Variations in Transport Derived from Satellite Altimeter Data over the Gulf Stream

NASA Technical Reports Server (NTRS)

Molinelli, Eugene; Lambert, Richard B., Jr.

1981-01-01

Variations in total change of sea surface height (delta h) across the Gulf Stream are observed using Seasat radar altimeter data. The sea surface height is related to transport within the stream by a two layer model. Variations in delta h are compared with previously observed changes in transport found to increase with distance downstream. No such increase is apparent since the satellite transports show no significant dependence on distance. Though most discrepancies are less than 50 percent, a few cases differ by about 100 percent and more. Several possible reasons for these discrepancies are advanced, including geoid error, but only two oceanographic contributions to the variability are examined, namely, limitations in the two layer model and meanders in the current. It is concluded that some of the discrepancies could be explained as changes in the density structure not accounted for by the two layer model.

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

Schoonover, Joseph; Dewar, William K.; Wienders, Nicolas

Robust and accurate Gulf Stream separation remains an unsolved problem in general circulation modeling whose resolution will positively impact the ocean and climate modeling communities. Oceanographic literature does not face a shortage of plausible hypotheses that attempt to explain the dynamics of the Gulf Stream separation, yet a single theory that the community agrees on is missing. We investigate the impact of the Deep Western Boundary Current, coastline curvature, and continental shelf steepening on the Gulf Stream separation within regional configurations of the MIT General Circulation Model. Artificial modifications to the regional bathymetry are introduced to investigate the sensitivity ofmore » the separation to each of these factors. Metrics for subsurface separation detection confirm the direct link between flow separation and the surface expression of the Gulf Stream in the Mid-Atlantic Bight. Conversely, the Gulf Stream separation exhibits minimal sensitivity to the presence of the DWBC and coastline curvature. The implications of these results to the development of a “separation recipe” for ocean modeling are discussed. Furthermore, we conclude adequate topographic resolution is a necessary, but not sufficient, condition for proper Gulf Stream separation.« less

A Moored System for Understanding the Temporal Variability of Prey Fields of Deep Diving Predators off Cape Hatteras and Response to Gulf Stream Fronts

DTIC Science & Technology

2015-09-30

Number: N000141310686 http://superpod.ml.duke.edu/ LONG-TERM GOALS Fisheries acoustics are routinely used for biomass and abundance surveys and...will be required every 10-12 months), allowing us to address the seasonality and the inter-annual variability in prey biomass and density in

Temperature of the Gulf Stream

NASA Technical Reports Server (NTRS)

2002-01-01

The Gulf Stream is one of the strong ocean currents that carries warm water from the sunny tropics to higher latitudes. The current stretches from the Gulf of Mexico up the East Coast of the United States, departs from North America south of the Chesapeake Bay, and heads across the Atlantic to the British Isles. The water within the Gulf Stream moves at the stately pace of 4 miles per hour. Even though the current cools as the water travels thousands of miles, it remains strong enough to moderate the Northern European climate. The image above was derived from the infrared measurements of the Moderate-resolution Imaging Spectroradiometer (MODIS) on a nearly cloud-free day over the east coast of the United States. The coldest waters are shown as purple, with blue, green, yellow, and red representing progressively warmer water. Temperatures range from about 7 to 22 degrees Celsius. The core of the Gulf Stream is very apparent as the warmest water, dark red. It departs from the coast at Cape Hatteras, North Carolina. The cool, shelf water from the north entrains the warmer outflows from the Chesapeake and Delaware Bays. The north wall of the Gulf Stream reveals very complex structure associated with frontal instabilities that lead to exchanges between the Gulf Stream and inshore waters. Several clockwise-rotating warm core eddies are evident north of the core of the Gulf Stream, which enhance the exchange of heat and water between the coastal and deep ocean. Cold core eddies, which rotate counter clockwise, are seen south of the Gulf Stream. The one closest to Cape Hatteras is entraining very warm Gulf Stream waters on its northwest circumference. Near the coast, shallower waters have warmed due to solar heating, while the deeper waters offshore are markedly cooler (dark blue). MODIS made this observation on May 8, 2000, at 11:45 a.m. EDT. For more information, see the MODIS-Ocean web page. The sea surface temperature image was created at the University of Miami using the 11- and 12-micron bands, by Bob Evans, Peter Minnett, and co-workers.

Atmospheric responses to sensible and latent heating fluxes over the Gulf Stream

NASA Astrophysics Data System (ADS)

Minobe, S.; Ida, T.; Takatama, K.

2016-12-01

Air-sea interaction over mid-latitude oceanic fronts such as the Gulf Stream attracted large attention in the last decade. Observational analyses and modelling studies revealed that atmospheric responses over the Gulf Stream including surface wind convergence, enhanced precipitation and updraft penetrating to middle-to-upper troposphere roughly on the Gulf Stream current axis or on the warmer flank of sea-surface temperature (SST) front of the Gulf Stream . For these atmospheric responses, oceanic information should be transmitted to the atmosphere via turbulent heat fluxes, and thus the mechanisms for atmospheric responses can be understood better by examining latent and sensible air-sea heat fluxes more closely. Thus, the roles of the sensible and latent heat fluxes are examined by conducting a series of numerical experiments using the IPRC Regional Atmospheric Model over the Gulf Stream by applying SST smoothing for latent and sensible heating separately. The results indicate that the sensible and latent heat fluxes affect the atmosphere differently. Sensible heat flux intensifies surface wind convergence to produce sea-level pressure (SLP) anomaly. Latent heat flux supplies moistures and maintains enhanced precipitation. The different heat flux components cause upward wind velocity at different levels.

Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico

USGS Publications Warehouse

Alexander, R.B.; Smith, R.A.; Schwarz, G.E.

2000-01-01

An increase in the flux of nitrogen from the Mississippi river during the latter half of the twentieth century has caused eutrophication and chronic seasonal hypoxia in the shallow waters of the Louisiana shelf in the northern Gulf of Mexico. This has led to reductions in species diversity, mortality of benthic communities and stress in fishery resources. There is evidence for a predominantly anthropogenic origin of the increased nitrogen flux, but the location of the most significant sources in the Mississippi basin responsible for the delivery of nitrogen to the Gulf of Mexico have not been clearly identified, because the parameters influencing nitrogen-loss rates in rivers are not well known. Here we present an analysis of data from 374 US monitoring stations, including 123 along the six largest tributaries to the Mississippi, that shows a rapid decline in the average first-order rate of nitrogen loss with channel size-from 0.45 day-1 in small streams to 0.005 day-1 in the Mississippi river. Using stream depth as an explanatory variable, our estimates of nitrogen-loss rates agreed with values from earlier studies. We conclude that the proximity of sources to large streams and rivers is an important determinant of nitrogen delivery to the estuary in the Mississippi basin, and possibly also in other large river basins.

The Gulf Stream frontal system: A key oceanographic feature in the habitat selection of the leatherback turtle?

NASA Astrophysics Data System (ADS)

Chambault, Philippine; Roquet, Fabien; Benhamou, Simon; Baudena, Alberto; Pauthenet, Etienne; de Thoisy, Benoît; Bonola, Marc; Dos Reis, Virginie; Crasson, Rodrigue; Brucker, Mathieu; Le Maho, Yvon; Chevallier, Damien

2017-05-01

Although some associations between the leatherback turtle Dermochelys coriacea and the Gulf Stream current have been previously suggested, no study has to date demonstrated strong affinities between leatherback movements and this particular frontal system using thorough oceanographic data in both the horizontal and vertical dimensions. The importance of the Gulf Stream frontal system in the selection of high residence time (HRT) areas by the North Atlantic leatherback turtle is assessed here for the first time using state-of-the-art ocean reanalysis products. Ten adult females from the Eastern French Guianese rookery were satellite tracked during post-nesting migration to relate (1) their horizontal movements to physical gradients (Sea Surface Temperature (SST), Sea Surface Height (SSH) and filaments) and biological variables (micronekton and chlorophyll a), and (2) their diving behaviour to vertical structures within the water column (mixed layer, thermocline, halocline and nutricline). All the turtles migrated northward towards the Gulf Stream north wall. Although their HRT areas were geographically remote (spread between 80-30 °W and 28-45 °N), all the turtles targeted similar habitats in terms of physical structures, i.e. strong gradients of SST, SSH and a deep mixed layer. This close association with the Gulf Stream frontal system highlights the first substantial synchronization ever observed in this species, as the HRTs were observed in close match with the autumn phytoplankton bloom. Turtles remained within the enriched mixed layer at depths of 38.5±7.9 m when diving in HRT areas, likely to have an easier access to their prey and maximize therefore the energy gain. These depths were shallow in comparison to those attained within the thermocline (82.4±5.6 m) while crossing the nutrient-poor subtropical gyre, probably to reach cooler temperatures and save energy during the transit. In a context of climate change, anticipating the evolution of such frontal structure under the influence of global warming is crucial to ensure the conservation of this vulnerable species.

On the dynamic forcing of short-term climate fluctuations by feedback mechanisms

NASA Technical Reports Server (NTRS)

Reiter, E. R.

1979-01-01

Various internal feedback mechanisms in the ocean atmosphere system were studied. A variability pattern of sea surface temperature with a quasibiennial oscillation (QBO) was detected off the coast of Senegal, in the Gulf of Guinea and even in the Gulf Stream as it leaves the North American continental shelf. Possible physical connections between some of these QBO's were pointed out by a hypothetical feedback model. Interaction of a QBO with the annual cycle may lead to beating frequencies resembling climatic trends of a duration of several years.

Multi-year Current Observations on the Shelf Slope off Cape Hatteras, NC

NASA Astrophysics Data System (ADS)

Muglia, M.

2017-12-01

As part of an observing and modeling effort by the North Carolina Renewable Ocean Energy Program to determine if the Gulf Stream is a viable marine hydrokinetic energy resource for the state, upper continental slope current measurements were made over a period of nearly four years off of Cape Hatteras, NC. Velocity profiles were measured by a near-bottom, upward-looking, 150-kHz Acoustic Doppler Current Profiler deployed at a depth of 230-260 m. The mooring was sited at the location where water from the Gulf Stream, Middle Atlantic Bight, South Atlantic Bight, and Slope Sea all converge. Measured tidal amplitudes here are 2 m. These observations are used to consider the temporal variability and vertical structure of the currents at this location at tidal to interannual periods at this complex location. Concurrent near-bottom water mass properties are considered.

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…

The Impact of Gulf Stream-Induced Diabatic Forcing on Coastal Mid-Atlantic Surface Cyclogenesis

NASA Astrophysics Data System (ADS)

Cione, Joseph Jerome

In this dissertation, numerical experiments were conducted using a mesoscale atmospheric model developed at North Carolina State University. Three sets of numerical experiments were conducted and were designed to: quantify the impact Gulf Stream frontal distance, initial surface air temperature and cold air outbreak timing each have on the subsequent development of the marine atmospheric boundary layer during periods of offshore cold advection; investigate critical processes associated with Gulf Stream -induced mesocyclogenesis and; elucidate the role SST gradients and surface fluxes of heat and moisture have on the intensification and track of propagating mesocyclonic systems within the highly baroclinic Gulf Stream region. A major finding from the offshore cold advection simulations is that the initial air-sea contrast is the dominant forcing mechanism linked to the offshore circulation development and marine boundary layer modification. Results from the mesocyclogenesis experiments indicate that surface cyclogenesis was simulated to occur along a Gulf Stream meander in a region where the gradients in sea surface temperature (SST) were maximized. Results from sensitivity experiments illustrate that changes in the Gulf Stream SST gradient pattern can act to alter the timing and degree of cyclonic development simulated, while the inclusion of surface fluxes and moist convective processes during the development phase act to strongly enhance the intensity and/or occurrence of simulated mesocyclogenesis. Both observational and numerical results from studies investigating the impact strong Gulf Stream SST gradients have on the development of pre-existing, propagating cyclonic systems show that the baroclinic nature of the low level environment near the circulation center (as well as the degree of simulated/observed surface cyclonic intensification) appear to be highly dependent upon the mesoscale storm track within the Gulf Stream frontal zone. Furthermore, the numerical storm track experiments conducted in this research illustrate that surfaces fluxes can act to significantly alter the storm track of the surface mesocyclone (in addition to impacting the overall intensification of the simulated cyclonic system). This work also presents the technique development and operational utilization of the recently devised Atlantic Surface Cyclone Intensification Index (ASCII). The index continues to be implemented by the National Weather Service at the Raleigh-Durham and surrounding coastal forecast offices, and to date, has been successfully utilized for 11 coastal winter storm events over the February 1994-January 1996 period.

Sea surface temperature variability in the Gulf of Mexico from 1734-2008 CE: A reconstruction using cross-dated Sr/Ca records from the coral Siderastrea siderea

NASA Astrophysics Data System (ADS)

DeLong, K. L.; Flannery, J. A.; Quinn, T. M.; Maupin, C. R.; Lin, K.; Shen, C.

2013-12-01

Sea surface temperature (SST) variability in the Gulf of Mexico impacts climate in Central and North America because the Gulf is a major source of moisture and is a source region for the Gulf Stream, which transports ocean heat northward. Here we use skeletal variations in coral Sr/Ca from three Siderastrea siderea coral colonies within the Dry Tortugas National Park in the southeastern Gulf of Mexico (24°42'N, 82°48'W) to develop 274 years of monthly-resolved SST variations. The cross-dated chronology, determined by counting annual density bands and correlating Sr/Ca variations, is verified by four replicated high precision 230Th dates (×1.7-37 years, 2σ). Calibration and verification of our replicated coral Sr/Ca-SST reconstruction with Dry Tortugas SST (r = 0.98 and 0.55 for monthly and 36-month smoothed, respectively; 1992-2008 CE) and Key West, Florida surface air temperature (1895-2008 CE) measurements reveals similar covariance (r = 0.96 and 0.56 for monthly and 36-month smoothed, respectively). The absolute coral SST reconstruction is consistent with SST recorded at the Dry Tortugas lighthouse from 1879-1907 CE indicating that this coral Sr/Ca-SST relationship is stable on centennial time scales. The Sr/Ca-SST reconstruction reveals ~2.0°C interannual variability, ~1.5°C decadal fluctuations, and a 0.7°C warming trend for the past 274 years. Secular variability in our reconstruction is similar to approximately decadally resolved planktic foraminifer Mg/Ca records from the northern Gulf of Mexico. The coral Sr/Ca-SST reconstruction reveals colder decades (~1.5°C) suggesting a reduction in moisture and ocean heat flux from the Gulf of Mexico. We find winter extremes are more variable than summer extremes (×2.2°C vs. ×1.6°C, 2σ) with a stronger warming trend (1°C) in the summers suggesting continued warming may increase coral bleaching.

Recent changes to the Gulf Stream causing widespread gas hydrate destabilization.

PubMed

Phrampus, Benjamin J; Hornbach, Matthew J

2012-10-25

The Gulf Stream is an ocean current that modulates climate in the Northern Hemisphere by transporting warm waters from the Gulf of Mexico into the North Atlantic and Arctic oceans. A changing Gulf Stream has the potential to thaw and convert hundreds of gigatonnes of frozen methane hydrate trapped below the sea floor into methane gas, increasing the risk of slope failure and methane release. How the Gulf Stream changes with time and what effect these changes have on methane hydrate stability is unclear. Here, using seismic data combined with thermal models, we show that recent changes in intermediate-depth ocean temperature associated with the Gulf Stream are rapidly destabilizing methane hydrate along a broad swathe of the North American margin. The area of active hydrate destabilization covers at least 10,000 square kilometres of the United States eastern margin, and occurs in a region prone to kilometre-scale slope failures. Previous hypothetical studies postulated that an increase of five degrees Celsius in intermediate-depth ocean temperatures could release enough methane to explain extreme global warming events like the Palaeocene-Eocene thermal maximum (PETM) and trigger widespread ocean acidification. Our analysis suggests that changes in Gulf Stream flow or temperature within the past 5,000 years or so are warming the western North Atlantic margin by up to eight degrees Celsius and are now triggering the destabilization of 2.5 gigatonnes of methane hydrate (about 0.2 per cent of that required to cause the PETM). This destabilization extends along hundreds of kilometres of the margin and may continue for centuries. It is unlikely that the western North Atlantic margin is the only area experiencing changing ocean currents; our estimate of 2.5 gigatonnes of destabilizing methane hydrate may therefore represent only a fraction of the methane hydrate currently destabilizing globally. The transport from ocean to atmosphere of any methane released--and thus its impact on climate--remains uncertain.

Seasonal occurrence of sperm whales (Physeter macrocephalus) around Kelvin Seamount in the Sargasso Sea in relation to oceanographic processes

NASA Astrophysics Data System (ADS)

Wong, Sarah N. P.; Whitehead, Hal

2014-09-01

Sperm whales (Physeter macrocephalus) are widely distributed in all oceans, but they are clumped geographically, generally in areas associated with high primary and secondary productivity. The warm, clear waters of the Sargasso Sea are traditionally thought to be low in productivity, however recent surveys have found large numbers of sperm whales there. The New England Seamount Chain bisects the north-western portion of the Sargasso Sea, and might influence the mesoscale eddies associated with the Gulf Stream; creating areas of higher productivity within the Sargasso Sea. We investigated the seasonal occurrence of sperm whales over Kelvin Seamount (part of the New England Seamount Chain) and how it is influenced by oceanographic variables. An autonomous recording device was deployed over Kelvin Seamount from May to June 2006 and November 2006 to June 2007. A total of 6505 hourly two-minute recordings were examined for the presence of sperm whale echolocation clicks. Sperm whales were more prevalent around Kelvin in the spring (April to June: mean=51% of recordings contained clicks) compared to the winter (November to March: mean=16% of recordings contained clicks). Sperm whale prevalence at Kelvin was related to chlorophyll-a concentration four weeks previous, eddy kinetic energy and month. The mesoscale activity associated with the Gulf Stream and the Gulf Stream's interaction with the New England Seamount Chain likely play an important role in sperm whale occurrence in this area, by increasing productivity and perhaps concentration of cephalopod species.

High-frequency internal waves and thick bottom mixed layers observed by gliders in the Gulf Stream

NASA Astrophysics Data System (ADS)

Todd, Robert E.

2017-06-01

Autonomous underwater gliders are conducting high-resolution surveys within the Gulf Stream along the U.S. East Coast. Glider surveys reveal two mechanisms by which energy is extracted from the Gulf Stream as it flows over the Blake Plateau, a portion of the outer continental shelf between Florida and North Carolina where bottom depths are less than 1000 m. Internal waves with vertical velocities exceeding 0.1 m s-1 and frequencies just below the local buoyancy frequency are routinely found over the Blake Plateau, particularly near the Charleston Bump, a prominent topographic feature. These waves are likely internal lee waves generated by the subinertial Gulf Stream flow over the irregular bathymetry of the outer continental shelf. Bottom mixed layers with O(100) m thickness are also frequently encountered; these thick bottom mixed layers likely form in the lee of topography due to enhanced turbulence generated by O(1) m s-1 near-bottom flows.

Interannual variability of ring formations in the Gulf Stream region

NASA Astrophysics Data System (ADS)

Sasaki, Y. N.

2016-02-01

An oceanic ring in the Gulf Stream (GS) region plays important roles in across-jet transport of heat, salt, momentum, and nutrients. This study examines interannual variability of rings shed from the GS jet and their properties using satellite altimeter observations from 1993 to 2013. An objective method is used to capture a ring shedding from the GS jet and track its movement. A spatial distribution of the ring formations in the GS region showed that both cyclonic (cold-core) and anticyclonic (warm-core) rings were most frequently formed around the New England Seamount chain between 62°-65°W, suggesting the importance of the bottom topography on the pinch-off process. These rings moved westward, although about two-third of these rings was reabsorbed by the GS jet. The number of ring formations, especially cyclonic ring formations, indicated prominent fluctuations on interannual to decadal timescales. The annual maximum number of the pinched-off rings is four times larger than the annual minimum number of the rings. These fluctuations of the ring formations were negatively correlated with the strength of the GS. This situation is similar that in the Kuroshio Extension region. The interannual variability of the number of ring formations is also negatively correlated with the North Atlantic Oscillation (NAO) index with one-year lag (NAO leads). Interannual variations of the propagation tendency and shape of rings are also discussed.

Secular Change and Inter-annual Variability of the Gulf Stream Position, 1993-2013, 70°-55°W

NASA Astrophysics Data System (ADS)

Bisagni, J. J.; Gangopadhyay, A.

2016-12-01

The Gulf Stream (GS) is the northeastward-flowing surface limb of the Atlantic Ocean meridional overturning circulation (AMOC) "conveyer belt" that flows towards Europe and the Nordic Seas. Changes in the GS position after its separation from the coast at Cape Hatteras, i.e., from 75°W to 50°W, may be key to understanding the AMOC, sea level variability and ecosystem behavior along the east coast of North America. In this study we compare secular change and inter-annual variability (IAV) of annual mean Gulf Stream North Wall (GSNW) position with equator-ward Labrador Current (LC) transport along the southwestern Grand Banks near 52° W using 21 years (1993-2013) of satellite altimeter data. Results at 70°, 65°, 60° and 55° W show a southward secular trend for the GSNW, decreasing to the west. IAV of de-trended GSNW position residuals also decreases to the west. The long-term secular trend of annual mean upper layer LC transport increases near 52° W. Furthermore, IAV of LC transport residuals near 52° W is significantly correlated with GSNW position residuals at 55° W at a lag of +1-year. Spectral analysis reveals inter-annual peaks at 5-7 years and 2-3 years for the North Atlantic Oscillation (NAO), GSNW (65°-55°W) and LC transport for 1993-2013. A volume calculation using the LC rms residual of +1.04 Sv near 52° W results in an estimated GSNW residual of 79 km, or 63% of the observed 125.6 km (1.13°) rms value at 55° W. A similar volume calculation using the positive long-term, upper-layer LC transport trend accounts for 68% of the observed southward shift of the GSNW over the 1993-2013 period. Our work provides observational evidence of direct interaction between the upper layers of the sub-polar and sub-tropical gyres within the North Atlantic over secular and inter-annual time scales as suggested by previous workers.

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

Impact of Data Assimilation And Resolution On Modeling The Gulf Stream Pathway

DTIC Science & Technology

2011-11-18

currents could be generated by either the Deep Western Boundary Current (DWBC) associated with the Meridional Overturning Circulation (MOC) or by...abyssal gyre centered directly beneath the surface gyre. Figure 7. Meridional overturning circulation stream function for four 1/12° global HYCOM... circulation and have a weak overturning circulation . The Gulf Stream path is poorly simulated without the steering by the abyssal circulation . A

The Oleander Program - 9 years of Gulf Stream Sampling and Still Going Strong!

NASA Astrophysics Data System (ADS)

Rossby, T.

2001-12-01

Starting in Fall 1992 we have been monitoring the currents between the mid-Atlantic Bight and the NW Sargasso Sea with an acoustic Doppler current profiler on the freighter CMV Oleander, which makes weekly roundtrips between Port Elizabeth, NJ and Bermuda. In addition, XBTs and surface salts have been taken on a monthly basis since 1979. These systematic observations of the upper ocean are giving us new insights into the structure of the Gulf Stream and adjacent waters. In this overview we will highlight some of the major findings of this ongoing program. One of the more striking observations is perhaps the structural stability of the Gulf Stream itself. Its shape can be characterized as a double-exponential which results from the mixing or homogenization of waters between the current and either side, but not across it. We show that 80 percent of the Eulerian eddy kinetic energy that is observed in the Gulf Stream can be described in terms of the meandering of a rigid double-exponential current. The remaining variability can be accounted for in terms of a few structural modes that are most likely associated with the meandering of the current. We have found that the transport of the current has been conspicuously stable, and will argue that past thoughts about large variations in transport may result from an inability to distinguish between the current itself and adjacent local recirculations of varying intensity. The distinction is made clear thanks to the repeat sampling. However, the Gulf Stream does exhibit significant variations in mean path on interannual time scales. These show a strong correlation with temperature-salinity anomalies in the Slope Sea. We suggest that both result from time-varying transports from the Labrador shelf, but there is presently considerable discussion as to whether the path shifting should be viewed as a thermohaline or a winddriven process. More generally, we use the above examples to argue that with more deliberate planning, the unparalleled and repeat access to in-situ sampling of the oceans provided by commercial shipping and cruise vessels could provide society with far more extensive and valuable information about the ocean and atmospheric conditions at sea. But for this to happen, the instrumentation needs to be optimized for completely automatic and unattended operation. This also means working with the merchant marine community to develop guidelines and procedures for future cooperative efforts.

Short-finned Pilot Whales (Globicephala macrorhynchus) Target Gulf Stream and Shelf Break Waters in the U.S. Mid-Atlantic Bight

NASA Astrophysics Data System (ADS)

Thorne, L. H.; Foley, H.; Webster, D.; Baird, R.; Swaim, Z.; Read, A.

2016-02-01

Short-finned pilot whales (Globicephala macrorhynchus) are deep-diving predators that feed on squid and regularly exploit prey at depths of more than 500 m. Detailed information on the habitat use of pilot whales in the Northwest Atlantic is lacking, which complicates management of the species, particularly for efforts to mitigate bycatch and depredation in the pelagic longline fishery. To address this limitation, we tracked the horizontal and vertical movements of short-finned pilot whales with LIMPET satellite-linked transmitters off Cape Hatteras, North Carolina, in 2014. We deployed 14 satellite tags and 4 satellite-linked depth recording tags, with deployments of 2 to 194 days (mean=57 days). Using randomly-generated temporally-matched pseudo-absences with modeled distance constraints and mixed-effects generalized additive models (GAMMs), we evaluated pilot whale movement relative to environmental variables (distance to shelf break, sea surface temperature SST), location of Gulf Stream, bathymetric slope, and depth). Pilot whales showed two types of behavior, showing a strong affinity for either the shelf break or waters of the Gulf Stream. Slope, distance to shelf break, and SST were significant predictors of habitat use (p<<0.001 for all variables, R2=0.40). Pilot whales demonstrated a preference for waters close to the shelf break, with warmer SST values (peak preference 25°C) and medium to high bathymetric slopes (peak preference 40 percent rise). We observed seasonal patterns in pilot whale movements, with whales diving to deeper depths in late summer and fall months than in spring months (Wilcoxon test, p<<0.001). Diving behavior was also significantly influenced by SST; pilot whales took longer and deeper dives in warmer waters (Pearson's correlation coefficients >0.40, p<<0.001). We use these results to develop spatial maps of pilot whale habitat relative to seasonal and environmental factors in order to identify areas and times of high risk for interactions between pilot whales and longline gear.

The branching of the Gulf Stream southeast of the Grand Banks

NASA Astrophysics Data System (ADS)

Krauss, W.; KäSe, R. H.; Hinrichsen, H.-H.

1990-08-01

During March-April 1987, 101 hydrographic stations were occupied on three sections spanning a triangle between the Azores (Faial), the southern tip of the Grand Banks of Newfoundland, and Bermuda. Information on the near-surface processes in the interior of the triangle were obtained from 32 satellite-tracked buoys deployed during the cruise and a composite infrared image based on cloud-free NOAA 9 data during April 1987. The data were combined to analyze the eddy field and the branching of the Gulf Stream into the North Atlantic Current and the Azores Current. Calculations of mass transports through the legs of the triangle gave a total of 46 Sv supplied by the Gulf Stream, 31 Sv of which left the area as the North Atlantic Current and westwind drift north of the Azores. The remaining 14 Sv continued towards east-southeast as the Azores Current and southern recirculation. Additional conductivity-temperature-depth stations from a cruise in April 1986 into the same area allowed also study of the large-scale circulation within that triangle in deeper layers. The Azores Current appears as a baroclinic stream which reaches down to approximately 1000 m. Intensive mixing was observed at the continental slope of Newfoundland between water of the Labrador Current and the Gulf Stream (mixed water). Owing to cabbeling and consecutive convective mixing, this water penetrates down to 2000 m depth and creates horizontal density gradients to the surrounding Gulf Stream water, which intensifies the North Atlantic Current. This process is considered to be an important energy source for this current.

June and August median streamflows estimated for ungaged streams in southern Maine

USGS Publications Warehouse

Lombard, Pamela J.

2010-01-01

Methods for estimating June and August median streamflows were developed for ungaged, unregulated streams in southern Maine. The methods apply to streams with drainage areas ranging in size from 0.4 to 74 square miles, with percentage of basin underlain by a sand and gravel aquifer ranging from 0 to 84 percent, and with distance from the centroid of the basin to a Gulf of Maine line paralleling the coast ranging from 14 to 94 miles. Equations were developed with data from 4 long-term continuous-record streamgage stations and 27 partial-record streamgage stations. Estimates of median streamflows at the continuous-record and partial-record stations are presented. A mathematical technique for estimating standard low-flow statistics, such as June and August median streamflows, at partial-record streamgage stations was applied by relating base-flow measurements at these stations to concurrent daily streamflows at nearby long-term (at least 10 years of record) continuous-record streamgage stations (index stations). Weighted least-squares regression analysis (WLS) was used to relate estimates of June and August median streamflows at streamgage stations to basin characteristics at these same stations to develop equations that can be used to estimate June and August median streamflows on ungaged streams. WLS accounts for different periods of record at the gaging stations. Three basin characteristics-drainage area, percentage of basin underlain by a sand and gravel aquifer, and distance from the centroid of the basin to a Gulf of Maine line paralleling the coast-are used in the final regression equation to estimate June and August median streamflows for ungaged streams. The three-variable equation to estimate June median streamflow has an average standard error of prediction from -35 to 54 percent. The three-variable equation to estimate August median streamflow has an average standard error of prediction from -45 to 83 percent. Simpler one-variable equations that use only drainage area to estimate June and August median streamflows were developed for use when less accuracy is acceptable. These equations have average standard errors of prediction from -46 to 87 percent and from -57 to 133 percent, respectively.

Effect of timber harvesting on stormflow characteristics in headwater streams of managed, forested watersheds in the Upper Gulf Coastal Plain in Mississippi

Treesearch

Byoungkoo Choi; Jeff A. Hatten; Janet C. Dewey; Kyoichi Otsuki; Dusong Cha

2013-01-01

Headwater streams are crucial parts of overall watershed dynamics because they comprise more than 50–80% of stream networks and watershed land areas. This study addressed the influence of headwater areas (ephemeral and intermittent) on stormflow characteristics following harvest within three first–order catchments in the Upper Gulf Coastal Plain of Mississippi. Four...

Proceedings of the Workshop on Gulf Stream Structure and Variability Held at Research Triangle Park, North Carolina on 1-2 April 1982.

DTIC Science & Technology

1982-04-01

Fear. Deep Sea Res., 16, 225-231. Salby, M. L., 1981: Rossby normal modes in nonuniform background configurations. Part I: Simple fields. Part II...CUJRRENT METER 1363 m~ 1/4" WIRE So - 1I? GLASS FLOATS IGO I CHAIN 720 m ANCHOR lAIR W1145141 3300 I- Fig. 2. Florida Current test mooring 325

Near-Surface Transport Pathways in the North Atlantic Ocean: Looking for Throughput from the Subtropical to the Subpolar Gyre

NASA Astrophysics Data System (ADS)

Rypina, I. I.; Pratt, L. J.; Lozier, M.

2011-12-01

Motivated by discrepancies between Eulerian transport estimates and the behavior of Lagrangian surface drifters, near-surface transport pathways and processes in the North Atlantic are studied using a combination of data, altimetric surface heights, statistical analysis of trajectories, and dynamical systems techniques. Particular attention is paid to the issue of the subtropical-to-subpolar intergyre fluid exchange. The velocity field used in this study is composed of a steady drifter-derived background flow, upon which a time-dependent altimeter-based perturbation is superimposed. This analysis suggests that most of the fluid entering the subpolar gyre from the subtropical gyre within two years comes from a narrow region lying inshore of the Gulf Stream core, whereas fluid on the offshore side of the Gulf Stream is largely prevented from doing so by the Gulf Stream core, which acts as a strong transport barrier, in agreement with past studies. The transport barrier near the Gulf Stream core is robust and persistent from 1992 until 2008. The qualitative behavior is found to be largely independent of the Ekman drift.

Impacts of Mesoscale Eddies on the Vertical Nitrate Flux in the Gulf Stream Region

NASA Astrophysics Data System (ADS)

Zhang, Shuwen; Curchitser, Enrique N.; Kang, Dujuan; Stock, Charles A.; Dussin, Raphael

2018-01-01

The Gulf Stream (GS) region has intense mesoscale variability that can affect the supply of nutrients to the euphotic zone (Zeu). In this study, a recently developed high-resolution coupled physical-biological model is used to conduct a 25-year simulation in the Northwest Atlantic. The Reynolds decomposition method is applied to quantify the nitrate budget and shows that the mesoscale variability is important to the vertical nitrate supply over the GS region. The decomposition, however, cannot isolate eddy effects from those arising from other mesoscale phenomena. This limitation is addressed by analyzing a large sample of eddies detected and tracked from the 25-year simulation. The eddy composite structures indicate that positive nitrate anomalies within Zeu exist in both cyclonic eddies (CEs) and anticyclonic eddies (ACEs) over the GS region, and are even more pronounced in the ACEs. Our analysis further indicates that positive nitrate anomalies mostly originate from enhanced vertical advective flux rather than vertical turbulent diffusion. The eddy-wind interaction-induced Ekman pumping is very likely the mechanism driving the enhanced vertical motions and vertical nitrate transport within ACEs. This study suggests that the ACEs in GS region may play an important role in modulating the oceanic biogeochemical properties by fueling local biomass production through the persistent supply of nitrate.

A vorticity budget for the Gulf Stream

NASA Astrophysics Data System (ADS)

Le Bras, Isabela; Toole, John

2017-04-01

We develop a depth-averaged vorticity budget framework to diagnose the dynamical balance of the Gulf Stream, and apply this framework to observations and the ECCO state estimate (Wunsch and Heimbach 2013) above the thermocline in the subtropical North Atlantic. Using the hydrographic and ADCP data along the WOCE/CLIVAR section A22 and a variety of wind stress data products, we find that the advective vorticity flux out of the western region is on the same order as the wind stress forcing over the eastern portion of the gyre. This is consistent with a large-scale balance between a negative source of vorticity from wind stress forcing and a positive source of vorticity in the western region. Additionally, the form of the vorticity flux indicates that the Gulf Stream has a significant inertial component. In the ECCO state estimate, we diagnose a seasonal cycle in advective vorticity flux across a meridional section associated with seasonal fluctuations in Gulf Stream transport. This vorticity flux is forced by wind stress over the eastern subtropical North Atlantic and balanced by lateral friction with the western boundary. The lateral friction in ECCO is a necessary parameterization of smaller scale processes that occur in the real ocean, and quantifying these remains an open and interesting question. This simplified framework provides a means to interpret large scale ocean dynamics. In our application, it points to wind stress forcing over the subtropical North Altantic as an important regulator of the Gulf Stream and hence the climate system.

Estimating occurrence and detection probabilities for stream-breeding salamanders in the Gulf Coastal Plain

USGS Publications Warehouse

Lamb, Jennifer Y.; Waddle, J. Hardin; Qualls, Carl P.

2017-01-01

Large gaps exist in our knowledge of the ecology of stream-breeding plethodontid salamanders in the Gulf Coastal Plain. Data describing where these salamanders are likely to occur along environmental gradients, as well as their likelihood of detection, are important for the prevention and management of amphibian declines. We used presence/absence data from leaf litter bag surveys and a hierarchical Bayesian multispecies single-season occupancy model to estimate the occurrence of five species of plethodontids across reaches in headwater streams in the Gulf Coastal Plain. Average detection probabilities were high (range = 0.432–0.942) and unaffected by sampling covariates specific to the use of litter bags (i.e., bag submergence, sampling season, in-stream cover). Estimates of occurrence probabilities differed substantially between species (range = 0.092–0.703) and were influenced by the size of the upstream drainage area and by the maximum proportion of the reach that dried. The effects of these two factors were not equivalent across species. Our results demonstrate that hierarchical multispecies models successfully estimate occurrence parameters for both rare and common stream-breeding plethodontids. The resulting models clarify how species are distributed within stream networks, and they provide baseline values that will be useful in evaluating the conservation statuses of plethodontid species within lotic systems in the Gulf Coastal Plain.

Water Masses and Nutrient Sources to the Gulf of Maine

PubMed Central

Townsend, David W.; Pettigrew, Neal R.; Thomas, Maura A.; Neary, Mark G.; McGillicuddy, Dennis J.; O’Donnell, James

2016-01-01

The Gulf of Maine, a semi-enclosed basin on the continental shelf of the northwest Atlantic Ocean, is fed by surface and deep water flows from outside the Gulf: Scotian Shelf Water from the Nova Scotian shelf that enters the Gulf at the surface, and Slope Water that enters at depth and along the bottom through the Northeast Channel. There are two types of Slope Water, Labrador Slope Water (LSW) and Warm Slope Water (WSW); it is these deep water masses that are the major source of dissolved inorganic nutrients to the Gulf. It has been known for some time that the volume inflow of Slope Waters of either type that enters the Gulf of Maine is variable, that it co-varies with the magnitude of inflowing Scotian Shelf Water, and that periods of greater inflows of Scotian Shelf Water have become more frequent in recent years, accompanied by reduced Slope Water inflows. We present here analyses of a ten-year record of data collected by moored sensors in Jordan Basin, in the interior Gulf of Maine, and in the Northeast Channel, along with recent and historical hydrographic and nutrient data, that help reveal the nature of Scotian Shelf Water and Slope Water inflows. Proportional inflows of nutrient-rich Slope Waters and nutrient-poor Scotian Shelf Waters alternate episodically with one another on time scales of months to several years, creating a variable nutrient field upon which the biological productivities of the Gulf of Maine and Georges Bank depend. Unlike decades past, the inflows of Slope Waters of either type do not appear to be correlated with the North Atlantic Oscillation, which had been shown earlier to influence the relative proportions of the two Slope Waters, WSW and LSW, that enter the Gulf. We suggest that of greater importance in recent years are more frequent, episodic influxes of colder, fresher, less dense, and low-nutrient Scotian Shelf Water into the Gulf of Maine, and concomitant reductions in the inflow of deep, nutrient-rich Slope Waters. We also discuss evidence of modified Gulf Stream ring water that penetrated to Jordan Basin in summer of 2013. PMID:27721519

Water Masses and Nutrient Sources to the Gulf of Maine.

PubMed

Townsend, David W; Pettigrew, Neal R; Thomas, Maura A; Neary, Mark G; McGillicuddy, Dennis J; O'Donnell, James

2015-01-01

The Gulf of Maine, a semi-enclosed basin on the continental shelf of the northwest Atlantic Ocean, is fed by surface and deep water flows from outside the Gulf: Scotian Shelf Water from the Nova Scotian shelf that enters the Gulf at the surface, and Slope Water that enters at depth and along the bottom through the Northeast Channel. There are two types of Slope Water, Labrador Slope Water (LSW) and Warm Slope Water (WSW); it is these deep water masses that are the major source of dissolved inorganic nutrients to the Gulf. It has been known for some time that the volume inflow of Slope Waters of either type that enters the Gulf of Maine is variable, that it co-varies with the magnitude of inflowing Scotian Shelf Water, and that periods of greater inflows of Scotian Shelf Water have become more frequent in recent years, accompanied by reduced Slope Water inflows. We present here analyses of a ten-year record of data collected by moored sensors in Jordan Basin, in the interior Gulf of Maine, and in the Northeast Channel, along with recent and historical hydrographic and nutrient data, that help reveal the nature of Scotian Shelf Water and Slope Water inflows. Proportional inflows of nutrient-rich Slope Waters and nutrient-poor Scotian Shelf Waters alternate episodically with one another on time scales of months to several years, creating a variable nutrient field upon which the biological productivities of the Gulf of Maine and Georges Bank depend. Unlike decades past, the inflows of Slope Waters of either type do not appear to be correlated with the North Atlantic Oscillation, which had been shown earlier to influence the relative proportions of the two Slope Waters, WSW and LSW, that enter the Gulf. We suggest that of greater importance in recent years are more frequent, episodic influxes of colder, fresher, less dense, and low-nutrient Scotian Shelf Water into the Gulf of Maine, and concomitant reductions in the inflow of deep, nutrient-rich Slope Waters. We also discuss evidence of modified Gulf Stream ring water that penetrated to Jordan Basin in summer of 2013.

Detection and interpretation of ocean roughness variations across the Gulf Stream inferred from radar cross section observations

NASA Technical Reports Server (NTRS)

Weissman, D. E.; Thompson, T. W.

1977-01-01

Radar cross section data shows that the Gulf Stream has a higher cross section per unit area (interpreted here as a greater roughness) than the water on the continental shelf. A steep gradient in cross section was often seen at the expected location of the western boundary. There were also longer-scale (10-20 km) gradual fluctuations within the stream of significant magnitude. These roughness variations are correlated with the surface shear stress that the local wind imposes on the sea. Using the available surface-truth information concerning the wind speed and direction, an assumed Gulf Stream velocity profile, and high-resolution ocean-surface temperature data obtained by the VHRR onboard a NOAA-NESS polar-orbiting satellite, the present study demonstrates that the computed surface stress variation bears a striking resemblance to the measured radar cross-section variations.

Variability in Sea Surface Height: A Qualitative Measure for the Meridional Overturning in the North Atlantic

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa

1999-01-01

Sea surface height (SSH) from altimeter observations from 1992 on and from modeling results is investigated to determine the modes of variability and the linkages to the state of oceanic circulation in the North Atlantic. First the altimeter and model simulated SSH are analyzed using the empirical orthogonal function (EOF) analysis. They are found to share a similar leading mode where the center of action is along the Gulf Stream and North Atlantic Current with opposite sign anomalies in the subpolar gyre and in the slope waters along the Eastern Seaboard. The time series of the leading EOF mode from the altimeter data shows that between winters of 1995 and 1996, SSH over the Gulf Stream decreased by about 12cm which change is reproduced by the model simulation. Based on the relationship from the model simulations between the time series of the SSH EOF1 and meridional heat transport, it is suggested that associated with this SSH change in 1995-96, the overturning has slowed down from its heights in the early 90's. Furthermore, it is shown that decadal variability in the leading SSH mode originates from the thermal forcing component. This adds confidence to the qualitative relationship between the state of overturning/meridional heat transport and SSH in the limited area described by the EOF1. SSH variability in the eastern side of the North Atlantic basin, outside the western boundary current region, is determined by local and remote (Rossby waves) wind stress curl forcing.

Transport driven by eddy momentum fluxes in the Gulf Stream Extension region

NASA Astrophysics Data System (ADS)

Greatbatch, R. J.; Zhai, X.; Claus, M.; Czeschel, L.; Rath, W.

2010-12-01

The importance of the Gulf Stream Extension region in climate and seasonal prediction research is being increasingly recognised. Here we use satellite-derived eddy momentum fluxes to drive a shallow water model for the North Atlantic Ocean that includes the realistic ocean bottom topography. The results show that the eddy momentum fluxes can drive significant transport, sufficient to explain the observed increase in transport of the Gulf Stream following its separation from the coast at Cape Hatteras, as well as the observed recirculation gyres. The model also captures recirculating gyres seen in the mean sea surface height field within the North Atlantic Current system east of the Grand Banks of Newfoundland, including a representation of the Mann Eddy.

Frontal Eddy Dynamics (FRED) experiment off North Carolina: Volume 1. Executive summary

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

Ebbesmeyer, C.C.

1989-03-01

In preparation for oil and gas lease sales on the outer continental shelf offshore of North Carolina, the Minerals Management Service was requested to investigate the potential transport and impacts of oil spilled offshore. The Gulf Stream and associated eddies are an important aspect of the transport. Although the speed and location of the Gulf Stream are reasonably well known, knowledge of the meanders of the Gulf Stream is limited. How the circulatory structure and movement of associated frontal eddies and filaments affect the North Carolina coastal waters is not clear. This study investigates the interactions of these circulatory elementsmore » and follows the evolution of frontal eddies as they migrate along the North Carolina coast.« less

Monthly Maps of Sea Surface Height in the North Atlantic and Zonal Indices for the Gulf Stream Using TOPEX/Poseidon Altimeter Data

NASA Technical Reports Server (NTRS)

Singh, Sandipa; Kelly, Kathryn A.

1997-01-01

Monthly Maps of sea surface height are constructed for the North Atlantic Ocean using TOPEX/Poseidon altimeter data. Mean sea surface height is reconstructed using a weighted combination of historical, hydrographic data and a synthetic mean obtained by fitting a Gaussian model of the Gulf Stream jet to altimeter data. The resultant mean shows increased resolution over the hydrographic mean, and incorporates recirculation information that is absent in the synthetic mean. Monthly maps, obtained by adding the mean field to altimeter sea surface height residuals, are used to derive a set of zonal indices that describe the annual cycle of meandering as well as position and strength of the Gulf Stream.

Collecting Currents with Water Turbines

NASA Astrophysics Data System (ADS)

Allen, J.; Allen, S.

2017-12-01

Our science poster is inspired by Florida Atlantic University's recent program to develop three types of renewable energy. They are using water turbines and the Gulf Stream Current to produce a renewable energy source. Wave, tidal and current driven energy. Our poster is called "Collecting Currents with Water Turbines". In our science poster, the purpose was to see which turbine design could produce the most power. We tested three different variables, the number of blades (four, six, and eight), the material of the blades and the shape of the blades. To test which number of blades produced the most power we cut slits into a cork. We used plastic from a soda bottle to make the blades and then we put the blades in the cork to make the turbines. We observed each blade and how much time it took for the water turbines to pull up 5 pennies. Currently water turbines are used in dams to make hydroelectric energy. But with FAU we could understand how to harness the Gulf Stream current off Florida's coast we could soon have new forms of renewable energy.

Impact Of Resolving Submesoscale Features On Modeling The Gulf Stream System

NASA Astrophysics Data System (ADS)

Chassignet, E.; Xu, X.

2016-02-01

Despite being one the best-known circulation pattern of the world ocean, the representation of the Gulf Stream, especially its energetic extension east of the New England Seamounts Chains in the western North Atlantic Ocean, has been a major challenge for ocean general circulation models even at eddy-rich resolutions. Here we show that, for the first time, a simulation of the North Atlantic circulation at 1/50° resolution realistically represents the narrow, energetic jet near 55°W when compared to observations, whereas similarly configured simulations at 1/25° and 1/12° resolution do not. This result highlights the importance of submesoscale features in driving the energetic Gulf Stream extension in the western North Atlantic. The results are discussed in terms of mesoscale and submesoscale energy power spectra.

Climatic teleconnections between the subtropical and polar North Atlantic during the Last Interglacial period (MIS5e)

NASA Astrophysics Data System (ADS)

Bauch, H. A.; Zhuravleva, A.

2017-12-01

Meridional gradients in sea surface temperature (SST) control ocean-atmosphere circulation patterns and, thus, regulate the global climate. Here we reconstruct variability of these gradients in the course of the Last Interglacial (MIS5e), by using sediment records from the low and high latitude North Atlantic which are linked via the Gulf Stream.In the Nordic Seas, i.e., at the northern end of the Gulf Stream extension, strong post-Saalian meltwater discharge reduced northward-directed transport of surface oceanic heat until the mid-MIS5e, resulting in a late and rather weak SST peak. To decipher the corresponding climatic changes in the area of the Gulf Stream origin, we employ stable isotopes data, planktic foraminifera assemblages as well as a new alkenone paleotemperature record from core drilled on the upper northern slope of the Little Bahama Bank. In addition, chemical composition of sediments (XRF data) was used to asses past sea level fluctuations and sedimentation regimes on this shallow-water carbonate bank. Significant variations in Sr/Ca ratios point to a two-fold structure of the Last Interglacial. Stabilized Sr/Ca values were reached only during the second phase of MIS5e, possibly representing the interval of maximum bank-top flooding after the northern hemisphere deglaciation terminated. Faunal-based proxies as well as oxygen isotopic gradients between surface and bottom-dwelling foraminifera corroborate existence of the two major climatic phases within the Last Interglacial, in agreement with the respective development in the polar region. This further suggests a strong climatic coupling between the subtropical and high-latitude North Atlantic with important implications for meridional SST gradients during the Last Interglacial.

Gulf Stream Temperature, Salinity and Transport During the Last Millennium

DTIC Science & Technology

2006-02-01

their relationship to 9 one another and to proxies of solar variability. Chapter 3 addresses the temperature and salinity components of the...Florida Current 618Oc varied coherently with proxies of atmospheric radiocarbon at low frequencies over 10 the last 5,000 years, suggesting a link...cooling that began around 1000 A.D. models and proxies used. This two-stage character of the LIA is not apparent in the Florida margin cores. 6.4

The dynamics of oceanic fronts. I - The Gulf Stream

NASA Technical Reports Server (NTRS)

Kao, T. W.

1980-01-01

The establishment and maintenance of the mean hydrographic properties of large-scale density fronts in the upper ocean is considered. The dynamics is studied by posing an initial value problem starting with a near-surface discharge of buoyant water with a prescribed density deficit into an ambient stationary fluid of uniform density; full time dependent diffusion and Navier-Stokes equations are then used with constant eddy diffusion and viscosity coefficients, together with a constant Coriolis parameter. Scaling analysis reveals three independent scales of the problem including the radius of deformation of the inertial length, buoyancy length, and diffusive length scales. The governing equations are then suitably scaled and the resulting normalized equations are shown to depend on the Ekman number alone for problems of oceanic interest. It is concluded that the mean Gulf Stream dynamics can be interpreted in terms of a solution of the Navier-Stokes and diffusion equations, with the cross-stream circulation responsible for the maintenance of the front; this mechanism is suggested for the maintenance of the Gulf Stream dynamics.

Preliminary estimates of Gulf Stream characteristics from TOPEX data and a precise gravimetric geoid

NASA Technical Reports Server (NTRS)

Rapp, Richard H.; Smith, Dru A.

1994-01-01

TOPEX sea surface height data has been used, with a gravimetric geoid, to calculate sea surface topography across the Gulf Stream. This topography was initially computed for nine tracks on cycles 21 to 29. Due to inaccurate geoid undulations on one track, results for eight tracks are reported. The sea surface topography estimates were used to calculate parameters that describe Gulf Stream characteristics from two models of the Gulf Stream. One model was based on a Gaussian representation of the velocity while the other was a hyperbolic representation of velocity or the sea surface topography. The parameters of the Gaussian velocity model fit were a width parameter, a maximum velocity value, and the location of the maximum velocity. The parameters of the hyperbolic sea surface topography model were the width, the height jump, position, and sea surface topography at the center of the stream. Both models were used for the eight tracks and nine cycles studied. Comparisons were made between the width parameters, the maximum velocities, and the height jumps. Some of the parameter estimates were found to be highly (0.9) correlated when the hyperbolic sea surface topography fit was carried out, but such correlations were reduced for either the Gaussian velocity fits or the hyperbolic velocity model fit. A comparison of the parameters derived from 1-year TOPEX data showed good agreement with values derived by Kelly (1991) using 2.5 years of Geosat data near 38 deg N, 66 deg W longitude. Accuracy of the geoid undulations used in the calculations was of order of +/- 16 cm with the accuracy of a geoid undulation difference equal to +/- 15 cm over a 100-km line in areas with good terrestrial data coverage. This paper demonstrates that our knowledge or geoid undulations and undulation differences, in a portion of the Gulf Stream region, is sufficiently accurate to determine characteristics of the jet when used with TOPEX altimeter data. The method used here has not been shown to be more accurate than methods that average altimeter data to form a reference surface used in analysis to obtain the Gulf Stream characteristics. However, the results show the geoid approach may be used in areas where lack of current meandering reduces the accuracy of the average surface procedure.

Ku-band ocean radar backscatter observations during SWADE

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Li, F. K.; Lou, S. H.; Neumann, G.

1993-01-01

We present results obtained by an airborne Ku-band scatterometer during the Surface Wave Dynamics Experiment (SWADE). The specific objective of this study is to improve our understanding of the relationship between ocean radar backscatter and near surface winds. The airborne scatterometer, NUSCAT, was flown on the NASA Ames C-130 over an instrumented oceanic area near 37 deg N and 74 deg W. A total of 10 flights from 27 Feb. to 9 Mar. 1991 were conducted. Radar backscatter at incidence angles of 0 to 60 deg were obtained. For each incidence angle, the NUSCAT antenna was azimuthally scanned in multiple complete circles to measure the azimuthal backscatter modulations. Both horizontal and vertical polarization backscatter measurements were made. In some of the flights, the cross-polarization backscatter was measured as well. Internal calibrations were carried out throughout each of the flights. Preliminary results indicate that the radar was stable to +/-0.3 dB for each flight. In this paper, we present studies of the backscatter measurements over several crossings of the Gulf Stream. In these crossings, large air-sea temperature differences were encountered and substantial changes in the radar cross section were observed. We summarize the observations and compare them to the changes of several wind variables across the Gulf Stream boundary. In one of the flights, the apparent wind near the cold side of the Gulf Stream was very low (less than 3 m/s). The behavior of the radar cross sections at such low wind speeds and a comparison with models are presented. A case study of the effects of swell on the absolute cross section and the azimuthal modulation pattern is presented. Significant wave heights larger than m were observed during SWADE. The experimentally observed effects of the swell on the radar backscatter are discussed. The effects are used to assess the uncertainties in wind retrieval due to underlying waves. A summary of azimuthal modulation from our ten-flight of NUSCAT data is given. Wind velocities, air and sea surface temperature, ocean spectrum, and other variables measured from aircraft and buoys are also shown.

Rotary motions and convection as a means of regulating primary production in warm core rings. [of ocean currents

NASA Technical Reports Server (NTRS)

Yentsch, C. S.; Phinney, D. A.

1985-01-01

The term 'ring' is generally used in the case of a subdivision of ocean eddies. in the present investigation, it denotes mesoscale features which are spawned by the Gulf Stream. This investigation is concerned with the mechanism involved in the regulation of the growth of phytoplankton by the physical oceanographic features of rings. Gulf Stream rings were first observed by Parker (1971) and Fuglister (1972) as a result of extensive temperature measurements from ships in the Gulf Stream. Attention is given to changes in density boundaries associated with the rotation of rings, a synthetic model of a newly formed warm core ring, convection-stabilization, the role of light, the influence of convective overturn in adding nutrients to surface waters of warm core rings, and two major areas which require study.

Predicting and explaining the movement of mesoscale oceanographic features using CLIPS

NASA Technical Reports Server (NTRS)

Bridges, Susan; Chen, Liang-Chun; Lybanon, Matthew

1994-01-01

The Naval Research Laboratory has developed an oceanographic expert system that describes the evolution of mesoscale features in the Gulf Stream region of the northwest Atlantic Ocean. These features include the Gulf Stream current and the warm and cold core eddies associated with the Gulf Stream. An explanation capability was added to the eddy prediction component of the expert system in order to allow the system to justify the reasoning process it uses to make predictions. The eddy prediction and explanation components of the system have recently been redesigned and translated from OPS83 to C and CLIPS and the new system is called WATE (Where Are Those Eddies). The new design has improved the system's readability, understandability and maintainability and will also allow the system to be incorporated into the Semi-Automated Mesoscale Analysis System which will eventually be embedded into the Navy's Tactical Environmental Support System, Third Generation, TESS(3).

Gulf stream velocity structure through combined inversion of hydrographic and acoustic Doppler data

NASA Technical Reports Server (NTRS)

Pierce, S. D.

1986-01-01

Near-surface velocities from an acoustic Doppler instrument are used in conjunction with CTD/O2 data to produce estimates of the absolute flow field off Cape Hatteras. The data set consists of two transects across the Gulf Stream made by the R/V Endeavor cruise EN88 in August 1982. An inverse procedure is applied which makes use of both the acoustic Doppler data and property conservation constraints. Velocity sections at approximately 73 deg. W and 71 deg. W are presented with formal errors of 1-2 cm/s. The net Gulf Stream transports are estimated to be 116 + or - 2 Sv across the south leg and 161 + or - 4 Sv across the north. A Deep Western Boundary Current transport of 4 + or - 1 Sv is also estimated. While these values do not necessarily represent the mean, they are accurate estimates of the synoptic flow field in the region.

The likelihood of winter sprites over the Gulf Stream

NASA Astrophysics Data System (ADS)

Price, Colin; Burrows, William; King, Patrick

2002-11-01

With the recent introduction of the Canadian Lightning Detection Network (CLDN), it was revealed that during the winter months every year, the highest lightning activity within the network occurs over the Gulf Stream, southeast of Nova Scotia. These storms over the Gulf Stream, in addition to being of importance to trans-Atlantic shipping and aviation, have an unusually high fraction of positive polarity lightning, with unusually large peak currents. Such intense positive lightning flashes are known to generate transient luminous events (TLEs) such as sprites and elves in the upper atmosphere. It is found that many of these large positive discharges produce extremely low frequency (ELF) electromagnetic radiation detected at a field station in the Negev Desert, Israel, 8000 km away, in agreement with previously documented sprite observations. Since these winter storms occur in the same location every year, it provides a good opportunity for field experiments focused on studying winter sprites and oceanic thunderstorms.

AIRSAR observations of the Gulf Stream with interpretation from sea truth and modeling

NASA Technical Reports Server (NTRS)

Valenzuela, G. R.; Chubb, S. R.; Marmorino, G. O.; Trump, C. L.; Lee, J. S.; Cooper, A. L.; Askari, F.; Keller, W. C.; Kaiser, J. A. C.; Mied, R. P.

1991-01-01

On 20 Jul., JPL/DC-8 synthetic aperture radar (SAR) participated in the 17-21 Jul. 1990 NRL Gulf Stream (GS) experiment in preparation for SIR-C missions in 1993, 1994, and 1996 for calibration purposes and to check modes and techniques for operation at our experimental site off the east coast of the US. During this experiment, coordinated and near simultaneous measurements were performed from ship (R/V Cape Henlopen) and other aircraft (NADC/P-3 and NRL/P-3) to address scientific questions relating to the origin of 'slick-like' features observed by Scully-Power, the refraction and modulation of waves by variable currents, the effect of current and thermal fronts on radar imagery signatures and the modification of Kelvin ship wakes by fronts. The JPL/DC-8 and NADC/P-3 SAR's are fully polarimetric systems. Their composite frequency range varies between P- and X-band. We describe in detail the Airborne SAR (AIRSAR) participation in the Jul. 1990 GS experiment and present preliminary results of the ongoing analysis and interpretation of the radar imagery in the context of ground truth, other remote measurements, and modeling efforts.

Florida, Bahamas, Cuba and Gulf Stream, USA

NASA Image and Video Library

1992-08-08

This unique photo offers a view of the Florida peninsula, western Bahamas, north central Cuba and the deep blue waters of the Gulf Stream, that hugs the east coast of Florida (27.0N, 82.0W). In addition to being an excellent photograph for showing the geographical relationships between the variety of landforms in this scene, the typical effect of the land-sea breeze is very much in evidence as few clouds over water, cumulus build up over landmass.

Sandals and Robes to Business Suits and Gulf Streams: Warfare in the 21st Century

DTIC Science & Technology

2011-04-20

movements and the extremist environments in which these movements operate. However, much like a franchise business enterprise, AQ is expanding its...2011, Small Wars Foundation April 20, 2011 Sandals and Robes to Business Suits and Gulf Streams: Warfare in the 21st Century by MG Michael T...comfortable in sandals and robes as they are wearing business suits and flying around the world in gulfstream aircraft. As confident in their ability to

Sources and Delivery of Nutrients to the Northwestern Gulf of Mexico from Streams in the South-Central United States1

PubMed Central

Rebich, Richard A; Houston, Natalie A; Mize, Scott V; Pearson, Daniel K; Ging, Patricia B; Evan Hornig, C

2011-01-01

Abstract SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed to estimate nutrient inputs [total nitrogen (TN) and total phosphorus (TP)] to the northwestern part of the Gulf of Mexico from streams in the South-Central United States (U.S.). This area included drainages of the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf hydrologic regions. The models were standardized to reflect nutrient sources and stream conditions during 2002. Model predictions of nutrient loads (mass per time) and yields (mass per area per time) generally were greatest in streams in the eastern part of the region and along reaches near the Texas and Louisiana shoreline. The Mississippi River and Atchafalaya River watersheds, which drain nearly two-thirds of the conterminous U.S., delivered the largest nutrient loads to the Gulf of Mexico, as expected. However, the three largest delivered TN yields were from the Trinity River/Galveston Bay, Calcasieu River, and Aransas River watersheds, while the three largest delivered TP yields were from the Calcasieu River, Mermentau River, and Trinity River/Galveston Bay watersheds. Model output indicated that the three largest sources of nitrogen from the region were atmospheric deposition (42%), commercial fertilizer (20%), and livestock manure (unconfined, 17%). The three largest sources of phosphorus were commercial fertilizer (28%), urban runoff (23%), and livestock manure (confined and unconfined, 23%). PMID:22457582

Global Autocorrelation Scales of the Partial Pressure of Oceanic CO2

NASA Technical Reports Server (NTRS)

Li, Zhen; Adamec, David; Takahashi, Taro; Sutherland, Stewart C.

2004-01-01

A global database of approximately 1.7 million observations of the partial pressure of carbon dioxide in surface ocean waters (pCO2) collected between 1970 and 2003 is used to estimate its spatial autocorrelation structure. The patterns of the lag distance where the autocorrelation exceeds 0.8 is similar to patterns in the spatial distribution of the first baroclinic Rossby radius of deformation indicating that ocean circulation processes play a significant role in determining the spatial variability of pCO2. For example, the global maximum of the distance at which autocorrelations exceed 0.8 averages about 140 km in the equatorial Pacific. Also, the lag distance at which the autocorrelation exceed 0.8 is greater in the vicinity of the Gulf Stream than it is near the Kuroshio, approximately 50 km near the Gulf Stream as opposed to 20 km near the Kuroshio. Separate calculations for times when the sun is north and south of the equator revealed no obvious seasonal dependence of the spatial autocorrelation scales. The pCO2 measurements at Ocean Weather Station (OWS) 'P', in the eastern subarctic Pacific (50 N, 145 W) is the only fixed location where an uninterrupted time series of sufficient length exists to calculate a meaningful temporal autocorrelation function for lags greater than a few days. The estimated temporal autocorrelation function at OWS 'P', is highly variable. A spectral analysis of the longest four pCO2 time series indicates a high level of variability occurring over periods from the atmospheric synoptic to the maximum length of the time series, in this case 42 days. It is likely that a relative peak in variability with a period of 3-6 days is related to atmospheric synoptic period variability and ocean mixing events due to wind stirring. However, the short length of available time series makes identifying temporal relationships between pCO2 and atmospheric or ocean processes problematic.

Gulf Coast Deep Water Port Facilities study. Appendix B. North Central Gulf Hydrobiological Zones.

DTIC Science & Technology

1973-04-01

bottom and surface salinities , but their effect is more noticeable at the surface. Because of variation in these factors along the Gulf Coast... effects of discharge on salinity have been considered above. Numerous streams empty into the Gulf of Mexico along its north central portion but the...1967) investigated various aspects of osmoregulation in blue crabs in Mississippi Sound and adjacent waters and observed that salinity and temperature

The Baselines Project: Establishing Reference Environmental Conditions for Marine Habitats in the Gulf of Mexico using Forecast Models and Satellite Data

NASA Astrophysics Data System (ADS)

Jolliff, J. K.; Gould, R. W.; deRada, S.; Teague, W. J.; Wijesekera, H. W.

2012-12-01

We provide an overview of the NASA-funded project, "High-Resolution Subsurface Physical and Optical Property Fields in the Gulf of Mexico: Establishing Baselines and Assessment Tools for Resource Managers." Data assimilative models, analysis fields, and multiple satellite data streams were used to construct temperature and photon flux climatologies for the Flower Garden Banks National Marine Sanctuary (FGBNMS) and similar habitats in the northwestern Gulf of Mexico where geologic features provide a platform for unique coral reef ecosystems. Comparison metrics of the products to in situ data collected during complimentary projects are also examined. Similarly, high-resolution satellite-data streams and advanced processing techniques were used to establish baseline suspended sediment load and turbidity conditions in selected northern Gulf of Mexico estuaries. The results demonstrate the feasibility of blending models and data into accessible web-based analysis products for resource managers, policy makers, and the public.

