Table of Contents

• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information

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.

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.

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"

Coverage: Southern Ocean

Project in the Southern Ocean aimed at maintaining a coherent patch of iron-enriched seawater for the duration of project and to interpret any iron-mediated effects on the patch by conducting measurements and performing experiments during this period of the project.

The Southern Ocean Iron RElease Experiment (SOIREE), was the first in situ iron fertilization experiment performed in the polar waters of the Southern Ocean. SOIREE was an interdisciplinary study involving participants from six countries, and took place in February 1999 south of the Polar Front in the Australasian-Pacific sector of the Southern Ocean.

Approximately 3800 kg of acidified FeSO4.7H2O and 165 g of the tracer sulphur hexafluoride (SF6) were added to a 65-m deep surface mixed layer over an area of ~50 km2. Initially, mean dissolved iron concentrations were ~2.7 nM, but decreased to ambient levels within days, requiring subsequent additions of 1550-1750 kg of acidified FeSO4.7H2O on days 3, 5 and 7 of the experiment.

During the 13-day site occupation, there were iron-mediated increases in phytoplankton growth rates, with marked increases in chlorophyll a (up to 2 µgl-1) and production rates (up to 1.3 gCm-2d-1). These resulted in subsequent changes in the pelagic ecosystem structure, and in the cycling of carbon, silica and sulphur, such as a 10% drawdown of surface CO2.

The SOIREE bloom persisted for >40 days following our departure from the site, as observed via SeaWiFS remotely sensed observations of Ocean Colour.

BCO-DMO Note:
All original data and metadata provided on a CD-Rom accompanying the Deep-Sea Research II 48 (2001) volume. The CD-Rom contains the main SOIREE datasets and ancillary information including the pre-experiment 'desktop' database study for site-selection, and satellite images of the SOIREE bloom.
© 2001 Elsevier Science Ltd. All rights reserved.

Related files

SOIREE Preliminary Voyage Report
SOIREE Introduction and Summary, Deep-Sea Research II 48 (2001) 2425-2438
SOIREE Cruise Track

Coverage: Global

The two main objectives of the Iron Synthesis program (SCOR Working Group proposal, 2005), are:
1. Data compilation: assembling a common open-access database of the in situ iron experiments, beginning with the first period (1993-2002; Ironex-1, Ironex-2, SOIREE, EisenEx, SEEDS-1; SOFeX, SERIES) where primary articles have already been published, to be followed by the 2004 experiments where primary articles are now in progress (EIFEX, SEEDS-2; SAGE, FeeP); similarly for the natural fertilizations S.O.JGOFS (1992), CROZEX (2004/2005) and KEOPS (2005).

2. Modeling and data synthesis of specific aspects of two or more such experiments for various topics such as physical mixing, phytoplankton productivity, overall ecosystem functioning, iron chemistry, CO2 budgeting, nutrient uptake ratios, DMS(P) processes, and combinations of these variables and processes.

SCOR Working Group proposal, 2005. "The Legacy of in situ Iron Enrichments: Data Compilation and Modeling".
http://www.scor-int.org/Working_Groups/wg131.htm

See also: SCOR Proceedings Vol. 42 Concepcion, Chile October 2006, pgs: 13-16 2.3.3 Working Group on The Legacy of in situ Iron Enrichments: Data Compilation and Modeling.

The first objective of the Iron Synthesis program involves a data recovery effort aimed at assembling a common, open-access database of data and metadata from a series of in-situ ocean iron fertilization experiments conducted between 1993 and 2005. Initially, funding for this effort is being provided by the Scientific Committee on Oceanic Research (SCOR) and the U.S. National Science Foundation (NSF).

Through the combined efforts of the principal investigators of the individual projects and the staff of Biological and Chemical Oceanography Data Management Office (BCO-DMO), data currently available primarily through individuals, disparate reports and data agencies, and in multiple formats, are being collected and prepared for addition to the BCO-DMO database from which they will be freely available to the community.

As data are contributed to the BCO-DMO office, they are organized into four overlapping categories:
1. Level 1, basic metadata
(e.g., description of project/study, general location, PI(s), participants);
2. Level 2, detailed metadata and basic shipboard data and routine ship's operations
(e.g., CTDs, underway measurements, sampling event logs);
3. Level 3, detailed metadata and data from specialized observations
(e.g., discrete observations, experimental results, rate measurements) and
4. Level 4, remaining datasets
(e.g., highest level of detailed data available from each study).

Collaboration with BCO-DMO staff began in March of 2008 and initial efforts have been directed toward basic project descriptions, levels 1 and 2 metadata and basic data, with detailed and more detailed data files being incorporated as they become available and are processed.

Related file

Program Documentation

The Iron Synthesis Program is funded jointly by the Scientific Committee on Oceanic Research (SCOR) and the U.S. National Science Foundation (NSF).