HYDROGRAPHIC SURVEY REPORT
Technical Report UNH-OPAL-1998-005
Convective Overturn Experiment
(CONVEX) CRUISE # 6
R/V OCEANUS (OC-316)
(Between 29 January and 02 February 1998)
F. L. Bub, W. S. Brown, & 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 F: Stations 24-12. Vertical
sections of temperature / salinity / sigma theta.
Figure 4.b. Hydrography Section B to G: Stations 35-32, 05-09.
Figure 4.c. Hydrography Section C to H: Stations 01-05, 44.
Figure 4.d. Hydrography Section D to I: Stations 36-43.
Figure 4.e. Hydrography Section J to E: Stations 26-31, 45-47, 49.
Figure 4.f. Hydrography Section C to F,G: Stations 01, 38, 46, 15, 10.
Figure 4.g. Hydrography Section D to F: Stations 36, 50, 49, 48, 12.
This report describes a set of hydrographic measurements obtained 29 January - 02 February 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 sixth of seven planned 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.
After a two hour delay to allow high winds to abate, the RV OCEANUS departed Woods Hole at 1100L (1600Z)
on 29 January 1998. After a transit via Cape Cod Canal, we arrived at the first hydrographic station
at the start of transect "C" at 2000L. With the exception of time spent checking central Wilkinson Basin
mooring functions and determining precise locations on 30 January, entire cruise dedicated to hydrographic
A total of 50 CTD profiles were collected (Figure 1.a.),
along with 7 "bongo net" plankton tows for A. Bucklin. We also deployed a drifter for R. Limeburner.
The last profile was completed 0110L 2 February and the ship returned to WHOI via Nantucket Shoals,
docking approximately 0830 on 2 Feburary 1998.
2.a. Scientific Party.
F. L. Bub (Chief Scientist), W. S. Brown, K. Garrison, P. Mupparapu, B. Strully, J. Salisbury, J. Lund,
J. R. Rogers, N. Mottola, L Smith.
2.b. Cruise Photos.
Click here to see CONVEX Cruise photos. Miscellaneous
CONVEX GIF photos 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 50 hydrographic stations during
29 January - 2 February 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). 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. For each station, 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
- Point B to G, tracking eastward through Massachusetts Bay and Wilkinson Basin
- Point C to H, tracking northeastward through Wilkinson Basin (Figure 4.c).
- Point D to I, tracking northeastward through Wilkinson Basin (Figure 4.d).
- Point J to E, tracking southward across Wilkinson Basin (Figure 4.e).
- Point C to F/G, tracking eastward across the southern Wilkinson Basin (Figure 4.f).
- Point D to F, tracking eastward across the southern Wilkinson Basin (Figure 4.g).
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-316 Cruise data including enroute ADCP, TSAL, navigation, bathymetry and observed weather records
will also be made available upon further processing.
We appreciate the efforts of Captain Bearse and the crew of R/V OCEANUSably as they preofessionally helped us conduct
this field program. The technical assistance of L. Stein is appreciated. We are grateful for the help provided by
T. Loder and R. Clauss in processing the bottle salinities. F. Bub, W. Brown, and P. Mupparapu are supported by NSF
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-316 (29 January-02 February 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 42.2985 70.1532 64 0059 30/01/98
02a 02b 42.4058 70.0305 95 0204 30/01/98
03a 03b 42.4998 69.8958 190 0347 30/01/98
04a 04b 42.6000 69.7685 233 0514 30/01/98
05a 05b 42.6967 69.6422 270 0643 30/01/98
06a 06b 42.6490 69.4140 240 0824 30/01/98
07a 07b 42.6002 69.1928 210 0957 30/01/98
08a 08b 42.5492 68.9762 205 1126 30/01/98
09a 09b 42.4993 68.7508 185 1256 30/01/98
10a 10b 42.3287 68.7500 180 1418 30/01/98
11a 11b 42.1655 68.7472 200 1626 30/01/98
12a 12b 41.9972 68.7485 150 1745 30/01/98
13a 13b 42.0962 68.8798 146 1907 30/01/98
14a 14b 42.1997 69.0058 175 2013 30/01/98
15a 15b 42.3017 69.1310 216 2123 30/01/98
16a 16b 42.4035 69.2558 245 2238 30/01/98
17a 17b 42.5025 69.3858 245 2343 30/01/98
18a 18b 42.6040 69.5137 250 0046 31/01/98
19a 19b 42.6982 69.6360 270 0243 31/01/98
20a 20b 42.7773 69.7810 255 0351 31/01/98
21a 21b 42.8530 69.9198 215 0543 31/01/98
22a 22b 42.9258 70.0605 83 0649 31/01/98
23a 23b 43.0010 70.2003 160 0751 31/01/98
24a 24b 43.0975 70.4022 89 0909 31/01/98
25a 25b 43.2788 70.2003 102 1045 31/01/98
26a 26b 43.4682 70.0028 106 1225 31/01/98
27a 27b 43.3163 69.9302 152 1404 31/01/98
28a 28b 43.1633 69.8587 180 1512 31/01/98
29a 29b 43.0075 69.7857 177 1621 31/01/98
30a 30b 42.8525 69.7120 200 1734 31/01/98
31a 31b 42.6980 69.6367 270 1858 31/01/98
32a 32b 42.6488 69.8548 244 2246 31/01/98
33a 33b 42.6007 70.0698 125 2358 31/01/98
34a 34b 42.5502 70.2863 110 0107 01/02/98
35a 35b 42.4947 70.5018 83 0210 01/02/98
36a 36b 42.0968 69.9038 120 0712 01/02/98
37a 37b 42.2467 69.8352 225 0839 01/02/98
38a 38b 42.3978 69.7695 270 1017 01/02/98
39a 39b 42.5522 69.7012 252 1144 01/02/98
40a 40b 42.7008 69.6383 270 1255 01/02/98
41a 41b 42.8518 69.5712 180 1530 01/02/98
42a 42b 43.0000 69.5002 153 1638 01/02/98
43a 43b 43.1518 69.4527 128 1803 01/02/98
44a 44b 42.7483 69.4257 160 2034 01/02/98
45a 45b 42.5467 69.5613 285 2209 01/02/98
46a 46b 42.3633 69.4735 230 2328 01/02/98
47a 47b 42.1822 69.3893 195 0144 02/02/98
48a 48b 41.9995 69.1027 190 0335 02/02/98
49a 49b 42.0018 69.3030 205 0443 02/02/98
50a 50b 41.9995 69.5047 205 0606 02/02/98