The Gulf Stream Pathway and the Impacts of the Eddy-Driven Abyssal Circulation and the Deep Western Boundary Current

DTIC Science & Technology

2008-07-06

bathymetry, wind forcing, and a meridional overturning circulation (MOC), the latter specified via ports in the northern and southern boundaries. The...small values below the sill depth in all of the simulations. e The upper ocean northward flow of the meridional overturning circulation (MOC) is...plus the northward upper ocean flow (14 Sv) of the meridional overturning circulation (MOC). The mean Gulf Stream IR northwall pathway ±lrr from

Proceedings of the Gulf Stream Workshop Held at West Greenwich, Rhode Island on 23-26 April 1985,

DTIC Science & Technology

1985-04-01

complex. We now realize that a correct dytiamical description must intrinsically couple the mass-, momentum -, energy-, and vorticity-fluxes of a strong mean...path and structure, and the mass- and momentum transport. 2. Meander dynamics "intrinsic" to the Gulf Stream, such as growth and propagation of...contribute to the dissipation of momentum through wave and form drag. A general study of the influence of the seamounts seems more appropriate for the

Electronic research and technology requirements for marine resources

NASA Technical Reports Server (NTRS)

Ewing, G. C.

1971-01-01

The Woods Hole air/space oceanographic program for 1969 is discussed. Studies included: (1) monitoring the sharp temperature boundary of the Gulf Stream by microwave and infrared observation, (2) spectrophotometry of the Gulf Stream and the adjacent continental slope and shelf water over Georges Bank, (3) interpretation of cloud and other meteorological data in terms of the effects of wind and sun on the upper ocean, (4) a sea state test plan, (5) systems research, and (6) ocean data recovery by aircraft and satellite.

Thunderstorm, Texas Gulf Coast, USA

NASA Image and Video Library

1990-04-29

This thunderstorm along the Texas Gulf Coast (29.0N, 95.0W), USA is seen as the trailing edge of a large cloud mass formed along the leading edge of a spring frontal system stretching northwest to southeast across the Texas Gulf Coast. This system brought extensive severe weather and flooding to parts of Texas and surrounding states. Muddy water discharging from coastal streams can be seen in the shallow Gulf of Mexico as far south as Lavaca Bay.

Hydrographic data from R/V endeavor cruise #90

NASA Technical Reports Server (NTRS)

Stalcup, M. D.; Joyce, T. M.; Barbour, R. L.; Dunworth, J. A.

1986-01-01

The final cruise of the NSF sponsored Warm Core Rings Program studied a Warm Core Ring (WCR) in the Fall of 1982 as it formed from a large northward meander of the Gulf Stream. This ring, known as 82-H or the eighth ring identified in 1982, formed over the New England Seamounts near 39.5 deg N, 65 deg W. Surveys using Expendable Bathythermographs, Conductivity-Temperature-Depth-Oxygen stations and Doppler Current Profiling provide a look at the genesis of a WCR. These measurements reveal that WCR 82-H separated from the Gulf Stream sometime between October 2-5. This ring was a typical WCR with a diameter of about 200 km and speeds in the high velocity core of the 175 cm/sec. Satellite imagery of 82-H following the cruise showed that it drifted WSW in the Slope Water region at almost 9 km/day, had at least one interaction with the Gulf Stream and was last observed on February 8, 1983 at 39 deg N, 72 deg W.

Influence of ENSO on Gulf Stream cyclogenesis and the North Atlantic storm track

NASA Astrophysics Data System (ADS)

Li, C.; Schemm, S.; Ciasto, L.; Kvamsto, N. G.

2015-12-01

There is emerging evidence that climate in the North Atlantic-European sector is sensitive to vacillations of tropical Pacific sea surface temperatures, in particular, the central Pacific flavour of the El Nino Southern Oscillation (ENSO) and concomitant trends in atmospheric heating. The frequency of central Pacific ENSOs appears to have increased over the last decades and some studies suggest it may continue increasing in the future, but the precise mechanisms by which these events affect the North Atlantic synoptic scale circulation are poorly understood. Here, we show that central Pacific ENSOs influence where midlatitude cyclogenesis occurs over the Gulf Stream, producing more cyclogenesis in the jet exit region rather than in the climatologically preferred jet entrance region. The cyclones forming over the Gulf Stream in central Pacific ENSO seasons tend to veer north, penetrating deeper into the Arctic rather than into continental Europe. The shift in cyclogenesis is linked to changes in the large scale circulation, namely, the upper-level trough formed in the lee of the Rocky Mountains.

Downscaling ocean conditions with application to the Gulf of Maine, Scotian Shelf and adjacent deep ocean

NASA Astrophysics Data System (ADS)

Katavouta, Anna; Thompson, Keith

2017-04-01

A high resolution regional model (1/36 degree) of the Gulf of Maine, Scotian Shelf and adjacent deep ocean (GoMSS) is developed to downscale ocean conditions from an existing global operational system. First, predictions from the regional GoMSS model in a one-way nesting set up are evaluated using observations from multiple sources including satellite-borne sensors of surface temperature and sea level, CTDs, Argo floats and moored current meters. It is shown that on the shelf, the regional model predicts more realistic fields than the global system because it has higher resolution and includes tides that are absent from the global system. However, in deep water the regional model misplaces deep ocean eddies and meanders associated with the Gulf Stream. This is because of unrealistic internally generated variability (associated with the one-way nesting set up) that leads to decoupling of the regional model from the global system in the deep water. To overcome this problem, the large scales (length scales > 90 km) of the regional model are spectrally nudged towards the global system fields. This leads to more realistic predictions off the shelf. Wavenumber spectra show that even though spectral nudging constrains the large scales, it does not suppress the variability on small scales; on the contrary, it favours the formation of eddies with length scales below the cut-off wavelength of the spectral nudging.

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.

Sources and Delivery of Nutrients to the Northwestern Gulf of Mexico from Streams in the South-Central United States

USGS Publications Warehouse

Rebich, R.A.; Houston, N.A.; Mize, S.V.; Pearson, D.K.; Ging, P.B.; Evan, Hornig C.

2011-01-01

SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed to estimate nutrient inputs [total nitrogen (TN) and total phosphorus (TP)] to the northwestern part of the Gulf of Mexico from streams in the South-Central United States (U.S.). This area included drainages of the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf hydrologic regions. The models were standardized to reflect nutrient sources and stream conditions during 2002. Model predictions of nutrient loads (mass per time) and yields (mass per area per time) generally were greatest in streams in the eastern part of the region and along reaches near the Texas and Louisiana shoreline. The Mississippi River and Atchafalaya River watersheds, which drain nearly two-thirds of the conterminous U.S., delivered the largest nutrient loads to the Gulf of Mexico, as expected. However, the three largest delivered TN yields were from the Trinity River/Galveston Bay, Calcasieu River, and Aransas River watersheds, while the three largest delivered TP yields were from the Calcasieu River, Mermentau River, and Trinity River/Galveston Bay watersheds. Model output indicated that the three largest sources of nitrogen from the region were atmospheric deposition (42%), commercial fertilizer (20%), and livestock manure (unconfined, 17%). The three largest sources of phosphorus were commercial fertilizer (28%), urban runoff (23%), and livestock manure (confined and unconfined, 23%). ?? 2011 American Water Resources Association. This article is a U.S. Government work and is in the public domain in the USA.

Gulf Atlantic Coastal Plain Long Term Agroecosystem Research site, Tifton, GA

Treesearch

Timothy Strickland; David D. Bosch; Dinku M. Endale; Thomas L. Potter

2016-01-01

The Gulf-Atlantic Coastal Plain (GACP) physiographic region is an important agricultural production area within the southeastern U.S. that extends from Delaware in the Northeast to the Gulf Coast of Texas. The region consists mainly of low-elevation flat to rolling terrain with numerous streams, abundant rainfall, a complex coastline, and many wetlands. The GACP Long ...

A multigear protocol for sampling crayfish assemblages in Gulf of Mexico coastal streams

Treesearch

William R. Budnick; William E. Kelso; Susan B. Adams; Michael D. Kaller

2018-01-01

Identifying an effective protocol for sampling crayfish in streams that vary in habitat and physical/chemical characteristics has proven problematic. We evaluated an active, combined-gear (backpack electrofishing and dipnetting) sampling protocol in 20 Coastal Plain streams in Louisiana. Using generalized linear models and rarefaction curves, we evaluated environmental...

Continuous proxy measurements reveal large mercury fluxes from glacial and forested watersheds in Alaska.

PubMed

Vermilyea, Andrew W; Nagorski, Sonia A; Lamborg, Carl H; Hood, Eran W; Scott, Durelle; Swarr, Gretchen J

2017-12-01

In this study, a stream from a glacially dominated watershed and one from a wetland, temperate forest dominated watershed in southeast Alaska were continuously monitored for turbidity and fluorescence from dissolved organic matter (FDOM) while grab samples for unfiltered (UTHg), particulate (PTHg), and filtered mercury (FTHg) where taken over three 4-day periods (May snowmelt, July glacial melt, and September rainy season) during 2010. Strong correlations were found between FDOM and UTHg concentrations in the wetland, temperate forest watershed (r 2 =0.81), while turbidity and UTHg were highly correlated in the glacially dominated watershed (r 2 =0.82). Both of these parameters (FDOM and turbidity) showed stronger correlations than concentration-discharge relationships for UTHg (r 2 =0.55 for glacial stream, r 2 =0.38 for wetland/forest stream), thus allowing for a more precise determination of temporal variability in UTHg concentrations and fluxes. The association of mercury with particles and dissolved organic matter (DOM) appears to depend on the watershed characteristics, such as physical weathering and biogeochemical processes regulating mercury transport. Thus employing watershed-specific proxies for UTHg (such as FDOM and turbidity) can be effective for quantifying mercury export from watersheds with variable landcover. The UTHg concentration in the forest/wetland stream was consistently higher than in the glacial stream, in which most of the mercury was associated with particles; however, due to the high specific discharge from the glacial stream during the melt season, the watershed area normalized flux of mercury from the glacial stream was 3-6 times greater than the wetland/forest stream for the three sampling campaigns. The annual specific flux for the glacial watershed was 19.9gUTHgkm -2 y -1 , which is higher than any non-mining impacted stream measured to date. This finding indicates that glacial watersheds of southeast Alaska may be important conduits of total mercury to the Gulf of Alaska. Copyright © 2017 Elsevier B.V. All rights reserved.

Verification of ADS-B performance to provide 5 nautical mile separation services in the Gulf of Mexico

DOT National Transportation Integrated Search

2010-01-01

Prior to Automatic Dependent SurveillanceBroadcast (ADS-B), non-radar separation was necessary in the Gulf of Mexico due to limited surveillance and air-ground communication. Five nautical mile separation using ADS-B improves capacity and streamli...

Temporal variability of the Atlantic meridional overturning circulation at 26.5 degrees N.

PubMed

Cunningham, Stuart A; Kanzow, Torsten; Rayner, Darren; Baringer, Molly O; Johns, William E; Marotzke, Jochem; Longworth, Hannah R; Grant, Elizabeth M; Hirschi, Joël J-M; Beal, Lisa M; Meinen, Christopher S; Bryden, Harry L

2007-08-17

The vigor of Atlantic meridional overturning circulation (MOC) is thought to be vulnerable to global warming, but its short-term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain. We combine continuous measurements of the MOC (beginning in 2004) using the purposefully designed transatlantic Rapid Climate Change array of moored instruments deployed along 26.5 degrees N, with time series of Gulf Stream transport and surface-layer Ekman transport to quantify its intra-annual variability. The year-long average overturning is 18.7 +/- 5.6 sverdrups (Sv) (range: 4.0 to 34.9 Sv, where 1 Sv = a flow of ocean water of 10(6) cubic meters per second). Interannual changes in the overturning can be monitored with a resolution of 1.5 Sv.

Variability of Relative Sea Level Rise: Spatial and Temporal Correlations in Northwest Gulf of Mexico

NASA Astrophysics Data System (ADS)

Tissot, P.; Reisinger, A. S.; Besonen, M. R.

2017-12-01

While our understanding of global sea level rise and its budget has made great progress over the past decade, the spatial and temporal variability of relative sea level rise along the coasts still needs to be better understood and quantified. We developed a technique to reduce the confidence intervals associated with relative sea level rise (RSLR) estimates for 15 tide gauges located along the Texas coast for the period 1993-2016. Seasonally detrended monthly mean water levels are highly correlated after removal of station-specific RSLR trends, which allows for the quantification of a common, low frequency oceanic signal. RSLR confidence intervals are reduced from over 1.9 mm/yr, on average 2.3mm, to less than 1.1 mm/yr, on average 0.7 mm/yr after removing this common signal. The resulting RSLR rates range from 3.0 to 8.4 mm/yr. The range is wider than the longer-term rates of 5.3, 3.8 and 1.9 mm/yr measured from north to south by the three National Water Level Observation Network (NWLON) stations covering the study area (over different and longer time spans). The results emphasize the importance of the spatial variability of the vertical land motion component of RSLR. The temporal variability of the coherent oceanic signal is not significantly correlated to the ENSO signal for the study period and is only weakly correlated to the AMO and PDO climate indices. The coherence of the signal is further investigated by comparison with other locations along the Gulf of Mexico and along the Northeast Atlantic coast. The results are discussed while considering strong local processes along the Northwest Gulf of Mexico, such as wind forcing and intermittent eddies and the spatially broader influence of the Gulf Stream. The local significance of the RSLR spatial and temporal differences are discussed in terms of the differences in inundation frequency for nuisance type flooding including comparing the time span to reach a probability of at least one nuisance flood event per year.

Downscaling ocean conditions with application to the Gulf of Maine, Scotian Shelf and adjacent deep ocean

NASA Astrophysics Data System (ADS)

Katavouta, Anna; Thompson, Keith R.

2016-08-01

The overall goal is to downscale ocean conditions predicted by an existing global prediction system and evaluate the results using observations from the Gulf of Maine, Scotian Shelf and adjacent deep ocean. The first step is to develop a one-way nested regional model and evaluate its predictions using observations from multiple sources including satellite-borne sensors of surface temperature and sea level, CTDs, Argo floats and moored current meters. It is shown that the regional model predicts more realistic fields than the global system on the shelf because it has higher resolution and includes tides that are absent from the global system. However, in deep water the regional model misplaces deep ocean eddies and meanders associated with the Gulf Stream. This is not because the regional model's dynamics are flawed but rather is the result of internally generated variability in deep water that leads to decoupling of the regional model from the global system. To overcome this problem, the next step is to spectrally nudge the regional model to the large scales (length scales > 90 km) of the global system. It is shown this leads to more realistic predictions off the shelf. Wavenumber spectra show that even though spectral nudging constrains the large scales, it does not suppress the variability on small scales; on the contrary, it favours the formation of eddies with length scales below the cutoff wavelength of the spectral nudging.

Glacially-megalineated limestone terrain of Anticosti Island, Gulf of St. Lawrence, Canada; onset zone of the Laurentian Channel Ice Stream

NASA Astrophysics Data System (ADS)

Eyles, Nick; Putkinen, Niko

2014-03-01

Anticosti is a large elongate island (240 km long, 60 km wide) in eastern Canada within the northern part of a deep water trough (Gulf of St. Lawrence) that terminates at the Atlantic continental shelf edge. The island's Pleistocene glaciological significance is that its long axis lay transverse to ice from the Quebec and Labrador sectors of the Laurentide Ice Sheet moving south from the relatively high-standing Canadian Shield. Recent glaciological reconstructions place a fast-flowing ice stream along the axis of the Gulf of St. Lawrence but supporting geologic evidence in terms of recognizing its hard-bedded onset zone and downstream streamlined soft bed is limited. Anticosti Island consists of gently southward-dipping limestone plains composed of Ordovician and Silurian limestones (Vaureal, Becscie and Jupiter formations) with north-facing escarpments transverse to regional ice flow. Glacial deposits are largely absent and limestone plains in the higher central plateau of the island retain a relict apparently ‘preglacial’ drainage system consisting of deeply-incised dendritic bedrock valleys. In contrast, the bedrock geomorphology of the lower lying western and eastern limestone plains of the island is strikingly different having been extensively modified by glacial erosion. Escarpments are glacially megalineated with a distinct ‘zig-zag’ planform reflecting northward-projecting bullet-shaped ‘noses’ (identified as rock drumlins) up to 2 km wide at their base and 4 km in length with rare megagrooved upper surfaces. Drumlins are separated by southward-closing, funnel-shaped ‘through valleys’ where former dendritic valleys have been extensively altered by the streaming of basal ice through gaps in the escarpments. Glacially-megalineated bedrock terrain such as on the western and eastern flanks of Anticosti Island is elsewhere associated with the hard-bedded onset zones of fast flowing ice streams and provides important ground truth for the postulated Laurentian Channel Ice Stream (LCIS) within the Gulf of St. Lawrence sector of the Laurentide Ice Sheet.

Present and past Gulf Stream variability in a cold-water coral area off Cape Lookout, West Atlantic

NASA Astrophysics Data System (ADS)

Mienis, F.; Pedersen, A.; Duineveld, G.; Seidenkrantz, M.; Fischel, A.; Matos, L.; Bane, J. M.; Frank, N.; Hebbeln, D.; Ross, S.

2012-12-01

Cold-water coral mounds are common on the SE slope of the US from Florida to Cape Hatteras between depths of 400-600 m. All coral areas lie in the vicinity of the Gulf Stream, which is characterized by strong currents transporting relatively warm water northwards. Thus far little is known about the recent and past environmental conditions inside the cold-water coral habitats on the SE US slope and particularly the effect of changing patterns of the Gulf Stream. Near Cape Lookout, which is the northern most cold-water coral area on the SE US slope, cold-water corals have formed mounds up to 60 m high with a tear drop shape, which are oriented in a SSW-NNE direction. Past explorations of major reef sites of N Carolina using remote and manned submersibles have shown living Lophelia pertusa colonies on the current facing side of the mound structures and a high biodiversity of associated fauna, especially fish. Two autonomous benthic landers were deployed amidst Lophelia reefs off Cape Lookout (NC) for a period of 6 months to define oceanographic patterns that are relevant for the development and persistence of cold-water coral ecosystems. Furthermore, a 3.6 m long piston core was collected in 2010 during a cruise with the R.V. Pelagia. This pistoncore was used to determine the changes of current strength through time, using foraminiferal counts, stable oxygen and carbon isotopes on foraminifera, XRF and magnetic susceptibility measurements. Cold-water coral fragments were dated with U/Th and foraminifera from the same depth interval were dated with C14. Bottom landers have recorded a number of events that are characterized by of peaks in temperature and salinity, coinciding with increased flow and turbidity. The current during these events was directed to the NNE. During some of these events temperature rose up to 9 degrees in one day. The temporary replacement of the colder bottom water by warm (and saline) water in combination with the strong currents to the NNE point at Gulfstream water moving over the deployment site as was confirmed by satellite images. The instantaneous increases in of the turbidity at the onset of warm events when the current speed increases, likely represent local erosion of the seafloor and of the coral mounds. Based on the foraminifera data three zones could be observed in the piston core (13000-10000 years, 10000-7200 years and 7200-4700 years. All zones show the gradual onshore movement of the Gulf Stream, which can be related to a rapid rise in sea-level after the last deglaciation. This movement has gradually widened the band of the Gulfstream thereby compressing the surface and deeper water masses. Current speed in the area are generally strong but weakened during periods of fresh water outflow in the North Atlantic, which weakened the thermohaline circulation. This was especially clear in zone 2 around 8200 years, due to a melt water pulse of lake Agassiz and Ojibway. Data presented here show that the Gulf Stream influenced cold-water coral growth and mound formation at the SE Us margin at present as well as in the past.

Differences in phosphorus and nitrogen delivery to the Gulf of Mexico from the Mississippi River Basin

USGS Publications Warehouse

Alexander, R.B.; Smith, R.A.; Schwarz, G.E.; Boyer, E.W.; Nolan, J.V.; Brakebill, J.W.

2008-01-01

Seasonal hypoxia in the northern Gulf of Mexico has been linked to increased nitrogen fluxes from the Mississippi and Atchafalaya River Basins, though recent evidence shows that phosphorus also influences productivity in the Gulf. We developed a spatially explicit and structurally detailed SPARROW water-quality model that reveals important differences in the sources and transport processes that control nitrogen (N) and phosphorus (P) delivery to the Gulf. Our model simulations indicate that agricultural sources in the watersheds contribute more than 70% of the delivered N and P. However, corn and soybean cultivation is the largest contributor of N (52%), followed by atmospheric deposition sources (16%); whereas P originates primarily from animal manure on pasture and rangelands (37%), followed by corn and soybeans (25%), other crops (18%), and urban sources (12%). The fraction of in-stream P and N load delivered to the Gulf increases with stream size, but reservoir trapping of P causes large local- and regional-scale differences in delivery. Our results indicate the diversity of management approaches required to achieve efficient control of nutrient loads to the Gulf. These include recognition of important differences in the agricultural sources of N and P, the role of atmospheric N, attention to P sources downstream from reservoirs, and better control of both N and P in close proximity to large rivers. ?? 2008 American Chemical Society.

Occurrence and amount of microplastic ingested by fishes in watersheds of the Gulf of Mexico.

PubMed

Phillips, Melissa B; Bonner, Timothy H

2015-11-15

Ingestion of microplastics by fishes could be an emerging environmental crisis because of the proliferation of plastic pollution in aquatic environments. Microplastics in marine ecosystems are well documented, however only one study has reported percent occurrence of microplastics in freshwater fishes. The purpose of this study was to quantify the occurrences and types of microplastics ingested by fishes within several freshwater drainages of the Gulf of Mexico and an estuary of the Gulf of Mexico. Among 535 fishes examined in this study, 8% of the freshwater fishes and 10% of the marine fishes had microplastics in their gut tract. Percentage occurrence of microplastics ingested by fishes in non-urbanized streams (5%) was less than that of one of the urbanized streams (Neches River; 29%). Percent occurrence of microplastics by habitat (i.e., benthic, pelagic) and trophic guilds (herbivore/omnivore, invertivore, carnivore) were similar. Low but widespread occurrences among drainages, habitat guilds, and trophic guilds indicate proliferation of plastic pollution within watersheds of the Gulf of Mexico, but consequences to fish health are unknown at this time. Copyright © 2015 Elsevier Ltd. All rights reserved.

Transport and Fate of Nutrients Along the U.S. East Coast

NASA Astrophysics Data System (ADS)

Hofmann, E. E.; Narvaez, D.; Friedrichs, M. A. M.; Najjar, R.; Tian, H.; Hyde, K.; Mannino, A.; Signorini, S. R.; Wilkin, J.; St-Laurent, P.

2017-12-01

As part of a NASA-funded multi-investigator project, a land-estuarine-ocean biogeochemical modeling system was implemented and verified with remote sensing and in situ data to examine processes controlling fluxes on land, their coupling to riverine systems, the delivery of materials to estuaries and the coastal ocean, and marine ecosystem responses to these changing riverine inputs and changing climate forcing. This modeling system is being used to develop nutrient budgets for the U.S. east coast continental shelf and to examine seasonal and interannual variability in nutrient fluxes. An important aspect of these nutrient budgets is the transport and fate of nutrients released along the inner shelf. Results from a five-year simulation (2004 to 2008) that used tracer releases from the main rivers along the Middle Atlantic Bight (MAB) and South Atlantic Bight (SAB) provide insights into transport pathways that connect the inner and outer continental shelf. Tracers released along the inner MAB spread along the shelf with a general southward and offshore transport. Inner shelf inputs from the large estuarine systems are transported to the mid and outer MAB shelf. Tracers that reach the mid to outer shelf can be entrained in the Gulf Stream. Export from the MAB to the SAB occurs during periods of southerly winds. Transport processes along the SAB are similar, but Gulf Stream entrainment is a larger component of tracer transport. Superimposed on the MAB and SAB transport patterns is considerable seasonal and interannual variability. The results from these retrospective simulations improve understanding of the coupling at the land-water interface and shelf-wide transport patterns that advance the ability to predict the effects of localized human impacts and broader-scale climate-related impacts on the U.S. east coast continental shelf system.

Physical oceanography of the US Atlantic and eastern Gulf of Mexico. Final report

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

Milliman, J.D.; Imamura, E.

The report provides a summary of the physical oceanography of the U.S. Atlantic and Eastern Gulf of Mexico and its implication to offshore oil and gas exploration and development. Topics covered in the report include: meteorology and air-sea interactions, circulation on the continental shelf, continental slope and rise circulation, Gulf Stream, Loop Current, deep-western boundary current, surface gravity-wave climatology, offshore engineering implications, implications for resource commercialization, and numerical models of pollutant dispersion.

Synthetic temperature profiles derived from Geosat altimetry: Comparison with air-dropped expendable bathythermograph profiles

NASA Astrophysics Data System (ADS)

Carnes, Michael R.; Mitchell, Jim L.; de Witt, P. Webb

1990-10-01

Synthetic temperature profiles are computed from altimeter-derived sea surface heights in the Gulf Stream region. The required relationships between surface height (dynamic height at the surface relative to 1000 dbar) and subsurface temperature are provided from regression relationships between dynamic height and amplitudes of empirical orthogonal functions (EOFs) of the vertical structure of temperature derived by de Witt (1987). Relationships were derived for each month of the year from historical temperature and salinity profiles from the region surrounding the Gulf Stream northeast of Cape Hatteras. Sea surface heights are derived using two different geoid estimates, the feature-modeled geoid and the air-dropped expendable bathythermograph (AXBT) geoid, both described by Carnes et al. (1990). The accuracy of the synthetic profiles is assessed by comparison to 21 AXBT profile sections which were taken during three surveys along 12 Geosat ERM ground tracks nearly contemporaneously with Geosat overflights. The primary error statistic considered is the root-mean-square (rms) difference between AXBT and synthetic isotherm depths. The two sources of error are the EOF relationship and the altimeter-derived surface heights. EOF-related and surface height-related errors in synthetic temperature isotherm depth are of comparable magnitude; each translates into about a 60-m rms isotherm depth error, or a combined 80 m to 90 m error for isotherms in the permanent thermocline. EOF-related errors are responsible for the absence of the near-surface warm core of the Gulf Stream and for the reduced volume of Eighteen Degree Water in the upper few hundred meters of (apparently older) cold-core rings in the synthetic profiles. The overall rms difference between surface heights derived from the altimeter and those computed from AXBT profiles is 0.15 dyn m when the feature-modeled geoid is used and 0.19 dyn m when the AXBT geoid is used; the portion attributable to altimeter-derived surface height errors alone is 0.03 dyn m less for each. In most cases, the deeper structure of the Gulf Stream and eddies is reproduced well by vertical sections of synthetic temperature, with largest errors typically in regions of high horizontal gradient such as across rings and the Gulf Stream front.

Controls on the early Holocene collapse of the Bothnian Sea Ice Stream

NASA Astrophysics Data System (ADS)

Clason, Caroline C.; Greenwood, Sarah L.; Selmes, Nick; Lea, James M.; Jamieson, Stewart S. R.; Nick, Faezeh M.; Holmlund, Per

2016-12-01

New high-resolution multibeam data in the Gulf of Bothnia reveal for the first time the subglacial environment of a Bothnian Sea Ice Stream. The geomorphological record suggests that increased meltwater production may have been important in driving rapid retreat of Bothnian Sea Ice during deglaciation. Here we apply a well-established, one-dimensional flow line model to simulate ice flow through the Gulf of Bothnia and investigate controls on retreat of the ice stream during the post-Younger Dryas deglaciation of the Fennoscandian Ice Sheet. The relative influence of atmospheric and marine forcings are investigated, with the modeled ice stream exhibiting much greater sensitivity to surface melting, implemented through surface mass balance and hydrofracture-induced calving, than to submarine melting or relative sea level change. Such sensitivity is supported by the presence of extensive meltwater features in the geomorphological record. The modeled ice stream does not demonstrate significant sensitivity to changes in prescribed ice stream width or overall bed slope, but local variations in basal topography and ice stream width result in nonlinear retreat of the grounding line, notably demonstrating points of short-lived retreat slowdown on reverse bed slopes. Retreat of the ice stream was most likely governed by increased ice surface meltwater production, with the modeled retreat rate less sensitive to marine forcings despite the marine setting.

Floodplain restoration enhances denitrification and reach-scale nitrogen removal in an agricultural stream

EPA Science Inventory

Streams of the agricultural Midwest export large quantities of nitrogen, which impairs downstream water quality, most notably in the Gulf of Mexico. The two-stage ditch is a novel restoration practice, in which floodplains are constructed alongside channelized ditches. During hi...

Pliocene shallow water paleoceanography of the North Atlantic ocean based on marine ostracodes

USGS Publications Warehouse

Cronin, T. M.

1991-01-01

Middle Pliocene marine ostracodes from coastal and shelf deposits of North and Central America and Iceland were studied to reconstruct paleotemperatures of shelf waters bordering portions of the Western Boundary Current System (including the Gulf Loop Current, Florida Current, Gulf Stream and North Atlantic Drift). Factor analytic transfer functions provided Pliocene August and February bottom-water temperatures of eight regions from the tropics to the subfrigid. The results indicate: (1) meridional temperature gradients in the western North Atlantic were less steep during the Pliocene than either today or during Late Pleistocene Isotope Stage 5e; (2) tropical and subtropical shelf waters during the Middle Pliocene were as warm as, or slightly cooler than today; (3) slightly cooler water was on the outer shelf off the southeastern and mid-Atlantic coast of the U.S., possibly due to summer upwelling of Gulf Stream water; (4) the shelf north of Cape Hatteras, North Carolina may have been influenced by warm water incursions from the western edge of the Gulf Stream, especially in summer; (5) the northeast branch of the North Atlantic Drift brought warm water to northern Iceland between 4 and 3 Ma; evidence from the Iceland record indicates that cold East Greenland Current water did not affect coastal Iceland between 4 and 3 Ma; (6) Middle Pliocene North Atlantic circulation may have been intensified, transporting more heat from the tropics to the Arctic than it does today. ?? 1991.

Long-term monitoring reveals cold-water corals in extreme conditions off the southeast US coast

NASA Astrophysics Data System (ADS)

Mienis, F.; Duineveld, G.; Davies, A. J.; Ross, S. W.; Lavaleye, M.; Van Weering, T.

2011-12-01

Cold-water corals are common on the SE slope of the US (SEUS) from Florida to Cape Hatteras between depths of 400-600 m. Near Cape Hatteras cold-water corals have formed mound structures that are up to 60 m high, which are mainly covered by living colonies of the coral species Lophelia pertusa. Past explorations of major reef sites of N Carolina using remote and manned submersibles have shown living Lophelia pertusa colonies on the current facing side of the mound structures and a high biodiversity of associated fauna, especially fish. The coral areas lie in the vicinity of the Gulf Stream characterized by strong currents transporting relatively warm water northwards along the SEUS slope. Thus far little is known about the environmental conditions inside the SEUS coral communities and particularly the effects of the nearby Gulf Stream. In December 2009 two autonomous benthic landers were deployed amidst Lophelia reefs off Cape Lookout (NC) for a period of 6 months to define oceanographic patterns that are relevant for the development and persistence of cold-water coral ecosystems. Landers recorded temperature, fluorescence, turbidity, and current speed and direction. Furthermore, a sediment trap was mounted on the landers that collected material at a 16-days interval. A first analysis of the lander data shows that instability of the Gulf Stream causes rapid rises in temperature, current speed and turbidity lasting for days to more than a week. Peak temperature and turbidity levels are the highest measured in coral habitats studied so far. We did not see clear cut effects of Gulf Stream instabilities on the near bed flux of phytodetritus as opposed to reports of meanders inducing upwelling and enhanced production in the photic zone. Data analyzed so far suggest that cwc habitats of Cape Lookout experience extreme and adverse conditions for prolonged periods. The findings of this study are compared with methodologically similar studies that have been conducted in coral habitats in the Gulf of Mexico and in the eastern North Atlantic.

Mechanism for the recent ocean warming events on the Scotian Shelf of eastern Canada

NASA Astrophysics Data System (ADS)

Brickman, D.; Hebert, D.; Wang, Z.

2018-03-01

In 2012, 2014, and 2015 anomalous warm events were observed in the subsurface waters in the Scotian Shelf region of eastern Canada. Monthly output from a high resolution numerical ocean model simulation of the North Atlantic ocean for the period 1990-2015 is used to investigate this phenomenon. It is found that the model shows skill in simulating the anomaly fields derived from various sources of data, and the observed warming trend over the last decade. From analysis of the model run it is found that the anomalies originate from the interaction between the Gulf Stream and the Labrador Current at the tail of the Grand Banks (south of Newfoundland). This interaction results in the creation of anomalous warm/salty (or cold/fresh) eddies that travel east-to-west along the shelfbreak. These anomalies penetrate into the Gulf of St. Lawrence, onto the Scotian Shelf, and into the Gulf of Maine via deep channels along the shelfbreak. The observed warming trend can be attributed to an increase in the frequency of creation of warm anomalies during the last decade. Strong anomalous events are commonly observed in the data and model, and thus should be considered as part of the natural variability of the coupled atmosphere-ocean system.

Using non-systematic surveys to investigate effects of regional climate variability on Australasian gannets in the Hauraki Gulf, New Zealand

NASA Astrophysics Data System (ADS)

Srinivasan, Mridula; Dassis, Mariela; Benn, Emily; Stockin, Karen A.; Martinez, Emmanuelle; Machovsky-Capuska, Gabriel E.

2015-05-01

Few studies have investigated regional and natural climate variability on seabird populations using ocean reanalysis datasets (e.g. Simple Ocean Data Assimilation (SODA)) that integrate atmospheric information to supplement ocean observations and provide improved estimates of ocean conditions. Herein we use a non-systematic dataset on Australasian gannets (Morus serrator) from 2001 to 2009 to identify potential connections between Gannet Sightings Per Unit Effort (GSPUE) and climate and oceanographic variability in a region of known importance for breeding seabirds, the Hauraki Gulf (HG), New Zealand. While no statistically significant relationships between GSPUE and global climate indices were determined, there was a significant correlation between GSPUE and regional SST anomaly for HG. Also, there appears to be a strong link between global climate indices and regional climate in the HG. Further, based on cross-correlation function coefficients and lagged multiple regression models, we identified potential leading and lagging climate variables, and climate variables but with limited predictive capacity in forecasting future GSPUE. Despite significant inter-annual variability and marginally cooler SSTs since 2001, gannet sightings appear to be increasing. We hypothesize that at present underlying physical changes in the marine ecosystem may be insufficient to affect supply of preferred gannet main prey (pilchard Sardinops spp.), which tolerate a wide thermal range. Our study showcases the potential scientific value of lengthy non-systematic data streams and when designed properly (i.e., contain abundance, flock size, and spatial data), can yield useful information in climate impact studies on seabirds and other marine fauna. Such information can be invaluable for enhancing conservation measures for protected species in fiscally constrained research environments.

Comparison data for Seasat altimetry in the western North Atlantic

NASA Technical Reports Server (NTRS)

Cheney, R. E.

1981-01-01

The radar altimeter flown on Seasat in 1978 collected approximately 1,000 orbits of high quality data (5-8 precision). In the western North Atlantic these data were combined with a detailed gravimetric geoid in an attempt to produce profiles of dynamic topography. In order to provide a basis for evaluation of these profiles, available oceanographic observations in the Gulf Stream/Sargasso Sea region have been compiled into a series of biweekly maps. The data include XBT's, satellite infrared imagery, and selected trajectories of surface drifters and sub-surface SOFAR floats. The maps document the known locations of the Gulf Stream, cyclonic and anticyclonic rings, and mid-ocean eddies during the period July to October 1978.

GEOS-3 ocean current investigation using radar altimeter profiling. [Gulf Stream surface topography

NASA Technical Reports Server (NTRS)

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

1978-01-01

Both quasi-stationary and dynamic departures from the marine geoid were successfully detected using altitude measurements from the GEOS-3 radar altimeter. The quasi-stationary departures are observed either as elevation changes in single pass profiles across the Gulf Stream or at the crowding of contour lines at the western and northern areas of topographic maps generated using altimeter data spanning one month or longer. Dynamic features such as current meandering and spawned eddies can be monitored by comparing monthly mean maps. Comparison of altimeter inferred eddies with IR detected thermal rings indicates agreement of the two techniques. Estimates of current velocity are made using derived slope estimates in conjunction with the geostrophic equation.

Secular change and inter-annual variability of the Gulf Stream position, 1993-2013, 70°-55°W

NASA Astrophysics Data System (ADS)

Bisagni, James J.; Gangopadhyay, Avijit; Sanchez-Franks, Alejandra

2017-07-01

The Gulf Stream (GS) is the northeastward-flowing surface limb of the Atlantic Ocean's meridional overturning circulation (AMOC) ;conveyer belt; that flows towards Europe and the Nordic Seas. Changes in the GS position after its separation from the coast at Cape Hatteras, i.e., from 75°W to 50°W, may be key to understanding the AMOC, sea level variability and ecosystem behavior along the east coast of North America. In this study we compare secular change and inter-annual variability (IAV) of the Gulf Stream North Wall (GSNW) position with equator-ward Labrador Current (LC) transport along the southwestern Grand Banks near 52°W using 21 years (1993-2013) of satellite altimeter data. Results at 55°, 60°, and 65°W show a significant southward (negative) secular trend for the GSNW, decreasing to a small but insignificant southward trend at 70°W. IAV of de-trended GSNW position residuals also decreases to the west. The long-term secular trend of annual mean upper layer (200 m) LC transport near 52°W is positive. Furthermore, IAV of LC transport residuals near 52°W along the southwestern Grand Banks are significantly correlated with GSNW position residuals at 55°W at a lag of +1-year, with positive (negative) LC transport residuals corresponding to southward (northward) GSNW positions one year later. The Taylor-Stephens index (TSI) computed from the first principal component of the GSNW position from 79° to 65°W shows a similar relationship with a more distal LC index computed along altimeter ground track 250 located north of the Grand Banks across Hamilton Bank in the western Labrador Sea. Increased (decreased) sea height differences along ground track 250 are significantly correlated with a more southward (northward) TSI two years later (lag of +2-years). Spectral analysis of IAV reveals corresponding spectral peaks at 5-7 years and 2-3 years for the North Atlantic Oscillation (NAO), GSNW (70°-55°W) and LC transport near 52°W for the 1993-2013 period suggesting a connection between these phenomena. An upper-layer (200 m) slope water volume calculation using the LC IAV rms residual of +1.04 Sv near 52°W results in an estimated GSNW IAV residual of 79 km, or 63% of the observed 125.6 km (1.13°) rms value at 55°W. A similar upper-layer slope water volume calculation using the positive long-term, upper-layer LC transport trend accounts for 68% of the mean observed secular southward shift of the GSNW between 55° and 70°W over the 1993-2013 period. Our work provides additional observational evidence of important interactions between the upper layers of the sub-polar and sub-tropical gyres within the North Atlantic over both secular and inter-annual time scales as suggested by previous studies.

Polarization and wavelength diversities of Gulf Stream fronts imaged by AIRSAR

NASA Technical Reports Server (NTRS)

Lee, J. S.; Jansen, R. W.; Marmorino, G. O.; Chubb, S. R.

1995-01-01

During the 1990 Gulf Stream Experiment, NASA/JPL AIRSAR imaged the north edge of the Gulf Stream near the coast of Virginia. Simultaneous in-situ measurements of currents, temperatures, salinities, etc. were made for several crossings of the north edge by the R/V Cape Henlopen. Measurements identified two fronts with shearing and converging flows. The polarimetric SAR images from the fronts showed two bright linear features. One of them corresponds to the temperature front, which separated the warm Gulf Stream water to the south from a cool, freshwater filament to the north. The other line, located about 8 km north of the temperature front, is believed to correspond to the velocity front between the filament and the slope water. At these fronts, wave-current interactions produced narrow bands of steep and breaking waves manifesting higher radar returns in polarimetric SAR images. In general, our AIRSAR imagery shows that the signal-to-clutter ratio of radar cross sections for the temperature front is higher than that of the velocity front. In this paper, we study the polarization and wavelength diversities of radar response of these two fronts using the P-, L-, and C-Band Polarimetric SAR data. The north-south flight path of the AIRSAR crossed the temperature front several times and provided valuable data for analysis. Three individual passes are investigated. We found that for the temperature front, the cross-pol (HV) responses are much higher than co-pol responses (VV and HH), and that P-Band HV has the highest signal to clutter ratio. For the velocity front, the ratio is the strongest in P-Band VV, and it is indistinguishable for all polarizations in C-Band. The radar cross sections for all three polarization (HH, HV, and VV) and for all three bands are modelled using an ocean wave model and a composite Bragg scattering model. In our initial investigations, the theoretical model agrees qualitatively with the AIRSAR observations.

The Use of Pre-Storm Boundary-Layer Baroclinicity in Determining and Operationally Implementing the Atlantic Surface Cyclone Intensification Index

NASA Astrophysics Data System (ADS)

Cione, Joseph; Pietrafes, Leonard J.

The lateral motion of the Gulf Stream off the eastern seaboard of the United States during the winter season can act to dramatically enhance the low-level baroclinicity within the coastal zone during periods of offshore cold advection. The ralative close proximity of the Gulf Stream current off the mid-Atlantic coast can result in the rapid and intense destabilization of the marine atmospheric boundary layer directly above and shoreward of the Gulf Stream within this region. This airmass modification period often precedes either wintertime coastal cyclogenesis or the cyclonic re-development of existing mid-latitude cyclones. A climatological study investigating the relationship between the severity of the pre-storm, cold advection period and subsequent cyclogenic intensification was undertaken by Cione et al. in 1993. Findings from this study illustrate that the thermal structure of the continental airmass as well as the position of the Gulf Stream front relative to land during the pre-storm period (i.e., 24-48 h prior to the initial cyclonic intensification) are linked to the observed rate of surface cyclonic deepening for storms that either advected into or initially developed within the Carolina-southeast Virginia offshore coastal zone. It is a major objective of this research to test the potential operational utility of this pre-storm low level baroclinic linkage to subsequent cyclogenesis in an actual National Weather Service (NWS) coastal winter storm forecast setting.The ability to produce coastal surface cyclone intensity forecasts recently became available to North Carolina State University researchers and NWS forecasters. This statistical forecast guidance utilizes regression relationships derived from a nine-season (January 1982-April 1990), 116-storm study conducted previously. During the period between February 1994 and February 1996, the Atlantic Surface Cyclone Intensification Index (ASCII) was successfully implemented in an operational setting by the NWS at the Raleigh-Durham (RAH) forecast office for 10 winter storms. Analysis of these ASCII forecasts will be presented.

Wave and Current Measurements From the Coastal Storms Program (CSP) Buoy 41012 off St. Augustine, FL

NASA Astrophysics Data System (ADS)

Crout, R. L.

2008-05-01

The Coastal Storms Program (CSP) is a NOAA program that involves several different branches within NOAA. Components of the National Ocean Service, the National Weather Service, the National Marine Fisheries Service, and the Office of Oceanic and Atmospheric Research participate in CSP, which is administered by the Coastal Services Center. CSP selects an area where an impact in support of the NOAA Societal Goals can be made. The first area selected was the northeast coast of Florida in 2002. In addition to coastal water level stations and modeling efforts, a 3-meter discuss buoy (WMO 41012) was deployed off the coast of St. Augustine, FL in approximately 38 meters of water. In addition to the normal complement of meteorological sensors, Buoy 41012 contained a sensor to measure directional waves at hourly intervals, a temperature-conductivity sensor to measure near-surface temperature and salinity, and a current profiler to obtain near-surface to near-bottom currents at hourly intervals. These data on the continental shelf provide a view of the oceanography on the inner margin of the Gulf Stream. The data are served over the National Data Buoy Center's web page and over the Global Telecommunications System. The waves and currents during the period from September 2005 through December 2007 are related to coastal storms, hurricanes, tides, and Gulf Stream intrusions. During several late fall and winter periods the waves exceeded 4.5 meters. The on-offshore component of the currents appears to be tidally driven, however, predominant on- and off-shore flows are observed in response to storms and Gulf Stream intrusions. The primary component of the flow is aligned alongshore and although the tidal influence is obvious, extended periods of northward and southward currents are observed. Currents approaching 2 knots are observed at various times during the period that the buoy has been active. The high currents appear to be in response to strong wind events (atmospheric frontal passages) and Gulf Stream intrusions.

Nonmigratory, 12-kHz, deep scattering layers of Sargasso Sea origin in warm-core rings

NASA Astrophysics Data System (ADS)

Conte, Maureen H.; Bishop, James B.; Backus, Richard H.

1986-11-01

Nonmigratory, 12-kHz, deep sound-scattering layers (NMDSLs) were entrained within Sargasso Sea-Gulf Stream waters during the formation of warm-core rings 82B and 82H. At night ring water was easily distinguished from Slope Water by the presence of these well-developed features between 200 and 550 m. The distribution of NMDSLs in 82H as a function of temperature and salinity matched Sargasso Sea distributions, indicating that Sargasso Sea water was present in the center of 82H at the time of its formation. However, the distribution of NMDSLs in the center of 82B a few weeks after its formation was more consistent with the distribution found in Gulf Stream-Sargasso Sea edge water. NMDSLs were a persistent feature of the lower thermostad and upper thermocline of 82B. Their distribution in the upper thermocline approximately paralleled the decrease in thickness of the thermostad and became shallower with increasing distance from ring center. The NMDSLs disappeared at the ring edge when the bottom of the thermostad became shallower than about 100 m. Their distribution within 30 km of ring center changed very little between April and June, whereas those found in the thermocline at greater distances from ring center showed greater dispersion with respect to temperature. Following several Gulf Stream interactions in July, the NMDSLs were significantly shallower, and lay in colder water. The continued presence of the deep NMDSLs in the thermocline, even though the latter was nearly 100 m shallower, indicates that the remaining thermocline had not been significantly exchanged with Gulf Stream or Slope Water during the interactions. The changes in the temperature of the water in which the NMDSLs were found in August suggest that core waters (30 km from ring center in June) were resorbed by the Gulf Stream and that only waters of 30 km radius remained to reform the ring. We found no evidence that the animals composing the NMDSLs adjusted their vertical distributions in response to changes in environmental properties; rather, the temporal changes we observed are best explained by the physical processes affecting ring structure. No qualitative decrease in NMDSL intensity was observed in 82B between April and August, suggesting that the sound scatterers can tolerate significant changes in depth, temperature and salinity. The gonostomatid fish Cyclothone braueri and the physonect siphonophores are possibly sources of the NMDSLs.

76 FR 59371 - Fisheries of the Caribbean, Gulf of Mexico and South Atlantic; Comprehensive Ecosystem-Based...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-26

... South Atlantic Region (Snapper- Grouper FMP), as prepared and submitted by the Council. CE-BA 2 also... South Atlantic EEZ bounded by the Gulf Stream as EFH for pelagic Sargassum. Octocoral FMU CE-BA 2 would.... EFH and EFH-HAPCs CE-BA 2 would also amend the South Atlantic FMPs as needed to designate new or...

Spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean.

PubMed

Zhang, Min; Zhang, Yuanling; Shu, Qi; Zhao, Chang; Wang, Gang; Wu, Zhaohua; Qiao, Fangli

2018-01-15

Analyses of the chlorophyll a concentration (chla) from satellite ocean color products have suggested the decadal-scale variability of chla linked to the climate change. The decadal-scale variability in chla is both spatially and temporally non-uniform. We need to understand the spatiotemporal evolution of chla in decadal or multi-decadal timescales to better evaluate its linkage to climate variability. Here, the spatiotemporal evolution of the chla trend in the North Atlantic Ocean for the period 1997-2016 is analyzed using the multidimensional ensemble empirical mode decomposition method. We find that this variable trend signal of chla shows a dipole pattern between the subpolar gyre and along the Gulf Stream path, and propagation along the opposite direction of the North Atlantic Current. This propagation signal has an overlapping variability of approximately twenty years. Our findings suggest that the spatiotemporal evolution of chla during the two most recent decades is part of the multidecadal variations and possibly regulated by the changes of Atlantic Meridional Overturning Circulation, whereas the mechanisms of such evolution patterns still need to be explored. Copyright © 2017 Elsevier B.V. All rights reserved.

Benthic study of the continental slope off Cape Hatteras, North Carolina. Volume 3. Appendices

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

Diaz, R.J.; Blake, J.A.; Lohse, D.P.

1993-03-01

The Point is an area that supports a most productive pelagic fishery, including tuna, swordfish, marlin, and more. The objective of the study is to analyze video tapes from near the Point, in order to provide data on epibenthic, megafaunal invertebrates including species composition, relative abundances, and large scale (1 km) distribution. The Point is not a defined spot on a chart. Although fishermen do use the steep shelf break for location, they generally look for the west wall of the Gulf Stream. The Point and the oil lease site coincidentally occur where the Gulf Stream parts the continental slope,more » just north of the eastern-most tip of Cape Hatteras.« less

Microwave responses of the western North Atlantic

NASA Technical Reports Server (NTRS)

Stacey, J. M.; Girard, M. A.

1985-01-01

Features and objects in the Western North Atlantic Ocean - the Eastern Seaboard of the United States - are observed from Earth orbit by passive microwaves. The intensities of their radiated flux signatures are measured and displayed in color as a microwave flux image. The features of flux emitting objects such as the course of the Gulf Stream and the occurrence of cold eddies near the Gulf Stream are identified by contoured patterns of relative flux intensities. The flux signatures of ships and their wakes are displayed and discussed. Metal data buoys and aircraft are detected. Signal to clutter ratios and probabilities of detection are computed from their measured irradiances. Theoretical models and the range equations that explain passive microwave detection using the irradiances of natural sources are summarized.

Stream carbon dynamics in low-gradient headwaters of a forested watershed

Treesearch

April Bryant-Mason; Y. Jun Xu; Johnny M. Grace

2013-01-01

Headwater streams drain more than 70 percent of the total watershed area in the United States. Understanding of carbon dynamics in the headwater systems is of particular relevance for developing best silvicultural practices to reduce carbon export. This study was conducted in a low-gradient, predominantly forested watershed located in the Gulf Coastal Plain region, to...

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.

Response of North Atlantic Ocean Chlorophyll a to the Change of Atlantic Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Zhang, Min; Zhang, Yuanling; Shu, Qi; Zhao, Chang; Wang, Gang; Wu, Zhaohua; Qiao, Fangli

2017-04-01

Changes in marine phytoplankton are a vital component in global carbon cycling. Despite this far-reaching importance, the variable trend in phytoplankton and its response to climate variability remain unclear. This work presents the spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean by using merged ocean color products for the period 1997-2016. We find a dipole pattern between the subpolar gyre and the Gulf Stream path,and chlorophyll a trend signal propagatedalong the opposite direction of the North Atlantic Current. Such a dipole pattern and opposite propagation of chlorophyll a signal are consistent with the recent distinctive signature of the slowdown of the Atlantic MeridionalOverturning Circulation (AMOC). It is suggested that the spatiotemporal evolution of chlorophyll a during the two most recent decades is a part of the multidecadal variation and regulated byAMOC, which could be used as an indicator of AMOC variations.

Skillful prediction of northern climate provided by the ocean

NASA Astrophysics Data System (ADS)

Årthun, Marius; Eldevik, Tor; Viste, Ellen; Drange, Helge; Furevik, Tore; Johnson, Helen L.; Keenlyside, Noel S.

2017-06-01

It is commonly understood that a potential for skillful climate prediction resides in the ocean. It nevertheless remains unresolved to what extent variable ocean heat is imprinted on the atmosphere to realize its predictive potential over land. Here we assess from observations whether anomalous heat in the Gulf Stream's northern extension provides predictability of northwestern European and Arctic climate. We show that variations in ocean temperature in the high latitude North Atlantic and Nordic Seas are reflected in the climate of northwestern Europe and in winter Arctic sea ice extent. Statistical regression models show that a significant part of northern climate variability thus can be skillfully predicted up to a decade in advance based on the state of the ocean. Particularly, we predict that Norwegian air temperature will decrease over the coming years, although staying above the long-term (1981-2010) average. Winter Arctic sea ice extent will remain low but with a general increase towards 2020.

Variability of sea-surface temperature in the South Atlantic bight as observed from satellite: Implications for offshore-spawning fish

NASA Astrophysics Data System (ADS)

Stegmann, P. M.; Yoder, J. A.

1996-06-01

We examined full-resolution (1 × 1 km) satellite images of sea-surface temperature (SST) over five consecutive years (1981-1986) covering the Atlantic menhaden ( Brevoortia tyrannus) recruitment period (November-April) in the SABRE (South Atlantic Bight recruitment experiment) study site. The results of our image time series indicated two processes which could be possible mechanisms for the onshore transport of fish larvae into coastal regions. One is the influx of warm Gulf Stream water that oscillates in and out of the Carolina Bays. These oscillations occurred throughout the study period over distances of 20-40 km and on time-scales as short as two days. The other is a tongue of relatively cold water located adjacent to the Virginia coast that moved southward and penetrated into Onslow Bay between January and March. Previous studies showed that Atlantic menhaden preferentially spawn in 18-22°C waters on the outer shelf. On the assumption that the 18°C isotherm (18DI) indicates where high larval abundance may occur, we used AVHRR-SST imagery to track the onshore-offshore movement of the 18DI along a transect extending onshore-offshore in Onslow Bay. Owing to seasonal warming and cooling, this isotherm was always found closest to the coast in early November, reached maximum offshore displacement by January/March, and then moved onshore again in April/May. Our results also showed that the position of this isotherm can move offshore or onshore in a matter of a few days. An important influence and possibly the major cause of the higher frequency displacements of the 18DI are Gulf Stream meanders or filaments moving through Onslow Bay. Our estimates of onshore isotherm speeds as determined from satellite SST ranged from 2 to 25 cm s -1 and are within the same order as those calculated by physical models or larval age determinations. If the onshore pulses of warm Gulf Stream water are indeed a mode by which menhaden larvae are transported cross-shelf, then the use of satellite-based observations to determine their frequency and onshore extent, as done in the present study, is a useful tool to study variations in fish recruitment.

Holocene climate and climate variability of the northern Gulf of Mexico and adjacent northern Gulf Coast: A review

USGS Publications Warehouse

Poore, Richard Z.

2008-01-01

Marine records from the northern Gulf of Mexico indicate that significant multidecadal- and century-scale variability was common during the Holocene. Mean annual sea-surface temperature (SST) during the last 1,400 years may have varied by 3°C, and excursions to cold SST coincide with reductions in solar output. Broad trends in Holocene terrestrial climate and environmental change along the eastern portion of the northern Gulf Coast are evident from existing pollen records, but the high-frequency details of climate variability are not well known. Continuous and well-dated records of climate change and climate variability in the western portion of the northern Gulf Coast are essentially lacking.Information on Holocene floods, droughts, and storm frequency along the northern Gulf Coast is limited. Records of floods may be preserved in continental shelf sediments, but establishing continuity and chronologies for sedimentary sequences on the shelf presents challenges due to sediment remobilization and redeposition during storms. Studies of past storm deposits in coastal lakes and marshes show promise for constructing records of past storm frequency. A recent summary of sea-level history of the northern Gulf Coast indicates sea level was higher than modern sea level several times during the last few thousand years.

Connection between encounter volume and diffusivity in geophysical flows

NASA Astrophysics Data System (ADS)

Rypina, Irina I.; Smith, Stefan G. Llewellyn; Pratt, Larry J.

2018-04-01

Trajectory encounter volume - the volume of fluid that passes close to a reference fluid parcel over some time interval - has been recently introduced as a measure of mixing potential of a flow. Diffusivity is the most commonly used characteristic of turbulent diffusion. We derive the analytical relationship between the encounter volume and diffusivity under the assumption of an isotropic random walk, i.e., diffusive motion, in one and two dimensions. We apply the derived formulas to produce maps of encounter volume and the corresponding diffusivity in the Gulf Stream region of the North Atlantic based on satellite altimetry, and discuss the mixing properties of Gulf Stream rings. Advantages offered by the derived formula for estimating diffusivity from oceanographic data are discussed, as well as applications to other disciplines.

Frontal Eddy Dynamics (FRED) experiment off North Carolina: Volume 2. Technical report

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

Ebbesmeyer, C.C.

1988-03-01

In preparation for oil and gas lease sales on the outer continental shelf offshore of North Carolina, the Minerals Management Service was requested to investigate the potential transport and impacts of oil spilled offshore. Of particular concern is estimating the movement of spilled oil, especially the probability of shoreward transport and/or beaching of the floatable fraction. Although the speed and location of the Gulf Stream are well known, knowledge of the meanders of the Gulf Stream is limited. How the circulatory structure and movement of associated frontal eddies and filaments affect the North Carolina coastal waters is not clear. Thismore » present study investigates the interactions of these circulatory elements and follows the evolution of frontal eddies as they migrate along the North Carolina coast.« less

On the dynamic forcing of short-term climate fluctuations by feedback mechanisms

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

Reiter, E.R.

1979-09-01

The energies involved in the general circulation of the atmosphere, especially the zonal available potential energy, show considerable interannual variability, suggesting the presence of various internal feedback mechanisms in the ocean-atmosphere system. Sea-surface temperature (SST) variations appear to have some effect on the hydrological cycle. The possible existence of feedback mechanisms between ocean and atmosphere seem to be evident in some of the data from the North Pacific and North Atlantic. One of these proposed mechanisms involves the variation in the convergence between the North and South Pacific trade-wind systems and is strongly reflected in rainfall variability within the drymore » region of the equatorial Pacific. Similar variations appear in low-latitude SST anomalies. The convergence between the two trade-wind systems in the Atlantic region also undergoes marked interannual variations. This quasi-biennial oscillation (QBO) in trade-wind convergence over the Atlantic appears to be tied to the global QBO of equatorial stratospheric winds and to regional rainfall regimes in the dry region of northeastern Brazil. A variability pattern of SST's with a QBO has been detected off the coast of Senegal, in the Gulf of Guinea and even in the Gulf Stream as it leaves the North American continental shelf. Possible physical connections between some of these QBO's are pointed out by a hypothetical feedback model. It is also suggested that interaction of a QBO with the annual cycle may lead to beating frequencies resembling climatic trends of a duration of several years.« less

The subsurface geology of the Florida-Hatteras shelf, slope, and inner Blake Plateau

USGS Publications Warehouse

Paull, Charles K.; Dillon, William P.

1979-01-01

The structure and stratigraphy of the Florida-Hatteras Slope and inner Blake Plateau was studied by means of 4,780 km of single-channel air gun seismic reflection profiles. Control for the seismic stratigraphy is provided by correlating reflecting units and paleontologically dated stratigraphic units identified in offshore wells and dredge hauls. Many Tertiary unconformities exist, and major regional unconformities at the end of the Oligocene and in the late Paleocene are mapped. Reflecting surfaces believed to represent the tops of the Cretaceous, Paleocene, and Oligocene extend throughout the region. Upper Cretaceous (pre-Maastrichtian) rocks on the southeastern side of the Carolina Platform form a large seaward-facing progradational wedge. The Upper Cretaceous rocks in the Southeast Georgia Embayment, are seismically transparent and on the inner Blake Plateau are cut by numerous small faults, perhaps due to compaction. Within the survey area relatively flat-lying Maastrichtian and Paleocene strata show no evidence that a feature similar to the present Florida-Hatteras Slope existed at the beginning of the Tertiary. Late Paleocene erosion, related to the initiation of the Gulf Stream flow, probably developed this regional unconformity. Eocene and Oligocene sediments landward of the present Gulf Stream form a thick sequence of seaward-dipping progradational beds. A seaward progradational wedge of Miocene to Holocene age covers a regionally traceable unconformity, which separates the Oligocene from the Miocene sediments. Under and seaward of the present Gulf Stream, the Eocene and younger sediment supply was much smaller and the buildup is comparatively insignificant. The difference in accumulation rates in the Eocene and younger sediments, landward and seaward of the Gulf Stream, is responsible for the Florida-Hatteras Slope. Tertiary isopach maps suggest that there is a well developed triangular depocenter under the shelf. The edges of the depocenter correspond with magnetic anomalies and it is suggested that the depocenter is related to differential subsidence during the Tertiary across older crustal structures. The Eocene and Oligocene units contain the aquifer onshore, and the aquifer probably remains in these units offshore. With this assumption the potential aquifer has been identified and traced under the shelf and slope.

Entrainment and mixing of shelf/slope waters in the near-surface Gulf Stream

NASA Astrophysics Data System (ADS)

Lillibridge, J. L., III; Hitchcock, G.; Rossby, T.; Lessard, E.; Mork, M.; Golmen, L.

1990-08-01

An interdisciplinary study of the entrainment of shelf and slope waters in the Gulf Stream front was undertaken in October 1985 northeast of Cape Hatteras. Fifteen hydrographic transects of the Gulf Stream front and of the shelf water intrusion known as Ford water were completed in 2 1/2 days with a towed undulating profiler, the SeaSoar, equipped with a conductivity-temperature-depth probe and a fluorometer. Upstream sections within 50 km of the shelf break show entrainment of surface and subsurface waters along the northern edge of the high-velocity Gulf Stream. The low-salinity core, first observed at 70 m, is subducted to >100 m. The subsurface Ford water is also at a maximum in chlorophyll, fluorescence, and dissolved oxygen and contains a distinct diatom assemblage of nearshore species. Productivity rates in the Ford water may be equivalent to those in slope waters. Expendable current profilers yield an estimated transport for subsurface shelf waters of 1 to 5×105 m3 s-1 and indicate that vertical shear at the depth of maximum static stability is typically 2×10-2 s-1. A bulk Richardson number is estimated over vertical scales of several meters by combining SeaSoar density profiles with velocity shear from concurrent expendable current profiler deployments. The minimum values are generally >1, and only infrequently are they at or below the 0.25 threshold for shear instability. The presence of double-diffusive processes around the low-salinity core of Ford water is indicated by elevated conductivity Cox numbers. The stability parameter "Turner angle" shows that low-salinity Ford water and its associated T-S property front are sites of double-diffusive mixing, given general agreement between the distributions of Turner angle and Cox number. We conclude that double-diffusive processes are more important than shear flow instability in governing cross-isopycnal mixing. However, downstream transit times are so swift that no measurable change or decay occurs in the Ford water. This explains the occurrence of distinct shelf water phytoplankton species within the low-salinity waters downstream of Cape Hatteras.

Significant bed elevation changes related to Gulf Stream dynamics on the South Carolina continental shelf

USGS Publications Warehouse

Gelfenbaum, G.; Noble, M.

1993-01-01

Photographs of the seabed taken from an instrumented bottom tripod located approximately 100 km east of Charleston, South Carolina, reveal bed elevation changes of over 20 cm between July and November 1978. The tripod was in 85 m of water and was equipped with two current meters at 38.7 and 100 cm from the bed, a pressure sensor, a transmissometer, which fouled early during the deployment, a temperature sensor and a camera. The sediment under the tripod was composed of poorly sorted sand, some shell debris and numerous small biological tubes. Bed roughness varied throughout the deployment from biologically-produced mounds (2-5 cm high and 5-20 cm diameter) to streaks to a smooth bed, depending upon the frequency and magnitude of the sediment transporting events. Even though these events were common, especially during the later part of the deployment, the bed was rarely rippled, and there was no evidence of large bedforms such as dunes or sand waves migrating through the field of view of the camera. Photographs did clearly show, however, a gradual net deposition of the bed of nearly 20 cm, followed by erosion of approximately 5 cm. The flow field near the bed was dominated by sub-tidal period currents. Hourly-averaged currents at 100 cm from the bed typically varied between 10 and 30 cm s-1 and occasionally were as high as 60 cm s-1. The large flow events were predominantly toward the southwest along the shelf in the opposite direction of the northeast flowing Gulf Stream. The cross-shore component of the flow near the bed was predominantly directed offshore due to a local topographic steering effect. Current, temperature and satellite data suggest that the largest flow events were associated with the advection of Gulf Stream filaments past the tripod. Erosion events, as seen from the photographs, were highly correlated with the passage of these Gulf Stream filaments past the tripod. Gradual deposition of sediment, which occurred during the first half of the deployment, appears to have been associated with the convergence of the near-bed sediment flux near the shelf break. ?? 1993.

