Background Information
The WOCE designated P16 line was sampled as part of the Climate Variability / Carbon Dioxide (CLIVAR/GO-SHIP/CO2) Repeat Hydrography Program, sponsored by the National Oceanic and Atmospheric Administration (NOAA) and National Science Foundation (NSF). The goal of the Repeat Hydrogaphy Program is to measure decadal changes in circulation, heat and fresh water budgets, and carbon inventory in the ocean. The cruises repeat a subset of the WOCE Hydrographic Program (WHP, now CCHDO) and Joint Global Ocean Flux Study (JGOFS) lines occupied in each major ocean basin in the 1990s. These measurements are of importance both for international research programs, such as CLIVAR/GO-SHIP or IMBER, and for operational activities such as the Global Ocean Observation System and the Global Climate Observing System. As outlined in the program documentation, one component of a global observing system for the physical climate/CO2 system should include periodic observations of hydrographic variables, CO2 system parameters, and other tracers. The large-scale observation component of the Ocean Carbon and Climate Change Program needs systematic observations of the invasion of anthropogenic carbon in the ocean superimposed on a variable natural background. The six topical areas addressed by the CLIVAR/GO-SHIP/CO2 Repeat Hydrography program are:
- carbon system studies;
- heat and freshwater storage and flux studies;
- deep and shallow water mass and ventilation studies;
- ocean acidification studies;
- calibration of autonomous sensors; and
- data for model calibration.
The P16 line, which lies nominally along 150-152°W, between 72°S and 55°N ( Fig. 1) was a reoccupation of a several meridional P16 cruises sampled during WOCE: P16N (NOAA CGC-91 cruise onboard R/V Discoverer in 1991, Feely et al. 1991); P16C (R/V T. Washington TUNES-3 cruise in 1991; NDP-060); P16S (R/V T. Washington TUNES-2 cruise in 1991, see NDP-054); and P16A (R/V Knorr Juno 9 cruise in 1992, see NDP-065).
The R/V Roger Revelle conducted the first CLIVAR/GO-SHIP/CO2 P16 cruise designated as P16S. The cruise departed from Papeete, Tahiti, on January 9, 2005 conducting hydrographic profiles at one-half degree spacing nominally along 150°W from 16°S to 71°S. Scientists completed 111 full-depth conductivity, temperature, and depth (CTD)/rosette/lowered acoustic Doppler current profiler (LADCP) casts, 4 shallow colored dissolved organic matter (CDOM) rosette casts, 21 bio-optical casts and 58 trace metals CTD/rosette casts. In addition twelve ARGOS floats were deployed. The cruise ended in Wellington, New Zealand, on February 19, 2005.
The R/V Thomas G. Thompson departed Papeete, Tahiti, on February 13, 2006, for the beginning of Leg 1 of Section P16N. The first station was at 17°S, 150°W. This station and the next station at 16°S, 150°W repeated the occupation of two stations sampled in 2005 as part of Section P16S. The ship then proceeded north conducting a full depth CTD/rosette/LADCP cast every 60 nm to 21°N, 152°W. Station spacing was decreased to 30 miles between 2°S and 2°N. Thirty-four 12-L Niskin type bottles were used to collect water samples from throughout the water column at each station. Each Niskin bottle was sub-sampled on deck for a variety of analyses. Twenty projects were represented on Leg 1 of the cruise. A 1000 m trace metal cast was conducted at every other station, except between 2°S and 1°N where a profile was collected at every station for a total of 23 trace metal casts. The trace metal casts were conducted at approximately the same locations as the primary profiles and were either before or after the full-depth casts depending on time of day. One optical profile was collected each day on stations that occurred between 10:00 and 14:00 local time. Near surface seawater (temperature, salinity, partial pressure of carbon dioxide [pCO2], acoustic Doppler current profiler [ADCP]) and atmospheric measurements (CO2, CFCs, aerosols) were also made along the cruise track. The last of 43 stations was completed on Thursday, March 2, 2006. The cruise ended in Honolulu, Hawaii, on March 3, 2006.
The R/V Thomas G. Thompson departed Honolulu, Hawaii, on March 10, 2006, for the start of Leg 2 of Section P16N. The first station was occupied at 22°N, 152°W. The ship then proceeded north while a full-depth CTD/rosette/LADCP cast was conducted every 60 nautical miles to 55°N, 152°W, where a series of 8 closely-spaced stations were conducted close to the Alaskan coast. Thirty-six 12-L Niskin bottles were used to collect water samples from throughout the water column at each station. Each Niskin bottle was sub-sampled on deck for a variety of analyses. Twenty projects were represented on Leg 2 of the cruise. A 1000 m trace metal cast was conducted approximately every other station for a total of 17 trace metal casts. The trace metal casts were conducted at approximately the same locations as the primary profiles and were either before or after the full-depth casts depending on time of day. One optical profile was collected each day on stations that occurred between 10:00 and 14:00 local time. A total of 41 stations were occupied on Leg 2. In addition, net tows were conducted at night at about 10 stations either while steaming towards a station or upon departure. As part of the Argo program, floats were deployed at 8 locations usually upon departure from a station. Underway measurements of surface seawater properties (temperature, salinity, pCO2, ADCP) and atmospheric concentrations of CO2, CFCs, and aerosols were also made along the cruise track. The last station was completed on Wednesday, March 29, 2006. The expedition ended in Kodiak, Alaska, on March 30, 2006.
This report presents methods, and analytical and quality control procedures for salinity, oxygen, nutrients, total carbon dioxide (TCO2), total alkalinity (TALK), pH, discrete CO2 partial pressure (pCO2), dissolved organic carbon (DOC), chlorofluorocarbons (CFCs), carbon isotopes, and underway carbon measurements performed on these cruises. For information about other measurements from the P16 cruises see the cruise reports at CLIVAR/GO-SHIP and Carbon Hydrographic Data Office (CCHDO).
