnosed. With confidence that the updated version of the Ames MGCM produces quite similar mean and eddy circulation statistics, the new climate model is well poised as a tool to pursue fundamental questions related to the spatial and seasonal variations of atmospheric water vapor on Mars, and to explore exchanges of water with non-atmospheric reservoirs and transport within its atmosphere. In particular, the role of surface sources and sinks can be explored, the range of water-vapor saturation altitudes can be investigated, and plausible precipitation mechanisms can be studied, for a range of atmospheric dust loadings, such future investigations can contribute to a comprehensive study of surface inventories, exchange mechanisms, and the relative importance of atmospheric transport Mars' water cycle. A listing of presentations made and manuscripts submitted during the course of this project is provided.

Nimbus 7 SMMR Derived Seasonal Variations in the Water Vapor, Liquid Water and Surface Winds over the Global Oceans

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Short, D. A.

1984-01-01

Monthly mean distributions of water vapor and liquid water contained in a vertical column of the atmosphere and the surface wind speed were derived from Nimbus Scanning Multichannel Microwave Radiometer (SMMR) observations over the global oceans for the period November 1978 to November 1979. The remote sensing techniques used to estimate these parameters from SMMR are presented to reveal the limitations, accuracies, and applicability of the satellite-derived information for climate studies. On a time scale of the order of a month, the distribution of atmospheric water vapor over the oceans is controlled by the sea surface temperature and the large scale atmospheric circulation. The monthly mean distribution of liquid water content in the atmosphere over the oceans closely reflects the precipitation patterns associated with the convectively and baroclinically active regions. Together with the remotely sensed surface wind speed that is causing the sea surface stress, the data collected reveal the manner in which the ocean-atmosphere system is operating. Prominent differences in the water vapor patterns from one year to the next, or from month to month, are associated with anomalies in the wind and geopotential height fields. In association with such circulation anomalies the precipitation patterns deduced from the meteorological network over adjacent continents also reveal anomalous distributions.

The water cycle in the general circulation model of the martian atmosphere

NASA Astrophysics Data System (ADS)

Shaposhnikov, D. S.; Rodin, A. V.; Medvedev, A. S.

2016-03-01

Within the numerical general-circulation model of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and Modeling), we have developed the water cycle block, which is an essential component of modern general circulation models of the Martian atmosphere. The MAOAM model has a spectral dynamic core and successfully predicts the temperature regime on Mars through the use of physical parameterizations typical of both terrestrial and Martian models. We have achieved stable computation for three Martian years, while maintaining a conservative advection scheme taking into account the water-ice phase transitions, water exchange between the atmosphere and surface, and corrections for the vertical velocities of ice particles due to sedimentation. The studies show a strong dependence of the amount of water that is actively involved in the water cycle on the initial data, model temperatures, and the mechanism of water exchange between the atmosphere and the surface. The general pattern and seasonal asymmetry of the water cycle depends on the size of ice particles, the albedo, and the thermal inertia of the planet's surface. One of the modeling tasks, which results from a comparison of the model data with those of the TES experiment on board Mars Global Surveyor, is the increase in the total mass of water vapor in the model in the aphelion season and decrease in the mass of water ice clouds at the poles. The surface evaporation scheme, which takes into account the turbulent rise of water vapor, on the one hand, leads to the most complete evaporation of ice from the surface in the summer season in the northern hemisphere and, on the other hand, supersaturates the atmosphere with ice due to the vigorous evaporation, which leads to worse consistency between the amount of the precipitated atmospheric ice and the experimental data. The full evaporation of ice from the surface increases the model sensitivity to the size of the polar cap; therefore, the increase in the latter leads to better results. The use of a more accurate dust scenario changes the model temperatures, which also strongly affects the water cycle.

Computational design of the basic dynamical processes of the UCLA general circulation model

NASA Technical Reports Server (NTRS)

Arakawa, A.; Lamb, V. R.

1977-01-01

The 12-layer UCLA general circulation model encompassing troposphere and stratosphere (and superjacent 'sponge layer') is described. Prognostic variables are: surface pressure, horizontal velocity, temperature, water vapor and ozone in each layer, planetary boundary layer (PBL) depth, temperature, moisture and momentum discontinuities at PBL top, ground temperature and water storage, and mass of snow on ground. Selection of space finite-difference schemes for homogeneous incompressible flow, with/without a free surface, nonlinear two-dimensional nondivergent flow, enstrophy conserving schemes, momentum advection schemes, vertical and horizontal difference schemes, and time differencing schemes are discussed.

Biogeochemical Proxies in Scleractinian Corals used to Reconstruct Ocean Circulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guilderson, T.P.; Kashgarian, M.; Schrag, D.P.

We utilize monthly {sup 14}C data derived from coral archives in conjunction with ocean circulation models to address two questions: (1) how does the shallow circulation of the tropical Pacific vary on seasonal to decadal time scales and (2) which dynamic processes determine the mean vertical structure of the equatorial Pacific thermocline. Our results directly impact the understanding of global climate events such as the El Nino-Southern Oscillation (ENSO). To study changes in ocean circulation and water mass distribution involved in the genesis and evolution of ENSO and decadal climate variability, it is necessary to have records of climate variablesmore » several decades in length. Continuous instrumental records are limited because technology for continuous monitoring of ocean currents has only recently been available, and ships of opportunity archives such as COADS contain large spatial and temporal biases. In addition, temperature and salinity in surface waters are not conservative and thus can not be independently relied upon to trace water masses, reducing the utility of historical observations. Radiocarbon ({sup 14}C) in sea water is a quasi-conservative water mass tracer and is incorporated into coral skeletal material, thus coral {sup 14}C records can be used to reconstruct changes in shallow circulation that would be difficult to characterize using instrumental data. High resolution {Delta}{sup 14}C timeseries such as these, provide a powerful constraint on the rate of surface ocean mixing and hold great promise to augment onetime surveys such as GEOSECS and WOCE. These data not only provide fundamental information about the shallow circulation of the Pacific, but can be used as a benchmark for the next generation of high resolution ocean models used in prognosticating climate change.« less

Biogeochemical Proxies in Scleractinian Corals used to Reconstruct Ocean Circulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guilderson, T P; Kashgarian, M; Schrag, D P

2001-02-23

We utilize monthly {sup 14}C data derived from coral archives in conjunction with ocean circulation models to address two questions: (1) how does the shallow circulation of the tropical Pacific vary on seasonal to decadal time scales and (2) which dynamic processes determine the mean vertical structure of the equatorial Pacific thermocline. Our results directly impact the understanding of global climate events such as the El Nino-Southern Oscillation (ENSO). To study changes in ocean circulation and water mass distribution involved in the genesis and evolution of ENSO and decadal climate variability, it is necessary to have records of climate variablesmore » several decades in length. Continuous instrumental records are limited because technology for continuous monitoring of ocean currents has only recently been available, and ships of opportunity archives such as COADS contain large spatial and temporal biases. In addition, temperature and salinity in surface waters are not conservative and thus can not be independently relied upon to trace water masses, reducing the utility of historical observations. Radiocarbon ({sup 14}C) in sea water is a quasi-conservative water mass tracer and is incorporated into coral skeletal material, thus coral {sup 14}C records can be used to reconstruct changes in shallow circulation that would be difficult to characterize using instrumental data. High resolution {Delta}{sup 14}C timeseries such as these, provide a powerful constraint on the rate of surface ocean mixing and hold great promise to augment onetime surveys such as GEOSECS and WOCE. These data not only provide fundamental information about the shallow circulation of the Pacific, but can be used as a benchmark for the next generation of high resolution ocean models used in prognosticating climate change.« less

Sensitivity of the Southern Ocean overturning circulation to surface buoyancy forcing

NASA Astrophysics Data System (ADS)

Morrison, A.; Hogg, A.; Ward, M.

2011-12-01

The southern limb of the ocean's meridional overturning circulation plays a key role in the Earth's response to climate change. The rise in atmospheric CO2 during glacial-interglacial transitions has been attributed to outgassing of enhanced upwelling water masses in the Southern Ocean. However a dynamical understanding of the physical mechanisms driving the change in overturning is lacking. Previous modelling studies of the Southern Ocean have focused on the effect of wind stress forcing on the overturning, while largely neglecting the response of the upper overturning cell to changes in surface buoyancy forcing. Using a series of eddy-permitting, idealised simulations of the Southern Ocean, we show that surface buoyancy forcing in the mid-latitudes is likely to play a significant role in setting the strength of the overturning circulation. Air-sea fluxes of heat and precipitation over the Antarctic Circumpolar Current region act to convert dense upwelled water masses into lighter waters at the surface. Additional fluxes of heat or freshwater thereby facilitate the meridional overturning up to a theoretical limit derived from Ekman transport. The sensitivity of the overturning to surface buoyancy forcing is strongly dependent on the relative locations of the wind stress profile, buoyancy forcing and upwelling region. The idealised model results provide support for the hypothesis that changes in upwelling during deglaciations may have been driven by changes in heat and freshwater fluxes, instead of, or in addition to, changes in wind stress. Morrison, A. K., A. M. Hogg, and M. L. Ward (2011), Sensitivity of the Southern Ocean overturning circulation to surface buoyancy forcing, Geophys. Res. Lett., 38, L14602, doi:10.1029/2011GL048031.

Large- to submesoscale surface circulation and its implications on biogeochemical/biological horizontal distributions during the OUTPACE cruise (southwest Pacific)

NASA Astrophysics Data System (ADS)

Rousselet, Louise; de Verneil, Alain; Doglioli, Andrea M.; Petrenko, Anne A.; Duhamel, Solange; Maes, Christophe; Blanke, Bruno

2018-04-01

The patterns of the large-scale, meso- and submesoscale surface circulation on biogeochemical and biological distributions are examined in the western tropical South Pacific (WTSP) in the context of the OUTPACE cruise (February-April 2015). Multi-disciplinary original in situ observations were achieved along a zonal transect through the WTSP and their analysis was coupled with satellite data. The use of Lagrangian diagnostics allows for the identification of water mass pathways, mesoscale structures, and submesoscale features such as fronts. In particular, we confirmed the existence of a global wind-driven southward circulation of surface waters in the entire WTSP, using a new high-resolution altimetry-derived product, validated by in situ drifters, that includes cyclogeostrophy and Ekman components with geostrophy. The mesoscale activity is shown to be responsible for counter-intuitive water mass trajectories in two subregions: (i) the Coral Sea, with surface exchanges between the North Vanuatu Jet and the North Caledonian Jet, and (ii) around 170° W, with an eastward pathway, whereas a westward general direction dominates. Fronts and small-scale features, detected with finite-size Lyapunov exponents (FSLEs), are correlated with 25 % of surface tracer gradients, which reveals the significance of such structures in the generation of submesoscale surface gradients. Additionally, two high-frequency sampling transects of biogeochemical parameters and microorganism abundances demonstrate the influence of fronts in controlling the spatial distribution of bacteria and phytoplankton, and as a consequence the microbial community structure. All circulation scales play an important role that has to be taken into account not only when analysing the data from OUTPACE but also, more generally, for understanding the global distribution of biogeochemical components.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashgarian, M; Guilderson, T P

We utilize monthly {sup 14}C data derived from coral archives in conjunction with ocean circulation models to address two questions: (1) how does the shallow circulation of the tropical Pacific vary on seasonal to decadal time scales and (2) which dynamic processes determine the mean vertical structure of the equatorial Pacific thermocline. Our results directly impact the understanding of global climate events such as the El Nino-Southern Oscillation (ENSO). To study changes in ocean circulation and water mass distribution involved in the genesis and evolution of ENSO and decadal climate variability, it is necessary to have records of climate variablesmore » several decades in length. Continuous instrumental records are limited because technology for continuous monitoring of ocean currents (e.g. satellites and moored arrays) has only recently been available, and ships of opportunity archives such as COADS contain large spatial and temporal biases. In addition, temperature and salinity in surface waters are not conservative and thus can not be independently relied upon to trace water masses, reducing the utility of historical observations. Radiocarbon in sea water is a quasi-conservative water mass tracer and is incorporated into coral skeletal material, thus coral {sup 14}C records can be used to reconstruct changes in shallow circulation that would be difficult to characterize using instrumental data. High resolution {Delta}{sup 14}C timeseries such as ours, provide a powerful constraint on the rate of surface ocean mixing and hold great promise to augment one time oceanographic surveys. {Delta}{sup 14}C timeseries such as these, not only provide fundamental information about the shallow circulation of the Pacific, but can also be directly used as a benchmark for the next generation of high resolution ocean models used in prognosticating climate. The measurement of {Delta}{sup 14}C in biological archives such as tree rings and coral growth bands is a direct record of the invasion of fossil fuel CO{sub 2} and bomb {sup 14}C into the atmosphere and surface oceans. Therefore the {Delta}{sup 14}C data that are produced in this study can be used to validate the ocean uptake of fossil fuel CO2 in coupled ocean-atmosphere models. This study takes advantage of the quasi-conservative nature of {sup 14}C as a water mass tracer by using {Delta}{sup 14}C time series in corals to identify changes in the shallow circulation of the Pacific. Although the data itself provides fundamental information on surface water mass movement the true strength is a combined approach which is greater than the individual parts; the data helps uncover deficiencies in ocean circulation models and the model results place long {Delta}{sup 14}C time series in a dynamic framework which helps to identify those locations where additional observations are most needed.« less

Mid-latitude afforestation shifts general circulation and tropical precipitation.

PubMed

Swann, Abigail L S; Fung, Inez Y; Chiang, John C H

2012-01-17

We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the Sahel and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO(2), but regional heating from the increase in forest cover is capable of driving unintended changes in circulation and precipitation. The ability of vegetation to affect remote circulation has implications for strategies for climate mitigation.

Meridional overturning circulations driven by surface wind and buoyancy forcing

NASA Astrophysics Data System (ADS)

Bell, M. J.

2016-02-01

A conceptual picture of the Meridional Overturning Circulation (MOC) is developed using 2- and 3-layer models governed by the planetary geostrophic equations and simple global geometries. The picture has four main elements. First cold water driven to the surface in the South Atlantic north of Drake passage by Ekman upwelling is transformed into warmer water by heat input at the surface from the atmosphere. Second the model's boundary conditions constrain the depths of the isopycnal layers to be almost flat along the eastern boundaries of the ocean. This results in, third, warm water reaching high latitudes in the northern hemisphere where it is transformed into cold water by surface heat loss. Finally it is assumed that western boundary currents are able to close the circulations. The results from a set of numerical experiments for the upwelling limb in the Southern Hemisphere are summarised in a simple conceptual schematic. Analytical solutions have been found for the down-welling limb assuming the wind stress in the Northern Hemisphere is negligible. Expressions for the depth of the isopycnal interface on the eastern boundary and the strength of the MOC obtained by combining these solutions in a 2-layer model are generally consistent with and complementary to those obtained by Gnandesikan (1999). The MOC in two basins one of which has a strong halocline is also discussed.

Assessing the performance of formulations for nonlinear feedback of surface gravity waves on ocean currents over coastal waters

NASA Astrophysics Data System (ADS)

Wang, Pengcheng; Sheng, Jinyu; Hannah, Charles

2017-08-01

This study presents applications of a two-way coupled wave-circulation modelling system over coastal waters, with a special emphasis of performance assessments of two different methods for nonlinear feedback of ocean surface gravity waves on three-dimensional (3D) ocean currents. These two methods are the vortex force (VF) formulation suggested by Bennis et al. (2011) and the latest version of radiation stress (RS) formulation suggested by Mellor (2015). The coupled modelling system is first applied to two idealized test cases of surf-zone scales to validate implementations of these two methods in the coupled wave-circulation system. Model results show that the latest version of RS has difficulties in producing the undertow over the surf zone. The coupled system is then applied to Lunenburg Bay (LB) of Nova Scotia during Hurricane Juan in 2003. The coupled system using both the VF and RS formulations generates much stronger and more realistic 3D circulation in the Bay during Hurricane Juan than the circulation-only model, demonstrating the importance of surface wave forces to the 3D ocean circulation over coastal waters. However, the RS formulation generates some weak unphysical currents outside the wave breaking zone due to a less reasonable representation for the vertical distribution of the RS gradients over a slopping bottom. These weak unphysical currents are significantly magnified in a two-way coupled system when interacting with large surface waves, degrading the model performance in simulating currents at one observation site. Our results demonstrate that the VF formulation with an appropriate parameterization of wave breaking effects is able to produce reasonable results for applications over coastal waters during extreme weather events. The RS formulation requires a complex wave theory rather than the linear wave theory for the approximation of a vertical RS term to improve its performance under both breaking and non-breaking wave conditions.

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1990-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T (sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1989-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T(sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

Potential alteration of fjordal circulation due to a large floating structure—Numerical investigation with application to Hood Canal basin in Puget Sound

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khangaonkar, Tarang; Wang, Taiping

Circulation in typical fjords is characterized by a shallow brackish layer at the surface over a deep long and narrow saltwater column. This surface layer is responsible for the outflow of water from the fjord, is easily disrupted by external forces, such as wind, and is influenced by freshwater inflow. In this paper, we postulate that the stability of fjordal circulation may also be vulnerable to impacts from anthropogenic alterations, such as floating structures, that could constrict the mixing and transport in the upper layers of the water column. The potential for alteration of circulation in Hood Canal, a silled-fjordmore » located inside Puget Sound, Washington, has been examined. Using classical analytical treatments along the lines formulated by Hansen and Rattray [1965], Rattray [1967], Dyer [1973] and more recently, MacCready [2004], we develop a solution applicable to a range of estuary classifications varying from a partially mixed estuary regime to classical fjord conditions. Both estuary types exist in the Puget Sound system, and we compare our analytical solution with observed data. The analysis is based on an exponential variation of eddy viscosity with depth, and it has been extended further with modifications of the free surface boundary conditions to develop a solution representing the presence of a floating bridge at the estuary/fjord entrance. The model results show that tidally averaged mean circulation under the influence of such a constraint could reduce by as much as 30 to 50 percent. The overall water quality of fjords and narrow estuaries is dependent on net circulation and flushing. A potential decrease in residual flow or a corresponding increase in residence time of this magnitude merits further study.« less

What Drives the Variability of the Atlantic Water Circulation in the Arctic Ocean?

NASA Astrophysics Data System (ADS)

Lique, C.; Johnson, H. L.

2016-02-01

The Atlantic Water (AW) layer in the Arctic Basin is isolated from the atmosphere by the overlaying surface layer; yet observations of the AW pan-Arctic boundary current have revealed that the velocities in this layer exhibit significant variations on all timescales. Here, analysis of a global ocean/sea ice model hindcast, complemented by experiments performed with an idealized process model, are used to investigate what controls the variability of AW circulation, with a focus on the role of wind forcing. The AW circulation carries the imprint of wind variations, both remotely over the Nordic and Barents seas where they force variability on the AW inflow to the Arctic Basin, and locally over the Arctic Basin through the forcing of the wind-driven Beaufort gyre, which modulates and transfers the wind variability to the AW layer. Our results further suggest that understanding variability in the large amount of heat contained within the AW layer requires a better understanding of the circulation within both AW and surface layers.

South Atlantic circulation in a world ocean model

NASA Astrophysics Data System (ADS)

England, Matthew H.; Garçon, Véronique C.

1994-09-01

The circulation in the South Atlantic Ocean has been simulated within a global ocean general circulation model. Preliminary analysis of the modelled ocean circulation in the region indicates a rather close agreement of the simulated upper ocean flows with conventional notions of the large-scale geostrophic currents in the region. The modelled South Atlantic Ocean witnesses the return flow and export of North Atlantic Deep Water (NADW) at its northern boundary, the inflow of a rather barotropic Antarctic Circumpolar Current (ACC) through the Drake Passage, and the inflow of warm saline Agulhas water around the Cape of Good Hope. The Agulhas leakage amounts to 8.7 Sv, within recent estimates of the mass transport shed westward at the Agulhas retroflection. Topographic steering of the ACC dominates the structure of flow in the circumpolar ocean. The Benguela Current is seen to be fed by a mixture of saline Indian Ocean water (originating from the Agulhas Current) and fresher Subantarctic surface water (originating in the ACC). The Benguela Current is seen to modify its flow and fate with depth; near the surface it flows north-westwards bifurcating most of its transport northward into the North Atlantic Ocean (for ultimate replacement of North Atlantic surface waters lost to the NADW conveyor). Deeper in the water column, more of the Benguela Current is destined to return with the Brazil Current, though northward flows are still generated where the Benguela Current extension encounters the coast of South America. At intermediate levels, these northward currents trace the flow of Antarctic Intermediate Water (AAIW) equatorward, though even more AAIW is seen to recirculate poleward in the subtropical gyre. In spite of the model's rather coarse resolution, some subtle features of the Brazil-Malvinas Confluence are simulated rather well, including the latitude at which the two currents meet. Conceptual diagrams of the recirculation and interocean exchange of thermocline, intermediate and deep waters are constructed from an analysis of flows bound between isothermal and isobaric surfaces. This analysis shows how the return path of NADW is partitioned between a cold water route through the Drake Passage (6.5 Sv), a warm water route involving the Agulhas Current sheeding thermocline water westward (2.5 Sv), and a recirculation of intermediate water originating in the Indian Ocean (1.6 Sv).

Using in-situ observations of atmospheric water vapor isotopes to benchmark and isotope-enabled General Circulation Models and improve ice core paleo-climate reconstruction

NASA Astrophysics Data System (ADS)

Steen-Larsen, Hans Christian; Sveinbjörnsdottir, Arny; Masson-Delmotte, Valerie; Werner, Martin; Risi, Camille; Yoshimura, Kei

2016-04-01

We have since 2010 carried out in-situ continuous water vapor isotope observations on top of the Greenland Ice Sheet (3 seasons at NEEM), in Svalbard (1 year), in Iceland (4 years), in Bermuda (4 years). The expansive dataset containing high accuracy and precision measurements of δ18O, δD, and the d-excess allow us to validate and benchmark the treatment of the atmospheric hydrological cycle's processes in General Circulation Models using simulations nudged to reanalysis products. Recent findings from both Antarctica and Greenland have documented strong interaction between the snow surface isotopes and the near surface atmospheric water vapor isotopes on diurnal to synoptic time scales. In fact, it has been shown that the snow surface isotopes take up the synoptic driven atmospheric water vapor isotopic signal in-between precipitation events, erasing the precipitation isotope signal in the surface snow. This highlights the importance of using General or Regional Climate Models, which accurately are able to simulate the atmospheric water vapor isotopic composition, to understand and interpret the ice core isotope signal. With this in mind we have used three isotope-enabled General Circulation Models (isoGSM, ECHAM5-wiso, and LMDZiso) nudged to reanalysis products. We have compared the simulations of daily mean isotope values directly with our in-situ observations. This has allowed us to characterize the variability of the isotopic composition in the models and compared it to our observations. We have specifically focused on the d-excess in order to characterize why both the mean and the variability is significantly lower than our observations. We argue that using water vapor isotopes to benchmark General Circulation Models offers an excellent tool for improving the treatment and parameterization of the atmospheric hydrological cycle. Recent studies have documented a very large inter-model dispersion in the treatment of the Arctic water cycle under a future global warming and greenhouse gas emission scenario. Our results call for action to create an international pan-Arctic monitoring water vapor isotope network in order to improve future projections of Arctic climate.

Coupling 3D groundwater modeling with CFC-based age dating to classify local groundwater circulation in an unconfined crystalline aquifer

NASA Astrophysics Data System (ADS)

Kolbe, Tamara; Marçais, Jean; Thomas, Zahra; Abbott, Benjamin W.; de Dreuzy, Jean-Raynald; Rousseau-Gueutin, Pauline; Aquilina, Luc; Labasque, Thierry; Pinay, Gilles

2016-12-01

Nitrogen pollution of freshwater and estuarine environments is one of the most urgent environmental crises. Shallow aquifers with predominantly local flow circulation are particularly vulnerable to agricultural contaminants. Water transit time and flow path are key controls on catchment nitrogen retention and removal capacity, but the relative importance of hydrogeological and topographical factors in determining these parameters is still uncertain. We used groundwater dating and numerical modeling techniques to assess transit time and flow path in an unconfined aquifer in Brittany, France. The 35.5 km2 study catchment has a crystalline basement underneath a ∼60 m thick weathered and fractured layer, and is separated into a distinct upland and lowland area by an 80 m-high butte. We used groundwater discharge and groundwater ages derived from chlorofluorocarbon (CFC) concentration to calibrate a free-surface flow model simulating groundwater flow circulation. We found that groundwater flow was highly local (mean travel distance = 350 m), substantially smaller than the typical distance between neighboring streams (∼1 km), while CFC-based ages were quite old (mean = 40 years). Sensitivity analysis revealed that groundwater travel distances were not sensitive to geological parameters (i.e. arrangement of geological layers and permeability profile) within the constraints of the CFC age data. However, circulation was sensitive to topography in the lowland area where the water table was near the land surface, and to recharge rate in the upland area where water input modulated the free surface of the aquifer. We quantified these differences with a local groundwater ratio (rGW-LOCAL), defined as the mean groundwater travel distance divided by the mean of the reference surface distances (the distance water would have to travel across the surface of the digital elevation model). Lowland, rGW-LOCAL was near 1, indicating primarily topographical controls. Upland, rGW-LOCAL was 1.6, meaning the groundwater recharge area is almost twice as large as the topographically-defined catchment for any given point. The ratio rGW-LOCAL is sensitive to recharge conditions as well as topography and it could be used to compare controls on groundwater circulation within or between catchments.

Coastal circulation and water-column properties in the War in the Pacific National Historical Park, Guam: measurements and modeling of waves, currents, temperature, salinity, and turbidity, April-August 2012

USGS Publications Warehouse

Storlazzi, Curt D.; Cheriton, Olivia M.; Lescinski, Jamie M.R.; Logan, Joshua B.

2014-01-01

The U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center (PCMSC) initiated an investigation in the National Park Service’s (NPS) War in the Pacific National Historical Park (WAPA) to provide baseline scientific information on coastal circulation and water-column properties along west-central Guam, focusing on WAPA’s Agat Unit, as it relates to the transport and settlement of coral larvae, fish, and other marine organisms. The oceanographic data and numerical circulation modeling results from this study demonstrate that circulation in Agat Bay was strongly driven by winds and waves at longer (>1 day) timescales and by the tides at shorter (<1 day) timescales; near-surface currents in deep water were primarily controlled by the winds, whereas currents on the shallow reef flats were dominated by wave-driven motions. Water-column properties exhibited strong seasonality coupled to the shift from the trade wind to the non-trade wind season. During the dry trade-wind season, waters were cooler and more saline. When the winds shifted to a more variable pattern, waters warmed and became less saline because of a combination of increased thermal insolation from lack of wind forcing and higher rainfall. Turbidity was relatively low in Agat Bay and was similar to levels measured elsewhere along west-central Guam. The numerical circulation modeling results provide insight into the potential paths of buoyant material released from a series of locations along west-central Guam under summer non-trade wind forcing conditions that characterize coral spawning events. This information may be useful in evaluating the potential zones of influence/impact resulting from transport by surface currents of material released from these select locations.

Pathways and hydrography in the Mesoamerican Barrier Reef System Part 2: Water masses and thermohaline structure

NASA Astrophysics Data System (ADS)

Carrillo, L.; Johns, E. M.; Smith, R. H.; Lamkin, J. T.; Largier, J. L.

2016-06-01

Hydrographic data from two oceanographic cruises conducted during March 2006 and January/February 2007 are used to investigate the thermohaline structure related to the observed circulation along the Mesoamerican Barrier Reef System (MBRS). From our observations we identify three water masses in the MBRS: the Caribbean Surface Water (CSW), North Atlantic Subtropical Underwater (SUW), and Tropical Atlantic Central Water (TACW). Little vertical structure in temperature is observed in the upper 100 m of the water column, but important differences are observed in the salinity distribution both horizontally and with depth. Freshwater inputs to the system from the mainland can be traced in the surface layer, with two possible sources: one from surface rivers located along the southern portion of the MBRS, and the other originating from an underground river system located along the northern portion of the MBRS. The thermohaline structure in the MBRS reflects the dynamics of the observed circulation. Uplifted isopycnals along most of the central and northern coastline of the MBRS reflect the effects of the strong geostrophic circulation flowing northward, i.e. the Yucatan Current. To the south along the MBRS, much weaker velocities are observed, with the Honduras Gyre dominating the flow in this region as presented during January/February 2007. These two regions are separated by onshore and divergent alongshore flow associated with the impingement of the Cayman Current on the shore and the MBRS.

Can increased poleward oceanic heat flux explain the warm Cretaceous climate?

NASA Astrophysics Data System (ADS)

Schmidt, Gavin A.; Mysak, Lawrence A.

1996-10-01

The poleward transport of heat in the mid-Cretaceous (100 Ma) is examined using an idealized coupled ocean-atmosphere model. The oceanic component consists of two zonally averaged basins representing the proto-Pacific and proto-Indian oceans and models the dynamics of the meridional thermohaline circulation. The atmospheric component is a simple energy and moisture balance model which includes the diffusive meridional transport of sensible heat and moisture. The ocean model is spun up with a variety of plausible Cretaceous surface temperature and salinity profiles, and a consistent atmosphere is objectively derived based on the resultant sea surface temperature and the surface heat and freshwater fluxes. The coupled model does not exhibit climate drift. Multiple equilibria of the coupled model are found that break the initial symmetry of the ocean circulation; several of these equilibria have one-cell (northern or southern sinking) thermohaline circulation patterns. Two main classes of circulation are found: circulations where the densest water is relatively cool and is formed at the polar latitudes and circulations where the densest water is warm, but quite saline, and the strongest sinking occurs at the tropics. In all cases, significant amounts of warm, saline bottom water are formed in the proto-Indian basin which modify the deepwater characteristics in the larger (proto-Pacific) basin. Temperatures in the deep ocean are warm, 10°-17°C, in agreement with benthic foraminiferal oxygen isotope data. The poleward transport of heat in the modeled Cretaceous oceans is larger than in some comparable models of the present day thermohaline circulation and significantly larger than estimates of similar processes in the present-day ocean. It is consistently larger in the polar sinking cases when compared with that seen in the tropical sinking cases, but this represents an increase of only 10%. The largest increase over present-day model transports is in the atmospheric latent heat transport, where an increased hydrological cycle (especially in the tropical sinking cases) contributes up to an extra 1 PW of poleward heat transport. Better constraints on the oceanic deepwater circulation during this period are necessary before the meridional circulation can be unambiguously described.

Sea ice and surface water circulation, Alaskan continental shelf

NASA Technical Reports Server (NTRS)

Wright, F. F. (Principal Investigator); Sharma, G. D.; Burns, J. J.

1973-01-01

The author has identified the following significant results. Sediments contributed by the Copper River in the Gulf of Alaska are carried westward along the shore as a distinct plume. Oceanic water relatively poor in suspended material appears to intrude near Montague Island, and turbid water between Middleton Island and Kayak Island is the result of Ekman between transport. An anticlockwise surface water circulation is observed in this region. Ground truth data indicate striking similarity with ERTS-1 imagery obtained on October 12, 1972. Observations of ERTS-1 imagery reveal that various characteristics and distribution of sea ice in the Arctic Ocean can be easily studied. Formation of different types of sea ice and their movement is quite discrenible. Sea ice moves parallel to the cost in near shore areas and to the northerly direction away from the coast.

Laboratory Experiments Investigating Glacier Submarine Melt Rates and Circulation in an East Greenland Fjord

NASA Astrophysics Data System (ADS)

Cenedese, C.

2014-12-01

Idealized laboratory experiments investigate the glacier-ocean boundary dynamics near a vertical 'glacier' (i.e. no floating ice tongue) in a two-layer stratified fluid, similar to Sermilik Fjord where Helheim Glacier terminates. In summer, the discharge of surface runoff at the base of the glacier (subglacial discharge) intensifies the circulation near the glacier and increases the melt rate with respect to that in winter. In the laboratory, the effect of subglacial discharge is simulated by introducing fresh water at melting temperatures from either point or line sources at the base of an ice block representing the glacier. The circulation pattern observed both with and without subglacial discharge resembles those observed in previous studies. The buoyant plume of cold meltwater and subglacial discharge water entrains ambient water and rises vertically until it finds either the interface between the two layers or the free surface. The results suggest that the meltwater deposits within the interior of the water column and not entirely at the free surface, as confirmed by field observations. The submarine melt rate increases with the subglacial discharge rate. Furthermore, the same subglacial discharge causes greater submarine melting if it exits from a point source rather than from a line source. When the subglacial discharge exits from two point sources, two buoyant plumes are formed which rise vertically and interact. The results suggest that the distance between the two subglacial discharges influences the entrainment in the plumes and consequently the amount of submarine melting and the final location of the meltwater within the water column. Hence, the distribution and number of sources of subglacial discharge may play an important role in glacial melt rates and fjord stratification and circulation. Support was given by NSF project OCE-113008.

Influence of the Yukon River on the Bering Sea

NASA Technical Reports Server (NTRS)

Dean, K.; Mcroy, C. P.

1987-01-01

The distribution of near-surface, turbid water, discharged by the Yukon River, was studied based on analysis of satellite imagery. The interannual analyses indicates that the net flow of near-surface, turbid water is northward of the delta across the entrance to Norton Sound. Only turbid water to the east enters Norton Sound and consists of 25% of the total area. Approximately 10% of the water circulates into the sound along the southern coast and is lost to view in the vicinity of Unalakleet. Suspended sediments transported by this southern circulation are primarily deposited along the southern coast. Three distinct zones within the turbid water were identified based on relative brightness levels. These zones appear to be primarily related to differences in suspended-sediment concentrations and position of the sediments in the water column. The extent of turbid water varies seasonally. It is most extensive June through October even though discharge of the Yukon River decreases substantially after July.

Surface changes in the North Atlantic meridional overturning circulation during the last millennium

PubMed Central

Wanamaker, Alan D.; Butler, Paul G.; Scourse, James D.; Heinemeier, Jan; Eiríksson, Jón; Knudsen, Karen Luise; Richardson, Christopher A.

2012-01-01

Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector. PMID:22692542

Surface changes in the North Atlantic meridional overturning circulation during the last millennium.

PubMed

Wanamaker, Alan D; Butler, Paul G; Scourse, James D; Heinemeier, Jan; Eiríksson, Jón; Knudsen, Karen Luise; Richardson, Christopher A

2012-06-12

Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector.

Circulation, Water Temperature, and Larval Settlement Over the Inner Continental Shelves of the Santa Barbara Channel, California

NASA Astrophysics Data System (ADS)

Fewings, M. R.; Washburn, L.; Ohlmann, C.; Blanchette, C.; Caselle, J.; Gotschalk, C.

2008-12-01

We use seven-year time series of wind stress, water velocity, and temperature in 15-18 m water depth to describe the circulation and water temperature over the inner continental shelves of the Channel Islands and California mainland in the Santa Barbara Basin. This area is strongly influenced by the California Current upwelling system. In turn, the water circulation in the Santa Barbara Basin influences the local marine ecosystem by affecting the water temperature and the supply of nutrients and larval fish and invertebrates. Larvae and nutrients traveling from the coast to the open ocean and back again must somehow pass through the inner shelf. The water circulation over the inner continental shelf of the Northern Channel Islands has not been described. Due to the shallowness of the water, an inner shelf has different physical dynamics than either the surfzone or the middle and outer continental shelf. We discuss the relative importance of upwelling- favorable along-shelf winds and of cross-shelf winds as forcing mechanisms for coastal upwelling circulations over the inner shelf; test whether the cross-shelf wind stress and surface gravity waves are important for cross-shelf circulation in the Santa Barbara Basin; and describe the subtidal patterns of water temperature, stratification, and velocity around the Channel Islands and their relation to observed larval settlement patterns. Cross-shelf circulation and the movement of water masses into and out of the Basin have implications for settlement and recruitment of many coastal species, including the economically important kelp rockfish, kelp bass, and sea urchin. Understanding the circulation of the Santa Barbara Basin and its inner shelves is a precursor to determining the source locations of the planktonic larvae. That information on source locations is essential for the design, siting, and assessment of existing and future marine protected areas in California and elsewhere.

Sub-tidal Circulation in a deep-silled fjord: Douglas Channel, British Columbia (Canada)

NASA Astrophysics Data System (ADS)

Wan, Di; Hannah, Charles; Foreman, Mike

2016-04-01

Douglas Channel, a deep fjord on the west coast of British Columbia, Canada, is the main waterway in Kitimat fjord system that opens to Queen Charlotte Sound and Hecate Strait. The fjord is separated from the open shelf by a broad sill that is about 150 m deep, and there is another sill (200 m) that separates the fjord into an outer and an inner basin. This study examines the low-frequency (from seasonal to meteorological bands) circulation in Douglas Channel from data collected from three moorings deployed during 2013-2015, and the water property observations collected during six cruises (2014 and 2015). Estuarine flow dominates the circulation above the sill-depth. The deep flows are dominated by a yearly renewal that takes place from early June to September, and this dense water renews both basins in the form of gravity currents at 0.1 - 0.2 m/s with a thickness of 100 m. At other times of the year, the deep flow structures and water properties suggest horizontal and vertical processes and support the re-circulation idea in the inner and the outer basins. The near surface current velocity fluctuations are dominated by the along-channel wind. Overall, the circulation in the meteorological band is a mix of the estuarine flow, direct wind driven flow, and the baroclinic response to changes to the surface pressure gradient caused by the wind driven currents.

Analysis of discontinuities across thin inhomogeneities, groundwater/surface water interactions in river networks, and circulation about slender bodies using slit elements in the Analytic Element Method

USDA-ARS?s Scientific Manuscript database

Groundwater and surface water contain interfaces across which hydrologic functions are discontinuous. Thin elements with high hydraulic conductivity in a porous media focus groundwater, which flows through such inhomogeneities and causes an abrupt change in stream function across their interfaces, a...

Free convection in the Matian atmosphere

NASA Technical Reports Server (NTRS)

Clow, G. D.; Haberle, R. M.

1990-01-01

The 'free convective' regime for the Martian atmospheric boundary layer (ABL) was investigated. This state occurs when the mean windspeed at the top of the ABL drops below some critical value U(sub c) and positive buoyant forces are present. Such forces can arise either from vertical temperature or water vapor gradients across the atmospheric surface layer. During free convection, buoyant forces drive narrow plumes that ascend to the inversion height with a return circulation consisting of broad slower-moving downdraughts. Horizontal pressure, temperature, windspeed, and water vapor fluctuations resulting form this circulation pattern can be quite large adjacent to the ground (within the surface layer). The local turbulent fluctuations cause non-zero mean surface stresses, sensible heat fluxes, and latent heat fluxes, even when the mean regional windspeed is zero. Although motions above the surface layer are insensitive to the nature of the surface, the sensible and latent heat fluxes are primarily controlled by processes within the interfacial sublayer immediately adjacent to the ground during free convection. Thus the distinction between aerodynamically smooth and rough airflow within the interfacial sublayer is more important than for the more typical situation where the mean regional windspeed is greater than U(sub c). Buoyant forces associated with water vapor gradients are particularly large on Mars at low pressures and high temperatures when the surface relative humidity is 100 percent, enhancing the likelihood of free convection under these conditions. On this basis, Ingersol postulated the evaporative heat losses from an icy surface on Mars at 237 K and current pressures would exceed the available net radiative flux at the surface, thus prohibiting ice from melting at low atmospheric pressures. Schumann has developed equations describing the horizontal fluctuations and mean vertical gradients occurring during free convection. Schumann's model was generalized to include convection driven by water vapor gradients and to include the effects of circulation above both aerodynamically smooth and rough surfaces.

Kanamycin Sulphate Loaded PLGA-Vitamin-E-TPGS Long Circulating Nanoparticles Using Combined Coating of PEG and Water-Soluble Chitosan

PubMed Central

Mustafa, Sanaul

2017-01-01

Kanamycin sulphate (KS) is a Mycobacterium tuberculosis protein synthesis inhibitor. Due to its intense hydrophilicity, KS is cleared from the body within 8 h. KS has a very short plasma half-life (2.5 h). KS is used in high concentrations to reach the therapeutic levels in plasma, which results in serious nephrotoxicity/ototoxicity. To overcome aforementioned limitations, the current study aimed to develop KS loaded PLGA-Vitamin-E-TPGS nanoparticles (KS-PLGA-TPGS NPs), to act as an efficient carrier for controlled delivery of KS. To achieve a substantial extension in blood circulation, a combined design, affixation of polyethylene glycol (PEG) to KS-PLGA-TPGS NPs and adsorption of water-soluble chitosan (WSC) (cationic deacetylated chitin) to particle surface, was raised for surface modification of NPs. Surface modified NPs (KS-PEG-WSC NPs) were prepared to provide controlled delivery and circulate in the bloodstream for an extended period of time, thus minimizing dosing frequency. In vivo pharmacokinetics and in vivo biodistribution following intramuscular administration were investigated. NPs surface charge was close to neutral +3.61 mV and significantly affected by the WSC coating. KS-PEG-WSC NPs presented striking prolongation in blood circulation, reduced protein binding, and long drew-out the blood circulation half-life with resultant reduced kidney sequestration vis-à-vis KS-PLGA-TPGS NPs. The studies, therefore, indicate the successful formulation development of KS-PEG-WSC NPs with reduced frequency of dosing of KS indicating low incidence of nephrotoxicity/ototoxicity. PMID:28352475

Deep water characteristics and circulation in the South China Sea

NASA Astrophysics Data System (ADS)

Wang, Aimei; Du, Yan; Peng, Shiqiu; Liu, Kexiu; Huang, Rui Xin

2018-04-01

This study investigates the deep circulation in the South China Sea (SCS) using oceanographic observations combined with results from a bottom layer reduced gravity model. The SCS water, 2000 m below the surface, is quite different from that in the adjacent Pacific Ocean, and it is characterized by its low dissolved oxygen (DO), high temperature and low salinity. The horizontal distribution of deep water properties indicates a basin-scale cyclonic circulation driven by the Luzon overflow. The results of the bottom layer reduced gravity model are consistent with the existence of the cyclonic circulation in the deep SCS. The circulation is stronger at the northern/western boundary. After overflowing the sill of the Luzon Strait, the deep water moves broadly southwestward, constrained by the 3500 m isobath. The broadening of the southward flow is induced by the downwelling velocity in the interior of the deep basin. The main deep circulation bifurcates into two branches after the Zhongsha Islands. The southward branch continues flowing along the 3500 m isobath, and the eastward branch forms the sub-basin scale cyclonic circulation around the seamounts in the central deep SCS. The returning flow along the east boundary is fairly weak. The numerical experiments of the bottom layer reduced gravity model reveal the important roles of topography, bottom friction, and the upwelling/downwelling pattern in controlling the spatial structure, particularly the strong, deep western boundary current.

An Oceanic General Circulation Model (OGCM) investigation of the Red Sea circulation: 2. Three-dimensional circulation in the Red Sea

NASA Astrophysics Data System (ADS)

Sofianos, Sarantis S.; Johns, William E.

2003-03-01

The three-dimensional circulation of the Red Sea is studied using a set of Miami Isopycnic Coordinate Ocean Model (MICOM) simulations. The model performance is tested against the few available observations in the basin and shows generally good agreement with the main observed features of the circulation. The main findings of this analysis include an intensification of the along-axis flow toward the coasts, with a transition from western intensified boundary flow in the south to eastern intensified flow in the north, and a series of strong seasonal or permanent eddy-like features. Model experiments conducted with different forcing fields (wind-stress forcing only, surface buoyancy forcing only, or both forcings combined) showed that the circulation produced by the buoyancy forcing is stronger overall and dominates the wind-driven part of the circulation. The main circulation pattern is related to the seasonal buoyancy flux (mostly due to the evaporation), which causes the density to increase northward in the basin and produces a northward surface pressure gradient associated with the downward sloping of the sea surface. The response of the eastern boundary to the associated mean cross-basin geostrophic current depends on the stratification and β-effect. In the northern part of the basin this results in an eastward intensification of the northward surface flow associated with the presence of Kelvin waves while in the south the traditional westward intensification due to Rossby waves takes place. The most prominent gyre circulation pattern occurs in the north where a permanent cyclonic gyre is present that is involved in the formation of Red Sea Outflow Water (RSOW). Beneath the surface boundary currents are similarly intensified southward undercurrents that carry the RSOW to the sill to flow out of the basin into the Indian Ocean.

Modeling hydrodynamics, water quality, and benthic processes to predict ecological effects in Narragansett Bay

EPA Science Inventory

The environmental fluid dynamics code (EFDC) was used to study the three dimensional (3D) circulation, water quality, and ecology in Narragansett Bay, RI. Predictions of the Bay hydrodynamics included the behavior of the water surface elevation, currents, salinity, and temperatur...

Interactions Between the Thermohaline Circulation and Tropical Atlantic SST in a Coupled General Circulation Model

NASA Technical Reports Server (NTRS)

Miller, Ron; Jiang, Xing-Jian; Travis, Larry (Technical Monitor)

2001-01-01

Tropical Atlantic SST shows a (statistically well-defined) decadal time scale in a 104-year simulation of unforced variability by a coupled general circulation model (CGCM). The SST anomalies superficially resemble observed Tropical Atlantic variability (TAV), and are associated with changes in the atmospheric circulation. Brazilian rainfall is modulated with a decadal time scale, along with the strength of the Atlantic trade winds, which are associated with variations in evaporation and the net surface heat flux. However, in contrast to observed tropical Atlantic variability, the trade winds damp the associated anomalies in ocean temperature, indicating a negative feedback. Tropical SST anomalies in the CGCM, though opposed by the surface heat flux, are advected in from the Southern Hemisphere mid-latitudes. These variations modulate the strength of the thermohaline circulation (THC): warm, salty anomalies at the equator sink drawing cold, fresh mid-latitude water. Upon reaching the equator, the latter inhibit vertical overturning and advection from higher latitudes, which allows warm, salty anomalies to reform, returning the cycle to its original state. Thus, the cycle results from advection of density anomalies and the effect of these anomalies upon the rate of vertical overturning and surface advection. This decadal modulation of Tropical Atlantic SST and the thermohaline circulation is correlated with ocean heat transport to the Northern Hemisphere high latitudes and Norwegian Sea SST. Because of the central role of equatorial convection, we question whether this mechanism is present in the current climate, although we speculate that it may have operated in palaeo times, depending upon the stability of the tropical water column.

Are Surface Waters Around Greenland Getting Saltier in a Warming Climate?

NASA Astrophysics Data System (ADS)

Vinogradova, N. T.; Ponte, R. M.; Piecuch, C. G.; Little, C. M.

2016-02-01

During the past two decades, most surface waters around Greenland ice sheet and in the Nordic Seas became significantly saltier. Given the fact that these waters feed the North Atlantic thermohaline circulation, an increase in surface salinity, which can exceed 0.2 psu in places, might have an important impact on the global ocean circulation and on future projections of the climate state. Surface salinification may seem counter-intuitive to the reported long-term increase in freshwater supply to the region from river discharge and ice melting, sparking debates about whether the freshening of the subpolar gyre has ceased, and whether the recent salinification, if continued, will be able to forestall the projected slowdown of the overturning circulation. Here we assess what controls contemporary salinity changes by examining various terms of the salinity budget, including the dilution effect due to air-sea fluxes of freshwater, fluxes of salt due to sea ice formation/melting, and ocean fluxes of salinity associated with advective and diffusive processes. We use an ocean state estimate produced by the ECCO consortium to consider the budgets over the period 1992-2011. ECCO estimates produce salinity fields close to the observations and, crucial for our purposes, permit closed budget diagnostics of salinity and respective fluxes. The budgets are formulated within the entire water column in order to examine three-dimensional structure of freshwater storage and establish a link between the surface and upper-ocean change in near-Greenland waters. Over the past two decades, patterns of change are evident in all budget terms, with ocean fluxes either offsetting or enhancing surface forcing, including the effects of sea ice dynamics. Interpretation is provided within the context of a changing climate, including intensification of the hydrological cycle and weakening of ocean transports and overturning, as well as natural decadal-to-interdacadal variability present in the system.

40 CFR 86.1335-90 - Cool-down procedure.

Code of Federal Regulations, 2010 CFR

2010-07-01

...'s internal or external surfaces except for water and air as prescribed in paragraphs (c) and (d) of this section. (c) For water-cooled engines, two types of cooling are permitted: (1) Water may be circulated through the engine's water coolant system. (i) The coolant may be flowed in either direction and...

The influence of surface waves on water circulation in a mid-Atlantic continental shelf region

NASA Technical Reports Server (NTRS)

Whitlock, C. H.; Talay, T. A.

1974-01-01

The importance of wave-induced currents in different weather conditions and water depths (18.3 m and 36.6 m) is assessed in a mid-Atlantic continental-shelf region. A review of general circulation conditions is conducted. Factors which perturb the general circulation are examined using analytic techniques and limited experimental data. Actual wind and wave statistics for the region are examined. Relative magnitudes of the various currents are compared on a frequency of annual occurrence basis. Results indicated that wave-induced currents are often the same order of magnitude as other currents in the region and become more important at higher wind and wave conditions. Wind-wave and ocean-swell characteristics are among those parameters which must be monitored for the analytical computation of continental-shelf circulation.

Microwave Investigation of the Mars Atmosphere and Surface

NASA Technical Reports Server (NTRS)

Gulkis, S.; Forget, F.; Janssen, M.; Riley, A. L.; Hartogh, P.; Clancy, T.; Allen, M.; Frerking, M.

2000-01-01

The Microwave Investigation of the Mars Atmosphere and Surface Experiment (MIMAS) is designed to address two major scientific goals: 1) To understand the three dimensional general circulation of the Martian atmosphere, and 2) To understand the hydrologic cycle of water on Mars, including the time-variable sources, sinks, and atmospheric transport of water vapor. The proposed instrument is a submillimeter wave, heterodyne receiver, with both continuum and very high spectral resolution capability. A small reflector antenna will be used to feed the receiver. Instrument heritage comes from the MIRO receiver, currently under design for the ESA Rosetta Mission, and from SWAS, a NASA astrophysics mission. The instrument will be able to measure atmospheric spectral lines from both water and carbon monoxide and use these lines as tracers of atmospheric winds. Measurement objectives of MIMAS are to measure surface temperature, atmospheric temperature from the surface up to an altitude of 60 km or more, the distribution of CO and H2O in the atmosphere, and certain wind fields (zonal and meridional). The global distribution of CO, as well as temperature distributions, will be used as input data for GCMs (general circulation models). Water vapor profiles will be used to understand the sources and sinks of water on Mars and to understand how it is transported globally by the general circulation. Zonal and meridional wind fields will provide further tests of the GCMs. An important aspect of this experiment is that the temperature and humidity measurements are insensitive to dust and ice condensates thereby making the measurement capability independent of the presence of dust clouds and ice particles. Temperature measurements derived from the data can be used in conjunction with infrared measurements to determine dust profiles.

Multi-stage circulating fluidized bed syngas cooling

DOEpatents

Liu, Guohai; Vimalchand, Pannalal; Guan, Xiaofeng; Peng, WanWang

2016-10-11

A method and apparatus for cooling hot gas streams in the temperature range 800.degree. C. to 1600.degree. C. using multi-stage circulating fluid bed (CFB) coolers is disclosed. The invention relates to cooling the hot syngas from coal gasifiers in which the hot syngas entrains substances that foul, erode and corrode heat transfer surfaces upon contact in conventional coolers. The hot syngas is cooled by extracting and indirectly transferring heat to heat transfer surfaces with circulating inert solid particles in CFB syngas coolers. The CFB syngas coolers are staged to facilitate generation of steam at multiple conditions and hot boiler feed water that are necessary for power generation in an IGCC process. The multi-stage syngas cooler can include internally circulating fluid bed coolers, externally circulating fluid bed coolers and hybrid coolers that incorporate features of both internally and externally circulating fluid bed coolers. Higher process efficiencies can be realized as the invention can handle hot syngas from various types of gasifiers without the need for a less efficient precooling step.

Tracer water transport and subgrid precipitation variation within atmospheric general circulation models

NASA Astrophysics Data System (ADS)

Koster, Randal D.; Eagleson, Peter S.; Broecker, Wallace S.

1988-03-01

A capability is developed for monitoring tracer water movement in the three-dimensional Goddard Institute for Space Science Atmospheric General Circulation Model (GCM). A typical experiment with the tracer water model follows water evaporating from selected grid squares and determines where this water first returns to the Earth's surface as precipitation or condensate, thereby providing information on the lateral scales of hydrological transport in the GCM. Through a comparison of model results with observations in nature, inferences can be drawn concerning real world water transport. Tests of the tracer water model include a comparison of simulated and observed vertically-integrated vapor flux fields and simulations of atomic tritium transport from the stratosphere to the oceans. The inter-annual variability of the tracer water model results is also examined.

Tracer water transport and subgrid precipitation variation within atmospheric general circulation models

NASA Technical Reports Server (NTRS)

Koster, Randal D.; Eagleson, Peter S.; Broecker, Wallace S.

1988-01-01

A capability is developed for monitoring tracer water movement in the three-dimensional Goddard Institute for Space Science Atmospheric General Circulation Model (GCM). A typical experiment with the tracer water model follows water evaporating from selected grid squares and determines where this water first returns to the Earth's surface as precipitation or condensate, thereby providing information on the lateral scales of hydrological transport in the GCM. Through a comparison of model results with observations in nature, inferences can be drawn concerning real world water transport. Tests of the tracer water model include a comparison of simulated and observed vertically-integrated vapor flux fields and simulations of atomic tritium transport from the stratosphere to the oceans. The inter-annual variability of the tracer water model results is also examined.

Millennial-Scale Variability in the Indian Monsoon and Links to Ocean Circulation

NASA Astrophysics Data System (ADS)

DeLong, K. A.; Came, R. E.; Johnson, J. E.; Giosan, L.

2014-12-01

Millennial-scale variability in the Indian monsoon was temporally linked to changes in global ocean circulation during the last glacial period, as evidenced by planktic-benthic foraminiferal stable isotope and trace element results from an intermediate depth sediment core from the northwestern Bay of Bengal. Paired planktic foraminiferal Mg/Ca and δ18Oc constrain sea surface temperatures and isolate millennial-scale variations in the δ18O of surface waters (δ18Osw), which resulted from changes in river runoff in the northwestern Bay. Concurrently with low δ18Osw events, benthic foraminiferal δ13C decreased, suggesting an increased influence of an aged water mass at this intermediate depth site during the low salinity events. Benthic foraminiferal Cd/Ca results support the identification of this water mass as aged Glacial Antarctic Intermediate Water (GAAIW). Lagged correlation analysis (r= 0.41) indicates that changes in subsurface properties led changes in surface properties by an average of 380 years. The implication is that Southern Hemisphere climate exerted a controlling influence on the Indian monsoon during the last glacial period.

Hydrological and glaciological balances on Antizana Volcano, Ecuador

NASA Astrophysics Data System (ADS)

Favier, V.; Cadier, E.; Coudrain, A.; Francou, B.; Maisincho, L.; Praderio, E.; Villacis, M.; Wagnon, P.

2006-12-01

Water supply for Quito, the capital of Ecuador, is partly fed by the water collected at the piedmont of Antizana ice covered stratovolcano. In order to assess the contribution of glaciers to the local water resources, a comparison of hydrological and glaciological datasets collected over the 1995-2005 period on Antizana Glacier 15 watershed was realized. Over the study period, Antizana glacier 15 retreated quickly, inducing an important water contribution to lower altitude discharges. However, comparison of hydrological and glaciological balances allowed observation of important missing runoffs due to underground circulations. Subsuperficial circulations were initially questioned due to the total disappearance of surface streams at the level of the frontal moraine, a surface stream being observed again downstream the moraine. Brine injections were performed upstream the moraine and in a small lake located on the moraine and restitution rates of salt were computed. Tracer experiments demonstrated a complete restitution of discharges implying that missing runoff were not involved in subsuperficial circulations but in deeper ones that may have flown through the fractured rock environment of the stratovlocano. Experiments also demonstrated that infiltrations occurred directly at the bedrock of the glaciers. Then, taking into account the weak discharges observed at the glacier front would induce computation of a strongly underestimated value of the actual water contribution from glaciers to lower altitude discharges. Finally, assessing water contribution from glaciers of Ecuador requires a comparison of glaciological and hydrological data.

Relative contributions of external forcing factors to circulation and hydrographic properties in a micro-tidal bay

NASA Astrophysics Data System (ADS)

Yoon, Seokjin; Kasai, Akihide

2017-11-01

The dominant external forcing factors influencing estuarine circulation differ among coastal environments. A three-dimensional regional circulation model was developed to estimate external influence indices and relative contributions of external forcing factors such as external oceanic forcing, surface heat flux, wind stress, and river discharge to circulation and hydrographic properties in Tango Bay, Japan. Model results show that in Tango Bay, where the Tsushima Warm Current passes offshore of the bay, under conditions of strong seasonal winds and river discharge, the water temperature and salinity are strongly influenced by surface heat flux and river discharge in the surface layer, respectively, while in the middle and bottom layers both are mainly controlled by open boundary conditions. The estuarine circulation is comparably influenced by all external forcing factors, the strong current, surface heat flux, wind stress, and river discharge. However, the influence degree of each forcing factor varies with temporal variations in external forcing factors as: the influence of open boundary conditions is higher in spring and early summer when the stronger current passes offshore of the bay, that of surface heat flux reflects the absolute value of surface heat flux, that of wind stress is higher in late fall and winter due to strong seasonal winds, and that of river discharge is higher in early spring due to snow-melting and summer and early fall due to flood events.

Anticipated Improvements to Net Surface Freshwater Fluxes from GPM

NASA Technical Reports Server (NTRS)

Smith, Eric A.

2005-01-01

Evaporation and precipitation over the oceans play very important roles in the global water cycle, upper-ocean heat budget, ocean dynamics, and coupled ocean-atmosphere dynamics. In the conventional representation of the terrestrial water cycle, the assumed role of the oceans is to act as near-infinite reservoirs of water with the main drivers of the water cycle being land- atmosphere interactions in which excess precipitation (P) over evaporation (E) is returned to the oceans as surface runoff and baseflow. Whereas this perspective is valid for short space and time scales -- fundamental principles, available observed estimates, and results from models indicate that the oceans play a far more important role in the large-scale water cycle at seasonal and longer timescales. Approximately 70-80% of the total global evaporation and precipitation occurs over oceans. Moreover, latent heat release into the atmosphere over the oceans is the major heat source driving global atmospheric circulations, with the moisture transported by circulations from oceans to continents being the major source of water precipitating over land. Notably, the major impediment in understanding and modeling the oceans role in the global water cycle is the lack of reliable net surface freshwater flux estimates (E - P fluxes) at the salient spatial and temporal resolutions, i.e., consistent coupled weekly to monthly E - P gridded datasets.

Cyclonic circulation of Saturn's atmosphere due to tilted convection

NASA Astrophysics Data System (ADS)

Afanasyev, Y. D.; Zhang, Y.

2018-03-01

Saturn displays cyclonic vortices at its poles and the general atmospheric circulation at other latitudes is dominated by embedded zonal jets that display cyclonic circulation. The abundance of small-scale convective storms suggests that convection plays a role in producing and maintaining Saturn's atmospheric circulation. However, the dynamical influence of small-scale convection on Saturn's general circulation is not well understood. Here we present laboratory analogue experiments and propose that Saturn's cyclonic circulation can be explained by tilted convection in which buoyancy forces do not align with the planet's rotation axis. In our experiments—conducted with a cylindrical water tank that is heated at the bottom, cooled at the top and spun on a rotating table—warm rising plumes and cold sinking water generate small anticyclonic and cyclonic vortices that are qualitatively similar to Saturn's convective storms. Numerical simulations complement the experiments and show that this small-scale convection leads to large-scale cyclonic flow at the surface and anticyclonic circulation at the base of the fluid layer, with a polar vortex forming from the merging of smaller cyclonic storms that are driven polewards.

Anthropogenic carbon in the ocean—Surface to interior connections

NASA Astrophysics Data System (ADS)

Groeskamp, Sjoerd; Lenton, Andrew; Matear, Richard; Sloyan, Bernadette M.; Langlais, Clothilde

2016-11-01

Quantifying the surface to interior transport of anthropogenic carbon (CA) is critical for projecting future carbon uptake and for improved understanding of the role of the oceans in the global carbon cycle. Here we develop and apply a diagnostic tool that provides a volumetric stream function in (CA,σ0) coordinates to calculate the total diapycnal CA transport in the ocean, where σ0 is the surface referenced potential density anomaly. We combine this with air-sea fluxes of CA to infer the internal ocean mixing of CA to obtain a closed globally integrated budget analyses of the ocean's CA transport. This diagnostic separates the contribution from the mean flow, seasonal cycles, trend, surface fluxes, and mixing in the distribution and the accumulation of CA in the ocean. We find that the redistribution of CA from the surface to the interior of the ocean is due to an interplay between circulation and mixing. The circulation component is dominated by the mean flow; however, effects due to seasonal cycles are significant for the CA redistribution. The two most important pathways for CA subduction are through the transformation of thermocline water (TW) into subantarctic mode water and by transformation of Circumpolar Deep Water (CDW) into lighter Antarctic Intermediate Water. The results suggest that an accurate representation of intermediate and mode water formation, deep water formation, and spatial and temporal distribution of ocean mixing in ocean models is essential to simulate and project the oceanic uptake of CA.

Tidal and residual circulation in a semi-arid bay: Coquimbo Bay, Chile

NASA Astrophysics Data System (ADS)

Valle-Levinson, Arnoldo; Moraga, Julio; Olivares, Jorge; Blanco, José Luis

2000-11-01

Velocity profiles and time-series data were combined with conductivity-temperature-depth (CTD) casts to describe the general circulation at tidal and subtidal scales in a bay of semi-arid climate, Coquimbo Bay (˜30°S), Chile. This was the first study that used a towed acoustic Doppler current profiler (ADCP) in coastal Chilean waters and is one of the very few in semi-arid bays. The ADCP was towed for two semi-diurnal tidal cycles in early austral autumn, between March 23 and 24, 1997 along a triangular trajectory that covered most of the bay. Additional data consisted of moored current meters and CTD casts. The observations indicated the presence of a surface layer, above the pycnocline, that showed predominantly diurnal variability forced by the breeze regime and by tides. The tidal circulation in the surface layer featured amplitudes of 10 cm/s within an anticyclonic gyre that occupied most of the bay. The subtidal circulation in the surface was characterized by a pair of counter-rotating gyres. The northernmost three-fourths of the bay showed an anticyclonic gyre, and the observations over the southern fourth implied a cyclonic gyre. The subtidal anticyclonic gyre had a counterpart rotating in opposite direction within a lower layer, underneath the pycnocline. The lower layer showed semidiurnal variability in addition to diurnal variability and was insulated by the pycnocline from heat and momentum fluxes through the air-water interface. Circulations that resemble estuarine and anti-estuarine patterns were found associated with the subtidal gyres. A horizontal divergence related to a 10 cm/s near-surface outflow around Point Tortuga, to the south of the bay entrance, allowed the development of upward motion off the Point, as evidenced by the tilt of the isopycnals at the entrance to the bay.

Groundwater-saline lakes interaction - The contribution of saline groundwater circulation to solute budget of saline lakes: a lesson from the Dead Sea

NASA Astrophysics Data System (ADS)

Kiro, Yael; Weinstein, Yishai; Starinsky, Abraham; Yechieli, Yoseph

2013-04-01

Saline lakes act as base level for both surface water and groundwater. Thus, a change in lake levels is expected to result in changes in the hydrogeological system in its vicinity, exhibited in groundwater levels, location of the fresh-saline water interface, sub-lacustrine groundwater discharge (SGD) and saline water circulation. All these processes were observed in the declining Dead Sea system, whose water level dropped by ~35 meters in the last 50 years. This work focuses mainly on the effect of circulation of Dead Sea water in the aquifer, which continues even in this very rapid base level drop. In general, seawater circulation in coastal aquifers is now recognized as a major process affecting trace element mass balances in coastal areas. Estimates of submarine groundwater discharge (SGD) vary over several orders of magnitude (1-1000000 m3/yr per meter shoreline). These estimates are sensitive to fresh-saline SGD ratios and to the temporal and spatial scales of the circulation. The Dead Sea system is an excellent natural field lab for studying seawater-groundwater interaction and large-scale circulation due to the absence of tides and to the minor role played by waves. During Dead Sea water circulation in the aquifer several geochemical reactions occur, ranging from short-term adsorption-desorption reactions and up to long-term precipitation and dissolution reactions. These processes affect the trace element distribution in the saline groundwater. Barite and celestine, which are supersaturated in the lake water, precipitate during circulation in the aquifer, reducing barium (from 5 to 1.5 mg/L), strontium (from 350 to 300 mg/L) and the long-lived 226Ra (from 145 to 60 dpm/L) in the saline groundwater. Redox-controlled reactions cause a decrease in uranium from 2.4 to 0.1 μg/L, and an increase in iron from 1 to 13 mg/L. 228Ra (t1/2=5.75 yr) activity in the Dead Sea is ~1 dpm/L and increase gradually as the saline water flows further inland until reaching steady-state activities (~27 dpm/L) with the aquifer sediments. The decrease in 226Ra and increase in 228Ra in the circulation process provide a robust method for calculating the amount of Dead Sea water circulating in the aquifer. This process can affect trace element concentrations in the Dead Sea and emphasize the potential of long-term seawater circulation in mass balances of saline water bodies.

Causes of strong ocean heating during glacial periods

NASA Astrophysics Data System (ADS)

Zimov, N.; Zimov, S. A.

2013-12-01

During the last deglaciation period, the strongest climate changes occurred across the North Atlantic regions. Analyses of borehole temperatures from the Greenland ice sheet have yielded air temperature change estimates of 25°C over the deglaciation period (Dahl-Jensen et al. 1998). Such huge temperature changes cannot currently be explained in the frames of modern knowledge about climate. We propose that glacial-interglacial cycles are connected with gradual warming of ocean interior waters over the course of glaciations and quick transport of accumulated heat from ocean to the atmosphere during the deglaciation periods. Modern day ocean circulation is dominated by thermal convection with cold waters subsiding in the Northern Atlantic and filling up the ocean interior with cold and heavy water. However during the glaciation thermal circulation stopped and ocean circulation was driven by 'haline pumps' -Red and Mediterranean seas connected with ocean with only narrow but deep straights acts as evaporative basins, separating ocean water into fresh water which returns to the ocean surface (precipitation) and warm but salty, and therefore heavy, water which flows down to the ocean floor. This haline pump is stratifying the ocean, allowing warmer water locate under the colder water and thus stopping thermal convection in the ocean. Additional ocean interior warming is driven by geothermal heat flux and decomposition of organic rain. To test the hypothesis we present simple ocean box model that describes thermohaline circulation in the World Ocean. The first box is the Red and Mediterranean sea, the second is united high-latitude seas, the third is the ocean surface, and the fourth the ocean interior. The volume of these water masses and straight cross-sections are taken to be close to real values. We have accepted that the exchange of water between boxes is proportional to the difference in water density in these boxes, Sun energy inputs to the ocean and sea surface are taken as constant. Energy income to the interior box from the geothermal heat flux is also taken as constant. Even though energy inputs are taken as constants, the model manages to recreate the glacial-interglacial cycles. In the glacial periods only haline circulation takes place, the ocean is strongly stratified, and the interior box accumulates heat, while high-latitudes accumulate ice. 112,000 years after glaciation starts, water density on the ocean bottom becomes equal to the density of water in high-latitude seas, strong thermal convection take place, and the ocean quickly (within 14,600 years) releases the heat. The magnitude and duration of such cycles correspond with magnitudes and durations reconstructed for actual glacial-interglacial cycles. From the proposed mechanism it follows that during the glaciations it is likely that the Arctic Ocean was a big reservoir of isotopically light fresh ice. If in a glacial period, the World Ocean were half filled with warm water from the Red Sea and bioproductivity of the ocean declined because of the slow circulation, then carbon storage within the ocean reservoir would decline by ~2000 Pg (10^15 g) of carbon.

The Southern Ocean's role in ocean circulation and climate transients

NASA Astrophysics Data System (ADS)

Thompson, A. F.; Stewart, A.; Hines, S.; Adkins, J. F.

2017-12-01

The ventilation of deep and intermediate density classes at the surface of the Southern Ocean impacts water mass modification and the air-sea exchange of heat and trace gases, which in turn influences the global overturning circulation and Earth's climate. Zonal variability occurs along the Antarctic Circumpolar Current and the Antarctic margins related to flow-topography interactions, variations in surface boundary conditions, and exchange with northern basins. Information about these zonal variations, and their impact on mass and tracer transport, are suppressed when the overturning is depicted as a two-dimensional (depth-latitude) streamfunction. Here we present an idealized, multi-basin, time-dependent circulation model that applies residual circulation theory in the Southern Ocean and allows for zonal water mass transfer between different ocean basins. This model efficiently determines the temporal evolution of the ocean's stratification, ventilation and overturning strength in response to perturbations in the external forcing. With this model we explore the dynamics that lead to transitions in the circulation structure between multiple, isolated cells and a three-dimensional, "figure-of-eight," circulation in which traditional upper and lower cells are interleaved. The transient model is also used to support a mechanistic explanation of the hemispheric asymmetry and phase lag associated with Dansgaard-Oeschger (DO) events during the last glacial period. In particular, the 200 year lag in southern hemisphere temperatures, following a perturbation in North Atlantic deep water formation, depends critically on the migration of Southern Ocean isopycnal outcropping in response to low-latitude stratification changes. Our results provide a self-consistent dynamical framework to explain various ocean overturning transitions that have occurred over the Earth's last 100,000 years, and motivate an exploration of these mechanisms in more sophisticated climate models.

Enceladus and Europa: How Does Hydrothermal Activity Begin at the Surface?

NASA Technical Reports Server (NTRS)

Matson, D. L.; Castillo-Rogez, J. C.; Johnson, T. V.; Lunine, J. I.; Davies, A. G.

2011-01-01

The question of how the surface hydrothermal activity (e.g., eruptive plumes and heat flow) is initiated can be addressed within the frame-work of our "Perrier Ocean" model. This model delivers the necessary heat and chemicals to support the heat flow and plumes observed by Cassini in Enceladus' South Polar Region. The model employs closed-loop circulation of water from a sub-surface ocean. The ocean is the main reservoir of heat and chemicals, including dissolved gases. As ocean water moves up toward the surface, pressure is re-duced and gases exsolve forming bubbles. This bub-bly mixture is less dense than the icy crust and the buoyant ocean-water mixture rises toward the surface. Near the surface, heat and chemicals, including some volatiles, are delivered to the chambers in which plumes form and also to shallow reservoirs that keep the surface ice "warm". (Plume operations, per se, are as described by Schmidt et al. and Postberg et al. and are adopted by us.) After transferring heat, the water cools, bubbles contract and dissolve, and the mixture is now relatively dense. It descends through cracks in the crust and returns to the ocean. Once the closed-loop circulation has started it is self-sustaining. Loss of water via the erupting plumes is relatively negligible compared to the amount needed to maintain the heat flow.We note that the activity described herein for the the "Perrier-Ocean" model could, a priori, apply to all small icy bodies that sheltered an interior ocean at some point in their history.

Chapman Conference on the Hydrologic Aspects of Global Climate Change, Lake Chelan, WA, June 12-14, 1990, Selected Papers

NASA Technical Reports Server (NTRS)

Lettenmaier, Dennis P. (Editor); Rind, D. (Editor)

1992-01-01

The present conference on the hydrological aspects of global climate change discusses land-surface schemes for future climate models, modeling of the land-surface boundary in climate models as a composite of independent vegetation, a land-surface hydrology parameterizaton with subgrid variability for general circulation models, and conceptual aspects of a statistical-dynamical approach to represent landscape subgrid-scale heterogeneities in atmospheric models. Attention is given to the impact of global warming on river runoff, the influence of atmospheric moisture transport on the fresh water balance of the Atlantic drainage basin, a comparison of observations and model simulations of tropospheric water vapor, and the use of weather types to disaggregate the prediction of general circulation models. Topics addressed include the potential response of an Arctic watershed during a period of global warming and the sensitivity of groundwater recharge estimates to climate variability and change.

Dynamics of the Water Circulations in the Southern South China Sea and Its Seasonal Transports

PubMed Central

Ooi, See Hai; Samah, Azizan Abu; Akbari, Abolghasem

2016-01-01

A three-dimensional Regional Ocean Modeling System is used to study the seasonal water circulations and transports of the Southern South China Sea. The simulated seasonal water circulations and estimated transports show consistency with observations, e.g., satellite altimeter data set and re-analysis data of the Simple Ocean Data Assimilation. It is found that the seasonal water circulations are mainly driven by the monsoonal wind stress and influenced by the water outflow/inflow and associated currents of the entire South China Sea. The intrusion of the strong current along the East Coast of Peninsular Malaysia and the eddies at different depths in all seasons are due to the conservation of the potential vorticity as the depth increases. Results show that the water circulation patterns in the northern part of the East Coast of Peninsular Malaysia are generally dominated by the geostrophic currents while those in the southern areas are due solely to the wind stress because of negligible Coriolis force there. This study clearly shows that individual surface freshwater flux (evaporation minus precipitation) controls the sea salinity balance in the Southern South China Sea thermohaline circulations. Analysis of climatological data from a high resolution Regional Ocean Modeling System reveals that the complex bathymetry is important not only for water exchange through the Southern South China Sea but also in regulating various transports across the main passages in the Southern South China Sea, namely the Sunda Shelf and the Strait of Malacca. Apart from the above, in comparision with the dynamics of the Sunda Shelf, the Strait of Malacca reflects an equally significant role in the annual transports into the Andaman Sea. PMID:27410682

Dynamics of the Water Circulations in the Southern South China Sea and Its Seasonal Transports.

PubMed

Daryabor, Farshid; Ooi, See Hai; Samah, Azizan Abu; Akbari, Abolghasem

2016-01-01

A three-dimensional Regional Ocean Modeling System is used to study the seasonal water circulations and transports of the Southern South China Sea. The simulated seasonal water circulations and estimated transports show consistency with observations, e.g., satellite altimeter data set and re-analysis data of the Simple Ocean Data Assimilation. It is found that the seasonal water circulations are mainly driven by the monsoonal wind stress and influenced by the water outflow/inflow and associated currents of the entire South China Sea. The intrusion of the strong current along the East Coast of Peninsular Malaysia and the eddies at different depths in all seasons are due to the conservation of the potential vorticity as the depth increases. Results show that the water circulation patterns in the northern part of the East Coast of Peninsular Malaysia are generally dominated by the geostrophic currents while those in the southern areas are due solely to the wind stress because of negligible Coriolis force there. This study clearly shows that individual surface freshwater flux (evaporation minus precipitation) controls the sea salinity balance in the Southern South China Sea thermohaline circulations. Analysis of climatological data from a high resolution Regional Ocean Modeling System reveals that the complex bathymetry is important not only for water exchange through the Southern South China Sea but also in regulating various transports across the main passages in the Southern South China Sea, namely the Sunda Shelf and the Strait of Malacca. Apart from the above, in comparision with the dynamics of the Sunda Shelf, the Strait of Malacca reflects an equally significant role in the annual transports into the Andaman Sea.

Violent storms within the sea: Dense water formation episodes in the Mediterranean.

NASA Astrophysics Data System (ADS)

Salat, J.

2009-09-01

The Mediterranean is a semi enclosed basin which receives surface water from the Atlantic Ocean. Most of this water is returned into the Ocean with higher density, spreading at more than 1000 m depth (the rest is transported by the atmosphere and the rivers to the Ocean surface). In terms of water budget, the Mediterranean is considered an evaporation basin, but the loss of water is neither the only process that increases the water density nor it is a steady or uniform process. The factors affecting the water density, temperature and salinity, are driven by mass and heat exchanges with the atmosphere. Those exchanges may be by direct contact or mediated by the land. Therefore, changes in water density depend on the water circulation and local weather conditions, both with seasonal and geographical constraints. As the compressibility of water is very low, stratification is expected and horizontal motion is the predominant in the sea interior. Among the few processes that may introduce a vertical component in the water motion are surface heat loss or evaporation that increase the surface water density triggering convective cells. Such processes will be enhanced by surface cooling or by dry continental winds, and counterbalanced by rain, river runoff, solar heating and condensation. Therefore dense water formation are more likely to occur when sea surface temperature is higher than the surface air temperature. There are several scales of convective motions in the ocean, starting from the formation of the surface mixed layer during summer, by night cooling, breezes, and occasional wind storms. During autumn and winter, the vertical scale of the mixing is increasing by steps, through wind storms and progressive cooling, to easily reach the bottom over the continental shelves, typically not deeper than 150 m. However, as the Gibraltar sill is relatively shallow (~350 m) in relation to the average Mediterranean basin (2000-3000 m), the stratification of the deeper layers is weak. Therefore, where and when the surface layer becomes well mixed, typically in winter, in the northern regions, conditions are given (pre-conditioning phase) to the occurrence of dense water formation episodes. Those episodes require the participation of strong cold and dry winds which force an intense evaporation. In the NW Mediterranean, such forcing may act over the continental shelves, like that of the Gulf of Lions, or over deep open seas, typically the central part east of Catalonia and south of Provence. Over the shelf, surface water is expected to be fresher because of the runoff (e.g. the Rhône). Along the continental margin the water circulation, geostrophically adapted, is cyclonic and the stratification in the centre is lower, then density reached may be higher in the central part than on the shelf. However, cooling will be more effective over the shelf as the heat content of the water column is lower because it is much shorter. Once density over the shelf is high enough, the bottom water overflows and violently sinks along the slope in relatively narrow areas through what has been called a cascading event. In the central part, dense water formed sinks almost vertically in funnels not larger than a few kilometres in diameter, and is accompanied by a compensating rise of water from great depth on all sides. In such open sea winter convection events, the dense water can sink some 800 m within a matter of hours and may reach the bottom level, >2500 m deep, within a couple of days. Such short and violent episodes, cascading or open sea convection, of a few days' duration supply enough water to feed the lower layer to compensate the outflow through the Strait of Gibraltar for several weeks. The repeated events in some few points across the Mediterranean, like those above mentioned, are maintaining the Mediterranean circulation and the water exchanges with the Ocean. The overall amount of dense water formed however is highly variable from one year to another according to the forcings involved and perturbations of the water circulation.

Enceladus: Starting Hydrothermal Activity

NASA Technical Reports Server (NTRS)

Matson, D. L.; Castillo-Rogez, J. C.; Johnson, T. V.; Lunine, J. I.; Davies, A. G.

2011-01-01

We describe a process for starting the hydrothermal activity in Enceladus' South Polar Region. The process takes advantage of fissures that reach the water table, about 1 kilometer below the surface. Filling these fissures with fresh ocean water initiates a flow of water up from an ocean that can be self-sustaining. In this hypothesis the heat to sustain the thermal anomalies and the plumes comes from a slightly warm ocean at depth. The heat is brought to the surface by water that circulates up, through the crust and then returns to the ocean.

Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.

PubMed

Schmidt, Matthew W; Vautravers, Maryline J; Spero, Howard J

2006-10-05

Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean-atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions.

Seaglider surveys at Ocean Station Papa: Circulation and water mass properties in a meander of the North Pacific Current

NASA Astrophysics Data System (ADS)

Pelland, Noel A.; Eriksen, Charles C.; Cronin, Meghan F.

2016-09-01

A Seaglider autonomous underwater vehicle augmented the Ocean Station Papa (OSP; 50°N, 145°W) surface mooring, measuring spatial structure on scales relevant to the monthly evolution of the moored time series. During each of three missions from June 2008 to January 2010, a Seaglider made biweekly 50 km × 50 km surveys in a bowtie-shaped survey track. Horizontal temperature and salinity gradients measured by these surveys were an order of magnitude stronger than climatological values and sometimes of opposite sign. Geostrophically inferred circulation was corroborated by moored acoustic Doppler current profiler measurements and AVISO satellite altimetry estimates of surface currents, confirming that glider surveys accurately resolved monthly scale mesoscale spatial structure. In contrast to climatological North Pacific Current circulation, upper-ocean flow was modestly northward during the first half of the 18 month survey period, and weakly westward during its latter half, with Rossby number O>(0.01>). This change in circulation coincided with a shift from cool and fresh to warm, saline, oxygen-rich water in the upper-ocean halocline, and an increase in vertical fine structure there and in the lower pycnocline. The anomalous flow and abrupt water mass transition were due to the slow growth of an anticyclonic meander within the North Pacific Current with radius comparable to the scale of the survey pattern, originating to the southeast of OSP.

Complex use of waste in wastewater and circulating water treatment from oil in heat power stations

NASA Astrophysics Data System (ADS)

Nikolaeva, L. A.; Iskhakova, R. Ya.

2017-06-01

Sewage and circulating water from oil of thermal power plants (TPP) generated in fuel-oil shops during washing of electrical equipment and its running into the storm drainage system from the industrial site has been considered in the paper. It has been suggested to use the carbonate sludge of water treatment modified with hydrophobing emulsion as a sorption material for waste and circulating water treatment in thermal power plants. The carbonate sludge is waste accumulated in clarifiers at the stage of natural water pretreatment. General technical characteristics of the sludge, such as moisture, bulk density, total pore volume, ash, etc., have been determined. It has been found that the sludge without additional treatment is a hydrophilic material that has low adsorption capacity and wettability with nonpolar compounds. Therefore, the sludge is treated with organosilicon compounds to reduce the moisture capacity and increase its floatation. Several types of sorption materials based on the carbonate sludge subjected to surface and volume hydrophobization have been developed. During the volume treatment, the hydrophobing compound has been introduced into the material along with the plastifier. In case of the surface treatment, heat-treated granules have been soaked into hydrophobing emulsion. It has been shown that surface hydrophobization is most economically advantageous, because it reduces the consumption of water-repelling agent, wherein the total pore volume and sorption capacity during surface hydrophobization increase by 45 and 25% compared to that during volume hydrophobization. Based on the obtained results, the most effective sorption material has been chosen. To produce this material, it is necessary to sequentially carry out mixing of carbonate sludge with the binder, granulation, calcination, impregnation with a waterrepellent emulsion, and drying of the finished material. The suggested technology to produce the material and use it as a sorbent allows efficient wastewater treatment from oil as well as reduction of anthropogenic pressure on the environment and economic costs of the station for nature protection measures.

