Search results

Title: Mapping marine habitats with high resolution sidescan sonar,
Description: The application of marine geophysics and GIS techniques to the characterization of benthic habitats has increased the ability of fisheries managers to assess distribution and habitat types beyond common practices. We report upon a 150 kHz sidescan sonar survey offshore of Kruzof Island, Alaska undertaken to characterize rockfish (Sebastes) habitat. Using GIS, MapGrafix and Map*Factory we determined the percentage of seafloor cover that exists in our survey area. Bathymetry in the study area was determined with sidescan interferometry. All XYZ data were gridded using Surfer and plotted in shaded relief, bathymetric contour, and 3-dimensional formats. Contoured bathymetry was used as an overlay in MapGrafix. Small sub-areas were extracted from the bathymetric data for closer study, and gridded in Surfer. Areas of the mosaic where backscatter patterns were not distinct were verified with hand samples and video collected with the submersible Delta. The use of submersibles for verification of interpreted lithologies and surface textures enables a high degree of accuracy for the interpretations. Lithotypes were lumped into larger groups based on morphology and fish associations with different morphologies verified using the submersible. The accuracy of digital maps from high-resolution sidescan sonar data allows a close quantification of the areal extents of these important features, directing the application of management strategies to critical areas., Cited By (since 1996):24, Oceanography, CODEN: OCACD, ,
Author: McRea Jr., Greene, O'Connell, Wakefield
Date: 1999-01-01T00:00:00Z

Title: Trace elements and primary production: Problems, effects and solutions,
Description: The measurement of primary production in the ocean is basic to biological oceanographic processes. Factors which control primary production are varied, but include micronutrients (i. e. , N and P) in sufficient supply, as well as many nanonutrients such as Cu, Mn and Zn. High levels of many of these trace constituents are toxic. Recent studies have shown that ambient concentrations of a number of nanonutrients in sea water are lower by an order of magnitude than previously believed., Cited By (since 1996):1, Oceanography, CODEN: NCSFD, ,
Author: Knauer, Martin
Date: 1983-01-01T00:00:00Z

Title: What controls dissolved iron concentrations in the world ocean?,
Description: Dissolved (<0.4 μm) iron has been measured in 354 samples at 30 stations in the North and South Pacific, Southern Ocean and North Atlantic by the Trace Metals Laboratory at Moss Landing Marine Laboratories. These stations are all more than 50 km from a continental margin. The global distribution of dissolved iron, which is derived from these profiles, is remarkable for several reasons. The dissolved iron profiles have a uniform shape with a nutrient-like profile at each station. Concentrations at the surface are all <0.2 nmol kg-1 and average 0.07 nmol kg-1. Below 500 m, the average concentration is 0.76 nmol kg-1. The largest value in the data set is 1.38 nmol kg-1. There is no inter-ocean fractionation, which is unique for an element with a nutrient-like profile. Published estimates of the iron residence time are on the order of 100 to 200 yr, indicative of rapid removal. Other elements with such short residence times are characterized by vertical profiles that decrease with depth and deep concentrations that decrease with age as water passes from the Atlantic to the Pacific. This is not the case for iron. The largest horizontal changes in dissolved iron are observed in gradients from the continental margin. There is only a factor of three difference between the minimum (0.4 nmol kg-1) and maximum (1.3 nmol kg-1) value in the data set at a depth near 750 m, where variability is at a maximum. The minimum concentrations are found at stations in the remote central Pacific and the maximum values occur at stations adjacent to the continental margin. The major source of iron in the deep sea is generally aeolian deposition. Integrated (surface to 500 m) concentrations of iron at each station are only weakly correlated with the aeolian iron deposition flux, however. This contrasts with other elements such as lead that also have strong atmospheric sources. These observations lead us to conclude that the nutrient-like profile is maintained by a mechanism that reduces the scavenging rate of dissolved iron at concentrations less than 0.6 nmol kg-1. This mechanism may be complexation by strong iron binding ligands, which have been found in both the Atlantic and Pacific at concentrations near 0.6 nM. This apparent solubility would act to diminish inter-ocean fractionation. It would allow a nutrient-like profile to develop before scavenging began to remove iron. In order to test the concept, we developed a numerical model to make quantitative predictions of dissolved iron concentrations from place to place. The dissolved iron source in the ocean interior is remineralization from sinking particulate organic matter. Scavenging removes dissolved iron only at concentrations greater than the apparent solubility. The only geographically variable parameter in the model is the export flux of carbon from the surface layer, which carries iron with it. The model generated dissolved iron profiles, based on measured or estimated values of the carbon export flux, are in remarkable agreement with the observed profiles at all stations from the North Atlantic through the Southern Ocean to the North Pacific., Cited By (since 1996):386, CODEN: MRCHB, Oceanography, , ,
Author: Johnson, Michael Gordon, Coale
Date: 1997-01-01T00:00:00Z

