Ocean Research

CLARIFYING OCEAN ROLE IN GLOBAL CLIMATE

Some time ago, the earth was believed to have an infinite size, capable of absorbing unlimited emission of pollutants to ocean, atmosphere, etc. However, Men are beginning to understand that the earth is far from infinite. The global environment may be divided into 5 spheres, the ocean, the atmosphere, the land, the snow/ice, the biota (including human being), and these five spheres are interrelated. There 5 spheres interact to one another, and the earth is a huge system which is driven by these interactions.

In recently Years, much discussions are made on the expansion of deserts and warning of the earth which may have been caused by destruction of global environment. Such anomaly, if any, should be caused by the upset balance in heat and matters in the interactions between atmosphere, ocean, etc. The earth on which we live is substantially affected by the interactions between atmosphere, ocean, etc. From this point of view, we are conducting researches for the clarification of the mechanisms of circulation and perturbation of ocean.

SIGNIFICANCE OF OCEAN OBSERVATION

OCEAN SYSTEM

The heat capacity of the ocean is approximately 1000 times as large as that of the atmosphere. The ocean transports heat with its current, supplies energy to the atmosphere, dissolves various substances to create chemical reactions, and supports huge variety of creatures, thereby plays a dominant role in stabilizing global environment and maintaining life on this planet.

JAMSTEC conducts surveys and researches to clarify these functions of ocean step by step.

ATMOSPHERIC SYSTEM

Clarifying the atmosphere means the circulation of heat and momentum in the atmosphere (wind), as well as substances (water, carbon dioxide, etc.).

Although the atmosphere is omnipresent on earth, we have little data of the atmosphere above ocean, thereby making it difficult to analyze meteorological phenomena. The role of ocean played in the motion of the atmosphere as the sources of water and heat is predominant. The data obtained in the oceanic observation are indispensable for meteorology and climatology.

SNOW/ICE SYSTEM

Since snow and ice have high albedo (reflectivity against solar radiation), and they occupy large areas on earth's surface, they have large effect on the global flow of water and heat, and influence meteorology and climate of earth. In particular, large amount of snow and ice stays on both poles throughout a year. Therefore, clarification of the role of snow and ice is important in analyzing global environment.

RESEARCH OF OCEANIC CIRCULATION

EL NINO OBSERVATION

There arose a large scale atmospheric and oceanic change in the tropical pacific from 1982 to 1983, which has been known as ENSO (El Nino and southern oscillation). The scale of this phenomenon was so large that it not only affected the tropical area, but the atmospheric circulation in the middle latitude have been changed. Many scientists alarmed that this ENSO may recur in the autumn of 1986. JAMSTEC, upon request of Science and Technology Agency, conducted survey and observation with marine survey vessel "Natsushima". The survey has been continued as a part of survey project of Japanese Pacific Climate Study (JAPACS) in cooperation with American and Australian authorities. The satellite data, containing information of wide sea areas, were utilized in parallel. The result shows that an positive sea level anomaly moved moved eastward from December 1986 to January 1987, as shown in the picture to the right. For further research, the satellite data and hydrographic data collected by observation ship are being analyzed.

GLOBAL OCEAN CIRCULATION OBSERVATION

It is known that Kuroshio Current flows from Taiwan through East China Sea, comes out to the Pacific Ocean at south of Kagoshima, meamders at the south of Kii Peninsula, and goes out to the east through Izu Archipelago. In addition to such tidal currents that flow the ocean surface, it is believed that there are deep tidal current that circulate in grand scale all over the whole Pacific Ocean, but there are little examples of actual measurement. As the sea water has large mass and specific heat, it has profound effect on the global warning. As a part of international cooperative research designed to clarify the actual status and mechanism of this global ocean circulation in deep sea, JAMSTEC is conducting surveys in the eastern Philippine Sea, for which it is believed that observation is particularly needed.

OCEAN CLIMATE SIMULATION MODEL

It is practically impossible to observe all parts of oceans throughout the world. Therefore, we use the observation results of a part of ocean to attempt to reproduce what should be happening throughout oceans and compare these simulated phenomena with observation results. By repeating such simulation and observation, we will be able to predict the oceanic phenomena.

Numerical Simulation of Tropical Pacific Sea Surface Temperature

This is a model output of sea surface temperature(SST) in the tropical Pacific Ocean. The model consists of 50x70 horizontal grid points and mixed-layer plus 8 underlying layers with realistic bottom topography.

The model was forced by climateological wind, turbulent kinetic energy, and atmospheric heat flux. The SST is not relaxed to observed SST.

Instead, the SST is predicted by model and total heat flux that uses SST is calculated in order to force the ocean surface mixed-layer.

This model was developed by Dr. Josef Oberhuber and has been used by Dr. Shoichiro Nakamoto and his collaborators of Climate Research Division of the Scrips Institution of Oceanography.

Global Ocean model simulation : Model result is here

OBSERVATION OF KUROSHIO CURRENT

The regions affiliated to Kuroshio Current are deeply related to the social and economic activities of Japan, and they are the marine zones where development of various resources looks most promising. For this reason,a comprehensive survey has been conducted in this region concerning the identification of regional characteristics and evaluation of development potential, under cooperation of governmental agencies (Hydrographic Department of Maritime Safety Agency, Meteorological Agency, Fisheries Agency, Science and Technology Agency). JAMSTEC's role was to identify the energy of Kuroshio Current. Although emphasis has been placed at first on the identification of status and phenomena of the sea, it became clear in the course of survey that the local phenomena were deeply related to with large scale oceanic phenomena (i.e., the subtropical circulation in the Western Pacific). Based on this new knowledge, a comprehensive survey is being conducted on the Kuroshio circulation system (Kuroshio Exploitation Utilization Research, 1986 to 1995). JAMSTEC is engaged in the estimation of the volume transport amount of Kuroshio in East China Sea and adjacent area, and the research of mixing process of water masses in the continental shelf region, with the objective of identifying the energy of Kuroshio.

OBSERVATION OF ARCTIC ZONE

The arctic zone is most sensitive to the global environmental change, and plays important role in relation to the global circulation of heat and matters. It has also become important to identify the environmental conditions of arctic zone in view of development of resources.

However, researches so far conducted are concentrated on tropical and mid-latitude regions, and there has not been a fully committed research on arctic zone, although some racers have been done on the antarctic zone. JAMSTEC is advancing the arctic zone researches under cooperation with various research institutions in Japan and abroad.