JAMSTEC

Long-term Observation and Research Plan for Utilizing the Oceanographic Research Vessel "MIRAI"

CONTENTS
  1. 1. Introduction

  2. Research Themes and Objectives
    2.1 Thermal Circulation
    2.1.1 Objectives
    2.1.2 Subjects of Observational Studies
      (1) Observational Studies in the Western Tropical Pacific Ocean
      (2) Observational Studies on Air-Sea Interaction
      (3) Observational Studies on the Variabilities of the Subtropical Gyre and the Subpolar Gyre in the North Pacific Ocean
      (4) Observational Studies in the Arctic Ocean
    2.2 Biogeochemical Cycle
    2.2.1 Objectives
    2.2.2 Subjects of Observational Studies
      (1) Observational Studies on the Material Cycle in the High Latitude Seas
      (2) Observational Studies on Primary Productivity in the Equatorial Pacific Ocean
    2.3 Pacific Ocean Marine Ecosystems
    2.3.1 Objectives
    2.3.2 Subjects of Observational Studies
      (1) Observational Studies on the Plankton Community
      (2) Observational Studies on the Ecosystems of Deep-sea Organisms
    2.4 Ocean Crust Dynamics
    2.4.1 Objectives
    2.4.2 Subjects of Observational Studies
      (1) Observational Studies on the Ocean Crust Dynamics of the Sea Floor

  3. Other Issues to be Promoted
    3.1 Validation of Satellite Data Sets
    3.2 Data Sets to be Obtained Routinely on R/V Mirai
    3.3 Utilization of Ocean Observing New Technologies
1. Introduction

The objective of this long-term plan, a follow-up of the Utilization Plan of the Oceanographic Research Vessel R/V Mirai prepared in September 1997 by the Operation System Planning Committee, is to establish scientific objectives and themes for observation and research to be conducted using R/V Mirai for the next 10 years and, at the same time, guidelines for preparing the Middle-term Operation Plan of R/V Mirai defining its cruise schedule for the coming 3 years.

Ideally, we wish we could use R/V Mirai for the widest possible public use. It is at the same time demanded that the ship be used to bring steady progress in studies with specific scientific objectives. The following policies have thus been adopted in establishing this long-term observation and research plan:
    (1) The framework consists of the four priority infrastructural research themes (thermal circulation, material cycle, marine ecosystems and ocean crust dynamics) as presented in the Report No. 4: "Japan's Promotion Measures for Oceanic Research, December 1993" of the Council for Ocean Development.
    (2) The R/V Mirai Observation Plan Subcommittee of the Earth Science and Technology Forum/the Global Observation Committee will have extensive hearings on different views which will be reflected on this plan.
    (3) The central aim is to come up with an outline of observation and research that maximizes the strong features of R/V Mirai .


The "Thermal Circulation" research theme will center on research to describe the complex processes of heat exchange that take place between the different depth layers from the sea surface to the ocean deep, and between the ocean (which has a heat capacity 1,000 times as much that of the atmosphere and represents as much as 98% of all water on earth) and the atmosphere since such exchanges play a major role in the thermal balance of the whole earth. Urgently needed is an understanding in detail of the changes in sea water temperatures and ocean currents that bring anomalies in the weather and the climate.

The "Material Cycle in the Ocean" theme will center on research to describe how carbon dioxide and other greenhouse gasses are carried through the ocean and distributed, and how they undergo changes in the ocean (which absorbs these materials in enormous amounts). The development of our capability to predict global warming is another priority under this theme.

The theme of "Pacific Ocean Marine Ecosystems" will pursue ecology of phyto- and zoo-planktons and other life in the ocean to describe their complex ecosystems in relation to the surrounding environments, while the "Ocean Crust Dynamics" theme aims at systematic studies to be carried out in the earth-wide context as to the causes of crust changes and the resultant phenomena taking place underneath the ocean

Our selection of these four themes is based on a recently emerging view (with the global environment issue in the background) that events taking place on earth must be understood within the context of the whole or as components of the entire system. The question of climate change, for example, involves complex physical biogeochemical processes that cross the boundaries of atmosphere, hydrosphere, terresphere, and biosphere and take place on different temporal and spatial scales. Our research, in a way, is an effort to untangle those complexly entangled processes step by step.

Take as an example the behavior of CO2 and other greenhouse gases in the atmosphere, a subject being dealt with in the "Material Cycle" theme. The study requires in turn research on the transport processes of these materials between the atmosphere and the ocean, the sea surface and the deeper seas, the sea water and the sea floor. This meanwhile presupposes sufficient progress in studies of sea water circulations and atmospheric circulations that will be addressed under the "Thermal Circulation" theme. The oceanic ecosystems in the meantime play an important role in efficiently transporting, down to the ocean's bottom through the food chain action, part of the carbon taken in by photosynthesis process of phytoplanktons in the surface layer of the ocean, while fossils of the species found in the ocean floor sediment and their compositions make possible to surmise the changes in the environments existed in the geological past. All these factors will have to be considered and weighed to make the sound basis to understand climate change. The maintenance of close liaison with other themes and studies is thus essential to make headway with each theme.

