Ocean Carbon and Biogeochemistry Data System

[OCB Home] [Go Back]

EDDIES cruise: OCEANUS 415-2 Tracer 1
PI notes for Tracer Injection and Sampling Sled Data

PI: Jim Ledwell (WHOI)

30 October 2007: Prepared for OCB data system by Nancy Copley (Biology Dept, WHOI) and Cyndy Chandler, BCO-DMO (MCG Dept, WHOI).

Contact: Jim Ledwell (WHOI)

Tracer Injection Sled Description

The tracer injection sled for the EDDIES project lowered to the target potential density surface and then towed along that surface at 0.5 m/s while the tracer is injected.  The sled is neutrally buoyant and is towed at the end of a 2-meter tether attached to the end of the CTD cable, which removes much of the ship motion.  To follow lower frequency displacements of the target surface, the winch is controlled automatically with feedback from a SeaBird 911plus CTD system (Ledwell et al., 1998).  The CTD has dual pumped C/T sensors mounted at the front of the sled to sample water not perturbed by the thermal wake of the sled.  Also with the CTD was the same WET Labs fluorometer that had been used on Survey 1 on the Oceanus CTD/Rosette system.  On the injection sled are also mounted injection orifices, pumps, batteries, fluid reservoirs, and control electronics for the injection.

Sampling Sled Description

The sampling sled is similar to the injection sled in that it carries the same SeaBird 9 CTD and the WET Labs fluorometer.  It is mounted directly at the end of the CTD cable, with no tether, and with an array of integrating samplers above and below it (Ledwell et al. 1998).  It is oriented into the flow with wedge-shaped panels on the aft end, and is also controlled to stay as near as possible to a target isopycnal surface.      

Ledwell et al., 1998

Ledwell, J. R., A. J. Watson, and C. S. Law, Mixing of a tracer in the pycnocline, J. Geophys. Res., 103 (C10), pp. 21,499-21,529, 1998.

Sled Data Description

Data from the casts with the injection and sampling sleds are divided into downcast, flights along the target surface, and upcasts, indicated by "down", "flight" and "up" in the filenames, respectively.

There are 2 injection casts, 003 and 004, and 7 sampler casts, 001 through 007.

The sled sampling events as reported in the cruise event log are:

#  cruise: OC415-2 EDDIES Tracer 1
# 
event         date      time  cast  lon      lat     ev_type       comments           
--------------------------------------------------------------------------- 
200507202354  20050720  2354  nd    nd       nd      Inject        Test               
200507211601  20050721  1601  1     -67.123  30.560  Inject        Start Inject       
200507211604  20050721  1604  1     -67.123  30.559  Inject        End Inject         
200507220001  20050722  0001  2     -67.001  30.595  Inject        Start Inject       
200507220018  20050722  0018  2     -67.003  30.591  Inject        End Inject         
200507230018  20050723  0018  3     -67.241  30.450  Inject        Start Inject       
200507231020  20050723  1020  3     -67.184  30.293  Inject        End Inject         
200507231540  20050723  1540  4     -67.271  30.308  Inject        Start Inject       
200507231800  20050723  1800  4     -67.259  30.265  Inject        End Inject         
200507262333  20050726  2333  1     -66.515  28.169  Sampler       Sampler Start      
200507270045  20050727  0045  1     -66.509  28.154  Sampler       Sampler End        
200507280032  20050728  0032  2     -67.429  30.233  Sampler       Sampler Start      
200507281202  20050728  1202  2     -67.190  30.017  Sampler       Sampler End        
200507290048  20050729  0048  3     -67.717  30.090  Sampler       Sampler Start      
200507291202  20050729  1202  3     -67.461  30.001  Sampler       Sampler End        
200507300024  20050730  0024  4     -67.567  29.934  Sampler       Sampler Start      
200507301201  20050730  1201  4     -67.618  30.161  Sampler       Sampler End        
200507310034  20050731  0034  5     -67.618  30.003  Sampler       Sampler Start      
200507311202  20050731  1202  5     -67.539  30.233  Sampler       Sampler End        
200508010127  20050801  0127  6     -67.653  29.911  Sampler       Sampler Start      
200508011230  20050801  1230  6     -67.642  30.159  Sampler       Sampler End        
200508020130  20050802  0130  7     -67.049  29.890  Sampler       Sampler Start      
200508021234  20050802  1234  7     -67.695  30.158  Sampler       Sampler End