How Circulation of Water Affects Freezing in Ponds

ERIC Educational Resources Information Center

Moreau, Theresa; Lamontagne, Robert; Letzring, Daniel

2007-01-01

One means of preventing the top of a pond from freezing involves running a circulating pump near the bottom to agitate the surface and expose it to air throughout the winter months. This phenomenon is similar to that of the flowing of streams in subzero temperatures and to the running of taps to prevent pipe bursts in winter. All of these cases…

Experimental investigation of moving surfaces for boundary layer and circulation control of airfoils and wings

NASA Astrophysics Data System (ADS)

Vets, Robert

An experimental study was conducted to assess the application of a moving surface to affect boundary layers and circulation around airfoils for the purpose of altering and enhancing aerodynamic performance of finite wings at moderate Reynolds numbers. The moving surface was established by a wide, lightweight, nylon belt that enveloped a wing's symmetric airfoil profile articulated via a friction drive cylinder such that the direction of the upper surface was in the direction of the free stream. A water tunnel visualization study accompanied wind tunnel testing at the University of Washington, Kirsten Wind Tunnel of finite wings. An experimental study was conducted to assess the application of a moving surface to affect boundary layers and circulation around airfoils for the purpose of altering and enhancing aerodynamic performance of finite wings at moderate Reynolds numbers. The moving surface was established by a wide, lightweight, nylon belt that enveloped a wing's symmetric airfoil profile articulated via a friction drive cylinder such that the direction of the upper surface was in the direction of the free stream. A water tunnel visualization study accompanied wind tunnel testing at the University of Washington, Kirsten Wind Tunnel of finite wings. The defining non-dimensional parameter for the system is the ratio of the surface velocity to the free stream velocity, us/Uo. Results show a general increase in lift with increasing us/Uo. The endurance parameter served as an additional metric for the system's performance. Examining the results of the endurance parameter shows general increase in endurance and lift with the moving surface activated. Peak performance in terms of increased endurance along with increased lift occurs at or slightly above us/Uo = 1. Water tunnel visualization showed a marked difference in the downwash for velocity ratios greater than 1, supporting the measured data. Reynolds numbers for this investigation were 1.9E5 and 4.3E5, relevant to the class of fixed wing, Tier-1, Unmanned Aerial Vehicles (UAV).

Land-surface influences on weather and climate

NASA Technical Reports Server (NTRS)

Baer, F.; Mintz, Y.

1984-01-01

Land-surface influences on weather and climate are reviewed. The interrelationship of vegetation, evapotranspiration, atmospheric circulation, and climate is discussed. Global precipitation, soil moisture, the seasonal water cycle, heat transfer, and atmospheric temperature are among the parameters considered in the context of a general biosphere model.

The Ocean`s Thermohaline Circulation in a Fish Tank

NASA Astrophysics Data System (ADS)

Lavender, K.; Joyce, P.; Graziano, L.; Harris, S.; Jaroslow, G.; Lea, C.; Schell, J.; Witting, J.

2005-12-01

This demonstration develops intuition about density stratification, a concept critical to understanding the ocean`s thermohaline circulation. In addition, students learn how temperature and salinity affect density, how these characteristics may be density-compensating, and students gain practice in graphing and interpreting vertical profiles and temperature-salinity (T-S) diagrams. The demonstration requires a rectangular fish tank (5-10 gallons) with a plexiglass partition, preparation of three colored ''water masses'' representing surface water (warm and fresh), ''mystery'' Mediterranean Water (warm and salty), and North Atlantic Deep Water (NADW; cold and salty), a kitchen sponge, and a temperature and salinity probe. Density may be computed using an Equation of State calculator (e.g. online version at http://fermi.jhuapl.edu/denscalc.html). The larger side of the fish tank is filled halfway with NADW, then surface water is layered on top by carefully pouring it on a floating sponge. A student volunteer measures the temperature and salinity of the two water masses, while another computes the densities. Students draw vertical profiles and T-S diagrams representing the temperature, salinity, and density of the water column. The properties of the ''mystery'' water are measured and students predict what will happen when the water is poured on the opposite side of the partition and is allowed to overflow into the layered water. If the density gradients are sufficiently large, a beautiful internal wave develops as the mystery water overflows the sill and becomes intermediate Mediterranean Water. If time permits, having a student blow on the surface illustrates the limited influence of ''wind'' with depth; an internal wave may by forced by depressing the thermocline with a large, flat spoon; and pouring extra NADW on the sponge floating at the surface may illustrate deep convection.

Multimillennium changes in dissolved oxygen under global warming: results from an AOGCM and offline ocean biogeochemical model

NASA Astrophysics Data System (ADS)

Yamamoto, A.; Abe-Ouchi, A.; Shigemitsu, M.; Oka, A.; Takahashi, K.; Ohgaito, R.; Yamanaka, Y.

2016-12-01

Long-term oceanic oxygen change due to global warming is still unclear; most future projections (such as CMIP5) are only performed until 2100. Indeed, few previous studies using conceptual models project oxygen change in the next thousands of years, showing persistent global oxygen reduction by about 30% in the next 2000 years, even after atmospheric carbon dioxide stops rising. Yet, these models cannot sufficiently represent the ocean circulation change: the key driver of oxygen change. Moreover, considering serious effect oxygen reduction has on marine life and biogeochemical cycling, long-term oxygen change should be projected for higher validity. Therefore, we used a coupled atmosphere-ocean general circulation model (AOGCM) and an offline ocean biogeochemical model, investigating realistic long-term changes in oceanic oxygen concentration and ocean circulation. We integrated these models for 2000 years under atmospheric CO2 doubling and quadrupling. After global oxygen reduction in the first 500 years, oxygen concentration in deep ocean globally recovers and overshoots, despite surface oxygen decrease and weaker Atlantic Meridional Overturning Circulation. Deep ocean convection in the Weddell Sea recovers and overshoots, after initial cessation. Thus, enhanced deep convection and associated Antarctic Bottom Water supply oxygen-rich surface waters to deep ocean, resulting global deep ocean oxygenation. We conclude that the change in ocean circulation in the Southern Ocean potentially drives millennial-scale oxygenation in the deep ocean; contrary to past reported long-term oxygen reduction and general expectation. In presentation, we will discuss the mechanism of response of deep ocean convection in the Weddell Sea and show the volume changes of hypoxic waters.

Atmospheric circulations of terrestrial planets orbiting low-mass stars

NASA Astrophysics Data System (ADS)

Edson, Adam; Lee, Sukyoung; Bannon, Peter; Kasting, James F.; Pollard, David

2011-03-01

Circulations and habitable zones of planets orbiting low-mass stars are investigated. Many of these planets are expected to rotate synchronously relative to their parent stars, thereby raising questions about their surface temperature distributions and habitability. We use a global circulation model to study idealized, synchronously rotating (tidally locked) planets of various rotation periods, with surfaces of all land or all water, but with an Earth-like atmosphere and solar insolation. The dry planets exhibit wide variations in surface temperature: >80 °C on the dayside to <-110 °C on the nightside for the 240-h rotator, for example. The water-covered aquaplanets are warmer and exhibit narrower ranges of surface temperatures, e.g., ∼40 °C to >-60 °C for the 240-h orbiter. They also have a larger habitable area, defined here as the region where average surface temperatures are between 0 °C and 50 °C. This concept has little relevance for either dry or aquaplanets, but might become relevant on a planet with both land area and oceans. The circulations on these tidally locked planets exhibit systematic changes as the rotation period is varied. However, they also reveal abrupt transitions between two different circulation regimes and multiple equilibria. For the dry planet, the transition occurs between a 4-day and a 5-day period, while for the aquaplanet, it occurs between a 3-day and a 4-day period. For both dry and aqua planets, this transition occurs when the Rossby deformation radius exceeds half the planetary radius. Further investigation on the dry planet reveals that multiple equilibria exist between 100- and 221-h periods. These multiple equilibria may be relevant for real planets within the habitable zones of late K and M stars, because these planets are expected to have rotation periods between 8 and 100 Earth days.

Deep and bottom water export from the Southern Ocean to the Pacific over the past 38 million years

USGS Publications Warehouse

van de Flierdt, T.; Frank, M.; Halliday, A.N.; Hein, J.R.; Hattendorf, B.; Gunther, D.; Kubik, P.W.

2004-01-01

The application of radiogenic isotopes to the study of Cenozoic circulation patterns in the South Pacific Ocean has been hampered by the fact that records from only equatorial Pacific deep water have been available. We present new Pb and Nd isotope time series for two ferromanganese crusts that grew from equatorial Pacific bottom water (D137-01, "Nova," 7219 m water depth) and southwest Pacific deep water (63KD, "Tasman," 1700 m water depth). The crusts were dated using 10Be/9Be ratios combined with constant Co-flux dating and yield time series for the past 38 and 23 Myr, respectively. The surface Nd and Pb isotope distributions are consistent with the present-day circulation pattern, and therefore the new records are considered suitable to reconstruct Eocene through Miocene paleoceanography for the South Pacific. The isotope time series of crusts Nova and Tasman suggest that equatorial Pacific deep water and waters from the Southern Ocean supplied the dissolved trace metals to both sites over the past 38 Myr. Changes in the isotopic composition of crust Nova are interpreted to reflect development of the Antarctic Circumpolar Current and changes in Pacific deep water circulation caused by the build up of the East Antarctic Ice Sheet. The Nd isotopic composition of the shallower water site in the southwest Pacific appears to have been more sensitive to circulation changes resulting from closure of the Indonesian seaway. Copyright 2004 by the American Geophysical Union.

Using MGS TES Data to Understand Water Cycling in Mars' North Polar Region

NASA Technical Reports Server (NTRS)

Tamppari, L. K.; Hale, A. S.; Bass, D. S.; Smith, M. D.

2003-01-01

The Martian water cycle is one of the three annual cycles on Mars, dust and CO2 being the other two. Despite the fact that detailed spacecraft data, including global and annual coverage in a variety of wavelengths, have been taken of Mars spanning more than 25 years, there are many outstanding questions regarding the water cycle. There is very little exposed water on Mars today, in either the atmosphere or on the surface although there is geological evidence of catastrophic flooding and continuously running water in past epochs in Mars' history as well as recent (within about 10,000 years ago) evidence for running water in the form of gullies. While there is little water in the atmosphere, water- ice clouds do form and produce seasonal clouds caused by general circulation and by storms. These clouds may in turn be controlling the cycling of the water within the general circulation.

Influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the Ross Sea, Antarctica

NASA Astrophysics Data System (ADS)

Dinniman, Michael S.; Klinck, John M.; Smith, Walker O.

2007-11-01

Satellite imagery shows that there was substantial variability in the sea ice extent in the Ross Sea during 2001-2003. Much of this variability is thought to be due to several large icebergs that moved through the area during that period. The effects of these changes in sea ice on circulation and water mass distributions are investigated with a numerical general circulation model. It would be difficult to simulate the highly variable sea ice from 2001 to 2003 with a dynamic sea ice model since much of the variability was due to the floating icebergs. Here, sea ice concentration is specified from satellite observations. To examine the effects of changes in sea ice due to iceberg C-19, simulations were performed using either climatological ice concentrations or the observed ice for that period. The heat balance around the Ross Sea Polynya (RSP) shows that the dominant term in the surface heat budget is the net exchange with the atmosphere, but advection of oceanic warm water is also important. The area average annual basal melt rate beneath the Ross Ice Shelf is reduced by 12% in the observed sea ice simulation. The observed sea ice simulation also creates more High-Salinity Shelf Water. Another simulation was performed with observed sea ice and a fixed iceberg representing B-15A. There is reduced advection of warm surface water during summer from the RSP into McMurdo Sound due to B-15A, but a much stronger reduction is due to the late opening of the RSP in early 2003 because of C-19.

The Global Enery and Water Cycle Experiment Science Strategy

NASA Technical Reports Server (NTRS)

Chahine, M. T.

1997-01-01

The distribution of water in the atmosphere and at the surface of the Earth is the most influential factor regulating our environment, not only because water is essential for life but also because through phase transitions it is the main energy source that control clouds and radiation and drives the global circulation of the atmosphere.

A Water Droplet Pinning and Heat Transfer Characteristics on an Inclined Hydrophobic Surface.

PubMed

Al-Sharafi, Abdullah; Yilbas, Bekir Sami; Ali, Haider; AlAqeeli, N

2018-02-15

A water droplet pinning on inclined hydrophobic surface is considered and the droplet heat transfer characteristics are examined. Solution crystallization of polycarbonate is carried out to create hydrophobic characteristics on the surface. The pinning state of the water droplet on the extreme inclined hydrophobic surface (0° ≤ δ ≤ 180°, δ being the inclination angle) is assessed. Heat transfer from inclined hydrophobic surface to droplet is simulated for various droplet volumes and inclination angles in line with the experimental conditions. The findings revealed that the hydrophobic surface give rise to large amount of air being trapped within texture, which generates Magdeburg like forces between the droplet meniscus and the textured surface while contributing to droplet pinning at extreme inclination angles. Two counter rotating cells are developed for inclination angle in the range of 0° < δ < 20° and 135° < δ < 180°; however, a single circulation cell is formed inside the droplet for inclination angle of 25° ≤ δ ≤ 135°. The Nusselt number remains high for the range of inclination angle of 45° ≤ δ ≤ 135°. Convection and conduction heat transfer enhances when a single and large circulation cell is formed inside the droplet.

Insights into ice-ocean interactions and fjord circulation from fjord sea surface temperatures at the Petermann Glacier, Greenland

NASA Astrophysics Data System (ADS)

Snow, T.; Shepherd, B.; Abdalati, W.; Scambos, T. A.

2016-12-01

Dynamic processes at marine-terminating outlet glaciers are responsible for over one-third of Greenland Ice Sheet (GIS) mass loss. Enhanced intrusion of warm ocean waters at the termini of these glaciers has contributed to elevated rates of ice thinning and terminus retreat over the last two decades. In situ oceanographic measurements and modeling studies show that basal melting of glaciers and subglacial discharge can cause buoyant plumes of water to rise to the fjord surface and influence fjord circulation characteristics. The temperature of these surface waters holds clues about ice-ocean interactions and small-scale circulation features along the glacier terminus that could contribute to outlet glacier mass loss, but the magnitude and duration of temperature variability remains uncertain. Satellite remote sensing has proven very effectiver for acquiring sea surface temperatuer (SST) data from these remote regions on a long-term, consistent basis and shows promise for identifying temperature anomalies at the ice front. However, these data sets have not been widely utilized to date. Here, we use satellite-derived sea surface temperatures to identify fjord surface outflow characteristics from 2000 to present at the Petermann Glacier, which drains 4% of the GIS and is experiencing 80% of its mass loss from basal melt. We find a general SST warming trend that coincides with early sea ice breakup and precedes two major calving events and ice speedup that began in 2010. Persistent SST anomalies along the terminus provide evidence of warm outflow that is consistent with buoyant plume model predictions. However, the anomalies are not evident early in the time series, suggesting that ocean inflow and ice-ocean interactions have experienced a regime shift since 2000. Our results provide valuable insight into fjord circulation patterns and the forcing mechanisms that contribute to terminus retreat. Comparing our results to ongoing modeling experiments, time series from other outlet glaciers, and coincident in situ measurements, will help to further explain the physical processes occurring at the ice-ocean boundary and provide useful insights into the changes taking place at other GIS marine-terminating outlet glaciers.

Effects of karst and geologic structure on the circulation of water and permeability in carbonate aquifers

USGS Publications Warehouse

Stringfield, V.T.; Rapp, J.R.; Anders, R.B.

1979-01-01

The results of the natural processes caused by solution and leaching of limestone, dolomite, gypsum, salt and other soluble rocks, is known as karst. Development of karst is commonly known as karstification, which may have a pronounced effect on the topography, hydrology and environment, especially where such karst features as sinkholes and vertical solution shafts extend below the land surface and intersect lateral solution passages, cavities, caverns and other karst features in carbonate rocks. Karst features may be divided into two groups: (1) surficial features that do not extend far below the surface; and (2) karst features such as sinkholes that extend below the surface and affect the circulation of water below. The permeability of the most productive carbonate aquifers is due chiefly to enlargement of fractures and other openings by circulation of water. Important controlling factors responsible for the development of karst and permeability in carbonate aquifers include: (1) climate, topography, and presence of soluble rocks; (2) geologic structure; (3) nature of underground circulation; and (4) base level. Another important factor is the condition of the surface of the carbonate rocks at the time they are exposed to meteoric water. A carbonate rock surface, with soil or relatively permeable, less soluble cover, is more favorable for initiation of karstification and solution than bare rocks. Water percolates downward through the cover to the underlying carbonate rocks instead of running off on the surface. Also, the water becomes more corrosive as it percolates through the permeable cover to the underlying carbonate rocks. Where there is no cover or the cover has been removed, the carbonate rocks become case hardened and resistant to erosion. However, in regions underlain not only by carbonate rocks but also by beds of anhydrite, gypsum and salt, such as the Hueco Plateau in southeastern New Mexico, subsurface solution may occur where water without natural acids moves down from bare rock surfaces through cracks to the beds that are more soluble than carbonate rocks. For example, in the area of Carlsbad Caverns in southeastern New Mexico, much of the water responsible for solution that formed the caverns apparently entered the groundwater system through large open fractures and did not form sinkhole topography. East of the Carlsbad Caverns, however, in the Pecos River Valley where the carbonate rocks are overlain by the less soluble Ogallala Formation of Late Tertiary age, solution began along escarpments as the Pecos River and its tributaries cut through the less soluble cover. As these escarpments retreated, sinkholes and other karst features developed. Joints or fractures are essential for initiation of downward percolation of water in compact carbonate rocks such as some Paleozoic limestone in which there is no intergranular permeability. Also joints or fractures and bedding planes may be essential in the initiation of lateral movement of water in the zone of saturation. Where conditions of recharge and discharge are favorable, groundwater may move parallel to the dip. However, the direction of movement of water in most carbonate rocks is not necessarily down dip or parallel to the dip. The general direction of movement of both surface and groundwater may be parallel to the strike in a breached anticline. Faults may restrict the lateral movement of water, especially if water-bearing beds are faulted against relatively impervious beds. Conversely, some fault may serve as avenues through which water may move as, for example, in the Cretaceous Edwards aquifer in the San Antonio area, Texas. Karst aquifers, chiefly carbonate rocks, may be placed in three groups according to water-bearing capacity. Water in aquifers of group 1 occurs chiefly in joints, fractures, and other openings that have not been enlarged by solution. The yield of wells is small. Aquifers in group 2, with low to intermediate yields, are those in which

Hydrographic characterization of southeast Arabian Sea during the wane of southwest monsoon and spring intermonsoon.

PubMed

Vimal Kumar, K G; Dinesh Kumar, P K; Smitha, B R; Habeeb Rahman, H; Josia, Jacob; Muraleedharan, K R; Sanjeevan, V N; Achuthankutty, C T

2008-05-01

Seasonal variation of the hydrography along the southeast Arabian Sea is described using data collected onboard FORV Sagar Sampada in September--October 2003 (later phase of Southwest monsoon, SWM) and March--April 2004 (Spring inter monsoon, SIM). During the later phase of the SWM, upwelling was in the withdrawal phase and the frontal structure was clearer in the northern sections (13 and 15 degrees N lat) indicating strong upwelling in the area. The driving force of upwelling is identified as the combination of alongshore wind stress and remote forcing with a latitudinal variability. Although a more prominent upwelling was found in the north, a maximum surface Chlorophyll-a was found in the south (10 degrees N). During the SIM, the area was characterized by oligotrophic water with relatively high Sea Surface Temperature (>29 degrees C) and low salinity (33.8 to 35.4). During March, the surface hydrography was found to be controlled mainly by the intrusion of low-saline waters from the south, while during September by the high saline water from the north. The presence of various water masses [Arabian Sea High Salinity Water (ASHSW), Persian Gulf Water (PGW), Red Sea Water (RSW)] and their seasonal variations in the region is discussed and their decreasing influence towards the south is noted during both periods of observation. During the SWM, the dynamic topography showed the equator-ward flow of the West India Coastal Current (WICC) at the surface and a pole-ward coastal under current at sub-thermocline depth. During the SIM, surface circulation revealed the WICC flowing pole-ward north of 13 degrees N, but equator-ward flow in the south, with a clockwise circulation around the Lakshadweep High.

An Improved Heat Budget Estimation Including Bottom Effects for General Ocean Circulation Models

NASA Technical Reports Server (NTRS)

Carder, Kendall; Warrior, Hari; Otis, Daniel; Chen, R. F.

2001-01-01

This paper studies the effects of the underwater light field on heat-budget calculations of general ocean circulation models for shallow waters. The presence of a bottom significantly alters the estimated heat budget in shallow waters, which affects the corresponding thermal stratification and hence modifies the circulation. Based on the data collected during the COBOP field experiment near the Bahamas, we have used a one-dimensional turbulence closure model to show the influence of the bottom reflection and absorption on the sea surface temperature field. The water depth has an almost one-to-one correlation with the temperature rise. Effects of varying the bottom albedo by replacing the sea grass bed with a coral sand bottom, also has an appreciable effect on the heat budget of the shallow regions. We believe that the differences in the heat budget for the shallow areas will have an influence on the local circulation processes and especially on the evaporative and long-wave heat losses for these areas. The ultimate effects on humidity and cloudiness of the region are expected to be significant as well.

Wind-driven Sea-Ice Changes Intensify Subsurface Warm Water Intrusion into the West Antarctic Land Ice Front

NASA Astrophysics Data System (ADS)

Li, X.; Gille, S. T.; shang-Ping, X.; Xie, S. P.; Holland, D. M.; Holland, M. M.

2016-12-01

The climate change observed around Antarctica in recent decades is characterized by distinct zonally asymmetric patterns, with the strongest changes over West Antarctica. These changes are marked by strong land ice melting and sea ice redistribution around West Antarctica. This is associated with temperature and circulation anomalies in the ocean and atmosphere around the same area. In this study, we comprehensively examine the coherency between these changes using a combination of observations and numerical simulations. Results show that the atmospheric circulation changes distinctly drive the changes in ocean circulation and sea ice distribution. In addition, the atmospheric circulation induced sea ice changes play an important role in lifting the subsurface ocean temperature and salinity around the West Antarctica. During recent decades, the Amundsen Sea Low (ASL) has deepened, especially in austral autumn and winter. This deepened ASL has intensified the offshore wind near the coastal regions of the Ross Sea. Driven by these atmospheric changes, more sea ice has formed near West Antarctica in winter. In contrast, more sea ice melts during the summer. This strengthened sea ice seasonality has been observed and successfully reproduced in the model simulation. The wind-driven sea ice changes causes a surface freshening over the Ross and Amundsen Seas, with a subsurface salinity increase over the Ross Sea. The additional fresh/salt water fluxes thus further change the vertical distribution of salinity and strengthen the stratification in the Ross and Amundsen Seas. As a result of the above ice-ocean process, the mixed-layer depth around the Ross and Amundsen Seas shallows. By weakening the vertical heat transport near the surface layer, and inducing an upward movement of the circumpolar deep water (CDW), this process freshened and cooled the surface layer, while the salinity and temperature in the sub-surface ocean are increased, extending from 150 meters to >700 meters. Around the Amundsen Sea, warm water touches the continent, which could potentially contribute to the accelerated land ice melting over this area.

Surface water and groundwater interactions in coastal wetlands

NASA Astrophysics Data System (ADS)

Li, Ling; Xin, Pei; Shen, Chengji

2014-05-01

Salt marshes are an important wetland system in the upper intertidal zone, interfacing the land and coastal water. Dominated by salt-tolerant plants, these wetlands provide essential eco-environmental services for maintaining coastal biodiversity. They also act as sediment traps and help stabilize the coastline. While they play an active role in moderating greenhouse gas emissions, these wetlands have become increasingly vulnerable to the impact of global climate change. Salt marshes are a complex hydrological system characterized by strong, dynamic interactions between surface water and groundwater, which underpin the wetland's eco-functionality. Bordered with coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur at different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil aeration conditions, which in turn affect marsh plant growth. This talk presents results and findings from recent numerical and experimental studies, focusing on the pore-water flow behaviour in the marsh soil under the influence of tides and density-gradients.

Regolith-atmosphere exchange of water in Mars' recent past

NASA Astrophysics Data System (ADS)

Steele, Liam J.; Balme, Matthew R.; Lewis, Stephen R.

2017-03-01

We investigate the exchange of water vapour between the regolith and atmosphere of Mars, and how it varies with different orbital parameters, atmospheric dust contents and surface water ice reservoirs. This is achieved through the coupling of a global circulation model (GCM) and a regolith diffusion model. GCM simulations are performed for hundreds of Mars years, with additional one-dimensional simulations performed for 50 kyr. At obliquities ɛ =15∘ and 30°, the thermal inertia and albedo of the regolith have more control on the subsurface water distribution than changes to the eccentricity or solar longitude of perihelion. At ɛ =45∘ , atmospheric water vapour abundances become much larger, allowing stable subsurface ice to form in the tropics and mid-latitudes. The circulation of the atmosphere is important in producing the subsurface water distribution, with increased water content in various locations due to vapour transport by topographically-steered flows and stationary waves. As these circulation patterns are due to topographic features, it is likely the same regions will also experience locally large amounts of subsurface water at different epochs. The dustiness of the atmosphere plays an important role in the distribution of subsurface water, with a dusty atmosphere resulting in a wetter water cycle and increased stability of subsurface ice deposits.

A new multi-proxy reconstruction of Atlantic deep ocean circulation during the warm mid-Pliocene

NASA Astrophysics Data System (ADS)

Riesselman, C. R.; Dowsett, H. J.; Scher, H. D.; Robinson, M. M.

2011-12-01

The mid-Pliocene (3.264 - 3.025 Ma) is the most recent interval in Earth's history with sustained global temperatures in the range of warming predicted for the 21st century, providing an appealing analog with which to examine the Earth system changes we might encounter in the coming century. Ongoing sea surface and deep ocean temperature reconstructions and coupled ocean-atmosphere general circulation model simulations by the USGS PRISM (Pliocene Research Interpretation and Synoptic Mapping) Group identify a dramatic North Atlantic warm anomaly coupled with increased evaporation in the mid-Pliocene, possibly driving enhanced meridional overturning circulation and North Atlantic Deep Water production. However deep ocean temperature is not a conclusive proxy for water mass, and most coupled model simulations predict transient decreases in North Atlantic Deep Water production in 21st century, presenting a contrasting picture of future warmer worlds. Here, we present early results from a new multi-proxy reconstruction of Atlantic deep ocean circulation during the warm mid-Pliocene, using δ13C of benthic foraminifera as a proxy for water mass age and the neodymium isotopic imprint on fossil fish teeth as a proxy for water mass source region along a three-site depth transect from the Walvis Ridge (subtropical South Atlantic). The deep ocean circulation reconstructions resulting from this project will add a new dimension to the PRISM effort and will be useful for both initialization and evaluation of future model simulations.

Winter and summer monsoon water mass, heat and freshwater transport changes in the Arabian Sea near 8°N

NASA Astrophysics Data System (ADS)

Stramma, Lothar; Brandt, Peter; Schott, Friedrich; Quadfasel, Detlef; Fischer, Jürgen

The differences in the water mass distributions and transports in the Arabian Sea between the summer monsoon of August 1993 and the winter monsoon of January 1998 are investigated, based on two hydrographic sections along approximately 8°N. At the western end the sections were closed by a northward leg towards the African continent at about 55°E. In the central basin along 8°N the monsoon anomalies of the temperature and density below the surface-mixed layer were dominated by annual Rossby waves propagating westward across the Arabian Sea. In the northwestern part of the basin the annual Rossby waves have much smaller impact, and the density anomalies observed there were mostly associated with the Socotra Gyre. Salinity and oxygen differences along the section reflect local processes such as the spreading of water masses originating in the Bay of Bengal, northward transport of Indian Central Water, or slightly stronger southward spreading of Red Sea Water in August than in January. The anomalous wind conditions of 1997/98 influenced only the upper 50-100 m with warmer surface waters in January 1998, and Bay of Bengal Water covered the surface layer of the section in the eastern Arabian Sea. Estimates of the overturning circulation of the Arabian Sea were carried out despite the fact that many uncertainties are involved. For both cruises a vertical overturning cell of about 4-6 Sv was determined, with inflow below 2500 m and outflow between about 300 and 2500 m. In the upper 300-450 m a seasonally reversing shallow meridional overturning cell appears to exist in which the Ekman transport is balanced by a geostrophic transport. The heat flux across 8°N is dominated by the Ekman transport, yielding about -0.6 PW for August 1993, and 0.24 PW for January 1998. These values are comparable to climatological and model derived heat flux estimates. Freshwater fluxes across 8°N also were computed, yielding northward freshwater fluxes of 0.07 Sv in January 1998 and 0.43 Sv in August 1993. From climatological salinities the stronger freshwater flux in August was found to be caused by the seasonal change of salinity storage in the Arabian Sea north of 8°N. The near-surface circulation follows complex pathways, with generally cyclonic-circulation in January 1998 affected at the eastern side by the Laccadive High, and anticyclonic circulation in August 1993.

Outflow Channels Influencing Martian Climate: Global Circulation Model Simulations with Emplaced Water

NASA Technical Reports Server (NTRS)

Santiago, D. L.; Colaprete, A.; Haberle, R. M.; Sloan, L. C.; Asphaug, E. I.

2005-01-01

The existence of surface water on Mars in past geologic epochs is inferred on the basis of geomorphologic interpretation of spaceflight images, and is supported by the recent Mars Odyssey identification of ice-rich soils [1]. The Mars Exploration Rovers have provided further chemical evidence for past surface hydrologic activity [2]. One issue is whether this water-rich climate ever existed in a steady state, or whether it was triggered by catastrophic events such as large impacts [3], and/ or catastrophic outburst floods, the topic of consideration here.

Water circulation and global mantle dynamics: Insight from numerical modeling

NASA Astrophysics Data System (ADS)

Nakagawa, Takashi; Nakakuki, Tomoeki; Iwamori, Hikaru

2015-05-01

We investigate water circulation and its dynamical effects on global-scale mantle dynamics in numerical thermochemical mantle convection simulations. Both dehydration-hydration processes and dehydration melting are included. We also assume the rheological properties of hydrous minerals and density reduction caused by hydrous minerals. Heat transfer due to mantle convection seems to be enhanced more effectively than water cycling in the mantle convection system when reasonable water dependence of viscosity is assumed, due to effective slab dehydration at shallow depths. Water still affects significantly the global dynamics by weakening the near-surface oceanic crust and lithosphere, enhancing the activity of surface plate motion compared to dry mantle case. As a result, including hydrous minerals, the more viscous mantle is expected with several orders of magnitude compared to the dry mantle. The average water content in the whole mantle is regulated by the dehydration-hydration process. The large-scale thermochemical anomalies, as is observed in the deep mantle, is found when a large density contrast between basaltic material and ambient mantle is assumed (4-5%), comparable to mineral physics measurements. Through this study, the effects of hydrous minerals in mantle dynamics are very important for interpreting the observational constraints on mantle convection.

Modeling the Impact of Fjord-glacier Geometry on Subglacial Plume, Wind, and Tidally-forced Circulation in Outlet Glacier Fjords

NASA Astrophysics Data System (ADS)

Carroll, D.; Sutherland, D.; Nash, J. D.; Shroyer, E.; de Steur, L.; Catania, G. A.; Stearns, L. A.

2016-12-01

The acceleration, retreat, and thinning of Greenland's outlet glaciers coincided with a warming of Atlantic waters, suggesting that marine-terminating glaciers are sensitive to ocean forcing. However, we still lack a precise understanding of what factors control the variability of ocean heat transport toward the glacier terminus. Here we use an idealized ocean general circulation model (3D MITgcm) to systematically evaluate how fjord circulation driven by subglacial plumes, wind stress (along-fjord and along-shelf), and tides depends on grounding line depth, fjord width, sill height, and latitude. Our results indicate that while subglacial plumes in deeply grounded systems can draw shelf waters over a sill and toward the glacier, shallowly grounded systems require external forcing to renew basin waters. We use a coupled sea ice model to explore the competing influence of tidal mixing and surface buoyancy forcing on fjord stratification. Passive tracers injected in the plume, fjord basin, and shelf waters are used to quantify turnover timescales. Finally, we compare our model results with a two-year mooring record to explain fundamental differences in observed circulation and hydrography in Rink Isbræ and Kangerlussuup Sermia fjords in west Greenland. Our results underscore the first-order effect that geometry has in controlling fjord circulation and, thus, ocean heat flux to the ice.

Time variable eddy mixing in the global Sea Surface Salinity maxima

NASA Astrophysics Data System (ADS)

Busecke, J. J. M.; Abernathey, R.; Gordon, A. L.

2016-12-01

Lateral mixing by mesoscale eddies is widely recognized as a crucial mechanism for the global ocean circulation and the associated heat/salt/tracer transports. The Salinity in the Upper Ocean Processes Study (SPURS) confirmed the importance of eddy mixing for the surface salinity fields even in the center of the subtropical gyre of the North Atlantic. We focus on the global salinity maxima due to their role as indicators for global changes in the hydrological cycle as well as providing the source water masses for the shallow overturning circulation. We introduce a novel approach to estimate the contribution of eddy mixing to the global sea surface salinity maxima. Using a global 2D tracer experiments in a 1/10 degree MITgcm setup driven by observed surface velocities, we analyze the effect of eddy mixing using a water mass framework, thus focussing on the diffusive flux across surface isohalines. This enables us to diagnose temporal variability on seasonal to inter annual time scales, revealing regional differences in the mechanism causing temporal variability.Sensitivity experiments with various salinity backgrounds reveal robust inter annual variability caused by changes in the surface velocity fields potentially forced by large scale climate.

Subsurface water and clay mineral formation during the early history of Mars.

PubMed

Ehlmann, Bethany L; Mustard, John F; Murchie, Scott L; Bibring, Jean-Pierre; Meunier, Alain; Fraeman, Abigail A; Langevin, Yves

2011-11-02

Clay minerals, recently discovered to be widespread in Mars's Noachian terrains, indicate long-duration interaction between water and rock over 3.7 billion years ago. Analysis of how they formed should indicate what environmental conditions prevailed on early Mars. If clays formed near the surface by weathering, as is common on Earth, their presence would indicate past surface conditions warmer and wetter than at present. However, available data instead indicate substantial Martian clay formation by hydrothermal groundwater circulation and a Noachian rock record dominated by evidence of subsurface waters. Cold, arid conditions with only transient surface water may have characterized Mars's surface for over 4 billion years, since the early-Noachian period, and the longest-duration aqueous, potentially habitable environments may have been in the subsurface.

Interannual variability of March snow mass over Northern Eurasia and its relation to the concurrent and preceding surface air temperature, precipitation and atmospheric circulation

NASA Astrophysics Data System (ADS)

Ye, Kunhui

2018-06-01

The interannual variability of March snow water equivalent (SWE) in Northern Eurasia and its influencing factors are studied. The surface air temperature (SAT) and precipitation are the dominant factors for the snow accumulation in northern Europe and the remaining region, respectively. The strongest contribution of SAT to snow accumulation is mainly found in those months with moderate mean SAT. The strongest contribution of precipitation is not collocated with the climatological maxima in precipitation. The leading mode of March SWE variability is obtained and characterized by a spatial dipole. Anomalies in atmospheric water vapor divergence, storm activity and the associated atmospheric circulation can explain many of the associated precipitation and SAT features. Anomalies in autumn Arctic sea ice concentration (SIC) over the Barents Sea and Kara Sea (B/K Sea) and a dipole pattern of November snow cover (SC) in Eurasia are also observed. The atmospheric circulation anomalies that resemble a negative phase of North Atlantic Oscillation (NAO)/Arctic Oscillation (AO) are strongly projected onto the wintertime atmospheric circulation. Both observations and model experiment support that the autumn B/K Sea SIC has some impacts on the autumn and AO/NAO-like wintertime atmospheric circulation patterns. The dipole pattern of November Eurasian SC seems to be strongly forced by the autumn B/K Sea SIC and its feedback to the atmospheric circulation is important. Therefore, the impacts of autumn B/K Sea SIC on the autumn/wintertime atmospheric circulation and thus the March SWE variability may be modulated by both constructive and destructive interference of autumn Eurasian SC.

Hydrothermal circulation at Mount St. Helens determined by self-potential measurements

USGS Publications Warehouse

Bedrosian, P.A.; Unsworth, M.J.; Johnston, M.J.S.

2007-01-01

The distribution of hydrothermal circulation within active volcanoes is of importance in identifying regions of hydrothermal alteration which may in turn control explosivity, slope stability and sector collapse. Self-potential measurements, indicative of fluid circulation, were made within the crater of Mount St. Helens in 2000 and 2001. A strong dipolar anomaly in the self-potential field was detected on the north face of the 1980-86 lava dome. This anomaly reaches a value of negative one volt on the lower flanks of the dome and reverses sign toward the dome summit. The anomaly pattern is believed to result from a combination of thermoelectric, electrokinetic, and fluid disruption effects within and surrounding the dome. Heat supplied from a cooling dacite magma very likely drives a shallow hydrothermal convection cell within the dome. The temporal stability of the SP field, low surface recharge rate, and magmatic component to fumarole condensates and thermal waters suggest the hydrothermal system is maintained by water vapor exsolved from the magma and modulated on short time scales by surface recharge. ?? 2006 Elsevier B.V. All rights reserved.

Water-walled microfluidics for high-optical finesse cavities

NASA Astrophysics Data System (ADS)

Maayani, Shai; Martin, Leopoldo L.; Carmon, Tal

2016-01-01

In submerged microcavities there is a tradeoff between resonant enhancement for spatial water and light overlap. Why not transform the continuously resonating optical mode to be fully contained in a water microdroplet per se? Here we demonstrate a sustainable 30-μm-pure water device, bounded almost completely by free surfaces, enabling >1,000,000 re-circulations of light. The droplets survive for >16 h using a technique that is based on a nano-water bridge from the droplet to a distant reservoir to compensate for evaporation. More than enabling a nearly-perfect optical overlap with water, atomic-level surface smoothness that minimizes scattering loss, and ~99% coupling efficiency from a standard fibre. Surface tension in our droplet is 8,000 times stronger than gravity, suggesting a new class of devices with water-made walls, for new fields of study including opto-capillaries.

Circulation and oxygenation of the glacial South China Sea

NASA Astrophysics Data System (ADS)

Li, Dawei; Chiang, Tzu-Ling; Kao, Shuh-Ji; Hsin, Yi-Chia; Zheng, Li-Wei; Yang, Jin-Yu Terence; Hsu, Shih-Chieh; Wu, Chau-Ron; Dai, Minhan

2017-05-01

Degree of oxygenation in intermediate water modulates the downward transferring efficiency of primary productivity (PP) from surface water to deep water for carbon sequestration, consequently, the storage of nutrients versus the delivery and sedimentary burial fluxes of organic matter and associated biomarkers. To better decipher the PP history of the South China Sea (SCS), appreciation about the glacial-interglacial variation of the Luzon Strait (LS) throughflow, which determines the mean residence time and oxygenation of water mass in the SCS interior, is required. Based on a well-established physical model, we conducted a 3-D modeling exercise to quantify the effects of sea level drop and monsoon wind intensity on glacial circulation pattern, thus, to evaluate effects of productivity and circulation-induced oxygenation on the burial of organic matter. Under modern climatology wind conditions, a 135 m sea-level drop results in a greater basin closeness and a ∼24% of reduction in the LS intermediate westward throughflow, consequently, an increase in the mean water residence time (from 19.0 to 23.0 years). However, when the wind intensity was doubled during glacial low sea-level conditon, the throughflow restored largely to reach a similar residence time (18.4 years) as today regardless its closeness. Comparing with present day SCS, surface circulation pattern in glacial model exhibits (1) stronger upwelling at the west off Luzon Island, and (2) an intensified southwestward jet current along the western boundary of the SCS basin. Superimposed hypothetically by stronger monsoon wind, the glacial SCS conditions facilitate greater primary productivity in the northern part. Manganese, a redox sensitive indicator, in IMAGES core MD972142 at southeastern SCS revealed a relatively reducing environment in glacial periods. Considering the similarity in the mean water residence time between modern and glacial cases, the reducing environment of the glacial southeastern SCS was thus ascribed to a productivity-induced rather than ventilation-induced consequence.

Flow and geochemistry of groundwater beneath a back-barrier lagoon: The subterranean estuary at Chincoteague Bay, Maryland, USA

USGS Publications Warehouse

Bratton, J.F.; Böhlke, J.K.; Krantz, D.E.; Tobias, C.R.

2009-01-01

To better understand large-scale interactions between fresh and saline groundwater beneath an Atlantic coastal estuary, an offshore drilling and sampling study was performed in a large barrier-bounded lagoon, Chincoteague Bay, Maryland, USA. Groundwater that was significantly fresher than overlying bay water was found in shallow plumes up to 8??m thick extending more than 1700??m offshore. Groundwater saltier than bay surface water was found locally beneath the lagoon and the barrier island, indicating recharge by saline water concentrated by evaporation prior to infiltration. Steep salinity and nutrient gradients occur within a few meters of the sediment surface in most locations studied, with buried peats and estuarine muds acting as confining units. Groundwater ages were generally more than 50??years in both fresh and brackish waters as deep as 23??m below the bay bottom. Water chemistry and isotopic data indicate that freshened plumes beneath the estuary are mixtures of water originally recharged on land and varying amounts of estuarine surface water that circulated through the bay floor, possibly at some distance from the sampling location. Ammonium is the dominant fixed nitrogen species in saline groundwater beneath the estuary at the locations sampled. Isotopic and dissolved-gas data from one location indicate that denitrification within the subsurface flow system removed terrestrial nitrate from fresh groundwater prior to discharge along the western side of the estuary. Similar situations, with one or more shallow semi-confined flow systems where groundwater geochemistry is strongly influenced by circulation of surface estuary water through organic-rich sediments, may be common on the Atlantic margin and elsewhere.

Boundary-layer diabatic processes, the virtual effect, and convective self-aggregation

NASA Astrophysics Data System (ADS)

Yang, D.

2017-12-01

The atmosphere can self-organize into long-lasting large-scale overturning circulations over an ocean surface with uniform temperature. This phenomenon is referred to as convective self-aggregation and has been argued to be important for tropical weather and climate systems. Here we use a 1D shallow water model and a 2D cloud-resolving model (CRM) to show that boundary-layer diabatic processes are essential for convective self-aggregation. We will show that boundary-layer radiative cooling, convective heating, and surface buoyancy flux help convection self-aggregate because they generate available potential energy (APE), which sustains the overturning circulation. We will also show that evaporative cooling in the boundary layer (cold pool) inhibits convective self-aggregation by reducing APE. Both the shallow water model and CRM results suggest that the enhanced virtual effect of water vapor can lead to convective self-aggregation, and this effect is mainly in the boundary layer. This study proposes new dynamical feedbacks for convective self-aggregation and complements current studies that focus on thermodynamic feedbacks.

Shifting Surface Currents in the Northern North Atlantic Ocean

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Rhines, Peter B.

2007-01-01

Analysis of surface drifter tracks in the North Atlantic Ocean from the time period 1990 to 2006 provides the first evidence that the Gulf Stream waters can have direct pathways to the Nordic Seas. Prior to 2000, the drifters entering the channels leading to the Nordic Seas originated in the western and central subpolar region. Since 2001 several paths from the western subtropics have been present in the drifter tracks leading to the Rockall Trough through which the most saline North Atlantic Waters pass to the Nordic Seas. Eddy kinetic energy from altimetry shows also the increased energy along the same paths as the drifters, These near surface changes have taken effect while the altimetry shows a continual weakening of the subpolar gyre. These findings highlight the changes in the vertical structure of the northern North Atlantic Ocean, its dynamics and exchanges with the higher latitudes, and show how pathways of the thermohaline circulation can open up and maintain or increase its intensity even as the basin-wide circulation spins down.

Links Between the Deep Western Boundary Current, Labrador Sea Water Formation and Export, and the Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Myers, Paul G.; Kulan, Nilgun

2010-05-01

Based on an isopyncal analysis of historical data, 3-year overlapping triad fields of objectively analysed temperature and salinity are produced for the Labrador Sea, covering 1949-1999. These fields are then used to spectrally nudge an eddy-permitting ocean general circulation model of the sub-polar gyre, otherwise forced by inter annually varying surface forcing based upon the Coordinated Ocean Reference Experiment (CORE). High frequency output from the reanalysis is used to examine Labrador Sea Water formation and its export. A number of different apprpoaches are used to estimate Labrador Sea Water formation, including an instanteous kinematic approach to calculate the annual rate of water mass subduction at a given density range. Historical transports are computed along sections at 53 and 56N for several different water masses for comparison with recent observations, showing a decline in the stength of the deep western boundary current with time. The variability of the strength of the meridional overturning circulation (MOC) from the reanalysis is also examined in both depth and density space. Linkages between MOC variability and water mass formation variability is considered.

Water Quality Monitoring in the Execution of Canal Remediation Methods in the Florida Keys

NASA Astrophysics Data System (ADS)

Serna, A.; Briceno, H.

2016-02-01

Monitoring data indicate relatively high nutrient concentrations in waters close to shore along the Florida Keys, and corresponding responses from the system, such as higher phytoplankton biomass, turbidity and light attenuation as well as lower oxygenation and lower salinities of the water column. These changes, associated to human impact, have become more obvious near canal mouths. Waters close to shore show characteristics closely related to those in residential canals, affected by quick movement of infiltrated runoff and wastewaters (septic tanks), tides and high water table. Many canals do not meet the minimum water quality (WQ) criteria established by the State of Florida and are a potential source of contaminants to near shore waters designated as Outstanding Florida Waters. Canal remediation is being conducted by the Monroe County targeting poor circulation and organic matter accumulation. The restoration technologies include reduction in weed wrack, enhanced circulation, organic removal and partial backfilling. The objective of WQ monitoring is to measure the status and trends of WQ parameters to evaluate progress toward achieving and maintaining WQ standards and protecting/restoring the living marine resources. Monitoring followed a Before-and-After-Control-Impact scheme (BACI). Field measurements, included diel observations and vertical profiles of physical-chemical properties (salinity, DO, %DO saturation, temperature and turbidity) and nutrient analysis. Comparing profiles between remediated and control canals indicated similar patterns in physicochemical properties, and suggesting larger seasonal than spatial variability. BACI diel observations, in surface and bottom waters of remediated canals indicated little difference for surface waters, but significant improvements for bottom waters. Most surface waters are well oxygenated, while bottom waters show a significant increase in DO following culvert installation.

Interannual variation of the South China Sea circulation during winter: intensified in the southern basin

NASA Astrophysics Data System (ADS)

Zu, Tingting; Xue, Huijie; Wang, Dongxiao; Geng, Bingxu; Zeng, Lili; Liu, Qinyan; Chen, Ju; He, Yunkai

2018-05-01

Surface geostrophic current derived from altimetry remote sensing data, and current profiles observed from in-situ Acoustic Doppler Current Profilers (ADCP) mooring in the northern South China Sea (NSCS) and southern South China Sea (SSCS) are utilized to study the kinetic and energetic interannual variability of the circulation in the South China Sea (SCS) during winter. Results reveal a more significant interannual variation of the circulation and water mass properties in the SSCS than that in the NSCS. Composite ananlysis shows a significantly reduced western boundary current (WBC) and a closed cyclonic eddy in the SSCS at the mature phase of El Niño event, but a strong WBC and an unclosed cyclonic circulation in winter at normal or La Niña years. The SST is warmer while the subsurface water is colder and fresher in the mature phase of El Niño event than that in the normal or La Niña years in the SSCS. Numerical experiments and energy analysis suggest that both local and remote wind stress change are important for the interannual variation in the SSCS, remote wind forcing and Kuroshio intrusion affect the circulation and water mass properties in the SSCS through WBC advection.

Buoyancy forcing and the MOC: insights from experiments, simulations and global models

NASA Astrophysics Data System (ADS)

White, B. L.; Passaggia, P. Y.; Zemskova, V.

2017-12-01

The driving forces behind the Meridional Overturning Circulation (MOC) have been widely debated, with wind-driven upwelling, surface buoyancy fluxes due to heating/cooling/freshwater input, and vertical diffusion due to turbulent mixing all thought to play significant roles. To explore the specific role of buoyancy forcing we present results from experiments and simulations of Horizontal Convection (HC), where a circulation is driven by differential buoyancy forcing applied along a horizontal surface. We interpret these results using energy budgets based on the local Available Potential Energy framework introduced in [Scotti and White, J. Fluid Mech., 2014]. We first describe HC experiments driven by the diffusion of salt in water across membranes localized at the surface, at Schmidt numbers {Sc}≈ 610 and Rayleigh numbers in the range 1012 < Ra=Δ b L3/(ν κ ) < 1017, where ν is the kinematic viscosity of water, κ is the diffusion coefficient of salt, L=[.5,2,5]m is the length of the different tanks and Δ b=g(ρ salt}-ρ {fresh}/ρ_{fresh is the reduced gravity difference. We show that the scaling follows a Nu ˜ Ra1/4 type scaling recently theorized by Shishkina et; al. (2016). We then present numerical results for rotating horizontal convection with a zonally re-entrant channel to represent the Southern Ocean branch of the MOC. While the zonal wind stress profile is important to the spatial pattern of the circulation, perhaps surprisingly, the energy budget shows only a weak dependence on the magnitude of the wind input, suggesting that surface APE generation by buoyancy forcing is dominant in driving the overturning circulation.

Changes in the Martian Circulation and Climate in Response to Orbital Parameter Variations

NASA Astrophysics Data System (ADS)

Richardson, M. I.; Wilson, R. J.

2000-10-01

Martian orbital parameters are known to vary on time scales greater than 105 years. Such variations, especially in obliquity, have important consequences for the spatial distribution of solar heating of the surface and atmosphere, and hence are expected to affect some form of quasi-periodic climate change. The impact of changing obliquity on surface temperatures, and hence on volatile stability have been widely addressed. However, the changing insolation patterns should also modify the circulation of the atmosphere. As the nature and rate of volatile transport, and the vigour of dust lifting and transport from the surface are critical aspects of the climate, the circulation response to orbital variations needs to be assessed. In this presentation, we show results from the Geophysical Fluid Dynamics Laboratory (GFDL) Mars General Circulation Model (GCM) in which the orbit of Mars has been varied: obliquities between 0 and 60, perihelion passage between Ls=70 and 250, and eccentricities between 0 and 0.12. In general, the total atmosphere and cap CO2 budget is held constant (i.e. we assume no exchange with the regolith), and that the rate of dust supply into the lowest model level remains constant. The impact of these assumptions are examined. Many of the anticipated changes in circulation are found to occur as obliquity is increased from 0: The Hadley cell strength and that of the winter polar jet are found to increase; The magnitude of the seasonal CO2 cycle increases, resulting in extensive seasonal ice caps; Surface winds strengthen resulting in greater surface stresses and likely stronger dust lifting; The cycle of water becomes more vigourous, with large column vapour amounts in the polar regions corresponding to higher cap surface temperatures. However, some results contrast with expectations: Although the surface wind strengths change with orbital parameters, the mean directions tend not to, with implications for aeolian geological features; Even at low obliquity, the model does not develop a permanent CO2 ice cap at either pole (this likely reflects the fact that uniform and non-varying ice properties are gravely inadequate to realistically simulate Martian polar ices); Water ice deposits do not stabilize at the equator, even at high obliquity - instead they slosh backwards-and-forwards between the seasonal ice caps, as they do at present. We note that the southern summer Hadley circulation remains the dominant cell when integrated over the annual cycle, even when the timing of perihelion passage is varied by 180 degrees. We suggest that this reflects the greater importance of the global topographic dichotomy for the strength of the mean meridional circulation over that of eccentricity.

Abrupt changes of intermediate-water oxygen in the northwestern Pacific during the last 27 kyr

NASA Astrophysics Data System (ADS)

Ishizaki, Yui; Ohkushi, Ken'ichi; Ito, Takashi; Kawahata, Hodaka

2009-04-01

An oxygen minimum zone (OMZ) currently exists at intermediate water depths on the northern Japanese margin in the northwestern Pacific. The OMZ results largely from a combination of high surface-water productivity and poor ventilation of intermediate waters. We investigated the late Quaternary history (last 27 kyr) of the intensity of this OMZ using changes in benthic foraminiferal carbon isotopes and assemblages in a sediment core taken on the continental slope off Shimokita Peninsula, northern Japan, at a water depth of 975 m. The core was located well within the region of the present-day OMZ and high surface-water productivity. The benthic foraminiferal δ13C values, which indicate millennial-scale fluctuations of nutrient contents at the sediment-water interface, were 0.48‰ lower during the last glacial maximum (LGM) than during the late Holocene. These results do not indicate the formation of glacial intermediate waters of subarctic Pacific origin, but rather the large contribution of high-nutrient water masses such as the Antarctic Intermediate Water, implying that the regional circulation pattern during the LGM was similar to that of modern times. Benthic foraminiferal assemblages underwent major changes in response to changes in dissolved oxygen concentrations in ocean floor sediments. The lowest oxygen and highest nutrient conditions, marked by dysoxic taxa and negative values of benthic foraminiferal δ13C, occurred during the Bølling/Allerød (B/A) and Pre-Boreal warming events. Dysoxic conditions in this region during these intervals were possibly caused by high surface-water productivity at times of reduced intermediate-water ventilation in the northwestern Pacific. The benthic assemblages show dysoxic events on approx. 100- to 200-year cycles during the B/A, reflecting centennial-scale productivity changes related to freshwater cycles and surface-water circulation in the North Pacific.

Understanding Spatial and Temporal Variations of Arctic Circulation Using Oxygen Isotopes of Seawater

NASA Astrophysics Data System (ADS)

Yin, L.; Kopans-Johnson, C. R.; LeGrande, A. N.; Kelly, S.

2015-12-01

The isotopic ratio of 18O to 16O in seawater (2005ppm in ocean water is defined as 𝛿18Oseawater≡0 permil or 0‰) is a fundamental ocean tracer due to its distinct linear relationship with salinity(𝛿18O -S) from regional inland freshwater sources. As opposed to salinity alone, 𝛿18O distinguishes river runoff from sea-ice melt and traces ocean circulation pathways from coastal to open waters and surface to deep waters. Observations from the past 60 years of 𝛿18O seawater were compiled into a database by Schimdt et al. (1999), and subsequently used to calculate a 3-dimensional 1°x1° 𝛿18O global gridded dataset by LeGrande and Schmidt (2006). Although the Schmidt et al. (1999) Global Seawater Oxygen-18 Database (𝛿18Oobs) contains 25,514 measurements used to calculate the global gridded dataset, LeGrande and Schmidt (2006) point out that, "data coverage varies greatly from region to region," with seasonal variability creating biases in areas where sea ice is present. Python Pandas is used to automate the addition of 2,942 records to the Schmidt et al. (1999) Global Seawater Oxygen-18 Database (𝛿18Oobs), and examine the spatial and temporal distributions of 18O in the Arctic Ocean. 10 initial water masses are defined using spatial and temporal trends, clusters of observations, and Arctic surface circulation. Jackknife slope analysis of water mass 𝛿18O -S is used to determine anomalous data points and regional hydrology, resulting in 4 distinct Arctic water masses. These techniques are used to improve the gridded 𝛿18Oseawater dataset by distinguishing unique water masses, and accounting for seasonal variability of complex high latitude areas.

Global Ocean Circulation During Cretaceous Time

NASA Astrophysics Data System (ADS)

Haupt, B. J.; Seidov, D.

2001-12-01

Present--day global thermohaline ocean circulation (TOC) is usually associated with high--latitude deep-water formation due to surface cooling. In this understanding of the TOC driven by the deep--water production, the warm deep ocean during Mesozoic--Cenozoic time is a challenge. It may be questioned whether warm deep--ocean water, which is direct geologic evidence, does reflect warm polar surface--ocean regions. For the warm Cretaceous, it is difficult to maintain strong poleward heat transport in the case of reduced oceanic thermal contrasts. Usually, atmospheric feedbacks, in conjunction with the increase of atmospheric concentrations of greenhouse gases, are employed in order to explain the warm equable Cretaceous--Eocene climate. However, there is no feasible physical mechanism that could maintain warm subpolar surface oceans in both hemispheres, an assumption often used in atmospheric modeling. Our numerical experiments indicate that having a relatively cool but saltier high--latitude sea surface in at least one hemisphere is sufficient for driving a strong meridional overturning. Thus freshwater impacts in the high latitudes may be responsible for a vigorous conveyor capable of maintaining sufficient poleward oceanic heat transport needed to keep the polar oceans ice--free. These results imply that evaporation-precipitation patterns during warm climates are especially important climatic factors that can redistribute freshwater to create hemispheric asymmetry of sea surface conditions capable of generating a sufficiently strong TOC, otherwise impossible in warm climates.

Near-Surface Monsoonal Circulation of the Vietnam East Sea from Lagrangian Drifters

DTIC Science & Technology

2015-09-30

Sea from Lagrangian Drifters Luca Centurioni Scripps Institution of Oceanography 9500 Gilman Drive Mail Code 0213 La Jolla, California 92103...Contribute to the study of coastal and open ocean current systems in sparsely sampled regions such us the South China Sea (SCS), using a Lagrangian ...We intend to make new Lagrangian and Eulerian observations to measure the seasonal circulation 1) in the coastal waters of Vietnam and 2) in the SCS

Evaluation of HCMM satellite data for estuarine tidal circulation patterns and thermal inertia soil moisture measurements. [Delaware Bay, Cooper River, and the Potomac River estuaries; Luverne, Minnesota, soil moisture, and water temperature of Lake Anna, Virginia

NASA Technical Reports Server (NTRS)

Wiesnet, D. R.; Mcginnis, D. F., Jr. (Principal Investigator); Matson, M.; Pritchard, J. A.

1981-01-01

Digital thermal maps of the Cooper River (SC) and the Potomac River estuaries were prepared from heat capacity mapping radiometer (HCMR) tapes. Tidal phases were correctly interpreted and verified. Synoptic surface circulation patterns were charted by location thermal fronts and water mass boundaries within the estuaries. Thermal anomalies were detected adjacent of a conventional power plant on the Potomac. Under optimum conditions, estuaries as small as the Cooper River can be monitored for generalized thermal/tidal circulation patterns by the HCMM-type IR sensors. The HCMM thermal inertia approach to estimating soil moisture at the Luverne (MN) test site was found to be unsatisfactory as a NESS operational satellite technique because of cloud cover interference. Thermal-IR data show similar structure of the Baltimore and Washington heat islands when compared to NOAA AVHRR thermal-IR data. Thermal anomalies from the warm water discharge water of a nuclear power plant were mapped in Lake Anna, Virginia.

The Influence of Ice-Ocean Interactions on Europa's Overturning Circulation

NASA Astrophysics Data System (ADS)

Zhu, P.; Manucharyan, G. E.; Thompson, A. F.; Goodman, J. C.; Vance, S.

2016-12-01

Jupiter's moon Europa appears to have a global liquid ocean, which is located beneath an ice shell that covers the moon's entire surface. Linking ocean dynamics and ice-ocean interactions is crucial to understanding observed surface features on Europa as well as other satellite measurements. Ocean properties and circulation may also provide clues as to whether the moon has the potential to support extraterrestrial life through chemical transport governed by ice-ocean interactions. Previous studies have identified a Hadley cell-like overturning circulation extending from the equator to mid latitudes. However, these model simulations do not consider ice-ocean interactions. In this study, our goal is to investigate how the ocean circulation may be affected by ice. We study two ice-related processes by building idealized models. One process is horizontal convection driven by an equator-to-pole buoyancy difference due to latitudinal ice transport at the ocean surface, which is found to be much weaker than the convective overturning circulation. The second process we consider is the freshwater layer formed by ice melting at the equator. A strong buoyancy contrast between the freshwater layer and the underlying water suppresses convection and turbulent mixing, which may modify the surface heat flux from the ocean to the bottom of the ice. We find that the salinity of the ocean below the freshwater layer tends to be homogeneous both vertically and horizontally with the presence of an overturning circulation. Critical values of circulation strength constrain the freshwater layer depth, and this relationship is sensitive to the average salinity of the ocean. Further coupling of temperature and salinity of the ice and the ocean that includes mutual influences between the surface heat flux and the freshwater layer may provide additional insights into the ice-ocean feedback, and its influence on the latitudinal difference of heat transport.

Tracking the Surface Circulation in Coastal Upwelling off Central and Northern California over Long Times and Large Areas.

NASA Astrophysics Data System (ADS)

Largier, J. L.; Garcia-Reyes, M.; Bjorkstedt, E.; Paduan, J. D.

2016-12-01

More than a decade of HF Radar data off central and northern California provides an unprecedented view of the flow structures and interannual variability in surface circulation in a coastal upwelling area. The interaction of the alongshore shelf jet with shoreline features and mesoscale eddies is well represented in direct analyses of HFR data and also important in improving the performance of data-assimilating models. While invaluable for operational response in the short-term, this long-term record of surface circulation is equally invaluable in ecosystem oceanography. With direct measurement of currents, the different expressions of upwelling can be disaggregated. Wind forcing, transport patterns and water properties can be evaluated independently and indexed independently. In doing this, it becomes clear that wind-current-temperature correlations change from place to place and year to year in any given region and that a single "upwelling index" is a blunt tool to track changes in pelagic and benthic communities in coastal upwelling areas.

Ocean circulation and biogeochemistry moderate interannual and decadal surface water pH changes in the Sargasso Sea

USGS Publications Warehouse

Nathalie F. Goodkin,; Bo-Shian Wang,; Chen-Feng You,; Konrad Hughen,; Prouty, Nancy G.; Bates, Nicholas; Scott Doney,

2015-01-01

The oceans absorb anthropogenic CO2 from the atmosphere, lowering surface ocean pH, a concern for calcifying marine organisms. The impact of ocean acidification is challenging to predict as each species appears to respond differently and because our knowledge of natural changes to ocean pH is limited in both time and space. Here we reconstruct 222 years of biennial seawater pH variability in the Sargasso Sea from a brain coral, Diploria labyrinthiformis. Using hydrographic data from the Bermuda Atlantic Time-series Study and the coral-derived pH record, we are able to differentiate pH changes due to surface temperature versus those from ocean circulation and biogeochemical changes. We find that ocean pH does not simply reflect atmospheric CO2 trends but rather that circulation/biogeochemical changes account for >90% of pH variability in the Sargasso Sea and more variability in the last century than would be predicted from anthropogenic uptake of CO2 alone.

GCM Simulation of the Large-scale North American Monsoon Including Water Vapor Tracer Diagnostics

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Walker, Gregory; Schubert, Siegfried D.; Sud, Yogesh; Atlas, Robert M. (Technical Monitor)

2001-01-01

The geographic sources of water for the large-scale North American monsoon in a GCM are diagnosed using passive constituent tracers of regional water'sources (Water Vapor Tracers, WVT). The NASA Data Assimilation Office Finite Volume (FV) GCM was used to produce a 10-year simulation (1984 through 1993) including observed sea surface temperature. Regional and global WVT sources were defined to delineate the surface origin of water for precipitation in and around the North American i'vionsoon. The evolution of the mean annual cycle and the interannual variations of the monsoonal circulation will be discussed. Of special concern are the relative contributions of the local source (precipitation recycling) and remote sources of water vapor to the annual cycle and the interannual variation of warm season precipitation. The relationships between soil water, surface evaporation, precipitation and precipitation recycling will be evaluated.

Adaptive scaling model of the main pycnocline and the associated overturning circulation

NASA Astrophysics Data System (ADS)

Fuckar, Neven-Stjepan

This thesis examines a number of crucial factors and processes that control the structure of the main pycnocline and the associated overturning circulation that maintains the ocean stratification. We construct an adaptive scaling model: a semi-empirical low-order theory based on the total transformation balance that linearly superimposes parameterized transformation rate terms of various mechanisms that participate in the water-mass conversion between the warm water sphere and the cold water sphere. The depth of the main pycnocline separates the light-water domain from the dense-water domain beneath the surface, hence we introduce a new definition in an integral form that is dynamically based on the large-scale potential vorticity (i.e., vertical density gradient is selected for the kernel function of the normalized vertical integral). We exclude the abyssal pycnocline from our consideration and limit our domain of interest to the top 2 km of water column. The goal is to understand the controlling mechanisms, and analytically predict and describe a wide spectrum of ocean steady states in terms of key large-scale indices relevant for understanding the ocean's role in climate. A devised polynomial equation uses the average depth of the main pycnocline as a single unknown (the key vertical scale of the upper ocean stratification) and gives us an estimate for the northern hemisphere deep water production and export across the equator from the parts of this equation. The adaptive scaling model aims to elucidate the roles of a limited number of dominant processes that determine some key upper ocean circulation and stratification properties. Additionally, we use a general circulation model in a series of simplified single-basin ocean configurations and surface forcing fields to confirm the usefulness of our analytical model and further clarify several aspects of the upper ocean structure. An idealized numerical setup, containing all the relevant physical and dynamical properties, is key to obtaining a clear understanding, uncomplicated by the effect of the real world geometry or intricacy of realistic surface radiative and turbulent fluxes. We show that wind-driven transformation processes can be decomposed into two terms separately driven by the mid-latitude westerlies and the low-latitude easterlies. Our analytical model smoothly connects all the classical limits describing different ocean regimes in a single-basin single-hemisphere geometry. The adjective "adaptive" refers to a simple and quantitatively successful adjustment to the description of a single-basin two-hemisphere ocean, with and without a circumpolar channel under the hemispherically symmetric surface buoyancy. For example, our water-mass conversion framework, unifying wind-driven and thermohaline processes, provides us with further insight into the "Drake Passage effect without Drake Passage". The modification of different transformation pathways in the Southern Hemisphere results in the equivalent net conversion changes. The introduction of hemispheric asymmetry in the surface density can lead to significant hemispheric differences in the main pycnocline structure. This demonstrates the limitations of our analytical model based on only one key vertical scale. Also, we show a strong influence of the northern hemisphere surface density change in high latitudes on the southern hemisphere stratification and circumpolar transport.

Infrared photography and imagery in water resources research

USGS Publications Warehouse

Robinove, Charles J.

1965-01-01

Infrared photography has restricted usefulness in general water resources studies but is particularly useful in special problems such as shoreline mapping. Infrared imagery is beginning to be used in water resources studies for the identification of surface and sub surface thermal anomalies as expressed at the surface and the measurement of apparent water surface temperatures. It will attain its maximum usefulness only when interpretation criteria for infrared imagery are fully developed. Several important hydrologic problems to which infrared imagery may be applied are: (1) determination of circulation and cooling of water in power plant cooling ponds, (2) measurement of river temperature and temperature decline downstream from power plants discharging heated water, (3) identification of submarine springs along coasts, and (4) measurement of temperature differences along streams as indicators of effluent seepage of ground water. Although it is possible at this time to identify many features of importance to hydrology by the use of infrared imagery, the task remaining is to develop criteria to show the hydrologic significance of the features.

An ocean large-eddy simulation of Langmuir circulations and convection in the surface mixed layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skyllingstad, E.D.; Denbo, D.W.

Numerical experiments were performed using a three-dimensional large-eddy simulation model of the ocean surface mixed layer that includes the Craik-Leibovich vortex force to parameterize the interaction of surface waves with mean currents. Results from the experiments show that the vortex force generates Langmuir circulations that can dominate vertical mixing. The simulated vertical velocity fields show linear, small-scale, coherent structures near the surface that extend downwind across the model domain. In the interior of the mixed layer, scales of motion increase to eddy sizes that are roughly equivalent to the mixed-layer depth. Cases with the vortex force have stronger circulations nearmore » the surface in contrast to cases with only heat flux and wind stress, particularly when the heat flux is positive. Calculations of the velocity variance and turbulence dissipation rates for cases with and without the vortex force, surface cooling, and wind stress indicate that wave-current interactions are a dominant mixing process in the upper mixed layer. Heat flux calculations show that the entrainment rate at the mixed-layer base can be up to two times greater when the vortex force is included. In a case with reduced wind stress, turbulence dissipation rates remained high near the surface because of the vortex force interaction with preexisting inertial currents. In deep mixed layers ({approximately}250 m) the simulations show that Langmuir circulations can vertically transport water 145 m during conditions of surface heating. Observations of turbulence dissipation rates and the vertical temperature structure support the model results. 42 refs., 20 figs., 21 tabs.« less

No inter-gyre pathway for sea-surface temperature anomalies in the North Atlantic.

PubMed

Foukal, Nicholas P; Lozier, M Susan

2016-04-22

Recent Lagrangian analyses of surface drifters have questioned the existence of a surface current connecting the Gulf Stream (GS) to the subpolar gyre (SPG) and have cast doubt on the mechanism underlying an apparent pathway for sea-surface temperature (SST) anomalies between the two regions. Here we use modelled Lagrangian trajectories to determine the fate of surface GS water and satellite SST data to analyse pathways of GS SST anomalies. Our results show that only a small fraction of the surface GS water reaches the SPG, the water that does so mainly travels below the surface mixed layer, and GS SST anomalies do not propagate into the SPG on interannual timescales. Instead, the inter-gyre heat transport as part of the Atlantic Meridional Overturning Circulation must be accomplished via subsurface pathways. We conclude that the SST in the SPG cannot be predicted by tracking SST anomalies along the GS.

No inter-gyre pathway for sea-surface temperature anomalies in the North Atlantic

PubMed Central

Foukal, Nicholas P.; Lozier, M. Susan

2016-01-01

Recent Lagrangian analyses of surface drifters have questioned the existence of a surface current connecting the Gulf Stream (GS) to the subpolar gyre (SPG) and have cast doubt on the mechanism underlying an apparent pathway for sea-surface temperature (SST) anomalies between the two regions. Here we use modelled Lagrangian trajectories to determine the fate of surface GS water and satellite SST data to analyse pathways of GS SST anomalies. Our results show that only a small fraction of the surface GS water reaches the SPG, the water that does so mainly travels below the surface mixed layer, and GS SST anomalies do not propagate into the SPG on interannual timescales. Instead, the inter-gyre heat transport as part of the Atlantic Meridional Overturning Circulation must be accomplished via subsurface pathways. We conclude that the SST in the SPG cannot be predicted by tracking SST anomalies along the GS. PMID:27103496

Salinity Remote Sensing and the Study of the Global Water Cycle

NASA Technical Reports Server (NTRS)

Lagerloef, G. S. E.; LeVine, David M.; Chao, Y.; Colomb, F. Raul; Font, J.

2007-01-01

The SMOS and AquariusISAC-D satellite missions will begin a new era to map the global sea surface salinity (SSS) field and its variability from space within the next twothree years. They will provide critical data needed to study the interactions between the ocean circulation, global water cycle and climate. Key scientific issues to address are (1) mapping large expanses of the ocean where conventional SSS data do not yet exist, (2) understanding the seasonal and interannual SSS variations and the link to precipitation, evaporation and sea-ice patterns, (3) links between SSS and variations in the oceanic overturning circulation, (4) air-sea coupling processes in the tropics that influence El Nino, and (4) closing the marine freshwater budget. There is a growing body of oceanographic evidence in the form of salinity trends that portend significant changes in the hydrologic cycle. Over the past several decades, highlatitude oceans have become fresher while the subtropical oceans have become saltier. This change is slowly spreading into the subsurface ocean layers and may be affecting the strength of the ocean's therrnohaline overturning circulation. Salinity is directly linked to the ocean dynamics through the density distribution, and provides an important signature of the global water cycle. The distribution and variation of oceanic salinity is therefore attracting increasing scientific attention due to the relationship to the global water cycle and its influence on circulation, mixing, and climate processes. The oceans dominate the water cycle by providing 86% of global surface evaporation (E) and receiving 78% of global precipitation (P). Regional differences in E-P, land runoff, and the melting or freezing of ice affect the salinity of surface water. Direct observations of E-P over the ocean have large uncertainty, with discrepancies between the various state-of-the-art precipitation analyses of a factor of two or more in many regions. Quantifying the climatic influence of the oceanic water cycle requires more accurately resolving the net air-sea water flux. Measuring global SSS trends on seasonal to interannual timescales by satellite is fundamental to this problem because the SSS trends represent detectable time-integrated signals of the variable marine hydrological cycle. Satellite measurements, coupled with an array of in situ observations, will provide global synoptic SSS fields for the first time history. These data will provide a strong constraint on climate models and data assimilation efforts, which must properly represent the freshwater budget in terms of E-P, ocean advection and surface layer mixing in order to accurately simulate the true ocean state. The SSS fields will allow us to quantify the covariability between the SSS and the strong seasonal E-P cycle in the tropics and high latitudes. Field measurement campaigns to exploit satellite and in situ measurements to close the seasonal E-P cycle over an ocean region are being considered. Lastly the satellite systems will monitor and trace the large long-lived SSS anomalies from year to year that have the potential to influence El Nino and the large scale ocean circulation.

North Atlantic variability and its links to European climate over the last 3000 years.

PubMed

Moffa-Sánchez, Paola; Hall, Ian R

2017-11-23

The subpolar North Atlantic is a key location for the Earth's climate system. In the Labrador Sea, intense winter air-sea heat exchange drives the formation of deep waters and the surface circulation of warm waters around the subpolar gyre. This process therefore has the ability to modulate the oceanic northward heat transport. Recent studies reveal decadal variability in the formation of Labrador Sea Water. Yet, crucially, its longer-term history and links with European climate remain limited. Here we present new decadally resolved marine proxy reconstructions, which suggest weakened Labrador Sea Water formation and gyre strength with similar timing to the centennial cold periods recorded in terrestrial climate archives and historical records over the last 3000 years. These new data support that subpolar North Atlantic circulation changes, likely forced by increased southward flow of Arctic waters, contributed to modulating the climate of Europe with important societal impacts as revealed in European history.

Large eddy simulation model for wind-driven sea circulation in coastal areas

NASA Astrophysics Data System (ADS)

Petronio, A.; Roman, F.; Nasello, C.; Armenio, V.

2013-12-01

In the present paper a state-of-the-art large eddy simulation model (LES-COAST), suited for the analysis of water circulation and mixing in closed or semi-closed areas, is presented and applied to the study of the hydrodynamic characteristics of the Muggia bay, the industrial harbor of the city of Trieste, Italy. The model solves the non-hydrostatic, unsteady Navier-Stokes equations, under the Boussinesq approximation for temperature and salinity buoyancy effects, using a novel, two-eddy viscosity Smagorinsky model for the closure of the subgrid-scale momentum fluxes. The model employs: a simple and effective technique to take into account wind-stress inhomogeneity related to the blocking effect of emerged structures, which, in turn, can drive local-scale, short-term pollutant dispersion; a new nesting procedure to reconstruct instantaneous, turbulent velocity components, temperature and salinity at the open boundaries of the domain using data coming from large-scale circulation models (LCM). Validation tests have shown that the model reproduces field measurement satisfactorily. The analysis of water circulation and mixing in the Muggia bay has been carried out under three typical breeze conditions. Water circulation has been shown to behave as in typical semi-closed basins, with an upper layer moving along the wind direction (apart from the anti-cyclonic veering associated with the Coriolis force) and a bottom layer, thicker and slower than the upper one, moving along the opposite direction. The study has shown that water vertical mixing in the bay is inhibited by a large level of stable stratification, mainly associated with vertical variation in salinity and, to a minor extent, with temperature variation along the water column. More intense mixing, quantified by sub-critical values of the gradient Richardson number, is present in near-coastal regions where upwelling/downwelling phenomena occur. The analysis of instantaneous fields has detected the presence of large cross-sectional eddies spanning the whole water column and contributing to vertical mixing, associated with the presence of sub-surface horizontal turbulent structures. Analysis of water renewal within the bay shows that, under the typical breeze regimes considered in the study, the residence time of water in the bay is of the order of a few days. Finally, vertical eddy viscosity has been calculated and shown to vary by a couple of orders of magnitude along the water column, with larger values near the bottom surface where density stratification is smaller.

Numerical model of the circulation and dispersion in the east Adriatic coastal waters

NASA Astrophysics Data System (ADS)

Beg Paklar, Gordana; Dzoic, Tomislav; Koracin, Darko; Matijevic, Slavica; Grbec, Branka; Ivatek-Sahdan, Stjepan

2017-04-01

The Regional Ocean Modeling System (ROMS) was implemented to reproduce physical properties of the area around submarine outlet Stobrec in the middle Adriatic coastal area. ROMS model run was forced with realistic atmospheric fields obtained from meteorological model Aladin, climatological river discharges, tides and dynamics of the surrounding area imposed at the open boundaries. Atmospheric forcing included momentum, heat and water fluxes calculated interactively from the Aladin surface fields during ROMS model simulations. Simulated fields from the Adriatic and shelf scale models were used to prescribe the initial and open boundary conditions for fine resolution coastal domain. Model results were compared with available CTD measurements and discussed in the light of the climatological circulation and thermohaline properties of the middle Adriatic coastal area. Variability in the circulation is related to the prevailing atmospheric conditions, changes in the hydrological conditions and water mass exchange at the open boundaries. Basic features of the coastal circulation are well reproduced by the ROMS model, as well as temperatures and salinities which are within corresponding seasonal intervals, although with lower stratification than measured ones. In order to reproduce dispersion of the passive tracer the ROMS model was coupled with Lagrangian dispersion model. Multiyear monitoring of the physical, chemical and biological parameters around the sewage outlet was used to assess the quality of the dispersion model results. Among measured parameters, redox potential of the surface sediment layer was selected to be compared with model results as its negative values are direct consequence of increased organic matter input that can be attributed to the sewage system inflow.

A Numerical Study of Currents, Water Surface Elevations, and Energy Dissipation in Chandeleur-Breton Sound, Louisiana.

DTIC Science & Technology

1978-02-01

Numerical methods in the form of a digital computer model were used to simulate and study the tide- and wind-induced circulation in Chandeleur -Breton...entrances through the Chandeleur Island chain, where speed reaches 50-60 cm/sec for short periods. Surface elevations were found to have an average tide range

Interhemispheric teleconnections: Late Pliocene change in Mediterranean outflow water linked to changes in Indonesian Through-Flow and Atlantic Meridional Overturning Circulation, a review and update

NASA Astrophysics Data System (ADS)

Sarnthein, Michael; Grunert, Patrick; Khélifi, Nabil; Frank, Martin; Nürnberg, Dirk

2018-03-01

The ultimate, possibly geodynamic control and potential impact of changes in circulation activity and salt discharge of Mediterranean outflow waters (MOW) on Atlantic meridional overturning circulation have formed long-standing objectives in paleoceanography. Late Pliocene changes in the distal advection of MOW were reconstructed on orbital timescales for northeast Atlantic DSDP/ODP sites 548 and 982 off Brittany and on Rockall Plateau, supplemented by a proximal record from Site U1389 west off Gibraltar, and compared to Western Mediterranean surface and deep-water records of Alboran Sea Site 978. From 3.43 to 3.3 Ma, MOW temperatures and salinities form a prominent rise by 2-4 °C and 3 psu, induced by a preceding and coeval rise in sea surface and deep-water salinity and increased summer aridity in the Mediterranean Sea. We speculate that these changes triggered an increased MOW flow and were ultimately induced by a persistent 2.5 °C cooling of Indonesian Through-Flow waters. The temperature drop resulted from the northward drift of Australia that crossed a threshold value near 3.6-3.3 Ma and led to a large-scale cooling of the eastern subtropical Indian Ocean and in turn, to a reduction of African monsoon rains. Vice versa, we show that the distinct rise in Mediterranean salt export after 3.4 Ma induced a unique long-term rise in the formation of Upper North Atlantic Deep Water, that followed with a phase lag of 100 ky. In summary, we present evidence for an interhemispheric teleconnection of processes in the Indonesian Gateways, the Mediterranean and Labrador Seas, jointly affecting Pliocene climate.

Recent intensification of the Walker Circulation and the role of natural sea surface temperature variability

NASA Astrophysics Data System (ADS)

Zhao, X.; Allen, R.

2017-12-01

In a warming world, the tropical atmospheric overturning circulation-including the Walker Circulation-is expected to weaken due to thermodynamic constraints. Tropical precipitation increases at a slower rate than water vapor-which increases according to Clausius Clapeyron scaling, assuming constant relative humidity-so the tropical overturning circulation slows down. This is supported by both observations and model simulations, which show a slowdown of the Walker Circulation over the 20th century. Model projections suggest a further weakening of the Walker Circulation in the 21st century. However, over the last several decades (1979-2014), multiple observations reveal a robust strengthening of the Walker Circulation. Although coupled CMIP5 simulations are unable to reproduce this strengthening, AMIP simulations-which feature the observed evolution of SSTs-are generally able to reproduce it. Assuming the ensemble mean sea surface temperatures (SSTs) from historical CMIP5 simulations accurately represent the externally forced SST response, the observed SSTs can be decomposed into a forced and an unforced component. CAM5 AMIP-type simulations driven by the unforced component of observed SSTs reproduce the observed strengthening of the Walker Circulation. Corresponding simulations driven by the forced component of observed SSTs yield a weaker Walker Circulation. These results are consistent with the zonal tropical SST gradient and the Bjerknes feedback. The unforced component of SSTs yield an increased SST gradient over tropical Pacific (a La Nina like pattern) and strengthening of the tropical trade winds, which constitute the lower branch of the Walker Circulation. The forced component of SSTs yields a zonally uniform tropical Pacific SST warming and a marginal weakening of the Walker Circulation. Our results suggest significant modulation of the tropical Walker Circulation by natural SST variability over the last several decades.