Large wood debris recruitment on differing riparian landforms along a Gulf Coastal Plain (USA) stream: a comparison of large floods and average flows

Treesearch

Stephen W. Golladay; Juliann M. Battle; Brian J. Palik

2007-01-01

In southeastern Coastal Plain streams, wood debris can be very abundant and is recruited from extensive forested floodplains. Despite importance of wood debris, there have been few opportunities to examine recruitment and redistribution of wood in an undisturbed setting, particularly in the southeastern Coastal Plain. Following extensive flooding in 1994, measurements...

Spatial and temporal ecological variability in the northern Gulf of Alaska: What have we learned since the Exxon Valdez oil spill?

NASA Astrophysics Data System (ADS)

Aderhold, Donna G. R.; Lindeberg, Mandy R.; Holderied, Kris; Pegau, W. Scott

2018-01-01

This special issue examines oceanographic and biological variability in the northern Gulf of Alaska region with an emphasis on recent monitoring efforts of the Gulf Watch Alaska (GWA) and Herring Research and Monitoring (HRM) programs funded by the Exxon Valdez Oil Spill Trustee Council (EVOSTC). These programs are designed to improve our understanding of how changing environmental conditions affect Gulf of Alaska ecosystems and the long-term status of resources injured by the Exxon Valdez oil spill.

Intraseasonal variability of sea level and circulation in the Gulf of Thailand: the role of the Madden-Julian Oscillation

NASA Astrophysics Data System (ADS)

Oliver, Eric C. J.

2014-01-01

Intraseasonal variability of the tropical Indo-Pacific ocean is strongly related to the Madden-Julian Oscillation (MJO). Shallow seas in this region, such as the Gulf of Thailand, act as amplifiers of the direct ocean response to surface wind forcing by efficient setup of sea level. Intraseasonal ocean variability in the Gulf of Thailand region is examined using statistical analysis of local tide gauge observations and surface winds. The tide gauges detect variability on intraseasonal time scales that is related to the MJO through its effect on local wind. The relationship between the MJO and the surface wind is strongly seasonal, being most vigorous during the monsoon, and direction-dependent. The observations are then supplemented with simulations of sea level and circulation from a fully nonlinear barotropic numerical ocean model (Princeton Ocean Model). The numerical model reproduces well the intraseasonal sea level variability in the Gulf of Thailand and its seasonal modulations. The model is then used to map the wind-driven response of sea level and circulation in the entire Gulf of Thailand. Finally, the predictability of the setup and setdown signal is discussed by relating it to the, potentially predictable, MJO index.

Multiplatform sampling (ship, aircraft, and satellite) of a Gulf Stream warm core ring

NASA Technical Reports Server (NTRS)

Smith, Raymond C.; Brown, Otis B.; Hoge, Frank E.; Baker, Karen S.; Evans, Robert H.

1987-01-01

The purpose of this paper is to demonstrate the ability to meet the need to measure distributions of physical and biological properties of the ocean over large areas synoptically and over long time periods by means of remote sensing utilizing contemporaneous buoy, ship, aircraft, and satellite (i.e., multiplatform) sampling strategies. A mapping of sea surface temperature and chlorophyll fields in a Gulf Stream warm core ring using the multiplatform approach is described. Sampling capabilities of each sensing system are discussed as background for the data collected by means of these three dissimilar methods. Commensurate space/time sample sets from each sensing system are compared, and their relative accuracies in space and time are determined. The three-dimensional composite maps derived from the data set provide a synoptic perspective unobtainable from single platforms alone.

Southeast Georgia embayment high-resolution seismic-reflection survey

USGS Publications Warehouse

Edsall, Douglas W.

1979-01-01

A high-resolution seismic survey of the offshore part of the Southeast Georgia Embayment on about a 20 km spacing was completed in 1976. A stratigraphic analyses of the data shows that the largest controlling factor in the depositional history of the shelf has been the Gulf Stream. These currents have shifted back and forth across the shelf, at times incising into shelf sediments, and at all times blocking much of the accumulation of Cenozoic sediments seaward of the Florida-Hatteras Slope. In the southern region the Gulf Stream maintained its present position since Miocene time, blocking the accumulation of Pliocene and younger rocks on the Plateau. Northward, in the middle, region the currents turned slightly to the northeast. The inner portion of the Blake Plateau has been scoured of sediments since the Paleocene in this area, and scouring has also occurred on the shelf from time to time. In the northern part of the survey area a more easterly flow of the Gulf Stream has allowed Eocene and younger rocks to be deposited on the Plateau. Line drawings and a geologic map show the distribution of the various Cretaceous and Cenozoic units. A number of potential environmental hazards or constraints to petroleum development seen in the reflection data are identified. Besides current scour and erosion features, these include gravity faults on the slope, a slump, faulting on the inner Blake Plateau, the shelf edge reef, and deep water reefs on the Blake Plateau.

First satellite tracks of the Endangered black-capped petrel

USGS Publications Warehouse

Jodice, Patrick G.R.; Ronconi, Robert A.; Rupp, Ernst; Wallace, George E.; Satgé, Yvan

2015-01-01

The black-capped petrel Pterodroma hasitata is an endangered seabird with fewer than 2000 breeding pairs restricted to a few breeding sites in Haiti and the Dominican Republic. To date, use areas at sea have been determined entirely from vessel-based surveys and opportunistic sightings and, as such, spatial and temporal gaps in our understanding of the species’ marine range are likely. To enhance our understanding of marine use areas, we deployed satellite tags on 3 black-capped petrels breeding on Hispaniola, representing the first tracking study for this species and one of the first published tracking studies for any breeding seabird in the Caribbean. During chick rearing, petrels primarily used marine habitats in the southern Caribbean Sea (ca. 18.0° to 11.5°N, 70.0° to 75.5°W) between the breeding site and the coasts of Venezuela and Colombia. Maximum distance from the breeding sites ranged from ca. 500 to 1500 km during the chick-rearing period. During the post-breeding period, each bird dispersed north and used waters west of the Gulf Stream offshore of the mid- and southern Atlantic coasts of the USA as well as Gulf Stream waters and deeper pelagic waters east of the Gulf Stream. Maximum distance from the breeding sites ranged from ca. 2000 to 2200 km among birds during the nonbreeding period. Petrels used waters located within 14 different exclusive economic zones, suggesting that international collaboration will benefit the development of management strategies for this species.

Quantifying and predicting historical and future patterns of carbon fluxes from the North American Continent to Ocean

NASA Astrophysics Data System (ADS)

Tian, H.; Zhang, B.; Xu, R.; Yang, J.; Yao, Y.; Pan, S.; Lohrenz, S. E.; Cai, W. J.; He, R.; Najjar, R. G.; Friedrichs, M. A. M.; Hofmann, E. E.

2017-12-01

Carbon export through river channels to coastal waters is a fundamental component of the global carbon cycle. Changes in the terrestrial environment, both natural (e.g., climatic change, enriched CO2 concentration, and elevated ozone concentration) and anthropogenic (e.g, deforestation, cropland expansion, and urbanization) have greatly altered carbon production, stocks, decomposition, movement and export from land to river and ocean systems. However, the magnitude and spatiotemporal patterns of lateral carbon fluxes from land to oceans and the underlying mechanisms responsible for these fluxes remain far from certain. Here we applied a process-based land model with explicit representation of carbon processes in stream and rivers (Dynamic Land Ecosystem Model: DLEM 2.0) to examine how changes in climate, land use, atmospheric CO2, and nitrogen deposition have affected the carbon fluxes from North American continent to Ocean during 1980-2015. Our simulated results indicated that terrestrial carbon export shows substantially spatial and temporal variability. Of the five sub-regions (Arctic coast, Pacific coast, Gulf of Mexico, Atlantic coast, and Great lakes), the Arctic sub-region provides the highest DOC flux, whereas the Gulf of Mexico sub-region provided the highest DIC flux. However, terrestrial carbon export to the arctic oceans showed increasing trends for both DOC and DIC, whereas DOC and DIC export to the Gulf of Mexico decreased in the recent decades. Future pattern of riverine carbon fluxes would be largely dependent on the climate change and land use scenarios.

NOAA Ecosystem Data Assembly Center for the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Parsons, A. R.; Beard, R. H.; Arnone, R. A.; Cross, S. L.; Comar, P. G.; May, N.; Strange, T. P.

2006-12-01

Through research programs at the NOAA Northern Gulf of Mexico Cooperative Institute (CI), NOAA is establishing an Ecosystem Data Assembly Center (EDAC) for the Gulf of Mexico. The EDAC demonstrates the utility of integrating many heterogeneous data types and streams used to characterized and identify ecosystems for the purpose of determining the health of ecosystems and identifying applications of the data within coastal resource management activities. Data streams include meteorological, physical oceanographic, ocean color, benthic, biogeochemical surveys, fishery, as well as fresh water fluxes (rainfall and river flow). Additionally the EDAC will provide an interface to the ecosystem data through an ontology based on the Coastal/Marine Ecological Classification System (CMECS). Applications of the ontological approach within the EDAC will be applied to increase public knowledge on habitat and ecosystem awareness. The EDAC plans to leverage companion socioeconomic studies to identify the essential data needed for continued EDAC operations. All data-management architectures and practices within the EDAC ensure interoperability with the Integrated Ocean Observing System (IOOS) national backbone by incorporating the IOOS Data Management and Communications Plan. Proven data protocols, standards, formats, applications, practices and architectures developed by the EDAC will be transitioned to the NOAA National Data Centers.

Coupling Meteorological, Land Surface and Water Temperature Models in the Mississippi River Basin

NASA Astrophysics Data System (ADS)

Tang, C.; Cooter, E. J.

2017-12-01

Water temperature is a significant factor influencing of the stream ecosystem and water management especially under climate change. In this study, we demonstrate a physically based semi-Lagrangian water temperature model (RBM) coupled with the Variable Infiltration Capacity (VIC) hydrology model and Weather Research & Forecasting Model (WRF) in the Mississippi River Basin (MRB). The results of this coupling compare favorably with observed water temperature data at river gages throughout the MRB. Further sensitivity analysis shows that mean water temperatures increase by 1.3°C, 1.5°C, and 1.8°C in northern, central and southern MRB zones, respectively, under a hypothetical uniform air temperature increase of 3°C. If air temperatures increase uniformly by 6°C in this scenario, then water temperatures are projected to increase by 3.3°C, 3.5°C and 4.0°C. Lastly, downscaled air temperatures from a global climate model are used to drive the coupled VIC and RBM model from 2020 to 2099. Average stream temperatures from 2020 to 2099 increase by 1°C to 8°C above 1950 to 2010 average water temperatures, with non-uniform increases along the river. In some portions of the MRB, stream temperatures could increase above survival thresholds for several native fish species, which are critical components of the stream ecosystem. The increased water temperature accelerates harmful algal blooming which results in a larger dead zone in the Gulf of Mexico.

Calcareous nannofossil evidence for the existence of the Gulf Stream during the late Maastrichtian

USGS Publications Warehouse

Watkins, D.K.; ,

2005-01-01

Upper Maastrichtian calcareous nannofossil assemblages, from eight cores on the South Carolina Coastal Plain (onshore set) and three deep sea drilling sites from the continental slope and abyssal hills (offshore set), were analyzed by correlation and principal component analysis to examine the ancient surface water thermal structure. In addition, a temperature index derived from independently published paleobiogeographic information was applied to the sample data. All three methods indicate a strong separation of the samples into onshore and offshore sets, with the offshore data set exhibiting significantly warmer paleotemperatures. The great disparity between these two sample sets indicates that there was a strong thermal contrast between the onshore and offshore surface water masses that persisted throughout the late Maastrichtian despite evident shortterm changes in fertility, productivity, and community structure. This suggests the Gulf Stream was present as a major oceanographic feature during the late Maastrichtian. Copyright 2005 by the American Geophysical Union.

Silver hake tracks changes in Northwest Atlantic circulation.

PubMed

Nye, Janet A; Joyce, Terrence M; Kwon, Young-Oh; Link, Jason S

2011-08-02

Recent studies documenting shifts in spatial distribution of many organisms in response to a warming climate highlight the need to understand the mechanisms underlying species distribution at large spatial scales. Here we present one noteworthy example of remote oceanographic processes governing the spatial distribution of adult silver hake, Merluccius bilinearis, a commercially important fish in the Northeast US shelf region. Changes in spatial distribution of silver hake over the last 40 years are highly correlated with the position of the Gulf Stream. These changes in distribution are in direct response to local changes in bottom temperature on the continental shelf that are responding to the same large scale circulation change affecting the Gulf Stream path, namely changes in the Atlantic meridional overturning circulation (AMOC). If the AMOC weakens, as is suggested by global climate models, silver hake distribution will remain in a poleward position, the extent to which could be forecast at both decadal and multidecadal scales.

Verification of Geosat sea surface topography in the Gulf Stream extension with surface drifting buoys and hydrographic measurements

NASA Astrophysics Data System (ADS)

Willebrand, J.; KäSe, R. H.; Stammer, D.; Hinrichsen, H.-H.; Krauss, W.

1990-03-01

Altimeter data from Geosat have been analyzed in the Gulf Stream extension area. Horizontal maps of the sea surface height anomaly relative to an annual mean for various 17-day intervals were constructed using an objective mapping procedure. The mean sea level was approximated by the dynamic topography from climatological hydrographic data. Geostrophic surface velocities derived from the composite maps (mean plus anomaly) are significantly correlated with surface drifter velocities observed during an oceanographie experiment in the spring of 1987. The drifter velocities contain much energy on scales less than 100 km which are not resolved in the altimetric maps. It is shown that the composite sea surface height also agrees well with ground verification from hydrographic data along sections in a triangle between the Azores, Newfoundland, and Bermuda, except in regions of high mean gradients.

Aerial Observations of Symmetric Instability at the North Wall of the Gulf Stream

NASA Astrophysics Data System (ADS)

Savelyev, I.; Thomas, L. N.; Smith, G. B.; Wang, Q.; Shearman, R. K.; Haack, T.; Christman, A. J.; Blomquist, B.; Sletten, M.; Miller, W. D.; Fernando, H. J. S.

2018-01-01

An unusual spatial pattern on the ocean surface was captured by thermal airborne swaths taken across a strong sea surface temperature front at the North Wall of the Gulf Stream. The thermal pattern on the cold side of the front resembles a staircase consisting of tens of steps, each up to ˜200 m wide and up to ˜0.3°C warm. The steps are well organized, clearly separated by sharp temperature gradients, mostly parallel and aligned with the primary front. The interpretation of the airborne imagery is aided by oceanographic measurements from two research vessels. Analysis of the in situ observations indicates that the front was unstable to symmetric instability, a type of overturning instability that can generate coherent structures with similar dimensions to the temperature steps seen in the airborne imagery. It is concluded that the images capture, for the first time, the surface temperature field of symmetric instability turbulence.

Remote sensing of Gulf Stream using GEOS-3 radar altimeter

NASA Technical Reports Server (NTRS)

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

1978-01-01

Radar altimeter measurements from the GEOS-3 satellite to the ocean surface indicated the presence of expected geostrophic height differences across the the Gulf Stream. Dynamic sea surface heights were found by both editing and filtering the raw sea surface heights and then referencing these processed data to a 5 minute x 5 minute geoid. Any trend between the processed data and the geoid was removed by subtracting out a linear fit to the residuals in the open ocean. The mean current velocity of 107 + or - 29 cm/sec calculated from the dynamic heights for all orbits corresponded with velocities obtained from hydrographic methods. Also, dynamic topographic maps were produced for August, September, and October 1975. Results pointed out limitations in the accuracy of the geoid, height anomaly deteriorations due to filtering, and lack of dense time and space distribution of measurements.

Cenozoic North American Drainage Basin Evolution, Sediment Yield, and Accumulation in the Gulf of Mexico Basin

NASA Astrophysics Data System (ADS)

Galloway, W.; Ganey-Curry, P. E.

2010-12-01

The Cenozoic fill of the Gulf of Mexico basin contains a continuous record of sediment supply from the North American continental interior for the past 65 million years. Regional mapping of unit thickness and paleogeography for 18 depositional episodes defines patterns of shifting entry points of continental fluvial systems and quantifies the total volume of sediment supplied during each episode. Eight fluvio-deltaic depocenters, named for geographic similarities to entry points and drainage basins of modern rivers, are present. From southwest to northeast, they are the Rio Bravo, Rio Grande, Guadalupe, Colorado, Houston-Brazos, Red, Mississippi, and Tennessee axes. Sediment volume was calculated from hand-contoured unit thickness maps compiled from basin-wide well and seismic control. Using a GIS algorithm to sum volumes within polygons bounding interpreted North American river contribution, the total extant volume was then calculated. General compaction factors were used to convert modern volume to quantitative approximations of total grain volume. Grain volume rate of supply for each depositional episode was then calculated. Values vary by more than an order of magnitude. Supply rate has commonly varied by two-fold or more between successive depositional episodes. Sediment supply is a significant, independent variable in development of stratigraphic sequences within the Gulf basin. Paleogeographic maps of the continental interior for eleven Cenozoic time intervals display the evolving and complex interplay of intracontinental tectonism, climate change, and drainage basin evolution. Five tectono-climatic eras are differentiated: Paleocene late Laramide era; early to middle Eocene terminal Laramide era; middle Cenozoic (Late Eocene—Early Miocene) dry, volcanogenic era; middle Neogene (Middle—Late Miocene) arid, extensional era; and late Neogene (Plio—Pleistocene) monsoonal, epeirogenic uplift era. Sediment supply to the GOM reflects the interplay of (1) areal extent of river drainage basins, (2) source area relief, (3) climate of the source areas and tributary systems, (4) source lithology, and (5) sediment storage within the upper drainage basin. Climate has played an important and complex role in modulating supply. In wet tropical to temperate climate regimes, abundant runoff efficiently removed entrained sediment. Arid climate limited runoff; resultant transport-limited tributaries and trunk streams deposited aggradational alluvial aprons, storing sediment in the drainage basin even in the absence of a structural depression. Eolian deposition commonly accompanied such alluvial aggradation. In contrast, seasonality and consequent runoff variability favored erosion and efficient sediment evacuation from the upper parts of drainage basins. Tectonism has played a prominent but equally complex role. Elevation of uplands by compression, crustal heating, or extrusive volcanism created primary loci of erosion and high sediment yield. At the same time, accompanying subsidence sometimes created long-lived sediment repositories that intercepted and sequestered sediment adjacent to sources. Regional patterns of uplift and subsidence relocated drainage divides and redirected trunk stream paths to the Gulf margin.

Nature Run for the North Atlantic Ocean Hurricane Region: System Evaluation and Regional Applications

NASA Astrophysics Data System (ADS)

Kourafalou, V.; Androulidakis, I.; Halliwell, G. R., Jr.; Kang, H.; Mehari, M. F.; Atlas, R. M.

2016-02-01

A prototype ocean Observing System Simulation Experiments (OSSE) system, first developed and data validated in the Gulf of Mexico, has been applied on the extended North Atlantic Ocean hurricane region. The main objectives of this study are: a) to contribute toward a fully relocatable ocean OSSE system by expanding the Gulf of Mexico OSSE to the North Atlantic Ocean; b) demonstrate and quantify improvements in hurricane forecasting when the ocean component of coupled hurricane models is advanced through targeted observations and assimilation. The system is based on the Hybrid Coordinate Ocean Model (HYCOM) and has been applied on a 1/250 Mercator mesh for the free-running Nature Run (NR) and on a 1/120 Mercator mesh for the data assimilative forecast model (FM). A "fraternal twin" system is employed, using two different realizations for NR and FM, each configured to produce substantially different physics and truncation errors. The NR has been evaluated using a variety of available observations, such as from AVISO, GDEM climatology and GHRSST observations, plus specific regional products (upper ocean profiles from air-borne instruments, surface velocity maps derived from the historical drifter data set and tropical cyclone heat potential maps derived from altimetry observations). The utility of the OSSE system to advance the knowledge of regional air-sea interaction processes related to hurricane activity is demonstrated in the Amazon region (salinity induced surface barrier layer) and the Gulf Stream region (hurricane impact on the Gulf Stream extension).

The North Atlantic Ocean Is in a State of Reduced Overturning

NASA Astrophysics Data System (ADS)

Smeed, D. A.; Josey, S. A.; Beaulieu, C.; Johns, W. E.; Moat, B. I.; Frajka-Williams, E.; Rayner, D.; Meinen, C. S.; Baringer, M. O.; Bryden, H. L.; McCarthy, G. D.

2018-02-01

The Atlantic Meridional Overturning Circulation (AMOC) is responsible for a variable and climatically important northward transport of heat. Using data from an array of instruments that span the Atlantic at 26°N, we show that the AMOC has been in a state of reduced overturning since 2008 as compared to 2004-2008. This change of AMOC state is concurrent with other changes in the North Atlantic such as a northward shift and broadening of the Gulf Stream and altered patterns of heat content and sea surface temperature. These changes resemble the response to a declining AMOC predicted by coupled climate models. Concurrent changes in air-sea fluxes close to the western boundary reveal that the changes in ocean heat transport and sea surface temperature have altered the pattern of ocean-atmosphere heat exchange over the North Atlantic. These results provide strong observational evidence that the AMOC is a major factor in decadal-scale variability of North Atlantic climate.

Skillful prediction of northern climate provided by the ocean

PubMed Central

Årthun, Marius; Eldevik, Tor; Viste, Ellen; Drange, Helge; Furevik, Tore; Johnson, Helen L.; Keenlyside, Noel S.

2017-01-01

It is commonly understood that a potential for skillful climate prediction resides in the ocean. It nevertheless remains unresolved to what extent variable ocean heat is imprinted on the atmosphere to realize its predictive potential over land. Here we assess from observations whether anomalous heat in the Gulf Stream's northern extension provides predictability of northwestern European and Arctic climate. We show that variations in ocean temperature in the high latitude North Atlantic and Nordic Seas are reflected in the climate of northwestern Europe and in winter Arctic sea ice extent. Statistical regression models show that a significant part of northern climate variability thus can be skillfully predicted up to a decade in advance based on the state of the ocean. Particularly, we predict that Norwegian air temperature will decrease over the coming years, although staying above the long-term (1981–2010) average. Winter Arctic sea ice extent will remain low but with a general increase towards 2020. PMID:28631732

A forty-three year museum study of northern cricket frog (Acris crepitans) abnormalities in Arkansas: upward trends and distributions.

PubMed

McCallum, Malcolm L; Trauth, Stanley E

2003-07-01

The northern cricket frog (Acris crepitans) is a resident of streams, rivers, and wetlands of eastern North America. We documented abnormalities in A. crepitans housed in the Arkansas State University Museum of Zoology Herpetology Collection. Abnormality frequency increased from 1957 to 2000 (chi 2 = 43.76, df = 3, P < 0.001). From 1957 through 1979 only 3.33% of specimens were unusual. This rate was 6.87% during the 1990s, and in 2000 it was 8.48%. High frequencies of abnormalities were identified in the following Ozark highland counties: Sharp, Lawrence, and Randolph. We observed 104 abnormalities among 1,464 frogs (7.10%). The differential abnormality frequencies observed between the Arkansas lowlands and highlands are striking. The Ozarks had significantly higher frequencies of abnormalities than other Arkansas regions (chi 2 = 59.76, df = 4, P < 0.001). The Ouachita Mountains had significantly higher frequencies than the Gulf Coastal Plain, Delta, or Arkansas River Valley (chi 2 = 13.172, df = 3, P < 0.01). There was no difference in abnormality frequency between the Gulf Coastal Plain, Delta, and Arkansas River Valley (chi 2 = 0.422, df = 2, P > 0.70). Proposed hypotheses for distributions include: 1) A. crepitans might possess naturally high abnormality levels, and land use practices of the Delta may reduce this variability; 2) an unknown xenobiotic may be in Ozark streams causing increased numbers of abnormalities; 3) the museum's collection effort may be skewed; 4) Delta habitat might be more favorable for green tree frogs (Hyla cinerea) allowing this species to drive out A. crepitans through competition; here, abnormal metamorphs are not detected because they are even less competitive than normal individuals.

Assimilation of Altimeter Data into a Quasigeostrophic Model of the Gulf Stream System. Part 2; Assimilation Results

NASA Technical Reports Server (NTRS)

Capotondi, Antonietta; Holland, William R.; Malanotte-Rizzoli, Paola

1995-01-01

The improvement in the climatological behavior of a numerical model as a consequence of the assimilation of surface data is investigated. The model used for this study is a quasigeostrophic (QG) model of the Gulf Stream region. The data that have been assimilated are maps of sea surface height that have been obtained as the superposition of sea surface height variability deduced from the Geosat altimeter measurements and a mean field constructed from historical hydrographic data. The method used for assimilating the data is the nudging technique. Nudging has been implemented in such a way as to achieve a high degree of convergence of the surface model fields toward the observations. Comparisons of the assimilation results with available in situ observations show a significant improvement in the degree of realism of the climatological model behavior, with respect to the model in which no data are assimilated. The remaining discrepancies in the model mean circulation seem to be mainly associated with deficiencies in the mean component of the surface data that are assimilated. On the other hand, the possibility of building into the model more realistic eddy characteristics through the assimilation of the surface eddy field proves very successful in driving components of the mean model circulation that are in relatively good agreement with the available observations. Comparisons with current meter time series during a time period partially overlapping the Geosat mission show that the model is able to 'correctly' extrapolate the instantaneous surface eddy signals to depths of approximately 1500 m. The correlation coefficient between current meter and model time series varies from values close to 0.7 in the top 1500 m to values as low as 0.1-0.2 in the deep ocean.

Observed and modeled mesoscale variability near the Gulf Stream and Kuroshio Extension

NASA Astrophysics Data System (ADS)

Schmitz, William J.; Holland, William R.

1986-08-01

Our earliest intercomparisons between western North Atlantic data and eddy-resolving two-layer quasi-geostrophic symmetric-double-gyre steady wind-forced numerical model results focused on the amplitudes and largest horizontal scales in patterns of eddy kinetic energy, primarily abyssal. Here, intercomparisons are extended to recent eight-layer model runs and new data which allow expansion of the investigation to the Kuroshio Extension and throughout much of the water column. Two numerical experiments are shown to have realistic zonal, vertical, and temporal eddy scales in the vicinity of the Kuroshio Extension in one case and the Gulf Stream in the other. Model zonal mean speeds are larger than observed, but vertical shears are in general agreement with the data. A longitudinal displacement between the maximum intensity in surface and abyssal eddy fields as observed for the North Atlantic is not found in the model results. The numerical simulations examined are highly idealized, notably with respect to basin shape, topography, wind-forcing, and of course dissipation. Therefore the zero-order agreement between modeled and observed basic characteristics of mid-latitude jets and their associated eddy fields suggests that such properties are predominantly determined by the physical mechanisms which dominate the models, where the fluctuations are the result of instability processes. The comparatively high vertical resolution of the model is needed to compare with new higher-resolution data as well as for dynamical reasons, although the precise number of layers required either kinematically or dynamically (or numerically) has not been determined; we estimate four to six when no attempt is made to account for bottom- or near-surface-intensified phenomena.

Development of Sr/Ca-d18O Temperature Calibrations of a Siderastrea siderea Coral from the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Wagner, A. J.; DeLong, K. L.; Kilbourne, H.; Slowey, N. C.

2016-12-01

The Gulf of Mexico (GOM) is sensitive to oceanic and atmospheric variability in both the Atlantic and Pacific Oceans (i.e., Atlantic Multidecadal Oscillation (AMO), El Niño Southern Oscillation (ENSO), Pacific North American pattern (PNA), and Pacific Decadal Oscillation (PDO)). The major GOM current, the Loop Current, feeds the Gulf Stream as it transports oceanic heat to the northern Atlantic Ocean. The northern GOM is the northernmost summer extent of the western hemisphere warm pool (WHWP) that drives oceanic moisture flux and precipitation into the Americas. Decadally-resolved foraminifera reconstructions from the northern GOM indicates SST was 2 to 4ºC colder on average than today during the Little Ice Age (LIA, 1850), whereas a subannually-resolved coral reconstruction from the southeastern GOM find 1.5 to 2ºC colder intervals and reduced areal extent of the WHWP on interannual time scales during some intervals of the LIA. However, records capable of resolving annual and subannual SST variability from the northern GOM, necessary for investigating WHWP northern extent, are still lacking. Here we present a new temperature reconstruction for the northern GOM derived from strontium-to-calcium (Sr/Ca) ratios of approximately monthly samples milled from a Siderastrea siderea coral core collected from the Flower Garden Banks National Marine Sanctuary (FGBNMS; 27° 52.5'N, 93° 49'W) growing at a water depth of 20 m. Coral Sr/Ca and δ18O is calibrated to reef temperature data from FGBNMS Hobotemp data loggers near the reef cap in 22 m water depth (1986-2004) and to NOAA OISST (1981-2004). Coral Sr/Ca co-varies with the reef temperature (r=0.95, p<0.05, n=146) and consistently captures winter values in reef temperature with slightly warmer summers (0.9ºC on average). Pseudocoral analysis is used to assess the relationships between SST and SSS in coral δ18O.

Massive subtropical icebergs and freshwater forcing of climate

NASA Astrophysics Data System (ADS)

Condron, Alan; Hill, Jenna

2014-05-01

High resolution seafloor mapping shows incredible evidence that massive (>300m thick) icebergs drifted more than 5,000 km along the United States continental margin to southern Florida during the last deglaciation. Here we discuss how the discovery of icebergs in this location highlights a previously unknown ocean circulation pathway capable of transporting icebergs and meltwater from the Northern Hemisphere ice sheets directly to the subtropical North Atlantic. This pathway questions the classical idea that freshwater forcing from meltwater floods and icebergs occurred primarily over the subpolar North Atlantic (50N - 70N), with little penetration to subtropical latitudes, south of 40N. Using a sophisticated, high-resolution (1/6 deg.) ocean model, capable of resolving the circulation of the coastal ocean in detail, we show that icebergs off the coast of Florida likely calved from ice streams in the Gulf of St Lawrence and Hudson Bay. We find that icebergs can only drift south of Cape Hatteras, and overcome the northward flow of the Gulf Stream, when they are entrained in a narrow, southward-flowing, coastal meltwater flood originating from the Laurentide Ice Sheet. This cold meltwater increases iceberg survival in the warm subtropics and flows in the opposite direction to the Gulf Stream along the coast, allowing icebergs to drift to southern Florida in less than 4 months. We conclude that during the last deglaciation, icebergs drifted south in massive meltwater floods that delivered freshwater to the subtropical North Atlantic. Our findings have important implications for understanding how changes in freshwater forcing triggered past abrupt climate change.

Migration Pathways, Behavioural Thermoregulation and Overwintering Grounds of Blue Sharks in the Northwest Atlantic

PubMed Central

Campana, Steven E.; Dorey, Anna; Fowler, Mark; Joyce, Warren; Wang, Zeliang; Yashayaev, Igor

2011-01-01

The blue shark Prionace glauca is the most abundant large pelagic shark in the Atlantic Ocean. Although recaptures of tagged sharks have shown that the species is highly migratory, migration pathways towards the overwintering grounds remain poorly understood. We used archival satellite pop-up tags to track 23 blue sharks over a mean period of 88 days as they departed the coastal waters of North America in the autumn. Within 1–2 days of entering the Gulf Stream (median date of 21 Oct), all sharks initiated a striking diel vertical migration, taking them from a mean nighttime depth of 74 m to a mean depth of 412 m during the day as they appeared to pursue vertically migrating squid and fish prey. Although functionally blind at depth, calculations suggest that there would be a ∼2.5-fold thermoregulatory advantage to swimming and feeding in the markedly cooler deep waters, even if there was any reduced foraging success associated with the extreme depth. Noting that the Gulf Stream current speeds are reduced at depth, we used a detailed circulation model of the North Atlantic to examine the influence of the diving behaviour on the advection experienced by the sharks. However, there was no indication that the shark diving resulted in a significant modification of their net migratory pathway. The relative abundance of deep-diving sharks, swordfish, and sperm whales in the Gulf Stream and adjacent waters suggests that it may serve as a key winter feeding ground for large pelagic predators in the North Atlantic. PMID:21373198

Intercomparison of the Gulf Stream in ocean reanalyses: 1993-2010

NASA Astrophysics Data System (ADS)

Chi, Lequan; Wolfe, Christopher L. P.; Hameed, Sultan

2018-05-01

In recent years, significant progress has been made in the development of high-resolution ocean reanalysis products. This paper compares aspects of the Gulf Stream (GS) from the Florida Straits to south of the Grand Banks-particularly Florida Strait transport, separation of the GS near Cape Hatteras, GS properties along the Oleander Line (from New Jersey to Bermuda), GS path, and the GS north wall positions-in 13 widely used global reanalysis products of various resolutions, including two unconstrained products. A large spread across reanalysis products is found. HYCOM and GLORYS2v4 stand out for their superior performance by most metrics. Some common biases are found in all discussed models; for example, the velocity structure of the GS near the Oleander Line is too symmetrical and the maximum velocity is too weak compared with observations. Less than half of the reanalysis products show significant correlations (at the 95% confidence level) with observations for the GS separation latitude at Cape Hatteras, the GS transport, and net transport across Oleander Line. The cross-stream velocity structure is further discussed by a theoretical model idealizing GS as a smoothed PV front.

Parameter sensitivity and identifiability for a biogeochemical model of hypoxia in the northern Gulf of Mexico

EPA Science Inventory

Local sensitivity analyses and identifiable parameter subsets were used to describe numerical constraints of a hypoxia model for bottom waters of the northern Gulf of Mexico. The sensitivity of state variables differed considerably with parameter changes, although most variables ...

Evidence of multidecadal climate variability and the Atlantic Multidecadal Oscillation from a Gulf of Mexico sea-surface temperature-proxy record

USGS Publications Warehouse

Poore, R.Z.; DeLong, K.L.; Richey, J.N.; Quinn, T.M.

2009-01-01

A comparison of a Mg/Ca-based sea-surface temperature (SST)-anomaly record from the northern Gulf of Mexico, a calculated index of variability in observed North Atlantic SST known as the Atlantic Multidecadal Oscillation (AMO), and a tree-ring reconstruction of the AMO contain similar patterns of variation over the last 110 years. Thus, the multidecadal variability observed in the instrumental record is present in the tree-ring and Mg/Ca proxy data. Frequency analysis of the Gulf of Mexico SST record and the tree-ring AMO reconstruction from 1550 to 1990 found similar multidecadal-scale periodicities (???30-60 years). This multidecadal periodicity is about half the observed (60-80 years) variability identified in the AMO for the 20th century. The historical records of hurricane landfalls reveal increased landfalls in the Gulf Coast region during time intervals when the AMO index is positive (warmer SST), and decreased landfalls when the AMO index is negative (cooler SST). Thus, we conclude that alternating intervals of high and low hurricane landfall occurrences may continue on multidecadal timescales along the northern Gulf Coast. However, given the short length of the instrumental record, the actual frequency and stability of the AMO are uncertain, and additional AMO proxy records are needed to establish the character of multidecadal-scale SST variability in the North Atlantic. ?? 2009 US Government.

Assessing trace metal pollution through high spatial resolution of surface sediments along the Tunis Gulf coast (southwestern Mediterranean).

PubMed

Ennouri, Rym; Zaaboub, Noureddine; Fertouna-Bellakhal, Mouna; Chouba, Lassad; Aleya, Lotfi

2016-03-01

Tunis Gulf (northern Tunisia, Mediterranean Sea) is of great economic importance due to its abundant fish resources. Rising urbanization and industrial development in the surrounding area have resulted in an increase in untreated effluents and domestic waste discharged into the gulf via its tributary streams. Metal (Cd, Pb, Hg, Cu, Zn, Fe, and Mn) and major element (Mg, Ca, Na, and K) concentrations were measured in the grain fine fraction <63 μm by atomic absorption spectrophotometry. Results showed varying spatial distribution patterns for metals, indicating complex origins and controlling factors such as anthropogenic activities. Sediment metal concentrations are ranked as follows: Fe > Mg > Zn > Mn > Pb > Cu > Cd > Hg. Metals tend to be concentrated in proximity to source points, suggesting that the mineral enrichment elements come from sewage of coastal towns and pollution from industrial dumps and located along local rivers, lagoons, and on the gulf shore itself. This study showed that trace metal and major element concentrations in surface sediments along the Tunis Gulf shores were lower than those found in other coastal areas of the Mediterranean Sea.

Timing and mechanisms for the deposition of the glaciomarine mud in and around the Gulf of Maine: A discussion of alternative models

USGS Publications Warehouse

Oldale, Robert N.

1989-01-01

Glaciomarine mud in the Gulf of Maine, characterized by rhythmic seismic layers that mimic the morphology of the underlying surface, is composed of subequal amounts of silt and clay, variable amounts of sand, and sparse gravel-sized clasts. The mud is Wisconsinan in age and was deposited during the retreat of the last ice sheet. A beginning date of 38 ka, proposed by King and Fader (1986) in their chronology of the last deglaciation, is considered too old. An alternative chronology, more consistent with the continental record to the west, is proposed here. ln this interpretation, deposition ofglaciomarine mud began about 18 ka when the late Wisconsinan ice retreated from Georges Bank, Great South Channel, and Northeast Channel and ended around 11 ka, when meltwater ceased to enter the Gulf of Maine. Basal-till melt-out from an ice shelf and bergs as the source of the glaciomarine mud, also proposed by King and Fader (1986), is thought to be inconsistent with the volume, widespread rhythmic bedding, and low stone content of the deposit. More likely the source of the glaciomarine mud was rock-flour-laden meltwater that entered the sea along the grounding line of a calving glacier or by way of subaerial meltwater streams. The rock flour was then dispersed by sediment plumes and was deposited when the sediment fell to the sea floor, aided by flocculation and biological agglutination. Rhythmic layers within the glaciomarine mud could represent annual cyclic sedimentation (varves) or cyclic events of lesser duration.

Evaluating the competing effects of lithology and sediment supply on the erosional dynamics of rivers crossing active faults.

NASA Astrophysics Data System (ADS)

Whittaker, Alex; Boulton, Sarah; Kent, Emiko; Zondervan, Jesse; Hann, Madeleine; Watkins, Stephen; Bell, Rebecca; Brooke, Sam

2017-04-01

Lithology and sediment supply influence the erosional dynamics of rivers crossing active faults and together these effects govern the style, timescale and means by which landscapes respond to their tectono-climatic boundary conditions. Here, for transient bedrock catchments in the Gediz Graben, Turkey, and the Gulf of Corinth, Greece, for which the timing and rate of active faulting is known, we quantify the relative importance of rock strength and sediment supply on models of fluvial incision. We determine rock type, strength and erodibility using a Schmidt hammer and structural measurements of joint density and size. We evaluate the downstream distribution of channel width and stream power and calculate the extent to which the latter scales with tectonic rates and rock strength. Sediment supply is constrained using estimates of bedrock exposure, transport capacities and erosional fluxes. For the Turkish examples, stream powers in the metamorphic rocks are four times greater than in the Neogene sediment units, indicating a four-fold difference in bedrock erodibility, K, for a two-fold variation in in Schmidt hammer hardness. In the Gulf of Corinth examples, we interpret differences in stream powers near the active faults to represent order of magnitude differences in bedrock erodibility between carbonate and sandstone/conglomerate units. We also observe that in both cases, significant along-strike variation in fault slip rate is not associated with an increase in stream power for the sedimentary rocks and we assess the extent to which this stream power deficit may also represent the effects of sediment-flux-dependent incision.

Data Used in Analyses of Trends, and Nutrient and Suspended-Sediment Loads for Streams in the Southeastern United States, 1973-2005

USGS Publications Warehouse

Staub, Erik L.; Peak, Kelly L.; Tighe, Kirsten C.; Sadorf, Eric M.; Harned, Douglas A.

2010-01-01

Water-quality data from selected surface-water monitoring sites in the Southeastern United States were assessed for trends in concentrations of nutrients, suspended sediment, and major constituents and for in-stream nutrient and suspended-sediment loads for the period 1973-2005. The area of interest includes river basins draining into the southern Atlantic Ocean, the Gulf of Mexico, and the Tennessee River-drainage basins in Hydrologic Regions 03 (South Atlantic - Gulf) and 06 (Tennessee). This data assessment is related to studies of several major river basins as part of the U.S. Geological Survey National Water-Quality Assessment Program, which was designed to assess national water-quality trends during a common time period (1993-2004). Included in this report are data on which trend tests could be performed from 44 U.S. Geological Survey National Water Information System (NWIS) sampling sites. The constituents examined include major ions, nutrients, and suspended sediment; the physical properties examined include pH, specific conductance, dissolved oxygen, and streamflow. Also included are data that were tested for trends from an additional 290 sites from the U.S. Environmental Protection Agency Storage and Retrieval (STORET) database. The trend analyses of the STORET data were limited to total nitrogen and total phosphorus concentrations. Data from 48 U.S. Geological Survey NWIS sampling sites with sufficient water-quality and continuous streamflow data for estimating nutrient and sediment loads are included. The methods of data compilation and modification used prior to performing trend tests and load estimation are described. Results of the seasonal Kendall trend test and the Tobit trend test are given for the 334 monitoring sites, and in-stream load estimates are given for the 48 monitoring sites. Basin characteristics are provided, including regional landscape variables and agricultural nutrient sources (annual variations in cropping and fertilizer use). The data and results presented in this report are in tabular format and can be downloaded and used by environmental researchers and water managers, particularly in the Southeast.

A numerical investigation of surface-induced mesocyclogenesis near the Gulf Stream

NASA Astrophysics Data System (ADS)

Cione, Joseph J.; Raman, Sethu

1995-10-01

A series of numerical experiments designed to simulate the initial development stages of low-level coastal mesocyclogenesis near the Gulf Stream was recently conducted. Under initially quiescent conditions, surface cyclogenesis in the control simulation occurs along a Gulf Stream meander in a region where the gradients in sea surface temperature (SST) are maximized. A low-level mesovortex on the order of 140km forms approximately 12 h into the simulation and continues to intensify through 42h. During the 24 48 h time period, a mesoscale frontal feature develops in direct response to strong diabatic forcing associated with sustained surface latent and sensible heating near the Gulf Stream frontal zone south of the main circulation center. Due to the non-linear advection of the frontal feature during this time period, the previously quasi-stationary circulation center drifts eastward (and away) from the thermal forcing associated with the large SST gradients found to the west. This eastward frontal propagation acts to decrease the magnitude of the low level horizontal air temperature gradient near the center of circulation throughout the 24 42 h development period. During the 42 48-h period, the relatively quick moving frontal feature acts to severely shear the nearly stationary center of circulation in the east west direction. As a result, the mesoscale system begins to fill during the final 6 h of integration. In addition to the control simulation, additional sensitivity experiments were conducted. These experiments were specifically designed to: (1) investigate how the magnitude of the Gulf Stream SST gradients affect the timing and degree of cyclonic development; (2) address the impact surface moisture fluxes and moist convection each have on the simulated low level mesocyclogenesis; (3) isolate the role surface sensible heating plays in the overall development of the simulated mesocyclone. Results from the SST gradient experiment indicate that a moderate enhancement of the SST distribution significantly affects the timing of the initial cyclogenesis and the maximum intensity of the simulated frontal circulation. For the "no turbulent heat flux" experiment, it appears that the elimination of surface sensible heating does not radically alter the overall structure of the simulated mesocyclone. However, the rate of development during the early stage of cyclogenesis, the absolute peak intensity of the system as well as the vertical depth of the simulated mesoscale frontal feature were all noticeably reduced when compared with the control simulation. The initial development of a closed low level circulation was delayed by nearly 18 h in the absence surface latent heat fluxes. Once formed, the system intensified throughout the 48-h period of integration, but unlike the control experiment, a mesoscale frontal feature south of the main circulation center was not simulated. Results from the "no surface moisture flux/no moist convection" simulation illustrate that moist convective processes play a dominant role in the overall development of the mesoscale cyclone. For this particular case, a weak and extremely shallow circulation was simulated after 24h. This circulation quickly eroded however, and was virtually non-existent for integration times greater than 39h.

Earth Observations taken by the STS-109 crew

NASA Image and Video Library

2002-03-05

STS109-719-076 (1-12 March 2002) --- The astronauts on board the Space Shuttle Columbia took this 70mm picture featuring part of the eastern sea board. The oblique view looks northward from South Florida to the southern Appalachians. Most of the southeastern United States appears in crisp, clear air in the wake of a cold front that has pushed well off the mainland. Only a few jet stream and low-level clouds remain over South Florida and Gulf Stream.

A Study of Oceans and Atmospheric Interactions Associated with Tropical Cyclone Activity using Earth Observing Technology

NASA Astrophysics Data System (ADS)

Abdullah, Warith; Reddy, Remata

From October 22nd to 30th, 2012 Hurricane Sandy was a huge storm of many abnormalities causing an estimated 50 billion dollars in damage. Tropical storm development states systems’ energy as product of warm sea surface temperatures (SST’s) and tropical cyclone heat potential (TCHP). Advances in Earth Observing (EO) technology, remote sensing and proxy remote sensing have allowed for accurate measurements of SST and TCHP information. In this study, we investigated rapid intensification of Sandy through EO applications for precipitable water vapor (PWAT), SST’s and TCHP during the period of October 27th. These data were obtained from NASA and NOAA satellites and NOAA National Buoy data center (NDBC). The Sensible Heat (Qs) fluxes were computed to determine available energy resulting from ocean-atmosphere interface. Buoy 41010, 120 NM east of Cape Canaveral at 0850 UTC measured 22.3 °C atmospheric temperatures and 27 °C SST, an interface of 4.7 °C. Sensible heat equation computed fluxes of 43.7 W/m2 at 982.0 mb central pressure. Sandy formed as late-season storm and near-surface air temperatures averaged > 21 °C according to NOAA/ESRL NCEP/NCAR reanalysis at 1000 mb and GOES 13 (EAST) geostationary water vapor imagery shows approaching cold front during October 27th. Sandy encountered massive dry air intrusion to S, SE and E quadrants of storm while travelling up U.S east coast but experienced no weakening. Cool, dry air intrusion was considered for PWAT investigation from closest sounding station during Oct. 27th 0900 - 2100 UTC at Charleston, SC station 72208. Measured PWAT totaled 42.97 mm, indicating large energy potential supply to the storm. The Gulf Stream was observed using NASA Short-term Prediction Research and Transition Center (SPoRT) MODIS SST analysis. The results show 5 °C warmer above average than surrounding cooler water, with > 25 °C water extent approximately 400 NM east of Chesapeake Bay and eddies > 26 °C. Results from sensible heat computations for atmospheric interface suggests unusual warmth associated with Gulf Stream current, such that it provided Sandy with enough kinetic energy to intensify at high latitude. The study further suggests that energy gained from Caribbean TCHP and Gulf Stream SST’s were largely retained by Sandy upon losing tropical-cyclone characteristics and merging with strong cold front and polar jet stream. Storms of Sandy’s magnitude and unusual source of energy resulting from Gulf Stream may indicate a building average for tropical cyclone development and intensity for North Atlantic, particularly as the GOM waters continue to warm on seasonal averages.

Modelling the temporal and spatial distribution of ecological variables in Beibu Gulf

NASA Astrophysics Data System (ADS)

Pan, H.; Huang, L.; Yang, S.; Shi, D.; Pan, W.

2017-12-01

Beibu Gulf is an important semi-enclosed gulf located in northern South China Sea. It is rich in natural resources and its coastal rim is undergoing a rapid economic growth in recent years. Study on the spatial and temporal distribution of ecological variables by the influence of physical and biological processes in Beibu Gulf can provide the theoretical basis for the utilization of resources and environmental protection. Based on the MEC three-dimensional hydrodynamic model, a nutrient-phytoplankton-zooplankton-detritus (NPZD) model was applied to simulate the distribution of ecological variables in Beibu Gulf. The result shows that the ecosystem in Beibu Gulf is significantly influenced by dynamic conditions. In autumn and winter, great amount of nutrient-rich water from western Guangdong coastal area passes through Qiongzhou Strait and flows into Beibu Gulf, with about 108.3×103 t of inorganic nitrogen and 3.7×103 t of phosphate annually, leading to phytoplankton bloom. In summer, most of the nutrients come from rivers so high concentrations of nutrients and chlorophyll-a appear on estuaries. The annual net nutrient inputs from South China Sea into Beibu Gulf are 66.6×103 t for inorganic nitrogen and 4.6×103 t for phosphate. Phytoplankton plays an important role in nutrients' refreshment: a) Absorption by the process of photosynthesis is the biggest nutrient sink. b) Cellular release from dead phytoplankton is the biggest source in inorganic budget, making up for 33.4% of nitrogen consumed by photosynthesis while the process of respiration is the biggest source in phosphate budget, making up for 32.4% of phosphorus consumed by photosynthesis. c) Mineralization from detritus is also a considerable supplement of inorganic nutrients. Overall, biological process has more influence than physical process on the nutrient cycle budget in Beibu Gulf. The comparison of the result with remote sensing and in-situ data indicates that the model is able to simulate the biogeochemical characteristics in Beibu Gulf.

On the size and distribution of rings and coherent vortices in the Sargasso Sea

NASA Astrophysics Data System (ADS)

Luce, David L.; Rossby, Tom

2008-05-01

The container motor vessel CMV Oleander, which operates between New Jersey and Bermuda, crosses the Gulf Stream and Sargasso Sea all year round on a semiweekly schedule. Using an acoustic Doppler current profiler, measurements of upper ocean currents have been made on a regular basis since the fall of 1992. In this paper we examine the database for evidence of axisymmetric coherent vortices including the distribution and intensity of cold core rings. To detect the existence of coherent vortices, the patterns of current vectors averaged between 40 and 80 m depth were fit to an axisymmetric Gaussian vortex model. The parameters of the model were axis location, maximum tangential, or swirl, speed, and radius at which the maximum swirl was measured. We were able to distinguish between the well-known cold core "rings" (CCRs) pinched from the Gulf Stream, and a population of cyclonic and anticyclonic "vortices" in the Sargasso Sea. Both the rings and the Sargasso Sea vortices showed radii of 64 ± 18 km, albeit with different swirl speeds. The rings, close to the Gulf Stream, exhibited a typical maximum swirl speed of 0.98 ± 0.40 m s-1 and a center relative vorticity of 0.64 ± 0.35 × 10-4 s-1, almost 80% of the planetary vorticity for the region. The more uniform population of Sargasso Sea vortices contained approximately equal numbers of cyclones and anticyclones, with mean speeds of +0.43 and -0.55 m s-1, and center relative vorticities of +0.24 × 10-4 s-1 and -0.29 × 10-4 s-1, respectively.

Interactions of phytoplankton, zooplankton and microorganisms

NASA Astrophysics Data System (ADS)

Pomeroy, L. R.; Paffenhöfer, G.-A.; Yoder, J. A.

We present evidence that there are significant interactions between heterotrophic microorganisms, doliolids and Fritillaria within intrusions of nutrient-rich Gulf Stream water stranding on the continental shelf. During the summer of 1981 cold, nutrient-rich water from below the surface of the Gulf Stream was repeatedly intruded and stranded on the continental shelf off northeastern Florida. On August 6 old, stranded Gulf Stream water depleted of nitrate occupied the lower layer on the outer shelf. The upper water was continental shelf water, older but of undefined age. On August 6 free-living bacteria were >10 6ml -1 everywhere at all depths, an order of magnitude greater than normal bacterial numbers on the northeastern Florida continental shelf. Over 10 days the numbers of free bacteria doubled while bacteria attached to particles increased by a factor of four. The adenylate/chlorophyll ratio showed that phytoplankton dominated the lower layers of intruded water, while the surface water became increasingly dominated by heterotrophic microorganisms (bacteria and protozoa) over 10 days. There were significant, negative correlations between bacteria and doliolids and between bacteria and Fritillaria. Regions of maximum bacterial numbers did not coincide with locations of salp swarms. The increased numbers of bacteria at all depths in a highly stratified system in which most phytoplankton are in the lower layer suggests a diverse source of bacterial growth substrates, some of which involve zooplankton as intermediaries. Production of autotrophs is more than twice that of microheterotrophs on average, but because of their differential distribution, microheterotrophs are the dominant biomass in much of the surface water and may be significant in energy flux to metazoan consumers as well as competitors for mutually useable sources of nutrition.

Comparative Molecular and Morphological Variation Analysis of Siderastrea (Anthozoa, Scleractinia) Reveals the Presence of Siderastrea stellata in the Gulf of Mexico.

PubMed

García, Norberto A Colín; Campos, Jorge E; Musi, José L Tello; Forsman, Zac H; Muñoz, Jorge L Montero; Reyes, Alejandro Monsalvo; González, Jesús E Arias

2017-02-01

The genus Siderastrea exhibits high levels of morphological variability. Some of its species share similar morphological characteristics with congeners, making their identification difficult. Siderastrea stellata has been reported as an intermediary of S. siderea and S. radians in the Brazilian reef ecosystem. In an earlier study conducted in Mexico, we detected Siderastrea colonies with morphological features that were not consistent with some siderastreid species previously reported in the Gulf of Mexico. Thus, we performed a combined morphological and molecular analysis to identify Siderastrea species boundaries from the Gulf of Mexico. Some colonies presented high morphologic variability, with characteristics that corresponded to Siderastrea stellata. Molecular analysis, using the nuclear ITS and ITS2 region, corroborated the morphological results, revealing low genetic variability between S. radians and S. stellata. Since the ITS sequences did not distinguish between Siderastrea species, we used the ITS2 region to differentiate S. stellata from S. radians. This is the first report of Siderastrea stellata and its variability in the Gulf of Mexico that is supported by morphological and molecular analyses.

Seasonal Progression and Interannual Variability of Nutrient and Chlorophyll-a Distributions in the Northern Gulf of Alaska, 1998-2010

NASA Astrophysics Data System (ADS)

Trahanovsky, K.; Whitledge, T. E.

2016-02-01

We examined nutrient and chlorophyll-a (chl) concentrations from bottle samples collected from 0-50 m depth in the Northern Gulf of Alaska along the Seward Line transect on 56 cruises from 1998-2010. We computed monthly average concentrations of macronutrients (N, P, and Si) and chlorophyll-a by depth at four major stations along the transect to describe the regular seasonal progression of the nutricline and typical water column distributions of chlorophyll-a in this seasonally productive, downwelling coastal zone. The across-shelf transect displayed two different patterns of seasonal progression clearly associated with the Alaska Coastal Current (ACC) and Alaskan Stream (AS) current systems. The annual cycle of nutrient drawdown and replenishment is remarkably consistent from year to year within each system and is well correlated with chl measurements. The spring bloom begins earlier and nutrient depletion is sustained longer in the near-shore ACC then in the AS system centered over the shelf break. Chlorophyll-a concentrations frequently peak at 10-20m depth in both systems during July through October, as nutrients remain depleted in the top 10m. Subsurface nutrients (20 - 50 m depth) begin to recover between July and August and then experience a secondary drawdown between August and October, consistent with higher chl levels observed during the fall bloom. Interannual variability in the progression of the nutricline and the relative contribution of subsurface chl to total chl is presented. Physical data demonstrate increasing stratification in this region due to climate change; the implications for nutrient dynamics and primary production are discussed.

Environmental Guide to the Virginia Capes Operating Area

DTIC Science & Technology

1973-03-01

invertebrates occupy the waters over the shelf. Among fishes found here are croakers, sea robins, sea bass, sharks, rays, bluefish , alewives, and...pelagic forms such as tuna, billfish, and bluefish migrate seasonally, occurring in greatest abun- dance along the Gulf Stream boundary in spring and

Ocean Current Power Generator. Final Report

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

O'Sullivan, G. A.

2002-07-26

The Ocean Power Generator is both technically and economically suitable for deployment in the Gulf Stream from the US Navy facility in Dania, Florida. Yet to be completed is the calibration test in the Chesapeake Bay with the prototype dual hydroturbine Underwater Electric Kite. For the production units a revised design includes two ballast tanks mounted as pontoons to provide buoyancy and depth control. The power rating of the Ocean Power Generator has been doubled to 200 kW ready for insertion into the utility grid. The projected cost for a 10 MW installation is $3.38 per watt, a cost thatmore » is consistent with wind power pricing when it was in its deployment infancy, and a cost that is far better than photovoltaics after 25 years of research and development. The Gulf Stream flows 24 hours per day, and water flow is both environmentally and ecologically perfect as a renewable energy source. No real estate purchases are necessary, and you cannot see, hear, smell, or touch an Ocean Power Generator.« less

Experiment evaluates ocean models and data assimiliation in the Gulf Stream

NASA Astrophysics Data System (ADS)

Willems, Robert C.; Glenn, S. M.; Crowley, M. F.; Malanotte-Rizzoli, P.; Young, R. E.; Ezer, T.; Mellor, G. L.; Arango, H. G.; Robinson, A. R.; Lai, C.-C. A.

Using data sets of known quality as the basis for comparison, a recent experiment explored the Gulf Stream Region at 27°-47°N and 80°-50°W to assess the nowcast/forecast capability of specific ocean models and the impact of data assimilation. Scientists from five universities and the Naval Research Laboratory/Stennis Space Center participated in the Data Assimilation and Model Evaluation Experiment (DAMEÉ-GSR).DAMEÉ-GSR was based on case studies, each successively more complex, and was divided into three phases using case studies (data) from 1987 and 1988. Phase I evaluated models' forecast capability using common initial conditions and comparing model forecast fields with observational data at forecast time over a 2-week period. Phase II added data assimilation and assessed its impact on forecast capability, using the same case studies as in phase I, and phase III added a 2-month case study overlapping some periods in Phases I and II.

An Experiment to Evaluate Skylab Earth Resources Sensors for Detection of the Gulf Stream. [Straits of Florida

NASA Technical Reports Server (NTRS)

Maul, G. A. (Principal Investigator); Gordon, H. R.; Baig, S. R.; Mccaslin, M.; Devivo, R. J.

1976-01-01

The author has identified the following significant results. An experiment to evaluate the Skylab earth resources package for observing ocean currents was performed in the Straits of Florida in January 1974. Data from the S190 photographic facility, S191 spectroradiometer and S192 multispectral scanner, were compared with surface observations. The anticyclonic edge of the Gulf Stream could be identified in the Skylab S190A and B photographs, but the cyclonic edge was obscured by clouds. The aircraft photographs were judged not useful for spectral analysis because vignetting caused the blue/green ratios to be dependent on the position in the photograph. The spectral measurement technique could not identify the anticyclonic front, but mass of Florida Bay water which was in the process of flowing into the Straits could be identified and classified. Monte Carlo simulations of the visible spectrum showed that the aerosol concentration could be estimated and a correction technique was devised.

Variability of the Baltic Sea level and floods in the Gulf of Finland

NASA Astrophysics Data System (ADS)

Kulikov, E. A.; Medvedev, I. P.

2013-03-01

The statistical analysis of the long-term data on the variability of the Baltic Sea level has revealed the complicated character of the wave field structure. The wave field formed by the variable winds and the disturbances of the atmospheric pressure in the Baltic Sea is a superposition of standing oscillations with random phases. The cross spectral analysis of the synchronous observation series of the level in the Gulf of Finland has shown that the nodal lines of the standing dilatational waves are clearly traced with frequencies corresponding to the distance from the nodal line to the top of the gulf (a quarter of the wave length). Several areas of the water basin with clearly expressed resonant properties may be distinguished: the Gulfs of Finland, Riga, and Bothnia, Neva Bay, etc. The estimations of the statistical correlation of the sea level oscillations with the variation of the wind and atmospheric pressure indicate the dominant role of the zonal wind component during the formation of the floods in the Gulf of Finland. The probable reason for the extreme floods in St. Petersburg may be the resonance rocking of the eigenmode oscillations corresponding to the basic fundamental seiche mode of the Gulf of Finland with a period of 27 h when the repeated atmospheric disturbances in the Baltic Sea occur with a period of 1-2 days.

Generation and Maintenance of Recirculations by Gulf Stream Instabilities

DTIC Science & Technology

1999-02-01

Francois Primeau for endless discus- sions of various scientific problems, Kirill Pankratov for useful advice on the numerical methods in fluid...recirculation. J. Phys. Oceanogr., 18, 662-682. [7] Davis C. A. and K. A. Emanuel, 1991 : Potential vorticity diagnostics of cyclo- genesis. Mon. Weather. Rev

Slow Adaptation in the Face of Rapid Warming Leads to the Collapse of Atlantic Cod in the Gulf of Maine

NASA Astrophysics Data System (ADS)

Pershing, A. J.; Alexander, M. A.; Hernandez, C.; Kerr, L. A.; Le Bris, A.; Mills, K.; Nye, J. A.; Record, N.; Scannell, H. A.; Scott, J. D.; Sherwood, G. D.; Thomas, A. C.

2016-02-01

Climate change is altering conditions in all marine ecosystems, but the pace of change is not uniform. Rapid changes in environmental conditions pose a challenge for resource management, especially when available tools or policies assume the environment is stationary. Between 2004 and 2013, the Gulf of Maine and northwest Atlantic Shelf warmed at a rate that few large marine ecosystems have ever experienced. This warming was associated with a northward shift in the Gulf Stream and with Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation. The unprecedented warming led to reduced recruitment and enhanced mortality of Atlantic cod. Fisheries management has built-in feedbacks designed to reduce quotas as populations decline, but the management process could not keep pace with the rapid temperature-related changes in the Gulf of Maine cod stock. Future recovery of this fishery now depends on both sound management and favorable temperatures. The experience in the Gulf of Maine highlights the need to incorporate environmental factors into resource management and to build resiliency in coupled social-ecological systems. It also highlights a need for scientific and policy guidance for managing species threatened by future warming.

Assimilation of TOPEX/POSEIDON altimeter data into a circulation model of the North Atlantic

NASA Astrophysics Data System (ADS)

Blayo, E.; Verron, J.; Molines, J. M.

1994-12-01

Assimilation experiments were conducted using the first 12 months of TOPEX/POSEIDON (T/P) altimeter measurements in a multilayered quasi-geostrophic model of the North Atlantic between 20°N and 60°N. These experiments demonstrate the feasibility of using T/P data to control a basin-scale circulation model by means of an assimilation procedure. Moreover, they allow us to recreate the four-dimensional behavior of the North Atlantic Ocean during the year October 1992-September 1993 and to improve our knowledge and understanding of such circulation patterns. For this study we used a four-layer quasigeostrophic model of high horizontal resolution (1/6° in latitude and longitude). The assimilation procedure used is an along-track, sequential, nudging technique. The evolution of the model general circulation is described and analyzed from a deterministic and statistical point of view, with special emphasis on the Gulf Stream area. The gross features of the North Atlantic circulation in terms of mean transport and circulation are reproduced, such as the path, penetration and recirculation of the Gulf Stream, and its meandering throughout the eastern basin. The North Atlantic Drift is, however, noticeably underestimated. A northern meander of the north wall of the Gulf Stream above the New England Seamount Chain is present for most of the year, while, just downstream, the southern part of the jet is subject to a 100-km southeastward deflection. The Azores current is shown to remain stable and to shift southward with time from the beginning of December 1992 to the end of April 1993, the amplitude of the shift being about 2°. The computation of the mean latitude of the Gulf Stream as a function of time shows an abrupt shift from a northern position to a southern position in January, and a reverse shift, from a southern position to a northern position, in July. Finally, some issues are addressed concerning the comparison of assimilation experiments using T/P data and Geosat data. The first results show that the T/P simulations are more energetic than the Geosat simulations, especially east of the Mid-Atlantic Ridge, for every wavelength from 50 km to 500 km. This property is also verified in the deep ocean. The predicted abyssal circulation is indeed more energetic in the T/P case, which is more in accordance with what we know of the real ocean. Moreover, the good T/P altimeter coverage near the coasts greatly improves the model eddy kinetic energy levels in these areas, especially east of 25°W.

