Oceanographic Investigations Research Articles

Precise orbit computation for the Geosat Exact Repeat Mission

We have conducted an extensive investigation of orbit determination strategies for the Geosat Exact Repeat Mission (ERM). The goal of our studies is to establish optimum geodetic parameters and procedures for the computation of the most accurate Geosat orbits possible and to apply these procedures for the routine computation of Geosat orbits during the ERM for the following purposes: (1) to enhance the value of the Geosat oceanographic investigations by providing the user community with improved ephemerides, (2) to develop orbit determination techniques for the upcoming altimetric mission TOPEX/POSEIDON, and (3) to assess the radial orbit accuracy obtainable with recently developed gravity models. To this end, ephemerides for the entire first year of the ERM have been computed using the GEODYN II orbit program on the Cyber 205 supercomputer system at the Goddard Space Flight Center. The GEM‐T1 gravity solution was used in developing solutions in 25 separate 17‐day arcs. Estimated radial orbit errors have been reduced from a level of 3‐m root‐mean‐square (rms) with the operational orbits to about the 85‐cm level. Both the operational and precision ephemerides were produced from the same tracking data collected by the U.S. Navy's Operational Network, so most of this improvement is due to improved force and measurement modeling. Recently, a more accurate gravity field, GEM‐T2, has become available. Preliminary orbit tests performed with the GEM‐T2 gravity model, along with Geosat TRANET‐2 Doppler data that have recently been acquired, suggest that radial orbit accuracies of about 35 cm rms can be achieved for Geosat.

Flow cytometric characterization and enumeration of Chrysochromulina polylepis during a bloom along the Norwegian coast

Flow cytometry was used to count the concentration of the alga Chrysochromulina polylepis Manton & Parke during a bloom along the Western and Southern Norwegian coasts. Fresh samples could be counted without fixation immediately after sampling. Flow-cyton~etric enumeration of the alga agreed well \nth direct counting in the microscope. C. polylepis was identified by its charactenstic combination of red fluorescence and scatter signal. These signature coordinates did not change significantly with time, depth or concentration. The flow-cytometric measurements could be performed even when the ship was running and in normal rough seas in offshore locations, whereas direct counting was impossible under such circumstances. Flow cytometry has been suggested as a valuable tool for the study of marine microorganisms (Olson et al. 1983, Yentsch et al. 1983a, b, Cucci et al. 1985, Wood et al. 1985). The potential of this technique has been explored and demonstrated in the biochen~ical literature (Muirhead et al. 1985), but progress in the use of shipboard flow cytomers has been slow. This may be partly because most flow cytometers are sensitive to motor vibration on board a ship, and also to wave motion. The design of most flow cytometers requires focusing a free falling stream of liquid, making shipboard experiments a 'frustrating experience' (Burlull 1987). In addition, in oceanographic investigations, enumeration of particles is desired. Because most flow cytometers have not been designed for counting, the use of internal standards, such as latex beads, are usually necessary for enumeration of particles. In the study reported here a n Argus 100-2 flow cytometer (Skatron, Norway) was used to discriminate and count phytoplankton during a bloom off the Southern and Western Norwegian coasts. This instrument weighs only 45 kg, which makes transportation and $1 Inter-Research/Printed in F. R. Germany installation on board convenient, and incorporates a sample stream which is hydrodynamically focused on the surface of a microscope coverslip (Steen & Lindmo 1979, Steen 1983). This d e s ~ g n is different from other flow cytometers, and proved to function even when the ship was steaming at 11 knots and in offshore waters. The instrument also incorporates a volumetrically quantitative injection system that allows direct counting of particle concentrations without the addition of

A new method for the rapid measurement of 224Ra in natural waters

We report a new method for the measurement of 24Ra ( T 1 2 = 3.6 days ) in natural waters. 224Ra preconcentrated from water samples by adsorption onto manganese-dioxide-impregnated acrylic fiber (Mn-fiber). The amount of 224Ra adsorbed on the fiber is determined by stripping its daughter, 220Rn, directly from the fiber bundle by circulating a stream of air through it and measuring the 220Rn activity concurrently. This method is simple, fast, sensitive, accurate and inexpensive. The counting system is portable, and is easily adapted for shipboard use in oceanographic investigations. The same equipment may also be used for measuring 228Th ( T 1 2 = 1.9 years ) and 226Ra ( T 1 2 = 1600 years ). 224Ra activities in water samples collected from continental shelf and estuarine waters of the eastern U.S. coast are presented.