As stated in the Utilization Plan, R/V Mirai with its large and sturdy hull can conduct observation through packed ice sea and other severe sea state seas as in winter North Pacific. The vessel can also carry a number of ocean observing buoys and perform their deployment and recovery tasks. The ship is also equipped with advanced observation equipment of varied kinds, such as a high volume sea water sampler reaching deep water, a continuous surface water sampler, and advanced sea water analyzers. The ship's advanced atmospheric observation equipment includes a C-band Doppler radar making rainfall measurements possible in the mid-ocean and an atmospheric gas sampler making a convenient tool for atmospheric chemistry. Also equipped for ocean floor dynamics study are: multi-narrow beam sea-floor mapper, sub-bottom profiler, gravity meter, magnetometer, and piston core sampler. Besides, the marine technicians are at hand to support observation activities conducted on board.

It is our aim that these strong points of R/V Mirai will be utilized to the maximum possible extent for global change science through well-coordinated interdisciplinary effort.

2. Research Themes and Objectives
2.1 Thermal Circulation
2.1.1 Objectives
There has lately been growing concern about climate change in the atmosphere and on the ocean. As is seen in an IPCC (Intergovernmental Panel on Climate Change) report, the government of each country is now requested to establish measures to cope with the issue. The measures must be based on sound scientific grounds, however. Yet, humanity's knowledge is not sufficient to understand clearly the basics of climate change, much less its detailed characteristics to be able to predict the change. Only since the 1980s, it is becoming clearer little by little that the behavior of earth's atmosphere, the component of the climate system, is largely dependent on oceanic fluctuations. A case in point is the XXXevent in the tropical ocean. XXX used to be a word used by local sailors to describe a seasonal phenomenon in which a warm current comes backward from north off the coast of Peru. It has been noted in recent years the warm current spreads much too extensively in the tropical East Pacific and remains there for a long time (a year or so) and this term has come to stand for such an abnormal oceanic event. At the same time, when XXX occurs, places of active cumulus troposphere deviate to the east. This in turn greatly influences global circulation of the atmosphere of not only the tropical areas but also many other places in the world, attracting people's attention the world over because of threats it poses to their life. The event has been tackled by scientists of the world in many ways through a number of international climate research projects such as the Tropical Ocean and Global Atmosphere (TOGA). Varied observation tools have come to be used almost routinely now e.g., Tropical Ocean Atmosphere (TAO) buoy array for meteorological parameters and water temperature; volunteer observing ships (VOS) for surface layer temperature; and drifting buoys for currents. For becoming able to predict the climate change using coupled ocean-atmosphere models, however, there still remain many processes that must be understood clearly on seasonal to interannual scales. It is thus necessary to further strengthen those observation networks. This is the reason that the development and maintenance of the TRITON Buoy network, each buoy equipped with high quality observation sensors for surface meteorology, water temperature, salinity, etc., is one of the major tasks expected of R/V Mirai..

Water circulates in the atmosphere and the earth by repeating thermal absorption and discharge in terms of the ice-water-water vapor phase change. The hydrological cycle may conveniently be classified into sea water circulation like ocean currents and fresh water circulation like clouds. In studying the fresh water circulation globally, we appreciate that the exchange between the ocean and the atmosphere plays an extremely important role since over 70% of the earth's surface is covered by the sea. Events such as Asian monsoons and XXX can only be understood from the standpoint of air-sea interaction. In particular, "rain" plays a key role as a medium in the air-sea interaction so that the precipitation mechanism must be understood thoroughly based on observation. There has been little experience in rainfall observation amidst the ocean mainly because of technical difficulties. Most past analyses depended on what scant data obtained at such places as isolated islands assuming that they represented data on the ocean too. However, we have since learned that the rainfall in the ocean requires treatment separate from the land based observation. We can say that thanks to the C-band Doppler radar system mounted on R/V Mirai as standard equipment, we have acquired for the first time a means to observe rainfall processes that occur in the middle of the ocean. (The Doppler radar will initially be used for air-sea interaction study in the tropical ocean. Its use will be expanded into higher latitude regions at a later date.)

As a typical example of variation taking place on a time scale every few to several years, XXXcan be cited. Its influence reaches middle- and high-latitude regions through various processes of the atmosphere and the ocean. Decadal scale variations, some of which have come to be noticed widely in recent years in relation to possible global warming, include interactions between the subtropical zone and the sub-Arctic zone, and between the sub-tropical and the tropical. In fact, the whole northern hemisphere forms a giant feedback system of interactions. We will thus need to develop a North Pacific-wide long-term observation network as well as one in the Tropical Pacific. However, intensive observation conducted in certain specific sea areas where the influence on climate change is especially great will be just as important. The existing air-sea combined models for heat exchange are so inadequate in terms of precision that there is a difference between models as big as 100 W/m2 in the middle latitude region. The difference is particularly big at the Kushiro Extension region. The Kushiro Extension region is an area where the decadal scale climate variations appear most strikingly, we have come to know that the tolerance there must be below 10 W/m2 for the models to be useful. This is just a illustration that we still have a lot to learn for modeling heat transport and others in parametrization of surface ocean mixed layers, atmospheric boundary layers, and horizontal turbulent mixing. In the warm water pool in the equatorial Pacific, a low salinity layer is formed in the surface layer due to heavy precipitation which interrupts vertical mixing so that the surface water becomes very warm. Such processes have not so far been modeled to satisfaction. We must improve the models by means of high precision observations. In other words, the understanding of the mechanisms of decadal scale climate variations in the Pacific requires study from two aspects: (1) long-term basin-scale observation networks to catch signals of climate change and (2) process studies via intensive field experiments. Particularly in intensive field observations, conventional measuring devices should be strengthened, while new observation technologies such as ocean acoustic tomography should also be actively sought. In operating R/V Mirai, it is important to keep a good balance of these two aspects.

