HYDROGRAPHIC SURVEY REPORT
Technical Report UNH-OPAL-1998-004
Convective Overturn Experiment
(CONVEX) CRUISE # 5
R/V OCEANUS (OC-315)
(Between 09 and 12 January 1998)
F.L. Bub, W.S. Brown, P. Mupparapu, and L.C. Smith
Ocean Process Analysis Laboratory (OPAL)
Institute for the Study of Earth, Ocean and Space
Department of Earth Sciences
University of New Hampshire
Durham, NH 03824
Research Sponsored by the National Science Foundation
2. Cruise Narrative
3a. Data Acquisition
Table 1. Surface Contours of Properties on Pressure and Density Surfaces.
Table 2. CTD Station Information.
Figure 1.a. Cruise Track, CTD Locations and UNH mooring sites. Stations
Figure 1.b. Station and mooring locations with Wilkinson Basin bathymetry
and water mass analysis region outlined.
Figure 2. Wilkinson Basin mooring configuration showing the Main Buoy (A),
thermistor chains (B & C), and guard buoys (D, E & G).
Figure 3.a.. Composite of CTD profiles in Wilkinson Basin. See
section 3.d.1 for a description.
Figure 3.b.. Temperature-Salinity Diagram for CTD profiles in
Figure 4.a. Hydrography Section A to WB to F: Stations 17-13, 03-07. Vertical sections of temperature / salinity / sigma theta.
Figure 4.b. Hydrography Section A to I to WB to G: Stations 17-20, 12-09.
This report describes the hydrographic measurements obtained 9-12 January 1998 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 fifth of seven University of New
Hampshire (UNH) cruises aboard the R/Vs ENDEAVOR and OCEANUS as part of this "Convective Overturn
Experiment" (CONVEX). This report and these data can be accessed through the RMRP Research Environmental
Data and Information Management System (REDIMS) via the WWW address:
Click here to read an introduction to the CONVEX program.
The RV Oceanus departed Woods Hole at 0900L on 08 January 1998. We passed through Cape Cod Canal enroute
to central Wilkinson Basin in the Gulf of Maine. The first CTD cast was made at 0100Z (0600 L EST) at the
mooring site. After surveying the site for botom bathymetry and locations of the existing guard buoys, a
second CTD cast occurred at 1120Z prior to buoy deployment. At 1540Z (1030L), we commenced rigging for
deployment of the Main Instrumented Buoy "A" (Figure 2). The anchor
was released at 1817Z (1317L) at 42 ° 42.08' N 69 ° 38.07' W. We then placed T-Chain "C" at
1952Z (1452L) and Guard Buoy "G" at 2052Z (1552L). The mooring configuration then consisted of the Main
Instrumented Buoy (A), two subsurface T-Chains (B and C), and two Guard Buoys (E and G).
A post-deployment CTD at 2040Z was followed by another 18 profiles in the pattern depicted by
Figure 1.a. Water samples were drawn for four nutrient sample profiles
and 10 CTD salinity calibrations. The final cast occurred at 0726Z 12 January and the Oceanus returned to
Woods Hole via Cape Cod Canal and docked the evening of 12 January 1998.
2.a. Scientific Party:
F. L. Bub (Chief Scientist), W. S. Brown, R. Regnier, and B. Strully. Coast Guard observer - M. Brooks.
Woods Hole Technician - L. Stein.
2.b. Cruise Photos
Click here to see
OC-315 Cruise photos.
GIF photos of the OC-315 scientific party and cruise work are included.
The R/V OCEANUS' SeaBird SBE 911 Plus CTD Profiler was used to measure
vertical profiles of electrical conductivity and temperature versus pressure at 22 hydrographic stations during
9-12 January 1998 (Figure 1.a).
Sensors on the CTD were factory calibrated on 9 October 1996. This CTD samples at a rate of 24 scans per second.
Salinity profiles were computed from these data using SeaBird software. Additional sensors on the SBE-911 also
recorded data for the measurement of dissolved oxygen, water transmissivity, fluorescence (Chl-a), and irradiance
(PAR). See Figure 3.a. for a composite of profiles. CTD data acquisition,
display and storage were managed by an on-board computer using the SeaBird software package SEASOFT.
At each station, the CTD was lowered at a rate of approximately 30 meters per minute to depths within 5-10 meters
of the bottom. Three to eight water samples were collected with a rossette of 5-liter Niskin bottles, and specimens
for nutrient and oxygen isotope analyses were gathered. At selected stations, the condutivity of one water sample
was determined using the UNH Guildline 8400A Autosal and the corresponding salinities were used to correct
salinity values derived from the raw CTD measurements.
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
- c. Data were filtered to ensure consistent response times using a low pass filter with time constant 0.15
- 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 a summary of data descriptions, corrections and estimated accuracy
The corrected hydrographic data are presented as:
- Station profile plots and property-property diagrams,
- Vertical section contour plots, and
- Horizontal pressure and desnity surface contour plots.