U.S., France plan ocean study

The National Oceanic and Atmospheric Administration (NOAA) and the Institut Francais de Recherche pour l'Exploitation de la Mer (IFREMER) recently announced plans to conduct joint oceanographic investigations on the Mid‐Atlantic Ridge from 1990 to 1992, according to an announcement from NOAA. The multidisciplinary project will focus on the structure, dynamics, and composition of the deep sea floor, the circulation and dispersion of hydrothermal fluids, the related biological communities, and the presence of metalliferous deposits on the Mid‐Atlantic Ridge. Several U.S. and French agencies will participate in the project, which is a continuation of work by the two countries on the East Pacific Rise.

THE COASTAL OCEAN OFF THE EAST COAST OF SOUTH AFRICA

SUMMARY The east coast of South Africa has a generally well-defined and narrow continental shelf area. This, combined with the poleward-flowing Agulhas Current, serves to characterise the coastal ocean in the region as an identifiable entity. Most physical oceanographic investigations have taken place off Natal, but more recently some intensive measurements have also been made off East London. The results are reviewed in terms of temperature and current variability under the prime influence of wind and the Agulhas Current. Different coastal regimes are identified, but the inherent variability emerges as a major factor. The consequences are discussed in relation to phenomena such as the ‘sardine run’.

Marine Outfall Studies in Development Areas of South Africa

A recent policy of decentralizing growth in South Africa has led to the designation of neu coastal development areas. Growth of such areas, stimulated by the attraction of industries should be accompanied by a careful assessment of possible associated marine pollution problems. In particular, the disposal of industrial and/or domestic effluents to sea may initially appear an attractive option to planners and developers. Consequently the investigation of the feasibility of the marine disposal option is an essential component of the planning process. An on-going series of such studies in nominated priority coastal development areas has been undertaken by the National Research Institute for Oceanology since 1980. This paper reviews the progress of these studies and outlines the preliminary engineering and oceanographic investigations. Two case studies, Saldanha and Richards Bay, are reviewed. In the latter case, some interesting design aspects of the recently completed outfall are discussed.

Satellite laser ranging and its applications

Satellite laser ranging (SLR) provides an important capability for precise orbit determination and for geophysical parameter estimation to support a number of contemporary geodynamic and oceanographic investigations. The precision of the SLR measurement has improved from the early meter-level systems to the current capabilities of a few centimeters for the best systems. The accuracy of the orbits and geophysical parameter recovery have shown an associated improvement. Polar motion with accuracies of 2 mas, station coordinates better than 10 cm, and interstation baseline rates indicative of tectonic motion are determined routinely with the current set of global SLR data. This discussion reviews the SLR measurement, analysis approach, and some of the recent results derived from the current SLR data set.

Application of the Courant-Isaacson-Rees method to solve the shallow-water hydrodynamic equations

A finite-difference scheme is presented to solve the shallow-water hydrodynamic equations which describe the behavior of natural water bodies under the influence of wind stress, atmospheric pressure gradients, and tides. The numerical technique, which is an extension of the two-dimensional method of Courant, Isaacson, and Rees (1952), proved to be accurate and computationally stable for two-dimensional oceanographic investigations. Numerical simulations are given for wind-driven circulation in the Ligurian Sea.

Dr Harvey Pirie and the Scottish National Antarctic Expedition (1902-4). Scottish science and medicine in the Falklands and Antarctica.

Shortly after receiving a science and medical degree at Edinburgh, Dr Harvey Pirie joined the Scottish National Antarctic Expedition (1902-4) under Bruce. The naturalist team explored East Falkland, Laurie Island in the South Orkneys, and made the first oceanographic investigation of the Weddell Sea. After sighting Antarctica and naming the coast seen Coats Land, they returned to the Clyde via Gough Island and Cape Town. After a period in Scottish private practice, Pirie became a bacteriologist; he joined the Colonial Medical Service in 1913 and served in Kenya. In 1918 he organised the bacteriological services at the South African Institute for Medical Research in Johannesburg, and became deputy-director, 1926-41.