The primary variables added to the database from the original INJ_00?_*.mat files are:

scan                 scan number
yearday            time in decimal days, referenced to 0 at start of 2005
temp0               temperature, primary sensor pair (T90, deg C))
temp1               temperature, secondary sensor pair (T90, deg C))
cond0               conductivity, primary sensor pair
cond1               conductivity, secondary sensor pair
press                pressure (dbar)
v5                    fluorometer voltage
pump_1            Tracer pump 1 status: 1=ON; 0=OFF;
pump_2            Tracer pump 2 status: 1=ON; 0=OFF;

and the derived variables are:

sal0                  Salinity, primary sensor pair
sal1                  Salinity, secondary sensor pair
fl                      Chlorophyll from fluorometer voltage, v5, (mg/m3):
                        fl = 3.5334*v5 - 0.3250, with v5 in volts

The primary variables added to the database from the original SAM_00?_*.mat files are:

scan                scan number
yearday            time in decimal days, referenced to 0 at start of 2005
lat                   decimal degrees north
lon                   decimal degrees east (negative in our case)
temp0              temperature, primary sensor pair (T90, deg C))
temp1              temperature, secondary sensor pair (T90, deg C))
cond0               conductivity, primary sensor pair
cond1               conductivity, secondary sensor pair
press                pressure (dbar)
v5                    fluorometer voltage
sampl               Sampler status: 1=ON; 0=OFF

and the derived variables are:

sal0                  Salinity, primary sensor pair
sal1                  Salinity, secondary sensor pair
fluor_Wetl         Chlorophyll from fluorometer voltage, v5, (mg/m3):
                        fluor = 3.5334*v5 - 0.3250, with v5 in volts

Salinity Calibration

A few salinity samples were taken during the tows during both OC415-2. 
The mean values should be subtracted from sal0, and potential temperature and potential density should be recalculated accordingly.

Cruise Name No. of samples Mean S - Autosal Std. Dev.
OC415-2 Tracer 1 12 0.0069 0.0023

 

PI notes pertaining to the Seabird 911plus CTD unit

SeaBird 911plus set up parameters

24 scans were averaged, so data were recorded at 1 hz.
A correction for the thermal mass effect was made with coefficients:
a = 0.027300,  b = 0.100000

Calibration coefficients used on this run:
conductivity sensor 0 Serial No = 224
g = -4.235789670000e+000
h = 5.030437210000e-001
i = -2.164846790000e-003
j = 1.373217080000e-004
CTcor = 3.250000000000e-006
CPcor = 3.616348326169e-230

conductivity sensor 1 Serial No = 763
g = -4.219668290000e+000
h = 4.468958890000e-001
i = 8.929849640000e-005
j = 1.422904140000e-005
CTcor = 3.250000000000e-006
CPcor = 3.616348326169e-230

temperature sensor 0: (ITS090) Serial No. = 1080
f0 = 1.000000e+003
g = 4.795938520000e-003
h = 6.727434680000e-004
i = 2.635684590000e-005
j = 2.154517740000e-006

temperature sensor 1: (ITS-90) Serial No. = 1085
f0 = 1.000000e+003
g = 4.858597320000e-003
h = 6.721669580000e-004
i = 2.508981820000e-005
j = 1.909927960000e-006

pressure Serial No = 59933
C1 = -4.462697000000e+004
C2 = -2.850590000000e-001
C3 = 1.241750000000e-002
D1 = 3.985600000000e-002
D2 = 0.000000000000e+000

pressure:
T1 = 3.041551000000e+001
T2 = -4.168600000000e-004
T3 = 3.885970000000e-006
T4 = 3.330870000000e-009
T5 = 0.000000000000e+000

Voltage Assignments:
V0 = n/a                      
V1 = n/a               
V2 = n/a                   
V3 = n/a                
V4 = n/a         
V5 = WetLabs Fluorometer
V6 = n/a         
V7 = n/a