PMEL Programs and Plans
Accomplishments in FY 98 and Plans for FY 99
Carbon Dioxide Program
Accomplishments in FY 98
The decadal to centenial component of NOAA's Climate and Global Change (C&GC)
Program addresses the need to assess and predict changes in climate on time
scales
of 10 to 100 years. One of the major components of this program concerns the
climatic impact of the anthropogenic production of "greenhouse gases" such as
carbon dioxide (CO2). CO2 is estimated to be responsible for roughly one-half
of
the "greenhouse gas" effect resulting from anthropogenic inputs of trace gases
to
the atmosphere. Because CO2 in the atmosphere absorbs long-wave radiation
emitted
from the earth's surface, the post-industrial increase of CO2 will have the
effect
of producing a higher equilibrium temperature of the troposphere. Credible
prediction of the magnitude of this temperature increase is a high priority
scientific issue. Recent model predictions suggest an increase of global mean
surface temperature of 1.5-4.0°C in the next century for a doubling of
atmospheric
CO2. Future decisions on regulating emissions of "greenhouse gases" should be
based on more accurate models which have been adequately tested against a well
designed system of measurements. Predicting global climate change as a
consequence
of CO2 emissions requires coupled atmosphere/ocean/bioshpere carbon models
that
realistically estimate the rate of growth of CO2 in the atmosphere, as well as
its
removal, redistribution and storage in the oceans and terrestrial biosphere.
The primary objective of NOAA's Ocean Atmosphere Carbon Dioxide Exchange Study
(OACES) is to quantitatively assess the fate of CO2 in the atmosphere and
oceans.
In order to accomplish this goal, the natural sources and sinks of carbon
dioxide
must be determined. During FY 98, the PMEL CO2 group determined the
distribution
of pCO2 in the equatorial Pacific during the 1997-98 ENSO event. Throughout
the
event pCO2 values showed a sharp decrease along the eastern edge of the warm
pool
which moved from west to east along the equator as the event developed. At
the end
of the ENSO event the Eastern Pacific abruptly moved into a strong La Niña
phase
beginning in May. Rapid increases in pCO2 (>600 µatm) were observed in the
eastern
Equatorial Pacific during this period.
Carbon Dioxide Program
Plans for FY 99
During FY 99, the Ocean-Atmosphere Carbon Exchange Study will provide data
reduction and synthesis of the current field data in the Atlantic, Pacific and
Indian Oceans, in collaboration with the participants of the DOE-CO2 Survey
Science
Team. In particular, the group will compare datasets with data obtained on
other
WOCE-WHP cruises and will provide internally consistent datasets encompassing
roughly sixteen cruises in the Pacific Ocean, fifteen cruises in the Indian
Ocean,
and ten cruises in the Atlantic. These datas will be used by the modeling
community for setting boundary conditions for general ocean circulation
models, to
determine the DIC inventory in each basin using several independent methods as
outlined in Wallace (1995), and to estimate anthropogenic CO2 increases in the
ocean Gruber et al., (1996) To facilitate comparisons of models and
observations,
the data will be gridded into similar box sizes as currently used in the
models.
CO2 fluxes between air and water are poorly constrained because of lack of
seasonal
and geographic coverage of pCO2 (air-water disequilibrium) values and
incomplete
understanding of factors controlling the air-sea exchange. In addition to
intensive
monitoring of carbon parameters and parameters influencing pCO2 levels in
surface
water on dedicated cruises sponsored by OACES, PMEL, and AOML have outfitted
the
NOAA Ship Ka'imimoana with a new automated CO2 system to monitor surface water
pCO2
on a continuous basis. While this effort has been a success we need more CO2
systems on NOAA ships to obtain the large area coverage. The new shipboard
design,
patterned after the systems recently built at AOML and PMEL, uses stop-flow
technology to reduce the amount of gas required for analysis by the LICOR
detector.
It will be improved to facilitate fully autonomous operation. The improvements
will
include automating draining of water traps, comprehensive self diagnostics by
the
program running the computer, and
automatic rebooting capabilities of the system if errors are detected. The
underway
system will be an integrated package for measurement of pCO2 in air and water
and
support sensors necessary to reduce the data (such as equilibrator
temperature,
location, salinity, sea surface temperature, and barometric pressure). The
comprehensive automated package will facilitate operations on ships of
opportunity.
The NOAA Ship Ka'imimoana, used to maintain the TAO moorings on six month
intervals, offers an excellent opportunity to determine seasonal and secular
trends
in the region.
In addition to this activity, we will continue our pCO2 instrument development
activities with the group at MBARI, directed by Francisco Chavez, to provide a
suite of chemical and biological sensors deployed on the 155W and 170W TAO
mooring
array in the equatorial Pacific in November 1997. The work leverages on
developmental efforts carried out by MBARI (with support from NOAA, NASA, and
PMEL)
over the past several years. The primary objectives of this project are: (1)
to
determine the relationships between physical forcing, primary production and
the
exchange of carbon dioxide between ocean and atmosphere; (2) to determine the
biological and chemical responses to climatic and ocean variability in the
equatorial Pacific; (3) to determine the spatial, seasonal and interannual
variability in primary production, carbon dioxide, and nutrient distributions;
and
(4) to determine the spatial, seasonal and interannual variability of sea
surface
pigment distributions to groundtruth sattelite measurements of ocean color.
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