320 research outputs found
Progress in the measurement of salinity and oxygen at the Woods Hole Oceanographic Institution
Improvements in the measurement of salinity and dissolved
oxygen during the past few years at WHOI have increased the accuracy of
salinity observations to +/- 0.001 ppt and that of dissolved oxygen
determinations to +/- 0.04 ml/1. These improvements are attributable to
the careful maintenance of the sample collection and analysis
equipment, the construction of portable, sea going laboratories in
which the temperature is constant to +/- 1 degree C and the skillful
use of an Autosal 8400-A salinometer and a Metrohm Titroprocessor by
well trained technicians. An automated data logging system eliminates
transcription errors and facilitates the timely calibration of the CTD
sensors.Funding was provided by the National Science Foundation
under grant Nos. OCE 85-15642 and OCE 82-13967
Hydrographic data from R. V. Endeavor cruise 129
Hydrographic and CTD data collected during R.V. Endeavor
cruise 129 are presented. These data include temperature, salinity
and dissolved oxygen observed at standard levels by a Neil Brown
Instrument Systems' CTD-02 profiler and salinity, dissolved oxygen,
silica, phosphate and nitrate values at the observed depths of the
collected water samples. Ninety- two stations were occupied on two
short sections within the Caribbean and one long meridional section
at (nominally) 64° West from the British Virgin Islands to the 200
m depth contour south of Newfoundland. Also presented are a series
of sectional profiles of the six observed parameters as a function
of depth.Funding was provided by the National Science Foundation
under grant Number OCE 84-14243
Dissolved oxygen measurments in sea water at the Woods Hole Oceanographic Institution
This report describes a modified Winkler titration technique that has been used for the past 25 years at the Woods Hole Oceanographic Institution (WHOI). During this time most of the dissolved oxygen measurements made at sea by WHOI personnel have been analyzed with this technique and only relatively minor, evolutionary changes in the procedures and equipment have occurred. These changes, however, have improved the precision and accuracy of deep-sea dissolved oxygen measurements to 0.005 ml/l and 0.02 ml/l respectively.Funding was provided by the National Science Foundation through grant Number OCE 87-16910
Automated oxygen titration and salinity determination
This report describes a newly developed automated Winkler titration system for dissolved oxygen in seawater which is presently in use at the Woods Hole Oceanographic Institution. This amperometric, calculated, endpoint system was compared with two different automated and one manual Winkler method during a recent cruise. The four different methods agreed to within about 0.04 ml/l. The system described here measures the titrant needed to reach the endpoint with a resolution better than 0.001 ml. The standard deviation of replicate samples is 0.005 ml/l and the accuracy is about 0.02 ml/l. A technique to automatically acquire conductivity ration measurements and calculate salinity using a Guildline Autosal Salinometer is also described.Funding was provided by the National Science Foundation through Grant No. OCE88-22542
A trans-Indian Ocean hydrographic section at latitude 32°South : data report of RRS Charles Darwin cruise #29
A trans-Indian Ocean hydrographic section employing CTD/O2 profilers was conducted between Africa and Australia during
austral spring 1987. The cruise track ranged between 29°S and 34°S; the average latitude of the crossing was 32°S. The purpose of
the cruise was to explore various aspects of the South Indian Ocean including the characteristics of the core water masses of this
ocean, the strength of the subtropical gyre, the structure and transport of deep western-boundary currents, and the net meridional
heat flux. A total of 109 CTD/O2 profiles with associated rosette water sample measurements and 347 XBT profiles were collected,
supplemented by underway upper ocean velocity, bathymetric and sea surface temperature and salinity data. This report detals the
data collection, calibration, and reduction methods, and summarizes the hydrographic observations.Funding was provided by the National Science Foundation through
Grant No. OCE 86-14497
A comparison of methods for the determination of dissolved oxygen in seawater
An intercalibration of dissolved oxygen methods was conducted at 2 stations
in the Sargasso Sea between April 28 and May 3, 1990. The experiment compared
three techniques using automated endpoint detection with the manual Winkler method using a starch endpoint. Institutions participating in the
intercomparison were the Bedford Institute of Oceanography (automated photometric
titration), the University of Delaware (automated amperometric titration), the
Scripps Institution of Oceanography (manual titration), and the Woods Hole
Oceanographic Institution (automated amperometric titration).
Differences in measured oxygen concentrations between institutions were
encouragingly small. However, small, systematic differences in dissolved oxygen
between institutions did exist. The range between the highest and lowest oxygen
values reported by the 4 institutions never exceeded 0.6% over the entire
concentration range studied (3.4 to 6.2 mlj1). The good agreement is probably
due to the use of the essentials of Carpenter's (1965) modification of the
Winkler method by all institutions.
The intercalibration revealed several aspects of dissolved oxygen
measurements that require further research: (1) the intercalibration should be
extended to very low oxygen concentrations; (2) procedures for measur ing and
applying corrections for the seawater blank need to be formalized; (3) a simple
procedure to measure the temperature of seawater at the time of sampling needs
to be developed; and (4) the solubility of atmospheric oxygen in the Winkler
reagents must be measured as a function of temperature.
