Geomagnetic variations in the British Isles and their relation to electrical currents in the ocean and shallow seas

1971 ◽  
Vol 270 (1204) ◽  
pp. 289-323 ◽  
Keyword(s):  
Geomagnetic Field ◽  
Sea Water ◽  
Vertical Component ◽  
Temporal Variations ◽  
Thin Strip ◽  
Vertical Force ◽  
British Isles ◽  
Geomagnetic Variations ◽  
The North ◽  
Shallow Seas

The analysis and interpretation of the temporal variations of the geomagnetic field observed at fortny nine stations in the British Isles are presented. The variations in the horizontal components are very similar over the whole area, while the variations of the vertical force may show large differences between stations less than 80km apart. At nearly all stations there is a correlation between the variations of the vertical component and some component of the horizontal field. For variations of period exceeding 120 min, this correlation is mainly caused by electric currents induced in the Atlantic Ocean. The results are compatible with the theoretical response derived for induction in a thin strip model of the Ocean For variations of a period less than 90 min, concentrations of current also flow in the sea water surrounding the British Isles. It is postulated that these currents too are produced by induction in the Ocean, being frequency dependent branch currents flowing from the Ocean into the shallow seas. A current concentration flowing NE-SW through southern Scotland has been delineated This current, which has frequency characteristics similar to the currents in the shallow seas, could be drive by an electric potential between the North and Irish Seas. The presence of a long narrow structure in the crust with only a small conductivity contrast would then be sufficient to channel the current and produce the observed anomaly in the geomagnetic field.

Geomagnetic depth sounding over the central Arctic Islands, Canada

1980 ◽  
Vol 17 (12) ◽  
pp. 1642-1652 ◽  
Author(s):  
Jon M. DeLaurier ◽  
E. R. Niblett ◽  
F. Plet ◽  
P. A. Camfield
Keyword(s):  
Sea Water ◽  
Vertical Component ◽  
Temporal Variations ◽  
Electromagnetic Response ◽  
Strong Suppression ◽  
Short Period ◽  
Sverdrup Basin ◽  
Depth Sounding ◽  
Geomagnetic Observations ◽  
Conductivity Contrast

In the spring of 1973, 3 days of simultaneous geomagnetic observations were obtained at six recording sites over the central Arctic Islands. The northern site, Isachsen, displayed the strong suppression of the amplitudes of short-period temporal variations in the vertical component that has been observed at Mould Bay, about 500 km to the southwest. One-dimensional conductivity models suggest high conductivities in the upper crust. Parkinson's arrows for short periods point to the inter-island channels of sea water but for long periods the arrows rotate to point to the deep Arctic Ocean. A large spatial variation of the in-phase correlated Z/H ratios is also observed along a profile across the central Arctic Islands. These ratios peak at the Cameron Island site, which is near the Sverdrup Basin – Franklinian Geosyncline geological boundary. In well-log resistivity data, a conductivity contrast of two orders of magnitude is observed across this margin. Electric currents therefore flow in the conductive sediments of the Sverdrup Basin and in the sea water in the inter-island channels. The electromagnetic response is similar to that near an ocean–continent margin but the peak response occurs "inland" by 300–400 km. Consequently, the margin of the resistive continent is located near the Franklinian – Sverdrup Basin boundary in the central Arctic Islands.

scholarly journals Magnetic storms disrupt nocturnal migratory activity in songbirds

2019 ◽  
Vol 15 (3) ◽  
pp. 20180918 ◽  
Author(s):  
Giuseppe Bianco ◽  
Mihaela Ilieva ◽  
Susanne Åkesson
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Visual Cues ◽  
Early Morning ◽  
Temporal Variations ◽  
Migratory Restlessness ◽  
Geomagnetic Variations ◽  
Migratory Activity ◽  
Solar Storm ◽  
Solar Storms

