Journal of Oceanography, Vol. 55, pp. 645 to 653. 1999
Overview of NOPACCS (Northwest Pacific Carbon
Cycle Study)
HIROYUKI T SUBOTA1,2,3, JOJI ISHIZAKA 4,5, A KIRA NISHIMURA 6 and YUTAKA W. WATANABE4
1
Hiroshima University
Institute of Environmental Sciences, Shin-Nippon Meteorological and Oceanographical
Consultant Co., Ltd., 1334-5 Riemon, Ooigawa-cho, Shida-gun, Shizuoka 421-0212, Japan
3
Kansai Environmental Engineering Center, Co., Ltd.,
1-3-5 Azuchi-cho, Chuou-ku, Osaka 541-0052, Japan
4
National Institute for Resources and Environment,
16-3 Onogawa, Tsukuba, Ibaraki 305-8569, Japan
5
Faculty of Fisheries, Nagasaki University, 1-14 Bunkyo, Nagasaki, Nagasaki 852-8521, Japan
6
Geological Survey of Japan, Tsukuba, Ibaraki 305-8567, Japan
2
(Received 13 August 1999; in revised form 30 September 1999; accepted 7 October 1999)
The Northwest Pacific Carbon Cycle Study (NOPACCS) was a program aimed at
investigating the carbon cycle of the North Pacific Ocean, which can be thought of as
a large reservoir of carbon dioxide. NOPACCS was also aimed at estimating the North
Pacific’s capacity as a carbon sink. Project design, scientific results, and data availability, and subsequent projects resulting from this project are also described in this
review. Studies of the upper ocean processes focused on the latitudinal differences in
the fugacity of carbon dioxide; and on the detail of plankton community structures.
Intermediate water was studied in relation to the formation of North Pacific Intermediate Water and the amount of accumulated anthropogenic carbon. The sedimentation process, past carbon cycle and coral reefs were also studied during the project. A
preliminary, overall view of the carbon cycle of the North Pacific was drawn from the
results of the project and compared to global values.
total carbon in the ocean is more than 50 times more than
it is in the atmosphere. Two major carbon flows are known
in the oceans: one is through formation of intermediate
and deep water by physical circulation (solubility pump);
and the second is conversion of inorganic carbon to organic carbon by photosynthesis and then transport to intermediate and deep waters and to the sediment (biological pump). In order to understand the carbon cycle in the
ocean, elucidation of both carbon flows is important.
The Northwest Pacific Carbon Cycle Study
(NOPACCS) was a Japanese national project designed to
deepen our understanding of the carbon cycle in the ocean.
In this paper, a brief overview of the project is given. The
project design is described in the next section. A brief
summary for the results for the following three main topics is described in subsequent sections: 1) upper ocean
processes and biological carbon cycle, 2) intermediate
water and anthropogenic carbon, 3) sedimentation, past
carbon cycle and coral reefs. In Section 6, a preliminary
and generalized view of the carbon cycle of the North
Pacific is given. Lastly, subsequent projects are introduced
in Section 7.
1. Introduction
Quantification of the carbon cycle has been discussed
internationally since the increase of anthropogenic carbon dioxide was recognized as an important factor in global climate change. Specifically, it is known as one of the
most abundant global warming gases. Global annual emissions of carbon dioxide from fossil fuel combustion and
deforestation are estimated to be 5.5 and 1.6 PgC yr–1,
respectively (Houghton et al., 1995), while accumulation
in the atmosphere is only 3.4 PgC yr–1 according to direct measurements of atmospheric carbon dioxide
(Keeling et al., 1989).
About 2 Pg of carbon is speculated to have been absorbed by the ocean, however the fate of about half that
carbon still remains uncertain, such that it has been called
a “missing sink” (Houghton et al., 1990). Over many
years, there has been discussion about whether the oceans
or terrestrial forests absorb more carbon than previously
thought and/or whether soil in the Northern hemisphere
accumulates organic carbon accumulates more than previously speculated (Tans et al., 1990). Whichever the case
is, the ocean is one of the largest carbon reservoirs, and
645
Copyright © The Oceanographic Society of Japan.
