Dynamic ocean topography from CryoSat-2: examining recent changes in ice-ocean stress and advancing a theory for Beaufort Gyre stabilization

NASA Astrophysics Data System (ADS)

Dewey, S.; Morison, J.; Kwok, R.; Dickinson, S.; Morison, D.; Andersen, R.

2017-12-01

Model and sparse observational evidence has shown the ocean current speed in the Beaufort Gyre to have increased and recently stabilized. However, full-basin altimetric observations of dynamic ocean topography (DOT) and ocean surface currents have yet to be applied to the dynamics of gyre stabilization. DOT fields from retracked CryoSat-2 retrievals in Arctic Ocean leads have enabled us to calculate 2-month average ocean geostrophic currents. These currents are crucial to accurately computing ice-ocean stress, especially because they have accelerated so that their speed rivals that of the overlying sea ice. Given these observations, we can shift our view of the Beaufort Gyre as a system in which the wind drives the ice and the ice drives a passive ocean to a system with the following feedback: After initial input of energy by wind, ice velocity decreases due to water drag and internal ice stress and the ocean drives the ice, reversing Ekman pumping and decelerating the gyre. This reversal changes the system from a persistently convergent regime to one in which freshwater is released from the gyre and doming of the gyre decreases, without any change in long-term average wind stress curl. Through these processes, the ice-ocean stress provides a key feedback in Beaufort Gyre stabilization.

Intraseasonal variability of upper-ocean currents and photosynthetic primary production along the U.S. west coast associated with the Madden-Julian Oscillation

NASA Astrophysics Data System (ADS)

Barrett, B.; Davies, A. R.; Steppe, C. N.; Hackbarth, C.

2017-12-01

In the first part of this study, time-lagged composites of upper-ocean currents from February to May of 1993-2016 were binned by active phase of the leading atmospheric mode of intraseasonal variability, the Madden-Julian Oscillation (MJO). Seven days after the convectively active phase of the MJO enters the tropical Indian Ocean, anomalously strong south-southeastward upper-ocean currents are observed along the majority of U.S. west coast. Seven days after the convectively active phase enters the tropical western Pacific Ocean, upper-ocean current anomalies reverse along the U.S. west coast, with weaker southward flow. A physical pathway to the ocean was found for both of these: (a) tropical MJO convection modulates upper-tropospheric heights and circulation over the Pacific Ocean; (b) those anomalous atmospheric heights adjust the strength and position of the Aleutian Low and Hawaiian High; (c) surface winds change in response to the adjusted atmospheric pressure patterns; and (d) those surface winds project onto upper-ocean currents. In the second part of this study, we investigated if the MJO modulated intraseasonal variability of surface wind forcing and upper-ocean currents projected onto phytoplankton abundance along the U.S. west coast. Following a similar methodology, time-lagged, level 3 chlorophyll-a satellite products (a proxy for photosynthetic primary production) were binned by active MJO phase and analyzed for statistical significance using the Student's t test. Results suggest that intraseasonal variability of biological production along the U.S. west coast may be linked to the MJO, particularly since the time scale of the life cycle of phytoplankton is similar to the time scale of the MJO.

Including eddies in global ocean models

NASA Astrophysics Data System (ADS)

Semtner, Albert J.; Chervin, Robert M.

The ocean is a turbulent fluid that is driven by winds and by surface exchanges of heat and moisture. It is as important as the atmosphere in governing climate through heat distribution, but so little is known about the ocean that it remains a “final frontier” on the face of the Earth. Many ocean currents are truly global in extent, such as the Antarctic Circumpolar Current and the “conveyor belt” that connects the North Atlantic and North Pacific oceans by flows around the southern tips of Africa and South America. It has long been a dream of some oceanographers to supplement the very limited observational knowledge by reconstructing the currents of the world ocean from the first principles of physics on a computer. However, until very recently, the prospect of doing this was thwarted by the fact that fluctuating currents known as “mesoscale eddies” could not be explicitly included in the calculation.

Estimating Ocean Currents from Automatic Identification System Based Ship Drift Measurements

NASA Astrophysics Data System (ADS)

Jakub, Thomas D.

Ship drift is a technique that has been used over the last century and a half to estimate ocean currents. Several of the shortcomings of the ship drift technique include obtaining the data from multiple ships, the time delay in getting those ship positions to a data center for processing and the limited resolution based on the amount of time between position measurements. These shortcomings can be overcome through the use of the Automatic Identification System (AIS). AIS enables more precise ocean current estimates, the option of finer resolution and more timely estimates. In this work, a demonstration of the use of AIS to compute ocean currents is performed. A corresponding error and sensitivity analysis is performed to help identify under which conditions errors will be smaller. A case study in San Francisco Bay with constant AIS message updates was compared against high frequency radar and demonstrated ocean current magnitude residuals of 19 cm/s for ship tracks in a high signal to noise environment. These ship tracks were only minutes long compared to the normally 12 to 24 hour ship tracks. The Gulf of Mexico case study demonstrated the ability to estimate ocean currents over longer baselines and identified the dependency of the estimates on the accuracy of time measurements. Ultimately, AIS measurements when combined with ship drift can provide another method of estimating ocean currents, particularly when other measurements techniques are not available.

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).

Shipborne LF-VLF oceanic lightning observations and modeling

NASA Astrophysics Data System (ADS)

Zoghzoghy, F. G.; Cohen, M. B.; Said, R. K.; Lehtinen, N. G.; Inan, U. S.

2015-10-01

Approximately 90% of natural lightning occurs over land, but recent observations, using Global Lightning Detection (GLD360) geolocation peak current estimates and satellite optical data, suggested that cloud-to-ground flashes are on average stronger over the ocean. We present initial statistics from a novel experiment using a Low Frequency (LF) magnetic field receiver system installed aboard the National Oceanic Atmospheric Agency (NOAA) Ronald W. Brown research vessel that allowed the detection of impulsive radio emissions from deep-oceanic discharges at short distances. Thousands of LF waveforms were recorded, facilitating the comparison of oceanic waveforms to their land counterparts. A computationally efficient electromagnetic radiation model that accounts for propagation over lossy and curved ground is constructed and compared with previously published models. We include the effects of Earth curvature on LF ground wave propagation and quantify the effects of channel-base current risetime, channel-base current falltime, and return stroke speed on the radiated LF waveforms observed at a given distance. We compare simulation results to data and conclude that previously reported larger GLD360 peak current estimates over the ocean are unlikely to fully result from differences in channel-base current risetime, falltime, or return stroke speed between ocean and land flashes.

Development of a new model for short period ocean tidal variations of Earth rotation

NASA Astrophysics Data System (ADS)

Schuh, Harald

2015-08-01

Within project SPOT (Short Period Ocean Tidal variations in Earth rotation) we develop a new high frequency Earth rotation model based on empirical ocean tide models. The main purpose of the SPOT model is its application to space geodetic observations such as GNSS and VLBI.We consider an empirical ocean tide model, which does not require hydrodynamic ocean modeling to determine ocean tidal angular momentum. We use here the EOT11a model of Savcenko & Bosch (2012), which is extended for some additional minor tides (e.g. M1, J1, T2). As empirical tidal models do not provide ocean tidal currents, which are re- quired for the computation of oceanic relative angular momentum, we implement an approach first published by Ray (2001) to estimate ocean tidal current veloci- ties for all tides considered in the extended EOT11a model. The approach itself is tested by application to tidal heights from hydrodynamic ocean tide models, which also provide tidal current velocities. Based on the tidal heights and the associated current velocities the oceanic tidal angular momentum (OTAM) is calculated.For the computation of the related short period variation of Earth rotation, we have re-examined the Euler-Liouville equation for an elastic Earth model with a liquid core. The focus here is on the consistent calculation of the elastic Love num- bers and associated Earth model parameters, which are considered in the Euler- Liouville equation for diurnal and sub-diurnal periods in the frequency domain.

Investigating the Relationship between Ocean Surface Currents and Seasonal Precipitation in the Western United States

NASA Astrophysics Data System (ADS)

Chiang, F.; AghaKouchak, A.

2017-12-01

While many studies have explored the predictive capabilities of teleconnections associated with North American climate, currently established teleconnections offer limited predictability for rainfall in the Western United States. A recent example was the 2015-16 California drought in which a strong ENSO signal did not lead to above average precipitation as was expected. From an exploration of climate and ocean variables available from satellite data, we hypothesize that ocean currents can provide additional information to explain precipitation variability and improve seasonal predictability on the West Coast. Since ocean currents are influenced by surface wind and temperatures, characterizing connections between currents and precipitation patterns has the potential to further our understanding of coastal weather patterns. For the study, we generated gridded point correlation maps to identify ocean areas with high correlation to precipitation time series corresponding to climate regions in the West Coast region. We also used other statistical measures to evaluate ocean `hot spot' regions with significant correlation to West Coast precipitation. Preliminary results show that strong correlations can be found in the tropical regions of the globe.

The role of vigorous current systems in the Southeast Indian Ocean in redistributing deep-sea sediments

NASA Astrophysics Data System (ADS)

Dutkiewicz, Adriana; Müller, Dietmar; Hogg, Andrew; Spence, Paul

2017-04-01

Understanding the transport of modern deep-sea sediment is critical for accurate models of climate-ocean history and the widespread use of the sedimentological record as a proxy for productivity where the connection between biogenic seafloor lithologies and sea-surface is tenuous. The Southern Ocean, where diatoms contribute the bulk of pelagic material to the seafloor forming an extensive belt of diatom ooze, is an exemplar. However, most of the key studies on large-scale sediment reworking in the Southern Ocean were conducted in the 1970s when relatively little was known about the oceanography of this region. At this time even our knowledge of the bathymetry and tectonic fabric, which underpin the distribution of deep-sea currents, were fairly general. The record of widespread regional disconformities in the abyssal plains of the Southern Ocean is well-established and indicates extensive erosion of deep-sea sediments throughout the Quaternary. Here we combine a high-resolution numerical model of bottom currents with sedimentological data to constrain the redistribution of sediment across the abyssal plains and adjacent mid-ocean ridges in the Southern Ocean. We use the global ocean-sea ice model (GFDL-MOM01) to simulate ocean circulation at a resolution that results in realistic velocities throughout the water column, and is ideal for estimating interaction between time-dependent bottom currents and ocean bathymetry. 230Th-normalized vertical sediment rain rates for 63 sites in the Southeast Indian Ocean, combined with satellite data-derived surface productivity, demonstrate that a wide belt of fast sedimentation rates (> 5.5 cm/kyr) along the Southeast Indian Ridge (SEIR) occurs in a region of low surface productivity bounded by two major disconformity fields associated with the Kerguelen Plateau to the east and the Macquarie Ridge to the west. Our ocean circulation model illustrates that the disconformity fields occur in regions of intense bottom current activity where current speeds reach 0.2 m/s and are favorable for generating intense nepheloid layers. These currents transport sediment towards and along the SEIR and through leaky fracture zones to regions where bottom currents speeds drop to < 0.03 m/s and fine particles settle out of suspension. We suggest that the anomalously high sedimentation rates along an 8,000 km-long segment of the SEIR represent a giant Pliocene-Holocene succession of contourite drifts. It is a major extension of the much smaller contourite east of Kerguelen and has accumulated since 3-5 Ma based on the age of the oldest crust underlying the deposit. These inferred contourite drifts provide exceptionally valuable drilling targets for high-resolution climatic investigations of the Southern Ocean. Understanding and quantifying the link between bottom current activity and sediment transport is critical for paleooceanographic and palaeoclimatic reconstructions and for understanding the history of current flow. Dutkiewicz, A., Müller, R.D., Hogg, A. McC., and Spence, P., 2016, Vigorous deep-sea currents cause global anomaly in sediment accumulation in the Southern Ocean, Geology, 44, 663-666, DOI: 10.1130/G38143.1

Investigating the role of wind in generating surface currents over the slope area of the Laptev Sea, Arctic Ocean

NASA Astrophysics Data System (ADS)

Patteson, R. N.

2017-12-01

Mixing mechanisms of the Arctic Ocean have profound impacts on sea ice, global ocean dynamics, and arctic communities. This project used a two-year long time series of ocean current velocities collected from eight moorings located on the Eurasian basin, as well as ERA-interim wind data, to compare and assess relationships between current and wind velocities at different depths. Determining the strength of these correlations will further scientific understanding of the degree to which wind influences mixing, with implications for heat flux, diffusion, and sea ice changes. Using statistical analysis, I calculated whether a significant relationship between wind velocity and ocean currents existed beginning at the surface level ( 50m) .The final correlation values, ranging from R = 0.11 to R = 0.28, indicated a weak relationship between wind velocity and ocean currents at the surface for all eight mooring sites. The results for the surface depth imply that correlation likely decreases with increasing depths, and thus further testing of deeper depth levels was unnecessary. This finding suggests that there is another dominant factor at play in the ocean; we postulate that topography exerts a significant influence on subsurface mixing. This study highlights the need for further research of the different mechanisms and their importance in influencing the dynamic structure of the ocean.

Terrestrial Observations from NOAA Operational Satellites.

PubMed

Yates, H; Strong, A; McGinnis, D; Tarpley, D

1986-01-31

Important applications to oceanography, hydrology, and agriculture have been developed from operational satellites of the National Oceanic and Atmospheric Administration and are currently expanding rapidly. Areas of interest involving the oceans include sea surface temperature, ocean currents, and ocean color. Satellites can monitor various hydrological phenomena, including regional and global snow cover, river and sea ice extent, and areas of global inundation. Agriculturally important quantities derived from operational satellite observations include precipitation, daily temperature extremes, canopy temperatures, insolation, and snow cover. This overview describes the current status of each area.

Studies related to ocean dynamics. Task 3.2: Aircraft Field Test Program to investigate the ability of remote sensing methods to measure current/wind-wave interactions

NASA Technical Reports Server (NTRS)

Huang, N. E.; Flood, W. A.; Brown, G. S.

1975-01-01

The feasibility of remote sensing of current flows in the ocean and the remote sensing of ocean currents by backscattering cross section techniques was studied. It was established that for capillary waves, small scale currents could be accurately measured through observation of wave kinematics. Drastic modifications of waves by changing currents were noted. The development of new methods for the measurement of capillary waves are discussed. Improvement methods to resolve data processing problems are suggested.

46 CFR 28.225 - Navigational information.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., each of the following publications: (i) Tide tables promulgated by the National Ocean Service; and (ii) Tidal current tables promulgated by the National Ocean Service, or a river current publication issued by...: (1) Marine charts of the area to be transited, published by the National Ocean Service, the National...

Combined Aircraft and Satellite-Derived Storm Electric Current and Lightning Rates Measurements and Implications for the Global Electric Circuit

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Blakeslee, Richard J.; Bateman, Monte G.

2010-01-01

Using rotating vane electric field mills and Gerdien capacitors, we measured the electric field profile and conductivity during 850 overflights of electrified shower clouds and thunderstorms spanning regions including the Southeastern United States, the Western Atlantic Ocean, the Gulf of Mexico, Central America and adjacent oceans, Central Brazil, and the South Pacific. The overflights include storms over land and ocean, with and without lightning, and with positive and negative fields above the storms. The measurements were made with the NASA ER-2 and the Altus-II high altitude aircrafts. Peak electric fields, with lightning transients removed, ranged from -1.0 kV/m to 16 kV/m, with a mean value of 0.9 kV/m. The median peak field was 0.29 kV/m. Integrating our electric field and conductivity data, we determined total conduction currents and flash rates for each overpass. With knowledge of the storm location (land or ocean) and type (with or without lightning), we determine the mean currents by location and type. The mean current for ocean storms with lightning is 1.6 A while the mean current for land storms with lightning is 1.0 A. The mean current for oceanic storms without lightning (i.e., electrified shower clouds) is 0.39 A and the mean current for land storms without lightning is 0.13 A. Thus, on average, land storms with or without lightning have about half the mean current as their corresponding oceanic storm counterparts. Over three-quarters (78%) of the land storms had detectable lightning, while less than half (43%) of the oceanic storms had lightning. We did not find any significant regional or latitudinal based patterns in our total conduction currents. By combining the aircraft derived storm currents and flash rates with diurnal lightning statistics derived from the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) low Earth orbiting satellites, we reproduce the diurnal variation in the global electric circuit (i.e., the Carnegie curve) to within 4% for all but two short periods of time. This excellent agreement with the Carnegie curve was obtained without any tuning or adjustment of the satellite or aircraft data. Given our data and assumptions, mean contributions to the global electric circuit are 0.7 kA (ocean) and 1.1 kA (land) from lightning-producing storms, and 0.22 kA (ocean) and 0.04 (land) from electrified shower clouds, resulting in a mean total conduction current estimate for the global electric circuit of 2.0 kA. Breaking the results down into mean storm counts reveals 1100 for land storms with lightning, 530 for ocean storms without lightning, 390 for ocean storms with lightning, and 330 for land storms without lightning.

New developments in satellite oceanography and current measurements

NASA Technical Reports Server (NTRS)

Huang, N. E.

1979-01-01

Principal satellite remote sensing techniques and instruments are described and attention is given to the application of such techniques to ocean current measurement. The use of radiometers, satellite tracking drifters, and altimeters for current measurement is examined. Consideration is also given to other applications of satellite remote sensing in physical oceanography, including measurements of surface wind stress, sea state, tides, ice, sea surface temperature, salinity, ocean color, and oceanic leveling.

Monitoring Maritime Conditions with Unmanned Systems During Trident Warrior 2013

DTIC Science & Technology

2014-01-01

Host- ing Autonomous Remote Craft or SHARC model ) that emit sounds and listen for reflected changes in response to ocean currents. Experiments tested...San Diego Scripps Institution of Oceanography were also deployed; these provided Acoustic Doppler Current Profiler (ADCP) 3D measurements of the...ocean currents as well as measurements of the surface meteorology . Figure 5(b) shows a schematic representa- tion of one wave glider and two ocean

System and method for measuring ocean surface currents at locations remote from land masses using synthetic aperture radar

NASA Technical Reports Server (NTRS)

Young, Lawrence E. (Inventor)

1991-01-01

A system for measuring ocean surface currents from an airborne platform is disclosed. A radar system having two spaced antennas wherein one antenna is driven and return signals from the ocean surface are detected by both antennas is employed to get raw ocean current data which are saved for later processing. There are a pair of global positioning system (GPS) systems including a first antenna carried by the platform at a first location and a second antenna carried by the platform at a second location displaced from the first antenna for determining the position of the antennas from signals from orbiting GPS navigational satellites. Data are also saved for later processing. The saved data are subsequently processed by a ground-based computer system to determine the position, orientation, and velocity of the platform as well as to derive measurements of currents on the ocean surface.

Solutions Network Formulation Report. Improving NOAA's Tides and Currents Through Enhanced Data Inputs from NASA's Ocean Surface Topography Mission

NASA Technical Reports Server (NTRS)

Guest, DeNeice C.

2006-01-01

The Nation uses water-level data for a variety of practical purposes, including hydrography, nautical charting, maritime navigation, coastal engineering, and tsunami and storm surge warnings (NOAA, 2002; Digby et al., 1999). Long-term applications include marine boundary determinations, tidal predictions, sea-level trend monitoring, oceanographic research, and climate research. Accurate and timely information concerning sea-level height, tide, and ocean current is needed to understand their impact on coastal management, disaster management, and public health. Satellite altimeter data products are currently used by hundreds of researchers and operational users to monitor ocean circulation and to improve scientists understanding of the role of the oceans in climate and weather. The NOAA (National Oceanic and Atmospheric Administration) National Ocean Service has been monitoring sea-level variations for many years (NOAA, 2006). NOAA s Tides & Currents DST (decision support tool, managed by the Center for Operational Oceanographic Products and Services, is the portal to a vast collection of oceanographic and meteorological data (historical and real-time), predictions, and nowcasts and forecasts. This report assesses the capacity of NASA s satellite altimeter data to meet societal decision support needs through incorporation into NOAA s Tides & Currents.

Impacts of the Mesoscale Ocean-Atmosphere Coupling on the Peru-Chile Ocean Dynamics: The Current-Induced Wind Stress Modulation

NASA Astrophysics Data System (ADS)

Oerder, V.; Colas, F.; Echevin, V.; Masson, S.; Lemarié, F.

2018-02-01

The ocean dynamical responses to the surface current-wind stress interaction at the oceanic mesoscale are investigated in the South-East Pacific using a high-resolution regional ocean-atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current-stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.

Determining the Ocean's Role on the Variable Gravity Field on Earth Rotation

NASA Technical Reports Server (NTRS)

Ponte, Rui M.

1999-01-01

A number of ocean models of different complexity have been used to study changes in the oceanic mass field and angular momentum and their relation to the variable Earth rotation and gravity field. Time scales examined range from seasonal to a few days. Results point to the importance of oceanic signals in driving polar motion, in particular the Chandler and annual wobbles. Results also show that oceanic signals have a measurable impact on length-of-day variations. Various circulation features and associated mass signals, including the North Pacific subtropical gyre, the equatorial currents, and the Antarctic Circumpolar Current play a significant role in oceanic angular momentum variability.

Model Scaling of Hydrokinetic Ocean Renewable Energy Systems

NASA Astrophysics Data System (ADS)

von Ellenrieder, Karl; Valentine, William

2013-11-01

Numerical simulations are performed to validate a non-dimensional dynamic scaling procedure that can be applied to subsurface and deeply moored systems, such as hydrokinetic ocean renewable energy devices. The prototype systems are moored in water 400 m deep and include: subsurface spherical buoys moored in a shear current and excited by waves; an ocean current turbine excited by waves; and a deeply submerged spherical buoy in a shear current excited by strong current fluctuations. The corresponding model systems, which are scaled based on relative water depths of 10 m and 40 m, are also studied. For each case examined, the response of the model system closely matches the scaled response of the corresponding full-sized prototype system. The results suggest that laboratory-scale testing of complete ocean current renewable energy systems moored in a current is possible. This work was supported by the U.S. Southeast National Marine Renewable Energy Center (SNMREC).

Ocean Bottom Pressure Seasonal Cycles and Decadal Trends from GRACE Release-05: Ocean Circulation Implications

NASA Astrophysics Data System (ADS)

Johnson, G. C.; Chambers, D. P.

2013-12-01

Ocean mass variations are important for diagnosing sea level budgets, the hydrological cycle and global energy budget, as well as ocean circulation variability. Here seasonal cycles and decadal trends of ocean mass from January 2003 to December 2012, both global and regional, are analyzed using GRACE Release 05 data. The trend of global flux of mass into the ocean approaches 2 cm decade-1 in equivalent sea level rise. Regional trends are of similar magnitude, with the North Pacific, South Atlantic, and South Indian oceans generally gaining mass and other regions losing mass. These trends suggest a spin-down of the North Pacific western boundary current extension and the Antarctic Circumpolar Current in the South Atlantic and South Indian oceans. The global average seasonal cycle of ocean mass is about 1 cm in amplitude, with a maximum in early October and volume fluxes in and out of the ocean reaching 0.5 Sv (1 Sv = 1 × 106 m3 s-1) when integrated over the area analyzed here. Regional patterns of seasonal ocean mass change have typical amplitudes of 1-4 cm, and include maxima in the subtropics and minima in the subpolar regions in hemispheric winters. The subtropical mass gains and subpolar mass losses in the winter spin up both subtropical and subpolar gyres, hence the western boundary current extensions. Seasonal variations in these currents are order 10 Sv, but since the associated depth-averaged current variations are only order 0.1 cm s-1, they would be difficult to detect using in situ oceanographic instruments. a) Amplitude (colors, in cm) and b) phase (colors, in months of the year) of an annual harmonic fit to monthly GRACE Release 05 CSR 500 km smoothed maps (concurrently with a trend and the semiannual harmonic). The 97.5% confidence interval for difference from zero is also indicated (solid black line). Data within 300 km of coastlines are not considered.

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

Wavemill Product Assessment- Defining Products and Evaluating Potential Performance from a Novel Spaceborne Interferometric SAR

NASA Astrophysics Data System (ADS)

Cotton, P. D.; Gommenginger, C.; Martin, A.; Marquez, J.; Burbidge, G.; Quilfen, Y.; Chapron, B.; Reppucci, A.; Buck, C.

2016-08-01

Ocean Surface Currents are one of the most important ocean properties for oceanographers and operators in the maritime domain. Improved monitoring of ocean currents is systematically the number one requirement that emerges from any science or end user requirement surveys.Wavemill is a novel hybrid interferometric SAR system first proposed by ESA/ESTEC [Buck, 2005]. It offers the possibility of generating two-dimensional wide swath, high resolution, high precision maps of surface current vectors and ocean topography [Buck et al., 2009]. Based on a single spacecraft, it avoids the difficulties of synchronisation and baseline estimation associated with other interferometric SAR systems based on two or more satellites (e.g. the "cartwheel" or "helix" concept).The Wavemill concept has developed steadily since its first inception in 2005. A number of Wavemill studies in recent years have gradually put together facts and figures to support the case for Wavemill as a possible space-borne mission.The Wavemill Product Assessment study (WaPA) aimed to define the scientific capabilities and limitations of a spaceborne Wavemill instrument in preparation for a possible submission of the Wavemill concept as a candidate Earth Explorer Core mission. The WaPA project team brought together expert scientists and engineers in the field of SAR imaging of ocean currents, and included the National Oceanography Centre (UK), Starlab (Spain), IFREMER (France) and Airbus Defence and Space (UK). Overall project management was provided by Satellite Oceanographic Consultants (UK). The approach taken included:- A review of SAR imaging of ocean currents in along-track interferometric mode to learn from previous experiments and modelling what key phenomena need to be accounted for to determine the true performance of a spaceborne Wavemill system- Validation of proposed Wavemill primary products based on Wavemill airborne proof-of-concept data and numerical simulations to determine the capabilities and limitations of a spaceborne Wavemill instrument for ocean current vector and sea surface height mapping.- An analysis of the potential for ocean wind vector retrieval from a spaceborne Wavemill instrument.- An investigation of possible secondary products from Wavemill relating to rivers, ocean/atmosphere interactions, ocean swell and cryospheric applications.An assessment of the synergy between Wavemill and ocean surface current products derived from other remote sensing techniques, accounting for the nature and variability of the measured properties, to identify any additional requirements on a future Wavemill mission.

Oceanic circulation models help to predict global biogeography of pelagic yellow-bellied sea snake

PubMed Central

Cotté, Cédric; Bailleul, Frédéric; Lalire, Maxime; Gaspar, Philippe

2016-01-01

It is well recognized that most marine vertebrates, and especially tetrapods, precisely orient and actively move in apparently homogeneous oceanic environments. Here, we investigate the presumptive role of oceanic currents in biogeographic patterns observed in a secondarily marine tetrapod, the yellow-bellied sea snake (Hydrophis [Pelamis] platurus). State-of-the-art world ocean circulation models show how H. platurus, the only pelagic species of sea snake, can potentially exploit oceanic currents to disperse and maintain population mixing between localities that spread over two-thirds of the Earth's circumference. The very close association of these snakes with surface currents seems to provide a highly efficient dispersal mechanism that allowed this species to range extensively and relatively quickly well beyond the central Indo-Pacific area, the centre of origin, abundance and diversity of sea snakes. Our results further suggest that the pan-oceanic population of this species must be extraordinarily large. PMID:27555651

Operational seasonal and interannual predictions of ocean conditions

NASA Technical Reports Server (NTRS)

Leetmaa, Ants

1992-01-01

Dr. Leetmaa described current work at the U.S. National Meteorological Center (NMC) on coupled systems leading to a seasonal prediction system. He described the way in which ocean thermal data is quality controlled and used in a four dimensional data assimilation system. This consists of a statistical interpolation scheme, a primitive equation ocean general circulation model, and the atmospheric fluxes that are required to force this. This whole process generated dynamically consist thermohaline and velocity fields for the ocean. Currently routine weekly analyses are performed for the Atlantic and Pacific oceans. These analyses are used for ocean climate diagnostics and as initial conditions for coupled forecast models. Specific examples of output products were shown both in the Pacific and the Atlantic Ocean.

Calculation of wind-driven surface currents in the North Atlantic Ocean

NASA Technical Reports Server (NTRS)

Rees, T. H.; Turner, R. E.

1976-01-01

Calculations to simulate the wind driven near surface currents of the North Atlantic Ocean are described. The primitive equations were integrated on a finite difference grid with a horizontal resolution of 2.5 deg in longitude and latitude. The model ocean was homogeneous with a uniform depth of 100 m and with five levels in the vertical direction. A form of the rigid-lid approximation was applied. Generally, the computed surface current patterns agreed with observed currents. The development of a subsurface equatorial countercurrent was observed.

Woods Hole Oceanographic Institution

Science.gov Websites

OCEAN Ocean Topics Oceanus Magazine Visual WHOI Blogs/Expeditions Exhibit Center JOIN US DONATE Technology Transfer 90% of international trade travels by ship Explore Ocean Topics Hydrothermal Vents Trenches Ocean Acidification Phytoplankton Currents, Gyres, & Eddies [ ALL OCEAN TOPICS ] Dive into our

Spaceborne Studies Of Ocean Circulation

NASA Astrophysics Data System (ADS)

Patzert, William C.

1984-08-01

The global view of the oceans seen by Seasat during its 1978 flight demonstrated the feasibility of ocean remote sensing. These first-ever global data sets of sea surface topography (altimeter) and marine winds (scatterometer) laid the foundation for two satellite missions planned for the late 1980's. The future missions are the next generation of altimeter and scatterometer to be flown aboard TOPEX (Topography Experiment) and NROSS (Navy Remote Ocean Sensing System), respectively. The data from these satellites will be coordinated with measurements made at sea to determine the driving forces of ocean circulation and to study the oceans role in climate variability. Sea surface winds (calculated from scatterometer measurements) are the fundamental driving force for ocean waves and currents (estimated from altimeter measurements). On a global scale, the winds and currents are approximately equal partners in redistributing the excess heat gained in the tropics from solar radiation to the cooler polar regions. Small perturbations in this system can dramatically alter global weather, such as the El Niho event of 1982-83. During an El Ni?io event, global wind patterns and ocean currents are perturbed causing unusual ocean warming in the tropical Pacfic Ocean. These ocean events are coupled to complex fluctuations in global weather. Only with satellites will we be able to collect the global data sets needed to study events such as El Ni?o. When TOPEX and NROSS fly, oceanographers will have the equivalent of meteorological high and low pressure charts of ocean topography as well as the surface winds to study ocean "weather." This ability to measure ocean circulation and its driving forces is a critical element in understanding the influence of oceans on society. Climatic changes, fisheries, commerce, waste disposal, and national defense are all involved.