There is a fear that, if changes occur in the earth's environment due to global warming, they can likely accelerate positive feedback leading to still further aggravation. Recent results of climate models show the most marked changes occur in the Arctic area. There, the feedback effect comes out most visibly through the ocean and ice. Moreover, this shows not just a simple climate warming which melts ice and further warming results. There are some scientists who point out that if ice melts and a large amount of fresh water flows into the Atlantic Ocean, thermohaline circulation will be suppressed, so that there is even a possibility of negative feedback which would lead back to a colder climate. Despite our awareness of the importance of studying Arctic climate, which will have great bearing upon our everyday life, the feedback systems study has been hampered for reasons of severe natural conditions and international politics. Nonetheless, the Arctic region requires no less effort than in other regions to accumulate in-situ data for climate and environment prediction models and for understanding elementary processes of the atmosphere and ice sea specific to the Polar area.

Global warming phenomena are generally believed to be attributable to artificial causes such as carbon dioxide and other greenhouse gas emissions. In quantitative analysis of global warming, however, it is necessary to separate those fluctuations which take place as nature's course of events and from those of forced response involving CO2 and other greenhouse gasses. The fluctuations inherent to nature may be studied as subject of oceanographic and climatological physics. Simply put, it is to understand the mechanisms of thermal circulations and their fluctuations. About a "climate jump" in the North Pacific Ocean that occurred in the mid-1970s and came to attract attention in recent years, some scientists view that it was related to the rise of sea surface temperature in the equatorial Pacific, particularly to a rise by 1 degree C in the east of the International Date Line. Thus the importance of the ocean for monitoring and predicting changes in the climate system is increasing. It may be said that to study material cycle processes of carbon dioxide and other greenhouse gasses and catch their fluctuations is to determine the fluctuations of external forcing by radiation associated with global warming. Since the volume of carbon accumulated in the ocean is said to be about 60 times as much the amount of carbon contained in the carbon dioxide in the atmosphere, it is quite important that we study its accumulation processes in the ocean. Extremely complicated processes associated with biological activities are involved, so that observational activities will have to be carried out in close linkage with research in material cycles and marine ecology.


2.1.2 Subjects of Observational Studies
(1) Observational Studies in the Western Tropical Pacific Ocean
To study about the variabilities of Asian monsoon and El Niño, the following observational studies are necessary with the expa nsion of TRITON buoys.
    (a) Air-sea fluxes in the tropical ocean
    It is necessary to survey the variabilities of the mixing layer in the warm pool through observation of heat flux, momentum flux and fresh water flux between the atmosphere and the ocean from the Western Tropical Pacific Ocean to the Eastern Indian Ocean.

    (b) Variabilities of currents in the tropical ocean
    In the warm pool region, there are inflows and outflows of not only the equatorial current system such as South Equatorial Current, Equatorial Undercurrent, North Equatorial Counter Current and North Equatorial Current but also low latitude western boundary currents such as Kuroshio Current, Mindanao Current, New Guinea Coastal Undercurrent and so on. It is necessary to research them, because these inflows and outflows are considered to be very influential to accumulation and dispersion of warm water.

    (c) Indonesian Throughflow and oceanic structure in and around the Indonesian Seas
    Warm and low salinity water is transported from the Pacific Ocean via Indonesian Archipelagoes to the Indian Sea; In order to promote the monsoon and ENSO studies, it is necessary to study the variabilities in the oceanic structure in the southern part of Philippine Sea, the eastern Indian Ocean and the Indonesian Throughflow. The Western Tropical Pacific Ocean is a key area from the viewpoint of global ocean circulation studies in terms of the passes of intermediate waters and deep waters from the mid latitude of the North and South Hemispheres.


(2)Observational Studies on Air-Sea Interaction
a. Precipitation mechanism over the tropical oceans
(a) Precipitation accompanied with large-scale phenomena
    Precipitation mechanisms of convective clouds which are accompanied with large-scale phenomena such as El Niño/Southern Oscillat ion and monsoon must be revealed. Especially, since it is often reported that well-organized convection systems widely in space (from 100km to several 1000km) and time (from a couple of days to several weeks) are often observed over the tropical oceans and they account for heavy presipitation, it is necessary to investigate the structure of such systems.

(b) Atmospheric radiation process
    In order to treat clouds and their interaction with solar and terrestrial radiation explicitly in global circulation models, intensive and fine observation is needed. Especially, it is necessary to investigate and evaluate the role of the diurnal cycle found in the atmospheric boundary layer and in the upper ocean, such as heat flux and sea surface temperature.

