A model for predicting changes in the electrical conductivity, practical salinity, and absolute salinity of seawater due to variations in relative chemical composition

Salinity determination in seawater has been carried out for almost 30 years using the Practical Salinity Scale 1978. However, the numerical value of so-called practical salinity, computed from electrical conductivity, differs slightly from the true or absolute salinity, defined as the mass of dissolved solids per unit mass of seawater. The difference arises because more recent knowledge about the composition of seawater is not reflected in the definition of practical salinity, which was chosen to maintain historical continuity with previous measures, and because of spatial and temporal variations in the relative composition of seawater. Accounting for these spatial variations in density calculations requires the calculation of a correction factor δ<i>S</i><sub>A</sub>, which is known to range from 0 to 0.03 g kg<sup>−1</sup> in the world oceans. Here a mathematical model relating compositional perturbations to δ<i>S</i><sub>A</sub> is developed, by combining a chemical model for the composition of seawater with a mathematical model for predicting the conductivity of multi-component aqueous solutions. Model calculations for this estimate of δ<i>S</i><sub>A</sub>, denoted δ<i>S</i><sub>R</sub><sup>soln</sup>, generally agree with estimates of δ<i>S</i><sub>A</sub> based on fits to direct density measurements, denoted δ<i>S</i><sub>R</sub><sup>dens</sup>, and show that biogeochemical perturbations affect conductivity only weakly. However, small systematic differences between model and density-based estimates remain. These may arise for several reasons, including uncertainty about the biogeochemical processes involved in the increase in Total Alkalinity in the North Pacific, uncertainty in the carbon content of IAPSO standard seawater, and uncertainty about the haline contraction coefficient for the constituents involved in biogeochemical processes. This model may then be important in constraining these processes, as well as in future efforts to improve parameterizations for δ<i>S</i><sub>A</sub>

Tomographic observations of deep convection and the thermal evolution of the Greenland Sea Gyre, 1988-1989

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1994The thermal evolution of the Greenland Sea Gyre is investigated using both historical data and tomographic results from the 1988-89 Greenland Sea Tomography Experiment. Thermal evolution of the gyre center divides naturally into three periods: a preconditioning phase (November-January), during which surface salinity is increased by brine rejection from ice formation and by entrainment but in which the mixed-layer deepens only slowly to a depth of some 150-200m, a deep mixing phase (February-March) during which the surface mixed-layer deepens rapidly to approximately 1500m in the gyre center purely under the influence of local surface cooling, and a restratification phase during which the products of deep mixing are replaced by inflowing Arctic Intermediate Water (AIW). The onset of the deep mixing phase occurs after ice formation in the gyre center stops, resulting in an area of open water where large heat fluxes can occur. In surrounding regions, including the odden region to the south, ice is still being formed, and the mixed layer does not deepen significantly. To the north and west, closer to the steep topography of the continental shelf, the inverse results show significant variability due to advection, and large temperature and heat content fluctuations with a period of about 50 days are seen. The effects of advection are deduced from heat and salt budgets, and appear to be important only during the restratification phase for intermediate depths, and only during the summer for the surface waters. Comparison of the tomographic results with point measurements indicates that deep mixing occurs in a field of small plumes in which dense water sinks downwards, surrounded by larger regions of upwelling. The plume geometry is consistent with that predicted by numerical and laboratory models. Dynamical processes for bringing the AIW to the surface in order to form deep water are not needed in this scenario, rather the surface waters are modified until they match the density of the AIW after which surface cooling drives convection

Airborne Radar Sounding of the Greenland Ice Sheet

Author Institution: Department of Geology, Bowling Green State University, Bowling Green, Ohio 43403Radar sounding is a technique used in recent years to determine the thickness of ice sheets and glaciers. A radar signal is transmitted through ice, a dielectric, is reflected from the bottom, and is received at some time after its transmission. The length of time which the radar pulse spends in the ice, the so-called "delay time of the pulse," can be related empirically to the thickness of ice sheets and glaciers with a maximum uncertainty of approximately 2 percent without considering errors in positioning, electronics, and other conditions. Airborne radar sounding was used, in 1966, to sound successfully nearly 10,000 km of the Greenland ice sheet, penetrating the ice to a depth of up to 3,000 m. This method is rapid, mobile, and accurate when compared with more conventional techniques and should prove to be a most valuable tool for the study of the thickness of glacial ice

