Showing papers by "National Ocean Service published in 1993"
TL;DR: In this paper, the continuous series of sea level at Key West, Florida commenced in 1913, but they have discovered sporadic measurements that date back to 1846, and they find that dH/dt is 0.19±0.01 cm/yr, and that dµH/t = [9.6±8.6]·10−3 cm/r.
Abstract: The continuous series of sea level at Key West, Florida commenced in 1913, but we have discovered sporadic measurements that date back to 1846. From records at the U.S. Army Corps of Engineers and the U.S. Coast and Geodetic Survey, the sea level series has been connected to a Summary (common) Datum. Thus, a gappy record of monthly and annual mean heights (H[t]), perhaps the United States' longest series over San Francisco (ca. 1854) or New York ( ca. 1856), can be tested to ascertain if the rise in relative sea level at this site is stationary. Applying first and second order least squares and two-phase regression analyses, we find that dH/dt is 0.19±0.01 cm/yr, and that d²H/dt²= [9.6±8.6]·10−3 cm/yr²; the two-phase regression shows H[t] rising 0.15±0.03 cm/yr before ca. 1925 and 0.23±0.01 cm/yr afterwards. Neither the second-order regression coefficient nor d²H/dt² nor the two-phase calculation are significant above the 75% confidence level, but all three are weakly consistent with accelerated rise. For the epoch 1951–1987, Key West sea level, corrected for post-glacial rebound, is best explained by concurrent measurements of 0–1,000 db dynamic height anomaly change.
111 citations
01 Jan 1993
TL;DR: In 1985, the NGS introduced GPS orbit formats and weekly orbit products based on those formats as discussed by the authors, which are very specific regarding contents, epoch interval, and arc length; however, the formats are general.
Abstract: In 1985 the NGS introduced GPS orbit formats and weekly orbit products based on those formats. The products are very specific regarding contents, epoch interval, and arc length; however, the formats are general. The formats permit any start time, any epoch interval, any number of epochs, and any number of satellites. These formats also accommodate partial orbital data for one or more satellites. These formats come In ASCII and binary and comprise either position data or position and velocity data. Although these formats have been used for 6–7 years and have been well received by the GPS community, it was decided that they would be enhanced to include satellite clock information. The 1985 (first generation) orbital formats and products will continue to be valid.
32 citations
TL;DR: The toxic effects of organic and saline extracts of sediment samples collected from 16 sites in Boston Harbor, Massachusetts and from 17 sites in the Hudson River-Raritan Bay estuary, New York were tested with the Microtox® bioassay as mentioned in this paper.
Abstract: The toxic effects of organic and saline extracts of sediment samples collected from 16 sites in Boston Harbor, Massachusetts and from 17 sites in the Hudson River-Raritan Bay estuary, New York were tested with the Microtox® bioassay. This bioassay measures changes in light production by bioluminescent marine bacteria exposed to sediment extracts. Organic solvent extracts of all 33 sediments showed some degree of toxicity, with sediment samples from sites in the urban areas of the bays being significantly more toxic than those from less urbanized areas of the bays. Saline extracts, however, were less toxic, only seven of 33 saline extracts produced a significant response using the recommended method of data analyses. The proportional decrease in bacterial light production at the highest concentration of saline sediment extract in the reaction mixture compared to the bacterial light production in the controls (saline light change—SLC) appeared to be a better indicator of sediment toxicity than generating a saline EC50 (the amount of sediment required to reduce bioluminescence 50%) value; 16 of 33 saline extracts produced a significant response (⩾10% reduction in bioluminescence). Organic extracts of sediments previously extracted with saline were also always toxic in the Microtox® bioassay but were less toxic than sediments not previously extracted. Organic EC50 and SLC were inversely related to concentrations of sediment contaminants, principally low- and high-molecular-weight polycyclic aromatic hydrocarbons (PAHs). This relationship was strongest for the organic solvent extracts of sediments tested in the bioassay. Organic solvent extracts of sediments from Boston Harbor were also significantly more toxic in the Microtox® bioassay than those from the Hudson-Raritan estuary, even though sediment concentrations of PAHs, a measure of anthropogenic contamination, were similar. The cause for the differential toxicity is unknown at this time, but chemical contaminants other than chlorinated hydrocarbons (CHs) and PAHs may be contributing to the observed toxicity in the Microtox® bioassay using organic extracts of sediment. Testing sediment toxicity using organic extracts of sediment with the Microtox® bioassay provides better estimates of toxicity due to sediment contaminants than using saline extracts of sediments.
29 citations
TL;DR: Satellite altimetry continues to have an extraordinary impact on the Earth sciences and is sure to be considered the most important new observing tool for marine geophysics and geology to emerge in recent times as discussed by the authors.
Abstract: Satellite altimetry continues to have an extraordinary impact on the Earth sciences. It is sure to be considered the most important new observing tool for marine geophysics and geology to emerge in recent times. Spacecraft that have used and are currently using radar altimeters to map sea-surface topography, and thereby marine gravity, include Geos-3, Seasat, Geosat, ERS-1, and Topex/Poseidon. To date, however, only Geosat altimeter data have possessed both the accuracy and density of coverage necessary to clearly resolve tectonic details in the marine gravity field on a global basis.
27 citations
18 Oct 1993
TL;DR: A 1200 kHz Broad Band Acoustic Doppler Current Profiler (BBADCP) from RD Instruments was tested in 1992 to determine its applicability to National Ocean Service programs as mentioned in this paper.
Abstract: A 1200 kHz Broad Band Acoustic Doppler Current Profiler (BBADCP) from RD Instruments was tested in 1992 to determine its applicability to National Ocean Service programs. A series of tow carriage tests was performed at the David Taylor Research Center and comparisons made with standard narrow band ADCP systems. Field tests were performed in the Patuxent River towing the BBADCP in a modified catamaran. The intent is to use the system to perform high resolution current transects from ships of opportunity in coastal waters and estuaries. These tests determined the maximum water track range and tested bottom tracking to depths of 40 meters. Comparisons were performed with a bottom-mounted 1200 kHz narrow band ADCP by anchoring the catamaran 50 meters down river from the platform. The results showed disturbing differences that cannot be adequately explained. Data are presented showing the results of laboratory and field tests and plans are discussed for future tests. >
3 citations