Oceanographic, topographic, and sediment interactions in deep water acoustic propagation. Part I. Sediment effects on water column propagation patterns

1994 ◽  
Vol 95 (3) ◽  
pp. 1344-1362 ◽  
Author(s):  
Jessie C. Carman
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Acoustic Propagation

scholarly journals The response of water column and sedimentary environments to the advent of the Messinian salinity crisis: insights from an onshore deep-water section (Govone, NW Italy)

2020 ◽  
pp. 1-17
Author(s):  
Mathia Sabino ◽  
Francesco Dela Pierre ◽  
Marcello Natalicchio ◽  
Daniel Birgel ◽  
Susanne Gier ◽  
...  
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Bottom Layer ◽  
Messinian Salinity Crisis ◽  
Sedimentary Environments ◽  
Water Column Stratification ◽  
Stratigraphic Architecture ◽  
Spatial Changes ◽  
Oxygen Stable Isotope ◽  
Nw Italy

Abstract During Messinian time, the Mediterranean underwent hydrological modifications culminating 5.97 Ma ago with the Messinian salinity crisis (MSC). Evaporite deposition and alleged annihilation of most marine eukaryotes were taken as evidence of the establishment of basin-wide hypersalinity followed by desiccation. However, the palaeoenvironmental conditions during the MSC are still a matter of debate, chiefly because most of its sedimentary record is buried below the abyssal plains of the present-day Mediterranean Sea. To shed light on environmental change at the advent and during the early phase of the MSC, we investigated the Govone section from the Piedmont Basin (NW Italy) using a multidisciplinary approach (organic geochemical, petrographic, and carbon and oxygen stable isotope analyses). The Govone section archives the onset of the crisis in a succession of organic-rich shales and dolomite-rich marls. The MSC part of the succession represents the deep-water equivalent of sulphate evaporites deposited at the basin margins during the first phase of the crisis. Our study reveals that the onset of the MSC was marked by the intensification of water-column stratification, rather than the establishment of widespread hypersaline conditions. A chemocline divided the water column into an oxygen-depleted, denser and more saline bottom layer and an oxygenated, upper seawater layer influenced by freshwater inflow. Vertical oscillations of the chemocline controlled the stratigraphic architecture of the sediments pertaining to the first stage of the MSC. Accordingly, temporal and spatial changes of water masses with different redox chemistries must be considered when interpreting the MSC event.

scholarly journals Limited mid-water scavenging of trawl discards

2003 ◽  
Vol 83 (4) ◽  
pp. 731-734 ◽  
Author(s):  
Karim Erzini ◽  
Pedro Monteiro ◽  
Artur Araújo ◽  
Margarida Castro
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Small Fish ◽  
Sea Birds ◽  
Trawl Fishing ◽  
Southern Portugal ◽  
Catch Rates ◽  
Electric Fishing ◽  
Scavenging Rates

The consumption or scavenging of fish in the water column at depths from 75 to 275 m in Algarve (southern Portugal) trawl fishing grounds was evaluated. Longlines were used to suspend baits throughout the water column while electric fishing reels were used to simulate sinking discards. Eighteen species were caught, with higher catch rates near the surface than near the bottom. However, scavenging rates were generally highest near the bottom and lowest in the middle of the water column. At depths less than 100 m the majority or all the fish were scavenged throughout the water column, while at depths greater than 200 m most of the fish were untouched after periods of time greater than would be required for them to sink to the bottom. Since other studies have shown that most small fish discards are scavenged at the surface by sea birds and most of the discarded species that sink are either too large or not attractive to pelagic predators, these results suggest that mid-water scavenging of trawl discards in deep water is relatively unimportant.

