Oceanographic Environment Research Articles

Regional Data Center (RDC) of FSUE «TINRO-centre»: its role in prediction of resource state for national fisheries and principal directions of activities

Regional Data Center (RDC) is 40 years old in 2014. Its main goals are accumulation of research data on Far-Eastern marine biological resources and their environments, as well as supervision for the data collection, validation and processing. Principal activities of RDC are: 1) development and implementation of computerize workplaces for scientific and technical personnel aboard research vessels and ashore; 2) logging of primary cruise materials on paper and their digitizing; 3) development and management of large databases (DB) for the information gathered in research cruises and fishery statistics; 4) creation of knowledge bases and geographic information systems (GIS) containing the processed results on long-term monitoring of marine ecosystems; 5 ) performing any user queries to the DB and GIS for quick information support of current scientific, practical and administrative activities in all departments of TINRO; 6) development of new methodological approaches to data processing and automation of related processes by creation of original software; 7 ) inter-institutional data exchange and creation of joint DB; 8) TINRO staff consulting on methodological issues of statistical and cartographic data processing; 9) development of regulations and normative documents regulating relationships in collection, storage and access to the information archived in RDC; 10) scientific researches, independent or joint with other laboratories. These ten trends are focused onto studies of marine ecosystems and their climatic and oceanographic environments, short-term and long-term forecasting of bioresources, rational management of fisheries and aquaculture, planning of research expeditions.

The physical oceanographic environment during the CCE-LTER Years: Changes in climate and concepts

The California Current System (CCS) has been studied by the California Cooperative Oceanic Fisheries Investigations program for many decades. Since 2004, the Southern California Bight (SCB) and the oceanic region offshore has also been the site for the California Current Ecosystem (CCE) Long-Term Ecological Research (LTER) program, which has established long-term observational time series and executed several Process Cruises to better understand physical–biological variations, fluxes and interactions. Since the inception of the CCE-LTER, many new ideas have emerged about what physical processes are the key controls on CCS dynamics. These new perspectives include obtaining a better understanding of what climate patterns exert influences on CCS physical variations and what physical controls are most important in driving CCE ecological changes.Physical oceanographic and climatological conditions in the CCS varied widely since the inception of the CCE-LTER observational time series, including unusual climate events and persistently anomalous states. Although the CCE-LTER project commenced in 2004 in the midst of normal ocean conditions near the climatological means, over the following decade, El Nino/Southern Oscillation conditions flickered weakly from warm to cold, with the Pacific Decadal Oscillation (PDO) generally tracking that behavior, while the North Pacific Gyre Oscillation (NPGO) evolved to persistent and strong positive conditions after 2007, indicative of enhanced upwelling from 2007 to 2012. Together the combined impact of the negative PDO state (La Nina conditions) and positive NPGO state (increased upwelling conditions) yielded remarkably persistent cool conditions in the CCS from late 2007 to early 2009 and from mid-2010 through 2012.The broad-scale climate variations that occurred over the North Pacific and CCS during this time period are discussed here to provide physical context for the CCE-LTER time series observations and the CCE-LTER Process Cruises. Data assimilation fits, using the Regional Ocean Modeling System four-dimensional data assimilation framework, were successfully executed for the 1-month time period surrounding each of the Process Cruises. The fits provide additional information about how the physical flows evolve during the course of the multi-week Process Cruises. Relating these physical states to the numerous biological measurements gathered by the CCE-LTER time series observations and during the Process Cruises will yield vital long-term perspective of how changing climate conditions control the ocean ecosystem in this region and information on how this important ecosystem can be expected to evolve over the coming decades.