Title: Establishing an objective basis for image compositing in satellite oceanography,
Description: This study strives to establish an objective basis for image compositing in satellite oceanography. Image compositing is a powerful technique for cloud filtering that often emphasizes cloud clearing at the expense of obtaining synoptic coverage. Although incomplete cloud removal in image compositing is readily apparent, the loss of synopticity, often, is not. Consequently, the primary goal of image compositing should be to obtain the greatest amount of cloud-free coverage or clarity in a period short enough that synopticity, to a significant degree, is preserved. To illustrate the process of image compositing and the problems associated with it, we selected a region off the coast of California and constructed two 16-day image composites, one, during the spring, and the second, during the summer of 2006, using Advanced Very High Resolution Radiometer (AVHRR) InfraRed (IR) satellite imagery. Based on the results of cloud clearing for these two 16-day sequences, rapid cloud clearing occurred up to day 4 or 5, followed by much slower cloud clearing out to day 16, suggesting an explicit basis for the growth in cloud clearing. By day 16, the cloud clearing had, in most cases, exceeded 95%. Based on these results, a shorter compositing period could have been employed without a significant loss in clarity. A method for establishing an objective basis for selecting the period for image compositing is illustrated using observed data. The loss in synopticity, which, in principle, could be estimated from pattern correlations between the images in the composite, was estimated from a separate time series of SST since the loss of synopticity, in our approach, is only a function of time. The autocorrelation function of the detrended residuals provided the decorrelation time scale and the basis for the decay process, which, together, define the loss of synopticity. The results show that (1) the loss of synopticity and the gain in clarity are inversely related, (2) an objective basis for selecting a compositing period corresponds to the day number where the decay and growth curves for synopticity and clarity intersect, and (3), in this case, the point of intersection occurred 3.2 days into the compositing period. By applying simple mathematics it was shown that the intersection time for the loss in synopticity and the growth in clarity is directly proportional to the initial conditions required to specify the clarity at the beginning of the compositing period, and inversely proportional to the sum of the rates of growth for clarity and the loss in synopticity. Finally, we consider these results to be preliminary in nature, and, as a result, hope that future work will bring forth significant improvements in the approach outlined in this study. © 2009 Elsevier Inc. All rights reserved., Cited By (since 1996):3, Oceanography, CODEN: RSEEA, ,
Author: Breaker, Armstrong, Endris
Date: 2010-01-01T00:00:00Z

Title: Cadmium flux in Los Angeles/Long Beach harbours and at sites along the California continental margin,
Description: Fluxes of dissolved cadmium were measured in situ using benthic flux chambers at stations in Los Angeles/Long Beach harbour and at sites on the California continental margin. Cadmium fluxes ranged from -0.212 to 0.118 μmol m-2 d-1 indicating that Cd flux may either be into or out of sediments. Correlations between Cd flux and carbon oxidation rate and between carbon oxidation rate and sulfate reduction indicate that anaerobic microbial degradation was the major process controlling both the sign and the magnitude of cadmium fluxes at stations in Los Angeles and Long Beach harbours. A simple box model based on sediment fluxes and water column concentrations indicates cadmium has a residence time of 47 days within the Los Angeles/Long Beach harbour system, similar to the hydraulic residence time. Sedimentary flux is, therefore, sufficient to account for water column cadmium concentration in inner harbour areas, suggesting that the sediments are the dominant source and sink of cadmium in these areas of the harbour. Comparison of the cadmium: phosphate ratio for the Los Angeles/Long Beach harbour water column with those reported for the northeast Pacific suggests that distributions of Cd in the study area were elevated over expected values but appear to be dominated by natural physical and biogeochemical processes. © 2001 Academic Press., Cited By (since 1996):9, Oceanography, CODEN: ECSSD, ,
Author: Colbert, Coale, Berelson, Johnson
Date: 2001-01-01T00:00:00Z

Title: A Late Pleistocene time-series of bottom-current speed in the Vema Channel,
Description: A coarsening of the mean particle size of the carbonate-free silt fraction from sea-floor samples below 4000 m in the Vema Channel has been used to separate high-velocity Antarctic Bottom Water (AABW) from the overlying, slower North Atlantic Deep Water (NADW). A time-series of fluctuations in bottom-current speed within the modern AABW/NADW transition zone was examined by determining the particle-size distribution of sediments from eight gravity cores with a high-resolution stratigraphy for the past 250 kyrs. The bottom-current paleospeed was inferred from a correlation of particle size in seafloor samples with mean current speed from nearby current-meters. The mean bottom-current speed at depths comparable to modern AABW was highest (7-10 cm/s) during interglacial to glacial transitions corresponding to the oxygen isotopic stage 6/7 and 4/5 boundaries and at present. The mean bottom-current speed at depths comparable to modern NADW was nearly uniform for most of the past 250 kyrs except during glacial oxygen isotopic stage 2 when the speed dropped to 2 cm/s, or one-half of the present speed. The application of the "calibrated" particle-size method to examine bottom-current paleospeed allows testing of paleoceanographic models which rely on assumptions or inferences of changes in bottom-water production rate during the late Pleistocene paleoclimatic fluctuations. © 1986., Cited By (since 1996):17, CODEN: PPPYA, , , Oceanography
Author: Ledbetter
Date: 1986-01-01T00:00:00Z

