Conductivity, Temperature And Depth Data Research Articles

Quantifying Patterns in Fish Assemblages and Habitat Use Along a Deep Submarine Canyon-Valley Feature Using a Remotely Operated Vehicle

The aim of this study was to document the composition and distribution of deep-water fishes associated with a submarine canyon-valley feature. A work-class Remotely Operated Vehicle (ROV) fitted with stereo-video cameras was used to record fish abundance and assemblage composition along transects at water depths between 300 and 900 metres. Three areas (A, B, C) were sampled along a submarine canyon-valley feature on the continental slope of tropical north-western Australia. Water conductivity/salinity, temperature, and depth were also collected using an ROV mounted Conductivity Temperature and Depth (CTD) instrument. Multivariate analyses were used to investigate fish assemblage composition, and species distribution models were fitted using boosted regression trees. These models were used to generate predictive maps of the occurrence of four abundant taxa over the survey areas. CTD data identified three water masses, tropical surface water, South Indian Central Water (centred ∼200 m depth), and a lower salinity Antarctic Intermediate Water (AAIW) ∼550 m depth. Distinct fish assemblages were found among areas and between canyon-valley and non-canyon habitats. The canyon-valley habitats supported more fish and taxa than non-canyon habitats. The fish assemblages of the deeper location (∼700–900 m, Area A) were different to that of the shallower locations (∼400–700 m, Areas B and C). Deep-water habitats were characterised by a Paraliparis (snail fish) species, while shallower habitats were characterised by the family Macrouridae (rat tails). Species distribution models highlighted the fine-scale environmental niche associations of the four most abundant taxa. The survey area had a high diversity of fish taxa and was dominated by the family Macrouridae. The deepest habitat had a different fish fauna to the shallower areas. This faunal break can be attributed to the influence of AAIW. ROVs provide a platform on which multiple instruments can be mounted and complementary streams of data collected simultaneously. By surveying fish in situ along transects of defined dimensions it is possible to produce species distribution models that will facilitate a greater insight into the ecology of deep-water marine systems.

Acoustic characterization of the new Arctic using mobile acoustic sources

The Naval Postgraduate School (NPS) participated in Ice Exercise 2016 (ICEX-16), a multi-national naval exercise conducted in the Beaufort Sea during March 2016. Operating at the remote Ice Camp SARGO, NPS deployed several conductivity, temperature and depth (CTD) sensors to capture oceanographic variability to 500 m depth while performing a series of propagation tests. Four mobile mid-frequency sources transmitted signals for approximately 10 hours each to a pair of vertical line array receivers positioned in the field to investigate depth, range, angular and specular characteristics of acoustic propagation and their correlation to variability in oceanographic structure and under-ice conditions. CTD data indicated significant variability in sound speed at 50 m depth where cold, fresh mixed-layer water interfaces with contrasting warm, saline Pacific Summer Water (PSW) that lays immediately below it. The data also show a persistent and stable subsurface sound channel existed as a result of the PSW with pe...

Acoustic characterization of the new Arctic during Ice Exercise 2016

The Naval Postgraduate School (NPS) participated in Ice Exercise 2016 (ICEX-16), a multi-national naval exercise conducted in the Beaufort Sea during March 2016. Operating at a remote ice camp, NPS deployed several conductivity, temperature and depth (CTD) sensors to capture oceanographic variability to 500 m depth while performing a series of propagation tests. Mobile and dipped mid-frequency sources transmitted signals to a pair of vertical line array receivers positioned in the field to investigate depth, range, angular and specular characteristics of acoustic propagation and their correlation to variability in oceanographic structure and under-ice conditions. CTD data indicate there was significant variability in sound speed at 50m depth where cold, fresh mixed-layer water interfaces with contrasting warm, saline Pacific Summer Water (PSW) that lays immediately below it. The data also show a persistent and stable subsurface sound channel existed as a result of the PSW with peak temperature at 80 m situated above colder Pacific Winter Water (PWW), resulting in a sound channel axis near 140 m depth. Both features have important implications on sonar performance in the Arctic. Modeled and measured transmission loss are compared to quantify the effects.

A practical approach to lake water density from electrical conductivity and temperature

Abstract. Density calculations are essential to study stratification, circulation patterns, internal wave formation and other aspects of hydrodynamics in lakes and reservoirs. Currently, the most common procedure is the use of CTD (conductivity, temperature and depth) profilers and the conversion of measurements of temperature and electrical conductivity into density. In limnic waters, such approaches are of limited accuracy if they do not consider lake-specific composition of solutes, as we show. A new approach is presented to correlate density and electrical conductivity, using only two specific coefficients based on the composition of solutes. First, it is necessary to evaluate the lake-specific coefficients connecting electrical conductivity with density. Once these coefficients have been obtained, density can easily be calculated based on CTD data. The new method has been tested against measured values and the most common equations used in the calculation of density in limnic and ocean conditions. The results show that our new approach can reproduce the density contribution of solutes with a relative error of less than 10 % in lake waters from very low to very high concentrations as well as in lakes of very particular water chemistry, which is better than all commonly implemented density calculations in lakes. Finally, a web link is provided for downloading the corresponding density calculator.

