3d. Presentations
4. Acknowledgements
5. References
Tables
Table 1. CTD Station Information
Figures
Figure 1. Jeffrey's Basin 1997 mooring configuration.
Figure 2. CTD salinity correction plots.
Appendix Figures
Individual profiles at each hydrographic station are presented on 2 pages:
Page A: Station profiles of temperature, salinity, sigma-theta
density, stability (N-squared) and temperature-salinity diagram (top 3
panels show surface layer profiles at higher resolution, remainder are
all on the same depth /property scale for intercomparison).
Page B: Station profiles of dissolved oxygen, transmissivity,
fluorometer (Chl-a), irradiance (PAR), temperature-dissolved oxygen and
salinity-dissolved oxygen diagrams when observed.
This report describes a set of hydrographic measurements obtained 18-19
May 1997 as part of the NSF-supported "Observational / Modeling Study
of Wintertime Convection and Water Mass Formation" in the western Gulf
of Maine (GOM). Herein we document the third of seven planned University
of New Hampshire (UNH) cruises aboard the R/Vs ENDEAVOR and OCEANUS as
part of this "Convective Overturn Experiment" (CONVEX) (see Bub et al.,
1997a). This report and these data can be accessed via the WWW address:
http://ekman.sr.unh.edu/OPAL/CONVEX/
1. Introduction
Click here to read an introduction to the CONVEX program
2. Cruise Narrative
The RV Endeavor was underway from the University of Rhode Island
Graduate School of Oceanography pier, Narragansett, RI at 0040L (0540Z).
She passed through the Cape Cod Canal enroute to Jeffreys Basin. After a
survey of bathymetry at the site, an oceanographic mooring (JB-97, Figure 1) was
placed at 1823L (2223Z) near 43� 00.12N 70� 09.50W. The deployed
instrument string included temperature and conductivity sensors at
nominal depths of 10, 30, 60 and 100 m, 14 thermistors at 10 m intervals
between 2 and 132 m, and an upward looking acoustic doppler current
profiler (ADCP) at 132 m depth (Figure 1). A CTD profile using the
Endeavor SeaBird SBE-911+ (measuring pressure, temperature,
conductivity, dissolved oxygen, fluorescense, PAR and light
transmission) was observed and the ship headed home.
While underway, ship instruments routinely recorded near-surface
temperature / salinity and a weather package (IMET) provided a
continuous records of air pressure, temperature, relative humidity, wind
speed / direction, short / long wave radiation, along with ship's
position and movement. A RDI 150 KHz ADCP recorded ocean current
structure along the ship's path.
Two drifters were launched for R. Limeburner at 0021L (0521Z) off Race
Point, MA at 42� 10.06N 70� 10.30W. After passing through Cape Cod
Canal, RV Endeavor returned to GSO at 1300L (1700Z).
Postlog: The JB-97 mooring was recovered aboard the UNH RV Gulf
Challenger on 14 June 1997. Due to conducting cable failure, the
temperature and conductivity data were not recoverable. The internally
recorded ADCP data have been recovered and analyses are in progress.
2.a. Scientific Party:
W. Brown (Chief Scientist), F. Bub, K. Morey, K. Garrison, P. Mupparapu, and T. Orvash (URI Marine Technician).
2.b. Cruise Photos
Click here to see EN-300 Cruise photos. GIF photos of the EN-300 scientific party and cruise work are included.
3.a. Hydrographic Data Acquisition
The R/V ENDEAVOR's SeaBird SBE 911 Plus CTD Profiler was used to measure
vertical profiles of electrical conductivity and temperature versus
pressure at 01 hydrographic station during 18 - 19 May 1997. Sensors on
the CTD were factory calibrated on 9 October 1996. This CTD sampled at a
rate of 24 scans per second. Salinity profiles were computed from these
data. Additional sensors on the SBE-911+ also recorded data for the
measurement of dissolved oxygen, water transmissivity, fluorescence
(Chl-a), and irradiance (PAR). Data acquisition, display and storage
were managed by an on-board computer using the SeaBird software package
SEASOFT.
At the station, the CTD was lowered at a rate of approximately 30 meters
per minute to depths within 5-10 meters of the bottom. Two to six water
samples were collected with a rossette of 5-liter Niskin bottles, and
specimens for nutrient and oxygen isotope analyses were gathered. For
each station, the conductivity of one water sample was determined using
ENDEAVOR's Guildline 8400A Autosal and the corresponding salinities was
used to correct salinity values derived from the raw CTD measurements ( Figure 2).