Keywords:
⋅ North Pacific,
⋅ carbon cycle,
⋅ biological pump,
⋅ intermediate water,
⋅ anthropogenic
carbon.
2. Project Design
The New Energy and Industrial Technology Development Organization (NEDO) launched the Industrial
Technology Research and Development Project on Global Environment in the fiscal year 1990, with financial
support and aid under the auspices of the Ministry of International Trade and Industry (MITI). As a part of this
project, the Northwest Pacific Carbon Cycle Study
(NOPACCS) was first planned by the Agency of Industrial Science and Technology (AIST) and commenced in
1990 for a period of seven years. Survey and research
activities were assigned by NEDO to the Kansai Environmental Engineering Center, Co., Ltd. (KEEC) to be
conducted in collaboration with the cooperation of two
institutions of AIST: National Institute for Resources and
Environment (NIRE) and Geological Survey of Japan
(GSJ), and with scientists from universities.
For the quantitative evaluation of the carbon cycle
in the ocean, a field survey was carried out to clarify
physical circulation, biogeochemical processes and accumulation of carbon on the seafloor. Meteorological,
oceanographical and biogeochemical information was
collected from the western North Pacific, mainly from
48°N to 15°S along 175°E, whilst onboard the R/V
Hakurei-Maru (1800 tons) which belongs to the Metal
Mining Agency of Japan. These survey areas were selected on the basis that they are far from continents and
include different climatic and oceanic zones.
The oceanic surveys and research were planned,
guided and controlled by the Executive Committee
(chaired by H. Tsubota) and the following working groups:
Soluble Materials Working Group (Leader: K. Harada),
Settling Particles Working Group (Leader: H. Kawahata),
Sediments Working Group (Leader: A. Nishimura), Biology Working Group (Leader: J. Ishizaka) and Modelling
Working Group (Leader: K. Nakata). Quality check of
the final data was carried out by Data Quality Control
Working Group (Leader: H. Tsubota).
3.
Upper Ocean Processes and Biological Carbon Cycle
Upper ocean processes are important because this is
the region where atmospheric CO2 dissolves into seawater
and where CO 2 in the seawater is released to the atmosphere. The partial pressures of carbon dioxide in the atmosphere and sea surface water were continuously measured along the survey tracks of each research cruise of
the project. A description of the latitudinal distribution
of the fugacity of carbon dioxide ( fCO 2 ) in the atmosphere and in the surface waters, along 175°E, from 1992
through 1996, is given in detail by Watai et al. (1999).
One of the important carbon flows from the upper
water to the deep water is the biological pump. The upper layer is important in the biological carbon cycle be646
H. Tsubota et al.
cause it is where primary production and most of biological activities occur. Studies of biological processes
in NOPACCS concentrated mostly on the description of
the structure of the plankton ecosystem and its function
in the carbon cycle along 175°E. Firstly, phytoplankton
communities were studied in detail along the lines of sizefractionation of chlorophyll- a, epifluorescence
microscopy and HPLC pigment analysis (Ishizaka, 1994;
Ishizaka et al., 1994; Suzuki et al., 1995, 1997). The study
indicated that concentrations of chlorophyll a at the surface were mostly very low at the southern end of the
Kuroshio front (40°N) and higher at the northern end with
a peak between 42–46°N during summer; and that the high
chlorophyll a region shifted to the south (to about 30°N)
during spring. The size-fraction of chlorophyll a showed
that the phytoplankton community consisted mostly of
small plankton except at the northern peak.
Epifluorescence microscopy and HPLC analyses indicated
that Prochlorococcus largely dominated the subtropical
area and microflagellates dominated the north. Those
analyses and absorption spectra studies clearly showed
latitudinal and vertical differences in the phytoplankton
community (Harimoto et al., 1999).
