First results of the MOSES experiment: Sea sediment conductivity and thickness determination, Bute Inlet, British Columbia, by magnetometric offshore electrical sounding

Geophysics ◽  
1985 ◽  
Vol 50 (1) ◽  
pp. 153-160 ◽  
Author(s):  
R. N. Edwards ◽  
L. K. Law ◽  
P. A. Wolfgram ◽  
D. C. Nobes ◽  
M. N. Bone ◽  
...  
Keyword(s):  
British Columbia ◽  
Sea Water ◽  
Sea Surface ◽  
Crustal Rock ◽  
Crustal Material ◽  
Electrical Method ◽  
Azimuthal Component ◽  
Type Curves ◽  
Sea Floor ◽  
Eigenvector Analysis

A static electrical method has been developed to determine the electrical resistivity of crustal rock beneath the sea. The transmitter is a vertical, long‐wire bipole, extending from the sea surface to the sea floor. A commutated current, generated on the ship, is fed to two large electrodes: one near the sea surface, the other at the end of a long insulated wire. The return path for the current is through the sea and the subjacent crust. The receiver is a self‐contained, remote, microprocessor‐controlled magnetometer which is deployed from the ship to the sea floor and subsequently recovered. The data are measurements of the azimuthal component of the magnetic field as a function of transmitter‐receiver horizontal separation. The acronym MOSES has been coined for the method. The choice of the name MOSES is appropriate because the system geometry is carefully arranged to remove many of the adverse effects of the relatively conductive sea water. In particular, accurate estimates of sea floor resistivity are possible because the data are proportional to the transmitted current from the source into the crustal material. A sea test of the method in a water depth of 640 m was conducted in the “V” shaped Bute Inlet, British Columbia. Transmitted power was 1.25 kW; averaging time at each transmitter location was 1 hour. Transmitter‐receiver separations ranged from 150 to 2 000 m. The resistivity and thickness of a sedimentary section beneath the sea were determined as 1.9⋅Ω m and 560 m, respectively. The interpretation was accomplished both by matching the data converted to apparent resistivity to corresponding model type curves and by generalized linear inverse theory. Errors in the final parameters were estimated at about 9.2 percent using a parameter eigenvector analysis. The interpreted resistivity is in accord with direct measurement on core samples of sediment porosity. The interpreted thickness is less than an upper limit determined by extrapolating local inlet topography beneath the sea.

COASTAL AND ESTUARINE SEDIMENT DYNAMICS IN THE MEZEN BAY AND ESTUARIES MEZEN AND KULOY

2018 ◽  
Author(s):  
Н. Демиденко ◽  
N. Demidenko
Keyword(s):  
River Water ◽  
River Discharge ◽  
Sea Water ◽  
Sediment Dynamics ◽  
Estuarine Sediment ◽  
Sea Surface ◽  
Cross Sectional ◽  
Sand Waves ◽  
Tidal Estuaries ◽  
High Concentrations

In the Mezen bay and estuaries Mezen and Kuloy can be high concentrations of mud suspension there, involving the formation at times mobile suspensions and settled mud. Within estuaries the river water is mixed with the sea water by the action of tidal motions, by waves on the sea surface and by the river discharge forcing its way to the sea. Nearly all shallow tidal estuaries, where currents exceed about 1,0m s-1 and where sand is present, have sand waves. Sand waves have a variety of cross-sectional and plan forms.

scholarly journals Absolute seasonal temperature estimates from clumped isotopes in bivalve shells suggest warm and variable greenhouse climate

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Niels J. de Winter ◽  
Inigo A. Müller ◽  
Ilja J. Kocken ◽  
Nicolas Thibault ◽  
Clemens V. Ullmann ◽  
...  
Keyword(s):  
Seasonal Variability ◽  
Sea Water ◽  
Isotope Composition ◽  
Sea Surface ◽  
Mean Annual Temperature ◽  
Seasonal Temperature ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Temperature Reconstructions ◽  
Bivalve Shells