Title: Direct ultraviolet spectrophotometric determination of total sulfide and iodide in natural waters,
Description: A technique is described that allows the determination of total dissolved sulfide in natural waters using direct ultraviolet detection of the HS- ion. The concentration of bisulfide is determined by measuring absorption from 214 to 300 nm and then deconvolution of the HS- spectra from the complex spectrum of natural fluids. A nonlinear least-squares fitting approach is used for the deconvolution. At a pH near 8, where >95% of total sulfide is present as HS-, the results are indistinguishable from total sulfide measured using the methylene blue method in a wide range of sample types and matrixes including freshwater from groundwater wells, marine hydrothermal vent fluids, and marine sediment porewaters. The method allows simultaneous determination of other UV-absorbing ions, including nitrate, bromide, and iodide, in samples with low total sulfide concentrations. Bisulfide concentrations can be determined in samples with low background absorption, such as well water and hydrothermal fluids, with a detection limit of <1 μM. The detection limit for bisulfide in sediment porewaters that have a high organic loading, which produces background absorbances of ∼0.5 A at 260 nm in a 1-cm cuvette, is 5 μM. The only chemical manipulation required is buffering acidic samples to pH > 7 and filtration of particulate-rich samples., Cited By (since 1996):36, Oceanography, CODEN: ANCHA, ,
Author: Guenther, Johnson, Coale
Date: 2001-01-01T00:00:00Z

Title: Spatial and habitat-rased variations in total and methyl mercury concentrations in surficial sediments in the San Francisco Bay-Delta,
Description: Recent studies indicate significant amounts of mercury (Hg) are annually transported into the San Francisco Bay-Delta (Bay-Delta) as a result of historic gold and Hg mining activities. We examined temporal and spatial variation in concentrations of total Hg (HgT) and monomethylmercury (MMHg) in surficial sediments of various ecosystem types in the Bay-Delta. We sampled surficial sediments across the Bay-Delta system and found HgT sediment concentrations in the central Delta were generally 100-200 ng g -1 and increased westward through Suisun Bay to 250-350 ng g -1. MMHg concentrations in the central Delta were between 1 and 3 ng g-1, while those in sediments in the perimeter waterways and adjacent bays were less than 1 ng g-1. Six sites were monitored monthly for over a year to identify seasonal changes in Hg sediment concentrations. Hg T sediment concentrations ranged from 48 to 382 ng g-1 and varied as a function of location not season. However, MMHg concentrations varied seasonally, increasing from 1 ng g-1 during winter months to 6 ng g-1 during spring and summer. Transects conducted at three marshes in the central Delta revealed MMHg sediment concentrations of 4-8 ng g-1at the interior and 2 ng g-1 at the exterior of the marshes. Habitat type was a major factor controlling MMHg concentration and the MMHg to HgT ratio in sediments of the Bay-Delta. MMHg was significantly correlated to HgT (r2 = 0.49) in marsh sediments. © 2007 American Chemical Society., Cited By (since 1996):24, Oceanography, CODEN: ESTHA, ,
Author: Heim, Coale, Stephenson, Choe, Gill, Foe
Date: 2007-01-01T00:00:00Z

Title: Continental-shelf sediment as a primary source of iron for coastal phytoplankton,
Description: The availability of iron, an essential nutrient, controls rates of phytoplankton primary productivity in the open-ocean, upwelling ecosystems of the equatorial Pacific. Upwelling injects large amounts of macronutrients into the euphotic zone of eastern boundary currents, such as the California Current System (CCS), where iron can become the limiting factor on productivity. Iron addition to samples from some areas of the CCS has been shown to increase rates of biomass production, but the processes that control iron availability in these systems remain poorly understood. Here we report measurements of dissolvable iron (that is, dissolved plus leachable iron at pH 3) in transects across the CCS in March of 1997 and 1998. We found high concentrations of iron in 1997 during strong upwelling conditions. During the 1998 El Nino, the concentration of dissolvable iron in surface waters was low, even though that year was marked by high river flow and low offshore salinity. These results indicate that the primary source of iron in the CCS is resuspension of particles in the benthic boundary layer, followed by upwelling of this iron-rich water, rather than direct riverine input. This source of iron must be an essential but variable component of the high productivity found in upwelling ecosystems., Cited By (since 1996):172 Oceanography, CODEN: NATUA, ,
Author: Johnson, Chavez, Friederich
Date: 1999-01-01T00:00:00Z