Dynamics of the Antarctic Circumpolar Current as seen by GRACE (Invited)

NASA Astrophysics Data System (ADS)

Thomas, M.; Dobslaw, H.; Bergmann, I.

2010-12-01

The Antarctic Circumpolar Current, being the strongest and longest ocean current on Earth, connects the three great ocean basins and contributes substantially to the global re-distribution of water masses, with a significant impact on global climate. Observational coverage from in-situ measurements is sparse due to the harsh environmental conditions, and satellite altimetry does not capture the full extent of the current due to seasonal sea-ice coverage. Ocean bottom pressure variations as sensed with the satellite gravity mission GRACE provide a promising way to broaden our observational basis. Besides monthly mean gravity fields that provide ocean bottom pressure variations averaged over 30 days, several alternative GRACE products with higher temporal resolution have been developed during the most recent years. These include 10-day solutions from GRGS Toulouse, weekly solutions from the GFZ Potsdam as well as constrained daily solutions from the University of Bonn which have been obtained by means of a Kalman filtering approach. In this presentation, ocean bottom pressure derived from these alternative GRACE releases will be contrasted against both in-situ observations and output from a numerical ocean model, highlighting the additional information contained in these GRACE solutions with respect to the standard monthly fields. By means of statistical analyses of ocean bottom pressure variations and barotropic transports it will be demonstrated how these new GRACE releases are contributing to our understanding of this highly dynamic great ocean conveyor.

Will high-resolution global ocean models benefit coupled predictions on short-range to climate timescales?

NASA Astrophysics Data System (ADS)

Hewitt, Helene T.; Bell, Michael J.; Chassignet, Eric P.; Czaja, Arnaud; Ferreira, David; Griffies, Stephen M.; Hyder, Pat; McClean, Julie L.; New, Adrian L.; Roberts, Malcolm J.

2017-12-01

As the importance of the ocean in the weather and climate system is increasingly recognised, operational systems are now moving towards coupled prediction not only for seasonal to climate timescales but also for short-range forecasts. A three-way tension exists between the allocation of computing resources to refine model resolution, the expansion of model complexity/capability, and the increase of ensemble size. Here we review evidence for the benefits of increased ocean resolution in global coupled models, where the ocean component explicitly represents transient mesoscale eddies and narrow boundary currents. We consider lessons learned from forced ocean/sea-ice simulations; from studies concerning the SST resolution required to impact atmospheric simulations; and from coupled predictions. Impacts of the mesoscale ocean in western boundary current regions on the large-scale atmospheric state have been identified. Understanding of air-sea feedback in western boundary currents is modifying our view of the dynamics in these key regions. It remains unclear whether variability associated with open ocean mesoscale eddies is equally important to the large-scale atmospheric state. We include a discussion of what processes can presently be parameterised in coupled models with coarse resolution non-eddying ocean models, and where parameterizations may fall short. We discuss the benefits of resolution and identify gaps in the current literature that leave important questions unanswered.

High-frequency and meso-scale winter sea-ice variability in the Southern Ocean in a high-resolution global ocean model

NASA Astrophysics Data System (ADS)

Stössel, Achim; von Storch, Jin-Song; Notz, Dirk; Haak, Helmuth; Gerdes, Rüdiger

2018-03-01

This study is on high-frequency temporal variability (HFV) and meso-scale spatial variability (MSV) of winter sea-ice drift in the Southern Ocean simulated with a global high-resolution (0.1°) sea ice-ocean model. Hourly model output is used to distinguish MSV characteristics via patterns of mean kinetic energy (MKE) and turbulent kinetic energy (TKE) of ice drift, surface currents, and wind stress, and HFV characteristics via time series of raw variables and correlations. We find that (1) along the ice edge, the MSV of ice drift coincides with that of surface currents, in particular such due to ocean eddies; (2) along the coast, the MKE of ice drift is substantially larger than its TKE and coincides with the MKE of wind stress; (3) in the interior of the ice pack, the TKE of ice drift is larger than its MKE, mostly following the TKE pattern of wind stress; (4) the HFV of ice drift is dominated by weather events, and, in the absence of tidal currents, locally and to a much smaller degree by inertial oscillations; (5) along the ice edge, the curl of the ice drift is highly correlated with that of surface currents, mostly reflecting the impact of ocean eddies. Where ocean eddies occur and the ice is relatively thin, ice velocity is characterized by enhanced relative vorticity, largely matching that of surface currents. Along the ice edge, ocean eddies produce distinct ice filaments, the realism of which is largely confirmed by high-resolution satellite passive-microwave data.

Evaluation of OSCAR ocean surface current product in the tropical Indian Ocean using in situ data

NASA Astrophysics Data System (ADS)

Sikhakolli, Rajesh; Sharma, Rashmi; Basu, Sujit; Gohil, B. S.; Sarkar, Abhijit; Prasad, K. V. S. R.

2013-02-01

The OSCAR (ocean surface current analysis real-time), which is a product derived from various satellite observations, has been evaluated in the tropical Indian Ocean (TIO) in two different ways. First, the OSCAR-derived monthly climatology has been compared with available drifter-derived climatology in the TIO. From the comparison of the two climatologies, one can infer that OSCAR product is able to capture the variabilities of the well-known surface current systems in the TIO reasonably well. Fourier analysis of the major current systems, as reproduced by OSCAR, shows that the dominant annual and semiannual periodicities, known to exist in these systems, have been faithfully picked up by OSCAR. Next, the evaluation has been carried out by comparing the OSCAR currents with currents measured by moored buoys. The zonal component of OSCAR-current is in good agreement with corresponding component of buoy-observed current with a correlation exceeding 0.7, while the match between the meridional components is poorer. The locations of the peaks of the mean and eddy kinetic energies are matching in both the climatologies, although the peak in the drifter climatology is stronger than the same in the OSCAR product. Finally, an important feature of Indian Ocean circulation, namely the reverse Wyrtki jet, occurring during anomalous dipole years, has been well-reproduced by OSCAR currents.

Ocean current surface measurement using dynamic elevations obtained by the GEOS-3 radar altimeter

NASA Technical Reports Server (NTRS)

Leitao, C. D.; Huang, N. E.; Parra, C. G.

1977-01-01

Remote Sensing of the ocean surface from the GEOS-3 satellite using radar altimeter data has confirmed that the altimeter can detect the dynamic ocean topographic elevations relative to an equipotential surface, thus resulting in a reliable direct measurement of the ocean surface. Maps of the ocean dynamic topography calculated over a one month period and with 20 cm contour interval are prepared for the last half of 1975. The Gulf Stream is observed by the rapid slope change shown by the crowding of contours. Cold eddies associated with the current are seen as roughly circular depressions.

Physics-based coastal current tomographic tracking using a Kalman filter.

PubMed

Wang, Tongchen; Zhang, Ying; Yang, T C; Chen, Huifang; Xu, Wen

2018-05-01

Ocean acoustic tomography can be used based on measurements of two-way travel-time differences between the nodes deployed on the perimeter of the surveying area to invert/map the ocean current inside the area. Data at different times can be related using a Kalman filter, and given an ocean circulation model, one can in principle now cast and even forecast current distribution given an initial distribution and/or the travel-time difference data on the boundary. However, an ocean circulation model requires many inputs (many of them often not available) and is unpractical for estimation of the current field. A simplified form of the discretized Navier-Stokes equation is used to show that the future velocity state is just a weighted spatial average of the current state. These weights could be obtained from an ocean circulation model, but here in a data driven approach, auto-regressive methods are used to obtain the time and space dependent weights from the data. It is shown, based on simulated data, that the current field tracked using a Kalman filter (with an arbitrary initial condition) is more accurate than that estimated by the standard methods where data at different times are treated independently. Real data are also examined.

Plastic and evolutionary responses of plankton to environmental change are influenced by drift in ocean currents

NASA Astrophysics Data System (ADS)

Doblin, M.; van Sebille, E.

2016-02-01

The analytical framework for understanding fluctuations in ocean habitats has typically involved a Eulerian view. However, for marine microbes, this framework does not take into account their transport in dynamic seascapes, implying that our current view of change for these critical organisms may be inaccurate. Using a modelling approach, we show that generations of upper ocean microbes experience along-trajectory temperature variability up to 10°C greater than seasonal fluctuations estimated in a static frame, and that this variability depends strongly on location. These findings demonstrate that drift in ocean currents contributes to environmental fluctuation experienced by microbes and suggests that microbial populations may be adapted to upstream rather than local conditions. In an empirical test, we demonstrate that microbes in a warm, poleward flowing western boundary current (East Australian Current) have a different thermal response curve to microbes in coastal water at the same latitude (p < 0.05). Our findings suggest that advection has the capacity to influence microbial community assemblies such that water masses with relatively small thermal fluctuations select for thermal specialists, and communities with broad temperature performance curves are found in locations where ocean currents are strong or along-trajectory temperature variation is high.

Ocean circulation studies

NASA Technical Reports Server (NTRS)

Koblinsky, C. J.

1984-01-01

Remotely sensed signatures of ocean surface characteristics from active and passive satellite-borne radiometers in conjunction with in situ data were utilized to examine the large scale, low frequency circulation of the world's oceans. Studies of the California Current, the Gulf of California, and the Kuroshio Extension Current in the western North Pacific were reviewed briefly. The importance of satellite oceanographic tools was emphasized.

Ocean Currents: Marine Science Activities for Grades 5-8. Teacher's Guide.

ERIC Educational Resources Information Center

Halversen, Catherine; Beals, Kevin; Strang, Craig

This teacher's guide attempts to answer questions such as: What causes ocean currents? What impact do they have on Earth's environment? and How have they influenced human history? Seven innovative activities are provided in which students can gain fascinating insights into the earth as the ocean planet. Activities focus on how wind, temperature,…

Detangling Spaghetti: Tracking Deep Ocean Currents in the Gulf of Mexico

ERIC Educational Resources Information Center

Curran, Mary Carla; Bower, Amy S.; Furey, Heather H.

2017-01-01

Creation of physical models can help students learn science by enabling them to be more involved in the scientific process of discovery and to use multiple senses during investigations. This activity achieves these goals by having students model ocean currents in the Gulf of Mexico. In general, oceans play a key role in influencing weather…

Proceedings of oceans 87. The ocean - an international workplace

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

Not Available

1987-01-01

This book includes proceedings containing 347 papers. Some of the topics are: ICE -Cold ocean and ice research; ICE-1-Icebergs; ICE-2-Sea ice and structures; IE-3-Cold ocean instrumentation; ICE-4-Ocean and ice; INS-Oceanographic instrumentation; INS-1-Acoustic Doppler Current profilers; ENG-1-New solutions to old problems; ENG-2-energy from the ocean; ENG-3-Cables and connectors; POL-Policy, education and technology transfer; POL-1-International issues; POL-2-Ocean space utilization; POL-3-Economics, planning and management; SCI-6-fish stock assessment; ACI-7-Coastal currents and sediment; SCI-9-Satellite navigation; SCI-10-Deep sea minerals and methods of recovery; ODS-Fifth working symposium on oceanographic data system; ODS-1-Data base management; UND-Underwater work systems; UND-1-Diving for science.

Surface currents in the Bohai Sea derived from the Korean Geostationary Ocean Color Imager (GOCI)

NASA Astrophysics Data System (ADS)

Jiang, L.; Wang, M.

2016-02-01

The first geostationary ocean color satellite sensor, the Geostationary Ocean Color Imager (GOCI) onboard the Korean Communication, Ocean, and Meteorological Satellite can monitor and measure ocean phenomena over an area of 2500 × 2500 km2 around the western Pacific region centered at 36°N and 130°E. Hourly measurements during the day around 9:00 to 16:00 local time are a unique capability of GOCI to monitor ocean features of higher temporal variability. In this presentation, we show some recent results of GOCI-derived ocean surface currents in the Bohai Sea using the Maximum Cross-Correlation (MCC) feature tracking method and compare the results with altimetry-inversed tidal current observations produced from Oregon State University (OSU) Tidal Inversion Software (OTIS). The performance of the GOCI-based MCC method is assessed and the discrepancies between the GOCI- and OTIS-derived currents are evaluated. A series of sensitivity studies are conducted with images from various satellite products and of various time differences, MCC adjustable parameters, and influence from other forcings such as wind, to find the best setups for optimal MCC performance. Our results demonstrate that GOCI can effectively provide real-time monitoring of not only water optical, biological, and biogeochemical variability, but also the physical dynamics in the region.

Drift in ocean currents impacts intergenerational microbial exposure to temperature.

PubMed

Doblin, Martina A; van Sebille, Erik

2016-05-17

Microbes are the foundation of marine ecosystems [Falkowski PG, Fenchel T, Delong EF (2008) Science 320(5879):1034-1039]. Until now, the analytical framework for understanding the implications of ocean warming on microbes has not considered thermal exposure during transport in dynamic seascapes, implying that our current view of change for these critical organisms may be inaccurate. Here we show that upper-ocean microbes experience along-trajectory temperature variability up to 10 °C greater than seasonal fluctuations estimated in a static frame, and that this variability depends strongly on location. These findings demonstrate that drift in ocean currents can increase the thermal exposure of microbes and suggests that microbial populations with broad thermal tolerance will survive transport to distant regions of the ocean and invade new habitats. Our findings also suggest that advection has the capacity to influence microbial community assemblies, such that regions with strong currents and large thermal fluctuations select for communities with greatest plasticity and evolvability, and communities with narrow thermal performance are found where ocean currents are weak or along-trajectory temperature variation is low. Given that fluctuating environments select for individual plasticity in microbial lineages, and that physiological plasticity of ancestors can predict the magnitude of evolutionary responses of subsequent generations to environmental change [Schaum CE, Collins S (2014) Proc Biol Soc 281(1793):20141486], our findings suggest that microbial populations in the sub-Antarctic (∼40°S), North Pacific, and North Atlantic will have the most capacity to adapt to contemporary ocean warming.

A perspective on sustained marine observations for climate modelling and prediction

PubMed Central

Dunstone, Nick J.

2014-01-01

Here, I examine some of the many varied ways in which sustained global ocean observations are used in numerical modelling activities. In particular, I focus on the use of ocean observations to initialize predictions in ocean and climate models. Examples are also shown of how models can be used to assess the impact of both current ocean observations and to simulate that of potential new ocean observing platforms. The ocean has never been better observed than it is today and similarly ocean models have never been as capable at representing the real ocean as they are now. However, there remain important unanswered questions that can likely only be addressed via future improvements in ocean observations. In particular, ocean observing systems need to respond to the needs of the burgeoning field of near-term climate predictions. Although new ocean observing platforms promise exciting new discoveries, there is a delicate balance to be made between their funding and that of the current ocean observing system. Here, I identify the need to secure long-term funding for ocean observing platforms as they mature, from a mainly research exercise to an operational system for sustained observation over climate change time scales. At the same time, considerable progress continues to be made via ship-based observing campaigns and I highlight some that are dedicated to addressing uncertainties in key ocean model parametrizations. The use of ocean observations to understand the prominent long time scale changes observed in the North Atlantic is another focus of this paper. The exciting first decade of monitoring of the Atlantic meridional overturning circulation by the RAPID-MOCHA array is highlighted. The use of ocean and climate models as tools to further probe the drivers of variability seen in such time series is another exciting development. I also discuss the need for a concerted combined effort from climate models and ocean observations in order to understand the current slow-down in surface global warming. PMID:25157195

The importance of altimeter and scatterometer data for ocean prediction

NASA Technical Reports Server (NTRS)

Hurlburt, H. E.

1984-01-01

The prediction of ocean circulation using satellite altimeter data is discussed. Three classes of oceanic response to atmospheric forcing are outlined and examined. Storms, surface waves, eddies, and ocean currents were evaluated in terms of forecasting time requirements. Scatterometer and radiometer applications to ocean prediction are briefly reviewed.

Oceanic circulation models help to predict global biogeography of pelagic yellow-bellied sea snake.

PubMed

Brischoux, François; Cotté, Cédric; Lillywhite, Harvey B; Bailleul, Frédéric; Lalire, Maxime; Gaspar, Philippe

2016-08-01

It is well recognized that most marine vertebrates, and especially tetrapods, precisely orient and actively move in apparently homogeneous oceanic environments. Here, we investigate the presumptive role of oceanic currents in biogeographic patterns observed in a secondarily marine tetrapod, the yellow-bellied sea snake (Hydrophis [Pelamis] platurus). State-of-the-art world ocean circulation models show how H. platurus, the only pelagic species of sea snake, can potentially exploit oceanic currents to disperse and maintain population mixing between localities that spread over two-thirds of the Earth's circumference. The very close association of these snakes with surface currents seems to provide a highly efficient dispersal mechanism that allowed this species to range extensively and relatively quickly well beyond the central Indo-Pacific area, the centre of origin, abundance and diversity of sea snakes. Our results further suggest that the pan-oceanic population of this species must be extraordinarily large. © 2016 The Author(s).

Self-Organizing Maps-based ocean currents forecasting system.

PubMed

Vilibić, Ivica; Šepić, Jadranka; Mihanović, Hrvoje; Kalinić, Hrvoje; Cosoli, Simone; Janeković, Ivica; Žagar, Nedjeljka; Jesenko, Blaž; Tudor, Martina; Dadić, Vlado; Ivanković, Damir

2016-03-16

An ocean surface currents forecasting system, based on a Self-Organizing Maps (SOM) neural network algorithm, high-frequency (HF) ocean radar measurements and numerical weather prediction (NWP) products, has been developed for a coastal area of the northern Adriatic and compared with operational ROMS-derived surface currents. The two systems differ significantly in architecture and algorithms, being based on either unsupervised learning techniques or ocean physics. To compare performance of the two methods, their forecasting skills were tested on independent datasets. The SOM-based forecasting system has a slightly better forecasting skill, especially during strong wind conditions, with potential for further improvement when data sets of higher quality and longer duration are used for training.

Self-Organizing Maps-based ocean currents forecasting system

PubMed Central

Vilibić, Ivica; Šepić, Jadranka; Mihanović, Hrvoje; Kalinić, Hrvoje; Cosoli, Simone; Janeković, Ivica; Žagar, Nedjeljka; Jesenko, Blaž; Tudor, Martina; Dadić, Vlado; Ivanković, Damir

2016-01-01

An ocean surface currents forecasting system, based on a Self-Organizing Maps (SOM) neural network algorithm, high-frequency (HF) ocean radar measurements and numerical weather prediction (NWP) products, has been developed for a coastal area of the northern Adriatic and compared with operational ROMS-derived surface currents. The two systems differ significantly in architecture and algorithms, being based on either unsupervised learning techniques or ocean physics. To compare performance of the two methods, their forecasting skills were tested on independent datasets. The SOM-based forecasting system has a slightly better forecasting skill, especially during strong wind conditions, with potential for further improvement when data sets of higher quality and longer duration are used for training. PMID:26979129

An Investigation of Fin and Blue Whales in the NE Pacific Ocean using Data from Cascadia Initiative Ocean Bottom Seismometers

DTIC Science & Technology

2014-09-30

the east and northeast by the ocean currents associated with the West Wind drift and Subarctic Current. Over 150 fin whale tracks ranging in duration...Mellinger, T.L. Rogers, R.P. Dziak, and M. Park. (2012). Acoustic density estimation of leopard seals. Abstracts, Birds and Mammals Session, Open

Navigational challenges in the oceanic migrations of leatherback sea turtles

PubMed Central

Sale, Alessandro; Luschi, Paolo

2009-01-01

The open-sea movements of marine animals are affected by the drifting action of currents that, if not compensated for, can produce non-negligible deviations from the correct route towards a given target. Marine turtles are paradigmatic skilful oceanic navigators that are able to reach remote goals at the end of long-distance migrations, apparently overcoming current drift effects. Particularly relevant is the case of leatherback turtles (Dermochelys coriacea), which spend entire years in the ocean, wandering in search of planktonic prey. Recent analyses have revealed how the movements of satellite-tracked leatherbacks in the Indian, Atlantic and Pacific Oceans are strongly dependent on the oceanic currents, up to the point that turtles are often passively transported over long distances. However, leatherbacks are known to return to specific areas to breed every 2–3 years, thus finding their way back home after long periods in the oceanic environment. Here we examine the navigational consequences of the leatherbacks' close association with currents and discuss how the combined reliance on mechanisms of map-based navigation and local orientation cues close to the target may allow leatherbacks to accomplish the difficult task of returning to specific sites after years spent wandering in a moving medium. PMID:19625321

Development and Utilization of Regional Oceanic Modeling System (ROMS). Delicacy, Imprecision, and Uncertainty of Oceanic Simulations: An Investigation with the Regional Oceanic Modeling System (ROMS). Submesoscale Flows and Mixing in the Ocean Surface Layer Using the Regional Oceanic Modeling System (ROMS). Eddy Effects in General Circulation, Spanning Mean Currents, Mesoscale Eddies, and Topographic Generation, including Submesoscale Nests

DTIC Science & Technology

2012-09-30

unbalanced motions is likely to occur. Due to an rapidly expanding set of investigation on oceanic flows at submesoscales, it is increasingly clear...Uchiyama, E. M. Lane, J. M. Restrepo, & J. C. McWilliams, 2011: A vortex force analysis of the interaction of rip currents and gravity waves. J. Geophys...particular topographic features, the torque is pervasively positive (cyclonic) along the Stream, in opposition to the anticyclonic wind curl in the

Motionally-induced electromagnetic fields generated by idealized ocean currents

NASA Astrophysics Data System (ADS)

Tyler, R. H.; Mysak, L. A.

Using the induction equation, we investigate the generation of electromagnetic fields by the motional electromagnetic induction due to ocean currents. In this paper, solutions are presented for a linear induction equation for the magnetic flux density vector which contains prescribed time-independent ocean current and conductivity fields. Once the magnetic flux density is known, the electric field and electric current density are easily obtained by differentiation. Solutions are given for several examples of idealized flow which include: 1) Vertically and horizontally sheared plane-parallel flow with depth-dependent conductivity; 2) A simple Stommel circulation gyre; and 3) Symmetric gyres. The results indicate that typical ocean current features induce magnetic fields with magnitudes reaching 100's of nT within the water and about 1-10 outside of the water. For the case of a field of gyres, the ocean-induced magnetic fields decay away from the ocean on spatial scales set by the horizontal scale of the ocean feature. At the altitudes of magnetic field satellite surveys, ocean-induced magnetic fields may retain values of a few nT, which are strong enough to be detected. Thus it is concluded that satellite observations of the earth's main magnetic field and, in particular, the observed temporal variations, could be affected by the ocean circulation. Summary and discussion In Section 3, we found exact solutions to the induction equation for idealized flows. The results gave magnitudes of about tens to hundreds of nT for the magnetic fields bH, about 10-5 V/m for the electric fields E, and about 10-5 A/m2 for the electric current density J induced by the ocean currents. These figures are in general agreement with the calculations of Lilley et al. (1993). In Section 4.2 we obtained solutions for the magnetic field above the ocean surface for the case of a Stommel gyre and a field of symmetric gyres. It was found in the last case that ocean gyres with a total transport of 100 Sv would have field magnitudes above the ocean of up to 23 nT and more typically between about 1 and 10 nT. The results also indicate that the decay scales for the magnetic field away from the ocean are of the same order as the horizontal scale of the flow. We calculated that flow features with scales of 100 km or more may retain magnitudes that are strong enough (a few nT) to be detected at satellite altitudes (300-500 km). Flows of smaller scale, however, would probably not be detected by current satellites. We have not explicitly solved for the magnetic fields that would be observed at magnetic observations on land since we have only treated cases of horizontally homogeneous conductivity. However, we conjecture that inland magnetic observations will also be affected by the ocean induction. The spatial decay inland from the ocean would again be set by the horizontal scale of the flow except when the electric currents involved in the induction are close to the coast. In this case there is a coastal effect, with the stronger fields decaying over a shorter scale. We have presented arguments which indicate that for uniform ocean conductivity s over a sediment layer of low conductivity, barotropic currents are efficient generators of electric fields but poor generators of electrical current and magnetic fields, while baroclinic currents are efficient generators of electrical current and magnetic fields, and (in our simple examples) poor generators of electric fields. When, however, s varies in the vertical, it appears that virtually all realistic forms of ocean circulation will be reasonably efficient generators of electrical current and magnetic fields. It is conceivable that the geomagnetic record from land and satellite observatories has captured oceanic signals. Another task before ocean and geomagnetic records can be linked, however, is to isolate the oceanic signal from the records which are known to be swarmed with magnetic signals from many other sources. How can we know that measured magnetic variations are due to variations in the ocean induction and not due to sources in the ionosphere or earth's core? This is a difficult problem, but there may be some ways to resolve it. Variations in ocean circulation or conductivity are rather slow compared to the rapid magnetic storms and most other variations due to external sources. Also the external effects at the earth's surface tend to have large spatial scales which allows removal using techniques such as 'remote referencing' as done by Lilley et al. (1993). With regard to sources in the earth's core, the geometric and electromagnetic filtering by the mantle are thought to prevent all but the lowest frequencies from reaching the earth's surface. Hence, it is conceivable that at the earth's surface, magnetic fields due to the earth's core can only appear as relatively smooth, slowly-varying fields with periods of decadal scale and longer. Hence, there is probably a fortuitous 'spectral window' through which we can view interannual variations in the ocean-induced fields. It is also important that the accuracy in measuring the time rate of change of the magnetic field on these time scales is greater than the accuracy of the field values (at least at the land observatories). This is because when differencing the magnetic series, errors in the baseline drift are reduced. Hence, it is probable that fluctuations in the ocean-induced magnetic fields would be easier to detect than the steady-state fields. The results presented here should also be helpful in designing future strategies for numerically modelling the ocean-induced electromagnetic fields. As we mentioned, (73) is similar in principle to the two-dimensional equation solved by Stephenson and Bryan (1992) but is more general, allowing for a more realistic description of conductivity and allowing for horizontal divergence in the conductivity transport. Other results in this paper may be helpful in finding new approaches to the problem of numerically modelling the oceanic induction. The flux form of the induction equation (18) could be a more convenient form to be used in established numerical algorithms using flux conservation. Also, (11) or (18) could be used with the Stokes or Divergence theorems to create a box-model description of global oceanic induction. When the scalar fluid property Λ described in Section 4.2.3 is taken to be a function of the conductivity, equation (76) is greatly simplified, suggesting that a three-dimensional numerical model using constant conductivity layers [similar in essence to the constant-density layer approach used in the OPYC ocean-circulation model written by Joseph Oberhuber (1993)] may be profitably exploited.

An overview of approaches and challenges for retrieving marine inherent optical properties from ocean color remote sensing

NASA Astrophysics Data System (ADS)

Werdell, P. Jeremy; McKinna, Lachlan I. W.; Boss, Emmanuel; Ackleson, Steven G.; Craig, Susanne E.; Gregg, Watson W.; Lee, Zhongping; Maritorena, Stéphane; Roesler, Collin S.; Rousseaux, Cécile S.; Stramski, Dariusz; Sullivan, James M.; Twardowski, Michael S.; Tzortziou, Maria; Zhang, Xiaodong

2018-01-01

Ocean color measured from satellites provides daily global, synoptic views of spectral water-leaving reflectances that can be used to generate estimates of marine inherent optical properties (IOPs). These reflectances, namely the ratio of spectral upwelled radiances to spectral downwelled irradiances, describe the light exiting a water mass that defines its color. IOPs are the spectral absorption and scattering characteristics of ocean water and its dissolved and particulate constituents. Because of their dependence on the concentration and composition of marine constituents, IOPs can be used to describe the contents of the upper ocean mixed layer. This information is critical to further our scientific understanding of biogeochemical oceanic processes, such as organic carbon production and export, phytoplankton dynamics, and responses to climatic disturbances. Given their importance, the international ocean color community has invested significant effort in improving the quality of satellite-derived IOP products, both regionally and globally. Recognizing the current influx of data products into the community and the need to improve current algorithms in anticipation of new satellite instruments (e.g., the global, hyperspectral spectroradiometer of the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission), we present a synopsis of the current state of the art in the retrieval of these core optical properties. Contemporary approaches for obtaining IOPs from satellite ocean color are reviewed and, for clarity, separated based their inversion methodology or the type of IOPs sought. Summaries of known uncertainties associated with each approach are provided, as well as common performance metrics used to evaluate them. We discuss current knowledge gaps and make recommendations for future investment for upcoming missions whose instrument characteristics diverge sufficiently from heritage and existing sensors to warrant reassessing current approaches.

Assessment of Energy Production Potential from Ocean Currents along the United States Coastline

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

Haas, Kevin

Increasing energy consumption and depleting reserves of fossil fuels have resulted in growing interest in alternative renewable energy from the ocean. Ocean currents are an alternative source of clean energy due to their inherent reliability, persistence and sustainability. General ocean circulations exist in the form of large rotating ocean gyres, and feature extremely rapid current flow in the western boundaries due to the Coriolis Effect. The Gulf Stream system is formed by the western boundary current of the North Atlantic Ocean that flows along the east coastline of the United States, and therefore is of particular interest as a potentialmore » energy resource for the United States. This project created a national database of ocean current energy resources to help advance awareness and market penetration in ocean current energy resource assessment. The database, consisting of joint velocity magnitude and direction probability histograms, was created from data created by seven years of numerical model simulations. The accuracy of the database was evaluated by ORNL?s independent validation effort documented in a separate report. Estimates of the total theoretical power resource contained in the ocean currents were calculated utilizing two separate approaches. Firstly, the theoretical energy balance in the Gulf Stream system was examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for subtropical gyres with the quasi-geostrophic balance between pressure gradient, Coriolis force, wind stress and friction driving the circulation. Parameters including water depth, natural dissipation rate and wind stress are calibrated in the model so that the model can reproduce reasonable flow properties including volume flux and energy flux. To represent flow dissipation due to turbines additional turbine drag coefficient is formulated and included in the model. Secondly, to determine the reasonableness of the total power estimates from the Stommel model and to help determine the size and capacity of arrays necessary to extract the maximum theoretical power, further estimates of the available power based on the distribution of the kinetic power density in the undisturbed flow was completed. This used estimates of the device spacing and scaling to sum up the total power that the devices would produce. The analysis has shown that considering extraction over a region comprised of the Florida Current portion of the Gulf Stream system, the average power dissipated ranges between 4-6 GW with a mean around 5.1 GW. This corresponds to an average of approximately 45 TWh/yr. However, if the extraction area comprises the entire portion of the Gulf Stream within 200 miles of the US coastline from Florida to North Carolina, the average power dissipated becomes 18.6 GW or 163 TWh/yr. A web based GIS interface, http://www.oceancurrentpower.gatech.edu/, was developed for dissemination of the data. The website includes GIS layers of monthly and yearly mean ocean current velocity and power density for ocean currents along the entire coastline of the United States, as well as joint and marginal probability histograms for current velocities at a horizontal resolution of 4-7 km with 10-25 bins over depth. Various tools are provided for viewing, identifying, filtering and downloading the data.« less

Remote sensing of ocean currents

NASA Technical Reports Server (NTRS)

Goldstein, R. M.; Zebker, H. A.; Barnett, T. P.