Birds possess a magnetic sense and rely on the Earth's magnetic field for orientation during migration. However, the geomagnetic field can be altered by solar activity at relative unpredictable intervals. How birds cope with the temporal geomagnetic variations caused by solar storms during migration is still unclear. We addressed this question by reproducing the effect of a solar storm on the geomagnetic field and monitoring the activity of three songbird species during autumn migration. We found that only the European robin reduced nocturnal migratory restlessness in response to simulated solar storms. At the same time, robins increased activity during early morning. We suggest that robins reduced activity at night when the perception of magnetic information would be strongly disrupted by temporal variations of the magnetic field, to extend their migration during daytime when several visual cues become available for orientation. The other two species, chiffchaff and dunnock, showing low or no nocturnal migratory activity, did not respond to the solar storm by changing activity.

Spatial and temporal variations in parasite prevalence and infracommunity structure in herring (Clupea harengus L.) caught to the west of the British Isles and in the North and Baltic Seas: implications for fisheries science

2007 ◽  
Vol 81 (2) ◽  
pp. 137-146 ◽  
Author(s):  
Neil Campbell ◽  
Marcus A. Cross ◽  
James C. Chubb ◽  
Carey O. Cunningham ◽  
Emma M. C. Hatfield ◽  
...  
Keyword(s):  
North Sea ◽  
Parasite Prevalence ◽  
Distribution Patterns ◽  
Temporal Variations ◽  
Parasite Fauna ◽  
Clupea Harengus ◽  
North Coast ◽  
British Isles ◽  
The West ◽  
The North

AbstractHerring Clupea harengus L. viscera were examined for endoparasitic infections as part of a multidisciplinary stock identification project (WESTHER, EU Contract no. Q5RS-2002-01 056) which applied a range of stock discrimination techniques to the same individual fishes to obtain comparable results for multivariate analysis. Spawning and non-spawning adults, and juvenile herring were caught, over 3 years, by commercial and research vessels from numerous locations to the west of the UK and Ireland, along with control samples of spawning fish from the eastern Baltic Sea, and juveniles from sites in the eastern and western North Sea, and the north of Norway. The metacercariae of two renicolid digeneans (Cercaria pythionike and Cercaria doricha), one larval nematode (Anisakis simplex s.s.) and one larval cestode (Lacistorhynchus tenuis) were selected as tag species. Results were compared with those from herring collected between 1973 and 1982, which suggested remarkable stability in the parasite fauna of herring in the study area. These species were used to compare the parasite infracommunities of spawning herring. A significant variation in infracommunity structure was observed between different spawning grounds. These results suggest that the parasite fauna of herring are spatially variable but remain temporally stable in both the short and long term. Significant differences in prevalence and abundance of infections and comparisons of parasite infracommunity enabled the separation of putative herring stocks west of the British Isles. Distinctive patterns of parasite infection in two different spawning groups off the north coast of Scotland suggest that this area is occupied by two spawning populations, one recruiting from the west of Scotland, the other from outside this area, and most likely from the eastern North Sea. The distribution patterns of L. tenuis, C. doricha and C. pythionike suggest the potential for fish that spawn in three distinct International Council for the Exploration of the Seas (ICES) management units to be present in mixed aggregations found over the Malin Shelf, with significant implications for management in this area.

COMPARATIVE CHARACTERISTIC OF SEA RADIANCE COEFFICIENT SPECTRA MEASURED REMOTELY IN COASTAL WATERS OF FIVE SEAS

2017 ◽  
Author(s):  
Vera Rostovtseva ◽  
Vera Rostovtseva ◽  
Igor Goncharenko ◽  
Igor Goncharenko ◽  
Dmitrii Khlebnikov ◽  
...  
Keyword(s):  
Sea Water ◽  
Calibration Method ◽  
Aral Sea ◽  
Comparative Characteristic ◽  
The Black Sea ◽  
North East ◽  
The North ◽  
Water Constituents ◽  
Characteristic Features ◽  
The Baltic

