Marine Ecosystems Research Department - jamstec japan agency ...

JAMSTEC 2002 Annual Report
Ocean Observation and Research Department
() Observational study for primary productivity and
biogenic gases
We carried out observation to estimate the relationship
between phytoplankton and the greenhouse effect
in the equatorial Pacific, where climate variations by
El Niño/southern oscillation (ENSO) are dominant.
Field observations were conducted by the R/V Mirai
from December to February along the
equator transect between E and W (MR-
K). The equatorial Pacific was in a condition of El
Niño during the cruise, hence the nitrate-depleted
western Pacific warm pool expanded beyond the dateline
and reached as far as W. Phytoplankton distribution
in surface seawater also shifted to the east,
then we observed the western edge of the chlorophyll
a distribution at W (Fig.). We found spatial
heterogeneity of phytoplankton caused by the transient
influx of nutrients, which fluctuates in response to
ENSO. In summary, it was clarified that ENSO influenced
both primary productivity and air-sea exchange
of CO in the equatorial Pacific.
Fig.17 Chlorophyll a map derived from SeaWiFS data (weekly
composite during 20 Jan. to 26 Jan. 2003) between 160E
and 160W, and between 20N and 20S.
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2. Personal Research
Study on high-resolution measurement of carbonate
chemistry
In this study, we will improve measuring systems to
speed up analyzing CO -system parameters such as
total CO (TCO ), total alkalinity (TAlk), etc. For this
purpose, we attempt to decrease sample volumes necessary
for the measurements, and to automate the
measuring systems.
Sample volume of TAlk measurement was successfully
decreased from ml to ml. In addition, we
automated the TAlk measuring system so that samples
can be measured continuously.
For pH measurement, we developed a spectrophotometric
pH measuring system. With this system, it
became possible to improve the analytical resolution
level and precision of pH measurements compared to
the previous method (potentiometric). In addition, we
automated the system so that samples can be measured
continuously.
Pilot study on the ocean general circulation and
distributions of heat and materials
Seawater transports heat and fresh water and regulates
global climate with the atmosphere. At the same
time, seawater ionizes and mineralizes materials and
transports nutrients, carbonates and so on. These transports
are regulated by wind-driven circulations and
Ekman transports at each basin and overturning circulations
connecting the basins. Purposes of this study
are ) to obtain transport maps in the North Pacific and
the Indian Ocean averaged over a decadal time scale
using the WOCE Hydrographic Program data (WHP
one time surveys occupied during to ), the
World Ocean Database (WOD), historical
hydrographic data around the Southern Ocean, and
wind data by the NCEP reanalysis, ) to make database
combining these data set in order to estimate heat and
material transports, and ) to investigate long-term
changes of the Antarctic overturn system and the distribution
of materials using the database.
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