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed

Ma, Xiaohui; Chang, Ping; Saravanan, R; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-12-04

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy-atmosphere interaction in forecast and climate models.

JPRS Report, Science & Technology, USSR: Earth Sciences

DTIC Science & Technology

1988-02-26

25 - d Phenomenological Description of Eddy Registered in Gulf Stream (V.A. Bubnov, N.P. Kuzmina , et al.; OKEANOLOGIYA, No 1, Jan-Feb 87) 26...Bubnov, N. P. Kuzmina and I. S. Podymov, Oceanology Insti- tute imeni P. P. Shirshov, USSR Academy of Sciences, Moscow] [Abstract] The 5th cruise of

Sensitivity Analysis of SWAT Nitrogen Simulations with and without In-Stream Processes

EPA Science Inventory

Nitrogen (N) losses to surface waters are of great concern on both national and regional scales. Scientists have concluded that large areas of hypoxia in the northern Gulf of Mexico are due to excessive nutrients derived primarily from agricultural runoff via the Mississippi Rive...

Dynamic hydrographic variations in northwestern Arabian Gulf over the past three decades: Temporal shifts and trends derived from long-term monitoring data.

PubMed

Al-Yamani, Faiza; Yamamoto, Takahiro; Al-Said, Turki; Alghunaim, Aws

2017-09-15

Hydrographic variables were monitored in northwestern Arabian Gulf over the past three decades and the time-series data were statistically analyzed. The results show that while salinity has undergone several shifts, seawater temperature exhibited a steady increasing trend since the 1980s. The observed salinity shows strong correlation with Shatt Al-Arab River discharge indicating primary contribution of freshwater to salinity among other factors (evaporation and desalination effluent). Recent data show that salinity is at its highest level in the last 30years with less pronounced seasonal variability in response to severe decline in the freshwater runoff into the northwestern Arabian Gulf. The changes in hydrographic conditions may have significant implications on hydrodynamics, water quality, and ecosystems in the Gulf. Thus, cooperation among the concerned countries - both coastal and riparian nations - would be essential for prevention of further major changes in the Gulf. Copyright © 2017 Elsevier Ltd. All rights reserved.

Distribution, abundance, and diversity of stream fishes under variable environmental conditions

Treesearch

Christopher M. Taylor; Thomas L. Holder; Richard A. Fiorillo; Lance R. Williams; R. Brent Thomas; Melvin L. Warren

2006-01-01

The effects of stream size and flow regime on spatial and temporal variability of stream fish distribution, abundance, and diversity patterns were investigated. Assemblage variability and species richness were each significantly associated with a complex environmental gradient contrasting smaller, hydrologically variable stream localities with larger localities...

Hierarchical, quantitative biogeographic provinces for all North American turtles and their contribution to the biogeography of turtles and the continent

USGS Publications Warehouse

Ennen, Joshua R.; Matamoros, Wilfredo A.; Agha, Mickey; Lovich, Jeffrey E.; Sweat, Sarah C.; Hoagstrom, Christopher W.

2017-01-01

Our study represents the first attempt to describe biogeographic provinces for North American (México, United States, and Canada) turtles. We analyzed three nested data sets separately: (1) all turtles, (2) freshwater turtles, and (3) aquatic turtles. We georeferenced North American turtle distributions, then we created presence–absence matrices for each of the three data sets. We used watershed unit as biogeographic units. We conducted an unweighted pair-group method with arithmetic mean clustering analysis on each Jaccard index distance matrix from our watershed species matrices to delineate biogeographic provinces. Provinces were then tested for significant differences in species compositions in a global model with the use of a one-way analysis of similarity. We conducted a best subset of environmental variables with maximum (rank) correlation with community dissimilarities that determined the best model of abiotic variables explaining province delineation (i.e., climate, topography, and stream channel). To identify which species contributed the most to province delineations, we conducted an indicator species analysis and a similarity-percentage analysis. There were 16 all-turtle provinces, 15 freshwater provinces, and 13 aquatic provinces. Species compositions delineating the provinces were explained by abiotic variables, including mean annual precipitation, mean precipitation seasonality, and diversity of streams. Province delineations correspond closely with geographical boundaries, many of which have Pleistocene origins. For example, rivers with a history of carrying glacial runoff (e.g., Arkansas, Mississippi) sometimes dissect upland provinces, especially for aquatic and semiaquatic turtles. Compared with freshwater fishes, turtles show greater sensitivity to decreased temperature with restriction of most taxa south of the last permafrost maximum. Turtles also exhibit higher sensitivity to climatic, geomorphic, and tectonic instability, with richness and endemism concentrated along the more stable Gulf of México and Atlantic (south of the last permafrost maximum) coasts. Although distribution data indicate two aquatic turtles are most cold tolerant (i.e., Chrysemys picta, Chelydra serpentina), aquatic turtles overall show the most restriction to warmer, wetter climates. Sequential addition of semiaquatic and terrestrial turtles into analyses shows, as expected, that these taxa flesh out turtle faunas in climatically harsh (e.g., grasslands) or remote (e.g., California, Sonoran Desert) regions. The turtle assemblages of southwestern versus southeastern North America are distinct. But there is a transition zone across the semiarid plains of the Texas Gulf Coast, High Plains, and Chihuahuan Desert, including a strong boundary congruent with the Cochise Filter-Barrier. This is not a simple subdivision of Neotropical versus Nearctic taxa, as some lineages from both realms span the transition zone.

Probability Distribution of Turbulent Kinetic Energy Dissipation Rate in Ocean: Observations and Approximations

NASA Astrophysics Data System (ADS)

Lozovatsky, I.; Fernando, H. J. S.; Planella-Morato, J.; Liu, Zhiyu; Lee, J.-H.; Jinadasa, S. U. P.

2017-10-01

The probability distribution of turbulent kinetic energy dissipation rate in stratified ocean usually deviates from the classic lognormal distribution that has been formulated for and often observed in unstratified homogeneous layers of atmospheric and oceanic turbulence. Our measurements of vertical profiles of micro-scale shear, collected in the East China Sea, northern Bay of Bengal, to the south and east of Sri Lanka, and in the Gulf Stream region, show that the probability distributions of the dissipation rate ɛ˜r in the pycnoclines (r ˜ 1.4 m is the averaging scale) can be successfully modeled by the Burr (type XII) probability distribution. In weakly stratified boundary layers, lognormal distribution of ɛ˜r is preferable, although the Burr is an acceptable alternative. The skewness Skɛ and the kurtosis Kɛ of the dissipation rate appear to be well correlated in a wide range of Skɛ and Kɛ variability.

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...

Changing climate in the Gulf of California

NASA Astrophysics Data System (ADS)

Lluch-Cota, Salvador E.; Parés-Sierra, Alejandro; Magaña-Rueda, Víctor O.; Arreguín-Sánchez, Francisco; Bazzino, Gastón; Herrera-Cervantes, Hugo; Lluch-Belda, Daniel

2010-10-01

We conducted a four year interdisciplinary collaborative project focused in the Gulf of California, the most important fishing region for Mexico. We reviewed published reports, collected and analyzed physical, chemical and ecological data sets, and developed models for the physical (atmosphere and ocean) and ecological components of this large marine ecosystem, to examine prevalent scientific questions regarding climate variability and change in the region, covering three time scales (ENSO, decadal-to-interdecadal, and long-term trend). We were able to describe how the Gulf of California influences the northward propagation of coastal trapped Kelvin waves associated with El Niño (ENSO) events, and how this signal, together with changes in the atmospheric forcing, results in a ENSO signature inside the Gulf. For the decadal-to-multidecadal scales, we found coherent trends among series, and with the Pacific Decadal Oscillation (PDO). The long-term temperature signal for the Gulf of California shows a warming that occurred in the mid 20th century, approximately a decade before that in the California Current. This signal is coherent with fluctuations in the industrial fisheries catch records (sardine and shrimps). For the recent decades we found no significant sustained long-term trend in any of the time series of physical and ecological variables that we considered. Instead, variability seems to be fully dominated by the interaction of PDO and ENSO. We stress the urgent need for more modeling efforts and the establishment of interdisciplinary (physical and biological) observation platforms for the marine environment in the Gulf of California.

Smoke in the Gulf of Mexico

NASA Technical Reports Server (NTRS)

2002-01-01

This Sea-viewing Wide Field-of-view Sensor (SeaWiFS) image of the Bay of Campeche, acquired January 17, 2001, shows a 300-kilometer long smoke plume streaming towards the northwest from around 19.4o North and 92o West, the location of the Akal oil field. In the lower right (southeast) corner of the image is the country of El Salvador, site of a magnitude 7.6 earthquake on January 13, 2001. On the Pacific side of Southern Mexico, the productive waters of the Gulf of Tehuantepec are visible. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

Temperature Calibration of a Northern Gulf of Mexico Siderastrea siderea Coral

NASA Astrophysics Data System (ADS)

Wagner, A. J.; DeLong, K. L.; Kilbourne, K. H.; Richey, J. N.; Jelinek, K.; Hickerson, E.; Slowey, N. C.

2015-12-01

The Gulf of Mexico (GOM) is sensitive to oceanic and atmospheric variability in both the Atlantic and Pacific Oceans (i.e., Atlantic Multidecadal Oscillation (AMO), El Niño Southern Oscillation (ENSO), Pacific North American Pattern (PNA), and Pacific Decadal Oscillation (PDO)). The major GOM current, the Loop Current, feeds the Gulf Stream as it transports oceanic heat to the northern Atlantic Ocean. The northern GOM is the northernmost summer extent of the western hemisphere warm pool (WHWP) that drives oceanic moisture flux and precipitation into the Americas. Decadally-resolved foraminifera reconstructions from the northern GOM indicates SST was 2 to 4ºC colder on average than today during the Little Ice Age (LIA, ~1850), whereas a subannually-resolved coral reconstruction from the southeastern GOM find 1.5 to 2ºC colder intervals and reduced areal extent of the WHWP on interannual time scales during some intervals of the LIA. However, records capable of resolving annual and subannual SST variability from the northern GOM, necessary for investigating WHWP northern extent, are still lacking. Here we present a new temperature reconstruction for the northern GOM derived from strontium-to-calcium (Sr/Ca) ratios of approximately monthly samples milled from a Siderastrea siderea coral core collected from the Flower Garden Banks National Marine Sanctuary (FGBNMS; 27° 52.5'N, 93° 49'W) growing at a water depth of 20 m. Coral Sr/Ca is calibrated to reef temperature data from FGBNMS Hobotemp data loggers near the reef cap in ~22 m water depth (1986-2004) and to NOAA OISST (1981-2004), which co-varies with the reef temperature (r=0.95, p<0.05, n=146) and consistently captures winter values in reef temperature with slightly warmer summers (0.9ºC on average). The Sr/Ca-SST calibration slope (-0.043, r=-0.89, n=136, p<0.01 for reef temperature; -0.039, r=-0.94, n=275, p<0.01 for OISST) agrees well with published coral Sr/Ca-SST calibrations for S. siderea in the southeastern GOM from shallower water depths.

Phytoplankton bloom in Persian Gulf

NASA Technical Reports Server (NTRS)

2002-01-01

There is a large amount of sediment clearly visible in the true-color image of the Persian Gulf, acquired on November 1, 2001, by MODIS. Carried by the confluence of the Tigris and Euphrates Rivers (at center), the sediment-laden waters appear light brown where they enter the northern end of the Persian Gulf and then gradually dissipate into turquoise swirls as they drift southward. The nutrients these sediments carry are helping to support a phytoplankton bloom in the region, which adds some darker green hues in the rich kaleidoscope of colors on the surface (see the high resolution image). The confluence of the Tigris and Euphrates Rivers marks the southernmost boundary between Iran (upper right) and Iraq (upper left). South of Iraq are the countries of Kuwait and Saudi Arabia. The red dots indicate the probable locations of fires burning at oil refineries. Thin black plumes of smoke can be seen streaming away from several of these.

Economic vulnerability to sea-level rise along the northern U.S. Gulf Coast

USGS Publications Warehouse

Thatcher, Cindy A.; Brock, John C.; Pendleton, Elizabeth A.

2013-01-01

The northern Gulf of Mexico coast of the United States has been identified as highly vulnerable to sea-level rise, based on a combination of physical and societal factors. Vulnerability of human populations and infrastructure to projected increases in sea level is a critical area of uncertainty for communities in the extremely low-lying and flat northern gulf coastal zone. A rapidly growing population along some parts of the northern Gulf of Mexico coastline is further increasing the potential societal and economic impacts of projected sea-level rise in the region, where observed relative rise rates range from 0.75 to 9.95 mm per year on the Gulf coasts of Texas, Louisiana, Mississippi, Alabama, and Florida. A 1-m elevation threshold was chosen as an inclusive designation of the coastal zone vulnerable to relative sea-level rise, because of uncertainty associated with sea-level rise projections. This study applies a Coastal Economic Vulnerability Index (CEVI) to the northern Gulf of Mexico region, which includes both physical and economic factors that contribute to societal risk of impacts from rising sea level. The economic variables incorporated in the CEVI include human population, urban land cover, economic value of key types of infrastructure, and residential and commercial building values. The variables are standardized and combined to produce a quantitative index value for each 1-km coastal segment, highlighting areas where human populations and the built environment are most at risk. This information can be used by coastal managers as they allocate limited resources for ecosystem restoration, beach nourishment, and coastal-protection infrastructure. The study indicates a large amount of variability in index values along the northern Gulf of Mexico coastline, and highlights areas where long-term planning to enhance resiliency is particularly needed.

IAS Mesoscale Surface Circulation Observed Through Satellite Altimetry and its Influence in a Small Scale, Coastal Domain, Studied with a ROMS Model of the Cariaco Basin.

NASA Astrophysics Data System (ADS)

Alvera-Azcarate, A.; Barth, A.; Virmani, J. I.; Weisberg, R. H.

2007-05-01

The Intra-Americas Sea (IAS) surface circulation is characterized by large scale currents. The Caribbean current, which originates in the Lesser Antilles, travels westwards through the Caribbean Sea and eastern Mexico and passes through the Gulf of Mexico to finally form the Gulf Stream. This complex system of currents is also characterized by a high mesoscale variability, such as eddies and meanders. The objectives of this work are twofold: first, the multi-scale surface circulation of the IAS is described using satellite altimetry. The topographic influence of the different basins forming the IAS, the characteristic time and spatial scales, and the time variability of the surface circulation will be addressed. The second objective is to analyze the influence of this large scale circulation on a small scale coastal domain with a ROMS-based model of the Cariaco basin (Venezuela). Cariaco is a deep (1400 m), semi-enclosed basin connected to the open ocean by two shallow channels (Tortuga and Centinela Channels). Its connection with the open sea, and therefore the ventilation of the basin, occurs in the surface layers. The Cariaco ROMS model will be used to study the exchanges of mass, heat and salt through the channels. A 1/60 degree ROMS model nested in the global 1/12 degree HYCOM model from the Naval Research Laboratory will be used for this study. In addition, a series of observations (satellite altimetry and in situ temperature, salinity and velocity data), will be used to assess the influence of the Caribbean circulation on the basin.

Assimilation of Altimeter Data into a Quasigeostrophic Model of the Gulf Stream System. Part 1; Dynamical Considerations

NASA Technical Reports Server (NTRS)

Capotondi, Antonietta; Malanotte-Rizzoli, Paola; Holland, William R.

1995-01-01

The dynamical consequences of constraining a numerical model with sea surface height data have been investigated. The model used for this study is a quasigeostrophic model of the Gulf Stream region. The data that have been assimilated are maps of sea surface height obtained as the superposition of sea surface height variability deduced from the Geosat altimeter measurements and a mean field constructed from historical hydrographic data. The method used for assimilating the data is the nudging technique. Nudging has been implemented in such a way as to achieve a high degree of convergence of the surface model fields toward the observations. The assimilation of the surface data is thus equivalent to the prescription of a surface pressure boundary condition. The authors analyzed the mechanisms of the model adjustment and the characteristics of the resultant equilibrium state when the surface data are assimilated. Since the surface data are the superposition of a mean component and an eddy component, in order to understand the relative role of these two components in determining the characteristics of the final equilibrium state, two different experiments have been considered: in the first experiment only the climatological mean field is assimilated, while in the second experiment the total surface streamfunction field (mean plus eddies) has been used. It is shown that the model behavior in the presence of the surface data constraint can be conveniently described in terms of baroclinic Fofonoff modes. The prescribed mean component of the surface data acts as a 'surface topography' in this problem. Its presence determines a distortion of the geostrophic contours in the subsurface layers, thus constraining the mean circulation in those layers. The intensity of the mean flow is determined by the inflow/outflow conditions at the open boundaries, as well as by eddy forcing and dissipation.

An initial SPARROW model of land use and in-stream controls on total organic carbon in streams of the conterminous United States

USGS Publications Warehouse

Shih, Jhih-Shyang; Alexander, Richard B.; Smith, Richard A.; Boyer, Elizabeth W.; Shwarz, Grogory E.; Chung, Susie

2010-01-01

Watersheds play many important roles in the carbon cycle: (1) they are a site for both terrestrial and aquatic carbon dioxide (CO2) removal through photosynthesis; (2) they transport living and decomposing organic carbon in streams and groundwater; and (3) they store organic carbon for widely varying lengths of time as a function of many biogeochemical factors. Using the U.S. Geological Survey (USGS) Spatially Referenced Regression on Watershed Attributes (SPARROW) model, along with long-term monitoring data on total organic carbon (TOC), this research quantitatively estimates the sources, transport, and fate of the long-term mean annual load of TOC in streams of the conterminous United States. The model simulations use surrogate measures of the major terrestrial and aquatic sources of organic carbon to estimate the long-term mean annual load of TOC in streams. The estimated carbon sources in the model are associated with four land uses (urban, cultivated, forest, and wetlands) and autochthonous fixation of carbon (stream photosynthesis). Stream photosynthesis is determined by reach-level application of an empirical model of stream chlorophyll based on total phosphorus concentration, and a mechanistic model of photosynthetic rate based on chlorophyll, average daily solar irradiance, water column light attenuation, and reach dimensions. It was found that the estimate of in-stream photosynthesis is a major contributor to the mean annual TOC load per unit of drainage area (that is, yield) in large streams, with a median share of about 60 percent of the total mean annual carbon load in streams with mean flows above 500 cubic feet per second. The interquartile range of the model predictions of TOC from in-stream photosynthesis is from 0.1 to 0.4 grams (g) carbon (C) per square meter (m-2) per day (day-1) for the approximately 62,000 stream reaches in the continental United States, which compares favorably with the reported literature range for net carbon fixation by phytoplankton in lakes and streams. The largest contributors per unit of drainage area to the mean annual stream TOC load among the terrestrial sources are, in descending order: wetlands, urban lands, mixed forests, agricultural lands, evergreen forests, and deciduous forests . It was found that the SPARROW model estimates of TOC contributions to streams associated with these land uses are also consistent with literature estimates. SPARROW model calibration results are used to simulate the delivery of TOC loads to the coastal areas of seven major regional drainages. It was found that stream photosynthesis is the largest source of the TOC yields ( about 50 percent) delivered to the coastal waters in two of the seven regional drainages (the Pacific Northwest and Mississippi-Atchafalaya-Red River basins ), whereas terrestrial sources are dominant (greater than 60 percent) in all other regions (North Atlantic, South Atlantic-Gulf, California, Texas-Gulf, and Great Lakes).

On the evolution of Atlantic Meridional Overturning Circulation Fingerprint and implications for decadal predictability in the North Atlantic

NASA Astrophysics Data System (ADS)

Zhang, Jinting; Zhang, Rong

2015-07-01

It has been suggested previously that the Atlantic Meridional Overturning Circulation (AMOC) anomaly associated with changes in the North Atlantic Deep Water formation propagates southward with an advection speed north of 34°N. In this study, using Geophysical Fluid Dynamics Laboratory Coupled Model version 2.1 (GFDL CM2.1), we show that this slow southward propagation of the AMOC anomaly is crucial for the evolution and the enhanced decadal predictability of the AMOC fingerprint—the leading mode of upper ocean heat content (UOHC) in the extratropical North Atlantic. A positive AMOC anomaly in northern high latitudes leads to a convergence/divergence of the Atlantic meridional heat transport (MHT) anomaly in the subpolar/Gulf Stream region, thus warming in the subpolar gyre (SPG) and cooling in the Gulf Stream region after several years. Recent decadal prediction studies successfully predicted the observed warm shift in the SPG in the mid-1990s. Our results here provide the physical mechanism for the enhanced decadal prediction skills in the SPG UOHC.

Mobile Bay, Alabama area seen in Skylab 4 Earth Resources Experiment Package

NASA Technical Reports Server (NTRS)

1974-01-01

A near vertical view of the Mobile Bay, Alabama area seen in this Skylab 4 Earth Resources Experiment Package S190-B (five-inch earth terrain camera) photograph taken from the Skylab space station in earth orbit. North of Mobile the Tombigbee and Alabama Rivers join to form the Mobile River. Detailed configuration of the individual stream channels and boundaries can be defined as the Mobile River flows into Mobile Bay and into the Gulf of Mexico. The Mobile River Valley with its numerous stream channels is a distinct light shade in contrast to the dark green shade of the adjacent areas. The red coloration of Mobile Bay reflects the sediment load carried into the bay by the rivers. The westerly movement of the shore currents at the mouth of Mobile Bay is shown by the contrasting light blue of the sediment-laden current the the blue of the Gulf. Agricultural areas east and west of Mobile Bay are characterized by a rectangular pattern in green to white shades. Color variations may reflect

The Glacial and Relative Sea Level History of Southern Banks Island, NT, Canada

NASA Astrophysics Data System (ADS)

Vaughan, Jessica Megan

The mapping and dating of surficial glacial landforms and sediments across southern Banks Island document glaciation by the northwest Laurentide Ice Sheet (LIS) during the last glacial maximum. Geomorphic landforms confirm the operation of an ice stream at least 1000 m thick in Amundsen Gulf that was coalescent with thin, cold-based ice crossing the island's interior, both advancing offshore onto the polar continental shelf. Raised marine shorelines across western and southern Banks Island are barren, recording early withdrawal of the Amundsen Gulf Ice Stream prior to the resubmergence of Bering Strait and the re-entry of Pacific molluscs ~13,750 cal yr BP. This withdrawal resulted in a loss of ~60,000 km2 of ice --triggering drawdown from the primary northwest LIS divide and instigating changes in subsequent ice flow. The Jesse moraine belt on eastern Banks Island records a lateglacial stillstand and/or readvance of Laurentide ice in Prince of Wales Strait (13,750 -- 12,750 cal yr BP). Fossiliferous raised marine sediments that onlap the Jesse moraine belt constrain final deglaciation to ~12,600 cal yr BP, a minimum age for the breakup of the Amundsen Gulf Ice Stream. The investigation of a 30 m thick and 6 km wide stratigraphic sequence at Worth Point, southwest Banks Island, identifies an advance of the ancestral LIS during the Mid-Pleistocene (sensu lato), substantially diversifying the glacial record on Banks Island. Glacial ice emplaced during this advance has persisted through at least two glacial-interglacial cycles, demonstrating the resilience of circumpolar permafrost. Pervasive deformation of the stratigraphic sequence also records a detailed history of glaciotectonism in proglacial and subglacial settings that can result from interactions between cold-based ice and permafrost terrain. This newly recognized history rejects the long-established paleoenvironmental model of Worth Point that assumed a simple 'layer-cake' stratigraphy.

The mean sea surface height and geoid along the Geosat subtrack from Bermuda to Cape Cod

NASA Astrophysics Data System (ADS)

Kelly, Kathryn A.; Joyce, Terrence M.; Schubert, David M.; Caruso, Michael J.

1991-07-01

Measurements of near-surface velocity and concurrent sea level along an ascending Geosat subtrack were used to estimate the mean sea surface height and the Earth's gravitational geoid. Velocity measurements were made on three traverses of a Geosat subtrack within 10 days, using an acoustic Doppler current profiler (ADCP). A small bias in the ADCP velocity was removed by considering a mass balance for two pairs of triangles for which expendable bathythermograph measurements were also made. Because of the large curvature of the Gulf Stream, the gradient wind balance was used to estimate the cross-track component of geostrophic velocity from the ADCP vectors; this component was then integrated to obtain the sea surface height profile. The mean sea surface height was estimated as the difference between the instantaneous sea surface height from ADCP and the Geosat residual sea level, with mesoscale errors reduced by low-pass filtering. The error estimates were divided into a bias, tilt, and mesoscale residual; the bias was ignored because profiles were only determined within a constant of integration. The calculated mean sea surface height estimate agreed with an independent estimate of the mean sea surface height from Geosat, obtained by modeling the Gulf Stream as a Gaussian jet, within the expected errors in the estimates: the tilt error was 0.10 m, and the mesoscale error was 0.044 m. To minimize mesoscale errors in the estimate, the alongtrack geoid estimate was computed as the difference between the mean sea level from the Geosat Exact Repeat Mission and an estimate of the mean sea surface height, rather than as the difference between instantaneous profiles of sea level and sea surface height. In the critical region near the Gulf Stream the estimated error reduction using this method was about 0.07 m. Differences between the geoid estimate and a gravimetric geoid were not within the expected errors: the rms mesoscale difference was 0.24 m rms.

Incorporating uncertainty into the ranking of SPARROW model nutrient yields from Mississippi/Atchafalaya River basin watersheds

USGS Publications Warehouse

Robertson, Dale M.; Schwarz, Gregory E.; Saad, David A.; Alexander, Richard B.

2009-01-01

Excessive loads of nutrients transported by tributary rivers have been linked to hypoxia in the Gulf of Mexico. Management efforts to reduce the hypoxic zone in the Gulf of Mexico and improve the water quality of rivers and streams could benefit from targeting nutrient reductions toward watersheds with the highest nutrient yields delivered to sensitive downstream waters. One challenge is that most conventional watershed modeling approaches (e.g., mechanistic models) used in these management decisions do not consider uncertainties in the predictions of nutrient yields and their downstream delivery. The increasing use of parameter estimation procedures to statistically estimate model coefficients, however, allows uncertainties in these predictions to be reliably estimated. Here, we use a robust bootstrapping procedure applied to the results of a previous application of the hybrid statistical/mechanistic watershed model SPARROW (Spatially Referenced Regression On Watershed attributes) to develop a statistically reliable method for identifying “high priority” areas for management, based on a probabilistic ranking of delivered nutrient yields from watersheds throughout a basin. The method is designed to be used by managers to prioritize watersheds where additional stream monitoring and evaluations of nutrient-reduction strategies could be undertaken. Our ranking procedure incorporates information on the confidence intervals of model predictions and the corresponding watershed rankings of the delivered nutrient yields. From this quantified uncertainty, we estimate the probability that individual watersheds are among a collection of watersheds that have the highest delivered nutrient yields. We illustrate the application of the procedure to 818 eight-digit Hydrologic Unit Code watersheds in the Mississippi/Atchafalaya River basin by identifying 150 watersheds having the highest delivered nutrient yields to the Gulf of Mexico. Highest delivered yields were from watersheds in the Central Mississippi, Ohio, and Lower Mississippi River basins. With 90% confidence, only a few watersheds can be reliably placed into the highest 150 category; however, many more watersheds can be removed from consideration as not belonging to the highest 150 category. Results from this ranking procedure provide robust information on watershed nutrient yields that can benefit management efforts to reduce nutrient loadings to downstream coastal waters, such as the Gulf of Mexico, or to local receiving streams and reservoirs.

Biological-Physical Coupling in the Gulf of Maine: Satellite and Model Studies of Phytoplankton Variability

NASA Technical Reports Server (NTRS)

Thomas, Andrew C.; Chai, F.; Townsend, D. W.; Xue, H.

2002-01-01

The goals of this project were to acquire, process, QC, archive and analyze SeaWiFS chlorophyll fields over the Gulf of Maine and Scotia Shelf region. The focus of the analysis effort was to calculate and quantify seasonality and interannual. variability of SeaWiFS-measured phytoplankton biomass in the study area and compare these to physical forcing and hydrography. An additional focus within this effort was on regional differences within the heterogeneous biophysical regions of the Gulf of Maine / Scotia Shelf. Overall goals were approached through the combined use of SeaWiFS and AVHRR data and the development of a coupled biology-physical numerical model.

Multi-species coral Sr/Ca-based sea-surface temperature reconstruction using Orbicella faveolata and Siderastrea siderea from the Florida Straits

USGS Publications Warehouse

Flannery, Jennifer A.; Richey, Julie N.; Thirumalai, Kaustubh; Poore, Richard Z.; DeLong, Kristine L.

2017-01-01

We present new, monthly-resolved Sr/Ca-based sea-surface temperature (SST) records from two species of massive coral, Orbicella faveolata and Siderastrea siderea, from the Dry Tortugas National Park, FL, USA (DTNP). We combine these new records with published data from three additional S. siderea coral colonies to generate a 278-year long multi-species stacked Sr/Ca-SST record from DTNP. The composite record of mean annual Sr/Ca-SST at DTNP shows pronounced decadal-scale variability with a range of 1 to 2°C. Notable cool intervals in the Sr/Ca-derived SST lasting about a decade centered at ~1845, ~1935, and ~1965 are associated with reduced summer Sr/Ca-SST (monthly maxima < 29°C), and imply a reduction in the spatial extent of the Atlantic Warm Pool (AWP). There is significant coherence between the composite DTNP Sr/Ca-SST record and the Atlantic Multidecadal Oscillation (AMO) index, with the AMO lagging Sr/Ca-SST at DTNP by 9 years. Low frequency variability in the Gulf Stream surface transport, which originates near DTNP, may provide a link for the lagged relationship between multidecadal variability at DTNP and the AMO.

Use of the quasi-geostrophic dynamical framework to reconstruct the 3-D ocean state in a high-resolution realistic simulation of North Atlantic.

NASA Astrophysics Data System (ADS)

Fresnay, Simon; Ponte, Aurélien

2017-04-01

The quasi-geostrophic (QG) framework has been, is and will be still for years to come a cornerstone method linking observations with estimates of the ocean circulation and state. We have used here the QG framework to reconstruct dynamical variables of the 3-D ocean in a state-of-the-art high-resolution (1/60 deg, 300 vertical levels) numerical simulation of the North Atlantic (NATL60). The work was carried out in 3 boxes of the simulation: Gulf Stream, Azores and Reykjaness Ridge. In a first part, general diagnostics describing the eddying dynamics have been performed and show that the QG scaling verifies in general, at depths distant from mixed layer and bathymetric gradients. Correlations with surface observables variables (e.g. temperature, sea level) were computed and estimates of quasi-geostrophic potential vorticity (QGPV) were reconstructed by the means of regression laws. It is shown that that reconstruction of QGPV exhibits valuable skill for a restricted scale range, mainly using sea level as the variable of regression. Additional discussion is given, based on the flow balanced with QGPV. This work is part of the DIMUP project, aiming to improve our ability to operationnaly estimate the ocean state.

Regional sea level variability in a high-resolution global coupled climate model

NASA Astrophysics Data System (ADS)

Palko, D.; Kirtman, B. P.

2016-12-01

The prediction of trends at regional scales is essential in order to adapt to and prepare for the effects of climate change. However, GCMs are unable to make reliable predictions at regional scales. The prediction of local sea level trends is particularly critical. The main goal of this research is to utilize high-resolution (HR) (0.1° resolution in the ocean) coupled model runs of CCSM4 to analyze regional sea surface height (SSH) trends. Unlike typical, lower resolution (1.0°) GCM runs these HR runs resolve features in the ocean, like the Gulf Stream, which may have a large effect on regional sea level. We characterize the variability of regional SSH along the Atlantic coast of the US using tide gauge observations along with fixed radiative forcing runs of CCSM4 and HR interactive ensemble runs. The interactive ensemble couples an ensemble mean atmosphere with a single ocean realization. This coupling results in a 30% decrease in the strength of the Atlantic meridional overturning circulation; therefore, the HR interactive ensemble is analogous to a HR hosing experiment. By characterizing the variability in these high-resolution GCM runs and observations we seek to understand what processes influence coastal SSH along the Eastern Coast of the United States and better predict future SLR.

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.

1400 yr multiproxy record of climate variability from the northern Gulf of Mexico

USGS Publications Warehouse

Richey, J.N.; Poore, R.Z.; Flower, B.P.; Quinn, T.M.

2007-01-01

A continuous decadal-scale resolution record of climate variability over the past 1400 yr in the northern Gulf of Mexico was constructed from a box core recovered in the Pigmy Basin, northern Gulf of Mexico. Proxies include paired analyses of Mg/Ca and δ18O in the white variety of the planktic foraminifer Globigerinoides ruber and relative abundance variations of G. sacculifer in the foraminifer assemblages. Two multi-decadal intervals of sustained high Mg/Ca indicate that Gulf of Mexico sea surface temperatures (SSTs) were as warm or warmer than near-modern conditions between 1000 and 1400 yr B.P. Foraminiferal Mg/Ca during the coolest interval of the Little Ice Age (ca. 250 yr B.P.) indicate that SST was 2–2.5 °C below modern SST. Four minima in the Mg/Ca record between 900 and 250 yr B.P. correspond with the Maunder, Spörer, Wolf, and Oort sunspot minima, suggesting a link between changes in solar insolation and SST variability in the Gulf of Mexico. An abrupt shift recorded in both δ18Ocalcite and relative abundance of G. sacculifer occurred ca. 600 yr B.P. The shift in the Pigmy Basin record corresponds with a shift in the sea-salt-sodium (ssNa) record from the Greenland Ice Sheet Project 2 ice core, linking changes in high-latitude atmospheric circulation with the subtropical Atlantic Ocean.

Evidence against a late Wisconsinan ice shelf in the Gulf of Maine

USGS Publications Warehouse

Oldale, R.N.; Williams, R.S.; Colman, Steven M.

1990-01-01

Proposals for the formation of a late Wisconsinan ice shelf in the Gulf of Maine during the retreat of the Laurentide Ice Sheet are considered to be inappropriate. An Antarctic-type ice shelf does not fit the field data that indicate temperate glacial, terrestrial, and marine climates for the region between 18 ka and 12 ka. A temperate ice shelf has no modern analogues and may be physically impossible. The preponderance of stratified drift in the Gulf of Maine region supports temperate climates during late Wisconsinan time. It also indicates that glacial meltwater, rather than ice in either an ice sheet or ice shelf, was the primary transport mechanism of glacial sediment and the source for the glaciomarine mud. For these reasons we have proposed glacial analogues for the deglaciation of the Gulf of Maine that consist of temperate or subpolar marine-based glaciers, characterized by depositional environments dominated by meltwater discharge directly to the sea or the sea by way of subaerial meltwater streams. These analogues include Alaskan fjord glaciers, glaciers on the Alaskan continental shelf that discharged meltwater directly into the sea in the not too distant past, and Austfonna (Nordaustandet, Svalbard, Norway) that is presently discharging meltwater in the sea along a grounded ice wall. This last example is the best modern-day analogue for the depositional environment for most of the glaciomarine mud in the Gulf of Maine and deglaciation of the Gulf. 

Prediction of stream fish assemblages from land use characteristics: implications for cost-effective design of monitoring programmes.

PubMed

Kristensen, Esben Astrup; Baattrup-Pedersen, Annette; Andersen, Hans Estrup

2012-03-01

Increasing human impact on stream ecosystems has resulted in a growing need for tools helping managers to develop conservations strategies, and environmental monitoring is crucial for this development. This paper describes the development of models predicting the presence of fish assemblages in lowland streams using solely cost-effective GIS-derived land use variables. Three hundred thirty-five stream sites were separated into two groups based on size. Within each group, fish abundance data and cluster analysis were used to determine the composition of fish assemblages. The occurrence of assemblages was predicted using a dataset containing land use variables at three spatial scales (50 m riparian corridor, 500 m riparian corridor and the entire catchment) supplemented by a dataset on in-stream variables. The overall classification success varied between 66.1-81.1% and was only marginally better when using in-stream variables than when applying only GIS variables. Also, the prediction power of a model combining GIS and in-stream variables was only slightly better than prediction based solely on GIS variables. The possibility of obtaining precise predictions without using costly in-stream variables offers great potential in the design of monitoring programmes as the distribution of monitoring sites along a gradient in ecological quality can be done at a low cost.

Gulf of Mexico soundscapes as indicators of ecological stressors

NASA Astrophysics Data System (ADS)

Sidorovskaia, N.; Li, K.; Tiemann, C.; Ackleh, A. S.; Tang, T.; Risbourg, J. H.

2016-12-01

Soundscapes in the Northern Gulf of Mexico are complex and represent a combination of anthropogenic noise (oil exploration and production, shipping, rig construction, etc.), bio-soundscapes (sound of marine mammals and fish), and geo-soundscapes (weather events, submarine landslides, distant earthquakes, natural gas seeps). We will discuss how Passive Acoustic Monitoring in the deep Gulf has been utilized during the past decade to study the soundscape variability on daily, monthly, and yearly timescales and what environmental information can be extracted from this variability. Isolation of bio-soundscapes, identification of their sources, and abundance estimates based on acoustic cues are used to track the recovery of marine mammal species after major ecological disasters, such as the recent 2010 oil spill. Association of acoustic activity of marine species with anthropogenic noise levels and other environmental variables can provide base data that can be used to build ecological models of habitat preferences for different marine species. Understanding how the variability of anthropogenic soundscapes correlates with marine species distributions is critically important for regional conservation and mitigation strategies. Such studies can also assist in forecasting the long-term ecosystem health status and ecosystem response to disturbances of different spatial and temporal extent, including slow variations associated with climate change. [This research was made possible in part by a grant from The Gulf of Mexico Research Initiative, and in part by funding provided by ONR and The Joint Industry Programme.

Nutrients and water masses in the Gulf of Maine - Georges Bank region: Variability and importance to blooms of the toxic dinoflagellate Alexandrium fundyense.

PubMed

Townsend, D W; McGillicuddy, D J; Thomas, M A; Rebuck, N R

2014-05-01

We report here the results of ten oceanographic survey cruises carried out in the Gulf of Maine - Georges Bank region of the Northwest Atlantic during the late spring to summer period in 2007, 2008 and 2010, for which we examine and characterize relationships among dissolved inorganic nutrient fields, water mass dynamics and cell densities of the toxic dinoflagellate Alexandrium fundyense . Nutrients are supplied to continental shelf waters of the Gulf of Maine - Georges Bank region by inflows of deep offshore water masses; once in the Gulf they are transported with the residual circulation and mix with surface waters, both in the Gulf and on the Bank. Those fluxes of offshore water masses and their nutrient loads are the major source of nutrients for phytoplankton production in the region, including annual blooms of A. fundyense in the Gulf and on Georges Bank. This much is already known. We suggest here that the locations and magnitude of A. fundyense blooms are controlled in part by variable nutrient fluxes to the interior Gulf of Maine from offshore, and, those interior Gulf of Maine waters are, in turn, the main nutrient source to Georges Bank, which are brought onto the Bank by tidal pumping on the Northern Flank. We present evidence that nitrate is the initial form of nitrogenous nutrient for A. fundyense blooms, but it is quickly depleted to limiting concentrations of less than 0.5 μM, at which time continued growth and maintenance of the population is likely fueled by recycled ammonium. We also show that phosphate may be the limiting nutrient over much of Georges Bank in summer, allowing recycled ammonium concentrations to increase. Our temperature-salinity analyses reveal spatial and temporal (seasonal and interannual) variability in the relative proportions of two deep source waters that enter the Gulf of Maine at depth through the Northeast Channel: Warm Slope Water (WSW) and Labrador Slope Water (LSW). Those two source waters are known to vary in their nutrient loads, with nitrate concentrations about 50% higher in WSW than LSW, for example, and as such the proportions of these two water masses to one another are important determinants of the overall nutrient loads in the interior Gulf. In addition to these deep slope water fluxes, we show evidence here of episodic fluxes of relatively fresh and low-nutrient shelf waters from the Nova Scotian Shelf, which enter the Gulf in pulses at depths between the surface and approximately 150 m, displacing deep slope waters, and consequently they significantly dilute the Gulf's interior waters, reducing nutrient concentrations and, in turn, affect the magnitude of A. fundyense blooms.

Nutrients and water masses in the Gulf of Maine - Georges Bank region: Variability and importance to blooms of the toxic dinoflagellate Alexandrium fundyense

PubMed Central

Townsend, D.W.; McGillicuddy, D.J.; Thomas, M.A.; Rebuck, N.R.

2015-01-01

We report here the results of ten oceanographic survey cruises carried out in the Gulf of Maine - Georges Bank region of the Northwest Atlantic during the late spring to summer period in 2007, 2008 and 2010, for which we examine and characterize relationships among dissolved inorganic nutrient fields, water mass dynamics and cell densities of the toxic dinoflagellate Alexandrium fundyense. Nutrients are supplied to continental shelf waters of the Gulf of Maine - Georges Bank region by inflows of deep offshore water masses; once in the Gulf they are transported with the residual circulation and mix with surface waters, both in the Gulf and on the Bank. Those fluxes of offshore water masses and their nutrient loads are the major source of nutrients for phytoplankton production in the region, including annual blooms of A. fundyense in the Gulf and on Georges Bank. This much is already known. We suggest here that the locations and magnitude of A. fundyense blooms are controlled in part by variable nutrient fluxes to the interior Gulf of Maine from offshore, and, those interior Gulf of Maine waters are, in turn, the main nutrient source to Georges Bank, which are brought onto the Bank by tidal pumping on the Northern Flank. We present evidence that nitrate is the initial form of nitrogenous nutrient for A. fundyense blooms, but it is quickly depleted to limiting concentrations of less than 0.5 μM, at which time continued growth and maintenance of the population is likely fueled by recycled ammonium. We also show that phosphate may be the limiting nutrient over much of Georges Bank in summer, allowing recycled ammonium concentrations to increase. Our temperature-salinity analyses reveal spatial and temporal (seasonal and interannual) variability in the relative proportions of two deep source waters that enter the Gulf of Maine at depth through the Northeast Channel: Warm Slope Water (WSW) and Labrador Slope Water (LSW). Those two source waters are known to vary in their nutrient loads, with nitrate concentrations about 50% higher in WSW than LSW, for example, and as such the proportions of these two water masses to one another are important determinants of the overall nutrient loads in the interior Gulf. In addition to these deep slope water fluxes, we show evidence here of episodic fluxes of relatively fresh and low-nutrient shelf waters from the Nova Scotian Shelf, which enter the Gulf in pulses at depths between the surface and approximately 150 m, displacing deep slope waters, and consequently they significantly dilute the Gulf's interior waters, reducing nutrient concentrations and, in turn, affect the magnitude of A. fundyense blooms. PMID:26028824

Reconstruction of the 3-D Dynamics From Surface Variables in a High-Resolution Simulation of North Atlantic

NASA Astrophysics Data System (ADS)

Fresnay, S.; Ponte, A. L.; Le Gentil, S.; Le Sommer, J.

2018-03-01

Several methods that reconstruct the three-dimensional ocean dynamics from sea level are presented and evaluated in the Gulf Stream region with a 1/60° realistic numerical simulation. The use of sea level is motivated by its better correlation with interior pressure or quasi-geostrophic potential vorticity (PV) compared to sea surface temperature and sea surface salinity, and, by its observability via satellite altimetry. The simplest method of reconstruction relies on a linear estimation of pressure at depth from sea level. Another method consists in linearly estimating PV from sea level first and then performing a PV inversion. The last method considered, labeled SQG for surface quasi-geostrophy, relies on a PV inversion but assumes no PV anomalies. The first two methods show comparable skill at levels above -800 m. They moderately outperform SQG which emphasizes the difficulty of estimating interior PV from surface variables. Over the 250-1,000 m depth range, the three methods skillfully reconstruct pressure at wavelengths between 500 and 200 km whereas they exhibit a rapid loss of skill between 200 and 100 km wavelengths. Applicability to a real case scenario and leads for improvements are discussed.

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed Central

Ma, Xiaohui; Chang, Ping; Saravanan, R.; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-01-01

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy–atmosphere interaction in forecast and climate models. PMID:26635077

The distribution of nutrients, dissolved oxygen and chlorophyll a in the upper Gulf of Nicoya, Costa Rica, a tropical estuary.

PubMed

Palter, Jaime; Coto, Sandra León; Ballestero, Daniel

2007-06-01

In the Gulf of Nicoya on the Pacific Coast of Costa Rica, nutrient rich equatorial subsurface water (ESW) is upwelled in much of the lower gulf. These offshore waters are often regarded as the major source of nutrients to the gulf. However, for most of the year, the ESW has little influence on the nutrient content of the upper gulf, which has a distinct character from the lower gulf. The upper gulf, extending 40 km north of the restriction between Puntarenas Peninsula and San Lucas Island, is bordered primarily by mangrove swamps, is less than 20 m deep, and is less saline than the lower gulf. We surveyed the upper gulf for dissolved inorganic nitrogen, phosphate, silicate, dissolved oxygen, and chlorophyll in November 2000, January and July 2001. All nutrients are more concentrated in the upper gulf during the rainy and transitional seasons than the dry season, significantly so for phosphate and silicate. Throughout the year, nutrients tend to be much more concentrated in the less saline water of the upper gulf. This trend indicates that discharge from the Tempisque River predominantly controls spatial and temporal nutrient variability in the upper gulf. However, nutrient rich ESW, upwelled offshore and mixed to form a mid-temperature intermediate water, may enter the inner gulf to provide an important secondary source of nutrients during the dry season.

Identify the dominant variables to predict stream water temperature

NASA Astrophysics Data System (ADS)

Chien, H.; Flagler, J.

2016-12-01

Stream water temperature is a critical variable controlling water quality and the health of aquatic ecosystems. Accurate prediction of water temperature and the assessment of the impacts of environmental variables on water temperature variation are critical for water resources management, particularly in the context of water quality and aquatic ecosystem sustainability. The objective of this study is to measure stream water temperature and air temperature and to examine the importance of streamflow on stream water temperature prediction. The measured stream water temperature and air temperature will be used to test two hypotheses: 1) streamflow is a relatively more important factor than air temperature in regulating water temperature, and 2) by combining air temperature and streamflow data stream water temperature can be more accurately estimated. Water and air temperature data loggers are placed at two USGS stream gauge stations #01362357and #01362370, located in the upper Esopus Creek watershed in Phonecia, NY. The ARIMA (autoregressive integrated moving average) time series model is used to analyze the measured water temperature data, identify the dominant environmental variables, and predict the water temperature with identified dominant variable. The preliminary results show that streamflow is not a significant variable in predicting stream water temperature at both USGS gauge stations. Daily mean air temperature is sufficient to predict stream water temperature at this site scale.

Spatial Patterns of Subtidal Benthic Invertebrates and Environmental Factors in the Nearshore Gulf of Maine

EPA Science Inventory

The spatial patterns of subtidal benthic invertebrates and physical-chemical variables in the nearshore Gulf of Maine (Acadian Biogeographic Province) were studied to provide information needed to calibrate benthic indices of environmental condition, determine physical-chemical f...

Organchlorine content and shell thickness in brown booby (Sula leucogaster) eggs in the Gulf of California and the southern Pacific coast of Mexico.

PubMed

Mellink, Eric; Riojas-López, Mónica E; Luévano-Esparza, Jaime

2009-07-01

We determined egg concentrations of organochlorines and thickness of eggshells from brown boobies at eight colonies ranging from the northern Gulf of California to southern Mexico. The only common residue was that of DDE, which was found in almost all eggs. DDE content apparently reflected pre-1990 DDT use in nearby agricultural areas and, at one site, intensive mosquito control for high-end tourism development. There were no inter-colony differences in eggshell thickness, and variation in this variable likely reflected individual bird characteristics and/or individual feeding source. This variable was not a good proxy to DDE exposure of brown boobies, under current DDE levels in the brown booby trophic chain. In the northern Gulf of California, eggshell thickness has recovered to pre-DDT conditions. Our data indicate that the Gulf of California and southwestern coast of Mexico have a healthy near-shore marine environment, as far as organochlorines are concerned.

Environmental variability, historical contingency, and the structure of regional fish and macroinvertebrate faunas in Ouachita Mountain stream systems

Treesearch

Lance R. Williams; Christopher M. Taylor; Melvin L. Warren; J. Alan Clingenpeel

2003-01-01

In 1990-1992, the United States Forest Service sampled six hydrologically variable streams paired in three different drainage basins in the Ouachita Mountains, Arkansas, U.S.A. Fishes, macroinvertebrates, and stream environmental variables were quantified for each stream. We used these data to examine the relationship between regional faunas (based on taxonomy and...

Watershed features and stream water quality: Gaining insight through path analysis in a Midwest urban landscape, USA

Treesearch

Jiayu Wu; Timothy W. Stewart; Janette R. Thompson; Randy Kolka; Kristie J. Franz

2015-01-01

Urban stream condition is often degraded by human activities in the surrounding watershed. Given the complexity of urban areas, relationships among variables that cause stream degradation can be difficult to isolate. We examined factors affecting stream condition by evaluating social, terrestrial, stream hydrology and water quality variables from 20 urban stream...

Centennial-scale winter climate variability over the last two millennia in the northern Gulf of Mexico based on paired δ18O and Mg/Ca in Globorotalia truncatulinoides

NASA Astrophysics Data System (ADS)

Fortiz, V.; Thirumalai, K.; Richey, J. N.; Quinn, T. M.

2014-12-01

We present a replicated record of paired foraminiferal δ18O and Mg/Ca variations in multi-cores collected from the Garrison Basin (26º43'N, 93º55'W) in the northern Gulf of Mexico (GOM). Using δ18O (sea surface temperature, SST; sea surface salinity, SSS proxy) and Mg/Ca (SST proxy) variations in non-encrusted planktic foraminifer Globorotalia truncatulinoides we produce time series spanning the last two millennia that is characterized by centennial-scale climate variability. We interpret geochemical variations in G. truncatulinoides to reflect winter climate variability because data from a sediment trap, located ~350 km east of the core site, reveal that annual flux of G. truncatulinoides is heavily weighted towards winter (peak production in January-February; Spear et al., 2011). Similar centennial-scale variability is also observed in the foraminiferal geochemistry of Globigerinoides ruber in the same multi-cores, which likely reflect mean annual climate variations. Our replicated results and comparisons to other SST reconstructions from the region lend confidence that the northern GOM surface ocean underwent large, centennial-scale variability, most likely dominated by changes in winter climate. This variability occurred in a time period where climate forcing is small and background conditions are similar to pre-industrial times. References: Spear, J.W.; Poore, R.Z., and Quinn, T.M., 2011, Globorotalia truncatulinoides (dextral) Mg/Ca as a proxy for Gulf of Mexico winter mixed-layer temperature: Evidence from a sediment trap in the northern Gulf of Mexico. Marine Micropaleontology, 80, 53-61.

Relationships between habitat quality and measured condition variables in Gulf of Mexico mangroves

EPA Science Inventory

Abstract Ecosystem condition assessments were conducted for 12 mangrove sites in the northern Gulf of Mexico. Nine sites were selected randomly; three were selected a priori based on best professional judgment to represent a poor, intermediate and good environmental condition. D...

77 FR 19169 - Fisheries of the Caribbean, Gulf of Mexico, and South Atlantic; Snapper-Grouper Fishery Off the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-30

... for ABC is the projected yield stream with a 70 percent probability of rebuilding success. The Council... to have an 81 percent chance of rebuilding in 10 years, greater than the 70 percent probability... AM applications. Should this ACT be used in the future to trigger AMs, then it may be expected to...

US Navy Operational Global Ocean and Arctic Ice Prediction Systems

DTIC Science & Technology

2014-09-01

meridional overturning circulation (Figure 29 in Hurlburt et al., 2011), when comparing a non-assimilative simulation with a data assimilative...boundary current regions of the Gulf Stream ( Atlantic ), the Kuroshio (Pacific), and the Agulhas and Somali Currents (both Indian). Consequently...Oceanic and Atmospheric Administration at the National Centers for Environmental Prediction (NCEP), initially for the North Atlantic (Mehra and

Life on the edge: carbon fluxes from wetland to ocean along Alaska's coastal temperate rain forest

Treesearch

Rhonda Mazza; Richard Edwards; David D' Amore

2010-01-01

Acre for acre, streams of the coastal temperate rain forest along the Gulf of Alaska export 36 times as much dissolved organic carbon as the world average. Rain and snow are the great connectors, tightly linking aquatic and terrestrial systems of this region. The freshwater that flushes over and through the forest floor leaches carbon...

Migrant Education. Third Annual Regional Workshop (Virginia Beach, Va., March 5-9, 1972).

ERIC Educational Resources Information Center

Nachman, Cynthia P., Comp.

The Third Annual Regional Workshop on Migrant Education was held on March 5-9, 1972 in Virginia Beach, Virginia. This conference was for migrant educators from the Eastern Stream states extending from the Gulf of Mexico north to New England. Over 480 participants met, coordinating their ideas and experiences to create a better world for the…

Dynamical Systems Analysis Of Transport In Flows Defined As Data Sets: Contaminant Control On The Coast Of Florida And Criteria For Warm Rings In The North Atlantic

NASA Astrophysics Data System (ADS)

Lekien, F.; Coulliette, C.

In this talk we will briefly describe the dynamical systems framework for Lagrangian transport. In particular, we will show how dynamical systems theory can now be uti- lized in the context of "real" problems, such as those derived from remote sensing observations or the input of a large scale numerical model. We will illustrate these ideas by two examples. Study of fluid transport near the Atlantic coast of Florida us- ing a velocity field observed experimentally from high frequency radar measurements reveals that dynamical systems theory can be used to reduce contaminant density in coastal areas. We also study intergyre transport in a quasigeostrophic model of the North Atlantic. We investigate the structure of eddies detaching from the Gulf Stream and prove that in a double gyre structure cyclonic rings cannot contain fluid from the other gyre. Only anticyclonic rings can contain "foreign" fluid coming from another gyre. This explains many phenomenons, such as why counter-clockwise rings South of the Gulf Stream contain colder fluid advected directly from the northern gyre, which has been illustrated in many observational studies.

Observed decline of the Atlantic Meridional Overturning circulation 2004 to 2012

NASA Astrophysics Data System (ADS)

Cunningham, Stuart; Smeed, David; Johns, William; Meinen, Chris; Rayner, Darren; Moat, Ben; Duchez, Aurelie; Bryden, Harry; Baringer Molly, O.; McCarthy, Gerard

2014-05-01

The Atlantic Meridional Overturning Circulation (AMOC) has been observed continuously at 26° N since April 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable based measurements of the Gulf Stream and satellite derived Ekman transport. The time series has recently been extended to October 2012 and the results show a downward trend since 2004. From April~2008 to March 2012 the AMOC was an average of 2.7 Sv weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the subtropical gyre above the thermocline. The increased southward flow of warm waters is balanced by a decrease in the southward flow of Lower North Atlantic Deep Water below 3000 m. The transport of Lower North Atlantic Deep Water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).

Observed fingerprint of a weakening Atlantic Ocean overturning circulation.

PubMed

Caesar, L; Rahmstorf, S; Robinson, A; Feulner, G; Saba, V

2018-04-01

The Atlantic meridional overturning circulation (AMOC)-a system of ocean currents in the North Atlantic-has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature 'fingerprint'-consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region-and is calibrated through an ensemble of model simulations from the CMIP5 project. We find this fingerprint both in a high-resolution climate model in response to increasing atmospheric carbon dioxide concentrations, and in the temperature trends observed since the late nineteenth century. The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Comparisons with recent direct measurements from the RAPID project and several other studies provide a consistent depiction of record-low AMOC values in recent years.

An approximate Kalman filter for ocean data assimilation: An example with an idealized Gulf Stream model

NASA Technical Reports Server (NTRS)

Fukumori, Ichiro; Malanotte-Rizzoli, Paola

1995-01-01

A practical method of data assimilation for use with large, nonlinear, ocean general circulation models is explored. A Kalman filter based on approximation of the state error covariance matrix is presented, employing a reduction of the effective model dimension, the error's asymptotic steady state limit, and a time-invariant linearization of the dynamic model for the error integration. The approximations lead to dramatic computational savings in applying estimation theory to large complex systems. We examine the utility of the approximate filter in assimilating different measurement types using a twin experiment of an idealized Gulf Stream. A nonlinear primitive equation model of an unstable east-west jet is studied with a state dimension exceeding 170,000 elements. Assimilation of various pseudomeasurements are examined, including velocity, density, and volume transport at localized arrays and realistic distributions of satellite altimetry and acoustic tomography observations. Results are compared in terms of their effects on the accuracies of the estimation. The approximate filter is shown to outperform an empirical nudging scheme used in a previous study. The examples demonstrate that useful approximate estimation errors can be computed in a practical manner for general circulation models.

An approximate Kalman filter for ocean data assimilation: An example with an idealized Gulf Stream model

NASA Astrophysics Data System (ADS)

Fukumori, Ichiro; Malanotte-Rizzoli, Paola

1995-04-01

A practical method of data assimilation for use with large, nonlinear, ocean general circulation models is explored. A Kaiman filter based on approximations of the state error covariance matrix is presented, employing a reduction of the effective model dimension, the error's asymptotic steady state limit, and a time-invariant linearization of the dynamic model for the error integration. The approximations lead to dramatic computational savings in applying estimation theory to large complex systems. We examine the utility of the approximate filter in assimilating different measurement types using a twin experiment of an idealized Gulf Stream. A nonlinear primitive equation model of an unstable east-west jet is studied with a state dimension exceeding 170,000 elements. Assimilation of various pseudomeasurements are examined, including velocity, density, and volume transport at localized arrays and realistic distributions of satellite altimetry and acoustic tomography observations. Results are compared in terms of their effects on the accuracies of the estimation. The approximate filter is shown to outperform an empirical nudging scheme used in a previous study. The examples demonstrate that useful approximate estimation errors can be computed in a practical manner for general circulation models.

The Gulf Stream in Ocean Reanalyses: 1993-2010

NASA Astrophysics Data System (ADS)

Chi, L.; Wolfe, C.; Hameed, S.

2017-12-01

In recent years, significant progress has been made in the development of high-resolution ocean reanalysis products. However, errors are likely to remain because of inadequate coverage of observations, model resolutions, physical parameterizations, etc. We compare the representation of the Gulf Stream (GS) in several widely used global reanalysis products with resolutions ranging from 1° to 1/12°. This intercomparison focuses on the Florida Current transport, the separation of GS near Cape Hatteras, GS properties along the Oleander Line (from New Jersey to Bermuda), GS path and the GS north wall positions between 73°W and 55°W. A large spread exists across the reanalysis products. HYCOM and GLORYS2v4 stand out for their top performance in most metrics. Some common biases are found in all discussed products; for example, the velocity structure of the GS near the Oleander Line is too symmetric and the maximum velocity is weaker than in observations. In addition, the annual mean values of GS separation latitude near Cape Hatteras, the GS transport, and net transport across Oleander Line (which runs from New Jersey to Bermuda), less than half of the reanalysis products are correlated to the observations at 95% confidence level.

Scientific Guidance for Rehabilitation of the Chesapeake Bay Ecosystem under the Changing Climate.

NASA Astrophysics Data System (ADS)

Boesch, D. F.; Johnson, Z. P.; Li, M.

2017-12-01

While the Chesapeake Bay is an estuary and not a marginal sea on the scale of the Baltic Sea or the Gulf of Mexico, it has a complex set of environmental issues and multiple political jurisdictions such that it can serve as a test bed for science-informed management in larger marine systems. In particular, the Chesapeake Bay possesses a relatively advanced effort to ameliorate eutrophication, reduce toxic stresses, rehabilitate critical habitats, and sustainably utilized resources. Furthermore, both scientists and managers are addressing these challenges while now beginning to incorporate the effects of changes in temperature, precipitation and runoff, sea level, ocean boundary conditions, and pH. Increases in temperature and sea level are already apparent and future conditions can be estimated from global model projections, although sea level and ocean exchanges are also affected by variations in Gulf Stream flows and mesoscale climate. Changes in the volume, seasonality and variability in freshwater delivery from the multiple rivers discharging to the bay are harder to project with confidence, but may have pervasive consequences for circulation, reducing nutrient loads to ameliorate eutrophication, biogeochemical processes, and biotic distributions and dynamics. Science is now challenged to inform multiple adaptation strategies, including minimizing the vulnerability of humans and infrastructure, sustaining important tidal wetlands, managing sediment resources, sustaining living resources, redefining achievable ecosystem rehabilitation goals, and achieving shifting goals for nutrient load reductions. At the same time, science will also have to identify effective means to meet these challenges while also reducing greenhouse gas emissions.

Identifying dissolved oxygen variability and stress in tidal freshwater streams of northern New Zealand.

PubMed

Wilding, Thomas K; Brown, Edmund; Collier, Kevin J

2012-10-01

Tidal streams are ecologically important components of lotic network, and we identify dissolved oxygen (DO) depletion as a potentially important stressor in freshwater tidal streams of northern New Zealand. Other studies have examined temporal DO variability within rivers and we build on this by examining variability between streams as a basis for regional-scale predictors of risk for DO stress. Diel DO variability in these streams was driven by: (1) photosynthesis by aquatic plants and community respiration which produced DO maxima in the afternoon and minima early morning (range, 0.6-4.7 g/m(3)) as a product of the solar cycle and (2) tidal variability as a product of the lunar cycle, including saline intrusions with variable DO concentrations plus a small residual effect on freshwater DO for low-velocity streams. The lowest DO concentrations were observed during March (early autumn) when water temperatures and macrophyte biomass were high. Spatial comparisons indicated that low-gradient tidal streams were at greater risk of DO depletions harmful to aquatic life. Tidal influence was stronger in low-gradient streams, which typically drain more developed catchments, have lower reaeration potential and offer conditions more suitable for aquatic plant proliferation. Combined, these characteristics supported a simple method based on the extent of low-gradient channel for identifying coastal streams at risk of DO depletion. High-risk streams can then be targeted for riparian planting, nutrient limits and water allocation controls to reduce potential ecological stress.

The role of forcing agents on biogeochemical variability along the southwestern Adriatic coast: The Gulf of Manfredonia case study

NASA Astrophysics Data System (ADS)

Specchiulli, Antonietta; Bignami, Francesco; Marini, Mauro; Fabbrocini, Adele; Scirocco, Tommaso; Campanelli, Alessandra; Penna, Pierluigi; Santucci, Angela; D'Adamo, Raffaele

2016-12-01

This study investigates how multiple forcing factors such as rivers, surface marine circulation and winds affect hydrology and biogeochemical processes in the Gulf of Manfredonia and the seas around the Gargano peninsula, in the south-western Adriatic Sea. The study adopted an integrated approach, using in situ and remote sensing data, as well as the output of current models. The data reveal variability in the area's hydrography induced by local freshwater sources, the Western Adriatic Current (WAC) flowing from the north along the Italian coast, and the current patterns under different wind regimes. Specifically, exchange with offshore waters in the gulf induces variability in salinity and biogeochemical content, even within the same season, i.e. winter, in our case. This strong dependence on physical and biogeochemical factors makes the Manfredonia-Gargano ecosystem vulnerable to climate change, which could compromise its important role as a nursery area for the Adriatic Sea.

Simulation of stream discharge and transport of nitrate and selected herbicides in the Mississippi River Basin

USGS Publications Warehouse

Broshears, R.E.; Clark, G.M.; Jobson, H.E.