Earthquake Statistics for Ohio

Author Institution: Seismological Observatory, Department of Geology, Bowling Green State UniversityPAWLOWICZ, EDMUND F. Earthquake statistics for Ohio. Ohio J. Sci. 75(2): 103, 1975

Primary Events in Photosynthetic Reaction Centers and Antennas: A Femtosecond Visible - Pump - Mid-Infrared - Probe Study

Grondelle, R. van [Promotor]Jones, M.R. [Copromotor

Salish Sea surface currents: real-time velocities from HF radar

Ocean Networks Canada has operated Salish Sea CODAR high-frequency (HF) surface radar systems for monitoring surface currents since 2012. The network of antennae continues to grow, with four arrays now deployed in the southern Strait of Georgia, two more planned for the Strait of Juan de Fuca, and several more installed and planned along BC’s northern coast. These arrays provide hourly maps of surface currents. In the Strait of Georgia, where the Fraser River and ocean tides meet, there are complex surface current patterns that vary under seasonal river and wind conditions. Data are used to understand the circulation, validate model simulations, and could be used to assist in oil spill tracking and search and rescue efforts. An overview of the systems, the currents, data quality procedures, and future plans will be presented

Para el querido público

Pablo Pawlowicz es el director ejecutivo del Taller de Teatro de la Universidad Nacional de La Plata. En esta nota, conversamos sobre su relación histórica con el Taller, las formas de trabajo, las obras en cartel y la importancia que tiene el teatro como una herramienta más en el aula, es decir, en el proceso de enseñanza - aprendizaje

How does stuff wash ashore in the Salish Sea?

How does stuff wash ashore in the Salish Sea? The shores of the Salish Sea are covered in logs and trash ranging from large half-destroyed floats down to small pieces of plastic. How does it all get there? Over the past 6 years nearly 500 drifters, equipped with GPS to record positions with an accuracy of a few meters every 10-20 minutes, have been released in these waters (see drifters.eos.ubc.ca), and they have washed ashore more than 700 times. This resulted in plenty of interesting anecdotes, as tracks show a variety of surprising behaviors (including getting run down by ships). But, in addition, a statistical analysis was used to answer some interesting general questions about the Salish Sea. For example: where do things like to wash ashore? Can they escape the Salish Sea by going out into the Pacific? At what stage of the tide does stuff tend to run aground? What\u27s the probability of grounding for items floating 20, 50, or 100m offshore? What are ocean currents like near the shore? The answers to these questions may improve modelling and policy (and they are fun science)

Simulated tomographic reconstruction of ocean features using drifting acoustic receivers and a navigated source

Author Posting. © Acoustical Society of America, 1995. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 98 (1995): 2270-2279, doi:10.1121/1.413341.Numerically simulated acoustic transmission from a single source of known position (for example, suspended from a ship) to receivers of partially known position (for example, sonobuoys dropped from the air) are used for tomographic mapping of ocean sound speed. The maps are evaluated for accuracy and utility. Grids of 16 receivers are employed, with sizes of 150, 300, and 700 km square. Ordinary statistical measures are used to evaluate the pattern similarity and thus the mapping capability of the system. For an array of 300 km square, quantitative error in the maps grows with receiver position uncertainty. The large and small arrays show lesser mapping capability than the mid-size array. Mapping errors increase with receiver position uncertainty for uncertainties less than 1000-m rms, but uncertainties exceeding that have less systematic effect on the maps. Maps of rms error of the field do not provide a complete view of the utility of the acoustic network. Features of maps are surprisingly reproducible for different navigation error levels, and give comparable information about mesoscale structures despite great variations in those levels.This work was supported by Office of Naval Research grants N00014-9l-J-1138 (Arctic Sciences )and N00014-92-I-1162 (Ocean Acoustics)