Large-scale effects on the regulation of tropical sea surface temperature

NASA Technical Reports Server (NTRS)

Hartmann, Dennis L.; Michelsen, Marc L.

1993-01-01

The dominant terms in the surface energy budget of the tropical oceans are absorption of solar radiation and evaporative cooling. If it is assumed that relative humidity in the boundary layer remains constant, evaporative cooling will increase rapidly with sea surface temperature (SST) because of the strong temperature dependence of saturation water vapor pressure. The resulting stabilization of SST provided by evaporative cooling is sufficient to overcome positive feedback contributed by the decrease of surface net longwave cooling with increasing SST. Evaporative cooling is sensitive to small changes in boundary-layer relative humidity. Large and negative shortwave cloud forcing in the regions of highest SST are supported by the moisture convergence associated with largescale circulations. In the descending portions of these circulations the shortwave cloud forcing is suppressed. When the effect of these circulations is taken into account by spatial averaging, the area-averaged cloud forcing shows no sensitivity to area-averaged SST changes associated with the 1987 warming event in the tropical Pacific. While the shortwave cloud forcing is large and important in the convective regions, the importance of its role in regulating the average temperature of the tropics and in modulating temperature gradients within the tropics is less clear. A heuristic model of SST is used to illustrate the possible role of large-scale atmospheric circulations on SST in the tropics and the coupling between SST gradients and mean tropical SST. The intensity of large-scale circulations responds sensitivity to SST gradients and affects the mean tropical SST by supplying dry air to the planetary boundary layer. Large SST gradients generate vigorous circulations that increase evaporation and reduce the mean SST.

Studies of Current Circulation at Ocean Waste Disposal Sites

NASA Technical Reports Server (NTRS)

Klemas, V. (Principal Investigator); Davis, G.; Henry, R.

1976-01-01

The author has identified the following significant results. Acid waste plume was observed in LANDSAT imagery fourteen times ranging from during dump up to 54 hours after dump. Circulation processes at the waste disposal site are highly storm-dominated, with the majority of the water transport occurring during strong northeasterlies. There is a mean flow to the south along shore. This appears to be due to the fact that northeasterly winds produce stronger currents than those driven by southeasterly winds and by the thermohaline circulation. During the warm months (May through October), the ocean at the dump site stratifies with a distinct thermocline observed during all summer cruising at depths ranging from 10 to 21 m. During stratified conditions, the near-bottom currents were small. Surface currents responded to wind conditions resulting in rapid movement of surface drogues on windy days. Mid-depth drogues showed an intermediate behavior, moving more rapidly as wind velocities increased.

On the Vertical Distribution of Local and Remote Sources of Water for Precipitation

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.

2001-01-01

The vertical distribution of local and remote sources of water for precipitation and total column water over the United States are evaluated in a general circulation model simulation. The Goddard Earth Observing System (GEOS) general circulation model (GCM) includes passive constituent tracers to determine the geographical sources of the water in the column. Results show that the local percentage of precipitable water and local percentage of precipitation can be very different. The transport of water vapor from remote oceanic sources at mid and upper levels is important to the total water in the column over the central United States, while the access of locally evaporated water in convective precipitation processes is important to the local precipitation ratio. This result resembles the conceptual formulation of the convective parameterization. However, the formulations of simple models of precipitation recycling include the assumption that the ratio of the local water in the column is equal to the ratio of the local precipitation. The present results demonstrate the uncertainty in that assumption, as locally evaporated water is more concentrated near the surface.

Disruption of a cyclonic eddy circulation by wind stress in Prince William Sound, Alaska

NASA Astrophysics Data System (ADS)

Halverson, Mark J.; Carter Ohlmann, J.; Johnson, Mark A.; Scott Pegau, W.

2013-07-01

Oceanographic observations made during the Sound Predictions 2009 field experiment in Prince William Sound, Alaska, have documented rapid changes in the upper water column (0-40m) circulation. An assortment of drifting buoys, sampling four different depths, and HF radar surface current mapping, revealed three modes of circulation: anticyclonic, open cyclonic, and closed cyclonic. Each mode was observed at least once within an 18-day window, and the transition between them took as little as a day. Time-resolved hydrographic measurements show that the mass field was variable, but generally arranged such that the surface geostrophic flow should be in a closed-core cyclonic eddy configuration. Observations show that the mass field was likely influenced by relatively low salinity water flowing into Prince William Sound from the shelf, and from local freshwater input. We quantitatively examine why a closed-core circulation was not always observed by focusing on the transition between the closed and open cyclonic flow patterns. The western region of the central sound is a key area for this transition. Here, the high-frequency radar revealed that the closed circulation was established when the net flow shifted direction from northward to southward. A detailed comparison of the meridional geostrophic and wind-driven flows, using measured winds and hydrographic data from CTD profiles and two autonomous vehicles, shows that the geostrophic flow was mostly southward while the wind-driven flow was mostly northward. A net southward flow can be caused by a decrease in the northward wind-driven flow or an increase in the southward geostrophic flow.

CO2 and circulation in the deglacial North Pacific

NASA Astrophysics Data System (ADS)

Taylor, B.; Rae, J. W. B.; Gray, W. R.; Rees-Owen, R. L.; Burke, A.

2017-12-01

The North Pacific is the largest carbon reservoir in the global ocean, but has not typically been thought to play an active role in deglacial CO2 rise based on its modern stratified state. Recent studies (Okazaki et al., 2010; Rae et al., 2014; Max et al., 2017), however, have suggested that a more dynamic circulation regime operated in the glacial and deglacial North Pacific and, as such, the role of the North Pacific in deglacial CO2 rise may have been underestimated. We present two new high-resolution boron isotope records of surface water pCO2 from the North West and North East Pacific spanning the last 22 kyrs. The two records show remarkable coherence over key intervals during the last deglaciation and highlight major changes over a number of abrupt climate events. At both sites, following the LGM, pCO2(sw) rises, coincident with a younging of North Pacific intermediate and deep waters. This suggests that increased local overturning mixed CO2-rich deep waters throughout the water column, likely contributing to CO2 outgassing during Heinrich Stadial 1 (HS1). Both records exhibit decreases in pCO2(sw) during the latter stages of HS1, which are immediately followed by a rapid increase in pCO2(sw) at the onset of the Bølling-Allerød (B/A). Radiocarbon and δ13C data indicate a collapse in North Pacific Intermediate Water formation at the onset of the B/A, which, combined with enhanced wind stress curl, would have allowed CO2-rich waters to mix into the surface ocean from intermediate-depths. The combination of high nutrient availability and a seasonally well-stratified mixed layer likely led to the abrupt increase in export productivity across the region; the excess surface water CO2 shows that alleviation of iron or light limitation could not have been its primary cause. Our new records highlight the importance of overturning circulation in the North Pacific in controlling productivity and CO2 release on glacial/interglacial timescales.

Miocene deepwater oceanography

NASA Astrophysics Data System (ADS)

Woodruff, Fay; Savin, Samuel M.

1989-02-01

A global synthesis of Miocene benthic foraminiferal carbon and oxygen isotopic and faunal abundance data indicates that Miocene thermohaline circulation evolved through three regimes corresponding approximately to early, middle, and late Miocene times. There is evidence for major qualitative differences between the circulation of the modern ocean and the Miocene ocean prior to 11 Ma. The 13C/12C ratios of the benthic foraminifera Cibicidoides are interpreted in terms of water mass aging, i.e., the progressive depletion of dissolved O2 and lowering of δ13C values as the result of oxidation of organic matter as water flows further from its sources at the surface of the oceans. Both isotopic and faunal data indicate that the early Miocene regime, from 22 to 15 Ma, was the most different from today's. During that interval intermediate and deep waters of both the Atlantic and the Pacific oceans aged in a northward direction, and the intermediate waters of the Indian, the South Atlantic and the South Pacific oceans were consistently the youngest in the global ocean. We speculate that early Miocene global thermohaline circulation may have been strongly influenced by the influx of warm saline water, Tethyan Indian Saline Water, from the Tethys into the northern Indian Ocean. The isotopic and faunal data suggest that flow from the Tethyan region into the Indian Ocean diminished or terminated at about 14 Ma. Isotopic and faunal data give no evidence for North Atlantic Deep Water (NADW) formation prior to about 14.5 Ma (with the exception of a brief episode in the early Miocene). From 14.5 to 11 Ma NADW formation was weak, and circumpolar and Antarctic water flooded the deep South Atlantic and South Pacific as the Antarctic ice cap grew. From about 10 Ma to the end of the Miocene, thermohaline circulation resembled the modern circulation in many ways. In latest Miocene time (6 to 5 Ma) circulation patterns were very similar to today's except that NADW formation was greatly diminished. The distribution pattern of siliceous oozes in Miocene sediments is consistent with our proposed reconstruction of thermohaline circulation. Major changes which occurred in circulation during the middle Miocene were probably related to the closing of the Tethys and may have contributed to rapid middle Miocene growth of the Antarctic ice cap. Appendices 1, 4, 6, and 7 are available withentire article on microfiche. Order fromAmerican Geophysical Union, 2000 FloridaAvenue, N.W., Washington, DC 20009.Document 88P-002; $5.00. Payment mustaccompany order.

Climate and the equilibrium state of land surface hydrology parameterizations

NASA Technical Reports Server (NTRS)

Entekhabi, Dara; Eagleson, Peter S.

1991-01-01

For given climatic rates of precipitation and potential evaporation, the land surface hydrology parameterizations of atmospheric general circulation models will maintain soil-water storage conditions that balance the moisture input and output. The surface relative soil saturation for such climatic conditions serves as a measure of the land surface parameterization state under a given forcing. The equilibrium value of this variable for alternate parameterizations of land surface hydrology are determined as a function of climate and the sensitivity of the surface to shifts and changes in climatic forcing are estimated.

The power of runoff

NASA Astrophysics Data System (ADS)

Wörman, A.; Lindström, G.; Riml, J.

2017-05-01

Although the potential energy of surface water is a small part of Earth's energy budget, this highly variable physical property is a key component in the terrestrial hydrologic cycle empowering geomorphological and hydrological processes throughout the hydrosphere. By downscaling of the daily hydrometeorological data acquired in Sweden over the last half-century this study quantifies the spatial and temporal distribution of the dominating energy components in terrestrial hydrology, including the frictional resistance in surface water and groundwater as well as hydropower. The energy consumed in groundwater circulation was found to be 34.6 TWh/y or a heat production of approximately 13% of the geothermal heat flux. Significant climate driven, periodic fluctuations in the power of runoff, stream flows and groundwater circulation were revealed that have not previously been documented. We found that the runoff power ranged from 173 to 260 TWh/y even when averaged over the entire surface of Sweden in a five-year moving window. We separated short-term fluctuations in runoff due to precipitation filtered through the watershed from longer-term seasonal and climate driven modes. Strong climate driven correlations between the power of runoff and climate indices, wind and solar intensity were found over periods of 3.6 and 8 years. The high covariance that we found between the potential energy of surface water and wind energy implies significant challenges for the combination of these renewable energy sources.

Holocene oscillations in temperature and salinity of the surface subpolar North Atlantic.

PubMed

Thornalley, David J R; Elderfield, Harry; McCave, I Nick

2009-02-05

The Atlantic meridional overturning circulation (AMOC) transports warm salty surface waters to high latitudes, where they cool, sink and return southwards at depth. Through its attendant meridional heat transport, the AMOC helps maintain a warm northwestern European climate, and acts as a control on the global climate. Past climate fluctuations during the Holocene epoch ( approximately 11,700 years ago to the present) have been linked with changes in North Atlantic Ocean circulation. The behaviour of the surface flowing salty water that helped drive overturning during past climatic changes is, however, not well known. Here we investigate the temperature and salinity changes of a substantial surface inflow to a region of deep-water formation throughout the Holocene. We find that the inflow has undergone millennial-scale variations in temperature and salinity ( approximately 3.5 degrees C and approximately 1.5 practical salinity units, respectively) most probably controlled by subpolar gyre dynamics. The temperature and salinity variations correlate with previously reported periods of rapid climate change. The inflow becomes more saline during enhanced freshwater flux to the subpolar North Atlantic. Model studies predict a weakening of AMOC in response to enhanced Arctic freshwater fluxes, although the inflow can compensate on decadal timescales by becoming more saline. Our data suggest that such a negative feedback mechanism may have operated during past intervals of climate change.

Environmental Assessment of the Relocation and Construction of a Military Working Dog (MWD) Kennel

DTIC Science & Technology

2006-12-01

specified area to function. Components include transportation and circulation (i.e., movement of vehicles), utilities, solid waste handling, and...sites to appropriate receiving surface waters. For several reasons, storm water systems can employ a variety of devices to slow the movement of water...football field) Fence 3,600 meters 05 CDCII Preschool Playground 8,800 05 CDCII Pretoddler Playground 5,225 05 CDCII Toddler Playground 6,450 05

A Non-Equilibrium Sediment Transport Model for Coastal Inlets and Navigation Channels

DTIC Science & Technology

2011-01-01

exchange of water , sediment, and nutrients between estuaries and the ocean. Because of the multiple interacting forces (waves, wind, tide, river...in parallel using OpenMP. The CMS takes advantage of the Surface- water Modeling System (SMS) interface for grid generation and model setup, as well...as for plotting and post- processing (Zundel, 2000). The circulation model in the CMS (called CMS-Flow) computes the unsteady water level and

Improving NOAA's NWLON Through Enhanced Data Inputs from NASA's Ocean Surface Topography

NASA Technical Reports Server (NTRS)

Guest, DeNeice C.

2010-01-01

This report assesses the benefit of incorporating NASA's OSTM (Ocean Surface Topography Mission) altimeter data (C- and Ku-band) into NOAA's (National Oceanic and Atmospheric Administration) NWLON (National Water Level Observation Network) DSS (Decision Support System). This data will enhance the NWLON DSS by providing additional inforrnation because not all stations collect all meteorological parameters (sea-surface height, ocean tides, wave height, and wind speed over waves). OSTM will also provide data where NWLON stations are not present. OSTM will provide data on seasurface heights for determining sea-level rise and ocean circulation. Researchers and operational users currently use satellite altimeter data products with the GSFCOO NASA data model to obtain sea-surface height and ocean circulation inforrnation. Accurate and tirnely inforrnation concerning sea-level height, tide, and ocean currents is needed to irnprove coastal tidal predictions, tsunarni and storm surge warnings, and wetland restoration.

The Aquarius Mission: Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

Koblinsky, Chester; Chao, Y.; deCharon, A.; Edelstein, W.; Hildebrand, P.; Lagerloef, G.; LeVine, D.; Pellerano, F.; Rahmat-Samii, Y.; Ruf, C.

2001-01-01

Aquarius is a new satellite mission concept to study the impact of the global water cycle on the ocean, including the response of the ocean to buoyancy forcing and the subsequent feedback of the ocean on the climate. The measurement objective of Aquarius is sea surface salinity, which reflects the concentration of freshwater at the ocean surface. Salinity affects the dielectric constant of sea water and, consequently, the radiometric emission of the sea surface to space. Rudimentary space observations with an L-band radiometer were first made from Skylab in the mid-70s and numerous aircraft missions of increasing quality and improved technology have been conducted since then. Technology is now available to carry out a global mission, which includes both an accurate L band (1.413 Ghz) radiometer and radar system in space and a global array of in situ observations for calibration and validation, in order to address key NASA Earth Science Enterprise questions about the global cycling of water and the response of the ocean circulation to climate change. The key scientific objectives of Aquarius examine the cycling of water at the ocean's surface, the response of the ocean circulation to buoyancy forcing, and the impact of buoyancy forcing on the ocean's thermal feedback to the climate. Global surface salinity will also improve our ability to model the surface solubility chemistry needed to estimate the air-sea exchange of CO2. In order to meet these science objectives, the NASA Salinity Sea Ice Working Group over the past three years has concluded that the mission measurement goals should be better than 0.2 practical salinity units (psu) accuracy, 100 km resolution, and weekly to revisits. The Aquarius mission proposes to meet these measurement requirements through a real aperture dual-polarized L band radiometer and radar system. This system can achieve the less than 0.1 K radiometric temperature measurement accuracy that is required. A 3 m antenna at approx. 600km altitude in a sun-synchronous orbit and 300 km swath can provide the desired 100 km resolution global coverage every week. Within this decade, it may be possible to combine satellite sea surface salinity measurements with ongoing satellite observations of temperature, surface height, air-sea fluxes; vertical profiles of temperature and salinity from the Argo program; and modern ocean/atmosphere modeling and data assimilation tools, in order to finally address the complex influence of buoyancy on the ocean circulation and climate.

Influence of longer dry seasons in the Southern Amazon on patterns of water vapor transport over northern South America and the Caribbean

NASA Astrophysics Data System (ADS)

Agudelo, Jhoana; Arias, Paola A.; Vieira, Sara C.; Martínez, J. Alejandro

2018-06-01

Several studies have identified a recent lengthening of the dry season over the southern Amazon during the last three decades. Some explanations to this lengthening suggest the influence of changes in the regional circulation over the Atlantic and Pacific oceans, whereas others point to the influence of vegetation changes over the Amazon rainforest. This study aims to understand the implications of more frequent long dry seasons in this forest on atmospheric moisture transport toward northern South America and the Caribbean region. Using a semi-Langrangian model for water vapor tracking, results indicate that longer dry seasons in the southern Amazon relate to reductions of water vapor content over the southern and eastern Amazon basin, due to significant reductions of evaporation and recycled precipitation rates in these regions, especially during the transition from dry to wet conditions in the southern Amazon. On the other hand, longer dry seasons also relate to enhanced atmospheric moisture content over the Caribbean and northern South America regions, mainly due to increased contributions of water vapor from oceanic regions and the increase of surface moisture convergence over the equatorial region. This highlights the importance of understanding the relative role of regional circulation and local surface conditions on modulating water vapor transport toward continental regions.

Anthropogenic Influence on the Changes of the Subtropical Gyre Circulation in the South Pacific in the 20th Century

NASA Astrophysics Data System (ADS)

Albrecht, F.; Pizarro, O.; Montecinos, A.

2016-12-01

The subtropical ocean gyre in the South Pacific is a large scale wind-driven ocean circulation, including the Peru-Chile Current, the westward South Equatorial Current, the East Australian Current, and the eastward South Pacific Current. Large scale ocean circulations play an essential role in the climate of the Earth over long and short term time scales.In the recent years a spin-up of this circulation has been recognized analyzing observations of sea level, temperature and salinity profiles, sea surface temperature and wind. Until now it is not clear whether this spin-up is decadal variability or whether it is a long-term trend introduced by anthropogenic forcing. This study aims to analyze whether and how anthropogenic forcing influences the position and the strength of the gyre in the 20th century. To determine that, yearly means of different variables of an ensemble of CMIP5 models are analyzed. The experiments 'historical' and 'historicalNat' are examined. The 'historical' experiment simulates the climate of the 20th century and the 'historicalNat' experiment covers the same time period, but only includes natural forcings. Comparing the outcomes of these two experiments is supposed to give information about the anthropogenic influence on the subtropical gyre of the South Pacific.The main variable we analyze is sea level change. This is directly related to the gyre circulation. The center of the gyre is characterized by a high pressure zone (high sea level) and the temporal and spatial variability of the sea level height field gives information about changes in the gyre circulation. The CMIP5 databank includes steric and dynamic sea level changes. Steric sea level, that is the contribution of temperature and salinity of the water, describes the major contribution to regional sea level change with respect to the global mean. Density changes contract or expand the water, which also changes the sea surface height. This does not only occur at the surface, but at all layers in the ocean. Sea level change thus integrates ocean variability throughout the depth of the ocean. Sea level simulations of the different experiments are compared using long-term trends, multi-year anomalies and EOF-Analysis. Changes in temperature and salinity in the deeper ocean are used to describe the development of the gyre below the surface.

Evidence for Interannual to Decadal Variations in Hadley and Walker Circulations and Links to Water and Energy Fluxes

NASA Technical Reports Server (NTRS)

Robertson, Franklin; Bosilovich, Michael; Miller, Timothy

2007-01-01

Mass and energy transports associated with the Hadley and Walker circulations are important components of the earth s climate system and are strongly linked to hydrologic processes. Interannual to decadal variation in these flows likely signify a combination of natural climate noise as well as a response to anthropgenic forcing. There remains considerable uncertainty in quantifying variations in these flows. Evidence in the surface pressure record supports a weakening of the Walker circulation over the Pacific in recent decades. Conversely the NCEP / NCAR and ERA 40 reanalyses indicate that the Hadley circulation has increased in strength over the last two decades, though these analyses depict significantly different mass circulation changes. Interestingly, the NCEP - II / DOE reanalysis contains essentially no Hadley circulation changes. Most climate model integrations anticipate a weakening of both tropical circulations associated with stronger static stability. Clearly there is much uncertainty not only with the mass transports, but also how they are linked to water and energy balance of the planet through variations in turbulent heat and radiative fluxes and horizontal exports / imports of energy. Here we examine heat and water budget variations from a number of reanalysis products and focus on the linear and nonlinear response of ENSO warm and cold events as opportunities to study budget variations over the past 15-20 years. Our analysis addresses such questions as To what extent do Hadley and Walker Cell variations compensate each other on mass and energy transport? Do static stability adjustments appear to constrain fractional precipitation response vs. fractional water vapor response? We appeal to constraints offered by GPCP precipitation, SSWI ocean evaporation estimates, and ISCCP-FD radiative fluxes, and other satellite data sets to interpret and confirm reanalysis-based diagnostics. Using our findings we also attempt to place in context the recent findings that tropical ocean evaporation increased by order 5% or more during the 1990s, reconciling this with GPCP precipitation variations.

Climatic Influences on Southern Makassar Strait Salinity Over the Past Century

NASA Astrophysics Data System (ADS)

Murty, S. A.; Goodkin, N. F.; Halide, H.; Natawidjaja, D.; Suwargadi, B.; Suprihanto, I.; Prayudi, D.; Switzer, A. D.; Gordon, A. L.

2017-12-01

The Indonesian Throughflow (ITF) is a globally important ocean current that fuels heat and buoyancy fluxes throughout the Indo-Pacific and is known to covary in strength with the El Niño Southern Oscillation at interannual time scales. A climate system with a less well-quantified impact on the ITF is the East Asian Winter Monsoon (EAWM), which drives less saline surface waters from the South China Sea (SCS) into the Makassar Strait, obstructing surface ITF flow. We present a subannually resolved record of sea surface salinity (SSS) from 1927 to 2011 based on coral δ18O from the Makassar Strait that reveals variability in the relative contributions of different source waters to the surface waters of the Makassar Strait during the boreal winter monsoon. We find that the EAWM (January-March) strongly influences interannual SSS variability during boreal winter over the twentieth century (r = 0.54, p << 0.0001), impacting surface water circulation in the SCS and Indonesian Seas.

Variational data assimilative modeling of the Gulf of Maine in spring and summer 2010

NASA Astrophysics Data System (ADS)

Li, Yizhen; He, Ruoying; Chen, Ke; McGillicuddy, Dennis J.

2015-05-01

A data assimilative ocean circulation model is used to hindcast the Gulf of Maine [GOM) circulation in spring and summer 2010. Using the recently developed incremental strong constraint 4D Variational data assimilation algorithm, the model assimilates satellite sea surface temperature and in situ temperature and salinity profiles measured by expendable bathythermograph, Argo floats, and shipboard CTD casts. Validation against independent observations shows that the model skill is significantly improved after data assimilation. The data-assimilative model hindcast reproduces the temporal and spatial evolution of the ocean state, showing that a sea level depression southwest of the Scotian Shelf played a critical role in shaping the gulf-wide circulation. Heat budget analysis further demonstrates that both advection and surface heat flux contribute to temperature variability. The estimated time scale for coastal water to travel from the Scotian Shelf to the Jordan Basin is around 60 days, which is consistent with previous estimates based on in situ observations. Our study highlights the importance of resolving upstream and offshore forcing conditions in predicting the coastal circulation in the GOM.

Variations in Atlantic surface ocean paleoceanography, 50°-80° N: A time-slice record of the last 30,000 years

NASA Astrophysics Data System (ADS)

Sarnthein, Michael; Jansen, Eystein; Weinelt, Mara; Arnold, Maurice; Duplessy, Jean Claude; Erlenkeuser, Helmut; FlatøY, Astrid; Johannessen, Gro; Johannessen, Truls; Jung, Simon; Koc, Nalan; Labeyrie, Laurent; Maslin, Mark; Pflaumann, Uwe; Schulz, Hartmut

1995-12-01

Eight time slices of surface-water paleoceanography were reconstructed from stable isotope and paleotemperature data to evaluate late Quaternary changes in density, current directions, and sea-ice cover in the Nordic Seas and NE Atlantic. We used isotopic records from 110 deep-sea cores, 20 of which are accelerator mass spectrometry (AMS)-14C dated and 30 of which have high (>8 cm /kyr) sedimentation rates, enabling a resolution of about 120 years. Paleotemperature estimates are based on species counts of planktonic foraminifera in 18 cores. The δ18O and δ13C distributions depict three main modes of surface circulation: (1) The Holocene-style interglacial mode which largely persisted over the last 12.8 14C ka, and probably during large parts of stage 3. (2) The peak glacial mode showing a cyclonic gyre in the, at least, seasonally ice-free Nordic Seas and a meltwater lens west of Ireland. Based on geostrophic forcing, it possibly turned clockwise, blocked the S-N flow across the eastern Iceland-Shetland ridge, and enhanced the Irminger current around west Iceland. It remains unclear whether surface-water density was sufficient for deepwater formation west of Norway. (3) A meltwater regime culminating during early glacial Termination I, when a great meltwater lens off northern Norway probably induced a clockwise circulation reaching south up to Faeroe, the northward inflow of Irminger Current water dominated the Icelandic Sea, and deepwater convection was stopped. In contrast to circulation modes two and three, the Holocene-style circulation mode appears most stable, even unaffected by major meltwater pools originating from the Scandinavian ice sheet, such as during δ18O event 3.1 and the Bölling. Meltwater phases markedly influenced the European continental climate by suppressing the "heat pump" of the Atlantic salinity conveyor belt. During the peak glacial, melting icebergs blocked the eastward advection of warm surface water toward Great Britain, thus accelerating buildup of the great European ice sheets; in the early deglacial, meltwater probably induced a southward flow of cold water along Norway, which led to the Oldest Dryas cold spell. An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG. (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 95PA01453, Variations in Atlantic surface ocean paleoceanography, 50°-80°N: A time-slice record of the last 30,000 years, M. Sarnthein et al.) Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00. Payment must accompany order.

Getting the Lead Out of Bermuda; The Legacy of a Forty Year Record in the North Atlantic Using a Transient Experiment in the Atmosphere and Water

NASA Astrophysics Data System (ADS)

Church, T. M.; Alleman, L. Y.; Veron, A. J. J.; Boyle, E. A.; Zurbrick, C.; Patterson, C. C.; Flegal, A. R., Jr.

2015-12-01

Some forty years ago, Schaule and Patterson established the first accurate profile of lead in waters off Bermuda. In evidence was a massive environmental insult from lead emissions being carried seaward by the atmosphere over the Sargasso Sea. Further documentation was possible using contiguous time series in the atmosphere on Bermuda, surface sea water nearby and recorded in local corals. Lead had then an overwhelming source from the combustion of gasoline, primarily in the USA and secondarily in Europe. These were carried to Bermuda on seasonally alternating temperate and trade winds from the west and east, respectively. The anthropogenic sources were well distinguished based on the unique radiogenic nature of stable lead isotopes in the gasoline being used by these countries. Subsequently, decreasing use in the west (USA) followed by that in the east (Europe) was isotopically evident. As such, the two signatures were subjected to transient mixing in the atmosphere and subsequently with depth in ocean. A transient experiment uses data during 1996-1998, a period of transition in leaded gasoline use in the USA and Europe. Here are complimentary records of lead concentration and stable isotopes in atmospheric deposition and surface waters. The results allow an isotopic mass balance, indicating much of the lead in Bermuda surface water at that time may not have been deposited locally. As such, it may be presumed to reflect easterly advection of some lead at the surface under limited scavenging via the prevailing subtropical gyre circulation. These annual circulation periods are consistent with both physical data and another lead isotopic mass balance in the east. Going forward, Bermuda time series of trace elements and isotopes such as lead could continue to record climatological (e.g. NAO) transients in atmospheric scavenging, potential impact on surface ecosystems, and changes in mixing into deeper waters of the Sargasso Sea and points further afield.

Warm and Saline Events Embedded in the Meridional Circulation of the Northern North Atlantic

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.

2011-01-01

Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand circulation between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced warm, saline waters reaching high latitudes, alternating with freshwater events originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical -subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The warm water limb of the Atlantic meridional overturning cell represented by SODA expanded in density/salinity space during these warm events. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the warming and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two ]layer circulation model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.

The dynamics of İzmir Bay under the effects of wind and thermohaline forces

NASA Astrophysics Data System (ADS)

Sayın, Erdem; Eronat, Canan

2018-04-01

The dominant circulation pattern of İzmir Bay on the Aegean Sea coast of Turkey is studied taking into consideration the influence of wind and thermohaline forces. İzmir Bay is discussed by subdividing the bay into outer, middle and inner areas. Wind is the most important driving force in the İzmir coastal area. There are also thermohaline forces due to the existence of water types of different physical properties in the bay. In contrast to the two-layer stratification during summer, a homogeneous water column exists in winter. The free surface version of the Princeton model (Killworth's 3-D general circulation model) is applied, with the input data obtained through the measurements made by the research vessel K. Piri Reis. As a result of the simulations with artificial wind, the strong consistent wind generates circulation patterns independent of the seasonal stratification in the bay. Wind-driven circulation causes cyclonic or anticyclonic movements in the middle bay where the distinct İzmir Bay Water (IBW) forms. Cyclonic movement takes place under the influence of southerly and westerly winds. On the other hand, northerly and easterly winds cause an anticyclonic movement in the middle bay. The outer and inner bay also have the wind-driven recirculation patterns expected.

Impact of Seawater Nonlinearities on Nordic Seas Circulation

NASA Astrophysics Data System (ADS)

Helber, R. W.; Wallcraft, A. J.; Shriver, J. F.

2017-12-01

The Nordic Seas (Greenland, Iceland, and Norwegian Seas) form an ocean basin important for Arctic-mid-latitude climate linkages. Cold fresh water from the Arctic Ocean and warm salty water from the North Atlantic Ocean meet in the Nordic Seas, where a delicate balance between temperature and salinity variability results in deep water formation. Seawater non-linearities are stronger at low temperatures and salinities making high-latitude oceans highly subject to thermbaricity and cabbeling. This presentation highlights and quantifies the impact of seawater non-linearities on the Nordic Seas circulation. We use two layered ocean circulation models, the Hybrid Coordinate Ocean Model (HYOCM) and the Modular Ocean Model version 6 (MOM6), that enable accurate representation of processes along and across density or neutral density surfaces. Different equations-of-state and vertical coordinates are evaluated to clarify the impact of seawater non-linearities. Present Navy systems, however, do not capture some features in the Nrodic Seas vertical structure. For example, observations from the Greenland Sea reveal a subsurface temperature maximum that deepens from approximately 1500 m during 1998 to 1800 m during 2005. We demonstrate that in terms of density, salinity is the largest source of error in Nordic Seas Navy forecasts, regional scale models can represent mesoscale features driven by thermobaricity, vertical coordinates are a critical issue in Nordic Sea circulation modeling.

Contribution of tropical cyclones to abnormal sea surface temperature warming in the Yellow Sea in December 2004

NASA Astrophysics Data System (ADS)

Kim, Taekyun; Choo, Sung-Ho; Moon, Jae-Hong; Chang, Pil-Hun

2017-12-01

Unusual sea surface temperature (SST) warming occurred over the Yellow Sea (YS) in December 2004. To identify the causes of the abnormal SST warming, we conducted an analysis on atmospheric circulation anomalies induced by tropical cyclones (TCs) and their impacts on upper ocean characteristics using multiple datasets. With the analysis of various datasets, we explored a new aspect of the relationship between TC activity and SST. The results show that there is a significant link between TC activity over the Northwest Pacific (NWP) and SST in the YS. The integrated effect of consecutive TCs activity induces a large-scale atmospheric cyclonic circulation anomaly over the NWP and consequently anomalous easterly winds over the YS and East China Sea. The mechanism of the unusually warm SST in the YS can be explained by considering TCs acting as an important source of Ekman heat transport that results in substantial intrusion of relatively warm surface water into the YS interior. Furthermore, TC-related circulation anomalies contribute to the retention of the resulting warm SST anomalies in the entire YS.

A high-resolution record of Holocene millennial-scale oscillations of surface water, foraminiferal paleoecology and sediment redox chemistry in the SE Brazilian margin

NASA Astrophysics Data System (ADS)

Dias, B. B.; Barbosa, C. F.; Albuquerque, A. L.; Piotrowski, A. M.

2014-12-01

Holocene millennial-scale oscillations and Bond Events (Bond et al. 1997) are well reported in the North Atlantic as consequence of fresh water input and weaking of the Atlantic Meridional Overturning Circulation (AMOC). It has been hypothesized that the effect of weaking of AMOC would lead to warming in the South Atlantic due to "heat piracy", causing surface waters to warm and a reorganization of surface circulation. There are few reconstructions of AMOC strength in the South Atlantic, and none with a high resolution Holocene record of changes of productivity and the biological pump. We reconstruct past changes in the surface water mass hydrography, productivity, and sediment redox changes in high-resolution in the core KCF10-01B, located 128 mbsl water depth off Cabo Frio, Brazil, a location where upwelling is strongly linked to surface ocean hydrography. We use Benthic Foraminiferal Accumulation Rate (BFAR) to reconstruct productivity, which reveals a 1.3kyr cyclicity during the mid- and late-Holocene. The geochemistry of trace and rare earth elements on foraminiferal Fe-Mn oxide coatings show changes in redox-sensitive elements indicating that during periods of high productivity there were more reducing conditions in sediment porewaters, producing a Ce anomaly and reduction and re-precipitation of Mn oxides. Bond events 1-7 were identified by a productivity increase along with reducing sediment conditions which was likely caused by Brazil Current displacement offshore allowing upwelling of the nutritive bottom water South Atlantic Central Waters (SACW) to the euphotic zone and a stronger local biological pump. In a global context, correlation with other records show that this occurred during weakened AMOC and southward displacement of the ITCZ. We conclude that Bond climatic events and millennial-scale variability of AMOC caused sea surface hydrographic changes off the Brazilian Margin leading to biological and geochemical changes recorded in coastal records. The 8.2kyr climatic event is reported here for the first time in South American coastal sediment records as high productivity conditions and a rapid change in porewater redox chemistry.

Oceanographic Aspects of Recent Changes in the Arctic

NASA Astrophysics Data System (ADS)

Morison, J. H.

2002-12-01

In the Arctic recent decadal-scale changes have marked the atmosphere, ocean, and land. Connections between the oceanographic changes and large-scale atmospheric circulation changes are emerging. Surface atmospheric pressure has shown a declining trend over the Arctic. In the 1990s, the Arctic Ocean circulation took on a more cyclonic character, and the front separating Atlantic-derived waters of the Eurasian Basin and the Pacific-derived waters of the Canadian Basin shifted counterclockwise. The temperature of Atlantic water in the Arctic Ocean reached record levels. The cold halocline, which isolates the surface from the warm Atlantic water, grew thinner disappearing entirely from the Amundsen Basin at one point [Steele and Boyd, 1998]. Arctic sea ice extent has decreased 3% per decade since the 1970s [Parkinson et al., 1999]. Sea ice thickness over much of the Arctic decreased 43% between 1958-1976 and 1993-1997 [Rothrock et al., 1999]. Arctic ecosystems have responded to these changes. Sea ice studies in the late 1990s indicate that the sea ice algal species composition changed from decades before, with the species recently being characterized by more brackish and freshwater forms. Barents Sea fisheries have shifted north following reductions in ice extent. Pacific salmon species have been found entering rivers in the Arctic. There is evidence that this complex of pan-Arctic changes is connected with the rising trend in the Arctic Oscillation (AO) or Northern Hemisphere atmospheric polar vortex in the 1990s. Theoretical evidence that a positive trend in the AO index might be indicative of greenhouse warming raises the possibility that the recent complex of changes is an Arctic characteristic of global climate change. Also, the changes in ice cover manifest a connection between the complex of change and global climate through ice-albedo feedback, by which reductions in ice cover reduce the amount of sunlight reflected from the earth's surface. Another important climate feedback is that the changes in ocean circulation and ice production have increased the amount of relatively fresh surface water exported to the sub-Arctic Seas, increasing stratification there, and arguably reducing the strength of the global thermohaline circulation. Since the mid-1990s the strength of the Polar Vortex (AO) has relaxed partially toward earlier levels. Recent observations show that Arctic Ocean water mass structure has relaxed somewhat towards climatology near the surface but is still changing at depth. The cold halocline has recovered in some areas. This reinforces the notion that the changes in the Arctic are tied to the atmospheric circulation of the whole northern hemisphere. The events of the last 10-15 years suggest ways the Arctic environment may be an indicator and agent of climate change and highlight the importance of a systematic program to observe the changing Arctic. References Parkinson C. L., D. J. Cavalieri, P. Gloersen, H. J. Zwally, and J. C. Comiso, 1999, Arctic sea ice extents, areas, and trends, 1978-1996, J. Geophys. Res., 104, 20,387-20,856. Rothrock, D. A., Y. Yu, and G. A. Maykut, 1999, Thinning of the Arctic sea-ice cover, Geophys. Res. Lett., 26(23), 3469-3472. Steele, M., and T. Boyd, 1998, Retreat of the cold halocline layer in the Arctic Ocean, J. Geophys. Res., 103, 10,419-10,435.

Combined simulation of carbon and water isotopes in a global ocean model

NASA Astrophysics Data System (ADS)

Paul, André; Krandick, Annegret; Gebbie, Jake; Marchal, Olivier; Dutkiewicz, Stephanie; Losch, Martin; Kurahashi-Nakamura, Takasumi; Tharammal, Thejna

2013-04-01

Carbon and water isotopes are included as passive tracers in the MIT general circulation model (MITgcm). The implementation of the carbon isotopes is based on the existing MITgcm carbon cycle component and involves the fractionation processes during photosynthesis and air-sea gas exchange. Special care is given to the use of a real freshwater flux boundary condition in conjunction with the nonlinear free surface of the ocean model. The isotopic content of precipitation and water vapor is obtained from an atmospheric GCM (the NCAR CAM3) and mapped onto the MITgcm grid system, but the kinetic fractionation during evaporation is treated explicitly in the ocean model. In a number of simulations, we test the sensitivity of the carbon isotope distributions to the formulation of fractionation during photosynthesis and compare the results to modern observations of δ13C and Δ14C from GEOSECS, WOCE and CLIVAR. Similarly, we compare the resulting distribution of oxygen isotopes to modern δ18O data from the NASA GISS Global Seawater Oxygen-18 Database. The overall agreement is good, but there are discrepancies in the carbon isotope composition of the surface water and the oxygen isotope composition of the intermediate and deep waters. The combined simulation of carbon and water isotopes in a global ocean model will provide a framework for studying present and past states of ocean circulation such as postulated from deep-sea sediment records.

Coastal circulation and water-column properties in the National Park of American Samoa, February–July 2015

USGS Publications Warehouse

Storlazzi, Curt; Cheriton, Olivia; Rosenberger, Kurt; Logan, Joshua; Clark, Timothy B.

2017-06-06

There is little information on the oceanography in the National Park of American Samoa (NPSA). The transport pathways for potentially harmful constituents of land-derived runoff, as well as larvae and other planktonic organisms, are driven by nearshore circulation patterns. To evaluate the processes affecting coral reef ecosystem health, it is first necessary to understand the oceanographic processes driving nearshore circulation, residence times, exposure rates, and transport pathways. Information on how the NPSA’s natural resources may be affected by anthropogenic sources of pollution, sediment runoff, larval transport, or modifications to the marine protected areas is critical to NPSA resource managers for understanding and ultimately managing coastal and marine resources. To address this need, U.S. Geological Survey and U.S. National Park Service researchers conducted a collaborative study in 2015 to determine coastal circulation patterns and water-column properties along north-central Tutuila, American Samoa, in an area focused on NPSA’s Tutuila Unit and its coral reef ecosystem. The continuous measurements of waves, currents, tides, and water-column properties from these instrument deployments over 150 days, coupled with available meteorological measurements of wind and rainfall, provide information on nearshore circulation and the variability in these hydrodynamic properties for NPSA’s Tutuila Unit. In general, circulation was strongly driven by regional winds at longer (greater than day) timescales and by tides at shorter (less than day) timescales. Flows were primarily directed along shore, with current speeds faster offshore to the north and slower closer to shore, especially in embayments. Water-column properties exhibit strong seasonality coupled to the shift from non-trade wind season to trade wind season. During the non-trade wind season that was characterized by variable winds and larger waves in the NPSA, waters were warmer, slightly more saline, relatively less optically clear, and more stratified. When winds shifted to a more consistent trade wind pattern in the austral fall, the waters cooled and became less stratified because of decreased insolation. There are consistent spatial patterns in water column characteristics—Waters were warmer and less saline near the surface and closer to shore, especially in embayments, which tended to be more turbid, less clear, and characterized by higher chlorophyll than waters offshore. Water residence times were shorter farther offshore and longer closer to shore and in embayments, but varied spatially because of different forcing. Warmer, lower salinity, higher chlorophyll, and more turbid waters in embayments tend to reside in those locations for much greater durations, resulting in greater exposure of embayment ecosystems to those waters. This is in contrast with waters farther offshore, where the combination of shorter residence times and cooler, higher salinity water results in less exposure to land runoff. Understanding coastal circulation patterns and water-column properties in NPSA’s waters along north-central Tutuila may help to better understand how meteorological and oceanographic processes, at the regional and local scale, affect coral reef health and sustainability in this region.

Unstable Pore-Water Flow in Intertidal Wetlands

NASA Astrophysics Data System (ADS)

Barry, D. A.; Shen, C.; Li, L.

2014-12-01

Salt marshes are important intertidal wetlands strongly influenced by interactions between surface water and groundwater. Bordered by coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur over vastly different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil condition, particularly aeration, which influences the marsh plant growth. Numerous studies have been carried out to examine the pore-water flow process in the marsh soil driven by tides, focusing on stable flow with the assumption of homogeneity in soil and fluid properties. This assumption, however, is questionable given the actual inhomogeneous conditions in the field. For example, the salinity of surface water in the tidal creek varies temporally and spatially due to the influence of rainfall and evapotranspiration as well as the freshwater input from upland areas to the estuary, creating density gradients across the marsh surface and within the marsh soil. Many marshes possess soil stratigraphy with low-permeability mud typically overlying high-permeability sandy deposits. Macropores such as crab burrows are commonly distributed in salt marsh sediments. All these conditions are prone to the development of non-uniform, unstable preferential pore-water flow in the marsh soil, for example, funnelling and fingering. Here we present results from laboratory experiments and numerical simulations to explore such unstable flow. In particular, the analysis aims to address how the unstable flow modifies patterns of local pore-water movement and solute transport, as well as the overall exchange between the marsh soil and creek water. The changes would influence not only the marsh soil condition for plant growth but also nutrient cycling in the marsh soil and discharge to the coastal sea.

Thermohaline variability in the Adriatic and Northern Ionian Seas observed from the Argo floats during 2010-2014

NASA Astrophysics Data System (ADS)

Kovačević, Vedrana; Ursella, Laura; Gačić, Miroslav; Notarstefano, Giulio; Menna, Milena; Bensi, Manuel; Civitarese, Giuseppe; Poulain, Pierre-Marie

2015-04-01

The Adriatic Sea is the northernmost basin of the Eastern Mediterranean Sea (EMed). At its southern end, the basin communicates with the adjacent Ionian Sea through the 80 km wide and 850 m deep Strait of Otranto. Due to the river discharge in the north and due to the strong winter cooling, the Adriatic is both a dilution basin and the dense water formation region. The basin-wide circulation is cyclonic. The circulation is however, energetic also at smaller spatial and temporal scales, and several circulation cells and mesoscale features are regularly observed equally along the littoral and in the open sea. The North Adriatic Dense Water (NAdDW) formed during winter is the densest water of the whole Mediterranean Sea (up to 1060 kg/m3). It flows as a density driven bottom current from the northern shelf toward south, filling the deep layers of the middle and southern Adriatic pits. The deep open-sea area of the South Adriatic Pit (SAP, 1200 m) feels the influence of a water mass exchange through the Strait of Otranto. Specifically, it receives salty and warm surface and Levantine Intermediate Waters from the Ionian Sea. Through the open-sea winter convection that homogenizes and ventilates 400-800 m thick upper water column, this salty water contributes to the formation of the Adriatic Deep Water (AdDW, 1029.17-1029.20 kg/m3), which is not as dense as the NAdDW. Both dense waters eventually mix and spill across the sill ventilating the deep and bottom layers of the Ionian Sea, and driving the deep thermohaline cell of the EMed. Thermohaline properties of the Adriatic Sea vary at wide spatial and temporal scales, and this in turn affects the properties of its dense waters. The long-term scales are of a particular interest, as they are often associated with the biogeochemical and biotic variability such as intrusion of alien species into the Adriatic Sea and interconnection with the adjacent Ionian basin. Due to the extremely variable meteo- and climatic conditions, the signal of the Adriatic dense waters can be fairly irregular and impulsive. Sporadic in-situ surveys by research vessels are not always sufficient to capture this irregularity and its consequences on the circulation. The Lagrangian platforms are disseminated within the whole Mediterranean through the international Argo program. They are a useful tool to assess some of the spatial and temporal variability in the two basins. Combining the information from the floats and in-situ CTD profiles from oceanographic campaigns, we picture the inter-annual variability of the thermohaline properties in general during 2010-2014. In addition, the peculiarities of the very dense water overflow that during 2012 spilled out form the Strait of Otranto into the Northern Ionian is evidenced. Also, by the remotely sensed sea surface topography, we depict the most prominent circulation features of the upper layer.

West Florida shelf circulation and temperature budget for the 1998 fall transition

NASA Astrophysics Data System (ADS)

He, Ruoying; Weisberg, Robert H.

2003-05-01

Mid-latitude continental shelves undergo a fall transition as the net heat flux changes from warming to cooling. Using in situ data and a numerical model we investigate the circulation on the west Florida shelf (WFS) for the fall transition of 1998. The model is a regional adaptation of the primitive equation, Princeton Ocean Model forced by NCEP reanalysis wind, air pressure, and heat flux fields, plus river inflows. After comparison with observations the model is used to draw inferences on the seasonal and synoptic scale features of the shelf circulation. By running twin experiments, one without and the other with an idealized Loop Current (LC), we explore the relative importance of local versus deep-ocean forcing. We find that local forcing largely controls the inner-shelf circulation, including changes from the Florida Panhandle in the north to regions farther south. The effects of the LC in fall 1998 are to reinforce the mid-shelf currents and to increase the across-shelf transports in the bottom Ekman layer, thereby accentuating the shoreward transport of cold, nutrient rich water of deep-ocean origin. A three-dimensional analysis of the temperature budget reveals that surface heat flux largely controls both the seasonal and synoptic scale temperature variations. Surface cooling leads to convective mixing that rapidly alters temperature gradients. One interesting consequence is that upwelling can result in near-shore warming as warmer offshore waters are advected landward. The temperature balances on the shelf are complex and fully three-dimensional.

Deconstructing the conveyor belt.

PubMed

Lozier, M Susan

2010-06-18

For the past several decades, oceanographers have embraced the dominant paradigm that the ocean's meridional overturning circulation operates like a conveyor belt, transporting cold waters equatorward at depth and warm waters poleward at the surface. Within this paradigm, the conveyor, driven by changes in deepwater production at high latitudes, moves deep waters and their attendant properties continuously along western boundary currents and returns surface waters unimpeded to deepwater formation sites. A number of studies conducted over the past few years have challenged this paradigm by revealing the vital role of the ocean's eddy and wind fields in establishing the structure and variability of the ocean's overturning. Here, we review those studies and discuss how they have collectively changed our view of the simple conveyor-belt model.

In-Line Measurement of Water Contents in Ethanol Using a Zeolite-Coated Quartz Crystal Microbalance

PubMed Central

Kim, Byoung Chul; Yamamoto, Takuji; Kim, Young Han

2015-01-01

A quartz crystal microbalance (QCM) was utilized to measure the water content in ethanol. For the improvement of measurement sensitivity, the QCM was modified by applying zeolite particles on the surface with poly(methyl methacrylate) (PMMA) binder. The measurement performance was examined with ethanol of 1% to 5% water content in circulation. The experimental results showed that the frequency drop of the QCM was related with the water content though there was some deviation. The sensitivity of the zeolite-coated QCM was sufficient to be implemented in water content determination, and a higher ratio of silicon to aluminum in the molecular structure of the zeolite gave better performance. The coated surface was inspected by microscopy to show the distribution of zeolite particles and PMMA spread. PMID:26516859

North Atlantic deep water formation and AMOC in CMIP5 models

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Wåhlin, Anna

2017-04-01

North Atlantic deep water formation processes and properties in climate models are indicative of their ability to simulate future ocean circulation, ventilation, carbon and heat uptake, and sea level rise. Historical time series of temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to reveal the causes and consequences of North Atlantic deep water formation in models. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. The trigger of deep convection varies among models; for one third it is intense surface cooling only, while the remaining two thirds also need upward mixing of subsurface warm salty water. The models with the most intense deep convection have the most accurate deep water properties, which are warmer and fresher than in the other models. They also have the strongest Atlantic Meridional Overturning Circulation (AMOC). For over half of the models, 40% of the variability of the AMOC is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas, with 3 and 4 years lag respectively. Understanding the dynamical drivers of the AMOC in models is key to realistically forecast a possible slow down and its consequences on the global circulation and marine life.

Simulation of Wind-Driven Circulation in the Salton Sea: Implications for Indigenous Ecosystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, Chris B.; Orlob, Gerald T.; Huston, David W.

The Salton Sea Authority is seeking methods for reducing water levels and controlling salinity within ranges that will protect beneficial uses of the Sea, its adjacent lands, and its indigenous ecosystems. Proposed solutions include various physical changes in the bathymetry and configuration of the Sea. Because circulation in the Sea is driven primarily by wind stresses imposed on the water surface, and circulation changes are likely to affect the Sea?s quality and ecology, a methodology for quantifying the effects of specific alternatives is required. For this purpose a mathematical model for simulation of the hydrodynamic behavior of the Sea hasmore » been developed, calibrated to data gathered by a field investigation conducted in 1997, and applied to alternative schemes that will isolate sections of the southern basin. The Salton Sea Hydrodynamic/Water Quality Model is constructed using the finite element method to represent the bathymetry of the Sea in a three-dimensional grid. Given certain boundary conditions, for example wind stresses imposed on the surface, the model solves the three-dimensional equations of motion and continuity, the advection-dispersion equation, and an equation of state dependent upon temperature and salinity, to obtain temporal and spatial descriptions of velocities and temperatures over a specified period of time. The model successfully replicated principal features of the Sea's behavior, especially the persistence of a counterclockwise gyre in the southern basin and seasonal stratification. Once calibrated, the model was applied to evaluate the possible effects of changing water surface elevations in the Sea and altering its configuration to isolate sections for evaporative concentration of salts. These effects, evident in changes in velocity, were quantified with regard to their possible impacts on the aquatic habitat and the health of the Salton Sea ecology. A comparative evaluation of alternatives is presented.« less

Defining the Habitat of Pacific Tuna of the Eastern Tropical Pacific from Satellite Imagery, Climatologies, and a Global Circulation Model

NASA Astrophysics Data System (ADS)

Kiefer, D. A.; Hinton, M. G.; Armstrong, E. M.; Harrison, D. P.; Menemenlis, D.; Hu, C.

2016-02-01

With support from NASA's Ecological Forecasting program, we have developed a Tuna Stock Assessment Support System, which merges time series of satellite imagery, a global ocean circulation model, climatology from field surveys, and fisheries data on catch and effort. The purpose of this software is to extract information on the habitat of skipjack, bigeye, and yellowfin tuna in the Eastern Tropical Pacific. The support system is based upon a 50-year record of catch and effort from long-line and purse seine vessels provide by the Inter-American Tropical Tuna Commission. This database, which covers thousands of kilometers of ocean surface, provides monthly information at a 1 degree spatial resolution for the purse seine fleet and 5 degree resolution for the long line fishery. This data is then merged in time and space with satellite imagery of sea surface temperature, chlorophyll, and height, as well as NODC climatologies of oxygen concentration and temperature, and output from NASA's ECCO-2 global circulation model, which provides 3-dimensional simulations of water density, current velocity, mixed layer depth, and sea surface height. Our analyses have yielded a broad range of understanding of the habitat and dynamics both the fish and the fisherman. The purse seine ground, which targets younger tuna, is constrained to waters where the hypoxic layer is shallow. The longline fishery, which targets older tuna, is not constrained by the hypoxic layer and has a much larger distribution. We have characterized the preferences of each species to environmental variables including the depth of the hypoxic layer, the depth of the water column, as well as sea surface height, temperature, and chlorophyll concentration. Finally, the analyses have revealed information on local depletion by fishing, the size distribution of the schools of younger fish, and the impact of ENSO on fishing activities.

Indian-Southern Ocean Latitudinal Transect (ISOLAT): A proposal for the recovery of high-resolution sedimentary records in the western Indian Ocean sector of the Southern Ocean

NASA Astrophysics Data System (ADS)

Mackensen, A.; Zahn, R.; Hall, I.; Kuhn, G.; Koc, N.; Francois, R.; Hemming, S.; Goldstein, S.; Rogers, J.; Ehrmann, W.

2003-04-01

Quantifying oceanic variability at timescales of oceanic, atmospheric, and cryospheric processes are the fundamental objectives of the international IMAGES program. In this context the Southern Ocean plays a leading role in that it is involved, through its influence on global ocean circulation and carbon budget, with the development and maintenance of the Earth's climate system. The seas surrounding Antarctica contain the world's only zonal circum-global current system that entrains water masses from the three main ocean basins, and maintains the thermal isolation of Antarctica from warmer surface waters to the north. Furthermore, the Southern Ocean is a major site of bottom and intermediate water formation and thus actively impacts the global thermohaline circulation (THC). This proposal is an outcome of the IMAGES Southern Ocean Working Group and constitutes one component of a suite of new IMAGES/IODP initiatives that aim at resolving past variability of the Antarctic Circumpolar Current (ACC) on orbital and sub-orbital timescales and its involvement with rapid global ocean variability and climate instability. The primary aim of this proposal is to determine millennial- to sub-centennial scale variability of the ACC and the ensuing Atlantic-Indian water transports, including surface transports and deep-water flow. We will focus on periods of rapid ocean and climate change and assess the role of the Southern Ocean in these changes, both in terms of its thermohaline circulation and biogeochemical inventories. We propose a suite of 11 sites that form a latitudinal transect across the ACC in the westernmost Indian Ocean sector of the Southern Ocean. The transect is designed to allow the reconstruction of ACC variability across a range of latitudes in conjunction with meridional shifts of the surface ocean fronts. The northernmost reaches of the transect extend into the Agulhas Current and its retroflection system which is a key component of the THC warm water return flow to the Atlantic. The principal topics are: (i) the response of the ACC to climate variability; (ii) the history of the Southern Ocean surface ocean fronts during periods of rapid climate change; (iii) the history of North Atlantic Deep Water (NADW) export to the deep South Indian Ocean; (iv) the variability of Southern Ocean biogeochemical fluxes and their influence on Circumpolar Deep Water (CDW) carbon inventories and atmospheric chemistry; and (v) the variability of surface ocean fronts and the Indian-Atlantic surface ocean density flux. To achieve these objectives we will generate fine-scale records of palaeoceanographic proxies that are linked to a variety of climatically relevant ocean parameters. Temporal resolution of the records, depending on sedimentation rates, will range from millennial to sub-centennial time scales. Highest sedimentation rates are expected at coring sites located on current-controlled sediment drifts, whereas dense sampling of cores with moderate sedimentation rates will enable at least millennial-scale events to be resolved.

Influence of the Aral Sea negative water balance on its seasonal circulation and ventilation patterns: use of a 3d hydrodynamic model.

NASA Astrophysics Data System (ADS)

Sirjacobs, D.; Grégoire, M.; Delhez, E.; Nihoul, J.

2003-04-01

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic model was adapted to address specifically the macroscale processes affecting the Aral Sea water circulation and ventilation. The particular goal of this research is to simulate the effect of lasting negative water balance on the 3D seasonal circulation, temperature, salinity and water-mixing fields of the Aral Sea. The original Aral Sea seasonal hydrodynamism is simulated with the average seasonal forcings corresponding to the period from 1956 to 1960. This first investigation concerns a period of relative stability of the water balance, before the beginning of the drying process. The consequences of the drying process on the hydrodynamic of the Sea will be studied by comparing this first results with the simulation representing the average situation for the years 1981 to 1985, a very low river flow period. For both simulation periods, the forcing considered are the seasonal fluctuations of wind fields, precipitation, evaporation, river discharge and salinity, cloud cover, air temperature and humidity. The meteorological forcings were adapted to the common optimum one-month temporal resolution of the available data sets. Monthly mean kinetic energy flux and surface tensions were calculated from daily ECMWF wind data. Monthly in situ precipitation, surface air temperature and humidity fields were interpolated from data obtained from the Russian Hydrological and Meteorological Institute. Monthly water discharge and average salinity of the river water were considered for both Amu Darya and Syr Darya river over each simulation periods. The water mass conservation routines allowed the simulation of a changing coastline by taking into account local drying and flooding events of particular grid points. Preliminary barotropic runs were realised (for the 1951-1960 situation, before drying up began) in order to get a first experience of the behaviour of the hydrodynamic model. These first runs provide results about the evolution of the following state variables: elevation of the sea surface, 3D fields of vertical and horizontal flows, 2D fields of average horizontal flows and finally the 3D fields of turbulent kinetic energy. The mean seasonal salinity and temperature fields (in-situ data gathered by the Russian Hydrological and Meteorological Institute) are available for the two simulated periods and will allow a first validation of the hydrodynamic model. Various satellites products were identified, collected and processed in the frame of this research project and will be used for the validation of the model outputs. Seasonal level changes measurements derived from water table change will serve for water balance validation and sea surface temperature for hydrodynamics validation.

Evapotranspiration and runoff from large land areas: Land surface hydrology for atmospheric general circulation models

NASA Technical Reports Server (NTRS)

Famiglietti, J. S.; Wood, Eric F.

1993-01-01

A land surface hydrology parameterization for use in atmospheric GCM's is presented. The parameterization incorporates subgrid scale variability in topography, soils, soil moisture and precipitation. The framework of the model is the statistical distribution of a topography-soils index, which controls the local water balance fluxes, and is therefore taken to represent the large land area. Spatially variable water balance fluxes are integrated with respect to the topography-soils index to yield our large topography-soils distribution, and interval responses are weighted by the probability of occurrence of the interval. Grid square averaged land surface fluxes result. The model functions independently as a macroscale water balance model. Runoff ratio and evapotranspiration efficiency parameterizations are derived and are shown to depend on the spatial variability of the above mentioned properties and processes, as well as the dynamics of land surface-atmosphere interactions.

Water quality of Cedar Creek reservoir in northeast Texas, 1977 to 1984

USGS Publications Warehouse

Leibbrand, Norman F.; Gibbons, Willard J.

1987-01-01

The concentrations of total inorganic nitrogen, total nitrogen, and total phosphorus were largest during summer stagnation in water near the bottom at the deepest sites. At site Ac, the largest total phosphorus concentration was 5.3 milligrams per liter for a bottom sample. The maximum total inorganic nitrogen concentration for the same sample was 2.5 milligrams per liter. Water near the surface of Cedar Creek Reservoir during summer stagnation and throughout the reservoir during winter circulation had total phosphorus and total inorganic nitrogen concentrations of less than 0.1 milligram per liter. Total nitrogen concentrations near the surface ranged from 0.3 to 1.1 milligrams per liter from January 1980 to August 1984.

A second-order Budkyo-type parameterization of landsurface hydrology

NASA Technical Reports Server (NTRS)

Andreou, S. A.; Eagleson, P. S.

1982-01-01

A simple, second order parameterization of the water fluxes at a land surface for use as the appropriate boundary condition in general circulation models of the global atmosphere was developed. The derived parameterization incorporates the high nonlinearities in the relationship between the near surface soil moisture and the evaporation, runoff and percolation fluxes. Based on the one dimensional statistical dynamic derivation of the annual water balance, it makes the transition to short term prediction of the moisture fluxes, through a Taylor expansion around the average annual soil moisture. A comparison of the suggested parameterization is made with other existing techniques and available measurements. A thermodynamic coupling is applied in order to obtain estimations of the surface ground temperature.

Drogue performance evaluation. Part 1: Data acquisition. [for accurate description of subsurface water circulation

NASA Technical Reports Server (NTRS)

Johnson, R. E.

1975-01-01

Surface buoy/subsurface drogue drag coupling was investigated. Data acquisition methods and techniques derived from several experimental cruises on the Chesapeake Bay are presented. Four buoys were utilized: three coupled to steel plates rigidly attached to each other at right angles and at various depths; and one spar type that did not require drag plates. Data from these surface floats and the drogue depth combinations were processed. Errors in tracking the surface buoys are discussed.

Results of the Winter Flow Experiments Conducted on December 7-8, February 7-8, and February 28-29, 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dressen, Donald S.; Beikmann, Mel

A winter flow regime has been proposed as a method of maintaining a non-freezing environment following the loss of circulation in the HDR Reservoir test facility when ambient temperature is below 32 °F. The regime, as presently envisioned, would automatically convert the surface facility from reservoir circulation to low rate reservoir production through the entire operating system except the EE-3A wellhead, the EE-2A x-mas tree, and the make-up/feed pump/water supply system.

Mackenzie Bay, Antarctica

NASA Image and Video Library

2017-12-08

Off the northeastern edge of Antarctica’s Amery Ice Shelf lies Mackenzie Bay, which was painted with a ghostly blue-green mass in early February 2012. Similarly colored tendrils also streamed northward across the ocean, their flow sometimes interrupted by icebergs. Multiple factors might account for the ghostly shapes, including low-lying clouds or katabatic winds—downslope winds blowing toward the coast, which can freeze the water at the ocean surface. But an intriguing and perhaps more likely explanation involves processes occurring below the ice shelf. An ice shelf is a thick slab of ice often fed by glaciers attached to the coastline. The shelf floats on the ocean surface, with seawater circulating underneath. Like most ice shelves, the Amery is very thick in the upstream area near the shore. It thins significantly as it stretches northward away from the continent. Water at depth is subject to much greater pressure than water at the surface, and one effect of this intense pressure is that it effectively lowers the freezing point. So water circulating at depth beneath the Amery Ice Shelf may be slightly below the temperature at which it would normally begin to freeze. As some that water wells up along the underbelly of the shelf, the pressure is reduced and the water begins to freeze even though the temperature may not change. As it freezes, this deep-ocean water forms needle-like crystals known as frazil. The crystals are only 3 to 4 millimeters (0.12 to 0.16 inches) wide, but a sufficient concentration of frazil can change the appearance of the water. A frazil-rich plume probably accounts for the blue-green waters off the Amery Ice Shelf in the image above. Modeling of ocean circulation beneath the shelf indicates just such a plume emerging in that location. Frazil-rich water explains the plume, and wind transport of the surface water explains the long streams extending northward. As the sub-iceshelf water mixes with surface water around the Antarctic coastline, the frazil is gradually melted and the streams disappear. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image of Mackenzie Bay and the ice shelf on February 12, 2012. NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Michon Scott with information from Helen A. Fricker, Scripps Institution of Oceanography; Robert Massom, Australian Antarctic Division; Ben Galton-Fenzi, University of Tasmania, Australia; and Florence Fetterer, Walt Meier, and Ted Scambos, National Snow and Ice Data Center. Credit: NASA Earth Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram Instrument: EO-1 - ALI

Water color and circulation southern Chesapeake Bay, part 1

NASA Technical Reports Server (NTRS)

Nichols, M. M.; Gordon, H. H.

1975-01-01

Satellite imagery from two EREP passes over the Rappahannock Estuary of the Chesapeake region is analyzed to chart colored water types, to delineate color boundaries and define circulatory patterns. Surface observations from boats and helicopters concurrent with Skylab overpass define the distributions of suspended sediment, transparency, temperature, salinity, phytoplankton, color of suspended material and optical ratio. Important features recorded by the imagery are a large-scale turbidity maximum and massive red tide blooms. Water movement is revealed by small-scale mixing patterns and tidal plumes of apparent sediment-laden water. The color patterns broadly reflect the bottom topography and the seaward gradient of suspended material between the river and the bay. Analyses of red, green and natural color photos by microdensitometry demonstrate the utility of charting water color types of potential use for managing estuarine water quality. The Skylab imagery is superior to aerial photography and surface observations for charting water color.

Observations of the summer Red Sea circulation

NASA Astrophysics Data System (ADS)

Sofianos, Sarantis S.; Johns, William E.

2007-06-01

Aiming at exploring and understanding the summer circulation in the Red Sea, a cruise was conducted in the basin during the summer of 2001 involving hydrographic, meteorological, and direct current observations. The most prominent feature, characteristic of the summer circulation and exchange with the Indian Ocean, is a temperature, salinity, and oxygen minimum located around a depth of 75 m at the southern end of the basin, associated with Gulf of Aden Intermediate Water inflowing from the Gulf of Aden during the summer season as an intruding subsurface layer. Stirring and mixing with ambient waters lead to marked increases in temperature (from 16.5 to almost 33°C) and salinity (from 35.7 to more than 38 psu) in this layer by the time it reaches midbasin. The observed circulation presents a very vigorous pattern with strong variability and intense features that extend the width of the basin. A permanent cyclone, detected in the northern Red Sea, verifies previous observations and modeling studies, while in the central sector of the basin a series of very strong anticyclones were observed with maximum velocities exceeding 1 m/s. The three-layer flow pattern, representative of the summer exchange between the Red Sea and the Gulf of Aden, is observed in the strait of Bab el Mandeb. In the southern part of the basin the layer flow is characterized by strong banking of the inflows and outflows against the coasts. Both surface and intermediate water masses involved in the summer Red Sea circulation present prominent spatial variability in their characteristics, indicating that the eddy field and mixing processes play an important role in the summer Red Sea circulation.

Submesoscale Rossby waves on the Antarctic circumpolar current.

PubMed

Taylor, John R; Bachman, Scott; Stamper, Megan; Hosegood, Phil; Adams, Katherine; Sallee, Jean-Baptiste; Torres, Ricardo

2018-03-01

The eastward-flowing Antarctic circumpolar current (ACC) plays a central role in the global ocean overturning circulation and facilitates the exchange of water between the ocean surface and interior. Submesoscale eddies and fronts with scales between 1 and 10 km are regularly observed in the upper ocean and are associated with strong vertical circulations and enhanced stratification. Despite their importance in other locations, comparatively little is known about submesoscales in the Southern Ocean. We present results from new observations, models, and theories showing that submesoscales are qualitatively changed by the strong jet associated with the ACC in the Scotia Sea, east of Drake Passage. Growing submesoscale disturbances develop along a dense filament and are transformed into submesoscale Rossby waves, which propagate upstream relative to the eastward jet. Unlike their counterparts in slower currents, the submesoscale Rossby waves do not destroy the underlying frontal structure. The development of submesoscale instabilities leads to strong net subduction of water associated with a dense outcropping filament, and later, the submesoscale Rossby waves are associated with intense vertical circulations.

Early Pliocene onset of modern Nordic Seas circulation related to ocean gateway changes.

PubMed

De Schepper, Stijn; Schreck, Michael; Beck, Kristina Marie; Matthiessen, Jens; Fahl, Kirsten; Mangerud, Gunn

2015-10-28

The globally warm climate of the early Pliocene gradually cooled from 4 million years ago, synchronous with decreasing atmospheric CO2 concentrations. In contrast, palaeoceanographic records indicate that the Nordic Seas cooled during the earliest Pliocene, before global cooling. However, a lack of knowledge regarding the precise timing of Nordic Seas cooling has limited our understanding of the governing mechanisms. Here, using marine palynology, we show that cooling in the Nordic Seas was coincident with the first trans-Arctic migration of cool-water Pacific mollusks around 4.5 million years ago, and followed by the development of a modern-like Nordic Seas surface circulation. Nordic Seas cooling precedes global cooling by 500,000 years; as such, we propose that reconfiguration of the Bering Strait and Central American Seaway triggered the development of a modern circulation in the Nordic Seas, which is essential for North Atlantic Deep Water formation and a precursor for more widespread Greenland glaciation in the late Pliocene.

Phosphonate removal from discharged circulating cooling water using iron-carbon micro-electrolysis.

PubMed

Zhou, Zhen; Qiao, Weimin; Lin, Yangbo; Shen, Xuelian; Hu, Dalong; Zhang, Jianqiao; Jiang, Lu-Man; Wang, Luochun

2014-01-01

Phosphonate is a commonly used corrosion and scale inhibitor for a circulating cooling water (CCW) system. Its discharge could cause eutrophication of receiving waters. The iron-carbon (Fe/C) micro-electrolysis technology was used to degrade and remove phosphonate from discharged CCW. The influences of initial pH, Fe/C ratio (FCR) and temperature on phosphonate removal were investigated in a series of batch tests and optimized by response surface methodology. The quadratic model of phosphonate removal was obtained with satisfactory degrees of fitness. The optimum conditions with total phosphorus removal efficiency of 95% were obtained at pH 7.0, FCR of 1.25, and temperature of 45 °C. The phosphonate removal mechanisms were also studied. Phosphonate removal occurred predominantly via two consecutive reactive phases: the degradation of phosphonate complexes (Ca-phosphonate) and the precipitation of Fe/C micro-electrolysis products (PO₄(3-), Ca²⁺ and Fe³⁺).

Influence of solar radiation absorbed by phytoplankton on the thermal structure and circulation of the tropical Atlantic Ocean

NASA Astrophysics Data System (ADS)

Frouin, Robert; Ueyoshi, Kyozo; Kampel, Milton

2007-09-01

Numerical experiments conducted with an ocean general ocean circulation model reveal the potential influence of solar radiation absorbed by phytoplankton on the thermal structure and currents of the Tropical Atlantic Ocean. In the model, solar radiation penetration is parameterized explicitly as a function of chlorophyll-a concentration, the major variable affecting water turbidity in the open ocean. Two types of runs are performed, a clear water (control) run with a constant minimum chlorophyll-a concentration of 0.02 mgm -3, and a turbid water (chlorophyll) run with space- and time-varying chlorophyll-a concentration from satellite data. The difference between results from the two runs yields the biological effects. In the chlorophyll run, nutrients and biology production are implicitly taken into account, even though biogeochemical processes are not explicitly included, since phytoplankton distribution, prescribed from observations, is the result of those processes. Due to phytoplankton-radiation forcing, the surface temperature is higher by 1-2 K on average annually in the region of the North Equatorial current, the Northern part of the South Equatorial current, and the Caribbean system, and by 3-4 K in the region of the Guinea current. In this region, upwelling is reduced, and heat trapped in the surface layers by phytoplankton is not easily removed. The surface temperature is lower by 1 K in the Northern region of the Benguela current, due to increased upwelling. At depth, the equatorial Atlantic is generally cooler, as well as the eastern part of the tropical basin (excluding the region of the sub-tropical gyres). The North and South equatorial currents, as well as the Equatorial undercurrent, are enhanced by as much as 3-4 cms -1, and the circulation of the subtropical gyres is increased. Pole-ward heat transport is slightly reduced North of 35°N, suggesting that phytoplankton, by increasing the horizontal return flow in the subtropical region, may exert a cooling influence on higher latitude regions. The findings indicate that biology-induced buoyancy plays a significant role, in an indirect if not direct way, in the variability of the Tropical Atlantic Ocean, with consequences on atmospheric circulation and climate.

Exploring Paleoclimatic and -Oceanographic Consequences for Arctic Beringia by the Eocene Formation and Progressive E-W Lengthening of the Aleutian Ridge (arc) Across the North Pacific Basin

NASA Astrophysics Data System (ADS)

Scholl, D. W.

2013-12-01

INTRODUCTION: During the past ~50 Myr, magmatic growth of the offshore Aleutian Ridge (AR) or arc and its progressive tectonic lengthening to the west cordoned off the NW corner of the Pacific Basin to formed the deep water (3000-4000 m), marginal sea of the Bering Sea Basin (BSB). Cordoning continuously altered the paths, depths, and locations of water-exchange passes controlling the circulation of waters between the north Pacific and the Bering Sea (BS), and, via the fixed Bering Strait, that entering the Pacific sector of the Arctic Basin. PRESENT PATTERN OF PACIFIC-BERING-ARCTIC WATER EXCHANGE: Cool, low salinity water of the Alaska Stream flowing west along the Pacific side of the AR crosses northward into the BS via tectonically controlled, inter-island passes. The largest volume (~9 SV) enters near the western end of the AR via Near Pass. Flow turns back to the east and CCW northward over the BSB. Surface water exits southward around the western end of the AR through the far western, deep-water (~4000 m) pass of Kamchatka Strait. Because water salinity is low, vertical thermohaline circulation (THC) does not occur over the BSB. However, the deposition of the larger Meiji Drift body, which is charged with Bering-sourced, detritus, on the Pacific side of Kamchatka Strait implies THC may have occurred in the past. Deep-water circulation is presently linked to the inflow of Pacific abyssal water via Kamchatka Strait. A small volume (~0.8 SV) of cool, low salinity water entering the BS mainly through eastern, shallow-silled passes continues northward across the broad Beringian shelf to enter the Arctic Ocean via the Bering Strait. EVOLUTION OF ALEUTIAN RIDGE: At it's inception, the arc massif of the AR likely extended only about 1200 km west of Alaska. Because convergence is increasingly oblique to the west, plate-boundary-driven, right-lateral strike-slip faulting extensionally fragmented the AR and progressively rotated and transported blocks and slivers westward toward Kamchatka. Water-exchange passes were created between them as the AR tectonically lengthened to ~2200 km at an estimated average speed of ~40-50 km/Myr. PALEOCEANOGRPAIC WONDERMENTS FOR PACIFIC SECTOR OF ARCTIC: The Arctic Ocean presently receives low salinity water entering the BS from the east. Prior to Northern Hemisphere glaciation, fossil plant and animal taxa document the BS was far more temperature than the cold, foggy, rawness of today, and surface waters were saltier and warmer than now. Although the BSB is today effectively closed to north-bound western Pacific circulation, during much of Tertiary it was open to the west. It can be posited that subtopical, western Pacific boundary currents (e.g., the Kuroshio Current) formerly entered the BS from the west and exited eastward--the reverse of now. Salty surface water in the BSB could have supported THC to begin construction of the Meiji drift body by southward outflow of abyssal BS water through Kamchatka Strait. To the north, when the Tertiary Bering Strait was open, BS water entering the Arctic Ocean may well have been sourced from the western subtropical Pacific rather than, as now, from the subboreal NE Pacific.

Characteristics of the water and dissolved matter circulation in the young-glacial catchment of the Czechowskie lake (Tuchola Pinewood Forest, Poland)

NASA Astrophysics Data System (ADS)

Brykala, Dariusz; Gierszewski, Piotr; Kaszubski, Michal

2014-05-01

The studies on the conditions of the water and dissolved matter circulation in the young-glacial catchment of the Czechowskie lake (Tuchola Pinewood Forest) have been conducted since 2012. They are implemented on the basis of an organised network monitoring surface water and groundwater. An important aim of the study is to assess the impact of both modern and fossil lakes on the regime of the outflow and the transformation of the water chemical properties. A high stability of the first groundwater table was recorded. During the study period the range of the groundwater level ranged from 0.17 to 0.92 m. In comparison with the small fluctuations in the groundwater level within the sandy outwash areas, a relatively high instability was shown by the shallow waters of the lake terraces. The measurements of the discharge showed that its average value at the outflow from the Czechowskie lake is 30 dm3s-1. It almost equals the total amount of water flowing into the lake through watercourses. The average specific runoff from the basin of the Czechowskie lake was 3 dm3s-1km-2. The total water mineralisation expressed as the sum of the ions is in the range from 70 to 750 mg dm-3. Both surface water, i.e. the water in streams and lakes, and underground water from different depths represent the bicarbonate-calcium-sulphate type characteristic of the young- glacial environment. The results of hydrochemical mapping and the analysis of the ionic composition of the water showed large spatial variability of the physico-chemical properties of the tested waters and, at the same time, high stability of their ionic composition. At the present stage of the research it is possible to identify the water enrichment zones in salts, which are basins of paleolakes filled with the organic-carbonate sediment, and the zones of salt precipitation within the contemporary lakes. The situation described above creates a specific, cascade model of the transformation of chemical properties of water circulating in the catchment. The presented results are a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis - ICLEA - of the Helmholtz Association.

Sea-surface circulation, sediment transport, and marine mammal distribution, Alaska continental shelf

NASA Technical Reports Server (NTRS)

Wright, F. F. (Principal Investigator); Sharma, G. D.; Burns, J. J.

1973-01-01

The author has identified the following significant results. Even though nonsynchronous, the ERTS-1 imagery of November 4, 1972, showed a striking similarity to the ground truth data obtained in late August and September, 1972. The comparison of the images with ground truth data revealed that the general water circulation pattern in Lower Cook Inlet is consistent through the Fall season and that ERTS-1 images in MSS bands 4 and 5 are capable of delineating water masses with a suspended load as low as 1 mg/liter. The ERTS-1 data and the ground truth data demonstrate clearly that the coriolis effect dominates circulation in Lower Cook Inlet. The configuration of plumes in Nushagak and Kuskokwim bays further indicates the influence of the coriolis effect on the movement of sea water at high latitudes. Comparison of MSS bands 4, 5, 6, and 7 suggest MSS-1 penetration of several meters into the water column. Sea ice analysis of available imagery was exceptionally rewarding. The imagery provided a rapid method to delineate and describe the ice types apparent in the photos. The ice types ranged from newly formed grease ice to heavy flows of disintegrating shore-fast ice. Sea ice maps showing the extent of different ice zones in the Chukchi Sea are being compiled.

The effects of cloud radiative forcing on an ocean-covered planet

NASA Technical Reports Server (NTRS)

Randall, David A.

1990-01-01

Cumulus anvil clouds, whose importance has been emphasized by observationalists in recent years, exert a very powerful influence on deep tropical convection by tending to radiatively destabilize the troposphere. In addition, they radiatively warm the column in which they reside. Their strong influence on the simulated climate argues for a much more refined parameterization in the General Circulation Model (GCM). For Seaworld, the atmospheric cloud radiative forcing (ACRF) has a powerful influence on such basic climate parameters as the strength of the Hadley circulation, the existence of a single narrow InterTropical Convergence Zone (ITCZ), and the precipitable water content of the atmosphere. It seems likely, however, that in the real world the surface CRF feeds back negatively to suppress moist convection and the associated cloudiness, and so tends to counteract the effects of the ACRF. Many current climate models have fixed sea surface temperatures but variable land-surface temperatures. The tropical circulations of such models may experience a position feedback due to ACRF over the oceans, and a negative or weak feedback due to surface CRF over the land. The overall effects of the CRF on the climate system can only be firmly established through much further analysis, which can benefit greatly from the use of a coupled ocean-atmospheric model.

TWO-DIMENSIONAL MODELING OF CURRENT CIRCULATION AND CONTAMINANT TRANSPORT IN SURFACE WATERS

EPA Science Inventory

The main objectives of this paper are to briefly describe and evaluate three different applications of two-dimensional, depth-averaged, finite-element models for hydrodynamics (RMA2) and transport (RMA4) ([1] and [2], respectively), which were run using the FastTABS user interfac...

Microearthquakes in the ahuachapan geothermal field, el salvador, central america.

PubMed

Ward, P L; Jacob, K H

1971-07-23

Microearthquakes occur on a steeply dipping plane interpreted here as the fault that allows hot water to circulate to the surface in the geothermal region. These small earthquakes are common in many geothermal areas and may occur because of the physical or chemical effects of fluids and fluid pressure.

Estimating habitat volume of living resources using three-dimensional circulation and biogeochemical models

NASA Astrophysics Data System (ADS)

Smith, Katharine A.; Schlag, Zachary; North, Elizabeth W.