Title: Estimating rates of acceleration based on the 157-year record of sea level from San Francisco, California, U.S.A.
Description: Breaker, L.C. and Ruzmaikin, A., 2013. Estimating rates of acceleration based on the 157-year record of sea level from San Francisco, California, U.S.A. The question of the acceleration of global sea level rise has gained increasing attention because the present rate of sea level rise is relatively small in comparison to the rates that are predicted to occur in the near future. Recent measurements have come under scrutiny on how to correctly analyze and interpret regional estimates of acceleration. In this context, we employ the Ensemble Empirical Mode Decomposition (EEMD), a data-adaptive method developed for the analysis of nonstationary and nonlinear data to estimate acceleration over the 157-year record of sea level from San Francisco, California. We define sea level acceleration (SLA) as the mean of the second differences of the residual from an EEMD. Using the residual provides a means by which to reduce or eliminate the contaminating influence of decadal and longer-period oscillations in sea level that are folded into estimates obtained using the conventional approach. For the entire record, a value of +0.011 ± 0.003 mm/y2 was obtained for the acceleration and its uncertainty, compared with +0.013 mm/y2, using the conventional approach. The effect of record length is examined by estimating the accelerations for truncated versions of the record, one starting in 1900 and a second in 1925. The accelerations differed in each case from the conventional values, as expected, because the methods are based on different definitions of SLA. © Coastal Education & Research Foundation 2013., Cited By (since 1996):1, Oceanography, CODEN: JCRSE
Author: Breaker, Ruzmaikin
Date: 2013-01-01T00:00:00Z

Title: Effect of iron limitation on the cadmium to phosphorus ratio of natural phytoplankton assemblages from the Southern Ocean,
Description: There is considerable interest in the biogeochemical cycling of cadmium (Cd) and phosphate (PO 4) in surface waters, driven in part by the ongoing development of a paleonutrient proxy that utilizes Cd preserved in fossil planktonic foraminifera to determine past PO 4 utilization efficiencies in ocean surface waters. The present article reports the results of a field study into the effects of Fe limitation on the Cd:P composition of natural assemblages of marine phytoplankton in the Antarctic Zone of the Pacific sector of the Southern Ocean. Iron enrichment to shipboard incubation bottles led to increases in community growth rate and final biomass. After 10.7 d of incubation, the climax community was dominated by large diatoms of the genus Fragillariopsis, Pseudonitzschia, and Nitzschia. Direct measurements of phytoplankton metal : P ratios from controlled shipboard experiments indicate that Cd:P, Co:P, and Zn:P ratios decreased from control values with increasing initial dissolved Fe concentrations in the incubation bottles, by factors of ∼2-10 at highest Fe additions. We suggest that the effect of Fe limitation on resident diatoms is to decrease growth rate, leading to elevated cellular Cd content. The dissolved Cd:P ratio in iron-limited surface waters of the Southern Ocean may, therefore, respond to the supply of Fe to the resident phytoplankton community, which has implications for the developing paleonutrient proxy. We suggest that the biological uptake of Cd and P is independent of the dissolved Cd:PO 4 ratio. As a consequence, the results argue against the use of empirical Rayleigh fractionation models or models with fixed phytoplankton uptake ratios to account for regional variability in surface water dissolved Cd:PO 4., Cited By (since 1996):33, Oceanography, CODEN: LIOCA, ,
Author: Cullen, Chase, Coale, Fitzwater, Sherrell
Date: 2003-01-01T00:00:00Z

Title: Sediment flushing observations, earthquake slumping, and benthic community changes in Monterey Canyon head,
Description: A large area of axis sediment (>500 m2) may be annually removed from the head of Monterey Submarine Canyon with the first onshore storm of the fall/winter storm season. In this scenario, flushing events are followed by accumulation of sediment and organic debris-especially macro algae-in the shallow axis. Net accumulation of this fill material increases during the calmer spring and summer until the next fall-flushing. The benthic community at a canyon axis station was characterized by highly fluctuating populations of opportunistic polychaete worm; and gammarid amphipods, primarily Capitella spp., Armandia brevis, and Orchomene pacifica. The canyon axis community was very different from communities living at two other stations where sudden flushing does not occur-an adjacent sloping-wall station and a sandflat station. Sloping-wall and sandflat stations harbored more and longer-lived species, larger individuals, and a less variable population structure during a year of sampling. The Loma Pricta earthquake in the fall of 1989 triggered small sediment slumps on the canyon walls, but it did not trigger axis-flushing. The usual seasonal flushing of the axis occurred 2 weeks after the earthquake with the arrival of the first storm. Benthic communities were reduced in abundance inside earthquake-induced slumps; however, the slumped areas were rapidly colonized by Prionospio pygmaea, a polychaete opportunist common to the sandflat. Surprisingly, the physical and biological impacts of the earthquake ware much less severe than the seasonal axis flushing associated with storms. Observations of sediment-flushing combined with measurements of benthic community changes in Monterey Canyon head represent a step towards an ecological model of mass wasting with implications for the continental shelf and slope and possibly the deep sea., Cited By (since 1996):33, Oceanography, CODEN: CSHRD, ,
Author: Okey
Date: 1997-01-01T00:00:00Z

