Showing papers by "National Ocean Service published in 1998"

The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis

Abstract: A new method for analysing nonlinear and non-stationary data has been developed. The key part of the method is the empirical mode decomposition method with which any complicated data set can be dec...

Coupling of Biennial Oceanic Rossby Waves with the Overlying Atmosphere in the Pacific Basin

Abstract: Anomalies of TOPEX/Poseidon sea level height (SLH), NCEP sea surface temperature (SST), and ECMWF meridional surface wind (MSW) and derived wind stress curl (WSC) are mapped biweekly over the global ocean from 60°S to 60°N for two years from 1993 to 1994. These anomalies (i.e., differences from the average over the two years) allow one cycle of biennial climate change to be examined, with the paucity of temporal degrees of freedom mitigated by greater numbers of spatial degrees of freedom. Time–longitude diagrams of SLH anomalies reveal biennial Rossby waves in the Pacific ocean with westward phase speeds in the extratropics (Tropics) faster (slower) than expected of free biennial Rossby waves. Complex empirical orthogonal function analysis of SLH, SST, MSW, and WSC anomalies finds the beta-refraction pattern of these biennial Rossby waves in all four variables over most of the eastern-central Pacific Ocean, suggesting that oceanic Rossby waves there are coupled with the overlying atmosphere. The...

Zooplankton feeding ecology : Grazing by marine copepods and cladocerans upon phytoplankton and cyanobacteria from Kingston Harbour, Jamaica

Abstract: Grazing by the copepods Tcworci /irrhiirutu and Acurlicr IiNjehorgii and the marine cladoceran Peiiilin uriro.~rri.~ on natural phytoplankton and cyanobacteria assemblages from Kingston Harbour. Jamaica, was examined in summer 1992. Food assemblages were often dominated by an unidentified filamentous cyanobacterium. with abundances of up to 1.16 x lo4 filaments.ml I. Other abundant phytoplankters included microflagellates and diatoms of the genus Nir:schiri. Mean clearance rates for the entire food assemblage ranged from 0.10 to 2.41 ml 'animal -I. h-', although most mean clearance rates were between 0.5 and I.5 ml . animal-' h- I. Patterns of selection of different food items by various grazers on different dates were variable and inconsistent. Microscopic measurements revealed that cyanobacterial filament lengths were shorter in grazed than initial aliquots during a cyanobacterium bloom in August. This suggests that grazers reduced lengths of many filaments by biting otl'portions, in addition to consuming entire filaments. Such 'filament clipping' of cyanobacteria filaments has been recorded previously in freshwater studies and suggests that grazers impact a larger portion of the phytoplankton assemblage than is accounted for by ingestion and clearance rates based only upon removal of filaments. Grazers exhibited no adverse effects from consuming cyanobacteria. Cyano- hacterkd are often considered to be toxic or of poor food quality for planktonic grazers. but due to the high abundance and dominance of filamentous cyanobacteria in Kingston Harbour. if these cyano- bacteria were ungrazed. there would at times be little alternative phytoplankton food for copepods and cladocerans. Our results suggest that the trophic role of tilamentous cyanobacteria in pelagic food webs of the tropical ocean should be further investigated and possibly reconsidered.

Toxicity of sediment associated PAHs to the estuarine crustaceans, Palaemonetes pugio and Amphiascus tenuiremis

Abstract: Toxicity of Sediment Associated PAHs to the Estuarine Crustaceans, Palaemonetes pugio and Amphiascus tenuiremis E. F. Wirth, M. H. Fulton, G. T. Chandler, P. B. Key, G. I, Scott 1 USDC, NOAA, National Ocean Service, Center for Coastal Environmental Health and Biomolecular Research at Charleston, 219 Fort Johnson Road, Charleston, SC 29412, USA 2 Department of Environmental Health Sciences, School of Public Health, University of South Carolina, Columbia, SC 29208, USA

New Technology for Shallow Water Hydrographic Surveys

Abstract: The United States Office of Coast Survey is developing technology for shallow water hydrographic surveys in order to increase the efficiency with which hydrographic data are acquired and to improve the likelihood that all potential dangers to navigation are detected in the course of a hydrographic survey. Three areas of technology hold the greatest promise for meeting those goals: Airborne Lidar Hydrography (ALH), Shallow Water Multibeam Sonars (SWMB), and digital side scan sonar, especially the Coast Survey’s new High Speed, High Resolution Side Scan Sonar (HSHRSSS). The Coast Survey expects that all its ALH surveys will be outsourced to private sector contractors, and that its SWMB and side scan sonar surveys will be accomplished by both NOAA survey vessels and by private sector contractors. This diversity of sources for survey data influences the strategy for managing these new technologies.

Modern Under-Keel Clearance Management

Abstract: This paper provides an overview of recent technological developments that have improved the ability to manage under-keel clearance (UKC) in ports. The inaccurate determination of the UKC of large-draft ships entering or leaving depthlimited ports can have serious safety, economic, and environmental consequences. A ship's master can manage his ship's UKC by: (1 ) taking actions that affect the ship's dynamic draft (such as changing the ship's speed) and (2) scheduling his ship's transit of the planned route to ensure that there will be sufficient water level for safe passage when the ship reaches locations with controlling depths. To do this, however, he must have accurate real-time and forecast environmental information along his route, as well as a validated method of predicting his ship's motion (and thus dynamic draft) for various situations. At a minimum, this information must include accurate charted depths and underwater hazards, water levels, and ship-specific channel-specific prediction formulas for dynamic draft (based on ship speed, static draft, and water depth). The dynamic draft calculation may also require information on currents, water density, and waves, swell, and/or seiching. Recently developed systems that can provide the necessary information for UKC management include: nowcast/forecast oceanographic model systems (a necessary step beyond real-time oceanographic systems); on-the-fly GPS systems to provide accurate ship motion data for calibrating dynamic-draft prediction systems; modern hydrographic measurement systems (such as shallowwater multibeam and side-scan sonar systems); and modern electronic nautical chart systems (and their supporting rapid update services). This paper includes discussion of what further improvements to these systems are needed to make effective UKC management a reality.