Underwater pulsed laser range-gated imaging model and its effect on image degradation and restoration

The imaging of underwater objects illuminated by artificial light has been of long-standing interest to investigators working in oceanographic environments. Pulsed lasers together with range-gated technology have been widely used for underwater optical imaging applications. In order to describe the formation of underwater range-gated images, a pulsed laser underwater imaging model based on pulse spatial and temporal broadening is proposed. Experiments based on a self-assembled laser range-gated imaging system were implemented in our laboratory. Results show good agreements between experiments and simulations. Both results also confirm higher image contrast toward the tail region of the target-reflected light. Furthermore, experiments on underwater image blur and restoration are also implemented and show good image recovery results. The modulation transfer function-based restoration mechanism also implies a way to eliminate the blur effect caused by light forward scattering.

Protocols for acoustic devices on cabled ocean observatories

Cabled ocean observatories offer an unprecedented opportunity for marine acoustic devices. With continuous power and high bandwidth, long-term broadband measurements from both passive and active systems are possible over a wide range of oceanographic environments. In particular, the cabled ocean observatories VENUS and NEPTUNE operated by Ocean Networks Canada offer a unique set of possibilities for acoustic research, ranging from littoral to mid-ocean ridge installations. Since 2006 fiber optic telecommunication cables have provided high power and up to GB data rates from nine distributed observatory Nodes across marine provinces, which include fjords, tidal straits, river deltas, continental shelves, slopes and rises, abyssal plains, and spreading margins. Experience from passive hydrophones as well as both mono- and bi-static active systems including echo-sounders, sonars, and many acoustic Doppler current devices will be discussed. This paper will review our experiences, provide examples, and propose protocols, or at least our suggested best practices, for many active and passive acoustic devices, including calibration, configuration, interference reduction techniques, bandwidth considerations, data handling, and data analysis and delivery methods.

Across-shore variability in plankton layering and abundance associated with physical forcing in Monterey Bay, California

The purpose of this study was to further our understanding of the role of the coastal physical oceanographic environment as a dynamic and constantly evolving habitat for plankton. Over a 3-week period in the summer of 2010, an array of moorings were deployed and shipboard and autonomous underwater vehicle (AUV) surveys were conducted to investigate the association between physical processes and plankton distributions over the Monterey Bay, California inner shelf. Acoustic backscatter, chlorophyll-a fluorescence, and high-resolution zooplankton imagery data collected during the shipboard surveys were used to map the distributions of phytoplankton and zooplankton; and profiles of temperature, salinity, oxygen, and nitrate from the AUV characterized the physical and chemical environment. A synthesis of underway and moored time series data provided insight into the histories of water masses in the area, and facilitated tracking of internal wave groups as they propagated towards shore. A near-bottom intrusion of recently-upwelled water was found to be strongly influenced by the diurnal tide, resulting in daily across-shelf excursions past the mooring array at the 20-m isobath. Behind the leading edge of the intrusion, the water column was highly stratified in temperature, salinity, oxygen, and nitrate; and thin layers of phytoplankton and zooplankton persisted at the upper boundary of the intrusion. In ambient waters shoreward of the intrusion, stratification was weak; copepod, appendicularian, and gelatinous zooplankton abundances were relatively low; and phytoplankton and acoustic backscatter were broadly distributed throughout the lower half of the water column. The arrival of two shoreward-propagating internal wave groups observed during the shipboard survey corresponded with disparate responses in plankton distribution. In the wake of the first wave group, phytoplankton and zooplankton layers thinned or converged; in the wake of the second wave group, an eight-fold increase in gelatinous zooplankton was observed. These findings reveal a strong coupling between physical processes and the abundance and vertical distribution of plankton. It is necessary to understand the underlying physical environment in order to understand the complex distribution of organisms in the sea.

