Airborne observations of the tropospheric CO2 distribution and its controlling factors over the South Pacific Basin

Highly precise measurements of CO2 mixing ratios were recorded aboard both the NASA DC-8 and P3-B aircraft during the Pacific Exploratory Mission-Tropics conducted in August-October 1996. Data were obtained at altitudes ranging from 0.1 to 12 km over a large portion of the South Pacific Basin representing the most geographically extensive CO2 data set recorded in this region. These data along with CO2 surface measurements from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) and the National Institute of Water and Atmospheric Research (NIWA) were examined to establish vertical and meridional gradients. The CO2 spatial distribution in the southern hemisphere appeared to be largely determined by interhemispheric transport as air masses with depleted CO2 levels characteristic of northern hemispheric air were frequently observed south of the Intertropical Convergence Zone. However, regional processes also played a role in modulating background concentrations. Comparisons of CO2 with other trace gases indicated that CO2 values were influenced by continental sources. Large scale plumes from biomass burning activities produced enhanced CO2 mixing ratios within the lower to midtroposphere over portions of the remote Pacific. An apparent CO2 source was observed in the NOAA/CMDL surface data between 15°N and 15°S and in the lower altitude flight data between 8°N and 8.5°S with a zone of intensity from 6.5°N to 1°S. Inferred from these data is the presence of a Southern Ocean sink from south of 15°S having two distinct zones seasonally out of phase with one another.

[1]  G. Pearman,et al.  Atmospheric carbon dioxide measurements in the Australian region: ten years of aircraft data , 1984 .

[2]  J. Lerner,et al.  Three‐dimensional model synthesis of the global methane cycle , 1991 .

[3]  Charles D. Keeling,et al.  Seasonal, latitudinal, and secular variations in the abundance and isotopic ratios of atmospheric CO2: 2. Results from oceanographic cruises in the tropical Pacific Ocean , 1984 .

[4]  L. P. Steele,et al.  Carbon dioxide and methane in the Arctic atmosphere , 1989 .

[5]  R F Weiss,et al.  Global air-sea flux of CO2: an estimate based on measurements of sea-air pCO2 difference. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[6]  Pieter P. Tans,et al.  Evidence for interannual variability of the carbon cycle from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network , 1994 .

[7]  G. S. Callendar.  On the Amount of Carbon Dioxide in the Atmosphere , 1958 .

[8]  T. C. Johns,et al.  A search for human influences on the thermal structure of the atmosphere , 1995, Nature.

[9]  Takakiyo Nakazawa,et al.  Temporal and spatial variations of upper tropospheric and lower stratospheric carbon dioxide , 1991 .

[10]  W. Komhyr,et al.  Semiautomatic nondispersive infrared analyzer apparatus for CO2 air sample analyses , 1983 .

[11]  G. W. Sachse,et al.  Airborne observations of spatial and temporal variability of tropospheric carbon dioxide , 1996 .

[12]  M. Ramonet,et al.  Longitudinal and vertical CO2 gradients over the subtropical/subantarctic oceanic sink , 1996 .

[13]  James M. Hoell,et al.  Pacific Exploratory Mission in the tropical Pacific: PEM-Tropics A, August-September 1996 , 1999 .

[14]  C. D. Keeling,et al.  Meridional eddy diffusion model of the transport of atmospheric carbon dioxide: 1. Seasonal carbon cycle over the tropical Pacific Ocean , 1986 .

[15]  C. D. Keeling,et al.  Meridional eddy diffusion model of the transport of atmospheric carbon dioxide: 2. Mean annual carbon cycle , 1986 .

[16]  J. Fishman,et al.  Observations of ozone concentrations in the Brazilian cerrado during the TRACE A field expedition , 1996 .

[17]  T. Nakazawa,et al.  Seasonal and meridional variations of atmospheric carbon dioxide in the lower troposphere of the northern and southern hemispheres , 1987 .

[18]  D. Cahoon,et al.  Carbon monoxide over the Amazon Basin during the 1985 dry season , 1988 .

[19]  D. Blake,et al.  Chemical characteristics of Pacific tropospheric air in the region of the Intertropical Convergence Zone and South Pacific Convergence Zone , 1999 .

[20]  D. Blake,et al.  A meteorological overview of the Pacific Exploratory Mission (PEM) Tropics period , 1999 .

[21]  D. Blake,et al.  Biomass burning emissions and vertical distribution of atmospheric methyl halides and other reduced carbon gases in the South Atlantic region , 1996 .

[22]  I. Fung,et al.  Observational Contrains on the Global Atmospheric Co2 Budget , 1990, Science.

[23]  H. Matsueda,et al.  Measurements of atmospheric CO2 and CH4 using a commercial airliner from 1993 to 1994 , 1996 .

[24]  S. Murayama,et al.  Longitudinally different variations of lower tropospheric carbon dioxide concentrations over the North Pacific Ocean , 1992 .

[25]  D. Blake,et al.  Factors influencing the upper free tropospheric distribution of reactive nitrogen over the South Atlantic during the TRACE A experiment , 1996 .

[26]  P. Tans,et al.  Atmospheric carbon dioxide measurements in the remote global troposphere, 1981-1984 , 1988 .

[27]  C. D. Keeling,et al.  Large‐scale atmospheric mixing as deduced from the seasonal and meridional variations of carbon dioxide , 1963 .

[28]  M. Wahlen,et al.  Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980 , 1995, Nature.

[29]  Philippe Ciais,et al.  Partitioning of ocean and land uptake of CO2 as inferred by δ13C measurements from the NOAA Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network , 1995 .

[30]  P. Tans,et al.  Latitudinal distribution of the sources and sinks of atmospheric carbon dioxide derived from surface observations and an atmospheric transport model , 1989 .

[31]  P. Tans,et al.  Atmospheric carbon dioxide at Mauna Loa Observatory: 2. Analysis of the NOAA GMCC data, 1974–1985 , 1989 .

[32]  D. Blake,et al.  Three-dimensional distribution of nonmenthane hydrocarbons and halocarbons over the northwestern Pacific during the 1991 Pacific Exploratory Mission (PEM-West A) , 1996 .