Another major endeavor of the biological study of
NOPACCS was the integration of the whole plankton
community size and taxonomic structure. Since most previous studies on plankton communities are limited to small
groups and small size ranges, several different methods
were used to identify the plankton community including
bacteria, phytoplankton and zooplankton in the size range
of 0.2 to 2000 µm diameter. A brief description of the
methods and an example of the analysis for the equatorial region were published by Kiyosawa et al. (1995) and
Ishizaka et al. (1997), respectively. Ishizaka et al. (1997)
showed that the plankton-carbon biomass at the equator,
175°E, was about 2000–3500 mgCm–2 in five visits in
September 1990–1993 and April 1994. The percentages
of the taxonomic groups in the biomass were 31–54, 15–
26, and 29–54% for phytoplankton, zooplankton and bacteria respectively, such that the hetetotrophic biomass was
more abundant. Bacteria and Prochlorococcus were most
abundant in the picoplankton size range, flagellates were
abundant in the nanoplankton and copepods were abundant in the mesoplankton. They also estimated the carbon biomass flow through the biological community using that data set.
Furthermore, an extension to the studies on community structure focused on the non-dominant, large diatoms
in the North Pacific (Takahashi, M. et al., 1999). Another
study conducted by Goes et al. (1999) derived relationships between temperature, chlorophyll a and nitrate from
the NOPACCS data, and used those relationships to estimate nitrate distribution in the North Pacific; and estimated new production using satellite ocean color and temperature data.
4.
Intermediate Water in the North Pacific and Uptake of Anthropogenic Carbon
When considering the balance of anthropogenic carbon, it is necessary to clarify how much atmospheric anthropogenic carbon the ocean absorbs and where it is accumulated in the ocean at present. High latitudinal areas
producing intermediate and deep water masses would
enhance oceanic absorption of atmospheric CO2 through
the following mechanisms: active gas exchange due to a
rough sea surface; high solubility due to low temperatures in winter; and high biological productivity. These
regions, therefore, would play an important role in the
absorption of anthropogenic CO2 released by human activities in the industrial era. In the North Pacific, intermediate water, called North Pacific Intermediate Water
(NPIW), is produced in the subpolar region (Reid, 1965;
Watanabe et al., 1994, 1995; Nishina and Fukasawa,
1999). The North Pacific subpolar region, therefore, may
play an important role in the absorption of excess CO2 in
the North Pacific (Tsunogai et al., 1993; Watanabe et al.,
1996).
Although recently developed models have been used
to estimate the formation of NPIW and uptake of anthropogenic CO2, the spatial distribution of anthropogenic
carbon, such as its inventory and uptake rate, is significantly different between the models. Thus, it is difficult
to know whether the results are reliable or not
(Siegenthaler and Sarmiento, 1993). Therefore, the
NOPACCS group tried to estimate the behavior of anthropogenic carbon, such as its spatial distribution, inventory and uptake, using comparisons between observational data and model calculations.
In the observational data-based approach, the
NOPACCS group measured fCO 2 , DIC, pH, alkalinity,
nutrients, dissolved oxygen and CFCs, mainly along
175°E twice a year during the period of 1990 to 1996.
The NOPACCS group estimated the spatial distribution
of anthropogenic carbon using mainly the back calculation method of Chen (1982) and by comparison of the
NOPACCS and 1973–1974 GEOSECS data set (Watanabe
et al., 1996, 1997). This estimate, however, has a significant problem in its assumptions. Chen (1982)’s approach
has not been appropriate generally and the uncertainties
associated with their estimates are regarded as being too
large. Some of the problems include: mixing of different
waters with unknown initial concentrations; the difficulty
of choosing an appropriate concentration of preindustrial
oceanic CO2 ; large uncertainties in the assumptions relating to the constant stochiometric ratio P:N:C:O; and
the use of AOU for determining the contribution of the
remineralization of organic matter (Shiller, 1981, 1982).