Application of lasers in oceanographic investigations (review)

Application of lasers in oceanographic investigations (review)

Spatial distribution of 0-group eel larvae (Anguilla sp.) in the Sargasso Sea

Both Atlantic eel species (Anguilla anguilla andA. rostrata) were collected in the Sargasso Sea during the 1979 cruise of the F. R. V. “Anton Dohrn” and R. V. “Friedrich Heincke”. A total of 3,097 0-group larvae were caught during 80 hauls using the Isaacs Kidd Midwater Trawl (55 hauls) and the 9-fold opening and closing net MOCNESS (25 hauls). 11 hauls of the MOCNESS indicated that the larvae showed a preference for the 150–175 m water depth during daytime and for the 50–75 m depth during night. The northern distribution limit seems to coincide with the “18°C-water” at the sea surface. The Antilla current characterised by higher temperatures and salinities could have been the southern distribution limit. The north-easternmost occurrence ofA. anguilla was noted at 50°W; the eastern distribution limit of this species could be farther east. The westernmost station at 69°W was positive for both species.A. anguilla, therefore, is very likely to occur beyond this area. The easternmost occurrence ofA. rostrata was noted at 52°W though sporadic and with increasing abundance towards the west. At the western end of the network of stations the highest concentration of larvae from both species was recorded. Oceanographic investigations reveal that the distribution of the smaller larvae (size-groups <7 mm and <10 mm) almost coincides with the assumed spawning area.

ARGO DM-54 and Raydist DRS positioning system stability

In 1978 NOAA procured the Cubic Western Data ARGO DM-54 system for use by the National Ocean Survey (NOS) for position location during hydrographic surveys and oceanographic investigations. The ARGO (Automatic Ranging Grid Overlay) positioning system is a pulsed phase comparison system operating in the medium frequency (MF) band (1.6–2 Mhz) using the ground wave component of the radiated signal. User results on the performance of medium range positioning systems vary widely (Munson, 1977). In NOS survey operations calibration errors or offsets have occurred when returning to fixed calibration points using medium-range positioning systems. To resolve the questions of calibration errors and system accuracy a program was initiated to measure the expected performance under operational conditions and to develop a standard field test procedure that could be used as an NOS input to the FIG Working Group 414b on positioning systems. In the initial phase of the program, stability tests under static conditions were conducted on the ARGO system in September 1978 and April 1979. These tests were conducted using the ARGO whip antenna at ranges of 18–440 km in a “test” range of the concave coast between New Jersey and North Carolina. As a result of these tests Cubic has developed phase stabilization circuitry for the ARGO system to minimize antenna detuning and subsequent lane jumps. This option was implemented and tested on the NOS ARGO system in January 1980. There are also a number of Raydist systems in the NOS inventory and the stability testing was extended to characterize the latest version of the Raydist DRS system. The Raydist system determines distance by means of phase comparison of continuous wave signals between 1.6–3.3 Mhz. The Raydist tests completed in November 1979 and the additional ARGO tests were conducted in the same “test” area at ranges of approximately 250 km using 100-ft antenna towers at the shore stations. The paper presents: (a) an analysis of long- and short-term stability results for the ARGO and Raydist systems; (b) system performance using different filtering or smoothing functions; and (c) an estimate of the effective day and nigh range of the ARGO system with a specified antenna configuration.

The design and use of an oscillating trolley wave-simulator, for installation in unidirectional flow flumes

The constructional details of an oscillating trolley arrangement, for installation in commercially available unidirectional flumes, is described. The apparatus is composed of commercially produced sub-assemblies and readily available materials. The oscillating trolley and flume have been used to simulate combinations of oscillatory (representing near-bed oscillatory motion of waves in shallow water) and unidirectional flows in investigations concerned with the response of various current meter impellers and the threshold of (Woodhead) sea bed drifters and non-cohesive sand sized sediment; some of the results of these investigations, of particular relevance to coastal oceanographic investigations, are summarized.

