-Global Environmental Monitoring-

Monitoring of GHGs along a North-south transect by ship of opportunity

Although ocean plays an important role in global warming, the continuous observation of greenhouse gases is difficult over the ocean without the suitable island. In order to supplement this, the behavior of greenhouse gases over the ocean is continuously observed on board a regular service cargo ship. Compared to research vessels, cargo ships are convenient to collect the data regularly for specified region. In order to obtain the background greenhouse gases concentration, i.e., concentrations of the greenhouse gases not directly effected by anthropogenic sources, an automatic sampler was installed on board a container freighter which sails between Japan and Australia (Photo 1).

The gases are sampled at the internal of 3° latitude about eight voyages a year to observe horizontal distribution and time series variation of gases in both northern and southern hemispheres, since 1992. From 1992 to 1995 the sampling was conducted on ship, Hakuba-Maru, and on ship, Southern Cross-Maru since 1996. Ship track and sampling points are shown in Fig 1.

The air samples, introduced from the intake situated at bows, pressurized and collected using the automatic gas sampler, set up in the hold, in the stainless steel bottles. The operation is started by the crew when the ship set sail from Australian port.

These bottles are recovered at Japanese port and the concentrations of CO2,N2O and CH4 are measured precisely at NIES (National Institute for Environmental Studies).

North-south gradients of these greenhouse gases(Fig.2) and their seasonality (Fig.3) are monitored from the results. Data from the similar sampling by M/S Skaugran between Canada and Japan(?`1995)are combined to build up the distributions of these gases from 54° N to 26° S.

Atomospheric GHGS
Fig.2 Latitudial Distribution of Atmospheric CO2, CH4, N2O, observed on Nov-Dec.1997
Southern Cross
Photo1:Southern Cross-Maru
Photo2:Automatic gas sampler
Fig.1:Example of sampling points by Southern Cross-Maru
(SC02 cruise in May 1996)
CH4 values
Fig.3 Time series of altitude-zone specific concentration and seasonal variation of GHGs

Last updated, Mar. 6, 2000
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