(c) Distribution map of clouds/precipitation
    Clouds/precipitation distribution map is needed to understand the fresh water and heat budgets over the oceans. In addition, what factors control this distribution is also needed to investigate. Recently, several studies revealed that it is common that the extremely dry air masses intrude from higher latitudes into the tropical western Pacific region and it prevents the deep convection from developing. It indicates that interaction between the tropical and extratropical must also be investigated.


b. Specific phenomena related to seasons and areas in the mid-latitude
Observational studies in terms of air-sea interaction for the following themes, which has characteristic of seasons and areas in the mid-latitude, must be promoted because they were only approached by land-base observation.
(a) Air-sea interaction related to Mei-yu front
(b) Heavy snowfall in the Japan Sea in winter
(c) Mechanism of typhoon in the middle latitude and its relation to ocean surface

c.Observation and research on the atmospheric chemistry over the sea
(a) Distribution of aerosol and ozone in the atmosphere over the sea
    Aerosol particles have a cooling effect on the surface of the earth by reflecting the sunlight (because albedo increases). The radiation effect of aerosol is attracting a great deal of attention recently. Since emission of sulfur dioxide and others has dramatically increased in Asia and the Pacific areas, they are considered as areas where atmospheric cooling effects are severe. When global warming is progressing, such local atmospheric cooling can be a cause of energy unbalance of the earth as a whole, leading to unusual weather. Since researches on aerosol of the seas including the West North Pacific Ocean have not been conducted sufficiently, the relation between aerosol and radiation effects has not been understood well yet. Therefore, its real mechanisms should be clarified soon.

    Ozone in the atmosphere also has been playing an important role in radiation and chemical processes. As for the troposphere over the sea where the chemical processes are different from those on the land, not many surveys of ozone have been conducted and the space time distribution of ozone has not been understood well; consequently, its observation over the sea is necessary.


(3) Observational Studies on the Variabilities of the Subtropical Gyre and the Subpolar Gyre in the North Pacific Ocean
a. Variations of decadal and interdecadal variation of the upper and the inte rmediate ocean circulation
b. Interactions between the atmosphere and the ocean, such as momentum and ma terial exchange processes under strong wind and high waves
c. Water and heat exchange processes between the marginal sea such as the Okh otsk Sea and the North Pacific Ocean

The Subtropical Gyre, especially the Kuroshio Extension region, and the Subarctic Gyre in the North Pacific are considered to be playing very important roles in global climate change because of a heat source to the atmosphere in a heat circulation and an absorbing zone of warming materials such as carbon dioxide in the material cycle. The North Pacific Intermediate Water, which is a typical least salinity layer in the mid latitude, is considered to be formed in the Subarctic Gyre after a sea water exchange process with one of marginal seas, the Okhotsk Sea. Among the seas where massive sea ice is created, the Okhotsk Sea locates at the lowest latitude in the world and the water of low temperature and high salinity, which is produced when sea ice is grown during winter season, becomes the water source of Oyashio system and is connected with the North Pacific Intermediate Water.

At the same time, it is pointed out that carbon dioxide is transported from the subarctic upper layer to the mid-latitude intermediate layer crossing the Kuroshio Extension. To improve the prediction of climate changes on a several decades scale, it is essential to understand the real situations of the following physics: variability of subarctic circulation system, formation and transport mechanisms of specific water masses represented by the North Pacific Intermediate Water" and absorption and transport processes of global warming materials such as carbon dioxide. Under the present circumstances, because of severe weather and maritime conditions during the winter, observation on the subarctic ocean including the Okhotsk Sea and the Bering Sea are behind those of other sea. It is necessary to start the researches there by making the best use of R/V Mirai .

(4) Observational Studies in the Arctic Ocean
a. Features of Atlantic Water circulation and its modification
    The Arctic Ocean is the final sea area where the Gulf Stream reaches. At the same time, it is the sea area adjoining to the Greenland Sea which is a starting area of abyssal circulation which moves around the whole earth. The oceanic structure of the Greenland Sea greatly affects on the fluctuation of the generation of deep water, and also affect on a residence time and a change process of the water of the Atlantic Ocean (water mass originated at the Gulf Stream) in the Arctic Ocean. It is said that the fluctuation of deep water generation not only the fluctuation of thermohaline circulation also affects the fluctuation of an atmospheric field at the middle latitude through the influence on the fluctuation of the intermediate water and upper water of the North Atlantic Ocean. The Atlantic Water flows along the continental shelf slope of the Arctic Ocean. Off the Barrow Point, Alaska, is an area where the shelf break of the Arctic Ocean locates nearest to the coast and the sea surface is exposed during summer season. By this research, CTD observation along/ across the continental shelf break and long period mooring observation should be carried out to evaluate a residence time and changes of the Atlantic Water in the Arctic Ocean.


b. Formation process of stratification structure of the Arctic Ocean
    The water mass exchange among a shelf region, continental shelf slope and a basin is a decisive process for the formation of the stratification structure of the Arctic Ocean. Vertical stratification determine the depth of vertical convection. The depth of convection gives great influences on the formation process of sea ice. Decisive phenomena for the stratification structure of the Arctic Ocean are considered to be the water mass exchange due to eddy motion on the continental shelf slope and the water mass exchange through submarine canyons, which should be qualitatively clarified.