Title: Cadmium in plankton: Elevated concentrations of Baja California,
Description: 135 Plankton samples were collected in the northwest Pacific Ocean and analyzed for their cadmium content. Concentrations were generally low (2 to 5 micrograms of cadmium per gram, dry wt) in all samples, except for the plankton collected off Baja California, where high values (10 to 20 parts per million) were consistently found on 2 cruises., Cited By (since 1996):24, Oceanography, CODEN: SCIEA, ,
Author: Martin, Broenkow
Date: 1975-01-01T00:00:00Z

Title: Effects of the 1997-1999 El Niño and La Niña events on zooplankton abundance and euphausiid community composition within the Monterey Bay coastal upwelling system,
Description: Zooplankton abundance and euphausiid community composition were sampled seasonally (spring, summer, fall) within Monterey Bay, California, between 1997 and 1999. Measurements of sea surface temperature (SST), mixed layer depth, and upwelling indices provided concurrent data on physical oceanographic parameters. Both total zooplankton and krill abundance dramatically declined in the summer of 1997 coincident with a rapid increase in SST and mixed layer depth. Changes in euphausiid community composition occurred in concert with the decline in overall abundance. The relative abundance of the southern neritic Nyctiphanes simplex increased from August to November in 1997, the abundance of cold temperate Euphausia pacifica decreased significantly, and that of the northern neritic Thysanoessa spinifera declined dramatically. The sudden appearance of an adult cohort of N. simplex in July 1997 suggests that rapid poleward flow characteristic of coastally trapped Kelvin waves occurred between June and July of 1997. The persistent presence of warm temperate and subtropical taxa in samples collected between August 1997 and October 1998 indicates that this poleward flow continued in 1998. Zooplankton abundance, euphausiid community composition, and physical oceanographic parameters gradually returned to a more typical upwelling-dominated state in the spring and summer of 1998. E. pacifica and T. spinifera abundances gradually increased during the summer and fall of 1998, while N. simplex abundance abruptly declined in the spring of 1998. However, this recovery was confined to a narrow coastal band as a result of the onshore movement of the oceanic waters of the California Current. This was reflected by higher than normal numbers of the oceanic Nematoscelis difficilis within samples collected during the spring and summer of 1998. By the spring and summer of 1999, both zooplankton and euphausiid abundance had increased to the highest levels recorded during the 3-year study. Both E. pacifica and T. spinifera abundance increased relative to 1998 while N. simplex was completely absent in all samples. These changes reflected the cooler, highly productive environmental conditions associated with the 1998/1999 La Niña. © 2002 Elsevier Science Ltd. All rights reserved., Cited By (since 1996):43, Oceanography, CODEN: POCNA, ,
Author: Marinovic, Croll, Gong, Benson, Chavez
Date: 2002-01-01T00:00:00Z

Title: Structural control of fluid flow: Offshore fluid seepage in the Santa Barbara Basin, California,
Description: Evidence of active and dormant fluid seepage in the Santa Barbara Basin is observed as active venting of gas and oil, bacterial mats, precipitates of authigenic carbonate, and mud and tar volcanoes. Fluid seepage occurs preferentially in the proximity to faults and faulted anticlines, and to slump scarps. Seepage next to faults and anticlines indicates that hydrocarbon migration and pore fluid expulsion is controlled structurally, with faults acting as preferred conduits for fluid flow across units of low matrix permeability. (C) 2000 Elsevier Science B.V. All rights reserved., Cited By (since 1996):38, Oceanography, CODEN: JGCEA, ,
Author: Eichhubl, Greene, Naehr, Maher
Date: 2000-01-01T00:00:00Z

Title: Stable isotopic ratios of lead in surface waters of the central Pacific,
Description: The geographic variation in the isotopic composition of lead in surface waters of the central Pacific provides new evidence of the global anthropogenic perturbation of the element's cycle. Ratios of 206Pb/207Pb decrease from 1.196 in the northern hemisphere (19°N, 158°W) to 1.176 in the southern hemisphere (15°S, 150°). This decrease parallels the geographic variation in surface concentrations of soluble lead which decrease from 13 ng kg-1 at the northern station to 4 ng kg-1 at the southern station. Both the 206Pb/207Pb and the 206Pb/208Pb ratios of those waters fit between the isotopic ratios of Australian (Broken Hill) and North American (Mississippi Valley) leads which are the predominant sources of leads in anthropogenic emissions to the Pacific Ocean basin., Cited By (since 1996):9, Oceanography, CODEN: MRCHB, ,
Author: Flegal, Schaule, Patterson
Date: 1984-01-01T00:00:00Z