AbstractSeasonal variability in sea surface temperatures plays a fundamental role in climate dynamics and species distribution. Seasonal bias can also severely compromise the accuracy of mean annual temperature reconstructions. It is therefore essential to better understand seasonal variability in climates of the past. Many reconstructions of climate in deep time neglect this issue and rely on controversial assumptions, such as estimates of sea water oxygen isotope composition. Here we present absolute seasonal temperature reconstructions based on clumped isotope measurements in bivalve shells which, critically, do not rely on these assumptions. We reconstruct highly precise monthly sea surface temperatures at around 50 °N latitude from individual oyster and rudist shells of the Campanian greenhouse period about 78 million years ago, when the seasonal range at 50 °N comprised 15 to 27 °C. In agreement with fully coupled climate model simulations, we find that greenhouse climates outside the tropics were warmer and more seasonal than previously thought. We conclude that seasonal bias and assumptions about seawater composition can distort temperature reconstructions and our understanding of past greenhouse climates.

Can Marine Cloud Brightening Reduce Sea-Surface Temperatures to Moderate Extreme Hurricanes and Typhoons?

2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Salter SH ◽  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Sea Water ◽  
Cloud Condensation Nuclei ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Marine Stratocumulus ◽  
Surface Temperatures ◽  
Stratocumulus Clouds ◽  
Cloud Tops

Elevated sea-surface temperatures are a necessary but not sufficient requirement for the formation of hurricanes and typhoons. This paper suggests a way to exploit this. Twomey [1] showed that cloud reflectivity depends on the size-distribution of cloud drops, with a large number of small drops reflecting more than a smaller number of larger ones. Mid-ocean air is cleaner than over land. Latham [2-4] suggested that reflectivity of marine stratocumulus clouds could be increased by releasing a submicron spray of filtered sea water into the bottom of the marine boundary layer. The salt residues left after evaporation would be mixed by turbulence through the full depth of the marine boundary layer and would be ideal cloud condensation nuclei. Those that reached a height where the air had a super-saturation above 100% by enough to get over the peak of the Köhler curve would produce an increased number of cloud drops and so trigger the Twomey effect. The increase in reflection from cloud tops back out to space would cool sea-surface water. We are not trying to increase cloud cover; we just want to make existing cloud tops whiter. The spray could be produced by wind-driven vessels cruising chosen ocean regions. The engineering design of sea-going hardware is well advanced. This paper suggests a way to calculate spray quantities and the number and cost of spray vessels to achieve a hurricane reduction to a more acceptable intensity. It is intended to show the shape of a possible calculation with credible if not exact assumptions. Anyone with better assumptions should be able to follow the process.

Identification of lithological units using geo-electrical method, Olabisi Onabanjo University Campus, Southwestern Nigeria

2021 ◽  
Vol 20 (1) ◽  
pp. 171-182
Author(s):  
S.A. Adekoya ◽  
H.T. Oladunjoye ◽  
J.O. Coker ◽  
O.A. Adenuga
Keyword(s):  
Subsurface Layer ◽  
Groundwater Potential ◽  
Imaging Data ◽  
Southwestern Nigeria ◽  
Electrical Method ◽  
Type Curves ◽  
Overburden Thickness ◽  
Weathered Layer ◽  
Porosity And Permeability ◽  
Subsurface Resistivity

The study presented the results obtained from estimation of the depth to the bsement bedrock (overburden thickness) in Olabisi Onabanjo University, Ago-Iwoye using two configurations of electrical resistivity methods. The study was aimed to delineate the stratigraphy and thicknesses of the subsurface layer present in the study area for comprehensive study of the lithostratigraphic information of the area. Vertical Electrical Sounding (VES) and 2-D Horizontal Electrical Profiling (HEP) techniques were used to obtain 1-D and 2-D subsurface resistivity images of the study area. The VES data were plotted manually on the Bi-log graph. The curve obtained was partially curve – matched to obtain the layer resistivities and thicknesses for further iteration. The 2-D resistivity imaging data were analyzed and processed to obtain the inverted (true) resistivity image. From the results, five (5) VES type curves weredelineated. These includes H, HA, QH and KH type. The geoelectric sections and 2-D resistivity images showed three to four geoelectric layers. These layers are topsoil/laterite, weathered basement, partly weathered/fractured basement and fresh basement. The study showed that materials with resistivity values that ranged between 10 and 298 Ωm and 152 and 589 Ωm representing clayey weathered layer and partly weathered/fractured basement were delineated beneath some sounding points. The clayey and weathered layer are indicative of soil formations that are inimical to foundation of civil engineering structure. Likewise, they can serve as reservoir for groundwater potential (if the porosity and permeability are high). Due to this, detailed lithostratigraphic evaluation through petrophysical analysis is encouraged for the purpose of mapping and correlation of the rock units before embarking on any engineering construction in the study area. The study concludes in providing assistance to subsequent research on the stratigraphic related studies in the area. Keywords: Geo-electric , Stratigraphy, Lithology, Layer,