1989-01-01

A method of remotely measuring near-surface ocean currents with a synthetic aperture radar (SAR) is described. The apparatus consists of a single SAR transmitter and two receiving antennas. The phase difference between SAR image scenes obtained from the antennas forms an interferogram that is directly proportional to the surface current. The first field test of this technique against conventional measurements gives estimates of mean currents accurate to order 20 percent, that is, root-mean-square errors of 5 to 10 centimeters per second in mean flows of 27 to 56 centimeters per second. If the full potential of the method could be realized with spacecraft, then it might be possible to routinely monitor the surface currents of the world's oceans.

The Physical Ocean.

ERIC Educational Resources Information Center

NatureScope, 1988

1988-01-01

Examines the physical properties of the ocean (including the composition of seawater; waves, currents, and tides) and the topography of the ocean floor. Included are (1) activities on oceans, saltwater, and the sea floor; and (2) questions, and a puzzle which can be copied. (Author/RT)

OceanNOMADS: Real-time and retrospective access to operational U.S. ocean prediction products

NASA Astrophysics Data System (ADS)

Harding, J. M.; Cross, S. L.; Bub, F.; Ji, M.

2011-12-01

The National Oceanic and Atmospheric Administration (NOAA) National Operational Model Archive and Distribution System (NOMADS) provides both real-time and archived atmospheric model output from servers at the National Centers for Environmental Prediction (NCEP) and National Climatic Data Center (NCDC) respectively (http://nomads.ncep.noaa.gov/txt_descriptions/marRutledge-1.pdf). The NOAA National Ocean Data Center (NODC) with NCEP is developing a complementary capability called OceanNOMADS for operational ocean prediction models. An NCEP ftp server currently provides real-time ocean forecast output (http://www.opc.ncep.noaa.gov/newNCOM/NCOM_currents.shtml) with retrospective access through NODC. A joint effort between the Northern Gulf Institute (NGI; a NOAA Cooperative Institute) and the NOAA National Coastal Data Development Center (NCDDC; a division of NODC) created the developmental version of the retrospective OceanNOMADS capability (http://www.northerngulfinstitute.org/edac/ocean_nomads.php) under the NGI Ecosystem Data Assembly Center (EDAC) project (http://www.northerngulfinstitute.org/edac/). Complementary funding support for the developmental OceanNOMADS from U.S. Integrated Ocean Observing System (IOOS) through the Southeastern University Research Association (SURA) Model Testbed (http://testbed.sura.org/) this past year provided NODC the analogue that facilitated the creation of an NCDDC production version of OceanNOMADS (http://www.ncddc.noaa.gov/ocean-nomads/). Access tool development and storage of initial archival data sets occur on the NGI/NCDDC developmental servers with transition to NODC/NCCDC production servers as the model archives mature and operational space and distribution capability grow. Navy operational global ocean forecast subsets for U.S waters comprise the initial ocean prediction fields resident on the NCDDC production server. The NGI/NCDDC developmental server currently includes the Naval Research Laboratory Inter-America Seas Nowcast/Forecast System over the Gulf of Mexico from 2004-Mar 2011, the operational Naval Oceanographic Office (NAVOCEANO) regional USEast ocean nowcast/forecast system from early 2009 to present, and the NAVOCEANO operational regional AMSEAS (Gulf of Mexico/Caribbean) ocean nowcast/forecast system from its inception 25 June 2010 to present. AMSEAS provided one of the real-time ocean forecast products accessed by NOAA's Office of Response and Restoration from the NGI/NCDDC developmental OceanNOMADS during the Deep Water Horizon oil spill last year. The developmental server also includes archived, real-time Navy coastal forecast products off coastal Japan in support of U.S./Japanese joint efforts following the 2011 tsunami. Real-time NAVOCEANO output from regional prediction systems off Southern California and around Hawaii, currently available on the NCEP ftp server, are scheduled for archival on the developmental OceanNOMADS by late 2011 along with the next generation Navy/NOAA global ocean prediction output. Accession and archival of additional regions is planned as server capacities increase.

Atmospheric Wind Relaxations and the Oceanic Response in the California Current Large Marine Ecosystem

NASA Astrophysics Data System (ADS)

Fewings, M. R.; Dorman, C. E.; Washburn, L.; Liu, W.

2010-12-01

On the West Coast of North America in summer, episodic relaxation of the upwelling-favorable winds causes warm water to propagate northward from southern to central California, against the prevailing currents [Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. Similar wind relaxations are an important characteristic of coastal upwelling ecosystems worldwide. Although these wind relaxations have an important influence on coastal ocean dynamics, no description exists of the regional atmospheric patterns that lead to wind relaxations in southern California, or of the regional ocean response. We use QuikSCAT wind stress, North American Regional Reanalysis atmospheric pressure products, water temperature and velocity from coastal ocean moorings, surface ocean currents from high-frequency radars, and MODIS satellite sea-surface temperature and ocean color images to analyze wind relaxation events and the ocean response. We identify the events based on an empirical index calculated from NDBC buoy winds [Melton et al. 2009]. We describe the regional evolution of the atmosphere from the Gulf of Alaska to Baja California over the few days leading up to wind relaxations, and the coastal ocean temperature, color, and current response off southern and central California. We analyze ~100 wind relaxation events in June-September during the QuikSCAT mission, 1999-2009. Our results indicate south-central California wind relaxations in summer are tied to mid-level atmospheric low-pressure systems that form in the Gulf of Alaska and propagate southeastward over 3-5 days. As the low-pressure systems reach southern California, the atmospheric pressure gradient along the coast weakens, causing the surface wind stress to relax to near zero. The weak wind signal appears first at San Diego and propagates northward. QuikSCAT data indicate the relaxed winds extend over the entire Southern California Bight and up to 200 km offshore of central California. Atmospheric dynamics in the Gulf of Alaska influence ocean conditions in central and southern California via these wind relaxations. The ocean response within a few km of the coast involves poleward-flowing currents that transport warm water out of the lees of capes and headlands and counter to the direction of the California Current [Send et al. 1987, Harms and Winant 1998, Winant et al. 2003, Melton et al. 2009]. A similar response occurs in the Benguela and Canary Current coastal upwelling systems. The ocean response involves both barotropic and baroclinic dynamics and is consistent with existing geophysical models of buoyant, coastally-trapped plumes [Washburn et al., in prep]. Our ongoing work includes i) studying the regional ocean response to determine its spatial extent, time evolution, and ocean-atmosphere coupling dynamics; ii) developing an atmospheric index to predict wind relaxations in southern California based on pressure in the Gulf of Alaska; iii) examining the strength and frequency of wind relaxations over the past 30 years for connections to El Niño and the Pacific Decadal Oscillation; and iv) predicting future variations in wind relaxations and the response of the California Current Large Marine Ecosystem.

Development and Testing of a Coupled Ocean-atmosphere Mesoscale Ensemble Prediction System

DTIC Science & Technology

2011-06-28

wind, temperature, and moisture variables, while the oceanographic ET is derived from ocean current, temperature, and salinity variables. Estimates of...wind, temperature, and moisture variables while the oceanographic ET is derived from ocean current temperature, and salinity variables. Estimates of...uncertainty in the model. Rigorously accurate ensemble methods for describing the distribution of future states given past information include particle

Spiraling pathways of global deep waters to the surface of the Southern Ocean.

PubMed

Tamsitt, Veronica; Drake, Henri F; Morrison, Adele K; Talley, Lynne D; Dufour, Carolina O; Gray, Alison R; Griffies, Stephen M; Mazloff, Matthew R; Sarmiento, Jorge L; Wang, Jinbo; Weijer, Wilbert

2017-08-02

Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution models. The analysis reveals that the northern-sourced deep waters enter the Antarctic Circumpolar Current via southward flow along the boundaries of the three ocean basins, before spiraling southeastward and upward through the Antarctic Circumpolar Current. 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 Antarctic Circumpolar Current, with a spatially nonuniform distribution. The timescale for half of the deep water to upwell from 30° S to the mixed layer is ~60-90 years.Deep waters of the Atlantic, Pacific and Indian Oceans upwell in the Southern Oceanbut the exact pathways are not fully characterized. Here the authors present a three dimensional view showing a spiralling southward path, with enhanced upwelling by eddy-transport at topographic hotspots.

Validation of Salinity Data from the Soil Moisture and Ocean Salinity (SMOS) and Aquarius Satellites in the Agulhas Current System

NASA Astrophysics Data System (ADS)

Button, N.

2016-02-01

The Agulhas Current System is an important western boundary current, particularly due to its vital role in the transport of heat and salt from the Indian Ocean to the Atlantic Ocean, such as through Agulhas rings. Accurate measurements of salinity are necessary for assessing the role of the Agulhas Current System and these rings in the global climate system are necessary. With ESA's Soil Moisture and Ocean Salinity (SMOS) and NASA's Aquarius/SAC-D satellites, we now have complete spatial and temporal (since 2009 and 2011, respectively) coverage of salinity data. To use this data to understand the role of the Agulhas Current System in the context of salinity within the global climate system, we must first understand validate the satellite data using in situ and model comparisons. In situ comparisons are important because of the accuracy, but they lack in the spatial and temporal coverage to validate the satellite data. For example, there are approximately 100 floats in the Agulhas Return Current. Therefore, model comparisons, such as the Hybrid Coordinate Ocean Model (HYCOM), are used along with the in situ data for the validation. For the validation, the satellite data, Argo float data, and HYCOM simulations were compared within box regions both inside and outside of the Agulhas Current. These boxed regions include the main Agulhas Current, Agulhas Return Current, Agulhas Retroflection, and Agulhas rings, as well as a low salinity and high salinity region outside of the current system. This analysis reveals the accuracy of the salinity measurements from the Aquarius/SAC-D and SMOS satellites within the Agulhas Current, which then provides accurate salinity data that can then be used to understand the role of the Agulhas Current System in the global climate system.

Drift in ocean currents impacts intergenerational microbial exposure to temperature

PubMed Central

Doblin, Martina A.; van Sebille, Erik

2016-01-01

Microbes are the foundation of marine ecosystems [Falkowski PG, Fenchel T, Delong EF (2008) Science 320(5879):1034–1039]. Until now, the analytical framework for understanding the implications of ocean warming on microbes has not considered thermal exposure during transport in dynamic seascapes, implying that our current view of change for these critical organisms may be inaccurate. Here we show that upper-ocean microbes experience along-trajectory temperature variability up to 10 °C greater than seasonal fluctuations estimated in a static frame, and that this variability depends strongly on location. These findings demonstrate that drift in ocean currents can increase the thermal exposure of microbes and suggests that microbial populations with broad thermal tolerance will survive transport to distant regions of the ocean and invade new habitats. Our findings also suggest that advection has the capacity to influence microbial community assemblies, such that regions with strong currents and large thermal fluctuations select for communities with greatest plasticity and evolvability, and communities with narrow thermal performance are found where ocean currents are weak or along-trajectory temperature variation is low. Given that fluctuating environments select for individual plasticity in microbial lineages, and that physiological plasticity of ancestors can predict the magnitude of evolutionary responses of subsequent generations to environmental change [Schaum CE, Collins S (2014) Proc Biol Soc 281(1793):20141486], our findings suggest that microbial populations in the sub-Antarctic (∼40°S), North Pacific, and North Atlantic will have the most capacity to adapt to contemporary ocean warming. PMID:27140608

Ocean eddy structure by satellite radar altimetry required for iceberg towing

USGS Publications Warehouse

Campbell, W.J.; Cheney, R.E.; Marsh, J.G.; Mognard, N.M.

1980-01-01

Models for the towing of large tabular icebergs give towing speeds of 0.5 knots to 1.0 knots relative to the ambient near surface current. Recent oceanographic research indicates that the world oceans are not principally composed of large steady-state current systems, like the Gulf Stream, but that most of the ocean momentum is probably involved in intense rings, formed by meanders of the large streams, and in mid-ocean eddies. These rings and eddies have typical dimensions on the order of 200 km with dynamic height anomalies across them of tens-of-centimeters to a meter. They migrate at speeds on the order of a few cm/sec. Current velocities as great as 3 knots have been observed in rings, and currents of 1 knot are common. Thus, the successful towing of icebergs is dependent on the ability to locate, measure, and track ocean rings and eddies. To accomplish this systematically on synoptic scales appears to be possible only by using satelliteborne radar altimeters. Ocean current and eddy structures as observed by the radar altimeters on the GEOS-3 and Seasat-1 satellites are presented and compared. Several satellite programs presently being planned call for flying radar altimeters in polar or near-polar orbits in the mid-1980 time frame. Thus, by the time tows of large icebergs will probably be attempted, it is possible synoptic observations of ocean rings and eddies which can be used to ascertain their location, size, intensity, and translation velocity will be a reality. ?? 1980.

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.

Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming.

PubMed

Cai, Wenju; Santoso, Agus; Wang, Guojian; Weller, Evan; Wu, Lixin; Ashok, Karumuri; Masumoto, Yukio; Yamagata, Toshio

2014-06-12

The Indian Ocean dipole is a prominent mode of coupled ocean-atmosphere variability, affecting the lives of millions of people in Indian Ocean rim countries. In its positive phase, sea surface temperatures are lower than normal off the Sumatra-Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) events of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries but devastating droughts in eastern Indian Ocean rim countries. Despite these serious consequences, the response of pIOD events to greenhouse warming is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD events will increase by almost a factor of three, from one event every 17.3 years over the twentieth century to one event every 6.3 years over the twenty-first century. We find that a mean state change--with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster warming in the western than the eastern equatorial Indian Ocean--facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD events, suggesting an increasing frequency of extreme climate and weather events in regions affected by the pIOD.

Survey on utility technology of a tidal and ocean current energy

NASA Astrophysics Data System (ADS)

Hirose, Manabu; Kadoyu, Masataka; Tanaka, Hiroyoshi

1987-06-01

A study is made to show the current technological levels in Japan and other nations regarding the conversion of tidal current or ocean current energy to electric power and to determine the latent energy quantities and energy-related characteristics of tidal and ocean currents. In Japan, relatively large-scale experiments made so far mostly used one of the following three types of devices: Savonius-wheel type, Darrieus-wheel type, and cross-flow-wheel type. Field experiments of tidal energy conversion have been performed at the Naruto and Kurushima Straits. The energy in the Kuroshio current is estimated at about 170 billion kWh per year. Ocean current energy does not undergo large seasonal variations. The total energy in major straits and channels in the Inland Sea and other sea areas to the west is estimated at about 124 billion kWh per year. Tidal current energy shows large seasonal variations, but it is possible to predict the changes. A survey is made to determine energy-related characteristics of a tidal current at Chichino-seto, Kagoshima Prefecture. At Chichino-seto, the flow velocity ranges from 0 to 2.2m/s, with a latent tidal current energy of about 70 kW, of which about 20 kW can actually be utilized.

Impact of the Agulhas Return Current on the glacial Subantarctic region in the South Indian Ocean

NASA Astrophysics Data System (ADS)

Ikehara, M.; Crosta, X.; Manoj, M. C.

2017-12-01

The Southern Ocean has played an important role in the evolution of the global climate system. The Southern Ocean circulation is dominated by the Antarctic Circumpolar Current (ACC), the world's longest and largest current system. Sea ice coverage on sea surface strongly affects the climate of the Southern Hemisphere through its impacts on the energy and gas budget, on the atmospheric circulation, on the hydrological cycle, and on the biological productivity. The Agulhas Return Current (ARC) originates from the Agulhas Current, the major western boundary current in the Indian Ocean, and transports heat from subtropical to subantarctic region. It's thought that the Agulhas leakage from the Indian Ocean to the Atlantic was reduced for the last glacial due to a northward shift of the westerlies and ACC, however, there are still unknown yet how the ARC was responded to the reduced Agulhas leakage. A piston core DCR-1PC was collected from the Del Caño Rise (46°S, 44°E, 2632m), Indian sector of the Southern Ocean. Core site located in the Subantarctic region between the Subtropical Front (STF) and Subantarctic Front (SAF). Age model of the core was established by radiocarbon dating of planktic foraminifer Globorotalia bulloides and oxygen isotope stratigraphy of benthic foraminifers Cibicidoides wuellerstorfi and Melonis bareelanus. Sediment of DCR-1PC show the cyclic changes of diatom/carbonate ooze sedimentation corresponding to Southern Ocean fronts' migrations on glacial-interglacial timescales. Records of ice-rafted debris (IRD) and oxygen isotope in planktic foraminfer G. bulloides suggest that the melting of sea ice was significantly increased during the last glacial maximum (LGM) in the Subantarctic surface water. Diatom assemblage based summer SST also shows the relative warmer condition in the Subantarctic during the LGM. These results might be explained by the strong influence of the Agulhas Return Current during the LGM in the Subantarctic. The reduced Agulhas leakage due to a northward shift of the westerlies and ACC impacted significantly on sea ice melting in the glacial Subantarctic region in the South Indian Ocean.

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.

NASA In Situ Data Needs to Support the Operational Calibration and Validation of Ocean Color Satellite Data Products

NASA Technical Reports Server (NTRS)

Werdel, P. Jeremy

2012-01-01

Calibrating ocean color satellite instruments and validating their data products requires temporal and spatial abundances of high quality in situ oceanographic data. The Consortium for Ocean Leadership Ocean Observing Initiative (OOl) is currently implementing a distributed array of in-water sensors that could provide a significant contribution to future ocean color activities. This workshop will scope the optimal way to use and possibly supplement the planned OOl infrastructure to maximize its utility and relevance for calibration and validation activities that support existing and planned NASA ocean color missions. Here, I present the current state of the art of NASA validation of ocean color data products, with attention to autonomous time-series (e.g., the AERONET -OC network of above-water radiometers), and outline NASA needs for data quality assurance metrics and adherence to community-vetted data collection protocols

Characterization of the surface wave variability in the California Current region from satellite altimetry.

NASA Astrophysics Data System (ADS)

Villas Boas, A. B.; Gille, S. T.; Mazloff, M. R.

2016-02-01

Surface gravity waves play a crucial role in upper-ocean dynamics, and they are an important mechanism by which the ocean exchanges energy with the overlying atmosphere. Surface waves are largely wind forced and can also be modulated by ocean currents via nonlinear wave-current interactions, leading to either an amplification or attenuation of the wave amplitude. Even though individual waves cannot be detected by present satellite altimeters, surface waves have the potential to produce a sea-state bias in altimeter measurements and can impact the sea-surface-height spectrum at high wavenumbers or frequencies. Knowing the wave climatology is relevant for the success of future altimeter missions, such as the Surface Water and Ocean Topography (SWOT). We analyse the seasonal, intra-annual and interannual variability of significant wave heights retrieved from over two decades of satellite altimeter data and assess the extent to which the variability of the surface wave field in the California Current region is modulated by the local wind and current fields.

Measuring currents, ice drift, and waves from space: the Sea surface KInematics Multiscale monitoring (SKIM) concept

NASA Astrophysics Data System (ADS)

Ardhuin, Fabrice; Aksenov, Yevgueny; Benetazzo, Alvise; Bertino, Laurent; Brandt, Peter; Caubet, Eric; Chapron, Bertrand; Collard, Fabrice; Cravatte, Sophie; Delouis, Jean-Marc; Dias, Frederic; Dibarboure, Gérald; Gaultier, Lucile; Johannessen, Johnny; Korosov, Anton; Manucharyan, Georgy; Menemenlis, Dimitris; Menendez, Melisa; Monnier, Goulven; Mouche, Alexis; Nouguier, Frédéric; Nurser, George; Rampal, Pierre; Reniers, Ad; Rodriguez, Ernesto; Stopa, Justin; Tison, Céline; Ubelmann, Clément; van Sebille, Erik; Xie, Jiping

2018-05-01

We propose a satellite mission that uses a near-nadir Ka-band Doppler radar to measure surface currents, ice drift and ocean waves at spatial scales of 40 km and more, with snapshots at least every day for latitudes 75 to 82°, and every few days for other latitudes. The use of incidence angles of 6 and 12° allows for measurement of the directional wave spectrum, which yields accurate corrections of the wave-induced bias in the current measurements. The instrument's design, an algorithm for current vector retrieval and the expected mission performance are presented here. The instrument proposed can reveal features of tropical ocean and marginal ice zone (MIZ) dynamics that are inaccessible to other measurement systems, and providing global monitoring of the ocean mesoscale that surpasses the capability of today's nadir altimeters. Measuring ocean wave properties has many applications, including examining wave-current interactions, air-sea fluxes, the transport and convergence of marine plastic debris and assessment of marine and coastal hazards.

Satellite Ocean Data Tools in the high school classroom.

NASA Astrophysics Data System (ADS)

Tweedie, M.; Snyder, H. D.

2007-12-01

The NASA-sponsored Ocean Motion website (http://www.oceanmotion.org) documents the story of humankind's interest in and observations of surface currents from the early seafaring Polynesians to present day satellite observations. Ocean surface current patterns impact our lives through their influences on the weather, climate, commerce, natural disasters and sea life. The Ocean Motion web site provides inquiry based, classroom ready materials for high school teachers and students to study ocean surface currents. In addition to the information resources posted on the website, there are also investigations that lead students to explore patterns and relationships through data products (color- coded map images, time series graphs and data tables). These investigations are done through an interactive browser interface that provides access to a wealth of oceanography data. This presentation focuses on use of surface current data and models in student investigations to illustrate application of basic science principles found in high school science curriculum. Skills developed using data to discover patterns and relationships will serve students in other courses as well as empower them to become stewards of the Earths environment.

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.

Effects of electrode gap and electric current on chlorine generation of electrolyzed deep ocean water.

PubMed

Hsu, Guoo-Shyng Wang; Hsu, Shun-Yao

2018-04-01

Electrolyzed water is a sustainable disinfectant, which can comply with food safety regulations and is environmental friendly. A two-factor central composite design was adopted for studying the effects of electrode gap and electric current on chlorine generation efficiency of electrolyzed deep ocean water. Deep ocean water was electrolyzed in a glass electrolyzing cell equipped with platinum-plated titanium anode and cathode in a constant-current operation mode. Results showed that current density, chlorine concentration, and electrolyte temperature increased with electric current, while electric efficiency decreased with electric current and electrode gap. An electrode gap of less than 11.7 mm, and a low electric current appeared to be a more energy efficient design and operation condition for the electrolysis system. Copyright © 2017. Published by Elsevier B.V.

Observing large-scale temporal variability of ocean currents by satellite altimetry - With application to the Antarctic circumpolar current

NASA Technical Reports Server (NTRS)

Fu, L.-L.; Chelton, D. B.

1985-01-01

A new method is developed for studying large-scale temporal variability of ocean currents from satellite altimetric sea level measurements at intersections (crossovers) of ascending and descending orbit ground tracks. Using this method, sea level time series can be constructed from crossover sea level differences in small sample areas where altimetric crossovers are clustered. The method is applied to Seasat altimeter data to study the temporal evolution of the Antarctic Circumpolar Current (ACC) over the 3-month Seasat mission (July-October 1978). The results reveal a generally eastward acceleration of the ACC around the Southern Ocean with meridional disturbances which appear to be associated with bottom topographic features. This is the first direct observational evidence for large-scale coherence in the temporal variability of the ACC. It demonstrates the great potential of satellite altimetry for synoptic observation of temporal variability of the world ocean circulation.

Planar maneuvering control of underwater snake robots using virtual holonomic constraints.

PubMed

Kohl, Anna M; Kelasidi, Eleni; Mohammadi, Alireza; Maggiore, Manfredi; Pettersen, Kristin Y

2016-11-24

This paper investigates the problem of planar maneuvering control for bio-inspired underwater snake robots that are exposed to unknown ocean currents. The control objective is to make a neutrally buoyant snake robot which is subject to hydrodynamic forces and ocean currents converge to a desired planar path and traverse the path with a desired velocity. The proposed feedback control strategy enforces virtual constraints which encode biologically inspired gaits on the snake robot configuration. The virtual constraints, parametrized by states of dynamic compensators, are used to regulate the orientation and forward speed of the snake robot. A two-state ocean current observer based on relative velocity sensors is proposed. It enables the robot to follow the path in the presence of unknown constant ocean currents. The efficacy of the proposed control algorithm for several biologically inspired gaits is verified both in simulations for different path geometries and in experiments.

Atlantic Oceanographic and Meteorological Laboratory of NOAA

Science.gov Websites

the physics of ocean currents and water properties, and on the role of the ocean in climate, weather © 2006 AOML. All rights reserved. Office of National Oceanic and Atmospheric Research National Oceanic and Atmospheric Administration Department of Commerce

A perspective on sustained marine observations for climate modelling and prediction.

PubMed

Dunstone, Nick J

2014-09-28

Here, I examine some of the many varied ways in which sustained global ocean observations are used in numerical modelling activities. In particular, I focus on the use of ocean observations to initialize predictions in ocean and climate models. Examples are also shown of how models can be used to assess the impact of both current ocean observations and to simulate that of potential new ocean observing platforms. The ocean has never been better observed than it is today and similarly ocean models have never been as capable at representing the real ocean as they are now. However, there remain important unanswered questions that can likely only be addressed via future improvements in ocean observations. In particular, ocean observing systems need to respond to the needs of the burgeoning field of near-term climate predictions. Although new ocean observing platforms promise exciting new discoveries, there is a delicate balance to be made between their funding and that of the current ocean observing system. Here, I identify the need to secure long-term funding for ocean observing platforms as they mature, from a mainly research exercise to an operational system for sustained observation over climate change time scales. At the same time, considerable progress continues to be made via ship-based observing campaigns and I highlight some that are dedicated to addressing uncertainties in key ocean model parametrizations. The use of ocean observations to understand the prominent long time scale changes observed in the North Atlantic is another focus of this paper. The exciting first decade of monitoring of the Atlantic meridional overturning circulation by the RAPID-MOCHA array is highlighted. The use of ocean and climate models as tools to further probe the drivers of variability seen in such time series is another exciting development. I also discuss the need for a concerted combined effort from climate models and ocean observations in order to understand the current slow-down in surface global warming. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Inter-Sensor Comparison of Satellite Ocean Color Products from GOCI and MODIS

DTIC Science & Technology

2013-02-26

current map for this region. However the NOCOM modeled and GOCI measured data need to be validate using in-situ measurements. ...collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION...Ocean Model (NCOM). 15. SUBJECT TERMS satellite ocean color products, GOCI, MODIS, phytoplankton 16. SECURITY CLASSIFICATION OF: a. REPORT

Quantifying dispersal from hydrothermal vent fields in the western Pacific Ocean

PubMed Central

Mitarai, Satoshi; Watanabe, Hiromi; Nakajima, Yuichi; Shchepetkin, Alexander F.; McWilliams, James C.

2016-01-01

Hydrothermal vent fields in the western Pacific Ocean are mostly distributed along spreading centers in submarine basins behind convergent plate boundaries. Larval dispersal resulting from deep-ocean circulations is one of the major factors influencing gene flow, diversity, and distributions of vent animals. By combining a biophysical model and deep-profiling float experiments, we quantify potential larval dispersal of vent species via ocean circulation in the western Pacific Ocean. We demonstrate that vent fields within back-arc basins could be well connected without particular directionality, whereas basin-to-basin dispersal is expected to occur infrequently, once in tens to hundreds of thousands of years, with clear dispersal barriers and directionality associated with ocean currents. The southwest Pacific vent complex, spanning more than 4,000 km, may be connected by the South Equatorial Current for species with a longer-than-average larval development time. Depending on larval dispersal depth, a strong western boundary current, the Kuroshio Current, could bridge vent fields from the Okinawa Trough to the Izu-Bonin Arc, which are 1,200 km apart. Outcomes of this study should help marine ecologists estimate gene flow among vent populations and design optimal marine conservation plans to protect one of the most unusual ecosystems on Earth. PMID:26929376

Quantifying dispersal from hydrothermal vent fields in the western Pacific Ocean.

PubMed

Mitarai, Satoshi; Watanabe, Hiromi; Nakajima, Yuichi; Shchepetkin, Alexander F; McWilliams, James C

2016-03-15

Hydrothermal vent fields in the western Pacific Ocean are mostly distributed along spreading centers in submarine basins behind convergent plate boundaries. Larval dispersal resulting from deep-ocean circulations is one of the major factors influencing gene flow, diversity, and distributions of vent animals. By combining a biophysical model and deep-profiling float experiments, we quantify potential larval dispersal of vent species via ocean circulation in the western Pacific Ocean. We demonstrate that vent fields within back-arc basins could be well connected without particular directionality, whereas basin-to-basin dispersal is expected to occur infrequently, once in tens to hundreds of thousands of years, with clear dispersal barriers and directionality associated with ocean currents. The southwest Pacific vent complex, spanning more than 4,000 km, may be connected by the South Equatorial Current for species with a longer-than-average larval development time. Depending on larval dispersal depth, a strong western boundary current, the Kuroshio Current, could bridge vent fields from the Okinawa Trough to the Izu-Bonin Arc, which are 1,200 km apart. Outcomes of this study should help marine ecologists estimate gene flow among vent populations and design optimal marine conservation plans to protect one of the most unusual ecosystems on Earth.