Therefore, the NOPACCS group used new observational data-based approaches such as the direct DIC comparison method (Wallace and Johnson, 1994; Slansky et
al., 1997; Ono et al., 1998, 1999) and C-13 method (Quay
et al., 1992) during any decadal intervals (Takahashi, Y.
et al., 1999; Ono et al., 1999). Unfortunately, at present,
because there are no sufficient oceanic carbonate species
data sets available, those approaches can not be used to
give detailed spatial distribution of anthropogenic carbon, although they may give a rough estimate.
Despite the lack of carbon data, many CFC data exist for the North Pacific region (Watanabe et al., 1994,
1997). Using CFC data without P:N:C:O, therefore,
Watanabe et al. (1999) obtained some information such
as the change over time in the spatial distribution of the
anthropogenic carbon accumulation rate, and the change
over time of the anthropogenic carbon uptake rate by integrating the spatial distribution of the anthropogenic
carbon accumulation rate. They also compared those results with those from the direct DIC comparison method
(Ono et al., 1998, 1999), and found a good agreement
between their method and the direct DIC comparison
method. The anthropogenic carbon uptake rate for the
whole North Pacific was estimated to be 0.50 ± 0.09 PgC
yr–1 between 1988–1998, suggesting that the North Pacific region is significantly important for the oceanic uptake of anthropogenic carbon.
In addition, the NOPACCS modeling group tried to
clarify the behavior of anthropogenic carbon using a 2 ×
2 degree general circulation model (GCM) with some
schemes using NOPACCS and climatological data
(Levitus, 1982). Ishida et al. (1995) and Ishida et al.
(1999) found that the GCM using the isopycnal diffusion
scheme was the best way to reconstruct the distribution
of NPIW.
They applied their model to the North Pacific to estimate the spatial distribution of anthropogenic carbon in
the North Pacific. The uptake rate of anthropogenic carbon in the North Pacific was 0.4 PgC yr–1, which almost
agrees with the observational data-based estimate
(Watanabe et al., 1999). However, the spatial distribution of anthropogenic carbon between the observational
data and their model is still significantly different. Especially, at the western and southern boundaries, the
NOPACCS group found significant differences in the inventories and penetration depths of CFCs and anthropogenic carbon. In future, it will be necessary to develop a
GCM model and use a sufficiently available data set like
WOCE or JGOFS to reconstruct a fine and precise spatial distribution of anthropogenic carbon.
5. Sedimentation, Past Carbon Cycle and Coral Reefs
During NOPACCS, sediments were researched intensively to better understand the carbon cycle in the
ocean. We collected and analyzed surface sediments from
a large number of sites, reaching 150, in the western Pacific Ocean. In the latter stage of NOPACCS, the carbon
Overview of NOPACCS
647
budget of coral reefs was studied, mainly based on the
partial pressures of CO 2 in surface seawater both inside
and outside of reefs, to evaluate their contribution to role
in the carbon cycle.
Basic data on sediment features, such as sediment
type, composition, texture, water content, sedimentation
rates, magnetic susceptibility, and color characteristics,
were determined regionally for the western Pacific Ocean.
