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GLODAP version 1.1 bottle data in Ocean Data View format
REFERENCE: R.M.Key, A. Kozyr, C.L. Sabine, K. Lee, R. Wanninkhof, J.L. Bullister, R.A. Feely, F.J. Millero, C. Mordy, and T.-H. Peng, A Global Ocean Carbon Climatology: Results from GLODAP, Global Biogeochemical Cycles, in press, 2004.
Data set construction
The GLODAP data set consists of 9618 hydrographic stations collected on 95 cruises during the WOCE era between 1985 and 1999, and 2393 historical hydrographic stations from 21 cruises occupied between 1972 and 1990. The fact that there is a time overlap is sufficient to indicate that division between the two was somewhat arbitrary. In this work we use the phrase WOCE stations/cruises/data to refer to stations occupied as part of either WOCE, JGOFS or OACES field work or slightly older cruises officially designated as WOCE sections (for example the Long-Lines cruises P01, P03 and P04 occupied in the late 1980s). Historical stations/cruises refers to all other data. No data older than GEOSECS are included due to difficulty in obtaining the data and to the generally lower quality standards which existed.Data were chosen to provide high quality global coverage. Most of the data sets were received from the data centers associated with the individual research programs. Additional data were received directly from chief scientists and individual investigators. Significant priority was given to cruises which included the carbon parameters of direct interest to GLODAP goals, however a limited number of cruises without carbon were included to provide more complete hydrographic, nutrient and oxygen coverage. Initial investigation implies that the GLODAP hydrography, nutrients and oxygen are sufficiently dense to provide a reasonable approximation of much larger (annual mean) compilations such as provided by Conkright et al. (2002). Details of the data base construction are important for some applications and interpretations. By its nature this information is tedious and is therefore included in Appendix 3 on page 38. Here only the briefest outline is given.
New data were converted to a common format and existing quality control flags (Joyce, et al.1994) were checked. When missing, QC flags were assigned usingWOCE conventions (Joyce, et al.1994). Any routinely calculated parameters which existed in the files were discarded. Parameter units were converted toWOCE convention as required. Once the decision was made on which cruises were to be included in an ocean compilation, the following steps were executed using a series of semi-automated computer routines:
The data from each cruise were reduced to a defined parameter list and column ordered then calibration factors and/or adjustments were applied (See "Calibration" on page 42.). The indi6 vidual cruises were merged into a single file adjusting the original station numbers in a prede fined manner which guaranteed uniqueness yet allowed the original number to be easily recovered. The parameter table is listed in Appendix 1 on page 21 and the adjustments tables are in Appendix 4 on page 45.
All parameters with a QC flag value of "questionable" (3) or "bad" (4) were deleted from the merged data set. "Replicate" flag values (6) were changed to "good" (2). "Not reported" flag values (5) and "sample collected" (1) flag values were changed to "good" in the instances where there actually was a value and to "missing" (9) otherwise. Values flagged 0 ("approximated") were left as is. The other possible WOCE QC flag values were almost never used in practice (a few CFC "7" flags were changed to 2, 3, or 4 during initial screening), so this procedure reduced the possible QC flag values to either approximated, good or not measured (0, 2 or 9).
Missing values for salinity, nutrients and oxygen were approximated by constrained vertical interpolation.
Potential temperature, potential density (sq, s1, s2 s3 s4) and apparent oxygen utilization (AOU) were calculated.
Stations with no reported samples were deleted and cruise year values were made Y2K compliant.
Partial pressure and "age" were calculated for CFC-11 and CFC-12; Bomb and natural radiocarbon estimates and radiocarbon age were calculated. All of these were appended to the existing data file.
Subsets of the data were transferred to various group members responsible for anthropogenic CO2 estimates in each ocean (C. Sabine and K. Lee). Once finalized these estimates were transferred to Princeton and merged into the master data files.
The entire data file was truncated to "single precision" and written as a comma separated ASCII file without regard to the number of decimal places retained. This is a short-coming of the procedure since insignificant digits exist in all calculated parameters. Correcting this problem isn't trivial since precision has varied over the time frame of the included data. [15] These files were subsequently transferred from Princeton to CDIAC where they were posted to the GLODAP web site (http://cdiac.esd.ornl.gov/oceans/glodap/ Glodap_home.htm). CDIAC (A. Kozyr) translated the ascii files into Ocean Data View format (Schlitzer, 2000,2003).
Calculated Values
see chapter 11.4 of Key etal, GBC, 2004.Converted to ODV collection format: A. Kozyr & R. Schlitzer (July/2004)
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