c. Fluctuations of water supply from rivers, sea ice and oceanic structure
    Supply of fresh water to the Chukchi Sea mainly depends on rivers which flow into the coast of Siberia of the Arctic Ocean and the Yukon River which flows into the Coast of Alaska of the Bering Sea. The fluctuations of the amount of fresh water in the Arctic Ocean contributes to that of sea ice; therefore, it is necessary to clarify about their qualitative role on the sea ice condition.


d. Interactions among atmosphere - sea Ice - ocean in coastal polyn'ya
    Along the coast of Chukchi Sea, even in winter, coastal polyn'ya in which the sea surface is exposed appears. The area where the coastal polyn'ya appears is a region where interactions between the atmosphere and the ocean are most significant. At the same time, sea ice is formed most prosperous and interactions between the sea ice and the ocean become most active. The appearance of the coastal polyn'ya during the winter season is related to geographical features of the coast. It is very important to investigate the interactions among the atmosphere - sea ice - ocean along the coast of the Chukchi Sea.


e. Radiation Balance in the Arctic Ocean
    It is necessary to obtain data in order to clarify radiation balance of the Arctic Ocean where the atmosphere, the sea ice and the ocean exist and the variations of the atmosphere, the sea ice and the ocean in the Arctic Ocean. Particularly during summer in the Arctic Ocean, it is considered that stratiformis frequently appear so that multiple scattering occurs between the clouds and the sea ice surface to function as albedo feedback. Radiation balance in the system connecting the atmosphere - the sea ice - the ocean should be surveyed under various conditions to evaluate through quantitative analysis. In order to do so, observation covering a large area is necessary; therefore, the survey by R/V Mirai with a Doppler radar is essential.

    The albedo on the sea ice or the snow surface is a very important parameter to decide the radiation balance by the system connecting the atmosphere - the sea ice - the ocean; therefore, it is essential to observe these albedo in a large area. At the same time, drilling of sea ice core is effective for research on transition of the physical process of interaction between the atmosphere and the sea ice.
2.2 Biogeochemical Cycle in the Ocean
2.2.1 Objectives
    Since the Industrial Revolution, concentration of carbon dioxide in the atmosphere has been increasing, so that there has been a growing concern about global warming. To predict a rise in global temperature, which in turn causes a rise in the sea level and changes in the ecological system, adequate understandingof the processes involved in the global cycle of human-origin carbon dioxide is mandatory. For this, it is necessary to understand the carbon cycle in the sea which covers 70% of the earth surface and contains carbon about 60 times as much carbon as in the atmospheric CO2. At present, many countries are conducting research on material cycle processes in various seas. At the same time, various biogeochemical models are being constructed to simulate the distribution of in the sea of various elements and the ocean's capacity for absorbing CO2. There is a view that the north-western part of the North Pacific Ocean and the Antarctic Ocean may be playing dominant roles in controlling material cycles in the global oceans, and even the entire earth's environment. It takes an all-out comprehensive biogeochemical observation and research effort however, to prove this point.

    This Plan will pursue the biogeochemical factors which control the behavior of carbon in not only the high latitude seas but also the world oceans to understand eventually the ocean's role in controlling the global environment. The north-western part of the North Pacific Ocean will be investigated in the first phase of the Plan and the Antarctic Ocean in the second phase to understand the material cycle in the present, the past and the future of these sea areas. Research will be carried out for ten years by R/V Mirai in areas where surveys used to be difficult because of severe weather. For the first five years, temporal (daily and seasonal) and spatial variations in the North Pacific will be surveyed. Changes on a longer time scale will be studied during the latter five years. The study in the Antarctic area could wait until at least first half of the Plan in the North Pacific is completed. The data to be obtained through these surveys will be combined with those obtained by other domestic and foreign surveys to develop an understanding of the material cycle on a global scale.

    The Plan will also pursue biochemical parameters in the equatorial upwelling region that spreads from the eastern Pacific to the central Pacific Ocean, in the warm pool region of the western Pacific Ocean and the area of the Indonesian Throughflow (from the western Pacific Ocean into the Indian Ocean). We expect that these observations will make possible evaluation of the primary productivity of phytoplanktons and the ocean's carbon dioxide fixing capacity as well as understanding of the relation between the fluctuations in biochemical phenomena and those in the climate in the low latitude sea.


