CHAPTER 1 • The Carbonate System in Marine Environments
21
1.4
Distribution of Carbonate Species
The distribution of the various components of the CO2 system in the oceans has been
studied by many workers. I will show the results at two stations in the North Atlantic
and Pacific Ocean (Millero 1997) to demonstrate the depth dependence in the two
major oceans. The current JGOFS CO2 measurements made as part of the WOCE hydrographic program should yield new CO2 measurements that will serve as a benchmark for the future. In this section we will discuss the distribution of the CO2 parameters.
1.4.1
Peo2
Unfortunately no historical data of sufficient accuracy is available for Pc0 2 in surface
waters of the oceans over time. The limited data presently available indicates that the
increase of Pc0 2 in the North Atlantic has a slope similar (1.5 ppm yr- I ) to the atmospheric values. The changes in Pco 2 in surface waters can be caused by:
1. removal by photosynthesis
2. removal by dissolution of CaC03
3. removal by solar heating
4. addition by oxidation of plant material
5. addition by formation of CaC03
6. addition by increases in CO2 in the atmosphere from fossil fuel burning
Unraveling all these effects is even more difficult due to the sluggish response of
the oceans to changes in the level of CO2 in the atmosphere. Recent measurements of
the Pc0 2 in the surface waters of the Atlantic Ocean are shown in Fig. 1.8. The higher
values of Pc0 2 near the equator are due to equatorial upwelling, making the region a
source of CO2• The lower values of Pco 2 in the polar regions are due to waters being
cold, and therefore serving as a sink for CO2• The complicated structure in the North
and South Atlantic oceans may be related to phytoplankton blooms. A north-south
profile of Pco 2 in the Pacific Ocean is similar to the Atlantic. The cold waters are a sink
for CO2 (-ilpco), while the upwelling waters are a source of CO2 (+ilpc0 2 ) to the atmosphere.
A number of workers have attempted to separate the causes of the changes in the
Pco 2 of surface waters due to physical (temperature and salinity) and biological (Chlorophyll) parameters. An example of such a separation is shown in Fig. 1.9 using the
Atlantic data. The relative importance, based on the magnitude of the changes, is in
the order of temperature, chlorophyll and salinity. This way of examining the importance of physical and biological processes neglects the importance of nutrients and
the formation of phytoplankton blooms that can pull down the surface values of Pc0 2 •
The effect of primary production on the levels of Pc0 2 and TC02 have recently been
demonstrated (see Fig. 1.10) in the Ironex-II study (Steinberg et al. 1998). The addition of Fe to the waters decreased the Pco 2 by 75 flatm and TC02 by 26 flmol kg-I. Studies
have shown that the pull down of CO2 by plankton occurs in the North Atlantic dur-
21
1.4
Distribution of Carbonate Species
The distribution of the various components of the CO2 system in the oceans has been
studied by many workers. I will show the results at two stations in the North Atlantic
and Pacific Ocean (Millero 1997) to demonstrate the depth dependence in the two
major oceans. The current JGOFS CO2 measurements made as part of the WOCE hydrographic program should yield new CO2 measurements that will serve as a benchmark for the future. In this section we will discuss the distribution of the CO2 parameters.
1.4.1
Peo2
Unfortunately no historical data of sufficient accuracy is available for Pc0 2 in surface
waters of the oceans over time. The limited data presently available indicates that the
increase of Pc0 2 in the North Atlantic has a slope similar (1.5 ppm yr- I ) to the atmospheric values. The changes in Pco 2 in surface waters can be caused by:
1. removal by photosynthesis
2. removal by dissolution of CaC03
3. removal by solar heating
4. addition by oxidation of plant material
5. addition by formation of CaC03
6. addition by increases in CO2 in the atmosphere from fossil fuel burning
Unraveling all these effects is even more difficult due to the sluggish response of
the oceans to changes in the level of CO2 in the atmosphere. Recent measurements of
the Pc0 2 in the surface waters of the Atlantic Ocean are shown in Fig. 1.8. The higher
values of Pc0 2 near the equator are due to equatorial upwelling, making the region a
source of CO2• The lower values of Pco 2 in the polar regions are due to waters being
cold, and therefore serving as a sink for CO2• The complicated structure in the North
and South Atlantic oceans may be related to phytoplankton blooms. A north-south
profile of Pco 2 in the Pacific Ocean is similar to the Atlantic. The cold waters are a sink
for CO2 (-ilpco), while the upwelling waters are a source of CO2 (+ilpc0 2 ) to the atmosphere.
A number of workers have attempted to separate the causes of the changes in the
Pco 2 of surface waters due to physical (temperature and salinity) and biological (Chlorophyll) parameters. An example of such a separation is shown in Fig. 1.9 using the
Atlantic data. The relative importance, based on the magnitude of the changes, is in
the order of temperature, chlorophyll and salinity. This way of examining the importance of physical and biological processes neglects the importance of nutrients and
the formation of phytoplankton blooms that can pull down the surface values of Pc0 2 •
The effect of primary production on the levels of Pc0 2 and TC02 have recently been
demonstrated (see Fig. 1.10) in the Ironex-II study (Steinberg et al. 1998). The addition of Fe to the waters decreased the Pco 2 by 75 flatm and TC02 by 26 flmol kg-I. Studies
have shown that the pull down of CO2 by plankton occurs in the North Atlantic dur-