CTD_MixedLayer

Data Object CTD - Mixed Layer

contact PIs:

name	title
Dr Edward Abraham	Principal Investigator

Dataset description

SOIREE Mixed Layer Depth
The mixed-layer depth is defined as the maximum depth at which the sea-water
density is less than the density at 5m + 0.1 kg m-3. This picks up the top of
the seasonal pycnocline, but is insensitive to the weaker stratification that
occurred during the latter part of the experiment.

There is considerable cast-to-cast variation, suggesting the presence of internal
waves. Despite this it appears that the average mixed-layer depth decreased by 5-10m
between the 9th and the 16th of February, and then shoaled by a similar amount during
the remainder of the experiment. The apparent rapid decrease between the 8th and the
9th of February is possibly due to the inclusion of CTD stations on the transect towards
the experimental site, and may just reflect the general northward deepening of the surface
layer.

The development of thermal stratification within the surface layer is visible from Day 5.
This stratification is an order of magnitude weaker than the stratification within the pycnocline

Comments preserved from the original file:
Defined as the maximum depth at which the density is less than the density at 5m + 0.1 kg/m3.

Casts where the mixed layer depth is undefined, either due to bad data or because the
cast was too short, are assigned a value of -1.

This depth is typically at the top of the seasonal pycnocline. During the latter part of the
experiment there was persistent weak stratification at shallower depths.

The upcast column is 0 for downcasts and 1 for upcasts.

Acquisition description

See SOIREE Preliminary Voyage Report
See comments preserved from original file in dataset description as well

CTD data collection for SOIREE used NIWA's Seabird 911plus CTD and related
instrumentation - operated in its standard configuration, and according to standard procedures.

Processing description

See SOIREE Preliminary Voyage Report
See comments preserved from original file in dataset description as well

CTD data processing followed standard procedures.
These processes routinely result in pressure, temperature, salinity and
dissolved oxygen data that conform to WOCE Hydrographic Programme standards
(see WOCE HP Operations Manual WHP 91-1). with the measurements referenced
to (calibrated against) their respective international standards.

For SOIREE, the main exception was that there was no water-sample dissolved
oxygen data collected during the cruise. This meant that the dissolved O2
data could not be reliably calibrated to WOCE standards and that they are
only crudely indicative. It would be possible to somewhat further enhance
these dissolved O2 data by applying a calibration from a previous or
following cruise that used the same sensor.

BCO-DMO Processing Notes
Generated from original mixed_layer_depth.xls file provided on the
Deep-Sea Research II 48 (2001) accompanying CD-Rom

BCO-DMO Edits
- parameter names modified to conform to BCO-DMO convention
- added 'T' to CTD Station number for compatibility with events in other spreadsheets
- date, time. Lat, lon added from SOIREE_Stations_MasterStationList.xls using GMT dates/times
- “-1” No data or Bad data flag changed to BCO-DMO standard of “nd"

Field Names List

Parameter	Description	Units
station	Station Id (Text String)	text
date	date	YYYYMMDD
lon	longitude, negative denotes West	decimal degrees
lat	latitude, negative denotes South	decimal degrees
time	time	HHMM
cast	CTD cast number	integer
Upcast	Up/Down Cast Flag (0=Down, 1=Up)	integer
Mixed_layer_depth	Mixed Layer Depth	meters

Platforms List

R/V Tangaroa 61TG_3052

Instruments List

CTD Sea-Bird 911:
NIWA's Seabird 911plus CTD and related instrumentation

This document is created from the content of the BCO-DMO metadata database. 2010-09-02 21:53:43

info app: /home/bco/dbase-v2 v.100108 CLC
Data URL: http://data.bco-dmo.org/jg/serv/BCO/Fe_Synthesis/SOIREE/61TG_3052/CTD_MixedLayer.