One-Dimensional Coupled Ecosystem-Carbon Flux Model for the Simulation of Biogeochemical Parameters at Ocean Weather Station P

NASA Technical Reports Server (NTRS)

Signorini, S.; McClain, C.; Christian, J.; Wong, C. S.

2000-01-01

In this Technical Publication, we describe the model functionality and analyze its application to the seasonal and interannual variations of phytoplankton, nutrients, pCO2 and CO2 concentrations in the eastern subarctic Pacific at Ocean Weather Station P (OWSP, 50 deg. N 145 deg. W). We use a verified one-dimensional ecosystem model, coupled with newly incorporated carbon flux and carbon chemistry components, to simulate 22 years (1958-1980) of pCO2 and CO2 variability at Ocean Weather Station P (OWS P). This relatively long period of simulation verifies and extends the findings of previous studies using an explicit approach for the biological component and realistic coupling with the carbon flux dynamics. The slow currents and the horizontally homogeneous ocean in the subarctic Pacific make OWS P one of the best available candidates for modeling the chemistry of the upper ocean in one dimension. The chlorophyll and ocean currents composite for 1998 illustrates this premise. The chlorophyll concentration map was derived from SeaWiFS data and the currents are from an OGCM simulation (from R. Murtugudde).

Slowing Ocean Acidification

NASA Astrophysics Data System (ADS)

Bravo, A.

2016-12-01

Currently our ocean's pH is 8.1, a decrease from 8.2 in the past 200 years since the beginning of the industrial revolution. The ocean absorbs about a third of the carbon dioxide (CO2) from the atmosphere, which is helpful to us, since reducing the amount of CO2 in the atmosphere shows global warming. However, what is the impact of all that CO2 on the ocean? I evaluated the effect of acidic water on bivalves, and found that the shells were broken down with exposure to increased acidity. I am concerned that continued ocean acidification will impact organisms that are unable to adapt to the changing ocean chemistry. While the US currently invests in alternative forms of energy including solar and wind, approximately 66% of our energy comes from sources that are releasing CO2 into the atmosphere. I want to explore the potential of wave energy as another form of renewable energy. When wind blows over the surface of the ocean, it creates a wave. Could this wave energy be a consistent clean energy source? Could a strategy to slow and reverse ocean acidification be found in the ocean?

Satellite Remote Sensing of Ocean Winds, Surface Waves and Surface Currents during the Hurricanes

NASA Astrophysics Data System (ADS)

Zhang, G.; Perrie, W. A.; Liu, G.; Zhang, L.

2017-12-01

Hurricanes over the ocean have been observed by spaceborne aperture radar (SAR) since the first SAR images were available in 1978. SAR has high spatial resolution (about 1 km), relatively large coverage and capability for observations during almost all-weather, day-and-night conditions. In this study, seven C-band RADARSAT-2 dual-polarized (VV and VH) ScanSAR wide images from the Canadian Space Agency (CSA) Hurricane Watch Program in 2017 are collected over five hurricanes: Harvey, Irma, Maria, Nate, and Ophelia. We retrieve the ocean winds by applying our C-band Cross-Polarization Coupled-Parameters Ocean (C-3PO) wind retrieval model [Zhang et al., 2017, IEEE TGRS] to the SAR images. Ocean waves are estimated by applying a relationship based on the fetch- and duration-limited nature of wave growth inside hurricanes [Hwang et al., 2016; 2017, J. Phys. Ocean.]. We estimate the ocean surface currents using the Doppler Shift extracted from VV-polarized SAR images [Kang et al., 2016, IEEE TGRS]. C-3PO model is based on theoretical analysis of ocean surface waves and SAR microwave backscatter. Based on the retrieved ocean winds, we estimate the hurricane center locations, maxima wind speeds, and radii of the five hurricanes by adopting the SHEW model (Symmetric Hurricane Estimates for Wind) by Zhang et al. [2017, IEEE TGRS]. Thus, we investigate possible relations between hurricane structures and intensities, and especially some possible effects of the asymmetrical characteristics on changes in the hurricane intensities, such as the eyewall replacement cycle. The three SAR images of Ophelia include the north coast of Ireland and east coast of Scotland allowing study of ocean surface currents respond to the hurricane. A system of methods capable of observing marine winds, surface waves, and surface currents from satellites is of value, even if these data are only available in near real-time or from SAR-related satellite images. Insight into high resolution ocean winds, waves and currents in hurricanes can be useful for intensity prediction, which has had relatively few improvements in the past 25 years. In 2018 RADARSAT Constellation Mission will be launched, increasing SAR coverage by 10×, allowing increased observations during the next hurricane season.

Climate Ocean Modeling on Parallel Computers

NASA Technical Reports Server (NTRS)

Wang, P.; Cheng, B. N.; Chao, Y.

1998-01-01

Ocean modeling plays an important role in both understanding the current climatic conditions and predicting future climate change. However, modeling the ocean circulation at various spatial and temporal scales is a very challenging computational task.

Impact of improved momentum transfer coefficients on the dynamics and thermodynamics of the north Indian Ocean

NASA Astrophysics Data System (ADS)

Parekh, Anant; Gnanaseelan, C.; Jayakumar, A.

2011-01-01

Long time series of in situ observations from the north Indian Ocean are used to compute the momentum transfer coefficients over the north Indian Ocean. The transfer coefficients behave nonlinearly for low winds (<4 m/s), when most of the known empirical relations assume linear relations. Impact of momentum transfer coefficients on the upper ocean parameters is studied using an ocean general circulation model. The model experiments revealed that the Arabian Sea and Equatorial Indian Ocean are more sensitive to the momentum transfer coefficients than the Bay of Bengal and south Indian Ocean. The impact of momentum transfer coefficients on sea surface temperature is up to 0.3°C-0.4°C, on mixed layer depth is up to 10 m, and on thermocline depth is up to 15 m. Furthermore, the impact on the zonal current is maximum over the equatorial Indian Ocean (i.e., about 0.12 m/s in May and 0.15 m/s in October; both May and October are the period of Wyrtki jets and the difference in current has potential impact on the seasonal mass transport). The Sverdrup transport has maximum impact in the Bay of Bengal (3 to 4 Sv in August), whereas the Ekman transport has maximum impact in the Arabian Sea (4 Sv during May to July). These highlight the potential impact of accurate momentum forcing on the results from current ocean models.

The oceanic influence on the rainy season of Peninsular Florida

NASA Astrophysics Data System (ADS)

Misra, Vasubandhu; Mishra, Akhilesh

2016-07-01

In this study we show that the robust surface ocean currents around Peninsular Florida, namely, the Loop and the Florida Currents, affect the terrestrial wet season of Peninsular Florida. We show this through two novel regional coupled ocean-atmosphere models with different bathymetries that dislocate and modulate the strength of these currents and thereby affect the overlying sea surface temperature (SST) and upper ocean heat content. This study show that a weaker current system produces colder coastal SSTs along the Atlantic coast of Florida that reduces the length of the wet season and the total seasonal accumulation of precipitation over Peninsular Florida relative to the regional climate model simulation, in which these currents are stronger. The moisture budget reveals that as a result of these forced changes to the temperature of the upper coastal Atlantic Ocean, overlying surface evaporation and atmospheric convection is modulated. This consequently changes the moisture flux convergence leading to the modulation of the terrestrial wet season rainfall over Peninsular Florida that manifests in changes in the length and distribution of daily rain rate of the wet season. The results of this study have implications on interpreting future changes to hydroclimate of Peninsular Florida owing to climate change and low-frequency changes to the Atlantic meridional overturning circulation that comprises the Loop and the Florida Currents as part of its upper branch.

STS-54 Earth observation of a ship wake in the Bay of Bengal

NASA Image and Video Library

1993-01-19

STS054-72-056 (13-19 Jan 1993) --- A ship wake in the Bay of Bengal is noticeable in this 70mm frame. The sun glint pattern on the ocean reveals many patterns of sea surface roughness related to currents, waves, wind roughening, and biology that and are not apparent when the ocean is viewed away from the Sun's reflection. In this view of the Bay of Bengal, southeast of Madras, India, sun glint highlights convergence zones between ocean currents (bright, linear features), a eddy, and the wake of a ship. In several locations where the ship has passed areas of current shear, the ship wake is distorted, indicating the relative current direction.

STS-54 Earth observation of a ship wake in the Bay of Bengal

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Earth observation taken aboard Endeavour, Orbiter Vehicle (OV) 105, is of a ship wake in the Bay of Bengal. The sun glint pattern on the ocean reveals many patterns of sea surface roughness related to currents, waves, wind roughening, and biology that and are not apparent when the ocean is viewed away from the sun's reflection. In this view of the Bay of Bengal, southeast of Madras, India, sun glint highlights convergence zones between ocean currents (bright, linear features), a eddy, and the wake of a ship. In several locations where the ship has passed areas of current shear, the ship wake is distorted, indicating the relative current direction.

76 FR 64329 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-18

... for Ocean Leadership, 1201 New York Avenue, NW., 4th Floor, Washington DC 20005. FOR FURTHER... discussions on ocean research, resource management, and other current issues in the ocean science and management communities. Dated: October 11, 2011. J.M. Beal, Lieutenant Commander, Office of the Judge...

76 FR 13999 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-15

..., and other current issues in the ocean science and management communities; including, the review and... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research and Resources Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research...

Earth and space science - Oceans

NASA Technical Reports Server (NTRS)

Stewart, R. H.

1983-01-01

Satellite observations of the oceans are now being used to obtain new information about the oceanic geoid, currents, winds, tides and the interaction of the ocean with the atmosphere. In addition, satellites routinely relay information from the sea surface to laboratories on land, and determine the position of instruments drifting on the sea surface.

76 FR 22083 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-20

... other current issues in the ocean science and management communities; including, the review and... DEPARTMENT OF DEFENSE Department of the Navy Meeting of the Ocean Research and Resources Advisory Panel AGENCY: Department of the Navy, DoD. ACTION: Notice of open meeting. SUMMARY: The Ocean Research...

Coastal Zone Color Scanner

NASA Technical Reports Server (NTRS)

Johnson, B.

1988-01-01

The Coastal Zone Color Scanner (CZCS) spacecraft ocean color instrument is capable of measuring and mapping global ocean surface chlorophyll concentration. It is a scanning radiometer with multiband capability. With new electronics and some mechanical, and optical re-work, it probably can be made flight worthy. Some additional components of a second flight model are also available. An engineering study and further tests are necessary to determine exactly what effort is required to properly prepare the instrument for spaceflight and the nature of interfaces to prospective spacecraft. The CZCS provides operational instrument capability for monitoring of ocean productivity and currents. It could be a simple, low cost alternative to developing new instruments for ocean color imaging. Researchers have determined that with global ocean color data they can: specify quantitatively the role of oceans in the global carbon cycle and other major biogeochemical cycles; determine the magnitude and variability of annual primary production by marine phytoplankton on a global scale; understand the fate of fluvial nutrients and their possible affect on carbon budgets; elucidate the coupling mechanism between upwelling and large scale patterns in ocean basins; answer questions concerning the large scale distribution and timing of spring blooms in the global ocean; acquire a better understanding of the processes associated with mixing along the edge of eddies, coastal currents, western boundary currents, etc., and acquire global data on marine optical properties.

Global Modeling of Internal Tides Within an Eddying Ocean General Circulation Model

DTIC Science & Technology

2012-06-01

atmosphere and ocean (Yu and Weller, 2007 ). Salinities in the upper ocean are set by the difference between evaporation and precipitation at the ocean...surface (Yu, 2007 ; Schmitt, 2008). Because the buoyancy (density) of seawater at the ocean surface is con- trolled by temperature and salinity, the...days, these currents mean- der and generate highly energetic meso- scale eddies (Schmitz, 1996a,b; Stammer , 1997), the spinning oceanic dynamical

Inter comparison of Tropical Indian Ocean features in different ocean reanalysis products

NASA Astrophysics Data System (ADS)

Karmakar, Ananya; Parekh, Anant; Chowdary, J. S.; Gnanaseelan, C.

2017-09-01

This study makes an inter comparison of ocean state of the Tropical Indian Ocean (TIO) in different ocean reanalyses such as global ocean data assimilation system (GODAS), ensemble coupled data assimilation (ECDA), ocean reanalysis system 4 (ORAS4) and simple ocean data assimilation (SODA) with reference to the in-situ buoy observations, satellite observed sea surface temperature (SST), EN4 analysis and ocean surface current analysis real time (OSCAR). Analysis of mean state of SST and sea surface salinity (SSS) reveals that ORAS4 is better comparable with satellite observations as well as EN4 analysis, and is followed by SODA, ECDA and GODAS. The surface circulation in ORAS4 is closer to OSCAR compared to the other reanalyses. However mixed layer depth (MLD) is better simulated by SODA, followed by ECDA, ORAS4 and GODAS. Seasonal evolution of error indicates that the highest deviation in SST and MLD over the TIO exists during spring and summer in GODAS. Statistical analysis with concurrent data of EN4 for the period of 1980-2010 supports that the difference and standard deviation (variability strength) ratio for SSS and MLD is mostly greater than one. In general the strength of variability is overestimated by all the reanalyses. Further comparison with in-situ buoy observations supports that MLD errors over the equatorial Indian Ocean (EIO) and the Bay of Bengal are higher than with EN4 analysis. Overall ORAS4 displays higher correlation and lower error among all reanalyses with respect to both EN4 analysis and buoy observations. Major issues in the reanalyses are the underestimation of upper ocean stability in the TIO, underestimation of surface current in the EIO, overestimation of vertical shear of current and improper variability in different oceanic variables. To improve the skill of reanalyses over the TIO, salinity vertical structure and upper ocean circulation need to be better represented in reanalyses.

TOPEX/POSEIDON - Mapping the ocean surface

NASA Technical Reports Server (NTRS)

Yamarone, C. A.; Rosell, S.; Farless, D. L.

1986-01-01

Global efforts are under way to model the earth as a complete planet so that weather patterns may be predicted on time scales of months and years. A major limitation in developing models of global weather is the inability to model the circulation of the oceans including the geostrophic surface currents. NASA will soon be initiating a satellite program to correct this deficiency by directly measuring these currents using the science of radar altimetry. Measurement of the ocean topography with broad, frequent coverage of all ocean basins for a long period of time will allow the derivation of the spatial and temporal behavior of surface ocean currents. The TOPEX/POSEIDON mission is a cooperative effort between NASA and the French Centre National d'Etudes Spatiales. This paper describes the goals of this research mission, the data type to be acquired, the satellite and sensors to be used to acquire the data, and the methods by which the data are to be processed and utilized.

The Indonesian Throughflow (ITF) and its impacts on the Indian Ocean during the global warming slowdown period

NASA Astrophysics Data System (ADS)

Makarim, S.; Liu, Z.; Yu, W.; Yan, X.; Sprintall, J.

2016-12-01

The global warming slowdown indicated by a slower warming rate at the surface layer accompanied by stronger heat transport into the deeper layers has been explored in the Indian Ocean. Although the mechanisms of the global warming slowdown are still under warm debate, some clues have been recognized that decadal La Nina like-pattern induced decadal cooling in the Pacific Ocean and generated an increase of the Indonesian Throughflow (ITF) transport in 2004-2010. However, how the ITF spreading to the interior of the Indian Ocean and the impact of ITF changes on the Indian Ocean, in particular its water mass transformation and current system are still unknown. To this end, we analyzed thermohaline structure and current system at different depths in the Indian Ocean both during and just before the global warming slowdown period using the ORAS4 and ARGO dataset. Here, we found the new edge of ITF at off Sumatra presumably as northward deflection of ITF Lombok Strait, and The Monsoon Onset Monitoring and Social Ecology Impact (MOMSEI) and Java Upwelling Variation Observation (JUVO) dataset confirmed this evident. An isopycnal mixing method initially proposed by Du et al. (2013) is adopted to quantify the spreading of ITF water in the Indian Ocean, and therefore the impacts of ITF changes on the variation of the Agulhas Current, Leuween Current, Bay of Bengal Water. This study also prevailed the fresher salinity in the Indian Ocean during the slowdown warming period were not only contributed by stronger transport of the ITF, but also by freshening Arabian Sea and infiltrating Antartic Intermediate Water (AAIW).

Perspectives for Expanded Ocean Observing on the Southeast Florida Shelf and between Cuba and the Bahamas and the US

NASA Astrophysics Data System (ADS)

Soloviev, A.; Dodge, R. E.; Proni, J.

2012-12-01

A long term ocean observing system was established on the Southeast Florida shelf near Ft. Lauderdale by the Nova Southeastern University Oceanographic Center (NSUOC) in late 1990s as a cooperative agreement between the NSU Oceanographic Center and USF College of Marine Science. The system has been supported and upgraded during a number of projects funded by the US federal government and private industries. Currently it consists of two ADCP moorings deployed at 240 m and 11 m isobath and coastal meteorological station and primarily serves to support the Office of Naval Research and other Federal agencies projects. During active observational phases, the area is monitored using the new generation of synthetic aperture radar (SAR) satellites (TerraSAR-X, Cosmo SkyMed, ALOS PALSAR, RADARSAT 2). The NSUOC Ocean observing system is a component of SECOORA, which has been integrating coastal and ocean observing data in the Southeast United States as a part of IOOS. In this paper we overview the results obtained during more than a decade of observations and discuss perspectives for expanded ocean observing on the Southeast Florida Shelf and between Cuba, Bahamas and US. Increased ocean observations are needed of the major western boundary current, known as the Loop Current in the Gulf of Mexico and the Florida Current in the Straits Florida. This ocean current occurs to the west and north of Cuba and along the southeast US. Observations will provide better understanding of the processes that maintain, and account for, the current variability and will be useful in myriad practical applications. A major application is the need to monitor the occurrence of, and to forecast entrainment, trajectories, and detrainment of, potential oil spills that may propagate from Cuban drilling sites located along the north coast of Cuba as well as from proposed drilling in the Bahamas. Such ocean observation information can be used as input for operational response models and result in best mitigation practices for an oil spill capable of significantly and adversely affecting US natural resources. The unique and valuable natural resources of the southeastern United States merit and need the best ocean observational system the scientific community can provide.

Southwest Pacific Ocean Circulation and Climate Experiment (SPICE) scientific advances and future west pacific coordination

NASA Astrophysics Data System (ADS)

Ganachaud, A. S.; Sprintall, J.; Lin, X.; Ando, K.

2016-02-01

The Southwest Pacific Ocean Circulation and Climate Experiment (SPICE) is an international research program under the auspices of CLIVAR (Climate Variability and Predictability). The key objectives are to understand the Southwest Pacific Ocean circulation and Convergence Zone (SPCZ) dynamics, as well as their influence on regional and basin-scale climate patterns. It was designed to measure and monitor the ocean circulation, and to validate and improve numerical models. South Pacific oceanic waters are carried from the subtropical gyre centre in the westward flowing South Equatorial Current (SEC), towards the southwest Pacific-a major circulation pathway that redistributes water from the subtropics to the equator and Southern Ocean. Water transit through the Coral and Solomon Seas is potentially of great importance to tropical climate prediction because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate ENSO and produce basin-scale climate feedbacks. On average, the oceanic circulation is driven by the Trade Winds, and subject to substantial variability, related with the SPCZ position and intensity. The circulation is complex, with the SEC splitting into zonal jets upon encountering island archipelagos, before joining either the East Australian Current or the New Guinea Costal UnderCurrent towards the equator. SPICE included large, coordinated in situ measurement programs and high resolution numerical simulations of the area. After 8 years of substantial in situ oceanic observational and modeling efforts, our understanding of the region has much improved. We have a refined description of the SPCZ behavior, boundary currents, pathways, and water mass transformation, including the previously undocumented Solomon Sea. The transports are large and vary substantially in a counter-intuitive way, with asymmetries and gating effects that depend on time scales. We will review the recent advancements and discuss our current knowledge gaps and important emerging research directions. In particular we will discuss how SPICE, along with the Northwestern Pacific Ocean Circulation and Climate Experiment (NPOCE) and Indonesian ThroughFlow (ITF) programs could evolve toward an integrative observing system under CLIVAR coordination.

Time-Domain Simulation of Along-Track Interferometric SAR for Moving Ocean Surfaces.

PubMed

Yoshida, Takero; Rheem, Chang-Kyu

2015-06-10

A time-domain simulation of along-track interferometric synthetic aperture radar (AT-InSAR) has been developed to support ocean observations. The simulation is in the time domain and based on Bragg scattering to be applicable for moving ocean surfaces. The time-domain simulation is suitable for examining velocities of moving objects. The simulation obtains the time series of microwave backscattering as raw signals for movements of ocean surfaces. In terms of realizing Bragg scattering, the computational grid elements for generating the numerical ocean surface are set to be smaller than the wavelength of the Bragg resonant wave. In this paper, the simulation was conducted for a Bragg resonant wave and irregular waves with currents. As a result, the phases of the received signals from two antennas differ due to the movement of the numerical ocean surfaces. The phase differences shifted by currents were in good agreement with the theoretical values. Therefore, the adaptability of the simulation to observe velocities of ocean surfaces with AT-InSAR was confirmed.

Time-Domain Simulation of Along-Track Interferometric SAR for Moving Ocean Surfaces

PubMed Central

Yoshida, Takero; Rheem, Chang-Kyu

2015-01-01

A time-domain simulation of along-track interferometric synthetic aperture radar (AT-InSAR) has been developed to support ocean observations. The simulation is in the time domain and based on Bragg scattering to be applicable for moving ocean surfaces. The time-domain simulation is suitable for examining velocities of moving objects. The simulation obtains the time series of microwave backscattering as raw signals for movements of ocean surfaces. In terms of realizing Bragg scattering, the computational grid elements for generating the numerical ocean surface are set to be smaller than the wavelength of the Bragg resonant wave. In this paper, the simulation was conducted for a Bragg resonant wave and irregular waves with currents. As a result, the phases of the received signals from two antennas differ due to the movement of the numerical ocean surfaces. The phase differences shifted by currents were in good agreement with the theoretical values. Therefore, the adaptability of the simulation to observe velocities of ocean surfaces with AT-InSAR was confirmed. PMID:26067197

Retrieving current and wind vectors from ATI SAR data: airborne evidence and inversion strategy

NASA Astrophysics Data System (ADS)

Martin, Adrien; Gommenginger, Christine; Chapron, Bertrand; Marquez, José; Doody, Sam

2017-04-01

Conventional and along-track interferometric (ATI) Synthetic Aperture Radar (SAR) sense the motion of the ocean surface by measuring the Doppler shift of reflected signals. Together with the water displacement associated with ocean currents, the SAR measurements are also affected by a Wind-wave induced Artefact Surface Velocity (WASV) caused by the velocity of Bragg scatterers and the orbital velocity of ocean surface gravity waves. The WASV has been modelled theoretically in past studies but has been estimated empirically only once using Envisat ASAR. Here we propose, firstly, to evaluate this WASV from airborne ATI SAR data, secondly, to validate the airborne retrieved surface current after correction of the WASV against HF radar measurements and thirdly to examine the best inversion strategy for a an Ocean Surface Current (OSC) satellite mission to retrieve accurately both the ocean surface current vector (OSCV) and the wind vector in the frame of an OSC satellite mission. The airborne ATI SAR data were acquired in the tidally dominated Irish Sea using a Wavemill-type dual-beam SAR interferometer. A comprehensive collection of airborne Wavemill data acquired in a star pattern over a well-instrumented site made it possible to estimate the magnitude and dependence on azimuth and incidence angle of the WASV. The airborne results compare favourably with those reported for Envisat ASAR, empirical model, which has been used to correct for it. Validation of the current retrieval capabilities of the proof-of-concept has been conducted against HF radar giving a precisions typically better than 0.1 m/s for surface current speed and 7° for direction. Comparisons with POLCOMS (1.8 km) indicate that the model reproduces well the overall temporal evolution but does not capture the high spatial variability of ocean surface currents at the maximum ebb flow. Airborne retrieved currents highlight a short-scale spatial variability up to 100m related to bathymetry channels, which are not observed (HF radar, 4km resolution) or simulated (POLCOMS, 1.8km). The inversion strategy points to the need for accurate measurement of both the backscatter amplitude and the Doppler information (either as a Doppler centroid frequency anomaly for SAR DCA, or as an interferometric phase for ATI) as well as the need for dual polarization capability (VV+HH) for non-ambiguous inversion. Preliminary inversion results show that the retrieval accuracy for OSC velocity better than 10 cm/s can be achieved but that the OSC accuracy is strongly sensitive to the wind direction relative to the antennas orientation. This concept is a unique opportunity to improve our understanding of the air-sea interaction, the ocean submesoscale dynamic and its impact on the oceanic vertical transport. This concept is particularly well fitted for these ocean surface current and wind vectors observations in coastal and polar regions.

77 FR 72831 - Meeting of the Ocean Research Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-06

... commentary. ADDRESSES: The meeting will be held at the Consortium for Ocean Leadership, 1201 New York Avenue... Committee Act (5 U.S.C. App. 2). The meeting will include discussions on ocean research, resource management, and other current issues in the ocean science and management communities. Dated: November 29, 2012. L...

76 FR 12088 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-04

...: The meeting will be held at the Consortium for Ocean Leadership, 1201 New York Avenue, NW., 4th Floor... U.S.C. App. 2). The meeting will include discussions on ocean research, resource management, and other current issues in the ocean science and management communities; including, the review and...

77 FR 42297 - Meeting of the Ocean Research and Resources Advisory Panel

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-18

... Consortium for Ocean Leadership, 1201 New York Avenue NW., 4th Floor, Washington, DC 2005. FOR FURTHER... discussions on ocean research, resource management, and other current issues in the ocean science and management communities. J.M. Beal, Lieutenant Commander, Office of the Judge Advocate General, U.S. Navy...

Fate of microplastics and mesoplastics carried by surface currents and wind waves: A numerical model approach in the Sea of Japan.

PubMed

Iwasaki, Shinsuke; Isobe, Atsuhiko; Kako, Shin'ichiro; Uchida, Keiichi; Tokai, Tadashi

2017-08-15

A numerical model was established to reproduce the oceanic transport processes of microplastics and mesoplastics in the Sea of Japan. A particle tracking model, where surface ocean currents were given by a combination of a reanalysis ocean current product and Stokes drift computed separately by a wave model, simulated particle movement. The model results corresponded with the field survey. Modeled results indicated the micro- and mesoplastics are moved northeastward by the Tsushima Current. Subsequently, Stokes drift selectively moves mesoplastics during winter toward the Japanese coast, resulting in increased contributions of mesoplastics south of 39°N. Additionally, Stokes drift also transports micro- and mesoplastics out to the sea area south of the subpolar front where the northeastward Tsushima Current carries them into the open ocean via the Tsugaru and Soya straits. Average transit time of modeled particles in the Sea of Japan is drastically reduced when including Stokes drift in the model. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Constrained circulation at Endeavour ridge facilitates colonization by vent larvae.

PubMed

Thomson, Richard E; Mihály, Steven F; Rabinovich, Alexander B; McDuff, Russell E; Veirs, Scott R; Stahr, Frederick R

2003-07-31

Understanding how larvae from extant hydrothermal vent fields colonize neighbouring regions of the mid-ocean ridge system remains a major challenge in oceanic research. Among the factors considered important in the recruitment of deep-sea larvae are metabolic lifespan, the connectivity of the seafloor topography, and the characteristics of the currents. Here we use current velocity measurements from Endeavour ridge to examine the role of topographically constrained circulation on larval transport along-ridge. We show that the dominant tidal and wind-generated currents in the region are strongly attenuated within the rift valley that splits the ridge crest, and that hydrothermal plumes rising from vent fields in the valley drive a steady near-bottom inflow within the valley. Extrapolation of these findings suggests that the suppression of oscillatory currents within rift valleys of mid-ocean ridges shields larvae from cross-axis dispersal into the inhospitable deep ocean. This effect, augmented by plume-driven circulation within rift valleys having active hydrothermal venting, helps retain larvae near their source. Larvae are then exported preferentially down-ridge during regional flow events that intermittently over-ride the currents within the valley.

Determining the Ocean's Role on the Variable Gravity Field and Earth Rotation

NASA Technical Reports Server (NTRS)

Ponte, Rui M.; Frey, H. (Technical Monitor)

2000-01-01

A number of ocean models of different complexity have been used to study changes in the oceanic angular momentum (OAM) and mass fields and their relation to the variable Earth rotation and gravity field. Time scales examined range from seasonal to a few days. Results point to the importance of oceanic signals in driving polar motion, in particular the Chandler and annual wobbles. Results also show that oceanic signals have a measurable impact on length-of-day variations. Various circulation features and associated mass signals, including the North Pacific subtropical gyre, the equatorial currents, and the Antarctic Circumpolar Current play a significant role in oceanic angular momentum variability. The impact on OAM values of an optimization procedure that uses available data to constrain ocean model results was also tested for the first time. The optimization procedure yielded substantial changes, in OAM, related to adjustments in both motion and mass fields,as well as in the wind stress torques acting on the ocean. Constrained OAM values were found to yield noticeable improvements in the agreement with the observed Earth rotation parameters, particularly at the seasonal timescale.

Video Animation of Ocean Topography From TOPEX/POSEIDON

NASA Technical Reports Server (NTRS)

Fu, Lee-Lueng; Leconte, Denis; Pihos, Greg; Davidson, Roger; Kruizinga, Gerhard; Tapley, Byron

1993-01-01

Three video loops showing various aspects of the dynamic ocean topography obtained from the TOPEX/POSEIDON radar altimetry data will be presented. The first shows the temporal change of the global ocean topography during the first year of the mission. The time-averaged mean is removed to reveal the temporal variabilities. Temporal interpolation is performed to create daily maps for the animation. A spatial smoothing is also performed to retain only the large-sale features. Gyre-scale seasonal changes are the main features. The second shows the temporal evolution of the Gulf Stream. The high resolution gravimetric geoid of Rapp is used to obtain the absolute ocean topography. Simulated drifters are used to visualize the flow pattern of the current. Meanders and rings of the current are the main features. The third is an animation of the global ocean topography on a spherical earth. The JGM-2 geoid is used to obtain the ocean topography...