A global survey of the impact on acoustic propagation of deep water warm core ocean eddies

1994 ◽  
Vol 95 (5) ◽  
pp. 2880-2880 ◽  
Author(s):  
David G. Browning ◽  
Raymond J. Christian ◽  
Linda S. Petitpas
Keyword(s):  
Deep Water ◽  
Acoustic Propagation ◽  
Ocean Eddies ◽  
Global Survey ◽  
Warm Core ◽  
The Impact

Elevated turbidity and dissolved manganese in deep water column near 10°47’S Central Indian Ridge: studies on hydrothermal activities

2020 ◽  
Vol 40 (5) ◽  
pp. 619-628 ◽  
Author(s):  
Durbar Ray ◽  
K. A. KameshRaju ◽  
A. Srinivas Rao ◽  
L. SuryaPrakash ◽  
Abhay V. Mudholkar ◽  
...  
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Central Indian Ridge ◽  
Indian Ridge ◽  
Hydrothermal Activities

scholarly journals Concept Tests for a New Wire Flying Vehicle Designed to Achieve High Horizontal Resolution Profiling in Deep Water

2011 ◽  
Vol 28 (12) ◽  
pp. 1657-1671 ◽  
Author(s):  
Chris Roman ◽  
Dave Hebert
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Free Stream ◽  
Horizontal Resolution ◽  
Vehicle Body ◽  
Scale Model ◽  
Stream Velocity ◽  
Wide Range ◽  
High Horizontal Resolution ◽  
Ship Speed

Abstract Efficiently profiling the water column to achieve both high vertical and horizontal resolution from a moving vessel in deep water is difficult. Current solutions, such as CTD tow-yos, moving vessel profilers, and undulating tow bodies, are limited by ship speed or water depth. As a consequence, it is difficult to obtain oceanographic sections with sufficient resolution to identify many relevant scales over the deeper sections of the water column. This paper presents a new concept for a profiling vehicle that slides up and down a towed wire in a controlled manner using the lift created by wing foils. The wings provide a novel low-power method of propulsion along the cable by using the free stream velocity of the wire moving through the water in similar fashion to a sailboat sailing up wind. Scale model tests show a wide range of achievable profiling glide slopes for tow cable angles between vertical and 45°, and effective isolation of cable strum vibration from the towed vehicle body. The concept is not depth limited and will offer two-dimensional resolution that meets or exceeds current undulating tow bodies over the full water column. Additionally, this system could be used simultaneously with many other deep towed instrument packages to produce complementary datasets.

scholarly journals Evidence of old carbon in the deep water column of the Panama Basin from natural radiocarbon measurements

1998 ◽  
Vol 25 (10) ◽  
pp. 1733-1736 ◽  
Author(s):  
Ellen R. M. Druffel ◽  
Sheila Griffin ◽  
Susumu Honjo ◽  
Steven J. Manganini
Keyword(s):  
Water Column ◽  
Deep Water

scholarly journals First access to the ocean beneath Ekströmisen, Antarctica, by means of hot-water drilling

1994 ◽  
Vol 20 ◽  
pp. 110-114 ◽  
Author(s):  
U. Nixdorf ◽  
H. Oerter ◽  
H. Miller
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Water Samples ◽  
Large Diameter ◽  
Hot Water ◽  
Easy Access ◽  
Ice Shelf ◽  
Valuable Data ◽  
The Past ◽  
Ultrasonic Echo

A hot-water drill developed during the past 2 years at Alfred-Wegener- Institut was used to penetrate Ekströmisen several times near the German wintering-over base, Neumayer (70°39´S, 08° 15´W). The drilling operation was very successful and the initial large diameter (≥ 35 cm) allowed easy access to the ocean. One hole was used to install an ultrasonic echo-sounder which recorded the ablation at the ice-shelf bottom continuously. Another hole was destined for emplacement of a thermistor string throughout the 237 m thick ice shelf for ice-temperature measurements. Several CTD profiles in the 175 m deep water column and the analysis of water samples provided valuable data for the understanding of ice-shelf-ocean interactions.

Sign in / Sign up

Export Citation Format

Share Document