On the front line: integrated habitat mapping for olive ridley sea turtles in the southeast Atlantic

AbstractAimKnowledge and understanding of marine vertebrate spatial ecology are required to identify sources of threat and highlight areas for conservation. Olive ridley sea turtles Lepidochelys olivacea are in decline in some regions, and data for the Eastern Atlantic are sparse. Here, we seek to describe observed, and potential, post‐nesting habitats for this species in the southeast Atlantic. We contextualize these with fisheries catch data to identify areas of potential threat from fisheries interaction for this species.LocationWest coast of Africa, southeast Atlantic.MethodsWe tracked 21 female olive ridley turtles, from two nesting sites, between 2007 and 2010. We used ensemble ecological niche modelling, integrated with knowledge on the physical and biological oceanographic environment, to identify regions where environmental variables exist that may be critical in defining post‐nesting habitats for this species. We further integrate fisheries catch data to contextualize potential threat from fisheries.ResultsWe describe key areas of observed, and potential, olive ridley turtle occurrence at sea, and reveal that there was considerable overlap of these conspecifics, from two distinct nesting regions, within the Angolan exclusive economic zone (EEZ). With the inclusion of fisheries catch data for the region, we highlight areas that have the potential for conflict with fishing activities known to result in bycatch.Main conclusionsThis study demonstrates that it is imperative that marine conservation policy recognizes the spatial extent of highly migratory species with expansive ranges. It also highlights that deficiencies exist in current knowledge of bycatch, both in gear specificity and in catch per unit effort. With integration of vessel monitoring system (VMS) data and those on fisheries catch, knowledge and understanding of bycatch may be improved, and this will ultimately facilitate development of appropriate management strategies and long‐term sustainability of fisheries and their supporting ecosystems.

The geochemistry of deep-sea coral skeletons: A review of vital effects and applications for palaeoceanography

Deep-sea corals were discovered over a century ago, but it is only over recent years that focused efforts have been made to explore the history of the oceans using the geochemistry of their skeletal remains. They offer a promising archive of past oceanic environments given their global distribution, layered growth patterns, longevity and preservation as well as our ability to date them using radiometric techniques. This paper provides an overview of the current state-of-the-art in terms of geochemical approaches to using deep-sea coral skeletons to explore the history of the ocean. Deep-sea coral skeletons have a wide array of morphologies (e.g. solitary cup corals, branching colonial corals) and materials (calcite, aragonite and proteins). As such their biomineralization strategies are diverse, leading to complex geochemistry within coral skeletons. Notwithstanding these complications, progress has been made on developing methods for reconstructing the oceanographic environment in the past using trace elements and isotopic methods. Promising approaches within certain coral groups include clumped isotopes and Mg/Li for temperature reconstructions, boron isotopes and radiocarbon for carbon cycling, εNd, and radiocarbon for circulation studies and δ15N, P/Ca and Ba/Ca for nutrient tracer studies. Likewise there is now a range of techniques for dating deep-sea corals skeletons (e.g. U-series, radiocarbon), and determining their growth rates (e.g. radiocarbon and 210Pb). Dating studies on historic coral populations in the Atlantic, Southern Ocean and Pacific point to climate and environmental changes being dominant controls on coral populations over millennial and orbital timescales. This paper provides a review of a range of successes and promising approaches. It also highlights areas in which further research would likely provide new insights into biomineralization, palaeoceanography and distribution of past coral populations.

Variation in Primary Molt in the Least Auklet

Abstract. Along with breeding and migration, molt is one of the most energetically expensive components of a bird's annual cycle. Auklets (tribe Aethiini) are apparently unique among the Alcidae in that flight-feather molt and breeding overlap. We compared the degree of overlap of primary molt with breeding in the Least Auklet (Aethia pusilla) at four colonies in varying oceanographic environments: Kiska Island (Aleutian Islands, Alaska, 52°N), St. George Island (Pribilof Islands, Alaska, 56°N), St. Paul Island (Pribilof Islands, 57°N), and Cape Ulyakhpen (Chukotka Peninsula, Russia, 64°N). We hypothesized that the onset and speed of feather replacement should be related to latitude or sea-ice dynamics. Flight-feather molt commenced during incubation with up to four primaries replaced by the end of chick rearing. At Kiska, we found no difference in molt rate between adult breeders and nonbreeders, but subadults started molt after adults and were more variable in when they started primary molt. At higher l...

