2014 JOIS CTD Data Files

25 Jun 2015

Sarah Zimmermann

Institute of Ocean Sciences

Fisheries & Oceans Canada

2014 JOIS CTD Data Files

IOS Cruise Number 2014-11

Cruise

There were 40 CTD casts performed aboard the CCGS Louis S. St-Laurent between September 21st and October 17th 2014 in the Canada Basin using a Sea-Bird Electonics Inc. SBE911+ CTD system with 24 10-L Niskins. Expendable CTDs, vertical net tows for zooplankton, moorings and ice-tethered profilers were also conducted, deployed and/or recovered during this trip.

CTD Data Summary

SBE 9+ CTD sn#724 was used for the full cruise, Casts 1 to 40.

The CTD data for down and upcasts are provided in 1-db averaged files (*.cnv), in Sea-Bird Electronic Inc.’s text format with one file per cast and separate files for down and up direction. The files contain both processed and unprocessed variables, described below.

The downcast files are the primary data set. The upcast files, useful for confirming unusual features seen in the downcast are provided for reference only.

Both primary and secondary temperature, conductivity and salinity are provided however the SECONDARY temperature, conductivity and salinity are recommended to be used as the primary salinity has a slight pressure dependence. The SECONDARY suite only were corrected for density inversions.

Accuracy:

Pressure0.015% of full scale (for SBE9+ 6800m is 1m)

Temperature+/- 0.001C

SalinitySTD of 0.0055PSU with water samples >300m

OxygenSTD of 0.015ml/l with water samples >300m

Downcast

Filename: d201411_xxxx.cnv where xxxx is cast number

Standard Sea-Bird Electronics Inc. processing steps were usedfollowed with additional processing in Matlab and Excel.

Pressure, primary and secondary temperature, primary and secondary conductivity, and oxygen have been calibrated.

Spikes in secondary temperature and secondary conductivity have been interpolated over. The flag word in the last column is made up of 3 numbers corresponding to Temperature, Conductivity, and Oxygen. The values of the numbers indicate: 0 = no QC; 2 = good; 6 = interpolated.

The derived variables, salinity, potential temperature, sigma-theta and sound velocity,were recalculated.

Transmission, Chlorphyll-a fluorescence, CDOM fluorescence, ISUS nitrate, altimetry,PARand SPAR are uncalibrated beyond using the factory provided calibration specified in the Sea-Bird confirguation section of the file header.

Upcast

Filename: u201411_xxxx.cnv where xxxx is cast number

Upcast is supplied only as it provides a reference for unusual features seen in the downcast.

No spikes have been removed.

Pressure, primary and secondary temperature, and primary and secondary conductivity have been calibrated. Calibration coefficients and correction values applicable to oxygen downcast data were applied however the upcast’s strong hysteresis was not addressed making it unusable.

Derived variables, salinity, potential temperature, sigma-theta and sound velocity, were recalculated.

Transmission, Chlorphyll-a fluorescence, CDOM fluorescence, ISUS nitrate, altimetry, PAR and SPAR are uncalibrated beyond using the factory provided calibration specified in the Sea-Bird confirguation section of the file header.

Processing notes pertinent to each sensor written into each file’s header:

#Processing Notes:

#

# SBE 911+CTD sn#724 was used for 2014-10 Casts 1,2 and 2014-11 Casts 1 to 40.

#

# Secondary temperature and conductivity are the parameters of choice as

# the primary conductivity shows slight pressure dependence.

#

# Primary and Secondary Temperature were corrected for drift seen between the

# Seabird pre and post cruise laboratory calibrations (SBE Appl. Note #31).

# Data were reprocessed using the pre-cruise calibration and a new offset.

#

# Primary and Secondary Conductivity were reprocessed using

# the Seabird post cruise laboratory calibration.

# Based on CTD lab calibration, historical data and repair work needed post-cruise

# on the Autosalinometer, it is believed the Autosal was reporting -0.002PSU and

# therefore was not used for the calibrating the CTD.

#

# Oxygen Seabird SBE43 was installed in the pumped flow following the

# primary temperature and conductivity sensors.

# Oxygen was calibrated by matching downcast oxygen voltage to upcast water samples.

# The CTD upcast data are avoided due to large hysteresis resulting from deep

# casts at cold temperatures. Separate fits (following Seabird Appnote64-2Jun12.pdf)

# were performed for groups:

# 2014-10 SBE43 #0435 Cast 1

# 2014-10 SBE43 #0435 Cast 2

# 2014-11 SBE43 #0435 Casts 1 to 23

# 2014-11 SBE43 #1435 Cast 24 to 40

# Following this, both a correction for drift (by cast) and a correction for a

# pressure dependent shape in the residuals was applied.

#

# Fluorometer Seapoint SCF # 3652 for Chla-a was used for all casts except

# Cast 30 which used a Seapoint SCF#3653. The fluorometer was installed

# in the pumped flow following the secondary temperature and conductivity sensors.

# No processing was performed, however due to cable issues creating bad data

# values of -9 were entered where the data are clearly bad in casts 28, 29 and 30.

# In Cast 34, the bad data from 0 to 70m during the downcast is replaced with good

# data from the upcast.

# Channel V0 is raw voltage from the fluorometer.

#

# Transmissometer WETLabs C-Star CST-1052DR was used up to Cast 34

# using a 18-June-2014 calibration from in-air open and blocked readings.

# Transmissometer WETLabs C-Star CST-993DR was used for Casts 35 to 40

# using a 30-June-2014 calibration from in-air open and blocked readings.

# Both transmissometers had noise issues and drifts to lower transmission values.

# The noise is likely due to cabling problems (also affecting the fluorometer sharing

# the same “Y” cable) and the drift may be related to the method of mounting

# the transmissometer to the rosette frame.

# Channel V1 is raw voltage from the transmissometer.

#

# CDOM WETLabs ECO CDOM #1076 sensor was on for Casts 3 to 40. No processing

# performed however values of -9 entered where sensor was not installed.

# Channel V4 is raw voltage from the CDOM.

#

# Satlantic’s ISUS V2 Nitrate sensor # 121 was used for Casts 1,20, 22, 28.

# No processing was performed, however values of -9 were entered for

# all casts where the ISUS was not installed.

# Channel Upoly0 is the unscaled output from

# the ISUS sensor (y = 1x+b).

#

# PAR Biospherical QSP-2300 sn70123 used for Casts 1 to 4.

# PAR SatLantic Cosine Log PAR sn 517 used for Casts 5 to 40.

# Surface PAR Biospherical QSR2200 SN20281 used on Casts 1 to 40.

# No processing performed.

#

# Quality Control edits were performed on

# downcast Secondary Temperature, Secondary Conductivity and Oxygen only.

# Flag word has 3 columns: Temperature, Conductivity, and Oxygen

# Flag_code: 0 = no QC; 2 = good; 6 = interpolated;

#

# Bottom depth is the maximum CTD depth plus the altimeter reading,

# or if the bottom was not reached, the depth is from the ship's Knudsen sounder.

#

# Temperatures, Conductivities, and Downcast Oxygen are calibrated.

# Salinities, Potential Temperature, SigmaTheta and SoundSpeed have been recalculated.

# Fluorometer, Transmissometer, CDOM Fluorometer, ISUS Nitrate, PAR, SPAR and

# Altimeter have not been processed.

#

# Version 2015-06-24