2001-01-01

Stream discharge and the transport of nitrate, atrazine, and metolachlor in the Mississippi River Basin were simulated using the DAFLOW/BLTM hydrologic model. The simulated domain for stream discharge included river reaches downstream from the following stations in the National Stream Quality Accounting Network: Mississippi River at Clinton, IA; Missouri River at Hermann, MO: Ohio River at Grand Chain, IL: And Arkansas River at Little Rock, AR. Coefficients of hydraulic geometry were calibrated using data from water year 1996; the model was validated by favourable simulation of observed discharges in water years 1992-1994. The transport of nitrate, atrazine, and metolachlor was simulated downstream from the Mississippi River at Thebes, IL, and the Ohio River at Grand Chain. Simulated concentrations compared favourably with observed concentrations at Baton Rouge, LA. Development of this model is a preliminary step in gaining a more quantitative understanding of the sources and fate of nutrients and pesticides delivered from the Mississippi River Basin to the Gulf of Mexico.

Spatial and seasonal variability of forested headwater stream temperatures in western Oregon, USA

Treesearch

J. A. Leach; D. H. Olson; P. D. Anderson; B. N. I. Eskelson

2017-01-01

Thermal regimes of forested headwater streams control the growth and distribution of various aquatic organisms. In a western Oregon, USA, case study we examined: (1) forested headwater stream temperature variability in space and time; (2) relationships between stream temperature patterns and weather, above-stream canopy cover, and geomorphic attributes; and (3) the...

OBSERVATIONS OF PHYTOPLANKTON SIZE STRUCTURE, NUTRIENTS, VARIABLE FLOURESCENCE, AND ALGAL PHOSPHATASE ACTIVITY IN A GULF COAST ESTUARY

EPA Science Inventory

During 2001, phytoplankton dynamics, physiology, and related environmental conditions were studied in Santa Rosa Sound, Florida, USA, at near-weekly intervals. Santa Rosa Sound is a component of the Pensacola Bay system located in the northern Gulf of Mexico. Environmental parame...

Impacts of climate change and variability on transportation systems and infrastructure : Gulf Coast study, phase 2 : task 3.1 : screening for vulnerability.

DOT National Transportation Integrated Search

2014-06-01

As part of Gulf Coast Study Phase 2, the U.S. Department of Transportation (U.S. DOT) sought to improve its understanding of how a metropolitan transportation systemincluding highways, ports, airports, rail, transit, and pipelinescould be affec...

Accessing the Gulf of Maine’s Climate Change Data Through Webtools

EPA Science Inventory

Climate variables have been measured in the Gulf of Maine and its watersheds for over one hundred years and long-standing time series are available at many different institutes. However, today’s managers looking for a quick answer to scientific questions rarely have the tim...

Investigations of the preferred modes of north Pacific jet variability, their downstream impacts, and tropical and extratropical precursors

NASA Astrophysics Data System (ADS)

Griffin, Kyle S.

Time extended EOF (TE-EOF) analysis is employed to examine the synoptic-scale evolution of the two leading modes of north Pacific jet stream variability, namely its zonal extension/retraction (TE-EOF 1) and the north/south shift of its exit region (TE-EOF 2). Composite analyses are constructed preceding and following peaks in the principal component associated with each of the two TE-EOFs, providing insight into the preferred evolutions of the north Pacific jet. Jet extension events are associated with an anomalous Gulf of Alaska cyclone, while jet retractions are associated with an anomalous ridge over the Aleutians. Similar but shifted upper level patterns are noted with the corresponding poleward/equatorward shifted jet phases, with the poleward (equatorward) shift of the jet exit region associated with anomalous low-level warmth (cold) over western North America. Such composites also suggest connections between certain phases of these leading modes of jet variability and deep convection in the tropics, a connection that has been challenging to physically diagnose in previous studies. The isentropic pressure depth measures the mass contained within an isentropic layer in a given grid column, enabling the tracking of mass exhausted by deep convection. The gradient of isentropic pressure depth is directly associated with the vertical geostrophic wind shear in that layer and thus provides a means to track the influence of convective mass flux on the evolution of the jet stream. A case study focused on the extreme North American warm episode of March 2012 demonstrates how positive pressure depth anomalies from a strong MJO event impact the jet stream over eastern Asia and drive a portion of the mid-latitude response that leads to the flow amplification and subsequent downstream warmth. This study demonstrates one way by which isentropic pressure depth can diagnose the impacts of tropical deep convection on the mid-latitude circulation. Using TE-EOFs, composites of isentropic pressure depth are constructed, to examine the evolution of pressure depth anomalies preceding each phase of the two leading modes of jet variability. In jet extension events, a large negative pressure depth anomaly in the 315-330 K isentropic layer and a positive pressure depth anomaly in the 340-355 K isentropic layer align north and south of the climatological jet exit region, respectively. A similar but opposite configuration is found in jet retraction events. During poleward shifted jet events, the configuration of pressure depth anomalies is comparable to that observed in jet extension events, but shifted poleward. Positive pressure depth anomalies in each set of events predominantly originate from either the Maritime Continent or East Asia and track along the climatological jet before impacting the exit region of the jet stream. Negative pressure depth anomalies have similar upstream origins before moving through the jet in a similar manner. These composite evolutions provide insight into the synoptic-scale evolutions that precede the preferred modes of jet variability, highlighting the influence of both mid-latitude weather systems and mass flux from tropical deep convection on North Pacific jet variability.

Coastal Fog in Atlantic Canada: Characterization and Projection in a Changing Climate

NASA Astrophysics Data System (ADS)

Duplessis, P.; Hartery, S.; Macdonald, A. M.; Wheeler, M.; Miller, J.; Bhatia, S.; Chang, R. Y. W.

2016-12-01

Marine and coastal fog in Atlantic Canada is usually advective and favored by the meeting of the warm Gulf Stream and cold Labrador Current. As moist warm air moves over cold water, it cools down and becomes supersaturated. The interactions between microphysical, dynamical and radiative processes can also be a determining element in the formation and persistence of fog, which makes fog forecasting a highly challenging task. Current parameterizations within models suffer notably from unresolved microphysical problems such as neglecting droplet concentration, which leads to errors in droplet density predictions of up to 50%. In the scope of improving our understanding of fog and its characteristics, our research group conducted a field study on the coast of Nova Scotia in Eastern Canada during the fog season of 2016. Meteorological variables, droplet and aerosol size distributions, chemical speciation and fog water composition were measured. Results from this study will be presented, along with projections in a changing climate.

Models that predict standing crop of stream fish from habitat variables: 1950-85.

Treesearch

K.D. Fausch; C.L. Hawkes; M.G. Parsons

1988-01-01

We reviewed mathematical models that predict standing crop of stream fish (number or biomass per unit area or length of stream) from measurable habitat variables and classified them by the types of independent habitat variables found significant, by mathematical structure, and by model quality. Habitat variables were of three types and were measured on different scales...

Assimilation of global versus local data sets into a regional model of the Gulf Stream system. 1. Data effectiveness

NASA Astrophysics Data System (ADS)

Malanotte-Rizzoli, Paola; Young, Roberta E.

1995-12-01

The primary objective of this paper is to assess the relative effectiveness of data sets with different space coverage and time resolution when they are assimilated into an ocean circulation model. We focus on obtaining realistic numerical simulations of the Gulf Stream system typically of the order of 3-month duration by constructing a "synthetic" ocean simultaneously consistent with the model dynamics and the observations. The model used is the Semispectral Primitive Equation Model. The data sets are the "global" Optimal Thermal Interpolation Scheme (OTIS) 3 of the Fleet Numerical Oceanography Center providing temperature and salinity fields with global coverage and with bi-weekly frequency, and the localized measurements, mostly of current velocities, from the central and eastern array moorings of the Synoptic Ocean Prediction (SYNOP) program, with daily frequency but with a very small spatial coverage. We use a suboptimal assimilation technique ("nudging"). Even though this technique has already been used in idealized data assimilation studies, to our knowledge this is the first study in which the effectiveness of nudging is tested by assimilating real observations of the interior temperature and salinity fields. This is also the first work in which a systematic assimilation is carried out of the localized, high-quality SYNOP data sets in numerical experiments longer than 1-2 weeks, that is, not aimed to forecasting. We assimilate (1) the global OTIS 3 alone, (2) the local SYNOP observations alone, and (3) both OTIS 3 and SYNOP observations. We assess the success of the assimilations with quantitative measures of performance, both on the global and local scale. The results can be summarized as follows. The intermittent assimilation of the global OTIS 3 is necessary to keep the model "on track" over 3-month simulations on the global scale. As OTIS 3 is assimilated at every model grid point, a "gentle" weight must be prescribed to it so as not to overconstrain the model. However, in these assimilations the predicted velocity fields over the SYNOP arrays are greatly in error. The continuous assimilation of the localized SYNOP data sets with a strong weight is necessary to obtain local realistic evolutions. Then assimilation of velocity measurements alone recovers the density structure over the array area. However, the spatial coverage of the SYNOP measurements is too small to constrain the model on the global scale. Thus the blending of both types of datasets is necessary in the assimilation as they constrain different time and space scales. Our choice of "gentle" nudging weight for the global OTIS 3 and "strong" weight for the local SYNOP data provides for realistic simulations of the Gulf Stream system, both globally and locally, on the 3- to 4-month-long timescale, the one governed by the Gulf Stream jet internal dynamics.

Northern North Atlantic Sea Surface Height and Ocean Heat Content Variability

NASA Technical Reports Server (NTRS)

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

2013-01-01

The evolution of nearly 20 years of altimetric sea surface height (SSH) is investigated to understand its association with decadal to multidecadal variability of the North Atlantic heat content. Altimetric SSH is dominated by an increase of about 14 cm in the Labrador and Irminger seas from 1993 to 2011, while the opposite has occurred over the Gulf Stream region over the same time period. During the altimeter period the observed 0-700 m ocean heat content (OHC) in the subpolar gyre mirrors the increased SSH by its dominantly positive trend. Over a longer period, 1955-2011, fluctuations in the subpolar OHC reflect Atlantic multidecadal variability (AMV) and can be attributed to advection driven by the wind stress ''gyre mode'' bringing more subtropical waters into the subpolar gyre. The extended subpolar warming evident in SSH and OHC during the altimeter period represents transition of the AMV from cold to warm phase. In addition to the dominant trend, the first empirical orthogonal function SSH time series shows an abrupt change 2009-2010 reaching a new minimum in 2010. The change coincides with the change in the meridional overturning circulation at 26.5N as observed by the RAPID (Rapid Climate Change) project, and with extreme behavior of the wind stress gyre mode and of atmospheric blocking. While the general relationship between northern warming and Atlantic meridional overturning circulation (AMOC) volume transport remains undetermined, the meridional heat and salt transport carried by AMOC's arteries are rich with decade-to-century timescale variability.

Medieval Warm Period Archives Preserved in Limpet Shells (Patella Vulgata) From Viking Deposits, United Kingdom

NASA Astrophysics Data System (ADS)

Mobilia, M.; Surge, D.

2008-12-01

The Medieval Warm Period (700-1100 YBP) represents a recent period of warm climate, and as such provides a powerful comparison to today's continuing warming trend. However, the spatial and temporal variability inherent in the Medieval Warm Period (MWP) makes it difficult to differentiate between global climate trends and regional variability. The continued study of this period will allow for the better understanding of temperature variability, both regional and global, during this climate interval. Our study is located in the Orkney Islands, Scotland, which is a critical area to understand climate dynamics. The North Atlantic Oscillation and Gulf Stream heavily influence climate in this region, and the study of climate intervals during the MWP will improve our understanding of the behavior of these climate mechanisms during this interval. Furthermore, the vast majority of the climate archive has been derived from either deep marine or arctic environments. Studying a coastal environment will offer valuable insight into the behavior of maritime climate during the MWP. Estimated seasonal sea surface temperature data were derived through isotopic analysis of limpet shells (Patella vulgata). Analysis of modern shells confirms that growth temperature tracks seasonal variation in ambient water temperature. Preliminary data from MWP shells record a seasonal temperature range comparable to that observed in the modern temperature data. We will extend the range of temperature data from the 10th through 14th centuries to advance our knowledge of seasonal temperature variability during the late Holocene.

Climatic variability in the Gulf of California associated with the Medieval Warm Period and the Little Ice Age

NASA Astrophysics Data System (ADS)

Flores-Castillo, O. D. L. A.; Martínez-López, A.; Perez-Cruz, L. L.

2017-12-01

Marine ecosystems close to the coasts are highly susceptible to be affected both by the variability due to natural processes of the climate system as well as by anthropogenic activities. The Gulf of California, located near the tropical Pacific region, whose influence on the long-term global climate has already been demonstrated, represents a great opportunity to assess the regional response to these effects. This study reconstructs some of the oceanographic and climatic conditions that occurred simultaneously with the Medieval Warm Period (MWP) and the Little Ice Age (LIA) climatic periods in the southern region of the gulf. This reconstruction was based on the use of multiple indirect indicators or proxies of paleoproduction and geochemistry (determined by isotope-ratios mass spectrometer interfaced with an elemental analyzer and inductively coupled plasma mass spectrometry) preserved in a high-resolution laminated sedimentary sequence collected in the slope of southeastern coast of the Gulf of California (24.2822 ° N and 108.3037 ° W). The main effects of these periods were higher precipitation conditions that generated a greater fluvial contribution during the MWP besides a bigger oxygenation of the water mass near the bottom. These conditions were followed by an increase in exported production, decrease in the oxygen content of the water near the bottom and an increase in the denitrification during the transition to the LIA. The results confirm the existence of oceanographic and climatic variability on a secular scale in the Gulf of California associated with both global climatic periods.

ECOLOGICAL ANALYSIS OF HYDROLOGIC DISTURBANCE REGIMES IN STREAMS OF NORTH AND SOUTH DAKOTA

EPA Science Inventory

Streamflow variability is an important component of physical disturbance in streams, and is likely to be a major organizing feature of habitat for stream fishes. The disturbance regime in streams is frequently described by the variability in streamflow from both floods and prolo...

U. S. GODAE: Global Ocean Prediction with the HYbrid Coordinate Ocean Model

DTIC Science & Technology

2009-01-01

2008). There are three major contributors to the strength of the Gulf Stream, (1) the wind forcing, (2) the Atlantic meridional overturning ...Smith, 2007. Resolution convergence and sensitivity studies with North Atlantic circulation models. Part I. The western boundary current system...σ-z coordinates, and (3) a baroclinic version of ADvanced CIRCulation (ADCIRC), the latter an unstructured grid model for baroclinic coastal

Validation Test Report for the Automated Optical Processing System (AOPS) Version 4.12

DTIC Science & Technology

2015-09-03

NPP) with the VIIRS sensor package as well as data from the Geostationary Ocean Color Imager (GOCI) sensor, aboard the Communication Ocean and...capability • Prepare the NRT Geostationary Ocean Color Imager (GOCI) data stream for integration into operations. • Improvements in sensor...Navy (DON) Environmental Data Records (EDRs) Expeditionary Warfare (EXW) Geostationary Ocean Color Imager (GOCI) Gulf of Mexico (GOM) Hierarchical

From SYNOP to AMOC: Stirring by deep cyclones and the evolution of Denmark Strait Overflow Water observed at Line W

NASA Astrophysics Data System (ADS)

Andres, M.; Toole, J. M.; Torres, D. J.; Smethie, W. M., Jr.; Joyce, T. M.; Curry, R. G.

2016-02-01

Shipboard velocity and property data from 18 transects across the North Atlantic Deep Western Boundary Current (DWBC) near 40˚N are analyzed to study the evolution of the Denmark Strait Overflow Water (DSOW) component of the DWBC and its mixing with the interior. The transects were made between 1994 and 2014 and lie along Line W, which reaches from the continental shelf south of New England to Bermuda. Measurements comprise velocity from lowered acoustic Doppler current profilers (LADCPs), CTD profiles, and trace gas chlorofluorocarbon (CFC) concentrations from bottle samples at discrete depths at 26 regular stations or a subset of these stations. In each transect, DSOW exhibits a distinct CFC concentration maximum in the abyssal ocean (> 3000 m depth) along the sloped western boundary. Sea surface height (SSH) maps from satellite altimetry indicate that quasi-stationary meander troughs of the Gulf Stream path in the upper ocean were present at Line W during 5 of the 18 sections. For these 5 sections, the LADCP velocity sections suggest the upper ocean trough is accompanied by a large cyclone in the deep ocean in the DSOW density layer. The occurrence of deep cyclones in conjunction with Gulf Stream troughs as inferred from the LADCP sections along Line W is consistent with previous observations (from 1988 to 1990) in the region from a moored array in the Synoptic Ocean Prediction (SYNOP) experiment. The SYNOP array suggested deep cyclones are present here about 35% of the time. The composite velocity section produced from the 5 Line W transects sampling through a Gulf Stream trough suggests that a typical cyclone reaches swirl speeds of greater than 30 cm/s at 3400 m depth and has a radius (distance between the center and the maximum velocity) of 75 km. The tracer data suggest that these cyclones affect not only the deep velocity structure along Line W, but also provide a mechanism for water exchange between the DWBC and the interior.

Holocene variability in the intensity of wind-gap upwelling in the tropical eastern Pacific

USGS Publications Warehouse

Toth, Lauren T.; Aronson, Richard B.; Cheng, Hai; Edwards, R. Lawrence

2015-01-01

Wind-driven upwelling in Pacific Panamá is a significant source of oceanographic variability in the tropical eastern Pacific. This upwelling system provides a critical teleconnection between the Atlantic and tropical Pacific that may impact climate variability on a global scale. Despite its importance to oceanographic circulation, ecology, and climate, little is known about the long-term stability of the Panamanian upwelling system or its interaction with climatic forcing on millennial time scales. Using a combination of radiocarbon and U-series dating of fossil corals collected in cores from five sites across Pacific Panamá, we reconstructed the local radiocarbon reservoir correction, ΔR, from ~6750 cal B.P. to present. Because the ΔR of shallow-water environments is elevated by upwelling, our data set represents a millennial-scale record of spatial and temporal variability of the Panamanian upwelling system. The general oceanographic gradient from relatively strong upwelling in the Gulf of Panamá to weak-to-absent upwelling in the Gulf of Chiriquí was present throughout our record; however, the intensity of upwelling in the Gulf of Panamá varied significantly through time. Our reconstructions suggest that upwelling in the Gulf of Panamá is weak at present; however, the middle Holocene was characterized by periods of enhanced upwelling, with the most intense upwelling occurring just after of a regional shutdown in the development of reefs at ~4100 cal B.P. Comparisons with regional climate proxies suggest that, whereas the Intertropical Convergence Zone is the primary control on modern upwelling in Pacific Panamá, the El Niño–Southern Oscillation drove the millennial-scale variability of upwelling during the Holocene.

Climate Change in U.S. South Atlantic, Gulf of Mexico and Caribbean Fisheries Regions

NASA Astrophysics Data System (ADS)

Roffer, M. A.; Hernandez, D. L.; Lamkin, J. T.; Pugliese, R.; Reichert, M.; Hall, C.

2016-02-01

A review of the recent evidence that climate change is affecting marine ecosystems in the U.S. fishery management zones of the South Atlantic, Gulf of Mexico and Caribbean regions will be presented. This will include affects on the living marine resources (including fish, invertebrates, marine mammals and turtles), fisheries, habitat and people. Emphasis will be given on the effects that impact managed species and the likely new challenges that they present to fishery managers. The evidence is being derived from the results of the "Climate Variability and Fisheries Workshop: Setting Research Priorities for the Gulf of Mexico, South Atlantic, and Caribbean Regions," October 26-28, 2015 in St. Petersburg Beach, Florida. Commonalities and regional differences will be presented in terms of how climate variability is likely to impact distribution, catch, catchability, socioeconomics, and management.

PHYTOPLANKTON DYNAMICS IN A GULF OF MEXICO ESTUARY: TIME SERIES OF SIZE STRUCTURE, NUTRIENTS, VARIABLE FLUORESCENCE AND ALGAL PHOSPHATASE ACTIVITY

EPA Science Inventory

Relationships between phytoplankton dynamics and physiology, and environmental conditions were studied in Santa Rosa Sound, Florida, USA, at near-weekly intervals during 2001. Santa Rosa Sound is a component of the Pensacola Bay estuary in the northern Gulf of Mexico. Parameters ...

School Culture and School Effectiveness in Emergencies: Lessons from Israeli Experience During the Gulf War.

ERIC Educational Resources Information Center

Harrison, Jo-Ann; Kuint, Sarah

1998-01-01

Examines the variability of Israeli schools' emergency preparedness and response to the Gulf War and the association of school culture with school effectiveness during this emergency. Policy guidelines should include recommendations for diagnosing and identifying dimensions of school culture (including religious beliefs and school ideology) that…

Tidal and atmospheric forcing of the upper ocean in the Gulf of California. I - Sea surface temperature variability

NASA Technical Reports Server (NTRS)

Paden, Cynthia A.; Winant, Clinton D.; Abbott, Mark R.

1991-01-01

SST variability in the northern Gulf of California is examined on the basis of findings of two years of satellite infrared imagery (1984-1986). Empirical orthogonal functions of the temporal and spatial SST variance for 20 monthly mean images show that the dominant SST patterns are generated by spatially varying tidal mixing in the presence of seasonal heating and cooling. Atmospheric forcing of the northern gulf appears to occur over large spatial scales. Area-averaged SSTs for the Guaymas Basin, island region, and northern basin exhibit significant fluctuations which are highly correlated. These fluctuations in SST correspond to similar fluctuations in the air temperature which are related to synoptic weather events over the gulf. A regression analysis of the SST relative to the fortnightly tidal range shows that tidal mixing occurs over the sills in the island region as well as on the shallow northern shelf. Mixing over the sills occurs as a result of large breaking internal waves of internal hydraulic jumps which mix over water in the upper 300-500 m.

Coastal circulation and hydrography in the Gulf of Tehuantepec, Mexico, during winter

NASA Astrophysics Data System (ADS)

Barton, E. D.; Lavín, M. F.; Trasviña, A.

2009-02-01

Winter observations of shelf and slope hydrography and currents in the inner Gulf of Tehuantepec are analysed from two field studies in 1989 and 1996 to specify the variability of near-shore conditions under varying wind stress. During the winter period frequent outbursts of 'Norte' winds over the central Gulf result in persistent alongshore inflows along both its eastern and western coasts. Wind-induced variability on time scales of several days strongly influences the shelf currents, but has greater effect on its western coast because of the generation and separation of anticyclonic eddies there. The steadier inflow (˜0.2 m s -1) on the eastern shelf is evident in a strong down-bowing of shallow isosurfaces towards the coast within 100 km of shore, below a wedge of warmer, fresher and lighter water. This persistent entry of less saline (33.4-34.0), warmer water from the southeast clearly originates in buoyancy input by rivers along the Central American coast, but is augmented by a general shoreward tendency (0.2 m s -1) in the southeastern Gulf. The resultant shallow tongue of anomalous water is generally swept offshore in the head of the Gulf and mixed away by the strong outflow and vertical overturning of the frequent 'Norte' events but during wind relaxations the warm, low-salinity coastal flow may briefly extend further west. In the head of the Gulf, flow is predominantly offshore (<0.2 m s -1) as the alongshore component alternates eastward and westward in association with elevation or depression, respectively, of the pycnocline against the shore. More saline, open ocean water is introduced from the north-western side of the Gulf by the inflow along the west coast. During extended wind relaxations, the flow becomes predominantly eastward beyond the shelf while nearshore the coastally trapped buoyant inflow from the southeast penetrates across the entire head of the gulf at least as far as its western limit. On the basis of these and other recent observations, it seems that the accepted view of a broad, persistent Costa Rica Coastal Current (CRCC) is the result of averaging over many relatively sparse observations and that the instantaneous CRCC is a highly variable and convoluted flow around and between constantly changing eddies. The buoyancy-driven shelf current reported here forms a hitherto unrecognized, but major, component of this CRCC system.

Late Holocene Hurricane Activity in the Gulf of Mexico from a Bayou Sediment Archive

NASA Astrophysics Data System (ADS)

Rodysill, J. R.; Donnelly, J. P.; Toomey, M.; Sullivan, R.; MacDonald, D.; Evans, R. L.; Ashton, A. D.

2012-12-01

Hurricanes pose a considerable threat to coastal communities along the Atlantic seaboard and in the Gulf of Mexico. The complex role of ocean and atmospheric dynamics in controlling storm frequency and intensity, and how these relationships could be affected by climate change, remains uncertain. To better predict how storms will impact coastal communities, it is vital to constrain their past behavior, in particular how storm frequency and intensity and the pattern of storm tracks have been influenced by past climate conditions. In an effort to characterize past storm behavior, our work contributes to the growing network of storm records along the Atlantic and Gulf coasts by reconstructing storm-induced deposits in the northern Gulf of Mexico during the Late Holocene. Previous work on the northern Gulf coast has shown considerable centennial-scale variability in the occurrence of intense hurricanes, much like the northern Atlantic coast and in the Caribbean Sea. The timing of active and quiet intervals during the last 1000 years amongst the Gulf Coast records appears to be anti-phased with stormy intervals along the North American east coast. The sparse spatial coverage of the existing intense hurricane reconstructions provides a limited view of the natural variability of intense hurricanes. A new, high resolution reconstruction of storms along the northern Gulf Coast would be beneficial in assembling the picture of the patterns of storminess during the Late Holocene. Our study site, Basin Bayou, is situated on the north side of Choctawhatchee Bay in northwest Florida. From 1851 to 2011, 68 storms have struck the coast within 75 miles of Basin Bayou, of which 10 were Category 3 or greater, making it a prime location to reconstruct intense hurricanes. Basin Bayou openly exchanges water with Choctawhatchee Bay through a narrow channel, which acts as a conduit for propagating storm surges, and potentially coarse-grained bay sediments, into the bayou. Our record is constructed from grain size analyses and core density measurements on multiple cores from Basin Bayou. The upper sediments were dated with 210Pb and 137Cs techniques and compared with the historical record of storms. We observe substantial centennial-scale variability in the occurrence of storm-induced deposits in Basin Bayou over the last 1500 years that aligns considerably well with the temporal distribution of intense storms from preexisting Gulf Coast reconstructions.

Large-Scale Effects of Timber Harvesting on Stream Systems in the Ouachita Mountains, Arkansas, USA

NASA Astrophysics Data System (ADS)

Williams, Lance R.; Taylor, Christopher M.; Warren, Melvin L., Jr.; Clingenpeel, J. Alan

2002-01-01

Using Basin Area Stream Survey (BASS) data from the United States Forest Service, we evaluated how timber harvesting influenced patterns of variation in physical stream features and regional fish and macroinvertebrate assemblages. Data were collected for three years (1990-1992) from six hydrologically variable streams in the Ouachita Mountains, Arkansas, USA that were paired by management regime within three drainage basins. Specifically, we used multivariate techniques to partition variability in assemblage structure (taxonomic and trophic) that could be explained by timber harvesting, drainage basin differences, year-to-year variability, and their shared variance components. Most of the variation in fish assemblages was explained by drainage basin differences, and both basin and year-of-sampling influenced macroinvertebrate assemblages. All three factors modeled, including interactions between drainage basins and timber harvesting, influenced variability in physical stream features. Interactions between timber harvesting and drainage basins indicated that differences in physical stream features were important in determining the effects of logging within a basin. The lack of a logging effect on the biota contradicts predictions for these small, hydrologically variable streams. We believe this pattern is related to the large scale of this study and the high levels of natural variability in the streams. Alternatively, there may be time-specific effects we were unable to detect with our sampling design and analyses.

Seasonal patterns of wind stress and wind stress curl over the Gulf of Mexico

NASA Astrophysics Data System (ADS)

de Velasco, Guillermo Gutiérrez; Winant, Clinton D.

1996-08-01

Meteorological observations from an array of stations deployed along the periphery of the Gulf of Mexico, between 1990 and 1993, are used to describe the seasonal fluctuations in patterns of atmospheric variables from a contemporary set of measurements. Seasonal maps of wind stress based on these measurements resemble wind stress maps based on ship observations, as published by Elliott [1979], rather than maps based on analyses of numerical weather forecasts, as published by Rhodes et al. [1989], particularly near the western boundary of the gulf. Seasonal maps of wind stress curl are characterized by positive curls over the western and southwestern gulf. The central result of this study is to document the important role of the mountain chain which extends along the southwestern section of the gulf in channeling the wind toward the Isthmus of Tehuantepec.

On the use of the earth resources technology satellite /LANDSAT-1/ in optical oceanography

NASA Technical Reports Server (NTRS)

Maul, G. A.; Gordon, H. R.

1975-01-01

Observations of the Gulf Stream System in the Gulf of Mexico were obtained in synchronization with LANDSAT-1. Computer enhanced images, which are necessary to extract useful oceanic information, show that the current can be observed by color (diffuse radiance) or sea state (specular radiance) effects associated with the cyclonic boundary even in the absence of a surface thermal signature. The color effect relates to the spectral variations in the optical properties of the water and its suspended particles, and is studied by radiative transfer theory. Significant oceanic parameters identified are: the probability of forward scattering, and the ratio of scattering to total attenuation. Several spectra of upwelling diffuse light are computed as a function of the concentration of particles and yellow substance.

Random Forest population modelling of striped and common-bottlenose dolphins in the Gulf of Taranto (Northern Ionian Sea, Central-eastern Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Carlucci, Roberto; Cipriano, Giulia; Paoli, Chiara; Ricci, Pasquale; Fanizza, Carmelo; Capezzuto, Francesca; Vassallo, Paolo

2018-05-01

This study provides the first estimates of density and abundance of the striped dolphin Stenella coeruleoalba and common bottlenose dolphin Tursiops truncatus in the Gulf of Taranto (Northern Ionian Sea, Central Mediterranean Sea) and identifies the predictive variables mainly influencing their occurrence and concentration in the study area. Conventional Distance Sampling (CDS) and the Delta approach on Random Forest (DaRF) methods have been applied to sightings data collected between 2009 and 2016 during standardized vessel-based surveys, providing similar outcomes. The mean value of density over the entire study area was 0.72 ± 0.26 specimens/km2 for the striped dolphin and 0.47 ± 0.09 specimens/km2 for the common bottlenose dolphin. The abundance estimated by DaRF in the Gulf of Taranto was 10080 ± 3584 specimens of S. coeruleoalba and 6580 ± 1270 specimens of T. truncatus, respectively. Eight predictive variables were selected, considering both the local physiographic features and human activities existing in the investigated area. The explanatory variables depth, distance from the coast, distance from industrial areas and distance from areas exploited by fishery seem to play a key role in influencing the spatial distribution of both species, whereas the geomorphological variables proved to be the most significant factors shaping the concentration of both dolphins. The establishment of a Specially Protected Area of Mediterranean Importance (SPAMI) according the SPA/BD Protocol in the Gulf of Taranto is indicated as an effective management tool for the conservation of both dolphin populations in the Central-eastern Mediterranean Sea.

Mesoscale and Synoptic Summertime Circulations and Their Impact on Visibility in the Arabian Gulf

NASA Astrophysics Data System (ADS)

Eleuterio, D. P.; Walker, A. L.

2005-12-01

Although frequently characterized as a region of relatively persistent northwesterly winds, often referred to as the 40-day shamal, several researchers have recognized significant temporal and spatial variability in the summer low level winds in the Arabian Gulf. In addition to the synoptically driven gradient between the subtropical high to the north and the monsoon trough across the Gulf of Oman and Northern Arabian Sea, there are complex interactions between the Saudi Arabian and Pakistani heat lows, land-sea breeze circulations, and coastal terrain influence due to the proximity of the Zagros Mountains. These interactions frequently result in several distinct wind regimes within the Arabian Gulf, to include weak thermally and dynamically forced southerlies in the southern Gulf, a diurnally varying region of convergence/ divergence across the central Gulf, and northwesterly shamal type flow in the northern Gulf. The relative orientation and strength of these wind regimes and the strength of the subsidence inversion at the top of the marine boundary layer greatly impact the aerosol loading over water and resulting visibility due to wind-blown sand, dust, and smoke. Several case studies are examined to explore the interaction between mesoscale and synoptic forcing and the resulting spatial and temporal variability in visibility and aerosol optical depth. Conditions range from two to three day periods of rapid and persistent regional clearing with freshening northwesterly winds, to persistent periods of moderate to poor visibility in marine haze under light winds, to large scale events that create a distinct wind and dust front, severely reducing visibility through much of Iraq, Kuwait, and Saudi Arabia, and extending well into the Arabian Gulf. These strong, widespread events may be correlated with synoptically forced conditions farther north. Alternatively, smaller scale regional plumes of mobilized dust are often created by mesoscale events which, in conjunction with oil smoke and industrial pollution, can rapidly reduce visibility in localized regions for periods of 1-2 days and are relatively difficult to forecast because of their mesoscale nature.

Physical associations to spring phytoplankton biomass interannual variability in the U.S. Northeast Continental Shelf

NASA Astrophysics Data System (ADS)

Saba, Vincent S.; Hyde, Kimberly J. W.; Rebuck, Nathan D.; Friedland, Kevin D.; Hare, Jonathan A.; Kahru, Mati; Fogarty, Michael J.

2015-02-01

The continental shelf of the Northeast United States and Nova Scotia is a productive marine ecosystem that supports a robust biomass of living marine resources. Understanding marine ecosystem sensitivity to changes in the physical environment can start with the first-order response of phytoplankton (i.e., chlorophyll a), the base of the marine food web. However, the primary physical associations to the interannual variability of chlorophyll a in these waters are unclear. Here we used ocean color satellite measurements and identified the local and remote physical associations to interannual variability of spring surface chlorophyll a from 1998 to 2013. The highest interannual variability of chlorophyll a occurred in March and April on the northern flank of Georges Bank, the western Gulf of Maine, and Nantucket Shoals. Complex interactions between winter wind speed over the Shelf, local winter water levels, and the relative proportions of Atlantic versus Labrador Sea source waters entering the Gulf of Maine from the previous summer/fall were associated with the variability of March/April chlorophyll a in Georges Bank and the Gulf of Maine. Sea surface temperature and sea surface salinity were not robust correlates to spring chlorophyll a. Surface nitrate in the winter was not a robust correlate to chlorophyll a or the physical variables in every case suggesting that nitrate limitation may not be the primary constraint on the interannual variability of the spring bloom throughout all regions. Generalized linear models suggest that we can resolve 88% of March chlorophyll a interannual variability in Georges Bank using lagged physical data.

Design and control of a variable geometry turbofan with an independently modulated third stream

NASA Astrophysics Data System (ADS)

Simmons, Ronald J.

Emerging 21st century military missions task engines to deliver the fuel efficiency of a high bypass turbofan while retaining the ability to produce the high specific thrust of a low bypass turbofan. This study explores the possibility of satisfying such competing demands by adding a second independently modulated bypass stream to the basic turbofan architecture. This third stream can be used for a variety of purposes including: providing a cool heat sink for dissipating aircraft heat loads, cooling turbine cooling air, and providing a readily available stream of constant pressure ratio air for lift augmentation. Furthermore, by modulating airflow to the second and third streams, it is possible to continuously match the engine's airflow demand to the inlet's airflow supply thereby reducing spillage and increasing propulsive efficiency. This research begins with a historical perspective of variable cycle engines and shows a logical progression to proposed architectures. Then a novel method for investigating optimal performance is presented which determines most favorable on design variable geometry settings, most beneficial moment to terminate flow holding, and an optimal scheduling of variable features for fuel efficient off design operation. Mission analysis conducted across the three candidate missions verifies that these three stream variable cycles can deliver fuel savings in excess of 30% relative to a year 2000 reference turbofan. This research concludes by evaluating the relative impact of each variable technology on the performance of adaptive engine architectures. The most promising technologies include modulated turbine cooling air, variable high pressure turbine inlet area and variable third stream nozzle throat area. With just these few features it is possible to obtain nearly optimal performance, including 90% or more of the potential fuel savings, with far fewer variable features than are available in the study engine. It is abundantly clear that three stream variable architectures can significantly outperform existing two stream turbofans in both fuel efficiency and at the vehicle system level with only a modest increase in complexity and weight. Such engine architectures should be strongly considered for future military applications.

Spring resource phenology and timing of songbird migration across the Gulf of Mexico

USGS Publications Warehouse

Paxton, Eben H.; Cohen, Emily B.; Németh, Zoltan; Zenzal, Theodore J.; Paxton, Kristina L.; Diehl, Robert H.; Moore, Frank R.

2015-01-01

Migratory songbirds are advancing their arrival to breeding areas in response to climatic warming at temperate latitudes. Less is understood about the impacts of climate changes outside the breeding period. Every spring, millions of migrating songbirds that overwinter in the Caribbean and Central and South America stop to rest and refuel in the first available habitats after crossing the Gulf of Mexico. We used capture data from a long-term banding station (20 years: 1993 to 2012) located on the northern coast of the Gulf to assess the passage timing of 17 species making northward migrations into eastern North America. We further assessed spring resource phenology as measured by normalized difference vegetation index (NDVI) on nonbreeding ranges and en route. We tested the hypotheses that spring passage timing has advanced during the past two decades and that annual variability in passage timing into eastern North America is related to spring resource phenology on stationary nonbreeding ranges and during passage south of the Gulf. Further, we assessed whether annual variability in resource phenology south of the Gulf was a good indicator of the conditions that migrants encountered upon first landfall in eastern North America. We found no trend in migration timing for species that migrate from South America and annual variability in their passage timing was unrelated to environmental conditions in nonbreeding ranges or en route. Species that migrate from Central America and the Caribbean delayed arrival by 2 to 3 days over the 20-year period and arrived later during years when conditions were dryer in nonbreeding ranges and passage areas south of the Gulf. Further, year to year variability in spring resource phenology in nonbreeding ranges and passage areas south of the Gulf were not good indicators of resource phenology upon arrival in eastern North America. Therefore, despite the fact that many migrant species have been arriving increasingly earlier to breeding grounds, the passage timing of 17 species into eastern North America has either not changed or is slightly later, due to drying spring conditions in Central America and the Caribbean. Our results suggest that Nearctic–Neotropical migratory birds adjust the rate of migration primarily within eastern North America and, in light of warmer temperatures in the temperate zone and earlier arrival timing to breeding ranges, species that overwinter in Central America and the Caribbean may be increasing the speed of migration within eastern North America.

War and Dissent: The Political Values of the American Professoriate.

ERIC Educational Resources Information Center

Shepherd, Gordon; Shepherd, Gary

1994-01-01

A national survey of 657 college faculty investigated political attitudes at the beginning of the Persian Gulf War (1991). To test hypotheses about the effects of age and cohort variables on faculty political values, reactions to the Gulf War were correlated with indicators of opposition to or support for the Vietnam War. (Author/MSE)

Proficiency as a Variable in Gulf EFL Students' Employment of Reading Strategies

ERIC Educational Resources Information Center

Endley, Martin J.

2016-01-01

This paper reports a study of the reading strategies used by twelve Arabic-speaking undergraduates at a major Gulf university when reading texts in English. The procedure employed was a think-aloud protocol followed by a semi-structured interview. Three research questions were addressed: (a) What are the primary comprehension problems encountered…

Global Positioning System En Route/Terminal Exploratory Tests.

DTIC Science & Technology

1982-12-01

the set in a Grumman G-159 Gulf stream during June and July 1981. •»-*r P "» _^„. ~kjfe. 11 H. "»> ’•! This report contains the test...i . ».....•. :. • i i r iia^ri 1 I.-—„., nlMllltt—’ PLOT STAAT TIME 21 42 20 PLOT ENO TIME 23 1» 20 DATE RECOnOFO- TIOtlM TIME OPS

Surface water supply of the United States, 1907-8, Part II. South Atlantic Coast and eastern Gulf of Mexico

USGS Publications Warehouse

,

1909-01-01

This volume contains results of flow measurements made on certain streams in the United States. The work was performed by the water-resources branch of the United States Geological Survey, either independently or in cooperation with organizations mentioned herein. These investigations are authorized by the organic law of the Geological Survey (Stat. L., vol. 20, p. 394)...

U.S. GODAE: Global Ocean Prediction with the HYbrid Coordinate Ocean Model

DTIC Science & Technology

2008-09-30

major contributors to the strength of the Gulf Stream, (1) the wind forcing, (2) the Atlantic meridional overturning circulation (AMOC), and (3) a...convergence and sensitivity studies with North Atlantic circulation models. Part I. The western boundary current system. Ocean Model., 16, 141-159...a baroclinic version of ADvanced CIRCulation (ADCIRC), the latter an unstructured grid model for baroclinic coastal/estuarian applications. NCOM is

Chemical and isotopic evidence of nitrogen transformation in the Mississippi River, 1997-98

USGS Publications Warehouse

Battaglin, William A.; Kendall, Carol; Chang, Cecily C.Y.; Silva, Steven R.; Campbell, D.H.

2001-01-01

Nitrate (NO3) and other nutrients discharged by the Mississippi River are suspected of causing a zone of depleted dissolved oxygen (hypoxic zone) in the Gulf of Mexico each summer. The hypoxic zone may have an adverse affect on aquatic life and commercial fisheries. The amount of NO3 delivered by the Mississippi River to the Gulf of Mexico is well documented, but the relative contributions of different sources of NO3, and the magnitude of subsequent in-stream transformations of NO3, are not well understood. Forty-two water samples collected in 1997 and 1998 at eight stations located either on the Mississippi River or its major tributaries were analysed for NO3, total nitrogen (N), atrazine, chloride concentrations and NO3 stable isotopes (δ15N and δ18O). These data are used to assess the magnitude and nature of in-stream N transformation and to determine if the δ15N and δ18O of NO3 provide information about NO3 sources and transformation processes in a large river system (drainage area 2 900 000 km2) that would otherwise be unavailable using concentration and discharge data alone. Results from 42 samples indicate that the δ15N and δ18O ratios between sites on the Mississippi River and its tributaries are somewhat distinctive, and vary with season and discharge rate. Of particular interest are two nearly Lagrangian sample sets, in which samples from the Mississippi River at St Francisville, LA, are compared with samples collected from the Ohio River at Grand Chain, II, and the Mississippi River at Thebes, IL. In both Lagrangian sets, mass-balance calculations indicate only a small amount of in-stream N loss. The stable isotope data from the samples suggest that in-stream N assimilation and not denitrification accounts for most of the N loss in the lower Mississippi River during the spring and early summer months.

Oceanic heterotrophic dinoflagellates: distribution, abundance, and role as microzooplankton

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

Lessard, E.J.

1984-01-01

The primary objectives of this thesis were to determine the distribution and abundance of heterotrophic dinoflagellates across the Gulf Stream system off Cape Hatteras and to assess the potential grazing impact of these microheterotrophs in plankton communities. A list of species encountered in this study and their trophic status based on epifluorescence is presented, as well as observations on the presence of external or internal symbionts. The abundance of heterotrophic dinoflagellates across the Gulf Stream region off Cape Hatteras was determined from bimonthly net tow samples over a year and from whole water samples in March. Their average abundance wasmore » twice that of net ciliates in the net plankton and ten times that of ciliates in the nanoplankton. An isotope technique was developed to measure grazing rates of individual dinoflaggellates and other microzooplankton which cannot be separated in natural populations on the basis of size. /sup 3/H-thymidine and /sup 14/C-bicarbonate were used to label natural heterotrophic (bacteria and bacterivores) and autotrophic (phytoplankton and herbivores) food, respectively. Estimates of the grazing impact of heterotrophic kinoflagellates relative to other groups of heterotrophs on phytoplankton and bacteria were made by combining abundance data and clearance rates. Such calculations suggested that heterotrophic dinoflagellates may be an important group of grazers in oceanic waters.« less

Observed decline of the Atlantic meridional overturning circulation 2004-2012

NASA Astrophysics Data System (ADS)

Smeed, D. A.; McCarthy, G. D.; Cunningham, S. A.; Frajka-Williams, E.; Rayner, D.; Johns, W. E.; Meinen, C. S.; Baringer, M. O.; Moat, B. I.; Duchez, A.; Bryden, H. L.

2014-02-01

The Atlantic meridional overturning circulation (AMOC) has been observed continuously at 26° N since April 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable-based measurements of the Gulf Stream and satellite derived Ekman transport. The time series has recently been extended to October 2012 and the results show a downward trend since 2004. From April 2008 to March 2012, the AMOC was an average of 2.7 Sv (1 Sv = 106 m3 s-1) weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the southward flow above the thermocline. The increased southward flow of warm waters is balanced by a decrease in the southward flow of lower North Atlantic deep water below 3000 m. The transport of lower North Atlantic deep water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).

Slowing of the Atlantic meridional overturning circulation at 25 degrees N.

PubMed

Bryden, Harry L; Longworth, Hannah R; Cunningham, Stuart A

2005-12-01

The Atlantic meridional overturning circulation carries warm upper waters into far-northern latitudes and returns cold deep waters southward across the Equator. Its heat transport makes a substantial contribution to the moderate climate of maritime and continental Europe, and any slowdown in the overturning circulation would have profound implications for climate change. A transatlantic section along latitude 25 degrees N has been used as a baseline for estimating the overturning circulation and associated heat transport. Here we analyse a new 25 degrees N transatlantic section and compare it with four previous sections taken over the past five decades. The comparison suggests that the Atlantic meridional overturning circulation has slowed by about 30 per cent between 1957 and 2004. Whereas the northward transport in the Gulf Stream across 25 degrees N has remained nearly constant, the slowing is evident both in a 50 per cent larger southward-moving mid-ocean recirculation of thermocline waters, and also in a 50 per cent decrease in the southward transport of lower North Atlantic Deep Water between 3,000 and 5,000 m in depth. In 2004, more of the northward Gulf Stream flow was recirculating back southward in the thermocline within the subtropical gyre, and less was returning southward at depth.

Silicon utilizing microorganisms in the sea act as the environmental bellwether which foretell future trends in weather fluctuations

NASA Astrophysics Data System (ADS)

Das, S.

2012-12-01

It is well known that the southerly shift of the Gulf Stream is associated with major storms, heavy rains and mudslide in the adjoining northern part of the globe. Phytoplanktons particularly their silicon utilizing members like diatoms were found to play a major part in this phenomenon. A decrease in silicon utilizing phytoplanktons and chlorophyll-a , which sometimes occurs even more than 10 fold was found associated with a parallel significant decrease of zooplanktons as reflected in the CPR survey, leads to fall of sea temperature causing a shift of the Gulf Stream. This sea temperature changes is also associated with cooling of the adjoining atmosphere in a remarkable way which leads to weather changes. The association of silicon utilizing diatoms and the ocean currents guides the future trends in the climatic swing known as NAO, one of the great fluctuations that occur in the global climate, the largest of which is the ENSO phenomenon in the Pacific Ocean, which cause destruction all around the tropics. When total density and biovolume of phytoplanktons were studied it was found that the changes of pennate diatoms was unique and occurred in an opposite way in comparison to green algae, blue green algae, chrysophyte, cryptophytes, dinoflagellates and green flagellates.

Nonlinear Gulf Stream Interaction with the Deep Western Boundary Current System: Observations and a Numerical Simulation

NASA Technical Reports Server (NTRS)

Dietrich, David E.; Mehra, Avichal; Haney, Robert L.; Bowman, Malcolm J.; Tseng, Yu-Heng

2003-01-01

Gulf Stream (GS) separation near its observed Cape Hatteras (CH) separation location, and its ensuing path and dynamics, is a challenging ocean modeling problem. If a model GS separates much farther north than CH, then northward GS meanders, which pinch off warm core eddies (rings), are not possible or are strongly constrained by the Grand Banks shelfbreak. Cold core rings pinch off the southward GS meanders. The rings are often re-absorbed by the GS. The important warm core rings enhance heat exchange and, especially, affect the northern GS branch after GS bifurcation near the New England Seamount Chain. This northern branch gains heat by contact with the southern branch water upstream of bifurcation, and warms the Arctic Ocean and northern seas, thus playing a major role in ice dynamics, thermohaline circulation and possible global climate warming. These rings transport heat northward between the separated GS and shelf slope/Deep Western Boundary Current system (DWBC). This region has nearly level time mean isopycnals. The eddy heat transport convergence/divergence enhances the shelfbreak and GS front intensities and thus also increases watermass transformation. The fronts are maintained by warm advection by the Florida Current and cool advection by the DWBC. Thus, the GS interaction with the DWBC through the intermediate eddy field is climatologically important.

Small-scale shear measurements during the Fine and Microstructure Experiment (Fame)

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

Gargett, A.E.; Osborn, T.R.

1981-03-20

The turbulent kinetic energy dissipation rate e is estimated from measurements of small-scale shear taken with a vertical profiler during the Fine and Microstructure Experiment (Fame). Typical profiles of e are presented for the different oceanographic regions sampled, the Gulf Stream, a mid-Sargasso site, and locations withoutin and with the 100 fathom (approx.2000 m) contour about the island of Bermuda. Heavily averaged values of e are presented as a funtion of mean Vaeisaela frequency N-bar, a fundamental scaling parameter for the oceanic internal wave field. A dependence of e-barproportionalN-bar is found for an ensemble of stations near Bermuda: functional dependencemore » for an ensemble of stations at the mid-Sargasso site is less clear, with results exhibiting an undersirable sensitivity to infrequent large events. Dissipation is found to increase as the island of Bermuda is approached from any direction: the density of measurements is insufficient to determine any azimuthal variation resulting from the anisotropic mean flow field about the island at the time. A set of three profiles across the Gulf Stream suggests that this is not a region of abnormally high dissipation, a conclusion supported by previous and concurrent measurements of temperature finestructure and microstructure.« less

Stream primary producers relate positively to watershed natural gas measures in north-central Arkansas streams.

PubMed

Austin, Bradley J; Hardgrave, Natalia; Inlander, Ethan; Gallipeau, Cory; Entrekin, Sally; Evans-White, Michelle A

2015-10-01

Construction of unconventional natural gas (UNG) infrastructure (e.g., well pads, pipelines) is an increasingly common anthropogenic stressor that increases potential sediment erosion. Increased sediment inputs into nearby streams may decrease autotrophic processes through burial and scour, or sediment bound nutrients could have a positive effect through alleviating potential nutrient limitations. Ten streams with varying catchment UNG well densities (0-3.6 wells/km(2)) were sampled during winter and spring of 2010 and 2011 to examine relationships between landscape scale disturbances associated with UNG activity and stream periphyton [chlorophyll a (Chl a)] and gross primary production (GPP). Local scale variables including light availability and water column physicochemical variables were measured for each study site. Correlation analyses examined the relationships of autotrophic processes and local scale variables with the landscape scale variables percent pasture land use and UNG metrics (well density and well pad inverse flow path length). Both GPP and Chl a were primarily positively associated with the UNG activity metrics during most sample periods; however, neither landscape variables nor response variables correlated well with local scale factors. These positive correlations do not confirm causation, but they do suggest that it is possible that UNG development can alleviate one or more limiting factors on autotrophic production within these streams. A secondary manipulative study was used to examine the link between nutrient limitation and algal growth across a gradient of streams impacted by natural gas activity. Nitrogen limitation was common among minimally impacted stream reaches and was alleviated in streams with high UNG activity. These data provide evidence that UNG may stimulate the primary production of Fayetteville shale streams via alleviation of N-limitation. Restricting UNG activities from the riparian zone along with better enforcement of best management practices should help reduce these possible impacts of UNG activities on stream autotrophic processes. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Spatio-Temporal Variability of Rainfall on Stream flow Prediction of Birr Watershed

NASA Astrophysics Data System (ADS)

Demisse, N. S.; Bitew, M. M.; Gebremichael, M.

2012-12-01

The effect of rainfall variability on our ability to forecast flooding events was poorly studied in complex terrain region of Ethiopia. In order to establish relation between rainfall variability and stream flow, we deployed 24 rain gauges across Birr watershed. Birr watershed is a medium size mountainous watershed with an area of 3000 km2 and elevation ranging between 1435 m.a.s.l and 3400 m.a.s.l in the central Ethiopia highlands. One summer monsoon rainfall of 2012 recorded at high temporal scale of 15 minutes interval and stream flow recorded at an hourly interval in three sub-watershed locations representing different scales were used in this study. Based on the data obtained from the rain gauges and stream flow observations, we quantify extent of temporal and spatial variability of rainfall across the watershed using standard statistical measures including mean, standard deviation and coefficient of variation. We also establish rainfall-runoff modeling system using a physically distributed hydrological model: the Soil and Water Assessment Tool (SWAT) and examine the effect of rainfall variability on stream flow prediction. The accuracy of predicted stream flow is measured through direct comparison with observed flooding events. The results demonstrate the significance of relation between stream flow prediction and rainfall variability in the understanding of runoff generation mechanisms at watershed scale, determination of dominant water balance components, and effect of variability on accuracy of flood forecasting activities.

Seasonal and Interannual Variability in Gulf of Maine Hydrodynamics: 2002-2011.

PubMed

Li, Yizhen; He, Ruoying; McGillicuddy, Dennis J

2014-05-01

In situ observations including long-term moored meteorological and oceanographic measurements and multi-year gulf-wide ship survey data are used to quantify interannual variability of surface wind, river runoff, and hydrographic conditions in the Gulf of Maine during summers 2002-2011. The cumulative upwelling index shows that upwelling (downwelling)-favorable wind conditions were most persistent in 2010 (2005) over the 10-year study period. River discharge was highest in 2005; peak runoff occurred in early April in 2010 as opposed to late April to middle May in other years. Moored time series show that coastal water temperature was 0.5-2 °C warmer than average in summer 2010, and about 2 °C colder than average in 2004. Coastal salinity in April 2010 was the lowest in the 10-year study period. Both moored Acoustic Doppler Current Profiler (ADCP) current measurements and dynamic height/geostrophic velocity calculations based on gulf-wide ship survey data show May-June 2010 had one of the weakest alongshore transports in the western Gulf of Maine during the 10-year study period, likely associated with intrusions of warm slope water and fresher-than-usual Scotian Shelf water. Comparisons of coastal currents to the Paralytic Shellfish Poisoning (PSP) closure maps resulting from A. fundyense blooms suggest a linkage between alongshore transport and the downstream extent of toxicity.

Sampling the stream landscape: Improving the applicability of an ecoregion-level capture probability model for stream fishes

USGS Publications Warehouse

Mollenhauer, Robert; Mouser, Joshua B.; Brewer, Shannon K.

2018-01-01

Temporal and spatial variability in streams result in heterogeneous gear capture probability (i.e., the proportion of available individuals identified) that confounds interpretation of data used to monitor fish abundance. We modeled tow-barge electrofishing capture probability at multiple spatial scales for nine Ozark Highland stream fishes. In addition to fish size, we identified seven reach-scale environmental characteristics associated with variable capture probability: stream discharge, water depth, conductivity, water clarity, emergent vegetation, wetted width–depth ratio, and proportion of riffle habitat. The magnitude of the relationship between capture probability and both discharge and depth varied among stream fishes. We also identified lithological characteristics among stream segments as a coarse-scale source of variable capture probability. The resulting capture probability model can be used to adjust catch data and derive reach-scale absolute abundance estimates across a wide range of sampling conditions with similar effort as used in more traditional fisheries surveys (i.e., catch per unit effort). Adjusting catch data based on variable capture probability improves the comparability of data sets, thus promoting both well-informed conservation and management decisions and advances in stream-fish ecology.

Predicting marine physical-biogeochemical variabilities in the Gulf of Mexico and southeastern U.S. shelf sea

NASA Astrophysics Data System (ADS)

He, R.; Zong, H.; Xue, Z. G.; Fennel, K.; Tian, H.; Cai, W. J.; Lohrenz, S. E.

2017-12-01

An integrated terrestrial-ocean ecosystem modeling system is developed and used to investigate marine physical-biogeochemical variabilities in the Gulf of Mexico and southeastern US shelf sea. Such variabilities stem from variations in the shelf circulation, boundary current dynamics, impacts of climate variability, as well as growing population and associated land use practices on transport of carbon and nutrients within terrestrial systems and their delivery to the coastal ocean. We will report our efforts in evaluating the performance of the coupled modeling system via extensive model and data comparisons, as well as findings from a suite of case studies and scenario simulations. Long-term model simulation results are used to quantify regional ocean circulation dynamics, nitrogen budget and carbon fluxes. Their corresponding sub-regional differences are also characterized and contrasted.

Simulation of stream discharge and transport of nitrate and selected herbicides in the Mississippi River Basin

NASA Astrophysics Data System (ADS)

Broshears, Robert E.; Clark, Gregory M.; Jobson, Harvey E.

2001-05-01

Stream discharge and the transport of nitrate, atrazine, and metolachlor in the Mississippi River Basin were simulated using the DAFLOW/BLTM hydrologic model. The simulated domain for stream discharge included river reaches downstream from the following stations in the National Stream Quality Accounting Network: Mississippi River at Clinton, IA; Missouri River at Hermann, MO; Ohio River at Grand Chain, IL; and Arkansas River at Little Rock, AR. Coefficients of hydraulic geometry were calibrated using data from water year 1996; the model was validated by favourable simulation of observed discharges in water years 1992-1994. The transport of nitrate, atrazine, and metolachlor was simulated downstream from the Mississippi River at Thebes, IL, and the Ohio River at Grand Chain. Simulated concentrations compared favourably with observed concentrations at Baton Rouge, LA. Development of this model is a preliminary step in gaining a more quantitative understanding of the sources and fate of nutrients and pesticides delivered from the Mississippi River Basin to the Gulf of Mexico. Published in 2001 by John Wiley & Sons, Ltd.

Global characteristics of stream flow seasonality and variability

USGS Publications Warehouse

Dettinger, M.D.; Diaz, Henry F.

2000-01-01

Monthly stream flow series from 1345 sites around the world are used to characterize geographic differences in the seasonality and year-to-year variability of stream flow. Stream flow seasonality varies regionally, depending on the timing of maximum precipitation, evapotranspiration, and contributions from snow and ice. Lags between peaks of precipitation and stream flow vary smoothly from long delays in high-latitude and mountainous regions to short delays in the warmest sectors. Stream flow is most variable from year to year in dry regions of the southwest United States and Mexico, the Sahel, and southern continents, and it varies more (relatively) than precipitation in the same regions. Tropical rivers have the steadiest flows. El Nin??o variations are correlated with stream flow in many parts of the Americas, Europe, and Australia. Many stream flow series from North America, Europe, and the Tropics reflect North Pacific climate, whereas series from the eastern United States, Europe, and tropical South America and Africa reflect North Atlantic climate variations.

Modeling the Seasonal and Interannual Variability of the Northern Gulf of California Salinity

DTIC Science & Technology

2011-02-15

Schwartzlose (1979), Masas de agua del Golfo de California, Cienc . Mar., 6, 43–63. Argote, M. L., A. Amador, M. F. Lavı’n, and J. R. Hunter (1995...entrance of the Gulf of California, Mexico, Cienc . Mar., 26, 561–583. Enfield, D. B. (1987), The intraseasonal oscillation in eastern Pacific sea levels

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

Kilbourne, K H; Quinn, T M; Guilderson, T P

Water that forms the Florida Current, and eventually the Gulf Stream, coalesces in the Caribbean from both subtropical and equatorial sources. The equatorial sources are made up of, in part, South Atlantic water moving northward and compensating for southward flow at depth related to meridional overturning circulation. Subtropical surface water contains relatively high amounts of radiocarbon ({sup 14}C), whereas equatorial waters are influenced by the upwelling of low {sup 14}C water and have relatively low concentrations of {sup 14}C. We use a 250-year record of {Delta}{sup 14}C in a coral from southwestern Puerto Rico along with previously published coral {Delta}{supmore » 14}C records as tracers of subtropical and equatorial water mixing in the northern Caribbean. Data generated in this study and from other studies indicate that the influence of either of the two water masses can change considerably on interannual to interdecadal time scales. Variability due to ocean dynamics in this region is large relative to variability caused by atmospheric {sup 14}C changes, thus masking the Suess effect at this site. A mixing model produced using coral {Delta}{sup 14}C illustrates the time varying proportion of equatorial versus subtropical waters in the northern Caribbean between 1963 and 1983. The results of the model are consistent with linkages between multidecadal thermal variability in the North Atlantic and meridional overturning circulation. Ekman transport changes related to tradewind variability are proposed as a possible mechanism to explain the observed switches between relatively low and relatively high {Delta}{sup 14}C values in the coral radiocarbon records.« less

Rapid grounding line migration induced by internal variability of a marine-terminating ice stream

NASA Astrophysics Data System (ADS)

Robel, A.; Schoof, C.; Tziperman, E.

2013-12-01

Numerous studies have found significant variability in the velocity of ice streams to be a prominent feature of geomorphologic records in the Siple Coast (Catania et al. 2012) and other regions in West Antarctica (Dowdeswell et al. 2008). Observations indicate that grounding line position is strongly influenced by ice stream variability, producing rapid grounding line migration in the recent past (Catania et al. 2006) and the modern (Joughin & Tulaczyk 2002). We analyze the interaction of grounding line mass flux and position in a marine-terminating ice stream using a stretch-coordinate flowline model. This model is based on that described in Schoof (2007), with a mesh refined near the grounding line to ensure accurate resolution of the mechanical transition zone. Here we have added lateral shear stress (Dupont & Alley 2005) and an undrained plastic bed (Tulaczyk et al. 2000). The parameter dependence of ice stream variability seen in this model compares favorably to both simpler (Robel et al. 2013) and more complex (van der Wel et al. 2013) models, though with some key differences. We find that thermally-induced internal ice stream variability can cause very rapid grounding line migration even in the absence of retrograde bed slopes or external forcing. Activation waves propagate along the ice stream length and trigger periods of rapid grounding line migration. We compare the behavior of the grounding line due to internal ice stream variability to changes triggered externally at the grounding line such as the rapid disintegration of buttressing ice shelves. Implications for Heinrich events and the Marine Ice Sheet Instability are discussed.

Isotopic and chemical composition of inorganic and organic water-quality samples from the Mississippi River Basin, 1997-98

USGS Publications Warehouse

Battaglin, William A.; Kendall, Carol; Chang, Cecily C.Y.; Silva, Steven R.; Campbell, Donald H.

2001-01-01

Nitrate (NO3) and other nutrients discharged by the Mississippi River combined with seasonal stratification of the water column are known to cause a zone of depleted dissolved oxygen (hypoxic zone) in the Gulf of Mexico each summer. About 120 water and suspended sediment samples collected in 1997 and 1998 from 24 locations in the Mississippi River Basin were analyzed for the isotope ratios δ15N and δ18O of dissolved NO3, and δ15N and δ13C of suspended particulate organic material (POM). Sampling stations include both large rivers (drainage areas more than 30,000 square kilometers) that integrate the effects of many land uses, and smaller streams (drainage areas less than 2,500 square kilometers) that have relatively uniform land use within their drainage areas. The data are used to determine sources and transformations of NO3 in the Mississippi River.Results of this study demonstrate that much of the NO3 in the Mississippi River originates in the agriculturally dominated basins of the upper midwestern United States and is transported without significant transformation or other loss to the Gulf of Mexico. Results from major tributaries that drain into the Mississippi River suggest that NO3 is not significantly altered by denitrification in its journey, ultimately, to the Gulf of Mexico. The spatial variability of isotope ratios among the smaller streams appears to be related to the dominant nitrogen source in the basins. There are some distinct isotope differences among land-use types. For example, for both NO3 and POM, the majority of δ15N isotope ratio values from basins dominated by urban and undeveloped land are less than +5 per mil, whereas the majority of values from basins dominated by row crops and row crops and/or livestock production are greater than +5 per mil. Also, the median δ18O of NO3 isotope ratio value (+14.0 per mil) from undeveloped basins is more than 6 per mil higher than the median value (+7.3 per mil) from the row crop dominated basins and 5 per mil higher than the median value (+9.0 per mil) from the row crop and/or livestock production dominated basins. The median δ18O of NO3 isotope ratio value (+21.5 per mil) from urban basins is 6.5 per mil higher than the median value (+14.0 per mil) from the undeveloped basins. The majority of NO3 concentrations are greater than 3 milligrams per liter (mg/L) in basins dominated by row crops and row crops and/or livestock production, whereas all NO3 concentrations are less than 2 mg/L in basins dominated by urban and undeveloped land.