Title: What's happening in Monterey Bay on seasonal to interdecadal time scales,
Description: Daily observations of sea-surface temperature (SST) have been acquired at the southern end of Monterey Bay in Pacific Grove, California since 1919. It is one of the longest oceanographic records off the west coast of North America. The record is examined to determine the major sources of variability in Monterey Bay and beyond, on time scales from seasonal to interdecadal. On seasonal time scales, the spring transition to coastal upwelling, often a major event along the coast of central California, is not well-expressed inside the bay but is detectable, occurring, on average, between mid-March and mid-April. The onset of the Davidson Current in Monterey Bay is well-defined, occurring, on average, in mid-October, ±2-3 weeks. Intraseasonal changes also occur during the spring and summer that may correspond to intrusions of warmer offshore waters into Monterey Bay. Intraseasonal oscillations with periods in the range of 40-50 days occur in Monterey Bay, but compared to their signature along the open coast, their event-like behavior is modified. The annual cycle of surface temperature in Monterey Bay is asymmetric with seasonal warming occurring during the spring and summer, and cooling during the fall. This asymmetry is primarily due to the net surface heat exchange which is positive for most of the year, and, to a lesser extent, the influence cold upwelled waters that are advected into the bay during the spring and summer, observations supported by a simple model that combines both the net surface heat exchange and thermal advection. On interannual time scales, the influence of El Niño warming events is strong. A comparison with the Northern Oscillation Index (NOI) using Singular Spectrum Analysis (SSA), shows that the El Niño signal is often as strong in SST at Pacific Grove as it is in the NOI. On interdecadal time scales, the influence of the Pacific Decadal Oscillation (PDO) is also relatively strong in Monterey Bay, again based on SSA. The integrated anomaly was calculated from the record and reveals regime shifts in Monterey Bay that occurred in 1929, an event that was apparently regional in scale, reflecting a transition from unusually cold to warmer conditions, and the regime change in the PDO that occurred in 1976. Each regime change can be approximated by a step-wise increase in temperature. Finally, linear trends were estimated for the entire record (∼+0.01°C/year), and for the 72-year period from 1930 to 2001 (+0.0042°C/year), i.e., following the regional regime change in 1929. The estimated trend for the last 72 years is not statistically significant; however, it is in close agreement with the long-term trend for the Intergovernmental Panel on Climate Change (IPCC) record of global surface temperature that spans almost 140 years (∼+0.005°C/year). Although the long-term increase in SST at Pacific Grove appears to be consistent with global warming, the integrated anomaly suggests that temperature increases in Monterey Bay have occurred rather abruptly and thus it becomes more difficult to invoke the global warming scenario. Finally, based on the monthly averaged data, the annual cycle, El Niño warming episodes, the PDO, the long-term trend, and the semiannual cycle account for approximately 44%, 18%, 6%, 4%, and 3% of the total variance, respectively, in SST at Pacific Grove. © 2005 Elsevier Ltd. All rights reserved., Cited By (since 1996):11, Oceanography, CODEN: CSHRD, ,
Author: Breaker
Date: 2005-01-01T00:00:00Z

Title: Analytical chemistry in oceanography,
Description: Cited By (since 1996):41, Oceanography, CODEN: ANCHA, , ,
Author: Johnson, Coale, Jannasch
Date: 1992-01-01T00:00:00Z

Title: Selenium in San Francisco Bay zooplankton: Potential effects of hydrodynamics and food web interactions,
Description: The potential toxicity of elevated selenium (Se) concentrations in aquatic ecosystems has stimulated efforts to measure Se concentrations in benthos, nekton, and waterfowl in San Francisco Bay (SF Bay). In September 1998, we initiated a 14 mo field study to determine the concentration of Se in SF Bay zooplankton, which play a major role in the Bay food web, but which have not previously been studied with respect to Se. Monthly vertical plankton tows were collected at several stations throughout SF Bay, and zooplankton were separated into two operationally defined size classes for Se analyses: 73-2,000 μm, and ≥2,000 μm. Selenium values ranged 1.02-6.07 μg Se g-1 dry weight. No spatial differences in zooplankton Se concentrations were found. However, there were inter- and intra-annual differences. Zooplankton Se concentrations were enriched in the North Bay in Fall 1999 when compared to other seasons and locations within and outside SF Bay. The abundance and biovolume of the zooplankton community varied spatially between stations, but not seasonally within each station. Smaller herbivorous-omnivorous zooplankton had higher Se concentrations than larger omnivorous-carnivorous zooplankton. Selenium concentrations in zooplankton were negatively correlated with the proportion of total copepod biovolume comprising the large carnivorous copepod Tortanus dextrilobatus, but positively correlated with the proportion of copepod biovolume comprising smaller copepods of the family Oithonidae, suggesting an important role of trophic level and size in regulating zooplankton Se concentrations., Cited By (since 1996):12, Oceanography, CODEN: ESTUD, ,
Author: Purkerson, Doblin, Bollens, Luoma, Cutter
Date: 2003-01-01T00:00:00Z