2.2.2 Subjects of Researches
(1) Observation and research on material cycle in the high latitude seas
In the high latitude sea area, the temperature of the sea water is low and the weather is often stormy. It is considered that, particularly in winter season, materials including carbon dioxide are actively exchanged between the atmosphere and the sea. Therefore, the high latitude sea area is one of very important areas for carbon cycle in the sea. Moreover, in connection with upwelling of deep water with high nutrients concentration, primary productivity of phytoplankton is high. Since diatoms are a dominant species in the area, carbon dioxide are efficiently fixed in the surface by organisms and transported to the intermediate and deep layers with many other materials. Therefore, systematic biogeochemical researches in the high latitude sea area with a long term basis are necessary. The results will shed a light on the role of the high latitude sea area in global environmental changes. Followings are four main research topics in the project.
(a) Material exchange process between the atmosphere and the ocean
The exchange process of green house gases between the atmosphere and the ocean will be studied. It is also necessary to estimate how much terrestrial materials are being transported to the surface layer of the ocean via the atmosphere or by floating ice. Input of terrestrial material to the surface water may stimulate the biological activity in the area.
(b) Relation between activities of organisms and material cycle
Since the deep water containing rich nutrients upwells in this area, primary production is high. Moreover, it is considered that carbon dioxide are efficiently fixed in the surface by organisms (mainly diatoms) and are transported to the intermediate and deep layers with many other materials. Particularly in spring, as a bloom occurs, activities of organisms affecting material removal reaches maximum. On the basis of these phenomena, it is necessary to evaluate the impact of biological activities on material cycle.
(c) Vertical and horizontal transport of materials
It is important to clarify the vertical and horizontal transport of dissolved materials and particulate matters in the northern part of the North Pacific. In this sea area, many sediment trap experiments have been conducted, but most of their deployment were on a short-term basis with limited geographical coverage. Sediment trap systems will be deployed during a period of the project in the area. In addition, radioisotopes will be used to trace the migration of dissolved and particulate matters, and their transformation processes.
(d) Paleoceanographic study of bottom sediment
Bottom sediment preserves a record of the past ocean such as temperature and productivity and current. There have been few paleoceanographic researches in the north western part of the North Pacific. It is necessary to promote researches on material sedimentation process on a geological time scale in the area. The results obtained will be used to test biogeochemical models developed based on the researches mentioned above.


(2) Observational Studies on Primary Productivity in the Equatorial Pacific Ocean
(a) Observation and research on primary productivity
Mechanisms of high concentration of nutrients - low concentration of phytoplankton in the equatorial upwelling area, deep ehlorophyll maximum layer in a warm pool and productivity of phytoplankton in the Indian Ocean due to Indonesian Throughflow will be studied. For this purpose, analysis of sea water collected with the clean sampling method, measurement of primary productivity by the in-situ incubation and continuous primary productivity observation by the ocean lider system on the research ship, R/V Mirai , will be conducted. Furthermore, on the basis of data of phytoplankton in a wide area obtained by a sea color sensor on satellite, temporal fluctuation of standing crop will be obtained. It is necessary to combine them with the observation data of primary productivity obtained by R/V Mirai to evaluate the primary productivity of a wide area.
(b) Observation of balance of carbon dioxide
In the equatorial upwelling region, the partial pressure of carbon dioxide in the sea water is much higher than that of the atmosphere because carbon dioxide is supplied from the deep sea. A part of the carbon dioxide is used for carbon assimilation by phytoplankton, but most of it is a emission source in the equatorial upwelling into the atmosphere. On the other hand, a partial pressure in a warm pool is equivalent to that of the atmosphere so that a equilibrium is kept. The balance of carbon dioxide between the atmosphere and the ocean in the equatorial upwelling region will be constantly observed by continuous analyzer of △ p (CO2) on R/V Mirai in order to estimate the exchange of ca rbon dioxide along the equator in time and space.
(c) Other observations on biochemical parameters
Judging from the observation and research so far, observations of other biochemical parameters affecting the primary productivity of phytoplankton are regarded to be important. It is known that in the open oceans, the productivity of phytoplankton is inhibited because of lack of iron ion. It is known that trace metals ion are also influential to production of phytoplankton. For the analysis of these phenomena, contamination of metals must be avoided from water sampling to analysis; therefore, highly advanced analysis technology is required.

As for nutrients, improvement of the accuracy of measurement, from the conventional micro-mol order to nano-mol order, is required. Particularly in oligotrophic area like in the warm pool, it is impossible to judge with the conventional detection limit of 0.2 micro-mol whether a production is new production utilizing a trace amount of nitrate or recycled production using ammonia discharged from zooplankton; therefore, it is necessary to develop highly precise and reliable analysis technology.

Furthermore, there are still many parameters which have not been observed by a sediment trap, for example, amount of increase of phytoplankton with equatorial upwelling and its sedimentation and those at deep chlorophyll maximum layer in the warm pool. These are biochemical parameters which are most significantly affected by climate fluctuations; consequently, observation and research on these parameters are very important.
2.3 Marine Ecosystem
2.3.1 Objectives
    It has been many years since the global environment became a serious world issue. Humanity is still groping for responsible measures to address the issue. Some proposals advanced to date appear to put so much load on one part of the ecosystem that the balance in marine ecosystem might be lost. To become able to correctly predict change in the global environment, the development of a clear understanding of the dynamics of fluctuations in the ecosystems in the vast oceans is essential. And we believe it is microplanktons that holds the key to the question. In the past, plankton communities have been a subject of study in practically all oceanographic research projects. Few studies have focused, however, on the characteristics of plankton communities that show large-scale fluctuations at short intervals. Two main reasons therefor: (1) Under stormy weather, difficulty to catch dynamic changes that may be taking place underwater, and (2) Conventional research vessels have not been equipped for speedy on-board analysis of test samples before their health condition is lost altogether. R/V Mirai will be used to carry out complex research programs on ecosystems that include plankton communities in the ocean. The ship is also expected to be used for continuous measurement of biomass and health condition of the ecosystems centering on planktons in subarctic seas, subtropical seas, and in the equatorial upwelling area.
    The relationships between different communities also need to be understood quantitatively Physical and chemical analyses should be carried out according to the plankton scale. It is our aim that the results of all these studies will converge into the understanding of the ecosystems structure in each sea area.
    In addition to the ecosystems in the surface layers of the ocean, we consider it important to pursue deep-sea ecosystems such as those dependent on chemosynthesis found in places on the ocean floor including their ecology and evolutionary processes.