Seasonal variability of water transport through the Straits of Gibraltar, Sicily and Corsica, derived from a high-resolution model of the Mediterranean circulation

NASA Astrophysics Data System (ADS)

Béranger, K.; Mortier, L.; Crépon, M.

2005-08-01

The variability of the water transport through three major straits of the Mediterranean Sea (Gibraltar, Sicily and Corsica) was investigated using a high-resolution model. This model of the Mediterranean circulation was developed in the context of the Mercator project. The region of interest is the western Mediterranean between the Strait of Gibraltar and the Strait of Sicily. The major water masses and the winter convection in the Gulf of Lions were simulated. The model reproduced the meso-scale and large-scale patterns of the circulation in very good agreement with recent observations. The western and the eastern gyres of the Alboran Sea were observed but high interannual variability was noticed. The Algerian Current splits into several branches at the longitude of the Strait of Sicily level, forming the Tyrrhenian branch, and, the Atlantic Ionian Stream and the Atlantic Tunisian Current in the eastern Mediterranean. The North Current retroflexed north of the Balearic Islands and a dome structure was observed in the Gulf of Lions. The cyclonic barotropic Algerian gyre, which was recently observed during the MATER and ELISA experiment, was evidenced in the simulation. From time-series of 10-day mean transport, the three straits presented a high variability at short time-scales. The transport was generally maximum, in April for the Strait of Gibraltar, in November for the Strait of Sicily, and in January for the Strait of Corsica. The amplitudes of the transport through the Straits of Gibraltar (0.11 Sv) and Sicily (0.30 Sv) presented a weaker seasonal variability than that of the Strait of Corsica (0.70 Sv). The study of the relation between transport and wind forcing showed that the transport through the Strait of Gibraltar is dependent on local zonal wind over short time-scales (70%), which was not the case for the other straits (less than 30%). The maximum (minimum) of the transport occurred for an eastward (westward) wind stress in the strait. An interannual event was noticed in November-December 2001, which corresponded to a very low transport (0.3 Sv), which was characterised by a cyclonic circulation in the western Alboran Sea. That circulation was also reproduced by the model for other periods than winter during the interannual simulation. The transport through the Strait of Sicily is not influenced by local wind. The wind stress curl of the northwestern Mediterranean influenced the transport through the Strait of Corsica.

Variable styles of rifting expressed in crustal structure across three rift segments of the Gulf of California

NASA Astrophysics Data System (ADS)

Lizarralde, D. D.; Axen, G. J.; Brown, H. E.; Fletcher, J. M.; Fernandez, A. G.; Harding, A. J.; Holbrook, W. S.; Kent, G. M.; Paramo, P.; Sutherland, F. H.; Umhoefer, P. J.

2007-05-01

We present a summary of results from a crustal-scale seismic experiment conducted in the southern Gulf of California. This experiment, the PESCADOR experiment, imaged crustal structure across three rift segments, the Alarcon, Guaymas, and San José del Cabo to Puerto Vallarta (Cabo-PV) segments, using seismic refraction/wide-angle reflection data acquired with airgun sources and recorded by closely spaced (10-15 km) ocean-bottom seismometers (OBSs). The imaged crustal structure reveals a surprisingly large variation in rifting style and magmatism between these segments: the Alarcon segment is a wide rift with apparently little syn-rift magmatism; the Guaymas segment is a narrow, magmatically robust rift; and the Cabo-PV segment is a narrow, magmatically "normal" rift. Our explanation for the observed variability is non-traditional in that we do not invoke mantle temperature, the factor commonly invoked to explain end-member volcanic and non-volcanic rifted margins, as the source of the considerable, though non-end-member variability we observe. Instead, we invoke mantle depletion related to pre-rift arc volcanism to account for observed wide, magma-poor rifting and mantle fertility and possibly the influence of sediments to account for robust rift and post-rift magmatism. These factors may commonly vary over small lateral spatial scales in regions that have transitioned from convergent to extensional tectonics, as is the case for the Gulf of California and many other rifts. Our hypothesis suggests that substantial lateral variability may exist within the uppermost mantle beneath the Gulf of California today, and it is hoped that ongoing efforts to image upper mantle structure here will provide tests for this hypothesis.

SPATIAL AND TEMPORAL VARIABILITY AND DRIVERS OF NET ECOSYSTEM METABOLISM IN WESTERN GULF OF MEXICO ESTUARIES

EPA Science Inventory

Net ecosystem metabolism (NEM) is becoming a commonly used ecological indicator of estuarine ecosystem metabolic rates. Estuarine ecosystem processes are spatially and temporally variable, but the corresponding variability in NEM has not been properly assessed. Spatial and temp...

Dynamical Evaluation of Ocean Models using the Gulf Stream as an Example

DTIC Science & Technology

2010-01-01

transport for the Atlantic meridional overturning circulation (AMOC) as the 3 nonlinear solutions discussed in Section 2. The model boundary is...Hellerman and Rosenstein (1983) wind stress climatology and the northward upper ocean flow (14 Sv) of the Atlantic meridional overturning circulation ... overturning circulation (AMOC) streamfunction with a 5 Sv contour interval from (a) 1/12° Atlantic MICOM, (b) 1/12° Atlantic HYCOM, and (c) 1/12

Dynamical Evaluation of Ocean Models Using the Gulf Stream as an Example

DTIC Science & Technology

2012-02-10

Hellerman and Rosenstein (1983) wind stress climatology and the northward upper ocean flow (14 Sv) of the Atlantic meridional overturning circulation ...30 35 55N 65N Fig. 21.14 Atlantic meridional overturning circulation (AMOC) streamfunction from the same four simulations as Fig. 21.11. An AMOC...typically develops a northern or southern bias. A shallow bias in the southward abyssal flow of the Atlan- tic Meridional Overturning Circulation (AMOC

Assessment of Climate Change and Freshwater Ecosystems of the Rocky Mountains, USA and Canada

NASA Astrophysics Data System (ADS)

Hauer, F. Richard; Baron, Jill S.; Campbell, Donald H.; Fausch, Kurt D.; Hostetler, Steve W.; Leavesley, George H.; Leavitt, Peter R.; McKnight, Diane M.; Stanford, Jack A.

1997-06-01

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may differ by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal baseflows. During the 2-3-month spring runoff period, rivers frequently discharge > 70% of their annual water budget and have instantaneous discharges 10-100 times mean low flow.Complex weather patterns characterized by high spatial and temporal variability make predictions of future conditions tenuous. However, general patterns are identifiable; northern and western portions of the region are dominated by maritime weather patterns from the North Pacific, central areas and eastern slopes are dominated by continental air masses and southern portions receive seasonally variable atmospheric circulation from the Pacific and the Gulf of Mexico. Significant interannual variations occur in these general patterns, possibly related to ENSO (El Niño-Southern Oscillation) forcing.Changes in precipitation and temperature regimes or patterns have significant potential effects on the distribution and abundance of plants and animals. For example, elevation of the timber-line is principally a function of temperature. Palaeolimnological investigations have shown significant shifts in phyto- and zoo-plankton populations as alpine lakes shift between being above or below the timber-line. Likewise, streamside vegetation has a significant effect on stream ecosystem structure and function. Changes in stream temperature regimes result in significant changes in community composition as a consequence of bioenergetic factors. Stenothermic species could be extirpated as appropriate thermal criteria disappear. Warming temperatures may geographically isolate cold water stream fishes in increasingly confined headwaters. The heat budgets of large lakes may be affected resulting in a change of state between dimictic and warm monomictic character. Uncertainties associated with prediction are increased by the planting of fish in historically fishless, high mountain lakes and the introduction of non-native species of fishes and invertebrates into often previously simple food-webs of large valley bottom lakes and streams. Many of the streams and rivers suffer from the anthropogenic effects of abstraction and regulation. Likewise, many of the large lakes receive nutrient loads from a growing human population.We concluded that: (1) regional climate models are required to resolve adequately the complexities of the high gradient landscapes; (2) extensive wilderness preserves and national park lands, so prevalent in the Rocky Mountain Region, provide sensitive areas for differentiation of anthropogenic effects from climate effects; and (3) future research should encompass both short-term intensive studies and long-term monitoring studies developed within comprehensive experimental arrays of streams and lakes specifically designed to address the issue of anthropogenic versus climatic effects.

Assessment of climate change and freshwater ecosystems of the Rocky Mountains, USA and Canada

USGS Publications Warehouse

Hauer, F. Richard; Baron, Jill S.; Campbell, D.H.; Fausch, K.D.; Hostetler, S.W.; Leavesley, G.H.; Leavitt, P.R.; McKnight, Diane M.; Stanford, J.A.

1997-01-01

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may differ by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal baseflows. During the 2-3-month 'spring runoff' period, rivers frequently discharge >70% of their annual water budget and have instantaneous discharges 10-100 times mean low flow. Complex weather patterns characterized by high spatial and temporal variability make predictions of future conditions tenuous. However, general patterns are identifiable; northern and western portions of the region are dominated by maritime weather patterns from the North Pacific, central areas and eastern slopes are dominated by continental air masses and southern portions receive seasonally variable atmospheric circulation from the Pacific and the Gulf of Mexico. Significant interannual variations occur in these general patterns, possibly related to ENSO (El Nin??o-Southern Oscillation) forcing. Changes in precipitation and temperature regimes or patterns have significant potential effects on the distribution and abundance of plants and animals. For example, elevation of the timber-line is principally a function of temperature. Palaeolimnological investigations have shown significant shifts in phyto- and zoo-plankton populations as alpine lakes shift between being above or below the timber-line. Likewise, streamside vegetation has a significant effect on stream ecosystem structure and function. Changes in stream temperature regimes result in significant changes in community composition as a consequence of bioenergetic factors. Stenothermic species could be extirpated as appropriate thermal criteria disappear. Warming temperatures may geographically isolate cole water stream fishes in increasingly confined headwaters. The heat budgets of large lakes may be affected resulting in a change of state between dimictic and warm monomictic character. Uncertainties associated with prediction are increased by the planting of fish in historically fishless, high mountain lakes and the introduction of non-native species of fishes and invertebrates into often previously simple food-webs of large valley bottom lakes and streams. Many of the streams and rivers suffer from the anthropogenic effects of abstraction and regulation. Likewise, many of the large lakes receive nutrient loads from a growing human population. We concluded that: (1) regional climate models are required to resolve adequately the complexities of the high gradient landscapes; (2) extensive wilderness preserves and national park lands, so prevalent in the Rocky Mountain Region, provide sensitive areas for differentiation of anthropogenic effects from climate effects; and (3) future research should encompass both short-term intensive studies and long-term monitoring studies developed within comprehensive experimental arrays of streams and lakes specifically designed to address the issue of anthropogenic versus climatic effects. ?? 1997 by John Wiley & Sons, Ltd.

A Digital Hydrologic Network Supporting NAWQA MRB SPARROW Modeling--MRB_E2RF1WS

USGS Publications Warehouse

Brakebill, J.W.; Terziotti, S.E.

2011-01-01

A digital hydrologic network was developed to support SPAtially Referenced Regression on Watershed attributes (SPARROW) models within selected regions of the United States. These regions correspond with the U.S. Geological Survey's National Water Quality Assessment (NAWQA) Program Major River Basin (MRB) study units 2, 3, 4, 5, and 7 (Preston and others, 2009). MRB2, covers the South Atlantic-Gulf and Tennessee River basins. MRB3, covers the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins. MRB4, covers the Missouri River basins. MRB5, covers the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins. MRB7, covers the Pacific Northwest River basins. The digital hydrologic network described here represents surface-water pathways (MRB_E2RF1) and associated catchments (MRB_E2RF1WS). It serves as the fundamental framework to spatially reference and summarize explanatory information supporting nutrient SPARROW models (Brakebill and others, 2011; Wieczorek and LaMotte, 2011). The principal geospatial dataset used to support this regional effort was based on an enhanced version of a 1:500,000 scale digital stream-reach network (ERF1_2) (Nolan et al., 2002). Enhancements included associating over 3,500 water-quality monitoring sites to the reach network, improving physical locations of stream reaches at or near monitoring locations, and generating drainage catchments based on 100m elevation data. A unique number (MRB_ID) identifies each reach as a single unit. This unique number is also shared by the catchment area drained by the reach, thus spatially linking the hydrologically connected streams and the respective drainage area characteristics. In addition, other relevant physical, environmental, and monitoring information can be associated to the common network and accessed using the unique identification number.

A Digital Hydrologic Network Supporting NAWQA MRB SPARROW Modeling--MRB_E2RF1

USGS Publications Warehouse

Brakebill, J.W.; Terziotti, S.E.

2011-01-01

A digital hydrologic network was developed to support SPAtially Referenced Regression on Watershed attributes (SPARROW) models within selected regions of the United States. These regions correspond with the U.S. Geological Survey's National Water Quality Assessment (NAWQA) Program Major River Basin (MRB) study units 2, 3, 4, 5, and 7 (Preston and others, 2009). MRB2, covers the South Atlantic-Gulf and Tennessee River basins. MRB3, covers the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins. MRB4, covers the Missouri River basins. MRB5, covers the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins. MRB7, covers the Pacific Northwest River basins. The digital hydrologic network described here represents surface-water pathways (MRB_E2RF1) and associated catchments (MRB_E2RF1WS). It serves as the fundamental framework to spatially reference and summarize explanatory information supporting nutrient SPARROW models (Brakebill and others, 2011; Wieczorek and LaMotte, 2011). The principal geospatial dataset used to support this regional effort was based on an enhanced version of a 1:500,000 scale digital stream-reach network (ERF1_2) (Nolan et al., 2002). Enhancements included associating over 3,500 water-quality monitoring sites to the reach network, improving physical locations of stream reaches at or near monitoring locations, and generating drainage catchments based on 100m elevation data. A unique number (MRB_ID) identifies each reach as a single unit. This unique number is also shared by the catchment area drained by the reach, thus spatially linking the hydrologically connected streams and the respective drainage area characteristics. In addition, other relevant physical, environmental, and monitoring information can be associated to the common network and accessed using the unique identification number.

The Role of Regional Factors in Structuring Ouachita Mountain Stream Assemblages

Treesearch

Lance R. Williams; Christopher M. Taylor; Melvin L. Warren; J. Alan Clingenpeel

2004-01-01

Abstract - We used Basin Area Stream Survey data from the USDA Forest Service, Ouachita National Forest to evaluate the relationship between regional fish and macroinvertebrate assemblages and environmental variability (both natural and anthropogenic). Data were collected for three years (1990-1992) from six hydrologically variable stream systems in...

Effects of geomorphology, habitat, and spatial location on fish assemblages in a watershed in Ohio, USA.

PubMed

D'Ambrosio, Jessica L; Williams, Lance R; Witter, Jonathan D; Ward, Andy

2009-01-01

In this paper, we evaluate relationships between in-stream habitat, water chemistry, spatial distribution within a predominantly agricultural Midwestern watershed and geomorphic features and fish assemblage attributes and abundances. Our specific objectives were to: (1) identify and quantify key environmental variables at reach and system wide (watershed) scales; and (2) evaluate the relative influence of those environmental factors in structuring and explaining fish assemblage attributes at reach scales to help prioritize stream monitoring efforts and better incorporate all factors that influence aquatic biology in watershed management programs. The original combined data set consisted of 31 variables measured at 32 sites, which was reduced to 9 variables through correlation and linear regression analysis: stream order, percent wooded riparian zone, drainage area, in-stream cover quality, substrate quality, gradient, cross-sectional area, width of the flood prone area, and average substrate size. Canonical correspondence analysis (CCA) and variance partitioning were used to relate environmental variables to fish species abundance and assemblage attributes. Fish assemblages and abundances were explained best by stream size, gradient, substrate size and quality, and percent wooded riparian zone. Further data are needed to investigate why water chemistry variables had insignificant relationships with IBI scores. Results suggest that more quantifiable variables and consideration of spatial location of a stream reach within a watershed system should be standard data incorporated into stream monitoring programs to identify impairments that, while biologically limiting, are not fully captured or elucidated using current bioassessment methods.

Can basin land use effects on physical characteristics of streams be determined at broad geographic scales?

USGS Publications Warehouse

Goldstein, R.M.; Carlisle, D.M.; Meador, M.R.; Short, T.M.

2007-01-01

The environmental setting (e.g., climate, topography, geology) and land use affect stream physical characteristics singly and cumulatively. At broad geographic scales, we determined the importance of environmental setting and land use in explaining variation in stream physical characteristics. We hypothesized that as the spatial scale decreased from national to regional, land use would explain more of the variation in stream physical characteristics because environmental settings become more homogeneous. At a national scale, stepwise linear regression indicated that environmental setting was more important in explaining variability in stream physical characteristics. Although statistically discernible, the amount of variation explained by land use was not remarkable due to low partial correlations. At level II ecoregion spatial scales (southeastern USA plains, central USA plains, and a combination of the western Cordillera and the western interior basins and ranges), environmental setting variables were again more important predictors of stream physical characteristics, however, as the spatial scale decreased from national to regional, the portion of variability in stream physical characteristics explained by basin land use increased. Development of stream habitat indicators of land use will depend upon an understanding of relations between stream physical characteristics and environmental factors at multiple spatial scales. Smaller spatial scales will be necessary to reduce the confounding effects of variable environmental settings before the effects of land use can be reliably assessed. ?? Springer Science+Business Media B.V. 2006.

Spatial heterogeneity of within-stream methane concentrations

NASA Astrophysics Data System (ADS)

Crawford, John T.; Loken, Luke C.; West, William E.; Crary, Benjamin; Spawn, Seth A.; Gubbins, Nicholas; Jones, Stuart E.; Striegl, Robert G.; Stanley, Emily H.

2017-05-01

Streams, rivers, and other freshwater features may be significant sources of CH4 to the atmosphere. However, high spatial and temporal variabilities hinder our ability to understand the underlying processes of CH4 production and delivery to streams and also challenge the use of scaling approaches across large areas. We studied a stream having high geomorphic variability to assess the underlying scale of CH4 spatial variability and to examine whether the physical structure of a stream can explain the variation in surface CH4. A combination of high-resolution CH4 mapping, a survey of groundwater CH4 concentrations, quantitative analysis of methanogen DNA, and sediment CH4 production potentials illustrates the spatial and geomorphic controls on CH4 emissions to the atmosphere. We observed significant spatial clustering with high CH4 concentrations in organic-rich stream reaches and lake transitions. These sites were also enriched in the methane-producing mcrA gene and had highest CH4 production rates in the laboratory. In contrast, mineral-rich reaches had significantly lower concentrations and had lesser abundances of mcrA. Strong relationships between CH4 and the physical structure of this aquatic system, along with high spatial variability, suggest that future investigations will benefit from viewing streams as landscapes, as opposed to ecosystems simply embedded in larger terrestrial mosaics. In light of such high spatial variability, we recommend that future workers evaluate stream networks first by using similar spatial tools in order to build effective sampling programs.

Variability, trends, and teleconnections of stream flows with large-scale climate signals in the Omo-Ghibe River Basin, Ethiopia.

PubMed

Degefu, Mekonnen Adnew; Bewket, Woldeamlak

2017-04-01

This study assesses variability, trends, and teleconnections of stream flow with large-scale climate signals (global sea surface temperatures (SSTs)) for the Omo-Ghibe River Basin of Ethiopia. Fourteen hydrological indices of variability and extremes were defined from daily stream flow data series and analyzed for two common periods, which are 1972-2006 for 5 stations and 1982-2006 for 15 stations. The Mann-Kendall's test was used to detect trends at 0.05 significance level, and simple correlation analysis was applied to evaluate associations between the selected stream flow indices and SSTs. We found weak and mixed (upward and downward) trend signals for annual and wet (Kiremt) season flows. Indices generated for high-flow (flood) magnitudes showed the same weak trend signals. However, trend tests for flood frequencies and low-flow magnitudes showed little evidences of increasing change. It was also found that El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are the major anomalies affecting stream flow variability in the Omo-Ghibe Basin. The strongest associations are observed between ENSO/Niño3.4 and the stream flow in August and September, mean Kiremt flow (July-September), and flood frequency (peak over threshold on average three peaks per year (POT3_Fre)). The findings of this study provide a general overview on the long-term stream flow variability and predictability of stream flows for the Omo-Ghibe River Basin.

Cholinergic autonomic dysfunction in veterans with Gulf War illness: confirmation in a population-based sample.

PubMed

Haley, Robert W; Charuvastra, Elizabeth; Shell, William E; Buhner, David M; Marshall, W Wesley; Biggs, Melanie M; Hopkins, Steve C; Wolfe, Gil I; Vernino, Steven

2013-02-01

The authors of prior small studies raised the hypothesis that symptoms in veterans of the 1991 Gulf War, such as chronic diarrhea, dizziness, fatigue, and sexual dysfunction, are due to cholinergic autonomic dysfunction. To perform a confirmatory test of this prestated hypothesis in a larger, representative sample of Gulf War veterans. Nested case-control study. Clinical and Translational Research Center, University of Texas Southwestern Medical Center, Dallas. Representative samples of Gulf War veterans meeting a validated case definition of Gulf War illness with 3 variants (called syndromes 1-3) and a control group, all selected randomly from the US Military Health Survey. Validated domain scales from the Autonomic Symptom Profile questionnaire, the Composite Autonomic Severity Score, and high-frequency heart rate variability from a 24-hour electrocardiogram. The Autonomic Symptom Profile scales were significantly elevated in all 3 syndrome groups (P< .001), primarily due to elevation of the orthostatic intolerance, secretomotor, upper gastrointestinal dysmotility, sleep dysfunction, urinary, and autonomic diarrhea symptom domains. The Composite Autonomic Severity Score was also higher in the 3 syndrome groups (P= .045), especially in syndrome 2, primarily due to a significant reduction in sudomotor function as measured by the Quantitative Sudomotor Axon Reflex Test, most significantly in the foot; the score was intermediate in the ankle and upper leg and was nonsignificant in the arm, indicating a peripheral nerve length-related deficit. The normal increase in high-frequency heart rate variability at night was absent or blunted in all 3 syndrome groups (P< .001). Autonomic symptoms are associated with objective, predominantly cholinergic autonomic deficits in the population of Gulf War veterans.

Mesoscale variability of water masses in the Arabian Sea as revealed by ARGO floats

NASA Astrophysics Data System (ADS)

Carton, X.; L'Hegaret, P.

2011-06-01

By analysing ARGO float data over the last four years, some aspects of the mesoscale variability of water masses in the Arabian Sea are described. The Red Sea Water outflow is strong in the Southwestern Gulf of Aden, in particular when a cyclonic gyre predominates in this region. Salinities of 36.5 and temperatures of 16 °C are found there between 600 and 1000 m depths. The Red Sea Water is more dilute in the eastern part of the Gulf, and fragments of this water mass can be advected offshore across the gulf or towards its northern coast by the regional gyres. The Red Sea Water outflow is also detected along the northeastern coast of Socotra, and fragments of RSW are found between one and three degrees of latitude north of this island. In the whole Gulf of Aden, the correlation between the deep motions of the floats and the SSH measured by altimetry is strong, at regional scale. The finer scale details of the float trajectories are more often related to the anomalous water masses that they encounter. The Persian Gulf Water (PGW) is found in the float profiles near Ras ash Sharbatat (near 57° E, 18° N), again with 36.5 in salinity and about 18-19 °C in temperature. These observations were achieved in winter when the southwestward monsoon currents can advect PGW along the South Arabian coast. Fragments of PGW are found in the Arabian Sea between 18 and 20° N and 63 and 65° E, showing that this water mass can escape the Gulf of Oman southeastward, in particular during summer.

Multiscale habitat suitability index models for priority landbirds in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions

Treesearch

John M. Tirpak; D. Todd Jones-Farrand; Frank R., III Thompson; Daniel J. Twedt; William B., III Uihlein

2009-01-01

Habitat Suitability Index (HSI) models were developed to assess habitat quality for 40 priority bird species in the Central Hardwoods and West Gulf Coastal Plain/Ouachitas Bird Conservation Regions. The models incorporated both site and landscape environmental variables from one of six nationally consistent datasets. Potential habitat was first defined from unique...

Modulation of Winter Precipitation Dynamics Over the Arabian Gulf by ENSO

NASA Astrophysics Data System (ADS)

Sandeep, S.; Ajayamohan, R. S.

2018-01-01

The Arabian Gulf (Gulf) and the surrounding regions are centers of intense economic activity. The precipitating weather systems that form over the Gulf are important for this predominantly arid region. It is suggested that El Niño-Southern Oscillation (ENSO) influences the Middle East precipitation variability through an equatorward shift of the subtropical jet. Here we present compelling evidence to illustrate the role of ENSO in modulating the local dynamics and moisture transport in initiating precipitation during different ENSO phases using satellite and reanalysis data. It is found that the moisture transport from the Red and Arabian Seas toward the Gulf is stronger during El Niño years. The pattern and strength of moisture transport toward the Gulf is weakened during La Niña and neutral years, with most of the transport directed toward the northern Gulf. Using a 120 h back trajectory analysis, it is found that while the air parcels coming toward the Gulf from the Arabian and Red Seas side originate at lower tropospheric levels, the air parcels from the Mediterranean originate at middle and upper tropospheric levels during El Niño years. In contrast, upper tropospheric air parcels originating over the southern Arabian Sea plays a dominant role on Gulf precipitation during La Niña and neutral years. The seasonal mean transients of zonal winds show a robust ENSO signature over the Gulf, indicating a favorable (less favorable) condition for the penetration of midlatitude eddies over the region during El Niño (La Niña) winters.

Three-Dimensional Structure of the Circulation Induced by a Shoaling Topographic Wave

NASA Astrophysics Data System (ADS)

Mizuta, G.; Hogg, N. G.

2003-12-01

Rectification of Rossby wave energy has been proposed as a mechanism for the maintenance of the recirculation cell of the Gulf Stream (Hogg 1988; Rizzoli et al. 1995). We investigated the three-dimensional structure of potential-vorticity flux and a mean flow induced by a topographic wave incident over a bottom slope analytically and numerically, focusing on the limit that bottom friction is the dominant dissipation process. In this limit it is shown that the topographic wave cannot be a steady source of the potential vorticity outside the bottom Ekman layer. Instead, the distribution of potential vorticity is determined from the initial transient of the topographic wave. This potential vorticity and the heat flux by the topographic wave at the bottom determine the mean flow, and give a relation between the horizontal and vertical scales of the mean flow. When the horizontal scale of the mean flow is larger than the internal deformation radius, the mean flow is almost constant with depth independent of whether or not the topographic wave is trapped near the bottom. Then the mean flow at the bottom is proportional to the divergence of vertically integrated Reynolds stress ∫ -D0 /line{u'v'} dz. This divergence, which is caused by bottom friction, is large when the group velocity, cg and the vertical scale, μ -1 of the wave motion are small. Thus the mean flow tends to be large where cg and μ -1 become small, and decreases as the topographic wave is dissipated by bottom friction. Since bottom friction also dissipates the mean flow, the mean flow asymptotes to a constant value as the friction becomes zero. These features of the potential-vorticity flux and the mean flow are reproduced in numerical experiments. It is also shown from the numerical experiment that the distribution of the mean flow depends on the amplitude of the wave because of the Doppler shift of the wave by the mean flow. These feature of the mean flow are preserved when we used stratification and bottom topography resembling to those over the continental slope near the Gulf Stream. The transport of the mean flow is about 20 Sv when the wave amplitude is about 2 cm/s. These numbers are similiar to those observed in the Gulf Stream region.

Modeling the drift of massive icebergs to the subtropical North Atlantic

NASA Astrophysics Data System (ADS)

Condron, A.; Hill, J. C.

2013-12-01

New evidence from high-resolution seafloor bathymetry data indicates that massive (>300m thick) icebergs from the Laurentide Ice Sheet (LIS) drifted south to the tip of Florida during the last deglaciation. This finding is particularly exciting as it contradicts evidence from marine sediments that icebergs were mainly confined to the subpolar North Atlantic (50 - 70N) at this time. Indeed, the freshwater released from icebergs melting in the subpolar gyre is repeatedly cited as a main trigger for a slow-down of the Atlantic MOC in the past, and the possible cause of any climate cooling related to the melting of the Greenland Ice Sheet in the future. Using a sophisticated iceberg model (MITberg), coupled to a high (18-km; 1/6 deg.) resolution ocean model (MITgcm), we investigate the ocean circulation dynamics required to allow icebergs to drift to the southern tip of Florida. We find that icebergs only reach this location if they turn right at the Grand Banks of Newfoundland, and stay inshore of the Gulf Stream all the way to Florida. Modern-day circulation dynamics do not readily allow this to happen as cold, southward flowing, Labrador Current Water (important for iceberg survival) has little penetration south of Cape Hatteras. However, when a liquid meltwater flood is released from Hudson Bay at the same time, icebergs are rapidly transported (inshore of the Gulf Stream) in a narrow, buoyant, coastal current all the way to southern Florida. The meltwater and icebergs result in a significant freshening of the subtropical North Atlantic and weaken the strength of the Gulf Stream, suggesting such an event would have a large cooling effect on climate. We are only able to simulate the flow of meltwater and icebergs to the subtropics by modeling ocean circulation at a resolution that is 5 - 10 times higher than the majority of existing paleoclimate models; at lower resolutions the narrow, coastal boundary currents important for iceberg transport to the subtropics are no longer resolved. Our results show convincing evidence that a large component of iceberg laden freshwater from the LIS had more of a subtropical impact than previously believed, suggesting the ';subpolar-freshening' hypothesis repeatedly cited in the literature as a trigger for abrupt climate change needs rethinking.

OSTM/Jason-2 and Jason-1 Tandem Mission View of the Gulf Stream

NASA Image and Video Library

2009-04-27

Created with altimeter data from NASA's Ocean Surface Topography Mission (OSTM)/Jason-2 satellite and the Jason-1 satellite, this image shows a portion of the Gulf Stream off the east coast of the United States. It demonstrates how much more detail is visible in the ocean surface when measured by two satellites than by one alone. The image on the left was created with data from OSTM/Jason-2. The image on the right is the same region but made with combined data from OSTM/Jason-2 and Jason-1.It shows the Gulf Stream's eddies and rings much more clearly. This image is a product of the new interleaved tandem mission of the Jason-1 and Ocean Surface Topography Mission (OSTM)/Jason-2 satellites. (The first global map from this tandem mission is available at PIA11859.) In January 2009, Jason-1 was maneuvered into orbit on the opposite side of Earth from its successor, OSTM/Jason-2 satellite. It takes 10 days for the satellites to cover the globe and return to any one place over the ocean. So, in this new tandem configuration, Jason-1 flies over the same region of the ocean that OSTM/Jason-2 flew over five days earlier. Its ground tracks fall mid-way between those of Jason-2, which are about 315 kilometers (195 miles) apart at the equator. Working together, the two spacecraft measure the surface topography of the ocean twice as often as would be possible with one satellite, and over a 10-day period, they return twice the amount of detailed measurements. Combining data from the two satellites makes it possible to map smaller, more rapidly changing features than one satellite could alone. These images show sea-level anomaly data from the first 14 days of the interleaved orbit of Jason-1 and OSTM/Jason-2, the period beginning on Feb. 20, 2009. An anomaly is a departure from a value averaged over a long period of time. Red and yellow are regions where sea levels are higher than normal. Purple and dark blue show where sea levels are lower. A higher-than-normal sea surface is usually a sign of warm waters below, while lower sea levels indicate cooler than normal temperatures. http://photojournal.jpl.nasa.gov/catalog/PIA11997

Temporal and spatial variability in North Carolina piedmont stream temperature

Treesearch

J.L. Boggs; G. Sun; S.G. McNulty; W. Swartley; Treasure E.; W. Summer

2009-01-01

Understanding temporal and spatial patterns of in-stream temperature can provide useful information to managing future impacts of climate change on these systems. This study will compare temporal patterns and spatial variability of headwater in-stream temperature in six catchments in the piedmont of North Carolina in two different geological regions, Carolina slate...

Multivariate geomorphic analysis of forest streams: Implications for assessment of land use impacts on channel condition

Treesearch

Richard. D. Wood-Smith; John M. Buffington

1996-01-01

Multivariate statistical analyses of geomorphic variables from 23 forest stream reaches in southeast Alaska result in successful discrimination between pristine streams and those disturbed by land management, specifically timber harvesting and associated road building. Results of discriminant function analysis indicate that a three-variable model discriminates 10...

Searching for a Gulf War syndrome using cluster analysis.

PubMed

Everitt, B; Ismail, K; David, A S; Wessely, S

2002-11-01

Gulf veterans report medically unexplained symptoms more frequently than non-Gulf veterans did. We examined whether Gulf and non-Gulf veterans could be distinguished by their patterns of symptom reporting. A k-means cluster analysis was applied to 500 randomly sampled veterans from each of three United Kingdom military cohorts of veterans; those deployed to the Gulf conflict between 1990 and 1991; to the Bosnia peacekeeping mission between 1992 and 1997; and military personnel who were in active service but not deployed to the Gulf (Era). Sociodemographic, health variables and scores for ten symptom groups were calculated. The gap statistic indicated the five-group solution as one that provided a particularly informative description of the structure in the data. Cluster 1 consisted of low scores for all symptom groups. Cluster 2 had veterans with highest symptom scores for musculoskeletal symptoms and high scores for psychiatric symptoms. Cluster 3 had high scores for psychiatric symptoms and marginally elevated scores for the remaining nine groups symptom groups. Cluster 4 had elevated scores for musculoskeletal symptoms only and cluster 5 was distinguishable from the other clusters in having high scores in all symptom groups, especially psychiatric and musculoskeletal. The findings do not support the existence of a unique syndrome affecting a subgroup of Gulf veterans but emphasize the excess of non-specific self-reported ill health in this group.

Thermohaline circulation in the Gulf of California

NASA Astrophysics Data System (ADS)

Bray, N. A.

1988-05-01

The Gulf of California, a narrow, semienclosed sea, is the only evaporative basin of the Pacific Ocean. As a result of evaporative forcing, salinities in the gulf are 1 to 2 ‰ higher than in the adjacent Pacific at the same latitude. This paper examines the thermohaline structure of the gulf and the means by which thermohaline exchange between the Pacific and the gulf occurs, over time scales of months to years. In addition to evaporative forcing, air-sea heat fluxes and momentum fluxes are important to thermohaline circulation in the gulf. From observations presented here, it appears that the gulf gains heat from the atmosphere on an annual average, unlike the Mediterranean and Red seas, which have comparable evaporative forcing. As a result, outflow from the gulf tends to be less dense than inflow from the Pacific. Winds over the gulf change direction with season, blowing northward in summer and southward in winter. This same seasonal pattern appears in near-surface transports averaged across the gulf. The thermohaline circulation, then, consists of outflow mostly between about 50 m and 250 m, inflow mostly between 250 m and 500 m, and a surface layer in which the direction of transport changes with seasonal changes in the large-scale winds. Using hydrographic observations from a section across the central gulf, total transport in or out of the northern gulf is estimated to be 0.9 Sv, heat gain from the atmosphere is estimated to be 20 to 50 W m-2, and evaporation is estimated to be 0.95 m yr-1. These estimates are annual averages, based on cruises from several years. Seasonal variations in thermohaline structure in the gulf are also examined and found to dominate the variance in temperature and density in the top 500 m of the water column. Salinity has little seasonal variability but does exhibit more horizontal variablility than temperature or density. Major year-to-year variations in thermohaline structure may be attributable to El Niño-Southern Oscillation events.

Classification of California streams using combined deductive and inductive approaches: Setting the foundation for analysis of hydrologic alteration

USGS Publications Warehouse

Pyne, Matthew I.; Carlisle, Daren M.; Konrad, Christopher P.; Stein, Eric D.

2017-01-01

Regional classification of streams is an early step in the Ecological Limits of Hydrologic Alteration framework. Many stream classifications are based on an inductive approach using hydrologic data from minimally disturbed basins, but this approach may underrepresent streams from heavily disturbed basins or sparsely gaged arid regions. An alternative is a deductive approach, using watershed climate, land use, and geomorphology to classify streams, but this approach may miss important hydrological characteristics of streams. We classified all stream reaches in California using both approaches. First, we used Bayesian and hierarchical clustering to classify reaches according to watershed characteristics. Streams were clustered into seven classes according to elevation, sedimentary rock, and winter precipitation. Permutation-based analysis of variance and random forest analyses were used to determine which hydrologic variables best separate streams into their respective classes. Stream typology (i.e., the class that a stream reach is assigned to) is shaped mainly by patterns of high and mean flow behavior within the stream's landscape context. Additionally, random forest was used to determine which hydrologic variables best separate minimally disturbed reference streams from non-reference streams in each of the seven classes. In contrast to stream typology, deviation from reference conditions is more difficult to detect and is largely defined by changes in low-flow variables, average daily flow, and duration of flow. Our combined deductive/inductive approach allows us to estimate flow under minimally disturbed conditions based on the deductive analysis and compare to measured flow based on the inductive analysis in order to estimate hydrologic change.

KSC-07pd3546

NASA Image and Video Library

2007-12-03

KENNEDY SPACE CENTER, FLA. -- STS-122 Pilot Alan Poindexter seems satisfied with the landing practice session he has just completed aboard a shuttle training aircraft, or STA, at Kennedy Space Center's Shuttle Landing Facility. Poindexter and Commander Steve Frick are preparing for the Dec. 6 launch on space shuttle Atlantis. The STA is a Grumman American Aviation-built Gulf Stream II jet that was modified to simulate an orbiter's cockpit, motion and visual cues, and handling qualities. Photo credit: NASA/Kim Shiflett

KSC-07pd3545

NASA Image and Video Library

2007-12-03

KENNEDY SPACE CENTER, FLA. -- STS-122 Commander Steve Frick seems satisfied with the landing practice session he has just completed aboard a shuttle training aircraft, or STA, at Kennedy Space Center's Shuttle Landing Facility. Frick and Pilot Alan Poindexter are preparing for the Dec. 6 launch on space shuttle Atlantis. The STA is a Grumman American Aviation-built Gulf Stream II jet that was modified to simulate an orbiter's cockpit, motion and visual cues, and handling qualities. Photo credit: NASA/Kim Shiflett

Data requirements in support of the marine weather service program

NASA Technical Reports Server (NTRS)

Travers, J.; Mccaslin, R. W.; Mull, M.

1972-01-01

Data support activities for the Marine Weather Service Program are outlined. Forecasts, cover anomolous water levels, including sea and swell, surface and breakers, and storm surge. Advisories are also provided for sea ice on the Great Lake and Cook inlet in winter, and in the Bering, Chukchi, and Beaufort Seas in summer. Attempts were made to deal with ocean currents in the Gulf Stream, areas of upwelling, and thermal structure at least down through the mixed layer.

Into the Second Century: Memphis Engineer District, 1976-1981

DTIC Science & Technology

1983-01-01

stream out of Lake Itasca in central Minnesota, the river begins a 2,340-mile journey to the Gulf of Mexico. In making the long journey, the river...McKellar Lake in honor of the senior Senator from Tennessee, Kenneth D. McKellar. Part of Tennessee Chute was dredged and then used as a slack...Missouri; and the Reelfoot -Obion areas in west Tennessee to monitor flood control structures. Under Phase I operations the Memphis District provided

Eddy Effects in the General Circulation, Spanning Mean Currents, Mesoscale Eddies, and Topographic Generation, Including Submesoscale Nests

DTIC Science & Technology

2013-09-30

bottom form stress (pressure force) and bottom boundary layers – all the aspects associated with turbulent flows over steep topography in the presence of...filaments, and eddies; topographic current separation, form stress , and submesoscale vortex generation; Our work on isoneutral diffusion for tracers...Bump region, are due to the contribution of the bottom stress curl. Fig. 4 shows how the Gulf Stream path is directly linked to the Bottom Pressure

Elemental variability in the coralline alga Lithophyllum yemenense as an archive of past climate in the Gulf of Aden (NW Indian Ocean).

PubMed

Caragnano, Annalisa; Basso, Daniela; Storz, David; Jacob, Dorrit E; Ragazzola, Federica; Benzoni, Francesca; Dutrieux, Eric

2017-04-01

This study presents the first algal thallus (skeleton) archive of Asian monsoon strength and Red Sea influence in the Gulf of Aden. Mg/Ca, Li/Ca, and Ba/Ca were measured in Lithophyllum yemenense from Balhaf (Gulf of Aden) using laser ablation inductively coupled plasma mass spectrometry, and Mg/Ca ratio oscillation was used to reconstruct the chronology (34 y). Oscillations of element rates corresponding to the algal growth between 1974 and 2008 were compared with recorded climate and oceanographic variability. During this period, sea surface temperatures (SST) in Balhaf recorded a warming trend of 0.55°C, corresponding to an increase in Mg and Li content in the algal thallus of 2.1 mol-% and 1.87 μmol-%, respectively. Lithophyllum yemenense recorded decadal SST variability by Li/Ca, and the influence of the Pacific El-Niño Southern Oscillation on the NW Indian Ocean climate system by Ba/Ca. Additionally, algal Mg/Ca, Li/Ca, and Ba/Ca showed strong and significant correlations with All Indian Rainfall in the decadal range indicating that these proxies can be useful for tracking variability in the Indian monsoon system, possibly due to changes of the surface wind system, with deep water upwelling in summer, and a distinct seasonality. © 2017 Phycological Society of America.

Deep-Sea Submarine 'Ben Franklin'

NASA Technical Reports Server (NTRS)

1969-01-01

The deep-sea submarine 'Ben Franklin' is being docked in the harbor. Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life. It also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effect of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Interior View of the Deep-Sea Research Submarine 'Ben Franklin'

NASA Technical Reports Server (NTRS)

1969-01-01

This is an interior view of the living quarters of the deep-sea research submarine 'Ben Franklin.' Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep- ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effect of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Deep-Sea Research Submarine 'Ben Franklin'

NASA Technical Reports Server (NTRS)

1969-01-01

This is an aerial view of the deep-sea research submarine 'Ben Franklin' at dock. Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Skylab

NASA Image and Video Library

1969-07-01

This is an aerial view of the deep-sea research submarine "Ben Franklin" at dock. Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Skylab

NASA Image and Video Library

1969-07-01

In this photograph, the deep-sea Research Submarine "Ben Franklin" drifts off the East Coast of the United States (U.S.) prior to submerging into the ocean. Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Skylab

NASA Image and Video Library

1969-07-01

This is an interior view of the living quarters of the deep-sea research submarine "Ben Franklin." Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep- ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effect of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (South Atlantic): Bluefish

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

Oliver, J.D.; Van Den Avyle, M.J.; Bozeman, E.L. Jr.

1989-04-01

Species profiles are literature summaries of the life history, distribution, and environmental requirements of coastal fishes and invertebrates. Profiles are prepared to assist with environmental impact assessment. The bluefish (Pomatomus saltatrix) is a valuable recreational and commercial fish on the Atlantic coast. In the South Atlantic Region the recreational catch exceeds the commercial catch. The bluefish is a migratory pelagic fish that generally travels northward in spring and summer and southward in fall and winter along the Atlantic seaboard. In the South Atlantic Region, spawning occurs primarily during spring waters just shoreward of the Gulf Stream form southern North Carolinamore » to Florida. Most larvae are carried northward by the Gulf Stream and are dispersed over the continental slope of the Middle Atlantic Region. Adult bluefish inhabit nearshore areas in the South Atlantic Region during their southerly migration in fall and winter. Larval bluefish eat mostly copepods, cladocerans, and invertebrate eggs; juveniles eat larger invertebrates and fishes. Adult bluefish eat fishes and seem to prefer schooling coastal species. Bluefish have been reported to avoid areas of low dissolved oxygen. Water turbidity may affect feeding because bluefish rely on vision to locate prey. Environmental disturbances which affect the dissolved oxygen concentration or turbidity of estuarine and nearshore waters may, therefore, affect bluefish distribution and feeding. 40 refs., 4 figs., 2 tabs.« less

Ocean backscatter across the Gulf Stream sea surface temperature front

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

Nghiem, S.V.; Li, F.K.

1997-06-01

Ocean backscatter was measured by the Jet Propulsion Laboratory, with the airborne NUSCAT K{sub u}-band scatterometer, across the Gulf Stream sea surface temperature front during the Surface Wave Dynamics Experiment off the coast of Virginia and Maryland in the winter of 1991. Backscatter across the front between the National Oceanic and Atmospheric Administration experimental coastal buoy A (44024) on the cold side and Discus C buoy (44023) on the warm side shows a difference of more than 5 dB for vertical polarization in many cases. This large frontal backscatter change is observed in all upwind, downwind, and crosswind directions. Themore » sea surface temperature difference measured by the buoys was about 9{degrees}C. The corresponding difference in wind speed cannot account for the large backscatter change in view of geophysical model functions depending only on neutral wind velocity such as SASS. The measured backscatter also has larger upwind-downwind and upwind-crosswind ratios compared to the model results. Furthermore, NUSCAT data reveal that upwind backscatter on the cold side was smaller than or close to crosswind backscatter on the warm side for incidence angles between 30{degrees} to 50{degrees}. This suggests that the temperature front can be detected by the scatterometer at these incidence angles for different wind directions in the cold and warm sides.« less

Fluorescence of dissolved organic matter: A comparison of north Pacific and north Atlantic Oceans during April 1991

NASA Technical Reports Server (NTRS)

Hoge, Frank E.; Swift, Robert N.; Yungel, James K.; Vodacek, Anthony

1993-01-01

Profiles of airborne-laser-induced fluorescence emission from dissolved organic matter in the upper ocean have been produced and compared for the Southern California Bight (SCB) and the Mid-Atlantic Bight (MAB). Findings were as follows. (1) The fluorescent components of dissolved organic matter (FDOM) are present in easily measurable quantities from near shore to well over 300 km offshore in the SCB and are likewise easily measurable in the coastal, shelf, slope, and Gulf Stream waters of the MAB. (2) The reange of FDOM in the MAB is considerably greater than that in the SCB. (3) The lowest FDOM levels observed in the SCB were higher than those found in the Gulf Stream. (4) The onshore-to-offshore spatial gradient of the FDOM was found to be considerably lower in the SCB than in the MAB, with the highest levels of FDOM being found immediately adjacent to the coast in the MAB. This suggests that the water adjacent to the SCB shoreline is not as strongly influenced by terrestrial and estuarine sources of FDOM as the MAB is. (5) The spatial distribution of the FDOM within both the SCB and the MAB is frequently coherent with the spatial distribution of chlorophyll determined form the concurrent airborne- laser- induced phytoplankton pigment fluorescence measurements. However, distinct noncoherency is sometimes observed, especially at water mass boundaries.

Impact of the Extreme Warming of 2012 on Shelfbreak Frontal Structure North of Cape Hatteras

NASA Astrophysics Data System (ADS)

Gawarkiewickz, G.

2014-12-01

Continental shelf circulation north of Cape Hatteras is complex, with southward flowing Middle Atlantic Bight shelf water intersecting the Gulf Stream and subducting offshore into the Gulf Stream. In May, 2012, a cruise was conducted in order to study the shelf circulation and acoustic propagation through fish schools in the area. An important aspect of the study was to use Autonomous Underwater Vehicles to map fish schools with a sidescan sonar. High-resolution hydrographic surveys to map the continental shelf water masses and shelfbreak frontal structure were sampled to relate oceanographic conditions to the fish school distributions. The cold pool water mass over the continental shelf in May 2012 was extremely warm, with temperature anomalies of up to 5 Degrees C relative to observations from the same area in May, 1996. The normal cross-shelf temperature gradients within the shelfbreak front were not present because of the warming. As a result, the shelf density field was much more buoyant than usual, which led to an accelerated shelfbreak jet. Moored velocity measurements at the 60 m isobath recorded alongshelf flow of as much as 0.6 m/s. The anticipated fish species were not observed over the continental shelf. Some comments on the forcing leading to the large scale warming will be presented, along with a brief discussion of the impact of the warming on the marine ecosystem in the northeast U.S.

"Submesoscale Soup" Vorticity and Tracer Statistics During the Lateral Mixing Experiment

NASA Astrophysics Data System (ADS)

Shcherbina, A.; D'Asaro, E. A.; Lee, C. M.; Molemaker, J.; McWilliams, J. C.

2012-12-01

A detailed view of upper-ocean velocity, vorticity, and tracer statistics was obtained by a unique synchronized two-vessel survey in the North Atlantic in winter 2012. In winter, North Atlantic Mode water region south of the Gulf Stream is filled with an energetic, homogeneous, and well-developed submesoscale turbulence field - the "submesoscale soup". Turbulence in the soup is produced by frontogenesis and the surface layer instability of mesoscale eddy flows in the vicinity of the Gulf Stream. This region is a convenient representation of the inertial range of the geophysical turbulence forward cascade spanning scales of o(1-100km). During the Lateral Mixing Experiment in February-March 2012, R/Vs Atlantis and Knorr were run on parallel tracks 1 km apart for 500 km in the submesoscale soup region. Synchronous ADCP sampling provided the first in-situ estimates of full 3-D vorticity and divergence without the usual mix of spatial and temporal aliasing. Tracer distributions were also simultaneously sampled by both vessels using the underway and towed instrumentation. Observed vorticity distribution in the mixed layer was markedly asymmetric, with sparse strands of strong anticyclonic vorticity embedded in a weak, predominantly cyclonic background. While the mean vorticity was close to zero, distribution skewness exceeded 2. These observations confirm theoretical and numerical model predictions for an active submesoscale turbulence field. Submesoscale vorticity spectra also agreed well with the model prediction.

A comparison of the structure, properties, and water mass composition of quasi-isotropic eddies in western boundary currents in an eddy-resolving ocean model

NASA Astrophysics Data System (ADS)

Rykova, Tatiana; Oke, Peter R.; Griffin, David A.

2017-06-01

Using output from a near-global eddy-resolving ocean model, we analyse the properties and characteristics of quasi-isotropic eddies in five Western Boundary Current (WBC) regions, including the extensions of the Agulhas, East Australian Current (EAC), Brazil-Malvinas Confluence (BMC), Kuroshio and Gulf Stream regions. We assess the model eddies by comparing to satellite and in situ observations, and show that most aspects of the model's representation of eddies are realistic. We find that the mean eddies differ dramatically between these WBC regions - all with some unique and noteworthy characteristics. We find that the vertical displacement of isopycnals of Agulhas eddies is the greatest, averaging 350-450 m at depths of over 800-900 m. EAC (BMC) eddies are the least (most) barotropic, with only 50% (85-90%) of the velocity associated with the barotropic mode. Kuroshio eddies are the most stratified, resulting in small isopycnal displacement, even for strong eddies; and Gulf Stream eddies carry the most heat. Despite their differences, we explicitly show that the source waters for anticyclonic eddies are a mix of the WBC water (from the boundary current itself) and water that originates equatorward of the WBC eddy-field; and cyclonic eddies are a mix of WBC water and water that originates poleward of the WBC eddy-field.

Wernher von Braun

NASA Image and Video Library

1969-07-01

This photograph depicts Dr. von Braun (at right, showing his back) and other NASA officials surveying the deep-sea research submarine "Ben Franklin." Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Wernher von Braun

NASA Image and Video Library

1969-07-01

This photograph depicts Dr. von Braun (fourth from far right) and other NASA officials surveying the deep-sea research submarine "Ben Franklin." Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Data assimilation and model evaluation experiment datasets

NASA Technical Reports Server (NTRS)

Lai, Chung-Cheng A.; Qian, Wen; Glenn, Scott M.

1994-01-01

The Institute for Naval Oceanography, in cooperation with Naval Research Laboratories and universities, executed the Data Assimilation and Model Evaluation Experiment (DAMEE) for the Gulf Stream region during fiscal years 1991-1993. Enormous effort has gone into the preparation of several high-quality and consistent datasets for model initialization and verification. This paper describes the preparation process, the temporal and spatial scopes, the contents, the structure, etc., of these datasets. The goal of DAMEE and the need of data for the four phases of experiment are briefly stated. The preparation of DAMEE datasets consisted of a series of processes: (1) collection of observational data; (2) analysis and interpretation; (3) interpolation using the Optimum Thermal Interpolation System package; (4) quality control and re-analysis; and (5) data archiving and software documentation. The data products from these processes included a time series of 3D fields of temperature and salinity, 2D fields of surface dynamic height and mixed-layer depth, analysis of the Gulf Stream and rings system, and bathythermograph profiles. To date, these are the most detailed and high-quality data for mesoscale ocean modeling, data assimilation, and forecasting research. Feedback from ocean modeling groups who tested this data was incorporated into its refinement. Suggestions for DAMEE data usages include (1) ocean modeling and data assimilation studies, (2) diagnosis and theoretical studies, and (3) comparisons with locally detailed observations.

Multistressor predictive models of invertebrate condition in the Corn Belt, USA

USGS Publications Warehouse

Waite, Ian R.; Van Metre, Peter C.

2017-01-01

Understanding the complex relations between multiple environmental stressors and ecological conditions in streams can help guide resource-management decisions. During 14 weeks in spring/summer 2013, personnel from the US Geological Survey and the US Environmental Protection Agency sampled 98 wadeable streams across the Midwest Corn Belt region of the USA for water and sediment quality, physical and habitat characteristics, and ecological communities. We used these data to develop independent predictive disturbance models for 3 macroinvertebrate metrics and a multimetric index. We developed the models based on boosted regression trees (BRT) for 3 stressor categories, land use/land cover (geographic information system [GIS]), all in-stream stressors combined (nutrients, habitat, and contaminants), and for GIS plus in-stream stressors. The GIS plus in-stream stressor models had the best overall performance with an average cross-validation R2 across all models of 0.41. The models were generally consistent in the explanatory variables selected within each stressor group across the 4 invertebrate metrics modeled. Variables related to riparian condition, substrate size or embeddedness, velocity and channel shape, nutrients (primarily NH3), and contaminants (pyrethroid degradates) were important descriptors of the invertebrate metrics. Models based on all measured in-stream stressors performed comparably to models based on GIS landscape variables, suggesting that the in-stream stressor characterization reasonably represents the dominant factors affecting invertebrate communities and that GIS variables are acting as surrogates for in-stream stressors that directly affect in-stream biota.

Occurrence and load of selected herbicides and metabolites in the lower Mississippi River

USGS Publications Warehouse

Clark, G.M.; Goolsby, D.A.

2000-01-01

Analyses of water samples collected from the Mississippi River at Baton Rouge, Louisiana, during 1991-1997 indicate that hundreds of metric tons of herbicides and herbicide metabolites are being discharged annually to the Gulf of Mexico. Atrazine, metolachlor, and the ethane-sulfonic acid metabolite of alachlor (alachlor ESA) were the most frequently detected herbicides and, in general, were present in the largest concentrations. Almost 80% of the annual herbicide load to the Gulf of Mexico occurred during the growing season from May to August. The concentrations and loads of alachlor in the Mississippi River decreased dramatically after 1993 in response to decreased use in the basin. In contrast, the concentrations and loads of acetochlor increased after 1994, reflecting its role as a replacement for alachlor. The peak annual herbicide load occurred in 1993, when approximately 640 metric tons (t) of atrazine, 320 t of cyanazine, 215 t of metolachlor, 53 t of simazine, and 50 t of alachlor were discharged to the Gulf of Mexico. The annual loads of atrazine and cyanazine were generally 1-2% of the amount annually applied in the Mississippi River drainage basin; the annual loads of acetochlor, alachlor, and metolachlor were generally less than 1%. Despite a reduction in atrazine use, historical data do not indicate a long-term downward trend in the atrazine load to the Gulf of Mexico. Although a relation (r2=0.62) exists between the atrazine load and stream discharge during May to August, variations in herbicide use and rainfall patterns within subbasins can have a large effect on herbicide loads in the Mississippi River Basin and probably explain a large part of the annual variation in atrazine load to the Gulf of Mexico. Copyright (C) 2000 Elsevier Science B.V.

Occurrence and load of selected herbicides and metabolites in the lower Mississippi River

USGS Publications Warehouse

Clark, Gregory M.; Goolsby, Donald A.

2000-01-01

Analyses of water samples collected from the Mississippi River at Baton Rouge, Louisiana, during 1991–1997 indicate that hundreds of metric tons of herbicides and herbicide metabolites are being discharged annually to the Gulf of Mexico. Atrazine, metolachlor, and the ethane-sulfonic acid metabolite of alachlor (alachlor ESA) were the most frequently detected herbicides and, in general, were present in the largest concentrations. Almost 80% of the annual herbicide load to the Gulf of Mexico occurred during the growing season from May to August. The concentrations and loads of alachlor in the Mississippi River decreased dramatically after 1993 in response to decreased use in the basin. In contrast, the concentrations and loads of acetochlor increased after 1994, reflecting its role as a replacement for alachlor. The peak annual herbicide load occurred in 1993, when approximately 640 metric tons (t) of atrazine, 320 t of cyanazine, 215 t of metolachlor, 53 t of simazine, and 50 t of alachlor were discharged to the Gulf of Mexico. The annual loads of atrazine and cyanazine were generally 1–2% of the amount annually applied in the Mississippi River drainage basin; the annual loads of acetochlor, alachlor, and metolachlor were generally less than 1%. Despite a reduction in atrazine use, historical data do not indicate a long-term downward trend in the atrazine load to the Gulf of Mexico. Although a relation (r2=0.62) exists between the atrazine load and stream discharge during May to August, variations in herbicide use and rainfall patterns within subbasins can have a large effect on herbicide loads in the Mississippi River Basin and probably explain a large part of the annual variation in atrazine load to the Gulf of Mexico.

Spatial heterogeneity of within-stream methane concentrations

USGS Publications Warehouse

Crawford, John T.; Loken, Luke C.; West, William E.; Crary, Benjamin; Spawn, Seth A.; Gubbins, Nicholas; Jones, Stuart E.; Striegl, Robert G.; Stanley, Emily H.

2017-01-01

Streams, rivers, and other freshwater features may be significant sources of CH4 to the atmosphere. However, high spatial and temporal variabilities hinder our ability to understand the underlying processes of CH4 production and delivery to streams and also challenge the use of scaling approaches across large areas. We studied a stream having high geomorphic variability to assess the underlying scale of CH4 spatial variability and to examine whether the physical structure of a stream can explain the variation in surface CH4. A combination of high-resolution CH4 mapping, a survey of groundwater CH4 concentrations, quantitative analysis of methanogen DNA, and sediment CH4 production potentials illustrates the spatial and geomorphic controls on CH4 emissions to the atmosphere. We observed significant spatial clustering with high CH4 concentrations in organic-rich stream reaches and lake transitions. These sites were also enriched in the methane-producing mcrA gene and had highest CH4 production rates in the laboratory. In contrast, mineral-rich reaches had significantly lower concentrations and had lesser abundances of mcrA. Strong relationships between CH4and the physical structure of this aquatic system, along with high spatial variability, suggest that future investigations will benefit from viewing streams as landscapes, as opposed to ecosystems simply embedded in larger terrestrial mosaics. In light of such high spatial variability, we recommend that future workers evaluate stream networks first by using similar spatial tools in order to build effective sampling programs.

Status and reproduction of Gulf coast strain walleye in a Tombigbee River tributary

USGS Publications Warehouse

Schramm, H.L.; Hart, J.; Hanson, L.A.

2004-01-01

Walleye (Sander vitreus [Mitchill]) are native to rivers and streams in the Mobile River basin in Mississippi and Alabama. These populations comprise a genetically unique strain (Gulf coast walleye, GCW) and represent the southernmost distribution of walleye in the United States. Luxapallila Creek was considered an important spawning site for GCW prior to and shortly after impoundment of the Tombigbee River in 1980. Extensive sampling in Luxapallila Creek in 2001 and 2002 collected only one larval walleye. Microsatellite DNA analysis suggested 14 of 16 adult walleye from Luxapallila Creek were hatchery-produced fish or their progeny. Controlled angling catch rates of adult walleye have declined since 1997. The scarcity of wild-spawned walleye and the similarity of wild-caught and hatchery broodstock walleye indicates that the GCW population in, or spawning in, Luxapallila Creek is sustained by stocking and recruitment from these stocked fish may be diminishing.

Ecoregions and stream morphology in eastern Oklahoma

USGS Publications Warehouse

Splinter, D.K.; Dauwalter, D.C.; Marston, R.A.; Fisher, W.L.

2010-01-01

Broad-scale variables (i.e., geology, topography, climate, land use, vegetation, and soils) influence channel morphology. How and to what extent the longitudinal pattern of channel morphology is influenced by broad-scale variables is important to fluvial geomorphologists and stream ecologists. In the last couple of decades, there has been an increase in the amount of interdisciplinary research between fluvial geomorphologists and stream ecologists. In a historical context, fluvial geomorphologists are more apt to use physiographic regions to distinguish broad-scale variables, while stream ecologists are more apt to use the concept of an ecosystem to address the broad-scale variables that influence stream habitat. For this reason, we designed a study using ecoregions, which uses physical and biological variables to understand how landscapes influence channel processes. Ecoregions are delineated by similarities in geology, climate, soils, land use, and potential natural vegetation. In the fluvial system, stream form and function are dictated by processes observed throughout the fluvial hierarchy. Recognizing that stream form and function should differ by ecoregion, a study was designed to evaluate how the characteristics of stream channels differed longitudinally among three ecoregions in eastern Oklahoma, USA: Boston Mountains, Ozark Highlands, and Ouachita Mountains. Channel morphology of 149 stream reaches was surveyed in 1st- through 4th-order streams, and effects of drainage area and ecoregion on channel morphology was evaluated using multiple regressions. Differences existed (?????0.05) among ecoregions for particle size, bankfull width, and width/depth ratio. No differences existed among ecoregions for gradient or sinuosity. Particle size was smallest in the Ozark Highlands and largest in the Ouachita Mountains. Bankfull width was larger in the Ozark Highlands than in the Boston Mountains and Ouachita Mountains in larger streams. Width/depth ratios of the Boston Mountains and Ozark Highlands were not statistically different. Significant differences existed, however, between the Boston Mountains and Ozark Highlands when compared individually to the Ouachita Mountains. We found that ecoregions afforded a good spatial structure that can help in understanding longitudinal trends in stream reach morphology surveyed at the reach scale. The hierarchy of the fluvial system begins within a broad, relatively homogenous setting that imparts control on processes that affect stream function. Ecoregions provide an adequate regional division to begin a large-scale geomorphic study of processes in stream channels. ?? 2010 Elsevier B.V.

Seasonal Overturning Circulation in the Red Sea

NASA Astrophysics Data System (ADS)

Yao, F.; Hoteit, I.; Koehl, A.

2010-12-01

The Red Sea exhibits a distinct seasonal overturning circulation. In winter, a typical two-layer exchange structure, with a fresher inflow from the Gulf of Aden on top of an outflow from the Red Sea, is established. In summer months (June to September) this circulation pattern is changed to a three-layer structure: a surface outflow from the Red Sea on top of a subsurface intrusion of the Gulf of Aden Intermediate Water and a weakened deep outflow. This seasonal variability is studied using a general circulation model, MITgcm, with 6 hourly NCEP atmospheric forcing. The model is able to reproduce the observed seasonal variability very well. The forcing mechanisms of the seasonal variability related to seasonal surface wind stress and buoyancy flux, and water mass transformation processes associated with the seasonal overturning circulation are analyzed and presented.

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

The Low-Level Flow Along the Gulf of California During the North American Monsoon.

NASA Astrophysics Data System (ADS)

Bordoni, S.; Stevens, B.

