Global Chemical and Physical Oceanography Group

Outline of Research Activities

Using JAMSTEC’s research vessels like the R/V Mirai, we conduct highly accurate observations that include, inter alia, Conductivity-Temperature-Depth (CTD) profiles; concentrations of chemical tracers such as dissolved oxygen, nutrients, and chlorofluorocarbons; CO2-system properties; carbon isotopes such as 13C and 14C and activities of radioisotopes such as cesium-137. By using the observed data (Fig. 1) along with information from sources such as satellite data, open-access databases, and outputs from four-dimensional data assimilation methods, we attempt to understand decadal-scale variations of the ocean environment. We estimate, for example, basin-scale changes of anthropogenic CO2 storage and heat content, the magnitude of ocean acidification, and changes of salinity. Data obtained from our observations are open to the public after a quality-control check. In addition to these activities, we develop analytical methods for measuring the chemical properties of seawater and observational techniques for quantifying the physical characteristics of marine waters to improve the accuracy of our observations.

>Figure 1. Observation lines of repeat hydrography. Red lines are those occupied by JAMSTEC.
Figure 1. Observation lines of repeat hydrography. Red lines are those occupied by JAMSTEC.

Goals and Objectives

To (1) accurately quantify large-scale environment changes such as global warming, progressive ocean acidification and its impact on marine ecosystems, and changes of the heat content of the ocean and the distribution of substances in seawater; and (2) contribute to the formulation of provisions for adaptation and mitigation, we report, inter alia, basin-scale changes in the characteristics of water masses based on analyses of the distributions of chemical tracers and decadal-scale changes of total alkalinity, pH, the saturation state of CaCO3 (Ω), and inventories of nutrients.

Expected Products

Fiscal year: 2014

Detection of progressive ocean acidification (pH and Ω) and variations of the heat content (warming of bottom water) in the subarctic region of the North Pacific

1. Ocean observations

We are continuing to make observations and measurements at the stations indicated in Fig. 2. These stations include stations along Leg 1, Leg 2 of the WHP-P1 line, and Ocean Station PAPA.

Figure 2. Map for the R/V Mirai cruise (MR14-04) from 9 July to 29, August, 2014 (52 days). During the cruise, we conduct CTD observations and water sampling at 121 stations.
Figure 2. Map for the R/V Mirai cruise (MR14-04) from 9 July to 29, August, 2014 (52 days). During the cruise, we conduct CTD observations and water sampling at 121 stations.

2. Analytical procedures for measuring physical parameters and concentrations of chemical tracers

We are carrying out studies to improve the precision and accuracy of our measurements. These studies include the following:

  • Pretreatment of samples for carbon isotopic analysis, measurement of the activity of radioactive cesium, and other measurements under the auspices of analytical commission
  • Improvement of analytical procedures for measuring physical parameters and concentrations of chemical tracers

3. Changes in the marine environment

By using high-quality data obtained from sources such as repeat hydrographic surveys, open-access databases, satellite data, and outputs from four-dimensional data assimilation methods, we estimate storage of CO2 and heat in the ocean, and we quantify decadal-scale environmental changes in marine chemistry and physics in terms of parameters such as pH and salinity.