춘계 베링해 알류산 해분의 해양환경 특성

The characteristics of the oceanographic environment in the Aleutian Basin of the Bering Sea during spring in 1996, 1997, and 1999 were clarified. An investigation of the water properties revealed five basic layers in the Bering Sea during spring: (1) a surface layer of warm and low-salinity water induced by solar heating, (2) a subsurface layer of cold and low-salinity water propagated slowly by heat from the surface layer, (3) a thermocline layer where salinity was constant but temperature sharply decreased, (4) a temperature inversion layer, and (5) a deep layer with a gradual decrease in temperature and increase in salinity toward the bottom. The ranges of water temperature and salinity were and 31.81-34.08 in 1996, and 31.9-34.06 in 1997, and and 32.0-34.11 in 1999, respectively. The water temperature of the surface layer was approximately higher in 1997 than in 1996 and 1999. The lowest temperature at a depth of 100-150 m was about lower in 1999 than in 1996 and 1997. Nutrient levels (nitrate, phosphate, and silicate) contributing to the control of the growth of phytoplankton were higher in the Aleutian Basin than in the eastern continental shelf and Bogoslof Island area. This was closely associated with the phytoplankton distribution. Nutrient concentrations were lowest at a depth of 25 m. The high primary production at that depth was confirmed from the vertical distribution of chlorophyll a. Chlorophyll a levels were above in some areas in 1996 and 1999, but below in most areas in 1997. Zooplankton density was about three times higher in 1999 than in 1997.

Biophysical patterns in benthic assemblage composition across contrasting continental margins off New Zealand

AbstractAimTo examine whether benthic assemblages are more diverse in a region of high topographic and oceanographic complexity by comparing benthic invertebrate assemblages across continental margins with contrasting environments.LocationChallenger Plateau and Chatham Rise, to the west and east of New Zealand, respectively.MethodsBenthic faunal data were sourced from extensive seabed surveys in 2007, when both margins were sampled with an epibenthic sled and a towed video system. Three methods were used to investigate benthic assemblages in relation to environmental variables: one based on individual species distribution models (SDMs) using boosted regression trees analysis (BRT), and two community‐based modelling methods using generalized dissimilarity modelling (GDM) and gradient forest analysis (GF), respectively. Each method was used to model and predict the turnover in assemblages with respect to environment – the ‘biophysical patterns’ – across the study region.ResultsAcross Chatham Rise, a complex oceanographic environment arising from steep gradients in productivity and temperature at the Subtropical Front produced a high diversity of assemblages associated with the sub‐Antarctic water mass, the Subtropical Front, steep‐sloping regions and fast tidal currents. In contrast, Challenger Plateau lies entirely beneath a single (subtropical) water mass, and assemblage diversity was lower, with a distinctive assemblage on the plateau itself and a deep‐water assemblage similar to the northern deep‐water assemblage of Chatham Rise. Across both regions, assemblage turnover was fastest in cold waters, at shallow depths and in deep mixed layers.Main conclusionsBenthic assemblages were more varied on Chatham Rise than on Challenger Plateau, supporting the hypothesis that environmentally heterogeneous margins have higher assemblage diversity. Differing assemblages on the northern and southern flanks of Chatham Rise suggest a biogeographical boundary for benthic taxa across the Subtropical Front. These results demonstrate that oceanographically and topographically complex margins have a diverse assemblage structure that should be considered in planning for the sustainable management of diversity.