Title: Ocean iron fertilization - Moving forward in a sea of uncertainty,
Description: It is premature to sell carbon offsets from ocean iron fertilization unless research provides the scientific foundation to evaluate risks and benefits., Cited By (since 1996):69, Oceanography, CODEN: SCIEA, ,
Author: Buesseler, Doney, Karl, Boyd, Caldeira, Chai, Coale, De Baar, Falkowski, Johnson, Lampitt, Michaels, Naqvi, Smetacek, Takeda, Watson
Date: 2008-01-01T00:00:00Z

Title: The effect of elevated levels of phaeophytin in natural water on variable fluorescence measured from phytoplankton,
Description: Variable fluorescence methods are becoming popular in studies related to aquatic photosynthesis. In natural ocean water, phytoplankton co-exist with their zooplankton and flagellate predators, viral parasites and the waste products of digested phytoplankton cells that contain phaeophytin (a chromophore produced by digestion of chlorophyll a). Fast repetition rate fluorometry, a technique mainly applied in phytoplankton studies, was used to evaluate and quantify the effect of phaeophytin abundance in sea water on variable fluorescence parameters: the photochemical quantum yield, Φ F (also known as F v/F m), and the functional cross-section of photosystem 2 (PS2), σ PS2. If the value of Φ F determined is lower than what it actually is, phytoplankton may be labeled as less healthy (or productive) than their true condition. Results were compared with data collected using another widely used variable fluorescence technique: pulse amplitude modulation (PAM). Our study concludes that for significantly elevated levels of phaeophytin in the water, the measured values of Φ F should be corrected to avoid misinterpretation. This conclusion is independent of the measuring instrument. In waters with phaeophytin levels that constitute less than ∼30% of the total measured pigment, no correction is required (<5% change in Φ F is expected). However, as phaeophytin levels rise the effect on Φ F increases and becomes more significant (e.g. Φ F appears 25% lower when the phaeophytin to total pigment ratio is ∼70%). High concentrations of phaeophytin are not often reported in the open ocean. However, in highly productive coastal waters, high levels of phaeophytin can be encountered. The functional cross-section (σ PS2) measurements are not affected by the presence of phaeophytin in the water., Cited By (since 1996):18, CODEN: JPLRD, , , Oceanography
Author: Fuchs, Zimmerman, Jaffe
Date: 2002-01-01T00:00:00Z

Title: Echo character of off-platform carbonates,
Description: A comprehensive study of the nature and distribution of echo types recorded on short-ping (2-5 msec), high-frequency (3.5 kHz) echograms combined with analyses of 100 bottom samples from the off-platform carbonate environment of Northwest Providence Channel (NWPC), Bahamas, has defined qualitative relationships between echo types, sedimentary processes and sediment types. Seven distinct echo types have been observed and their areal distributions mapped. These seven types fall into three larger groups: (I) Distinct; (II) Indistinct; and (III) Hyperbolic. A strong correlation of echo character with sediment type exists for the one distinct (IB) and two indistinct (IIA and IIB) echo types observed. Muddy, pelagic sediments occur in regions characterized by distinct, sharp, continuous, parallel, sub-bottom reflectors (Type IB). Pelagic sediments interbedded with coarse-sediment gravity-flow deposits or slope breccia are characterized by indistinct, discontinuous, intermittent sub-bottom reflectors (Type IIA). Coarse current-winnowed sands or thick biolithoclastic turbidites found near the surface correlate with regions characterized by an indistinct, prolonged echo with no sub-bottom reflectors (Type IIB). Hyperbolic echoes were observed from both erosional and constructional features. The most common echo type (IIIA) in NWPC consists of large, irregular, overlapping hyperbolae with varying vertex elevations above the sea floor which originate from areas of large-scale submarine erosional topography. This echo type is much more common on the slope south of Little Bahama Bank than north of Great Bahama Bank, indicating different sedimentary processes operative along these two deep carbonate bank margins. In contrast, echoes consisting of discrete single hyperbolae with approximately equal vertex elevations above the sea floor (Type IIIG) correlate with in-situ constructional deep-water bioherms (lithoherms). This study demonstrates the usefulness of 3.5-kHz profiles in mapping near-surface off-platform carbonate sediments. The relationships between echo types and sedimentary processes and/or sediment types described here in a region with good bottom-sample control may serve as a model to facilitate rapid mapping of off-platform carbonates in areas where there is less control. © 1979., Cited By (since 1996):6, Oceanography, CODEN: MAGEA, ,
Author: Mullins, Boardman, Neumann
Date: 1979-01-01T00:00:00Z