Systematic sampling of surface sediments in the western
Pacific Ocean showed general distribution patterns of
specified compositions, such as lipids with a terrestrial
origin (Ohkouchi et al., 1997), the strontium isotopic
composition of the non-carbonate components of
sediments (Asahara et al., 1999), and magnetic particles
(Yamazaki and Ioka, 1997). These fundamental data will
largely contribute to our understanding of the present
transportation of particulate material and to reconstructing the paleo-environment based on core sequences. Primary production of the past several hundred thousand
years was reconstructed based mainly on carbon contents
of the sediments, and it was shown that it reflects past
and present oceanographic conditions. The values of, and
variation in those data are large in the marginal seas and
high latitude areas, and small in the equatorial area and
subtropical gyre. Glacial and interglacial periods contrast
greatly in the former areas but much less so in the latter
areas (Kawahata et al., 1996). The difference in primary
production between glacial and interglacial times has been
discussed in relation to the contribution of oceans to the
carbon cycle. Atmospheric CO 2 concentration in glacial
times, which is ca. 80 ppmv lower than those in interglacial times, is thought to have been caused mainly by activation of productivity in the oceans. Reconstruction of
primary production in the western Pacific Ocean supports
this hypothesis, but in specific areas, it is revealed that
shifts in high productivity zones have repeated between
glacial and interglacial times. The synchronous latitudinal migration of the transitional zones between subtropical and subarctic waters of the Northern and Southern
Hemisphere was determined based on primary productivity proxies, and carbon and opal fluxes in the core sequences (Kawahata et al., 1999). Particulated materials
formed in the surface water sink in the water column
through decomposition and dissolution until they finally
reach the sea bottom. This process is called the biological pump. The sedimentation process, especially at the
sea bottom, is important in changing sinking particles into
sediment particles. Sedimentation was researched using
sediment traps. Planktonic foraminifers, one of the most
important microfossils in sediments of the open ocean
environment, were analysed from the sediment trap samples and it was clearly shown that the total number of
planktonic foraminifers reflect seasonal and regional
oceanographic conditions (Eguchi et al., 1999). This sim-
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H. Tsubota et al.
plified proxy using planktonic foraminifers will be used
as a tool of oceanographic reconstruction.
Vertical transportation of Cadmium was determined
by analysis of the sediment trap samples (Noriki et al.,
1999). It is very important to know the processes and factors controlling cadmium content in the water column,
because cadmium contents in the foraminiferal tests have
been used as the most important proxy of nutrient contents of ambient seawater. Coral reefs are the highest productivity areas of the open ocean and are often called oases
of the Ocean. To evaluate the contribution of coral reefs
to the carbon cycle, we must determine the ration of production of calcium carbonate to organic carbon. During
NOPAACS, the R/V Hakurei-Maru visited Palau Barrier
Reef, Majuro Atoll, and the Great Barrier Reef. The fCO 2
were measured in surface seawater both in and around
the coral reefs. All coral reefs had higher fCO 2 inside the
reefs than outside of them, which suggests that oceanic
coral reefs have the potential to release CO 2 into the atmosphere. The surface water fCO 2 of the lagoons depended on the water circulation pattern and speed in the
reef system but generally they all had the potential to release CO2 (Suzuki and Kawahata, 1999).
With the exception of the research mentioned in the
above, other important data on the geology, paleontology,
and geophysics were also collected. Those data gave information on the precise correlation between magnetic
susceptibility and the sediment sequences for local areas
(Ioka and Yamazaki, 1992), and it was possible to establish the intensity of the magnetic field in the late Quaternary (Yamazaki et al., 1995).
During the NOPACCS study, almost all sediment
samples were taken from the open marine ocean environment, and were used to reconstruct long-term environmental change, although with poor resolution. Therefore,
a high resolution environmental study analyzing sediment
core samples with high sedimentation rates, and a study
on sedimentary processes are required to establish a proxy
of primary production.
6. Carbon Cycle of the North Pacific
The North Pacific is one of the largest oceans on the
globe, encompassing more than 20% of the area and volume of the global oceans. Thus, the North Pacific is one
of the important oceans in the global carbon cycle. Using
the data and knowledge collected through NOPACCS, we
attempt here to describe the carbon cycle in the North
Pacific.
In order to describe the carbon cycle, the area and
reservoir of the carbon should be defined. Thus, we excluded the marginal seas and defined the equator as the
southern boundary. Three layers were separated vertically;
surface (0–200 m), intermediate (200–1000 m) and deep
Fig. 1. Carbon cycle in the North Pacific. Unit is PgC (1015 gC, 1 billion ton), and values in brackets are increasing rates of
anthropogenic carbon. #1: CO 2 amount in the global atmosphere in 1993. #2: Average increasing rate of CO2 in the global
atmosphere during 1990–1995. #3a: Accumulation rate of anthropogenic carbon in the North Pacific in 1993 estimated by a
numerical model (Ishida et al., 1999). #3b: Accumulation rate of anthropogenic carbon in the North Pacific in 1993 estimated
by observations of dissolved inorganic carbon and CFCs (Watanabe et al., 1996). #4: Accumulation rate of anthropogenic
carbon in the deep layer of North Pacific on 1993 estimated by observations of CFCs and DIC (Watanabe et al., 1996).