2007-05-01

Six-years (1999-2004) of QuikSCAT near-surface ocean winds are used to study the flow over the northeast Pacific and the Gulf of California (GoC) during the North American Monsoon season. The wind data show that the onset of the summer season is accompanied by a reversal of the flow along the GoC, with the establishment of a mean southerly wind throughout the gulf. This reversal occurs in late spring and precedes the onset of the monsoonal rains. In the heart of the monsoon season, the time-mean flow is found to be composed of periods of enhanced southerly winds associated with gulf surges. The role that gulf surges play in modulating the GoC mean southerly flow is further explored by performing an EOF analysis of the summertime daily wind anomalies. A gulf surge mode emerges from this analysis as the leading EOF, with the corresponding principal component time series interpretable as an objective index for gulf surge occurrence. This index is used as a reference time series for regression analysis, to explore the relationship between gulf surges and precipitation over the core and marginal regions of the monsoon, as well as the manifestation of these transient events in the large-scale circulation. It is found that, although seemingly mesoscale features confined over the GoC, gulf surges are intimately linked to patterns of large-scale variability of the eastern Pacific ITCZ and greatly contribute to the definition of the northward extent of the monsoonal rains.

The Gulf of Mexico ecosystem, six years after the Macondo oil well blowout

NASA Astrophysics Data System (ADS)

Joye, Samantha B.; Bracco, Annalisa; Özgökmen, Tamay M.; Chanton, Jeffrey P.; Grosell, Martin; MacDonald, Ian R.; Cordes, Erik E.; Montoya, Joseph P.; Passow, Uta

2016-07-01

The Gulf of Mexico ecosystem is a hotspot for biological diversity and supports a number of industries, from tourism to fishery production to oil and gas exploration, that serve as the economic backbone of Gulf coast states. The Gulf is a natural hydrocarbon basin, rich with stores of oil and gas that lie in reservoirs deep beneath the seafloor. The natural seepage of hydrocarbons across the Gulf system is extensive and, thus, the system's biological components experience ephemeral, if not, frequent, hydrocarbon exposure. In contrast to natural seepage, which is diffuse and variable over space and time, the 2010 Macondo oil well blowout, represented an intense, focused hydrocarbon infusion to the Gulf's deepwaters. The Macondo blowout drove rapid shifts in microbial populations and activity, revealed unexpected phenomena, such as deepwater hydrocarbon plumes and marine "oil snow" sedimentation, and impacted the Gulf's pelagic and benthic ecosystems. Understanding the distribution and fate of Macondo oil was limited to some degree by an insufficient ability to predict the physical movement of water in the Gulf. In other words, the available physical oceanographic models lacked critical components. In the past six years, much has been learned about the physical oceanography of the Gulf, providing transformative knowledge that will improve the ability to predict the movement of water and the hydrocarbons they carry in future blowout scenarios. Similarly, much has been learned about the processing and fate of Macondo hydrocarbons. Here, we provide an overview of the distribution, fate and impacts of Macondo hydrocarbons and offer suggestions for future research to push the field of oil spill response research forward.

Warming of the Global Ocean: Spatial Structure and Water-Mass Trends

NASA Technical Reports Server (NTRS)

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

2016-01-01

This study investigates the multidecadal warming and interannual-to-decadal heat content changes in the upper ocean (0-700 m), focusing on vertical and horizontal patterns of variability. These results support a nearly monotonic warming over much of the World Ocean, with a shift toward Southern Hemisphere warming during the well-observed past decade. This is based on objectively analyzed gridded observational datasets and on a modeled state estimate. Besides the surface warming, a warming climate also has a subsurface effect manifesting as a strong deepening of the midthermocline isopycnals, which can be diagnosed directly from hydrographic data. This deepening appears to be a result of heat entering via subduction and spreading laterally from the high-latitude ventilation regions of subtropical mode waters. The basin-average multidecadal warming mainly expands the subtropical mode water volume, with weak changes in the temperature-salinity (u-S) relationship (known as ''spice'' variability). However, the spice contribution to the heat content can be locally large, for example in Southern Hemisphere. Multidecadal isopycnal sinking has been strongest over the southern basins and weaker elsewhere with the exception of the Gulf Stream/North Atlantic Current/subtropical recirculation gyre. At interannual to decadal time scales, wind-driven sinking and shoaling of density surfaces still dominate ocean heat content changes, while the contribution from temperature changes along density surfaces tends to decrease as time scales shorten.

A Decadal Climate Cycle in the North Atlantic Ocean as Simulated by the ECHO Coupled GCM.

NASA Astrophysics Data System (ADS)

Grötzner, A.; Latif, M.; Barnett, T. P.

1998-05-01

In this paper a decadal climate cycle in the North Atlantic that was derived from an extended-range integration with a coupled ocean-atmosphere general circulation model is described. The decadal mode shares many features with the observed decadal variability in the North Atlantic. The period of the simulated oscillation, however, is somewhat longer than that estimated from observations. While the observations indicate a period of about 12 yr, the coupled model simulation yields a period of about 17 yr. The cyclic nature of the decadal variability implies some inherent predictability at these timescales.The decadal mode is based on unstable air-sea interactions and must be therefore regarded as an inherently coupled mode. It involves the subtropical gyre and the North Atlantic oscillation. The memory of the coupled system, however, resides in the ocean and is related to horizontal advection and to the oceanic adjustment to low-frequency wind stress curl variations. In particular, it is found that variations in the intensity of the Gulf Stream and its extension are crucial to the oscillation. Although differing in details, the North Atlantic decadal mode and the North Pacific mode described by M. Latif and T. P. Barnett are based on the same fundamental mechanism: a feedback loop between the wind driven subtropical gyre and the extratropical atmospheric circulation.

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

NASA Astrophysics Data System (ADS)

Galperin, Boris; Mellor, George L.

1990-09-01

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

Small stream ecosystem variability in the Sierra Nevada of California

Treesearch

C.T. Hunsaker; S.M. Eagan

2003-01-01

The quality of aquatic and riparian ecosystems is a function of their condition and the integrity of adjacent uplands in their watersheds. While small streams make up a large proportion of the overall stream network, our knowledge of how they function is still limited. The Kings River Experimental Watershed (KREW) was initiated in 2000 to quantify the variability in...

The relative influence of nutrients and habitat on stream metabolism in agricultural streams

USGS Publications Warehouse

Frankforter, J.D.; Weyers, H.S.; Bales, J.D.; Moran, P.W.; Calhoun, D.L.

2010-01-01

Stream metabolism was measured in 33 streams across a gradient of nutrient concentrations in four agricultural areas of the USA to determine the relative influence of nutrient concentrations and habitat on primary production (GPP) and respiration (CR-24). In conjunction with the stream metabolism estimates, water quality and algal biomass samples were collected, as was an assessment of habitat in the sampling reach. When data for all study areas were combined, there were no statistically significant relations between gross primary production or community respiration and any of the independent variables. However, significant regression models were developed for three study areas for GPP (r 2 = 0.79-0.91) and CR-24 (r 2 = 0.76-0.77). Various forms of nutrients (total phosphorus and area-weighted total nitrogen loading) were significant for predicting GPP in two study areas, with habitat variables important in seven significant models. Important physical variables included light availability, precipitation, basin area, and in-stream habitat cover. Both benthic and seston chlorophyll were not found to be important explanatory variables in any of the models; however, benthic ash-free dry weight was important in two models for GPP. ?? 2009 The Author(s).

Understanding the Patterns and Causes of Variability in Distribution, Habitat Use, Abundance, Survival and Reproductive Rates of Three Species of Cetacean in the Alboran Sea, Western Mediterranean

DTIC Science & Technology

2014-09-30

Almeria to Granada ; and the third one would cover the area of the Gulf of Vera with some incursion down in Almeria. The last two groups seem to have... Granada and Gulf of Vera, and no recaptures between those and the Strait of Gibraltar), and on the other hand from satellite tagging of several pilot

The summer North Atlantic Oscillation (SNAO) variability on decadal to paleoclimate time scales

NASA Astrophysics Data System (ADS)

Linderholm, H. W.; Folland, C. K.; Zhang, P.; Gunnarson, B. E.; Jeong, J. H.; Ren, H.

2017-12-01

The summer North Atlantic Oscillation (SNAO), strongly related to the latitude of the North Atlantic and European summer storm tracks, exerts a considerable influence on European summer climate variability and extremes. Here we extend the period covered by the SNAO from July and August to June, July and August (JJA). As well as marked interannual variability, the JJA SNAO has shown a large inter-decadal change since the 1970s. Decadally averaged, there has been a change from a very positive to a rather negative SNAO phase. This change in SNAO phase is opposite in sign from that expected by a number of climate models under enhanced greenhouse forcing by the late twenty first century. It has led to noticeably wetter summers in North West Europe in the last decade. On interannual to multidecadal timescales, SNAO variability is linked to variations in North Atlantic sea surface temperature (SST): observations and models indicate an association between the Atlantic Multi-decadal Oscillation (AMO) where the cold (warm) phase of the AMO corresponds a positive (negative) phase of the SNAO. Observations also indicate a link with SST in the Gulf Stream region of the North Atlantic where, particularly on decadal time scales, SST warming may favour a more positive phase of the SNAO. Influences of Arctic climate change on North Atlantic and European atmospheric circulation may also exist, particularly reduced sea ice coverage, perhaps favouring the negative phase of the SNAO. A new tree-ring data based JJA SNAO reconstruction extending over the last millennium, as well as climate model output for the same period, enables us to examine the influence of North Atlantic SST and Arctic sea-ice coverage, as well as SNAO impacts on European summer climate, in a long-term, pre-industrial context.

Do Riparian Buffers Protect Stream Invertebrate Communities in South American Atlantic Forest Agricultural Areas?

PubMed

Hunt, L; Marrochi, N; Bonetto, C; Liess, M; Buss, D F; Vieira da Silva, C; Chiu, M-C; Resh, V H

2017-12-01

We investigated the influence and relative importance of insecticides and other agricultural stressors in determining variability in invertebrate communities in small streams in intensive soy-production regions of Brazil and Paraguay. In Paraguay we sampled 17 sites on tributaries of the Pirapó River in the state of Itapúa and in Brazil we sampled 18 sites on tributaries of the San Francisco River in the state of Paraná. The riparian buffer zones generally contained native Atlantic forest remnants and/or introduced tree species at various stages of growth. In Brazil the stream buffer width was negatively correlated with sediment insecticide concentrations and buffer width was found to have moderate importance in mitigating effects on some sensitive taxa such as mayflies. However, in both regions insecticides had low relative importance in explaining variability in invertebrate communities, while various habitat parameters were more important. In Brazil, the percent coverage of soft depositional sediment in streams was the most important agriculture-related explanatory variable, and the overall stream-habitat score was the most important variable in Paraguay streams. Paraguay and Brazil both have laws requiring forested riparian buffers. The ample forested riparian buffer zones typical of streams in these regions are likely to have mitigated the effects of pesticides on stream invertebrate communities. This study provides evidence that riparian buffer regulations in the Atlantic Forest region are protecting stream ecosystems from pesticides and other agricultural stressors. Further studies are needed to determine the minimum buffer widths necessary to achieve optimal protection.

Health effects in Army Gulf War veterans possibly exposed to chemical munitions destruction at Khamisiyah, Iraq: Part I. Morbidity associated with potential exposure.

PubMed

Mahan, Clare M; Page, William F; Bullman, Tim A; Kang, Han K

2005-11-01

In March 1991, U.S. troops detonated the Khamisiyah, Iraq, ammunition depot, possibly releasing two chemical warfare agents, sarin and cyclosarin. The long-term health effects associated with possible exposure to these chemical warfare agents are unknown. This study was undertaken to investigate whether possible exposure was associated with morbidity among Army Gulf War veterans using morbidity data for 5,555 Army veterans who were deployed to the Gulf region. Responses to 86 self-assessed health measures, as reported in the 1995 Department of Veterans Affairs National Health Survey of Gulf War Era Veterans, were evaluated. We found little association between potential exposure and health, after adjustment for demographic variables, and conclude that potential exposure to sarin or cyclosarin at Khamisiyah does not seem to have adversely affected self-perceived health status, as evidenced by a wide range of health measures.

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

DTIC Science & Technology

1993-04-01

beamwidth of 2 degrees . Hie had interesting data wideband backscatter in the 2-50 kHz band and on profiles, including hydrothermal plumes ob- forward...civil aviation. Academician P. Naza- gravity in casting Al-Pb alloys. This process renko is rector of the institut’. and Professor N . produces a...pro- east -west sections across 36’ N from Gibraltar to grams such as WOCE (World Ocean Circulation Bermuda and northwest across the Gulf Stream

Cultural Resources Reconnaissance Study of the Black Warrior-Tombigbee System Corridor, Alabama. Volume 1. Archaeology.

DTIC Science & Technology

1983-01-01

hazel alder (Alnus serrulata), and lead plant (Amerpha fruticasa) often gain dominance on low stream banks. A great variety of woody vines groww in...Early Archaic ecosystems for the Midwest may be highly signifi- cant. From 8000 to about 5000 B.P. in southwest Alabama mobile groups apparently...n-48) of the Gulf Formational or Early Woodland sites within the BWT project area. Middle to Late Woodi -nd Site Locations The summary locational

SEASAT views oceans and sea ice with synthetic aperture radar

NASA Technical Reports Server (NTRS)

Fu, L. L.; Holt, B.

1982-01-01

Fifty-one SEASAT synthetic aperture radar (SAR) images of the oceans and sea ice are presented. Surface and internal waves, the Gulf Stream system and its rings and eddies, the eastern North Pacific, coastal phenomena, bathymetric features, atmospheric phenomena, and ship wakes are represented. Images of arctic pack and shore-fast ice are presented. The characteristics of the SEASAT SAR system and its image are described. Maps showing the area covered, and tables of key orbital information, and listing digitally processed images are provided.

Sediment microbial activity and its relation to environmental variables along the eastern Gulf of Finland coastline

NASA Astrophysics Data System (ADS)

Polyak, Yulia; Shigaeva, Tatyana; Gubelit, Yulia; Bakina, Ludmila; Kudryavtseva, Valentina; Polyak, Mark

2017-07-01

Sediment microbial activity and its relationship with the main environmental factors and pollutants were examined in the coastal area of the eastern Gulf of Finland, Baltic Sea. The activity of two common oxidoreductase enzymes: dehydrogenase (DA) and catalase (CA) varied significantly between 13 study sites. In the Neva Bay the highest microbial activities (DA: 2.64 mg TFF (10 g- 1) day- 1, CA: 6.29 mg H2O2 g- 1) were recorded, while in the outer estuary the minimum values of dehydrogenase and catalase were measured. DA, CA, and abundances of culturable heterotrophic bacteria (CHB) were positively correlated with each other, while biomass of green opportunistic algae was independent of both microbial activities and CHB. Enzymatic activity was found to be strongly positively correlated with sediment particle size and organic matter content, but unrelated to the other studied environmental parameters (temperature, pH, and salinity). Principal components analysis (PCA), controlling for environmental variables, supported direct effects of metal and oil contamination on sediment microbial activity. Also it had shown the similar patterns for algal biomass and metals. Our results suggest that copper and hydrocarbons are the main anthropogenic variables influencing enzyme distribution along the eastern Gulf of Finland coastline.

Variability of lotic macroinvertebrate assemblages and stream habitat characteristics across hierarchical landscape classifications.

PubMed

Mykrä, Heikki; Heino, Jani; Muotka, Timo

2004-09-01

Streams are naturally hierarchical systems, and their biota are affected by factors effective at regional to local scales. However, there have been only a few attempts to quantify variation in ecological attributes across multiple spatial scales. We examined the variation in several macroinvertebrate metrics and environmental variables at three hierarchical scales (ecoregions, drainage systems, streams) in boreal headwater streams. In nested analyses of variance, significant spatial variability was observed for most of the macroinvertebrate metrics and environmental variables examined. For most metrics, ecoregions explained more variation than did drainage systems. There was, however, much variation attributable to residuals, suggesting high among-stream variation in macroinvertebrate assemblage characteristics. Nonmetric multidimensional scaling (NMDS) and multiresponse permutation procedure (MRPP) showed that assemblage composition differed significantly among both drainage systems and ecoregions. The associated R-statistics were, however, very low, indicating wide variation among sites within the defined landscape classifications. Regional delineations explained most of the variation in stream water chemistry, ecoregions being clearly more influential than drainage systems. For physical habitat characteristics, by contrast, the among-stream component was the major source of variation. Distinct differences attributable to stream size were observed for several metrics, especially total number of taxa and abundance of algae-scraping invertebrates. Although ecoregions clearly account for a considerable amount of variation in macroinvertebrate assemblage characteristics, we suggest that a three-tiered classification system (stratification through ecoregion and habitat type, followed by assemblage prediction within these ecologically meaningful units) will be needed for effective bioassessment of boreal running waters.

Acoustic and aerodynamic performance investigation of inverted velocity profile coannular plug nozzles. [variable cycle engines

NASA Technical Reports Server (NTRS)

Knott, P. R.; Blozy, J. T.; Staid, P. S.

1981-01-01

The results of model scale parametric static and wind tunnel aerodynamic performance tests on unsuppressed coannular plug nozzle configurations with inverted velocity profile are discussed. The nozzle configurations are high-radius-ratio coannular plug nozzles applicable to dual-stream exhaust systems typical of a variable cycle engine for Advanced Supersonic Transport application. In all, seven acoustic models and eight aerodynamic performance models were tested. The nozzle geometric variables included outer stream radius ratio, inner stream to outer stream ratio, and inner stream plug shape. When compared to a conical nozzle at the same specific thrust, the results of the static acoustic tests with the coannular nozzles showed noise reductions of up to 7 PNdB. Extensive data analysis showed that the overall acoustic results can be well correlated using the mixed stream velocity and the mixed stream density. Results also showed that suppression levels are geometry and flow regulation dependent with the outer stream radius ratio, inner stream-to-outer stream velocity ratio and inner stream velocity ratio and inner stream plug shape, as the primary suppression parameters. In addition, high-radius ratio coannular plug nozzles were found to yield shock associated noise level reductions relative to a conical nozzle. The wind tunnel aerodynamic tests showed that static and simulated flight thrust coefficient at typical takeoff conditions are quite good - up to 0.98 at static conditions and 0.974 at a takeoff Mach number of 0.36. At low inner stream flow conditions significant thrust loss was observed. Using an inner stream conical plug resulted in 1% to 2% higher performance levels than nozzle geometries using a bent inner plug.

Influence of geology on arsenic concentrations in ground and surface water in central Lesvos, Greece.

PubMed

Aloupi, Maria; Angelidis, Michael O; Gavriil, Apostolos M; Koulousaris, Michael; Varnavas, Soterios P

2009-04-01

The occurrence of As was studied in groundwater used for human consumption and irrigation, in stream water and sediments and in water from thermal springs in the drainage basin of Kalloni Gulf, island of Lesvos, Greece, in order to investigate the potential influence of the geothermal field of Polichnitos-Lisvori on the ground and surface water systems of the area. Total dissolved As varied in the range <0.7-88.3 microg L(-1) in groundwater, 41.1-90.7 microg L(-1) in thermal spring water and 0.4-13.2 microg L(-1) in stream water, whereas As concentrations in stream sediments varied between 2.0-21.9 mg kg(-1). Four out of 31 groundwater samples exceeded the EC standard of 10 microg L(-1). The survey revealed an enrichment in both surface and groundwater hydrological systems in the northern part of the area (average concentrations of As in groundwater, stream water and stream sediment: 8.0 microg L(-1), 8.8 microg L(-1) and 15.0 mg kg(-1) respectively), in association with the volcanic bedrocks, while lower As concentrations were found in the eastern part (average concentrations in groundwater, stream water and stream sediment: 2.9 microg L(-1), 1.7 microg L(-1) and 5.9 mg kg(-1) respectively), which is dominated by ophiolitic ultramafic formations. The variation of As levels between the different parts of the study area suggests that local geology exerts a determinant influence on As geochemical behaviour. On the other hand, the geothermal activity manifested in the area of Polichnitos-Lisvori does not affect the presence of As in groundwater and streams.

Red Sea Outflow Experiment (REDSOX): Descent and initial spreading of Red Sea Water in the northwestern Indian Ocean

NASA Astrophysics Data System (ADS)

Bower, A.; Johns, W.; Peters, H.; Fratantoni, D.

2003-04-01

Two comprehensive surveys were carried out during 2001 to investigate the dense overflow and initial spreading of Red Sea Water (RSW) in the Gulf of Aden. The cruises were timed to coincide with the climatological maximum (February) and minimum (August) periods of outflow transport. The surveys included high-resolution CTD/lowered ADCP/shipboard ADCP observations in the descending plume and in the western gulf, and trajectories from 50 acoustically-tracked RAFOS floats released at the center of the equilibrated RSW (650 m). The measurements reveal a complicated descending plume structure in the western gulf with three main pathways for the high salinity RSW. Different mixing intensities along these pathways lead to variable penetration depths of the Red Sea plume between 450-900 m in the Gulf of Aden. The observations also revealed the hydrographic and velocity structure of large, energetic, deep-reaching mesoscale eddies in the gulf that fundamentally impact the spreading rates and pathways of RSW. Both cyclones and anticyclones were observed, with horizontal scales up to 250 km and azimuthal speeds as high as 0.5 m/s. The eddies appear to reach nearly to the sea floor and entrain RSW from the western gulf at mid-depth. Post-cruise analysis of SeaWiffs imagery suggests that some of these eddies form in the Indian Ocean and propagate into the gulf.

Monsoon-driven variability in the southern Red Sea and the exchange with the Indian Ocean

NASA Astrophysics Data System (ADS)

Sofianos, S. S.; Papadopoulos, V. P.; Abualnaja, Y.; Nenes, A.; Hoteit, I.

2016-02-01

Although progress has been achieved in describing and understanding the mean state and seasonal cycle of the Red Sea dynamics, their interannual variability is not yet well evaluated and explained. The thermohaline characteristics and the circulation patterns present strong variability at various time scales and are affected by the strong and variable atmospheric forcing and the exchange with the Indian Ocean and the gulfs located at the northern end of the basin. Sea surface temperature time-series, derived from satellite observations, show considerable trends and interannual variations. The spatial variability pattern is very diverse, especially in the north-south direction. The southern part of the Red Sea is significantly influenced by the Indian Monsoon variability that affects the sea surface temperature through the surface fluxes and the circulation patterns. This variability has also a strong impact on the lateral fluxes and the exchange with the Indian Ocean through the strait of Bab el Mandeb. During summer, there is a reversal of the surface flow and an intermediate intrusion of a relatively cold and fresh water mass. This water originates from the Gulf of Aden (the Gulf of Aden Intermediate Water - GAIW), is identified in the southern part of the basin and spreads northward along the eastern Red Sea boundary to approximately 24°N and carried across the Red Sea by basin-size eddies. The GAIW intrusion plays an important role in the heat and freshwater budget of the southern Red Sea, especially in summer, impacting the thermohaline characteristics of the region. It is a permanent feature of the summer exchange flow but it exhibits significant variation from year to year. The intrusion is controlled by a monsoon-driven pressure gradient in the two ends of the strait and thus monsoon interannual variability can laterally impose its signal to the southern Red Sea thermohaline patterns.

Testing common stream sampling methods for broad-scale, long-term monitoring

Treesearch

Eric K. Archer; Brett B. Roper; Richard C. Henderson; Nick Bouwes; S. Chad Mellison; Jeffrey L. Kershner

2004-01-01

We evaluated sampling variability of stream habitat sampling methods used by the USDA Forest Service and the USDI Bureau of Land Management monitoring program for the upper Columbia River Basin. Three separate studies were conducted to describe the variability of individual measurement techniques, variability between crews, and temporal variation throughout the summer...

Fish Assemblage Structure Under Variable Environmental Conditions in the Ouachita Mountains

Treesearch

Christopher M. Taylor; Lance R. Williams; Riccardo A. Fiorillo; R. Brent Thomas; Melvin L. Warren

2004-01-01

Abstract - Spatial and temporal variability of fish assemblages in Ouachita Mountain streams, Arkansas, were examined for association with stream size and flow variability. Fishes and habitat were sampled quarterly for four years at 12 sites (144 samples) in the Ouachita Mountains Ecosystem Management Research Project, Phase III watersheds. Detrended...

A watershed scale spatially-distributed model for streambank erosion rate driven by channel curvature

NASA Astrophysics Data System (ADS)

McMillan, Mitchell; Hu, Zhiyong

2017-10-01

Streambank erosion is a major source of fluvial sediment, but few large-scale, spatially distributed models exist to quantify streambank erosion rates. We introduce a spatially distributed model for streambank erosion applicable to sinuous, single-thread channels. We argue that such a model can adequately characterize streambank erosion rates, measured at the outsides of bends over a 2-year time period, throughout a large region. The model is based on the widely-used excess-velocity equation and comprised three components: a physics-based hydrodynamic model, a large-scale 1-dimensional model of average monthly discharge, and an empirical bank erodibility parameterization. The hydrodynamic submodel requires inputs of channel centerline, slope, width, depth, friction factor, and a scour factor A; the large-scale watershed submodel utilizes watershed-averaged monthly outputs of the Noah-2.8 land surface model; bank erodibility is based on tree cover and bank height as proxies for root density. The model was calibrated with erosion rates measured in sand-bed streams throughout the northern Gulf of Mexico coastal plain. The calibrated model outperforms a purely empirical model, as well as a model based only on excess velocity, illustrating the utility of combining a physics-based hydrodynamic model with an empirical bank erodibility relationship. The model could be improved by incorporating spatial variability in channel roughness and the hydrodynamic scour factor, which are here assumed constant. A reach-scale application of the model is illustrated on ∼1 km of a medium-sized, mixed forest-pasture stream, where the model identifies streambank erosion hotspots on forested and non-forested bends.

El-Niño/Southern Oscillation (ENSO) influences on monthly NO 3 load and concentration, stream flow and precipitation in the Little River Watershed, Tifton, Georgia (GA)

NASA Astrophysics Data System (ADS)

Keener, V. W.; Feyereisen, G. W.; Lall, U.; Jones, J. W.; Bosch, D. D.; Lowrance, R.

2010-02-01

SummaryAs climate variability increases, it is becoming increasingly critical to find predictable patterns that can still be identified despite overall uncertainty. The El-Niño/Southern Oscillation is the best known pattern. Its global effects on weather, hydrology, ecology and human health have been well documented. Climate variability manifested through ENSO has strong effects in the southeast United States, seen in precipitation and stream flow data. However, climate variability may also affect water quality in nutrient concentrations and loads, and have impacts on ecosystems, health, and food availability in the southeast. In this research, we establish a teleconnection between ENSO and the Little River Watershed (LRW), GA., as seen in a shared 3-7 year mode of variability for precipitation, stream flow, and nutrient load time series. Univariate wavelet analysis of the NINO 3.4 index of sea surface temperature (SST) and of precipitation, stream flow, NO 3 concentration and load time series from the watershed was used to identify common signals. Shared 3-7 year modes of variability were seen in all variables, most strongly in precipitation, stream flow and nutrient load in strong El Niño years. The significance of shared 3-7 year periodicity over red noise with 95% confidence in SST and precipitation, stream flow, and NO 3 load time series was confirmed through cross-wavelet and wavelet-coherence transforms, in which common high power and co-variance were computed for each set of data. The strongest 3-7 year shared power was seen in SST and stream flow data, while the strongest co-variance was seen in SST and NO 3 load data. The strongest cross-correlation was seen as a positive value between the NINO 3.4 and NO 3 load with a three-month lag. The teleconnection seen in the LRW between the NINO 3.4 index and precipitation, stream flow, and NO 3 load can be utilized in a model to predict monthly nutrient loads based on short-term climate variability, facilitating management in high risk seasons.

Summer temperature patterns in the headwater streams of the Oregon coast range

Treesearch

Liz Dent; Danielle Vick; Kyle Abraham; Stephen Schoenholtz; Sherri Johnson

2008-01-01

Cool summertime stream temperature is an important component of high-quality aquatic habitat in Oregon coastal streams. Within the Oregon Coast Range, small headwater streams make up a majority of the stream network, yet little information is available on temperature patterns and the longitudinal variability for these streams. In this paper we describe preharvest...

Investigating the chlorophyll-a variability in the Gulf of Taranto (North-western Ionian Sea) by a multi-temporal analysis of MODIS-Aqua Level 3/Level 2 data

NASA Astrophysics Data System (ADS)

Ciancia, Emanuele; Coviello, Irina; Di Polito, Carmine; Lacava, Teodosio; Pergola, Nicola; Satriano, Valeria; Tramutoli, Valerio

2018-03-01

The analysis of chlorophyll-a (chl-a) variability on a long-term basis could allow detecting possible issues in the whole marine ecosystem functioning. The Gulf of Taranto (Southern Italy), in the North-western Ionian Sea (Mediterranean Sea), has been affected by several environmental threats in the last decade, thus deserving the implementation of an adequate monitoring system able to provide accurate indications about the variability of the most relevant bio-optical parameters. In this context, the main objectives of this study are to investigate the long-term chl-a variability in the Gulf of Taranto and identify the occurrence of any past spatiotemporal anomalies by implementing the multi-temporal Robust Satellite Technique (RST) on a 12-year (2003-2015) period of MODIS/AQUA Level 3/Level 2 chlorophyll-a data. The achieved results show well-clustered near-surface positive chl-a anomalies during the January-February 2011 period. This detected offshore phytoplankton bloom may be related to sub-basin processes, such as the inflow of the Western Adriatic Coastal Current (WACC), probably fostered by the cyclonic reversal of the Bimodal Oscillating System (BiOS) mechanism. Therefore, the RST approach proved successful in detecting chl-a anomalous variations with a high level of confidence regardless of the absolute value measured, thus suggesting its exportability in other areas with different site-setting conditions.

Mesoscale spatial variability of selected aquatic invertebrate community metrics from a minimally impaired stream segment

USGS Publications Warehouse

Gebler, J.B.

2004-01-01

The related topics of spatial variability of aquatic invertebrate community metrics, implications of spatial patterns of metric values to distributions of aquatic invertebrate communities, and ramifications of natural variability to the detection of human perturbations were investigated. Four metrics commonly used for stream assessment were computed for 9 stream reaches within a fairly homogeneous, minimally impaired stream segment of the San Pedro River, Arizona. Metric variability was assessed for differing sampling scenarios using simple permutation procedures. Spatial patterns of metric values suggest that aquatic invertebrate communities are patchily distributed on subsegment and segment scales, which causes metric variability. Wide ranges of metric values resulted in wide ranges of metric coefficients of variation (CVs) and minimum detectable differences (MDDs), and both CVs and MDDs often increased as sample size (number of reaches) increased, suggesting that any particular set of sampling reaches could yield misleading estimates of population parameters and effects that can be detected. Mean metric variabilities were substantial, with the result that only fairly large differences in metrics would be declared significant at ?? = 0.05 and ?? = 0.20. The number of reaches required to obtain MDDs of 10% and 20% varied with significance level and power, and differed for different metrics, but were generally large, ranging into tens and hundreds of reaches. Study results suggest that metric values from one or a small number of stream reach(es) may not be adequate to represent a stream segment, depending on effect sizes of interest, and that larger sample sizes are necessary to obtain reasonable estimates of metrics and sample statistics. For bioassessment to progress, spatial variability may need to be investigated in many systems and should be considered when designing studies and interpreting data.

Centennial-scale links between Atlantic Ocean dynamics and hydroclimate over the last 4400 years: Insights from the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Thirumalai, K.; Quinn, T. M.; Okumura, Y.; Richey, J. N.; Partin, J. W.; Poore, R. Z.

2015-12-01

Surface circulation in the Atlantic Ocean is an important mediator of global climate and yet its variability is poorly constrained on centennial timescales. Changes in the Atlantic meridional overturning circulation (AMOC) have been implicated in late Holocene climate variability in the Western Hemisphere, although the relationship between AMOC variability and hydroclimate is uncertain due to the lack of sufficiently highly resolved proxy records. Here we present a replicated reconstruction of sea-surface temperature (SST) and salinity (SSS) from the Garrison Basin in the northern Gulf of Mexico (NGOM) spanning the last 4,400 years to better constrain past sea-surface conditions. We generated time series of paired Mg/Ca (SST proxy) and δ18O (SST and SSS proxy) variations in planktic foraminifer Globigerinoides ruber (white variety) from three multi-cores collected in 2010. Using a Monte Carlo-based technique we produce a stacked record from the three multi-cores and constrain analytical, calibration, chronological, and sampling uncertainties. We apply this technique to existing paired Mg/Ca- δ18O studies in the Gulf of Mexico and Atlantic Ocean to facilitate comparison between time-uncertain proxy reconstructions. The Garrison Basin stack exhibits large centennial-scale variability (σSST~0.6°C; δ18Osw~0.17‰) and indicates a substantially cool (0.9±0.5°C) and fresh (0.26±0.1‰) Little Ice Age (LIA; 1450-1850 A.D.), corroborating extant records from the Gulf of Mexico. Focusing on the last millennium, we analyze a suite of oceanic and terrestrial proxy records to demonstrate a centennial-scale link between salt advection in the Atlantic Ocean, a diagnostic parameter of ocean circulation, and hydroclimate in the adjacent continents. The ensuing multiproxy relationships seem to be consistent with spatial field correlations of limited salinity and rainfall instrumental/reanalysis data, which suggest that NGOM salinity varies with large-scale Atlantic Ocean circulation and continental precipitation. Our results imply significant centennial-scale variability over the late Holocene and are consistent with limited observational analysis indicating a slowdown of AMOC during the LIA.

Geochemical characteristics of Heavy metals of river sediment from the main rivers at Texas, USA.

NASA Astrophysics Data System (ADS)

Matsumoto, I.; Hoffman, D.; MacAlister, J.; Ishiga, H.

2008-12-01

Trinity River is one of the biggest rivers which flows through Dallas and Fort Worth two big cities of USA and are highly populated. Trinity river drains into the Gulf of Mexico. Sediment samples collected from various points along the upper and lower streams were subjected to content analysis and elution analysis (using liquate (flow) out test) on the heavy metals like Cd, CN, Pb, Cr, As, Hg, Ni, Zn and Cu from the river sediment for the purpose of environment assessment. A total of 22 sample points were identified from upper stream to lower stream and samples were collected such that almost the whole stream length of Trinity River is covered. Results show that heavy metal content through out the river stream is below the recommended limits posing no immediate environmental threat. However, the experimental results show clear impact of human population in bigger cities on heavy metal concentrations in the river sediments as compared to smaller cities with low human population. It could be seen from the analysis that all the heavy metals show relatively high content and high elution value in Dallas and Fort Worth. As we move away from the big cities, the value of content and elution of sediment decreased by natural dilution effect by the river. And we also present the data of the Colorado and San Antonio rivers.

A framework to assess the impacts of climate change on stream health indicators in Michigan watersheds

NASA Astrophysics Data System (ADS)

Woznicki, S. A.; Nejadhashemi, A. P.; Tang, Y.; Wang, L.

2016-12-01

Climate change is projected to alter watershed hydrology and potentially amplify nonpoint source pollution transport. These changes have implications for fish and macroinvertebrates, which are often used as measures of aquatic ecosystem health. By quantifying the risk of adverse impacts to aquatic ecosystem health at the reach-scale, watershed climate change adaptation strategies can be developed and prioritized. The objective of this research was to quantify the impacts of climate change on stream health in seven Michigan watersheds. A process-based watershed model, the Soil and Water Assessment Tool (SWAT), was linked to adaptive neuro-fuzzy inferenced (ANFIS) stream health models. SWAT models were used to simulate reach-scale flow regime (magnitude, frequency, timing, duration, and rate of change) and water quality variables. The ANFIS models were developed based on relationships between the in-stream variables and sampling points of four stream health indicators: the fish index of biotic integrity (IBI), macroinvertebrate family index of biotic integrity (FIBI), Hilsenhoff biotic index (HBI), and number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa. The combined SWAT-ANFIS models extended stream health predictions to all watershed reaches. A climate model ensemble from the Coupled Model Intercomparison Project Phase 5 (CMIP5) was used to develop projections of changes to flow regime (using SWAT) and stream health indicators (using ANFIS) from a baseline of 1980-2000 to 2020-2040. Flow regime variables representing variability, duration of extreme events, and timing of low and high flow events were sensitive to changes in climate. The stream health indicators were relatively insensitive to changing climate at the watershed scale. However, there were many instances of individual reaches that were projected to experience declines in stream health. Using the probability of stream health decline coupled with the magnitude of the decline, maps of vulnerable stream ecosystems were developed, which can be used in the watershed management decision-making process.

Optimal boundary conditions for ORCA-2 model

NASA Astrophysics Data System (ADS)

Kazantsev, Eugene

2013-08-01

A 4D-Var data assimilation technique is applied to ORCA-2 configuration of the NEMO in order to identify the optimal parametrization of boundary conditions on the lateral boundaries as well as on the bottom and on the surface of the ocean. The influence of boundary conditions on the solution is analyzed both within and beyond the assimilation window. It is shown that the optimal bottom and surface boundary conditions allow us to better represent the jet streams, such as Gulf Stream and Kuroshio. Analyzing the reasons of the jets reinforcement, we notice that data assimilation has a major impact on parametrization of the bottom boundary conditions for u and v. Automatic generation of the tangent and adjoint codes is also discussed. Tapenade software is shown to be able to produce the adjoint code that can be used after a memory usage optimization.

Near-coastal ocean variability off southern Tamaulipas - northern Veracruz, western Gulf of Mexico, during spring-summer 2013

NASA Astrophysics Data System (ADS)

Rivas, David

2016-04-01

Six months of observations from a near-coastal mooring deployed off southern Tamaulipas-northern Veracruz coast (western Gulf of Mexico) during spring-summer 2013 provides velocity, temperature, salinity, sea level, and dissolved oxygen series in a region which ocean dynamics is still poorly understood. As shown in a preceding analysis of this region's winter circulation for winter 2012-2013, coastal trapped motions associated with the regional invasion of synoptic cold fronts modulate the local variability; this pattern remains in the spring 2013, when even more intense events of alongshore flow (>50 cm/s) are observed. This intensified flow is associated with a significant decrease in the dissolved oxygen, most probably related to an influence of hypoxic waters coming from the northern Gulf. In late spring-mid summer, the wind pattern corresponds to persistent southeasterly winds that favor the occurrence of a local upwelling, which maintains a local thermal reduction (>3 degrees Celsius) and is associated with a persistent northward flow (>30 cm/s). The late summer was characterized by a significant tropical-cyclone activity, when a depression, a storm, and a hurricane affected the western Gulf. These tropical systems caused an intense precipitation and hence an important intensification of the local riverine discharge, and the winds enhanced the mixing of such riverine waters, via mostly kinetic stirring and Ekman pumping.

The Gulf of Lions' hydrodynamics

NASA Astrophysics Data System (ADS)

Millot, Claude

1990-09-01

From an hydrodynamical point of view, the Gulf of Lions can be considered as a very complex region, because several intense and highly variable phenomena compete simultaneously. These processes include the powerful general circulation along the continental slope, the formation of dense water both on the shelf and offshore, a seasonal variation of stratification and the extreme energies associated with meteorological conditions. The cloudless atmospheric conditions encountered generally in the northwestern Mediterranean Sea have enabled us to make use of, over more than 10 years, large use of various satellite imageries. The large space and time variability of the hydrodynamical features, a complex topography and a noticeable fishing activity, represent certain difficulties to the collection of observations in situ. We have obtained, therefore, only a few current time series on the slope; those obtained on the shelf only cover the summer period. Models have been elaborated to help us understand the reasons for the general circulation. Observational programmes to be carried out in the forthcoming years will probably provide us with more definitive results on the Gulf of Lions' hydrodynamics.

Significant spatial variability of bioavailable PAHs in water column and sediment porewater in the Gulf of Mexico 1 year after the Deepwater Horizon oil spill.

PubMed

Hong, Yongseok; Wetzel, Dana; Pulster, Erin L; Hull, Pete; Reible, Danny; Hwang, Hyun-Min; Ji, Pan; Rifkin, Erik; Bouwer, Edward

2015-10-01

One year after the Deepwater Horizon oil spill accident, semipermeable membrane devices (SPMDs) and polyethylene devices (PEDs) were deployed in wetland areas and coastal areas of the Gulf of Mexico (GOM) to monitor polycyclic aromatic hydrocarbons (PAHs). The measured PAH levels with the PEDs in coastal areas were 0.05-1.9 ng/L in water and 0.03-9.7 ng/L in sediment porewater. With the SPMDs, the measured PAH levels in wetlands (Barataria Bay) were 1.4-73 ng/L in water and 3.3-107 ng/L in porewater. The total PAH concentrations in the coastal areas were close to the reported baseline PAH concentrations in GOM; however, the total PAH concentrations in the wetland areas were one or two orders of magnitude higher than those reported in the coastal areas. In light of the significant spatial variability of PAHs in the Gulf's environments, baseline information on PAHs should be obtained in specific areas periodically.

Large-scale climatic phenomena drive fluctuations in macroinvertebrate assemblages in lowland tropical streams, Costa Rica: The importance of ENSO events in determining long-term (15y) patterns

PubMed Central

Ramírez, Alonso; Pringle, Catherine M.

2018-01-01

Understanding how environmental variables influence the distribution and density of organisms over relatively long temporal scales is a central question in ecology given increased climatic variability (e.g., precipitation, ENSO events). The primary goal of our study was to evaluate long-term (15y time span) patterns of climate, as well as environmental parameters in two Neotropical streams in lowland Costa Rica, to assess potential effects on aquatic macroinvertebrates. We also examined the relative effects of an 8y whole-stream P-enrichment experiment on macroinvertebrate assemblages against the backdrop of this long-term study. Climate, environmental variables and macroinvertebrate samples were measured monthly for 7y and then quarterly for an additional 8y in each stream. Temporal patterns in climatic and environmental variables showed high variability over time, without clear inter-annual or intra-annual patterns. Macroinvertebrate richness and abundance decreased with increasing discharge and was positively related to the number of days since the last high discharge event. Findings show that fluctuations in stream physicochemistry and macroinvertebrate assemblage structure are ultimately the result of large-scale climatic phenomena, such as ENSO events, while the 8y P-enrichment did not appear to affect macroinvertebrates. Our study demonstrates that Neotropical lowland streams are highly dynamic and not as stable as is commonly presumed, with high intra- and inter-annual variability in environmental parameters that change the structure and composition of freshwater macroinvertebrate assemblages. PMID:29420548

Temporal Patterns and Environmental Correlates of Macroinvertebrate Communities in Temporary Streams.

PubMed

Botwe, Paul K; Barmuta, Leon A; Magierowski, Regina; McEvoy, Paul; Goonan, Peter; Carver, Scott

2015-01-01

Temporary streams are characterised by short periods of seasonal or annual stream flow after which streams contract into waterholes or pools of varying hydrological connectivity and permanence. Although these streams are widespread globally, temporal variability of their ecology is understudied, and understanding the processes that structure community composition in these systems is vital for predicting and managing the consequences of anthropogenic impacts. We used multivariate and univariate approaches to investigate temporal variability in macroinvertebrate compositional data from 13 years of sampling across multiple sites from autumn and spring, in South Australia, the driest state in the driest inhabited continent in the world. We examined the potential of land-use, geographic and environmental variables to predict the temporal variability in macroinvertebrate assemblages, and also identified indicator taxa, that is, those highly correlated with the most significantly associated physical variables. Temporal trajectories of macroinvertebrate communities varied within site in both seasons and across years. A combination of land-use, geographic and environmental variables accounted for 24% of the variation in community structure in autumn and 27% in spring. In autumn, community composition among sites were more closely clustered together relative to spring suggesting that communities were more similar in autumn than in spring. In both seasons, community structure was most strongly correlated with conductivity and latitude, and community structure was more associated with cover by agriculture than urban land-use. Maintaining temporary streams will require improved catchment management aimed at sustaining seasonal flows and critical refuge habitats, while also limiting the damaging effects from increased agriculture and urban developments.

Temporal Patterns and Environmental Correlates of Macroinvertebrate Communities in Temporary Streams

PubMed Central

Botwe, Paul K.; Barmuta, Leon A.; Magierowski, Regina; McEvoy, Paul; Goonan, Peter; Carver, Scott

2015-01-01

Temporary streams are characterised by short periods of seasonal or annual stream flow after which streams contract into waterholes or pools of varying hydrological connectivity and permanence. Although these streams are widespread globally, temporal variability of their ecology is understudied, and understanding the processes that structure community composition in these systems is vital for predicting and managing the consequences of anthropogenic impacts. We used multivariate and univariate approaches to investigate temporal variability in macroinvertebrate compositional data from 13 years of sampling across multiple sites from autumn and spring, in South Australia, the driest state in the driest inhabited continent in the world. We examined the potential of land-use, geographic and environmental variables to predict the temporal variability in macroinvertebrate assemblages, and also identified indicator taxa, that is, those highly correlated with the most significantly associated physical variables. Temporal trajectories of macroinvertebrate communities varied within site in both seasons and across years. A combination of land-use, geographic and environmental variables accounted for 24% of the variation in community structure in autumn and 27% in spring. In autumn, community composition among sites were more closely clustered together relative to spring suggesting that communities were more similar in autumn than in spring. In both seasons, community structure was most strongly correlated with conductivity and latitude, and community structure was more associated with cover by agriculture than urban land-use. Maintaining temporary streams will require improved catchment management aimed at sustaining seasonal flows and critical refuge habitats, while also limiting the damaging effects from increased agriculture and urban developments. PMID:26556711

Hydrologic connectivity and the contribution of stream headwaters to ecological integrity at regional scales

USGS Publications Warehouse

Freeman, Mary C.; Pringle, C.M.; Jackson, C.R.

2007-01-01

Cumulatively, headwater streams contribute to maintaining hydrologic connectivity and ecosystem integrity at regional scales. Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle. Headwater streams compose over two-thirds of total stream length in a typical river drainage and directly connect the upland and riparian landscape to the rest of the stream ecosystem. Altering headwater streams, e.g., by channelization, diversion through pipes, impoundment and burial, modifies fluxes between uplands and downstream river segments and eliminates distinctive habitats. The large-scale ecological effects of altering headwaters are amplified by land uses that alter runoff and nutrient loads to streams, and by widespread dam construction on larger rivers (which frequently leaves free-flowing upstream portions of river systems essential to sustaining aquatic biodiversity). We discuss three examples of large-scale consequences of cumulative headwater alteration. Downstream eutrophication and coastal hypoxia result, in part, from agricultural practices that alter headwaters and wetlands while increasing nutrient runoff. Extensive headwater alteration is also expected to lower secondary productivity of river systems by reducing stream-system length and trophic subsidies to downstream river segments, affecting aquatic communities and terrestrial wildlife that utilize aquatic resources. Reduced viability of freshwater biota may occur with cumulative headwater alteration, including for species that occupy a range of stream sizes but for which headwater streams diversify the network of interconnected populations or enhance survival for particular life stages. Developing a more predictive understanding of ecological patterns that may emerge on regional scales as a result of headwater alterations will require studies focused on components and pathways that connect headwaters to river, coastal and terrestrial ecosystems. Linkages between headwaters and downstream ecosystems cannot be discounted when addressing large-scale issues such as hypoxia in the Gulf of Mexico and global losses of biodiversity.

Tracking contaminants down the Mississippi

USGS Publications Warehouse

Swarzenski, P.; Campbell, P.

2004-01-01

The Mississippi River and its last major downstream distributary, the Atchafalaya River, provide approximately 90 percent of the freshwater input to the Gulf of Mexico. Analyses of sediment cores using organic and inorganic tracers as well as bethic foraminifera appear to provide a reliable record of the historic variability of hypoxia in the northern Gulf of Mexico over the past few centuries. Natural variability in hypoxic events may be driven largely by flooding cycles of El Nin??o/La Nin??a prior to recent increases in nutrient loading. Specifically, large floods in 1979, 1983, 1993 and 1998, compounded with the widespread use of fertilizers, also appear at least partially responsible for the recent (post-1980) dramatic increase of hypoxic events in the Mississippi Bight.

Interaction between urbanization and climate variability amplifies watershed nitrate export in Maryland

USGS Publications Warehouse

Kaushal, S.S.; Groffman, P.M.; Band, L.E.; Shields, C.A.; Morgan, R.P.; Palmer, Margaret A.; Belt, K.T.; Swan, C.M.; Findlay, S.E.G.; Fisher, G.T.

2008-01-01

We investigated regional effects of urbanization and land use change on nitrate concentrations in approximately 1,000 small streams in Maryland during record drought and wet years in 2001-2003. We also investigated changes in nitrate-N export during the same time period in 8 intensively monitored small watersheds across an urbanization gradient in Baltimore, Maryland. Nitrate-N concentrations in Maryland were greatest in agricultural streams, urban streams, and forest streams respectively. During the period of record drought and wet years, nitrate-N exports in Baltimore showed substantial variation in 6 suburban/urban streams (2.9-15.3 kg/ha/y), 1 agricultural stream (3.4-38.9 kg/ha/y), and 1 forest stream (0.03-0.2 kg/ ha/y). Interannual variability was similar for small Baltimore streams and nearby well-monitored tributaries and coincided with record hypoxia in Chesapeake Bay. Discharge-weighted mean annual nitrate concentrations showed a variable tendency to decrease/increase with changes in annual runoff, although total N export generally increased with annual runoff. N retention in small Baltimore watersheds during the 2002 drought was 85%, 99%, and 94% for suburban, forest, and agricultural watersheds, respectively, and declined to 35%, 91%, and 41% during the wet year of 2003. Our results suggest that urban land use change can increase the vulnerability of ecosystem nitrogen retention functions to climatic variability. Further work is necessary to characterize patterns of nitrate-N export and retention in small urbanizing watersheds under varying climatic conditions to improve future forecasting and watershed scale restoration efforts aimed at improving nitrate-N retention. ?? 2008 American Chemical Society.

The paradox of cooling streams in a warming world: Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

USGS Publications Warehouse

Arismendi, Ivan; Johnson, Sherri; Dunham, Jason B.; Haggerty, Roy; Hockman-Wert, David

2012-01-01

Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream temperature. Here, we examined the evidence for this using long-term stream temperature data from minimally and highly human-impacted sites located across the Pacific continental United States. Based on hypothesized climate impacts, we predicted that we should find warming trends in the maximum, mean and minimum temperatures, as well as increasing variability over time. These predictions were not fully realized. Warming trends were most prevalent in a small subset of locations with longer time series beginning in the 1950s. More recent series of observations (1987-2009) exhibited fewer warming trends and more cooling trends in both minimally and highly human-influenced systems. Trends in variability were much less evident, regardless of the length of time series. Based on these findings, we conclude that our perspective of climate impacts on stream temperatures is clouded considerably by a lack of long-termdata on minimally impacted streams, and biased spatio-temporal representation of existing time series. Overall our results highlight the need to develop more mechanistic, process-based understanding of linkages between climate change, other human impacts and stream temperature, and to deploy sensor networks that will provide better information on trends in stream temperatures in the future.

Dr. von Braun on top of the Deep-Sea Research Submarine 'Ben Franklin'

NASA Technical Reports Server (NTRS)

1969-01-01

This photograph depicts Dr. von Braun (at right, showing his back) and other NASA officials surveying the deep-sea research submarine 'Ben Franklin.' Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Dr. von Braun on Top of the Deep-Sea Research Submarine 'Ben Franklin'

NASA Technical Reports Server (NTRS)

1969-01-01

This photograph depicts Dr. von Braun (fourth from far right) and other NASA officials surveying the deep-sea research submarine 'Ben Franklin.' Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Deep-Sea Research Submarine 'Ben Franklin' at the East Coast of the United States

NASA Technical Reports Server (NTRS)

1969-01-01

In this photograph, the deep-sea Research Submarine 'Ben Franklin' drifts off the East Coast of the United States (U.S.) prior to submerging into the ocean. Named for American patriot and inventor Ben Franklin, who discovered the Gulf Steam, the 50-foot Ben Franklin was built between 1966 and 1968 in Switzerland for deep-ocean explorer Jacques Piccard and the Grumman Aircraft Engineering Corporation. The submersible made a famous 30-day drift dive off the East Coast of the United States and Canada in 1969 mapping the Gulf Stream's currents and sea life, and also made space exploration history by studying the behavior of aquanauts in a sealed, self-contained, self-sufficient capsule for NASA. On July 14, 1969, the Ben Franklin was towed to the high-velocity center of the Stream off the coast of Palm Beach, Florida. With a NASA observer on board, the sub descended to 1,000 feet off of Riviera Beach, Florida and drifted 1,400 miles north with the current for more than four weeks, reemerging near Maine. During the course of the dive, NASA conducted exhaustive analyses of virtually every aspect of onboard life. They measured sleep quality and patterns, sense of humor and behavioral shifts, physical reflexes, and the effects of a long-term routine on the crew. The submarine's record-shattering dive influenced the design of Apollo and Skylab missions and continued to guide NASA scientists as they devised future marned space-flight missions.

Trophic Ecology and Movement Patters of Tiger Sharks (Galeocerdo Cuvier) off the Western North Atlantic Coastal and Continental Shelf Waters

NASA Astrophysics Data System (ADS)

Sancho, G.; Edman, R.; Frazier, B.; Bubley, W.

2016-02-01

Understanding the trophic dynamics and habitat utilization of apex predators is central to inferring their influence on different marine landscapes and to help design effective management plans for these animals. Tiger sharks (Galeocerdo cuvier) are abundant in shelf and offshore Gulf Stream waters of the western North Atlantic Ocean, and based on movements from individuals captured in Florida and Bahamas, seem to avoid coastal and shelf waters off South Carolina and Georgia. This contradicts reports of tiger sharks regularly being caught nearshore by anglers in these states, indicating that separate sub-populations may exist in the western North Atlantic. In the present study we captured Tiger Sharks in coastal waters off South Carolina in 2014 and 2015 in order to describe their movement patterns through acoustic and satellite tagging, and trophic dynamics through stable isotope analyses. Movement data show that these tiger sharks repeatedly visit particular inshore areas and mainly travel over the continental shelf, but rarely venture offshore beyond the continental shelf edge. Ongoing C and N stable isotope analyses of muscle, blood and skin tissues from adult and juvenile tiger sharks, as well as from potential prey species and primary producers, will help determine if their diets are based on inshore, shelf or offshore based food webs. Tiger sharks exploiting nearshore environments and shelf waters have much higher probabilities of interacting with humans than individuals occupying far offshore Gulf Stream habitats.

Integrated Observations From Fixed and AUV Platforms in the Littoral Zone at the SFOMC Coastal Ocean Observatory

NASA Astrophysics Data System (ADS)

Dhanak, M. R.

2001-12-01

A 12-hour survey of the coastal waters off the east coast of Florida at the South Florida Ocean Measurement Center (SFOMC) coastal ocean observatory, during summer 1999, is described to illustrate the observatory's capabilities for ocean observation. The facility is located close to the Gulf Stream, the continental shelf break being only 3 miles from shore and is therefore influenced by the Gulf Stream meanders and the instability of the horizontal shear layer at its edge. As a result, both cross-shelf and along-shelf components of currents in the littoral zone can undergo dramatic +/- 0.5 m/s oscillations. Observations of surface currents from an OSCR, and of subsurface structure from an autonomous underwater vehicle (AUV) platform, a bottom-mounted ADCP and CT-chain arrays during the survey will be described and compared. The AUV on-board sensors included upward and downward looking 1200kHz ADCP, a CTD package and a small-scale turbulence package, consisting of two shear probes and a fast-response thermistor. Prevailing atmospheric conditions were recorded at an on-site buoy. The combined observations depict flows over a range of scales. Acknowledgements: The observations from the OSCR are due to Nick Shay and Tom Cook (University of Miami), and from the bottom-mounted ADCP, CT chain arrays and the surface buoy are due to Alex Soloviev (Nova Southeastern University) and Mark Luther and Bob Weisberg (University of South Florida).

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Basin Characteristics, 2002 Geospatial_Data_Presentation_Form: tabular digital data

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents basin characteristics for the year 2002 compiled for every MRB_E2RF1 catchment of selected Major River Basins (MRBs, Crawford and others, 2006). These characteristics are reach catchment shape index, stream density, sinuosity, mean elevation, mean slope and number of road-stream crossings. The source data sets are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) RF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011) and the U.S. Census Bureau's TIGER/Line Files (U.S. Census Bureau,2006). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Heat and salt budgets over the Gulf Stream North Wall during LatMix survey in winter 2012.

NASA Astrophysics Data System (ADS)

Sanchez-Rios, A.; Shearman, R. K.; D'Asaro, E. A.; Lee, C.; Gula, J.; Klymak, J. M.

2016-02-01

As part of the ONR-sponsored LatMix Experiment, ship-based and glider-based observations following a Lagrangian float are used to examine the evolution of temperature, salinity and density along the Gulf Stream north wall in wintertime. Satellite observations during the survey and the in-situ measurements showed the presence of submesoscale (<10 km) features along the front. Models have successfully reproduced similar features, but observations are lacking, particularly at the small scales needed to understand their role in the transport of heat and salt across the front and out of the mixed layer. Calculating the trend in time at each depth and cross-front location we found an increase of heat and salinity in regions where the strongest cross-front gradients of velocity were observed at the mixed layer and around 150m depth, these changes are density compensated and suggest isopycnal mixing and a connection between the mixed layer and subsurface layers. The large Rossby number (Ro>1) calculated for this regions corroborates the possibility of submesoscale dynamics. Using a heat and salinity budget, we show that surface forcing, entrainment from below and advection by the mean flow velocities are not sufficient to explain the observed rate of change of heat and salinity in the mixed layer. Although confidence estimates prevent an accurate flux divergence calculation, Reynold flux estimates are consistent with a cross-frontal exchange that can reproduce the observed temporal trends.

Benthic foraminifera records in marine sediments during the Holocene from Pescadero basin, Gulf of California, Mexico

NASA Astrophysics Data System (ADS)

Valdez, M.; Perez-Cruz, L. L.; Roy, P.; Monreal, M.; Fenero, R.

2013-05-01

Gravity core T-56 (256 cm length) was collected in Pescadero Basin located on the western side of the Gulf of California within the oxygen minim zone (OMZ) at 597 cm depth, aboard of the R/V "El Puma". Pescadero basin is located at mouth of the gulf; because of its location is sensitive to record the changes in the gulf and in the Eastern Pacific Ocean. The sedimentary sequence is analyzed to contribute to the understanding the oceanographic variability in the southern part of the gulf of California during the Holocene using benthic foraminifera assemblages and organic carbon as proxies of organic matter flux and bottom water oxygenation. In general, the core is characterized by silty-clay sediments, and it exhibits a turbidite between 198 and 134 cm, distinguished by sandy sediments and reworking material. From 134 cm to the top shows a visible laminated structure. The initial chronology is based on three AMS radiocarbon dates, and estimated sedimentation rates are 0.22 and 0.19 mm/yr for the first 32 cm of the core. Six radiocarbon dates are in progress. Preliminary results of benthic foraminiferal assemblages showed that species of Bolivina are dominated, mainly megalospheric forms, from 134 cm to top of the core. They are small and thin-shelled forms (e.g., Bolivina subadvena, Bolivina minuta, Bolivina seminuda, Bolivina plicata), and also Buliminella, Cassidulina and Epistominella are abundant. In particular, species of Bolivina are environmental indicators and exhibit a typical reproductive dimorphism. The predominance of the genus Bolivina suggest organic flux variations, because of the productivity changes that might be related to changes in ocean circulation and in the environmental variability in the region.

PHYTOPLANKTON NUTRIENT STATUS AND VARIABLE FLUORESCENCE MEASUREMENTS IN A GULF COAST ESTUARY

EPA Science Inventory

Changes in variable fluorescence parameters such as the maximum quantum yield of fluorescence (a.k.a. photosynthetic efficiency and Fv/Fm) have been related to nutrient status in single-species cultures. To test if changes in Fv/Fm of mixed natural assemblages were related to nut...

Gulf of California biogeographic regions based on coastal zone color scanner imagery

NASA Astrophysics Data System (ADS)

SantamaríA-Del-Angel, Eduardo; Alvarez-Borrego, Saúl; Müller-Karger, Frank E.

1994-04-01

Topographically, the Gulf of California is divided into a series of basins and trenches that deepen to the south. Maximum depth at the mouth is greater than 3000 m. Most of the northern gulf is less than 200 m deep. The gulf has hydrographic features conducive to high primary productivity. Upwelling events have been described on the basis of temperature distributions at the eastern coast during winter and spring and at the western coast during summer. Tidal amplitude may be as high as 9 m in the upper gulf. On the basis of discrete phytoplankton sampling, the gulf was previously divided into four geographic regions. This division took into consideration only the space distribution, taxonomic composition, and abundance of microphytoplankton. With the availability of the coastal zone color scanner (CZCS) imagery, we were able to include the time variability of pigments to make a more detailed biogeographic division of the gulf. With weekly composites of the imagery, we generated time series of pigment concentrations for 33 locations throughout the gulf and for the whole life span of the CZCS. The time series show a clear seasonal variation, with maxima in winter and spring and minima in summer. The effect of upwelling at the eastern coast is clearly evident, with high pigment concentrations. The effect of the summer upwelling off the Baja California coast is not evident in these time series. Time series from locations on the western side of the gulf also show maxima in winter and spring that are due to the eddy circulation that brings upwelled water from the eastern side. Principal-component analysis was applied to define 14 regions. Ballenas Channel, between Angel de la Guarda and Baja California, and the upper gulf always appeared as very distinct regions. Some of these 14 regions relate to the geographic distributions of important faunal groups, including the benthos, or their life cycles. For example, the upper gulf is a place for reproduction and the nursery of many fish species, marine mammals and birds are specially abundant in Ballenas Channel, sardine spawning mostly occurs in the central gulf in spring, and shrimp are abundant off mainland Mexico.

Dynamics of stream water TOC concentrations in a boreal headwater catchment: Controlling factors and implications for climate scenarios

NASA Astrophysics Data System (ADS)

Köhler, S. J.; Buffam, I.; Seibert, J.; Bishop, K. H.; Laudon, H.

2009-06-01

SummaryTwo different but complementary modelling approaches for reproducing the observed dynamics of total organic carbon (TOC) in a boreal stream are presented. One is based on a regression analysis, while the other is based on riparian soil conditions using a convolution of flow and concentration. Both approaches are relatively simple to establish and help to identify gaps in the process understanding of the TOC transport from soils to catchments runoff. The largest part of the temporal variation of stream TOC concentrations (4-46 mg L -1) in a forested headwater stream in the boreal zone in northern Sweden may be described using a four-parameter regression equation that has runoff and transformed air temperature as sole input variables. Runoff is assumed to be a proxy for soil wetness conditions and changing flow pathways which in turn caused most of the stream TOC variation. Temperature explained a significant part of the observed inter-annual variability. Long-term riparian hydrochemistry in soil solutions within 4 m of the stream also captures a surprisingly large part of the observed variation of stream TOC and highlights the importance of riparian soils. The riparian zone was used to reproduce stream TOC with the help of a convolution model based on flow and average riparian chemistry as input variables. There is a significant effect of wetting of the riparian soil that translates into a memory effect for subsequent episodes and thus contributes to controlling stream TOC concentrations. Situations with high flow introduce a large amount of variability into stream water TOC that may be related to memory effects, rapid groundwater fluctuations and other processes not identified so far. Two different climate scenarios for the region based on the IPCC scenarios were applied to the regression equation to test what effect the expected increase in precipitation and temperature and resulting changes in runoff would have on stream TOC concentrations assuming that the soil conditions remain unchanged. Both scenarios resulted in a mean increase of stream TOC concentrations of between 1.5 and 2.5 mg L -1 during the snow free season, which amounts to approximately 15% more TOC export compared to present conditions. Wetter and warmer conditions in the late autumn led to a difference of monthly average TOC of up to 5 mg L -1, suggesting that stream TOC may be particularly susceptible to climate variability during this season.

Discovery of a spawning ground reveals diverse migration strategies in Atlantic bluefin tuna (Thunnus thynnus).

