GLODAP Introduction
Overview
The GLobal Ocean Data Analysis Project (GLODAP) is a cooperative effort to coordinate global synthesis projects funded through the National Oceanic and Atmospheric Administration (NOAA), the U.S. Department of Energy (DOE), and the National Science Foundation (NSF) as part of the Joint Global Ocean Flux Study - Synthesis and Modeling Project (JGOFS-SMP).
Cruises conducted as part of the World Ocean Circulation Experiment (WOCE), JGOFS, and the NOAA Ocean-Atmosphere Exchange Study (OACES) over the decade of the 1990s have created an oceanographic database of unparalleled quality and quantity. These data provide an important asset to the scientific community investigating carbon cycling in the oceans.
The central objective of this project is to generate a unified data set to help determine the global distributions of both natural and anthropogenic inorganic carbon, including radiocarbon. These estimates provide an important benchmark against which future observational studies will be compared. They also provide tools for the direct evaluation of numerical ocean carbon models.
Project Summaries
Synthesis and interpretation of the NOAA/DOE Global CO2 Survey Data
P.I.s - C. L. Sabine, R. M. Key, R. A. Feely, J. L. Bullister, F. J. Millero, R. Wanninkhof, T.-H. Peng, and A. Kozyr
Funding agency - NOAA Climate and Global Change Program & DOE
Over approximately an 8-year period (1990-1998) the global CO2 survey produced over 15 times more high-quality carbon measurements than had previous survey efforts. These data were collected on more than 50 individual cruises by more than a dozen different analytical laboratories. For these data to be useful for evaluating global-scale issues (e.g., the oceanic inventory of anthropogenic CO2 ) they must be unified into an internally consistent data set. Wherever possible, we tried to include survey data from parallel international survey programs. The international data were extremely important for filling in ocean regions not covered by the US cruises. The final result is a data set with more than 12,000 oceanographic stations with 353,042 unique samples (see the map). We have put a great deal of effort into evaluating the quality of the survey data and recommending adjustments where necessary.
The evaluations were conducted at the basin scale starting with the Indian Ocean, then the Pacific, and finally the Atlantic. The results of this extensive data compilation and evaluation are presented here. Some of the scientific products derived from this data synthesis project are also presented in Publications.
Data Synthesis for the WOCE Radiocarbon Program
P.I. - R. M. Key
Funding agency - Physical Oceanography Program, NSF
Nearly 14,000 samples were collected for 14C analysis as part of the Worls Ocean Circulation Experiment (WOCE) Hydrographic Program. Large-volume samples from the deep Pacific were analyzed using the traditional β-counting technique at the University of Miami and the University of Washington (G. Ostlund and M. Stuiver, respectively). The majority of samples, however, were analyzed by accelerator mass spectrometry (AMS) at Woods Hole Oceanographic Institution (WHOI), a National Ocean Sciences AMS (NOSAMS) facility. One of the primary reasons for measuring 14C in the upper ocean during WOCE was to study thermocline ventilation on a decadal time scale. The Geochemical Ocean Section Study (GEOSECS) program provided the first look at the penetration of bomb-produced 14C into the thermocline.
This data has proven to be extremely useful to classical studies of thermocline processes and to the calibration and verification of numerical global circulation models. The WOCE data set is a second snapshot of the time-integrated result of mixing and ventilation. At the time of GEOSECS the 14C distribution in the upper ocean was primarily driven by air-sea gas exchange.
In the interim between the two programs, the strength of that driving force - i.e. the air-sea gradient in Δ14C - decreased significantly. The distribution at the time of WOCE will show significantly more influence by large-scale mixing and will provide a much greater challenge to modelers. The synthesized results from this project are presented here. We also include the results of an improved technique for isolating the bomb component of the 14C signal.