Progress of Chinese research in physical oceanography of the Southern Ocean

Oceanographic surveying has been one of the key missions of the Chinese National Antarctic Research Expeditionsince 1984. Using the field data obtained in these surveys and the results from remote sensing and numerical models, Chinesephysical oceanographers have investigated the water masses, fronts and circulation patterns in the Southern Ocean. The results ofnearly 30 years of research are summarized in this paper. Most oceanographic observations by Chinese researchers have been conductedin Prydz Bay and the adjacent seas. CTD (Conductivity Temperature and Depth) data, collected during the past 20 years,have been applied to study several features of the water masses in this region: The spatial variation of warm summer surface water,the northward extension of shelf water, the flow of ice shelf water from the cavity beneath the Amery Ice Shelf, the upwelling ofthe Circumpolar Deep Water, and the formation of the Antarctic Bottom Water. The circulation and its dynamic factors have beenanalyzed with dynamic heights calculated from CTD data as well as by numerical models. The structure and strength of the frontsin the southeast Indian Ocean and the Drake Passage were investigated with underway XBT/XCTD (Expendable Bathythermograph/Expendable CTD) and ADCP (Acoustic Doppler Current Profiler) data. Their interannual variations have been determinedand the factors of influence, especially the atmospheric forcing and mesoscale oceanic processes, were studied using remote sensingdata. The dynamic mechanism of the Antarctic Circumpolar Current (ACC) was analyzed by theoretical models. The transportand pattern of the ACC have been well reproduced by coupled sea ice-ocean models. Additional details of ACC variability wereidentified based on satellite altimeter data. The response of the ACC to climate change was studied using reanalysis data. Prospectsfor future research are presented at the end of this paper.

Tides, the PIG, and "warm" water

The present rapid melting of the Pine Island Glacier (PIG) has been attributed to basal melting driven by the ocean. Specifically, this ocean melting is attributed to currents and tides pumping "warm" Circumpolar Deep Water (CDW) into the ice shelf cavity. To identify tidal activity in the region, an observational time series of yo-yo CTD (Conductivity, Temperature, and Depth) data collected in the PIG outflow region was analyzed. The water column in front of the PIG consisted of two primary layers, a meltwater layer exiting the ice shelf cavity over a layer of CDW. Semidiurnal tides were present in both layers, with both the strength and direction of the tides differing between the two layers. The upper layer tides were stronger and directed in and out of the cavity, while the lower layer tides were primarily directed along the front of the cavity. Energy was found to be transferred from the semidiurnal tide to other frequencies and to be reflected by the ice shelf front. These mechanisms were most prominent at the interfaces between layers and indicate potential mixing between the layers. In conclusion, tides were found to contribute to the circulation into the ice shelf cavity and also to mixing of the exiting water, which influences pumping of the CDW into the ice shelf cavity and melting of the PIG.

Effects of sill processes on the distribution of epineustonic competent larvae in a stratified system of Southern Chile

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 324:95-104 (2006) - doi:10.3354/meps324095 Effects of sill processes on the distribution of epineustonic competent larvae in a stratified system of Southern Chile Carlos Molinet1,6,7,*, Arnoldo Valle-Levinson2, Carlos A. Moreno3,7, Mario Cáceres4, Mónica Bello5, Manuel Castillo5 1Instituto de Acuicultura, Universidad Austral de Chile, Los Pinos s/n, Puerto Montt, Chile 2Department of Civil and Coastal Engineering, University of Florida, 365 Weil Hall, PO Box 116580, Gainesville, Florida 32611, USA 3Instituto de Ecología y Evolución, Universidad Austral de Chile, Casilla 567, Valdivia, Chile 4Universidad de Valparaiso, Facultad de Ciencias del Mar y Recursos Naturales, Av. Borgoño 16344, Viña del Mar, Chile 5Servicio Hidrográfico y Oceanográfico de la Armada de Chile, Errazuriz 232, Casilla 324, Valparaíso, Chile 6Centro Universitario de la Trapananda, Portales 73, Coyhaique, Chile 7Centro de Investigaciones en Ecosistemas Patagónicos, Bilbao 550, Coyhaique, Chile *Email: cmolinet@uach.cl ABSTRACT: The inlets of southern Chile are characterized by a well-defined pycnocline which, acting in concert with the biological characteristics of larvae, is believed to influence planktonic larval distribution. Here, we assessed the effects of stratified flow over a sill on the spatial abundance and distribution of epineustonic competent larvae of Concholepas concholepas. We used measurements of velocity profiles using an Acoustic Doppler Current Profiler (ADCP), intensive plankton collections combined with simultaneous conductivity, temperature and depth (CTD) profiles, monitoring of the pycnocline depth, and temperature records from moored thermistors. Evidence of Bernoulli aspiration and an intratidal transient front was observed over the sill from CTD data and an echo-sounder trace. ADCP measurements showed intensified recirculation in the residual flow over the sill. This oceanographic feature coincided with high abundances of epineustonic competent larvae of C. concholepas over the sill area. We found evidence indicating that physical mechanisms related to sill processes can influence epineustonic competent larval distribution in a stratified system. We also propose a conceptual model that brings together larval behaviour and stratified flow patterns to explain the rise of epineustonic larvae to the surface and larval aggregation over a sill. KEY WORDS: Bernoulli aspiration · Sill · Epineustonic larvae · Stratified system · Southern Chile Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 324. Online publication date: October 23, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Hydrography and geostrophic currents in the Northern Gulf of California during the 1997–1998 El Niño