Seasat Altimeter Calibration: Initial Results

Preliminary analysis of radar altimeter data indicates that the instrument has met its specifications for measuring spacecraft height above the ocean surface (+/- 10 centimeters) and significant wave height (+/- 0.5 meter). There is ample evidence that the radar altimeter, having undergone development through three earth orbit missions [Skylab, Geodynamics Experimental Ocean Satellite 3 (GEOS-3), and Seasat], has reached a level of precision that now makes possible its use for important quantitative oceanographic investigations and practical applications.

A study of the subarctic boundary region in the Western North Pacific

During autumn 1968 an oceanographic investigation was conducted in the region of the Subarctic boundary between 155°E and 180°. The geostrophic flow of the upper 500 m was remarkably similar in direction; hence the salinity-minimum, Intermediate water must have the same path of flow as water at the surface. A water mass analysis revealed a decrease in the percentage of Subarctic water to the south and east, plus an increase in the homogeneity of water to the east, which supports Reid's conclusions that the salinity minimum results mainly from lateral mixing in the pycnocline in this region. Salinity at the minimum increases toward the south and east, and the density at this level also increases slightly from the western to the central Pacific, perhaps as a result of unequal vertical mixing above and below the minimum.

Results of oceanological investigations by the “north pole”; drifting stations

Abstract The principal stages of oceanographic investigation by the Soviet Union's series of North Pole drift‐ice stations are reviewed. It is shown how the findings of these floating research stations, beginning with North Pole‐1 in 1937, gave rise to modern views on the character of bottom topography, water masses, water and ice circulation and marine life in the Arctic Basin. The main results of the studies are described.

Suspended-sediment sampling towers as used on the intertidal flats of the Wash, eastern England

The design, construction and field application of systems for collecting samples of suspended material in tidal waters over an intertidal zone are described. Each sampler consists of: a tower framework; sample containers for the water-sediment mixture; and a series of mechanical or electromechanical release mechanisms to control the instant of sampling (in relation to the tidal cycle). The suspended-sediment sampling systems were used over 40 tidal cycles across an intertidal flat in the Wash. The systems have demonstrated that an extensive sampling programme can be undertaken at low cost and using minimum manpower in the field. However, it is also considered that the mechanisms and sampling techniques described have broader applications in estuarine and oceanographic investigations.

On the Drift Ice of the Sea of Okhotsk

In this paper, the outline of the meteorologic and the oceanographic investigation on the drift ice formation in the Sea of Okhotsk is given.The main factor which affects the ice formation in the Sea of Okhotsk is the existence of a thin mixing layer of very low salinity less than 100m in thickness on the surface of the Sea.The origin of this low salinity water is considered to come from the inflow of large amount of water from Siberia. According to FUKUTOMI mean total amount of ice in the Sea of Okhotsk is approximately 120×103m3 in winter.

Two‐month study of Caribbean Currents is part of fifteen‐nation program

A new aspect to a three‐year international oceanographic investigation of the Caribbean and Gulf of Mexico began in July with U.S. scientists and ships participating.The prime objective of the two‐month operation, part of a larger program involving some fifteen countries, is an intensive study of the circulation patterns of the area to determine the processes by which these patterns take place. The U.S. efforts are concentrated in the western Caribbean, Yucatan Channel, and the southeastern part of the Gulf of Mexico. A large portion of the U.S. participation is being conducted by NOAA.

Advance U.S. Oceanographic Survey Vessel Commissioned in October

The U.S. Coast and Geodetic Survey Ship Researcher, the first of a new class of scientific survey vessels developed for full‐range oceanographic investigations on the high seas and the continental shelves, was commissioned in October in Miami.The nine‐million‐dollar floating laboratory is electronically equipped to probe the ocean's deepest regions. When fully operational, the Researcher will carry the most advanced data acquisition system ever placed aboard an oceanographic vessel. The heart of the $750,000 system is a computer with a capacity of 100,000 arithmetic calculations per second, sufficient to enable it to automatically sample, process, and record oceanographic, geophysical, hydrographic, and meteorological data.