2018-07-01

Coupled three-dimensional circulation and biogeochemical models predict changes in water properties that can be used to define fish habitat, including physiologically important parameters such as temperature, salinity, and dissolved oxygen. However, methods for calculating the volume of habitat defined by the intersection of multiple water properties are not well established for coupled three-dimensional models. The objectives of this research were to examine multiple methods for calculating habitat volume from three-dimensional model predictions, select the most robust approach, and provide an example application of the technique. Three methods were assessed: the "Step," "Ruled Surface", and "Pentahedron" methods, the latter of which was developed as part of this research. Results indicate that the analytical Pentahedron method is exact, computationally efficient, and preserves continuity in water properties between adjacent grid cells. As an example application, the Pentahedron method was implemented within the Habitat Volume Model (HabVol) using output from a circulation model with an Arakawa C-grid and physiological tolerances of juvenile striped bass (Morone saxatilis). This application demonstrates that the analytical Pentahedron method can be successfully applied to calculate habitat volume using output from coupled three-dimensional circulation and biogeochemical models, and it indicates that the Pentahedron method has wide application to aquatic and marine systems for which these models exist and physiological tolerances of organisms are known.

Iodine susceptibility of pseudomonads grown attached to stainless steel surfaces

NASA Technical Reports Server (NTRS)

Pyle, B. H.; McFeters, G. A.

1990-01-01

Pseudomonads were adapted to grow in phosphate-buffered water and on stainless steel surfaces to study the iodine sensitivity of attached and planktonic cells. Cultures adapted to low nutrient growth were incubated at room temperature in a circulating reactor system with stainless steel coupons to allow biofilm formation on the metal surfaces. In some experiments, the reactor was partially emptied and refilled with buffer at each sampling time to simulate a "fill-and-draw" water system. Biofilms of attached bacteria, resuspended biofilm bacteria, and reactor suspension, were exposed to 1 mg l-1 iodine for 2 min. Attached bacterial populations which established on coupons within 3 to 5 days displayed a significant increase in resistance to iodine. Increased resistance was also observed for resuspended cells from the biofilm and planktonic bacteria in the system suspension. Generally, intact biofilms and resuspended biofilm cells were most resistant, followed by planktonic bacteria and phosphate buffer cultures. Thus, biofilm formation on stainless steel surfaces within water systems can result in significantly increased disinfection resistance of commonly-occurring water-borne bacteria that may enhance their ability to colonise water treatment and distribution systems.

Increase in Agulhas leakage due to poleward shift of Southern Hemisphere westerlies.

PubMed

Biastoch, A; Böning, C W; Schwarzkopf, F U; Lutjeharms, J R E

2009-11-26

The transport of warm and salty Indian Ocean waters into the Atlantic Ocean-the Agulhas leakage-has a crucial role in the global oceanic circulation and thus the evolution of future climate. At present these waters provide the main source of heat and salt for the surface branch of the Atlantic meridional overturning circulation (MOC). There is evidence from past glacial-to-interglacial variations in foraminiferal assemblages and model studies that the amount of Agulhas leakage and its corresponding effect on the MOC has been subject to substantial change, potentially linked to latitudinal shifts in the Southern Hemisphere westerlies. A progressive poleward migration of the westerlies has been observed during the past two to three decades and linked to anthropogenic forcing, but because of the sparse observational records it has not been possible to determine whether there has been a concomitant response of Agulhas leakage. Here we present the results of a high-resolution ocean general circulation model to show that the transport of Indian Ocean waters into the South Atlantic via the Agulhas leakage has increased during the past decades in response to the change in wind forcing. The increased leakage has contributed to the observed salinification of South Atlantic thermocline waters. Both model and historic measurements off South America suggest that the additional Indian Ocean waters have begun to invade the North Atlantic, with potential implications for the future evolution of the MOC.

Sea Surface Salinity Variability from Simulations and Observations: Preparing for Aquarius

NASA Technical Reports Server (NTRS)

Jacob, S. Daniel; LeVine, David M.

2010-01-01

Oceanic fresh water transport has been shown to play an important role in the global hydrological cycle. Sea surface salinity (SSS) is representative of the surface fresh water fluxes and the upcoming Aquarius mission scheduled to be launched in December 2010 will provide excellent spatial and temporal SSS coverage to better estimate the net exchange. In most ocean general circulation models, SSS is relaxed to climatology to prevent model drift. While SST remains a well observed variable, relaxing to SST reduces the range of SSS variability in the simulations (Fig.1). The main objective of the present study is to simulate surface tracers using a primitive equation ocean model for multiple forcing data sets to identify and establish a baseline SSS variability. The simulated variability scales are compared to those from near-surface argo salinity measurements.

The Arsenic crisis in Bangladesh (Invited)

NASA Astrophysics Data System (ADS)

Harvey, C.; Ashfaque, K.; Neumann, R. B.; Badruzzaman, B.; Ali, A.

2010-12-01

The Ganges Delta suffers from water-borne disease. Arsenic in the groundwater pumped from drinking water wells is causing severe and widespread disease, and these wells were installed, in part, to avoid pathogens in the surface water supply. I will discuss the hydrogeologic controls of arsenic concentrations in groundwater, specifically the role of enhanced groundwater circulation driven by irrigation pumping and the effects of the solute loads transported into aquifers with recharge through different surface features, such as rice fields, rivers, and ponds. I will contrast the approaches taken in Southeast Asia for studying groundwater contamination with methods used in the U.S. I will compare findings from several sites in the region and consider how improved models of the coupled hydrologic and biogeochemical system can be used to provide safer water.

Investigation of Deep Ocean Circulation and Mixing Using Ar-39 (Invited)

NASA Astrophysics Data System (ADS)

Smethie, W. M.; Schlosser, P.

2013-12-01

Ar-39 is a radioactive noble gas that forms in the atmosphere by cosmic ray interaction with Ar-40. It has a half-life of 269 years and its production rate in the atmosphere has varied no more than 7% during the past 1000 years. It enters the surface ocean with an average equilibration time of about one month and thus the entire surface ocean, except for ice covered regions at high latitudes, is in quasi-equilibrium with the atmospheric Ar-39:Ar ratio. The well known input to the ocean, radioactive decay constant and chemical inertness make Ar-39 an ideal tracer of circulation and mixing in the deep ocean, where anthropogenic transient tracers such as CFCs and tritium have not yet penetrated. However, due to the difficult measurement, only about 125 oceanic Ar-39 samples have been measured to date. This was done by counting the decays of Ar-39 atoms and required a half liter of argon gas per sample, extracted from about 1500 liters of water. The 125 samples that have been measured provide a glimpse of the information that can be gained from Ar-39 observations. In the Pacific Ocean three vertical profiles show a decrease in Ar-39 from the surface mixed layer through the thermocline to a minimum at intermediate depths and an increase from there to the bottom. This reflects formation of bottom water around the Antarctic continent, spreading of this water northward and upwelling and mixing into intermediate depths. The lowest concentration was 6×4% modern which is equivalent to a 900-1600 year isolation time from the surface. In the Atlantic Ocean newly formed North Atlantic Deep Water has an Ar-39 concentration of about 85% modern compared to 55% modern for newly formed Antarctic Bottom Water and reach values as low as about 40% modern in the interior reflecting the more rapid ventilation of the deep Atlantic Ocean relative to the deep Pacific Ocean. In the Arctic Ocean the mean residence time of deep water in the Nansen, Amundsen and Makarov Basins based on Ar-39 are about 270, 190, and 330 years respectively. Radiocarbon also provides information on circulation and mixing in the deep ocean and thousands of measurements have been made. However, the distributions of Ar-39 and C-14 are different due to the large difference in their half-lives (269 years and 5730 years respectively). Measurement of both tracers provides information on the relative importance of advection and mixing in the deep ocean and provides more accurate transit times than can be obtained with only one of these tracers. In the Atlantic Ocean, where the deep water is roughly a two-end member mixture of northern component and southern component water, the age of the two components can be estimated from simultaneous measurement of Ar-39 and C-14. The few existing measurements suggest that the northern component water has an age range of 40-200 years and the southern component water a range of 60-600 years. Development of the ATTA method for measuring radioactive noble gases offers great potential to dramatically increase the number of samples that can be measured for Ar-39, which could greatly improve our understanding of mixing and circulation in the deep ocean.

Local diurnal wind-driven variabiity and upwelling in a small coastal embayment

NASA Astrophysics Data System (ADS)

Walter, R. K.; Reid, E. C.; Davis, K. A.; Armenta, K. J.; Merhoff, K.; Nidzieko, N.

2017-12-01

The oceanic response to high-frequency local diurnal wind forcing is examined in a small coastal embayment located along an understudied stretch of the central California coast. We show that local diurnal wind forcing is the dominant control on nearshore temperature variability and circulation patterns. A complex empirical orthogonal function (CEOF) analysis of velocities in San Luis Obispo Bay reveals that the first-mode CEOF amplitude time series, which accounts for 47.9% of the variance, is significantly coherent with the local wind signal at the diurnal frequency and aligns with periods of weak and strong wind forcing. The diurnal evolution of the hydrographic structure and circulation in the bay is examined using both individual events and composite-day averages. During the late afternoon, the local wind strengthens and results in a sheared flow with near-surface warm waters directed out of the bay and a compensating flow of colder waters into the bay over the bottom portion of the water column. This cold water intrusion into the bay causes isotherms to shoal toward the surface and delivers subthermocline waters to shallow reaches of the bay, representing a mechanism for small-scale upwelling. When the local winds relax, the warm water mass advects back into the bay in the form of a buoyant plume front. Local diurnal winds are expected to play an important role in nearshore dynamics and local upwelling in other small coastal embayments with important implications for various biological and ecological processes.

Local diurnal wind-driven variability and upwelling in a small coastal embayment

NASA Astrophysics Data System (ADS)

Walter, Ryan K.; Reid, Emma C.; Davis, Kristen A.; Armenta, Kevin J.; Merhoff, Kevin; Nidzieko, Nicholas J.

2017-02-01

The oceanic response to high-frequency local diurnal wind forcing is examined in a small coastal embayment located along an understudied stretch of the central California coast. We show that local diurnal wind forcing is the dominant control on nearshore temperature variability and circulation patterns. A complex empirical orthogonal function (CEOF) analysis of velocities in San Luis Obispo Bay reveals that the first-mode CEOF amplitude time series, which accounts for 47.9% of the variance, is significantly coherent with the local wind signal at the diurnal frequency and aligns with periods of weak and strong wind forcing. The diurnal evolution of the hydrographic structure and circulation in the bay is examined using both individual events and composite-day averages. During the late afternoon, the local wind strengthens and results in a sheared flow with near-surface warm waters directed out of the bay and a compensating flow of colder waters into the bay over the bottom portion of the water column. This cold water intrusion into the bay causes isotherms to shoal toward the surface and delivers subthermocline waters to shallow reaches of the bay, representing a mechanism for small-scale upwelling. When the local winds relax, the warm water mass advects back into the bay in the form of a buoyant plume front. Local diurnal winds are expected to play an important role in nearshore dynamics and local upwelling in other small coastal embayments with important implications for various biological and ecological processes.

Mesoscale modeling of the water vapor cycle at Mawrth Vallis: a Mars2020 and ExoMars exploration rovers high-priority landing site

NASA Astrophysics Data System (ADS)

Pla-García, Jorge

2017-04-01

Introduction: The Mars Regional Atmospheric Modeling System (MRAMS) was used to predict meteorological conditions that are likely to be encountered by the Mars 2020 (NASA) Rover at several of their respective proposed landing sites during entry, descent, and landing at Ls5 [1] and by the ExoMars (ESA) Rover at one of the final landing sites. MRAMS is ideally suited for this type of investigation; the model is explicitly designed to simu-late Mars' atmospheric circulations at the mesoscale and smaller with realistic, high-resolution surface proper-ties [2, 3]. One of the sights studied for both rovers was Mawrth Vallis (MV), an ancient water outflow channel with light colored clay-rich rocks in the mid-latitude north hemisphere (Oxia Palus quadrangle). MV is the northernmost of the Mars2020 and ExoMars landing sites and the closest to the northern polar cap water source. The primary source of water vapor to the atmosphere is the northern polar cap during the northern summer. In order to highlight MV habitability implications, additional numerical experiments at Ls90, 140 and 180, highest column abundance of water vapor is found over MV [4], were performed to study how the atmospheric circulation connects MV with the polar water source. Once the winter CO2 retreats, the underlying polar water ice is exposed and begins to sublimate. The water is transported equatorward where it is manifested in the tropical aphelion cloud belt. If transport is assumed to be the result of the summer Hadley Cell, then the polar water is carried aloft in the northern high latitude rising branch before moving equatorward and eventually toward the southern high latitudes. Thus, the mean meridional summer circulation precludes a direct water vapor connection between MV and the polar source. Around the equinoxes (Ls0 and Ls180), there is a brief transition period where the rising branch quickly crosses from one hemisphere into the other as it migrates to its more typical solstitial location. During this transition, there is surface convergence into the rising branch (similar to the inter-tropical convergence zone on Earth), and dual Hadley cells with one circulation in each hemisphere. At this time, the mean surface winds flow from the high latitudes to equator in both hemispheres, providing the possibility for a direct vapor connection [5, 6]. It is likely that transient waves (e.g., storm systems) as well as boundary currents associated with planetary-scale stationary waves could advect and mix water equatorward, along the surface, in opposition to the Hadley Cell. Conclusion: We are studying whether moist air in northern spring/summer makes it to the surface of Mawrth at Ls 90, Ls 140 and Ls 180, three periods with high column abundance of water vapor at mid/high latitudes. The objective is to determine if the circulation (mean or regional) is favorable for the transport of water vapor from the north polar cap to MV where it might activate hygroscopic salts and/or chlorides [7]. Relative humidity at those different seasons is estimated to test for consistency with column abundances derived from orbit observations. If moist air makes it to MV during Ls90, 140 and/or 180, it should be a go-to site due to enhanced habitability implications. References: [1] Pla-García, J., & Rafkin, S. C., 2015: Meteorological predictions for Mars 2020 Exploration Rov-er high-priority landing sites throug MRAMS Mesoscale Modeling. In EGU General Assembly Conference Abstracts (Vol. 17, p. 12605). [2] Rafkin, S. C. R., Haberle, R. M., and T. I. Michaels, 2001: The Mars Regional Atmospheric Modeling System (MRAMS): Model description and selected simulations. Icarus, 151, 228-256. [3] Rafkin, S. C. R., M. R. V. Sta. Maria, and T. I. Michaels, 2002: Simulation of the atmospheric thermal circulation of a martian volcano using a mesoscale numerical model. Nature, 419, 697-699. [4] Jakosky, B.M., and C.B. Farmer, 1982: The seasonal and global behavior of water vapor in the Mars atmosphere: complete global results of the Viking Atmospheric Water Detector experiment, J. Geophys. Res., 87, 2999-3019. [5] Pla-García, Rafkin S. C. R. et al., 2016: The Meteorology of Gale Crater as Determined from Rover Environ-mental Monitoring Station Observations and Numerical Modeling. Part I: Comparison of Model Simulations with Observations. Icarus, 280, 103-113. [6] Rafkin S. C. R., Pla-García J. et al., 2016: The Meteorology of Gale Crater as Determined from Rover Envi-ronmental Monitoring Station Observations and Numerical Modeling. Part II: Interpretation. Icarus, 280, 103-113. [7] Fairén, A. G., A. F. Davila, D. Lim, N. Bramall, R. Bonaccorsi, J. Zavaleta, E. R. Uceda, C. Stoker, J. Wierzchos, R. Amils, J. M. Dohm, D. Andersen & C. McKay, 2010: Astrobiology through the ages of Mars. Astrobiology, 10(8), 821-843.

Indian Ocean Surface Circulations and Their Connection to Indian Ocean Dipole, Identified From Ocean Surface Currents Analysis Real Time (OSCAR) Data

DTIC Science & Technology

2008-06-01

31 1. Seasonal Development .......................................................................32 2. Winter Monsoon...summary of the monsoon system in the Indian Ocean. The top part indicates the wind cycle; the lower part shows the major currents that develop in...energy interests in the Indian Ocean’s waters. The rapid economic progress in developing nations, such as India and South Africa, also adds up their

Recovery of condensate water quality in power generator's surface condenser

NASA Astrophysics Data System (ADS)

Kurniawan, Lilik Adib

2017-03-01

In PT Badak NGL Plant, steam turbines are used to drive major power generators, compressors, and pumps. Steam exiting the turbines is condensed in surface condensers to be returned to boilers. Therefore, surface condenser performance and quality of condensate water are very important. One of the recent problem was caused by the leak of a surface condenser of Steam Turbine Power Generator. Thesteam turbine was overhauled, leaving the surface condenser idle and exposed to air for more than 1.5 years. Sea water ingress due to tube leaks worsens the corrosionof the condenser shell. The combination of mineral scale and corrosion product resulting high conductivity condensate at outlet condenser when we restarted up, beyond the acceptable limit. After assessing several options, chemical cleaning was the best way to overcome the problem according to condenser configuration. An 8 hour circulation of 5%wt citric acid had succeed reducing water conductivity from 50 μmhos/cm to below 5 μmhos/cm. The condensate water, then meets the required quality, i.e. pH 8.3 - 9.0; conductivity ≤ 5 μmhos/cm, therefore the power generator can be operated normally without any concern until now.

Upper layer circulation, hydrography, and biological response of the Andaman waters during winter monsoon based on in situ and satellite observations

NASA Astrophysics Data System (ADS)

Chandran, Salini Thaliyakkattil; Raj, Smitha Bal; Ravindran, Sajeev; Narayana, Sanjeevan Vellorkirakathil

2018-05-01

Upper layer circulation, hydrography, and biological response of Andaman waters during winter monsoon are assessed based on the observations carried out onboard FORV Sagar Sampada during January 2009 and November-December 2011. Cool and dry air carried by the moderate winds (6 m/s) from north and northeast indicates the influence of northeast monsoon (NEM) in the area during the observation time. The characteristics of physical parameters and the water mass indicate that the southeastern side is dominated by the less saline water from South China Sea intruded through the Malacca Strait, whereas the northeast is influenced by the freshwater from Ayeyarwady-Salween river system. The western side of the Andaman and Nicobar Islands exhibits similar properties of Bay of Bengal (BoB) water as evidenced in the T-S relation. Circulation pattern is uniform for the upper 88 m and is found to be more geostrophic rather than wind driven. Magnitude of the current velocity varies between 100 and 900 mm/s in November-December 2011 with strong current (900 mm/s) near Katchal and Nancowry islands and 100 and 1000 mm/s in January 2009 recording strong current (1000 mm/s) near the Little Nicobar Island. The Andaman waters are observed as less productive during the season based on the satellite-derived surface chl-a (0.1-0.4 mg/m3) and column-integrated primary productivity (PP) (100-275 mgC/m2/d).

North Atlantic deep water formation and AMOC in CMIP5 models

NASA Astrophysics Data System (ADS)

Heuzé, Céline

2017-07-01

Deep water formation in climate models is indicative of their ability to simulate future ocean circulation, carbon and heat uptake, and sea level rise. Present-day temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to assess the biases, causes and consequences of North Atlantic deep convection in models. The majority of models convect too deep, over too large an area, too often and too far south. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. Half of the models convect in response to local cooling or salinification of the surface waters; only a third have a dynamic relationship between freshwater coming from the Arctic and deep convection. The models with the most intense deep convection have the warmest deep waters, due to a redistribution of heat through the water column. For the majority of models, the variability of the Atlantic Meridional Overturning Circulation (AMOC) is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas up to 2 years before. In turn, models with the strongest AMOC have the largest heat export to the Arctic. Understanding the dynamical drivers of deep convection and AMOC in models is hence key to realistically forecasting Arctic oceanic warming and its consequences for the global ocean circulation, cryosphere and marine life.

Simulation of ground-water flow, surface-water flow, and a deep sewer tunnel system in the Menomonee Valley, Milwaukee, Wisconsin

USGS Publications Warehouse

Dunning, C.P.; Feinstein, D.T.; Hunt, R.J.; Krohelski, J.T.

2004-01-01

Numerical models were constructed for simulation of ground-water flow in the Menomonee Valley Brownfield, in Milwaukee, Wisconsin. An understanding of ground-water flow is necessary to develop an efficient program to sample ground water for contaminants. Models were constructed in a stepwise fashion, beginning with a regional, single-layer, analytic-element model (GFLOW code) that provided boundary conditions for a local, eight layer, finite-difference model (MODFLOW code) centered on the Menomonee Valley Brownfield. The primary source of ground water to the models is recharge over the model domains; primary sinks for ground water within the models are surface-water features and the Milwaukee Metropolitan Sewerage District Inline Storage System (ISS). Calibration targets were hydraulic heads, surface-water fluxes, vertical gradients, and ground-water infiltration to the ISS. Simulation of ground-water flow by use of the MODFLOW model indicates that about 73 percent of recharge within the MODFLOW domain circulates to the ISS and 27 percent discharges to gaining surface-water bodies. In addition, infiltration to the ISS comes from the following sources: 36 percent from recharge within the model domain, 45 percent from lateral flow into the domain, 15 percent from Lake Michigan, and 4 percent from other surface-water bodies. Particle tracking reveals that the median traveltime from the recharge point to surface-water features is 8 years; the median time to the ISS is 255 years. The traveltimes to the ISS are least over the northern part of the valley, where dolomite is near the land surface. The distribution of traveltimes in the MODFLOW simulation is greatly influenced by the effective porosity values assigned to the various lithologies.

Observed Spatial and Temporal Variability of Subglacial Discharge-Driven Plumes in Greenland's Outlet Glacial Fjords

NASA Astrophysics Data System (ADS)

Sutherland, D.; Carroll, D.; Nash, J. D.; Shroyer, E.; Mickett, J.; Stearns, L. A.; Fried, M.; Bartholomaus, T.; Catania, G. A.

2015-12-01

Hydrographic and velocity observations in Greenland's outlet glacier fjords have revealed, unsurprisingly, a rich set of dynamics over a range of spatial and temporal scales. Through teasing apart the distinct processes that control circulation within these fjords, we are likely to better understand the impact of fjord circulation on modulating outlet glacier dynamics, and thus, changes in Greenland Ice Sheet mass balance. Here, we report on data from the summers of 2013-2015 in two neighboring fjords in the Uummannaq Bay region of west Greenland: Kangerlussuup Sermia (KS) and Rink Isbræ (RI). We find strong subglacial discharge driven plumes in both systems that evolve on synoptic and seasonal time scales, without the complicating presence of other circulation processes. The plumes both modify fjord water properties and respond to differences in ambient water properties, supporting the notion that a feedback exists between subglacial discharge plume circulation and water mass properties. This feedback between subglacial discharge and water properties potentially influences submarine melt rates at the glacier termini. Observed plume properties, including the vertical structure of velocity, and temperature and salinity anomalies, are compared favorably to model estimates. In KS, we find a near-surface intensified plume with high sediment content that slows and widens as it evolves downstream. In contrast, the plume in RI is entirely subsurface, ranging from 100-300 m depth at its core during summer, although it shows similar temperature, salinity, and optical backscatter signals to the KS plume. Importantly, the distinct vertical plume structures imprint on the overall water mass properties found in each fjord, raising the minimum temperatures by up to 1-2°C in the case of RI.

Arctic sea-ice variability and its implication to the path of pollutants under a changing climate

NASA Astrophysics Data System (ADS)

Castro-Morales, K.; Gerdes, R.; Riemann-Campe, K.; Köberle, C.; Losch, M.

2012-04-01

The increasing concentration of pollutants from anthropogenic origin in the Arctic atmosphere, water, sediments and biota has been evident during the last decade. The sea-ice is an important vehicle for pollutants in the Arctic Ocean. Pollutants are taken up by precipitation and dry atmospheric deposition over the snow and ice cover during winter and released to the ocean during melting. Recent changes in the sea-ice cover of the Arctic Ocean affect the fresh water balance and the oceanic circulation, and with it, the fate of pollutants in the system. The Arctic Ocean is characterized by complex dynamics and strong stratification. Thus, to evaluate the current and future changes in the Arctic circulation high-resolution models are needed. As part of the EU FP7 project ArcRisk (under the scope of the IPY), we use a high resolution regional sea-ice-ocean coupled model covering the Arctic Ocean and the subpolar North Atlantic based on the Massachusetts Institute of Technology - circulation model (MITgcm). Under realistic atmospheric forcing we obtain hindcast results of circulation patterns for the period 1990 - 2010 for validation of the model. We evaluate possible consequences on the pathways and transport of contaminants by downscaling future climate scenario runs available in the coupled model intercomparison project (CMIP3) for the following fifty years. Particular interest is set in the Barents Sea. In this shallow region strong river runoff, sea-ice delivered from the interior of the Arctic Ocean and warm waters from the North Atlantic current are main sources of contaminants. Under a changing climate, a higher input of contaminants delivered to surface waters is expected, remaining in the interior of the Arctic Ocean in a strongly stratified water column remaining.

Surface current observatons--Beaufort Sea, 1972

USGS Publications Warehouse

Barnes, Peter; Garlow, Richard

1975-01-01

Sediment transport via water and ice in the Beaufort Sea off northern Alaska is related to the movement of the surficial waters. As development proceeds along the north slope of alaska, a knowledge of the potential drift trajectories of water, ice, sediment and pollutants will be needed. In an attempt to better define the probable paths and rates of transport, 4200 surface drift cards were dropped during the U.S. Coast Guard WEBSEC cruise of August and September, 1972. The results of this release are the subject of this report. Because the data presented here will be used primarily by those interested in solving problems of transport, the emphasis has been placed on data presentation rather than a detailed analysis of the circulation. (Sinha-OEIS)

Importance of Ekman transport and gyre circulation change on seasonal variation of surface dissolved iron in the western subarctic North Pacific

NASA Astrophysics Data System (ADS)

Nakanowatari, Takuya; Nakamura, Tomohiro; Uchimoto, Keisuke; Nishioka, Jun; Mitsudera, Humio; Wakatsuchi, Masaaki

2017-05-01

Iron (Fe) is an essential nutrient for marine phytoplankton and it constitutes an important element in the marine carbon cycle in the ocean. This study examined the mechanisms controlling seasonal variation of dissolved Fe (dFe) in the western subarctic North Pacific (WSNP), using an ocean general circulation model coupled with a simple biogeochemical model incorporating a dFe cycle fed by two major sources (atmospheric dust and continental shelf sediment). The model reproduced the seasonal cycle of observed concentrations of dFe and macronutrients at the surface in the Oyashio region with maxima in winter (February-March) and minima in summer (July-September), although the simulated seasonal amplitudes are a half of the observed values. Analysis of the mixed-layer dFe budget indicated that both local vertical entrainment and lateral advection are primary contributors to the wintertime increase in dFe concentration. In early winter, strengthened northwesterly winds excite southward Ekman transport and Ekman upwelling over the western subarctic gyre, transporting dFe-rich water southward. In mid to late winter, the southward western boundary current of the subarctic gyre and the outflow from the Sea of Okhotsk also bring dFe-rich water to the Oyashio region. The contribution of atmospheric dust to the dFe budget is several times smaller than these ocean transport processes in winter. These results suggest that the westerly wind-induced Ekman transport and gyre circulation systematically influence the seasonal cycle of WSNP surface dFe concentration.

ERTS-1 observes algal blooms in Lake Erie and Utah Lake

NASA Technical Reports Server (NTRS)

Strong, A. E.

1973-01-01

During late summer when the surface waters of Lake Erie reach their maximum temperature an algal bloom is likely to develop. Such phenomena have been noticed on other shallow lakes using ERTS-1 and characterize eutrophic conditions. The concentration of the algae into long streamers provides additional information on surface circulations. To augment the ERTS-1 MSS data of Lake Erie an aircraft was flown to provide correlative thermal-IR and additional multiband photographs. The algal bloom is highly absorptive in the visible wavelengths but reverses contrast with the surrounding water in the near-IR bands. The absorption of shortwave energy heats the dark brown algal mass, providing a hot surface target for the thermal-IR scanner.

Salinity history of the northern Atlantic during the last deglaciation

NASA Astrophysics Data System (ADS)

Broecker, Wallace S.

1990-08-01

The claim has been made (see Broecker et al., 1988) that production of North Atlantic Deep Water terminated during Younger Dryas time and that the onset of this termination occurred about 11,000 years ago when the flow of meltwater from a large segment of the southern margin of the Laurentide ice sheet was diverted from the Mississippi to the St. Lawrence drainage. Fairbanks [1989] points out a serious weakness in this argument. Based on a sea level curve derived from radiocarbon dates on coral obtained from borings made off the Barbados coast, he suggests that a lull in the melting of the ice caps during Younger Dryas time may have more than compensated for the impact of the diversion. The purpose of this paper is to reassess the situation regarding the origin of the Younger Dryas in light of this new evidence. Currently the salinity of surface waters in the northern Atlantic is influenced by three fluxes. Water vapor transport from the Atlantic drainage basin to the Pacific-Indian basin tends to raise the salinity of the entire Atlantic. The excess over evaporation of precipitation and runoff poleward of 40°N tends to reduce the salinity of waters in this region relative to the Atlantic average. The conveyor circulation of the Atlantic trades more salty waters of the Atlantic with less salty waters outside the Atlantic tending to drive down the Atlantic's salinity. The conveyor circulation also flushes the northern Atlantic, pushing its salinity toward the mean for the Atlantic. During the period of deglaciation meltwater emanating from the Laurentide and Scandinavian ice sheets was also important. This flux tended to lower not only the salinity of the entire Atlantic but also the salinity of surface waters in the northern Atlantic relative to the Atlantic's mean. As deepwater formation in the northern Atlantic depends critically on the salinity of surface waters, the interactions among these fluxes can change the strength of the conveyor.

Tidal truncation and barotropic convergence in a channel network tidally driven from opposing entrances

USGS Publications Warehouse

Warner, J.C.; Schoellhamer, D.; Schladow, G.

2003-01-01

Residual circulation patterns in a channel network that is tidally driven from entrances on opposite sides are controlled by the temporal phasing and spatial asymmetry of the two forcing tides. The Napa/Sonoma Marsh Complex in San Francisco Bay, CA, is such a system. A sill on the west entrance to the system prevents a complete tidal range at spring tides that results in tidal truncation of water levels. Tidal truncation does not occur on the east side but asymmetries develop due to friction and off-channel wetland storage. The east and west asymmetric tides meet in the middle to produce a barotropic convergence zone that controls the transport of water and sediment. During spring tides, tidally averaged water-surface elevations are higher on the truncated west side. This creates tidally averaged fluxes of water and sediment to the east. During neap tides, the water levels are not truncated and the propagation speed of the tides controls residual circulation, creating a tidally averaged flux in the opposite direction. ?? 2003 Elsevier Science B.V. All rights reserved.

The implementation and validation of improved land-surface hydrology in an atmospheric general circulation model

NASA Technical Reports Server (NTRS)

Johnson, Kevin D.; Entekhabi, Dara; Eagleson, Peter S.

1993-01-01

New land-surface hydrologic parameterizations are implemented into the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). These parameterizations are: 1) runoff and evapotranspiration functions that include the effects of subgrid-scale spatial variability and use physically based equations of hydrologic flux at the soil surface and 2) a realistic soil moisture diffusion scheme for the movement of water and root sink in the soil column. A one-dimensional climate model with a complete hydrologic cycle is used to screen the basic sensitivities of the hydrological parameterizations before implementation into the full three-dimensional GCM. Results of the final simulation with the GISS GCM and the new land-surface hydrology indicate that the runoff rate, especially in the tropics, is significantly improved. As a result, the remaining components of the heat and moisture balance show similar improvements when compared to observations. The validation of model results is carried from the large global (ocean and land-surface) scale to the zonal, continental, and finally the regional river basin scales.

Application of LANDSAT satellite imagery and oceanographic data for verification of an upwelling mathematical model. [Atlantic Coast of Brazil

NASA Technical Reports Server (NTRS)

Dejesusparada, N. (Principal Investigator); Tanaka, K.; Almeida, E. G.

1978-01-01

The author has identified the following significant results. Data obtained during the cruise of the Cabo Frio and from LANDSAT imagery are used to discuss the characteristics of a linear model which simulates wind induced currents calculated from meteorological conditions at the time of the mission. There is a significant correspondance between the model of simulated horizontal water circulation, sea surface temperature, and surface currents observed on LANDSAT imagery. Close approximations were also observed between the simulation of vertical water movement (upwelling) and the oceanographic measurements taken along a series of points of the prevailing currents.

Thermotransduction and heat stress in dental structures during orthodontic debonding : Effectiveness of various cooling strategies.

PubMed

Kley, Philipp; Frentzen, Matthias; Küpper, Katharina; Braun, Andreas; Kecsmar, Susann; Jäger, Andreas; Wolf, Michael

2016-05-01

Recent studies have indicated possible thermal damage to pulpal tissue during orthodontic debonding. This study aimed to analyze the thermal loads acting upon dental structures and their transfer to the pulp during orthodontic debonding. Specific goals were to analyze temperature changes in local dental tissues, thermotransduction to the pulp cavity, and the effectiveness of common cooling strategies and of simulated intrapulpal circulation. Metal brackets were bonded to five extracted human molars and subsequently removed. While a carbide bur was applied to debond the residual composite from the tooth surface, various cooling strategies (no/air/water cooling) were employed with or without simulated intrapulpal circulation, accompanied by temperature measurements with a thermographic infrared camera on the enamel surface and with measuring probes in the pulp cavity. Appropriate evaluation software was used to calculate the enamel-to-pulp temperature gradients and for statistical analysis. Significant differences in temperature rise and heat development over time, both on the enamel surfaces and in the pulp cavities were found. The mean temperature rises associated with no/air/water cooling were 90.7/46.6/9.2 °C on the enamel surface versus 9/8/4.6 °C inside the pulp. However, thermotransduction from enamel to pulp remained below 10 % of the surface measurements in all groups. Simulated intrapulpal microcirculation was found to significantly reduce intrapulpal temperature levels. During debonding of residual bracket adhesives, provided that a carbide bur is properly used, our data indicate a low risk of reaching critical intrapulpal temperatures even in the absence of dedicated cooling and no risk if the instrumentation is accompanied by air or water cooling.

Pathways of basal meltwater from Antarctic ice shelves: A model study

NASA Astrophysics Data System (ADS)

Kusahara, Kazuya; Hasumi, Hiroyasu

2014-09-01

We investigate spreading pathways of basal meltwater released from all Antarctic ice shelves using a circumpolar coupled ice shelf-sea ice-ocean model that reproduces major features of the Southern Ocean circulation, including the Antarctic Circumpolar Current (ACC). Several independent virtual tracers are used to identify detailed pathways of basal meltwaters. The spreading pathways of the meltwater tracers depend on formation sites, because the meltwaters are transported by local ambient ocean circulation. Meltwaters from ice shelves in the Weddell and Amundsen-Bellingshausen Seas in surface/subsurface layers are effectively advected to lower latitudes with the ACC. Although a large portion of the basal meltwaters is present in surface and subsurface layers, a part of the basal meltwaters penetrates into the bottom layer through active dense water formation along the Antarctic coastal margins. The signals at the seafloor extend along the topography, showing a horizontal distribution similar to the observed spreading of Antarctic Bottom Water. Meltwaters originating from ice shelves in the Weddell and Ross Seas and in the Indian sector significantly contribute to the bottom signals. A series of numerical experiments in which thermodynamic interaction between the ice shelf and ocean is neglected regionally demonstrates that the basal meltwater of each ice shelf impacts sea ice and/or ocean thermohaline circulation in the Southern Ocean. This article was corrected on 10 OCT 2014. See the end of the full text for details.

A time-dependent, three-dimensional model of the Delaware Bay and River system. Part 2: Three-dimensional flow fields and residual circulation

NASA Astrophysics Data System (ADS)

Galperin, Boris; Mellor, George L.

1990-09-01

The three-dimensional model of Delaware Bay, River and adjacent continental shelf was described in Part 1. Here, Part 2 of this two-part paper demonstrates that the model is capable of realistic simulation of current and salinity distributions, tidal cycle variability, events of strong mixing caused by high winds and rapid salinity changes due to high river runoff. The 25-h average subtidal circulation strongly depends on the wind forcing. Monthly residual currents and salinity distributions demonstrate a classical two-layer estuarine circulation wherein relatively low salinity water flows out at the surface and compensating high salinity water from the shelf flows at the bottom. The salinity intrusion is most vigorous along deep channels in the Bay. Winds can generate salinity fronts inside and outside the Bay and enhance or weaken the two-layer circulation pattern. Since the portion of the continental shelf included in the model is limited, the model shelf circulation is locally wind-driven and excludes such effects as coastally trapped waves and interaction with Gulf Stream rings; nevertheless, a significant portion of the coastal elevation variability is hindcast by the model. Also, inclusion of the shelf improves simulation of salinity inside the Bay compared with simulations where the salinity boundary condition is specified at the mouth of the Bay.

A zonally averaged, three-basin ocean circulation model for climate studies

NASA Astrophysics Data System (ADS)

Hovine, S.; Fichefet, T.

1994-09-01

A two-dimensional, three-basin ocean model suitable for long-term climate studies is developed. The model is based on the zonally averaged form of the primitive equations written in spherical coordinates. The east-west density difference which arises upon averaging the momentum equations is taken to be proportional to the meridional density gradient. Lateral exchanges of heat and salt between the basins are explicitly resolved. Moreover, the model includes bottom topography and has representations of the Arctic Ocean and of the Weddell and Ross seas. Under realistic restoring boundary conditions, the model reproduces the global conveyor belt: deep water is formed in the Atlantic between 60 and 70°N at a rate of about 17 Sv (1 Sv=106 m3 s-1) and in the vicinity of the Antarctic continent, while the Indian and Pacific basins show broad upwelling. Superimposed on this thermohaline circulation are vigorous wind-driven cells in the upper thermocline. The simulated temperature and salinity fields and the computed meridional heat transport compare reasonably well with the observational estimates. When mixed boundary conditions (i.e., a restoring condition on sea-surface temperature and flux condition on sea-surface salinity) are applied, the model exhibits an irregular behavior before reaching a steady state characterized by self-sustained oscillations of 8.5-y period. The conveyor-belt circulation always results at this stage. A series of perturbation experiments illustrates the ability of the model to reproduce different steady-state circulations under mixed boundary conditions. Finally, the model sensitivity to various factors is examined. This sensitivity study reveals that the bottom topography and the presence of a submarine meridional ridge in the zone of the Drake Passage play a crucial role in determining the properties of the model bottom-water masses. The importance of the seasonality of the surface forcing is also stressed.

Mindanao Dome variability over the last 160 kyr: Episodic glacial cooling of the West Pacific Warm Pool

NASA Astrophysics Data System (ADS)

Bolliet, Timothé; Holbourn, Ann; Kuhnt, Wolfgang; Laj, Carlo; Kissel, Catherine; Beaufort, Luc; Kienast, Markus; Andersen, Nils; Garbe-Schönberg, Dieter

2011-02-01

We present sea surface, upper thermocline, and benthic δ18O data, as well as temperature and paleoproductivity proxy data, from the International Marine Global Change Study Program (IMAGES) Core MD06-3067 (6°31‧N, 126°30‧E, 1575 m water depth), located in the western equatorial Pacific Ocean within the flow path of the Mindanao Current. Our records reveal considerable glacial-interglacial and suborbital variability in the Mindanao Dome upwelling over the last 160 kyr. Dome activity generally intensified during glacial intervals resulting in cooler thermocline waters, whereas it substantially declined during interglacials, in particular in the early Holocene and early marine oxygen isotope stage (MIS) 5e, when upwelling waters did not reach the thermocline. During MIS 3 and MIS 2, enhanced surface productivity together with remarkably low SST and low upper ocean thermal contrast provide evidence for episodic glacial upwelling to the surface, whereas transient surface warming marks periodic collapses of the Mindanao Dome upwelling during Heinrich events. We attribute the high variability during MIS 3 and MIS 2 to changes in the El Niño Southern Oscillation state that affected boreal winter monsoonal winds and upper ocean circulation. Glacial upwelling intensified when a strong cyclonic gyre became established, whereas El Niño-like conditions during Heinrich events tended to suppress the cyclonic circulation, reducing Ekman transport. Thus, our findings demonstrate that variations in the Mindanao Dome upwelling are closely linked to the position and intensity of the tropical convection and also reflect far-field influences from the high latitudes.

Slip stream apparatus and method for treating water in a circulating water system

DOEpatents

Cleveland, J.R.

1997-03-18

An apparatus is described for treating water in a circulating water system that has a cooling water basin which includes a slip stream conduit in flow communication with the circulating water system, a source of acid solution in flow communication with the slip stream conduit, and a decarbonator in flow communication with the slip stream conduit and the cooling water basin. In use, a slip stream of circulating water is drawn from the circulating water system into the slip stream conduit of the apparatus. The slip stream pH is lowered by contact with an acid solution provided from the source thereof. The slip stream is then passed through a decarbonator to form a treated slip stream, and the treated slip stream is returned to the cooling water basin. 4 figs.

Assessing Atmospheric Water Injection from Oceanic Impacts

NASA Technical Reports Server (NTRS)

Pierazzo, E.

2005-01-01

Collisions of asteroids and comets with the Earth s surface are rare events that punctuate the geologic record. Due to the vastness of Earth s oceans, oceanic impacts of asteroids or comets are expected to be about 4 times more frequent than land impacts. The resulting injections of oceanic water into the upper atmosphere can have important repercussions on Earth s climate and atmospheric circulation. However, the duration and overall effect of these large injections are still unconstrained. This work addresses atmospheric injections of large amounts of water in oceanic impacts.

Correlation of coastal water turbidity and current circulation with ERTS-1 and Skylab imagery

NASA Technical Reports Server (NTRS)

Klemas, V.; Otley, M.; Philpot, W.; Wethe, C.; Rogers, R.; Shah, N.

1974-01-01

The article reviews investigations of current circulation patterns, suspended sediment concentration, coastal frontal systems, and waste disposal plumes based on visual interpretation and digital analysis of ERTS-1 and Skylab/EREP imagery. Data on conditions in the Delaware Bay area were obtained from 10 ERTS-1 passes and one Skylab pass, with simultaneous surface and airborne sensing. The current patterns and sediments observed by ERTS-1 correlated well with ground-based observations. Methods are suggested which would make it possible to identify certain pollutants and sediment types from multispectral scanner data.

Enceladus' Interior: A Liquid Circulation Model

NASA Astrophysics Data System (ADS)

Matson, Dennis L.; Johnson, Torrence; Lunine, Jonathan; Castillo-Rogez, Julie

We are studying a model for Enceladus' interior in which the water, gas, dust and heat are supplied to the plumes by a relatively deeply circulating brine solution. Data indicates such a source for the erupting material. On the basis of ammonia in the plume gas Waite et al. [1] suggested that the jets might originate from a liquid water region under Enceladus' icy surface. Postberg et al. [2] noted that the presence of ". . . grains that are rich in sodium salts (0.5-2 percent by mass). . . can arise only if the plumes originate from liquid water." Waite et al. [1] also regard the some of the plume chemicals as evidence for interactions with an ice layer presumably overlying the liquid water reservoir. They suggest that this could be in the form of dissociation of clathrate hydrates [3]. Additionally, there is a large heat flow of more than 15 GW [4, 5] coming out of Enceladus' south polar region. We consider a model that brings heat and chemical species up to the surface from a reservoir or "ocean" located below the ice crust that may be many tens of kilometers thick. Water transits to the surface via vertical conduits. The Cassini INMS data suggest that the water has a relatively large gas content of order a few percent. As the water travels upward and the pressure is released, exolving gases form bubbles. Since the bubbly liquid is less dense than the ice, it moves upward. (This part of the model is a variant of the "Perrier Ocean" Europa model of Crawford and Stevenson [6]. A similar model was studied for Ganymede by Murchie and Head [7].) Postberg et al. [2] model the plume eruptions that result from the water, gases, salts, and other chemicals that our circulation model provides. In the near-surface reservoir feeding the plumes, bubbles reaching the surface of the water pop and throw a very fine spray. Some of these very small droplets of brine exit with the plume gas and provide the observed salt-rich dust particles [2]. Much of the water-borne heat is transferred to the near-surface ice. The water is now relatively cold and dense. It absorbs the remaining bubbles and descends via fractures or defects in the ice, and percolates down to the "ocean". The water is in intimate contact with the ice and chemical interactions and heat exchange are possible. While the formation of the briny "ocean" was envisioned as due to the exclusion of non-water chemical species from the ice as it froze [8], a number of mechanisms permit a variety of organic and inorganic species to be present in the ice. The downward percolation of briny water facilitates these by making a large volume of the ice accessible along the crack surfaces. References: [1] J. H. Waite Jr et al., Nature, 460, 487-490 (2009). [2] F. Postberg et al., Nature, 459, 1098-1101 (2009). [3] S. W. Kieffer et al., Science, 314, 1764-1766 (2006). [4] C. Howett, J. R. Spencer, J. Pearl, M. Segura, Bull. Am. Astron. Soc., 41, 1122 (2009). [5] O. Abramov, J. R. Spencer, Icarus, 199, 189-196 (2009). [6] G. D. Crawford, D. J. Stevenson, Icarus, 73, 66-79 (1988). [7] S. L. Murchie, J. W. Head, LPS XVII, 583-584 (1986). [8] M. Y. Zolotov, Geophysical Research Letters, 34, L23203 (2007). This work has been conducted at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration, and for JIL under the program "Incentivazione alla mobilita' di studiosi straineri italiani residenti all'estero" of Italy.

Portrait of a Warming Ocean and Rising Sea Levels: Trend of Sea Level Change 1993-2008

NASA Technical Reports Server (NTRS)

2008-01-01

Warming water and melting land ice have raised global mean sea level 4.5 centimeters (1.7 inches) from 1993 to 2008. But the rise is by no means uniform. This image, created with sea surface height data from the Topex/Poseidon and Jason-1 satellites, shows exactly where sea level has changed during this time and how quickly these changes have occurred.

It's also a road map showing where the ocean currently stores the growing amount of heat it is absorbing from Earth's atmosphere and the heat it receives directly from the Sun. The warmer the water, the higher the sea surface rises. The location of heat in the ocean and its movement around the globe play a pivotal role in Earth's climate.

Light blue indicates areas in which sea level has remained relatively constant since 1993. White, red, and yellow are regions where sea levels have risen the most rapidly up to 10 millimeters per year and which contain the most heat. Green areas have also risen, but more moderately. Purple and dark blue show where sea levels have dropped, due to cooler water.

The dramatic variation in sea surface heights and heat content across the ocean are due to winds, currents and long-term changes in patterns of circulation. From 1993 to 2008, the largest area of rapidly rising sea levels and the greatest concentration of heat has been in the Pacific, which now shows the characteristics of the Pacific Decadal Oscillation (PDO), a feature that can last 10 to 20 years or even longer.

In this 'cool' phase, the PDO appears as a horseshoe-shaped pattern of warm water in the Western Pacific reaching from the far north to the Southern Ocean enclosing a large wedge of cool water with low sea surface heights in the eastern Pacific. This ocean/climate phenomenon may be caused by wind-driven Rossby waves. Thousands of kilometers long, these waves move from east to west on either side of the equator changing the distribution of water mass and heat.

This image of sea level trend also reveals a significant area of rising sea levels in the North Atlantic where sea levels are usually low. This large pool of rapidly rising warm water is evidence of a major change in ocean circulation. It signals a slow down in the sub-polar gyre, a counter-clockwise system of currents that loop between Ireland, Greenland and Newfoundland.

Such a change could have an impact on climate since the sub-polar gyre may be connected in some way to the nearby global thermohaline circulation, commonly known as the global conveyor belt. This is the slow-moving circulation in which water sinks in the North Atlantic at different locations around the sub-polar gyre, spreads south, travels around the globe, and slowly up-wells to the surface before returning around the southern tip of Africa. Then it winds its way through the surface currents in the Atlantic and eventually comes back to the North Atlantic.

It is unclear if the weakening of the North Atlantic sub-polar gyre is part of a natural cycle or related to global warming.

This image was made possible by the detailed record of sea surface height measurements begun by Topex/Poseidon and continued by Jason-1. The recently launched Ocean Surface Topography Mission on the Jason-2 satellite (OSTM/Jason-2) will soon take over this responsibility from Jason-1. The older satellite will move alongside OSTM/Jason-2 and continue to measure sea surface height on an adjacent ground track for as long as it is in good health.

Topex/Poseidon and Jason-1 are joint missions of NASA and the French space agency, CNES. OSTM/Jason-2 is collaboration between NASA; the National Oceanic and Atmospheric Administration; CNES; and the European Organisation for the Exploitation of Meteorological Satellites. JPL manages the U.S. portion of the missions for NASA's Science Mission Directorate, Washington, D.C.

Improved fine-scale transport model performance using AUV and HSI feedback in a tidally dominated system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hibler, Lyle F.; Maxwell, Adam R.; Miller, Lee M.

2008-08-22

Applied numerical circulation and transport modeling study of Sequim Bay, WA focused on the simulation of the redistribution of rhodamine dye release at the water surface. Model sensitivity to bathymetric variation, side-wall boundary conditions, and thermal stratification is examined. Model results compared to observational datasets.

Complementary Use of Glider Data, Altimetry, and Model for Exploring Mesoscale Eddies in the Tropical Pacific Solomon Sea

NASA Astrophysics Data System (ADS)

Gourdeau, L.; Verron, J.; Chaigneau, A.; Cravatte, S.; Kessler, W.

2017-11-01

Mesoscale activity is an important component of the Solomon Sea circulation that interacts with the energetic low-latitude western boundary currents of the South Tropical Pacific Ocean carrying waters of subtropical origin before joining the equatorial Pacific. Mixing associated with mesoscale activity could explain water mass transformation observed in the Solomon Sea that likely impacts El Niño Southern Oscillation dynamics. This study makes synergetic use of glider data, altimetry, and high-resolution model for exploring mesoscale eddies, especially their vertical structures, and their role on the Solomon Sea circulation. The description of individual eddies observed by altimetry and gliders provides the first elements to characterize the 3-D structure of these tropical eddies, and confirms the usefulness of the model to access a more universal view of such eddies. Mesoscale eddies appear to have a vertical extension limited to the Surface Waters (SW) and the Upper Thermocline Water (UTW), i.e., the first 140-150 m depth. Most of the eddies are nonlinear, meaning that eddies can trap and transport water properties. But they weakly interact with the deep New Guinea Coastal Undercurrent that is a key piece of the equatorial circulation. Anticyclonic eddies are particularly efficient to advect salty and warm SW coming from the intrusion of equatorial Pacific waters at Solomon Strait, and to impact the characteristics of the New Guinea Coastal Current. Cyclonic eddies are particularly efficient to transport South Pacific Tropical Water (SPTW) anomalies from the North Vanuatu Jet and to erode by diapycnal mixing the high SPTW salinity.

Circulation and oxygen cycling in the Mediterranean Sea: Sensitivity to future climate change

NASA Astrophysics Data System (ADS)

Powley, Helen R.; Krom, Michael D.; Van Cappellen, Philippe

2016-11-01

Climate change is expected to increase temperatures and decrease precipitation in the Mediterranean Sea (MS) basin, causing substantial changes in the thermohaline circulation (THC) of both the Western Mediterranean Sea (WMS) and Eastern Mediterranean Sea (EMS). The exact nature of future circulation changes remains highly uncertain, however, with forecasts varying from a weakening to a strengthening of the THC. Here we assess the sensitivity of dissolved oxygen (O2) distributions in the WMS and EMS to THC changes using a mass balance model, which represents the exchanges of O2 between surface, intermediate, and deep water reservoirs, and through the Straits of Sicily and Gibraltar. Perturbations spanning the ranges in O2 solubility, aerobic respiration kinetics, and THC changes projected for the year 2100 are imposed to the O2 model. In all scenarios tested, the entire MS remains fully oxygenated after 100 years; depending on the THC regime, average deep water O2 concentrations fall in the ranges 151-205 and 160-219 µM in the WMS and EMS, respectively. On longer timescales (>1000 years), the scenario with the largest (>74%) decline in deep water formation rate leads to deep water hypoxia in the EMS but, even then, the WMS deep water remains oxygenated. In addition, a weakening of THC may result in a negative feedback on O2 consumption as supply of labile dissolved organic carbon to deep water decreases. Thus, it appears unlikely that climate-driven changes in THC will cause severe O2 depletion of the deep water masses of the MS in the foreseeable future.

40 CFR 230.23 - Current patterns and water circulation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... or fill material can modify current patterns and water circulation by obstructing flow, changing the direction or velocity of water flow, changing the direction or velocity of water flow and circulation, or otherwise changing the dimensions of a water body. As a result, adverse changes can occur in: Location...

40 CFR 230.23 - Current patterns and water circulation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... or fill material can modify current patterns and water circulation by obstructing flow, changing the direction or velocity of water flow, changing the direction or velocity of water flow and circulation, or otherwise changing the dimensions of a water body. As a result, adverse changes can occur in: Location...

40 CFR 230.23 - Current patterns and water circulation.

Code of Federal Regulations, 2014 CFR

2014-07-01

... or fill material can modify current patterns and water circulation by obstructing flow, changing the direction or velocity of water flow, changing the direction or velocity of water flow and circulation, or otherwise changing the dimensions of a water body. As a result, adverse changes can occur in: Location...

Recharge and Topographical Controls on Groundwater Circulation in Shallow Crystalline Rock Aquifers revealed by CFC-based Age Data

NASA Astrophysics Data System (ADS)

Kolbe, T.; Abbott, B. W.; Marçais, J.; Thomas, Z.; Aquilina, L.; Labasque, T.; Pinay, G.; De Dreuzy, J. R.

2016-12-01

Groundwater transit time and flow path are key factors controlling nitrogen retention and removal capacity at the catchment scale (Abbott et al., 2016), but the relative importance of hydrogeological and topographical factors in determining these parameters remains uncertain (Kolbe et al., 2016). To address this unknown, we used numerical modelling techniques calibrated with CFC groundwater age data to quantify transit time and flow path in an unconfined aquifer in Brittany, France. We assessed the relative importance of parameters (aquifer depth, porosity, arrangement of geological layers, and permeability profile), hydrology (recharge rate), and topography in determining characteristic flow distances (Leray et al., 2016). We found that groundwater flow was highly local (mean travel distance of 350 m) but also relatively old (mean CFC age of 40 years). Sensitivity analysis revealed that groundwater travel distances were not sensitive to geological parameters within the constraints of the CFC age data. However, circulation was sensitive to topography in lowland areas where the groundwater table was close to the land surface, and to recharge rate in upland areas where water input modulated the free surface of the aquifer. We quantified these differences with a local groundwater ratio (rGW-LOCAL) defined as the mean groundwater travel distance divided by the equivalent surface distance water would have traveled along the land surface. Lowland rGW-LOCAL was near 1, indicating primarily topographic controls. Upland rGW-LOCALwas 1.6, meaning the groundwater recharge area was substantially larger than the topographically-defined catchment. This ratio was applied to other catchments in Brittany to test its relevance in comparing controls on groundwater circulation within and among catchments. REFERENCES Abbott et al., 2016, Using multi-tracer inference to move beyond single-catchment ecohydrology. Earth-Science Reviews. Kolbe et al., 2016, Coupling 3D groundwater modeling with CFC-based age dating to classify local groundwater circulation in an unconfined crystalline aquifer. J. Hydrol. Leray et al., 2016, Residence time distributions for hydrologic systems: Mechanistic foundations and steady-state analytical solutions. J. Hydrol.

Characterizing ocean gyres formation within a bay using vorticity and HF radar measurements

NASA Astrophysics Data System (ADS)

Ragnoli, E.; Donncha, F. O.; Hartnett, M.

2012-04-01

In situations in which wind forcing plays a dominant role in surface currents it becomes important to understand its correlation with parameters that can be used to characterise circulation patterns within a bay. These datasets can then be used in the detection and characterisation of ocean gyres. A network of high frequency radars (NUIG CODAR) is deployed within Galway Bay, on the West Coast of Ireland as a backbone system within an integrated coastal ocean observation system. This system provides real-time synoptic measurements of both ocean surface currents and surface waves across the entire bay. In this work, vorticity is identified as a defining quantity for the characterisation of circulating flow patterns (in particular for the detection of ocean gyres) and it is directly calculated from the measured velocity vectors of NUIG CODAR. A correlation study with wind and tide measurements is then undertaken in order to investigate the dependencies between vorticity and those parameters. A comprehensive NUIG CODAR, weather station and tide gauge monitoring program was conducted over a 30 days period and the data collected analysed for the correlation with the computed vorticity. Tidal information from the FES2004 Global tidal atlas defined surface elevations at the open sea boundaries in the west and in the south. Data from a tide gauge deployed within the bay, which provided real-time tidal data at 6 minute intervals, was used to fine-tune model elevations. A weather station located at National University of Ireland, Galway provided measured wind data for the model. The NUIG CODAR coastal observation system detects strong, non-persistent, gyre formation within Galway Bay. During periods of relatively large tidal ranges (order 4m) and light wind conditions well defined, cyclonic circulation is developed within the bay. The correlation analysis shows that the gyres tend to form soon after high tide and last until the next low water; the gyre structure is transported about the bay with the bulk advection of tidal motion. This is the first time this feature has been observed and the significance of its consequences on water circulation will be the subject of future research.

Partitioning the effects of Global Warming on the Hydrological Cycle with Stable Isotopes in Water Vapor

NASA Astrophysics Data System (ADS)

Dee, S. G.; Russell, J. M.; Nusbaumer, J. M.; Konecky, B. L.; Buenning, N. H.; Lee, J. E.; Noone, D.

2016-12-01

General circulation models (GCMs) suggest that much of the global hydrological cycle's response to anthropogenic warming will be caused by increased lower-tropospheric water vapor concentrations and associated feedbacks. However, fingerprinting changes in the global hydrological cycle due to anthropogenic warming remains challenging. Held and Soden (2006) predicted that as lower-tropospheric water vapor increases, atmospheric circulation will weaken as climate warms to maintain the surface energy budget. Unfortunately, the strength of this feedback and the fallout for other branches of the hydrological cycle is difficult to constrain in situ or with GCMs alone. We demonstrate the utility of stable hydrogen isotope ratios in atmospheric water vapor to quantitatively trace changes in atmospheric circulation and convective mass flux in a warming world. We compare water isotope-enabled GCM experiments for control (present-day) CO2 vs. high CO2(2x, 4x) atmospheres in two GCMs, IsoGSM and iCAM5. We evaluate changes in the distribution of water vapor, vertical velocity (omega), and the stream function between these experiments in order to identify spatial patterns of circulation change over the tropical Pacific (where vertical motion is strong) and map the δD of water vapor associated with atmospheric warming. We also probe the simulations to isolate isotopic signatures associated with water vapor residence time, precipitation efficiency, divergence, and cloud physics. We show that there are robust mechanisms that moisten the troposphere and weaken convective mass flux, and that these mechanisms can be tracked using the δD of water vapor. Further, we find that these responses are most pronounced in the upper troposphere. These findings provide a framework to develop new metrics for the detection of global warming impacts to the hydrological cycle. Further, currently available satellite missions measure δD in the atmospheric boundary layer, the free atmosphere, or the total column; our study suggests that more accurate upper troposphere measurements (above 500hPa) may be needed to detect changes in convective mass flux using water vapor isotope ratios.

Influence of land-surface evapotranspiration on the earth's climate

NASA Technical Reports Server (NTRS)

Shukla, J.; Mintz, Y.

1982-01-01

Land-surface evapotranspiration is shown to strongly influence global fields of rainfall, temperature and motion by calculations using a numerical model of the atmosphere, confirming the general belief in the importance of evapotranspiration-producing surface vegetation for the earth's climate. The current version of the Goddard Laboratory atmospheric general circulation model is used in the present experiment, in which conservation equations for mass, momentum, moisture and energy are expressed in finite-difference form for a spherical grid to calculate (1) surface pressure field evolution, and (2) the wind, temperature, and water vapor fields at nine levels between the surface and a 20 km height.

Kinetics of scheelite dissolution in groundwater: defining the release rate of tungsten contamination from a natural source

NASA Astrophysics Data System (ADS)

Montgomery, S. D.; Mckibben, M. A.

2011-12-01

Tungsten, an emerging contaminant, has no EPA standard for its permissible levels in drinking water. At sites in California, Nevada, and Arizona there may be a correlation between elevated levels of tungsten in drinking water and clusters of childhood acute lymphocytic leukemia (ALL). Developing a better understanding of how tungsten is released from rocks into surface and groundwaters is therefore of growing environmental interest. Knowledge of tungstate ore mineral weathering processes, particularly the rates of dissolution of scheelite (CaWO4) in groundwater, could improve models of how tungsten is released and transported in natural waters. Our research is focusing on experimental determination of the rates and products of tungstate mineral dissolution in synthetic groundwater, as a function of temperature, pH and mineral surface area. The initial rate method is being used to develop rate laws. Batch reactor experiments are conducted within constant temperature circulation baths over a pH range of 2-9. Cleaned scheelite powder with grain diameters of 106-150um is placed between two screens in a sample platform and then placed inside a two liter Teflon vessel filled with synthetic groundwater. Ports on the vessel allow sample extraction, temperature and pH measurement, gas inflow, and water circulation. Aliquots of solution are taken periodically for product analysis by ICP -MS. Changes in mineral surface characteristics are monitored using SEM and EDS methods. Results so far reveal that the dissolution of scheelite is incongruent at both neutral and low pH. Solid tungstic acid forms on scheelite mineral surfaces under acidic conditions, implying that this phase controls the dissolution rate in acidic environments. The influence of dissolved CO2 and resultant calcium carbonate precipitation on the dissolution of scheelite at higher pH is also being investigated. The rate law being developed for scheelite dissolution will be useful in reactive-transport computer codes designed to model tungsten contamination in a variety of surface and groundwater settings.

Implications of summertime marine stratocumulus on the North American climate

NASA Technical Reports Server (NTRS)

Clark, John H. E.

1994-01-01

This study focuses on the effects of summertime stratocumulus over the eastern Pacific. This cloud is linked to the semi-permanent sub-tropical highs that dominate the low-level circulation over the Pacific and Atlantic. Subsidence on the eastern flank of these highs creates an inversion based about 800 m above sea level that caps moist air near the surface. This air overlies cool waters driven by upwelling along the coastal regions of North America. Strong surface north-westerlies mix the boundary layer enough to saturate the air just below the capping inversion. Widespread stratocumulus is thus formed. All calculations were carried out using the GENESIS general circulation model that was run at MSFC. Among the more important properties of the model is that it includes radiative forcing due to absorption of solar radiation and the emission of infrared radiation, interactive clouds (both stratocumulus and cumulus types), exchanges of heat and moisture with the lower boundary. Clouds are interactive in the sense that they impact the circulation by modifying the fields of radiative heating and turbulent fluxes of heat and moisture in the boundary layer. In turn, clouds are modified by the winds through the advection of moisture. In order to isolate the effects of mid- and high-latitude stratocumulus, two runs were made with the model: one with and the other without stratocumulus. The runs were made for a year, but with perpetual July conditions, i.e., solar forcing was fixed. The diurnal solar cycle, however, was allowed for. The sea surface temperature distribution was fixed in both runs to represent climatological July conditions. All dependent variables were represented at 12 surfaces of constant sigma = p/p(sub O), where p is pressure and p(sub O) is surface pressure. To facilitate analysis, model output was transformed to constant pressure surfaces. Structures no smaller in size than 7.5 degrees longitude and 4.5 degrees in latitude were resolved. Smaller features of the circulation were parameterized. The model thus captures synoptic- and planetary-scale circulation features.

Fog and rain in the Amazon

PubMed Central

Anber, Usama; Gentine, Pierre; Wang, Shuguang; Sobel, Adam H.

2015-01-01

The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents. PMID:26324902

Fog and rain in the Amazon

DOE PAGES

Anber, Usama; Gentine, Pierre; Wang, Shuguang; ...

2015-08-31

The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget.more » Finally, these results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anber, Usama; Gentine, Pierre; Wang, Shuguang

The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget.more » Finally, these results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents.« less

Aichi Virus in Sewage and Surface Water, the Netherlands

PubMed Central

Rutjes, Saskia A.; Takumi, Katsuhisa; Husman, Ana Maria de Roda

2013-01-01

Detection of Aichi virus in humans was initially reported in Japan in 1989. To establish a timeline for the prevalence of Aichi virus infection among humans in the Netherlands, we conducted molecular analysis of archival water samples from 1987–2000 and 2009–2012. Aichi virus RNA was detected in 100% (8/8) of sewage samples and 100% (7/7) of surface water samples collected during 1987–2000 and 100% (8/8) of sewage samples and 71% (5/7) of surface water samples collected during 2009–2012. Several genotype A and B Aichi virus lineages were observed over the 25-year period studied, but the time course of viral genetic diversity showed recent expansion of the genotype B population over genotype A. Our results show that Aichi virus has been circulating among the human population in the Netherlands since before its initial detection in humans was reported and that genotype B now predominates in this country. PMID:23876456

Estimation of effective hydrologic properties of soils from observations of vegetation density. M.S. Thesis; [water balance of watersheds in Clinton, Maine and Santa Paula, California

NASA Technical Reports Server (NTRS)

Tellers, T. E.

1980-01-01

An existing one-dimensional model of the annual water balance is reviewed. Slight improvements are made in the method of calculating the bare soil component of evaporation, and in the way surface retention is handled. A natural selection hypothesis, which specifies the equilibrium vegetation density for a given, water limited, climate-soil system, is verified through comparisons with observed data and is employed in the annual water balance of watersheds in Clinton, Ma., and Santa Paula, Ca., to estimate effective areal average soil properties. Comparison of CDF's of annual basin yield derived using these soil properties with observed CDF's provides excellent verification of the soil-selection procedure. This method of parameterization of the land surface should be useful with present global circulation models, enabling them to account for both the non-linearity in the relationship between soil moisture flux and soil moisture concentration, and the variability of soil properties from place to place over the Earth's surface.

Response to CO2 Transient Increase in the GISS Coupled Model: Regional Coolings in a Warming Climate

NASA Technical Reports Server (NTRS)

Russell, Gary L.; Rind, David

1999-01-01

The (GISS) Goddard Institute for Space Studies coupled atmosphere-ocean model is used to investigate the effect of increased atmospheric CO2 by comparing a compounded 1 percent CO2 increase experiment with a control simulation. After 70 years of integration, the global surface air temperature in the 1 percent CO2 experiment is 1.43 C warmer. In spite of this global warming, there are two distinct regions, the northern Atlantic Ocean and the southern Pacific Ocean, where the surface air temperature is up to 4 C cooler. This situation is maintained by two positive feedbacks: a local effect on convection in the South Pacific and a non-local impact on the meridional circulation in the North Atlantic. The poleward transport of latent energy and dry static energy by the atmosphere is greater in the 1 percent CO2 experiment, caused by warming and therefore increased water vapor and greater greenhouse capacity at lower latitudes. The larger atmospheric transports tend to reduce upward vertical fluxes of heat and moisture from the ocean surface at high latitudes, which has the effect of stabilizing the ocean, reducing both convection and the thermohaline circulation. With less convection, less warm water is brought up from below, and with a reduced North Atlantic thermohaline circulation (by 30 percent at time of CO2 doubling), the poleward energy transport by the oceans decreases. The colder water then leads to further reductions in evaporation, decreases of salinity at high latitudes, continued stabilization of the ocean, and maintenance of reduced convection and meridional overturning. Although sea ice decreases globally, it increases in the cooling regions which reduces the overall climate sensitivity; its effect is most pronounced in the Southern Hemisphere. Tropical warming has been observed over the past several decades; if modeling studies such as this and others which have produced similar effects are valid, these processes may already be beginning.

Establishing and applying of a coupled individual based model of edible jellyfish(Rhopilema esculentum Kishinouye) releasing in the Liaodong Bay

NASA Astrophysics Data System (ADS)

Yin, Liping; Qiao, Fangli

2017-04-01

A three-dimensional circulation-surface wave coupled hydrodynamic model coupled with an individual-based jellyfish model was established to investigate the influence of physical process on edible jellyfish releasing stock enhancement in Liaodong Bay. Sensitivity experiments show that the wind intensity and direction have both direct and indirect impacts on the distribution of the jellyfish. When the wind is strong, the surface current in Liaodong Bay has the same direction of the wind. Under the co-effect of the ocean current transport and the surface wind transport, the jellyfish inhabits in the northeast of Liaodong bay, which is consistent with the observation. In the circumstance of weak wind, the circulation is clockwise and the jellyfish will spread around the 5m isobaths following the circulation. Research of the jellyfish distribution shows that the releasing jellyfish will stay in Liaodong bay in its whole life history, hence Liaodong Bay is a quite suitable area for enhancement releasing. The influence of the temperature on releasing region and date is also investigated. The threshold date during 2008 to 2016 is calculated, which is the date when the temperature of water within 10m isobaths in Liaodong Bay rises up to 15oC. In 2010, the threshold date came about one week later while the medusa releasing date remains the same in 2009. As a result, higher fatality rate of medusa caused by the cold water resulted in lower recapture rate in 2010. Therefore, the releasing date and location should be varied according to environmental conditions. The threshold date tends to appear earlier during 2008 to 2016, which suggests an earlier releasing date. In summer, due to the cold water mass intrusion from the south, the releasing date in the north area should be earlier than in the south.

Slip stream apparatus and method for treating water in a circulating water system

DOEpatents

Cleveland, Joe R.

1997-01-01

An apparatus (10) for treating water in a circulating water system (12) t has a cooling water basin (14) includes a slip stream conduit (16) in flow communication with the circulating water system (12), a source (36) of acid solution in flow communication with the slip stream conduit (16), and a decarbonator (58) in flow communication with the slip stream conduit (16) and the cooling water basin (14). In use, a slip stream of circulating water is drawn from the circulating water system (12) into the slip stream conduit (16) of the apparatus (10). The slip stream pH is lowered by contact with an acid solution provided from the source (36) thereof. The slip stream is then passed through a decarbonator (58) to form a treated slip stream, and the treated slip stream is returned to the cooling water basin (14).

Turning Ocean Mixing Upside Down

NASA Astrophysics Data System (ADS)

Ferrari, Raffaele; Mashayek, Ali; Campin, Jean-Michael; McDougall, Trevor; Nikurashin, Maxim

2015-11-01

It is generally understood that small-scale mixing, such as is caused by breaking internal waves, drives upwelling of the densest ocean waters that sink to the ocean bottom at high latitudes. However the observational evidence that small-scale mixing is more vigorous close to the ocean bottom than above implies that small-scale mixing converts light waters into denser ones, thus driving a net sinking of abyssal water. It is shown that abyssal waters return to the surface along weakly stratified boundary layers, where the small-scale mixing of density decays to zero. The net ocean meridional overturning circulation is thus the small residual of a large sinking of waters, driven by small-scale mixing in the stratified interior, and an equally large upwelling, driven by the reduced small-scale mixing along the ocean boundaries. Thus whether abyssal waters upwell or sink in the net cannot be inferred simply from the vertical profile of mixing intensity, but depends also on the ocean hypsometry, i.e. the shape of the bottom topography. The implications of this result for our understanding of the abyssal ocean circulation will be presented with a combination of numerical models and observations.

Research on the identification of inefficient and invalid circulation in ultra-high water cut stage

NASA Astrophysics Data System (ADS)

Han, Shaoxin

2018-06-01

After oil field entered into ultra-high water cut stage, big channels are formed in some oil and water wells and lead to the inefficient and ineffective circulation of injected water, which not only inhibit the increase of recovery ratio of oil and gas, but also cause the waste of resources. This article selects three static parameters and four dynamic parameters which can perform inefficient and ineffective circulation characteristics between oil and water wells, integrates the fuzzy mathematics theory, establishes fuzzy comprehensive evaluation model to identify the inefficient and ineffective circulation wells in the research area, on this basis, inefficient and ineffective circulation position is further determined through the logging curve characteristics and logging ratio method, the identification of inefficient and ineffective circulation "determine well and layer" is achieved, and provide powerful basis for governance work of inefficient and ineffective circulation.

Shelf Circulation Induced by an Orographic Wind Jet

NASA Astrophysics Data System (ADS)

Ràfols, Laura; Grifoll, Manel; Jordà, Gabriel; Espino, Manuel; Sairouní, Abdel; Bravo, Manel

2017-10-01

The dynamical response to cross-shelf wind-jet episodes is investigated. The study area is located at the northern margin of the Ebro Shelf, in the Northwestern (NW) Mediterranean Sea, where episodes of strong northwesterly wind occur. In this case, the wind is channeled through the Ebro Valley and intensifies upon reaching the sea, resulting in a wind jet. The wind-jet response in terms of water circulation and vertical density structure is investigated using a numerical model. The numerical outputs agree with water current observations from a high-frequency radar. Additionally, temperature, sea level, and wind measurements are also used for the skill assessment of the model. For the wind-jet episodes, the numerical results show a well-defined two-layer circulation in the cross-shelf direction, with the surface currents in the direction of the wind. This pattern is consistent with sea level set-down due to the wind effect. The comparison of the vertical structure response for different episodes revealed that the increase of stratification leads to an onshore displacement of the transition from inner shelf to mid-shelf. In general, the cross-shelf momentum balance during a wind-jet episode exhibits a balance between the frictional terms and the pressure gradient in shallow waters, shifting to a balance between the Coriolis force and the wind stress terms in deeper waters.

What sediment plumes at tide water glaciers can tell us about fjord circulation and subglacial hydrology

NASA Astrophysics Data System (ADS)

Schild, K. M.; Hawley, R. L.

2013-12-01

Marine-terminating outlet glaciers discharge most of Greenland's mass, but the subglacial transport of meltwater is not well understood. The coincident rise in both ice velocity and surface melt during the last decade points to a possible link between the amount of surface melt, glacier velocities, and discharge rates through processes including basal lubrication and/or an increase in melt at the terminus due to discharge plume enhanced entrainment of warm ocean waters. Characterizing the response of the Greenland Ice Sheet to increasing melt is limited in part by the lack of direct observation of the subglacial system. We use ground-based observations (time lapse cameras, DMI weather stations) and satellite remote sensing (MODIS) to infer the subglacial hydrological evolution of a tidewater glacier by identifying the lag between meltwater availability, inferred from warm temperatures and supraglacial lake drainage, and the appearance of a sediment plume at the terminus. The detection of sediment plumes is constrained by melange presence in the spring and decreasing solar illumination in the fall. At Rink Isbræ, West Greenland, we find the appearance of sediment plumes lagging the onset of positive temperatures from 2007-2011 by approximately 44 days, but the plumes are present as the melange clears suggesting this lag may be much shorter but is undetectable. We also observe an abundance of sediment plumes each season (11-25 individual events), which indicates supraglacial drainage events are not the sole source for all sediment plumes. These findings suggest multiple passageways exist from the surface to the subglacial system and the presence of a well-established drainage network early in the melt season. In this poster, we will discuss potential mechanisms for the episodic nature of the recorded plume events; whether they are the product of variable subglacial water supply (suggesting the presence of pulse drainages from subglacial storage basins), highly variable fjord circulation (only allowing subglacial sediment plumes to appear at the surface under specific fjord and plume conditions), or a combination. A clearer understanding of sediment plumes are important for understanding the subglacial hydrological system of tidewater glaciers, as well as gauging the impact of rapid fresh water delivery to melange/sea ice extent in the fjord, terminus stability, submarine melting and fjord circulation.

Isotopic evaluation of ocean circulation in the Late Cretaceous North American seaway

NASA Astrophysics Data System (ADS)

Coulson, Alan B.; Kohn, Matthew J.; Barrick, Reese E.

2011-12-01

During the mid- and Late Cretaceous period, North America was split by the north-south oriented Western Interior Seaway. Its role in creating and maintaining Late Cretaceous global greenhouse conditions remains unclear. Different palaeoceanographic reconstructions portray diverse circulation patterns. The southward extent of relatively cool, low-salinity, low-δ18O surface waters critically distinguishes among these models, but past studies of invertebrates could not independently assess water temperature and isotopic compositions. Here we present oxygen isotopes in biophosphate from coeval marine turtle and fish fossils from western Kansas, representing the east central seaway, and from the Mississippi embayment, representing the marginal Tethys Ocean. Our analyses yield precise seawater isotopic values and geographic temperature differences during the main transition from the Coniacian to the early Campanian age (87-82 Myr), and indicate that the seaway oxygen isotope value and salinity were 2‰ and 3‰ lower, respectively, than in the marginal Tethys Ocean. We infer that the influence of northern freshwater probably reached as far south as Kansas. Our revised values imply relatively large temperature differences between the Mississippi embayment and central seaway, explain the documented regional latitudinal palaeobiogeographic zonation and support models with relatively little inflow of surface waters from the Tethys Ocean to the Western Interior Seaway.

Ocean circulation and properties in Petermann Fjord, Greenland

NASA Astrophysics Data System (ADS)

Johnson, H. L.; Münchow, A.; Falkner, K. K.; Melling, H.

2011-01-01

The floating ice shelf of Petermann glacier interacts directly with the ocean and is thought to lose at least 80% of its mass through basal melting. Based on three opportunistic ocean surveys in Petermann Fjord we describe the basic oceanography: the circulation at the fjord mouth, the hydrographic structure beneath the ice shelf, the oceanic heat delivered to the under-ice cavity, and the fate of the resulting melt water. The 1100 m deep fjord is separated from neighboring Hall Basin by a sill between 350 and 450 m deep. Fjord bottom waters are renewed by episodic spillover at the sill of Atlantic water from the Arctic. Glacial melt water appears on the northeast side of the fjord at depths between 200 m and that of the glacier's grounding line (about 500 m). The fjord circulation is fundamentally three-dimensional; satellite imagery and geostrophic calculations suggest a cyclonic gyre within the fjord mouth, with outflow on the northeast side. Tidal flows are similar in magnitude to the geostrophic flow. The oceanic heat flux into the fjord appears more than sufficient to account for the observed rate of basal melting. Cold, low-salinity water originating in the surface layer of Nares Strait in winter intrudes far under the ice. This may limit basal melting to the inland half of the shelf. The melt rate and long-term stability of Petermann ice shelf may depend on regional sea ice cover and fjord geometry, in addition to the supply of oceanic heat entering the fjord.

Thermal circulation patterns and turbulent fluxes along steep mountain slopes

NASA Astrophysics Data System (ADS)

Nadeau, D. F.; Pardyjak, E.; Higgins, C. W.; Huwald, H.; Baerenbold, F.; Parlange, M. B.

2010-12-01

In hydrology, it is crucial to understand the atmospheric flow dynamics in mountainous terrain to predict turbulent exchanges of heat and moisture accurately at the regional scale. Under clear sky and weak synoptic conditions, these land-atmosphere interactions are driven by thermal circulations that take place over a strong diurnal cycle. During the day, winds travel up the mountain slopes and at night, they travel down toward to the bottom of the valley. Little is known about how the transition between these two regimes takes place over steep slopes. The Slope Experiment at La Fouly (SELF) in the Swiss Alps was designed to investigate these transition periods throughout summer 2010. In this paper, we will present the first results obtained from this field campaign. Data from a network of 16 wireless surface stations is used to define catchment wide micrometeorological processes such as slope and valley wind system development, while detailed measurements of the turbulent processes on a steep idealized slope (20 to 45 degrees) were also made. The slope was instrumented along a transect with four towers (including a surface energy budget station and 10 m tower with sonic anemometers), 13 surface temperature measurement stations and a tethered balloon system to capture the complex interplay between surface and atmosphere. Initial data presented will include basic circulation pattern development and measurements of the turbulent fluxes of water vapor, heat and momentum on the slope.

A mathematical model for human brain cooling during cold-water near-drowning.

PubMed

Xu, X; Tikuisis, P; Giesbrecht, G

1999-01-01

A two-dimensional mathematical model was developed to estimate the contributions of different mechanisms of brain cooling during cold-water near-drowning. Mechanisms include 1) conductive heat loss through tissue to the water at the head surface and in the upper airway and 2) circulatory cooling to aspirated water via the lung and via venous return from the scalp. The model accounts for changes in boundary conditions, blood circulation, respiratory ventilation of water, and head size. Results indicate that conductive heat loss through the skull surface or the upper airways is minimal, although a small child-sized head will conductively cool faster than a large adult-sized head. However, ventilation of cold water may provide substantial brain cooling through circulatory cooling. Although it seems that water breathing is required for rapid "whole" brain cooling, it is possible that conductive cooling may provide some advantage by cooling the brain cortex peripherally and the brain stem centrally via the upper airway.

Variability of Changjiang Diluted Water revealed by a 45-year long-term ocean hindcast and Self-Organizing Maps analysis

NASA Astrophysics Data System (ADS)

Zeng, Xiangming; He, Ruoying; Zong, Haibo

2017-08-01

Based on long-term realistic ocean circulation hindcast for in the Bohai, Yellow, and East China Seas, 45 years (1961-2005) of sea surface salinity data were analyzed using Self-Organizing Maps (SOM) to have a better understanding of the Changjiang Diluted Water (CDW) variation. Three spatial patterns were revealed by the SOM: normal, transition, and extension. The normal pattern mainly occurs from December to May while the CDW hugs China's east coast closely and flows southward. The extension pattern is dominant from June to October when the CDW extends northwestward toward Jeju Island in an omega shape. The transition pattern prevails for the rest of the year. Pattern-averaged temperature, circulation, and chlorophyll-a concentration show significant differences. CDW area and its eastern most extension were explored as a function of the Changjiang runoff and regional upwelling index. We found that Changjiang runoff and upwelling index can be reasonable predictors for the overall CDW area, while ambient circulation determines the distribution and structure of the CDW, and thus the CDW eastern most extension.