A numerical world ocean general circulation model Part I. Basic design and barotropic experiment

NASA Astrophysics Data System (ADS)

Han, Young-June

1984-08-01

A new six-layer world ocean general circulation model based on the primitive system of equations is described in detail and its performance in the case of a homogeneous ocean is described. These test integrations show that the model is capable of reproducing the observed mean barotropic or vertically-integrated transport, as well as the seasonal variability of the major ocean gyres. The surface currents, however, are dominated by the Ekman transport, and such non-linear features as the western boundary currents and the equatorial countercurrents are poorly represented. The abyssal boundary countercurrents are also absent due to the lack of thermohaline forcing. The most conspicuous effect of the bottom topography on a homogeneous ocean is seen in the Southern ocean where the calculated Antarctic circumpolar transport through the Drake passage ( ≈ 10 Sv, with bathymetry included) greatly underestimates the observed transport (≈ 100 Sv).

Historical processes and contemporary ocean currents drive genetic structure in the seagrass Thalassia hemprichii in the Indo-Australian Archipelago.

PubMed

Hernawan, Udhi E; van Dijk, Kor-Jent; Kendrick, Gary A; Feng, Ming; Biffin, Edward; Lavery, Paul S; McMahon, Kathryn

2017-02-01

Understanding spatial patterns of gene flow and genetic structure is essential for the conservation of marine ecosystems. Contemporary ocean currents and historical isolation due to Pleistocene sea level fluctuations have been predicted to influence the genetic structure in marine populations. In the Indo-Australian Archipelago (IAA), the world's hotspot of marine biodiversity, seagrasses are a vital component but population genetic information is very limited. Here, we reconstructed the phylogeography of the seagrass Thalassia hemprichii in the IAA based on single nucleotide polymorphisms (SNPs) and then characterized the genetic structure based on a panel of 16 microsatellite markers. We further examined the relative importance of historical isolation and contemporary ocean currents in driving the patterns of genetic structure. Results from SNPs revealed three population groups: eastern Indonesia, western Indonesia (Sunda Shelf) and Indian Ocean; while the microsatellites supported five population groups (eastern Indonesia, Sunda Shelf, Lesser Sunda, Western Australia and Indian Ocean). Both SNPs and microsatellites showed asymmetrical gene flow among population groups with a trend of southwestward migration from eastern Indonesia. Genetic diversity was generally higher in eastern Indonesia and decreased southwestward. The pattern of genetic structure and connectivity is attributed partly to the Pleistocene sea level fluctuations modified to a smaller level by contemporary ocean currents. © 2016 John Wiley & Sons Ltd.

Dispersion of deep-sea hydrothermal vent effluents and larvae by submesoscale and tidal currents

NASA Astrophysics Data System (ADS)

Vic, Clément; Gula, Jonathan; Roullet, Guillaume; Pradillon, Florence

2018-03-01

Deep-sea hydrothermal vents provide sources of geochemical materials that impact the global ocean heat and chemical budgets, and support complex biological communities. Vent effluents and larvae are dispersed and transported long distances by deep ocean currents, but these currents are largely undersampled and little is known about their variability. Submesoscale (0.1-10 km) currents are known to play an important role for the dispersion of biogeochemical materials in the ocean surface layer, but their impact for the dispersion in the deep ocean is unknown. Here, we use a series of nested regional oceanic numerical simulations with increasing resolution (from δx = 6 km to δx = 0.75 km) to investigate the structure and variability of highly-resolved deep currents over the Mid-Atlantic Ridge (MAR) and their role on the dispersion of the Lucky Strike hydrothermal vent effluents and larvae. We shed light on a submesoscale regime of oceanic turbulence over the MAR at 1500 m depth, contrasting with open-ocean - i.e., far from topographic features - regimes of turbulence, dominated by mesoscales. Impacts of submesoscale and tidal currents on larval dispersion and connectivity among vent populations are investigated by releasing neutrally buoyant Lagrangian particles at the Lucky Strike hydrothermal vent. Although the absolute dispersion is overall not sensitive to the model resolution, submesoscale currents are found to significantly increase both the horizontal and vertical relative dispersion of particles at O(1-10) km and O(1-10) days, resulting in an increased mixing of the cloud of particles. A fraction of particles are trapped in submesoscale coherent vortices, which enable transport over long time and distances. Tidal currents and internal tides do not significantly impact the horizontal relative dispersion. However, they roughly double the vertical dispersion. Specifically, particles undergo strong tidally-induced mixing close to rough topographic features, which allows them to rise up in the water column and to cross topographic obstacles. The mesoscale variability controls at first order the connectivity between hydrothermal sites and we do not have long enough simulations to conclude on the connectivity between the different MAR hydrothermal sites. However, our simulations suggest that the connectivity might be increased by submesoscale and tidal currents, which act to spread the cloud of particles and help them cross topographic barriers.

Current transport of leatherback sea turtles (Dermochelys coriacea) in the ocean.

PubMed

Luschi, P; Sale, A; Mencacci, R; Hughes, G R; Lutjeharms, J R E; Papi, F

2003-11-07

While the long-distance movements of pelagic vertebrates are becoming known thanks to satellite telemetry, the factors determining their courses have hardly been investigated. We have analysed the effects of oceanographic factors on the post-nesting movements of three satellite-tracked leatherback turtles (Dermochelys coriacea) moving in the southwest Indian Ocean. By superimposing the turtle tracks on contemporaneous images of sea-surface temperatures and sea height anomalies, we show that currentrelated features dominate the shape of the reconstructed routes. After an initial offshore movement, turtles moved along straight routes when in the core of the current, or executed loops within eddies. Large parts of the routes were strikingly similar to those of surface drifters tracked in the same region. These findings document that long-lasting oceanic movements of marine turtles may be shaped by oceanic currents.

Current transport of leatherback sea turtles (Dermochelys coriacea) in the ocean.

PubMed Central

Luschi, P; Sale, A; Mencacci, R; Hughes, G R; Lutjeharms, J R E; Papi, F

2003-01-01

While the long-distance movements of pelagic vertebrates are becoming known thanks to satellite telemetry, the factors determining their courses have hardly been investigated. We have analysed the effects of oceanographic factors on the post-nesting movements of three satellite-tracked leatherback turtles (Dermochelys coriacea) moving in the southwest Indian Ocean. By superimposing the turtle tracks on contemporaneous images of sea-surface temperatures and sea height anomalies, we show that currentrelated features dominate the shape of the reconstructed routes. After an initial offshore movement, turtles moved along straight routes when in the core of the current, or executed loops within eddies. Large parts of the routes were strikingly similar to those of surface drifters tracked in the same region. These findings document that long-lasting oceanic movements of marine turtles may be shaped by oceanic currents. PMID:14667360

Integration of WERA Ocean Radar into Tsunami Early Warning Systems

NASA Astrophysics Data System (ADS)

Dzvonkovskaya, Anna; Helzel, Thomas; Kniephoff, Matthias; Petersen, Leif; Weber, Bernd

2016-04-01

High-frequency (HF) ocean radars give a unique capability to deliver simultaneous wide area measurements of ocean surface current fields and sea state parameters far beyond the horizon. The WERA® ocean radar system is a shore-based remote sensing system to monitor ocean surface in near real-time and at all-weather conditions up to 300 km offshore. Tsunami induced surface currents cause increasing orbital velocities comparing to normal oceanographic situation and affect the measured radar spectra. The theoretical approach about tsunami influence on radar spectra showed that a tsunami wave train generates a specific unusual pattern in the HF radar spectra. While the tsunami wave is approaching the beach, the surface current pattern changes slightly in deep water and significantly in the shelf area as it was shown in theoretical considerations and later proved during the 2011 Japan tsunami. These observed tsunami signatures showed that the velocity of tsunami currents depended on a tsunami wave height and bathymetry. The HF ocean radar doesn't measure the approaching wave height of a tsunami; however, it can resolve the surface current velocity signature, which is generated when tsunami reaches the shelf edge. This strong change of the surface current can be detected by a phased-array WERA system in real-time; thus the WERA ocean radar is a valuable tool to support Tsunami Early Warning Systems (TEWS). Based on real tsunami measurements, requirements for the integration of ocean radar systems into TEWS are already defined. The requirements include a high range resolution, a narrow beam directivity of phased-array antennas and an accelerated data update mode to provide a possibility of offshore tsunami detection in real-time. The developed software package allows reconstructing an ocean surface current map of the area observed by HF radar based on the radar power spectrum processing. This fact gives an opportunity to issue an automated tsunami identification message by the WERA radars to TEWS. The radar measurements can be used to confirm a pre-warning and raise a tsunami alert. The output data of WERA processing software can be easily integrated into existing TEWS due to flexible data format, fast update rate and quality control of measurements. The archived radar data can be used for further hazard analysis and research purposes. The newly launched Tsunami Warning Center in Oman is one of the most sophisticated tsunami warning system world-wide applying a mix of well proven state-of-the-art subsystems. It allows the acquisition of data from many different sensor systems including seismic stations, GNSS, tide gauges, and WERA ocean radars in one acquisition system providing access to all sensor data via a common interface. The TEWS in Oman also integrates measurements of a modern network of HF ocean radars to verify tsunami simulations, which give additional scenario quality information and confirmation to the decision support.

Evaluation of the Harmful Algal Bloom Mapping System (HABMapS) and Bulletin

NASA Technical Reports Server (NTRS)

Hall, Callie; Zanoni, Vicki; Estep, Leland; Terrie, Gregory; D'Sa, Eurico; Pagnutti, Mary

2004-01-01

The National Oceanic and Atmospheric Administration (NOAA) Harmful Algal Bloom (HAB) Mapping System and Bulletin provide a Web-based geographic information system (GIS) and an e-mail alert system that allow the detection, monitoring, and tracking of HABs in the Gulf of Mexico. NASA Earth Science data that potentially support HABMapS/Bulletin requirements include ocean color, sea surface temperature (SST), salinity, wind fields, precipitation, water surface elevation, and ocean currents. Modeling contributions include ocean circulation, wave/currents, along-shore current regimes, and chlorophyll modeling (coupled to imagery). The most immediately useful NASA contributions appear to be the 1-km Moderate Resolution Imaging Spectrometer (MODIS) chlorophyll and SST products and the (presently used) SeaWinds wind vector data. MODIS pigment concentration and SST data are sufficiently mature to replace imagery currently used in NOAA HAB applications. The large file size of MODIS data is an impediment to NOAA use and modified processing schemes would aid in NOAA adoption of these products for operational HAB forecasting.

Turbines in the ocean

NASA Astrophysics Data System (ADS)

Smith, F. G. W.; Charlier, R. H.

1981-10-01

It is noted that the relatively high-speed ocean currents flowing northward along the east coast of the U.S. may be able to supply a significant proportion of the future electric power requirements of urban areas. The Gulf Stream core lies only about 20 miles east of Miami; here its near-surface water reaches velocities of 4.3 miles per hour. Attention is called to the estimate that the energy available in the current of the Gulf Stream adjacent to Florida is approximately equivalent to that generated by 25 1,000-megawatt power plants. It is also contended that this power could be produced at competitive prices during the 1980s using large turbines moored below the ocean surface near the center of the Stream. Assuming an average ocean-current speed between 4 and 5 knots at the current core, the power density of a hydroturbine could reach 410 watts per square foot, about 100 times that of a wind-driven device of similar scale operating in an airflow of approximately 11 knots.

Analysis and Modeling of Intense Oceanic Lightning

NASA Astrophysics Data System (ADS)

Zoghzoghy, F. G.; Cohen, M.; Said, R.; Lehtinen, N. G.; Inan, U.

2014-12-01

Recent studies using lightning data from geo-location networks such as GLD360 suggest that lightning strokes are more intense over the ocean than over land, even though they are less common [Said et al. 2013]. We present an investigation of the physical differences between oceanic and land lightning. We have deployed a sensitive Low Frequency (1 MHz sampling rate) radio receiver system aboard the NOAA Ronald W. Brown research vessel and have collected thousands of lightning waveforms close to deep oceanic lightning. We analyze the captured waveforms, describe our modeling efforts, and summarize our findings. We model the ground wave (gw) portion of the lightning sferics using a numerical method built on top of the Stanford Full Wave Method (FWM) [Lehtinen and Inan 2008]. The gwFWM technique accounts for propagation over a curved Earth with finite conductivity, and is used to simulate an arbitrary current profile along the lightning channel. We conduct a sensitivity analysis and study the current profiles for land and for oceanic lightning. We find that the effect of ground conductivity is minimal, and that stronger oceanic radio intensity does not result from shorter current rise-time or from faster return stroke propagation speed.

Global ocean monitoring for the World Climate Research Programme.

PubMed

Revelle, R; Bretherton, F

1986-07-01

Oceanic research and modelling for the World Climate Research Program will utilize several recently-developed instruments and measuring techniques as well as well-tested, long-used instruments. Ocean-scanning satellites will map the component of the ocean-surface topography related to ocean currents and mesoscale eddies and to fluctuating water volumes caused by ocean warming and cooling. Other satellite instruments will measure the direction and magnitude of wind stress on the sea surface, surface water temperatures, the distribution of chlorophyll and other photosynthetic pigments, the characteristics of internal waves, and possible precipitation over the ocean. Networks of acoustic transponders will obtain a three-dimensional picture of the distribution of temperature from the surface down to mid-depth and of long-term changes in temperature at depth. Ocean research vessels will determine the distribution and fate of geochemical tracers and will also make high-precision, deep hydrographic casts. Ships of opportunity, using expendable instruments, will measure temperature, salinity and currents in the upper water layers. Drifting and anchored buoys will also measure these properties as well as those of the air above the sea surface. Tide gauges installed on islands and exposed coastal locations will measure variations in monthly and shorter-period mean sea level. These tide gauges will provide 'ground truth' for the satellite maps of sea-surface topography, and will also determine variations in ocean currents and temperature.All these instruments will be used in several major programs, the most ambitious of which is the World Ocean Circulation Experiment (WOCE) designed to obtain global measurements of major currents throughout the world ocean, greater understanding of the transformation of water masses, and the role of advective, convective, and turbulent processes in exchange of properties between surface and deep-ocean layers.A five- to ten-year experiment-"Tropical Oceans and Global Atmosphere (TOGA)"-will be undertaken to sudy the sequence of events of air-sea interactions in the tropical oceans and their impact on climatic variations on land-for example, variations in the strength and location of the Indian Ocean monsoon, droughts in low latitudes, and climatic fluctuations in temperate latitudes.Experimental and continuing time series will be taken at fixed locations to obtain a better picture of the magnitude and causes of ocean climate variability. National and multinational systematic repeated measurements along selected ocean transects or in specific ocean areas will be taken to determine oceanic variability and teleconnections between oceanic and atmospheric processes. Examples are the long Japanese section along the meridian of 137° E and the 'Sections' program of the USSR and several other countries in Energy-Active zones.The results from this wide range of observations and experiments will be used to guide and define mathematical models of the ocean circulation and its interactions with the atmosphere.It can be shown that biogeochemical processes in the ocean play an important role in determining the carbon dioxide content of the atmosphere and thus in causing long-term climatic changes. Variations in the biological productivity of sub-surface waters cause variations in the effectveness of the biological pump which carries organic carbon down into deeper waters where it is oxidized. Studies of ice cores from 20 000 to 30 000 yr before the present indicate that atmospheric carbon dioxide varied by a factor of 2 within times of the order of 100 yr, and these variations were accompanied by large excursions in atmospheric temperature. Thus, ocean climatic monitoring must take into account measurements of both biological and physical variations in the ocean.

Real-Time Ocean Prediction System for the East Coast of India

NASA Astrophysics Data System (ADS)

Warrior, H. V.

2016-02-01

The primary objective of the research work reported in this abstract was to develop a Realtime Environmental model for Ocean Dispersion and Impact (as part of an already in-place Decision Support System) for the purpose of radiological safety for the area along Kalpakkam (East Indian) coast. This system involves combining real-time ocean observations with numerical models of ocean processes to provide hindcasts, nowcasts and forecasts of currents, tides and waves. In this work we present the development of an Automated Coupled Atmospheric - Ocean Model (we call it IIT-CAOM) used to forecast the sea surface currents, sea surface temperature (SST) and salinity etc of the Bay of Bengal region under the influence of transient and unsteady atmospheric conditions. This method uses a coupling of Atmosphere and Ocean model. The models used here are the WRF for atmospheric simulations and POM for the ocean counterpart. It has a 3 km X 3 km resolution. This Coupled Model uses GFS (Global Forecast System) Data or FNL (Final Analyses) Data as initial conditions for jump-starting the atmospheric model. The Atmospheric model is run first thus extracting air temperature, wind speed and relative humidity. The heat flux subroutine computes the net heat flux, using above mentioned parameters data. The net heat flux feeds to the ocean model by simply adding net heat flux subroutine to the ocean model code without changing the model original structure. The online forecast of the IIT-CAOM is currently available in the web. The whole system has been automized and runs without any more manual support. The IIT-CAOM simulations have been carried out for Kalpakkam region, which is located on the East coast of India, about 70 km south of Chennai in Tamilnadu State and a three day forecast of sea surface currents, sea surface temperature (SST) and salinity, etc have been obtained.

Upwelling Response to Hurricane Isaac in Geostrophic Oceanic Vortices

NASA Astrophysics Data System (ADS)

Jaimes, B.; Shay, L. K.; Brewster, J. K.; Schuster, R.

2013-05-01

As a tropical cyclone (TC) moves over the ocean, the cyclonic curl of the wind stress produces a region of upwelling waters under the TC center that is compensated by downwelling waters at regions outside the center. Direct measurements conducted during hurricane Rita and recent numerical studies indicate that this is not necessarily the case when TCs move over geostrophic oceanic features, where its background relative vorticity impacts wind-driven horizontal current divergence and the upwelling velocity. Modulation of the upwelling response in these energetic oceanic regimes impacts vertical mixing across the oceanic mixed layer base, air-sea fluxes into the atmosphere, and ultimately storm intensity. As part of NOAA Intensity Forecasting Experiment, an experiment was conducted during the passage of TC Isaac over the energetic geostrophic eddy field in the Gulf of Mexico in August 2012. Expendable bathythermographs, current profilers, and conductivity-temperature-depth probes were deployed in Isaac from NOAA WP-3D aircraft during four in-storm flights to measure oceanic variability and its impact on TC-driven upwelling and surface fluxes of heat and momentum. During intensification to hurricane, the cyclonic curl of the wind stress of Isaac extended over a region of more than 300 km in diameter (4 to 5 times the radius of maximum winds). Isaac's center moved over a cold cyclonic feature, while its right and left sides moved over warm anticyclones. Contrasting upwelling and downwelling regimes developed inside the region of cyclonic curl of the wind stress. Both positive (upwelling) and negative (downwelling) vertical displacements of 40 and 60 m, respectively, were measured inside the region of cyclonic curl of the wind stress, which are between 3 to 4 times larger than predicted vertical displacements for a quiescent ocean based on scaling arguments. Oceanic mixed layer (OML) currents of 0.2 to 0.7 m s-1 were measured, which are about 50% smaller than the expected velocity response under quiescent oceanic conditions. Although OML currents were measured inside the core of cyclonic curl of the wind stress, their orientation is not consistent with horizontally divergent flows typically found in upwelling regimes under TC centers. Theoretical predictions that consider background relative vorticity effects on the upwelling response mimic the contrasting upwelling/downwelling regimes inside the region of cyclonic curl of the wind stress. These results point to an important modulation of the OML current and upwelling response by background oceanic flows, where the upwelling velocity is a function of the curl of wind-intensified pre-storm geostrophic currents, rather than just a function of the curl of the wind stress. Thus, properly initializing temperature and salinity fields in numerical models is needed to accurately represent these oceanic processes in coupled forecast models.

Highlighting patterns of fungal diversity and composition shaped by ocean currents using the East China Sea as a model.

PubMed

Li, Wei; Wang, Mengmeng; Pan, Haoqin; Burgaud, Gaëtan; Liang, Shengkang; Guo, Jiajia; Luo, Tian; Li, Zhaoxia; Zhang, Shoumei; Cai, Lei

2018-01-01

How ocean currents shape fungal transport, dispersal and more broadly fungal biogeography remains poorly understood. The East China Sea (ECS) is a complex and dynamic habitat with different water masses blending microbial communities. The internal transcribed spacer 2 region of fungal rDNA was analysed in water and sediment samples directly collected from the coastal (CWM), Kuroshio (KSWM), Taiwan warm (TWM) and the shelf mixed water mass (MWM), coupled with hydrographic properties measurements, to determine how ocean currents impact the fungal community composition. Almost 9k fungal operational taxonomic units (OTUs) spanning six phyla, 25 known classes, 102 orders and 694 genera were obtained. The typical terrestrial and freshwater fungal genus, Byssochlamys, was dominant in the CWM, while increasing abundance of a specific OTU affiliated with Aspergillus was revealed from coastal to open ocean water masses (TWM and KSWM). Compared with water samples, sediment harboured an increased diversity with distinct fungal communities. The proximity of the Yangtze and Qiantang estuaries homogenizes the surface water and sediment communities. A significant influence of ocean currents on community structure was found, which is believed to reduce proportionally the variation explained by environmental parameters at the scale of the total water masses. Dissolved oxygen and depth were identified as the major parameters structuring the fungal community. Our results indicate that passive fungal dispersal driven by ocean currents and river run-off, in conjunction with the distinct hydrographic conditions of individual water masses, shapes the fungal community composition and distribution pattern in the ECS. © 2017 John Wiley & Sons Ltd.

A modelling study of the influence of anomalous wind forcing over the Barents Sea on the Atlantic water flow to the Arctic Ocean in the period 1979-2004

NASA Astrophysics Data System (ADS)

Marciniak, Jakub; Schlichtholz, Pawel; Maslowski, Wieslaw

2016-04-01

Arctic climate system is influenced by oceanic heat transport with the Atlantic water (AW) streaming towards the Arctic Ocean in two branches, through the deep Fram Strait and the shallow Barents Sea. In Fram Strait, the AW submerges below the Polar surface water and then flows cyclonically along the margin of the Arctic Ocean as a subsurface water mass in the Arctic Slope Current. In contrast to the Fram Strait branch, which is the major source of heat for the Arctic Ocean, most of the heat influx to the Barents Sea through the Barents Sea opening (BSO) is passed to the atmosphere. Only cold remnants of AW outflow to the Arctic Ocean through the northeastern gate of the Barents Sea. Some AW entering the Barents Sea recirculates westward, contributing to an outflow from the Barents Sea through the BSO along the shelf slope south of Bear Island, in the Bear Island Slope Current. Even though the two-branched AW flow toward the Arctic Ocean has been known for more than a century, little is known about co-variability of heat fluxes in the two branches, its mechanisms and climatic implications. Recent studies indicate that the Bear Island Slope Current may play a role in this co-variability. Here, co-variability of the flow through the BSO and Fram Strait is investigated using a pan-Arctic coupled ice-ocean hindcast model run for the period 1979-2004 and forced with daily atmospheric data from the ECMWF. Significant wintertime co-variability between the volume transport in the Bear Island and Arctic slope currents and its link to wind forcing over the Barents Sea is confirmed. It is found that the volume transports in these currents are, however, not correlated in the annual mean and that the wintertime co-variability of these currents has no immediate effect on either the net heat flux through the BSO or the net heat flux divergence in the Barents Sea. It is shown that the main climatic effect of wind forcing over the northern Barents Sea shelf is to induce temperature anomalies in the Murman/West Novaya Zemlya current system on the eastern side of the Barents Sea. These anomalies affect sea ice in the eastern Barents Sea 1-3 months later, but are not completely lost on the interactions with the sea ice and local atmosphere. Statistically significant subsurface temperature anomalies driven by anomalous winds over the Barents Sea join, on their exit to the Arctic Ocean through St. Anna Trough, the Arctic Slope Current, in which they persist for several years.

Dynamic relationship between ocean bottom pressure and bathymetry around northern part of Hikurangi

NASA Astrophysics Data System (ADS)

Muramoto, T.; Inazu, D.; Ito, Y.; Hino, R.; Suzuki, S.

2017-12-01

In recent years, observation using ocean bottom pressure recorders for the purpose of the evaluation of sea floor crustal deformation is in great vogue. The observation network set up for the observation of sea floor is densely spaced compared with the instrument network for the observation of ocean. Therefore, it has the characteristic that it can observe phenomena on a local scale. In this study, by using these in situ data, we discuss ocean phenomena on a local scale. In this study, we use a high-resolution ocean model (Inazu Ocean Model) driven by surface air pressure and surface wind vector published by the Japan Meteorological Agency. We perform a hindcast experiment for ocean bottom pressure anomaly from April 2013 to June 2017. Then, we compare these results with in situ data. In this study, we use observed pressure records which were recorded by autonomous type instrument spanning a period from April 2013 to June 2017 off the coast of North Island in New Zealand. Consequently, we found this model can simulate not only the amplitude but also phase of non-tidal oceanic variation of East Cape Current (ECC) off the coast of North Island of New Zealand. Then, we calculate cross-correlation coefficient between the data at the OBP sites. We revealed that the ocean bottom pressure shows different behavior on the west side from the east side of edge of the continental shelf. This result implies that the submarine slope induces a dynamic effect and contributes to the seasonal variation of ocean bottom pressure. In addition, we calculate the velocity of the surface current in this area using our model, and consider the relationship between it and ocean bottom pressure variation. Taken together, we can say that the barotropic flow in the direction of south-west extends to the bottom of the sea in this area. Therefore, the existence of local cross-isobath currents is suggested. Our result indicates bathymetry has dynamic effect to ocean circulation on local scale and at the same time the surface ocean circulation contributes to ocean bottom pressure considerably.

Equatorial oceanography. [review of research

NASA Technical Reports Server (NTRS)

Cane, M. A.; Sarachik, E. S.

1983-01-01

United States progress in equatorial oceanography is reviewed, focusing on the low frequency response of upper equatorial oceans to forcing by the wind. Variations of thermocline depth, midocean currents, and boundary currents are discussed. The factors which determine sea surface temperature (SST) variability in equatorial oceans are reviewed, and the status of understanding of the most spectacular manifestation of SST variability, the El Nino-Southern Oscillation phenomenon, is discussed. The problem of observing surface winds, regarded as a fundamental factor limiting understanding of the equatorial oceans, is addressed. Finally, an attempt is made to identify those current trends which are expected to bear fruit in the near and distant future.

Global Electric Circuit Implications of Total Current Measurements over Electrified Clouds

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Blakeslee, Richard J.; Bateman, Monte G.

2009-01-01

We determined total conduction (Wilson) currents and flash rates for 850 overflights of electrified clouds spanning regions including the Southeastern United States, the Western Atlantic Ocean, the Gulf of Mexico, Central America and adjacent oceans, Central Brazil, and the South Pacific. The overflights include storms over land and ocean, with and without lightning, and with positive and negative Wilson currents. We combined these individual storm overflight statistics with global diurnal lightning variation data from the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) to estimate the thunderstorm and electrified shower cloud contributions to the diurnal variation in the global electric circuit. The contributions to the global electric circuit from lightning producing clouds are estimated by taking the mean current per flash derived from the overflight data for land and ocean overflights and combining it with the global lightning rates (for land and ocean) and their diurnal variation derived from the LIS/OTD data. We estimate the contribution of non-lightning producing electrified clouds by assuming several different diurnal variations and total non-electrified storm counts to produce estimates of the total storm currents (lightning and non-lightning producing storms). The storm counts and diurnal variations are constrained so that the resultant total current diurnal variation equals the diurnal variation in the fair weather electric field (+/-15%). These assumptions, combined with the airborne and satellite data, suggest that the total mean current in the global electric circuit ranges from 2.0 to 2.7 kA, which is greater than estimates made by others using other methods.

Importance of ocean mesoscale variability for air-sea interactions in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Putrasahan, D. A.; Kamenkovich, I.; Le Hénaff, M.; Kirtman, B. P.

2017-06-01

Mesoscale variability of currents in the Gulf of Mexico (GoM) can affect oceanic heat advection and air-sea heat exchanges, which can influence climate extremes over North America. This study is aimed at understanding the influence of the oceanic mesoscale variability on the lower atmosphere and air-sea heat exchanges. The study contrasts global climate model (GCM) with 0.1° ocean resolution (high resolution; HR) with its low-resolution counterpart (1° ocean resolution with the same 0.5° atmosphere resolution; LR). The LR simulation is relevant to current generation of GCMs that are still unable to resolve the oceanic mesoscale. Similar to observations, HR exhibits positive correlation between sea surface temperature (SST) and surface turbulent heat flux anomalies, while LR has negative correlation. For HR, we decompose lateral advective heat fluxes in the upper ocean into mean (slowly varying) and mesoscale-eddy (fast fluctuations) components. We find that the eddy flux divergence/convergence dominates the lateral advection and correlates well with the SST anomalies and air-sea latent heat exchanges. This result suggests that oceanic mesoscale advection supports warm SST anomalies that in turn feed surface heat flux. We identify anticyclonic warm-core circulation patterns (associated Loop Current and rings) which have an average diameter of 350 km. These warm anomalies are sustained by eddy heat flux convergence at submonthly time scales and have an identifiable imprint on surface turbulent heat flux, atmospheric circulation, and convective precipitation in the northwest portion of an averaged anticyclone.

MHK Hydrofoils Design, Wind Tunnel Optimization and CFD Analysis Report for the Aquantis 2.5MW Ocean Current Generation Device

DOE Data Explorer

Shiu, Henry; Swales, Henry; Van Damn, Case

2015-06-03

Dataset contains MHK Hydrofoils Design and Optimization and CFD Analysis Report for the Aquantis 2.5 MW Ocean Current Generation Device, as well as MHK Hydrofoils Wind Tunnel Test Plan and Checkout Test Report.