3.b. Data Processing
The CTD data were processed using a series of SeaBird SEASOFT programs (listed in parentheses) in which:
- a. Raw hexidecimal CTD output is converted into engineering
units (DATCNV). Only downcast data were used to produce station
profiles. Bottles samples were taken during upcasts and average CTD data
at each bottle depth were stored (ROSSUM).
- b. Noise contamination greater than 2 standard deviations
from 50 point sections was removed (WILDEDIT). In addition, CTD downcast
data associated with downward velocities of less than 25 cm/s (due to
looping) were discarded (LOOPEDIT).
- c. Data were filtered to ensure consistent response times using a low pass filter with time constant 0.15 sec (FILTER).
- d. Data were averaged into 1 decibar (dbar) bins (BINAVG)
to produce profiles of temperature, salinity, etc., versus pressure from
the unequally-spaced cast data from each station.
- e. These profile data were stored as ASCII files on floppy disks for post-processing and plotting.
Click here for data descriptions, corrections and estimated accuracy/precision
3.d. Data Presentations
The corrected hydrographic data are presented as:
(1) Station profile plots and property-property diagrams; and
(2) Vertical section contour plots.
3.d.1. Vertical Profile Plots:
For each of the CTD stations, page "A" presents a set of profiles
(potential temperature, salinity, sigma-theta) and potential temperature
- salinity diagrams (Figure 01A). The upper surface to 125 m deep plots
represent zoomed details of water property structure in the main
thermocline (halocline, pycnocline) zone (horizontal scales vary). The
middle plots present these water property structures for the entire
water column (scales are fixed to facilitate). A Brunt-Vaisaila
frequency (N-squared) plot indicates water column stability.
On page "B" are presented CTD station profiles of measured dissolved
oxygen, transmissivity, fluorometer (Chl-a), irradiance (PAR), as well
as computed sound velocity, temperature-dissolved oxygen, and
salinity-dissolved oxygen diagrams (Figures 01B). Note that during the
first part of the cruise, the dissolved oxygen and PAR sensors were not
working.
3.d.2. Data Files
Preliminary profiles can be made available immediately as (a) ASCII
files upon request to Frank.Bub@unh.edu. Upon final quality control, we
will provide (b) JGOFD default files through an ftp site.
Other EN-300 Cruise data including enroute ADCP, TSAL, navigation,
bathymetry and observed weather records. These will also be made
available upon further processing.
4. Acknowledgements
The invaluable assistance of Karen Garrison, Susan Becker, Steve
Gaudreau, Glenn Rice, and Greg Young resulted in an extremely successful
hydrographic survey. We appreciate the efforts of Captain Tyler and
crew of R/V ENDEAVOR, and URI ocean technician Jan Szelag, as they
helped us conduct this field program. We are also grateful for the help
provided by T. Loder and S. Becker in processing the bottle salinities.
F. Bub, W. Brown, and P. Mupparapu are supported by NSF Grant
OCE-9530249.
5. References
Bub et al., 1997a, Hydrographic Survey Report, R/V Endeavor EN-291
CONVEX Cruise # 1, UNH/OPAL, Durham, NH, January 22, 1997, accessable
via http://ekman.sr.unh.edu/OPAL/CONVEX/EN291/en291_report.html.
Fofonoff, N. P. and R. C. Millard Jr., 1983. Algorithms for compilation
of fundamental properties of seawater, UNESCO Technical Papers in Marine
Science, no. 44. UNESCO, Paris, France, 53 pages.
Garrison, K. M. and W. S. Brown, 1989. Hydrographic survey in the Gulf
of Maine July-August 1987, UNH Tech. Rpt. No. UNHMP-T/DR-SG-89-5, Univ.
of NH, Durham, NH.
Morgan, P. P., 1994, SEAWATER Software Version 1.2b, CSIRO Division of Oceanography, Hobart, AUS.
CTD station information for the R/V ENDEAVOR Cruise EN-300 (18-19 May
1997). Profiles, as described above (3.d.), may be viewed by clicking
on A or B.
CTD station Latitude Longitude Water Depth Time Date
number (deg min N) (deg min W) (meters) (Z) (DD/MM/YY)
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