Submesoscale Rossby waves on the Antarctic circumpolar current

PubMed Central

Bachman, Scott; Sallee, Jean-Baptiste

2018-01-01

The eastward-flowing Antarctic circumpolar current (ACC) plays a central role in the global ocean overturning circulation and facilitates the exchange of water between the ocean surface and interior. Submesoscale eddies and fronts with scales between 1 and 10 km are regularly observed in the upper ocean and are associated with strong vertical circulations and enhanced stratification. Despite their importance in other locations, comparatively little is known about submesoscales in the Southern Ocean. We present results from new observations, models, and theories showing that submesoscales are qualitatively changed by the strong jet associated with the ACC in the Scotia Sea, east of Drake Passage. Growing submesoscale disturbances develop along a dense filament and are transformed into submesoscale Rossby waves, which propagate upstream relative to the eastward jet. Unlike their counterparts in slower currents, the submesoscale Rossby waves do not destroy the underlying frontal structure. The development of submesoscale instabilities leads to strong net subduction of water associated with a dense outcropping filament, and later, the submesoscale Rossby waves are associated with intense vertical circulations. PMID:29670936

Interactions of Multiple Atmospheric Circulation Drive the Drought in Tarim River Basin.

PubMed

Wu, Yong-Ping; Feng, Guo-Lin; Li, Bai-Lian

2016-05-20

Global warming is likely to cause overall drying of land surfaces and aridity increasing leading to expansion of dry climate zones. There is an increased risk of extremely arid environment and large deserts developed progressively in the central Asia. However, the key factors causing the drying in mid-Asia remain inconclusive. Here, we analyzed the relationship among precipitation, water vapor transportation in Tarim River Basin (TRB) and Multiple Atmospheric Circulation (MAC) to explore the mechanism of MAC driving the drying in TRB, through comparing MAC between abundant and scarce precipitation years. We found that Westerly Circulation (WC) and Asian Summer Monsoon (ASM) are likely to promote the precipitation respectively. Whereas, they not only have their own influence but also restrict each other and facilitate the forming of peculiar water vapor transport channel for TRB, which is probably to restrain the precipitation and its distribution pattern and accelerate the drying in this region. Our results enrich the findings on mechanisms of wet places becoming wetter while dry areas getting drier under the global warming.

Interactions of Multiple Atmospheric Circulation Drive the Drought in Tarim River Basin

NASA Astrophysics Data System (ADS)

Wu, Yong-Ping; Feng, Guo-Lin; Li, Bai-Lian

2016-05-01

Global warming is likely to cause overall drying of land surfaces and aridity increasing leading to expansion of dry climate zones. There is an increased risk of extremely arid environment and large deserts developed progressively in the central Asia. However, the key factors causing the drying in mid-Asia remain inconclusive. Here, we analyzed the relationship among precipitation, water vapor transportation in Tarim River Basin (TRB) and Multiple Atmospheric Circulation (MAC) to explore the mechanism of MAC driving the drying in TRB, through comparing MAC between abundant and scarce precipitation years. We found that Westerly Circulation (WC) and Asian Summer Monsoon (ASM) are likely to promote the precipitation respectively. Whereas, they not only have their own influence but also restrict each other and facilitate the forming of peculiar water vapor transport channel for TRB, which is probably to restrain the precipitation and its distribution pattern and accelerate the drying in this region. Our results enrich the findings on mechanisms of wet places becoming wetter while dry areas getting drier under the global warming.

Geothermal heating enhances atmospheric asymmetries on synchronously rotating planets

NASA Astrophysics Data System (ADS)

Haqq-Misra, Jacob; Kopparapu, Ravi Kumar

2015-01-01

Earth-like planets within the liquid water habitable zone of M-type stars may evolve into synchronous rotators. On these planets, the substellar hemisphere experiences perpetual daylight while the opposing antistellar hemisphere experiences perpetual darkness. Because the night-side hemisphere has no direct source of energy, the air over this side of the planet is prone to freeze out and deposit on the surface, which could result in atmospheric collapse. However, general circulation models (GCMs) have shown that atmospheric dynamics can counteract this problem and provide sufficient energy transport to the antistellar side. Here, we use an idealized GCM to consider the impact of geothermal heating on the habitability of synchronously rotating planets. Geothermal heating may be expected due to tidal interactions with the host star, and the effects of geothermal heating provide additional habitable surface area and may help to induce melting of ice on the antistellar hemisphere. We also explore the persistence of atmospheric asymmetries between the Northern and Southern hemispheres, and we find that the direction of the meridional circulation (for rapidly rotating planets) or the direction of zonal wind (for slowly rotating planets) reverses on either side of the substellar point. We show that the zonal circulation approaches a theoretical state similar to a Walker circulation only for slowly rotating planets, while rapidly rotating planets show a zonal circulation with the opposite direction. We find that a cross-polar circulation is present in all cases and provides an additional mechanism of mass and energy transport from the substellar to antistellar point. Characterization of the atmospheres of synchronously rotating planets should include consideration of hemispheric differences in meridional circulation and examination of transport due to cross-polar flow.

Reconstruct the past thermocline circulation in the Atlantic: calcification depths and Mg/Ca-temperature calibrations for 6 deep-dwelling planktonic foraminifera

NASA Astrophysics Data System (ADS)

Cleroux, C.; deMenocal, P.; Arbuszewski, J.; Linsley, B.

2012-04-01

The subtropical cells are shallow meridional overturning circulations driven by the atmospheric circulation and the deep thermohaline circulation. They connect the mid-latitude and the tropic, release latten heat to the atmosphere and impact climate on decadal to longer time scale. The upper water column temperature and salinity structures of the ocean reflect this circulation. We present proxies to study these past structures. We performed stable oxygen isotope (δ18O) and trace element ratio measurements on one surface-dwelling (G. ruber)1 and six deep-dwelling planktonic foraminifera species (N. dutertrei, G. inflata, G. tumida, G. truncatulinoides, G. hirsuta and G. crassaformis) on 66 coretops spanning from 35°N to 20°S along the Mid-Atlantic ridge. Comparison between measured δ18O and predicted δ18O (using water column temperature and seawater δ18O), shows that N. dutertrei, G. tumida, G. hirsuta and G. crassaformis keep the same apparent calcification depth along the transect (respectively: 125m, 150m, 700m and 800m). Calcification at two depth levels was also tested. For the six deep-dwelling species, we establish Mg/Ca-temperature calibrations with both atlas temperature at the calcification depth and isotopic temperature. We present Mg/Ca-temperature equations for species previously very poorly calibrated. The δ18O and temperature (Mg/Ca derived) on the six planktonic foraminifera species faithfully reproduce the modern water column structure of the upper 800 m depth, establishing promising proxies for past subsurface reconstruction. 1 Arbuszewski, J. J., P. B. deMenocal, A. Kaplan, and C. E. Farmer (2010), On the fidelity of shell-derived δ18Oseawater estimates, Earth and Planetary Science Letters, 300(3-4), 185-196.

Dependence of the Onset of the Runaway Greenhouse Effect on the Latitudinal Surface Water Distribution of Earth-Like Planets

NASA Astrophysics Data System (ADS)

Kodama, T.; Nitta, A.; Genda, H.; Takao, Y.; O'ishi, R.; Abe-Ouchi, A.; Abe, Y.

2018-02-01

Liquid water is one of the most important materials affecting the climate and habitability of a terrestrial planet. Liquid water vaporizes entirely when planets receive insolation above a certain critical value, which is called the runaway greenhouse threshold. This threshold forms the inner most limit of the habitable zone. Here we investigate the effects of the distribution of surface water on the runaway greenhouse threshold for Earth-sized planets using a three-dimensional dynamic atmosphere model. We considered a 1 bar atmosphere whose composition is similar to the current Earth's atmosphere with a zonally uniform distribution of surface water. As previous studies have already showed, we also recognized two climate regimes: the land planet regime, which has dry low-latitude and wet high-latitude regions, and the aqua planet regime, which is globally wet. We showed that each regime is controlled by the width of the Hadley circulation, the amount of surface water, and the planetary topography. We found that the runaway greenhouse threshold varies continuously with the surface water distribution from about 130% (an aqua planet) to 180% (the extreme case of a land planet) of the present insolation at Earth's orbit. Our results indicate that the inner edge of the habitable zone is not a single sharp boundary, but a border whose location varies depending on planetary surface condition, such as the amount of surface water. Since land planets have wider habitable zones and less cloud cover, land planets would be good targets for future observations investigating planetary habitability.

Simulation of Lake Victoria Circulation Patterns Using the Regional Ocean Modeling System (ROMS).

PubMed

Nyamweya, Chrispine; Desjardins, Christopher; Sigurdsson, Sven; Tomasson, Tumi; Taabu-Munyaho, Anthony; Sitoki, Lewis; Stefansson, Gunnar

2016-01-01

Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September-May) and mixing (June-August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore-offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria.

The Potential for Predicting Precipitation on Seasonal-to-Interannual Timescales

NASA Technical Reports Server (NTRS)

Koster, R. D.

1999-01-01

The ability to predict precipitation several months in advance would have a significant impact on water resource management. This talk provides an overview of a project aimed at developing this prediction capability. NASA's Seasonal-to-Interannual Prediction Project (NSIPP) will generate seasonal-to-interannual sea surface temperature predictions through detailed ocean circulation modeling and will then translate these SST forecasts into forecasts of continental precipitation through the application of an atmospheric general circulation model and a "SVAT"-type land surface model. As part of the process, ocean variables (e.g., height) and land variables (e.g., soil moisture) will be updated regularly via data assimilation. The overview will include a discussion of the variability inherent in such a modeling system and will provide some quantitative estimates of the absolute upper limits of seasonal-to-interannual precipitation predictability.

Water masses transform at mid-depths over the Antarctic Continental Slope

NASA Astrophysics Data System (ADS)

Mead Silvester, Jess; Lenn, Yueng-Djern; Polton, Jeffrey; Phillips, Helen E.; Morales Maqueda, Miguel

2017-04-01

The Meridional Overturning Circulation (MOC) controls the oceans' latitudinal heat distribution, helping to regulate the Earth's climate. The Southern Ocean is the primary place where cool, deep waters return to the surface to complete this global circulation. While water mass transformations intrinsic to this process predominantly take place at the surface following upwelling, recent studies implicate vertical mixing in allowing transformation at mid-depths over the Antarctic continental slope. We deployed an EM-Apex float near Elephant Island, north of the Antarctic Peninsula's tip, to profile along the slope and use potential vorticity to diagnose observed instabilities. The float captures direct heat exchange between a lens of Upper Circumpolar Deep Water (UCDW) and surrounding Lower Circumpolar Deep Waters (LCDW) at mid-depths and over the course of several days. Heat fluxes peak across the top and bottom boundaries of the UCDW lens and peak diffusivities across the bottom boundary are associated with shear instability. Estimates of diffusivity from shear-strain finestructure parameterisation and heat fluxes are found to be in reasonable agreement. The two-dimensional Ertel potential vorticity is elevated both inside the UCDW lens and along its bottom boundary, with a strong contribution from the shear term in these regions and instabilities are associated with gravitational and symmetric forcing. Thus, shear instabilities are driving turbulent mixing across the lower boundary between these two water masses, leading to the observed heat exchange and transformation at mid-depths over the Antarctic continental slope. This has implications for our understanding of the rates of upwelling and ocean-atmosphere exchanges of heat and carbon at this critical location.

Synoptic Traveling Weather Systems on Mars: Effects of Radiatively-Active Water Ice Clouds

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.; Kahre, Melinda A.; Haberle, Robert; Atsuki Urata, Richard

2016-10-01

Atmospheric aerosols on Mars are critical in determining the nature of its thermal structure, its large-scale circulation, and hence the overall climate of the planet. We conduct multi-annual simulations with the latest version of the NASA Ames Mars global climate model (GCM), gcm2.3+, that includes a modernized radiative-transfer package and complex water-ice cloud microphysics package which permit radiative effects and interactions of suspended atmospheric aerosols (e.g., water ice clouds, water vapor, dust, and mutual interactions) to influence the net diabatic heating. Results indicate that radiatively active water ice clouds profoundly affect the seasonal and annual mean climate. The mean thermal structure and balanced circulation patterns are strongly modified near the surface and aloft. Warming of the subtropical atmosphere at altitude and cooling of the high latitude atmosphere at low levels takes place, which increases the mean pole-to-equator temperature contrast (i.e., "baroclinicity"). With radiatively active water ice clouds (RAC) compared to radiatively inert water ice clouds (nonRAC), significant changes in the intensity of the mean state and forced stationary Rossby modes occur, both of which affect the vigor and intensity of traveling, synoptic period weather systems. Such weather systems not only act as key agents in the transport of heat and momentum beyond the extent of the Hadley circulation, but also the transport of trace species such as water vapor, water ice-clouds, dust and others. The northern hemisphere (NH) forced Rossby waves and resultant wave train are augmented in the RAC case: the modes are more intense and the wave train is shifted equatorward. Significant changes also occur within the subtropics and tropics. The Rossby wave train sets up, combined with the traveling synoptic-period weather systems (i.e., cyclones and anticyclones), the geographic extent of storm zones (or storm tracks) within the NH. A variety of circulation features will be presented which indicate contrasts between the RAC and nonRAC cases, and which highlight key effects radiatively-active clouds have on physical and dynamical processes active in the current climate of Mars.

Synoptic Traveling Weather Systems on Mars: Effects of Radiatively-Active Water Ice Clouds

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery; Kahre, Melinda; Haberle, Robert; Urata, Richard

2017-01-01

Atmospheric aerosols on Mars are critical in determining the nature of its thermal structure, its large-scale circulation, and hence the overall climate of the planet. We conduct multi-annual simulations with the latest version of the NASA Ames Mars global climate model (GCM), gcm2.3+, that includes a modernized radiative-transfer package and complex water-ice cloud microphysics package which permit radiative effects and interactions of suspended atmospheric aerosols (e.g., water ice clouds, water vapor, dust, and mutual interactions) to influence the net diabatic heating. Results indicate that radiatively active water ice clouds profoundly affect the seasonal and annual mean climate. The mean thermal structure and balanced circulation patterns are strongly modified near the surface and aloft. Warming of the subtropical atmosphere at altitude and cooling of the high latitude atmosphere at low levels takes place, which increases the mean pole-to-equator temperature contrast (i.e., "baroclinicity"). With radiatively active water ice clouds (RAC) compared to radiatively inert water ice clouds (nonRAC), significant changes in the intensity of the mean state and forced stationary Rossby modes occur, both of which affect the vigor and intensity of traveling, synoptic period weather systems. Such weather systems not only act as key agents in the transport of heat and momentum beyond the extent of the Hadley circulation, but also the transport of trace species such as water vapor, water ice-clouds, dust and others. The northern hemisphere (NH) forced Rossby waves and resultant wave train are augmented in the RAC case: the modes are more intense and the wave train is shifted equatorward. Significant changes also occur within the subtropics and tropics. The Rossby wave train sets up, combined with the traveling synoptic period weather systems (i.e., cyclones and anticyclones), the geographic extent of storm zones (or storm tracks) within the NH. A variety of circulation features will be presented which indicate contrasts between the RAC and nonRAC cases, and which highlight key effects radiatively-active clouds have on physical and dynamical processes active in the current climate of Mars.

Synoptic Traveling Weather Systems on Mars: Effects of Radiatively-Active Water Ice Clouds

NASA Technical Reports Server (NTRS)

Hollingsworth, Jeffery; Kahre, Melinda; Haberle, Robert; Urata, Richard

2017-01-01

Atmospheric aerosols on Mars are critical in determining the nature of its thermal structure, its large-scale circulation, and hence the overall climate of the planet. We conduct multi-annual simulations with the latest version of the NASA Ames Mars global climate model (GCM), gcm2.3+, that includes a modernized radiative-transfer package and complex water-ice cloud microphysics package which permit radiative effects and interactions of suspended atmospheric aerosols (e.g., water ice clouds, water vapor, dust, and mutual interactions) to influence the net diabatic heating. Results indicate that radiatively active water ice clouds profoundly affect the seasonal and annual mean climate. The mean thermal structure and balanced circulation patterns are strongly modified near the surface and aloft. Warming of the subtropical atmosphere at altitude and cooling of the high latitude atmosphere at low levels takes place, which increases the mean pole-to-equator temperature contrast (i.e., "baroclinicity"). With radiatively active water ice clouds (RAC) compared to radiatively inert water ice clouds (nonRAC), significant changes in the intensity of the mean state and forced stationary Rossby modes occur, both of which affect the vigor and intensity of traveling, synoptic period weather systems.Such weather systems not only act as key agents in the transport of heat and momentum beyond the extent of the Hadley circulation, but also the transport of trace species such as water vapor, water ice-clouds, dust and others. The northern hemisphere (NH) forced Rossby waves and resultant wave train are augmented in the RAC case: the modes are more intense and the wave train is shifted equatorward. Significant changes also occur within the subtropics and tropics. The Rossby wave train sets up, combined with the traveling synoptic period weather systems (i.e., cyclones and anticyclones), the geographic extent of storm zones (or storm tracks) within the NH. A variety of circulation features will be presented which indicate contrasts between the RAC and nonRAC cases, and which highlight key effects radiatively-active clouds have on physical and dynamical processes active in the current climate of Mars.

Modeling the periodic stratification and gravitational circulation in San Francisco Bay, California

USGS Publications Warehouse

Cheng, Ralph T.; Casulli, Vincenzo

1996-01-01

A high resolution, three-dimensional (3-D) hydrodynamic numerical model is applied to San Francisco Bay, California to simulate the periodic tidal stratification caused by tidal straining and stirring and their long-term effects on gravitational circulation. The numerical model is formulated using fixed levels in the vertical and uniform computational mesh on horizontal planes. The governing conservation equations, the 3-D shallow water equations, are solved by a semi-implicit finite-difference scheme. Numerical simulations for estuarine flows in San Francisco Bay have been performed to reproduce the hydrodynamic properties of tides, tidal and residual currents, and salt transport. All simulations were carried out to cover at least 30 days, so that the spring-neap variance in the model results could be analyzed. High grid resolution used in the model permits the use of a simple turbulence closure scheme which has been shown to be sufficient to reproduce the tidal cyclic stratification and well-mixed conditions in the water column. Low-pass filtered 3-D time-series reveals the classic estuarine gravitational circulation with a surface layer flowing down-estuary and an up-estuary flow near the bottom. The intensity of the gravitational circulation depends upon the amount of freshwater inflow, the degree of stratification, and spring-neap tidal variations.

Production regimes in four eastern boundary current systems

NASA Technical Reports Server (NTRS)

Carr, M. E.; Kearns, E. J.

2003-01-01

High productivity (maxima 3 g C m(sup -2)day(sup -1)) of the Eastern Boundary Currents (EBCs), i.e. the California, Peru-Humboldt, Canary and Benguela Currents, is driven by a combination of local forcing and large-scale circulation. The characteristics of the deep water brought to the surface by upwelling favorable winds depend on the large-scale circulation patterns. Here we use a new hydrographic and nutrient climatology together with satellite measurements ofthe wind vector, sea-surface temperature (SST), chlorophyll concentration, and primary production modeled from ocean color to quantify the meridional and seasonal patterns of upwelling dynamics and biological response. The unprecedented combination of data sets allows us to describe objectively the variability for small regions within each current and to characterize the governing factors for biological production. The temporal and spatial environmental variability was due in most regions to large-scale circulation, alone or in combination with offshore transport (local forcing). The observed meridional and seasonal patterns of biomass and primary production were most highlycorrelated to components representing large-scale circulation. The biomass sustained by a given nutrient concentration in the Atlantic EBCs was twice as large as that of the Pacific EBCs. This apparent greater efficiency may be due toavailability of iron, physical retention, or differences in planktonic community structure.

Annual subsurface transport of a red tide dinoflagellate to its bloom area: Water circulation patterns and organism distributions in the Chesapeake Bay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tyler, M.A.; Seliger, H.H.

1978-03-01

An annual, long range, subsurface transport of Prorocentrum mariae-lebouriae, from the mouth of the Chesapeake Bay to its bloom area in the upper bay, a distance of 240 km, is described and completely documented. Prorocentrum in surface outflowing waters at the mouth of the bay is recruited in late winter into more dense inflowing coastal waters. Strong stratification produced by late winter--early spring surface runoff results in the development of a stable pycnocline. Prorocentrum, now in northward-flowing bottom waters, is retained in these bottom waters. It accumulates in a subsurface concentration maximum below the pycnocline and is transported northward tomore » reach its bloom area in the Patapsco River and north of the Bay Bridge by late spring. The rapidly decreasing depth of the upper bay causes the pycnocline to rise, mixing the previously light-limited Prorocentrum and its nutrient-rich bottom waters to the surface, where rapid growth ensues. Once the dinoflagellate is in surface waters, positive phototaxis, combined with both wind- and tide-driven surface convergences, produce dense surface patches or red tides. Prorocentrum is effectively retained in the bay until late winter by sequential inoculation into the tributary estuaries on the western shore, which exchange relatively slowly with bay waters. By late winter the annual cycle is complete. Prorocentrum is again in surface waters at the mouth of the bay where it is reintroduced into northward-flowing bottom waters. The mechanisms described provide a key to understanding the origins of subsurface chlorophyll maxima and the delivery of toxic dinoflagellates to coastal bloom areas.« less

Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

PubMed

Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F

2014-07-03

Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the Bølling-Allerød interstadial.

Pathways and Hydrography in the Mesoamerican Barrier Reef System Part 1: Circulation

NASA Astrophysics Data System (ADS)

Carrillo, L.; Johns, E. M.; Smith, R. H.; Lamkin, J. T.; Largier, J. L.

2015-10-01

Acoustic Doppler Current Profiler (ADCP) measurements and surface drifters released from two oceanographic cruises conducted during March 2006 and January/February 2007 are used to investigate the circulation off the Mesoamerican Barrier Reef System (MBRS). We show that the MBRS circulation can be divided into two distinct regimes, a northern region dominated by the strong, northward-flowing Yucatan Current, and a southern region with weaker southward coastal currents and the presence of the Honduras Gyre. The latitude of impingement of the Cayman Current onto the coastline varies with time, and creates a third region, which acts as a boundary between the northern and southern circulation regimes. This circulation pattern yields two zones in terms of dispersal, with planktonic propagules in the northern region being rapidly exported to the north, whereas plankton in the southern and impingement regions may be retained locally or regionally. The latitude of the impingement region shifts interannually and intra-annually up to 3° in latitude. Sub-mesoscale features are observed in association with topography, e.g., flow bifurcation around Cozumel Island, flow wake north of Chinchorro Bank and separation of flow from the coast just north of Bahia de la Ascencion. This third feature is evident as cyclonic recirculation in coastal waters, which we call the Ascencion-Cozumel Coastal Eddy. An understanding of the implications of these different circulation regimes on water mass distributions, population connectivity, and the fate of land-based pollutants in the MBRS is critically important to better inform science-based resource management and conservation plans for the MBRS coral reefs.

Sea Ice Flows, Sea of Okhotsk, CIS

NASA Image and Video Library

1991-05-06

STS039-84-29AL (28 April-6 May 1991) --- This nearly vertical photograph of the North Atlantic, taken outside of the sunglint pattern, illustrates the extreme contrast between highly reflective ice, having a large percentage of between-crystal air space, and the low-reflectance water, which absorbs most of the light that propagates into it from the air. The ice drifts along with the surface currents and wind and may therefore be used as a natural Langranian* tracer. Photographs such as this, taken several times over the course of a mission, may be used to investigate near-surface circulation in high-latitude oceans. *A Langranian tracer is anything that can be tracked as it drifts along with the water, as opposed to staying in one position and measuring how fast the water goes by.

Process for the preparation of calcium superoxide

NASA Technical Reports Server (NTRS)

Ballou, E. V.; Wood, P. C.; Wydeven, T. J.; Spitze, L. A. (Inventor)

1978-01-01

Calcium superoxide is prepared in high yields by spreading a quantity of calcium peroxide diperoxyhydrate on the surface of a container, positioning said container in a vacuum chamber on a support structure through which a coolant fluid can be circulated, partially evacuating said vacuum chamber, allowing the temperature of the diperoxyhydrate to reach the range of about 0 to about 40 C; maintaining the temperature selected for a period of time sufficient to complete the disproproriation of the diperoxyhydrate to calcium superoxide, calcium hydroxide, oxygen, and water; constantly and systematically removing the water as it is formed by sweeping the reacting material with a current of dry inert gas and/or by condensation of said water on a cold surface; backfilling the chamber with a dry inert gas; and finally, recovering the calcium superoxide produced.

49 CFR 230.61 - Arch tubes, water bar tubes, circulators and thermic siphons.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Arch tubes, water bar tubes, circulators and... MAINTENANCE STANDARDS Boilers and Appurtenances Washing Boilers § 230.61 Arch tubes, water bar tubes... water bar tubes shall thoroughly be cleaned mechanically, washed, and inspected. Circulators and thermic...

Estimation of effective hydrologic properties of soils from observations of vegetation density

NASA Technical Reports Server (NTRS)

Tellers, T. E.; Eagleson, P. S.

1980-01-01

A one-dimensional model of the annual water balance is reviewed. Improvements are made in the method of calculating the bare soil component of evaporation, and in the way surface retention is handled. A natural selection hypothesis, which specifies the equilibrium vegetation density for a given, water limited, climate soil system, is verified through comparisons with observed data. Comparison of CDF's of annual basin yield derived using these soil properties with observed CDF's provides verification of the soil-selection procedure. This method of parameterization of the land surface is useful with global circulation models, enabling them to account for both the nonlinearity in the relationship between soil moisture flux and soil moisture concentration, and the variability of soil properties from place to place over the Earth's surface.

Meteorologic, oceanographic, and geomorphic controls on circulation and residence time in a coral reef-lined embayment: Faga'alu Bay, American Samoa

NASA Astrophysics Data System (ADS)

Storlazzi, C. D.; Cheriton, O. M.; Messina, A. M.; Biggs, T. W.

2018-06-01

Water circulation over coral reefs can determine the degree to which reef organisms are exposed to the overlying waters, so understanding circulation is necessary to interpret spatial patterns in coral health. Because coral reefs often have high geomorphic complexity, circulation patterns and the duration of exposure, or "local residence time" of a water parcel, can vary substantially over small distances. Different meteorologic and oceanographic forcings can further alter residence time patterns over reefs. Here, spatially dense Lagrangian surface current drifters and Eulerian current meters were used to characterize circulation patterns and resulting residence times over different regions of the reefs in Faga'alu Bay, American Samoa, during three distinct forcing periods: calm, strong winds, and large waves. Residence times varied among different geomorphic zones of the reef and were reflected in the spatially varying health of the corals across the embayment. The relatively healthy, seaward fringing reef consistently had the shortest residence times, as it was continually flushed by wave breaking at the reef crest, whereas the degraded, sheltered, leeward fringing reef consistently had the longest residence times, suggesting this area is more exposed to land-based sources of pollution. Strong wind forcing resulted in the longest residence times by pinning the water in the bay, whereas large wave forcing flushed the bay and resulted in the shortest residence times. The effect of these different forcings on residence times was fairly consistent across all reef geomorphic zones, with the shift from wind to wave forcing shortening mean residence times by approximately 50%. Although ecologically significant to the coral organisms in the nearshore reef zones, these shortened residence times were still 2-3 times longer than those associated with the seaward fringing reef across all forcing conditions, demonstrating how the geomorphology of a reef environment sets a first-order control on reef health.

Carbon and Neodymium Isotopic Fingerprints of Atlantic Deep Ocean Circulation During the Warm Pliocene

NASA Astrophysics Data System (ADS)

Riesselman, C. R.; Scher, H.; Robinson, M. M.; Dowsett, H. J.; Bell, D. B.

2012-12-01

Earth's future climate may resemble the mid-Piacenzian Age of the Pliocene, a time when global temperatures were sustained within the range predicted for the coming century. Surface and deep water temperature reconstructions and coupled ocean-atmosphere general circulation model simulations by the USGS PRISM (Pliocene Research Interpretation and Synoptic Mapping) Group identify a dramatic North Atlantic warm surface temperature anomaly in the mid-Piacenzian (3.264 - 3.025 Ma), accompanied by increased evaporation. The anomaly is detected in deep waters at 46°S, suggesting enhanced meridional overturning circulation and more southerly penetration of North Atlantic Deep Water (NADW) during the PRISM interval. However deep water temperature proxies are not diagnostic of water mass and some coupled model simulations predict transient decreases in NADW production in the 21st century, presenting a contrasting picture of future climate. We present a new multi-proxy investigation of Atlantic deep ocean circulation during the warm mid-Piacenzian, using δ13C of benthic foraminifera as a proxy for water mass age and the neodymium isotopic composition of fossil fish teeth (ɛNd) as a proxy for water mass source and mixing. This reconstruction utilizes both new and previously published data from DSDP and ODP cores along equatorial (Ceara Rise), southern mid-latitude (Walvis Ridge), and south Atlantic (Meteor Rise/Agulhas Ridge) depth transects. Additional end-member sites in the regions of modern north Atlantic and Southern Ocean deep water formation provide a Pliocene baseline for comparison. δ13C throughout the Atlantic basin is remarkably homogenous during the PRISM interval. δ13C values of Cibicidoides spp. and C. wuellerstorfi largely range between 0‰ and 1‰ at North Atlantic, shallow equatorial, southern mid-latitude, and south Atlantic sites with water depths from 2000-4700 m; both depth and latitudinal gradients are generally small (~0.3‰). However, equatorial Ceara Rise sites below 3500 m diverge, with δ13C values as low as -1.2‰ at ~3.15 Ma. The uniquely negative δ13C values at deep Ceara rise sites suggest that, during PRISM warmth, the oldest Atlantic deep waters may have resided along the modern deep western boundary current, while younger deep water masses were concentrated to the south and east. In the modern Atlantic, the ɛNd value of southern-sourced waters is more radiogenic than that of northern-sourced waters, providing a complimentary means to characterize Pliocene water mass geometry. ɛNd values from shallow (2500 m) and deep (4700 m) Walvis Ridge sites average -10 and -11 respectively; the shallow site is somewhat more radiogenic than published coretop ɛNd (-12), suggesting enhanced Pliocene influence of southern-sourced water masses. Ongoing analytical efforts will fingerprint Piacenzian ɛNd from north and south deep water source regions and will target additional depth transect ɛNd, allowing us to investigate the possibility that "older" carbon isotopic signatures at western equatorial sites reflect entrainment of proto-NADW while "younger" signatures at southern and eastern sites reflect the influence of southern-sourced deep water.

Can Arctic sea-ice melt be explained by atmospheric meridional transports? (Invited)

NASA Astrophysics Data System (ADS)

Tjernstrom, M. K.; Graversen, R. G.

2010-12-01

The Arctic summer sea ice is melting away at an alarming rate, and it is now expected that an principally sea-ice free Arctic summer will occur much earlier than projected by the IPCC AR4 models. At the same time Arctic near-surface temperatures are rising at a rate much faster than the global average. The processes responsible for these changes are debated and many claim that local feedbacks, such as the surface albedo feedback, are the main culprits while other argue that remote effects, such as atmospheric circulation changes on synoptic and hemispheric scales, are the most important. We will explore the effects of the meridional transport by synoptic and larger scale atmospheric circulation on recent changes, using reanalysis data. It will be illustarated how this transport can contribute significant amounts of sensible heat, but also of atmospheric moisture such that local cloud feedbacks as well as the direct greenhouse effect of the water vapor contributes significantly to the surface energy balance over the Arctic polar cap.

The Fraser Gyre: A cyclonic eddy off the coast of eastern Australia

NASA Astrophysics Data System (ADS)

Azis Ismail, Mochamad Furqon; Ribbe, Joachim; Karstensen, Johannes; Lemckert, Charles; Lee, Serena; Gustafson, Johann

2017-06-01

This paper examines the on-shelf circulation of the eastern Australian continental shelf for a region off southeast Queensland. We identify a characteristic seasonally reoccurring wind-driven cyclonic flow. It influences the cross-shelf exchange with the East Australian Current (EAC), which is the western boundary current of the South Pacific Ocean. We refer to this cyclonic circulation as the Fraser Gyre. It is located south of Fraser Island between about 25 °S and 27 °S. The region is adjacent to the intensification zone of the EAC where the current accelerates and establishes a swift, albeit seasonally variable southward boundary flow. Through the analysis of several data sets including remotely sensed sea surface temperature and sea surface height anomaly, satellite tracked surface drifters, ocean and atmospheric reanalysis data as well as geostrophic currents from altimetry, we find that the on-shelf Fraser Gyre develops during the southern hemisphere autumn and winter months. The gyre is associated with a longshore near-coast northward flow. Maximum northward on-shelf depth averaged velocities are estimated with about 0.15-0.26 ms-1. The flow turns eastward just to the south of Fraser Island and joins the persistent southward EAC flow along the shelf break. The annual mean net cross-shelf outward and inward flow associated with the gyre is about -1.17 ± 0.23 Sv in the north and 0.23 ± 0.13 Sv (1 Sv = 106 m3s-1) in the south. Mean seasonal water renewal time scales of the continental shelf are longest during austral winter with an average of about 3.3 days due to the Fraser Gyre retaining water over the shelf, however, monthly estimates range from 2 to 8 days with the longer timescale during the austral autumn and winter. The southerly wind during austral autumn and winter is identified as controlling the on shelf circulation and is the principal driver of the seasonally appearing Fraser Gyre. The conceptual model of the Fraser Gyre is consistent with general physical principals of the coastal shelf circulation. A southerly wind is associated with surface layer flow toward the coast, a near coast positive SSHa with a current in the direction of the wind, down-welling and export of shelf water. The Fraser Gyre influenced cross-shelf exchanges are possibly facilitating the offshore transport of fish larvae, sediments, nutrients, river discharges, and other properties across the shelf break and into the southward flowing EAC during the austral autumn and winter.

Space and Missile Defense Acquisitions: Periodic Assessment Needed to Correct Parts Quality Problems in Major Programs

DTIC Science & Technology

2011-06-01

understanding of the global water cycle and the accuracy of precipitation forecasts. GPM is composed of a core spacecraft carrying two main instruments: a dual...developed by NASA and the Space Agency of Argentina (Comisión Nacional de Actividades Espaciales) to investigate the links between the global water ... cycle , ocean circulation, and the climate. It will measure global sea surface salinity. The Aquarius science goals are to observe and model the

The circulation of Prince William Sound

NASA Technical Reports Server (NTRS)

Muench, R. D. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Results suggest that sediment-laden plumes of fresh water from rivers may be useful tracers, due to their high visibility, of surface water motion. The two useable images obtained to date corroborate that westerly flow was occurring in the Gulf of Alaska just south of Prince William Sound, and that an inflow into Prince William Sound was occurring concurrently with flood tides on both occasions. River plumes are useful tracers, but poor weather conditions somewhat limit the use of satellite imagery.

Contribution of topographically generated submesoscale turbulence to Southern Ocean overturning

NASA Astrophysics Data System (ADS)

Ruan, Xiaozhou; Thompson, Andrew F.; Flexas, Mar M.; Sprintall, Janet

2017-11-01

The ocean's global overturning circulation regulates the transport and storage of heat, carbon and nutrients. Upwelling across the Southern Ocean's Antarctic Circumpolar Current and into the mixed layer, coupled to water mass modification by surface buoyancy forcing, has been highlighted as a key process in the closure of the overturning circulation. Here, using twelve high-resolution hydrographic sections in southern Drake Passage, collected with autonomous ocean gliders, we show that Circumpolar Deep Water originating from the North Atlantic, known as Lower Circumpolar Deep Water, intersects sloping topography in narrow and strong boundary currents. Observations of strong lateral buoyancy gradients, enhanced bottom turbulence, thick bottom mixed layers and modified water masses are consistent with growing evidence that topographically generated submesoscale flows over continental slopes enhance near-bottom mixing, and that cross-density upwelling occurs preferentially over sloping topography. Interactions between narrow frontal currents and topography occur elsewhere along the path of the Antarctic Circumpolar Current, which leads us to propose that such interactions contribute significantly to the closure of the overturning in the Southern Ocean.

7 CFR 305.20 - Treatment requirements.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Have equipment that is capable of adequately circulating air or water (as relevant to the treatment... must contain requirements for equipment, temperature, water quality, circulation, and other measures... APHIS. The work plan must contain requirements for equipment, temperature, water quality, circulation...

Sea, ice and surface water circulation, Alaskan Continental Shelf

NASA Technical Reports Server (NTRS)

Wright, F. F. (Principal Investigator); Sharma, G. D.

1972-01-01

The author has identified the following significant results. Two cruises were conducted in Cook Inlet to obtain ground truth. Forty-seven stations during 22-23 August and 68 stations during 25-29 September 1972 were occupied and temperature, salinity, percent light transmission, and suspended load of surface waters obtained. Similar data at various depths was also obtained at selected stations. Cook Inlet is an estuary with complex mixing of river discharges and ocean water. The Upper Cook Inlet shows a gradual and systematic decrease in salinity, however, west of Kenai the mixing of waters is complex. The sediments in suspension originating at the head of the inlet generally settle out east of Kenai and Drift River. Sediment load in suspension decreased gradually from 1700 mg/1 near Anchorage to about 50 mg/1 in the Narrows. In the Lower Cook Inlet the suspended load varied between 1-10 mg/1. Surface waters with sediments in suspension and ocean water with relatively lower sediment concentration are clearly discernible in ERTS-1 images obtained during September 18, 1972 pass over Cook Inlet. The movement and mixing of these waters can also be delineated in the images.

The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation

PubMed Central

Cózar, Andrés; Martí, Elisa; Duarte, Carlos M.; García-de-Lomas, Juan; van Sebille, Erik; Ballatore, Thomas J.; Eguíluz, Victor M.; González-Gordillo, J. Ignacio; Pedrotti, Maria L.; Echevarría, Fidel; Troublè, Romain; Irigoien, Xabier

2017-01-01

The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris. PMID:28439534

The Galapagos Spreading Centre at 86o W: a detailed geothermal field study.

USGS Publications Warehouse

Green, K.E.; Von Herzen, R. P.; Williams, D.L.

1981-01-01

We report here measurements of the heat flow field of the Galapagos Spreading Center on crust of age less than 1.0 m.y. The 443 measurements in an area of about 570 km2 reveal the general planform of the geothermal flux and permit the first truly areal estimate of the near-axis conductive heat flux. The intrusion process and associated hydrothermal circulation dominate the surface heat flow pattern, with circulation apparently continuing beyong the limits of our survey. The areal average of the conductive heat flux is 7.1+-0.8 HFU (295+-33 m W/m2), about one-third the heat flux predicted by plate models. The remaining heat is apparently removed by venting of hydrothermal waters at the spreading axis and through basalt outcrops and hydrothermal mounds off axis. The pattern of surface heat flux is lineated parallel to the axis and the strongly lineated topography. Sharp lateral gradients in the heat flow, greater than 10 HFU/km near escarpments and commonly expressed as high heat flow at the tops of the scarps and lower heat flow in the valleys, may indicate a local concentration of the circulation by surface fault systems and/or variable sediment thickness. -Authors

The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation.

PubMed

Cózar, Andrés; Martí, Elisa; Duarte, Carlos M; García-de-Lomas, Juan; van Sebille, Erik; Ballatore, Thomas J; Eguíluz, Victor M; González-Gordillo, J Ignacio; Pedrotti, Maria L; Echevarría, Fidel; Troublè, Romain; Irigoien, Xabier

2017-04-01

The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris.

A Trip Through the Virtual Ocean: Understanding Basic Oceanic Process Using Real Data and Collaborative Learning

NASA Astrophysics Data System (ADS)

Hastings, D. W.

2012-12-01

How can we effectively teach undergraduates the fundamentals of physical, chemical and biological processes in the ocean? Understanding physical circulation and biogeochemical processes is essential, yet it can be difficult for an undergraduate to easily grasp important concepts such as using temperature and salinity as conservative tracers, nutrient distribution, ageing of water masses, and thermocline variability. Like many other topics, it is best learned not in a lecture setting, but working with real data: plotting values, making predictions, and making mistakes. Part I: Using temperature and salinity values from any location in the world ocean (World Ocean Atlas), combined with an excellent user interface (http://ferret.pmel.noaa.gov), students are asked to answer a series of specific questions related to ocean circulation. Using established temperature and salinity values to characterize different water masses, students are able to identify various water masses and gain insight to physical circulation processes. Questions related to ocean circulation include: How far south and at what depth does NADW extend into the S. Atlantic? Is deep water formed in the North Pacific? How and why does the depth of the thermocline vary with latitude in the Atlantic Ocean? How deep does the Mediterranean Water descend as it leaves the Straits of Gibraltar? How far into the Atlantic can you see the influence of the Amazon River? Is there any Antarctic Bottom Water in the North Pacific? Collaborating with another student typically leads to increased engagement. Especially in large lecture settings, where one teacher is not able to address student questions or concerns, working in pairs or in groups of three is best. Part II: Using the same web-based viewer and data set students are subsequently assigned one oceanic property (phosphate, nitrate, silicate, O2, or AOU) and asked to construct three different plots: 1) vertical depth profile at one location; 2) latitude vs. depth at 20°W; and 3) a latitude vs. longitude at 4,000 m depth in the entire ocean. Students do this work at home, and come to class prepared with hypotheses that explain variations of their variable observed in their figures. Nutrients, for example, are typically depleted in the surface ocean, increase at intermediate depths, and then typically decrease in deep water. How do oceanic processes drive these variations? In the context of the other variables, and with the help of other group members, they typically develop an understanding of surface productivity, respiration of organic matter in deeper waters, upwelling of deeper water, ocean circulation, insolation, evaporation, precipitation, and temperature dependence of gas solubility. Students then prepare a written explanation to accompany the plots. Cartoon-like depictions of nutrient profiles typically presented in introductory texts have their place, but they lack the complexity inherent in real data. The objective is to mimic the excitement of discovery and the challenge of developing a hypothesis to explain existing data. The ability to develop viable hypotheses to explain real data with real variability are what motivate and inspire many scientists. How can we expect to motivate and inspire students with lackluster descriptions of ocean processes?

Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean

USGS Publications Warehouse

Biscaye, P.E.; Eittreim, S.L.

1977-01-01

Vertical profiles of light scattering from over 1000 L-DGO nephelometer stations in the Atlantic Ocean have been used to calculate mass concentrations of suspended particles based on a calibration from the western North American Basin. From these data are plotted the distributions of particulate concentrations at clear water and in the more turbid near-bottom water. Clear water is the broad minimum in concentration and light scattering that occurs at varying mid-depths in the water column. Concentrations at clear water are as much as one-to-two orders of magnitude lower than those in surface water but still reflect a similar geographic distribution: relatively higher concentrations at ocean margins, especially underneath upwelling areas, and the lowest concentrations underneath central gyre areas. These distributions within the clear water reflect surface-water biogenic productivity, lateral injection of particles from shelf areas and surface circulation patterns and require that the combination of downward vertical and horizontal transport processes of particles retain this pattern throughout the upper water column. Below clear water, the distribution of standing crops of suspended particulate concentrations in the lower water column are presented. The integration of mass of all particles per unit area (gross particulate standing crop) reflects a relative distribution similar to that at the surface and at clear water levels, superimposed on which is the strong imprint of boundary currents along the western margins of the Atlantic. Reducing the gross particulate standing crop by the integral of the concentration of clear water yields a net particulate standing crop. The distribution of this reflects primarily the interaction of circulating abyssal waters with the ocean bottom, i.e. a strong nepheloid layer which is coincident with western boundary currents and which diminishes in intensity equatorward. The resuspended particulate loads in the nepheloid layer of the basins west of the Mid-Atlantic Ridge, resulting from interaction of abyssal currents with the bottom, range from ??? 2 ?? 106 tons in the equatorial Guyana Basin to ??? 50 ?? 106 tons in the North American Basin. The total resuspended particulate load in the western basins (111 ?? 106 tons) is almost an order of magnitude greater than that in the basins east of the Mid-Atlantic Ridge (13 ?? 106 tons). The net northward flux of resuspended particles carried in the AABW drops from ??? 8 ?? 106 tons/year between the southern and northern ends of the Brazil Basin and remains ??? 1 ?? 106 tons/year across the Guyana Basin. ?? 1977.

Clinical trial of a novel surface cooling system for fever control in neurocritical care patients.

PubMed

Mayer, Stephan A; Kowalski, Robert G; Presciutti, Mary; Ostapkovich, Noeleen D; McGann, Elaine; Fitzsimmons, Brian-Fred; Yavagal, Dileep R; Du, Y Evelyn; Naidech, Andrew M; Janjua, Nazli A; Claassen, Jan; Kreiter, Kurt T; Parra, Augusto; Commichau, Christopher

2004-12-01

To compare the efficacy of a novel water-circulating surface cooling system with conventional measures for treating fever in neuro-intensive care unit patients. Prospective, unblinded, randomized controlled trial. Neurologic intensive care unit in an urban teaching hospital. Forty-seven patients, the majority of whom were mechanically ventilated and sedated, with fever > or =38.3 degrees C for >2 consecutive hours after receiving 650 mg of acetaminophen. Subjects were randomly assigned to 24 hrs of treatment with a conventional water-circulating cooling blanket placed over the patient (Cincinnati SubZero, Cincinnati OH) or the Arctic Sun Temperature Management System (Medivance, Louisville CO), which employs hydrogel-coated water-circulating energy transfer pads applied directly to the trunk and thighs. Diagnoses included subarachnoid hemorrhage (60%), cerebral infarction (23%), intracerebral hemorrhage (11%), and traumatic brain injury (4%). The groups were matched in terms of baseline variables, although mean temperature was slightly higher at baseline in the Arctic Sun group (38.8 vs. 38.3 degrees C, p = .046). Compared with patients treated with the SubZero blanket (n = 24), Arctic Sun-treated patients (n = 23) experienced a 75% reduction in fever burden (median 4.1 vs. 16.1 C degrees -hrs, p = .001). Arctic Sun-treated patients also spent less percent time febrile (T > or =38.3 degrees C, 8% vs. 42%, p < .001), spent more percent time normothermic (T < or =37.2 degrees C, 59% vs. 3%, p < .001), and attained normothermia faster than the SubZero group median (2.4 vs. 8.9 hrs, p = .008). Shivering occurred more frequently in the Arctic Sun group (39% vs. 8%, p = .013). The Arctic Sun Temperature Management System is superior to conventional cooling-blanket therapy for controlling fever in critically ill neurologic patients.

Anomalous levels of 90Sr and 239,240Pu in Florida corals: Evidence of coastal processes

NASA Astrophysics Data System (ADS)

Purdy, Caroline B.; Druffel, Ellen R. M.; Livingston, Hugh D.

1989-06-01

Strontium-90, a radionuclide whose primary source is fallout from nuclear weapons testing, serves as a tritium-like tracer of ocean circulation. The historical record of 90Sr activities in the annual bands of island corals have been shown by other investigators to reflect the 90Sr concentration in surface waters at those site. Strontium-90 activities measured in annual bands in Montastrea annularis from the Florida Keys are 30-120% higher than those in corresponding peak activity years (1960-1965) of a Bermuda coral ( Diploria). The Bermuda 90Sr activity record reflects the fallout source only, whereas the additional 90Sr activity in the Florida Keys is expected to reflect a coastal runoff source as well as the fallout. The coastal circulation patterns off the northern and western edge of the Florida Current further act to concentrate and prolong the exposure of the runoff 90Sr to the corals. Six measured 239,240Pu activities in the Florida coral are 30% of 239,240Pu activities in island coral records previously reported. Since Pu is expected to be scavenged by particles in coastal waters, this decrease in 239,240Pu substantiates the importance of coastal influences in the Florida 90Sr record. Strontium-90 activities measured in subannual coral bands from 1973 to 1974 reflect seasonal changes in the 90Sr concentrations in the surface layer of the coastal waters. This may reflect Loop Current intrusion events. The seasonal and long-term coral 90Sr data presented in this paper suggests that coastal 90Sr coral time series may be very useful for documenting coastal circulation patterns.

Role of changed Indo-Pacific atmospheric circulation in the recent disconnect between the Indian summer monsoon and ENSO

NASA Astrophysics Data System (ADS)

Feba, F.; Ashok, K.; Ravichandran, M.

2018-04-01

We explore the decadal variability of teleconnection from tropical Pacific to the Indian summer monsoon rainfall (ISMR) using various observational and Reanalysis datasets for the period 1958-2008. In confirmation with the earlier findings, we find that the interannual correlations between the various SST indices of ENSO and ISMR have continued to weaken. Interestingly, we find that even the robust lead correlations of the tropical pacific warm-water-volume with ISMR have weakened since late 1970s. Our analysis suggests that there is a relative intensification of the cross-equatorial flow from the southern hemisphere into the equatorial Indian Ocean associated with ISMR due to strenghtening of Mascarene High. Further, a shift in the surface wind circulation associated with monsoon over the northern pacific since late 1970s has resulted in a strenghtened cyclonic seasonal circulation south-east of Japan. These changed circulation features are a shift from the known circulation-signatures that efficiently teleconnect El Niño forcing to South Asia. These recent changes effectively weakened the teleconnection of the El Niño to ISMR.

Changing surface water conditions for the last 500 ka in the Southeast Atlantic: Implications for variable influences of Agulhas leakage and Benguela upwelling

NASA Astrophysics Data System (ADS)

Petrick, Benjamin F.; McClymont, Erin L.; Marret, Fabienne; van der Meer, Marcel T. J.

2015-09-01

The Southeast Atlantic Ocean is an important component of global ocean circulation, as it includes heat and salt transfer into the Atlantic through the Agulhas leakage as well as the highly productive Benguela upwelling system. Here we reconstruct sea surface temperatures (SSTs) from Ocean Drilling Program (ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the late Pleistocene (0-500 ka). The UK'37 index and dinoflagellate cyst assemblages are used to reconstruct SSTs, δDalkenone is used to reconstruct changes in sea surface salinity, and mass accumulation rates of alkenones and chlorine pigments are quantified to detect changing marine export productivity. The greatest amplitude of SST warming precedes decreases in benthic δ18O and therefore occurs early in the transition from glacials to interglacials. The δDalkenone, as a salinity indicator, increases before SSTs, suggesting that the pattern of Agulhas leakage is more complex than suggested by SST proxies. Marine isotope stage (MIS) 10 shows an anomalous pattern: it is marked by a pronounced increase in chlorine concentration, which may be related to enhanced/expanded Benguela upwelling reaching the core site. We find no evidence of an absence of Agulhas leakage throughout the record, suggesting that there is no Agulhas cutoff even during MIS 10. Finally, the ODP Site 1087 record shows an increasing strength of Agulhas leakage towards the present day, which may have impacted the intensity of the Atlantic meridional overturning circulation. As a result, the new analyses from ODP Site 1087 demonstrate a complex interaction between influences of the Benguela upwelling and the Agulhas leakage through the late Pleistocene, which are inferred here to reflect changing circulation patterns in the Southern Ocean and in the atmosphere.

Studies of the Earth Energy Budget and Water Cycle Using Satellite Observations and Model Analyses

NASA Technical Reports Server (NTRS)

Campbell, G. G.; VonderHarr, T. H.; Randel, D. L.; Kidder, S. Q.

1997-01-01

During this research period we have utilized the ERBE data set in comparisons to surface properties and water vapor observations in the atmosphere. A relationship between cloudiness and surface temperature anomalies was found. This same relationship was found in a general circulation model, verifying the model. The attempt to construct a homogeneous time series from Nimbus 6, Nimbus 7 and ERBE data is not complete because we are still waiting for the ERBE reanalysis to be completed. It will be difficult to merge the Nimbus 6 data in because its observations occurred when the average weather was different than the other periods, so regression adjustments are not effective.

The Closure History of the Central American Seaway and its Relationship to Ocean Circulation and Climate

NASA Astrophysics Data System (ADS)

Waite, A. J.; Martin, E. E.; Lawrence, K. T.; Ladlow, C. G.; Newkirk, D.

2014-12-01

Paleoceanographic and ecologic studies suggest that gradual shoaling of the Central American Seaway (CAS) as the Isthmus of Panama rose between ~13 to 2 Ma caused a stepwise shutdown of deep, intermediate, and shallow Pacific water flow through the seaway into the Caribbean. This diminishing communication is thought to have significantly influenced surface currents, ocean circulation at depth, and ultimately regional and global climate. However, new studies of Panama's volcanic/tectonic history suggest the isthmus rose much earlier than previous estimates, calling into question many of our accepted implications for this gateway event under the 'Panama Hypothesis,' including strengthened thermohaline circulation, North Atlantic Deep Water production, increased North Atlantic temperature, and ties to Northern Hemisphere glaciation. Despite considerable research, few paleoceanographic studies have directly examined the possibility of earlier events in the closure history of the CAS and thus the precise linkages and timing are not well defined. To investigate early restricted CAS flow related to sill formation or pulsed exhumation events, we examine two sets of independent paleoceanographic reconstructions from Ocean Drilling Program sediment cores from the region. We assess the presence of Pacific waters within the Caribbean over the last 30 Ma via the Nd-isotopic composition of fish teeth from several Caribbean sites; these records point to sustained transport of Pacific waters into the Caribbean from at least 30 to 10 Ma. Further, alkenone-derived sea surface temperature (SST) reconstructions from the Eastern Equatorial Pacific (EEP) indicate the presence of consistently warm (>27 °C) waters in the EEP from ~12 to ~5 Ma, after which time SSTs at sites within the modern cold tongue begin to cool appreciably. The SST data imply that the EEP cold tongue, which some studies suggest is linked in part to the rise of the Panamanian isthmus, did not develop until after 5 Ma. Collectively, these paleoceanographic reconstructions and model outputs indicate notable communication of water between the Pacific and the Caribbean until at least 10 Ma and provide improved understanding of the sequence of events associated with the rise of the Isthmus of Panama and closure of the CAS.

Understanding Changes in Water Availability in the Rio Grande/Rio Bravo del Norte Basin Under the Influence of Large-Scale Circulation Indices Using the Noah Land Surface Model

NASA Technical Reports Server (NTRS)

Khedun, C. Prakash; Mishra, Ashok K.; Bolten, John D.; Beaudoing, Hiroko K.; Kaiser, Ronald A.; Giardino, J. Richard; Singh, Vijay P.

2012-01-01

Water availability plays an important role in the socio-economic development of a region. It is however, subject to the influence of large-scale circulation indices, resulting in periodic excesses and deficits. An assessment of the degree of correlation between climate indices and water availability, and the quantification of changes with respect to major climate events is important for long-term water resources planning and management, especially in transboundary basins as it can help in conflict avoidance. In this study we first establish the correlation of the Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) with gauged precipitation in the Rio Grande basin, and quantify the changes in water availability using runoff generated from the Noah land surface model. Both spatial and temporal variations are noted, with winter and spring being most influenced by conditions in the Pacific Ocean. Negative correlation is observed at the headwaters and positive correlation across the rest of the basin. The influence of individual ENSO events, classified using four different criteria, is also examined. El Ninos (La Ninas) generally cause an increase (decrease) in runoff, but the pattern is not consistent; percentage change in water availability varies across events. Further, positive PDO enhances the effect of El Nino and dampens that of La Nina, but during neutral/transitioning PDO, La Nina dominates meteorological conditions. Long El Ninos have more influence on water availability than short duration high intensity events. We also note that the percentage increase during El Ninos significantly offsets the drought-causing effect of La Ninas.

Coastal loading and transport of Escherichia coli at an embayed beach in Lake Michigan

USGS Publications Warehouse

Ge, Z.; Nevers, M.B.; Schwab, D.J.; Whitman, R.L.

2010-01-01

A Chicago beach in southwest Lake Michigan was revisited to determine the influence of nearshore hydrodynamic effects on the variability of Escherichia coli (E. coli) concentration in both knee-deep and offshore waters. Explanatory variables that could be used for identifying potential bacteria loading mechanisms, such as bed shear stress due to a combined wave-current boundary layer and wave runup on the beach surface, were derived from an existing wave and current database. The derived hydrodynamic variables, along with the actual observed E. coli concentrations in the submerged and foreshore sands, were expected to reveal bacteria loading through nearshore sediment resuspension and swash on the beach surface, respectively. Based on the observation that onshore waves tend to result in a more active hydrodynamic system at this embayed beach, multiple linear regression analysis of onshore-wave cases further indicated the significance of sediment resuspension and the interaction of swash with gull-droppings in explaining the variability of E. coli concentration in the knee-deep water. For cases with longshore currents, numerical simulations using the Princeton Ocean Model revealed current circulation patterns inside the embayment, which can effectively entrain bacteria from the swash zone into the central area of the embayed beach water and eventually release them out of the embayment. The embayed circulation patterns are consistent with the statistical results that identified that 1) the submerged sediment was an additional net source of E. coli to the offshore water and 2) variability of E. coli concentration in the knee-deep water contributed adversely to that in the offshore water for longshore-current cases. The embayed beach setting and the statistical and numerical methods used in the present study have wide applicability for analyzing recreational water quality at similar marine and freshwater sites. ?? 2010 American Chemical Society.

Sensitivity of open-water ice growth and ice concentration evolution in a coupled atmosphere-ocean-sea ice model

NASA Astrophysics Data System (ADS)

Shi, Xiaoxu; Lohmann, Gerrit

2017-09-01

A coupled atmosphere-ocean-sea ice model is applied to investigate to what degree the area-thickness distribution of new ice formed in open water affects the ice and ocean properties. Two sensitivity experiments are performed which modify the horizontal-to-vertical aspect ratio of open-water ice growth. The resulting changes in the Arctic sea-ice concentration strongly affect the surface albedo, the ocean heat release to the atmosphere, and the sea-ice production. The changes are further amplified through a positive feedback mechanism among the Arctic sea ice, the Atlantic Meridional Overturning Circulation (AMOC), and the surface air temperature in the Arctic, as the Fram Strait sea ice import influences the freshwater budget in the North Atlantic Ocean. Anomalies in sea-ice transport lead to changes in sea surface properties of the North Atlantic and the strength of AMOC. For the Southern Ocean, the most pronounced change is a warming along the Antarctic Circumpolar Current (ACC), owing to the interhemispheric bipolar seasaw linked to AMOC weakening. Another insight of this study lies on the improvement of our climate model. The ocean component FESOM is a newly developed ocean-sea ice model with an unstructured mesh and multi-resolution. We find that the subpolar sea-ice boundary in the Northern Hemisphere can be improved by tuning the process of open-water ice growth, which strongly influences the sea ice concentration in the marginal ice zone, the North Atlantic circulation, salinity and Arctic sea ice volume. Since the distribution of new ice on open water relies on many uncertain parameters and the knowledge of the detailed processes is currently too crude, it is a challenge to implement the processes realistically into models. Based on our sensitivity experiments, we conclude a pronounced uncertainty related to open-water sea ice growth which could significantly affect the climate system sensitivity.

Preliminary Evaluation of Convective Heat Transfer in a Water Shield for a Surface Power Reactor

NASA Technical Reports Server (NTRS)

Pearson J. Boise; Reid, Robert S.

2007-01-01

As part of the Vision for Space Exploration, the end of the next decade will bring man back to the surface of the moon. A crucial issue for the establishment of human presence on the moon will be the availability of compact power sources. This presence could require greater than 10's of kWt's in follow on years. Nuclear reactors are well suited to meet the needs for power generation on the lunar or Martian surface. Radiation shielding is a key component of any surface power reactor system. Several competing concepts exist for lightweight, safe, robust shielding systems such as a water shield, lithium hydride (LiH), and boron carbide. Water offers several potential advantages, including reduced cost, reduced technical risk, and reduced mass. Water has not typically been considered for space reactor applications because of the need for gravity to fix the location of any vapor that could form radiation streaming paths. The water shield concept relies on the predictions of passive circulation of the shield water by natural convection to adequately cool the shield. This prediction needs to be experimentally evaluated, especially for shields with complex geometries. NASA Marshall Space Flight Center has developed the experience and facilities necessary to do this evaluation in its Early Flight Fission - Test Facility (EFF-TF).

Fluvial valleys in the heavily cratered terrains of Mars: Evidence for paleoclimatic change?

NASA Technical Reports Server (NTRS)

Gulick, V. C.; Baker, V. R.

1993-01-01

Whether the formation of the Martian valley networks provides unequivocal evidence for drastically different climatic conditions remains debatable. Recent theoretical climate modeling precludes the existence of a temperate climate early in Mars' geological history. An alternative hypothesis suggests that Mars had a globally higher heat flow early in its geological history, bringing water tables to within 350 m of the surface. While a globally higher heat flow would initiate ground water circulation at depth, the valley networks probably required water tables to be even closer to the surface. Additionally, it was previously reported that the clustered distribution of the valley networks within terrain types, particularly in the heavily cratered highlands, suggests regional hydrological processes were important. The case for localized hydrothermal systems is summarized and estimates of both erosion volumes and of the implied water volumes for several Martian valley systems are presented.

500 kyr of Indian Ocean Walker Circulation Variability Using Foraminiferal Mg/Ca and Stable Isotopes

NASA Astrophysics Data System (ADS)

Groeneveld, J.; Mohtadi, M.; Lückge, A.; Pätzold, J.

2017-12-01

The tropical Indian Ocean is a key location for paleoclimate research affected by different oceanographic and atmospheric processes. Annual climate variations are strongly controlled by the Indian and Asian Monsoon characterized by bi-annually reversing trade winds. Inter-annual climate variations in the Walker circulation are caused by the Indian Ocean Dipole and El Niño-Southern Oscillation resulting in either heavy flooding or severe droughts like for example the famine of 2011 in eastern Africa. Oceanographically the tropical western Indian Ocean receives water masses from the Indonesian Gateway area, sub-Antarctic waters that upwell south of the equator, and the outflow waters from the highly saline Red Sea. On the other hand, the tropical western Indian Ocean is a major source for providing water masses to the Agulhas Current system. Although the eastern Indian Ocean has been studied extensively, the tropical western Indian Ocean is still lacking in high quality climate-archives that have the potential to provide important information to understand how the ocean and atmospheric zonal circulation have changed in the past, and possibly will change in the future. Until now there were no long sediment cores available covering several glacial-interglacial cycles in the tropical western Indian Ocean. Core GeoB 12613-1, recovered during RV Meteor Cruise M75/2 east of the island of Pemba off Tanzania, provides an open-ocean core with well-preserved sediments covering the last five glacial-interglacial cycles ( 500 kyr). Mg/Ca and stable isotopes on both surface- and thermocline dwelling foraminifera have been performed to test how changes in sea water temperatures and relative sea water salinity were coupled on orbital time scales. The results are compared with similar records generated for the tropical eastern Indian Ocean in core SO139-74KL off Sumatra. Water column stratification on both sides of the Indian Ocean and the cross-basin gradients in sea water temperature and relative salinity varied both on millennial and orbital time scales implying changes in the Walker circulation.

Evaluating the skills of isotope-enabled general circulation models against in situ atmospheric water vapor isotope observations

NASA Astrophysics Data System (ADS)

Steen-Larsen, H. C.; Risi, C.; Werner, M.; Yoshimura, K.; Masson-Delmotte, V.

2017-01-01

The skills of isotope-enabled general circulation models are evaluated against atmospheric water vapor isotopes. We have combined in situ observations of surface water vapor isotopes spanning multiple field seasons (2010, 2011, and 2012) from the top of the Greenland Ice Sheet (NEEM site: 77.45°N, 51.05°W, 2484 m above sea level) with observations from the marine boundary layer of the North Atlantic and Arctic Ocean (Bermuda Islands 32.26°N, 64.88°W, year: 2012; south coast of Iceland 63.83°N, 21.47°W, year: 2012; South Greenland 61.21°N, 47.17°W, year: 2012; Svalbard 78.92°N, 11.92°E, year: 2014). This allows us to benchmark the ability to simulate the daily water vapor isotope variations from five different simulations using isotope-enabled general circulation models. Our model-data comparison documents clear isotope biases both on top of the Greenland Ice Sheet (1-11‰ for δ18O and 4-19‰ for d-excess depending on model and season) and in the marine boundary layer (maximum differences for the following: Bermuda δ18O = 1‰, d-excess = 3‰; South coast of Iceland δ18O = 2‰, d-excess = 5‰; South Greenland δ18O = 4‰, d-excess = 7‰; Svalbard δ18O = 2‰, d-excess = 7‰). We find that the simulated isotope biases are not just explained by simulated biases in temperature and humidity. Instead, we argue that these isotope biases are related to a poor simulation of the spatial structure of the marine boundary layer water vapor isotopic composition. Furthermore, we specifically show that the marine boundary layer water vapor isotopes of the Baffin Bay region show strong influence on the water vapor isotopes at the NEEM deep ice core-drilling site in northwest Greenland. Our evaluation of the simulations using isotope-enabled general circulation models also documents wide intermodel spatial variability in the Arctic. This stresses the importance of a coordinated water vapor isotope-monitoring network in order to discriminate amongst these model behaviors.

Life cycle strategies of copepods in coastal upwelling zones

NASA Astrophysics Data System (ADS)

Peterson, W.

1998-06-01

Life cycles of copepods of coastal upwelling zones are of the multigenerational type—as many as 10 or more generations may be produced each year, depending upon water temperature, food concentration and length of the upwelling season. Abundant food resources and moderate temperature convey advantages to those copepods living in coastal upwelling zones, however, there is a clear disadvantage in that coastal upwelling zones are highly advective environments. Typically, water circulation patterns are such that surface waters are carried offshore, deeper waters carried onshore and most of the water column over the continental shelf is moving equatorward. The challenge to copepod species that inhabit upwelling systems is life cycle closure—how do eggs, nauplii, juveniles and adults avoid being swept out of these ecosystems in the face of persistent transport out of the system? In this review, I first list the species which dominate coastal upwelling ecosystems then discuss three variations on the multigenerational life cycle scheme that are observed in upwelling systems. The latter part of the review is devoted to discussion of how individuals are retained in the productive continental shelf waters within coastal upwelling ecosystems. The suggestion is made that the only copepod species that successfully achieve life cycle closure in such systems are those that are preadapted to upwelling circulation patterns. Our quantitative understanding of the relative importance of physical factors (such as advection) and biological factors (birth, growth, and mortality) on life cycle strategies and population dynamics is quite rudimentary. It would help our understanding if there were more field studies and more computer modeling studies that focused on seasonal cycles of abundance, development times and vertical distribution of life cycle stages, and measurements of water circulation patterns.

A Catchment-Based Approach to Modeling Land Surface Processes in a GCM. Part 2; Parameter Estimation and Model Demonstration

NASA Technical Reports Server (NTRS)

Ducharne, Agnes; Koster, Randal D.; Suarez, Max J.; Stieglitz, Marc; Kumar, Praveen

2000-01-01

The viability of a new catchment-based land surface model (LSM) developed for use with general circulation models is demonstrated. First, simple empirical functions -- tractable enough for operational use in the LSM -- are established that faithfully capture the control of topography on the subgrid variability of soil moisture and the surface water budget, as predicted by theory. Next, the full LSM is evaluated offline. Using forcing and validation datasets developed for PILPS Phase 2c, the minimally calibrated model is shown to reproduce observed evaporation and runoff fluxes successfully in the Red-Arkansas River Basin. A complementary idealized study that employs the range of topographic variability seen over North America demonstrates that the simulated surface water budget does vary strongly with topography, which can, by itself, induce variations in annual evaporation as high as 20%.

On the Stability of Liquid Water on Present Day Mars

NASA Technical Reports Server (NTRS)

Haberle, Robert M.; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

The mean annual surface pressure and temperature on present day Mars do not allow for the long term stability of liquid water on the surface. However, theoretical arguments have been advanced that suggest liquid water could form in transient events even though it would not be in equilibrium with the environment. Using a Mars General Circulation Model, we calculate where and for how long the surface pressure and surface temperature meet the minimum requirements for this metastability of liquid water. These requirements are that the pressure and temperature must be above the triple point of water, but below its boiling point. We find that there are five regions on Mars where these requirements are periodically satisfied: in the near equatorial regions of Amazonis, Arabia, and Elysium, and in the Hellas and Argyre impact basins. Whether liquid water ever forms in these regions depends on the availability of ice and heat, and on the evaporation rate. The latter is poorly understood for low pressure CO2 environments, but is likely to be so high that melting occurs rarely, if at all. However, in the relatively recent past, surface pressures may have been higher than they are today perhaps by as much as a factor of 2 or 3. Under these circumstances melting would have been easier to achieve. We plan to undertake laboratory experiments to better understand the potential for melting in low pressure environments.

Gravity Scaling of a Power Reactor Water Shield

NASA Technical Reports Server (NTRS)

Reid, Robert S.; Pearson, J. Boise

2008-01-01

Water based reactor shielding is being considered as an affordable option for use on initial lunar surface power systems. Heat dissipation in the shield from nuclear sources must be rejected by an auxiliary thermal hydraulic cooling system. The mechanism for transferring heat through the shield is natural convection between the core surface and an array of thermosyphon radiator elements. Natural convection in a 100 kWt lunar surface reactor shield design has been previously evaluated at lower power levels (Pearson, 2007). The current baseline assumes that 5.5 kW are dissipated in the water shield, the preponderance on the core surface, but with some volumetric heating in the naturally circulating water as well. This power is rejected by a radiator located above the shield with a surface temperature of 370 K. A similarity analysis on a water-based reactor shield is presented examining the effect of gravity on free convection between a radiation shield inner vessel and a radiation shield outer vessel boundaries. Two approaches established similarity: 1) direct scaling of Rayleigh number equates gravity-surface heat flux products, 2) temperature difference between the wall and thermal boundary layer held constant on Earth and the Moon. Nussult number for natural convection (laminar and turbulent) is assumed of form Nu = CRa(sup n). These combined results estimate similarity conditions under Earth and Lunar gravities. The influence of reduced gravity on the performance of thermosyphon heat pipes is also examined.

Subglacial discharge-driven renewal of tidewater glacier fjords

NASA Astrophysics Data System (ADS)

Carroll, Dustin; Sutherland, David A.; Shroyer, Emily L.; Nash, Jonathan D.; Catania, Ginny A.; Stearns, Leigh A.

2017-08-01

The classic model of fjord renewal is complicated by tidewater glacier fjords, where submarine melt and subglacial discharge provide substantial buoyancy forcing at depth. Here we use a suite of idealized, high-resolution numerical ocean simulations to investigate how fjord circulation driven by subglacial plumes, tides, and wind stress depends on fjord width, grounding line depth, and sill height. We find that the depth of the grounding line compared to the sill is a primary control on plume-driven renewal of basin waters. In wide fjords the plume exhibits strong lateral recirculation, increasing the dilution and residence time of glacially-modified waters. Rapid drawdown of basin waters by the subglacial plume in narrow fjords allows for shelf waters to cascade deep into the basin; wide fjords result in a thin, boundary current of shelf waters that flow toward the terminus slightly below sill depth. Wind forcing amplifies the plume-driven exchange flow; however, wind-induced vertical mixing is limited to near-surface waters. Tidal mixing over the sill increases in-fjord transport of deep shelf waters and erodes basin stratification above the sill depth. These results underscore the first-order importances of fjord-glacier geometry in controlling circulation in tidewater glacier fjords and, thus, ocean heat transport to the ice.

Terrestrial water cycle and the impact of climate change.

PubMed

Tao, Fulu; Yokozawa, Masayuki; Hayashi, Yousay; Lin, Erda

2003-06-01

The terrestrial water cycle and the impact of climate change are critical for agricultural and natural ecosystems. In this paper, we assess both by running a macro-scale water balance model under a baseline condition and 2 General Circulation Model (GCM)-based climate change scenarios. The results show that in 2021-2030, water demand will increase worldwide due to climate change. Water shortage is expected to worsen in western Asia, the Arabian Peninsula, northern and southern Africa, northeastern Australia, southwestern North America, and central South America. A significant increase in surface runoff is expected in southern Asia and a significant decrease is expected in northern South America. These changes will have implications for regional environment and socioeconomics.

Surface Currents and Winds at the Delaware Bay Mouth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muscarella, P A; Barton, N P; Lipphardt, B L

2011-04-06

Knowledge of the circulation of estuaries and adjacent shelf waters has relied on hydrographic measurements, moorings, and local wind observations usually removed from the region of interest. Although these observations are certainly sufficient to identify major characteristics, they lack both spatial resolution and temporal coverage. High resolution synoptic observations are required to identify important coastal processes at smaller scales. Long observation periods are needed to properly sample low-frequency processes that may also be important. The introduction of high-frequency (HF) radar measurements and regional wind models for coastal studies is changing this situation. Here we analyze synoptic, high-resolution surface winds andmore » currents in the Delaware Bay mouth over an eight-month period (October 2007 through May 2008). The surface currents were measured by two high-frequency radars while the surface winds were extracted from a data-assimilating regional wind model. To illustrate the utility of these monitoring tools we focus on two 45-day periods which previously were shown to present contrasting pictures of the circulation. One, the low-outflow period is from 1 October through 14 November 2007; the other is the high-outflow period from 3 March through 16 April 2008. The large-scale characteristics noted by previous workers are clearly corroborated. Specifically the M2 tide dominates the surface currents, and the Delaware Bay outflow plume is clearly evident in the low frequency currents. Several new aspects of the surface circulation were also identified. These include a map of the spatial variability of the M2 tide (validating an earlier model study), persistent low-frequency cross-mouth flow, and a rapid response of the surface currents to a changing wind field. However, strong wind episodes did not persist long enough to set up a sustained Ekman response.« less

Aquarius and Remote Sensing of Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, David M.; Lagerloef, G. S. E.; Torrusio, S.

2012-01-01

Aquarius is an L-band radiometer and scatterometer instrument combination designed to map the salinity field at the surface of the ocean from space. The instrument is designed to provide global salinity maps on a monthly basis with a spatial resolution of 150 km and an accuracy of 0.2 psu. The science objective is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This data will promote understanding of ocean circulation and its role in the global water cycle and climate.

Global water cycle and the coevolution of the Earth's interior and surface environment.

PubMed

Korenaga, Jun; Planavsky, Noah J; Evans, David A D

2017-05-28

The bulk Earth composition contains probably less than 0.3% of water, but this trace amount of water can affect the long-term evolution of the Earth in a number of different ways. The foremost issue is the occurrence of plate tectonics, which governs almost all aspects of the Earth system, and the presence of water could either promote or hinder the operation of plate tectonics, depending on where water resides. The global water cycle, which circulates surface water into the deep mantle and back to the surface again, could thus have played a critical role in the Earth's history. In this contribution, we first review the present-day water cycle and discuss its uncertainty as well as its secular variation. If the continental freeboard has been roughly constant since the Early Proterozoic, model results suggest long-term net water influx from the surface to the mantle, which is estimated to be 3-4.5×10 14  g yr -1 on the billion years time scale. We survey geological and geochemical observations relevant to the emergence of continents above the sea level as well as the nature of Precambrian plate tectonics. The global water cycle is suggested to have been dominated by regassing, and its implications for geochemical cycles and atmospheric evolution are also discussed.This article is part of the themed issue 'The origin, history and role of water in the evolution of the inner Solar System'. © 2017 The Author(s).

Global water cycle and the coevolution of the Earth’s interior and surface environment

PubMed Central

Planavsky, Noah J.; Evans, David A. D.

2017-01-01

The bulk Earth composition contains probably less than 0.3% of water, but this trace amount of water can affect the long-term evolution of the Earth in a number of different ways. The foremost issue is the occurrence of plate tectonics, which governs almost all aspects of the Earth system, and the presence of water could either promote or hinder the operation of plate tectonics, depending on where water resides. The global water cycle, which circulates surface water into the deep mantle and back to the surface again, could thus have played a critical role in the Earth’s history. In this contribution, we first review the present-day water cycle and discuss its uncertainty as well as its secular variation. If the continental freeboard has been roughly constant since the Early Proterozoic, model results suggest long-term net water influx from the surface to the mantle, which is estimated to be 3−4.5×1014 g yr−1 on the billion years time scale. We survey geological and geochemical observations relevant to the emergence of continents above the sea level as well as the nature of Precambrian plate tectonics. The global water cycle is suggested to have been dominated by regassing, and its implications for geochemical cycles and atmospheric evolution are also discussed. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’. PMID:28416728

Hydrological and chlorofluoromethane measurements of the Indonesian throughflow entering the Indian Ocean

NASA Astrophysics Data System (ADS)

Fieux, M.; Andrié, C.; Charriaud, E.; Ilahude, A. G.; Metzl, N.; Molcard, R.; Swallow, J. C.

1996-05-01

The Java Australia Dynamic Experiment high-resolution February-March 1992 conductivity-temperature-depth and chlorofluoromethane section obtained between Australia and Bali and on the sills between Flores, Sumba, Sawu, Roti, and the Australian continental shelf allows detailed examination of the water masses distribution and their inferred circulation. A sharp hydrological front between the Indonesian waters and the southern Indian Ocean waters is found between 13°S and 14°S in both seasons (February-March 1992 and August 1989). It separates the high-salinity surface waters to the south from the lower-salinity surface waters derived from the Indonesian Seas to the north. It reaches the surface in February 1992, whereas it was capped by a particularly low salinity surface layer in August 1989. Near Bali, the NW monsoon of February-March produces large intrusions of low-salinity water from the Java Sea, through Lombok Strait in the upper 100 m. At depth, the North Indian Intermediate Water, flowing along the Indonesian coast, brings salty, low-oxygen and low-chlorofluorocarbon water. It enters the Sawu Sea through Sumba Strait toward the east, while it undergoes strong mixing with the Indonesian Seas water. The primary pathway of the Indonesian waters is found north of the front and south of the North Indian Intermediate Water, between 13°S and 9°30'S, and the associated salinity minimum can be followed all across the Indian Ocean.

The effect of surface boundary conditions on the climate generated by a coarse-mesh general circulation model

NASA Technical Reports Server (NTRS)

Cohen, C.

1981-01-01

A hierarchy of experiments was run, starting with an all water planet with zonally symmetric sea surface temperatures, then adding, one at a time, flat continents, mountains, surface physics, and realistic sea surface temperatures. The model was run with the sun fixed at a perpetual January. Ensemble means and standard deviations were computed and the t-test was used to determine the statistical significance of the results. The addition of realistic surface physics does not affect the model climatology to as large as extent as does the addition of mountains. Departures from zonal symmetry of the SST field result in a better simulation of the real atmosphere.

Monitoring and Modeling the Tibetan Plateau's climate system and its impact on East Asia.

PubMed

Ma, Yaoming; Ma, Weiqiang; Zhong, Lei; Hu, Zeyong; Li, Maoshan; Zhu, Zhikun; Han, Cunbo; Wang, Binbin; Liu, Xin

2017-03-13

The Tibetan Plateau is an important water source in Asia. As the "Third Pole" of the Earth, the Tibetan Plateau has significant dynamic and thermal effects on East Asian climate patterns, the Asian monsoon process and atmospheric circulation in the Northern Hemisphere. However, little systematic knowledge is available regarding the changing climate system of the Tibetan Plateau and the mechanisms underlying its impact on East Asia. This study was based on "water-cryosphere-atmosphere-biology" multi-sphere interactions, primarily considering global climate change in relation to the Tibetan Plateau -East Asia climate system and its mechanisms. This study also analyzed the Tibetan Plateau to clarify global climate change by considering multi-sphere energy and water processes. Additionally, the impacts of climate change in East Asia and the associated impact mechanisms were revealed, and changes in water cycle processes and water conversion mechanisms were studied. The changes in surface thermal anomalies, vegetation, local circulation and the atmospheric heat source on the Tibetan Plateau were studied, specifically, their effects on the East Asian monsoon and energy balance mechanisms. Additionally, the relationships between heating mechanisms and monsoon changes were explored.

Monitoring and Modeling the Tibetan Plateau’s climate system and its impact on East Asia

PubMed Central

Ma, Yaoming; Ma, Weiqiang; Zhong, Lei; Hu, Zeyong; Li, Maoshan; Zhu, Zhikun; Han, Cunbo; Wang, Binbin; Liu, Xin

2017-01-01

The Tibetan Plateau is an important water source in Asia. As the “Third Pole” of the Earth, the Tibetan Plateau has significant dynamic and thermal effects on East Asian climate patterns, the Asian monsoon process and atmospheric circulation in the Northern Hemisphere. However, little systematic knowledge is available regarding the changing climate system of the Tibetan Plateau and the mechanisms underlying its impact on East Asia. This study was based on “water-cryosphere-atmosphere-biology” multi-sphere interactions, primarily considering global climate change in relation to the Tibetan Plateau -East Asia climate system and its mechanisms. This study also analyzed the Tibetan Plateau to clarify global climate change by considering multi-sphere energy and water processes. Additionally, the impacts of climate change in East Asia and the associated impact mechanisms were revealed, and changes in water cycle processes and water conversion mechanisms were studied. The changes in surface thermal anomalies, vegetation, local circulation and the atmospheric heat source on the Tibetan Plateau were studied, specifically, their effects on the East Asian monsoon and energy balance mechanisms. Additionally, the relationships between heating mechanisms and monsoon changes were explored. PMID:28287648

Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic meridional overturning circulation

NASA Astrophysics Data System (ADS)

Hong, Yu; Moore, John C.; Jevrejeva, Svetlana; Ji, Duoying; Phipps, Steven J.; Lenton, Andrew; Tilmes, Simone; Watanabe, Shingo; Zhao, Liyun

2017-03-01

We analyze the multi-earth system model responses of ocean temperatures and the Atlantic Meridional Overturning Circulation (AMOC) under an idealized solar radiation management scenario (G1) from the Geoengineering Model Intercomparison Project. All models simulate warming of the northern North Atlantic relative to no geoengineering, despite geoengineering substantially offsetting the increases in mean global ocean temperatures. Increases in the temperature of the North Atlantic Ocean at the surface (˜0.25 K) and at a depth of 500 m (˜0.10 K) are mainly due to a 10 Wm-2 reduction of total heat flux from ocean to atmosphere. Although the AMOC is slightly reduced under the solar dimming scenario, G1, relative to piControl, it is about 37% stronger than under abrupt4 × CO2 . The reduction of the AMOC under G1 is mainly a response to the heat flux change at the northern North Atlantic rather than to changes in the water flux and the wind stress. The AMOC transfers heat from tropics to high latitudes, helping to warm the high latitudes, and its strength is maintained under solar dimming rather than weakened by greenhouse gas forcing acting alone. Hence the relative reduction in high latitude ocean temperatures provided by solar radiation geoengineering, would tend to be counteracted by the correspondingly active AMOC circulation which furthermore transports warm surface waters towards the Greenland ice sheet, warming Arctic sea ice and permafrost.