Sea radiance coefficient, defined as the ratio of the sunlight reflected by the water bulk to the sunlight illuminating the water surface, is one of the most informative optical characteristics of the seawater that can be obtained by passive remote sensing. We got the sea radiance coefficient spectra by processing the data obtained in measurements from board a moving ship. Using sea radiance coefficient optical spectra it is possible to estimate water constituents concentration and their distribution over the aquatory of interest. However, thus obtained sea radiance coefficient spectra are strongly affected by weather and measurement conditions and needs some calibration. It was shown that practically all the spectra of sea radiance coefficient have some generic peculiarities regardless of the type of sea waters. These peculiarities can be explained by the spectrum of pure sea water absorption. Taking this into account a new calibration method was developed. The measurements were carried out with the portative spectroradiometers from board a ship in the five different seas: at the north-east coast of the Black Sea, in the Gdansk Bay of the Baltic Sea, in the west part of the Aral Sea, in the Kara Sea with the Ob’ Bay and in the Philippine Sea at the coast of Taiwan. The new method of calibration was applied to the obtained spectra of the sea radiance coefficient that enabled us to get the corresponding absorption spectra and estimate the water constituents concentration in every region. The obtained concentration estimates were compared to the values obtained in water samples taken during the same measurement cycle and available data from other investigations. The revealed peculiarities of the sea radiance coefficient spectra in the aquatories under exploration were compared to the corresponding water content and some characteristic features were discussed.

scholarly journals Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

2012 ◽  
Vol 16 (7) ◽  
pp. 1845-1862 ◽  
Author(s):  
F. Jørgensen ◽  
W. Scheer ◽  
S. Thomsen ◽  
T. O. Sonnenborg ◽  
K. Hinsby ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Sea Level Rise ◽  
Sea Level ◽  
Preferential Flow ◽  
Sea Water ◽  
Saline Water ◽  
Seismic Survey ◽  
Salinity Distribution ◽  
Geological Structures ◽  
The North

Abstract. Geophysical techniques are increasingly being used as tools for characterising the subsurface, and they are generally required to develop subsurface models that properly delineate the distribution of aquifers and aquitards, salt/freshwater interfaces, and geological structures that affect groundwater flow. In a study area covering 730 km2 across the border between Germany and Denmark, a combination of an airborne electromagnetic survey (performed with the SkyTEM system), a high-resolution seismic survey and borehole logging has been used in an integrated mapping of important geological, physical and chemical features of the subsurface. The spacing between flight lines is 200–250 m which gives a total of about 3200 line km. About 38 km of seismic lines have been collected. Faults bordering a graben structure, buried tunnel valleys, glaciotectonic thrust complexes, marine clay units, and sand aquifers are all examples of geological structures mapped by the geophysical data that control groundwater flow and to some extent hydrochemistry. Additionally, the data provide an excellent picture of the salinity distribution in the area and thus provide important information on the salt/freshwater boundary and the chemical status of groundwater. Although the westernmost part of the study area along the North Sea coast is saturated with saline water and the TEM data therefore are strongly influenced by the increased electrical conductivity there, buried valleys and other geological elements are still revealed. The mapped salinity distribution indicates preferential flow paths through and along specific geological structures within the area. The effects of a future sea level rise on the groundwater system and groundwater chemistry are discussed with special emphasis on the importance of knowing the existence, distribution and geometry of the mapped geological elements, and their control on the groundwater salinity distribution is assessed.

scholarly journals Carbon-14 in the Southern Indian Ocean

Radiocarbon ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 684-692 ◽  
Author(s):  
Georgette Delibrias
Keyword(s):  
Surface Water ◽  
Indian Ocean ◽  
Water Samples ◽  
Sea Water ◽  
Time Lag ◽  
Vertical Profiles ◽  
Carbon 14 ◽  
Middle Latitudes ◽  
The North ◽  
The Indian Ocean