2.3.2 Subjects of Observational Studies
(1) Observational Studies on the Plankton Community
It is desirable to carry out drift observations about once a month in each season in the Bering Sea, a typical subarctic sea area, in the North Pacific polar front sea area, which has the worlds highest productivity, in the south-western part of the North Pacific Ocean which is a typical subtropical sea area and in the equatorial upwelling zone with has high productivity in spite of it being in a subtropical sea area. As for the Bering Sea and the North Pacific polar front sea area, the emphasis of the research should be laid on those spring months when big changes can be expected and on those winter months when virtually no research has been done to date.
(a) Detailed research on the standing crop and biological activities of each b iotic community (bacteria, zooplankton and phytoplankton in pico and nano scales, macro phytoplankton, micro-zooplankton and macro-zooplankton)
(b) To obtain data on fluctuations of dissolved materials related to discharge and absorption from and to plankton
(c) Measurements of standing crop and settling rates of particulate organisms
(d) To obtain data on minute fluctuations in physical quantities

(2) Observational Studies on the Ecosystems of Deep-sea Organisms
Regarding biotic communities based on chemosynthetic activity such as the biotic community of cold upwelling belts and those of hydrothermal vents in deep sea areas, communities consisting of extremely similar species are often found in other places which are geographically disconnected. Therefore, it is very important to study the formation process of biotic communities that consist of the same or similar species to those of other communities which lie several thousand kilometers away.

Regarding the origin of ordinary deep-sea organisms (biotic communities not based on chemosynthesis), there are two theories: (1) moved from high latitude sea areas to the deep sea area and (2) the deep sea area is a rich zone for the formation of species. It is necessary to prove which theory is correct.

(a) Biotic communities based on chemosynthetic activity
The distribution of biotic communities based on chemosynthetic activity in the ocean is shown in Figure 2.3-1 which has been synthesized from data compiled by various countries including Japan. Regarding communities that contain the bivalve, Calyptogena, which is typical of biotic communities based on chemosynthetic activity, its distribution is shown in Figure 2.3-2. It is prevalent in the eastern and western parts of the Pacific Ocean but cannot be found in chemosynthetic communities in the south western part of the Pacific Ocean. Since Calyptogena is an autotroph having symbiotic bacteria, it is thought to occur mainly in chemosynthetic communities. Although the existence of communities which would connect the east Pacific Ocean with the west Pacific Ocean is supposed, only the communities on the plate subduction process areas of the Kurile Trench and Aleutian Trench have been investigated, as shown in Figure 2.3-3. Other sites in this area have not yet become a target for research into chemosynthetic communities. Likewise, animals which have similar distributional features the Calyptogena are the bivalve, Thyasiridae and the hirsyte species, Nautilinielidae. Therefore, the area including the Kurile Trench and Aleutian Trench in the north western part of the Pacific Ocean is very important (Figure 2.3-4).

(b) Biotic communities not based on chemosynthetic activity (Deep sea biotic c ommunity)
The theory that states the origin of deep sea biota is that they moved from high latitude areas to the deep sea is based on the similar water temperatures of these places making such movement possible. In fact, it has been found that for the biota in the bathyal area of Sagami Bay, for example, the crustacea or paralo mismultispina, fishes, echinodermata and mollusca include many species common to those in high latitude areas. The other theory that states that the deep sea itself is a rich zone for the generation of species is based on the fact that diversification of benthic species reaches a maximum at 2000 to 3000 m in depth and that this is higher than that in shallow water areas. In order to investigate either theory, however, it is very important for research by R/V Mirai to be carried out in both high latitude and deep sea areas.
2.4 Ocean Crust Dynamics
2.4.1 Objectives
    The breakup of the Gondwanaland and the consequent redistribution of ocean and land induced environmental changes throughout the earth since Cretaceous, such as initiation of western boundary current, Antarctic circum polar current and other currents, changes in their paths by age and following environmental changes such as their interactions between the atmosphere and the wind system. These changes occurring on the earth's surface together with the global and regional crustal deformation occurring on the sea floor at present are derived from mass transportation and convection in the earth's interior. The objective of the study is quantitative estimation of the phenomena occurring on and inside the earth through investigation of the global-scale activities of the earth's interior and clarifying the dynamics of the oceanic plates causing such activities. The most important in order to accomplish the objective is to collect all kinds of data from the whole earth with equal weight, from the earth's core up to the surface layer.

    Fluctuations of the solid earth are influencing the global environmental change by discharging heat and material from the earth's interior into the hydrosphere and the atmosphere. To clarify these phenomena, it is essential to construct a model of the earth's interior fluctuation based on overall observation data. At the same time, accretion, evolution and subduction of oceanic plates should be comprehensively studied through numerical experiments together with the above-mentioned observation study. Furthermore, it is necessary to specify the driving force and the energy source of the motion of oceanic plates.