3.d.1. Vertical CTD Profile Plots.
Individual profiles may be viewed via Table 2. A composite of all CTD profiles
is shown as Figure 3.a and an expanded T-S diagram as
Figure 3.b. Data are presented on two pages per station:
- Page A - Station profiles of temperature, salinity, sigma-theta density, stability (N-squared) and a
temperature-salinity diagram. The upper three plots (surface to 100 m deep) 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. These plots are all on the same depth / property
scale for intercomparison. A Brunt-Vaisaila frequency (N-squared) plot indicates water column stability.
- Page B - When data are available, this page shows station profiles of measured dissolved oxygen,
transmissivity, fluorescence (Chl-a), solar irradiance (PAR), as well as computed sound velocity, temperature -
dissolved oxygen, and salinity - dissolved oxygen diagrams.
3.d.2. Vertical Hydrographic Sections.
Potential temperature, salinity, and sigma-theta sections for the following transects are presented.
Each plot spans 200 km and horizontal scales are preserved. Contour intervals are indicated on plots.
The CTD station numbers are shown along the top horizontal axis and the ocean bottom (based on depths
at CTD stations) is shaded.
Point A to F, tracking southeastward through Jeffreys and Wilkinson Basins on Figure 4.a, and
Point A to G, tracking southeastward through Jeffreys and Wilkinson Basins on Figure 4.b.
3.d.3. Horizontal Pressure and Density Surfaces.
Contoured surfaces may be accessed via Table 1.
Contours of temperature, salinity and density fields on the 5, 25, 50, 100, 150 and 200 dbar pressure surfaces
(equivalent to depth in m) and the sigma theta 26.00 density surface (mid water column) are presented for information.
The 5 m field is the mean of the 0-10 m layer. Dynamic height fields indicate geostrophic shear.
Cyan regions show where the ocean bottom is shallower than the plotted surface.
CTD profiles at the red dots (x indicates no data). Wilkinson Basin mooring marked by the wheel.
Red lines bound region of the CONVEX water mass analyses. Plotted contour intervals, along with data extrema and
search epsilon, are indicated in captions.
3.d.4. Data Files.
Profiles can be made available as (a) ASCII files upon request to
Upon final quality control, we will provide (b) JGOFS default files through a ftp site.
Other OC-315 Cruise data including enroute ADCP, TSAL, navigation, bathymetry and observed weather records
will also be made available upon further processing.
The valuable work of Ken Morey, Dan Howard and Karen Garrison resulted in the successful deployment
of the Wilkinson Basin Buoy and hydrographic survey. We appreciate the efforts of Captain Bearse and
crew of R/V OCEANUS as they helped us conduct this field program. We are grateful for the help
provided by T. Loder and A. Wang / V. Pilon in processing the bottle salinities.
F. Bub, W. Brown, and P. Mupparapu are supported by NSF Grant OCE-9530249.
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.
These fields are briefly described in section 3.d.3. Pressure (P),
Temperature (T), Salinity (S), Density (D), and Dynamic Height (DH) are contoured at the specfied
pressure or density levels.
|26.00 sigma theta
Hydrographic station information for the R/V OCEANUS Cruise OC-315 (09 - 12 January 1998). Position,
depth, date, and time are for the bottom of the cast. Profiles, which are described in
section 3.d.1, may be viewed by clicking on ##A or ##B. See Figure 1.a
for station locations.
CTD station Latitude Longitude Water Depth Time Date
number (deg min N) (deg min W) (meters) (Z) (DD/MM/YY)
01A 01B 42.7052 69.6415 270 0122 10/01/98
02A 02B 42.6988 69.6338 265 1130 10/01/98
03A 03B 42.7002 69.6357 265 2040 10/01/98
04A 04B 42.5268 69.4137 235 2248 10/01/98
05A 05B 42.3527 69.1927 240 0036 11/01/98
06A 06B 42.1763 68.9677 157 0225 11/01/98
07A 07B 41.9990 68.7477 140 0401 11/01/98
08A 08B 42.2462 68.7463 205 0546 11/01/98
09A 09B 42.4955 68.7467 185 0736 11/01/98
10A 10B 42.5670 69.0457 170 0914 11/01/98
11A 11B 42.6343 69.3395 210 1049 11/01/98
12A 12B 42.7037 69.6307 265 1238 11/01/98
13A 13B 42.7985 69.8230 240 1846 11/01/98
14A 14B 42.8990 70.0012 140 2013 11/01/98
15A 15B 42.9983 70.1997 170 2136 11/01/98
16A 16B 43.0723 70.3488 110 2245 11/01/98
17A 17B 43.2000 70.4883 031 2357 11/01/98
18A 18B 43.1185 70.1400 140 0133 12/01/98
19A 19B 43.0875 69.7813 165 0311 12/01/98
20A 20B 42.8933 69.7083 175 0430 12/01/98
21A 21B 42.6970 69.6290 270 0550 12/01/98
22A 22B 42.5468 69.8160 255 0726 12/01/98