14C measurements were carried out on sea water samples collected in 1973, in the Indian ocean. The results obtained for 9 vertical profiles between 27° S and 48°S are presented. In surface water, the bomb 14C content is maximum at middle latitudes. A time lag relative to the north hemisphere bomb 14C delivery is apparent. In the more southern latitudes, 14C content remains very low.

scholarly journals FxLMS Method for Suppressing In-Wheel Switched Reluctance Motor Vertical Force Based on Vehicle Active Suspension System

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Yan-yang Wang ◽  
Yi-nong Li ◽  
Wei Sun ◽  
Chao Yang ◽  
Guang-hui Xu
Keyword(s):  
Vertical Component ◽  
Active Suspension ◽  
Radial Force ◽  
Suspension System ◽  
Vertical Force ◽  
Least Mean Square ◽  
Active Suspensions ◽  
Switched Reluctance ◽  
Resonance Frequencies ◽  
Suspension Performance

The vibration of SRM obtains less attention for in-wheel motor applications according to the present research works. In this paper, the vertical component of SRM unbalanced radial force, which is named as SRM vertical force, is taken into account in suspension performance for in-wheel motor driven electric vehicles (IWM-EV). The analysis results suggest that SRM vertical force has a great effect on suspension performance. The direct cause for this phenomenon is that SRM vertical force is directly exerted on the wheel, which will result in great variation in tyre dynamic load and the tyre will easily jump off the ground. Furthermore, the frequency of SRM vertical force is broad which covers the suspension resonance frequencies. So it is easy to arouse suspension resonance and greatly damage suspension performance. Aiming at the new problem, FxLMS (filtered-X least mean square) controller is proposed to improve suspension performance. The FxLMS controller is based on active suspension system which can generate the controllable force to suppress the vibration caused by SRM vertical force. The conclusion shows that it is effective to take advantage of active suspensions to reduce the effect of SRM vertical force on suspension performance.

Modeling Transit Flow Through Port Gates and Connecting Channel in Baltic Sea—Liepaja Port—Liepaja Lake System

2021 ◽  
Vol 8 ◽  
Author(s):  
Vilnis Frishfelds ◽  
Juris Sennikovs ◽  
Uldis Bethers ◽  
Jens Murawski ◽  
Andrejs Timuhins
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Sea Water ◽  
Lake System ◽  
The North ◽  
Transit Flow ◽  
Trade Channel ◽  
Calm Weather ◽  
Set Up ◽  
The Baltic

This study investigates a water transport features by extending Copernicus Marine Environment Service (CMEMS) to the Liepaja coast-port-channel-lake system with a two-way nested model. The Liepaja lake and Liepaja port are connected by Trade channel. The Liepaja port has three gates—the openings in wave breakers connecting the port aquatory with the Baltic sea. Each of gates has a corresponding dredged channel for securing the navigation. A hydrodynamic model is set up to study the flow and water level in this system. The area of the port gates, port and Trade channel are resolved by 33 m grid. The model results are verified against currents and sea level observations inside/outside port, Trade channel and Liepaja lake. Results and observations show that strong currents occur in the Trade channel in case of rapid sea level change in Baltic sea despite the Trade channel is rather shallow at the connection with Liepaja lake. The northern part of the Liepaja lake gets filled with brackish water during storm surge events. The channel has notable alternating current also during a relatively calm weather due to the port seiches. Long and narrow shape of the channel implies the Helmholtz type oscillations between the lake and the port with a period in approximately semidiurnal range. Hydrodynamic simulations describe well these oscillations but the phase of hourly scale oscillations in the port may differ in case of weak external forcing. Water exchange is significantly increased by the transit (gate to gate) sea currents. This transit flow usually occurs between South or Central gate and the North gate carrying sea water into the port. Northward flow of the surface layer is more characteristic in the port aquatory due the prevailing south-western winds. There are intense morphological processes at the coastline and underwater slope near the Liepaja port due to a sandy western coastline of Latvia, long fetch of the waves and strong currents at the port gates. Liepaja port is one of the Latvian ports in HywasPort operational service of hydrodynamics, waves and siltation.

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