scholarly journals The Formation and Composition of the Gas Content of Sea Ice

1979 ◽  
Vol 22 (86) ◽  
pp. 67-81 ◽  
Author(s):  
V. L. Tsurikov
Keyword(s):  
Sea Ice ◽  
Sea Water ◽  
Major Effect ◽  
Relative Volume ◽  
Gas Content ◽  
Dominant Factor ◽  
Sea Floor ◽  
Sea Bottom ◽  
Initial Freezing ◽  
Air Pockets

Abstract The different factors contributing to the formation of the gas porosity of sea ice are: (Ia) gases captured during the formation of the initial ice cover, (Ib) gases released from solution during the initial freezing of sea-water, (Ic) the inclusion of gases rising from the sea bottom, (2a) the substitution of gas for brine drained from the ice during times of melting, (2b) the release of gas from the brine within the ice during the course of partial freezing, and (2c) the formation of voids filled with water vapour during the course of internal melting. An analysis is made of each of these processes and it is concluded that processes Ib, 2a, and 2C are important. Process Ic may also be a major effect but it is difficult to evaluate until the rate of gas release from the sea floor is better known. The migration of air pockets into the ice from the overlying snow is shown to be a possible but not a significant effect. Available data on the composition of gas in sea ice are reviewed and it is shown to be significantly different from air. Possible causes for these differences are discussed. The porosity of sea ice, i.e. the total relative volume of its gas plus its brine inclusions, is one of the factors strongly affecting its strength, as has been shown by Tsurikov (1947) and by Weeks and Assur (1968). In seas with high salinities the effect of the presence of brine within the ice will usually be the dominant factor. However on water bodies with low salinities the effect of the gas included within the ice may be greater than the effect of the brine. Despite its significance there have not been any attempts at a quantitative analysis of the entrapment of gas in sea ice. This paper is an attempt at such a study.

scholarly journals Ice Conditions of an Arctic Polynya: North Water in Winter

1986 ◽  
Vol 32 (112) ◽  
pp. 383-390 ◽  
Author(s):  
Konrad Steffen
Keyword(s):  
Sea Water ◽  
Surface Condition ◽  
Open Water ◽  
Sea Surface ◽  
Aerial Images ◽  
The Arctic ◽  
The North ◽  
North Water ◽  
Ice Conditions ◽  
Fast Ice

AbstractThe surface condition of the North Water was investigated during two winters (i.e. the three polynyas: Smith Sound polynya, Lady Ann Strait polynya, and Barrow Strait polynya). Since no detailed information was available on ice conditions and the extent of open water during winter, radiometric temperature measurements of the sea surface had to be taken along a flight line of 2650 km from an altitude of 300 m. From November to March 1978-79 and 1980-81, 14 remote-sensing flights were carried out. On the basis of the radiometric measurements, the following ice types were identified: ice-free, dark nilas, light nilas, grey ice, grey-white ice, and white ice. A comparison between the thermal and the visual ice classification (the latter being based on grey tones of the aerial images) showed a deviation of 3%. The analysis showed that in November, December, and January more than 50% of the Smith Sound polynya was covered by young ice, nilas, and ice-free, whereas in February and March white ice was dominant. Moreover, it was found that the two polynyas in Smith Sound and Lady Ann Strait were much smaller than previously believed. In Barrow Strait, a semi-permanent polynya was observed in the winter of 1980-81. The occurrence of polynyas in Barrow Strait seems to be connected with the location of the fast-ice edge. On the basis of the calculated ice-type distribution and heat-flux rates for different ice types, an energy loss of 178 W m-2was found on the surface of the Smith Sound polynya due to open water and thin ice for the winter months November to March. Compared with other ice-covered sea surfaces in the Arctic, the heat release by the sea-water in the Smith Sound polynya is about 100 W m-2larger.