PubMed

Richardson, David E; Marancik, Katrin E; Guyon, Jeffrey R; Lutcavage, Molly E; Galuardi, Benjamin; Lam, Chi Hin; Walsh, Harvey J; Wildes, Sharon; Yates, Douglas A; Hare, Jonathan A

2016-03-22

Atlantic bluefin tuna are a symbol of both the conflict between preservationist and utilitarian views of top ocean predators, and the struggle to reach international consensus on the management of migratory species. Currently, Atlantic bluefin tuna are managed as an early-maturing eastern stock, which spawns in the Mediterranean Sea, and a late-maturing western stock, which spawns in the Gulf of Mexico. However, electronic tagging studies show that many bluefin tuna, assumed to be of a mature size, do not visit either spawning ground during the spawning season. Whether these fish are spawning in an alternate location, skip-spawning, or not spawning until an older age affects how vulnerable this species is to anthropogenic stressors including exploitation. We use larval collections to demonstrate a bluefin tuna spawning ground in the Slope Sea, between the Gulf Stream and northeast United States continental shelf. We contend that western Atlantic bluefin tuna have a differential spawning migration, with larger individuals spawning in the Gulf of Mexico, and smaller individuals spawning in the Slope Sea. The current life history model, which assumes only Gulf of Mexico spawning, overestimates age at maturity for the western stock. Furthermore, individual tuna occupy both the Slope Sea and Mediterranean Sea in separate years, contrary to the prevailing view that individuals exhibit complete spawning-site fidelity. Overall, this complexity of spawning migrations questions whether there is complete independence in the dynamics of eastern and western Atlantic bluefin tuna and leads to lower estimates of the vulnerability of this species to exploitation and other anthropogenic stressors.

Discovery of a spawning ground reveals diverse migration strategies in Atlantic bluefin tuna (Thunnus thynnus)

PubMed Central

Richardson, David E.; Marancik, Katrin E.; Guyon, Jeffrey R.; Lutcavage, Molly E.; Galuardi, Benjamin; Lam, Chi Hin; Walsh, Harvey J.; Wildes, Sharon; Yates, Douglas A.; Hare, Jonathan A.

2016-01-01

Atlantic bluefin tuna are a symbol of both the conflict between preservationist and utilitarian views of top ocean predators, and the struggle to reach international consensus on the management of migratory species. Currently, Atlantic bluefin tuna are managed as an early-maturing eastern stock, which spawns in the Mediterranean Sea, and a late-maturing western stock, which spawns in the Gulf of Mexico. However, electronic tagging studies show that many bluefin tuna, assumed to be of a mature size, do not visit either spawning ground during the spawning season. Whether these fish are spawning in an alternate location, skip-spawning, or not spawning until an older age affects how vulnerable this species is to anthropogenic stressors including exploitation. We use larval collections to demonstrate a bluefin tuna spawning ground in the Slope Sea, between the Gulf Stream and northeast United States continental shelf. We contend that western Atlantic bluefin tuna have a differential spawning migration, with larger individuals spawning in the Gulf of Mexico, and smaller individuals spawning in the Slope Sea. The current life history model, which assumes only Gulf of Mexico spawning, overestimates age at maturity for the western stock. Furthermore, individual tuna occupy both the Slope Sea and Mediterranean Sea in separate years, contrary to the prevailing view that individuals exhibit complete spawning-site fidelity. Overall, this complexity of spawning migrations questions whether there is complete independence in the dynamics of eastern and western Atlantic bluefin tuna and leads to lower estimates of the vulnerability of this species to exploitation and other anthropogenic stressors. PMID:26951668

Assessing the accuracy and stability of variable selection ...

EPA Pesticide Factsheets

Random forest (RF) modeling has emerged as an important statistical learning method in ecology due to its exceptional predictive performance. However, for large and complex ecological datasets there is limited guidance on variable selection methods for RF modeling. Typically, either a preselected set of predictor variables are used, or stepwise procedures are employed which iteratively add/remove variables according to their importance measures. This paper investigates the application of variable selection methods to RF models for predicting probable biological stream condition. Our motivating dataset consists of the good/poor condition of n=1365 stream survey sites from the 2008/2009 National Rivers and Stream Assessment, and a large set (p=212) of landscape features from the StreamCat dataset. Two types of RF models are compared: a full variable set model with all 212 predictors, and a reduced variable set model selected using a backwards elimination approach. We assess model accuracy using RF's internal out-of-bag estimate, and a cross-validation procedure with validation folds external to the variable selection process. We also assess the stability of the spatial predictions generated by the RF models to changes in the number of predictors, and argue that model selection needs to consider both accuracy and stability. The results suggest that RF modeling is robust to the inclusion of many variables of moderate to low importance. We found no substanti

Influence of the Bermuda High on interannual variability of summertime ozone in the Houston-Galveston-Brazoria region

NASA Astrophysics Data System (ADS)

Wang, Yuxuan; Jia, Beixi; Wang, Sing-Chun; Estes, Mark; Shen, Lu; Xie, Yuanyu

2016-12-01

The Bermuda High (BH) quasi-permanent pressure system is the key large-scale circulation pattern influencing summertime weather over the eastern and southern US. Here we developed a multiple linear regression (MLR) model to characterize the effect of the BH on year-to-year changes in monthly-mean maximum daily 8 h average (MDA8) ozone in the Houston-Galveston-Brazoria (HGB) metropolitan region during June, July, and August (JJA). The BH indicators include the longitude of the BH western edge (BH-Lon) and the BH intensity index (BHI) defined as the pressure gradient along its western edge. Both BH-Lon and BHI are selected by MLR as significant predictors (p < 0.05) of the interannual (1990-2015) variability of the HGB-mean ozone throughout JJA, while local-scale meridional wind speed is selected as an additional predictor for August only. Local-scale temperature and zonal wind speed are not identified as important factors for any summer month. The best-fit MLR model can explain 61-72 % of the interannual variability of the HGB-mean summertime ozone over 1990-2015 and shows good performance in cross-validation (R2 higher than 0.48). The BH-Lon is the most important factor, which alone explains 38-48 % of such variability. The location and strength of the Bermuda High appears to control whether or not low-ozone maritime air from the Gulf of Mexico can enter southeastern Texas and affect air quality. This mechanism also applies to other coastal urban regions along the Gulf Coast (e.g., New Orleans, LA, Mobile, AL, and Pensacola, FL), suggesting that the BH circulation pattern can affect surface ozone variability through a large portion of the Gulf Coast.

Passive Microwave Measurements of Salinity: The Gulf Stream Experiment

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Koblinsky, C.; Haken, M.; Howden, S.; Bingham, F.; Hildebrand, Peter H. (Technical Monitor)

2001-01-01

Passive microwave sensors at L-band (1.4 GHz) operating from aircraft have demonstrated that salinity can be measured with sufficient accuracy (I psu) to be scientifically meaningful in coastal waters. However, measuring salinity in the open ocean presents unresolved issues largely because of the much greater accuracy (approximately 0.2 psu) required of global maps to be scientifically viable. The development of a satellite microwave instrument to make global measurements of SSS (Sea Surface Salinity) is the focus of a joint JPL/GSFC/NASA ocean research program called Aquarius. In the summer of 1999 a series of measurements called, The Gulf Stream Experiment, were conducted as part of research at the Goddard Space Flight Center to test the potential for passive microwave remote sensing of salinity in the open ocean. The measurements consisted of airborne microwave instruments together with ships and drifters for surface truth. The study area was a 200 km by 100 km rectangle about 250 km east of Delaware Bay between the continental shelf waters and north wall of the Gulf Stream. The primary passive instruments were the ESTAR radiometer (L-band, H-pol) and the SLFMR radiometer (L-band, V-pol). In addition, the instruments on the aircraft included a C-band radiometer (ACMR), an ocean wave scatterometer (ROWS) and an infrared radiometer (for surface temperature). These instruments were mounted on the NASA P-3 Orion aircraft. Sea surface measurements consisted of thermosalinograph data provided by the R/V Cape Henlopen and the MN Oleander, and data from salinity and temperature sensors on three surface drifters deployed from the R/V Cape Henlopen. The primary experiment period was August 26-September 2, 1999. During this period the salinity field within the study area consisted of a gradient on the order of 2-3 psu in the vicinity of the shelf break and a warm core ring with a gradient of 1-2 psu. Detailed maps were made with the airborne sensors on August 28 and 29 and on September 2 flights were made over the surface drifters to look for effects due to a change in surface roughness resulting from the passage of Hurricane Dennis. Results show a good agreement between the microwave measurements and ship measurements of salinity. The features of the brightness temperature maps correspond well with the features of the salinity field measured by the ship and drifters and a preliminary retrieval of salinity compares well with the ship data.

From geospatial observations of ocean currents to causal predictors of spatio-economic activity using computer vision and machine learning

NASA Astrophysics Data System (ADS)

Popescu, Florin; Ayache, Stephane; Escalera, Sergio; Baró Solé, Xavier; Capponi, Cecile; Panciatici, Patrick; Guyon, Isabelle

2016-04-01

The big data transformation currently revolutionizing science and industry forges novel possibilities in multi-modal analysis scarcely imaginable only a decade ago. One of the important economic and industrial problems that stand to benefit from the recent expansion of data availability and computational prowess is the prediction of electricity demand and renewable energy generation. Both are correlates of human activity: spatiotemporal energy consumption patterns in society are a factor of both demand (weather dependent) and supply, which determine cost - a relation expected to strengthen along with increasing renewable energy dependence. One of the main drivers of European weather patterns is the activity of the Atlantic Ocean and in particular its dominant Northern Hemisphere current: the Gulf Stream. We choose this particular current as a test case in part due to larger amount of relevant data and scientific literature available for refinement of analysis techniques. This data richness is due not only to its economic importance but also to its size being clearly visible in radar and infrared satellite imagery, which makes it easier to detect using Computer Vision (CV). The power of CV techniques makes basic analysis thus developed scalable to other smaller and less known, but still influential, currents, which are not just curves on a map, but complex, evolving, moving branching trees in 3D projected onto a 2D image. We investigate means of extracting, from several image modalities (including recently available Copernicus radar and earlier Infrared satellites), a parameterized representation of the state of the Gulf Stream and its environment that is useful as feature space representation in a machine learning context, in this case with the EC's H2020-sponsored 'See.4C' project, in the context of which data scientists may find novel predictors of spatiotemporal energy flow. Although automated extractors of Gulf Stream position exist, they differ in methodology and result. We shall attempt to extract more complex feature representation including branching points, eddies and parameterized changes in transport and velocity. Other related predictive features will be similarly developed, such as inference of deep water flux long the current path and wider spatial scale features such as Hough transform, surface turbulence indicators and temperature gradient indexes along with multi-time scale analysis of ocean height and temperature dynamics. The geospatial imaging and ML community may therefore benefit from a baseline of open-source techniques useful and expandable to other related prediction and/or scientific analysis tasks.

BIOLOGICAL INTEGRITY IN MID-ATLANTIC COASTAL PLAINS HEADWATER STREAMS

EPA Science Inventory

The objective of this study was to assess the applicability of using landscape variables in conjunction with water quality and benthic data to efficiently estimate stream condition of select headwater streams in the Mid-Atlantic Coastal Plains. Eighty-two streams with riffle sit...

National and regional comparisons between Strahler order and stream size

EPA Science Inventory

Water body size is one of the most important factors affecting the structure and function of aquatic ecosystems. The categorical variable, Strahler stream order, is frequently used as an indirect estimate of stream size. Other indirect estimates of stream size, such as catchmen...

Dune-dammed lakes of the Nebraska Sand Hills: Geologic setting and paleoclimatic implications

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

Loope, D.B.; Swinehart, J.B.

1992-01-01

Within the western half of this grass-stabilized dunefield, about 1,000 interdune lakes are grouped into two clusters here named the Blue and Birdwood lake basins. In the lake basins, those parts of the valley not filled by dune sand are occupied by modern lakes and Holocene lake sediments. The Blue Creek dam is mounded transverse to flow; spill-over of the lake basin takes place over bedrock on the east side of the dam when lake level is 2 m higher than present. The permeability of dune sand prevents massive overflow, and thereby contributes to the integrity and longevity of themore » dam. Preserved lake sediments in the basin indicate that Blue Creek was obstructed prior to 13,000 yr BP, probably during glacial maximum (18,000 yr BP). Extensive peats dated at 1,500-1,000 yr BP lie directly on fluvial sand and gravel along the Calamus River, a stream that presently discharges a nearly constant 350 cfs. These sediments indicate blockage of streams also took place when linear dunes were active in the eastern Sand Hills in Late Holocene time. With the onset of an arid episode, dunes forming an interfluves curtail the severity of runoff events. As the regional water table drops, drainages go dry and dunes move uncontested into blocking positions. Although drainages of the eastern Sand Hills appear to have repeatedly broken through sand-blocked channels, the Blue and Birdwood lake basins are still blocked by Late Pleistocene dune dams. The repeated episodes of stream blockage and interbedded lake sediments and dune sands behind the extant dams record several strong fluctuations in Holocene climate. Recently proposed climatic models indicate that the northward flow of warm, moist air from the Gulf of Mexico is enhanced when the Gulf's surface temperature is low and the Bermuda high is intensified and in a western position. When the Bermuda high moves eastward, the core of the North American continent becomes desiccated.« less

Stream water temperature limits occupancy of salamanders in mid-Atlantic protected areas

USGS Publications Warehouse

Grant, Evan H. Campbell; Wiewel, Amber N. M.; Rice, Karen C.

2014-01-01

Stream ecosystems are particularly sensitive to urbanization, and tolerance of water-quality parameters is likely important to population persistence of stream salamanders. Forecasted climate and landscape changes may lead to significant changes in stream flow, chemical composition, and temperatures in coming decades. Protected areas where landscape alterations are minimized will therefore become increasingly important for salamander populations. We surveyed 29 streams at three national parks in the highly urbanized greater metropolitan area of Washington, DC. We investigated relationships among water-quality variables and occupancy of three species of stream salamanders (Desmognathus fuscus, Eurycea bislineata, and Pseudotriton ruber). With the use of a set of site-occupancy models, and accounting for imperfect detection, we found that stream-water temperature limits salamander occupancy. There was substantial uncertainty about the effects of the other water-quality variables, although both specific conductance (SC) and pH were included in competitive models. Our estimates of occupancy suggest that temperature, SC, and pH have some importance in structuring stream salamander distribution.

Effects of watershed land use and geomorphology on stream low flows during severe drought conditions in the southern Blue Ridge Mountains, Georgia and North Carolina, United States

Treesearch

Katie Price; C. Jackson; Albert Parker; Trond Reitan; John Dowd; Mike Cyterski

2011-01-01

Land use and physiographic variability influence stream low flows, yet their interactions and relative influence remain unresolved. Our objective was to assess the influence of land use and watershed geomorphic characteristics on low-flow variability in the southern Blue Ridge Mountains of North Carolina and Georgia. Ten minute interval discharge data for 35 streams (...

Field study and simulation of diurnal temperature effects on infiltration and variably saturated flow beneath an ephemeral stream

USGS Publications Warehouse

Dudek Ronan, Anne; Prudic, David E.; Thodal, Carl E.; Constantz, Jim

1998-01-01

Two experiments were performed to investigate flow beneath an ephemeral stream and to estimate streambed infiltration rates. Discharge and stream-area measurements were used to determine infiltration rates. Stream and subsurface temperatures were used to interpret subsurface flow through variably saturated sediments beneath the stream. Spatial variations in subsurface temperatures suggest that flow beneath the streambed is dependent on the orientation of the stream in the canyon and the layering of the sediments. Streamflow and infiltration rates vary diurnally: Streamflow is lowest in late afternoon when stream temperature is greatest and highest in early morning when stream temperature is least. The lower afternoon Streamflow is attributed to increased infiltration rates; evapotranspiration is insufficient to account for the decreased Streamflow. The increased infiltration rates are attributed to viscosity effects on hydraulic conductivity from increased stream temperatures. The first set of field data was used to calibrate a two-dimensional variably saturated flow model that includes heat transport. The model was calibrated to (1) temperature fluctuations in the subsurface and (2) infiltration rates determined from measured Streamflow losses. The second set of field data was to evaluate the ability to predict infiltration rates on the basis of temperature measurements alone. Results indicate that the variably saturated subsurface flow depends on downcanyon layering of the sediments. They also support the field observations in indicating that diurnal changes in infiltration can be explained by temperature dependence of hydraulic conductivity. Over the range of temperatures and flows monitored, diurnal stream temperature changes can be used to estimate streambed infiltration rates. It is often impractical to maintain equipment for determining infiltration rates by traditional means; however, once a model is calibrated using both infiltration and temperature data, only relatively inexpensive temperature monitoring can later yield infiltration rates that are within the correct order of magnitude.

NATURAL AND HUMAN FACTORS STRUCTURING FISH ASSEMBLAGES IN WEST VIRGINIA WADEABLE STREAMS

EPA Science Inventory

We surveyed fishes and environmental variables in 119 stream basins to identify natural and anthropogenic factors structuring fish assemblages. We collected fishes and physico-chemical variables using standardized EPA methods and compiled basin characteristics (e.g., land cover)...

Quality of Streams in Johnson County, Kansas, and Relations to Environmental Variables, 2003-07

USGS Publications Warehouse

Rasmussen, Teresa J.; Poulton, Barry C.; Graham, Jennifer L.

2009-01-01

The quality of streams and relations to environmental variables in Johnson County, northeastern Kansas, were evaluated using water, streambed sediment, land use, streamflow, habitat, algal periphyton (benthic algae), and benthic macroinvertebrate data. Water, streambed sediment, and macroinvertebrate samples were collected in March 2007 during base flow at 20 stream sites that represent 11 different watersheds in the county. In addition, algal periphyton samples were collected twice (spring and summer 2007) at one-half of the sites. Environmental data including water and streambed-sediment chemistry data (primarily nutrients, fecal-indicator bacteria, and organic wastewater compounds), land use, streamflow, and habitat data were used in statistical analyses to evaluate relations between biological conditions and variables that may affect them. This report includes an evaluation of water and streambed-sediment chemistry, assessment of habitat conditions, comparison of biological community attributes (such as composition, diversity, and abundance) among sampling sites, placement of sampling sites into impairment categories, evaluation of biological data relative to environmental variables, and evaluation of changes in biological communities and effects of urbanization. This evaluation is useful for understanding factors that affect stream quality, for improving water-quality management programs, and for documenting changing conditions over time. The information will become increasingly important for protecting streams in the future as urbanization continues. Results of this study indicate that the biological quality at nearly all biological sampling sites in Johnson County has some level of impairment. Periphyton taxa generally were indicative of somewhat degraded conditions with small to moderate amounts of organic enrichment. Camp Branch in the Blue River watershed was the only site that met State criteria for full support of aquatic life in 2007. Since 2003, biological quality improved at one rural sampling site, possibly because of changes in wastewater affecting the site, and declined at three urban sites possibly because of the combined effects of ongoing development. Rural streams in the western and southern parts of the county, with land-use conditions similar to those found at the State reference site (Captain Creek), continue to support some organisms normally associated with healthy streams. Several environmental factors contribute to biological indicators of stream quality. The primary factor explaining biological quality at sites in Johnson County was the amount of urbanization upstream in the watershed. Specific conductance of stream water, which is a measure of dissolved solids in water and is determined primarily by the amount of groundwater contributing to streamflow, the amount of urbanization, and discharges from wastewater and industrial sites, was strongly negatively correlated with biological stream quality as indicated by macroinvertebrate metrics. Concentration of polycyclic aromatic hydrocarbons (PAHs) in streambed sediment also was negatively correlated with biological stream quality. Individual habitat variables that most commonly were positively correlated with biological indicators included stream sinuosity, buffer length, and substrate cover diversity. Riffle substrate embeddedness and sediment deposition commonly were negatively correlated with favorable metric scores. Statistical analysis indicated that specific conductance, impervious surface area (a measure of urbanization), and stream sinuosity explained 85 percent of the variance in macroinvertebrate communities. Management practices affecting environmental variables that appear to be most important for Johnson County streams include protection of stream corridors, measures that reduce the effects of impervious surfaces associated with urbanization, reduction of dissolved solids in stream water, reduction of PAHs entering streams and

Multinomial N-mixture models improve the applicability of electrofishing for developing population estimates of stream-dwelling Smallmouth Bass

USGS Publications Warehouse

Mollenhauer, Robert; Brewer, Shannon K.

2017-01-01

Failure to account for variable detection across survey conditions constrains progressive stream ecology and can lead to erroneous stream fish management and conservation decisions. In addition to variable detection’s confounding long-term stream fish population trends, reliable abundance estimates across a wide range of survey conditions are fundamental to establishing species–environment relationships. Despite major advancements in accounting for variable detection when surveying animal populations, these approaches remain largely ignored by stream fish scientists, and CPUE remains the most common metric used by researchers and managers. One notable advancement for addressing the challenges of variable detection is the multinomial N-mixture model. Multinomial N-mixture models use a flexible hierarchical framework to model the detection process across sites as a function of covariates; they also accommodate common fisheries survey methods, such as removal and capture–recapture. Effective monitoring of stream-dwelling Smallmouth Bass Micropterus dolomieu populations has long been challenging; therefore, our objective was to examine the use of multinomial N-mixture models to improve the applicability of electrofishing for estimating absolute abundance. We sampled Smallmouth Bass populations by using tow-barge electrofishing across a range of environmental conditions in streams of the Ozark Highlands ecoregion. Using an information-theoretic approach, we identified effort, water clarity, wetted channel width, and water depth as covariates that were related to variable Smallmouth Bass electrofishing detection. Smallmouth Bass abundance estimates derived from our top model consistently agreed with baseline estimates obtained via snorkel surveys. Additionally, confidence intervals from the multinomial N-mixture models were consistently more precise than those of unbiased Petersen capture–recapture estimates due to the dependency among data sets in the hierarchical framework. We demonstrate the application of this contemporary population estimation method to address a longstanding stream fish management issue. We also detail the advantages and trade-offs of hierarchical population estimation methods relative to CPUE and estimation methods that model each site separately.

Combined impacts of tidal energy extraction and sea level rise in the Gulf of Maine

NASA Astrophysics Data System (ADS)

Hashemi, M. R.; Kresning, B.

2016-12-01

The objective of this study was to assess the combined effects of SLR and tidal energy extraction on the dynamics of tides in the Gulf of Maine in both US and Canadian waters. The dynamics of tides in the Gulf of Maine is dominated by tidal resonance, which generates one of the largest tidal ranges in the world. Further, sea level rise (SLR) is affecting tidal circulations globally, and in the Gulf of Maine. A large tidal energy resource is available in the Gulf of Maine, particularly in the Bay of Fundy, and is expected to be harvested in the future. Currently, more than 6 projects are operational or under development in this region (in both US and Canadian waters). Understanding the far-field impacts of tidal-stream arrays is important for future development of tidal energy extraction. The impacts include possible changes in water elevation, which can potentially increase flooding in coastal areas. Further, SLR can affect tidal energy resources and the impacts of tidal energy extraction during the project lifetime - which is usually more than 25 years. A tidal model of the Gulf of Maine was developed using Regional Ocean Model System (ROMS) at one arcminute scale. An array of turbines were simulated in the model. After validation of the model at NOAA tidal gauge stations and NERACOOS buoys, several scenarios; including SLR scenario, and tidal extraction scenario, were examined. In particular, the results of a recent research was used to assess the impacts of SLR on the boundary of the model domain, which was neglected in previous studies. The results of the impacts of the tidal energy extraction with and without the SLR were presented, and compared with those from literature. This includes the decrease of tidal range and M2 amplitude in Minas Basin due to the 2.5 GW extraction scenario, and possible changes in Massachusetts coastal area. The impacts were compared with the level of uncertainty in the model. It was shown that the impact of SLR on the dynamics of tides is more than those from energy extraction assuming 2.5 GW extraction in Minas Passage.

Insomnia Severity, Subjective Sleep Quality, and Risk for Obstructive Sleep Apnea in Veterans With Gulf War Illness.

PubMed

Chao, Linda L; Abadjian, Linda R; Esparza, Iva L; Reeb, Rosemary

2016-09-01

Despite the fact that sleep disturbances are common in veterans with Gulf War Illness (GWI), there has been a paucity of published sleep studies in this veteran population to date. Therefore, the present study examined subjective sleep quality (assessed with the Pittsburgh Sleep Quality Index), insomnia severity (assessed with the Insomnia Severity Index), and risk for obstructive sleep apnea (assessed with the STOP questionnaire) in 98 Gulf War veterans. Veterans with GWI, defined either by the Kansas or Centers for Disease Control and Prevention criteria, had greater risk for obstructive sleep apnea (i.e., higher STOP scores) than veterans without GWI. This difference persisted even after accounting for potentially confounding demographic (e.g., age, gender) and clinical variables. Veterans with GWI, defined by either the Kansas or Centers for Disease Control and Prevention criteria, also had significantly greater insomnia severity and poorer sleep quality than veterans without GWI (p < 0.05), even after accounting for potentially confounding variables. Furthermore, there were significant, positive correlations between insomnia severity, subjective sleep quality, and GWI symptom severity (p ≤ 0.01). In stepwise linear regression models, insomnia severity significantly predicted GWI status over and above demographic and clinical variables. Together these findings provide good rationale for treating sleep disturbances in the management of GWI. Reprint & Copyright © 2016 Association of Military Surgeons of the U.S.

Statistically extracted fundamental watershed variables for estimating the loads of total nitrogen in small streams

USGS Publications Warehouse

Kronholm, Scott C.; Capel, Paul D.; Terziotti, Silvia

2016-01-01

Accurate estimation of total nitrogen loads is essential for evaluating conditions in the aquatic environment. Extrapolation of estimates beyond measured streams will greatly expand our understanding of total nitrogen loading to streams. Recursive partitioning and random forest regression were used to assess 85 geospatial, environmental, and watershed variables across 636 small (<585 km2) watersheds to determine which variables are fundamentally important to the estimation of annual loads of total nitrogen. Initial analysis led to the splitting of watersheds into three groups based on predominant land use (agricultural, developed, and undeveloped). Nitrogen application, agricultural and developed land area, and impervious or developed land in the 100-m stream buffer were commonly extracted variables by both recursive partitioning and random forest regression. A series of multiple linear regression equations utilizing the extracted variables were created and applied to the watersheds. As few as three variables explained as much as 76 % of the variability in total nitrogen loads for watersheds with predominantly agricultural land use. Catchment-scale national maps were generated to visualize the total nitrogen loads and yields across the USA. The estimates provided by these models can inform water managers and help identify areas where more in-depth monitoring may be beneficial.

Relation of phytoplankton species to ecosystem definition in the northwest Atlantic using remote sensing data

NASA Astrophysics Data System (ADS)

Devred, Emmanuel; Sathyendranath, Shubha; Fuentes-yaco, Cesar; Maass, Heidi; Platt, Trevor

2005-08-01

In this work, we present a new method for dynamic assignment of the boundaries of the ecological provinces of the North West Atlantic. The results are compared with the distribution of diatoms in the study area. Both analyses rely on ocean-colour data for the region. Diatoms were identified using remoteely-sensed data on the basis of their species-dependent absorption characteristics, which were embedded in a simple reflectance model(Sathyendranath et al., 2004). Maps of diatom distributions were produced for the area. Satellite-derived chlorophyll biomass and sea surface temperature (MODIS data) for the same period were used to redefine, in a dynamic way, the static borders of the ecological provinces (Sathyendranath et al., 1995; Longhurst 1998). The analyses were carried on two-week composite images, at different times of the year (April-May, July and October), to examine seasonal variability in the boundaries. The boundaries of provinces and the occurrence of diatoms were spatially coherent. Diatoms were favoured in rich waters on the continental shelf and in cold waters at high latitudes. In provinces labelled as oligotrophic (subtropical gyre and Gulf Stream), very negligible fractions of diatoms were found at any time of the year.

Environmental and anthropogenic factors affecting the probability of occurrence of Oncomegas wageneri (Cestoda: Trypanorhyncha) in the southern Gulf of Mexico.

PubMed

Vidal-Martínez, Víctor M; Torres-Irineo, Edgar; Romero, David; Gold-Bouchot, Gerardo; Martínez-Meyer, Enrique; Valdés-Lozano, David; Aguirre-Macedo, M Leopoldina

2015-11-26

Understanding the environmental and anthropogenic factors influencing the probability of occurrence of the marine parasitic species is fundamental for determining the circumstances under which they can act as bioindicators of environmental impact. The aim of this study was to determine whether physicochemical variables, polyaromatic hydrocarbons or sewage discharge affect the probability of occurrence of the larval cestode Oncomegas wageneri, which infects the shoal flounder, Syacium gunteri, in the southern Gulf of Mexico. The study area included 162 sampling sites in the southern Gulf of Mexico and covered 288,205 km(2), where the benthic sediments, water and the shoal flounder individuals were collected. We used the boosted generalised additive models (boosted GAM) and the MaxEnt to examine the potential statistical relationships between the environmental variables (nutrients, contaminants and physicochemical variables from the water and sediments) and the probability of the occurrence of this parasite. The models were calibrated using all of the sampling sites (full area) with and without parasite occurrences (n = 162) and a polygon area that included sampling sites with a depth of 1500 m or less (n = 134). Oncomegas wageneri occurred at 29/162 sampling sites. The boosted GAM for the full area and the polygon area accurately predicted the probability of the occurrence of O. wageneri in the study area. By contrast, poor probabilities of occurrence were obtained with the MaxEnt models for the same areas. The variables with the highest frequencies of appearance in the models (proxies for the explained variability) were the polyaromatic hydrocarbons of high molecular weight (PAHH, 95 %), followed by a combination of nutrients, spatial variables and polyaromatic hydrocarbons of low molecular weight (PAHL, 5 %). The contribution of the PAHH to the variability was explained by the fact that these compounds, together with N and P, are carried by rivers that discharge into the ocean, which enhances the growth of hydrocarbonoclastic bacteria and the productivity and number of the intermediate hosts. Our results suggest that sites with PAHL/PAHH ratio values up to 1.89 promote transmission based on the high values of the prevalence of O. wageneri in the study area. In contrast, PAHL/PAHH ratio values ≥ 1.90 can be considered harmful for the transmission stages of O. wageneri and its hosts (copepods, shrimps and shoal flounders). Overall, the results indicate that the PAHHs affect the probability of occurrence of this helminth parasite in the southern Gulf of Mexico.

Sediment from the Tigris and Euphrates

NASA Technical Reports Server (NTRS)

2002-01-01

There is a large amount of sediment clearly visible in the true-color image of the Persian Gulf, acquired on November 1, 2001, by the Moderate-resolution Imaging Spectroradiometer (MODIS). Carried by the confluence of the Tigris and Euphrates Rivers (at center), the sediment-laden waters appear light brown where they enter the northern end of the Persian Gulf and then gradually dissipate into turquoise swirls as they drift southward. The nutrients these sediments carry are helping to support a phytoplankton bloom in the region, which adds some darker green hues in the rich kaleidoscope of colors on the surface (see the high resolution image). The confluence of the Tigris and Euphrates Rivers marks the southernmost boundary between Iran (upper right) and Iraq (upper left). South of Iraq are the countries of Kuwait and Saudi Arabia. The red dots indicate the probable locations of fires burning at oil refineries. Thin black plumes of smoke can be seen streaming away from several of these. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

Variable mixer propulsion cycle

NASA Technical Reports Server (NTRS)

Rundell, D. J.; Mchugh, D. P.; Foster, T.; Brown, R. H. (Inventor)

1978-01-01

A design technique, method and apparatus are delineated for controlling the bypass gas stream pressure and varying the bypass ratio of a mixed flow gas turbine engine in order to achieve improved performance. The disclosed embodiments each include a mixing device for combining the core and bypass gas streams. The variable area mixing device permits the static pressures of the core and bypass streams to be balanced prior to mixing at widely varying bypass stream pressure levels. The mixed flow gas turbine engine therefore operates efficiently over a wide range of bypass ratios and the dynamic pressure of the bypass stream is maintained at a level which will keep the engine inlet airflow matched to an optimum design level throughout a wide range of engine thrust settings.

Relation of watershed setting and stream nutrient yields at selected sites in central and eastern North Carolina, 1997-2008

USGS Publications Warehouse

Harden, Stephen L.; Cuffney, Thomas F.; Terziotti, Silvia; Kolb, Katharine R.

2013-01-01

Data collected between 1997 and 2008 at 48 stream sites were used to characterize relations between watershed settings and stream nutrient yields throughout central and eastern North Carolina. The focus of the investigation was to identify environmental variables in watersheds that influence nutrient export for supporting the development and prioritization of management strategies for restoring nutrient-impaired streams. Nutrient concentration data and streamflow data compiled for the 1997 to 2008 study period were used to compute stream yields of nitrate, total nitrogen (N), and total phosphorus (P) for each study site. Compiled environmental data (including variables for land cover, hydrologic soil groups, base-flow index, streams, wastewater treatment facilities, and concentrated animal feeding operations) were used to characterize the watershed settings for the study sites. Data for the environmental variables were analyzed in combination with the stream nutrient yields to explore relations based on watershed characteristics and to evaluate whether particular variables were useful indicators of watersheds having relatively higher or lower potential for exporting nutrients. Data evaluations included an examination of median annual nutrient yields based on a watershed land-use classification scheme developed as part of the study. An initial examination of the data indicated that the highest median annual nutrient yields occurred at both agricultural and urban sites, especially for urban sites having large percentages of point-source flow contributions to the streams. The results of statistical testing identified significant differences in annual nutrient yields when sites were analyzed on the basis of watershed land-use category. When statistical differences in median annual yields were noted, the results for nitrate, total N, and total P were similar in that highly urbanized watersheds (greater than 30 percent developed land use) and (or) watersheds with greater than 10 percent point-source flow contributions to streamflow had higher yields relative to undeveloped watersheds (having less than 10 and 15 percent developed and agricultural land uses, respectively) and watersheds with relatively low agricultural land use (between 15 and 30 percent). The statistical tests further indicated that the median annual yields for total P were statistically higher for watersheds with high agricultural land use (greater than 30 percent) compared to the undeveloped watersheds and watersheds with low agricultural land use. The total P yields also were higher for watersheds with low urban land use (between 10 and 30 percent developed land) compared to the undeveloped watersheds. The study data indicate that grouping and examining stream nutrient yields based on the land-use classifications used in this report can be useful for characterizing relations between watershed settings and nutrient yields in streams located throughout central and eastern North Carolina. Compiled study data also were analyzed with four regression tree models as a means of determining which watershed environmental variables or combination of variables result in basins that are likely to have high or low nutrient yields. The regression tree analyses indicated that some of the environmental variables examined in this study were useful for predicting yields of nitrate, total N, and total P. When the median annual nutrient yields for all 48 sites were evaluated as a group (Model 1), annual point-source flow yields had the greatest influence on nitrate and total N yields observed in streams, and annual streamflow yields had the greatest influence on yields of total P. The Model 1 results indicated that watersheds with higher annual point-source flow yields had higher annual yields of nitrate and total N, and watersheds with higher annual streamflow yields had higher annual yields of total P. When sites with high point-source flows (greater than 10 percent of total streamflow) were excluded from the regression tree analyses (Models 2–4), the percentage of forested land in the watersheds was identified as the primary environmental variable influencing stream yields for both total N and total P. Models 2, 3 and 4 did not identify any watershed environmental variables that could adequately explain the observed variability in the nitrate yields among the set of sites examined by each of these models. The results for Models 2, 3, and 4 indicated that watersheds with higher percentages of forested land had lower annual total N and total P yields compared to watersheds with lower percentages of forested land, which had higher median annual total N and total P yields. Additional environmental variables determined to further influence the stream nutrient yields included median annual percentage of point-source flow contributions to the streams, variables of land cover (percentage of forested land, agricultural land, and (or) forested land plus wetlands) in the watershed and (or) in the stream buffer, and drainage area. The regression tree models can serve as a tool for relating differences in select watershed attributes to differences in stream yields of nitrate, total N, and total P, which can provide beneficial information for improving nutrient management in streams throughout North Carolina and for reducing nutrient loads to coastal waters.

Seasonal changes in the diurnal in-stream nitrate concentration oscillations

NASA Astrophysics Data System (ADS)

Rusjan, S.; Mikoš, M.

2009-04-01

A variability of seasonal changes in the diurnal in-stream NO3-N concentration oscillations was studied through high-frequency measurements of the stream-water's physical, chemical parameters (in-stream NO3-N concentration, water temperature, dissolved oxygen, pH) and hydrometeorological variables (stream discharge, solar radiation) under hydrologically stable conditions. The study was carried out in 2006, within the 42 km2 forested Padež stream watershed in the southwestern part of Slovenia, which is characterized by distinctive hydrogeological settings (flysch) and climate conditions (transitional area between the Mediterranean and continental climate). Fine temporal resolution of the data measured at 15 minute intervals enabled the identification of the main driving factors responsible for the seasonal variability in the diurnal pattern of the streamwater NO3-N concentrations vs. seasonal and diurnal behavior of meteorological and other water chemistry constituents. Seasonal variability of the shifts in daily maximum (up to 6 hours) and minimum NO3-N concentrations (between 1 and 3 hours) and changes in the amplitude of the daily NO3-N concentration oscillations (in order of 0.1-0.3 mg/l-N) offer supplementary evidence of the in-stream NO3-N processing by photoautotrophs. A wavelet analysis was further used to acquire clear, de-noised NO3-N concentration signals on which models in the form of Fourier series were build, reaching R2 values between 0.73 and 0.94. The models can be used to simulate the in-stream NO3-N oscillating signal in order to obtain more accurate assessment of the NO3-N exports from the forested watershed in different seasonal settings, undisturbed by the changing hydrological conditions.

Seasonal Changes in diurnal in-Stream Nitrate Concentration Oscillations

NASA Astrophysics Data System (ADS)

Rusjan, Simon; Mikoš, Matjaž; Mitja, Brilly; Vidmar, Andrej

2010-05-01

A variability of seasonal changes in the diurnal in-stream NO3-N concentration oscillations was studied through high-frequency measurements of the stream-water's physical, chemical parameters (in-stream NO3-N concentration, water temperature, dissolved oxygen, pH) and hydrometeorological variables (stream discharge, solar radiation) under hydrologically stable conditions. The study was carried out in 2006, within the 42 km2 forested Padež stream watershed in the southwestern part of Slovenia, which is characterized by distinctive hydrogeological settings (flysch) and climate conditions (transitional area between the Mediterranean and continental climate). Fine temporal resolution of the data measured at 15 minute intervals enabled the identification of the main driving factors responsible for the seasonal variability in the diurnal pattern of the streamwater NO3-N concentrations vs. seasonal and diurnal behavior of meteorological and other water chemistry constituents. Seasonal variability of the shifts in daily maximum (up to 6 hours) and minimum NO3-N concentrations (between 1 and 3 hours) and changes in the amplitude of the daily NO3-N concentration oscillations (in order of 0.1-0.3 mg/l-N) offer supplementary evidence of the in-stream NO3-N processing by photoautotrophs. A wavelet analysis was further used to acquire clear, de-noised NO3-N concentration signals on which models in the form of Fourier series were build, reaching R2 values between 0.73 and 0.94. The models can be used to simulate the in-stream NO3-N oscillating signal in order to obtain more accurate assessment of the NO3-N exports from the forested watershed in different seasonal settings, undisturbed by the changing hydrological conditions.

Challenges in modelling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

NASA Astrophysics Data System (ADS)

Sedigh Marvasti, S.; Gnanadesikan, A.; Bidokhti, A. A.; Dunne, J. P.; Ghader, S.

2015-07-01

We examine interannual variability of phytoplankton blooms in northwestern Arabian Sea and Gulf of Oman. Satellite data (SeaWIFS ocean color) shows two climatological blooms in this region, a wintertime bloom peaking in February and a summertime bloom peaking in September. A pronounced anti-correlation between the AVISO sea surface height anomaly (SSHA) and chlorophyll is found during the wintertime bloom. On a regional scale, interannual variability of the wintertime bloom is thus dominated by cyclonic eddies which vary in location from one year to another. These results were compared against the outputs from three different 3-D Earth System models. We show that two coarse (1°) models with the relatively complex biogeochemistry (TOPAZ) capture the annual cycle but neither eddies nor the interannual variability. An eddy-resolving model (GFDL CM2.6) with a simpler biogeochemistry (miniBLING) displays larger interannual variability, but overestimates the wintertime bloom and captures eddy-bloom coupling in the south but not in the north. The southern part of the domain is a region with a much sharper thermocline and nutricline relatively close to the surface, in which eddies modulate diffusive nutrient supply to the surface (a mechanism not previously emphasized in the literature). We suggest that for the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies. This is a challenge in the Northern Arabian Sea as it requires capturing the details of the outflow from the Persian Gulf.

The paradox of cooling streams in a warming world: regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

Treesearch

Ivan Arismendi; Sherri L. Johnson; Jason B. Dunham; Roy Haggerty

2012-01-01

Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream...

Prediction of pesticide toxicity in Midwest streams

USGS Publications Warehouse

Shoda, Megan E.; Stone, Wesley W.; Nowell, Lisa H.

2016-01-01

The occurrence of pesticide mixtures is common in stream waters of the United States, and the impact of multiple compounds on aquatic organisms is not well understood. Watershed Regressions for Pesticides (WARP) models were developed to predict Pesticide Toxicity Index (PTI) values in unmonitored streams in the Midwest and are referred to as WARP-PTI models. The PTI is a tool for assessing the relative toxicity of pesticide mixtures to fish, benthic invertebrates, and cladocera in stream water. One hundred stream sites in the Midwest were sampled weekly in May through August 2013, and the highest calculated PTI for each site was used as the WARP-PTI model response variable. Watershed characteristics that represent pesticide sources and transport were used as the WARP-PTI model explanatory variables. Three WARP-PTI models—fish, benthic invertebrates, and cladocera—were developed that include watershed characteristics describing toxicity-weighted agricultural use intensity, land use, agricultural management practices, soil properties, precipitation, and hydrologic properties. The models explained between 41 and 48% of the variability in the measured PTI values. WARP-PTI model evaluation with independent data showed reasonable performance with no clear bias. The models were applied to streams in the Midwest to demonstrate extrapolation for a regional assessment to indicate vulnerable streams and to guide more intensive monitoring.

Concentrations and annual fluxes of sediment-associated chemical constituents from conterminous US coastal rivers using bed sediment data

USGS Publications Warehouse

Horowitz, Arthur J.; Stephens, Verlin C.; Elrick, Kent A.; Smith, James J.

2012-01-01

Coastal rivers represent a significant pathway for the delivery of natural and anthropogenic sediment-associated chemical constituents to the Atlantic, Pacific and Gulf of Mexico coasts of the conterminous USA. This study entails an accounting segment using published average annual suspended sediment fluxes with published sediment-associated chemical constituent concentrations for (1) baseline, (2) land-use distributions, (3) population density, and (4) worldwide means to estimate concentrations/annual fluxes for trace/major elements and total phosphorus, total organic and inorganic carbon, total nitrogen, and sulphur, for 131 coastal river basins. In addition, it entails a sampling and subsequent chemical analysis segment that provides a level of ‘ground truth’ for the calculated values, as well as generating baselines for sediment-associated concentrations/fluxes against which future changes can be evaluated. Currently, between 260 and 270 Mt of suspended sediment are discharged annually from the conterminous USA; about 69% is discharged from Gulf rivers (n = 36), about 24% from Pacific rivers (n = 42), and about 7% from Atlantic rivers (n = 54). Elevated sediment-associated chemical concentrations relative to baseline levels occur in the reverse order of sediment discharges:Atlantic rivers (49%)>Pacific rivers (40%)>Gulf rivers (23%). Elevated trace element concentrations (e.g. Cu, Hg, Pb, Zn) frequently occur in association with present/former industrial areas and/or urban centres, particularly along the northeast Atlantic coast. Elevated carbon and nutrient concentrations occur along both the Atlantic and Gulf coasts but are dominated by rivers in the urban northeast and by southeastern and Gulf coast (Florida) ‘blackwater’ streams. Elevated Ca, Mg, K, and Na distributions tend to reflect local petrology, whereas elevated Ti, S, Fe, and Al concentrations are ubiquitous, possibly because they have substantial natural as well as anthropogenic sources. Almost all the elevated sediment-associated chemical concentrations found in conterminous US coastal rivers are lower than worldwide averages.

What controls channel form in steep mountain streams?

NASA Astrophysics Data System (ADS)

Palucis, M. C.; Lamb, M. P.

2017-07-01

Steep mountain streams have channel morphologies that transition from alternate bar to step-pool to cascade with increasing bed slope, which affect stream habitat, flow resistance, and sediment transport. Experimental and theoretical studies suggest that alternate bars form under large channel width-to-depth ratios, step-pools form in near supercritical flow or when channel width is narrow compared to bed grain size, and cascade morphology is related to debris flows. However, the connection between these process variables and bed slope—the apparent dominant variable for natural stream types—is unclear. Combining field data and theory, we find that certain bed slopes have unique channel morphologies because the process variables covary systematically with bed slope. Multiple stable states are predicted for other ranges in bed slope, suggesting that a competition of underlying processes leads to the emergence of the most stable channel form.

Perpetual Ocean - Gulf Stream

NASA Image and Video Library

2017-12-08

This image shows ocean surface currents around the world during the period from June 2005 through Decmeber 2007. Go here to view a video of this data: www.flickr.com/photos/gsfc/7009056027/ NASA/Goddard Space Flight Center Scientific Visualization Studio NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Oceanographic Interpretation of Apollo Photographs. Coastal Oceanographic and Sedimentologic Interpretation of Apollo 9 Space Photographs; Carolina's Continental Shelf, USA

NASA Technical Reports Server (NTRS)

Mairs, R. L.

1971-01-01

Apollo 9 photographs, color band separations, and oceanographic and meteorological data are used in the study of the origin, movement, and dissipation of masses of discolored water near the shores of North and South Carolina. A model has been developed incorporating jet theory, climatology, currents, surface temperatures, color separations, and other oceanographic data to explain the processes involved in the life cycle of the discolored water masses. Special treatment is afforded the Gulf Stream boundary definition and the Cape Hatteras oceanographic barrier.

Satellite altitude determination uncertainties

NASA Technical Reports Server (NTRS)

Siry, J. W.

1972-01-01

Satellite altitude determination uncertainties will be discussed from the standpoint of the GEOS-C satellite, from the longer range viewpoint afforded by the Geopause concept. Data are focused on methods for short-arc tracking which are essentially geometric in nature. One uses combinations of lasers and collocated cameras. The other method relies only on lasers, using three or more to obtain the position fix. Two typical locales are looked at, the Caribbean area, and a region associated with tracking sites at Goddard, Bermuda and Canada which encompasses a portion of the Gulf Stream in which meanders develop.

Operations summary for the convection and moisture experiment (CAMEX)

NASA Technical Reports Server (NTRS)

Griffin, V. L.; Guillory, A. R.; Susko, M.; Arnold, J. E.

1994-01-01

During the fall of 1993, NASA sponsored a field program called the Convection and Moisture Experiment (CAMEX) at Wallops Island, Virginia. CAMEX was a multidisciplinary experiment design to measure the three dimensional moisture fields over Wallops Island and to characterize the multifrequency radiometric signature of tropical convection over the Gulf Stream and southeastern Atlantic Ocean. This document summarizes the daily CAMEX activities, including ground and aircraft (NASA ER-2) operations, and includes 'quick-look' summaries of data acquisition along with data examples provided by the various CAMEX PI's.

Horizontal and Vertical Structure of Velocity, Potential Vorticity and Energy in the Gulf Stream.

DTIC Science & Technology

1985-02-01

before. Finally, the equation for heat conservation, using standard . - notation, is: T u + w 3 RHS (2-15) at ax ay + where the RHS may include source and...may be rewritten: a o f 0 2 ah 30i .. .iaT + -R2 -+ w2! = RHS . at goz az Under an assumption of negligible mixing (i.e., RHS is small), vertical...Hk( + v.) Kk - 2i + 2 2 --k (k + N - P available potential energy EKE eddy kinetic energy MKE - mean kinetic energy RHS - right hand side LHS -left

Are macroinvertebrate functional traits useful in differentiating hydrologically variable small piedmont streams and their recovery from drought?

EPA Science Inventory

We quantified benthic macroinvertebrates in six small (1st order) Alabama piedmont streams from 1994-1998. Streams spanned a gradient of hydrologic permanence from typically intermittent to perennial, the degree of permanence for a given stream depending on water year. Initial sa...

Hydrodynamic trapping in the Cretaceous Nahr Umr lower sand of the North Area, Offshore Qatar

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

Wells, P.R.A.

A hydrodynamic model is described to account for oil and gas occurrences in the Cretaceous of offshore Qatar, in the Arabian Gulf. Variable and inconsistent fluid levels and variable formation water potentials and salinities cannot be explained by combinations of stratigraphic and structural trapping. Indeed, there is no structural closure to the southwest of the oil and gas accumulations. The water-potential and salinity data and oil distribution are consistent with this model and indicate that a vigorous hydrodynamic system pervades the Cretaceous of the Arabian Gulf region. Extensive upward cross-formational discharge is taking place in the North Area. This cross-formationmore » water flow could be partly responsible for localized leaching and reservoir enhancement in the chalky limestones.« less

Impacts of climate change and variability on transportation systems and infrastructure : Gulf Coast study, phase 2 : task 2 : climate variability and change in Mobile, Alabama.

DOT National Transportation Integrated Search

2012-09-01

Despite increasing confidence in global climate change projections in recent years, projections of : climate effects at local scales remains scarce. Location-specific risks to transportation systems : imposed by changes in climate are not yet well kn...

Interannual variability in the extent of wetland-stream connectivity within the Prairie Pothole Region

Treesearch

Melanie Vanderhoof; Laurie Alexander

2016-01-01

The degree of hydrological connectivity between wetland systems and downstream receiving waters can be expected to influence the volume and variability of stream discharge. The Prairie Pothole Region contains a high density of depressional wetland features, a consequence of glacial retreat. Spatial variability in wetland density, drainage evolution, and precipitation...

National Hydrography Dataset (NHD)

USGS Publications Warehouse

,

2001-01-01

The National Hydrography Dataset (NHD) is a feature-based database that interconnects and uniquely identifies the stream segments or reaches that make up the nation's surface water drainage system. NHD data was originally developed at 1:100,000 scale and exists at that scale for the whole country. High resolution NHD adds detail to the original 1:100,000-scale NHD. (Data for Alaska, Puerto Rico and the Virgin Islands was developed at high-resolution, not 1:100,000 scale.) Like the 1:100,000-scale NHD, high resolution NHD contains reach codes for networked features and isolated lakes, flow direction, names, stream level, and centerline representations for areal water bodies. Reaches are also defined to represent waterbodies and the approximate shorelines of the Great Lakes, the Atlantic and Pacific Oceans and the Gulf of Mexico. The NHD also incorporates the National Spatial Data Infrastructure framework criteria set out by the Federal Geographic Data Committee.

Interannual variability of soft-bottom macrobenthic communities of the NW Gulf of Mexico in relationship to the Deepwater Horizon oil spill.

PubMed

Salcedo, Diana L; Soto, Luis A; Estradas-Romero, Alejandro; Botello, Alfonso V

2017-01-30

A 3-year research program was undertaken to assess potential environmental disturbance caused by the Deepwater Horizon oil spill to the soft-bottom macrobenthic communities within Mexican waters of the northwestern Gulf of Mexico. Community properties and temporal/spatial variability were analyzed besides toxicant parameters such as hydrocarbons and trace-metals. Overall infaunal density increased, taxa proportion changed, and small-size opportunistic organisms prevailed throughout the study. Annual abundance-biomass comparison (ABC) curves revealed progressive stress scenarios from moderate to severe. Concentrations of vanadium, nickel, cobalt, PAHs and AHs increased gradually over time. However, low correlations between benthic density and biogeochemical variables were determined. Initially, sedimentary properties were the main drivers of benthic community structure; subsequently, nickel, vanadium and PAHs, indicative of anthropogenic effect, were highlighted. Interannual variability in the macroinfauna was attributed to the synergy of several environmental factors. Undoubtedly, compounds derived from fossil fuels had a significant disturbance role, but their source remains uncertain. Copyright © 2016 Elsevier Ltd. All rights reserved.

Disparity in ST-segment Elevation Myocardial Infarction Practices and Outcomes in Arabian Gulf Countries (Gulf COAST Registry)

PubMed Central

Zubaid, Mohammad; Rashed, Wafa; Alsheikh-Ali, Alawi A.; Garadah, Taysir; Alrawahi, Najib; Ridha, Mustafa; Akbar, Mousa; Alenezi, Fahad; Alhamdan, Rashed; Almahmeed, Wael; Ouda, Hussam; Al-Mulla, Arif; Baslaib, Fahad; Shehab, Abdulla; Alnuaimi, Abdulla; Amin, Haitham

2017-01-01

Objectives: The objective of this study is to describe contemporary management and 1-year outcomes of patients hospitalized with ST-segment elevation myocardial infarction (STEMI) in Arabian Gulf countries. Methods: Data of patients admitted to 29 hospitals in four Gulf countries [Bahrain, Kuwait, Oman, United Arab Emirates (UAE)] with the diagnosis of STEMI were analyzed from Gulf locals with acute coronary syndrome (ACS) events (Gulf COAST) registry. This was a longitudinal, observational registry of consecutive citizens, admitted with ACS from January 2012 to January 2013. Patient management and outcomes were analyzed and compared between the four countries. Results: A total of 1039 STEMI patients were enrolled in Gulf COAST Registry. The mean age was 58 years, and there was a high prevalence of diabetes (47%). With respect to reperfusion, 10% were reperfused with primary percutaneous coronary intervention, 66% with fibrinolytic therapy and 24% were not reperfused. Only one-third of patients who received fibrinolytic therapy had a door-to-needle time of 30 min or less. The in-hospital mortality rate was 7.4%. However, we noted a significant regional variability in mortality rate (3.8%-11.9%). In adjusted analysis, patients from Oman were 4 times more likely to die in hospital as compared to patients from Kuwait. Conclusions: In the Gulf countries, fibrinolytic therapy is the main reperfusion strategy used in STEMI patients. Most patients do not receive this therapy according to timelines outlined in recent practice guidelines. There is a significant discrepancy in outcomes between the countries. Quality improvement initiatives are needed to achieve better adherence to management guidelines and close the gap in outcomes. PMID:28706594

LARGE-SCALE PATTERNS OF STREAMFLOW DISTURBANCE AND FISH COMMUNITIES IN UPPER MISSOURI RIVER BASIN, USA

EPA Science Inventory

Patterns of streamflow variability are likely to be a major organizing feature of the habitat template for stream fishes. Functional organization of stream communities has been linked to streamflow, especially to patterns of flow variability that describe the physical disturbanc...

LARGE-SCALE PATTERNS OF STREAMFLOW DISTURBANCE AND FISH ASSEMBLAGES IN UPPER MISSOURI RIVER BASIN, USA

EPA Science Inventory

Patterns of streamflow variability are likely to be a major organizing feature of the habitat template for stream fishes. Ecological organization of stream communities has been linked to streamflow, especially to patterns of flow variability that describe the physical disturbanc...

The Role of Ocean Currents in the Temperature Selection of Plankton: Insights from an Individual-Based Model

PubMed Central

Hellweger, Ferdi L.; van Sebille, Erik; Calfee, Benjamin C.; Chandler, Jeremy W.; Zinser, Erik R.; Swan, Brandon K.; Fredrick, Neil D.

2016-01-01

Biogeography studies that correlate the observed distribution of organisms to environmental variables are typically based on local conditions. However, in cases with substantial translocation, like planktonic organisms carried by ocean currents, selection may happen upstream and local environmental factors may not be representative of those that shaped the local population. Here we use an individual-based model of microbes in the global surface ocean to explore this effect for temperature. We simulate up to 25 million individual cells belonging to up to 50 species with different temperature optima. Microbes are moved around the globe based on a hydrodynamic model, and grow and die based on local temperature. We quantify the role of currents using the “advective temperature differential” metric, which is the optimum temperature of the most abundant species from the model with advection minus that from the model without advection. This differential depends on the location and can be up to 4°C. Poleward-flowing currents, like the Gulf Stream, generally experience cooling and the differential is positive. We apply our results to three global datasets. For observations of optimum growth temperature of phytoplankton, accounting for the effect of currents leads to a slightly better agreement with observations, but there is large variability and the improvement is not statistically significant. For observed Prochlorococcus ecotype ratios and metagenome nucleotide divergence, accounting for advection improves the correlation significantly, especially in areas with relatively strong poleward or equatorward currents. PMID:27907181

Geomorphic effectiveness of a long profile shape and the role of inherent geological controls in the Himalayan hinterland area of the Ganga River basin, India

NASA Astrophysics Data System (ADS)

Sonam; Jain, Vikrant

2018-03-01

Long profiles of rivers provide a platform to analyse interaction between geological and geomorphic processes operating at different time scales. Identification of an appropriate model for river long profile becomes important in order to establish a quantitative relationship between the profile shape, its geomorphic effectiveness, and inherent geological characteristics. This work highlights the variability in the long profile shape of the Ganga River and its major tributaries, its impact on stream power distribution pattern, and role of the geological controls on it. Long profile shapes are represented by the sum of two exponential functions through the curve fitting method. We have shown that coefficients of river long profile equations are governed by the geological characteristics of subbasins. These equations further define the spatial distribution pattern of stream power and help to understand stream power variability in different geological terrains. Spatial distribution of stream power in different geological terrains successfully explains spatial variability in geomorphic processes within the Himalayan hinterland area. In general, the stream power peaks of larger rivers lie in the Higher Himalaya, and rivers in the eastern hinterland area are characterised by the highest magnitude of stream power.

Hydrographic Variability off the Coast of Oman

NASA Astrophysics Data System (ADS)

Belabbassi, L.; Dimarco, S. F.; Jochens, A. E.; Al Gheilani, H.; Wang, Z.

2010-12-01

Data from hydrographic transects made in 2001 and 2002 and between 2007 and 2009 were obtained from the Oman Ministry of Fisheries Wealth. Property-depth plots of temperature, salinity, and dissolved oxygen were produced for all transects and in all months for which data were available. These were analyzed for temporal and spatial variability. For all transects, there exist large variability on various timescales, with strong spatial variability. Two common features that are seen in the hydrographic data sets are the Persian Gulf Water (PGW) and a layer of continuous low oxygen concentrations in the lower part of the water column. Plots of salinity produced for transects located in the northern part of the Gulf of Oman show a one-unit increase in salinity of the water at the bottom of deepest station during the months of August and September as compared to the other months. Similarly, cross-shelf contour plots of temperature shows an increase in water temperature near the bottom station during the months of August and September. These indicate the presence of the PGW outflow in the northern part of the Gulf of Oman. For dissolved oxygen distributions, hydrographic transects that did not extend far offshore show monthly differences in the presence of water with low oxygen concentrations. For transects that do extend far offshore and also show a layer of low oxygen water throughout the year, there is generally a monthly difference on whether this water is found close to the surface or deeper in the water column. The variability seen in the data could only be explained by comparing these data to data collected from the real time cable ocean observing system installed by Lighthouse R &D Enterprise in the Oman Sea and the Arabian Sea in 2005. The analysis of these data reveal that the variability observed is related to processes such as ocean conditions, monsoonal cycle, and extreme weather events.

On the predictability of high water level along the US East Coast: can the Florida Current measurement be an indicator for flooding caused by remote forcing?

NASA Astrophysics Data System (ADS)

Ezer, Tal; Atkinson, Larry P.

2017-06-01

Recent studies show that in addition to wind and air pressure effects, a significant portion of the variability of coastal sea level (CSL) along the US East Coast can be attributed to non-local factors such as variations in the Gulf Stream and the North Atlantic circulation; these variations can cause unpredictable coastal flooding. The Florida Current transport (FCT) measurement across the Florida Straits monitors those variations, and thus, the study evaluated the potential of using the FCT as an indicator for anomalously high water level along the coast. Hourly water level data from 12 tide gauge stations over 12 years are used to construct records of maximum daily water levels (MDWL) that are compared with the daily FCT data. An empirical mode decomposition (EMD) approach is used to divide the data into high-frequency modes (periods T < ˜30 days), middle-frequency modes (˜30 days < T < ˜90 days), and low-frequency modes (˜90 days < T < ˜1 year). Two predictive measures are tested: FCT and FCT change (FCC). FCT is anti-correlated with MDWL in high-frequency modes but positively correlated with MDWL in low-frequency modes. FCC on the other hand is always anti-correlated with MDWL for all frequency bands, and the high water signal lags behind FCC for almost all stations, thus providing a potential predictive skill (i.e., whenever a weakening trend is detected in the FCT, anomalously high water is expected along the coast over the next few days). The MDWL-FCT correlation in the high-frequency modes is maximum in the lower Mid-Atlantic Bight, suggesting influence from the meandering Gulf Stream after it separates from the coast. However, the correlation in low-frequency modes is maximum in the South Atlantic Bight, suggesting impact from variations in the wind pattern over subtropical regions. The middle-frequency and low-frequency modes of the FCT seem to provide the best predictor for medium to large flooding events; it is estimated that ˜10-25% of the sea level variability in those modes can be attributed to variations in the FCT. An example from Hurricane Joaquin (September-October, 2015) demonstrates how an offshore storm that never made landfall can cause a weakening of the FCT and unexpected high water level and flooding along the US East Coast. A regression-prediction model based on the MDWL-FCT correlation shows some skill in estimating high water levels during past storms; the water level prediction is more accurate for slow-moving and offshore storms than it is for fast-moving storms. The study can help to improve water level prediction since current storm surge models rely on local wind but may ignore remote forcing.

Variable cycle engines for advanced supersonic transports

NASA Technical Reports Server (NTRS)

Howlett, R. A.; Kozlowski, H.

1975-01-01

Variable Cycle Engines being studied for advanced commercial supersonic transports show potential for significant environmental and economic improvements relative to 1st generation SST engines. The two most promising concepts are: a Variable Stream Control Engine and a Variable Cycle Engine with a rear flow-control valve. Each concept utilizes variable components and separate burners to provide independent temperature and velocity control for two coannular flow streams. Unique fuel control techniques are combined with cycle characteristics that provide low fuel consumption, similar to a turbojet engine, for supersonic operation. This is accomplished while retaining the good subsonic performance features of a turbofan engine. A two-stream coannular nozzle shows potential to reduce jet noise to below FAR Part 36 without suppressors. Advanced burner concepts have the potential for significant reductions in exhaust emissions. In total, these unique engine concepts have the potential for significant overall improvements to the environmental and economic characteristics of advanced supersonic transports.

Photophysiological and light absorption properties of phytoplankton communities in the river-dominated margin of the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Chakraborty, Sumit; Lohrenz, Steven E.; Gundersen, Kjell

2017-06-01

Spatial and temporal variability in photophysiological properties of phytoplankton were examined in relationship to phytoplankton community composition in the river-dominated continental margin of the northern Gulf of Mexico (NGOM). Observations made during five research cruises in the NGOM included phytoplankton photosynthetic and optical properties and associated environmental conditions and phytoplankton community structure. Distinct patterns of spatial and temporal variability in photophysiological parameters were found for waters dominated by different phytoplankton groups. Photophysiological properties for locations associated with dominance by a particular group of phytoplankton showed evidence of photoacclimation as reflected by differences in light absorption and pigment characteristics in relationship to different light environments. The maximum rate of photosynthesis normalized to chlorophyll (PmaxB) was significantly higher for communities dominated (>60% biomass) by cyanobacteria + prochlorophyte (cyano + prochl). The initial slope of the photosynthesis-irradiance (P-E) curve normalized to chlorophyll (αB) was not clearly related to phytoplankton community structure and no significant differences were found in PmaxB and αB between different geographic regions. In contrast, maximum quantum yield of carbon fixation in photosynthesis (Φcmax) differed significantly between regions and was higher for diatom-dominated communities. Multiple linear regression models, specific for the different phytoplankton communities, using a combination of environmental and bio-optical proxies as predictor variables showed considerable promise for estimation of the photophysiological parameters on a regional scale. Such an approach may be utilized to develop size class-specific or phytoplankton group-specific primary productivity models for the NGOM.