Shallow circulation groundwater - the main type of water containing hazardous radon concentration

NASA Astrophysics Data System (ADS)

Przylibski, Tadeusz

2010-05-01

Radon dissolves in water very good. As an effect this gas is present in surface and groundwater, which are used in households. The range of Rn-222 concentration in water is very wide, it changes from below 1 Bq/dm3 up to several hundreds of thousands Bq/dm3. Inhabitants may be exposed to an important additional dose from ionizing radiation if they use in household radon water (concentration of Rn-222 between 100 and 999.9(9) Bq/dm3), high-radon water (1000 - 9999.9(9) Bq/dm3) or extreme-radon water (10 000 Bq/dm3 and more). Value of the dose depends on the amount of radon released from water during cooking, washing, taking bath or shower, and it not depends on the amount of radon dissolved in drinked water or water used for making a meal. Radon released from water to the air in a house may be inhaled by inhabitants and increase the risk of lung cancer. Knowing the risk, international organizations, i.e. WHO, publish the recommendations concerning admissible levels of radon concentration in water in the intake (before supplying households). In a few countries these recommendations became a law (i.e. USA, England, Finland, Sweden, Russia, Czech Rep., Slowak Rep.). Law regulations force to measuring concentrations of radon dissolved in water in all the intakes of water supplying hauseholds. Knowing radon behaviour in the environment it is possible to select certain types of water, which may contain the highest radon concentration. As a result one may select these intakes of water, which should be particularly controled with regard to possible hazardous radon cencentration. Radon concentration in surface water depends on partial pressure of this gas over the water table - in the atmosphere. Partial pressure of radon in the atmosphere is very low, so the radon concentration in surface water is usually low and as a rule it is not higher than several, rarely several tens of Bq/dm3. In the spring, where the groundwater flows out on the surface, and groundwater become a surface water forming a stream, radon very quickly escapes to the atmosphere. This is the main reason, that even in regions, where the bottoms of streams and rivers are formed by the rocks containing high amounts of radium (and uranium), surface waters very quickly lose radon escaping to the atmosphere. Concluding, surface waters cannot be the source of hazardous radon concentration. One may expect completely different situation in the case of groundwater. When the groundwater is exploited without any contact with the atmosphere, it contains higher concentration of Rn-222, than surface water in the same neighbourhood with regard to geological structure. Concentration of radon dissolved in groundwater depends first of all on the emanation coefficient of the reservoir rock. This coefficient may be calculated taking into account a few parameters, like cancentration of parent Ra-226 isotope in the reservoir rocks, effective porosity of the rock and the density of the grain framework of the rock. The way of radium atoms disposition in crystals or mineral grains of rock with reference to the pores and cracks filled with groundwater is also an important parameter. Calculations made by the author for more than 100 intakes of groundwater proove, that the highest values of emanation coefficient are characteristic for the rocks in the weathering zone - on the depths between surface level and 30 - 50 m below surface level. Groundwater exploited from the rocks of this zone contains the highest concentration of Rn-222. On the greater depths even high Ra-226 content in the reservoir rock does not affect to the Rn-222 concentration in groundwater flowing through this rock. Summing up, potentially the great radon concentration may contain groundwater of shallow circulation (up to ~50 m b.s.l.), flowing through weathered resrvoir rock with high content of parent Ra-226 isotope.

A next generation altimeter for mapping the sea surface height variability: opportunities and challenges

NASA Astrophysics Data System (ADS)

Fu, Lee-Lueng; Morrow, Rosemary

2016-07-01

The global observations of the sea surface height (SSH) have revolutionized oceanography since the beginning of precision radar altimetry in the early 1990s. For the first time we have continuous records of SSH with spatial and temporal sampling for detecting the global mean sea level rise, the waxing and waning of El Niño, and the ocean circulation from gyres to ocean eddies. The limit of spatial resolution of the present constellation of radar altimeters in mapping SSH variability is approaching 100 km (in wavelength) with 3 or more simultaneous altimetric satellites in orbit. At scales shorter than 100 km, the circulation contains substantial amount of kinetic energy in currents, eddies and fronts that are responsible for the stirring and mixing of the ocean, especially from the vertical exchange of the upper ocean with the deep. A mission currently in development will use the technique of radar interferometry for making high-resolution measurement of the height of water over the ocean as well as on land. It is called Surface Water and Ocean Topography (SWOT), which is a joint mission of US NASA and French CNES, with contributions from Canada and UK. SWOT promises the detection of SSH at scales approaching 15 km, depending on the sea state. SWOT will make SSH measurement over a swath of 120 km with a nadir gap of 20 km in a 21-day repeat orbit. A conventional radar altimeter will provide measurement along the nadir. This is an exploratory mission with applications in oceanography and hydrology. The increased spatial resolution offers an opportunity to study ocean surface processes to address important questions about the ocean circulation. However, the limited temporal sampling poses challenges to map the evolution of the ocean variability that changes rapidly at the small scales. The measurement technique and the development of the mission will be presented with emphasis on its science program with outlook on the opportunities and challenges.

Seasonal-to-Interannual Variability in Antarctic Sea-Ice Dynamics, and Its Impact on Surface Fluxes and Water Mass Production

NASA Technical Reports Server (NTRS)

Drinkwater, Mark R.

1999-01-01

Strong seasonal and interannual signals in Antarctic bottom-water outflow remain unexplained yet are highly correlated with anomalies in net sea-ice growth in coastal polynyas. The mechanisms responsible for driving salination and replenishment and rejuvenation of the dense shelf "source" waters likely also generate pulses of bottom water outflow. The objective of this research is to investigate time-scales of variability in the dynamics of sea-ice in the Southern Ocean in order to determine the primary sites for production of dense shelf waters. We are using a merged satellite/buoy sea-ice motion data set for the period 1978-present day to compute the dynamics of opening and closing of coastal polynyas over the continental shelf. The Ocean Circulation and Climate Advanced Model (OCCAM) ocean general circulation model with coupled sea-ice dynamics is presently forced using National Center for Environmental Prediction (NCEP) data to simulate fluxes and the salination impact of the ocean shelf regions. This work is relevant in the context of measuring the influence of polar sea-ice dynamics upon polar ocean characteristics, and thereby upon global thermohaline ocean circulation. Interannual variability in simulated net freezing rate in the Southern Weddell Sea is shown for the period 1986-1993. There is a pronounced maximum of ice production in 1988 and minimum in 1991 in response to anomalies in equatorward meridional wind velocity. This follows a similar approximate 8-year interannual cycle in Sea Surface Temperature (SST) and satellite-derived ice-edge anomalies reported elsewhere as the "Antarctic Circumpolar Wave." The amplitude of interannual fluctuations in annual net ice production are about 40% of the mean value, implying significant interannual variance in brine rejection and upper ocean heat loss. Southward anomalies in wind stress induce negative anomalies in open water production, which are observed in passive microwave satellite images. Thus, cycles of enhanced poleward wind stress reduce ice growth by compacting the ice along the coastline and closing open water in leads and polynyas. Model simulations confirm that years of low ice production, such as 1991, coincide with years of lower than normal bottom water outflow. Future plans include the assimilation of satellite ice concentrations and ice drift dynamics to more accurately constrain boundary conditions in the model.

A GCM Recent History of the Northern Martian Polar Layered Deposits

NASA Technical Reports Server (NTRS)

Levrard, B.; Laskar, J.; Forget, F.; Montmessin, F.

2003-01-01

The polar layered deposits are thought to contain alternate layers of water and dust in different proportions resulting from the astronomical forcing of the martian climate. In particular, longterm variations in the orbital and axial elements of Mars are presumed to generate variations of the latitudes of surface water ice stability and of the amount of water exchanged in the polar areas. At high obliquity, simplified climate models and independent general circulation simulations suggest a transfer of water ice from the north polar region to tropical areas, whereas at lower and present obliquities, water ice is expected to be stable only at the poles. If so, over obliquity cycles, water ice may be redistributed between the surface water reservoirs leading to their incremental building or disintegration depending on the rates of water transfer. If only a relative limited amount of the available water is exchanged on orbital timescales, this may provide an efficient mechanism for the formation of the observed polar deposits. Within this context, GCM simulations of the martian water cycle have been performed for various obliquities ranging from 15 degrees to 45 degrees and for a large set of initial water ice locations to determine the rate of water exchange between the surface water reservoirs as a function of the obliquity. Propagating these rates over the last 10 Ma orbital history gives a possible recent evolution of these reservoirs.

Seasonal overturning circulation in the Red Sea: 2. Winter circulation

NASA Astrophysics Data System (ADS)

Yao, Fengchao; Hoteit, Ibrahim; Pratt, Larry J.; Bower, Amy S.; Köhl, Armin; Gopalakrishnan, Ganesh; Rivas, David

2014-04-01

The shallow winter overturning circulation in the Red Sea is studied using a 50 year high-resolution MITgcm (MIT general circulation model) simulation with realistic atmospheric forcing. The overturning circulation for a typical year, represented by 1980, and the climatological mean are analyzed using model output to delineate the three-dimensional structure and to investigate the underlying dynamical mechanisms. The horizontal model circulation in the winter of 1980 is dominated by energetic eddies. The climatological model mean results suggest that the surface inflow intensifies in a western boundary current in the southern Red Sea that switches to an eastern boundary current north of 24°N. The overturning is accomplished through a cyclonic recirculation and a cross-basin overturning circulation in the northern Red Sea, with major sinking occurring along a narrow band of width about 20 km along the eastern boundary and weaker upwelling along the western boundary. The northward pressure gradient force, strong vertical mixing, and horizontal mixing near the boundary are the essential dynamical components in the model's winter overturning circulation. The simulated water exchange is not hydraulically controlled in the Strait of Bab el Mandeb; instead, the exchange is limited by bottom and lateral boundary friction and, to a lesser extent, by interfacial friction due to the vertical viscosity at the interface between the inflow and the outflow.

Development of the Technologies for Stabilization Treatment of the Water of the Recycling Cooling Systems at Thermal Power Plants

NASA Astrophysics Data System (ADS)

Vlasov, S. M.; Chichirova, N. D.; Chichirov, A. A.; Vlasova, A. Yu.; Filimonova, A. A.; Prosvirnina, D. V.

2018-02-01

A turbine-condensate cooling system is one of the less stable and most hard-to-control systems of maintaining optimal water chemistry. A laboratory recycling cooling water test facility, UVO-0.3, was developed for physical simulation of innovative zero-discharge water chemistry conditions and improvement of technological flowcharts of stabilization treatment of the initial and circulating water of the recycling cooling systems at thermal power plants. Experiments were conducted in the UVO-0.3 facility to investigate the processes that occur in the recycling water supply system and master new technologies of stabilization of the initial and circulating water. It is shown that, when using untreated initial water, scaling cannot be prevented even under low concentration levels. The main reason for the activation of scale depositing is the desorption of carbon dioxide that results in alkalization of the circulating water and, as a consequence, a displacement of the chemical reaction equilibrium towards the formation of slightly soluble hardness ions. Some techniques, viz., liming and alkalization of the initial water and the by-pass treatment of the circulating water, are considered. New engineering solutions have been developed for reducing the amount of scale-forming substances in the initial and circulating water. The best results were obtained by pretreating the initial water with alkalizing agents and simultaneously bypassing and treating part of the circulating water. The obtained experimental data underlie the process flowcharts of stabilization treatment of the initial and circulating TPP water that ensure scale-free and noncorrosive operation and meet the corresponding environmental requirements. Under the bypassing, the specific rates of the agents and the residual hardness are reduced compared with the conventional pretreatment.

A Phosphate Minimum in the Oxygen Minimum Zone (OMZ) off Peru

NASA Astrophysics Data System (ADS)

Paulmier, A.; Giraud, M.; Sudre, J.; Jonca, J.; Leon, V.; Moron, O.; Dewitte, B.; Lavik, G.; Grasse, P.; Frank, M.; Stramma, L.; Garcon, V.

2016-02-01

The Oxygen Minimum Zone (OMZ) off Peru is known to be associated with the advection of Equatorial SubSurface Waters (ESSW), rich in nutrients and poor in oxygen, through the Peru-Chile UnderCurrent (PCUC), but this circulation remains to be refined within the OMZ. During the Pelágico cruise in November-December 2010, measurements of phosphate revealed the presence of a phosphate minimum (Pmin) in various hydrographic stations, which could not be explained so far and could be associated with a specific water mass. This Pmin, localized at a relatively constant layer ( 20<220 m) and with a patchy distribution mainly between 10 and 16°S, is confirmed and characterized in details from the complementary hydrological data acquired during the German Meteor cruise M77 (Legs 3 and 4, January-February 2009). The significant Pmin present an intense minimum with a mean vertical phosphate decrease of 0.6 µM but highly variable between 0.1 and 2.2 µM. In average, these Pmin are associated with a predominant mixing of SubTropical Under- and Surface Waters (STUW and STSW: 20 and 40%, respectively) within ESSW ( 25%), complemented evenly by overlying (ESW, TSW: 8%) and underlying waters (AAIW, SPDW: 7%). The hypotheses and mechanisms leading to the Pmin formation in the OMZ are further explored and discussed, considering the physical regional contribution associated with various circulation pathways ventilating the OMZ and the local biogeochemical contribution including the potential diazotrophic activity.

A simple hydrologically based model of land surface water and energy fluxes for general circulation models

NASA Technical Reports Server (NTRS)

Liang, XU; Lettenmaier, Dennis P.; Wood, Eric F.; Burges, Stephen J.

1994-01-01

A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory (GFDL) general circulation model (GCM) is described. The new model is comprised of a two-layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max-Planck-Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long-term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment (FIFE) intensive field campaigns in the summer-fall of 1987 to validate the surface energy fluxes.

Comparison of circulation times of thermal waters discharging from the Idaho batholith based on geothermometer temperatures, helium concentrations, and 14C measurements

USGS Publications Warehouse

Mariner, R.H.; Evans, William C.; Young, H.W.

2006-01-01

Circulation times of waters in geothermal systems are poorly known. In this study, we examine the thermal waters of the Idaho batholith to verify whether maximum system temperatures, helium concentrations, and 14C values are related to water age in these low-to-moderate temperature geothermal systems. He/N2 values of gas collected from thermal waters that circulate solely through distinct units of the Idaho batholith correlate linearly with Na-K-(4/3)Ca geothermometer temperatures, showing that both variables are excellent indicators of relative water age. Thermal waters that circulate in early Tertiary (45-50 Ma) granite of the Sawtooth batholith have 3.5 times more helium than thermal waters of the same aquifer temperature that circulate through the main Cretaceous granite (average 91 Ma). Hot spring waters circulating in hydrothermally altered parts of the batholith have very little dissolved helium and no correlation between He/N2 values and geothermometer temperatures. Thermal waters discharging from the Idaho batholith are more depleted in deuterium than modern precipitation in the area. Recharge to these geothermal systems occurred from at least 10,000 BP for the cooler systems up to about 33,000 BP for the hotter systems.

Three-dimensional hydrodynamic modelling study of reverse estuarine circulation: Kuwait Bay.

PubMed

Alosairi, Y; Pokavanich, T; Alsulaiman, N

2018-02-01

Hydrodynamics and associated environmental processes have always been of major concern to coastal-dependent countries, such as Kuwait. This is due to the environmental impact that accompanies the economic and commercial activities along the coastal areas. In the current study, a three-dimensional numerical model is utilized to unveil the main dynamic and physical properties of Kuwait Bay during the critical season. The model performance over the summer months (June, July and August 2012) is assessed against comprehensive field measurements of water levels, velocity, temperature and salinity data before using the model to describe the circulation as driven by tides, gravitational convection and winds. The results showed that the baroclinic conditions in the Bay are mainly determined by the horizontal salinity gradient and to much less extent temperature gradient. The gradients stretched over the southern coast of the Bay where dense water is found at the inner and enclosed areas, while relatively lighter waters are found near the mouth of the Bay. This gradient imposed a reversed estuarine circulation at the main axis of the Bay, particularly during neap tides when landward flow near the surface and seaward flow near the bed are most evident. The results also revealed that the shallow areas, including Sulaibikhat and Jahra Bays, are well mixed and generally flow in the counter-clockwise direction. Clockwise circulations dominated the northern portion of the Bay, forming a sort of large eddy, while turbulent fields associated with tidal currents were localized near the headlands. Copyright © 2017 Elsevier Ltd. All rights reserved.

An undercurrent off the east coast of Sri Lanka

NASA Astrophysics Data System (ADS)

Anutaliya, Arachaporn; Send, Uwe; McClean, Julie L.; Sprintall, Janet; Rainville, Luc; Lee, Craig M.; Priyantha Jinadasa, S. U.; Wallcraft, Alan J.; Metzger, E. Joseph

2017-12-01

The existence of a seasonally varying undercurrent along 8° N off the east coast of Sri Lanka is inferred from shipboard hydrography, Argo floats, glider measurements, and two ocean general circulation model simulations. Together, they reveal an undercurrent below 100-200 m flowing in the opposite direction to the surface current, which is most pronounced during boreal spring and summer and switches direction between these two seasons. The volume transport of the undercurrent (200-1000 m layer) can be more than 10 Sv in either direction, exceeding the transport of 1-6 Sv carried by the surface current (0-200 m layer). The undercurrent transports relatively fresher water southward during spring, while it advects more saline water northward along the east coast of Sri Lanka during summer. Although the undercurrent is potentially a pathway of salt exchange between the Arabian Sea and the Bay of Bengal, the observations and the ocean general circulation models suggest that the salinity contrast between seasons and between the boundary current and interior is less than 0.09 in the subsurface layer, suggesting a small salt transport by the undercurrent of less than 4 % of the salinity deficit in the Bay of Bengal.

Gulf of Mexico Loop Current Interactions with the West Florida Shelf and its Influence on Harmful Algae Blooms

NASA Astrophysics Data System (ADS)

Liu, Y.; Weisberg, R. H.

2016-02-01

Interactions of the Loop Current (LC) system with the West Florida Shelf (WFS) are examined using 20+ years (1993 - 2015) of Ssalto/Duacs multi-mission altimetry data in the eastern Gulf of Mexico. Characteristic patterns of LC system sea surface height and surface geostrophic currents are extracted by an unsupervised neural network, Self-Organizing Map, along with their frequencies of occurrence. These current patterns suggest linkages with harmful algae bloom occurrences as recorded by in situ K. brevis cell counts. It is argued that LC system interactions with the shelf slope play an important role in WFS ecology through the upwelling of new inorganic nutrients across the shelf break. This is particularly important when the LC impinges on the southwest corner of the WFS slope, thereby impacting shallow water isobaths and setting the entire shelf circulation into motion. If such conditions persist, then deeper ocean waters with elevated nutrient content may broach the shelf and be transported landward. Resetting the nutrient state of the shelf by the coastal ocean circulation in response to deep-ocean forcing demonstrates the importance of physical oceanography in shelf ecology.

Influence of the Yukon River on the Bering Sea

NASA Technical Reports Server (NTRS)

Dean, Kenneson G.; Mcroy, C. Peter

1988-01-01

Physical and biological oceanography of the northern Bering Sea including the influence of the Yukon River were studied. Satellite data acquired by the Advanced Very High Resolution Radiometer (AVHRR), the LANDSAT Multispectral Scanner (MSS) and the Thematic Mapper (TM) sensor were used to detect sea surface temperatures and suspended sediments. Shipboard measurements of temperature, salinity and nutrients were acquired through the Inner Shelf Transfer and Recycling (ISHTAR) project and were compared to digitally enhanced and historical satellite images. The satellite data reveal north-flowing, warm water along the Alaskan coast that is highly turbid with complex patterns of surface circulation near the Yukon River delta. To the west near the Soviet Union, cold water, derived from an upwelling, mixes with shelf water and also flows north. The cold and warm water coincide with the Anadyr, Bering Shelf and Alaskan coastal water masses. Generally, warm Alaskan coastal water forms near the coast and extends offshore as the summer progresses. Turbid water discharged by the Yukon River progresses in the same fashion but extends northward across the entrance to Norton Sound, attaining its maximum surface extent in October. The Anadyr water flows northward and around St. Lawrence Island, but its extent is highly variable and depends upon mesoscale pressure fields in the Arctic Ocean and the Bering Sea.

Canary Current and North Equatorial Current from an inverse box model

NASA Astrophysics Data System (ADS)

HernáNdez-Guerra, Alonso; Fraile-Nuez, Eugenio; López-Laatzen, Federico; MartíNez, Antonio; Parrilla, Gregorio; VéLez-Belchí, Pedro

2005-12-01

The large-scale Canary Basin circulation is estimated from a box inverse model applied to hydrographic data from a quasi-synoptic survey carried out in September 2003. The cruise consisted of 76 full depth CTD and oxygen stations. Circulation is required to nearly conserve mass and anomalies of salinity and heat within layers bounded by neutral surfaces. It permits advective and diffusive exchange between layers and an adjustment of the Ekman transport and the freshwater flux divergences. The Canary Current at the thermocline layer transports a net mass of 4.7 ± 0.8 Sv southward north of the Canary Islands from the African coast to 19°W. It is divided into a northward circulation at a rate of 1.1 ± 0.5 Sv between the African coast and Lanzarote Island and a southward transport of 5.8 ± 0.6 Sv. It transports North Atlantic Central Water and organic matters advected offshore by the filaments protruding from the upwelling system off northwest Africa. At 24°N, the Canary Current feeds the North Equatorial Current that transports a mixture of North and South Atlantic Central Waters westward. In the intermediate layer a southwestward flow of 1.2 ± 1.1 Sv transports Mediterranean Water to the Subtropical Gyre, though the highest salt flux is transported by a meddy. Oxygen distribution and mass transport suggest a northeastward deep flow of a water mass colder than 2.2°C consisting of diluted Antarctic Bottom Water. The heat and freshwater divergences and the average dianeutral velocity and diffusion between the sections and the African coast are negligible.

Factors Influencing the Formation of Corrosive Conditions in Puget Sound and the Extreme Conditions Observed During Summer 2015 Associated with the NE Pacific Warm Anomaly (a.k.a. The Blob)

NASA Astrophysics Data System (ADS)

Alin, S. R.; Curry, B.; Newton, J.; Feely, R. A.; Sutton, A.

2016-02-01

Puget Sound is a complex glacial estuarine system that receives input from many rivers and streams, in addition to runoff from the urban and agricultural environments surrounding the southern part of the Salish Sea ecosystem. A series of glacial sills restrict estuarine circulation such that intrusions of seawater only occur episodically, resulting in long residence times in some parts of the basin. Through survey cruises and stationary time-series, we have observed the dynamic biogeochemical cycles in various sub-basins of Puget Sound since 2008. Areas of Puget Sound with restricted circulation may experience conditions of high pCO2, low pH, and low aragonite saturation state throughout the year. Historically, the highest pCO2 and lowest pH and aragonite saturation states have been observed in early fall in Hood Canal. Upwelling of dense, nutrient- and CO2-rich but oxygen-poor water along the coast provides the marine source water for Puget Sound's deep waters. We estimate that marine waters entering Puget Sound via the Strait of Juan de Fuca are now corrosive 95% of the time, representing a 26% increase in frequency since the preindustrial era. Both river inputs and intense primary production in surface waters drive remineralization in deep waters of Puget Sound basins, contributing to the formation of corrosive conditions in waters below the productive surface. In addition, we estimate that regionally enhanced atmospheric CO2 content may result in an increase in CO2 uptake in the region. In 2015 many features of the seasonal carbon cycle were accelerated relative to earlier years, as a result of the influence of the NE Pacific warm anomaly. In southern Hood Canal, the surface spring bloom began weeks earlier than usual, and in July, we saw the lowest estimated pH and aragonite saturation values in deep waters observed to date in Washington marine environments, which was about two months earlier than historical seasonal minima in pH and aragonite saturation.

Oceanographic Controls on the Variability of Ice-Shelf Basal Melting and Circulation of Glacial Meltwater in the Amundsen Sea Embayment, Antarctica

NASA Astrophysics Data System (ADS)

Kimura, Satoshi; Jenkins, Adrian; Regan, Heather; Holland, Paul R.; Assmann, Karen M.; Whitt, Daniel B.; Van Wessem, Melchoir; van de Berg, Willem Jan; Reijmer, Carleen H.; Dutrieux, Pierre

2017-12-01

Ice shelves in the Amundsen Sea Embayment have thinned, accelerating the seaward flow of ice sheets upstream over recent decades. This imbalance is caused by an increase in the ocean-driven melting of the ice shelves. Observations and models show that the ocean heat content reaching the ice shelves is sensitive to the depth of thermocline, which separates the cool, fresh surface waters from warm, salty waters. Yet the processes controlling the variability of thermocline depth remain poorly constrained. Here we quantify the oceanic conditions and ocean-driven melting of Cosgrove, Pine Island Glacier (PIG), Thwaites, Crosson, and Dotson ice shelves in the Amundsen Sea Embayment from 1991 to 2014 using a general circulation model. Ice-shelf melting is coupled to variability in the wind field and the sea-ice motions over the continental shelf break and associated onshore advection of warm waters in deep troughs. The layer of warm, salty waters at the calving front of PIG and Thwaites is thicker in austral spring (June-October) than in austral summer (December-March), whereas the seasonal cycle at the calving front of Dotson is reversed. Furthermore, the ocean-driven melting in PIG is enhanced by an asymmetric response to changes in ocean heat transport anomalies at the continental shelf break: melting responds more rapidly to increases in ocean heat transport than to decreases. This asymmetry is caused by the inland deepening of bathymetry and the glacial meltwater circulation around the ice shelf.

Secondary Channel Bifurcation Geometry: A Multi-dimensional Problem

NASA Astrophysics Data System (ADS)

Gaeuman, D.; Stewart, R. L.

2017-12-01

The construction of secondary channels (or side channels) is a popular strategy for increasing aquatic habitat complexity in managed rivers. Such channels, however, frequently experience aggradation that prevents surface water from entering the side channels near their bifurcation points during periods of relatively low discharge. This failure to maintain an uninterrupted surface water connection with the main channel can reduce the habitat value of side channels for fish species that prefer lotic conditions. Various factors have been proposed as potential controls on the fate of side channels, including water surface slope differences between the main and secondary channels, the presence of main channel secondary circulation, transverse bed slopes, and bifurcation angle. A quantitative assessment of more than 50 natural and constructed secondary channels in the Trinity River of northern California indicates that bifurcations can assume a variety of configurations that are formed by different processes and whose longevity is governed by different sets of factors. Moreover, factors such as bifurcation angle and water surface slope vary with discharge level and are continuously distributed in space, such that they must be viewed as a multi-dimensional field rather than a single-valued attribute that can be assigned to a particular bifurcation.

Water Resource Assessment in KRS Reservoir Using Remote Sensing and GIS Modelling

NASA Astrophysics Data System (ADS)

Manubabu, V. H.; Gouda, K. C.; Bhat, N.; Reddy, A.

2014-12-01

In the recent time the fresh water resource becomes very important because of various reasons like population growth, pollution, over exploitation of the ground water resources etc. As there is no efficient and proper measures for recharging ground water exists and also the climatological impacts on water resources like global warming exacerbating water shortages, growing populations and rising demand for freshwater in agriculture, industry, and energy production. There is a need and challenging task for analyzing the future changes in regional water availability and it is also very much necessary to asses and predict the fresh water present in a lake or reservoir to make better decision making in the optimal usage of surface water. In the present study is intended to provide a practical discussion of methodology that deals with how to asses and predict amount of surface water available in the future using Remote Sensing(RS) data , Geographical Information System(GIS) techniques, and GCM (Global Circulation Model). Basically the study emphasized over one of the biggest reservoir i.e. the Krishna Raja Sagara (KRS) reservoir situated in the state of Karnataka in India. Multispectral satellite images like IRS LISS III and Landsat L8 from different open source web portals like NRSC-Bhuvan and NASA Earth Explorer respectively are used for the present analysis. The multispectral satellite images are used to identify the temporal changes of the water quantity in the reservoir for the period 2000 to 2014. Also the water volume are being calculated using Advances Space born Thermal Emission and Reflection Radiometer (ASTER) Global DEM over the reservoir basin. The hydro meteorological parameters are also studied using multi-source observed data and the empirical water budget models for the reservoir in terms of rainfall, temperature, run off, water inflow and outflow etc. are being developed and analyzed. Statistical analysis are also carried out to quantify the relation between reservoir water volume and the hydrological parameters (Figure 1). A general circulation model (GCM) is used for the prediction of major hydro meteorological parameters like rainfall and using the GCM predictions the water availability in terms of water volume in future are simulated using the empirical water budget model.

Ocean Transport Pathways to a World Heritage Fringing Coral Reef: Ningaloo Reef, Western Australia.

PubMed

Xu, Jiangtao; Lowe, Ryan J; Ivey, Gregory N; Jones, Nicole L; Zhang, Zhenlin

2016-01-01

A Lagrangian particle tracking model driven by a regional ocean circulation model was used to investigate the seasonally varying connectivity patterns within the shelf circulation surrounding the 300 km long Ningaloo Reef in Western Australia (WA) during 2009-2010. Forward-in-time simulations revealed that surface water was transported equatorward and offshore in summer due to the upwelling-favorable winds. In winter, however, water was transported polewards down the WA coast due to the seasonally strong Leeuwin Current. Using backward-in-time simulations, the subsurface transport pathways revealed two main source regions of shelf water reaching Ningaloo Reef: (1) a year-round source to the northeast in the upper 100 m of water column; and (2) during the summer, an additional source offshore and to the west of Ningaloo in depths between ~30 and ~150 m. Transient wind-driven coastal upwelling, onshore geostrophic transport and stirring by offshore eddies were identified as the important mechanisms influencing the source water origins. The identification of these highly time-dependent transport pathways and source water locations is an essential step towards quantifying how key material (e.g., nutrients, larvae, contaminants, etc.) is exchanged between Ningaloo Reef and the surrounding shelf ocean, and how this is mechanistically coupled to the complex ocean dynamics in this region.

Ocean Transport Pathways to a World Heritage Fringing Coral Reef: Ningaloo Reef, Western Australia

PubMed Central

Xu, Jiangtao; Lowe, Ryan J.; Ivey, Gregory N.; Jones, Nicole L.; Zhang, Zhenlin

2016-01-01

A Lagrangian particle tracking model driven by a regional ocean circulation model was used to investigate the seasonally varying connectivity patterns within the shelf circulation surrounding the 300 km long Ningaloo Reef in Western Australia (WA) during 2009–2010. Forward-in-time simulations revealed that surface water was transported equatorward and offshore in summer due to the upwelling-favorable winds. In winter, however, water was transported polewards down the WA coast due to the seasonally strong Leeuwin Current. Using backward-in-time simulations, the subsurface transport pathways revealed two main source regions of shelf water reaching Ningaloo Reef: (1) a year-round source to the northeast in the upper 100 m of water column; and (2) during the summer, an additional source offshore and to the west of Ningaloo in depths between ~30 and ~150 m. Transient wind-driven coastal upwelling, onshore geostrophic transport and stirring by offshore eddies were identified as the important mechanisms influencing the source water origins. The identification of these highly time-dependent transport pathways and source water locations is an essential step towards quantifying how key material (e.g., nutrients, larvae, contaminants, etc.) is exchanged between Ningaloo Reef and the surrounding shelf ocean, and how this is mechanistically coupled to the complex ocean dynamics in this region. PMID:26790154

Land- and sea-surface impacts on local coastal breezes

NASA Astrophysics Data System (ADS)

Veron, D. E.; Hughes, C.; Gilchrist, J.; Lodise, J.; Goldman, W.

2014-12-01

The state of Delaware has seen significant increases in population along the coastline in the past three decades. With this increase in population have come changes to the land surface, as forest and farmland has been converted to residential and commercial purposes, causing changes in the surface roughness, temperature, and land-atmosphere fluxes. There is also a semi-permanent upwelling center in the spring and summer outside the Delaware Bay mouth that significantly changes the structure of the sea surface temperature both inside and outside the Bay. Through a series of high resolution modeling and observational studies, we have determined that in cases of strong synoptic forcing, the impact of the land-surface on the boundary layer properties can be advected offshore, creating a false coastline and modifying the location and timing of the sea breeze circulation. In cases of weak synoptic forcing, the influence of the upwelling and the tidal circulation of the Delaware Bay waters can greatly change the location, strength, and penetration of the sea breeze. Understanding the importance of local variability in the surface-atmosphere interactions on the sea breeze can lead to improved prediction of sea breeze onset, penetration, and duration which is important for monitoring air quality and developing offshore wind power production.

A Semi-Implicit, Three-Dimensional Model for Estuarine Circulation

USGS Publications Warehouse

Smith, Peter E.

2006-01-01

A semi-implicit, finite-difference method for the numerical solution of the three-dimensional equations for circulation in estuaries is presented and tested. The method uses a three-time-level, leapfrog-trapezoidal scheme that is essentially second-order accurate in the spatial and temporal numerical approximations. The three-time-level scheme is shown to be preferred over a two-time-level scheme, especially for problems with strong nonlinearities. The stability of the semi-implicit scheme is free from any time-step limitation related to the terms describing vertical diffusion and the propagation of the surface gravity waves. The scheme does not rely on any form of vertical/horizontal mode-splitting to treat the vertical diffusion implicitly. At each time step, the numerical method uses a double-sweep method to transform a large number of small tridiagonal equation systems and then uses the preconditioned conjugate-gradient method to solve a single, large, five-diagonal equation system for the water surface elevation. The governing equations for the multi-level scheme are prepared in a conservative form by integrating them over the height of each horizontal layer. The layer-integrated volumetric transports replace velocities as the dependent variables so that the depth-integrated continuity equation that is used in the solution for the water surface elevation is linear. Volumetric transports are computed explicitly from the momentum equations. The resulting method is mass conservative, efficient, and numerically accurate.

The study of the hydrological regime extreme effects of the Caspian Sea during the XX-XXI centuries

NASA Astrophysics Data System (ADS)

Yaitskaya, Natalia

2016-04-01

The Caspian Sea - the unique largest enclosed inland body of water on Earth. Significant periodic sea level fluctuations are a typical feature of the sea. In the XIX-XX centuries a number of comprehensive studies of the Caspian Sea was carried out. The results are published in the papers, monographs and climatic atlases. But a number of fundamental questions about the features of the hydrological regime of the Caspian Sea is still open: 1. How does the water circulation change during the level variations? 2. What is the effect of heterogeneity of evaporation from the water surface on the formation of the flow field in the conditions of long-term level changes? 3. How does the water salinity regime change depending on the sea level position, water circulation, river flow and different climatic influences? 4. What is the effect of extreme events (multi-hazards) (ice, storms, destruction of the coasts) on coastal infrastructure? In 2016, the project aims to study hydrological regime extreme effects of the Caspian Sea was supported by the Russian Foundation for Basic Research. Within this project all of the above problems will be solved. Geographic information system "Caspian Sea" for the storage and data processing, including a database of primary oceanographic information for the period of instrumental observations (1897-2013), cartographic database (1921-2011) and tools for multidimensional analysis of spatio-temporal information is the basis of the study. The scheme of interconnected hydrodynamic models (Caspian Sea MODel - Ocean Model - Wind wave model) was developed. The important factors are taken into account in the structure of the models: long-term and seasonal dynamics of the sea waves parameters, new long-term values of evaporation from the shallow waters areas of the Caspian Sea, water circulation. Schemes of general seasonal circulation of the Caspian Sea and the Northern Caspian at different positions of the sea level in XX-XXI centuries using interconnected models will be reconstructed. Forecast of seasonal water circulation for the most probable climate change scenarios in the future will be done. Conceptual scheme of calculations of the multi-hazards (ice storms, the destruction of the coasts) in the Caspian Sea was developed. The similar method of calculation was successfully applied to the prediction of natural hazards in the Sea of Azov. The reported study was funded by RFBR, according to the research project No.16-35-60046 mol_a_dk.

One-year Monitoring of Iodine-129 spread in Pacific Ocean After the 2011 Fukushima Daiichi Nuclear Power Plant Accident

NASA Astrophysics Data System (ADS)

Chang, C.; Burr, G. S.; Jull, A. T.; Pandey, A.; Thiemens, M. H.; Biddulph, D.; Russell, J. L.

2012-12-01

The long-lived radionuclide Iodine-129 is well known as a useful environmental tracer. At present, the global I-129 in surface water is about 1-2 orders of magnitude higher than pre-1990 levels. The anthropogenic I-129 signal produced from industrial nuclear fuel reprocessing plants is known to be the primary source of I-129 in marine surface waters of the Atlantic, and elevated I-129 values are found globally. On March 11, 2011, the Great East Japan Earthquake produced a devastating tsunami that severely damaged the Fukushima Daiichi Nuclear Power Plant. The damage caused a substantial release of radionuclides into the atmosphere and ocean in the weeks following the catastrophe. We expect to be able to identify I-129 from surface seawater in the Pacific Ocean. We will present I-129 results of water samples collected weekly near Scripps Institution of Oceanography, San Diego, CA for a year. We also have a pair of measurements collected a year apart from Kaohsiung, Taiwan. By establishing I-129 time series, we can observe the spread of I-129 in the surface waters of the Pacific Ocean that resulted from the accidental releases. This information can also be used to better understand surface ocean circulation.

The Effect of Climate Change on Ozone Depletion through Changes in Stratospheric Water Vapour

NASA Technical Reports Server (NTRS)

Kirk-Davidoff, Daniel B.; Hintsa, Eric J.; Anderson, James G.; Keith, David W.

1999-01-01

Several studies have predicted substantial increases in Arctic ozone depletion due to the stratospheric cooling induced by increasing atmospheric CO2 concentrations. But climate change may additionally influence Arctic ozone depletion through changes in the water vapor cycle. Here we investigate this possibility by combining predictions of tropical tropopause temperatures from a general circulation model with results from a one-dimensional radiative convective model, recent progress in understanding the stratospheric water vapor budget, modelling of heterogeneous reaction rates and the results of a general circulation model on the radiative effect of increased water vapor. Whereas most of the stratosphere will cool as greenhouse-gas concentrations increase, the tropical tropopause may become warmer, resulting in an increase of the mean saturation mixing ratio of water vapor and hence an increased transport of water vapor from the troposphere to the stratosphere. Stratospheric water vapor concentration in the polar regions determines both the critical temperature below which heterogeneous reactions on cold aerosols become important (the mechanism driving enhanced ozone depletion) and the temperature of the Arctic vortex itself. Our results indicate that ozone loss in the later winter and spring Arctic vortex depends critically on water vapor variations which are forced by sea surface temperature changes in the tropics. This potentially important effect has not been taken into account in previous scenarios of Arctic ozone loss under climate change conditions.

Impact of lakes and wetlands on present and future boreal climate

NASA Astrophysics Data System (ADS)

Poutou, E.; Krinner, G.; Genthon, C.

2002-12-01

Impact of lakes and wetlands on present and future boreal climate The role of lakes and wetlands in present-day high latitude climate is quantified using a general circulation model of the atmosphere. The atmospheric model includes a lake module which is presented and validated. Seasonal and spatial wetland distribution is calculated as a function of the hydrological budget of the wetlands themselves and of continental soil whose runoff feeds them. Wetland extent is simulated and discussed both in simulations forced by observed climate and in general circulation model simulations. In off-line simulations, forced by ECMWF reanalyses, the lake model simulates correctly observed lake ice durations, while the wetland extent is somewhat underestimated in the boreal regions. Coupled to the general circulation model, the lake model yields satisfying ice durations, although the climate model biases have impacts on the modeled lake ice conditions. Boreal wetland extents are overestimated in the general circulation model as simulated precipitation is too high. The impact of inundated surfaces on the simulated climate is strongest in summer when these surfaces are ice-free. Wetlands seem to play a more important role than lakes in cooling the boreal regions in summer and in humidifying the atmosphere. The role of lakes and wetlands in future climate change is evaluated by analyzing simulations of present and future climate with and without prescribed inland water bodies.

Numerical Simulation of the Large-Scale North American Monsoon Water Sources

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Sud, Yogesh C.; Schubert, Siegfried D.; Walker, Gregory K.

2002-01-01

A general circulation model (GCM) that includes water vapor tracer (WVT) diagnostics is used to delineate the dominant sources of water vapor for precipitation during the North American monsoon. A 15-year model simulation carried out with one-degree horizontal resolution and time varying sea surface temperature is able to produce reasonable large-scale features of the monsoon precipitation. Within the core of the Mexican monsoon, continental sources provide much of the water for precipitation. Away from the Mexican monsoon (eastern Mexico and Texas), continental sources generally decrease with monsoon onset. Tropical Atlantic Ocean sources of water gain influence in the southern Great Plains states where the total precipitation decreases during the monsoon onset. Pacific ocean sources do contribute to the monsoon, but tend to be weaker after onset. Evaluating the development of the monsoons, soil water and surface evaporation prior to monsoon onset do not correlate with the eventual monsoon intensity. However, the most intense monsoons do use more local sources of water than the least intense monsoons, but only after the onset. This suggests that precipitation recycling is an important factor in monsoon intensity.

Formation and ridging of flaw leads in the eastern Canadian Beaufort Sea. Special Session C06 on: “Physical, biological and biogeochemical processes associated with young thin ice types”

NASA Astrophysics Data System (ADS)

Prinsenberg, S. J.

2009-12-01

Formation and ridging of flaw leads in the eastern Canadian Beaufort Sea. Simon Prinsenberg1 and Yves Graton2 1Bedford Inst. of Oceanography, Fisheries and Oceans Canada P.O. Box1006, Dartmouth, Nova Scotia, B2Y 4A2, Canada prinsenbergs@mar.dfo-mpo.gc.ca 2Inst. National de la Recherche Scientifique-Eau, INRS-ETE University of Quebec at Quebec City, Quebec yvesgratton@eteinrs.ca During the winter of 2008, the flaw lead south of Banks Island repeatedly opened and closed representing an elongated region where periodically the large ice growth stimulates the densification of the surface layer due to salt rejection and instigates a local circulation pattern that will affect the biological processes of the region. Helicopter-borne sensors were available to monitor the aftermath of one of the rapid closing of the flaw lead into extensive elongated rubble field using a Canadian Ice breaker, CCGS Amundsen, as a logistic base. After the wind reversed a new open flaw lead 20km wide restarting a new flaw lead formation cycle. Ice thickness and surface roughness data were collected from the rubble field and adjacent open flaw lead with an Electromagnetic-Laser system. The strong wind event of April 4-5 2009 generated a large linear 1.5km wide ice rubble field up to 8-10m thick when the 60cm thick, 18km wide flaw lead was crunched into land-fast by the 1.5m thick offshore pack ice. It is expected that during rapid ice growth in a flaw lead, salt rejection increase the density of the surface water layer producing a surface depression (Low) and cyclonic circulation. In contrast at depth, the extra surface dense water produces a high in the horizontal pressure field and anti-cyclonic circulation which remains after the rapid ice growth within the flaw lead stops. One of such remnants may have been observed during the CFL-IPY winter survey.

Century/millennium internal climate oscillations in an ocean-atmosphere-continental ice sheet model

NASA Technical Reports Server (NTRS)

Birchfield, Edward G.; Wang, Huaxiao; Rich, Jonathan J.

1994-01-01

We demonstrate in a simple climate model that there exist nonlinear feedbacks between the atmosphere, ocean, and ice sheets capable of producing century/millennium timescale internal oscillations resembling those seen in the paleoclimate record. Feedbacks involve meridional heat and salt transports in the North Atlantic, surface ocean freshwater fluxes associated with melting and growing continental ice sheets in the northen hemisphere and with Atlantic to Pacific water vapor transport. The positive feedback between the production of North Atlantic Deep Water (NADW) and the meridional salt transport by the Atlantic thermohaline circulation tends to destabilize the climate system, while the negative feedback between the freshwater flux, either to or from the continental ice sheets, and meridional heat flux to the high-latitude North Atlantic, accomplished by the thermohaline circulation, stabilizes the system. The thermohaline circulation plays a central role in both positive and negative feedbacks because of its transport of both heat and salt. Because of asymmetries between the growth and melt phases the oscillations are, in general, accompanied by a growing or decreasing ice volume over each cycle, which in the model is reflected by increasing or decreasing mean salinity.

An overview of new insights from 6 years of salinity data from SMOS mission

NASA Astrophysics Data System (ADS)

Nicolas, R.

2015-12-01

Measurements of salt held in surface seawater are becoming ever-more important for oceanographers and climatologists to gain a deeper understanding of ocean circulation and Earth's water cycle. ESA's SMOS mission is proving essential for this aim. Launched in 2009, SMOS has provided the longest continuous record (now ~6 years) of sea-surface salinity measurements from space. The salinity of surface seawater is controlled largely by the balance between evaporation and precipitation, but freshwater from rivers and the freezing and melting of ice also cause changes in concentrations. Along with temperature, salinity drives ocean circulation - the thermohaline circulation - which, in turn, plays a key role in the global climate. With a wealth of salinity data from SMOS now in hand complemented by measurements from the NASA-CONAE Aquarius satellite, which uses a different measuring technique. In this talk we shall provide an overview of how the SMOS mission - now celebrating 6 years in orbit - is providing detailed global measurements of SSS. An ensemble of key ocean processes for climate and biochemistry can now be determined and monitored for the first time from space : the detailed salinity structure of tropical instability waves along the equator and the salt exchanged across major oceanic current fronts, the occurrences of large-scale salinity anomalies in the Pacific and Indian oceans related to important climate indexes are also well-evidenced in the six year-long data. In addition, the dispersal of freshwater into the ocean from the major large tropical rivers (Amazon, Orinoco and Congo), their impact on tropical cyclone (TC) intensification and the oceanic imprints of the intense rainfall in the ITCZ and under TC can now be regularly monitored to better understand the variability of the oceanic part of the global water cycle. We will present how SMOS data, along with concurrent in situ Argo ocean-profile data, other satellite observations of sea-surface temperature, sea-surface height, surface-wind stress and ocean colour, are now providing new opportunities to investigate the surface and subsurface ocean mesoscale dynamics. The talk will tentatively illustrate how this type of data synergy is the key to unlock further scientific insight and increase our knowledge of the hydrologic cycle.

An electrical analogy relating the Atlantic multidecadal oscillation to the Atlantic meridional overturning circulation.

PubMed

Kurtz, Bruce E

2014-01-01

The Atlantic meridional overturning circulation (AMOC) is the northward flow of surface water to subpolar latitudes where deepwater is formed, balanced by southward abyssal flow and upwelling in the vicinity of the Southern Ocean. It is generally accepted that AMOC flow oscillates with a period of 60-80 years, creating a regular variation in North Atlantic sea surface temperature known as the Atlantic multidecadal oscillation (AMO). This article attempts to answer two questions: how is the AMOC driven and why does it oscillate? Using methods commonly employed by chemical engineers for analyzing processes involving flowing liquids, apparently not previously applied to trying to understand the AMOC, an equation is developed for AMOC flow as a function of the meridional density gradient or the corresponding temperature gradient. The equation is based on the similarity between the AMOC and an industrial thermosyphon loop cooler, which circulates a heat transfer liquid without using a mechanical pump. Extending this equation with an analogy between the flow of heat and electricity explains why the AMOC flow oscillates and what determines its period. Calculated values for AMOC flow and AMO oscillation period are in good agreement with measured values.

An Electrical Analogy Relating the Atlantic Multidecadal Oscillation to the Atlantic Meridional Overturning Circulation

PubMed Central

Kurtz, Bruce E.

2014-01-01

The Atlantic meridional overturning circulation (AMOC) is the northward flow of surface water to subpolar latitudes where deepwater is formed, balanced by southward abyssal flow and upwelling in the vicinity of the Southern Ocean. It is generally accepted that AMOC flow oscillates with a period of 60–80 years, creating a regular variation in North Atlantic sea surface temperature known as the Atlantic multidecadal oscillation (AMO). This article attempts to answer two questions: how is the AMOC driven and why does it oscillate? Using methods commonly employed by chemical engineers for analyzing processes involving flowing liquids, apparently not previously applied to trying to understand the AMOC, an equation is developed for AMOC flow as a function of the meridional density gradient or the corresponding temperature gradient. The equation is based on the similarity between the AMOC and an industrial thermosyphon loop cooler, which circulates a heat transfer liquid without using a mechanical pump. Extending this equation with an analogy between the flow of heat and electricity explains why the AMOC flow oscillates and what determines its period. Calculated values for AMOC flow and AMO oscillation period are in good agreement with measured values. PMID:24940739

Atlantic meridional overturning circulation during the Last Glacial Maximum.

PubMed

Lynch-Stieglitz, Jean; Adkins, Jess F; Curry, William B; Dokken, Trond; Hall, Ian R; Herguera, Juan Carlos; Hirschi, Joël J-M; Ivanova, Elena V; Kissel, Catherine; Marchal, Olivier; Marchitto, Thomas M; McCave, I Nicholas; McManus, Jerry F; Mulitza, Stefan; Ninnemann, Ulysses; Peeters, Frank; Yu, Ein-Fen; Zahn, Rainer

2007-04-06

The circulation of the deep Atlantic Ocean during the height of the last ice age appears to have been quite different from today. We review observations implying that Atlantic meridional overturning circulation during the Last Glacial Maximum was neither extremely sluggish nor an enhanced version of present-day circulation. The distribution of the decay products of uranium in sediments is consistent with a residence time for deep waters in the Atlantic only slightly greater than today. However, evidence from multiple water-mass tracers supports a different distribution of deep-water properties, including density, which is dynamically linked to circulation.

The global topography mission gains momentum

USGS Publications Warehouse

Farr, Tom; Evans, Diane; Zebker, Howard; Harding, David; Bufton, Jack; Dixon, Timothy; Vetrella, S.; Gesch, Dean B.

1995-01-01

An accurate description of the surface elevation of the Earth is of fundamental importance to many branches of Earth science. Continental topographic data are required for studies of hydrology, ecology, glaciology, geomorphology, and atmospheric circulation. For example, in hydrologic and terrestrial ecosystem studies, topography exerts significant control on intercepted solar radiation, water runoff and subsurface water inventory, microclimate, vegetation type and distribution, and soil development. The topography of the polar ice caps and mountain glaciers directly reflects ice-flow dynamics and is closely linked to global climate and sea level change.

Seasonal variations of thermocline circulation and ventilation in the Indian Ocean

NASA Astrophysics Data System (ADS)

You, Yuzhu

1997-05-01

Two seasonal hydrographic data sets, including temperature, salinity, dissolved oxygen, and nutrients, are used in a mixing model which combines cluster analysis with optimum multiparameter analysis to determine the spreading and mixing of the thermocline waters in the Indian Ocean. The mixing model comprises a system of four major source water masses, which were identified in the thermocline through cluster analysis. They are Indian Central Water (ICW), North Indian Central Water (NICW) interpreted as aged ICW, Australasian Mediterranean Water (AAMW), and Red Sea Water (RSW)/Persian Gulf Water (PGW). The mixing ratios of these water masses are quantified and mapped on four isopycnal surfaces which span the thermocline from 150 to 600 m in the northern Indian Ocean, on two meridional sections along 60°E and 90°E, and on two zonal sections along 10°S and 6°N. The mixing ratios and pathways of the thermocline water masses show large seasonal variations, particularly in the upper 400-500 m of the thermocline. The most prominent signal of seasonal variation occurs in the Somali Current, the western boundary current, which appears only during the SW (summer) monsoon. The northward spreading of ICW into the equatorial and northern Indian Ocean is by way of the Somali Current centered at 300-400 m on the σθ=26.7 isopycnal surface during the summer monsoon and of the Equatorial Countercurrent during the NE (winter) monsoon. More ICW carried into the northern Indian Ocean during the summer monsoon is seen clearly in the zonal section along 6°N. NICW spreads southward through the western Indian Ocean and is stronger during the winter monsoon. AAMW appears in both seasons but is slightly stronger during the summer in the upper thermocline. The westward flow of AAMW is by way of the South Equatorial Current and slightly bends to the north on the σθ=26.7 isopycnal surface during the summer monsoon, indicative of its contribution to the western boundary current. Outflow of RSW/PGW seems effectively blocked by the continuation of strong northward jet of the Somali Current along the western Arabian Sea during the summer, giving a rather small contribution of only up to 20% in the Arabian Sea. A schematic summer and winter thermocline circulation emerges from this study. Both hydrography and water - mass mixing ratios suggest that the contribution of the water from the South Indian Ocean and from the Indo-Pacific through flow controls the circulation and ventilation in the western boundary region during the summer. However, during the winter the water is carried into the eastern boundary by the Equatorial Countercurrent and leaks into the eastern Bay of Bengal, from where the water is advected into the northwestern Indian Ocean by the North Equatorial Current. The so-called East Madagascar Current as a southward flow occurs only during the summer, as is suggested by both hydrography and water-mass mixing patterns from this paper. During the winter (austral summer) the current seems reversal to a northward flow along east of Madagascar, somewhat symmetrical to the Somali Current in the north.

California coastal processes study, LANDSAT 2

NASA Technical Reports Server (NTRS)

Pirie, D. M.; Steller, D. D. (Principal Investigator)

1977-01-01

The authors have identified the following significant results. By using suspended sediments as tracers, objectives were met by qualitative definition of the nearshore circulation along the entire coast of California with special study sites at Humboldt Bay, the mouth of the Russian River, San Francisco Bay, Monterey Bay, and the Santa Barbara Channel. Although LANDSAT primarily imaged fines and silts in the surface waters, the distribution of sediments allowed an examination of upwelling, convergences and coastal erosion and deposition. In Monterey Bay and Humboldt Bay, these coastal phenomena were used to trace seasonal trends in surface currents.

Variability of the Somali Current and eddies during the southwest monsoon regimes

NASA Astrophysics Data System (ADS)

Trott, Corinne B.; Subrahmanyam, Bulusu; Murty, V. S. N.

2017-09-01

The meso-scale eddies and currents in the Arabian Sea are analyzed using different satellite observations, Simple Oceanic Data Assimilation (SODA) reanalysis, and Ocean Reanalysis System 4 (ORAS4) from 1993 to 2016 to investigate the impacts of Southwest (SW) Monsoon strength on Somali Current (SC) mesoscale circulations such as the Great Whirl (GW), the Socotra Eddy (SE), the Southern Gyre (SG), and smaller eddies. Increased Ekman pumping during stronger SW monsoons strengthens coastal upwelling along the Somali coast. The Arabian Sea basin-wide anticyclonic circulation and presence of the GW form mesoscale circulation patterns favourable to advection of upwelled waters eastward into the central Arabian Sea. In September, after the SW monsoon winds reach peak strength in July and August, a higher number of discrete anticyclonic eddies with higher (> 20 cm) sea surface height anomalies develop in strong and normal intensity SW monsoon seasons than weaker SW monsoon seasons.

Spin-Down of the North Atlantic Subpolar Circulation

NASA Technical Reports Server (NTRS)

Hakkinen, S.; Rhines, P. B.

2004-01-01

Dramatic changes have occurred in the mid-to-high-latitude North Atlantic Ocean as evidenced by TOPEX/Poseidon observations of sea surface height (SSH) in the subpolar gyre and the Gulf Stream. Analysis of altimeter data shows that subpolar SSH has increased during the 1990s and the geostrophic velocity derived from altimeter data shows a decline in the gyre circulation. Direct current-meter observations in the boundary current of the Labrador Sea support the trend in the 199Os, and, together with hydrographic data show that in the mid-late 1990s the trend extends deep in the water column. We find that buoyancy forcing over the northern North Atlantic has a dynamic effect consistent with the altimeter data and hydrographic observations: a weak thermohaline forcing and the subsequent decay of the domed structure of the subpolar isopycnals would give rise to the observed anticyclonic circulation trend.

Nitrous oxide and methane in Atlantic and Mediterranean waters in the Strait of Gibraltar: Air-sea fluxes and inter-basin exchange

NASA Astrophysics Data System (ADS)

de la Paz, M.; Huertas, I. E.; Flecha, S.; Ríos, A. F.; Pérez, F. F.

2015-11-01

The global ocean plays an important role in the overall budget of nitrous oxide (N2O) and methane (CH4), as both gases are produced within the ocean and released to the atmosphere. However, for large parts of the open and coastal oceans there is little or no spatial data coverage for N2O and CH4. Hence, a better assessment of marine emissions estimates is necessary. As a contribution to remedying the scarcity of data on marine regions, N2O and CH4 concentrations have been determined in the Strait of Gibraltar at the ocean Fixed Time series (GIFT). During six cruises performed between July 2011 and November 2014 samples were collected at the surface and various depths in the water column, and subsequently measured using gas chromatography. From this we were able to quantify the temporal variability of the gas air-sea exchange in the area and examine the vertical distribution of N2O and CH4 in Atlantic and Mediterranean waters. Results show that surface Atlantic waters are nearly in equilibrium with the atmosphere whereas deeper Mediterranean waters are oversaturated in N2O, and a gradient that gradually increases with depth was detected in the water column. Temperature was found to be the main factor responsible for the seasonal variability of N2O in the surface layer. Furthermore, although CH4 levels did not reveal any feature clearly associated with the circulation of water masses, vertical distributions showed that higher concentrations are generally observed in the Atlantic layer, and that the deeper Mediterranean waters are considerably undersaturated (by up to 50%). Even though surface waters act as a source of atmospheric N2O during certain periods, on an annual basis the net N2O flux in the Strait of Gibraltar is only 0.35 ± 0.27 μmol m-2 d-1, meaning that these waters are almost in a neutral status with respect to the atmosphere. Seasonally, the region behaves as a slight sink for atmospheric CH4 in winter and as a source in spring and fall. Approximating the circulation pattern in the Strait to a bi-layer scheme, N2O exchange between basins was also calculated, and a net export from the Mediterranean Sea to the Atlantic Ocean equivalent to 39 μmol m-2 d-1 was found.

Wind effect on diurnal thermally driven flow in vegetated nearshore of a lake

NASA Astrophysics Data System (ADS)

Lin, Y. T.

2014-12-01

In this study, a highly idealized model is developed to discuss the interplay of diurnal heating/cooling induced buoyancy and wind stress on thermally driven flow over a vegetated slope. Since the model is linear, the horizontal velocity components can be broken into buoyancy-driven and surface wind-driven parts. Due to the presence of rooted emergent vegetation, the circulation strength even under the surface wind condition is still significantly reduced, and the transient (adjustment) stage for the initial conditions is shorter than that without vegetation. The flow in shallows is dominated by a viscosity/buoyancy balance as the case without wind, while the effect of wind stress is limited to the upper layer in deep water. In the lower layer of deep regions, vegetative drag is prevailing except the near bottom regions, where viscosity dominates. Under the unidirectional wind condition, a critical dimensionless shear stress to stop the induced flow can be found and is a function of horizontal location . For the periodic wind condition, if the two forcing mechanisms work in concert, the circulation magnitude can be increased. For the case where buoyancy and wind shear stress act against each other, the circulation strength is reduced and its structure becomes more complex. However, the flow magnitudes near the bottom for and are comparable because surface wind almost has no influence.

The Galapagos Spreading Center at 86°W: A detailed geothermal field study

NASA Astrophysics Data System (ADS)

Green, Kenneth E.; von Herzen, Richard P.; Williams, David L.

1981-02-01

Appendix is available with entire article on microfiche. Orderfrom American Geophysical Union, 2000 Florida Avenue, N.W.,Washington, D.C. 20009. Document J80-013; $01.00. Payment mustaccompany order. We report here measurements of the heat flow field of the Galapagos Spreading Center on crust of age less than 1.0 m.y. The 443 measurements in an area of about 570 km2 reveal the general planform of the geothermal flux and permit the first truly areal estimate of the near-axis conductive heat flux. The intrusion process and associated hydrothermal circulation dominate the surface heat flow pattern, with circulation apparently continuing beyond the limits of our survey. The areal average of the conductive heat flux is 7.1 ± 0.8 HFU (295 ± 33 mW/m2), about one-third the heat flux predicted by plate models. The remaining heat is apparently removed by venting of hydrothermal waters at the spreading axis and through basalt outcrops and hydrothermal mounds off axis. The pattern of surface heat flux is lineated parallel to the axis and the strongly lineated topography. Sharp lateral gradients in the heat flow, greater than 10 HFU/km near escarpments and commonly expressed as high heat flow at the tops of the scarps and lower heat flow in the valleys, may indicate a local concentration of the circulation by surface fault systems and/or variable sediment thickness.

The leading mode of observed and CMIP5 ENSO-residual sea surface temperatures and associated changes in Indo-Pacific climate

USGS Publications Warehouse

Funk, Christopher C.; Hoell. Andrew,

2015-01-01

WPWM circulation changes appear consistent with a Matsuno–Gill-like atmospheric response associated with an ocean–atmosphere dipole structure contrasting increased (decreased) western (eastern) Pacific precipitation, SSHs, and ocean temperatures. These changes have enhanced the Walker circulation and modulated weather on a global scale. An AGCM experiment and the WPWM of global boreal spring precipitation indicate significant drying across parts of East Africa, the Middle East, the southwestern United States, southern South America, and Asia. Changes in the WPWM have tracked closely with precipitation and the increase in drought frequency over the semiarid and water-insecure areas of East Africa, the Middle East, and southwest Asia.

Modelling of surface-water temperature for the estimation of the Czech fishery productivity under the climate change

NASA Astrophysics Data System (ADS)

Svobodová, Eva; Trnka, Miroslav; Kopp, Radovan; Mareš, Jan; Dubrovský, Martin; Spurný, Petr; Žalud, Zděněk

2015-04-01

Freshwater fish production is significantly correlated with water temperature which is expected to increase under the climate change. This study is dealing with the estimation of the change of water temperature in productive ponds and its impact on the fishery in the Czech Republic. Calculation of surface-water temperature which was based on three-day mean of the air temperature was developed and tested in several ponds in three main fish production areas. Output of surface-water temperature model was compared with measured data and showed that the lower range of model accuracy is surface-water temperature 3°C, under this temperature threshold the model loses its predictive competence. In the expecting of surface-water temperature above the temperature 3°C the model has proved the well consistence between observed and modelled surface-water temperature (R 0.79 - 0.96). Verified model was applied in the conditions of climate change determined by the pattern scaling method, in which standardised scenarios were derived from five global circulation models MPEH5, CSMK3, IPCM4, GFCM21 and HADGEM. Results were evaluated with regard to thresholds which characterise the fish species requirements on water temperature. Used thresholds involved the upper temperature threshold for fish survival and the tolerable number of days in continual period with mentioned threshold surface-water temperature. Target fish species were Common carp (Cyprinus carpio), Maraene whitefish (Coregonus maraena), Northern whitefish (Coregonus peled) and Rainbow trout (Oncorhynchus mykis). Results indicated the limitation of the Czech fish-farming in terms of i) the increase of the length of continual periods with surface-water temperature above the threshold appropriate to given fish species toleration, ii) the increase of the number of continual periods with surface-water temperature above the threshold, both appropriate to given fish species toleration, and iii) the increase of overall number of days within the continual period with temperature above the threshold tolerated by given fish species. ACKNOWLEDGEMENTS: This study was funded by project "Building up a multidisciplinary scientific team focused on drought" No. CZ.1.07/2.3.00/20.0248.

Observation of water mass characteristics in the southwestern Mariana Trench

NASA Astrophysics Data System (ADS)

Xu, H.; Xie, Q.; Hong, B.

2016-12-01

The identification of large water mass characteristic can help oceanographer to better understand the oceanic circulation structures and other physical processes in open oceans. In current stage, the water mass characteristics were recognized well by extensive observation in the upper ocean, however, it was rarely studied in deep oceans, especially for deep trench with > 6000 m depth. In this study, we use observed data collected by CTDs during several surveys to investigate the water mass physical characteristic and transport in the world deepest trench, `Challenger Deep', in the southwestern Mariana Trench. The preliminary results show complex vertical structures of water mass in this trench. From surface to 4500 m, the water masses are occupied by typical tropical surface water, NPTUW, NPMW, NPIW and NPDW. Under 4500m, the water mass shows mixing characteristics of NPDW and AABW, which indicate AABW can be transported by form the deep ocean of the South Ocean to Northwestern Pacific and it can affect local water mass characteristics. The baroclinic geostrophic current calculated from the CTDs data shows the westerly transport of water mass can reach about 1.0 SV in the trench which is close to previous results.

Water Ice Cloud Opacities and Temperatures Derived from the Viking IRTM Data Set

NASA Technical Reports Server (NTRS)

TamppariL. K.; Zurek, R. W.; Paige, D. A.

1999-01-01

The degree to which water ice clouds play a role in the Mars climate is unknown. Latent heating of water ice clouds is small and since most hazes appeared to be thin (tau less than or = 1) their radiative effects have been neglected. Condensation likely limits the vertical extent of water vapor in the water column and a lowering of the condensation altitude, as seen in the northern spring and summer, could increase the seasonal exchange of water between the atmosphere and the surface. It has been suggested that water ice cloud formation is more frequent and widespread in the aphelic hemisphere (currently the northern). This may limit water to the northern hemisphere through greater exchange with the regolith and through restricted southward transport of water vapor by the Mars Hadley circulation. In addition, it has been suggested that water ice cloud formation also controls the vertical distribution of atmospheric dust in some seasons. This scavenging of dust may Continuing from the IRTM cloud maps, derived cloud opacities and cloud temperatures for several locations and seasons will be presented. Sensitivities to cloud particle sizes, surface temperature, and dust opacity will be discussed.

Water and the thermal evolution of carbonaceous chondrite parent bodies

NASA Technical Reports Server (NTRS)

Grimm, Robert E.; Mcsween, Harry Y., Jr.

1989-01-01

Two hypotheses are proposed for the aqueous alteration of carbonaceous chondrites within their parent bodies, in which respectively the alteration occurs (1) throughout the parent body interior, or (2) in a postaccretional surface regolith; both models assume an initially homogeneous mixture of ice and rock that is heated through the decay of Al-26. Water is seen to exert a powerful influence on chondrite evolution through its role of thermal buffer, permitting substitution of a low temperature aqueous alteration for high temperature recrystallization. It is quantitatively demonstrated that liquid water may be introduced by either hydrothermal circulation, vapor diffusion from below, or venting due to fracture.

Changes in Ocean Circulation with an Ice-Free Arctic: Reconstructing Early Holocene Arctic Ocean Circulation Using Geochemical Signals from Individual Neogloboquadrina pachyderma (sinistral) Shells

NASA Astrophysics Data System (ADS)

Livsey, C.; Spero, H. J.; Kozdon, R.

2016-12-01

The impacts of sea ice decrease and consequent hydrologic changes in the Arctic Ocean will be experienced globally as ocean and atmospheric temperatures continue to rise, though it is not evident to what extent. Understanding the structure of the Arctic water column during the early/mid Holocene sea ice minimum ( 6-10 kya), a post-glacial analogue of a seasonally ice-free Arctic, will help us to predict what the changes we can expect as the Earth warms over the next century. Neogloboquadrina pachyderma (sinistral; Nps) is a species of planktonic foraminifera that dominates assemblages in the polar oceans. This species grows its chambers (ontogenetic calcite) in the surface waters and subsequently descends through the water column to below the mixed layer where it quickly adds a thick crust of calcite (Kohfeld et al., 1996). Therefore, geochemical signals from both the surface waters and sub-mixed layer depths are captured within single Nps shells. We were able to target <5 μm - sized domains for δ18O using secondary ion mass spectrometry (SIMS), therefore capturing signals from both the ontogenetic and crust calcite in single Nps shells. This data was combined with laser ablation- inductively coupled mass spectrometry (LA-ICPMS) Mg/Ca profiles of trace metals through the two layers of calcite of the same shells, to determine the thermal structure of the water column. Combining δ18O, temperature, and salinity gradients from locations across the Arctic basin allow us to reconstruct the hydrography of the early Holocene Arctic sea ice minimum. These results will be compared with modern Arctic water column characteristics in order to develop a conceptual model of Arctic Ocean oceanographic change due to global warming. Kohfeld, K.E., Fairbanks, R.G., Smith, S.L., Walsh, I.D., 1996. Neogloboquadrina pachyderma(sinistral coiling) as paleoceanographic tracers in polar oceans: Evidence from northeast water polynya plankton tows, sediment traps, and surface sediments. Paleoceanography 11, 679-699.

Cloud Formation and Water Transport on Mars after Major Outflow Events

NASA Technical Reports Server (NTRS)

Santiago, D. L.; Colaprete, A.; Kreslavsky, M.; Kahre, M. A.; Asphaug, E.

2012-01-01

The triggering of a robust water cycle on Mars might have been caused by the gigantic flooding events evidenced by outflow channels. We use the Ames Mars General Circulation Model (MGCM) to test this hypothesis, studying how these presumably abrupt eruptions of water might have affected the climate of Mars in the past. We model where the water ultimately went as part of a transient atmospheric water cycle, to answer questions including: (1) Can sudden introductions of large amounts of water on the Martian surface lead to a new equilibrated water cycle? (2) What are the roles of water vapor and water ice clouds to sudden changes in the water cycle on Mars? (3) How are radiative feedbacks involved with this? (4) What is the ultimate fate of the outflow water? (5) Can we tie certain geological features to outflow water redistributed by the atmosphere?

Longitudinal differentiation among pelagic populations in a planktic foraminifer

PubMed Central

Ujiié, Yurika; Asami, Takahiro; de Garidel-Thoron, Thibault; Liu, Hui; Ishitani, Yoshiyuki; de Vargas, Colomban

2012-01-01

Evolutionary processes in marine plankton have been assumed to be dependent on the oceanic circulation system, which transports plankton between populations in marine surface waters. Gene flow facilitated by oceanic currents along longitudinal gradients may efficiently impede genetic differentiation of pelagic populations in the absence of confounding marine environmental effects. However, how responsible oceanic currents are for the geographic distribution and dispersal of plankton is poorly understood. We examined the phylogeography of the planktic foraminifer Pulleniatina obliquiloculata in the Indo-Pacific Warm Pool (IPWP) by using partial small subunit ribosomal DNA (SSU rDNA) sequences. We found longitudinal clines in the frequencies of three distinct genetic types in the IPWP area. These frequencies were correlated with environmental factors that are characteristic of three water masses in the IPWP. Noteworthy, populations inhabiting longitudinally distant water masses at the Pacific and Indian sides of the IPWP were genetically different, despite transportation of individuals via oceanic currents. These results demonstrate that populations of pelagic plankton have diverged genetically among different water masses within a single climate zone. Changes of the oceanic circulation system could have impacted the geographic patterns of dispersal and divergence of pelagic plankton. PMID:22957176

Simulated variability of the Atlantic meridional overturning circulation

NASA Astrophysics Data System (ADS)

Bentsen, M.; Drange, H.; Furevik, T.; Zhou, T.

To examine the multi-annual to decadal scale variability of the Atlantic Meridional Overturning Circulation (AMOC) we conducted a four-member ensemble with a daily reanalysis forced, medium-resolution global version of the isopycnic coordinate ocean model MICOM, and a 300-years integration with the fully coupled Bergen Climate Model (BCM). The simulations of the AMOC with both model systems yield a long-term mean value of 18 Sv and decadal variability with an amplitude of 1-3 Sv. The power spectrum of the inter-annual to decadal scale variability of the AMOC in BCM generally follows the theoretical red noise spectrum, with indications of increased power near the 20-years period. Comparison with observational proxy indices for the AMOC, e.g. the thickness of the Labrador Sea Water, the strength of the baroclinic gyre circulation in the North Atlantic Ocean, and the surface temperature anomalies along the mean path of the Gulf Stream, shows similar trends and phasing of the variability, indicating that the simulated AMOC variability is robust and real. Mixing indices have been constructed for the Labrador, the Irminger and the Greenland-Iceland-Norwegian (GIN) seas. While convective mixing in the Labrador and the GIN seas are in opposite phase, and linked to the NAO as observations suggest, the convective mixing in the Irminger Sea is in phase with or leads the Labrador Sea. Newly formed deep water is seen as a slow, anomalous cold and fresh, plume flowing southward along the western continental slope of the Atlantic Ocean, with a return flow of warm and saline water on the surface. In addition, fast-travelling topographically trapped waves propagate southward along the continental slope towards equator, where they go east and continue along the eastern rim of the Atlantic. For both types of experiments, the Northern Hemisphere sea level pressure and 2 m temperature anomaly patterns computed based on the difference between climate states with strong and weak AMOC yields a NAO-like pattern with intensified Icelandic low and Azores high, and a warming of 0.25-0.5 °C of the central North Atlantic sea-surface temperature (SST). The reanalysis forced simulations indicate a coupling between the Labrador Sea Water production rate and an equatorial Atlantic SST index in accordance with observations. This coupling is not identified in the coupled simulation.

Pronounced centennial-scale Atlantic Ocean climate variability correlated with Western Hemisphere hydroclimate.

PubMed

Thirumalai, Kaustubh; Quinn, Terrence M; Okumura, Yuko; Richey, Julie N; Partin, Judson W; Poore, Richard Z; Moreno-Chamarro, Eduardo

2018-01-26

Surface-ocean circulation in the northern Atlantic Ocean influences Northern Hemisphere climate. Century-scale circulation variability in the Atlantic Ocean, however, is poorly constrained due to insufficiently-resolved paleoceanographic records. Here we present a replicated reconstruction of sea-surface temperature and salinity from a site sensitive to North Atlantic circulation in the Gulf of Mexico which reveals pronounced centennial-scale variability over the late Holocene. We find significant correlations on these timescales between salinity changes in the Atlantic, a diagnostic parameter of circulation, and widespread precipitation anomalies using three approaches: multiproxy synthesis, observational datasets, and a transient simulation. Our results demonstrate links between centennial changes in northern Atlantic surface-circulation and hydroclimate changes in the adjacent continents over the late Holocene. Notably, our findings reveal that weakened surface-circulation in the Atlantic Ocean was concomitant with well-documented rainfall anomalies in the Western Hemisphere during the Little Ice Age.

Pronounced centennial-scale Atlantic Ocean climate variability correlated with Western Hemisphere hydroclimate

USGS Publications Warehouse

Thirumalai, Kaustubh; Quinn, Terrence M.; Okumura, Yuko; Richey, Julie; Partin, Judson W.; Poore, Richard Z.; Moreno-Chamarro, Eduardo

2018-01-01

Surface-ocean circulation in the northern Atlantic Ocean influences Northern Hemisphere climate. Century-scale circulation variability in the Atlantic Ocean, however, is poorly constrained due to insufficiently-resolved paleoceanographic records. Here we present a replicated reconstruction of sea-surface temperature and salinity from a site sensitive to North Atlantic circulation in the Gulf of Mexico which reveals pronounced centennial-scale variability over the late Holocene. We find significant correlations on these timescales between salinity changes in the Atlantic, a diagnostic parameter of circulation, and widespread precipitation anomalies using three approaches: multiproxy synthesis, observational datasets, and a transient simulation. Our results demonstrate links between centennial changes in northern Atlantic surface-circulation and hydroclimate changes in the adjacent continents over the late Holocene. Notably, our findings reveal that weakened surface-circulation in the Atlantic Ocean was concomitant with well-documented rainfall anomalies in the Western Hemisphere during the Little Ice Age.

Intermediate and deep water mass distribution in the Pacific during the Last Glacial Maximum inferred from oxygen and carbon stable isotopes

NASA Astrophysics Data System (ADS)

Herguera, J. C.; Herbert, T.; Kashgarian, M.; Charles, C.

2010-05-01

Intermediate ocean circulation changes during the last Glacial Maximum (LGM) in the North Pacific have been linked with Northern Hemisphere climate through air-sea interactions, although the extent and the source of the variability of the processes forcing these changes are still not well resolved. The ventilated volumes and ages in the upper wind driven layer are related to the wind stress curl and surface buoyancy fluxes at mid to high latitudes in the North Pacific. In contrast, the deeper thermohaline layers are more effectively ventilated by direct atmosphere-sea exchange during convective formation of Subantarctic Mode Waters (SAMW) and Antarctic Intermediate Waters (AAIW) in the Southern Ocean, the precursors of Pacific Intermediate Waters (PIW) in the North Pacific. Results reported here show a fundamental change in the carbon isotopic gradient between intermediate and deep waters during the LGM in the eastern North Pacific indicating a deepening of nutrient and carbon rich waters. These observations suggest changes in the source and nature of intermediate waters of Southern Ocean origin that feed PIW and enhanced ventilation processes in the North Pacific, further affecting paleoproductivity and export patters in this basin. Furthermore, oxygen isotopic results indicate these changes may have been accomplished in part by changes in circulation affecting the intermediate depths during the LGM.

Global monitoring of Sea Surface Salinity with Aquarius

NASA Technical Reports Server (NTRS)

Lagerloef, G. S. E.; LeVine, D. M.; Chao, Yi; Colomb, R.; Nollmann, I.

2005-01-01

Aquarius is a microwave remote sensing system designed to obtain global maps of the surface salinity field of the oceans from space. It will be flown on the Aquarius/SAC-D mission, a partnership between the USA (NASA) and Argentina (CONAE) with launch scheduled for late in 2008. The objective of Aquarius is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This will provide data to address scientific questions associated with ocean circulation and its impact on climate. For example, salinity is needed to understand the large scale thermohaline circulation, driven by buoyancy, which moves large masses of water and heat around the globe. Of the two variables that determine buoyancy (salinity and temperature), temperature is already being monitored. Salinity is the missing variable needed to understand this circulation. Salinity also has an important role in energy exchange between the ocean and atmosphere, for example in the development of fresh water lenses (buoyant water that forms stable layers and insulates water below from the atmosphere) which alter the air-sea coupling. Aquarius is a combination radiometer and scatterometer (radar) operating at L-band (1.413 GHz for the radiometer and 1.26 GHz for the scatterometer). The primary instrument,for measuring salinity is the radiometer which is able to detect salinity because of the modulation salinity produces on the thermal emission from sea water. This change is detectable at the long wavelength end of the microwave spectrum. The scatterometer will provide a correction for surface roughness (waves) which is one of the greatest unknowns in the retrieval. The sensor will be in a sun-synchronous orbit at about 650 km with equatorial crossings of 6am/6pm. The antenna for these two instruments is a 3 meter offset fed reflector with three feeds arranged in pushbroom fashion looking away from the sun toward the shadow side of the orbit to minimize sunglint. The mission goal is to produce maps of the salinity field globally once each month with an accuracy of 0.2 psu and a spatial resolution of 100 km. This will be adequate to address l&ge scale features of the salinity field of the open ocean. The temporal resolution is sufficient to address seasonal changes and a three year mission is planned to-collect sufficient data to look for interannual variation. Aquarius is being developed by NASA as part of the Earth System Science Pathfinder (ESSP) program. The SAC-D mission is being developed by CONAE and will include the space craft and several additional instruments, including visible and infrared cameras and a microwave radiometer to monitor rain and wind velocity over the oceans, and sea ice.

SWOT: The Surface Water and Ocean Topography Mission. Wide- Swath Altimetric Elevation on Earth

NASA Technical Reports Server (NTRS)

Fu, Lee-Lueng (Editor); Alsdorf, Douglas (Editor); Morrow, Rosemary; Rodriguez, Ernesto; Mognard, Nelly

2012-01-01

The elevation of the surface of the ocean and freshwater bodies on land holds key information on many important processes of the Earth System. The elevation of the ocean surface, called ocean surface topography, has been measured by conventional nadirlooking radar altimeter for the past two decades. The data collected have been used for the study of large-scale circulation and sea level change. However, the spatial resolution of the observations has limited the study to scales larger than about 200 km, leaving the smaller scales containing substantial kinetic energy of ocean circulation that is responsible for the flux of heat, dissolved gas and nutrients between the upper and the deep ocean. This flux is important to the understanding of the ocean's role in regulatingfuture climate change.The elevation of the water bodies on land is a key parameter required for the computation of storage and discharge of freshwater in rivers, lakes, and wetlands. Globally, the spatial and temporal variability of water storage and discharge is poorly known due to the lack of well-sampled observations. In situ networks measuring river flows are declining worldwide due to economic and political reasons. Conventional altimeter observations suffers from the complexity of multiple peaks caused by the reflections from water, vegetation canopy and rough topography, resulting in much less valid data over land than over the ocean. Another major limitation is the large inter track distance preventing good coverage of rivers and other water bodies.This document provides descriptions of a new measurement technique using radar interferometry to obtain wide-swath measurement of water elevation at high resolution over both the ocean and land. Making this type of measurement, which addresses the shortcomings of conventional altimetry in both oceanographic and hydrologic applications, is the objective of a mission concept called Surface Water and Ocean Topography (SWOT), which was recommended by the National Research Council's first decadal survey of NASA's Earth science program. This document provides wide-ranging examples of research opportunities in oceanography and land hydrology that would be enabled by the new type of measurement. Additional applications in many other branches of Earth System science ranging from ocean bathymetry to sea ice dynamics are also discussed. Many of the technical issues in making the measurement are discussed as well. Also presented is a preliminary design of the SWOT Mission concept, which is being jointly developed by NASA and CNES, with contributions from the Canadian Space Agency.