Controls on the global distribution of contourite drifts: Insights from an eddy-resolving ocean model

NASA Astrophysics Data System (ADS)

Thran, Amanda C.; Dutkiewicz, Adriana; Spence, Paul; Müller, R. Dietmar

2018-05-01

Contourite drifts are anomalously high sediment accumulations that form due to reworking by bottom currents. Due to the lack of a comprehensive contourite database, the link between vigorous bottom water activity and drift occurrence has yet to be demonstrated on a global scale. Using an eddy-resolving ocean model and a new georeferenced database of 267 contourites, we show that the global distribution of modern contourite drifts strongly depends on the configuration of the world's most powerful bottom currents, many of which are associated with global meridional overturning circulation. Bathymetric obstacles frequently modify flow direction and intensity, imposing additional finer-scale control on drift occurrence. Mean bottom current speed over contourite-covered areas is only slightly higher (2.2 cm/s) than the rest of the global ocean (1.1 cm/s), falling below proposed thresholds deemed necessary to re-suspend and redistribute sediments (10-15 cm/s). However, currents fluctuate more frequently and intensely over areas with drifts, highlighting the role of intermittent, high-energy bottom current events in sediment erosion, transport, and subsequent drift accumulation. We identify eddies as a major driver of these bottom current fluctuations, and we find that simulated bottom eddy kinetic energy is over three times higher in contourite-covered areas in comparison to the rest of the ocean. Our work supports previous hypotheses which suggest that contourite deposition predominantly occurs due to repeated acute events as opposed to continuous reworking under average-intensity background flow conditions. This suggests that the contourite record should be interpreted in terms of a bottom current's susceptibility to experiencing periodic, high-speed current events. Our results also highlight the potential role of upper ocean dynamics in contourite sedimentation through its direct influence on deep eddy circulation.

The role of ocean currents for carbonate platform stratigraphy (Invited)

NASA Astrophysics Data System (ADS)

Betzler, C.; Lindhorst, S.; Luedmann, T.; Eberli, G. P.; Reijmer, J.; Huebscher, C. P.

2013-12-01

Breaks and turnovers in carbonate bank growth and development record fluctuations in sea-level and environmental changes. For the carbonate banks of the Bahamas, the Maldives, the Queensland, and the Marion Plateau, sea-level changes and synchronous oceanographic and atmospheric circulation events were recorded through compositional and architectural changes. Most of these major carbonate edifices contain drift deposits, indicating that oceanic currents were a major driver of carbonate-bank evolution. It is proposed that such currents have a larger imprint on the growth patterns and the stratigraphic packaging of carbonates than previously thought. In the Bahamas, slope facies of carbonate banks exposed to deep oceanic currents are not arranged into sediment-texture controlled and depth-dependant strike-continuous facies belts. Facies patterns are controlled by the interplay of shallow-water input, succeeding sediment sorting as well as redistribution and erosion processes. This complements the classical windward - leeward classification of carbonate platform slopes and accounts for the significant and potentially dominant process of alongslope sediment transport and dispersal. Deep oceanic currents also have the potential to steepen the carbonate bank slopes, through sediment winnowing at the distal slope, such as for example in the Maldives. This process can be enhanced as the bank grows and expands in size which may accelerate currents. Oceanic current onset or amplification, however, may also account for slope steepening as an externally, i.e. climate-driven agent, thus forcing the banks into an aggradation mode of growth which is not a response to sea-level fluctuations or a result of the windward / leeward exposure of the bank edge. Ignorance of the impact of currents on platforms and platform slopes may lead to an erroneous conclusion that changes in sediment production, distribution, and morphologies of sediment bodies are features solely related to sea-level changes.

Study of sea ice in the Sea of Okhotsk and its influence on the Oyashio current

NASA Technical Reports Server (NTRS)

Watanabe, K.; Kuroda, R.; Hata, K.; Akagawa, M. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Two photographic techniques were applied to Skylab S190A multispectral pictures for extracting oceanic patterns at the sea surface separately from cloud patterns. One is the image-masking technique and another a stereographic analysis. The extracted oceanic patterns were interpreted as areas where the amount, or the concentration of phytoplankton was high by utilizing surface data of water temperature, ocean current by GEK, and microplankton.

Global Ocean Vertical Velocity From a Dynamically Consistent Ocean State Estimate

NASA Astrophysics Data System (ADS)

Liang, Xinfeng; Spall, Michael; Wunsch, Carl

2017-10-01

Estimates of the global ocean vertical velocities (Eulerian, eddy-induced, and residual) from a dynamically consistent and data-constrained ocean state estimate are presented and analyzed. Conventional patterns of vertical velocity, Ekman pumping, appear in the upper ocean, with topographic dominance at depth. Intense and vertically coherent upwelling and downwelling occur in the Southern Ocean, which are likely due to the interaction of the Antarctic Circumpolar Current and large-scale topographic features and are generally canceled out in the conventional zonally averaged results. These "elevators" at high latitudes connect the upper to the deep and abyssal oceans and working together with isopycnal mixing are likely a mechanism, in addition to the formation of deep and abyssal waters, for fast responses of the deep and abyssal oceans to the changing climate. Also, Eulerian and parameterized eddy-induced components are of opposite signs in numerous regions around the global ocean, particularly in the ocean interior away from surface and bottom. Nevertheless, residual vertical velocity is primarily determined by the Eulerian component, and related to winds and large-scale topographic features. The current estimates of vertical velocities can serve as a useful reference for investigating the vertical exchange of ocean properties and tracers, and its complex spatial structure ultimately permits regional tests of basic oceanographic concepts such as Sverdrup balance and coastal upwelling/downwelling.

The Physics of Marine Biology.

ERIC Educational Resources Information Center

Conn, Kathleen

1992-01-01

Discusses ways in which marine biology can be integrated into the physics classroom. Topics suggested for incorporation include the harmonic motion of ocean waves, ocean currents, the interaction of visible light with ocean water, pressure, light absorption, and sound transfer in water. (MDH)

Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons

PubMed Central

Azpiroz-Zabala, Maria; Cartigny, Matthieu J. B.; Talling, Peter J.; Parsons, Daniel R.; Sumner, Esther J.; Clare, Michael A.; Simmons, Stephen M.; Cooper, Cortis; Pope, Ed L.

2017-01-01

Seabed-hugging flows called turbidity currents are the volumetrically most important process transporting sediment across our planet and form its largest sediment accumulations. We seek to understand the internal structure and behavior of turbidity currents by reanalyzing the most detailed direct measurements yet of velocities and densities within oceanic turbidity currents, obtained from weeklong flows in the Congo Canyon. We provide a new model for turbidity current structure that can explain why these are far more prolonged than all previously monitored oceanic turbidity currents, which lasted for only hours or minutes at other locations. The observed Congo Canyon flows consist of a short-lived zone of fast and dense fluid at their front, which outruns the slower moving body of the flow. We propose that the sustained duration of these turbidity currents results from flow stretching and that this stretching is characteristic of mud-rich turbidity current systems. The lack of stretching in previously monitored flows is attributed to coarser sediment that settles out from the body more rapidly. These prolonged seafloor flows rival the discharge of the Congo River and carry ~2% of the terrestrial organic carbon buried globally in the oceans each year through a single submarine canyon. Thus, this new structure explains sustained flushing of globally important amounts of sediment, organic carbon, nutrients, and fresh water into the deep ocean. PMID:28983506

Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons.

PubMed

Azpiroz-Zabala, Maria; Cartigny, Matthieu J B; Talling, Peter J; Parsons, Daniel R; Sumner, Esther J; Clare, Michael A; Simmons, Stephen M; Cooper, Cortis; Pope, Ed L

2017-10-01

Seabed-hugging flows called turbidity currents are the volumetrically most important process transporting sediment across our planet and form its largest sediment accumulations. We seek to understand the internal structure and behavior of turbidity currents by reanalyzing the most detailed direct measurements yet of velocities and densities within oceanic turbidity currents, obtained from weeklong flows in the Congo Canyon. We provide a new model for turbidity current structure that can explain why these are far more prolonged than all previously monitored oceanic turbidity currents, which lasted for only hours or minutes at other locations. The observed Congo Canyon flows consist of a short-lived zone of fast and dense fluid at their front, which outruns the slower moving body of the flow. We propose that the sustained duration of these turbidity currents results from flow stretching and that this stretching is characteristic of mud-rich turbidity current systems. The lack of stretching in previously monitored flows is attributed to coarser sediment that settles out from the body more rapidly. These prolonged seafloor flows rival the discharge of the Congo River and carry ~2% of the terrestrial organic carbon buried globally in the oceans each year through a single submarine canyon. Thus, this new structure explains sustained flushing of globally important amounts of sediment, organic carbon, nutrients, and fresh water into the deep ocean.

33 CFR 164.33 - Charts and publications.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Ocean Service, U.S. Army Corps of Engineers, or a river authority that— (i) Are of a large enough scale...) For the area to be transited, the current edition of, or applicable current extract from: (i) Tide tables published by private entities using data provided by the National Ocean Service. (ii) Tidal...

Ocean Science Video Challenge Aims to Improve Science Communication

NASA Astrophysics Data System (ADS)

Showstack, Randy

2013-10-01

Given today's enormous management and protection challenges related to the world's oceans, a new competition calls on ocean scientists to effectively communicate their research in videos that last up to 3 minutes. The Ocean 180 Video Challenge, named for the number of seconds in 3 minutes, aims to improve ocean science communication while providing high school and middle school teachers and students with new and interesting educational materials about current science topics.

A Surface "Superconvergence" Pathway Connecting the South Indian Ocean to the Subtropical South Pacific Gyre

NASA Astrophysics Data System (ADS)

Maes, C.; Grima, N.; Blanke, B.; Martinez, E.; Paviet-Salomon, T.; Huck, T.

2018-02-01

We study the dispersion and convergence of marine floating material by surface currents from a model reanalysis that represents explicitly mesoscale eddy variability. Lagrangian experiments about the long-term evolution (29 years) of an initially homogeneous concentration of particles are performed at global scale with horizontal current at one fourth degree resolution and refreshed daily over the 1985-2013 period. Results not only confirm and document the five known sites of surface convergence at the scale of individual oceanic basins but also reveal a convergent pathway connecting the South Indian subtropical region with the convergence zone of the South Pacific through the Great Australian Bight, the Tasman Sea, and the southwest Pacific Ocean. This "superconvergent" pathway at the ocean surface is robust and permanent over a distance longer than 8,000 km. The current variability is crucial to sustain this pathway.

Observations of Near-Surface Current Shear Help Describe Oceanic Oil and Plastic Transport

NASA Astrophysics Data System (ADS)

Laxague, Nathan J. M.; Ö-zgökmen, Tamay M.; Haus, Brian K.; Novelli, Guillaume; Shcherbina, Andrey; Sutherland, Peter; Guigand, Cédric M.; Lund, Björn; Mehta, Sanchit; Alday, Matias; Molemaker, Jeroen

2018-01-01

Plastics and spilled oil pose a critical threat to marine life and human health. As a result of wind forcing and wave motions, theoretical and laboratory studies predict very strong velocity variation with depth over the upper few centimeters of the water column, an observational blind spot in the real ocean. Here we present the first-ever ocean measurements of the current vector profile defined to within 1 cm of the free surface. In our illustrative example, the current magnitude averaged over the upper 1 cm of the ocean is shown to be nearly four times the average over the upper 10 m, even for mild forcing. Our findings indicate that this shear will rapidly separate pieces of marine debris which vary in size or buoyancy, making consideration of these dynamics essential to an improved understanding of the pathways along which marine plastics and oil are transported.

North Atlantic Ocean OSSE system development: Nature Run evaluation and application to hurricane interaction with the Gulf Stream

NASA Astrophysics Data System (ADS)

Kourafalou, Vassiliki H.; Androulidakis, Yannis S.; Halliwell, George R.; Kang, HeeSook; Mehari, Michael M.; Le Hénaff, Matthieu; Atlas, Robert; Lumpkin, Rick

2016-11-01

A high resolution, free-running model has been developed for the hurricane region of the North Atlantic Ocean. The model is evaluated with a variety of observations to ensure that it adequately represents both the ocean climatology and variability over this region, with a focus on processes relevant to hurricane-ocean interactions. As such, it can be used as the "Nature Run" (NR) model within the framework of Observing System Simulation Experiments (OSSEs), designed specifically to improve the ocean component of coupled ocean-atmosphere hurricane forecast models. The OSSE methodology provides quantitative assessment of the impact of specific observations on the skill of forecast models and enables the comprehensive design of future observational platforms and the optimization of existing ones. Ocean OSSEs require a state-of-the-art, high-resolution free-running model simulation that represents the true ocean (the NR). This study concentrates on the development and data based evaluation of the NR model component, which leads to a reliable model simulation that has a dual purpose: (a) to provide the basis for future hurricane related OSSEs; (b) to explore process oriented studies of hurricane-ocean interactions. A specific example is presented, where the impact of Hurricane Bill (2009) on the eastward extension and transport of the Gulf Stream is analyzed. The hurricane induced cold wake is shown in both NR simulation and observations. Interaction of storm-forced currents with the Gulf Stream produced a temporary large reduction in eastward transport downstream from Cape Hatteras and had a marked influence on frontal displacement in the upper ocean. The kinetic energy due to ageostrophic currents showed a significant increase as the storm passed, and then decreased to pre-storm levels within 8 days after the hurricane advanced further north. This is a unique result of direct hurricane impact on a western boundary current, with possible implications on the ocean feedback on hurricane evolution.

Ocean Tracks: Investigating Marine Migrations in a Changing Ocean

NASA Astrophysics Data System (ADS)

Krumhansl, R.; Kochevar, R. E.; Aluwihare, L.; Bardar, E. W.; Hirsch, L.; Hoyle, C.; Krumhansl, K.; Louie, J.; Madura, J.; Mueller-Northcott, J.; Peach, C. L.; Trujillo, A.; Winney, B.; Zetterlind, V.; Busey, A.

2015-12-01

The availability of scientific data sets online opens up exciting new opportunities to raise students' understanding of the worlds' oceans and the potential impacts of climate change. The Oceans of Data Institute at EDC; Stanford University; and the Scripps Institution of Oceanography have been collaborating, with the support of three National Science Foundation grants over the past 5 years, to bring marine science data sets into high school and undergraduate classrooms. These efforts have culminated in the development of a web-based student interface to data from the Tagging of Pacific Predators (TOPP) program, NOAA's Global Drifter Program, and NASA Earth-orbiting satellites through a student-friendly Web interface, customized data analysis tools, multimedia supports, and course modules. Ocean Tracks (http://oceantracks.org), which incorporates design principles based on a broad range of research findings in fields such as cognitive science, visual design, mathematics education and learning science, focuses on optimizing students' opportunities to focus their cognitive resources on viewing and comparing data to test hypotheses, while minimizing the time spent on downloading, filtering and creating displays. Ocean Tracks allows students to display the tracks of elephant seals, white sharks, Bluefin tuna, albatross, and drifting buoys along with sea surface temperature, chlorophyll-A, bathymetry, ocean currents, and human impacts overlays. A graphing tool allows students to dynamically display parameters associated with the track such as speed, deepest daily dive and track tortuosity (curviness). These interface features allow students to engage in investigations that mirror those currently being conducted by scientists to understand the broad-scale effects of changes in climate and other human activities on ocean ecosystems. In addition to supporting the teaching of the Ocean and Climate Literacy principles, high school curriculum modules facilitate the teaching of content, practices and cross-cutting concepts in the Framework for K-12 Science Education. Undergraduate modules currently under development support the teaching of content related to marine productivity, ocean circulation and upwelling, animal-environment interactions, ocean ecosystems, and human impacts.

Southern Ocean air-sea heat flux, SST spatial anomalies, and implications for multi-decadal upper ocean heat content trends.

NASA Astrophysics Data System (ADS)

Tamsitt, V. M.; Talley, L. D.; Mazloff, M. R.

2014-12-01

The Southern Ocean displays a zonal dipole (wavenumber one) pattern in sea surface temperature (SST), with a cool zonal anomaly in the Atlantic and Indian sectors and a warm zonal anomaly in the Pacific sector, associated with the large northward excursion of the Malvinas and southeastward flow of the Antarctic Circumpolar Current (ACC). To the north of the cool Indian sector is the warm, narrow Agulhas Return Current (ARC). Air-sea heat flux is largely the inverse of this SST pattern, with ocean heat gain in the Atlantic/Indian, cooling in the southeastward-flowing ARC, and cooling in the Pacific, based on adjusted fluxes from the Southern Ocean State Estimate (SOSE), a ⅙° eddy permitting model constrained to all available in situ data. This heat flux pattern is dominated by turbulent heat loss from the ocean (latent and sensible), proportional to perturbations in the difference between SST and surface air temperature, which are maintained by ocean advection. Locally in the Indian sector, intense heat loss along the ARC is contrasted by ocean heat gain of 0.11 PW south of the ARC. The IPCC AR5 50 year depth-averaged 0-700 m temperature trend shows surprising similarities in its spatial pattern, with upper ocean warming in the ARC contrasted by cooling to the south. Using diagnosed heat budget terms from the most recent (June 2014) 6-year run of the SOSE we find that surface cooling in the ARC is balanced by heating from south-eastward advection by the current whereas heat gain in the ACC is balanced by cooling due to northward Ekman transport driven by strong westerly winds. These results suggest that spatial patterns in multi-decadal upper ocean temperature trends depend on regional variations in upper ocean dynamics.

Broken Chains: The Effect of Ocean Acidification on Bivalve and Echinoid Development

NASA Astrophysics Data System (ADS)

Richardson, K.

2016-12-01

Global warming is one of the most urgent issues facing the interconnected systems of our planet. One important impact of global warming is ocean acidification, which is a change in the pH of the oceans due to increased levels of carbon dioxide in the atmosphere. This can harm ocean life in many ways, including the disintegration of reef structures and the weakening of many types of sea animals' shells. The purpose of this project is to assess the efficacy of a novel method of raising the pH of increasingly acidic ocean waters. The experiment was set up with water of varying pH levels. There were three different experiment groups, including current ocean water (pH 8.1), increased acidity ocean water (pH 7.5), and an increased acidity ocean water with an activated carbon filter (pH 7.5). Six bivalve shells were placed in each solution . Mass loss data was taken from bivalve shells every three days over the course of thirty days (for a total of ten measurements). I hypothesized that the carbon filter would improve the pH of the ocean water (by raising the pH from 7.5) to that of normal ocean water (pH 8.1). The data showed that while the acidic ocean water shell's weight decreased (by 13%), the acidic water with the filter and current ocean water decreased by 0.3% and 0.5%, respectively. Overall, the activated carbon filter decreased the amount of weight change from the acidic water. The data is applicable to helping solve ocean acidification - activated charcoal greatly improved the effects of very acidic ocean water, which could be used in the future to help offset the impact of ocean acidification on its creatures.

Bio-Optical Measurement and Modeling of the California Current and Southern Oceans

NASA Technical Reports Server (NTRS)

Mitchell, B. Gregg; Mitchell, B. Greg

2003-01-01

The SIMBIOS project's principal goals are to validate standard or experimental ocean color products through detailed bio-optical and biogeochemical measurements, and to combine Ocean optical observations with modeling to contribute to satellite vicarious radiometric calibration and algorithm development.

The Earth Gravitational Model 1996: The NCCS: Resource for Development, Resource for the Future

NASA Technical Reports Server (NTRS)

2002-01-01

For centuries, men have attempted to understand the climate system through observations obtained from Earth's surface. These observations yielded preliminary understanding of the ocean currents, tides, and prevailing winds using visual observation and simple mechanical tools as their instruments. Today's sensitive, downward-looking radar systems, called altimeters, onboard satellites can measure globally the precise height of the ocean surface. This surface is largely that of the equipotential gravity surface, called the geoid - the level surface to which the oceans would conform if there were no forces acting on them apart from gravity, as well as having a significant 1-2- meter-level signal arising from the motion of the ocean's currents.

Summary of Almost 20 Years of Storm Overflight Electric Field, Conductivity, Flash Rate, and Current Statistics

NASA Technical Reports Server (NTRS)

Blakeslee, Richard J.; Mach, Douglas M.; Bateman, Monte J.; Bailey, Jeffrey C.

2011-01-01

We present total conduction (Wilson) currents for more than 1000 high-altitude aircraft overflights of electrified clouds acquired over nearly two decades. The overflights include a wide geographical sample of storms over land and ocean, with and without lightning, and with positive (i.e., upward-directed) and negative current. Peak electric field, with lightning transients removed, ranged from -1.0 kV/m to 16. kV/m, with mean (median) of 0.9 kV/m (0.29 kV/m). Total conductivity at flight altitude ranged from 0.6 pS/m to 3.6 pS/m, with mean and median of 2.2 pS/m. Peak current densities ranged from -2.0 nA m(exp -2) to 33.0 nA m(exp -2) with mean (median) of 1.9 nA m(exp -2) (0.6 nA m(exp -2)). Total upward current flow from storms in our dataset ranged from -1.3 to 9.4 A. The mean current for storms with lightning is 1.7 A over ocean and 1.0 A over land. The mean current for electrified shower clouds (i.e. electrified storms without lightning) is 0.41 A for ocean and 0.13 A for land. About 78% (43%) of the land (ocean) storms have detectable lightning. Land storms have 2.8 times the mean flash rate as ocean storms (2.2 versus 0.8 flashes min-1, respectively). Approximately 7% of the overflights had negative current. The mean and median currents for positive (negative) polarity storms are 1.0 and 0.35 A (-0.30 and -0.26 A). We found no regional or latitudinal-based patterns in our storm currents, nor support for simple scaling laws between cloud top height and lightning flash rate.

Summary of Almost 20 Years of Storm Overflight Electric Field, Conductivity, Flash Rates, and Electric Current Statistics

NASA Technical Reports Server (NTRS)

Blakeslee, Richard J.; Mach, Douglas M.; Bateman, Monte J.; Bailey, Jeffrey C.

2011-01-01

We determined total conduction currents and flash rates for around 900 high-altitude aircraft overflights of electrified clouds over 17 years. The overflights include a wide geographical sample of storms over land and ocean, with and without lightning, and with positive (i.e., upward-directed) and negative current. Peak electric field, with lightning transients removed, ranged from -1.0 kV m(sup -1) to 16. kV m(sup -1), with mean (median) of 0.9 kV m(sup -1) (0.29 kV m(sup -1)). Total conductivity at flight altitude ranged from 0.6 pS m(sup -1) to 3.6 pS m(sup -1), with mean and median of 2.2 pS m(sup -1). Peak current densities ranged from -2.0 nA m(sup -2) to 33.0 nA m(sup -2) with mean (median) of 1.9 nA m(sup -2) (0.6 nA m(sup -2)). Total upward current flow from storms in our dataset ranged from -1.3 to 9.4 A. The mean current for storms with lightning is 1.6 A over ocean and 1.0 A over land. The mean current for electrified shower clouds (i.e. electrified storms without lightning) is 0.39 A for ocean and 0.13 A for land. About 78% (43%) of the land (ocean) storms have detectable lightning. Land storms have 2.8 times the mean flash rate as ocean storms (2.2 versus 0.8 flashes min(sup -1), respectively). Approximately 7% of the overflights had negative current. The mean and median currents for positive (negative) polarity storms are 1.0 and 0.35 A (-0.30 and -0.26 A). We found no regional or latitudinal-based patterns in our storm currents, nor support for simple scaling laws between cloud top height and lightning flash rate.

First satellite tracks of South Atlantic sea turtle ‘lost years’: seasonal variation in trans-equatorial movement

PubMed Central

Mendilaharsu, Milagros L.; dei Marcovaldi, Maria A. G.; Sacco, Alexander E.; Lopez, Gustave; Pires, Thais; Swimmer, Yonat

2017-01-01

In the South Atlantic Ocean, few data exist regarding the dispersal of young oceanic sea turtles. We characterized the movements of laboratory-reared yearling loggerhead turtles from Brazilian rookeries using novel telemetry techniques, testing for differences in dispersal during different periods of the sea turtle hatching season that correspond to seasonal changes in ocean currents. Oceanographic drifters deployed alongside satellite-tagged turtles allowed us to explore the mechanisms of dispersal (passive drift or active swimming). Early in the hatching season turtles transited south with strong southward currents. Late in the hatching season, when currents flowed in the opposite direction, turtles uniformly moved northwards across the Equator. However, the movement of individuals differed from what was predicted by surface currents alone. Swimming velocity inferred from track data and an ocean circulation model strongly suggest that turtles' swimming plays a role in maintaining their position within frontal zones seaward of the continental shelf. The long nesting season of adults and behaviour of post-hatchlings exposes young turtles to seasonally varying ocean conditions that lead some individuals further into the South Atlantic and others into the Northern Hemisphere. Such migratory route diversity may ultimately buffer the population against environmental changes or anthropologic threats, fostering population resiliency. PMID:29212722

A biologically relevant method for considering patterns of oceanic retention in the Southern Ocean

NASA Astrophysics Data System (ADS)

Mori, Mao; Corney, Stuart P.; Melbourne-Thomas, Jessica; Klocker, Andreas; Sumner, Michael; Constable, Andrew

2017-12-01

Many marine species have planktonic forms - either during a larval stage or throughout their lifecycle - that move passively or are strongly influenced by ocean currents. Understanding these patterns of movement is important for informing marine ecosystem management and for understanding ecological processes generally. Retention of biological particles in a particular area due to ocean currents has received less attention than transport pathways, particularly for the Southern Ocean. We present a method for modelling retention time, based on the half-life for particles in a particular region, that is relevant for biological processes. This method uses geostrophic velocities at the ocean surface, derived from 23 years of satellite altimetry data (1993-2016), to simulate the advection of passive particles during the Southern Hemisphere summer season (from December to March). We assess spatial patterns in the retention time of passive particles and evaluate the processes affecting these patterns for the Indian sector of the Southern Ocean. Our results indicate that the distribution of retention time is related to bathymetric features and the resulting ocean dynamics. Our analysis also reveals a moderate level of consistency between spatial patterns of retention time and observations of Antarctic krill (Euphausia superba) distribution.

Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon

NASA Astrophysics Data System (ADS)

Chang, Ping; Zhang, Rong; Hazeleger, Wilco; Wen, Caihong; Wan, Xiuquan; Ji, Link; Haarsma, Reindert J.; Breugem, Wim-Paul; Seidel, Howard

2008-07-01

Abrupt changes in the African monsoon can have pronounced socioeconomic impacts on many West African countries. Evidence for both prolonged humid periods and monsoon failures have been identified throughout the late Pleistocene and early Holocene epochs. In particular, drought conditions in West Africa have occurred during periods of reduced North Atlantic thermohaline circulation, such as the Younger Dryas cold event. Here, we use an ocean-atmosphere general circulation model to examine the link between oceanographic changes in the North Atlantic Ocean and changes in the strength of the African monsoon. Our simulations show that when North Atlantic thermohaline circulation is substantially weakened, the flow of the subsurface North Brazil Current reverses. This leads to decreased upper tropical ocean stratification and warmer sea surface temperatures in the equatorial South Atlantic Ocean, and consequently reduces African summer monsoonal winds and rainfall over West Africa. This mechanism is in agreement with reconstructions of past climate. We therefore suggest that the interaction between thermohaline circulation in the North Atlantic Ocean and wind-driven currents in the tropical Atlantic Ocean contributes to the rapidity of African monsoon transitions during abrupt climate change events.

Constraints on Europa's Ocean Composition Imposed by Its Surface Composition

NASA Astrophysics Data System (ADS)

Johnson, P. V.; Hodyss, R. P.; Vu, T. H.; Choukroun, M.

2017-12-01

Of the non-terrestrial environments within our Solar System, Europa's global liquid water ocean is arguably the most likely to be habitable. As such, understanding the habitability of Europa's ocean is of great interest to astrobiology and is the focus of missions currently being considered for further exploration of Europa. However, direct analysis of the ocean is unlikely in the foreseeable future. As such, our best means of constraining the subsurface ocean composition and its subsequent habitability currently is by further study of Europa's surface chemical composition. Recently, there has been a body of work published that looks at the chemistry of frozen brines representing putative ocean compositions. Here we take a simplified model of a four ionic component (Na, Mg, SO4, Cl) solution and map out what minerals are formed upon freezing as a function of relative ionic concentration, pH, etc. A `flow-chart' of the freezing sequence was developed based on both published and recently acquired experimental results. In performing this exercise, we are able to begin making meaningful links between observations of the surface chemistry and the chemical environment of the internal ocean.

Low helium flux from the mantle inferred from simulations of oceanic helium isotope data

NASA Astrophysics Data System (ADS)

Bianchi, Daniele; Sarmiento, Jorge L.; Gnanadesikan, Anand; Key, Robert M.; Schlosser, Peter; Newton, Robert

2010-09-01

The high 3He/ 4He isotopic ratio of oceanic helium relative to the atmosphere has long been recognized as the signature of mantle 3He outgassing from the Earth's interior. The outgassing flux of helium is frequently used to normalize estimates of chemical fluxes of elements from the solid Earth, and provides a strong constraint to models of mantle degassing. Here we use a suite of ocean general circulation models and helium isotope data obtained by the World Ocean Circulation Experiment to constrain the flux of helium from the mantle to the oceans. Our results suggest that the currently accepted flux is overestimated by a factor of 2. We show that a flux of 527 ± 102 mol year - 1 is required for ocean general circulation models that produce distributions of ocean ventilation tracers such as radiocarbon and chlorofluorocarbons that match observations. This new estimate calls for a reevaluation of the degassing fluxes of elements that are currently tied to the helium fluxes, including noble gases and carbon dioxide.

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.

Equatorial Indian Ocean subsurface current variability in an Ocean General Circulation Model

NASA Astrophysics Data System (ADS)

Gnanaseelan, C.; Deshpande, Aditi

2018-03-01

The variability of subsurface currents in the equatorial Indian Ocean is studied using high resolution Ocean General Circulation Model (OGCM) simulations during 1958-2009. February-March eastward equatorial subsurface current (ESC) shows weak variability whereas strong variability is observed in northern summer and fall ESC. An eastward subsurface current with maximum amplitude in the pycnocline is prominent right from summer to winter during strong Indian Ocean Dipole (IOD) years when air-sea coupling is significant. On the other hand during weak IOD years, both the air-sea coupling and the ESC are weak. This strongly suggests the role of ESC on the strength of IOD. The extension of the ESC to the summer months during the strong IOD years strengthens the oceanic response and supports intensification and maintenance of IODs through modulation of air sea coupling. Although the ESC is triggered by equatorial winds, the coupled air-sea interaction associated with IODs strengthens the ESC to persist for several seasons thereby establishing a positive feedback cycle with the surface. This suggests that the ESC plays a significant role in the coupled processes associated with the evolution and intensification of IOD events by cooling the eastern basin and strengthening thermocline-SST (sea surface temperature) interaction. As the impact of IOD events on Indian summer monsoon is significant only during strong IOD years, understanding and monitoring the evolution of ESC during these years is important for summer monsoon forecasting purposes. There is a westward phase propagation of anomalous subsurface currents which persists for a year during strong IOD years, whereas such persistence or phase propagation is not seen during weak IOD years, supporting the close association between ESC and strength of air sea coupling during strong IOD years. In this study we report the processes which strengthen the IOD events and the air sea coupling associated with IOD. It also unravels the connection between equatorial Indian Ocean circulation and evolution and strengthening of IOD.