Correlation between iodine isotopes (129I and 127I) species and marine parameters in the Baltic Sea

Iodine is a bio-intermediate and redox-sensitive element in the oceans and understanding the relationship between transformation of iodine species promotes them as indicators of biochemical cycling in the ecosystems. To gain an insight into the transformation of iodine species, correlations between the iodine species (127IO3−, 127I−, 129I−, 129IO3−) and marine parameters (temperature, salinity, oxygen, total phosphorus, nitrate and ammonium) are assessed here for the Baltic Sea during different seasons. The datasets used cover the periods of August 2006, April 2007 and November 2009. The results indicate that the correlations between radioactive 129I, stable 127I species and marine parameters mainly response to their respective sources as well as oceanographic environments. Also, insignificant correlations of iodine species and nutrients data (total phosphorus, nitrate and ammonium) are observed, suggesting that transformation activity of iodine species in the Baltic Sea is not directly linked to biological production.

A western perspective on research in underwater acoustics and acoustical oceanography

Underwater acoustics and acoustical oceanography are both concerned with sound underwater, the distinction between them being that the former deals primarily with forward problems such as acoustic propagation and scattering, whereas the latter involves the inversion of sound fields to obtain information about the oceanographic environment. Over recent years in the USA and Europe, both disciplines have tended to move away from the use of dedicated acoustic sources, over concern about damage that such sources may inflict on marine mammals. Ambient noise has, to some extent, replaced dedicated sources as the sound field of choice, since it offers the prospect of returning a wealth of information about ocean processes but without the threat to the marine mammal population. To extract such information, the properties of the noise field itself must be well understood (underwater acoustics), as must the inversion procedures necessary to recover the information contained in the noise (acoustical oceanography). A brief introduction to the properties of ambient noise fields will be followed by several examples of noise inversions, the latter illustrating not only the utility of ambient noise inversions but also the complexity of typical noise fields in the ocean. (Research supported by the Office of Naval Research).

Classification of remote Pacific coral reefs by physical oceanographic environment

[1] The oceanographic environment is a key element in structuring coral reef ecosystems by setting the range of physical and chemical conditions in which coral reef-builders live. A cluster analysis of physical and chemical oceanographic data is used to classify coral habitats in the remote tropical and subtropical Pacific Ocean based on average temperature, temperature seasonal cycle, nutrient levels, salinity, aragonite saturation state, storm frequency, intense hurricane hits, and dissolved oxygen as well as temperature anomalies in degree heating weeks. The resulting seven geographic habitats are stable to perturbations in types of data used in the cluster analysis. Based on recent coral reef survey data in the area, the coral cover was related to the identified geographic regions. The habitats tend to be geographically clustered, and each is characterized by a unique combination of oceanographic conditions. Previous studies suggest coral reef habitats are associated with a uniform array of oceanographic conditions, while our results demonstrate that finer-scale variations in physical variables may control coral reef environments. The results better define the physical environment of remote coral reefs, forming a foundation for future work addressing physical habitat perturbation and anthropogenic impacts on reefs.

Seasonal variation in the oxygen isotopic composition of different‐sized planktonic foraminifer Neogloboquadrina pachyderma (sinistral) in the northwestern North Pacific and implications for reconstruction of the paleoenvironment

The oxygen isotope value (δ18O) of planktonic foraminifer shells is one of the most commonly used proxies to reconstruct the paleoenvironment. Neogloboquadrina pachyderma (sinistral) (N. pachyderma (sin.)) is a dominant foraminifer in subpolar and polar region that is used extensively for high‐latitude paleoreconstruction. The present study examined seasonal variation in δ18O of N. pachyderma (sin.) using sediment trap samples collected over 3.5 years in the northwestern North Pacific Ocean. The vital offset value was about −1‰, which agrees with previous plankton tow studies. Large shell individuals (180–250 μm) secrete their shells in a shallower and warmer environment than small ones (125–180 μm), and the difference in δ18O between shell size showed seasonal variation. Although large individuals calcify at a slower rate with slightly heavier δ18O than small individuals, differences between size classes mainly reflect different habitation in the water column and are related to seasonal changes in stratification. During summer, large individuals would calcify mainly at 25–35 m depth, while small individuals calcify near the pycnocline at ∼45 m. During winter, both size classes calcify at or slightly above the weak pycnocline at 45–65 m. Thus, the shell δ18O could record the oceanographic environment around pycnocline depth, and size‐specific differences in δ18O reflect water column stratification. The annual flux‐weighted δ18O corresponded to non‐flux‐weighted mean δ18O value due to the equal contribution of two flux peaks and differences between size classes also related to the stratification. It suggests that fossil δ18O data could represent the annual mean environment around pycnocline and past stratification.

