ISLSCP Initiative II

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Carbon Data

Air Sea CO₂ Gas Exchange

This data set contains the calculated ney ocean-air CO₂ flux and sea-air pCO₂ difference. These estimates are based on approximately 1 million measurements made for the pCO₂ in surface waters of the global ocean since the International Geophysical Year, 1956-59. Only the ocean water pCO₂ values measured using direct gas-seawater equilibration methods are used. Observations made in the equatorial Pacific between 10°N and 10°S during El Niño events have been excluded from the data set. Thus, the results represent the climatological distributions under non-El Niño conditions. Since the measurements were made in different years, during which the atmospheric pCO₂ was increasing, they were corrected to a single reference year (arbitrarily chosen to be 1995) on the basis of the following assumptions. Surface waters in subtropical gyres mix vertically at slow rates with subsurface waters due to the presence of strong stratification at the base of the mixed layer. This will allow a long contact time with the atmosphere to exchange CO₂. Therefore, their CO₂ chemistry tends to follow the atmospheric CO₂ increase. Accordingly, the pCO₂ measured in a given month and year is corrected to the same month of the reference year 1995 using changes in the atmospheric CO₂ concentration occurred during this period. Oceanic pCO₂ measurements made after the beginning of 1979 have been corrected to 1995 using the atmospheric CO₂ concentration data from the GLOBALVIEW-CO₂ database (2000), in which the zonal mean atmospheric concentrations (for each 0.05 in sine of latitude) within the planetary boundary layer are summarized for each month since 1979 to 2000. Pre-1979 oceanic pCO₂ data were corrected to 1979 using the annual mean trend for the global mean atmospheric CO₂ concentration constructed from the Mauna Loa data of Keeling and Whorf (2000), and then from 1979 to 1995 using the GLOBALVIEW-CO₂ database. Measurements for pCO₂ made in the following areas have been corrected for the time of observation; 45 °N - 50 °S in the Atlantic Ocean, north of 50 °S in the Indian Ocean, 40 °N-50 °S in the western Pacific west of the date line, and 40 °N-60 °S in the eastern Pacific east of the date line.

Data Provider: Taro Takahashi, Stewart C. Sutherland, Rik H. Wanninkhof, Richard A. Feely, Ray F. Weiss, David W. Chipman, Nicholas Bates, Jon Olafsson, Christopher Sabine, A. Poisson, N. Metzl, B. Tilbrook, Y. Nojiri , C. Sweeney

Data Files (ISLSCP II Disc #1)

Data Set Documentation

Image Viewing Tutorial

File Information

There are 3 PKZipped archive files containing data. They are:

• air_sea_data_5d.zip -- contains the 2 original ASCII data tables, d-pco2 and co2flux.

• air_sea_maps_5d.zip -- contains 24 monthly average maps at 5x4 degrees, created by the ISLSCP Staff, 12 for d-pco2 and 12 for co2flux.

• air_sea_maps_1d.zip -- contains 24 monthly average maps at 1x1 degrees, created by the ISLSCP Staff, 12 for d-pco2 and 12 for co2flux.

The ISLSCP staff have extracted the data for each month from the two original data files and written them to ASCII arrays containing 72 samples (pixels) by 45 rows. All samples within one line are separated by a single space with unequal number of bytes per line. A value of -999.9 indicates land cells and values of -888.8 indicate cells with sea ice.
      The ISLSCP staff took the 5x4 degree map files listed above and processed them again, filling in blank pixels along the coastlines using averaging of all the surrounding pixels, then expanding each pixel in a line 5 times, then copying each line 4 times. This preserved the original missing values of -999.9. Additionally, the ISLSCP 2 1-degree Land Mask was overlayed on the files, inserting the land (listed as -99.9) at a finer scale than the original 5x4 degree data. Thus, there is missing land data listed as -99.9, then additional missing data listed as -999.9. Sea ice is indicated by -888.8..
      WARNING: This 1x1 degree product is for browse use only. These data files are not interpolated between the original 5x4 pixels. Thus the data is very "blocky", and values at specific pixels are not exact. Use this data with caution and always refer to the original tabular data files for specific information.

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Revision Date: March 7, 2003