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traps_PSiwatercol
Data Object SedimentTraps - PSi Water Column
contact PIs:
Dataset description
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.
Acquisition description
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.
Processing description
See SOIREE Preliminary Voyage Report
See NOTES in Dataset description and Acquisition decription
BCO-DMO Processing Notes
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
Field Names List
| Parameter | Description | Units |
|---|
| Date_NZST | Date NZST | YYYYMMDD |
| lon | longitude, negative denotes West | decimal degrees |
| lat | latitude, negative denotes South | decimal degrees |
| date_UTC | UTC Date | YYYYMMDD |
| time_UTC | UTC time | HHMM |
| depth | Sample depth | meters |
| SOIREEDay | SOIREE Experiment Day
T1 = 0000 h NZST 10/02/99 + 24 hours | Text |
| Patch | Patch Location (In/Out) | Text |
| StationId | CTD Station/Cast Id
| Text |
| Vol_Filtered | Volume filtered | mlitres |
| Psi_B | Psi in mmol/m3 or umol/litre | mmol/m3; umol/litre |
| Psi_A | Psi in ug/litre | ug/litre |
| POC | POC | mmol/m3 |
| Si_C | Si_C | molar |
Platforms List
Instruments List
- Sediment Trap:
MULTI-trap dimensions:
Length (L, m): 0.58 Trap length with baffles inserted;
L without baffles: 0.525 m
AR without baffles: 7.50
Trap volume without baffles: 2.021 litres
Inside diameter (Di, m): 0.07
Outside diameter (Do, m): 0.08
Aspect ratio (AR): 8.29
Aspect ratio with salt (AR): 7.29 Basal brine added to a height of 1-trap diameter (7 cm)
Collection area (A, m2): 0.00385
Trap volume (V, m3): 0.00223
Trap volume (V, litres): 2.232
Baffle length (Lb, m): 0.08
Baffle diameter (Dib, m): 0.01
Baffle aspect ratio (ARb): 5.77
- CTD Seabird 911:
NIWA's Seabird 911plus CTD and related instrumentation
This document is created from the content of the BCO-DMO metadata database. 2010-03-16 03:35:16
info app: /home/bco/dbase-v2 v.100108 CLC
Data URL: http://data.bco-dmo.org/jg/serv/BCO/Fe_Synthesis/SOIREE/61TG_3052/traps_PSiwatercol.