Conductivity, temperature and depth (CTD) data taken during July and November 1997 and March 1998 are used to analyze the hydrographic conditions in the Northern Gulf of California during the 1997–98 El Niño. The CTD data are compared to data from other years and an anomalous high salinity, lower density water is found near the bottom, whereas a relatively fresh surface layer is found on the eastern side of the gulf during July. The relatively fresh surface water is attributed to advection of tropical waters from the Pacific Ocean. During November and March, positive surface temperature anomalies are identified. Geostrophic currents are calculated across an entire cross section of the gulf passing through the northern tip of Angel de la Guarda Island using either salt or mass conservation as constraints. The most salient feature of the geostrophic currents is the existence of relatively intense bottom currents. The bottom current on the eastern side of the island is southeastward, toward the mouth of the gulf, during July, whereas it is toward the head of the gulf on the western side of the island. This pattern is inverted during November and March and, in all cases, suggests a near-bottom circulation between both basins separated by the island. The near-bottom current toward the head of the gulf on the eastern side of the island appears to be a permanent feature associated with the exchange of the northern gulf. Therefore, the high near-bottom salinities during July, coupled with a current toward the mouth of the gulf, are attributed to an anomalous condition created by the El Niño event. This condition is consistent with a subsidence of Gulf of California waters, flowing toward the mouth. Fluxes of salt and heat estimated from geostrophic currents are compared to seasonal estimates. The July heat flux is about three times greater than the seasonal value, and there appears to be an overall phase shift with respect to the seasonal cycle.

Calculation of fine-scale sound-field structure based on towed CTD (conductivity, temperature, and depth) chain measurements

In July 2002, an experiment was conducted off the coast of southern California in which the two-dimensional temperature and salinity field was measured directly using a towed CTD chain. The sensor spacing was smaller (2 to 8 m) near the surface (above 30 m) in order to better resolve the mixed layer and thermocline; the depth of the lowest sensor was about 150 m. The path of each tow was back and forth across the same section of ocean such that ocean dynamic features observed in the CTD data were recorded in expanded and compressed states depending on the ship’s heading. The range of each run was a few kilometers, with data taken in 1-s increments. This yielded a high-resolution field suitable for analyzing the propagation behavior of high frequencies. Using the fine-scale measurements of the sound-speed field and an acoustic propagation model based on an FFT-realized parabolic equation, the sound field was calculated reflecting the observed ocean dynamic features. Modeling of scintillation in acoustic intensity will be discussed in the context of spice theory. [Work supported by ONR Code 321US.]

Simulation and analysis on seasonal variability of average salinity in the Yellow Sea

The CTD (conductivity, temperature and depth) data collected by six China-Korea joint cruises during 1996–1998 and the climatological data suggest that the seasonal variability of average salinity in the Yellow Sea (Sa) presents a general sinusoid pattern. To study the mechanism of the variability, annual cycles ofSa were simulated and a theoretical analysis based on the governing equations was reported.

Salinity sensors on seals: use of marine predators to carry CTD data loggers

Diving marine predators have been used to collect data on ocean temperature, but salinity measurements have not previously been incorporated into predator-borne data loggers. Here we present data on initial calibration and field trials of a new conductivity, temperature and depth (CTD) data logger used alongside a satellite-positioning transmitter to provide three-dimensional oceanographic information. This provides CTD data analogous to that collected by a ship-deployed undulating oceanographic recorder. Calibration tests of these units showed a near-field effect caused by the proximity of material to the tag, but demonstrate that the resulting data offset can be removed by post hoc calibration. Field tests of the system were conducted on 16 female Antarctic fur seals ( Arctocephalus gazella) at Bird Island, South Georgia. These results matched those found by standard ship-based survey techniques, but suggest temporal variability in the structure and location of the two water masses found to the north of South Georgia. Overall, this initial proof-of-concept work is encouraging; future refinement of this technique is likely to provide an additional data source for both oceanographers and biologists.