Table of Contents

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

SOIREE Sediment Traps - Water column PSi (biogenic) results

METHOD:
Biogenic silica content was determined on filtered samples (47 mm , 0.4 um Nuclepore) after digestion in 0.2 M NaOH, following the methods of Ragueneau and Tréguer (1994).
Estimated accuracy of replicate analyses: ±5-10%
Blank filter: 15 ug
Digest blanks (no filter): indistinguishable from background levels

NOTES
1. The initial and OUTSIDE PATCH water column integrated PSi values from SOIREE were higher than expected for Southern Ocean HNLC waters. For example, published data from Bernard Queginuer (France) in the Atlantic sector of the Southern Ocean indicates maximum BSi concentrations of 1.6 umolSi/l in the vicinity of the Polar Front (53-54°S), with maximums in surrounding HNLC waters of 0.25 umolSi/l. SOIREE PSi water column concentrations reached a maximum of 25 umolSi/l with an average across all profiles of 5.8 umolSi/l and surface values outside the iron-fertilised patch (2-4 umol/l) which were not substantially different from that measured inside the patch during the SOIREE bloom (except on Day T10)

2. There is no obvious indication from either sampling or analytical techniques that the PSi values are artificially inflated due to sample handling, etc.

3. Charette & Buesseler (2000, G3) suggest that a previous export event must have occurred prior to SOIREE due to a substantial 234Th deficit relative to 238U, which might explain the SOIREE POC results. Since there is no indication from daily SeaWiFS images of a surface bloom from Nov 1998-Jan 1999 (C. Law pers. comm., 1999), nor any "memory" of such an event in the pCO2 data (Watson et al., 2000, Nature), Charette & Buesseler (2000) suggested that such a bloom is likely to have been a subsurface feature, or that there was a significant delay in export

4. PSi values inside and outside the SOIREE patch were similar despite 6-fold and 3-fold increases in chlorophyll a concentrations and phytoplankton abundance, respectively, inside the iron-fertilised patch (Boyd et al., 2000, Nature)

5. Therefore, we conclude that perhaps there was a significant detrital PSi component in the water column at the time that the SOIREE site was occupied, representing organic material derived from a previous bloom/export event.

6. Given the uncertainties, however, it is wise to treat the interpretation of the above PSi data with caution.
 

See SOIREE Preliminary Voyage Report

METHOD:
Biogenic silica content was determined on filtered samples (47 mm , 0.4 um Nuclepore) after digestion in 0.2 M NaOH, following the methods of Ragueneau and Tréguer (1994).
Estimated accuracy of replicate analyses: ±5-10%
Blank filter: 15 ug
Digest blanks (no filter): indistinguishable from background levels

NOTES
1. The initial and OUTSIDE PATCH water column integrated PSi values from SOIREE were higher than expected for Southern Ocean HNLC waters. For example, published data from Bernard Queginuer (France) in the Atlantic sector of the Southern Ocean indicates maximum BSi concentrations of 1.6 umolSi/l in the vicinity of the Polar Front (53-54°S), with maximums in surrounding HNLC waters of 0.25 umolSi/l. SOIREE PSi water column concentrations reached a maximum of 25 umolSi/l with an average across all profiles of 5.8 umolSi/l and surface values outside the iron-fertilised patch (2-4 umol/l) which were not substantially different from that measured inside the patch during the SOIREE bloom (except on Day T10)

2. There is no obvious indication from either sampling or analytical techniques that the PSi values are artificially inflated due to sample handling, etc.

3. Charette & Buesseler (2000, G3) suggest that a previous export event must have occurred prior to SOIREE due to a substantial 234Th deficit relative to 238U, which might explain the SOIREE POC results. Since there is no indication from daily SeaWiFS images of a surface bloom from Nov 1998-Jan 1999 (C. Law pers. comm., 1999), nor any "memory" of such an event in the pCO2 data (Watson et al., 2000, Nature), Charette & Buesseler (2000) suggested that such a bloom is likely to have been a subsurface feature, or that there was a significant delay in export

4. PSi values inside and outside the SOIREE patch were similar despite 6-fold and 3-fold increases in chlorophyll a concentrations and phytoplankton abundance, respectively, inside the iron-fertilised patch (Boyd et al., 2000, Nature)

5. Therefore, we conclude that perhaps there was a significant detrital PSi component in the water column at the time that the SOIREE site was occupied, representing organic material derived from a previous bloom/export event.

6. Given the uncertainties, however, it is wise to treat the interpretation of the above PSi data with caution.
 

See SOIREE Preliminary Voyage Report
See NOTES in Dataset description and Methods & Sampling

Generated from original file SOIREE_Export_final.xls, Tab: PSiwatercolumn
provided on the Deep-Sea Research II 48 (2001) accompanying CD-Rom

BCO-DMO Notes
For some stations, there was no match for StationId and Patch location
The StationId would not agree with the patch location of In/Out in other files
In these cases, what seemed to be the most reasonable match was used
These problem station are identified below by StationId
StationId T1144-2 Out: Date_UTC, Time_UTC, Lon, Lat are questionable
StationId T1147-1 In: Date_UTC, Time_UTC, Lon, Lat are questionable
StationId T1151-1 In: Date_UTC, Time_UTC, Lon, Lat are questionable
StationId T1154 In: Date_UTC, Time_UTC, Lon, Lat are questionable

BCO-DMO Edits
- parameter names modified to conform to BCO-DMO convention
- date_UTC, time_UTC, lat, lon added from files:
SOIREE_Stations_CTDSampling.xls
SOIREE_Stations_MasterStationList.xls
SOIREE_CTD_Summary
- Blank rows in original sheet removed
- 'nd' added to blank cells
- Made column header record one line
- Formatted Date (NZST) to YYYYMMDD

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

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).