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Monitoring of
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2. Outline and Results
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To measure the CO2 sink and source intensities and their temporal changes in the North Pacific, observations have been conducted since 1995 with the help of shipping companies by installing CO2 measuring instruments onboard ships. The first volunteer observation ship (VOS) was M/S Skaugran (Photo. 1) of Seaboard International Shipping Co., Canada, and observations were carried out from March 1995 to September 1999. The ship usually sailed from Vancouver, BC, to Japanese ports and then back to U.S. West Coast ports or to Vancouver, BC, every 6 to 7 weeks, and so data from 8 to 9 round-trips per year were obtained. M/S Skaugran provided good coverage north of 34oN in the North Pacific (Fig. 1), and the monthly distribution of the ocean surface pCO2 for the 4-year period was acquired. Panels (a) to (d) in Fig. 2 show the maps of delta pCO2 (ΔpCO2) obtained for February, May, August, and November. ΔpCO2 is the partial pressure difference of CO2 between the ocean and atmosphere, meaning that the ocean is the source when the value is positive and the sink when negative. The maps in Fig. 2 show the 4-year average of ΔpCO2 measured on the surface of the North Pacific Ocean each month.

M/S Skaugran Fig.1 Cuise routes
Figure 1. Cruise routes of M/S Skaugran

fig.2 Cruise routes of Skaugran

The second VOS was M/S Alligator Hope (Photo. 2) of MO Line Co., Japan, which operated from November 1999 to May 2001. This container cargo ship operated between Japan and the U.S. West Coast at 5-week intervals. The calling ports were Seattle in the U.S. and Vancouver in Canada. Oceanic pCO2 was observed between Tokyo and Seattle and between Vancouver and Tokyo. From the 16 round-trips within the period, frequent observations of the high latitude area in the Pacific were obtained. A fully automated onboard system was installed and its operation was contracted out to an onboard seaman (Fig. 3). The 6-year datasets obtained through Skaugran and Alligator Hope provided useful information about the interannual variability of ΔpCO2 in the North Pacific, which has significantly smaller amplitude than that in the Equatorial Pacific area.

PyxisThe third VOS is M/S Pyxis (Photo. 3) of Toyofuji Shipping Co., Japan, which is a car carrier from Japan to the U.S. She has two major sailing routes: one from Toyohashi, Japan to Portland, Oakland, and Long Beach, and the other to U.S. East Coast ports via the Panama Canal. Fig. 4 shows the ship's routes for fiscal 2003. More areas at mid- and low-latitudes in the North Pacific are now covered than with the previous two VOSs. The 20-40oN latitude band in the Pacific is a large CO2 sink area; however, the east/west difference is very significant. Observations from Pyxis will give useful coverage in this important area of the Pacific.

Corresponding to the successful ocean surface pCO2 measurement by VOSs in the CGER/NIES program, our partners around the globe have started similar types of observation using cargo ships and research vessels-of-opportunity. In a European project, which has been implemented by research groups from Norway, the UK, Germany, and Spain since 2001, the North Atlantic is being covered by three cargo ships and one Antarctic supply ship. NIES is collaborating with Kiel University, Germany, in the North Atlantic mid-latitude observation by a car carrier. The United States has also started a VOS pCO2 program in the Pacific and the Atlantic. In partnership with shipping companies, preparations are underway to conduct a new pCO2 observation program by installing pCO2 systems on a newly built ship, which is scheduled to sail from Japan to Australia and New Zealand starting in early 2006.

The VOS program by CGER/NIES is linked to our atmospheric observations. The maritime atmosphere has been sampled by an automatic canister sampling system, as well as an atmospheric CO2 analyzer which is indispensable for identifying ΔCO2 (ocean minus atmosphere). In the oceanic CO2 monitoring program, measurements of greenhouse gases, such as CO2, CO2 isotopes, CH4, and N2O, together with gases related to the global carbon cycle and atmospheric chemistry, such as O2/N2 ratio, ozone, and CO, are being conducted using onboard instruments or by canister sampling.

M/S Alligator Hope

fig3. System

Cruise route map

Figure 4.  Cruise route map of
M/S Pyxis for fiscal 2006
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