Metadata Report for BODC Series Reference Number 541508

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Narrative Documents

No Narrative Document information held in the BODC database

Project Information

World Ocean Circulation Experiment (WOCE)

The World Ocean Circulation Experiment (WOCE) was a major international experiment which made measurements and undertook modelling studies of the deep oceans in order to provide a much improved understanding of the role of ocean circulation in changing and ameliorating the Earth's climate.

WOCE had two major goals:

• Goal 1. To develop models to predict climate and to collect the data necessary to test them.

• Goal 2. To determine the representativeness of the Goal 1 observations and to deduce cost effective means of determining long-term changes in ocean circulation.

The ACCLAIM Programme in the South Atlantic and Southern Oceans

Introduction

The ACCLAIM (Antarctic Circumpolar Current Levels by Altimetry and Island Measurements) programme in the South Atlantic and Southern Oceans consists of measurements from coastal tide gauges and bottom pressure stations, together with an ongoing research programme in satellite altimetry. ACCLAIM is the Proudman Oceanographic Laboratory's main contribution to WOCE (and, in particular, to WOCE Core 2) and one of its objectives is the study of variations of the Antarctic Circumpolar Current. ACCLAIM is managed within the Global Sea Level Change (GSLC) group at POL led by Dr.J.M.Vassie.

The history of the development of ACCLAIM is described in the report by Spencer et al. (1993)

Phase 1

From Spencer et al. (1993) it can be seen that in Phase 1 of ACCLAIM from 1983, measurements at coastal tide gauge sites took the form of sub-surface pressure (SSP) measurements (units of pressure e.g. mbar) rather than sea level (units of length e.g. centimetres). SSP is here defined as the total, measured pressure recorded by a sub-surface pressure transducer, a measurement which includes the pressure load from the atmosphere as well as from the water column. It is absolutely essential that any user of ACCLAIM data realises which data type (either SSP or sea level) is being analysed.

The Phase 1 coastal SSP data were acquired in different ways (e.g. with a diver-replaced Aanderaa pressure gauge at Ascension, or with a Digiquartz in the sea sensor at St.Helena, see Spencer et al. 1993 for details) and with different pressure integration periods (e.g. quarter hour, half hour, one hour). For WOCE Centre purposes the original data have generally been filtered to give one hour sampling.

However, common to all records is an uncertainty connected with potential offset biases and drifts in the pressure sensors. At some sites (e.g. St.Helena) extensive tide pole data are also available and biases and long term drifts in the sensor data may eventually be rectified (this is under study at present). However, the drifts in general mean that in most cases the records should not be used, without further careful attention in particular studies, for the study of timescales seasonal or longer.

Phase 2

From around early 1993, the gauges at many of the sites were replaced by Phase 2 ACCLAIM 'B gauges' which record SSP, air pressure and sea level as described in Woodworth et al. (1996)

The Phase 2 coastal sea level data have precise datum control (see Woodworth et al. 1996 for details) and can certainly be used for long term studies. These data have also been contributed to the Permanent Service for Mean Sea Level (PSMSL) and Global Sea Level Observing System (GLOSS).

Ancilliary Data

Some of the Phase 1 data and all the Phase 2 coastal data will also contain ancillary information on air pressures and sea temperatures from ACCLAIM sensors. Several of these records contain large gaps. However, the GSLC group at POL has collected extensive sets of such ancillary data from meteorological agencies for its own analysis purposes, and should be able to provide further advice.

Deep Ocean Measurements

SSP measurements at deep ocean bottom pressure stations (together with inverted echo sounder and temperature measurements) have also been a feature of ACCLAIM. Measurements at Amsterdam and Kerguelen in the Indian Ocean are described in Vassie et al. (1994).

While most recording is now concentrated in the Scotia Sea - Drake Passage area of the Southern Ocean as part of WOCE Core 2. Tidal constituents from these recorders have contributed to the IAPSO Pelagic Constants data base maintained by the PSMSL at Bidston on behalf of IAPSO.

References

Spencer, R., Foden, P.R., McGarry, C., Harrison, A.J., Vassie, J.M., Baker, T.F., Smithson, M.J., Harangozo, S.A. and Woodworth, P.L. 1993.
The ACCLAIM programme in the South Atlantic and Southern Oceans. International Hydrographic Review, 70, 7-21.

Vassie, J.M., Harrison, A.J., Woodworth, P.L., Harangozo, S.A., Smithson, M.J. and Thompson, S.R. 1994.
On the temporal variability of the transport between Amsterdam and Kerguelen Islands. Journal of Geophysical Research, 99(C1), 937-949.

Woodworth, P.L., Vassie, J.M., Spencer, R. and Smith, D.E. 1996.
Precise datum control for pressure tide gauges. Marine Geodesy 19(1), 1-20.

Data Activity or Cruise Information

No Data Activity or Cruise Information held for the Series

Fixed Station Information

Fixed Station Information

Port Stanley-A Phase 2 Site History

Please Note: This is a different data set from Port Stanley-B Phase 2, they are not linked in any way.

Parameters Recorded

where:

SL = ASLVTD01 = Sea Level

Tide Gauge Benchmark (TGBM)

Public Works Office Benchmark (PWD BM)

Benchmark Relationships

Tide gauge zero (TGZ) = Chart datum

TGZ = 6.258m below PWD BM
TGZ = 0.132m below Ordanance Datum (OD)

Quality Assessment

All data have been tidally analysed and constants and residuals checked. Records have been visually inspected for spikes, timing and datum shifts. In most cases, records listed as marked below are isoleted spikes, rather than long periods of bad data.

Possible datum shift 01 Oct 1974 0300hrs +30cm

Possible datum shift 12 Nov 1974 2000hrs -30cm

Related Fixed Station activities are detailed in Appendix 1

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: Port Stanley-A - Phase 2

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