#5: Amount of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in the North Pacific. #6: Biomass of
surface plankton community in the North Pacific. #7: Sinking particle flux and sedimentation rate in the North Pacific.
(1000 m–bottom). The reservoirs of carbon are dissolved
inorganic carbon (DIC), dissolved organic carbon (DOC),
and surface plankton biomass. Some of the fluxes between
those reservoirs, air-sea interaction, and sinking to the
bottom were also estimated. Anthropogenic emissions of
carbon were also considered.
Average data of DIC and DOC for 24 NOPACCS stations were integrated over the North Pacific Ocean for
the surface, intermediate, and deep layers. Only the surface DIC data were integrated separately for the north
and south of 40°N because the values were significantly
different. Surface plankton biomass was calculated from
the data collected with 17 data during 1990–1994 from
four stations of NOPACCS cruises and from data collected
in the English Channel and Bermuda as reported by
Holligan et al. (1984) and Caron et al. (1995), respectively. Carbon biomass of bacteria, phytoplankton, and
zooplankton was integrated by regression with surface
chlorophyll concentrations and Coastal Zone Color Scanner (CZCS, Feldman et al., 1989) satellite phytoplankton
pigment data.
Particle sinking fluxes of organic material and CaCO3
were calculated for seven stations of NOPACCS. The
values were averaged for each layer and integrated over
the area. The sedimentation rate was calculated assuming 80% terrigeous and 10% organic materials with the
sedimentation rate of terrigeous material at 0.2 gm–2y–1
(ref.). The accumulation rate of anthropogenic carbon was
estimated by a numerical model and field observations.
The minimum and maximum values were estimated by a
numerical model (Ishida et al., 1999) and by field data
(Watanabe et al., 1996).
Figure 1 shows the resultant carbon cycle in the North
Pacific Ocean. The largest amount of carbon was accumulated as DIC at 7330, 1552, and 355 PgC for the deep,
intermediate, and surface layers, respectively. DOC was
Overview of NOPACCS
649
Table 1. Comparison of area, volume, biomass, sinking particle flux, sedimentation rate, dissolved organic carbon (DOC), dissolved inorganci carbon (DIC), and anthropogenic carbon in the North Pacific and in the global ocean. Values per total surface
area and per unit surface area were shown. Ratios indicated the ratios between the values of the North Pacific and global
ocean.
119, 31, 11 PgC. Biomass of the surface plankton community was 0.08, 0.06, and 0.08 PgC for phytoplankton,
zooplankton, and bacteria, respectively, and only 10–6 of
the DIC and DOC. Particulate organic carbon transported
by the biological pump was 2.3 ± 0.7 PgCy–1, and about
26% dissolved in the intermediate layer while most of
the remainder dissolved in the deep layer. Accumulation
of anthropogenic carbon was estimated at 0.4–0.7
PgCy–1 in the North Pacific Ocean, and it was mostly accumulated in the surface to intermediate waters.
Table 1 shows the comparison of the North Pacific
values with the global ocean. The North Pacific is 21%
of the area and 26% of the volume of the global ocean.
The amount of DOC and DIC it contains is 24% and 23%
of the values of the global ocean, respectively, and those
values indicate that the North Pacific Ocean is close to
the mean of the global value.