The intercalibration also revealed that analytical techniques required for
precise and accurate volumetric measurements were often not applied, even by
experienced analysts. It was found that uncalibrated pipets were used to
dispense standards, that the volumes of oxygen flasks were not corrected for
buoyancy, and that corrections for the thermal expansion of aqueous solutions were often not applied.This research was supported by National Science Foundation Grants OCE 88-
22542 and OCE 88-21977 and OCE 89-07815. Preparation and distribution of this
report by the WHP Office, Woods Hole Oceanographic Institution, Woods Hole, MA.
02543 USA, was supported by NSF Grant OCE 89-07815
Regional High-Resolution Benthic Habitat Data From Planet Dove Imagery For Conservation Decision-Making and Marine Planning
High-resolution benthic habitat data fill an important knowledge gap for many areas of the world and are essential for strategic marine conservation planning and implementing effective resource management. Many countries lack the resources and capacity to create these products, which has hindered the development of accurate ecological baselines for assessing protection needs for coastal and marine habitats and monitoring change to guide adaptive management actions. The PlanetScope (PS) Dove Classic SmallSat constellation delivers high-resolution imagery (4 m) and near-daily global coverage that facilitates the compilation of a cloud-free and optimal water column image composite of the Caribbean’s nearshore environment. These data were used to develop a first-of-its-kind regional thirteen-class benthic habitat map to 30 m water depth using an object-based image analysis (OBIA) approach. A total of 203,676 km2 of shallow benthic habitat across the Insular Caribbean was mapped, representing 5% coral reef, 43% seagrass, 15% hardbottom, and 37% other habitats. Results from a combined major class accuracy assessment yielded an overall accuracy of 80% with a standard error of less than 1% yielding a confidence interval of 78–82%. Of the total area mapped, 15% of these habitats (31,311.7 km2) are within a marine protected or managed area. This information provides a baseline of ecological data for developing and executing more strategic conservation actions, including implementing more effective marine spatial plans, prioritizing and improving marine protected area design, monitoring condition and change for post-storm damage assessments, and providing more accurate habitat data for ecosystem service models
Globally Gridded Satellite (GridSat) Observations for Climate Studies
Geostationary satellites have provided routine, high temporal resolution Earth observations since the 1970s. Despite the long period of record, use of these data in climate studies has been limited for numerous reasons, among them: there is no central archive of geostationary data for all international satellites, full temporal and spatial resolution data are voluminous, and diverse calibration and navigation formats encumber the uniform processing needed for multi-satellite climate studies. The International Satellite Cloud Climatology Project set the stage for overcoming these issues by archiving a subset of the full resolution geostationary data at approx.10 km resolution at 3 hourly intervals since 1983. Recent efforts at NOAA s National Climatic Data Center to provide convenient access to these data include remapping the data to a standard map projection, recalibrating the data to optimize temporal homogeneity, extending the record of observations back to 1980, and reformatting the data for broad public distribution. The Gridded Satellite (GridSat) dataset includes observations from the visible, infrared window, and infrared water vapor channels. Data are stored in the netCDF format using standards that permit a wide variety of tools and libraries to quickly and easily process the data. A novel data layering approach, together with appropriate satellite and file metadata, allows users to access GridSat data at varying levels of complexity based on their needs. The result is a climate data record already in use by the meteorological community. Examples include reanalysis of tropical cyclones, studies of global precipitation, and detection and tracking of the intertropical convergence zone
High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data II: The Spring Equatorial Stripe
This is the second paper in a series aimed at finding high-redshift quasars
from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by
the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this
paper, we present 22 high-redshift quasars (z>3.6) discovered from ~250 deg^2
of data in the spring Equatorial Stripe, plus photometry for two previously
known high-redshift quasars in the same region of sky. Our success rate of
identifying high-redshift quasars is 68%. Five of the newly discovered quasars
have redshifts higher than 4.6 (z=4.62, 4.69, 4.70, 4.92 and 5.03). All the
quasars have i* < 20.2 with absolute magnitude -28.8 < M_B < -26.1 (h=0.5,
q_0=0.5). Several of the quasars show unusual emission and absorption features
in their spectra, including an object at z=4.62 without detectable emission
lines, and a Broad Absorption Line (BAL) quasar at z=4.92.Comment: 28 pages, AJ in press (Jan 2000), final version with minor changes;
high resolution finding charts available at
http://www.astro.princeton.edu/~fan/paper/qso2.htm
Sloan Digital Sky Survey Imaging of Low Galactic Latitude Fields: Technical Summary and Data Release
The Sloan Digital Sky Survey (SDSS) mosaic camera and telescope have obtained
five-band optical-wavelength imaging near the Galactic plane outside of the
nominal survey boundaries. These additional data were obtained during
commissioning and subsequent testing of the SDSS observing system, and they
provide unique wide-area imaging data in regions of high obscuration and star
formation, including numerous young stellar objects, Herbig-Haro objects and
young star clusters. Because these data are outside the Survey regions in the
Galactic caps, they are not part of the standard SDSS data releases. This paper
presents imaging data for 832 square degrees of sky (including repeats), in the
star-forming regions of Orion, Taurus, and Cygnus. About 470 square degrees are
now released to the public, with the remainder to follow at the time of SDSS
Data Release 4. The public data in Orion include the star-forming region NGC
2068/NGC 2071/HH24 and a large part of Barnard's loop.Comment: 31 pages, 9 figures (3 missing to save space), accepted by AJ, in
press, see http://photo.astro.princeton.edu/oriondatarelease for data and
paper with all figure
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