    The theory of plate tectonics which has been established as a paradigm of the earth science proved to be applicable to many of the geological phenomena on the earth's surface. However, recent geophysical and geological surveys revealed many phenomena which can not be explained by the plate tectonics only. In a wide sea area from the central part of the South Pacific Ocean to the active marginal basins in the Southwestern Pacific Ocean, a number of phenomena which look like regional deformation due to the upwelling of gigantic plume have been observed so far. So, in the next step, we should re-evaluate on the basis of the "Plume Tectonics" a series of geological phenomena including the breakup of pangaea, formation of new seas, spreading at ridges, subduction processes at trenches, formation of seamounts and others.These studies are necessary not only for understanding fluctuation mechanisms of the earth's interior but also for establishment of theory of seismic activities and volcanic activities which can be eventually applied for disaster prevention. These studies are also necessary as pre site survey for deep-sea drilling cruise (ODP, OD21) in the near future.


2.4.2 Subjects of research
(1) Observational Studies on the Ocean Crust Dynamics of the Sea Floor
Systematic data acquisition for modelling of the fluctuation of the earth's interior should be taken into account in the first step, mainly at the plate boundaries (mid-oceanic ridge, trench, transform fault), plume-origin seamounts and oceanic plateaus, which are most active on the sea floor which are easier to observe the earth's interior due to the thinner crust.

In order to evaluate the fluctuations of the solid earth interior correctly, numerical simulation of a short-period fluctuation of the earth and the quantitative estimation of the heat and mass balance of the earth' s surface are to be carried out at first. In addition to these studies, the clarification of dynamics of the whole solid earth down to the core should be conducted, And the present situations of the earth in the long-period fluctuations led by the dynamics should be understood. Taking these objects into consideration, it is necessary to study first the sub-bottom structure and circulation of heat and materials and the dynamics of the earth's interior step by step. As an issue for the time being, from the viewpoints of accretion, evolution and subduction of the oceanic plates, it is to be planned to investigate a detailed structure of crust/upper mantle, crustal deformation and distribution of stress, discharged amount of heat and materials as well as material compositions and physical properties in the mid-oceanic ridge system, hot spot zones and subduction zones.

As for the Antarctic sea area, it is said that there was once Gondwanaland, the Antarctic plate was formed due to the breakup of the Gondowanaland and is mostly surrounded by the mid-oceanic ridges and continuously expanding even now. Although the data from this area are essential to study on the above-mentioned phenomena, systematic marine observation in this area are greatly behind compared with other sea areas, and so this area remains blank for data to solve the problems and evaluate quantitatively due to restrictions of sea conditions. Therefore, the study on the history of formation and development of Antarctic sea and their driving force should be included as one of objectives in the long-term science plan. After observation data of the northern hemisphere are accumulated, intensive observation and research of the Antarctic sea should be carried out. Then, on the basis of these results, phenomena in time and space of the whole earth system should be evaluated quantitatively to reproduce them completely by numerical simulation.

Methodology:
3. Other Issues to be Promoted
3.1 Validation and Satellite Data Sets
    Ocean research vessel is highly reliable in surveys of elemental processes and in high precision observation, but satellite data sets are essential for observation of vast areas over a long period. On the other hand, to make use of satellite data for research of global climate change, they must be verified and checked sufficiently. From these aspects, the observation onR/V Miraii and that by satellites mutually play complementary roles. It is expected that using data sets from both will accomplish highly efficient research results.
    Missions of the earth observation satellites include various subjects such as those for the ocean, the atmosphere and the land. The missions except for the land are closely related to the researches mentioned so far. TRMM, ADEOS 2 and ALOS are the earth observation satellites which are planned to be launched within five-year. From these satellites, the following physical parameters related to the ocean research will be obtained.

      SatelliteLaunching Year Physical Parameters
      TRMM 1997 precipitation
      ADEOS2 2000 sea surface temperature, amount of chlorophyll, sea surface winds, aerosol, air temperature, water vapor, APAR, and distribution of sea ice
      ALOS 2002 Internal waves

    For verification of these physical parameters, intercomparison with in situ data is necessary. In the vast sea area on the earth, for whichR/V Mirai is an extremely useful platform. Moreover,R/V Mirai has been mounted with many and various observational equipments, most of which are appropriate for verification of data from satellites. Therefore, to useR/V Mirai for such verification and checking for the earth observation satellites will be extremly useful.

3.2 Data Sets to be Obtained Routinely onR/V Mirai
    The following basic data should be routinely obtained to verify and check the data from the above satellites as well as to obtain the data sets which have been prevented from gathering in the stormy seas.

      Meteorological data
      Continuous data of sea water by intake method
      (sea surface temperature and salinity)
      ADCP current data


    Measurements of partial pressure of carbon dioxide in the ocean and the atmosphere shall be routinely obtained in a few key areas.

3.3 Utilization of Ocean Observing Technologies
    OnR/V Mirai , advanced observation technologies should be applied in order to contribute to raise the level of the observation technologies of the world. Particularly, ocean acoustic tomography, Doppler radar, ocean LIDAR and others are expected to be used. It is also necessary to take all measures to keep up the most advanced and highest level of equipment on boardR/V Mirai in the future as well.