Title: Dissolved organic carbon in the Atlantic, Southern and Pacific oceans,
Description: The amount of dissolved organic carbon (DOC) in sea water is controversial 1,2. Using a high-temperature catalytic oxidation (HTCO) technique, Sugimura and Suzuki 3 reported that surface waters contained 2-4 times as much DOC as that measured previously using wet chemistry and ultraviolet oxidation techniques 4,5. They also observed a relationship between DOC content and apparent oxygen utilization suggesting that the consumption of DOC is responsible for oxygen depletion in the deep sea. How to reconcile the apparent differences between these techniques has not been clear. Here we provide independent confirmation of the findings of Sugimura and Suzuki. We collected surface and deep waters from the equatorial Pacific Ocean, the Drake passage and the Atlantic Ocean south of Iceland, and analysed their DOC content using the HTCO methodology 3. We found DOC concentrations 2-3 times higher than those measured previously. These results imply that the carbon content of the oceans has previously been underestimated by 10 12 (1,000 billion) tonnes, and that the new estimated total of 1,800 billion tonnes represents one of the largest carbon reservoirs on Earth 6. We found no evidence of a cause-and-effect relationship between DOC and apparent oxygen utilization., Cited By (since 1996):35, Oceanography, CODEN: NATUA, ,
Author: Martin, Fitzwater
Date: 1992-01-01T00:00:00Z

Title: Accumulation rate and mixing of shelf sediments in the Monterey Bay National Marine Sanctuary,
Description: The distribution of excess 210Pb in 31 sediment cores was used to determine modern (last 100 yr) mass accumulation rates and the depth of sediment mixing on the continental shelf between Pacifica and Monterey, California, USA. Apparent mass accumulation rates average 0.27 g cm-2 yr-1 and range from 0.42 g cm-2 yr-1 to 0.12 g cm-2 yr-1. Accumulation rates were highest at mid-shelf water depths (60-100 m) adjacent to major rivers and near the head of the Ascension submarine canyon. Cores from water depths of less than 65 m had low, uniform 210Pb activity profiles and sandy textures. The uppermost 5-13 cm of 15 cores had uniform 210Pb activity profiles above a region of steadily decreasing 210Pb activity. This phenomenon was attributed to sediment mixing. The thickness of this upper layer of uniform 210Pb activity decreased southward from 13 cm, west of Pacifica, to less than 5 cm, near Monterey Canyon. This southward decrease may be attributed to shallower bioturbation in the southern study area. Integrated excess 210Pb activities were generally higher where sedimentation rates were high. They were also higher with increasing distance from major rivers. Thus, sedimentation rate alone does not explain the distribution of integrated excess 210Pb in this study area. Excess 210Pb in the seafloor is controlled by other factors such as sediment texture, the atmospheric deposition rate of 210Pb, and the residence time of sediment particles in the water column. © 2002 Elsevier Science B.V. All rights reserved., Cited By (since 1996):28, CODEN: MAGEA, , , Oceanography
Author: Lewis, Coale, Edwards, Marot, Douglas, Burton
Date: 2002-01-01T00:00:00Z

Title: Boundary-interior exchange: Reviewing the idea that internal-wave mixing enhances lateral dispersal near continental margins,
Description: Near-boundary mixing affects the dispersal of seawater constituents and may have important consequences for ecological and geological processes since continental boundaries are a fundamental source of lithogenic sediments, nutrients, iron and carbon. This paper examines the idea that gravitational collapse after near-boundary vertical mixing events leads to enhanced dispersal in the horizontal (along-isopycnal) direction. Dye studies from the continental shelf and laboratory investigations of intrusions generated by internal-wave breaking suggest that this is a viable mechanism for offshore dispersal of boundary-layer fluid. However, there have been few attempts to examine this process in the ocean or to quantify it in a form amenable to parameterization. Here this process is considered primarily for continental slopes and conditions of relatively uniform stratification, rather than for shelves where the boundary can intersect a front or seasonal thermocline. This paper reviews a selection of studies examining this concept in the laboratory and ocean, and reviews studies linking internal-wave reflection and mixing to the offshore dispersal of suspended sediment from continental margins. © 2006 Elsevier Ltd. All rights reserved., Cited By (since 1996):27, Oceanography, CODEN: DSROE, ,
Author: McPhee-Shaw
Date: 2006-01-01T00:00:00Z

Digital Commons of Moss Landing Marine Laboratories

Managing our Digital Assets

Pages

Pages