Trends and variability in the Hadley circulation over the Last Millennium from the proxy record

NASA Astrophysics Data System (ADS)

Horlick, K. A.; Noone, D.; Hakim, G. J.; Tardif, R.; Anderson, D. M.; Perkins, W. A.; Erb, M. P.; Steig, E. J.

2017-12-01

The Hadley circulation (HC) is the dominant atmospheric overturning circulation controlling variability in precipitation distribution in the tropics and subtropics, affecting agricultural production and water resource allocation, among other human civilizational dependencies. A lack of pre-instrumental data-model synthesis has been cited as the barrier to diagnostic analyses of the variability in width, position, and intensity of the HC and its response to anthropogenic forcing. We analyze the HC, and its rising limb associated with the Intertropical Convergence Zone (ITCZ), over the past 1000 years using the Last Millennium Reanalysis (LMR) (Hakim et al. 2016). The LMR systematically blends the dynamical constraints of climate models with a proxy network of coral, tree ring, and ice core records. It allows for a spatiotemporal analysis with robust uncertainty measures. A three dimensional analysis of LMR wind fields shows an centennial-scale circulatory trend over the last 200 years resembling that which might be expected from an ENSO and PDO-like structure. An observed aridification of both the central equatorial Pacific and the southwest United States, a strengthening of the east-west sea surface temperature and sea level pressure gradient in the equatorial Pacific, and a strengthening of the Walker overturning circulation suggest a more "La Niña-like" mean state. This is compared to our statistical description of the centennial-scale mean circulation and variability of the previous millennia. Similarly, precipitation and relative humidity trends suggest expansion and asymmetric meridional movement of the Hadley circulation as a result of asymmetric shifts in mean ITCZ position and intensity. These observations are then compared to free running model simulations, other instrumental reanalysis products, and late-Holocene aerosol, solar, and greenhouse forcings. This LMR reconstruction improves upon previous work by enabling a proxy-consistent, quantitative analysis of Hadley circulation intensity, structure, and variability rather than relying on simpler empirical reconstructions of variables like surface temperature alone.

Changing Arctic Ocean freshwater pathways.

PubMed

Morison, James; Kwok, Ron; Peralta-Ferriz, Cecilia; Alkire, Matt; Rigor, Ignatius; Andersen, Roger; Steele, Mike

2012-01-04

Freshening in the Canada basin of the Arctic Ocean began in the 1990s and continued to at least the end of 2008. By then, the Arctic Ocean might have gained four times as much fresh water as comprised the Great Salinity Anomaly of the 1970s, raising the spectre of slowing global ocean circulation. Freshening has been attributed to increased sea ice melting and contributions from runoff, but a leading explanation has been a strengthening of the Beaufort High--a characteristic peak in sea level atmospheric pressure--which tends to accelerate an anticyclonic (clockwise) wind pattern causing convergence of fresh surface water. Limited observations have made this explanation difficult to verify, and observations of increasing freshwater content under a weakened Beaufort High suggest that other factors must be affecting freshwater content. Here we use observations to show that during a time of record reductions in ice extent from 2005 to 2008, the dominant freshwater content changes were an increase in the Canada basin balanced by a decrease in the Eurasian basin. Observations are drawn from satellite data (sea surface height and ocean-bottom pressure) and in situ data. The freshwater changes were due to a cyclonic (anticlockwise) shift in the ocean pathway of Eurasian runoff forced by strengthening of the west-to-east Northern Hemisphere atmospheric circulation characterized by an increased Arctic Oscillation index. Our results confirm that runoff is an important influence on the Arctic Ocean and establish that the spatial and temporal manifestations of the runoff pathways are modulated by the Arctic Oscillation, rather than the strength of the wind-driven Beaufort Gyre circulation.

Exploring exomoon atmospheres with an idealized general circulation model

NASA Astrophysics Data System (ADS)

Haqq-Misra, Jacob; Heller, René

2018-06-01

Recent studies have shown that large exomoons can form in the accretion disks around super-Jovian extrasolar planets. These planets are abundant at about 1 AU from Sun-like stars, which makes their putative moons interesting for studies of habitability. Technological advances could soon make an exomoon discovery with Kepler or the upcoming CHEOPS and PLATO space missions possible. Exomoon climates might be substantially different from exoplanet climates because the day-night cycles on moons are determined by the moon's synchronous rotation with its host planet. Moreover, planetary illumination at the top of the moon's atmosphere and tidal heating at the moon's surface can be substantial, which can affect the redistribution of energy on exomoons. Using an idealized general circulation model with simplified hydrologic, radiative, and convective processes, we calculate surface temperature, wind speed, mean meridional circulation, and energy transport on a 2.5 Mars-mass moon orbiting a 10-Jupiter-mass at 1 AU from a Sun-like star. The strong thermal irradiation from a young giant planet causes the satellite's polar regions to warm, which remains consistent with the dynamically-driven polar amplification seen in Earth models that lack ice-albedo feedback. Thermal irradiation from young, luminous giant planets onto water-rich exomoons can be strong enough to induce water loss on a planet, which could lead to a runaway greenhouse. Moons that are in synchronous rotation with their host planet and do not experience a runaway greenhouse could experience substantial polar melting induced by the polar amplification of planetary illumination and geothermal heating from tidal effects.

Probabilistic Water Availability Prediction in the Rio Grande Basin using Large-scale Circulation Indices as Precursor

NASA Astrophysics Data System (ADS)

Khedun, C. P.; Mishra, A. K.; Giardino, J. R.; Singh, V. P.

2011-12-01

Hydrometeorological conditions, and therefore water availability, is affected by large-scale circulation indices. In the Rio Grande, which is a transboundary basin shared between the United States and Mexico, the Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) influence local hydrological conditions. Different sub-regions of the basin exhibit varying degrees of correlation, but in general, an increase (decrease) in runoff during El Niños (La Niñas) is noted. Positive PDO enhances the effect of El Niño and dampens the negative effect of La Niña, and when it is in its neutral/transition phase, La Niña dominates climatic conditions and reduces water availability. Further, lags of up to 3 months have been found between ENSO and precipitation in the basin. We hypothesize that (1) a trivariate statistical relationship can be established between the two climate indices and water availability, and (2) the relationship can be used to predict water availability based on projected PDO and ENSO conditions. We use copula to establish the dependence between climate indices and water availability. Water availability is generated from Noah land surface model (LSM), forced with the North American Land Data Assimilation System Phase 2 (NLDAS-2). The model is run within NASA GSFC's Land Information System. LSM generated runoff gives a more realistic picture of available surface water as it is not affected by anthropogenic changes, such as the construction of dams, diversions, and other land use land cover changes, which may obscure climatic influences. Marginals from climate indices and runoff are from different distribution families, thus conventional functional forms of multivariate frequency distributions cannot be employed. Copulas offer a viable alternative as marginals from different families can be combined into a joint distribution. Uncertainties in the statistical relationship can be determined and the statistical model can be used for prediction purposes. The outcome of the study can provide advanced warning on the expected state of surface water, based on projected ENSO and PDO conditions. Such warning may help trigger drought management plans in both the US and Mexico for example, and ensure the long-term sustainable management of water in the basin.

Lakes-paleolakes cascade system and its role in shaping the runoff and chemical properties of water in the young-glacial catchment - example from the Tuchola Pinewood Forest (Northern Poland)

NASA Astrophysics Data System (ADS)

Gierszewski, Piotr; Brykała, Dariusz; Kaszubski, Michał; Plessen, Birgit

2016-04-01

The impact of paleolake basins, filled up with organic mineral deposits, in the transformation of the chemical properties of the outflow is generally ignored. Defining their role and importance in the water and matter cycles is one of the objectives of the hydrological and hydrochemical monitoring, which has been run in the catchment of Lake Czechowskie since mid-2012. The axis of the Lake Czechowskie catchment is a hydrographical system made of river and lake sections. Lake sections are not only present-day lakes (Głęboczek and Czechowskie), but also basins of the lakes functioned in the past, which are now biogenic plains. Lake sections of the system are connected by short valley sections, mostly of a gap character. The size and variability of surface water runoff from the basin is mainly affected by groundwater and the size of evaporation. Stable groundwater table provides stability of the river discharge, even during the periods of significant precipitation deficit. Groundwater fluctuation ranges registered during the period from May 2012 to September 2015 were between 0.17 and 1.25 m. The smallest were in the deepest piezometers located in watershed areas, and the largest in the shallow groundwater of lake terraces. The small dynamics of the groundwater states is reflected by slight fluctuations of water levels in Lake Czechowskie, which in the analyzed period amounted 0.40 cm. The surface of paleolake Trzechowskie, cut by a system of drainage ditches, is the area where an essential part of the surface runoff from the monitored catchment is formed. Large water resources in this part of the catchment are evidenced by the specific runoff value, which amounts to 25 dm3s-1km2. It is much larger than the whole basin specific runoff which reaches 11 dm3s-1km2. The measurements showed that the average surface runoff from Lake Czechowskie in the analyzed period was 0,065 m3s-1 and was similar to the size of the water influx via watercourses supplying the lake. On the basis of this value it was calculated that the theoretical time to replace the water in Lake Czechowskie is 2.8 years. The hydrochemical study showed that the studied ground- and surface waters represent the same bicarbonate-calcium-sulphate hydrochemical type. Against the background of a homogeneous ionic composition, the spatial variation of their overall salinity is very large. This is reflected by the values of electrolytic conductivity, which in the study period ranged from 76 to 1218 μSṡcm-1. The most mineralized (700-800 μSṡcm-1) are the waters of streams migrating in the organic-carbonate formations of the paleolakes and shallow groundwater in these areas. The lowest mineralization is showed by the groundwater circulating in sandy sediments of outwash plains. Mineralization of the Lake Czechowskie water of approx. 340 μSṡcm-1 is a result of supplying the lake from both sources and the effect of biogeochemical processes occurring in the lake. The hydrochemical monitoring results showed that the zones of water enrichment in salts are associated with paleolake basins filled with the organic-carbonate sediment, while the salt precipitation zones with lakes. The results of the study of matter flow in the basin of Lake Czechowskie showed that paleolakes equally affect the runoff volume and the transformation of the chemical properties of the water circulating in the basin as the lakes functioning today. The lakes and paleolakes create a cascade system of interconnected basins. Depending on the place they occupy in the cascade, their effect on the water circulation and transformation of matter is different. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analyses - ICLEA- of the Helmholtz Association, Grant No VH-VI-415.

Temperature field study of hot water circulation pump shaft system

NASA Astrophysics Data System (ADS)

Liu, Y. Y.; Kong, F. Y.; Daun, X. H.; Zhao, R. J.; Hu, Q. L.

2016-05-01

In the process of engineering application under the condition of hot water circulation pump, problems of stress concentration caused by the temperature rise may happen. In order to study the temperature field in bearing and electric motor chamber of the hot water circulation pump and optimize the structure, in present paper, the model of the shaft system is created through CREO. The model is analyzed by ANSYS workbench, in which the thermal boundary conditions are applied to calculate, which include the calorific values from the bearings, the thermal loss from electric motor and the temperature from the transporting medium. From the result, the finite element model can reflect the distribution of thermal field in hot water circulation pump. Further, the results show that the maximum temperature locates in the bearing chamber.The theoretical guidance for the electric motor heat dissipation design of the hot water circulation pump can be achieved.

Gulf of Aden eddies and their impact on Red Sea Water

NASA Astrophysics Data System (ADS)

Bower, Amy S.; Fratantoni, David M.; Johns, William E.; Peters, Hartmut

2002-11-01

New oceanographic observations in the Gulf of Aden in the northwestern Indian Ocean have revealed large, energetic, deep-reaching mesoscale eddies that fundamentally influence the spreading rates and pathways of intermediate-depth Red Sea Water (RSW). Three eddies were sampled in February 2001, two cyclonic and one anticyclonic, with diameters 150-250 km. Both cyclones had surface-intensified velocity structure with maxima ~0.5 m s-1, while the equally-energetic anticyclone appeared to be decoupled from the surface circulation. All three eddies reached nearly to the 1000-2000 m deep sea floor, with speeds as high as 0.2-0.3 m s-1 extending through the depth range of RSW. Comparison of salinity and direct velocity measurements indicates that the eddies advect and stir RSW through the Gulf of Aden. Anomalous water properties in the center of the anticyclonic eddy point to a possible formation site in the Somali Current System.

High sub-seasonal variability in water volume transports, revealed through a new ocean monitoring initiative using autonomous gliders

NASA Astrophysics Data System (ADS)

Heslop, E.; Ruiz, S.; Allen, J.; Tintoré, J.

2012-04-01

One of the clear challenges facing oceanography today is to define variability in ocean processes at a seasonal and sub-seasonal scale, in order to clearly identify the signature of both natural large-scale climatic oscillations and the long-term trends brought about by the human-induced change in atmospheric composition. Without visibility of this variance, which helps to determine the margins of significance for long-term trends and decipher cause and effect, the inferences drawn from sparse data points can be misleading. The cyclonic basin scale circulation pattern in the Western Mediterranean has long been known; the role/contribution that processes in the Balearic Basin play in modifying this is less well defined. The Balearic Channels (channels between the Balearic Islands) are constriction points on this basin scale circulation that appear to exert a controlling influence on the north/south exchange of water masses. Understanding the variability in current flows through these channels is important, not just for the transport of heat and salt, but also for ocean biology that responds to physical variability at the scale of that variability. Earlier studies at a seasonal scale identified; an interannual summer/winter variation of 1 Sv in the strength of the main circulation pattern and a high cruise-to-cruise variability in the pattern and strength of the flows through the channels brought about by mesoscale activity. Initial results using new high-resolution data from glider based monitoring missions across the Ibiza Channel (the main exchange channel in the Balearic Basin), combined with ship and contemporaneous satellite data, indicate surprisingly high and rapid changes in the flows of surface and intermediate waters imposed on the broad seasonal cycle. To date the data suggests that there are three potential 'modes' of water volume transport, generated from the interplay between basin and mesoscale circulation. We will review the concept of transport modes as seen through the earlier seasonal ship based studies and demonstrate that the scales of variability captured by the glider monitoring provides a unique view of variability in this circulation system, which is as high on a weekly timescale as the previously identified seasonal cycle.

Wind driven nutrient and subsurface chlorophyll-a enhancement in the Bay of La Paz, Gulf of California

NASA Astrophysics Data System (ADS)

Coria-Monter, Erik; Monreal-Gómez, María Adela; Salas de León, David Alberto; Durán-Campos, Elizabeth; Merino-Ibarra, Martín

2017-09-01

Nutrient and chlorophyll-a distributions in the Bay of La Paz, Gulf of California, Mexico were analyzed during the late spring of 2004 to assess their relations to hydrography and circulation patterns. The results show the presence of both Gulf of California Water and Subtropical Subsurface Water. Water circulation was dominated by wind stress driven cyclonic circulation along f / H contours (f is planetary vorticity and H is depth), and upwelling resulting from the divergence shows a vertical velocity of ∼0.4 m d-1. Nutrient concentrations were higher in the center of the cyclonic pattern, where a rise in the nutricline contributed nutrients to the euphotic layer as a result of Ekman pumping. The vertical section showed the presence of a chlorophyll-a maximum at the thermocline shoaling to a depth of only 12 m. Along the surface, two peaks of chlorophyll-a were observed, one at Boca Grande and another off San Juan de la Costa, associated with upwelling and mixing derived from current interactions with abrupt topographies. The chlorophyll-a maximum increased from 0.8 mg m-3 in the external part of the cyclonic pattern to 2.0 mg m-3 in its center. The vertically integrated chlorophyll-a concentrations followed a similar pattern, rising from 10 to 20 mg m-2 and reaching their highest values in the center of the cyclonic circulation pattern. A schematic model was developed to describe processes that occur in late spring: the wind stress driven cyclonic structure promotes upward nutrient flux, which in turn drives an enhancement of chlorophyll-a. Upwelling was found to be the main mechanism of fertilization responsible for the enhancement of productivity levels by means of nutrient transport into the euphotic zone during spring. Other chlorophyll enhancement areas point to the occurrence of additional fertilization processes that may derive from interactions between cyclonic circulation patterns and the topography off of San Juan de la Costa, where phosphate mining occurs.

Modeling South Pacific Ice-Ocean Interactions in the Global Climate System

NASA Technical Reports Server (NTRS)

Holland, David M.; Jenkins, Adrian; Jacobs, Stanley S.

2001-01-01

The objective of this project has been to improve the modeling of interactions between large Antarctic ice shelves and adjacent regions of the Southern Ocean. Our larger goal is to gain a better understanding of the extent to which the ocean controls ice shelf attrition, thereby influencing the size and dynamics of the Antarctic Ice Sheet. Melting and freezing under ice shelves also impacts seawater properties, regional upwelling and sinking and the larger-scale ocean circulation. Modifying an isopycnal coordinate general circulation model for use in sub-ice shelf cavities, we found that the abrupt change in water column thickness at an ice shelf front does not form a strong barrier to buoyancy-driven circulation across the front. Outflow along the ice shelf base, driven by melting of the thickest ice, is balanced by deep inflow. Substantial effort was focused on the Filchner-Ronne cavity, where other models have been applied and time-series records are available from instruments suspended beneath the ice. A model comparison indicated that observed changes in the production of High Salinity Shelf Water could have a major impact on circulation within the cavity. This water propagates into the cavity with an asymmetric seasonal signal that has similar phasing and shape in the model and observations, and can be related to winter production at the sea surface. Even remote parts of the sub-ice shelf cavity are impacted by external forcing on sub-annual time scales. This shows that cavity circulations and products, and therefore cavity shape, will respond to interannual variability in sea ice production and longer-term climate change. The isopycnal model gives generally lower net melt rates than have been obtained from other models and oceanographic data, perhaps due to its boundary layer formulation, or the lack of tidal forcing. Work continues on a manuscript describing the Ross cavity results.

Numerical Simulation of the Water Cycle Change Over the 20th Century

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Schubert, Siegfried D.

2003-01-01

We have used numerical models to test the impact of the change in Sea Surface Temperatures (SSTs) and carbon dioxide (CO2) concentration on the global circulation, particularly focusing on the hydrologic cycle, namely the global cycling of water and continental recycling of water. We have run four numerical simulations using mean annual SST from the early part of the 20th century (1900-1920) and the later part (1980-2000). In addition, we vary the CO2 concentrations for these periods as well. The duration of the simulations is 15 years, and the spatial resolution is 2 degrees. We use passive tracers to study the geographical sources of water. Surface evaporation from predetermined continental and oceanic regions provides the source of water for each passive tracer. In this way, we compute the percent of precipitation of each region over the globe. This can also be used to estimate precipitation recycling. In addition, we are using the passive tracers to independently compute the global cycling of water (compared to the traditional, Q/P calculation).

Mapping Global Ocean Surface Albedo from Satellite Observations: Models, Algorithms, and Datasets

NASA Astrophysics Data System (ADS)

Li, X.; Fan, X.; Yan, H.; Li, A.; Wang, M.; Qu, Y.

2018-04-01

Ocean surface albedo (OSA) is one of the important parameters in surface radiation budget (SRB). It is usually considered as a controlling factor of the heat exchange among the atmosphere and ocean. The temporal and spatial dynamics of OSA determine the energy absorption of upper level ocean water, and have influences on the oceanic currents, atmospheric circulations, and transportation of material and energy of hydrosphere. Therefore, various parameterizations and models have been developed for describing the dynamics of OSA. However, it has been demonstrated that the currently available OSA datasets cannot full fill the requirement of global climate change studies. In this study, we present a literature review on mapping global OSA from satellite observations. The models (parameterizations, the coupled ocean-atmosphere radiative transfer (COART), and the three component ocean water albedo (TCOWA)), algorithms (the estimation method based on reanalysis data, and the direct-estimation algorithm), and datasets (the cloud, albedo and radiation (CLARA) surface albedo product, dataset derived by the TCOWA model, and the global land surface satellite (GLASS) phase-2 surface broadband albedo product) of OSA have been discussed, separately.

Rita Roars Through a Warm Gulf September 22, 2005

NASA Image and Video Library

2005-09-22

This sea surface height map of the Gulf of Mexico, with the Florida peninsula on the right and the Texas-Mexico Gulf Coast on the left, is based on altimeter data from four satellites including NASA’s Topex/Poseidon and Jason. Red indicates a strong circulation of much warmer waters, which can feed energy to a hurricane. This area stands 35 to 60 centimeters (about 13 to 23 inches) higher than the surrounding waters of the Gulf. The actual track of a hurricane is primarily dependent upon steering winds, which are forecasted through the use of atmospheric models. However, the interaction of the hurricane with the upper ocean is the primary source of energy for the storm. Hurricane intensity is therefore greatly affected by the upper ocean temperature structure and can exhibit explosive growth over warm ocean currents and eddies. Eddies are currents of water that run contrary to the direction of the main current. According to the forecasted track through the Gulf of Mexico, Hurricane Rita will continue crossing the warm waters of a Gulf of Mexico circulation feature called the Loop Current and then pass near a warm-water eddy called the Eddy Vortex, located in the north central Gulf, south of Louisiana. http://photojournal.jpl.nasa.gov/catalog/PIA06427

Where do winds come from? A new theory on how water vapor condensation influences atmospheric pressure and dynamics

NASA Astrophysics Data System (ADS)

Makarieva, A. M.; Gorshkov, V. G.; Sheil, D.; Nobre, A. D.; Li, B.-L.

2013-01-01

Phase transitions of atmospheric water play a ubiquitous role in the Earth's climate system, but their direct impact on atmospheric dynamics has escaped wide attention. Here we examine and advance a theory as to how condensation influences atmospheric pressure through the mass removal of water from the gas phase with a simultaneous account of the latent heat release. Building from fundamental physical principles we show that condensation is associated with a decline in air pressure in the lower atmosphere. This decline occurs up to a certain height, which ranges from 3 to 4 km for surface temperatures from 10 to 30 °C. We then estimate the horizontal pressure differences associated with water vapor condensation and find that these are comparable in magnitude with the pressure differences driving observed circulation patterns. The water vapor delivered to the atmosphere via evaporation represents a store of potential energy available to accelerate air and thus drive winds. Our estimates suggest that the global mean power at which this potential energy is released by condensation is around one per cent of the global solar power - this is similar to the known stationary dissipative power of general atmospheric circulation. We conclude that condensation and evaporation merit attention as major, if previously overlooked, factors in driving atmospheric dynamics.

Water mass circulation and weathering inputs in the Labrador Sea based on coupled Hf-Nd isotope compositions and rare earth element distributions

NASA Astrophysics Data System (ADS)

Filippova, Alexandra; Frank, Martin; Kienast, Markus; Rickli, Jörg; Hathorne, Ed; Yashayaev, Igor M.; Pahnke, Katharina

2017-02-01

The Labrador Sea is one of the key areas for deep water formation driving the Atlantic thermohaline circulation and thus plays an important role in Northern Hemisphere climatic fluctuations. In order to better constrain the overturning processes and the origins of the distinct water masses, combined dissolved Hf-Nd isotopic compositions and rare earth element (REE) distribution patterns were obtained from four water depth profiles along a section across the Labrador Sea. These were complemented by one surface sample off the southern tip of Greenland, three shallow water samples off the coast of Newfoundland, and two deep water samples off Nova Scotia. Although light REEs are markedly enriched in the surface waters off the coast of Newfoundland compared to north Atlantic waters, the REE concentration profiles are essentially invariant throughout the water column across the Labrador Sea. The hafnium concentrations of surface waters exhibit a narrow range between 0.6 and 1 pmol/kg but are not significantly higher than at depth. Neodymium isotope signatures (ɛNd) vary from unradiogenic values between -16.8 and -14.9 at the surface to more radiogenic values near -11.0 at the bottom of the Labrador Sea mainly reflecting the advection of the Denmark Strait Overflow Water and North East Atlantic Deep Water, the signatures of which are influenced by weathering contributions from Icelandic basalts. Unlike Nd, water column radiogenic Hf isotope signatures (ɛHf) are more variable representing diverse weathering inputs from the surrounding landmasses. The least radiogenic seawater ɛHf signatures (up to -11.7) are found in surface waters close to Greenland and near the Canadian margin. This reflects the influence of recirculating Irminger Current Waters, which are affected by highly unradiogenic inputs from Greenland. A three to four ɛHf unit difference is observed between Denmark Strait Overflow Water (ɛHf ∼ -4) and North East Atlantic Deep Water (ɛHf ∼ -0.1), although their source waters have essentially the same ɛNd signature. This most likely reflects different weathering signals of hafnium delivered to Denmark Strait Overflow Water and North East Atlantic Deep Water (incongruent weathering of old rocks from Greenland versus basaltic rocks from Iceland). In addition, the ɛHf data resolve two layers within the main body of Labrador Sea Water not visible in the ɛNd distribution, which are shallow Labrador Sea Water (ɛHf ∼ -2) and deep Labrador Sea Water (ɛHf ∼ -4.5). The latter layer was formed between the late 1980's and mid 1990's during the last cold state of the Labrador Sea and underwent substantial modification since its formation through the admixture of Irminger Water, Iceland Slope Water and North East Atlantic Deep Water, which is reflected in its less radiogenic ɛHf signature. The overall behavior of Hf in the water column suggests its higher sensitivity to local changes in weathering inputs on annual to decadal timescales. Although application of Hf isotopes as a tracer for global water mass mixing is complicated by their susceptibility to incongruent weathering inputs they are a promising tracer of local processes in restricted basins such as the Labrador Sea.

Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems

NASA Astrophysics Data System (ADS)

Hunt, George L.; Drinkwater, Kenneth F.; Arrigo, Kevin; Berge, Jørgen; Daly, Kendra L.; Danielson, Seth; Daase, Malin; Hop, Haakon; Isla, Enrique; Karnovsky, Nina; Laidre, Kristin; Mueter, Franz J.; Murphy, Eugene J.; Renaud, Paul E.; Smith, Walker O.; Trathan, Philip; Turner, John; Wolf-Gladrow, Dieter

2016-12-01

We compare and contrast the ecological impacts of atmospheric and oceanic circulation patterns on polar and sub-polar marine ecosystems. Circulation patterns differ strikingly between the north and south. Meridional circulation in the north provides connections between the sub-Arctic and Arctic despite the presence of encircling continental landmasses, whereas annular circulation patterns in the south tend to isolate Antarctic surface waters from those in the north. These differences influence fundamental aspects of the polar ecosystems from the amount, thickness and duration of sea ice, to the types of organisms, and the ecology of zooplankton, fish, seabirds and marine mammals. Meridional flows in both the North Pacific and the North Atlantic oceans transport heat, nutrients, and plankton northward into the Chukchi Sea, the Barents Sea, and the seas off the west coast of Greenland. In the North Atlantic, the advected heat warms the waters of the southern Barents Sea and, with advected nutrients and plankton, supports immense biomasses of fish, seabirds and marine mammals. On the Pacific side of the Arctic, cold waters flowing northward across the northern Bering and Chukchi seas during winter and spring limit the ability of boreal fish species to take advantage of high seasonal production there. Southward flow of cold Arctic waters into sub-Arctic regions of the North Atlantic occurs mainly through Fram Strait with less through the Barents Sea and the Canadian Archipelago. In the Pacific, the transport of Arctic waters and plankton southward through Bering Strait is minimal. In the Southern Ocean, the Antarctic Circumpolar Current and its associated fronts are barriers to the southward dispersal of plankton and pelagic fishes from sub-Antarctic waters, with the consequent evolution of Antarctic zooplankton and fish species largely occurring in isolation from those to the north. The Antarctic Circumpolar Current also disperses biota throughout the Southern Ocean, and as a result, the biota tends to be similar within a given broad latitudinal band. South of the Southern Boundary of the ACC, there is a large-scale divergence that brings nutrient-rich water to the surface. This divergence, along with more localized upwelling regions and deep vertical convection in winter, generates elevated nutrient levels throughout the Antarctic at the end of austral winter. However, such elevated nutrient levels do not support elevated phytoplankton productivity through the entire Southern Ocean, as iron concentrations are rapidly removed to limiting levels by spring blooms in deep waters. However, coastal regions, with the upward mixing of iron, maintain greatly enhanced rates of production, especially in coastal polynyas. In these coastal areas, elevated primary production supports large biomasses of zooplankton, fish, seabirds, and mammals. As climate warming affects these advective processes and their heat content, there will likely be major changes in the distribution and abundance of polar biota, in particular the biota dependent on sea ice.

Evaluating GCM land surface hydrology parameterizations by computing river discharges using a runoff routing model: Application to the Mississippi basin

NASA Technical Reports Server (NTRS)

Liston, G. E.; Sud, Y. C.; Wood, E. F.

1994-01-01

To relate general circulation model (GCM) hydrologic output to readily available river hydrographic data, a runoff routing scheme that routes gridded runoffs through regional- or continental-scale river drainage basins is developed. By following the basin overland flow paths, the routing model generates river discharge hydrographs that can be compared to observed river discharges, thus allowing an analysis of the GCM representation of monthly, seasonal, and annual water balances over large regions. The runoff routing model consists of two linear reservoirs, a surface reservoir and a groundwater reservoir, which store and transport water. The water transport mechanisms operating within these two reservoirs are differentiated by their time scales; the groundwater reservoir transports water much more slowly than the surface reservior. The groundwater reservior feeds the corresponding surface store, and the surface stores are connected via the river network. The routing model is implemented over the Global Energy and Water Cycle Experiment (GEWEX) Continental-Scale International Project Mississippi River basin on a rectangular grid of 2 deg X 2.5 deg. Two land surface hydrology parameterizations provide the gridded runoff data required to run the runoff routing scheme: the variable infiltration capacity model, and the soil moisture component of the simple biosphere model. These parameterizations are driven with 4 deg X 5 deg gridded climatological potential evapotranspiration and 1979 First Global Atmospheric Research Program (GARP) Global Experiment precipitation. These investigations have quantified the importance of physically realistic soil moisture holding capacities, evaporation parameters, and runoff mechanisms in land surface hydrology formulations.

Reversed flow of Atlantic deep water during the Last Glacial Maximum.

PubMed

Negre, César; Zahn, Rainer; Thomas, Alexander L; Masqué, Pere; Henderson, Gideon M; Martínez-Méndez, Gema; Hall, Ian R; Mas, José L

2010-11-04

The meridional overturning circulation (MOC) of the Atlantic Ocean is considered to be one of the most important components of the climate system. This is because its warm surface currents, such as the Gulf Stream, redistribute huge amounts of energy from tropical to high latitudes and influence regional weather and climate patterns, whereas its lower limb ventilates the deep ocean and affects the storage of carbon in the abyss, away from the atmosphere. Despite its significance for future climate, the operation of the MOC under contrasting climates of the past remains controversial. Nutrient-based proxies and recent model simulations indicate that during the Last Glacial Maximum the convective activity in the North Atlantic Ocean was much weaker than at present. In contrast, rate-sensitive radiogenic (231)Pa/(230)Th isotope ratios from the North Atlantic have been interpreted to indicate only minor changes in MOC strength. Here we show that the basin-scale abyssal circulation of the Atlantic Ocean was probably reversed during the Last Glacial Maximum and was dominated by northward water flow from the Southern Ocean. These conclusions are based on new high-resolution data from the South Atlantic Ocean that establish the basin-scale north to south gradient in (231)Pa/(230)Th, and thus the direction of the deep ocean circulation. Our findings are consistent with nutrient-based proxies and argue that further analysis of (231)Pa/(230)Th outside the North Atlantic basin will enhance our understanding of past ocean circulation, provided that spatial gradients are carefully considered. This broader perspective suggests that the modern pattern of the Atlantic MOC-with a prominent southerly flow of deep waters originating in the North Atlantic-arose only during the Holocene epoch.

Climatic controls on the snowmelt hydrology of the northern Rocky Mountains

USGS Publications Warehouse

Pederson, G.T.; Gray, S.T.; Ault, T.; Marsh, W.; Fagre, D.B.; Bunn, A.G.; Woodhouse, C.A.; Graumlich, L.J.

2011-01-01

The northern Rocky Mountains (NRMs) are a critical headwaters region with the majority of water resources originating from mountain snowpack. Observations showing declines in western U.S. snowpack have implications for water resources and biophysical processes in high-mountain environments. This study investigates oceanic and atmospheric controls underlying changes in timing, variability, and trends documented across the entire hydroclimatic-monitoring system within critical NRM watersheds. Analyses were conducted using records from 25 snow telemetry (SNOTEL) stations, 148 1 April snow course records, stream gauge records from 14 relatively unimpaired rivers, and 37 valley meteorological stations. Over the past four decades, midelevation SNOTEL records show a tendency toward decreased snowpack with peak snow water equivalent (SWE) arriving and melting out earlier. Temperature records show significant seasonal and annual decreases in the number of frost days (days ???0??C) and changes in spring minimum temperatures that correspond with atmospheric circulation changes and surface-albedo feedbacks in March and April. Warmer spring temperatures coupled with increases in mean and variance of spring precipitation correspond strongly to earlier snowmeltout, an increased number of snow-free days, and observed changes in streamflow timing and discharge. The majority of the variability in peak and total annual snowpack and streamflow, however, is explained by season-dependent interannual-to-interdecadal changes in atmospheric circulation associated with Pacific Ocean sea surface temperatures. Over recent decades, increased spring precipitation appears to be buffering NRM total annual streamflow from what would otherwise be greater snow-related declines in hydrologic yield. Results have important implications for ecosystems, water resources, and long-lead-forecasting capabilities. ?? 2011 American Meteorological Society.

Global-scale water circulation in the Earth's mantle: Implications for the mantle water budget in the early Earth

NASA Astrophysics Data System (ADS)

Nakagawa, Takashi; Spiegelman, Marc W.

2017-04-01

We investigate the influence of the mantle water content in the early Earth on that in the present mantle using numerical convection simulations that include three processes for redistribution of water: dehydration, partitioning of water into partially molten mantle, and regassing assuming an infinite water reservoir at the surface. These models suggest that the water content of the present mantle is insensitive to that of the early Earth. The initial water stored during planetary formation is regulated up to 1.2 OMs (OM = Ocean Mass; 1.4 ×1021 kg), which is reasonable for early Earth. However, the mantle water content is sensitive to the rheological dependence on the water content and can range from 1.2 to 3 OMs at the present day. To explain the evolution of mantle water content, we computed water fluxes due to subducting plates (regassing), degassing and dehydration. For weakly water dependent viscosity, the net water flux is almost balanced with those three fluxes but, for strongly water dependent viscosity, the regassing dominates the water cycle system because the surface plate activity is more vigorous. The increased convection is due to enhanced lubrication of the plates caused by a weak hydrous crust for strongly water dependent viscosity. The degassing history is insensitive to the initial water content of the early Earth as well as rheological strength. The degassing flux from Earth's surface is calculated to be approximately O (1013) kg /yr, consistent with a coupled model of climate evolution and mantle thermal evolution.

Experimental Evaluation of a Water Shield for a Surface Power Reactor

NASA Technical Reports Server (NTRS)

Pearson, J. Boise; Reid, Robert S.

2006-01-01

As part of the Vision for Space Exploration the end of the next decade will bring man back to the surface of the moon. One of the most critical issues for the establishment of human presence on the moon will be the availability of compact power sources. The establishment of man on the moon will require power from greater than 10's of kWt's in follow on years. Nuclear reactors are extremely we11 suited to meet the needs for power generation on the lunar or Martian surface. reactor system. Several competing concepts exist for lightweight, safe, robust shielding systems such as a water shield, lithium hydride (LiH), Boron Carbide, and others. Water offers several potential advantages, including reduced cost, reduced technical risk, and reduced mass. Water has not typically been considered for space reactor applications because of the need for gravity to remove the potential for radiation streaming paths. The water shield concept relies on predictions of passive circulation of the shield water by natural convection to adequately cool the shield. This prediction needs to be experimentally evaluated, especially for shields with complex geometries. MSFC has developed the experience and fac necessary to do this evaluation in the Early Flight Fission - Test Facility (EFF-TF).

Demonstrating the Alaska Ocean Observing System in Prince William Sound

NASA Astrophysics Data System (ADS)

Schoch, G. Carl; McCammon, Molly

2013-07-01

The Alaska Ocean Observing System and the Oil Spill Recovery Institute developed a demonstration project over a 5 year period in Prince William Sound. The primary goal was to develop a quasi-operational system that delivers weather and ocean information in near real time to diverse user communities. This observing system now consists of atmospheric and oceanic sensors, and a new generation of computer models to numerically simulate and forecast weather, waves, and ocean circulation. A state of the art data management system provides access to these products from one internet portal at http://www.aoos.org. The project culminated in a 2009 field experiment that evaluated the observing system and performance of the model forecasts. Observations from terrestrial weather stations and weather buoys validated atmospheric circulation forecasts. Observations from wave gages on weather buoys validated forecasts of significant wave heights and periods. There was an emphasis on validation of surface currents forecasted by the ocean circulation model for oil spill response and search and rescue applications. During the 18 day field experiment a radar array mapped surface currents and drifting buoys were deployed. Hydrographic profiles at fixed stations, and by autonomous vehicles along transects, were made to acquire measurements through the water column. Terrestrial weather stations were the most reliable and least costly to operate, and in situ ocean sensors were more costly and considerably less reliable. The radar surface current mappers were the least reliable and most costly but provided the assimilation and validation data that most improved ocean circulation forecasts. We describe the setting of Prince William Sound and the various observational platforms and forecast models of the observing system, and discuss recommendations for future development.

Response of the North Atlantic dynamic sea level and circulation to Greenland meltwater and climate change in an eddy-permitting ocean model

NASA Astrophysics Data System (ADS)

Saenko, Oleg A.; Yang, Duo; Myers, Paul G.

2017-10-01

The response of the North Atlantic dynamic sea surface height (SSH) and ocean circulation to Greenland Ice Sheet (GrIS) meltwater fluxes is investigated using a high-resolution model. The model is forced with either present-day-like or projected warmer climate conditions. In general, the impact of meltwater on the North Atlantic SSH and ocean circulation depends on the surface climate. In the two major regions of deep water formation, the Labrador Sea and the Nordic Seas, the basin-mean SSH increases with the increase of the GrIS meltwater flux. This SSH increase correlates with the decline of the Atlantic meridional overturning circulation (AMOC). However, while in the Labrador Sea the warming forcing and GrIS meltwater input lead to sea level rise, in the Nordic Seas these two forcings have an opposite influence on the convective mixing and basin-mean SSH (relative to the global mean). The warming leads to less sea-ice cover in the Nordic Seas, which favours stronger surface heat loss and deep mixing, lowering the SSH and generally increasing the transport of the East Greenland Current. In the Labrador Sea, the increased SSH and weaker deep convection are reflected in the decreased transport of the Labrador Current (LC), which closes the subpolar gyre in the west. Among the two major components of the LC transport, the thermohaline and bottom transports, the former is less sensitive to the GrIS meltwater fluxes under the warmer climate. The SSH difference across the LC, which is a component of the bottom velocity, correlates with the long-term mean AMOC rate.

Investigating the Interannual Variability of the Circulation and Water Mass Formation in the Red Sea

NASA Astrophysics Data System (ADS)

Sofianos, S. S.; Papadopoulos, V. P.; Denaxa, D.; Abualnaja, Y.

2014-12-01

The interannual variability of the circulation and water mass formation in the Red Sea is investigated with the use of a numerical model and the combination of satellite and in-situ observations. The response of Red Sea to the large-scale variability of atmospheric forcing is studied through a 30-years simulation experiment, using MICOM model. The modeling results demonstrate significant trends and variability that are mainly located in the central and northern parts of the basin. On the other hand, the exchange pattern between the Red Sea and the Indian Ocean at the strait of Bab el Mandeb presents very weak interannual variability. The results verify the regularity of the water mass formation processes in the northern Red Sea but also show significant variability of the circulation and thermohaline conditions in the areas of formation. Enhanced water mass formation conditions are observed during specific years of the simulation (approximately five years apart). Analysis of recent warm and cold events in the northernmost part of the basin, based on a combination of atmospheric reanalysis results and oceanic satellite and in-situ observations, shows the importance of the cyclonic gyre that is prevailing in this part of the basin. This gyre can effectively influence the sea surface temperature (SST) and intensify or mitigate the winter effect of the atmospheric forcing. Upwelling induced by persistent periods of the gyre functioning drops the SST over the northernmost part of the Red Sea and can produce colder than normal winter SST even without extreme atmospheric forcing. These mechanisms are crucial for the formation of intermediate and deep water masses in the Red Sea and the strength of the subsequent thermohaline cells.

Coherent Structures and Evolution of Vorticity in Short-Crested Breaking Surface Waves

NASA Astrophysics Data System (ADS)

Kirby, James; Derakhti, Morteza

2017-11-01

We employ a multi-phase LES/VOF code to study turbulence and coherent structures generated during breaking of short-crested surface water waves. We examine the evolution of coherent vortex structures evolving at the scale of the width of the breaking event, and their long-time interaction with smaller vortex loops formed by the local instability of the breaking crest. Long-time results are often characterized by the detachment of the larger scale vortex loop from the surface and formation of a closed vortex ring. The evolution of circulation for the vortical flow field is examined. The initial concentration of forcing close to the free surface leads to spatial distributions of both span-wise and vertical vorticity distributions which are concentrated close to the surface. This result, which persists into shallow water, is at odds with the basic simplicity of the Peregrine mechanism, suggesting that even shallow flows such as the surf zone should be regarded as being forced (in dissipative situations) by a wave-induced surface stress rather than a uniform-over-depth body force. The localized forcing leads to the development of a complex pattern of stream-wise vorticity, comparable in strength to the vertical and span-wise components, and also persist into shallow water. NSF OCE-1435147.

Observations and modelling of subglacial discharge and heat transport in Godthåbsfjord (Greenland, 64 °N)

NASA Astrophysics Data System (ADS)

Bendtsen, Jørgen; Mortensen, John; Rysgaard, Søren

2017-04-01

Subglacial discharge from tidewater outlet glaciers forms convective bouyant freshwater plumes ascending close the glacier face, and entrainment of ambient bottom water increases the salinity of the water until the plume reaches its level of neutral buoyancy at sub-surface levels or reaches the surface. Relatively warm bottom water masses characterize many fjords around Greenland and therefore entrainment would also increase the temperature in the plumes and, thereby, impact the heat transport in the fjords. However, relatively few oceanographic measurements have been made in or near plumes from subglacial discharge and, therefore, the potential for subglacial discharge for increasing heat transport towards the tidewater outlet glaciers are poorly understood. We present the first direct hydrographic measurements in a plume from subglacial discharge in Godthåbsfjord (located on the western coast of Greenland) where a XCTD was launched from a helicopter directly into the plume. Measurements of the surface salinity showed that the plume only contained 7% of freshwater at the surface, implying a large entrainment with a mixing ratio of 1:13 between outflowing meltwater and saline fjord water. These observations are analyzed together with seasonal observations of ocean heat transport towards the tidewater outlet glaciers in Godthåbsfjord and we show that subglacial discharge only had modest effects on the overall heat budget in front of the glacier. These results were supported from a high-resolution three-dimensional model of Godthåbsfjord. The model explicitly considered subglacial freshwater discharge from three tidewater outlet glaciers where entrainment of bottom water was taken into account. Model results showed that subglacial discharge only affected the fjord circulation relatively close ( 10 km) to the glaciers. Thus, the main effect on heat transport was due to the freshwater discharge itself whereas the subsurface discharge and associated entrainment only had a minor dynamical effect on the fjord circulation. However, mixing of bottom water by subglacial discharge also brings large amounts of nutrients to the surface and estimates of the potential nutrient transport show that this may have a significant impact on the biological production in front of tidewater outlet glaciers. Related publications: Bendtsen, J., Mortensen, J., Lennert, K. and S. Rysgaard (2015), Heat sources for glacial ice melt in a West Greenland tidewater outlet glacier fjord: the role of subglacial freshwater discharge, Geophys. Res. Lett., 42, doi:10.1002/2015GL063846. Bendtsen, J., Mortensen, J., and Rysgaard, S. (2015), Modelling subglacial discharge and its influence on ocean heat transport in Arctic fjords, Ocean Dynamics, 65, 1535-1546, 10.1007/s10236-015-0883-1. Mortensen, J., J. Bendtsen, K. Lennert, and S. Rysgaard (2014), Seasonal variability of the circulation system in a west Greenland tidewater outlet glacier fjord, Godthåbsfjord (64°N), J. Geophys. Res. Earth Surf., 119, 2591-2603, doi:10.1002/2014JF003267. Mortensen, J., Bendtsen, J., Motyka, R. J., Lennert, K., Truffer, M., Fahnestock, M. and S. Rysgaard (2013), On the seasonal freshwater stratification in the proximity of fast-flowing tidewater outlet glaciers in a sub-Arctic sill fjord. J. Geophys. Res. 118, 1-14, doi:10.1002/jgrc.20134.

Baroclinic flows, transports, and kinematic properties in a cyclonic-anticyclonic-cyclonic ring triad in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Vidal, VíCtor M. V.; Vidal, Francisco V.; HernáNdez, Abel F.; Meza, Eustorgio; PéRez-Molero, José M.

1994-04-01

During October-November 1986 the baroclinic circulation of the central and western Gulf of Mexico was dominated by an anticyclonic ring that was being bisected by two north and south flanking cyclonic rings. The baroclinic circulation revealed a well-defined cyclonic-anticyclonic-cyclonic triad system. The anticyclone's collision against the western gulf continental slope at 22.5°N, 97°W originated the north and south flanking cyclonic rings. The weakening of the anticyclone's relative vorticity, during the collision, was compensated by along-shelf north (26 cm s-1) and south (58 cm s-1) jet currents and by the anticyclone's flanking water mass's gain of cyclonic vorticity from lateral shear contributed by east (56 cm s-1) and west (42 cm s-1) current jets with individual mass transports of ˜18 Sv. Within the 0-1000 and 0-500 dbar layers and across 96°W the magnitudes of the colliding westward transports were 17.80 and 8.59 Sv, respectively. These corresponding transports were 85 and 94% balanced by along-shelf jet currents north and south of the anticyclone's collision zone. This indicates that only minor amounts (<15%) of the anticyclone's colliding westward transports might have flowed into the western gulf's continental shelf water mass or else they sank into deeper water along the continental slope during the anticyclone's collision event. The resultant effect of the coupled interaction between the anticyclone and the cyclonic pair was the surging of the water mass in the cyclones and its sinking in the anticyclone. This mechanism controlled the magnitude, direction, location of vertical advection, and transfer of kinetic energy from the upper to the deeper water layers. Our vertical transport estimates through the 1000-m-depth surface revealed a net vertical descending transport of 0.4 Sv for the ring triad system. This mass flux occurred primordially within the south central gulf region and most likely constituted a principal mechanism that propelled the gulf's deep horizontal circulation. The volume renewal time is ˜5 years for the ring triad system within 0-1000 dbar. The volume renewal time for the gulf's deep water layer (2000-3000 dbar), estimated as a function of its horizontal outflowing mass flux (1.96 Sv), is of the same order of magnitude and reveals that the deeper layer of the Gulf of Mexico is as well ventilated as its upper layer (0-1000 dbar). The ring triad's surface kinematic properties were derived from the sea surface baroclinic circulation field referenced to 500 dbar. Within this layer, individual ring geometries were conserved. Maximum tangential ring velocities were 60 and 58 cm s-1, for the north and south cyclones respectively, and 30 cm s-1 for the anticyclone. The corresponding periods of revolution were 16, 19, and 26 days, and vertical velocities calculated at the rings' peripheries, where maximum horizontal divergence was encountered, were 1.5, 1.0, and -1.0 m d-1.

COTHERM: Modelling fluid-rock interactions in Icelandic geothermal systems

NASA Astrophysics Data System (ADS)

Thien, Bruno; Kosakowski, Georg; Kulik, Dmitrii

2014-05-01

Mineralogical alteration of reservoir rocks, driven by fluid circulation in natural or enhanced geothermal systems, is likely to influence the long-term performance of geothermal power generation. A key factor is the change of porosity due to dissolution of primary minerals and precipitation of secondary phases. Porosity changes will affect fluid circulation and solute transport, which, in turn, influence mineralogical alteration. This study is part of the Sinergia COTHERM project (COmbined hydrological, geochemical and geophysical modeling of geotTHERMal systems) that is an integrative research project aimed at improving our understanding of the sub-surface processes in magmatically-driven natural geothermal systems. We model the mineralogical and porosity evolution of Icelandic geothermal systems with 1D and 2D reactive transport models. These geothermal systems are typically high enthalphy systems where a magmatic pluton is located at a few kilometers depth. The shallow plutons increase the geothermal gradient and trigger the circulation of hydrothermal waters with a steam cap forming at shallow depth. We investigate two contrasting geothermal systems: Krafla, for which the water recharge consists of meteoritic water; and Reykjanes, for which the water recharge mainly consists of seawater. The initial rock composition is a fresh basalt. We use the GEM-Selektor geochemical modeling package [1] for calculation of kinetically controlled mineral equilibria between the rock and the ingression water. We consider basalt minerals dissolution kinetics according to Palandri & Kharaka [2]. Reactive surface areas are assumed to be geometric surface areas, and are corrected using a spherical-particle surface/mass relationship. For secondary minerals, we consider the partial equilibrium assuming that the primary mineral dissolution is slow, and the secondary mineral precipitation is fast. Comparison of our modeling results with the mineralogical assemblages observed in the field by Gudmundsson & Arnorsson [3] and by Icelandic partners of the COTHERM project suggests that the concept of partial equilibrium with instantaneous precipitation of secondary minerals is not sufficient to satisfactorily describe the experimental data. Considering kinetic controls also for secondary minerals appears as indispensable to properly describe the geothermal system evolution using a reactive transport modelling approach [4]. [1] Kulik D.A., Wagner T., Dmytrieva S.V., Kosakowski G., Hingerl F.F., Chudnenko K.V., Berner U., 2013. GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes. Computational Geosciences 17, 1-24. http://gems.web.psi.ch. [2] Palandri, J.L., Kharaka, Y.K., 2004. A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modelling. U.S.Geological Survey, Menlo Park, CA, pp. 1-64. [3] Gudmundsson B.T., Arnorsson S., 2005. Secondary mineral-fluid equilibria in the Krafla and Namafjall geothermal systems, Iceland. Applied Geochememistry 20, 1607-1625. [4] Kosakowski, G., & Watanabe, N., 2013. OpenGeoSys-Gem: A numerical tool for calculating geochemical and porosity changes in saturated and partially saturated media. Physics and Chemistry of the Earth, Parts A/B/C. doi:10.1016/j.pce.2013.11.008

Antarctic boundary layer parametrization in a general circulation model: 1-D simulations facing summer observations at Dome C

NASA Astrophysics Data System (ADS)

Vignon, Etienne; Hourdin, Frédéric; Genthon, Christophe; Gallée, Hubert; Bazile, Eric; Lefebvre, Marie-Pierre; Madeleine, Jean-Baptiste; Van de Wiel, Bas J. H.

2017-07-01

The parametrization of the atmospheric boundary layer (ABL) is critical over the Antarctic Plateau for climate modelling since it affects the climatological temperature inversion and the negatively buoyant near-surface flow over the ice-sheet. This study challenges state-of-the-art parametrizations used in general circulation models to represent the clear-sky summertime diurnal cycle of the ABL at Dome C, Antarctic Plateau. The Laboratoire de Météorologie Dynamique-Zoom model is run in a 1-D configuration on the fourth Global Energy and Water Cycle Exchanges Project Atmospheric Boundary Layers Study case. Simulations are analyzed and compared to observations, giving insights into the sensitivity of one model that participates to the intercomparison exercise. Snow albedo and thermal inertia are calibrated leading to better surface temperatures. Using the so-called "thermal plume model" improves the momentum mixing in the diurnal ABL. In stable conditions, four turbulence schemes are tested. Best simulations are those in which the turbulence cuts off above 35 m in the middle of the night, highlighting the contribution of the longwave radiation in the ABL heat budget. However, the nocturnal surface layer is not stable enough to distinguish between surface fluxes computed with different stability functions. The absence of subsidence in the forcings and an underestimation of downward longwave radiation are identified to be likely responsible for a cold bias in the nocturnal ABL. Apart from model-specific improvements, the paper clarifies on which are the critical aspects to improve in general circulation models to correctly represent the summertime ABL over the Antarctic Plateau.

Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean

NASA Astrophysics Data System (ADS)

Tamsitt, V.; Abernathey, R. P.; Mazloff, M. R.; Wang, J.; Talley, L. D.

2018-03-01

Upwelling of northern deep waters in the Southern Ocean is fundamentally important for the closure of the global meridional overturning circulation and delivers carbon and nutrient-rich deep waters to the sea surface. We quantify water mass transformation along upwelling pathways originating in the Atlantic, Indian, and Pacific and ending at the surface of the Southern Ocean using Lagrangian trajectories in an eddy-permitting ocean state estimate. Recent related work shows that upwelling in the interior below about 400 m depth is localized at hot spots associated with major topographic features in the path of the Antarctic Circumpolar Current, while upwelling through the surface layer is more broadly distributed. In the ocean interior upwelling is largely isopycnal; Atlantic and to a lesser extent Indian Deep Waters cool and freshen while Pacific deep waters are more stable, leading to a homogenization of water mass properties. As upwelling water approaches the mixed layer, there is net strong transformation toward lighter densities due to mixing of freshwater, but there is a divergence in the density distribution as Upper Circumpolar Deep Water tends become lighter and dense Lower Circumpolar Deep Water tends to become denser. The spatial distribution of transformation shows more rapid transformation at eddy hot spots associated with major topography where density gradients are enhanced; however, the majority of cumulative density change along trajectories is achieved by background mixing. We compare the Lagrangian analysis to diagnosed Eulerian water mass transformation to attribute the mechanisms leading to the observed transformation.

Ground water in the Springfield-Salem plateaus of southern Missouri and northern Arkansas

USGS Publications Warehouse

Harvey, Edward Joseph

1980-01-01

Average ground-water conditions have not changed significantly in the Springfield-Salem plateaus section of southern Missouri and northern Arkansas in the past 25 years except in the vicinity of well fields. The amount of ground water pumped is approximately 200 cubic feet per second, which is about 5 percent of the total discharge at the 80 percent point on flow-duration curves for major streams. Ground-water recharge is variable and occurs through sinkholes by infiltration in upland areas of good permeability, and through streambeds that lose flow. Main waterbearing zones lie in the Potosi Dolomite and the lower dolomite and sandstone of the Gasconade Dolomite. Cavernous connections from ground surface to depths as great as 1,500 feet occur in the West Plains area, Mo., and result in deep circulation of water. Municipal well-water in the area often becomes turbid after rainstorms, despite well depths of 1 ,500 feet and 950 to 1,000 feet of pressure-grouted casing. Ground-water movement is generaly north and south from the crest of the Springfield-Salem plateaus, which extend across southern Missouri from the St. Francois Mountains to the southwest. Interbasin diversion of surface- and ground-water flow is common. (USGS)

Cenozoic Circulation History of the North Atlantic Ocean From Seismic Stratigraphy of the Newfoundland Ridge Drift Complex

NASA Astrophysics Data System (ADS)

Boyle, P. R.; Romans, B.; Norris, R. D.; Tucholke, B. E.; Swift, S. A.; Sexton, P. F.

2014-12-01

In the North Atlantic Ocean, contour-following bottom currents have eroded regional unconformities and deposited contourite drifts that exceed two km in thickness and extend for 100s of km. The character of deep-water masses that are conveyed through ocean basins by such currents influence global heat transfer and ocean-atmosphere partitioning of CO2. The Newfoundland Ridge Drift Complex lies directly under the modern Deep Western Boundary Current southeast of Newfoundland, close to the site of overturning in the northwest Atlantic Ocean and at the intersection of the warm Gulf Stream and cool Labrador surface currents. To the south are regions of the western North Atlantic basin that are influenced by southern- as well as northern-sourced bottom waters. Here, we document the evolution of North Atlantic deep-water circulation by seismic-stratigraphic analysis of the long-lived and areally extensive Newfoundland Ridge Drift Complex. IODP Expedition 342 boreholes provide age control on seismic units, allowing sedimentation patterns to be placed in a temporal framework. We find three major phases of sedimentation: pre-contourite drift (~115-50 Ma), active contourite drift (~50-2.6 Ma), and late-contourite drift (~2.6-0 Ma). Bottom-current-controlled deposition of terrigenous-rich sediment began at ~50 Ma, which correlates to the onset of a long-term global cooling trend. A further change in deep circulation near the Eocene-Oligocene transition (~30 Ma) is indicated by more focused drift sedimentation with greatly increased accumulation rates and stratal architecture dominated by mud waves. At ~2.6 Ma to present the axis of drift accumulation shifted markedly towards shallower water depths, corresponding with the onset of Northern Hemisphere ice sheets. We discuss how these reorganizations of deep circulation correlate with results of other North Atlantic seismic stratigraphic studies to the north and south.

Wind-driven changes of surface current, temperature, and chlorophyll observed by satellites north of New Guinea

NASA Astrophysics Data System (ADS)

Radenac, Marie-Hélène; Léger, Fabien; Messié, Monique; Dutrieux, Pierre; Menkes, Christophe; Eldin, Gérard

2016-04-01

Satellite observations of wind, sea level and derived currents, sea surface temperature (SST), and chlorophyll are used to expand our understanding of the physical and biological variability of the ocean surface north of New Guinea. Based on scarce cruise and mooring data, previous studies differentiated a trade wind situation (austral winter) when the New Guinea Coastal Current (NGCC) flows northwestward and a northwest monsoon situation (austral summer) when a coastal upwelling develops and the NGCC reverses. This circulation pattern is confirmed by satellite observations, except in Vitiaz Strait where the surface northwestward flow persists. We find that intraseasonal and seasonal time scale variations explain most of the variance north of New Guinea. SST and chlorophyll variabilities are mainly driven by two processes: penetration of Solomon Sea waters and coastal upwelling. In the trade wind situation, the NGCC transports cold Solomon Sea waters through Vitiaz Strait in a narrow vein hugging the coast. Coastal upwelling is generated in westerly wind situations (westerly wind event, northwest monsoon). Highly productive coastal waters are advected toward the equator and, during some westerly wind events, toward the eastern part of the warm pool. During El Niño, coastal upwelling events and northward penetration of Solomon Sea waters combine to influence SST and chlorophyll anomalies.

Holocene evolution of the North Atlantic subsurface transport

NASA Astrophysics Data System (ADS)

Repschläger, Janne; Garbe-Schönberg, Dieter; Weinelt, Mara; Schneider, Ralph

2017-04-01

Previous studies suggested that short-term freshening events in the subpolar gyre can be counterbalanced by advection of saline waters from the subtropical gyre and thus stabilize the Atlantic Meridional Overturning Circulation (AMOC). However, little is known about the inter-gyre transport pathways. Here, we infer changes in surface and subsurface transport between the subtropical and polar North Atlantic during the last 11 000 years, by combining new temperature and salinity reconstructions obtained from combined δ18O and Mg / Ca measurements on surface and subsurface dwelling foraminifera with published foraminiferal abundance data from the subtropical North Atlantic, and with salinity and temperature data from the tropical and subpolar North Atlantic. This compilation implies an overall stable subtropical warm surface water transport since 10 ka BP. In contrast, subsurface warm water transport started at about 8 ka but still with subsurface heat storage in the subtropical gyre. The full strength of intergyre exchange was probably reached only after the onset of northward transport of warm saline subsurface waters at about 7 ka BP, associated with the onset of the modern AMOC mode. A critical evaluation of different potential forcing mechanisms leads to the assumption that freshwater supply from the Laurentide Ice Sheet was the main control on subtropical to subpolar ocean transport at surface and subsurface levels.

Variability of Basal Melt Beneath the Pine Island Glacier Ice Shelf, West Antarctica

NASA Technical Reports Server (NTRS)

Bindschadler, Robert; Vaughan, David G.; Vornberger, Patricia

2011-01-01

Observations from satellite and airborne platforms are combined with model calculations to infer the nature and efficiency of basal melting of the Pine Island Glacier ice shelf, West Antarctica, by ocean waters. Satellite imagery shows surface features that suggest ice-shelf-wide changes to the ocean s influence on the ice shelf as the grounding line retreated. Longitudinal profiles of ice surface and bottom elevations are analyzed to reveal a spatially dependent pattern of basal melt with an annual melt flux of 40.5 Gt/a. One profile captures a persistent set of surface waves that correlates with quasi-annual variations of atmospheric forcing of Amundsen Sea circulation patterns, establishing a direct connection between atmospheric variability and sub-ice-shelf melting. Ice surface troughs are hydrostatically compensated by ice-bottom voids up to 150m deep. Voids form dynamically at the grounding line, triggered by enhanced melting when warmer-than-average water arrives. Subsequent enlargement of the voids is thermally inefficient (4% or less) compared with an overall melting efficiency beneath the ice shelf of 22%. Residual warm water is believed to cause three persistent polynyas at the ice-shelf front seen in Landsat imagery. Landsat thermal imagery confirms the occurrence of warm water at the same locations.

46 CFR 56.50-45 - Circulating pumps.

Code of Federal Regulations, 2011 CFR

2011-10-01

... circulating pump and emergency means for circulating water through the main condenser shall be provided. The... circulating pump and the condenser. (b) Independent sea suctions shall be provided for the main circulating...

Boundary Layer Height and Buoyancy Determine the Horizontal Scale of Convective Self-Aggregation

DOE PAGES

Yang, Da

2018-01-24

Organized rainstorms and their associated overturning circulations can self-emerge over an ocean surface with uniform temperature in cloud-resolving simulations. This phenomenon is referred to as convective self-aggregation. Convective self-aggregation is argued to be an important building block for tropical weather systems and may help regulate tropical atmospheric humidity and thereby tropical climate stability. Here the author presents a boundary layer theory for the horizontal scale λ of 2D (x, z) convective self-aggregation by considering both the momentum and energy constraints for steady circulations. This theory suggests that λ scales with the product of the boundary layer height h and themore » square root of the amplitude of density variation between aggregated moist and dry regions in the boundary layer, and that this density variation mainly arises from the moisture variation due to the virtual effect of water vapor. Furthermore, this theory predicts the following: 1) the order of magnitude of λ is ~2000 km, 2) the aspect ratio of the boundary layer λ/h increases with surface warming, and 3) λ decreases when the virtual effect of water vapor is disabled. These predictions are confirmed using a sui te of cloud-resolving simulations spanning a wide range of climates.« less

Boundary Layer Height and Buoyancy Determine the Horizontal Scale of Convective Self-Aggregation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Da

Organized rainstorms and their associated overturning circulations can self-emerge over an ocean surface with uniform temperature in cloud-resolving simulations. This phenomenon is referred to as convective self-aggregation. Convective self-aggregation is argued to be an important building block for tropical weather systems and may help regulate tropical atmospheric humidity and thereby tropical climate stability. Here the author presents a boundary layer theory for the horizontal scale λ of 2D (x, z) convective self-aggregation by considering both the momentum and energy constraints for steady circulations. This theory suggests that λ scales with the product of the boundary layer height h and themore » square root of the amplitude of density variation between aggregated moist and dry regions in the boundary layer, and that this density variation mainly arises from the moisture variation due to the virtual effect of water vapor. Furthermore, this theory predicts the following: 1) the order of magnitude of λ is ~2000 km, 2) the aspect ratio of the boundary layer λ/h increases with surface warming, and 3) λ decreases when the virtual effect of water vapor is disabled. These predictions are confirmed using a sui te of cloud-resolving simulations spanning a wide range of climates.« less

Wintertime re-ventilation of the East Greenland Current's Atlantic-origin Overflow Water in the western Iceland Sea

NASA Astrophysics Data System (ADS)

Våge, Kjetil; Håvik, Lisbeth; Papritz, Lukas; Spall, Michael; Moore, Kent

2017-04-01

The Deep Western Boundary Current constitutes the lower limb of the Atlantic Meridional Overturning Circulation, and, as such, is a crucial component of the Earth's climate system. The largest and densest contribution to the current stems from the overflow plume that passes through Denmark Strait. A main source of Denmark Strait Overflow Water (DSOW) is the East Greenland Current (EGC). The DSOW transported by the EGC originates from the Atlantic inflow into the Nordic Seas. This is then transformed into Atlantic-origin Overflow Water while progressing northward through the eastern part of the Nordic Seas. Here we show, using measurements from autonomous gliders deployed from fall 2015 to spring 2016, that the Atlantic-origin Overflow Water transported toward Denmark Strait by the EGC was re-ventilated while transiting the western Iceland Sea in winter. In summer, this region is characterized by an upper layer of cold, fresh Polar Surface Water that is thought to prevent convection. But in fall and winter this fresh water mass is diverted toward the Greenland shelf by enhanced northerly winds, which results in a water column that is preconditioned for convection. Severe heat loss from the ocean to the atmosphere offshore of the ice edge subsequently causes the formation of deep mixed layers. This further transforms the Atlantic-origin Overflow Water and impacts the properties of the DSOW, and hence the deepest and densest component of the lower limb of the Atlantic Meridional Overturning Circulation.

Response of a comprehensive climate model to a broad range of external forcings: relevance for deep ocean ventilation and the development of late Cenozoic ice ages

NASA Astrophysics Data System (ADS)

Galbraith, Eric; de Lavergne, Casimir

2018-03-01

Over the past few million years, the Earth descended from the relatively warm and stable climate of the Pliocene into the increasingly dramatic ice age cycles of the Pleistocene. The influences of orbital forcing and atmospheric CO2 on land-based ice sheets have long been considered as the key drivers of the ice ages, but less attention has been paid to their direct influences on the circulation of the deep ocean. Here we provide a broad view on the influences of CO2, orbital forcing and ice sheet size according to a comprehensive Earth system model, by integrating the model to equilibrium under 40 different combinations of the three external forcings. We find that the volume contribution of Antarctic (AABW) vs. North Atlantic (NADW) waters to the deep ocean varies widely among the simulations, and can be predicted from the difference between the surface densities at AABW and NADW deep water formation sites. Minima of both the AABW-NADW density difference and the AABW volume occur near interglacial CO2 (270-400 ppm). At low CO2, abundant formation and northward export of sea ice in the Southern Ocean contributes to very salty and dense Antarctic waters that dominate the global deep ocean. Furthermore, when the Earth is cold, low obliquity (i.e. a reduced tilt of Earth's rotational axis) enhances the Antarctic water volume by expanding sea ice further. At high CO2, AABW dominance is favoured due to relatively warm subpolar North Atlantic waters, with more dependence on precession. Meanwhile, a large Laurentide ice sheet steers atmospheric circulation as to strengthen the Atlantic Meridional Overturning Circulation, but cools the Southern Ocean remotely, enhancing Antarctic sea ice export and leading to very salty and expanded AABW. Together, these results suggest that a `sweet spot' of low CO2, low obliquity and relatively small ice sheets would have poised the AMOC for interruption, promoting Dansgaard-Oeschger-type abrupt change. The deep ocean temperature and salinity simulated under the most representative `glacial' state agree very well with reconstructions from the Last Glacial Maximum (LGM), which lends confidence in the ability of the model to estimate large-scale changes in water-mass geometry. The model also simulates a circulation-driven increase of preformed radiocarbon reservoir age, which could explain most of the reconstructed LGM-preindustrial ocean radiocarbon change. However, the radiocarbon content of the simulated glacial ocean is still higher than reconstructed for the LGM, and the model does not reproduce reconstructed LGM deep ocean oxygen depletions. These ventilation-related disagreements probably reflect unresolved physical aspects of ventilation and ecosystem processes, but also raise the possibility that the LGM ocean circulation was not in equilibrium. Finally, the simulations display an increased sensitivity of both surface air temperature and AABW volume to orbital forcing under low CO2. We suggest that this enhanced orbital sensitivity contributed to the development of the ice age cycles by amplifying the responses of climate and the carbon cycle to orbital forcing, following a gradual downward trend of CO2.

Impacts of Soil-aquifer Heat and Water Fluxes on Simulated Global Climate

NASA Technical Reports Server (NTRS)

Krakauer, N.Y.; Puma, Michael J.; Cook, B. I.

2013-01-01

Climate models have traditionally only represented heat and water fluxes within relatively shallow soil layers, but there is increasing interest in the possible role of heat and water exchanges with the deeper subsurface. Here, we integrate an idealized 50m deep aquifer into the land surface module of the GISS ModelE general circulation model to test the influence of aquifer-soil moisture and heat exchanges on climate variables. We evaluate the impact on the modeled climate of aquifer-soil heat and water fluxes separately, as well as in combination. The addition of the aquifer to ModelE has limited impact on annual-mean climate, with little change in global mean land temperature, precipitation, or evaporation. The seasonal amplitude of deep soil temperature is strongly damped by the soil-aquifer heat flux. This not only improves the model representation of permafrost area but propagates to the surface, resulting in an increase in the seasonal amplitude of surface air temperature of >1K in the Arctic. The soil-aquifer water and heat fluxes both slightly decrease interannual variability in soil moisture and in landsurface temperature, and decrease the soil moisture memory of the land surface on seasonal to annual timescales. The results of this experiment suggest that deepening the modeled land surface, compared to modeling only a shallower soil column with a no-flux bottom boundary condition, has limited impact on mean climate but does affect seasonality and interannual persistence.

Sources and processes affecting the distribution of dissolved Nd isotopes and concentrations in the West Pacific

NASA Astrophysics Data System (ADS)

Behrens, Melanie K.; Pahnke, Katharina; Schnetger, Bernhard; Brumsack, Hans-Jürgen

2018-02-01

In the Atlantic, where deep circulation is vigorous, the dissolved neodymium (Nd) isotopic composition (expressed as ɛNd) is largely controlled by water mass mixing. In contrast, the factors influencing the ɛNd distribution in the Pacific, marked by sluggish circulation, is not clear yet. Indication for regional overprints in the Pacific is given based on its bordering volcanic islands. Our study aims to clarify the impact and relative importance of different Nd sources (rivers, volcanic islands), vertical (bio)geochemical processes and lateral water mass transport in controlling dissolved ɛNd and Nd concentration ([Nd]) distributions in the West Pacific between South Korea and Fiji. We find indication for unradiogenic continental input from South Korean and Chinese rivers to the East China Sea. In the tropical West Pacific, volcanic islands supply Nd to surface and subsurface waters and modify their ɛNd to radiogenic values of up to +0.7. These radiogenic signatures allow detailed tracing of currents flowing to the east and differentiation from westward currents with open ocean Pacific ɛNd composition in the complex tropical Pacific zonal current system. Modified radiogenic ɛNd of West Pacific intermediate to bottom waters upstream or within our section also indicates non-conservative behavior of ɛNd due to boundary exchange at volcanic island margins, submarine ridges, and with hydrothermal particles. Only subsurface to deep waters (3000 m) in the open Northwest Pacific show conservative behavior of ɛNd. In contrast, we find a striking correlation of extremely low (down to 2.77 pmol/kg Nd) and laterally constant [Nd] with the high-salinity North and South Pacific Tropical Water, indicating lateral transport of preformed [Nd] from the North and South Pacific subtropical gyres into the study area. This observation also explains the previously observed low subsurface [Nd] in the tropical West Pacific. Similarly, Western South Pacific Central Water, Antarctic Intermediate Water, and Lower Circumpolar Deep Water in the southern and equatorial West Pacific are marked by vertically and laterally almost invariant [Nd] indicating a dominance of conservative behavior of [Nd]. In contrast, Central and Intermediate Water in the North West Pacific are characterized by increasing [Nd] with depth reflecting Nd release from particles. Overall, our data demonstrate a dominant lateral transport control on [Nd] distributions and clear non-conservative modification of ɛNd in the West Pacific. The latter affords tracing of surface and subsurface zonal transport in the tropical Pacific, but prevents the use of ɛNd as strictly conservative tracer of the major meridionally circulating water masses in the West Pacific between 15°S and 28°N.

Karst geomorphology and hydrology of the Shenandoah Valley near Harrisonburg, Virginia

USGS Publications Warehouse

Doctor, Daniel H.; Orndorff, Wil; Maynard, Joel; Heller, Matthew J.; Casile, Gerolamo C.

2014-01-01

The karst of the central Shenandoah Valley has characteristics of both shallow and deep phreatic formation. This field guide focuses on the region around Harrisonburg, Virginia, where a number of these karst features and their associated geologic context can be examined. Ancient, widespread alluvial deposits cover much of the carbonate bedrock on the western side of the valley, where shallow karstification has resulted in classical fluviokarst development. However, in upland exposures of carbonate rock, isolated caves exist atop hills not affected by surface processes other than exposure during denudation. The upland caves contain phreatic deposits of calcite and fine-grained sediments. They lack any evidence of having been invaded by surface streams. Recent geologic mapping and LIDAR (light detection and ranging) elevation data have enabled interpretive association between bedrock structure, igneous intrusions, silicification and brecciation of host carbonate bedrock, and the location of several caves and karst springs. Geochemistry, water quality, and water temperature data support the broad categorization of springs into those affected primarily by shallow near-surface recharge, and those sourced deeper in the karst aquifer. The deep-seated karst formation occurred in the distant past where subvertical fracture and fault zones intersect thrust faults and/or cross-strike faults, enabling upwelling of deep-circulating meteoric groundwater. Most caves formed in such settings have been overprinted by later circulation of shallow groundwater, thus removing evidence of the history of earliest inception; however, several caves do preserve evidence of an earlier formation.

Effects of glacial meltwater inflows and moat freezing on mixing in an ice-covered antarctic lake as interpreted from stable isotope and tritium distributions

USGS Publications Warehouse

Miller, L.G.; Aiken, G.R.

1996-01-01

Perennially ice-covered lakes in the McMurdo Dry Valleys have risen several meters over the past two decades due to climatic warming and increased glacial meltwater inflow. To elucidate the hydrologic responses to changing climate and the effects on lake mixing processes we measured the stable isotope (??18O and ??D) and tritium concentrations of water and ice samples collected in the Lake Fryxell watershed from 1987 through 1990. Stable isotope enrichment resulted from evaporation in stream and moat samples and from sublimation in surface lake-ice samples. Tritium enrichment resulted from exchange with the postnuclear atmosphere in stream and moat samples. Rapid injection of tritiated water into the upper water column of the make and incorporation of this water into the ice cover resulted in uniformly elevated tritium contents (> 3.0 TU) in these reservoirs. Tritium was also present in deep water, suggesting that a component of bottom water was recently at the surface. During summer, melted lake ice and stream water forms the moat. Water excluded from ice formation during fall moat freezing (enriched in solutes and tritium, and depleted in 18O and 2H relative to water below 15-m depth) may sink as density currents to the bottom of the lake. Seasonal lake circulation, in response to climate-driven surface inflow, is therefore responsible for the distribution of both water isotopes and dissolved solutes in Lake Fryxell.

Submersible purification system for radioactive water

DOEpatents

Abbott, Michael L.; Lewis, Donald R.

1989-01-01

A portable, submersible water purification system for use in a pool of water containing radioactive contamination includes a prefilter for filtering particulates from the water. A resin bed is then provided for removal of remaining dissolved, particulate, organic, and colloidal impurities from the prefiltered water. A sterilizer then sterilizes the water. The prefilter and resin bed are suitably contained and are submerged in the pool. The sterilizer is water tight and located at the surface of the pool. The water is circulated from the pool through the prefilter, resin bed, and sterilizer by suitable pump or the like. In the preferred embodiment, the resin bed is contained within a tank which stands on the bottom of the pool and to which a base mounting the prefilter and pump is attached. An inlet for the pump is provided adjacent the bottom of the pool, while the sterilizer and outlet for the system is located adjacent the top of the pool.

California State Waters Map Series: offshore of San Francisco, California

USGS Publications Warehouse

Cochrane, Guy R.; Johnson, Samuel Y.; Dartnell, Peter; Greene, H. Gary; Erdey, Mercedes D.; Golden, Nadine E.; Hartwell, Stephen R.; Endris, Charles A.; Manson, Michael W.; Sliter, Ray W.; Kvitek, Rikk G.; Watt, Janet Tilden; Ross, Stephanie L.; Bruns, Terry R.; Cochrane, Guy R.; Cochran, Susan A.

2015-01-01

Circulation over the continental shelf in the Offshore of San Francisco map area is dominated by the southward-flowing California Current, an eastern limb of the North Pacific Gyre that flows from Oregon to Baja California. At its midpoint offshore of central California, the California Current transports subarctic surface waters southeastward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. Ocean temperatures offshore of central California have increased over the past 50 years, driving an ecosystem shift from the productive subarctic regime towards a depopulated subtropical environment.

Modeling of Dense Water Production and Salt Transport from Alaskan Coastal Polynyas

NASA Technical Reports Server (NTRS)

Signorini, Sergio R.; Cavalieri, Donald J.

2000-01-01

The main significance of this paper is that a realistic, three-dimensional, high-resolution primitive equation model has been developed to study the effects of dense water formation in Arctic coastal polynyas. The model includes realistic ambient stratification, realistic bottom topography, and is forced by time-variant surface heat flux, surface salt flux, and time-dependent coastal flow. The salt and heat fluxes, and the surface ice drift, are derived from satellite observations (SSM/I and NSCAT sensors). The model is used to study the stratification, salt transport, and circulation in the vicinity of Barrow Canyon during the 1996/97 winter season. The coastal flow (Alaska coastal current), which is an extension of the Bering Sea throughflow, is formulated in the model using the wind-transport regression. The results show that for the 1996/97 winter the northeastward coastal current exports 13% to 26% of the salt produced by coastal polynyas upstream of Barrow Canyon in 20 to 30 days. The salt export occurs more rapidly during less persistent polynyas. The inclusion of ice-water stress in the model makes the coastal current slightly weaker and much wider due to the combined effects of surface drag and offshore Ekman transport.

Regional climates in the GISS general circulation model: Surface air temperature

NASA Technical Reports Server (NTRS)

Hewitson, Bruce

1994-01-01

One of the more viable research techniques into global climate change for the purpose of understanding the consequent environmental impacts is based on the use of general circulation models (GCMs). However, GCMs are currently unable to reliably predict the regional climate change resulting from global warming, and it is at the regional scale that predictions are required for understanding human and environmental responses. Regional climates in the extratropics are in large part governed by the synoptic-scale circulation and the feasibility of using this interscale relationship is explored to provide a way of moving to grid cell and sub-grid cell scales in the model. The relationships between the daily circulation systems and surface air temperature for points across the continental United States are first developed in a quantitative form using a multivariate index based on principal components analysis (PCA) of the surface circulation. These relationships are then validated by predicting daily temperature using observed circulation and comparing the predicted values with the observed temperatures. The relationships predict surface temperature accurately over the major portion of the country in winter, and for half the country in summer. These relationships are then applied to the surface synoptic circulation of the Goddard Institute for Space Studies (GISS) GCM control run, and a set of surface grid cell temperatures are generated. These temperatures, based on the larger-scale validated circulation, may now be used with greater confidence at the regional scale. The generated temperatures are compared to those of the model and show that the model has regional errors of up to 10 C in individual grid cells.

ENSO related sea surface salinity variability in the equatorial Pacific

NASA Astrophysics Data System (ADS)

Qu, T.

2016-12-01

Recently available satellite and Argo data have shown coherent, large-scale sea surface salinity (SSS) variability in the equatorial Pacific. Based on this variability, several SSS indices of El Nino have been introduced by previous studies. Combining results from an ocean general circulation model with available satellite and in-situ observations, this study investigates the SSS variability and its associated SSS indices in the equatorial Pacific. The ocean's role and in particular the vertical entrainment of subtropical waters in this variability are discussed, which suggests that the SSS variability in the equatorial Pacific may play some active role in ENSO evolution.

Wind-driven upwelling effects on cephalopod paralarvae: Octopus vulgaris and Loliginidae off the Galician coast (NE Atlantic)

NASA Astrophysics Data System (ADS)

Otero, Jaime; Álvarez-Salgado, X. Antón; González, Ángel F.; Souto, Carlos; Gilcoto, Miguel; Guerra, Ángel

2016-02-01

Circulation patterns of coastal upwelling areas may have central consequences for the abundance and cross-shelf transport of the larval stages of many species. Previous studies have provided evidences that larvae distribution results from a combination of subtidal circulation, species-specific behaviour and larval sources. However, most of these works were conducted on organisms characterised by small-sized and abundant early life phases. Here, we studied the influence of the hydrography and circulation of the Ría de Vigo and adjacent shelf (NW Iberian upwelling system) on the paralarval abundance of two contrasting cephalopods, the benthic common octopus (Octopus vulgaris) and the pelagic squids (Loliginidae). We sampled repeatedly a cross-shore transect during the years 2003-2005 and used zero inflated models to accommodate the scarcity and patchy distribution of cephalopod paralarvae. The probability of catching early stages of both cephalopods was higher at night. Octopus paralarvae were more abundant in the surface layer at night whereas loliginids preferred the bottom layer regardless of the sampling time. Abundance of both cephalopods increased when shelf currents flowed polewards, water temperature was high and water column stability was low. The probability of observing an excess of zero catches decreased during the year for octopus and at high current speed for loliginids. In addition, the circulation pattern conditioned the body size distribution of both paralarvae; while the average size of the captured octopuses increased (decreased) with poleward currents at daylight (nighttime), squids were smaller with poleward currents regardless of the sampling time. These results contribute to the understanding of the effects that the hydrography and subtidal circulation of a coastal upwelling have on the fate of cephalopod early life stages.

Calculating Freshwater Input from Iceberg Melt in Greenlandic Fjords by Combining In Situ Observations of Iceberg Movement with High Resolution Satellite Imagery

NASA Astrophysics Data System (ADS)

Sulak, D. J.; Sutherland, D.; Stearns, L. A.; Hamilton, G. S.