Suppression of the 2010 Alexandrium fundyense bloom by changes in physical, biological, and chemical properties of the Gulf of Maine.

For the period 2005-2009, the abundance of resting cysts in bottom sediments from the preceding fall was a first-order predictor of the overall severity of spring-summer blooms of Alexandrium fundyense in the western Gulf of Maine and southern New England. Cyst abundance off mid-coast Maine was significantly higher in fall 2009 than it was preceding a major regional bloom in 2005. A seasonal ensemble forecast was computed using a range of forcing conditions for the period 2004-2009, suggesting that a large bloom was likely in the western Gulf of Maine in 2010. This did not materialize, perhaps because environmental conditions in spring-summer 2010 were not favorable for growth of A.fundyense. Water mass anomalies indicate a regional-scale change in circulation with direct influence on A. fundyense's niche. Specifically, near-surface waters were warmer, fresher, more stratified, and had lower nutrients than during the period of observations used to construct the ensemble forecast. Moreover, a weaker-than-normal coastal current lessened A. fundyense transport into the western Gulf of Maine and Massachusetts Bay. Satellite ocean color observations indicate the 2010 spring phytoplankton bloom was more intense than usual. Early-season nutrient depletion may have caused a temporal mismatch with A. fundyense's endogenous clock that regulates the timing of cyst germination. These findings highlight the difficulties of ecological forecasting in a changing oceanographic environment, and underscore the need for a sustained observational network to drive such forecasts.

Different Means to the Same End: Long-Distance Migrant Seabirds from Two Colonies Differ in Behaviour, Despite Common Wintering Grounds

Although seabirds that are trans-equatorial migrants show apparently broad overlap among populations in the non-breeding season, such large-scale pattern may conceal subtle but nevertheless key differences in migratory behaviour. These specializations could reflect adaptation to different environments during the breeding season, carry-over effects from the breeding to the nonbreeding period, or asymmetries in competitive ability of birds of different origin. We compared the migratory and wintering behaviour of Cory's shearwaters Calonectris diomedea nesting in Berlengas and in the Selvagens, two colonies in contrasting oceanographic environments, separated by ca. 1200 km. Although no differences were found in winter distribution, there was a marked divergence in timing, route and the use of staging areas during the postbreeding (autumn) migration. Birds from Berlengas typically travelled to oceanic waters in the North Atlantic for an extended stopover, whereas those from Selvagens rarely did so. In the South Atlantic, birds from Selvagens spent more time in flight, perhaps because they had higher energy and nutrient requirements for feather replacement compared to birds from Berlengas, which moult more flight feathers during breeding. Stable isotope analyses of feathers suggested that this variation in activity patterns was unrelated to trophic ecology. Differences in migration routes and stopovers may expose populations to distinct threats, and should be taken into consideration when defining units for conservation purposes and developing appropriate management strategies.