When the global value of the surface plankton
biomass was estimated from the same regression relationship, the global surface plankton biomass was estimated
at 1.28 PgC. The comparison of that value with one for
the North Pacific were 17% and 24% with and without
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N. O. Eguchi et al.
marginal seas. This indicates that marginal seas are important for the surface plankton biomass of the North
Pacific Ocean. The global value is smaller than the IPCC
value of 3 PgC, and this may be because of the elimination of the intermediate to deep layer biomass as well as
coastal and larger organisms.
Carbon flux through the biological pump was about
twice as much as the IPCC value and indicates the possibility of high biological pump; however, the values are
the simple integration of the average over a few stations.
Thus it is probably necessary to integrate it with satellite
data. On the other hand, the sedimentation rate to the
bottom was only 2% of the global value. This may be
caused by the dissolution of CaCO 3 due to a shallower
compensation depth and deeper bottom depth in the North
Pacific than in the Atlantic.
Accumulation of anthropogenic carbon, estimated by
a regional numerical model, was similar to the mean value
of 2 PgCy–1 given by the IPCC. However, the estimated
values for CFC and DIC are about 70% larger than the
average value and indicate the possibility of high absorption in the North Pacific Ocean (Ishizaka et al., 1998).
Table 2. Accuracy and precision required in WOCE Hydrographic Program (WHP) for temperature, salinity, pressure, DO,
nutrients and in Scientific Committee on Oceanic Research (SCOR) for pH, alkalinity, total inorganic carbon, partial pressure
of CO2, and the present conditions of NOPACCS.
7. Data Availability
Data collected by NOPACCS is generally available
to the public (Tsubota et al., 1999). The present status of
accuracy and precision of some of NOPACCS data, in
comparison to the requirements of the WOCE
Hydrographic Program (WHP) and of the Scientific Committee on Oceanic Research (SCOR), are given in Table
2. Hydrographic data from 1992–1995 were quality controlled and collated in a CD-ROM which is available from
the Japan Oceanographic Data Center (JODC). Some of
the data is also available from the NOPACCS Homepage
(http://www.aist.go.jp/RIODB/nopaccs/). Other data is
also in preparation for publication, and further information is available from the authors.
8. From NOPACCS to SEA-COSMIC and NPTT
The project, NOPACCS, continued over seven years
and finished in 1996. As described in this and other papers, many new findings and data related to the carbon
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N. O. Eguchi et al.
cycle in the North Pacific have accumulated as a result of
the project. Because the ocean is one of the largest reservoirs of carbon, the possibility of sequestration of CO 2
into the intermediate layer of ocean has been discussed
(Handa and Ohsumi, 1995). Thus, MITI and NEDO have
started a new project, SEA-COSMIC (Study of Environmental Assessment for CO2 Ocean Sequestration for Mitigation of Climate change) commencing in the fiscal year
of 1997 with a plan to continue for five years (http://
www.seacosmic.org). The final goals of the oceanographic
studies of SEA-COSMIC are 1) the development of methods to predict how much CO 2 is sequestrated in the North
Pacific and 2) the development of methods for environmental assessment of CO2 ocean sequestration, which is
different from more basic study, NOPACCS, using more
refined techniques the those used in NOPACCS. However, for those purposes, it is also necessary to understand the natural carbon cycle in the North Pacific so some
of the studies conducted in NOPACCS are being contin-
ued. Joint Global Ocean Flux Study (JGOFS) also recently
formed a North Pacific Task Team (NPTT) and started a
time series observation of the carbon related materials in
the north-western sub-arctic Pacific (KNOT: Kyodo-Cooperation North pacific Ocean Time series) (Bychkow and
Saino, 1998). SEA-COSMIC is collaborating with the
NPTT and KNOT projects.
Acknowledgements
The authors would like to express their thanks to the
captains, officers and crew of Hakurei-Maru for their
excellent onboard work, and to hard working scientists
onboard. This research was supported by the Northwest
Pacific Carbon Cycle Study assigned to the Kansai Environmental Engineering Center Co., Ltd. by the New Energy and Industrial Technology Development Organization.
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Overview of NOPACCS
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