Insights from a Half-Century of Oceanographic Observations

The Ryōfū-Maru 2 ran the 137º E transect from 1967 to 1995.

Dr. Masuzawa Jōtarō.

Sampling along the 137º E meridian has been conducted for over 50 years by the JMA.

A CTD rosette used to measure conductivity (salinity), temperature, and depth with 36 Nansen (or Niskin) bottles for sampling seawater from discrete depths is deployed via a winch and cable. The device sends real-time, continuous data back to the ship, where researchers can trigger water sampling.

Researchers examine Nansen bottles and the reversing thermometers, which lock in the temperature measured at depth, that were used prior to the introduction of the CTD rosette capable of continuous, real-time measurements of the water column. Temperatures are read from the thermometers and water subsampled from each bottle. Temperature and salinity data are only obtained for the discretely sampled depths.

The JMA operates another research vessel, the Keifū-Maru 2.