Land - Ocean Climate Linkages and the Human Evolution - New ICDP and IODP Drilling Initiatives in the East African Rift Valley and SW Indian Ocean

NASA Astrophysics Data System (ADS)

Zahn, R.; Feibel, C.; Co-Pis, Icdp/Iodp

2009-04-01

The past 5 Ma were marked by systematic shifts towards colder climates and concomitant reorganizations in ocean circulation and marine heat transports. Some of the changes involved plate-tectonic shifts such as the closure of the Panamanian Isthmus and restructuring of the Indonesian archipelago that affected inter-ocean communications and altered the world ocean circulation. These changes induced ocean-atmosphere feedbacks with consequences for climates globally and locally. Two new ICDP and IODP drilling initiatives target these developments from the perspectives of marine and terrestrial palaeoclimatology and the human evolution. The ICDP drilling initiative HSPDP ("Hominid Sites and Paleolakes Drilling Project"; ICDP ref. no. 10/07) targets lacustrine depocentres in Ethiopia (Hadar) and Kenya (West Turkana, Olorgesailie, Magadi) to retrieve sedimentary sequences close to the places and times where various species of hominins lived over currently available outcrop records. The records will provide a spatially resolved record of the East African environmental history in conjunction with climate variability at orbital (Milankovitch) and sub-orbital (ENSO decadal) time scales. HSPDP specifically aims at (1) compiling master chronologies for outcrops around each of the depocentres; (2) assessing which aspects of the paleoenvironmental records are a function of local origin (hydrology, hydrogeology) and which are linked with regional or larger-scale signals; (3) correlating broad-scale patterns of hominin phylogeny with the global beat of climate variability and (4) correlating regional shifts in the hominin fossil and archaeological record with more local patterns of paleoenvironmental change. Ultimately the aim is to test hypotheses that link physical and cultural adaptations in the course of the hominin evolution to local environmental change and variability. The IODP initiative SAFARI ("Southern African Climates, Agulhas Warm Water Transports and Retroflection, and Interocean Exchanges"; IODP ref. no. 702-full) aims at deciphering the late Neogene ocean history of the SW Indian Ocean. SAFARI specifically targets the Agulhas Current in the SW Indian Ocean that constitutes the strongest western boundary current in the southern hemisphere oceans. The Current transports warm and saline surface waters from the tropical Indian Ocean to the southern tip of Africa. Exchanges with the atmosphere influence eastern and southern African climates including individual weather systems such as extra-tropical cyclone formation in the region and rainfall patterns. Ocean models further suggest the "leakage" of Agulhas water around South Africa into the Atlantic potentially modulates the Atlantic meridional overturning circulation (MOC) with consequences for climate globally. The SAFARI drilling initiative aims to retrieve a suite of long drill cores along the southeast African margin and in the Indian-Atlantic ocean gateway. SAFARI will shed light on the history of Agulhas Current warm water transports along the southeast African margin during the late Neogene and its linking with ocean-climate developments. Specific objectives of SAFARI are to test (1) the sensitivity of the Agulhas Current to changing climates of the Plio/Pleistocene, including upstream forcing linked with equatorial Indian Ocean changes and Indonesian Throughflow; (2) the Current's influence on eastern and southern Africa climates, including rain fall patterns and vegetation changes; (3) buoyancy transfer to the Atlantic by Agulhas leakage around southern Africa, and (4) the contribution of variable Agulhas Leakage to shifts of the Atlantic MOC during episodes of major ocean and climate reorganizations of the past 5 Ma. These studies will provide insight into the Current's influence on eastern and southern African terrestrial climates, including its possible impact on the late Neogene evolution of large mammals including hominids. The ICDP and IODP drilling campaigns will enable us to establish the linkages between the ocean climatology of the SW Indian and terrestrial climates of Eastern Africa during key periods of global climate change. Combining the ICDP records of East African terrestrial climate at key hominin sites with IODP records of marine climate variability at the SE African continental margin will help to test if pulses of hominin evolutionary innovation were linked with periods of enhanced variability of local terrestrial environments and marine climatology of the Indian Ocean. * co-PIs of the ICDP initiative HSPDP are A.S. Cohen, R. Arrowsmith, A.K. Behrensmeyer, C. Feibel, R. Johnson, Z. Kubsa, D. Olago, R. Potts, R. Renaut * co-PIs of the IODP initiative SAFARI are R. Zahn, I. Hall, R. Schneider, M. Á. Bárcena, S. Barker, A. Biastoch, Chr. Charles, J. Compton, R. Cowling, P. Diz, L. Dupont, J.-A. Flores, S. Goldstein, S. Hemming, K. Holmgren, J. Lee-Thorp, G. Knorr, C. Lear, A. Mazaud, G. Mortyn, F. Peeters, B. Preu, R. Rickaby, J. Rogers, A. Rosell-Mele, Chr. Reason, V. Spiess, M. Trauth, G. Uenzelmann-Neben, S. Weldeab, P. Ziveri

Oceanic Lightning versus Continental Lightning: VLF Peak Current Discrepancies

NASA Astrophysics Data System (ADS)

Dupree, N. A., Jr.; Moore, R. C.

2015-12-01

Recent analysis of the Vaisala global lightning data set GLD360 suggests that oceanic lightning tends to exhibit larger peak currents than continental lightning (lightning occurring over land). The GLD360 peak current measurement is derived from distant measurements of the electromagnetic fields emanated during the lightning flash. Because the GLD360 peak current measurement is a derived quantity, it is not clear whether the actual peak currents of oceanic lightning tend to be larger, or whether the resulting electromagnetic field strengths tend to be larger. In this paper, we present simulations of VLF signal propagation in the Earth-ionosphere waveguide to demonstrate that the peak field values for oceanic lightning can be significantly stronger than for continental lightning. Modeling simulations are performed using the Long Wave Propagation Capability (LWPC) code to directly evaluate the effect of ground conductivity on VLF signal propagation in the 5-15 kHz band. LWPC is an inherently narrowband propagation code that has been modified to predict the broadband response of the Earth-Ionosphere waveguide to an impulsive lightning flash while preserving the ability of LWPC to account for an inhomogeneous waveguide. Furthermore, we evaluate the effect of return stroke speed on these results.

Evaluation of hydrodynamic ocean models as a first step in larval dispersal modelling

NASA Astrophysics Data System (ADS)

Vasile, Roxana; Hartmann, Klaas; Hobday, Alistair J.; Oliver, Eric; Tracey, Sean

2018-01-01

Larval dispersal modelling, a powerful tool in studying population connectivity and species distribution, requires accurate estimates of the ocean state, on a high-resolution grid in both space (e.g. 0.5-1 km horizontal grid) and time (e.g. hourly outputs), particularly of current velocities and water temperature. These estimates are usually provided by hydrodynamic models based on which larval trajectories and survival are computed. In this study we assessed the accuracy of two hydrodynamic models around Australia - Bluelink ReANalysis (BRAN) and Hybrid Coordinate Ocean Model (HYCOM) - through comparison with empirical data from the Australian National Moorings Network (ANMN). We evaluated the models' predictions of seawater parameters most relevant to larval dispersal - temperature, u and v velocities and current speed and direction - on the continental shelf where spawning and nursery areas for major fishery species are located. The performance of each model in estimating ocean parameters was found to depend on the parameter investigated and to vary from one geographical region to another. Both BRAN and HYCOM models systematically overestimated the mean water temperature, particularly in the top 140 m of water column, with over 2 °C bias at some of the mooring stations. HYCOM model was more accurate than BRAN for water temperature predictions in the Great Australian Bight and along the east coast of Australia. Skill scores between each model and the in situ observations showed lower accuracy in the models' predictions of u and v ocean current velocities compared to water temperature predictions. For both models, the lowest accuracy in predicting ocean current velocities, speed and direction was observed at 200 m depth. Low accuracy of both model predictions was also observed in the top 10 m of the water column. BRAN had more accurate predictions of both u and v velocities in the upper 50 m of water column at all mooring station locations. While HYCOM predictions of ocean current speed were generally more accurate than BRAN, BRAN predictions of both ocean current speed and direction were more accurate than HYCOM along the southeast coast of Australia and Tasmania. This study identified important inaccuracies in the hydrodynamic models' estimations of the real ocean parameters and on time scales relevant to larval dispersal studies. These findings highlight the importance of the choice and validation of hydrodynamic models, and calls for estimates of such bias to be incorporated in dispersal studies.

European Science Notes Information Bulletin. Report on Current European and Middle Eastern Science

DTIC Science & Technology

1992-10-01

oceanographers. This has occurred at a time of current radar systems . The independent develop- rapidly increasing government interest in and fund...over each area in which surface current is ment of the waves (some motions caused by wave determined (for HF systems , averaging time spans action and...Ocean Observing System ; high-resolution model capabilities; ocean- atmosphere interface; Surface Density Depression Pool; forecasting INTRODUCTION tion

Horizontal and vertical distributions of larval fishes around an isolated oceanic island in the tropical Pacific

NASA Astrophysics Data System (ADS)

Boehlert, George W.; Watson, William; Sun, L. Charles

1992-04-01

Ichthyoplankton and oceanographic sampling was conducted in November 1984 in waters surrounding Johnston Atoll (16°44'N, 169°32'W), a small, isolated atoll in the central Pacific Ocean. The typical flow pattern in this region is westward; the nearest island is in the Hawaiian Archipelago, 760 km away. Most collections were dominated by oceanic taxa. In the 0-50 m stratum, larval densities were relatively uniform horizontally, but densities down-current of the island tended to be higher, and fish eggs were concentrated there. In the 50-100 m stratum, larval abundance on the down-current side of the island was markedly higher than either up-current or farther down-current. Oceanic taxa did not display this pattern, while marked areas of very high abundance characterized the island-related taxa, the most abundant including the gobiid Eviota epiphanes and the apogonid Pseudamiops sp. Estimates of geostrophic flow indicate that the region down-current of the atoll was one of return flow associated with apparent mesoscale eddies or meanders north and west of the island. This region may serve as a down-current retention area for the pelagic larvae of island-related taxa and may facilitate recruitment back to the source populations.

Using a global ocean circulation model to conduct a preliminary risk assessment of oil spills in the Atlantic

NASA Astrophysics Data System (ADS)

Jacobs, Zoe; Popova, Katya; Hirschi, Joel; Coward, Andrew; Yool, Andrew; van Gennip, Simon; Anifowose, Babtunde; Harrington-Missin, Liam

2017-04-01

Although oil blowouts from deep-water drilling happen very rarely, they can cause catastrophic damage to the environment. Despite such potentially high impacts, relatively little research effort has gone into understanding subsurface oil plumes in the deep ocean. In this study, we demonstrate the significance of this problem and offer potential solutions using a novel approach based on a leading-edge, high-resolution global ocean circulation model. We present examples demonstrating: (a) the importance of ocean circulation in the propagation of oil spills; and (b) likely circulation footprints for oil spills at four key locations in the Atlantic Ocean that exist in different circulation regimes - the shelves of Brazil, the Gulf of Guinea, the Gulf of Mexico and the Faroe-Shetland Channel. In order to quantify the variability at each site on seasonal timescales, interannual timescales and at different depths, we utilize the Modified Hausdorff Distance (MHD), which is a shape-distance metric that measures the similarity between two shapes. The scale of the footprints across the four focus locations varies considerably and is determined by the main circulation features in their vicinity. For example, the hypothetical oil plume can be affected by variations in the speed and location of a particular current (e.g. Brazil Current at the Brazilian shelf site) or be influenced by different currents entirely depending on the release depth, month and year (e.g. Angola Current or Southern Equatorial Current at the Gulf of Guinea site). Overall, our results demonstrate the need to use state of the art global, or basin-scale, ocean circulation models when assessing the environmental impacts of proposed oil drilling activities.

Global Modeling of Internal Tides Within an Eddying Ocean General Circulation Model

DTIC Science & Technology

2012-05-31

heat between the atmosphere and ocean (Yu and Weller, 2007 ). Salinities in the upper ocean are set by the difference between evaporation and...precipitation at the ocean surface (Yu, 2007 ; Schmitt, 2008). Because the buoyancy (density) of seawater at the ocean surface is con- trolled by...timescales of about 10–200 days, these currents mean- der and generate highly energetic meso- scale eddies (Schmitz, 1996a,b; Stammer , 1997), the spinning

Charting the Course for Ocean Science in the United States for the Next Decade: An Ocean Research Priorities Plan and Implementation Strategy

DTIC Science & Technology

2007-01-26

ocean affects calcifying organisms, such as corals , with significant effects to reefs , the ecosystems they support, and their ability to pro- tect...water coral reefs , to open- ocean systems. For example, increasing ocean acidity, altered biogeochemistry, changing current patterns, loss of sea ice...for example, large swings in the populations of commercial fisheries, changes in seabird-population distributions, and coral - reef -bleaching events

Development and Utilization of Regional Oceanic Modeling System (ROMS). Delicacy, Imprecision, and Uncertainty of Oceanic Simulations: An Investigation with the Regional Oceanic Modeling System (ROMS). Mixing in the Ocean Surface Layer Using the Regional Oceanic Modeling System (ROMS).

DTIC Science & Technology

2011-09-30

community use for ROMS is biogeochemisty: chemical cycles, water quality, blooms , micro-nutrients, larval dispersal, biome transitions, and coupling to...J.C. McWilliams, X. Capet, and J. Kurian, 2010: Heat balance and eddies in the Peru- Chile Current System. Climate Dynamics, 37, in press. doi10.1007

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.

Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations

NASA Astrophysics Data System (ADS)

Paulot, F.; Jacob, D. J.; Johnson, M. T.; Bell, T. G.; Baker, A. R.; Keene, W. C.; Lima, I. D.; Doney, S. C.; Stock, C. A.

2015-08-01

Current global inventories of ammonia emissions identify the ocean as the largest natural source. This source depends on seawater pH, temperature, and the concentration of total seawater ammonia (NHx(sw)), which reflects a balance between remineralization of organic matter, uptake by plankton, and nitrification. Here we compare [NHx(sw)] from two global ocean biogeochemical models (BEC and COBALT) against extensive ocean observations. Simulated [NHx(sw)] are generally biased high. Improved simulation can be achieved in COBALT by increasing the plankton affinity for NHx within observed ranges. The resulting global ocean emissions is 2.5 TgN a-1, much lower than current literature values (7-23 TgN a-1), including the widely used Global Emissions InitiAtive (GEIA) inventory (8 TgN a-1). Such a weak ocean source implies that continental sources contribute more than half of atmospheric NHx over most of the ocean in the Northern Hemisphere. Ammonia emitted from oceanic sources is insufficient to neutralize sulfate aerosol acidity, consistent with observations. There is evidence over the Equatorial Pacific for a missing source of atmospheric ammonia that could be due to photolysis of marine organic nitrogen at the ocean surface or in the atmosphere. Accommodating this possible missing source yields a global ocean emission of ammonia in the range 2-5 TgN a-1, comparable in magnitude to other natural sources from open fires and soils.

Using provenance of terrigenous sediment to reconstruct the Agulhas Leakage during the Early and Late Pleistocene

NASA Astrophysics Data System (ADS)

Pearson, B.; Franzese, A. M.

2017-12-01

The Agulhas Current, the strongest western boundary current in the southern hemisphere, is uniquely characterized by its strong retroflection. The current carries water southward from the Indian Ocean toward the cape of South Africa, before turning back on itself. At this point of retroflection, some of the current's flow escapes into the southern Atlantic Ocean. This transfer of water from the Indian Ocean to Atlantic Ocean makes up the Agulhas Leakage. The Leakage occurs in a series of eddies and rings located in the Cape Basin south of the African continent. Scientific literature demonstrates that relatively buoyant leakage water has been a determining factor varying strength of the Atlantic Meridional Ocean Current (AMOC), during glacial-interglacial cycles. It has been demonstrated that radiogenic isotope, major, and trace element concentrations serve as a proxy for terrigenous sediment provenance in the Agulhas region. Current understanding is that terrigenous sediment provenance is older during warmer periods of deposition. This corresponds to more input from southeastern African end members, and thus a stronger Agulhas Current, during warming periods in the paleoclimate record. Conversely, younger terrigenous sediment deposited during colder periods, such as the Last Glacial Maximum, suggests a weaker Agulhas Current, and less Agulhas Leakage. In 2016, on the International Ocean Discovery Program Expedition 361, sediment cores were drilled at 6 sites in the Greater Agulhas region. A major goal of the expedition was to expand knowledge of the relation between changes in the Agulhas System and changes in paleoclimate, southern African climate, and AMOC. We analyzed sediment from Expedition 361 Site U1479 (35°03.53'S; 17°24.06'E; 2615 mbsl) located where the Agulhas Leakage occurs. We measured Argon, strontium isotope ratios, ɛNd, trace and major element concentrations on the <2 micron clay fraction. Preliminary results foretell promising findings. For instance, for the Early Pleistocene ( 1.3 - 1.5 Ma), K-Ar model ages correlate with shipboard measurements of natural gamma radiation, which show approximate 41 kyr periodicity.

Oceanic Platform of the Canary Islands: an ocean testbed for ocean energy converters

NASA Astrophysics Data System (ADS)

González, Javier; Hernández-Brito, Joaquín.; Llinás, Octavio

2010-05-01

The Oceanic Platform of the Canary Islands (PLOCAN) is a Governmental Consortium aimed to build and operate an off-shore infrastructure to facilitate the deep sea research and speed up the technology associated. This Consortium is overseen by the Spanish Ministry of Science and Innovation and the Canarian Agency for Research and Innovation. The infrastructure consists of an oceanic platform located in an area with depths between 50-100 meters, close to the continental slope and four kilometers off the coast of Gran Canaria, in the archipelago of the Canary Islands. The process of construction will start during the first months of 2010 and is expected to be finished in mid-year 2011. PLOCAN serves five strategic lines: an integral observatory able to explore from the deep ocean to the atmosphere, an ocean technology testbed, a base for underwater vehicles, an innovation platform and a highly specialized training centre. Ocean energy is a suitable source to contribute the limited mix-energy conformed in the archipelago of the Canary Islands with a total population around 2 million people unequally distributed in seven islands. Islands of Gran Canaria and Tenerife support the 80% of the total population with 800.000 people each. PLOCAN will contribute to develop the ocean energy sector establishing a marine testbed allowing prototypes testing at sea under a meticulous monitoring network provided by the integral observatory, generating valuable information to developers. Reducing costs throughout an integral project management is an essential objective to be reach, providing services such as transportation, customs and administrative permits. Ocean surface for testing activities is around 8 km2 with a depth going from 50 to 100 meters, 4km off the coast. Selected areas for testing have off-shore wind power conditions around 500-600 W/m2 and wave power conditions around 6 kW/m in the East coast and 10 kW/m in the North coast. Marine currents in the Canary Islands are not particularly powerful with values around 40-50 cm/s. However a detailed assessment, based on field measurements, will be conducted in the near future with the aim to identify specific areas close to the coast with stronger currents which make suitable the deployment of marine current turbines. Although the base Platform is not still available, PLOCAN has already started the activity as an ocean testbed providing services to a wave energy converter patented by the Spanish company PIPO Systems. A scaled 1:5 prototype will be deployed during January 2010 and monitored for several months. Current facilities available include some ODAS buoys (temperature, salinity, pH, oxygen, turbidity, wind, etc.), wave rider buoy, current meter profilers (ADCP and electromagnetic), system for data management, remote operated vehicles (ROV), autonomous underwater vehicles (AUV), and an oceanographic vessel. Future facilities include high frequency radar for wave and current measurements and submarine electro-optical cables to connect the Platform with the energy converters and with the shore station.

Small scale currents and ocean wave heights: from today's models to future satellite observations with CFOSAT and SKIM

NASA Astrophysics Data System (ADS)

Ardhuin, Fabrice; Gille, Sarah; Menemenlis, Dimitris; Rocha, Cesar; Rascle, Nicolas; Gula, Jonathan; Chapron, Bertrand

2017-04-01

Tidal currents and large oceanic currents, such as the Agulhas, Gulf Stream and Kuroshio, are known to modify ocean wave properties, causing extreme sea states that are a hazard to navigation. Recent advances in the understanding and modeling capability of ocean currents at scales of 10 km or less have revealed the ubiquitous presence of fronts and filaments. Based on realistic numerical models, we show that these structures can be the main source of variability in significant wave heights at scales less than 200 km, including important variations at 10 km. This current-induced variability creates gradients in wave heights that were previously overlooked and are relevant for extreme wave heights and remote sensing. The spectrum of significant wave heights is found to be of the order of 70⟨Hs ⟩2/(g2⟨Tm0,-1⟩2) times the current spectrum, where ⟨Hs ⟩ is the spatially-averaged significant wave height, ⟨Tm0,-1⟩ is the average energy period, and g is the gravity acceleration. This small scale variability is consistent with Jason-3 and SARAL along-track variability. We will discuss how future satellite mission with wave spectrometers can help observe these wave-current interactions. CFOSAT is due for launch in 2018, and SKIM is a proposal for ESA Earth Explorer 9.

Indian Ocean analyses

NASA Technical Reports Server (NTRS)

Meyers, Gary

1992-01-01

The background and goals of Indian Ocean thermal sampling are discussed from the perspective of a national project which has research goals relevant to variation of climate in Australia. The critical areas of SST variation are identified. The first goal of thermal sampling at this stage is to develop a climatology of thermal structure in the areas and a description of the annual variation of major currents. The sampling strategy is reviewed. Dense XBT sampling is required to achieve accurate, monthly maps of isotherm-depth because of the high level of noise in the measurements caused by aliasing of small scale variation. In the Indian Ocean ship routes dictate where adequate sampling can be achieved. An efficient sampling rate on available routes is determined based on objective analysis. The statistical structure required for objective analysis is described and compared at 95 locations in the tropical Pacific and 107 in the tropical Indian Oceans. XBT data management and quality control methods at CSIRO are reviewed. Results on the mean and annual variation of temperature and baroclinic structure in the South Equatorial Current and Pacific/Indian Ocean Throughflow are presented for the region between northwest Australia and Java-Timor. The mean relative geostrophic transport (0/400 db) of Throughflow is approximately 5 x 106 m3/sec. A nearly equal volume transport is associated with the reference velocity at 400 db. The Throughflow feeds the South Equatorial Current, which has maximum westward flow in August/September, at the end of the southeasterly Monsoon season. A strong semiannual oscillation in the South Java Current is documented. The results are in good agreement with the Semtner and Chervin (1988) ocean general circulation model. The talk concludes with comments on data inadequacies (insufficient coverage, timeliness) particular to the Indian Ocean and suggestions on the future role that can be played by Data Centers, particularly with regard to quality control of data as research bodies are replaced by operational bodies in the Global Ocean Observing System.

Tow Tank Dynamic Test Rig Drawings and Bill of Materials for the Aquantis 2.5 MW Ocean Current Generation Device

DOE Data Explorer

Swales, Henry; Banko, Richard; Coakley, David

2015-06-03

Aquantis 2.5 MW Ocean Current Generation Device, Tow Tank Dynamic Test Rig Drawings and Bill of Materials. This submission contains information on the equipment for the scaled model tow tank testing. The information includes hardware, test protocols, and plans.

Large-scale phenomena, chapter 3, part D

NASA Technical Reports Server (NTRS)

1975-01-01

Oceanic phenomena with horizontal scales from approximately 100 km up to the widths of the oceans themselves are examined. Data include: shape of geoid, quasi-stationary anomalies due to spatial variations in sea density and steady current systems, and the time dependent variations due to tidal and meteorological forces and to varying currents.

Mooring Measurements of the Abyssal Circulations in the Western Pacific Ocean

NASA Astrophysics Data System (ADS)

Wang, J.; Wang, F.

2016-12-01

A scientific observing network in the western tropical Pacific has initially been established by the Institute of Oceanology, Chinese Academy of Sciences (IOCAS). Using fifteen moorings that gives unprecedented measurements in the intermediate and abyssal layers, we present multi-timescale variations of the deep ocean circulations prior to and during 2015 El Niño event. The deep ocean velocities increase equatorward with high standard deviation and nearly zero mean. The deep ocean currents mainly flow in meridional direction in the central Philippine Basin, and are dominated by a series of alternating westward and eastward zonal jets in the Caroline Basin. The currents in the deep channel connecting the East and West Mariana Basins mainly flow southeastward. Seasonal variation is only present in the deep jets in the Caroline Basin, associating with vertical propagating annual Rossby wave. The high-frequency flow bands are dominated by diurnal, and semi-diurnal tidal currents, and near-inertial currents. The rough topography has a strong influence on the abyssal circulations, including the intensifications in velocity and internal tidal energy, and the formation of upwelling flow.

Towards the impact of eddies on the response of the global ocean circulation to Southern Ocean gateway opening

NASA Astrophysics Data System (ADS)

Viebahn, Jan; von der Heydt, Anna S.; Dijkstra, Henk A.

2014-05-01

During the past 65 Million (Ma) years, Earth's climate has undergone a major change from warm 'greenhouse' to colder 'icehouse' conditions with extensive ice sheets in the polar regions of both hemispheres. The Eocene-Oligocene (~34 Ma) and Oligocene-Miocene (~23 Ma) boundaries reflect major transitions in Cenozoic global climate change. Proposed mechanisms of these transitions include reorganization of ocean circulation due to critical gateway opening/deepening, changes in atmospheric CO2-concentration, and feedback mechanisms related to land-ice formation. A long-standing hypothesis is that the formation of the Antarctic Circumpolar Current due to opening/deepening of Southern Ocean gateways led to glaciation of the Antarctic continent. However, while this hypothesis remains controversial, its assessment via coupled climate model simulations depends crucially on the spatial resolution in the ocean component. More precisely, only high-resolution modeling of the turbulent ocean circulation is capable of adequately describing reorganizations in the ocean flow field and related changes in turbulent heat transport. In this study, for the first time results of a high-resolution (0.1° horizontally) realistic global ocean model simulation with a closed Drake Passage are presented. Changes in global ocean temperatures, heat transport, and ocean circulation (e.g., Meridional Overturning Circulation and Antarctic Coastal Current) are established by comparison with an open Drake Passage high-resolution reference simulation. Finally, corresponding low-resolution simulations are also analyzed. The results highlight the essential impact of the ocean eddy field in palaeoclimatic change.

Quantifying the Bering Strait Oceanic Fluxes and their Impacts on Sea-Ice and Water Properties in the Chukchi and Beaufort Seas and Western Arctic Ocean for 2013-2014

DTIC Science & Technology

2014-09-30

Right) Sea Surface Temperature (SST) MODIS/Aqua level 1 image from 26th August 2004 (courtesy of Ocean Color Data Processing Archive, NASA/Goddard...was extremely good. The ADCPs and lower level temperature and salinity sensors all returned complete records. All 3 moorings also carried upper... Pavlov , and M. Kulakov (1999), The Siberian Coastal Current: a wind- and buoyancy-forced Arctic coastal current, J. Geophys. Res., 104(C12), 29697

Ocean-Wave Dynamics Analysis during Hurricane Ida and Norida Using a Fully Coupled Modeling System

NASA Astrophysics Data System (ADS)

Olabarrieta, M.; Warner, J. C.; Armstrong, B. N.

2010-12-01

Extreme storms, such as hurricanes and extratropical storms play a dominant role in shaping the beaches of the East and Gulf Coasts of the United States. Future tropical depressions will be more intense than in the present climate (Assessment Report of IPCC, 2007) and therefore coastal areas are likely to become more susceptible to their effects. The major damage caused by these extreme events is associated with the duration of the storm, storm intensity, waves, and the total water levels reached during the storm. Numerical models provide a useful approach to study the spatial and temporal distribution of these parameters. However, the correct estimation of the total water levels and wind wave heights through numerical modeling requires accurate representation of the air-sea interface dynamics. These processes are highly complex due to the variable interactions between winds, ocean waves and currents near the sea surface. In the present research we use the COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modeling system (Warner et al., 2010) to address the key role of the atmosphere-ocean-wave interactions during Hurricane Ida and its posterior evolution to NorIda, November 2009. This northeastern storm was one of the most costly in the past two decades and likely in the top five of the past century. One interesting aspect of the considered period is that it includes two very different atmospheric extreme conditions, a hurricane and a northeastern storm, developed in regions with very different oceanographic characteristics. By performing a suite of numerical runs we are able to isolate the effect of the interaction terms between the atmosphere (WRF model), the ocean (ROMS model) and the wave propagation and generation model (SWAN). Special attention is given to the role of the ocean surface roughness and high resolution SST fields on the atmospheric boundary layers dynamics and consequently these effects on the wind wave generation, surface currents and storm surge. The effects of ocean currents on wind wave generation and propagations are also analyzed. The model results are compared to different data sources, including GOES satellite infrared data, JASON-1 and JASON-2 altimeter data, CODAR measurements, and wave and tidal information from the NDBC and the National Tidal Database respectively. The results identified that the inclusion of the ocean roughness on the atmospheric module greatly improves the wind intensity estimation and therefore also the wind waves and the storm surge amplitude. For example, during the passage of Ida through the Gulf of Mexico the wind speeds are reduced due to the wave induced ocean roughness, resulting in better agreement with the measured winds. During NorIda, the effect of the surface roughness changed the form and dimension of the main low pressure cell, affecting the intensity and direction of the winds. Three different ocean roughness closure models are analyzed, with the wave-age based closure model providing the best results. Ocean currents are also shown to affect wave spectral characteristics through the generation and propagation processes. Changes within 15% on the significant wave height are detected in areas affected by the main oceanic currents: the Gulf Stream and the Loop Current.

