Outline of Research Cruises of

Research Vessel "MIRAI" during Fiscal Year 2000



MR00-K03 Observational studies on the Material Cycle in the High Latitude Sea.
› Objectives : The northern North Pacific, especially its western part, has been attracting attention of chemical oceanographers because of its importance in global biogeochemical cycles of carbon and its related materials, which have a great impact to the climate change of the earth. In addition, physical oceanographers have been interested in that region with respect to the formation of the North Pacific Intermediate Water. Despite its importance, there has been few systematic survey to cover the temporal and spatial variation of biogeochemical processes in the area. Main goal of this study is to clarify the behavior of carbon and its related materials in the area, and then to estimate the impact of high latitude seas on the global climate change.

MR00|K04 Observationl Studies on Air Sea Interaction.
› Objectives : Water and heat flux is one of the most important factor to understand the ENSO(El Nino and Southern Oscillaticn ) and the Mcnsccn which affect the global climate. Especially the precipitation is the key phenomena playing the important role for the water and heat flux. So, the interaction between the ocean and the atmosphere are studied focusing on the precipitation. Mainly by using powerful tool shipboard C-band Doppler radar, the precipitation mechanism of the convection which develop in the intertropical convergence zone (ITCZ) and the influence of the precipitation onto the ocean surface structure will be surveyed.

MR00-K05 The Subtropical Gyre and the Subpolar Gyre in the North Pacific Ocean.
›Objectives : Oceanic conditions in the subtropical and subarctic gyres, especially in and around the Kuroshio Extension, are thought to be important to the North Pacific decadal/interdecadal climate variabilities. In terms of global heat budget, the ocean in this region transfers the heat obtained in the tropis to the atmosphere. The area could also be a reservoir of greenhouse gases as anthropogenic CO2 by deep oceanic convection in winter season which may convey these gasses to deep ocean.

MR00-K06 Observational Studies in the Arctic Ocean
›Objectives : The continental shelf in the Arctic Ocean is a place where remarkable positive and negative buoyancy flux is being supplied due to an inflow of fresh water, melting and formation of sea ice and etc. Also, a cold halocline water exists between the surface mixed layer and the Atlantic Water in a wide range of the Arctic Ocean.
The lower layer of this cold halocline contains maximum silicate concentration and minimum dissolve oxygen, therefore the origin of such water mass may exists on the continental shelf. The formation, maintenance, and variations of the cold halocline may have significant influence on a oceanic structure in the Arctic Ocean.
Toward the understanding of various processes in the cold halocline, we have to know shelf brake processes such as instability, eddy formation, water exchange and water mass formation due to surface cooling on the shelf and in the canyons as well.
The purposes of this study are to collect dates covering decades scale on ocean structure, buoyancy flux, and year to year variations of sea ice extent and so on, then carry out assessment on influence of shelf - basin interaction processes to the climate system in the Arctic Ocean.

MR00-K07 Observational Studies in the Western Tropical Pacific Ocean and Observational @@@@@@@@@Studies on Air Sea Interaction
› Objectives : For the purpose of understanding the role of the warm water pool to EI Nino and Asian Monsoon, which affect the social and economical activities in the East Asian countries including Japan, we will conduct the observational studies on the oceanic and atmospheric variabilities.
The major theme is to clarify the heat, freshwater and momentum balances in the surface mixed layer in the warm water pool in the western Pacific Ocean as well as the eastern Indian Ocean. In this study, we will also expect to understand the role of salinity, horizontal advection of heat and freshwater, and equatorial waves such as Kelvin waves to the change of the surface mixed layer. We will also study how the Pacific Ocean and the Indian Ocean interact mutually by exchange of heat and fresh water through the Indonesian Seas.
We will also conduct atmospheric observation mainly using a Doppler radar system (C-band) to understand the cloud systems over the tropical ocean.

MR00-K08 Observational studies on Primary Productivity in the Equatorial Pacific Ocean
› Objectives : The equatorial Pacific has distinguished characteristics, those are it occupies a large region of the world's ocean and the warmest water of the planet exists there. The western equatorial Pacific contains so-called warn water pool. Nitrate is depleted there and primary production is small. In the central and eastern equatorial Pacific, vertical flux of nutrients is enhance due to Quasi-stationary up welling caused by equatorial divergence and consequently chlorophyll a concentration and primary production rate increased along the equator. However, primary production and biomass are not as high as would be expected from the flux of nutrients could support. This is called high nutrient low chlorophyll situation. Since this east to west asymmetry is affected by ENSO event, there is a significant variability in physical characters on seasonal-interannual scale with impact to biogeochemistry, as well potentially with the similar scale of variability. The objective of our cruise is to investigate the mechanism of this biogeochemical variability especially in the western equatorial Pacific.

MR01-K01 Observational Studies in the Western Tropical Pacific Ocean
› Objectives : 'For the purpose of understanding the role of the warm water pool to EI Nino and Asian Monsoon, which affect the social and economical activities in the East Asian countries including Japan, we will conduct the observational studies on the oceanic and atmospheric variabilities.
The major theme is to clarify the heat, freshwater and momentum balances in the surface mixed layer in the warm water pool in the western pacific Ocean as well as the eastern Indian Ocean. In this study, we will also expect to understand the role of salinity, horizontal advection of heat and freshwater, and equatorial waves such as kelvin waves to the change of the surface mixed layer. We will also study how the Pacific Ocean and the Indian Ocean interact mutually by exchange of heat and fresh water through the Indonesian Seas.