scholarly journals A New Algorithm to Estimate Chlorophyll-A Concentrations in Turbid Yellow Sea Water Using a Multispectral Sensor in a Low-Altitude Remote Sensing System

2019 ◽  
Vol 11 (19) ◽  
pp. 2257
Author(s):  
Ji-Yeon Baek ◽  
Young-Heon Jo ◽  
Wonkook Kim ◽  
Jong-Seok Lee ◽  
Dawoon Jung ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Chlorophyll A ◽  
Sea Water ◽  
Two Dimensions ◽  
Sea Surface ◽  
Measurement Unit ◽  
Observation System ◽  
Low Altitude ◽  
Multispectral Camera

In this study, a low-altitude remote sensing (LARS) observation system was employed to observe a rapidly changing coastal environment-owed to the regular opening of the sluice gate of the Saemangeum seawall-off the west coast of South Korea. The LARS system uses an unmanned aerial vehicle (UAV), a multispectral camera, a global navigation satellite system (GNSS), and an inertial measurement unit (IMU) module to acquire geometry information. The UAV system can observe the coastal sea surface in two dimensions with high temporal (1 s−1) and spatial (20 cm) resolutions, which can compensate for the coarse spatial resolution of in-situ measurements and the low temporal resolution of satellite observations. Sky radiance, sea surface radiance, and irradiance were obtained using a multispectral camera attached to the LARS system, and the remote sensing reflectance (Rrs) was accordingly calculated. In addition, the hyperspectral radiometer and in-situ chlorophyll-a concentration (CHL) measurements were obtained from a research vessel to validate the Rrs observed using the multispectral camera. Multi-linear regression (MLR) was then applied to derive the relationship between Rrs of each wavelength observed using the multispectral sensor on the UAV and the in-situ CHL. As a result of applying MLR, the correlation and root mean square error (RMSE) between the remotely sensed and in-situ CHLs were 0.94 and ~0.8 μg L−1, respectively; these results show a higher correlation coefficient and lower RMSE than those of other, previous studies. The newly derived algorithm for the CHL estimation enables us to survey 2D CHL images at high temporal and spatial resolutions in extremely turbid coastal oceans.

Introduction

1967 ◽  
Vol 252 (777) ◽  
pp. 169-171 ◽  
Keyword(s):  
Southern Ocean ◽  
Oceanic Islands ◽  
Sea Surface ◽  
Large Measure ◽  
Sea Floor ◽  
Nature Conservancy ◽  
Antarctic Ecosystem ◽  
History Of ◽  
Antarctic Continent ◽  
The Antarctic

Mr President, ladies and gentlemen: it is my pleasure, in opening this two-day conference on the terrestrial Antarctic ecosystem, to welcome you as contributors of papers and, as I shall hope, participants in the discussions with which we will conclude each of the four sessions of our meeting. This symposium was first suggested and has, in very large measure, been organized by Dr Martin Holdgate whom we regretfully, but nevertheless most warmly congratulate on his recent translation from the post of Senior Biologist of the British Antarctic Survey to that of Deputy Director of the Nature Conservancy. The furtherance of Antarctic biology in recent years owes much to Dr Holdgate’s energetic and imaginative direction, and I am glad to have this opportunity of acknowledging our indebtedness to him for arranging this discussion. The Antarctic continent, half as large again as Australia, and the surrounding Southern Ocean, in area about one-fifth of the world’s sea surface were, by their very remoteness from the maritime nations of the northern hemisphere, late of exploration. But, while it is little more than 75 years since man first set foot on the Antarctic continent, the more accessible waters of the Southern Ocean have an appreciably longer history of exploration, dating from the pioneering voyages of Captain Cook some 200 years ago. Biological investigations in Antarctica were, therefore, for long concerned almost entirely with observations and studies of animals living in the open ocean or on the sea floor rather than with the terrestrial and freshwater floras and faunas of the continental margin and oceanic islands which, either because of difficulties of access or limitations of time imposed by ships’ programmes, were rarely surveyed in detail.

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