2015-12-01

Understanding fjord circulation in Greenland's outlet glacial fjords is crucial to explaining recent temporal and spatial variability in glacier dynamics, as well as freshwater transport on the continental shelf. The fjords are commonly assumed to exhibit a plume driven circulation that draws in warmer and saltier Atlantic-origin water toward the glacier at depth. Freshwater input at glacier termini directly drives this circulation and significantly influences water column stratification, which indirectly feeds back on the plume driven circulation. Previous work has focused on freshwater inputs from surface runoff and submarine melting, but the contribution from iceberg melt, a potentially important freshwater source, has not been quantified. Here, we develop a new technique combining in situ observations of movement from iceberg-mounted GPS units with multispectral satellite imagery from Landsat 8. The combination of datasets allows us to examine the details of iceberg movement and quantify mean residence times in a given fjord. We then use common melt rate parameterizations to estimate freshwater input for a given iceberg, utilizing novel satellite-derived iceberg distributions to scale up to a fjord-wide freshwater contribution. We apply this technique to Rink Isbræ and Kangerlussuup Sermia in west Greenland, and Helheim Glacier in southeast Greenland. The analysis can be rapidly expanded to look at other systems as well as seasonal and interannual changes in how icebergs affect the circulation and stratification of Greenland's outlet glacial fjords. Ultimately, this work will lead to a more complete understanding of the wide range of factors that control the observed regional variability in Greenland's glaciers.

An Oceanic General Circulation Model (OGCM) investigation of the Red Sea circulation, 1. Exchange between the Red Sea and the Indian Ocean

NASA Astrophysics Data System (ADS)

Sofianos, Sarantis S.; Johns, William E.

2002-11-01

The mechanisms involved in the seasonal exchange between the Red Sea and the Indian Ocean are studied using an Oceanic General Circulation Model (OGCM), namely the Miami Isopycnic Coordinate Ocean Model (MICOM). The model reproduces the basic characteristics of the seasonal circulation observed in the area of the strait of Bab el Mandeb. There is good agreement between model results and available observations on the strength of the exchange and the characteristics of the water masses involved, as well as the seasonal flow pattern. During winter, this flow consists of a typical inverse estuarine circulation, while during summer, the surface flow reverses, there is an intermediate inflow of relatively cold and fresh water, and the hypersaline outflow at the bottom of the strait is significantly reduced. Additional experiments with different atmospheric forcing (seasonal winds, seasonal thermohaline air-sea fluxes, or combinations) were performed in order to assess the role of the atmospheric forcing fields in the exchange flow at Bab el Mandeb. The results of both the wind- and thermohaline-driven experiments exhibit a strong seasonality at the area of the strait, which is in phase with the observations. However, it is the combination of both the seasonal pattern of the wind stress and the seasonal thermohaline forcing that can reproduce the observed seasonal variability at the strait. The importance of the seasonal cycle of the thermohaline forcing on the exchange flow pattern is also emphasized by these results. In the experiment where the thermohaline forcing is represented by its annual mean, the strength of the exchange is reduced almost by half.

Pathways of upwelling deep waters to the surface of the Southern Ocean

NASA Astrophysics Data System (ADS)

Tamsitt, Veronica; Drake, Henri; Morrison, Adele; Talley, Lynne; Dufour, Carolina; Gray, Alison; Griffies, Stephen; Mazloff, Matthew; Sarmiento, Jorge; Wang, Jinbo; Weijer, Wilbert

2017-04-01

Upwelling of Atlantic, Indian and Pacific deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of anthropogenic carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. Here we go beyond the two-dimensional view of Southern Ocean upwelling, to show detailed Southern Ocean upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution ocean and climate models. The northern deep waters enter the Antarctic Circumpolar Current (ACC) via narrow southward currents along the boundaries of the three ocean basins, before spiraling southeastward and upward through the ACC. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the southern ACC boundary, with a spatially nonuniform distribution, regionalizing warm water supply to Antarctic ice shelves and the delivery of nutrient and carbon-rich water to the sea surface. The timescale for half of the deep water to upwell from 30°S to the mixed layer is on the order of 60-90 years, which has important implications for the timescale for signals to propagate through the deep ocean. In addition, we quantify the diabatic transformation along particle trajectories, to identify where diabatic processes are important along the upwelling pathways.

The relation between AMOC, gyre circulation, and meridional heat transports in the North Atlantic in model simulations of the last millennium

NASA Astrophysics Data System (ADS)

Jungclaus, J. H.; Moreno-Chamarro, E.; Lohmann, K.; Zanchettin, D.

2016-02-01

While it is clear that the Atlantic Meridional Overturning Circulation (AMOC) is responsible for meridional heat transfer from the South Atlantic and the tropics to the North Atlantic, the majority of the heat transport in the northern North Atlantic and the Nordic seas is carried by the gyre system. However, the detailed mechanisms determining the interaction between and the temporal modulation of the components of the northward heat transport system are not clear. Long-term climate records and model simulations can help to identify important processes and to provide background for the changes that are presently observed. Multi-centennial proxy records from the subpolar North Atlantic and the Nordic Seas indicate, for example, an out-of-phase behavior of sea surface temperature and gyre circulation between the two regions with consequences for regional climate. Paleoceanographic evidence from Fram Strait shows a pronounced modulation of heat transfer to the Arctic by the Atlantic Water layer during the last 2000 years and reconstructions from the Subpolar North Atlantic suggest a role of ocean circulation in the transition between the Medieval Climate Anomaly and the Little Ice Age. Here we explore a small ensemble of last millennium simulations, carried out with the Max Planck Institute Earth System Model, and analyze mechanisms connecting the AMOC and gyre circulation and their relation to external forcing. Our results support the important role of the Subpolar Gyre strength and the related meridional mass and temperature fluxes. We find that the modulation of the northward heat transport into the Nordic Seas and the Arctic has pronounced impact on sea-ice distribution, ocean-atmosphere interaction, and the surface climate in Scandinavia and Western Europe.

The relation between AMOC, gyre circulation, and meridional heat transports in the North Atlantic in model simulations of the last millennium

NASA Astrophysics Data System (ADS)

Jungclaus, Johann; Moreno-Chamarro, Eduardo; Lohmann, Katja

2016-04-01

While it is clear that the Atlantic Meridional Overturning Circulation (AMOC) is responsible for meridional heat transfer from the South Atlantic and the tropics to the North Atlantic, the majority of the heat transport in the northern North Atlantic and the Nordic seas is carried by the gyre system. However, the detailed mechanisms determining the interaction between and the temporal modulation of the components of the northward heat transport system are not clear. Long-term climate records and model simulations can help to identify important processes and to provide background for the changes that are presently observed. Multi-centennial proxy records from the subpolar North Atlantic and the Nordic Seas indicate, for example, an out-of-phase behavior of sea surface temperature and gyre circulation between the two regions with consequences for regional climate. Paleoceanographic evidence from Fram Strait shows a pronounced modulation of heat transfer to the Arctic by the Atlantic Water layer during the last 2000 years and reconstructions from the Subpolar North Atlantic suggest a role of ocean circulation in the transition between the Medieval Climate Anomaly and the Little Ice Age. Here we explore a small ensemble of last millennium simulations, carried out with the Max Planck Institute Earth System Model, and analyze mechanisms connecting the AMOC and gyre circulation and their relation to external forcing. Our results support the important role of the Subpolar Gyre strength and the related meridional mass and temperature fluxes. We find that the modulation of the northward heat transport into the Nordic Seas and the Arctic has pronounced impact on sea-ice distribution, ocean-atmosphere interaction, and the surface climate in Scandinavia and Western Europe.

Monsoon-driven variability in the southern Red Sea and the exchange with the Indian Ocean

NASA Astrophysics Data System (ADS)

Sofianos, S. S.; Papadopoulos, V. P.; Abualnaja, Y.; Nenes, A.; Hoteit, I.

2016-02-01

Although progress has been achieved in describing and understanding the mean state and seasonal cycle of the Red Sea dynamics, their interannual variability is not yet well evaluated and explained. The thermohaline characteristics and the circulation patterns present strong variability at various time scales and are affected by the strong and variable atmospheric forcing and the exchange with the Indian Ocean and the gulfs located at the northern end of the basin. Sea surface temperature time-series, derived from satellite observations, show considerable trends and interannual variations. The spatial variability pattern is very diverse, especially in the north-south direction. The southern part of the Red Sea is significantly influenced by the Indian Monsoon variability that affects the sea surface temperature through the surface fluxes and the circulation patterns. This variability has also a strong impact on the lateral fluxes and the exchange with the Indian Ocean through the strait of Bab el Mandeb. During summer, there is a reversal of the surface flow and an intermediate intrusion of a relatively cold and fresh water mass. This water originates from the Gulf of Aden (the Gulf of Aden Intermediate Water - GAIW), is identified in the southern part of the basin and spreads northward along the eastern Red Sea boundary to approximately 24°N and carried across the Red Sea by basin-size eddies. The GAIW intrusion plays an important role in the heat and freshwater budget of the southern Red Sea, especially in summer, impacting the thermohaline characteristics of the region. It is a permanent feature of the summer exchange flow but it exhibits significant variation from year to year. The intrusion is controlled by a monsoon-driven pressure gradient in the two ends of the strait and thus monsoon interannual variability can laterally impose its signal to the southern Red Sea thermohaline patterns.

Integrated exploration for low-temperature geothermal resources in the Honey Lake Basin, California

USGS Publications Warehouse

Schimschal, U.

1991-01-01

An integrated exploration study is presented to locate low-temperature geothermal reservoirs in the Honey Lake area of northern California. Regional studies to locate the geothermal resources included gravity, infra-red, water-temperature, and water-quality analyses. Five anomalies were mapped from resistivity surveys. Additional study of three anomalies by temperature-gradient and seismic methods was undertaken to define structure and potential of the geothermal resource. The gravity data show a graben structure in the area. Seismic reflection data indicate faults associated with surface-resistivity and temperature-gradient data. The data support the interpretation that the shallow reservoirs are replenished along the fault zones by deeply circulating heated meteoric waters. -Author

Water mass formation and circulation in the Persian Gulf and water exchange with the Indian Ocean

NASA Astrophysics Data System (ADS)

Yao, Fengchao

The Persian Gulf is a shallow, semi-enclosed marginal sea where the Persian Gulf Water (PGW), one of the most saline water masses in the world, is formed due to the arid climate. The PGW flushes out of the Persian Gulf as a deep outflow and induces a surface inflow of the Indian Ocean Surface Water (IOSW), driving an inverse-estuarine type water exchange through the Strait of Hormuz. In this dissertation, the circulation and water mass transformation processes in the Persian Gulf and the water exchange with the Indian Ocean through the Strait of Hormuz, in response to the atmospheric forcing, are studied using the HYbrid Coordinate Ocean Model (HYCOM). The model is driven by surface wind stress, heat and fresh water fluxes derived from two sources: the COADS (Comprehensive Ocean-Atmosphere Data Set) monthly climatology and high frequency (2-hourly) MM5 (The Fifth-Generation NCAR/Penn State Mesoscale Model) output. This study is motivated by the time series measurements in the Strait during December 1996 to March 1998 by Johns et al. (2003), which also serve as a major benchmark for evaluating the model results. The simulations with climatological forcing show that the IOSW propagates in two branches into the Gulf, one along the Iranian coast toward the northern gulf and the other one onto the southern banks driven by the Ekman drift by the prevailing northwesterly winds. These two branches of inflow form two cyclonic gyres in the northern and in the southern gulf respectively. Cold, saline deep waters are formed both in the northern gulf and in the southern gulf during the wintertime cooling period and their exports contribute seasonally to the outflow in the strait. After formation in winter, the dense water in the shallow southwestern gulf spills off into the strait and causes high-salinity pulses in the outflow in the strait, a phenomenon also present in the observations. The export of dense waters from the northern gulf persists throughout the year, with the largest cold water export in summer. The intrusion of the IOSW in the model extends much farther into the Gulf in summer than in winter, which is in agreement with observations. By analyzing the salt balance in the basin and conducting sensitivity experiments, we show that it is the balance between the advection of IOSW and vertical upward flux induced by vertical mixing that mainly controls the seasonal variation of the surface salinity. The surface salinity in winter is increased by upward mixing from saltier subsurface waters, which is caused by the strong vertical mixing condition maintained by the surface heat loss. Surface wind stress, which opposes the inflow and is stronger in winter than in summer, plays a secondary role in modulating the seasonal intrusion of the IOSW. The MM5 high frequency forcing, capable of resolving synoptic weather events, leads to increased heat loss in winter, enhanced vertical mixing and higher annual mean evaporation rate. In the simulation with the high frequency forcing, the waters in the gulf are generally about 3°C colder and 1 psu fresher than with COADS forcing, and agree better with observations. The high-frequency forcing has little effect on the export of the dense waters from the northern gulf but delays the spillage of the waters from the southern gulf to April. A notable synoptic feature of the simulations is the annual appearance of eddies along the intruding salinity front. The typical sizes of the fully developed eddies in summer are about 100 km, about 3 times of the local Rossby deformation radius, consistent with a baroclinic instability process. The existence of these eddies is confirmed in satellite images of surface temperature in the Gulf.

Aquarius: An Instrument to Monitor Sea Surface Salinity from Space

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lagerloef, G. S .E.; Colomb, R.; Yueh, S.; Pellerano, F.

2007-01-01

Aquarius is a combined passive/active L-band microwave instrument that is being developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, global water cycle, and climate. Aquarius is part of the Aquarius/SAC-D mission, which is a partnership between the U.S. (National Aeronautics and Space Administration) and Argentina (CONAE). The primary science objective of this mission is to monitor the seasonal and interannual variation of the large-scale features of the surface salinity field in the open ocean with a spatial resolution of 150 km and a retrieval accuracy of 0.2 psu globally on a monthly basis.

Dynamics of collision of a vortex ring and a planar surface

NASA Astrophysics Data System (ADS)

McErlean, Michael; Krane, Michael; Fontaine, Arnold

2009-11-01

The dynamics of the impact between a vortex ring and a planar surface orientated perpendicular to the direction of travel are presented. High Reynolds number vortex rings are injected into a quiescent tank of water using a piston-cylinder generator before colliding with a target at a long distance. Both the pressure at the stagnation point on the surface and the force imparted to the target by the ring impact are measured directly. The changes in both are related to the ring motion and deformation captured by high speed digital video, and DPIV measurements. These relations are used to develop a scaling law relation between impact force and vortex ring circulation, speed, and size.

Further evidence for a link between Late Pleistocene North Atlantic surface temperatures and North Atlantic deep-water production

NASA Astrophysics Data System (ADS)

Boyle, Edward A.; Rosener, Paula

1990-10-01

Reduced surface temperatures, salinity and North Atlantic Deep-Water (NADW) formation rate may be mechanistically linked. Previous studies have demonstrated the co-occurrence of lowered high-latitude T and NADW during glacial maxima and the brief ( t 1000 yr) Younger Dryas cooling event 10,500 years ago. This behavior also appears as a feature of a recent coupled ocean/atmosphere general circulation model. Here, it is shown that rapid fluctuations in North Atlantic surface temperatures (as indicated by variations from 7 to 22% left-cooling N. pachyderma) during oxygen isotope stage 3 also may be linked to fluctuations in deep-water chemistry (as indicated by benthic Cd/Ca variations from 0.080 to 0.120 μmol. mol. -1). Two complete cycles in both properties are observed in 30 cm of sediment; bioturbation modeling suggests that the true extrema are muted and that the reproducibility of replicate analyses is primarily limited by the sampling statistics of bioturbated mixrure. The current evidence raises the question of whether NADW is regulated by a "switch" or by a "valve".

A sigma-coordinate primitive equation model for studying the circulation in the South Atlantic Part II: Meridional transports and seasonal variability

NASA Astrophysics Data System (ADS)

Marchesiello, P.; Barnier, B.; de Miranda, A. P.

1998-04-01

The mean and seasonal variability of the circulation and meridional heat transport in the South Atlantic are investigated using a set of numerical experiments. The primitive equation model uses a topography-following (sigma) coordinate. The model domain is limited to the South Atlantic basin. Artificial boundaries at Drake Passage, between Brazil and Angola, and between South Africa and Antarctica are treated as open boundaries. Finally, recent and self-consistent estimates of seasonal fluxes are used to define a model-dependent atmospheric forcing. Quasi-diagnostic simulations forced by constant climatological winds are first conducted to determine the sensitivity of model solutions to bottom topography smoothing, and to diagnose meridional fluxes from a mass field that is relaxed to the annual climatology of Levitus (1982). Model results show good agreement with known climatological circulation features in this basin, especially in the Confluence Region, where coarse resolution models usually give smooth structures. Sensitivity studies show that the more detailed features of the circulation are influenced by the model bathymetry. The model simulates a meridional circulation whose upper branch (the return flow that balances the southward flow of North Atlantic Deep Water) is composed of Intermediate (IW) and Thermocline (TW) Waters. The transport of IW is found to be predominant, and the value of meridional heat transport consequently falls within the low estimates. We notice that the meridional heat balance is sensitive to the position of the Confluence. When this region occurs too far south, the amount of IW contributing to the return flow of the overturning cell is reduced. Prognostic simulations forced by seasonal winds and heat fluxes are studied to quantify the impact of wind forcing on the circulation in the South Atlantic. Particular attention is focused on meridional transports at 30°S. Analysis of the mean annual circulation confirms that the upper branch of the meridional circulation is predominantly composed of IW (9 Sv), rather than TW (5.3 Sv). The mean transport of the lower branch is 16 Sv, in agreement with recent estimates by Schlitzer (1996). The annual meridional heat transport (0.29 PW) is still within the low estimates, but agrees well with other estimates that give a dominant role to IW (Rintoul, 1991). Original results also concern the variability of the upper branch of the meridional circulation. It is shown that the wind creates seasonal variability in the Subtropical Gyre, which has a marked impact on the water mass balance in the South Atlantic. In winter, a large convergence to the north of the Subtropical Gyre (27°S) reduces the northward flow of IW, whereas stronger Ekman pumping favors an equatorward transport of TW. In summer, this convergence disappears and a larger transport of IW is allowed. Thus a more complex scheme is proposed for the meridional circulation, in which local wind forcing in the South Atlantic Basin has a significant role in preconditioning the surface waters of the global overturning cell.

Marine resources. [coastal processes, ice, oceanography, and living marine resources

NASA Technical Reports Server (NTRS)

Tilton, E. L., III

1974-01-01

Techniques have been developed for defining coastal circulation patterns using sediment as a natural tracer, allowing the formulation of new circulation concepts in some geographical areas and, in general, a better capability for defining the seasonal characteristics of coastal circulation. An analytical technique for measurement of absolute water depth based upon the ratios of two MSS channels has been developed. Suspended sediment has found wide use as a tracer, but a few investigators have reported limited success in measuring the type and amount of sediment quantitatively from ERTS-1 digital data. Significant progress has been made in developing techniques for using ERTS-1 data to locate, identify, and monitor sea and lake ice. Ice features greater than 70 meters in width can be detected, and both arctic and antarctic icebergs have been identified. In the application area of living marine resources, the use of ERTS-1 image-density patterns as a potential indicator of fish school location has been demonstrated for one coastal commercial resource, menhaden. ERTS-1 data have been used to locate ocean current boundaries using ERTS-1 image-density enhancement, and some techniques are under development for measurement of suspended particle concentration and chlorophyll concentration. The interrelationship of water color and surface characteristics (sea state) are also being studied to improve spectral and spatial interpretive techniques.

Wave–turbulence interaction-induced vertical mixing and its effects in ocean and climate models

PubMed Central

Qiao, Fangli; Yuan, Yeli; Deng, Jia; Dai, Dejun; Song, Zhenya

2016-01-01

Heated from above, the oceans are stably stratified. Therefore, the performance of general ocean circulation models and climate studies through coupled atmosphere–ocean models depends critically on vertical mixing of energy and momentum in the water column. Many of the traditional general circulation models are based on total kinetic energy (TKE), in which the roles of waves are averaged out. Although theoretical calculations suggest that waves could greatly enhance coexisting turbulence, no field measurements on turbulence have ever validated this mechanism directly. To address this problem, a specially designed field experiment has been conducted. The experimental results indicate that the wave–turbulence interaction-induced enhancement of the background turbulence is indeed the predominant mechanism for turbulence generation and enhancement. Based on this understanding, we propose a new parametrization for vertical mixing as an additive part to the traditional TKE approach. This new result reconfirmed the past theoretical model that had been tested and validated in numerical model experiments and field observations. It firmly establishes the critical role of wave–turbulence interaction effects in both general ocean circulation models and atmosphere–ocean coupled models, which could greatly improve the understanding of the sea surface temperature and water column properties distributions, and hence model-based climate forecasting capability. PMID:26953182

Nearshore circulation and water-column properties in the Skagit River Delta, northern Puget Sound, Washington: juvenile Chinook Salmon habitat availability in the Swinomish Channel

USGS Publications Warehouse

Grossman, Eric E.; Stevens, Andrew W.; Gelfenbaum, Guy; Curran, Christopher

2007-01-01

Time-series and spatial measurements of nearshore hydrodynamic processes and water properties were made in the Swinomish Channel to quantify the net direction and rates of surface water transport that influence habitat for juvenile Chinook salmon along their primary migratory corridor between the Skagit River and Padilla Bay in northern Puget Sound, Washington. During the spring outmigration of Skagit River Chinook between March and June 2007, currents measured with fixed acoustic doppler current profilers (ADCP) at the south and north end of the Swinomish Channel and with roving ADCP revealed that the currents are highly asymmetric with a dominant flow to the north (toward Padilla Bay). Maximum surface current velocities reached 1.5 m/s and were generally uniform across the channel near McGlinn Island Causeway. Transport times for surface water to travel the 11 km from the southern end of Swinomish Channel at McGlinn Island to Padilla Bay ranged from 2.1 hours to 5.5 days. The mean travel time was ~1 day, while 17 percent of the time, transport of water and passive particles occurred within 3.75 hours. Surface water in the Swinomish Channel during this time was generally very saline 20-27 psu, except south of the Rainbow Bridge in the town of La Conner where it ranged 0-15 psu depending on tide and Skagit River discharge. This salinity regime restricts suitable low salinity (

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhaoqing; Wang, Taiping

A three-dimensional coastal ocean model with a tidal turbine module was used in this paper to study the effects of tidal energy extraction on temperature and salinity stratification and density driven two-layer estuarine circulation. Numerical experiments with various turbine array configurations were carried out to investigate the changes in tidally mean temperature, salinity and velocity profiles in an idealized stratified estuary that connects to coastal water through a narrow tidal channel. The model was driven by tides, river inflow and sea surface heat flux. To represent the realistic size of commercial tidal farms, model simulations were conducted based on amore » small percentage of the total number of turbines that would generate the maximum extractable energy in the system. Model results indicated that extraction of tidal energy will increase the vertical mixing and decrease the stratification in the estuary. Extraction of tidal energy has stronger impact on the tidally-averaged salinity, temperature and velocity in the surface layer than the bottom. Energy extraction also weakens the two-layer estuarine circulation, especially during neap tides when tidal mixing the weakest and energy extraction is the smallest. Model results also show that energy generation can be much more efficient with higher hub height with relatively small changes in stratification and two-layer estuarine circulation.« less

Changes in Microbial Plankton Assemblages Induced by Mesoscale Oceanographic Features in the Northern Gulf of Mexico.

PubMed

Williams, Alicia K; McInnes, Allison S; Rooker, Jay R; Quigg, Antonietta

2015-01-01

Mesoscale circulation generated by the Loop Current in the Northern Gulf of Mexico (NGOM) delivers growth-limiting nutrients to the microbial plankton of the euphotic zone. Consequences of physicochemically driven community shifts on higher order consumers and subsequent impacts on the biological carbon pump remain poorly understood. This study evaluates microbial plankton <10 μm abundance and community structure across both cyclonic and anti-cyclonic circulation features in the NGOM using flow cytometry (SYBR Green I and autofluorescence parameters). Non-parametric multivariate hierarchical cluster analyses indicated that significant spatial variability in community structure exists such that stations that clustered together were defined as having a specific 'microbial signature' (i.e. statistically homogeneous community structure profiles based on relative abundance of microbial groups). Salinity and a combination of sea surface height anomaly and sea surface temperature were determined by distance based linear modeling to be abiotic predictor variables significantly correlated to changes in microbial signatures. Correlations between increased microbial abundance and availability of nitrogen suggest nitrogen-limitation of microbial plankton in this open ocean area. Regions of combined coastal water entrainment and mesoscale convergence corresponded to increased heterotrophic prokaryote abundance relative to autotrophic plankton. The results provide an initial assessment of how mesoscale circulation potentially influences microbial plankton abundance and community structure in the NGOM.

The Influence of Water Circulation on Dissolved Organic Matter Dynamics in Bald Head Creek

NASA Astrophysics Data System (ADS)

Lebrasse, M. C.; Osburn, C. L.; Bohnenstiehl, D. R.; He, R.

2016-12-01

Dissolved organic matter (DOM) plays an important role in biogeochemical cycles in estuaries such as tidal creeks draining coastal wetlands such as salt marshes. However, significant knowledge gaps remain regarding the quantity and quality of the DOM that tidally exchanges between salt marshes and their adjacent estuaries. Tidal movements play a central role in lateral exchanges of materials and bidirectional flow results in the mixing of DOM from marsh plants and estuarine DOM. The aim of this study was to better understand the role of water circulation on the distribution and quality of DOM in Bald Head Creek, a tributary to the Cape Fear River estuary in eastern North Carolina. Dissolved organic carbon (DOC) concentration, stable carbon isotopes, and chromophoric DOM (CDOM) absorbance at 254 nm (a254) were used to distinguish between DOM quantity and quality at three locations along the creek: Site 3 (upstream), Site 2 (middle stream), and Site 1 (near the creek mouth). Samples were collected over four tidal cycles between March-August 2016 and compared to time series data collected approximately weekly from 2014-2016. DOM characteristics differed substantially over the tidal cycle. Higher CDOM and DOC concentration were observed at low tide than at high tide at all three sites, suggesting greater export of carbon from the marsh into the creek as the tides recede. Analysis of CDOM quality based on specific UV absorbance at 254 nm (SUVA254) and spectral slope ratio (SR) showed that the marsh end-member (Site 3) source of DOM had greater aromaticity and higher molecular weight. Site 1 showed greater variability over the tidal cycle most likely due to a greater tidal influence, being closer to the mouth. Additionally, an unmanned surface vehicle (USV) and a hydrodynamic model were used to map water circulation and DOC concentration along the creek to compute exchanges with the adjacent estuary. Results suggest that estuarine OM dynamics are strongly controlled by the circulation of water, especially for tidal creeks where tidal pumping can dominate lateral fluxes of DOM to adjacent waters.

The GEM-Mars general circulation model for Mars: Description and evaluation

NASA Astrophysics Data System (ADS)

Neary, L.; Daerden, F.

2018-01-01

GEM-Mars is a gridpoint-based three-dimensional general circulation model (GCM) of the Mars atmosphere extending from the surface to approximately 150 km based on the GEM (Global Environmental Multiscale) model, part of the operational weather forecasting and data assimilation system for Canada. After the initial modification for Mars, the model has undergone considerable changes. GEM-Mars is now based on GEM 4.2.0 and many physical parameterizations have been added for Mars-specific atmospheric processes and surface-atmosphere exchange. The model simulates interactive carbon dioxide-, dust-, water- and atmospheric chemistry cycles. Dust and water ice clouds are radiatively active. Size distributed dust is lifted by saltation and dust devils. The model includes 16 chemical species (CO2, Argon, N2, O2, CO, H2O, CH4, O3, O(1D), O, H, H2, OH, HO2, H2O2 and O2(a1Δg)) and has fully interactive photochemistry (15 reactions) and gas-phase chemistry (31 reactions). GEM-Mars provides a good simulation of the water and ozone cycles. A variety of other passive tracers can be included for dedicated studies, such as the emission of methane. The model has both a hydrostatic and non-hydrostatic formulation, and together with a flexible grid definition provides a single platform for simulations on a variety of horizontal scales. The model code is fully parallelized using OMP and MPI. Model results are evaluated by comparison to a selection of observations from instruments on the surface and in orbit, relating to atmosphere and surface temperature and pressure, dust and ice content, polar ice mass, polar argon, and global water and ozone vertical columns. GEM-Mars will play an integral part in the analysis and interpretation of data that is received by the NOMAD spectrometer on the ESA-Roskosmos ExoMars Trace Gas Orbiter. The present paper provides an overview of the current status and capabilities of the GEM-Mars model and lays the foundations for more in-depth studies in support of the NOMAD mission.

Integration of remote sensing and geographic information systems for Great Lakes water quality monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lathrop, R.G. Jr.

1988-01-01

The utility of three operational satellite remote sensing systems, namely, the Landsat Thematic Mapper (TM), the SPOT High Resolution Visible (HRV) sensors and the NOAA Advanced Very High Resolution Radiometer (AVHRR), were evaluated as a means of estimating water quality and surface temperature. Empirical calibration through linear regression techniques was used to relate near-simultaneously acquired satellite radiance/reflectance data and water quality observations obtained in Green Bay and the nearshore waters of Lake Michigan. Four dates of TM and one date each of SPOT and AVHRR imagery/surface reference data were acquired and analyzed. Highly significant relationships were identified between the TMmore » and SPOT data and secchi disk depth, nephelometric turbidity, chlorophyll a, total suspended solids (TSS), absorbance, and surface temperature (TM only). The AVHRR data were not analyzed independently but were used for comparison with the TM data. Calibrated water quality image maps were input to a PC-based raster GIS package, EPPL7. Pattern interpretation and spatial analysis techniques were used to document the circulation dynamics and model mixing processes in Green Bay. A GIS facilitates the retrieval, query and spatial analysis of mapped information and provides the framework for an integrated operational monitoring system for the Great Lakes.« less

Water softening by induced crystallization in fluidized bed.

PubMed

Chen, Yuefang; Fan, Rong; An, Danfeng; Cheng, Yujie; Tan, Hazel

2016-12-01

Fluidized bed and induced crystallization technology were combined to design a new type of induced crystallization fluidized bed reactor. The added particulate matter served as crystal nucleus to induce crystallization so that the insoluble material, which was in a saturated state, could precipitate on its surface. In this study, by filling the fluidized bed with quartz sand and by adjusting water pH, precipitation of calcium carbonate was induced on the surface of quartz sand, and the removal of water hardness was achieved. With a reactor influent flow of 60L/hr, a fixed-bed height of 0.5m, pH value of 9.5, quartz sand nuclear diameter of 0.2-0.4mm, and a reflux ratio of 60%, the effluent concentration of calcium hardness was reduced to 60mg/L and 86.6% removal efficiency was achieved. The resulting effluent reached the quality standard set for circulating cooling water. Majority of the material on the surface of quartz sand was calculated to be calcium carbonate based on energy spectrum analysis and moisture content was around 15.994%. With the low moisture content, dewatering treatment is no longer required and this results to cost savings on total water treatment process. Copyright © 2016. Published by Elsevier B.V.

Equatorial dynamics in a 2 {1}/{2}- layer model

NASA Astrophysics Data System (ADS)

McCreary, Julian P.; Yu, Zuojun

A nonlinear, 2 {1}/{2}- layer model is used to study the dynamics of wind-driven equatorial ocean circulation, including the generation of mean flows and instabilities. The model allows water to entrain into, and detrain from, the upper layer, and as a consequence the temperatures of the two active layers can vary. The model ocean basin is rectangular, extends 100° zonally, and for most solutions has open boundaries at 15°S and 15°N. All solutions are forced by a switched-on wind field that is an idealized version of the Pacific trades: the wind is westward, uniform in the meridional direction (so it has no curl), located primarily in the central and eastern oceans, and in most cases it has an amplitude of 0.5 dyn cm -2. For reasonable choices of parameters, solutions adjust to have a realistic equatorial circulation with a westward surface jet, an eastward undercurrent, and with upwelling and cool sea surface temperature in the eastern ocean. Most of the meridional circulation (81% of the transport) is part of a closed tropical circulation cell, in which water upwells in the eastern, equatorial ocean and downwells elsewhere in the basin; the rest participates in a mid-latitude circulation cell with lower-layer water entering the basin and upper-layer water leaving it through the open boundaries. Three basic types of unstable disturbances are generated in the eastern ocean: two of them are antisymmetric about the equator, one being surface-trapped with a period of about 21 days (f 1), and the other predominantly a lower-layer oscillation with periods ranging from 35 to 53 days (f 2) that causes the undercurrent to meander; the third is symmetric with a period of about 28 days (f 0) and a structure like that of a first-meridional-mode Rossby wave. The amplitudes of the disturbances are sensitive to model parameters, and as parameter values are varied systematically solutions appear to follow variations of the quasi-periodic route to turbulence, one of the common transitions to chaotic behavior. Realistic mean flows develop only when detrainment and lower-layer cooling are present in the model physics, processes that are necessary for the generation of a tropical circulation cell: without detrainment, water accumulutes in the upper layer until entrainment ceases and the model adjusts to Sverdrup balance, which is a state of rest for a wind without curl; without cooling, the temperature of the lower layer slowly rises until it approaches that of the upper layer. The mean-momentum budget for the upper layer shows that the model's Reynolds-stress terms are not a significant part of the momentum balance, having a maximum amplitude only about 19% of the wind stress. In contrast, the mean-heat budget demonstrates that eddy heating warms the cold tongue significantly, with an amplitude as large as the heating through the surface. Interestingly, the time-averaged continuity equations indicate that the instabilities tend to increase the upward tilt of the upper-layer interface toward the equator. When layer temperatures are kept fixed only a weak version of disturbance f 1 develops, indicating that the equatorial temperature front is an important aspect of instability dynamics. In fact, a frontal instability does exist in the model; it involves the conversion of mean to eddy potential energy, but it is the mean energy associated with the variable upper-layer temperature field, rather than with tilted layer interfaces, as is the case for traditional baroclinic instability. Perturbation-energy budgets suggest that frontal, barotropic and Kelvin-Helmholtz instabilities are energy sources for the disturbances, whereas traditional baroclinic instability is an energy sink. The two, fastest growing, antisymmetric, unstable-wave solutions to a linearized version of the model correspond closely to disturbances f 1 and f 2 from the nonlinear model, and perturbation-energy budgets for these waves indicate that their energy sources are primarily frontal instability and lower-layer barotropic instability, respectively.

Salinity minima, water masses and surface circulation in the Eastern Tropical Pacific off Mexico and surrounding areas

NASA Astrophysics Data System (ADS)

Portela, Esther; Beier, Emilio; Godínez, Victor; Castro, Rubén; Desmond Barton, Eric

2016-04-01

The seasonal variations of the water masses and their interactions are analyzed in the Tropical Pacific off Mexico (TPOM) and four contiguous areas of on the basis of new extensive hydrographic database. The regional water masses intervals are redefined in terms of Absolute Salinity (SA) in g kg-1 and Conservative Temperature (Θ) according to TEOS - 10. The California Current System Water (CCSW) mass is introduced as an improved description of the former California Current Water (CCW) together with the Subarctic Water (SAW) to describe better the characteristics of the components of the California Current System. Hydrographic data, Precipitation-Evaporation balance and geostrophic currents were used to investigate the origin and seasonality of two salinity minima in the area. The shallow salinity minimum of around 33.5 g kg-1 originated in the California Current System and became saltier but less dense water as it traveled to the southeast. It can be identified as a mixture of CCSW and tropical waters. The surface salinity minimum of 32 - 33 g kg-1 was seen as a sharp surface feature in the TPOM from August to November. It was produced by the arrival of tropical waters from the south in combination with the net precipitation in the area during these months. This result provides new evidence of the presence of the poleward-flowing Mexican Coastal Current and, for the first time, of its seasonal pattern of variation.

Application of Satellite Gravimetry for Water Resource Vulnerability Assessment

NASA Technical Reports Server (NTRS)

Rodell, Matthew

2012-01-01

The force of Earth's gravity field varies in proportion to the amount of mass near the surface. Spatial and temporal variations in the gravity field can be measured via their effects on the orbits of satellites. The Gravity Recovery and Climate Experiment (GRACE) is the first satellite mission dedicated to monitoring temporal variations in the gravity field. The monthly gravity anomaly maps that have been delivered by GRACE since 2002 are being used to infer changes in terrestrial water storage (the sum of groundwater, soil moisture, surface waters, and snow and ice), which are the primary source of gravity variability on monthly to decadal timescales after atmospheric and oceanic circulation effects have been removed. Other remote sensing techniques are unable to detect water below the first few centimeters of the land surface. Conventional ground based techniques can be used to monitor terrestrial water storage, but groundwater, soil moisture, and snow observation networks are sparse in most of the world, and the countries that do collect such data rarely are willing to share them. Thus GRACE is unique in its ability to provide global data on variations in the availability of fresh water, which is both vital to life on land and vulnerable to climate variability and mismanagement. This chapter describes the unique and challenging aspects of GRACE terrestrial water storage data, examples of how the data have been used for research and applications related to fresh water vulnerability and change, and prospects for continued contributions of satellite gravimetry to water resources science and policy.

The effects of oil-in-water nanoemulsion polyethylene glycol surface density on intracellular stability, pharmacokinetics, and biodistribution in tumor bearing mice.

PubMed

Hak, Sjoerd; Garaiova, Zuzana; Olsen, Linda Therese; Nilsen, Asbjørn Magne; de Lange Davies, Catharina

2015-04-01

Lipid-based nanoparticles are extensively studied for drug delivery. These nanoparticles are often surface-coated with polyethylene glycol (PEG) to improve their biodistribution. Until now, the effects of varying PEG surface density have been studied in a narrow and low range. Here, the effects of high and a broad range of PEG surface densities on the in vivo performance of lipid-based nanoparticles were studied. Oil-in-water nanoemulsions were prepared with PEG surface densities of 5-50 mol%. Confocal microscopy was used to assess intracellular disintegration in vitro. In vivo pharmacokinetics and biodistribution in tumor bearing mice were studied using a small animal optical imager. PEG surface density did not affect intracellular nanoemulsion stability. Surprisingly, circulation half-lives decreased with increasing PEG surface density. A plausible explanation was that nanoemulsion with high (50 mol%) PEG surface density activated the complement in a whole blood assay, whereas nanoemulsion with low (5 mol%) PEG density did not. In vivo, nanoemulsion with low PEG surface density was mostly confined to the tumor and organs of the mononuclear phagocyte system, whereas nanoemulsion with high PEG density accumulated throughout the mouse. Optimal PEG surface density of lipid-based nanoparticles for tumor targeting was found to be below 10 mol%.

Chemistry-Climate Interactions in the Goddard Institute for Space Studies General Circulation Model. 2; New Insights into Modeling the Pre-Industrial Atmosphere

NASA Technical Reports Server (NTRS)

Grenfell, J. Lee; Shindell, D. T.; Koch, D.; Rind, D.; Hansen, James E. (Technical Monitor)

2002-01-01

We investigate the chemical (hydroxyl and ozone) and dynamical response to changing from present day to pre-industrial conditions in the Goddard Institute for Space Studies General Circulation Model (GISS GMC). We identify three main improvements not included by many other works. Firstly, our model includes interactive cloud calculations. Secondly we reduce sulfate aerosol which impacts NOx partitioning hence Ox distributions. Thirdly we reduce sea surface temperatures and increase ocean ice coverage which impact water vapor and ground albedo respectively. Changing the ocean data (hence water vapor and ozone) produces a potentially important feedback between the Hadley circulation and convective cloud cover. Our present day run (run 1, control run) global mean OH value was 9.8 x 10(exp 5) molecules/cc. For our best estimate of pre-industrial conditions run (run 2) which featured modified chemical emissions, sulfate aerosol and sea surface temperatures/ocean ice, this value changed to 10.2 x 10(exp 5) molecules/cc. Reducing only the chemical emissions to pre-industrial levels in run 1 (run 3) resulted in this value increasing to 10.6 x 10(exp 5) molecules/cc. Reducing the sulfate in run 3 to pre-industrial levels (run 4) resulted in a small increase in global mean OH (10.7 x 10(exp 5) molecules/cc). Changing the ocean data in run 4 to pre-industrial levels (run 5) led to a reduction in this value to 10.3 x 10(exp 5) molecules/cc. Mean tropospheric ozone burdens were 262, 181, 180, 180, and 182 Tg for runs 1-5 respectively.

Simulation of Dust Radiative Impact on the Red Sea Using Coupled Regional Ocean/Atmosphere Modeling System

NASA Astrophysics Data System (ADS)

Stenchikov, G. L.; Osipov, S.

2016-12-01

This study focuses on the Middle East regional climate response to the dust aerosol radiative forcing. MODIS and SEVIRI satellite observations show extremely high (exceeding 1) dust optical depths over the southern Red Sea during the summer season. The significant north-to-south gradient of the dust optical depth over the Red Sea persists throughout the entire year. The radiative forcing of dust at the sea surface exceeds 120 Wm-2. The effect of this forcing to the Red Sea thermal regime and circulations is not well quantified yet. Therefore here we employ the Regional Ocean Modeling system (ROMS) fully coupled with the Weather Research and Forecasting (WRF) model to study the impact of dust on the Red Sea. The WRF was modified to interactively account for the radiative effect of dust. Daily spectral optical properties of dust are computed using Mie, T-matrix and geometric optics approaches, and are based on the SEVIRI climatological optical depth. The WRF model parent and nested domains are configured over the Middle East and North Africa (MENA) region and over the Red Sea with 30 and 10 km resolution, respectively. The ROMS model over the Red Sea has 2 km grid spacing. The simulations show that, in the equilibrium response, dust causes 0.5-0.7K cooling of the Red Sea surface waters, and weakens the overturning circulation in the Red Sea. The salinity distribution, fresh water and heat budgets are significantly perturbed. This indicates that dust plays an important role in formation of the Red Sea energy balance and circulation regimes, and has to be thoroughly accounted for in the future modeling studies.

Periodic fluctuations in deep water formation due to sea ice

NASA Astrophysics Data System (ADS)

Saha, R.

2012-12-01

During the last ice age, several abrupt warming events took place, known as Dansgaard-Oeschger (D-O) events. Their effects were felt globally, although the North Atlantic experienced the largest temperature increase. The leading hypothesis to explain their occurrence postulates that the warming was caused by abrupt disruptions of the North Atlantic Current due to meltwater discharge from destabilized ice sheets (Heinrich events). However, the number of warming events outnumber the those of ice-sheet collapse. Thus, the majority of D-O events are not attributed to surface freshwater anomalies, and the underlying mechanism behind their occurrence remain unexplained. Using a simple dynamical model of sea ice and an overturning circulation, I show the existence of self-sustained relaxation oscillations in the overturning circulation. The insulating effect of sea ice is shown to paradoxically lead to a net loss of heat from the top layer of the polar ocean when sea ice retreats. Repeated heat loss results in a denser top layer and a destabilized water column, which triggers convection. The convective state pulls the system out of its preferred mode of circulation, setting up relaxation oscillations. The period of oscillations in this case is linked to the geometry of the ocean basin, if solar forcing is assumed to remain constant. If appropriate glacial freshwater forcing is applied to the model, a pattern of oscillation is produced that bears remarkable similarity to the observed fluctuations in North Atlantic climate between 50,000 and 30,000 years before present.; Comparison of NGRIP δ 18-O (proxy for near surface air temperature) between 50,000 and 30,000 years before present, showing Bond cycles (left) with the model output when forced with appropriate glacial freshwater forcing (right).

The Southern Ocean in the Coupled Model Intercomparison Project phase 5

PubMed Central

Meijers, A. J. S.

2014-01-01

The Southern Ocean is an important part of the global climate system, but its complex coupled nature makes both its present state and its response to projected future climate forcing difficult to model. Clear trends in wind, sea-ice extent and ocean properties emerged from multi-model intercomparison in the Coupled Model Intercomparison Project phase 3 (CMIP3). Here, we review recent analyses of the historical and projected wind, sea ice, circulation and bulk properties of the Southern Ocean in the updated Coupled Model Intercomparison Project phase 5 (CMIP5) ensemble. Improvements to the models include higher resolutions, more complex and better-tuned parametrizations of ocean mixing, and improved biogeochemical cycles and atmospheric chemistry. CMIP5 largely reproduces the findings of CMIP3, but with smaller inter-model spreads and biases. By the end of the twenty-first century, mid-latitude wind stresses increase and shift polewards. All water masses warm, and intermediate waters freshen, while bottom waters increase in salinity. Surface mixed layers shallow, warm and freshen, whereas sea ice decreases. The upper overturning circulation intensifies, whereas bottom water formation is reduced. Significant disagreement exists between models for the response of the Antarctic Circumpolar Current strength, for reasons that are as yet unclear. PMID:24891395

Nutrient pumping by submesoscale circulations in the mauritanian upwelling system

NASA Astrophysics Data System (ADS)

Hosegood, P. J.; Nightingale, P. D.; Rees, A. P.; Widdicombe, C. E.; Woodward, E. M. S.; Clark, D. R.; Torres, R. J.

2017-12-01

Observations made within a cold filament in the Mauritanian upwelling system demonstrate that intense submesoscale circulations at the peripheral edges of the filament are likely responsible for anomalously high levels of observed primary productivity by resupplying nutrients to the euphotic zone. Measurements made on the shelf within the recently upwelled water reveal that primary production (PP) of 8.2 gC/m-2 day-1 was supported by nitrate concentrations (NC) of 8 mmol m-3. Towards the front that defined the edge of the filament containing the upwelled water as it was transported offshore, PP dropped to 1.6 gC m-2 day-1 whilst NC dropped to 5.5 mmol m-3. Thus, whilst the observed nutrients on the shelf accounted for 90% of new production, this value dropped to ∼60% near the filament's front after accounting for vertical turbulent fluxes and Ekman pumping. We demonstrate that the N15 was likely to have been supplied at the front by submesoscale circulations that were directly measured as intense vertical velocities ⩾100 m day-1 by a drifting acoustic Doppler current profiler that crossed a submesoscale surface temperature front. At the same time, a recently released tracer was subducted out of the mixed layer within 24 h of release, providing direct evidence that the frontal circulations were capable of accessing the reservoir of nutrients beneath the pycnocline. The susceptibility of the filament edge to submesoscale instabilities was demonstrated by O(1) Rossby numbers at horizontal scales of 1-10 km. The frontal circulations are consistent with instabilities arising from a wind-driven nonlinear Ekman buoyancy flux generated by the persistent northerly wind stress that has a down-front component at the northern edge of the inshore section of the filament. The prevalence of submesoscale instabilities and their associated vertical circulations are proposed to be a key mechanism operating at sub-grid scales and sustaining new production throughout the upwelling system.

46 CFR 56.50-45 - Circulating pumps.

Code of Federal Regulations, 2010 CFR

2010-10-01

... APPURTENANCES Design Requirements Pertaining to Specific Systems § 56.50-45 Circulating pumps. (a) A main circulating pump and emergency means for circulating water through the main condenser shall be provided. The... circulating pump and the condenser. (b) Independent sea suctions shall be provided for the main circulating...

Comparison of GCM subgrid fluxes calculated using BATS and SiB schemes with a coupled land-atmosphere high-resolution model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Jinmei; Arritt, R.W.

The importance of land-atmosphere interactions and biosphere in climate change studies has long been recognized, and several land-atmosphere interaction schemes have been developed. Among these, the Simple Biosphere scheme (SiB) of Sellers et al. and the Biosphere Atmosphere Transfer Scheme (BATS) of Dickinson et al. are two of the most widely known. The effects of GCM subgrid-scale inhomogeneities of surface properties in general circulation models also has received increasing attention in recent years. However, due to the complexity of land surface processes and the difficulty to prescribe the large number of parameters that determine atmospheric and soil interactions with vegetation,more » many previous studies and results seem to be contradictory. A GCM grid element typically represents an area of 10{sup 4}-10{sup 6} km{sup 2}. Within such an area, there exist variations of soil type, soil wetness, vegetation type, vegetation density and topography, as well as urban areas and water bodies. In this paper, we incorporate both BATS and SiB2 land surface process schemes into a nonhydrostatic, compressible version of AMBLE model (Atmospheric Model -- Boundary-Layer Emphasis), and compare the surface heat fluxes and mesoscale circulations calculated using the two schemes. 8 refs., 5 figs.« less

Aquarius SAC-D Launch

NASA Image and Video Library

2011-06-09

A Delta II rocket launches with the Aquarius/SAC-D spacecraft payload from Space Launch Complex 2 at Vandenberg Air Force Base, Calif. on Friday, June 10, 2011. The joint U.S./Argentinian Aquarius/Satélite de Aplicaciones Científicas (SAC)-D mission will map the salinity at the ocean surface, information critical to improving our understanding of two major components of Earth's climate system: the water cycle and ocean circulation. Photo Credit: (NASA/Bill Ingalls)

The Modelling Analysis of the Response of Convective Transport of Energy and Water to Multiscale Surface Heterogeneity over Tibetan Plateau

NASA Astrophysics Data System (ADS)

SUN, G.; Hu, Z.; Ma, Y.; Ma, W.

2017-12-01

The land-atmospheric interactions over a heterogeneous surface is a tricky issue for accurately understanding the energy-water exchanges between land surface and atmosphere. We investigate the vertical transport of energy and water over a heterogeneous land surface in Tibetan Plateau during the evolution of the convective boundary layer using large eddy simulation (WRF_LES). The surface heterogeneity is created according to remote sensing images from high spatial resolution LandSat ETM+ images. The PBL characteristics over a heterogeneous surface are analyzed in terms of secondary circulations under different background wind conditions based on the horizontal and vertical distribution and evolution of wind. The characteristics of vertical transport of energy and heat over a heterogeneous surface are analyzed in terms of the horizontal distribution as well as temporal evolution of sensible and latent heat fluxes at different heights under different wind conditions on basis of the simulated results from WRF_LES. The characteristics of the heat and water transported into the free atmosphere from surface are also analyzed and quantified according to the simulated results from WRF_LES. The convective transport of energy and water are analyzed according to horizontal and vertical distributions of potential temperature and vapor under different background wind conditions. With the analysis based on the WRF_LES simulation, the performance of PBL schemes of mesoscale simulation (WRF_meso) is evaluated. The comparison between horizontal distribution of vertical fluxes and domain-averaged vertical fluxes of the energy and water in the free atmosphere is used to evaluate the performance of PBL schemes of WRF_meso in the simulation of vertical exchange of energy and water. This is an important variable because only the energy and water transported into free atmosphere is able to influence the regional and even global climate. This work would will be of great significance not only for understanding the land atmosphere interactions over a heterogeneous surface by evaluating and improving the performance PBL schemes in WRF-meso, but also for the understanding the profound effect of Tibetan Plateau on the regional and global climate.

The Relationship between Climate and Iceland Scotland Overflow Water During Mid-Late Pleistocene Interglacials

NASA Astrophysics Data System (ADS)

Nuber, S.; Thornalley, D.; Forman, M.; Barker, S.; Oppo, D.

2016-12-01

Ocean circulation has been identified as an important climate feedback mechanism in a warming world. An area of particular importance in global ocean circulation is the high latitude North Atlantic and the Nordic Seas. Here, cooling of northward flowing warm surface water produces dense deep water which sinks to the ocean floor and returns southward as part of the Atlantic Meridional Overturning Circulation (AMOC). Density structures in the Nordic Seas can change as a response to enhanced freshwater input (e.g. from the melting Greenland Ice Sheet or a stronger hydrological cycle) which in turn may perturb the AMOC. It is therefore important that we develop our understanding of the relationship between climate and the return flow of dense water formed in the high latitude North Atlantic, focusing in particular on past warm climates that can act as partial analogues for future global warming scenarios. Previous work investigating the Holocene has revealed long-term trends in the strength of the dense overflow from the Nordic Seas into the North Atlantic via Iceland Scotland Overflow Water (ISOW). These changes have been related to variations in the freshwater budget and the water densities in the Nordic Seas (Thornalley et al., 2013). Across earlier interglacials, ISOW dynamics remain poorly constrained. To gain a more complete understanding of the coupling of climate and ISOW during past warm climates, we reconstructed ISOW flow speeds across an additional five Pleistocene interglacials, using the sortable silt proxy and a newly developed calibration curve. We find that there is large variability in inferred ISOW flow speeds between interglacials, as well as different temporal evolution of flow speed through the various interglacials. Our results suggest that preceded deglacial dynamics may be an important influence on the interglacial ISOW flow structure and highlight the tight coupling between climate and the ISOW.

Mechanisms of flow and water mass variability in Denmark Strait

NASA Astrophysics Data System (ADS)

Moritz, Martin; Jochumsen, Kerstin; Quadfasel, Detlef; Mashayekh Poul, Hossein; Käse, Rolf H.

2017-04-01

The dense water export through Denmark Strait contributes significantly to the lower limb of the Atlantic Meridional Overturning Circulation. Overflow water is transported southwestward not only in the deep channel of the Strait, but also within a thin bottom layer on the Greenland shelf. The flow on the shelf is mainly weak and barotropic, exhibiting many recirculations, but may eventually contribute to the overflow layer in the Irminger Basin by spilling events in the northern Irminger Basin. Especially the circulation around Dohrn Bank and the Kangerdlussuaq Trough contribute to the shelf-basin exchange. Moored observations show the overflow in Denmark Strait to be stable during the last 20 years (1996-2016). Nevertheless, flow variability was noticed on time scales of eddies and beyond, i.e. on weekly and interannual scales. Here, we use a combination of mooring data and shipboard hydrographic and current data to address the dominant modes of variability in the overflow, which are (i) eddies, (ii) barotropic pulsations of the plume, (iii) lateral shifts of the plume core position, and (iv) variations in vertical extension, i.e. varying overflow thickness. A principle component analysis is carried out and related to variations in sea surface height and wind stress, derived from satellite measurements. Furthermore, a test for topographic waves is performed. Shelf contributions to the overflow core in the Irminger Basin are identified from measurements of temperature and salinity, as well as velocity, which were obtained during recent cruises in the region. The flow and water mass pattern obtained from the observational data is compared to simulations in a high resolution regional model (ROMS), where tracer release experiments and float deployments were carried out. The modelling results allow a separation between different atmospheric forcing modes (NAO+ vs NAO- situations), which impact the water mass distribution and alter the dense water pathways on the Greenland shelf. Finally, the results are discussed with respect to other regional model studies on the circulation in the northern Irminger Basin.

The 2014 southeast Brazil austral summer drought: regional scale mechanisms and teleconnections

NASA Astrophysics Data System (ADS)

Coelho, Caio A. S.; de Oliveira, Cristiano Prestrelo; Ambrizzi, Tércio; Reboita, Michelle Simões; Carpenedo, Camila Bertoletti; Campos, José Leandro Pereira Silveira; Tomaziello, Ana Carolina Nóbile; Pampuch, Luana Albertani; Custódio, Maria de Souza; Dutra, Lívia Marcia Mosso; Da Rocha, Rosmeri P.; Rehbein, Amanda

2016-06-01

The southeast region of Brazil experienced in austral summer 2014 a major drought event leading to a number of impacts in water availability for human consumption, agricultural irrigation and hydropower production. This study aims to perform a diagnostic analysis of the observed climate conditions during this event, including an inspection of the occurred precipitation anomalies in the context of previous years, and an investigation of possible relationships with sea surface temperatures and atmospheric circulation patterns. The sea surface temperature analysis revealed that the southwestern South Atlantic Ocean region near the coast of southeast Brazil showed strong negative association with precipitation over southeast Brazil, indicating that increased sea temperatures in this ocean region are consistent with reduced precipitation as observed in summer 2014. The circulation analysis revealed prevailing anti-cyclonic anomalies at lower levels (850 hPa) with northerly anomalies to the west of southeast Brazil, channeling moisture from the Amazon towards Paraguay, northern Argentina and southern Brazil, and drier than normal air from the South Atlantic Ocean towards the southeast region of Brazil. This circulation pattern was found to be part of a large-scale teleconnection wave train linked with the subsidence branch of the Walker circulation in the tropical east Pacific, which in turn was generated by an anomalous tropical heat source in north/northeastern Australia. A regional Hadley circulation with an ascending branch to the south of the subsidence branch of the Walker circulation in the tropical east Pacific was identified as an important component connecting the tropical and extratropical circulation. The ascending branch of this Hadley circulation in the south Pacific coincided with an identified Rossby wave source region, which contributed to establishing the extratropical component of the large-scale wave train connecting the south Pacific and the Atlantic region surrounding southeast Brazil. This connection between the Pacific and the Atlantic was confirmed with Rossby ray tracing analyses. The local circulation response was associated to downward air motion (subsidence) over Southeast Brazil, contributing to the expressive negative precipitation anomalies observed during summer 2014, and leading to a major drought event in the historical context. The analysis of atmospheric and oceanic patterns of this event helped defining a schematic framework leading to the observed drought conditions in southeast Brazil, including the involved teleconnections, blocking high pressure, radiative and humidity transport effects.

Geoethical Approach to Antarctic Subglacial Lakes Exploration

NASA Astrophysics Data System (ADS)

Talalay, Pavel; Markov, Alexey; Sysoev, Mikhail

2014-05-01

Antarctic subglacial aquatic environment have become of great interest to the science community because they may provide unique information about microbial evolution, the past climate of the Earth, and the formation of the Antarctic ice sheet. Nowadays it is generally recognized that a vast network of lakes, rivers, and streams exists thousands of meters beneath Antarctic Ice Sheets. Up to date only four boreholes accessed subglacial aquatic system but three of them were filled with high-toxic drilling fluid, and the subglacial water was contaminated. Two recent exploration programs proposed by UK and USA science communities anticipated direct access down to the lakes Ellsworth and Whillans, respectively, in the 2012/2013 Antarctic season. A team of British scientists and engineers engaged in the first attempt to drill into Lake Ellsworth but failed. US research team has successfully drilled through 800 m of Antarctic ice to reach a subglacial lake Whillans and retrieve water and sediment samples. Both activities used hot-water drilling technology to access lakes. Hot water is considered by the world science community as the most clean drilling fluid medium from the present point of view but it cannot solve environmental problems in total because hot-water even when heated to 90 °C, filtered to 0.2 μm, and UV treated at the surface could pick up microorganisms from near-surface snow and circulate them in great volume through the borehole. Another negative impact of hot-water circulation medium is thermal pollution of subglacial water. The new approach to Antarctic subglacial lakes exploration is presented by sampling technology with recoverable autonomous sonde which is equipped by two hot-points with heating elements located on the bottom and top sides of the sonde. All down-hole sonde components will be sterilized by combination of chemical wash, HPV and UV sterilization prior using. At the beginning of the summer season sonde is installed on the surface of the Antarctic ice sheet above subglacial lake. All equipment is got into working trim, the bottom hot-point is powered, and the sonde starts to melt down to the ice sheet bed. The personnel leave the site, and all further operations are going on in semi-automatic mode. The melted water does not recover from the hole and refreezes behind the sonde. Electric line for power supply and communication with down-hole sensors is released from the coil installed inside the sonde. Since the sonde enters into the subglacial lake, it samples the water and examines subglacial conditions. After sampling, the motor connected with coil is switched on, and the top hot-point is put into action. The sonde begins to recover itself to the surface by spooling the cable and melting overlying ice with the help of the upper hot-point. Since 8-9 months from starting, the sonde reaches the surface and waits the personnel for servicing and moving to the next site. The big advantage of the proposed technology is that subglacial lake would be measured and sampled while subglacial water is reliably isolated from surface environment.

Effect of circulation on wastewater treatment by Lemna gibba and Lemna minor (floating aquatic macrophytes).

PubMed

Demirezen Yilmaz, Dilek; Akbulut, Hatice

2011-01-01

In this study, laboratory tests were performed in order to examine growth characteristics of floating aquatic macrophytes (Lemna gibba and Lemna minor) in the presence of wastewater with circulation. The results showed that circulation of the waste water enhanced the kinetics of the process, as compared to the control systems. However, prolonged application of high circulation level had a different effect. In the presence of circulation with aquatic plants, there was additional 85.3-88.2% for BODs and 59.6-66.8% for COD decreases in the water quality indicators. In this study, the effectiveness of L. gibba and L. minor with circulation addition for the removal of four heavy metals (Pb, Ni, Mn, and Cu) from waste water was also investigated. Results from analysis confirmed the accumulation of different metals within the plant and a corresponding decrease of metals in the waste water. At the end of the study of circulation, L. gibba provided the metal removal for Cu, Pb, Ni, and Mn in the waste water as the ratio of 57%, 60%, 60%, and 62%, respectively. In this context, the best results were obtained when the action of L. gibba and L. minor plants, was combined with that of circulation. It is shown that in the presence of L. gibba and L. minor plants that are supplemented with circulation, the national standards of biochemical oxygen demand (BOD5) 27-33 mgL(-1) and chemical oxygen demand (COD) 62-78 mgL(-1) for L. minor and L. gibba, respectively, were reached after treatment. The new results can be used for design calculations regarding expected removal of pollutants by aquatic floating plants.

The evolution of the Cappadocia Geothermal Province, Anatolia (Turkey): geochemical and geochronological evidence

NASA Astrophysics Data System (ADS)

Şener, M. Furkan; Şener, Mehmet; Uysal, I. Tonguç

2017-12-01

Cappadocia Geothermal Province (CGP), central Turkey, consists of nine individual geothermal regions controlled by active regional fault systems. This paper examines the age dating of alteration minerals and the geochemistry (trace elements and isotopes) of the alteration minerals and geothermal waters, to assess the evolution of CGP in relation to regional tectonics. Ar-Ar age data of jarosite and alunite show that the host rocks were exposed to oxidizing conditions near the Earth's surface at about 5.30 Ma. Based on the δ18O-δD relationhip, water samples had a high altitude meteoric origin. The δ34S values of jarosite and alunite indicate that water samples from the southern part of the study area reached the surface after circulation through volcanic rocks, while northern samples had traveled to the surface after interacting with evaporates at greater depths. REY (rare earth elements and yttrium) diagrams of alteration minerals (especially illite, jarosite and alunite) from rock samples, taken from the same locations as the water samples, display a similar REY pattern to water samples. This suggests that thermal fluids, which reached the surface along a fault zone and caused the mineral alteration in the past, had similar chemical composition to the current geothermal water. The geothermal conceptual model, which defines a volcanically heated reservoir and cap rocks, suggests there are no structural drawbacks to the use of the CGP geothermal system as a resource. However, fluid is insufficient to drive the geothermal system as a result of scanty supply of meteoric water due to evaporation significantly exceeding rainfall.

Satellite-Observed Vertical Structures of Clouds over the Amazon Basin

NASA Astrophysics Data System (ADS)

Wu, M.; Lee, J. E.

2017-12-01

The long wet season of the Amazon basin currently plays a critical role in the terrestrial ecosystem, regulating carbon balance and supporting high biodiversity. It has been argued that the land surface processes are important in maintaining high precipitation; yet, how the land-atmosphere interactions modulate the atmospheric processes are not completely understood. As a first step toward solving this problem, here we examine the vertical structures of clouds and the thermodynamics of the atmosphere over the entire basin at the different time of the year. We combine the vertical distribution of cloud water content from CloudSat, and the atmospheric thermodynamic conditions from the ECMWF ERA-interim reanalysis to compare and contrast the atmospheric condition at different time of the year-the wet, dry, and dry-to-wet transition seasons-and in different regions-ever-wet evergreen broadleaf forests, wet evergreen broadleaf forests with a dry season, and dry wooded grasslands/woodlands-following water stress gradient. In the ever-wet and wet regions, a large amount of cloud ice water is present in the upper atmosphere (above 11km) and convective available potential energy (CAPE) is high during the transition season, supporting the claim that the convective activity is strongest during the transition season. In the dry region, there are more cloud water above 8km over woodlands than over wooded grasslands during the dry and transition seasons, indicating the influence of the land cover. We also classified our data following the large-scale circulation pattern, and the CloudSat data support more deep convective activities in the wet and dry regions when the wind blows from the east during the wet and transition seasons. As a next step, we will focus more on linking the cloud structure to the large-scale circulation and surface processes.

Assessment of the Vulnerability of Water Resources to Seasonal Fires Across the Northern Sub-Saharan African Region

NASA Technical Reports Server (NTRS)

Ichoku, Charles M.

2010-01-01

The northern sub-Saharan African (NSSA) region, extending from the southern fringes of the Sahara to the Equator, and stretching west to east from the Atlantic to the Indian ocean coasts, plays a prominent role in the distribution of Saharan dust and other airborne matter around the region and to other parts of the world, the genesis of global atmospheric circulation, and the birth of such major (and often catastrophic) events as hurricanes. Therefore, this NSSA region represents a critical variable in the global climate change equation. Recent satellite-based studies have revealed that the NSSA region has one of the highest biomass-burning rates per unit land area among all regions of the world. Because of the high concentration and frequency of fires in this region, with the associated abundance of heat release and gaseous and particulate smoke emissions, biomass-burning activity is believed to be a major driver of the regional carbon, energy, and water cycles. We acknowledge that the rainy season in the NSSA region is from April to September while biomass burning occurs mainly during the dry season (October to March). Nevertheless, these two phenomena are indirectly coupled to each other through a chain of complex processes and conditions, including land-cover and surface-albedo changes, the carbon cycle, evapotranspiration, drought, desertification, surface water runoff, ground water recharge, and variability in atmospheric composition, heating rates, and circulation. In this presentation, we will examine the theoretical linkages between these processes, discuss the preliminary results based on satellite data analysis, and provide an overview of plans for more integrated research to be conducted over the next few years.

Natural flows of H2-rich fluids in the ophiolites of Oman and the Philippines: Tectonic control of migration pathways and associated diagenetic processes

NASA Astrophysics Data System (ADS)

Deville, E. P.; Prinzhofer, A.; Vacquand, C.; Chavagnac, V.; Monnin, C.; Ceuleneer, G.; Arcilla, C. A.

2009-12-01

We compare the geological environments of sites of emission of natural hydrogen in the Oman ophiolite and the Zambales ophiolite (Luzon, Philippines). The genesis of natural H2 results from the interaction between ultrabasic rocks and aqueous solutions circulating in deep fracture networks, by oxidation of metals (Fe2+, Mn2+) and reduction of water, probably under high temperature conditions. This process generates very reducing conditions capable of destabilizing other molecules (notably reduction of deep CO2 being transformed into CH4 by Fisher-Tropsch type reactions). Nitrogen is also commonly associated to the H2-rich fluids. H2 flows are associated with the expulsion of hyperalkaline waters rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal thrust plane of the ophiolites and the peridotite-gabbro contact (Moho). Within the fracture networks, gas and water separate probably at shallow depth, i.e. close to the top of the upper aquifer level. Locally high flows of gas migrate vertically through fracture pathways and they are able to inflame spontaneously on the surface. Aqueous fluids tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. This water circulation induces a chain of diagenetic reactions starting in the fracture systems and continuing at the surface where it leads to the precipitation of calcite, aragonite, brucite and more rarely portlandite. This chain of diagenetic reactions is associated with the capture of the atmospheric CO2 during the precipitation of carbonates.

The Global Ocean Observing System

NASA Technical Reports Server (NTRS)

Kester, Dana

1992-01-01

A Global Ocean Observing System (GOOS) should be established now with international coordination (1) to address issues of global change, (2) to implement operational ENSO forecasts, (3) to provide the data required to apply global ocean circulation models, and (4) to extract the greatest value from the one billion dollar investment over the next ten years in ocean remote sensing by the world's space agencies. The objectives of GOOS will focus on climatic and oceanic predictions, on assessing coastal pollution, and in determining the sustainability of living marine resources and ecosystems. GOOS will be a complete system including satellite observations, in situ observations, numerical modeling of ocean processes, and data exchange and management. A series of practical and economic benefits will be derived from the information generated by GOOS. In addition to the marine science community, these benefits will be realized by the energy industries of the world, and by the world's fisheries. The basic oceanic variables that are required to meet the oceanic and predictability objectives of GOOS include wind velocity over the ocean, sea surface temperature and salinity, oceanic profiles of temperature and salinity, surface current, sea level, the extent and thickness of sea ice, the partial pressure of CO2 in surface waters, and the chlorophyll concentration of surface waters. Ocean circulation models and coupled ocean-atmosphere models can be used to evaluate observing system design, to assimilate diverse data sets from in situ and remotely sensed observations, and ultimately to predict future states of the system. The volume of ocean data will increase enormously over the next decade as new satellite systems are launched and as complementary in situ measuring systems are deployed. These data must be transmitted, quality controlled, exchanged, analyzed, and archived with the best state-of-the-art computational methods.

Seasonal Dynamics of Dissolved Organic Carbon Under Complex Circulation Schemes on a Large Continental Shelf: The Northern South China Sea

NASA Astrophysics Data System (ADS)

Meng, Feifei; Dai, Minhan; Cao, Zhimian; Wu, Kai; Zhao, Xiaozheng; Li, Xiaolin; Chen, Junhui; Gan, Jianping

2017-12-01

We examined the distribution and seasonality of dissolved organic carbon (DOC) based on a large data set collected from the northern South China Sea (NSCS) shelf under complex circulation schemes influenced by river plume, coastal upwelling, and downwelling. The highest surface values of ˜117 μmol L-1 were observed nearshore in summer suggesting high DOC supplies from the river inputs, whereas the lowest surface values of ˜62 μmol L-1 were on the outer shelf in winter due to entrainment of DOC-poor subsurface water under strengthened vertical mixing. While the summer coastal upwelling brought lower DOC from offshore depth to the nearshore surface, the winter coastal downwelling delivered higher surface DOC to the midshelf deep waters from the inner shelf fueled by the China Coastal Current (CCC) transporting relatively high DOC from the East China Sea to the NSCS. The intensified winter downwelling generated a cross-shelf DOC transport of 3.1 × 1012 g C over a large shelf area, which induced a significant depression of the NSCS DOC inventory in winter relative to in autumn. In addition to the variable physical controls, net biological production of DOC was semiquantified in both the river plume (2.8 ± 3.0 μmol L-1) and coastal upwelling (3.1 ± 1.3 μmol L-1) in summer. We demonstrated that the NSCS shelf had various origins of DOC including riverine inputs, inter-shelf transport and in situ production. Via cross-shelf transport, the accumulated DOC would be exported to and stored in the deep ocean, suggesting that continental shelves are a potentially effective carbon sink.

Changing surface water conditions for the last 500 ka in the Southeast Atlantic:Tracking Agulhas leakage using UK37' and δD

NASA Astrophysics Data System (ADS)

Petrick, Benjamin; McClymont, Erin; van der Meer, Marcel; Marret, Fabienne

2015-04-01

The Southeast Atlantic Ocean is an important component of global ocean circulation, as it includes heat and salt transfer into the Atlantic through Agulhas Leakage. Here, we reconstruct sea surface temperatures (SSTs) and sea surface salinity from Ocean Drilling Program (ODP) Site 1087 in the Southeast Atlantic to investigate surface ocean circulation patterns during the late Pleistocene (0-500 ka). The alkenone-derived U37K'index and assemblages of dinoflagellate cysts are used to reconstruct SSTs. The hydrogen isotope composition of the alkenones (δDalkenone) is used to reconstruct changes in sea-surface salinity. The greatest amplitude of SST warming precedes decreases in benthic δ18O and therefore occurs early in the transition from glacials to interglacials. The timing of the early warming is consistent with previously published foraminifera reconstructions from the same site (Caley et al., 2012). However, δDalkenone decreases at the start of interglacials, suggesting that sea surface salinity increased earlier than the deglacial warmings, and indicating that the pattern of Agulhas leakage is more complex than suggested by SST proxies alone. Furthermore, the δDalkenonevalues indicate a strong salinity increases occurred before both MIS 11 and MIS 1, which are both periods where there is evidence of connection between increased Agulhas Leakage and a stronger Atlantic meridional overturning circulation (AMOC). Finally, the ODP site 1087 record shows an overall trend of increasing SSTs and δDalkenone towards the present day, suggesting that Agulhas leakage has strengthened since 500 ka, which may have impacted the intensity of the AMOC. Caley, T., Giraudeau, J., Malaize, B., Rossignol, L., Pierre, C., 2012. Agulhas leakage as a key process in the modes of Quaternary climate changes. Proc. Natl. Acad. Sci. 109, 6835-6839. doi:10.1073/pnas.1115545109

CAUSES: Diagnosis of the Summertime Warm Bias in CMIP5 Climate Models at the ARM Southern Great Plains Site

NASA Astrophysics Data System (ADS)

Zhang, Chengzhu; Xie, Shaocheng; Klein, Stephen A.; Ma, Hsi-yen; Tang, Shuaiqi; Van Weverberg, Kwinten; Morcrette, Cyril J.; Petch, Jon

2018-03-01

All the weather and climate models participating in the Clouds Above the United States and Errors at the Surface project show a summertime surface air temperature (T2 m) warm bias in the region of the central United States. To understand the warm bias in long-term climate simulations, we assess the Atmospheric Model Intercomparison Project simulations from the Coupled Model Intercomparison Project Phase 5, with long-term observations mainly from the Atmospheric Radiation Measurement program Southern Great Plains site. Quantities related to the surface energy and water budget, and large-scale circulation are analyzed to identify possible factors and plausible links involved in the warm bias. The systematic warm season bias is characterized by an overestimation of T2 m and underestimation of surface humidity, precipitation, and precipitable water. Accompanying the warm bias is an overestimation of absorbed solar radiation at the surface, which is due to a combination of insufficient cloud reflection and clear-sky shortwave absorption by water vapor and an underestimation in surface albedo. The bias in cloud is shown to contribute most to the radiation bias. The surface layer soil moisture impacts T2 m through its control on evaporative fraction. The error in evaporative fraction is another important contributor to T2 m. Similar sources of error are found in hindcast from other Clouds Above the United States and Errors at the Surface studies. In Atmospheric Model Intercomparison Project simulations, biases in meridional wind velocity associated with the low-level jet and the 500 hPa vertical velocity may also relate to T2 m bias through their control on the surface energy and water budget.

Horizontal convection with mechanical stirring

NASA Astrophysics Data System (ADS)

Griffiths, Ross; Stewart, Kial; Hughes, Graham

2012-11-01

The effects of turbulent mixing on convective circulation forced by a horizontal gradient of buoyancy at the surface is examined using laboratory experiments in which a salt flux is introduced at the surface, at one end of a box, and a freshwater buoyancy condition is applied over the rest of the surface. Horizontal rods are oscillated and yo-yoed continuously through the water column, providing a diffusivity that can be calibrated. The convection reaches a stationary state having zero net salt flux. We find that for small stirring rates the small but finite volume flux from the dense source is significant and a virtual source correction is required to take this into account. The density stratification and overturning volume transport are consistent with a theoretical model for high Rayleigh numbers: the transport ψ increases with diffusivity κ (ψg ~ gκ 1 / 4) . The results show that vertical mixing in the boundary layer is important, particularly in setting the density of the interior and the overturning rate. However, interior mixing is unimportant, which raises an interesting question over whether abyssal mixing rates in the ocean play any significant role in setting the abyssal ocean density or the transport in the Meridional Overturning Circulation.

Antarctic and Southern Ocean influences on Late Pliocene global cooling

USGS Publications Warehouse

McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross D.

2012-01-01

The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ~3.3 Ma, followed by a coastal sea surface temperature cooling of ~2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world.

Antarctic and Southern Ocean influences on Late Pliocene global cooling

PubMed Central

McKay, Robert; Naish, Tim; Carter, Lionel; Riesselman, Christina; Dunbar, Robert; Sjunneskog, Charlotte; Winter, Diane; Sangiorgi, Francesca; Warren, Courtney; Pagani, Mark; Schouten, Stefan; Willmott, Veronica; Levy, Richard; DeConto, Robert; Powell, Ross D.

2012-01-01

The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ∼3.3 Ma, followed by a coastal sea surface temperature cooling of ∼2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world. PMID:22496594

Interior Pathways to Dissipation of Mesoscale Energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nadiga, Balasubramanya T.

This talk at Goethe University asks What Powers Overturning Circulation? How does Ocean Circulation Equilibrate? There is a HUGE reservoir of energy sitting in the interior ocean. Can fluid dynamic instabilities contribute to the mixing required to drive global overturning circulation? Study designed to eliminate distinguished horizontal surfaces such as bottom BL and surface layer

High-frequency fluctuations in Denmark Strait transport

NASA Astrophysics Data System (ADS)

Haine, T. W. N.

2010-07-01

Denmark Strait ocean current transport exhibits quasi-regular fluctuations immediately south of the sill with periods of 2-4 days. The transport variability is similar to the mean transport itself. Using a circulation model we explore prospects to monitor the fluctuations. The model has realistic transport and shows water leaving Denmark Strait in equivalent-barotropic cyclones that are nearly geostrophic and correlate with sea-surface height (SSH). Existing satellite altimeter observations of SSH have adequate space/time sampling to reconstruct the transport fluctuations using a regression developed from the model results, but measurement error overwhelms the signal. From the model results, the pending Surface Water and Ocean Topography (SWOT) wide-swath altimeter appears accurate enough, and with good-enough coverage, to allow the transport fluctuations to be reconstructed. Bottom pressure recorders at the exit of the Denmark Strait can also reproduce the transport variability.

Observational constraints on the global atmospheric CO2 budget

NASA Technical Reports Server (NTRS)

Tans, Pieter P.; Fung, Inez Y.; Takahashi, Taro

1990-01-01

Observed atmospheric concentrations of CO2 and data on the partial pressures of CO2 in surface ocean waters are combined to identify globally significant sources and sinks of CO2. The atmospheric data are compared with boundary layer concentrations calculated with the transport fields generated by a general circulation model (GCM) for specified source-sink distributions. In the model the observed north-south atmospheric concentration gradient can be maintained only if sinks for CO2 are greater in the Northern than in the Southern Hemisphere. The observed differences between the partial pressure of CO2 in the surface waters of the Northern Hemisphere and the atmosphere are too small for the oceans to be the major sink of fossil fuel CO2. Therefore, a large amount of the CO2 is apparently absorbed on the continents by terrestrial ecosystems.

A study of natural circulation in the evaporator of a horizontal-tube heat recovery steam generator

NASA Astrophysics Data System (ADS)

Roslyakov, P. V.; Pleshanov, K. A.; Sterkhov, K. V.

2014-07-01

Results obtained from investigations of stable natural circulation in an intricate circulation circuit with a horizontal layout of the tubes of evaporating surface having a negative useful head are presented. The possibility of making a shift from using multiple forced circulation organized by means of a circulation pump to natural circulation in vertical heat recovery steam generator is estimated. Criteria for characterizing the performance reliability and efficiency of a horizontal evaporator with negative useful head are proposed. The influence of various design solutions on circulation robustness is considered. With due regard of the optimal parameters, the most efficient and least costly methods are proposed for achieving more stable circulation in a vertical heat recovery steam generator when a shift is made from multiple forced to natural circulation. A procedure for calculating the circulation parameters and an algorithm for checking evaporator performance reliability are developed, and recommendations for the design of heat recovery steam generator, nonheated parts of natural circulation circuit, and evaporating surface are suggested.

Observed cloud reflectivities and liquid water paths: An update

NASA Technical Reports Server (NTRS)

Coakley, James A., Jr.; Snider, Jack B.

1990-01-01

The FIRE microwave radiometer observations of liquid water path from San Nicolas Island and simultaneous NOAA AVHRR observations of cloud reflectivity were used to test a relationship between cloud liquid water path and cloud reflectivity that is often used in general circulation climate models (Stephens, 1978). The results of attempts to improve the data analysis which was described at the previous FIRE Science Team Workshop and elsewhere (Coakley and Snider, 1989) are reported. The improvements included the analysis of additional satellite passes over San Nicolas and sensitivity studies to estimate the effects on the observed reflectivities due to: (1) nonzero surface reflectivities beneath the clouds; (2) the anisotropy of the reflected radiances observed by the AVHRR; (3) small scale spatial structure in the liquid water path; and (4) adjustments to the calibration of AVHRR.

The forcing of southwestern Asia teleconnections by low-frequency sea surface temperature variability during boreal winter

USGS Publications Warehouse

Hoell, Andrew; Funk, Christopher C.; Mathew Barlow,

2015-01-01

Southwestern Asia, defined here as the domain bounded by 20°–40°N and 40°–70°E, which includes the nations of Iraq, Iran, Afghanistan, and Pakistan, is a water-stressed and semiarid region that receives roughly 75% of its annual rainfall during November–April. The November–April climate of southwestern Asia is strongly influenced by tropical Indo-Pacific variability on intraseasonal and interannual time scales, much of which can be attributed to sea surface temperature (SST) variations. The influences of lower-frequency SST variability on southwestern Asia climate during November–April Pacific decadal SST (PDSST) variability and the long-term trend in SST (LTSST) is examined. The U.S. Climate Variability and Predictability Program (CLIVAR) Drought Working Group forced global atmospheric climate models with PDSST and LTSST patterns, identified using empirical orthogonal functions, to show the steady atmospheric response to these modes of decadal to multidecadal SST variability. During November–April, LTSST forces an anticyclone over southwestern Asia, which results in reduced precipitation and increases in surface temperature. The precipitation and tropospheric circulation influences of LTSST are corroborated by independent observed precipitation and circulation datasets during 1901–2004. The decadal variations of southwestern Asia precipitation may be forced by PDSST variability, with two of the three models indicating that the cold phase of PDSST forces an anticyclone and precipitation reductions. However, there are intermodel circulation variations to PDSST that influence subregional precipitation patterns over the Middle East, southwestern Asia, and subtropical Asia. Changes in wintertime temperature and precipitation over southwestern Asia forced by LTSST and PDSST imply important changes to the land surface hydrology during the spring and summer.