Phytoplankton biomass and microbial abundances during the spring upwelling season in the coastal area off Concepción, central-southern Chile: Variability around a time series station

In the coastal system off Concepción, time series observations at a fixed station (St. 18) have shown strong seasonal changes in the oceanographic environment of the upper layer (<35 m depth), accompanied by large increases in phytoplankton biomass during the spring-summer upwelling season. These blooms, dominated by microplanktonic diatoms, have usually overshadowed the relevance of the smaller microbial components during upwelling. This study focuses on the variability of oceanographic conditions and their association with the structure of the planktonic community (size fractionated chlorophyll-a and microbial abundances) in the upper layer during the upwelling season, examining the extent to which St. 18 is representative of the coastal system off Concepción during springtime. For this purpose, data from three consecutive springs (2004, 2005, 2006) were compared, which included cruises for all years (8 stations around St. 18) as well as monthly sampling at St. 18. Most of the spatial (submesoscale) variability in chlorophyll-a and the microbial components was not significant, but data dispersion around mean values was high. Water column structure (temperature and salinity) in the upper layer explained a significant fraction (25–65%) of the spatial variability in most of the planktonic components; their responses to oceanographic variability were linear in some cases and non-linear in others. For the most part, St. 18 appears to adequately represent mean oceanographic conditions and the structure of planktonic communities in the coastal waters off Concepción during springtime, however spatial variability needs to be taken into account in the interpretations of temporal changes at this fixed station as well as in assessments of carbon flow within, and exportation processes from, this upwelling system.

Collection of Larval Bluefin Tuna (Thunnus Thynnus) Outside Documented Western Atlantic Spawning Grounds

Atlantic bluefin tuna, Thunnus thynnus (Linnaeus, 1758), are highly migratory and capable of traversing large distances throughout the North Atlantic Ocean. However, the majority of spawning activity has only been reported from the Mediterranean Sea and Gulf of Mexico. In early April 2009, low numbers of very small larval bluefin tuna were collected within and south of the Yucatan Channel, and along the western boundary of the Loop Current, northeast of Campeche Bank. In situ current velocity measurements showed that these larvae were collected in moderate to strong northward flow regimes, suggesting that they were spawned outside of the Gulf of Mexico. Here we describe the location and oceanographic environment of these larval bluefin tuna collections, and compare the 2009 data with some historical collections in the area.

Three dimensional parabolic equation modeling of acoustic intensity fluctuations due to internal wave phenomena.

During the Shallow Water 2006 (SW06) experiment, a J-15 acoustic source deployed from the Research Vessel Sharp transmitted broadband (50–450 Hz) chirp signals 15 km away from a vertical line array. The array was intentionally positioned near the shelf-break front and in an area where internal waves are known to occur. During the same time an internal wave, labeled event 44, passed through the sound field such that the internal wave front was near parallel to the acoustic transmission path. Measured data show substantial intensity fluctuations that vary over time and space due to complex multimode and multipath (both two and three dimensional) interference patterns. This presentation compares three dimensional modeling results using the experimental geometry, acoustic signal parameters, and a simulated oceanographic environment based on environmental moorings and ship-born sensors to mimic the measured internal wave event. A modified version of the three dimensional Monterey–Miami parabolic equation (MMPE) code, which incorporates a user-defined sound speed field, is used. Measured and modeled intensity fluctuations are compared during dominating horizontal regimes such as refraction, focusing, and defocusing. Modal-dependent time-arrival analysis during the different horizontal regimes is examined. A sensitivity study of different sea-bottom properties is explored. [Work sponsored by the Office of Naval Research.]

Environmental knowledge and operational effectiveness at the NATO Undersea Research Centre.

One of the primary areas of research at the NATO Undersea Research Centre (NURC) is environmental knowledge and operational effectiveness. The objective of this work is to provide environmental information in support of maritime operations from the planning stages through to real‐time decision making. Generically, this is accomplished by parametrizing the environment according to need and providing the best knowledge available for each parameter including uncertainty. In practice, the environment is measured using a variety of mobile and remote sensors, including AUVs, with the aim of improving high‐resolution models of the oceanographic environment. In turn, these models and measurements are used as input for operational planning and prediction tools. This talk will describe recent and upcoming experimental work at the NURC designed to test these concepts and their application to acoustic based planning and prediction tools. The goal is to demonstrate the use of these concepts to improve prediction capabilities for transmission loss and signal excess in an operational area.