Characteristics of inertial currents observed in offshore wave records

NASA Astrophysics Data System (ADS)

Gemmrich, J.; Garrett, C.

2012-04-01

It is well known that ambient currents can change the amplitude, direction and frequency of ocean surface waves. Regions with persistent strong currents, such as the Agulhas current off the east coast of South Africa, are known as areas of extreme waves, and wave height modulations of up to 50% observed in the shallow North Sea have been linked to tidal currents. In the open ocean, inertial currents, while intermittent, are typically the most energetic currents with speeds up to 0.5 m/s, and can interact with the surface wave field to create wave modulation, though this has not previously been reported. We use long records of significant wave heights from buoy observations in the northeast Pacific and show evidence of significant modulation at frequencies that are slightly higher than the local inertial frequency. Quite apart from the relevance to surface waves, this result can provide a consistent and independent measurement, over a wide range of latitudes, of the frequency blue-shift, the strength and intermittency of ocean surface inertial currents. Near-inertial waves constitute the most energetic portion of the internal wave band and play a significant role in deep ocean mixing. So far, observational data on near-surface inertial currents has tended to come from short records that do not permit the reliable determination of the frequency blue-shift, though this is an important factor affecting the energy flux from the surface into deeper waters. Long records from routine wave height observations are widely available and could help to shed new light globally on the blue-shift and on the characteristics of inertial currents.

Connecting Middle School, Oceanography, and the Real World.

ERIC Educational Resources Information Center

Brown, Susan W.; Hansen, Terri M.

2000-01-01

Introduces an activity that features 16 oceanography work stations and integrates other disciplines. Assigns students different oceanic life forms and requires students to work in stations. Explains seven of 16 stations which cover oil spills, the periodic table, ocean floor, currents, and classification of oceanic organisms. (YDS)

NWS Marine Forecast Areas

Science.gov Websites

Currents Global Ocean Model Sea Surface Temperatures Gulf Stream ASCII Data Gulf Stream Comparison Gridded ASCAT Scatterometer Winds Lightning Strike Density Satellite Imagery Ocean Global Ocean Model , 2017 19:10:57 UTC Disclaimer Information Quality Help Glossary Privacy Policy Freedom of Information

Upper Ocean Momentum Response to Hurricane Forcing

NASA Astrophysics Data System (ADS)

Shay, L. K.; Jaimes de la Cruz, B.; Uhlhorn, E.

2016-02-01

The oceanic velocity response of the Loop Current (LC) and its complex warm and cold eddy field to hurricanes is critical to evaluate coupled operational forecast models. Direct velocity measurements of ocean current (including temperature and salinity) fields during hurricanes are needed to understand these complex interaction processes. As part of NOAA Intensity Forecasting Experiments, airborne expendable bathythermographs (AXBT), Conductivity-Temperature-Depth (AXCTD), and Current Profilers (AXCP) probes have been deployed in several major hurricanes from the NOAA research aircraft over the Gulf. Over the last decade, profilers were deployed in Isidore and Lili, Katrina and Rita, Gustav and Ike and Isaac-all of which interacted with the LC and warm eddy field. Central to these interactions under hurricane forcing is the level of sea surface cooling (typically about 1oC) induced by the wind-forced current response in the LC complex. Vertical current shear and instability (e.g., Richardson number) at the base of the oceanic mixed layer is often arrested by the strong upper ocean currents associated with the LC of 1 to 1.5 m s-1. By contrast, the SST cooling response often exceeds 3.5 to 4oC away from the LC complex in the Gulf Common Water. A second aspect of the interaction between the surface wind field and the LC is that the vorticity of the background flows (based on altimetry) enhances upwelling and downwelling processes by projecting onto the wind stress. This process modulates vertical mixing process at depth by keeping the Richardson numbers above criticality. Thus, the ocean cooling is less in the LC complex allowing for a higher and more sustained enthalpy flux as determined from global positioning system sondes deployed in these storms. This level of cooling (or lack thereof) in the LC complex significant impacts hurricane intensity that often reaches severe status which affects offshore structures and coastal communities at landfall in the northern Gulf of Mexico.

Observed intraseasonal and seasonal variability of the West India Coastal Current on the continental slope

NASA Astrophysics Data System (ADS)

Amol, P.; Shankar, D.; Fernando, V.; Mukherjee, A.; Aparna, S. G.; Fernandes, R.; Michael, G. S.; Khalap, S. T.; Satelkar, N. P.; Agarvadekar, Y.; Gaonkar, M. G.; Tari, A. P.; Kankonkar, A.; Vernekar, S. P.

2014-06-01

We present current data from acoustic Doppler current profilers (ADCPs) moored on the continental slope off the west coast of India. The data were collected at four locations (roughly at Kanyakumari, Kollam, Goa, and Mumbai) extending from ˜ 7° to ˜ 20°N during 2008-2012. The observations show that a seasonal cycle, including an annual cycle, is present in the West India Coastal Current (WICC); this seasonal cycle, which strengthens northward, shows considerable interannual variability and is not as strongly correlated along the coast as in climatologies based on ship drifts or the altimeter. The alongshore decorrelation of the WICC is much stronger at intraseasonal periods, which are evident during the winter monsoon all along the coast. This intraseasonal variability is stronger in the south. A striking feature of the WICC is upward phase propagation, which implies an undercurrent whose depth becomes shallower as the season progresses. There are also instances when the phase propagates downward. At the two southern mooring locations off Kollam and Kanyakumari, the cross-shore current, which is usually associated with eddy-like circulations, is comparable to the alongshore current on occasions. A comparison with data from the OSCAR (Ocean Surface Currents Analyses Real-time) data product shows not only similarities, but also significant differences, particularly in the phase. One possible reason for this phase mismatch between the ADCP current at 48 m and the OSCAR current, which represents the current in the 0-30 m depth range, is the vertical phase propagation. Current products based on Ocean General Circulation Models like ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and GODAS (Global Ocean Data Assimilation System) show a weaker correlation with the ADCP current, and ECCO2 does capture some of the observed variability.

The atmospheric ocean: eddies and jets in the Antarctic Circumpolar Current.

PubMed

Thompson, Andrew F

2008-12-28

Although the Antarctic Circumpolar Current (ACC) is the longest and the strongest oceanic current on the Earth and is the primary means of inter-basin exchange, it remains one of the most poorly represented components of global climate models. Accurately describing the circulation of the ACC is made difficult owing to the prominent role that mesoscale eddies and jets, oceanic equivalents of atmospheric storms and storm tracks, have in setting the density structure and transport properties of the current. The successes and limitations of different representations of eddy processes in models of the ACC are considered, with particular attention given to how the circulation responds to changes in wind forcing. The dynamics of energetic eddies and topographically steered jets may both temper and enhance the sensitivity of different aspects of the ACC's circulation to changes in climate.

Genetic algorithm for investigating flight MH370 in Indian Ocean using remotely sensed data

NASA Astrophysics Data System (ADS)

Marghany, Maged; Mansor, Shattri; Shariff, Abdul Rashid Bin Mohamed

2016-06-01

This study utilized Genetic algorithm (GA) for automatic detection and simulation trajectory movements of flight MH370 debris. In doing so, the Ocean Surface Topography Mission(OSTM) on the Jason- 2 satellite have been used within 1 and half year covers data to simulate the pattern of Flight MH370 debris movements across the southern Indian Ocean. Further, multi-objectives evolutionary algorithm also used to discriminate uncertainty of flight MH370 imagined and detection. The study shows that the ocean surface current speed is 0.5 m/s. This current patterns have developed a large anticlockwise gyre over a water depth of 8,000 m. The multi-objectives evolutionary algorithm suggested that objects are existed on satellite data are not flight MH370 debris. In addition, multiobjectives evolutionary algorithm suggested that the difficulties to acquire the exact location of flight MH370 due to complicated hydrodynamic movements across the southern Indian Ocean.

Waves: Internal Tides

NASA Technical Reports Server (NTRS)

Ray, Richard D.

1999-01-01

Oceanic internal tides are internal waves with tidal periodicities. They are ubiquitous throughout the ocean, although generally more pronounced near large bathymetric features such as mid-ocean ridges and continental slopes. The internal vertical displacements associated with these waves can be extraordinarily large. Near some shelf breaks where the surface tides are strong, internal displacements (e.g., of an isothermal surface) can exceed 200 meters. Displacements of 10 meters in the open ocean are not uncommon. The associated current velocities are usually comparable to or larger than the currents of the surface tide. On continental shelves internal tides can occasionally generate packets of internal solitons, which are detectable in remote sensing imagery. Other common nonlinear features are generation of higher harmonics (e.g., 6-hr waves) and wave breaking. Internal tides are known to be an important energy source for mixing of shelf waters. Recent research suggests that they may also be a significant energy source for deep-ocean mixing.

Large mesopelagic fishes biomass and trophic efficiency in the open ocean.

PubMed

Irigoien, Xabier; Klevjer, T A; Røstad, A; Martinez, U; Boyra, G; Acuña, J L; Bode, A; Echevarria, F; Gonzalez-Gordillo, J I; Hernandez-Leon, S; Agusti, S; Aksnes, D L; Duarte, C M; Kaartvedt, S

2014-01-01

With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total fishes biomass. However, recent acoustic observations show that mesopelagic fishes biomass could be significantly larger than the current estimate. Here we combine modelling and a sensitivity analysis of the acoustic observations from the Malaspina 2010 Circumnavigation Expedition to show that the previous estimate needs to be revised to at least one order of magnitude higher. We show that there is a close relationship between the open ocean fishes biomass and primary production, and that the energy transfer efficiency from phytoplankton to mesopelagic fishes in the open ocean is higher than what is typically assumed. Our results indicate that the role of mesopelagic fishes in oceanic ecosystems and global ocean biogeochemical cycles needs to be revised as they may be respiring ~10% of the primary production in deep waters.

The oceanic biological pump modulates the atmospheric transport of persistent organic pollutants to the Arctic.

PubMed

Galbán-Malagón, Cristóbal; Berrojalbiz, Naiara; Ojeda, María-José; Dachs, Jordi

2012-05-29

Semivolatile persistent organic pollutants have the potential to reach remote environments, such as the Arctic Ocean, through atmospheric transport and deposition. Here we show that this transport of polychlorinated biphenyls to the Arctic Ocean is strongly retarded by the oceanic biological pump. A simultaneous sampling of atmospheric, seawater and plankton samples was performed in July 2007 in the Greenland Current and Atlantic sector of the Arctic Ocean. The atmospheric concentrations declined during atmospheric transport over the Greenland Current with estimated half-lives of 1-4 days. These short half-lives can be explained by the high air-to-water net diffusive flux, which is similar in magnitude to the estimated settling fluxes in the water column. Therefore, the decrease of atmospheric concentrations is due to sequestration of atmospheric polychlorinated biphenyls by enhanced air-water diffusive fluxes driven by phytoplankton uptake and organic carbon settling fluxes (biological pump).

Large mesopelagic fishes biomass and trophic efficiency in the open ocean

PubMed Central

Irigoien, Xabier; Klevjer, T. A.; Røstad, A.; Martinez, U.; Boyra, G.; Acuña, J. L.; Bode, A.; Echevarria, F.; Gonzalez-Gordillo, J. I.; Hernandez-Leon, S.; Agusti, S.; Aksnes, D. L.; Duarte, C. M.; Kaartvedt, S.

2014-01-01

With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total fishes biomass. However, recent acoustic observations show that mesopelagic fishes biomass could be significantly larger than the current estimate. Here we combine modelling and a sensitivity analysis of the acoustic observations from the Malaspina 2010 Circumnavigation Expedition to show that the previous estimate needs to be revised to at least one order of magnitude higher. We show that there is a close relationship between the open ocean fishes biomass and primary production, and that the energy transfer efficiency from phytoplankton to mesopelagic fishes in the open ocean is higher than what is typically assumed. Our results indicate that the role of mesopelagic fishes in oceanic ecosystems and global ocean biogeochemical cycles needs to be revised as they may be respiring ~10% of the primary production in deep waters. PMID:24509953

Corrections to the MODIS Aqua Calibration Derived From MODIS Aqua Ocean Color Products

NASA Technical Reports Server (NTRS)

Meister, Gerhard; Franz, Bryan Alden

2013-01-01

Ocean color products such as, e.g., chlorophyll-a concentration, can be derived from the top-of-atmosphere radiances measured by imaging sensors on earth-orbiting satellites. There are currently three National Aeronautics and Space Administration sensors in orbit capable of providing ocean color products. One of these sensors is the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, whose ocean color products are currently the most widely used of the three. A recent improvement to the MODIS calibration methodology has used land targets to improve the calibration accuracy. This study evaluates the new calibration methodology and describes further calibration improvements that are built upon the new methodology by including ocean measurements in the form of global temporally averaged water-leaving reflectance measurements. The calibration improvements presented here mainly modify the calibration at the scan edges, taking advantage of the good performance of the land target trending in the center of the scan.

Static Electric Fields and Lightning Over Land and Ocean in Florida Thunderstorms

NASA Technical Reports Server (NTRS)

Wilson, J. G.; Cummins, K. L.; Simpson, A. A.; Hinckley, A.

2017-01-01

Natural cloud-to-ground (CG) lightning and the charge structure of the associated clouds behave differently over land and ocean. Existing literature has raised questions over the years on the behavior of thunderstorms and lightning over oceans, and there are still open scientific questions. We expand on the observational datasets by obtaining identical electric field observations over coastal land, near-shore, and deep ocean regions during both clear air and thunderstorm periods. Oceanic observations were obtained using two 3-meter NOAA buoys that were instrumented with Campbell Scientific electric field mills to measure the static electric fields. These data were compared to selected electric field records from the existing on-shore electric field mill suite of 31 sensors at Kennedy Space Center (KSC). CG lightning occurrence times, locations and peak current values for both on-shore and ocean were provided by the U.S. National Lightning Detection Network. The buoy instruments were first evaluated on-shore at the Florida coast, to calibrate field enhancements and to confirm proper behavior of the system in elevated-field environments. The buoys were then moored 20NM and 120NM off the coast of KSC in February (20NM) and August (120NM) 2014. Statistically larger CG peak currents were reported over the deep ocean for first strokes and for subsequent strokes with new contacts points. Storm-related static fields were significantly larger at both oceanic sites, likely due to decreased screening by nearby space charge. Time-evolution of the static field during storm development and propagation indicated weak or missing lower positive charge regions in most storms that initiated over the deep ocean, supporting one mechanism for the observed high peak currents in negative first strokes over the deep ocean. This project also demonstrated the practicality of off-shore electric field measurements for safety-related decision making at KSC.

Circulation of the gyres of the world ocean: Observation modeling using TOPEX/Poseidon altimeter data

NASA Technical Reports Server (NTRS)

Fu, Lee-Lueng; Zlotnicki, V.; Holland, W. R.; Malanotte-Rizzoli, P.

1991-01-01

The overall objectives of the proposed investigation are to study the dynamics of the large-scale recirculating cells of water in the ocean, which are loosely defined as 'gyres' in this study. A gyre is normally composed of a swift western boundary current (e.g., the Gulf Stream and the Kuroshio), a tight recirculating cell attached to the current, and a large-scale sluggish return flow. The water, of course, is not entirely recirculating within a gyre. The exchange of water among gyres is an important process in maintaining the meridional heat transport of the ocean. The gyres constitute a major mode of water movement in the ocean and play significant roles in the global climate system.

Biogeochemical and ecological impacts of boundary currents in the Indian Ocean

NASA Astrophysics Data System (ADS)

Hood, Raleigh R.; Beckley, Lynnath E.; Wiggert, Jerry D.

2017-08-01

Monsoon forcing and the unique geomorphology of the Indian Ocean basin result in complex boundary currents, which are unique in many respects. In the northern Indian Ocean, several boundary current systems reverse seasonally. For example, upwelling coincident with northward-flowing currents along the coast of Oman during the Southwest Monsoon gives rise to high productivity which also alters nutrient stoichiometry and therefore, the species composition of the resulting phytoplankton blooms. During the Northeast Monsoon most of the northern Indian Ocean boundary currents reverse and favor downwelling. Higher trophic level species have evolved behavioral responses to these seasonally changing conditions. Examples from the western Arabian Sea include vertical feeding migrations of a copepod (Calanoides carinatus) and the reproductive cycle of a large pelagic fish (Scomberomorus commerson). The impacts of these seasonal current reversals and changes in upwelling and downwelling circulations are also manifested in West Indian coastal waters, where they influence dissolved oxygen concentrations and have been implicated in massive fish kills. The winds and boundary currents reverse seasonally in the Bay of Bengal, though the associated changes in upwelling and productivity are less pronounced. Nonetheless, their effects are observed on the East Indian shelf as, for example, seasonal changes in copepod abundance and zooplankton community structure. In contrast, south of Sri Lanka seasonal reversals in the boundary currents are associated with dramatic changes in the intensity of coastal upwelling, chlorophyll concentration, and catch per unit effort of fishes. Off the coast of Java, monsoon-driven changes in the currents and upwelling strongly impact chlorophyll concentrations, seasonal vertical migrations of zooplankton, and sardine catch in Bali Strait. In the southern hemisphere the Leeuwin is a downwelling-favorable current that flows southward along western Australia, though local wind forcing can lead to transient near shore current reversals and localized coastal upwelling. The poleward direction of this eastern boundary current is unique. Due to its high kinetic energy the Leeuwin Current sheds anomalous, relatively high chlorophyll, warm-core, downwelling eddies that transport coastal diatom communities westward into open ocean waters. Variations in the Leeuwin transport and eddy generation impact many higher trophic level species including the recruitment and fate of rock lobster (Panulirus cygnus) larvae. In contrast, the transport of the Agulhas Current is very large, with sources derived from the Mozambique Channel, the East Madagascar Current and the southwest Indian Ocean sub-gyre. Dynamically, the Agulhas Current is upwelling favorable; however, the spatial distribution of prominent surface manifestations of upwelling is controlled by local wind and topographic forcing. Meanders and eddies in the Agulhas Current propagate alongshore and interact with seasonal changes in the winds and topographic features. These give rise to seasonally variable localized upwelling and downwelling circulations with commensurate changes in primary production and higher trophic level responses. Due to the strong influence of the Agulhas Current, many neritic fish species in southeast Africa coastal waters have evolved highly selective behaviors and reproductive patterns for successful retention of planktonic eggs and larvae. For example, part of the Southern African sardine (Sardinops sagax) stock undergoes a remarkable northward migration enhanced by transient cyclonic eddies in the shoreward boundary of the Agulhas Current. There is evidence from the paleoceanographic record that these currents and their biogeochemical and ecological impacts have changed significantly over glacial to interglacial timescales. These changes are explored as a means of providing insight into the potential impacts of climate change in the Indian Ocean.

Upper-Ocean Processes under the Stratus Cloud Deck in the Southeast Pacific Ocean

DTIC Science & Technology

2010-01-01

resolving Hybrid Coordinate Ocean Model (HYCOM). Both are compared with estimates based on Woods Hole Oceano - graphic Institution (WHOI) Improved...Jason-1 and Jason-2 sea surface heights and geostrophic currents (computed from absolute topography) produced by Segment Sol Multimissions d’Altimétrie

Atmospheric correction of AVIRIS data in ocean waters

NASA Technical Reports Server (NTRS)

Terrie, Gregory; Arnone, Robert

1992-01-01

Hyperspectral data offers unique capabilities for characterizing the ocean environment. The spectral characterization of the composition of ocean waters can be organized into biological and terrigenous components. Biological photosynthetic pigments in ocean waters have unique spectral ocean color signatures which can be associated with different biological species. Additionally, suspended sediment has different scattering coefficients which result in ocean color signatures. Measuring the spatial distributions of these components in the maritime environments provides important tools for understanding and monitoring the ocean environment. These tools have significant applications in pollution, carbon cycle, current and water mass detection, location of fronts and eddies, sewage discharge and fate etc. Ocean color was used from satellite for describing the spatial variability of chlorophyll, water clarity (K(sub 490)), suspended sediment concentration, currents etc. Additionally, with improved atmospheric correction methods, ocean color results produced global products of spectral water leaving radiance (L(sub W)). Ocean color results clearly indicated strong applications for characterizing the spatial and temporal variability of bio-optical oceanography. These studies were largely the results of advanced atmospheric correction techniques applied to multispectral imagery. The atmosphere contributes approximately 80 percent - 90 percent of the satellite received radiance in the blue-green portion of the spectrum. In deep ocean waters, maximum transmission of visible radiance is achieved at 490nm. Conversely, nearly all of the light is absorbed by the water at wavelengths greater than about 650nm and thus appears black. These spectral ocean properties are exploited by algorithms developed for the atmospheric correction used in satellite ocean color processing. The objective was to apply atmospheric correction techniques that were used for procesing satellite Coastal Zone Color Scanner (CZCS) data to AVIRIS data. Quantitative measures of L(sub W) from AVIRIS are compared with ship ground truth data and input into bio-optical models.

Oceanic dispersion of Fukushima-derived Cs-137 in the coastal, offshore, and open oceans simulated by multiple oceanic general circulation models

NASA Astrophysics Data System (ADS)

Kawamura, H.; Furuno, A.; Kobayashi, T.; In, T.; Nakayama, T.; Ishikawa, Y.; Miyazawa, Y.; Usui, N.

2017-12-01

To understand the concentration and amount of Fukushima-derived Cs-137 in the ocean, this study simulates the oceanic dispersion of Cs-137 by an oceanic dispersion model SEA-GEARN-FDM developed at Japan Atomic Energy Agency (JAEA) and multiple oceanic general circulation models. The Cs-137 deposition amounts at the sea surface were used as the source term in oceanic dispersion simulations, which were estimated by atmospheric dispersion simulations with a Worldwide version of System for Prediction of Environmental Emergency Dose Information version II (WSPEEDI-II) developed at JAEA. The direct release from the Fukushima Daiichi Nuclear Power Plant into the ocean based on in situ Cs-137 measurements was used as the other source term in oceanic dispersion simulations. The simulated air Cs-137 concentrations qualitatively replicated those measured around the North Pacific. The accumulated Cs-137 ground deposition amount in the eastern Japanese Islands was consistent with that estimated by aircraft measurements. The oceanic dispersion simulations relatively well reproduced the measured Cs-137 concentrations in the coastal and offshore oceans during the first few months after the Fukushima disaster, and in the open ocean during the first year post-disaster. It was suggested that Cs-137 dispersed along the coast in the north-south direction during the first few months post-disaster, and were subsequently dispersed offshore by the Kuroshio Current and Kuroshio Extension. Mesoscale eddies accompanied by the Kuroshio Current and Kuroshio Extension played an important role in dilution of Cs-137. The Cs-137 amounts were quantified in the coastal, offshore, and open oceans during the first year post-disaster. It was demonstrated that Cs-137 actively dispersed from the coastal and offshore oceans to the open ocean, and from the surface layer to the deeper layer in the North Pacific.

75 FR 5708 - Ocean Dumping; Designation of Ocean Dredged Material Disposal Sites Offshore of the Siuslaw River...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-04

... suspended by wave action near the bottom, and are moved by bottom currents or directly as bedload. Tidal, wind and wave forces contribute to generating bottom currents, which act in relation to the sediment... littoral zone, limit wave effects due to mounding, and keep material from reentering the navigation channel...

The Gulf Stream and Density of Fluids

ERIC Educational Resources Information Center

Landstrom, Erich

2006-01-01

A few kilometers from the shores of Palm Beach County, Florida, is the Gulf Stream current--a remarkable "river" within an ocean. The current's journey across the Atlantic Ocean connects southeast Florida and southwest Great Britain as it streams steadily north at speeds of 97 km a day; moving 100 times as much water as all the rivers on…

A review of climate change impacts on birds

Treesearch

Robert W. Butler; William Taylor

2005-01-01

Regions of the world with high coastal zone biological productivity often support large numbers of birds. Important sources of this productivity are oceanographic upwelling created by winds and ocean currents, and runoff from the land. It is suggested that climate change effects on winds and ocean currents will potentially affect the timing and magnitude of coastal...

Internal Waves, South China Sea

NASA Technical Reports Server (NTRS)

1983-01-01

Subsurface ocean currents, frequently referred to as internal waves, are frequently seen from space under the right lighting conditions when depth penetration can be achieved. These internal waves observed in the South China Sea off the SE coast of the island of Hainan (18.5N, 110.5E) visibly demonstrate turbidity in the ocean's depths at the confluence of conflicting currents.

An improved dual-frequency technique for the remote sensing of ocean currents and wave spectra

NASA Technical Reports Server (NTRS)

Schuler, D. L.; Eng, W. P.

1984-01-01

A two frequency microwave radar technique for the remote sensing of directional ocean wave spectra and surface currents is investigated. This technique is conceptually attractive because its operational physical principle involves a spatial electromagnetic scattering resonance with a single, but selectable, long gravity wave. Multiplexing of signals having different spacing of the two transmitted frequencies allows measurements of the entire long wave ocean spectrum to be carried out. A new scatterometer is developed and experimentally tested which is capable of making measurements having much larger signal/background values than previously possible. This instrument couples the resonance technique with coherent, frequency agility radar capabilities. This scatterometer is presently configured for supporting a program of surface current measurements.

Optimum interpolation analysis of basin-scale ¹³⁷Cs transport in surface seawater in the North Pacific Ocean.

PubMed

Inomata, Y; Aoyama, M; Tsumune, D; Motoi, T; Nakano, H

2012-12-01

¹³⁷Cs is one of the conservative tracers applied to the study of oceanic circulation processes on decadal time scales. To investigate the spatial distribution and the temporal variation of ¹³⁷Cs concentrations in surface seawater in the North Pacific Ocean after 1957, a technique for optimum interpolation (OI) was applied to understand the behaviour of ¹³⁷Cs that revealed the basin-scale circulation of Cs ¹³⁷Cs in surface seawater in the North Pacific Ocean: ¹³⁷Cs deposited in the western North Pacific Ocean from global fallout (late 1950s and early 1960s) and from local fallout (transported from the Bikini and Enewetak Atolls during the late 1950s) was further transported eastward with the Kuroshio and North Pacific Currents within several years of deposition and was accumulated in the eastern North Pacific Ocean until 1967. Subsequently, ¹³⁷Cs concentrations in the eastern North Pacific Ocean decreased due to southward transport. Less radioactively contaminated seawater was also transported northward, upstream of the North Equatorial Current in the western North Pacific Ocean in the 1970s, indicating seawater re-circulation in the North Pacific Gyre.

The Global Drifter Program Currents, Sea Surface Temperature, Atmospheric Pressure and Waves in the World's OceanThe Global Drifter Program Currents, Sea Surface Temperature, Atmospheric Pressure and Waves in the World's Ocean

NASA Astrophysics Data System (ADS)

Centurioni, Luca

2017-04-01

The Global Drifter Program is the principal component of the Global Surface Drifting Buoy Array, a branch of NOAA's Global Ocean Observing System and a scientific project of the Data Buoy Cooperation Panel (DBCP). The DBCP is an international program coordinating the use of autonomous data buoys to observe atmospheric and oceanographic conditions over ocean areas where few other measurements are taken. The Global Drifter Program maintains an array of over 1,250 Lagrangian drifters, reporting in near real-time and designed measure 15 m depth Lagrangian currents, sea surface temperature (SST) and sea level atmospheric pressure (SLP), among others, to fulfill the needs to observe the air-sea interface at temporal and spatial scales adequate to support short to medium-range weather forecasting, ocean state estimates and climate science. This overview talk will discuss the main achievements of the program, the main impacts for satellite SST calibration and validation, for numerical weather prediction, and it will review the main scientific findings based on the use of Lagrangian currents. Finally, we will present new developments in Lagrangian drifter technology, which include special drifters designed to measure sea surface salinity, wind and directional wave spectra. New opportunities for expanding the scope of the Global Drifter Program will be discussed.

The artificial object detection and current velocity measurement using SAR ocean surface images

NASA Astrophysics Data System (ADS)

Alpatov, Boris; Strotov, Valery; Ershov, Maksim; Muraviev, Vadim; Feldman, Alexander; Smirnov, Sergey

2017-10-01

Due to the fact that water surface covers wide areas, remote sensing is the most appropriate way of getting information about ocean environment for vessel tracking, security purposes, ecological studies and others. Processing of synthetic aperture radar (SAR) images is extensively used for control and monitoring of the ocean surface. Image data can be acquired from Earth observation satellites, such as TerraSAR-X, ERS, and COSMO-SkyMed. Thus, SAR image processing can be used to solve many problems arising in this field of research. This paper discusses some of them including ship detection, oil pollution control and ocean currents mapping. Due to complexity of the problem several specialized algorithm are necessary to develop. The oil spill detection algorithm consists of the following main steps: image preprocessing, detection of dark areas, parameter extraction and classification. The ship detection algorithm consists of the following main steps: prescreening, land masking, image segmentation combined with parameter measurement, ship orientation estimation and object discrimination. The proposed approach to ocean currents mapping is based on Doppler's law. The results of computer modeling on real SAR images are presented. Based on these results it is concluded that the proposed approaches can be used in maritime applications.

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

Small-scale open ocean currents have large effects on wind wave heights

NASA Astrophysics Data System (ADS)

Ardhuin, Fabrice; Gille, Sarah T.; Menemenlis, Dimitris; Rocha, Cesar B.; Rascle, Nicolas; Chapron, Bertrand; Gula, Jonathan; Molemaker, Jeroen

2017-06-01

Tidal currents and large-scale oceanic currents are known to modify ocean wave properties, causing extreme sea states that are a hazard to navigation. Recent advances in the understanding and modeling capability of open ocean currents have revealed the ubiquitous presence of eddies, fronts, and filaments at scales 10-100 km. Based on realistic numerical models, we show that these structures can be the main source of variability in significant wave heights at scales less than 200 km, including important variations down to 10 km. Model results are consistent with wave height variations along satellite altimeter tracks, resolved at scales larger than 50 km. The spectrum of significant wave heights is found to be of the order of 70>>2/>(g2>>2>) times the current spectrum, where >> is the spatially averaged significant wave height, >> is the energy-averaged period, and g is the gravity acceleration. This variability induced by currents has been largely overlooked in spite of its relevance for extreme wave heights and remote sensing.