scholarly journals Accounting for sea floor properties in the assessment of underwater noise radiated from ships in shallow water

2020 ◽  
Author(s):  
Valentin Meyer ◽  
Christian Audoly
Keyword(s):  
Shallow Water ◽  
Underwater Noise ◽  
Sea Floor

Gametogenesis and the reproductive cycle in the deep-sea anemone Paracalliactis stephensoni (Cnidaria: Actiniaria)

1990 ◽  
Vol 70 (1) ◽  
pp. 163-172 ◽  
Author(s):  
Michel Praet-Van
Keyword(s):  
Organic Matter ◽  
Shallow Water ◽  
Deep Sea ◽  
Phytoplankton Bloom ◽  
Sea Anemone ◽  
Bay Of Biscay ◽  
Sea Anemones ◽  
Spring Phytoplankton Bloom ◽  
Sea Floor ◽  
Ultrastructural Investigation

This ultrastructural investigation of gametogenesis in a deep-sea anemone of the Bay of Biscay trawled around 2000 m depth, contributes to the knowledge of biology and strategy of reproduction of deep-sea benthos.This sea anemone is dioecious. The sperm appears very similar to those of shallow water sea anemones of the genus, Calliactis. The ultrastructural investigation of oogenesis allows the characteristics of the stages of previtellogenesis and vitellogenesis to be defined. The latter begins with a period of lipogenesis correlated with the formation of a trophonema. Mature oocytes measure up to 180 (im in diameter. Study of spermatogenesis and oogenesis reveals that spawning occurs in April/May. In males, the main area of testicular cysts, full of sperm, reaches maximal development from March to May and, in females, the percentage of mature oocytes decreases from 33% in April to 1% in May.Spawning may be induced by the advent in the deep-sea of the products of the spring phytoplankton bloom. This period of spawning, during the increased deposition of organic matter to the deep-sea floor, may be an advantageous strategy for early development of Paracalliactis.

The horizontal correlation of long range bottom reverberation in shallow water with inclined sea floor

2012 ◽  
Vol 131 (4) ◽  
pp. 3279-3279 ◽  
Author(s):  
Shi-e Yang ◽  
Bo Gao ◽  
Sheng-chun Piao
Keyword(s):  
Shallow Water ◽  
Long Range ◽  
Sea Floor

Towards a standard for the measurement of underwater noise from impact pile driving in shallow water

2014 ◽  
Vol 136 (4) ◽  
pp. 2216-2216
Author(s):  
Peter H. Dahl ◽  
Pete D. Theobald ◽  
Stephen P. Robinson
Keyword(s):  
Shallow Water ◽  
Pile Driving ◽  
Underwater Noise

On Lagrangian drift in shallow-water waves on moderate shear

2010 ◽  
Vol 660 ◽  
pp. 221-239 ◽  
Author(s):  
W. R. C. PHILLIPS ◽  
A. DAI ◽  
K. K. TJAN
Keyword(s):  
Boundary Layer ◽  
Shear Flow ◽  
Shallow Water ◽  
Water Waves ◽  
Stokes Drift ◽  
Shallow Water Waves ◽  
Sea Floor ◽  
Langmuir Circulations ◽  
A Minor ◽  
The Waves

The Lagrangian drift in anO(ϵ) monochromatic wave field on a shear flow, whose characteristic velocity isO(ϵ) smaller than the phase velocity of the waves, is considered. It is found that although shear has only a minor influence on drift in deep-water waves, its influence becomes increasingly important as the depth decreases, to the point that it plays a significant role in shallow-water waves. Details of the shear flow likewise affect the drift. Because of this, two temporal cases common in coastal waters are studied, viz. stress-induced shear, as would arise were the boundary layer wind-driven, and a current-driven shear, as would arise from coastal currents. In the former, the magnitude of the drift (maximum minus minimum) in shallow-water waves is increased significantly above its counterpart, viz. the Stokes drift, in like waves in otherwise quiescent surroundings. In the latter, on the other hand, the magnitude decreases. However, while the drift at the free surface is always oriented in the direction of wave propagation in stress-driven shear, this is not always the case in current-driven shear, especially in long waves as the boundary layer grows to fill the layer. This latter finding is of particular interest vis-à-vis Langmuir circulations, which arise through an instability that requires differential drift and shear of the same sign. This means that while Langmuir circulations form near the surface and grow downwards (top down), perhaps to fill the layer, in stress-driven shear, their counterparts in current-driven flows grow from the sea floor upwards (bottom up) but can never fill the layer.

scholarly journals Airborne Electromagnetic Sea Ice Thickness Sounding in Shallow, Brackish Water Environments of the Caspian and Baltic Seas

2006 ◽  
Author(s):  
Christian Haas
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Brackish Water ◽  
Low Frequency ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Sea Floor ◽  
Airborne Electromagnetic ◽  
The Baltic ◽  
Engineering Projects

Ice engineering projects often rely on the knowledge of ice thickness in shallow, brackish water like in the Baltic and Caspian Seas. By means of field data and model results, the paper shows that helicopter-borne electromagnetic induction measurements using frequencies of 3.68 and 112 kHz can yield accurate thickness estimates with salinities as low as 3 ppt. The higher frequency yields the strongest EM signals. In addition, in shallow water the higher frequency is less sensitive to the sea floor signal, and can thus be used in water depths as shallow as 4 to 6 m, depending on flying altitude. Because the low frequency signal is very sensitive on shallow water depth, a combination of both signals will allow the retrieval of both ice thickness and water depth.

Underwater noise measurements during a year long Shallow Water Canada Basin Acoustic Propagation experiment from 2016 to 2017

2018 ◽  
Vol 143 (3) ◽  
pp. 1831-1831
Author(s):  
Mohsen Badiey ◽  
Ying-Tsong Lin ◽  
Sean Pecknold ◽  
Altan Turgut ◽  
Megan S. Ballard ◽  
...  
Keyword(s):  
Shallow Water ◽  
Acoustic Propagation ◽  
Canada Basin ◽  
Underwater Noise ◽  
Noise Measurements ◽  
Propagation Experiment
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