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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D8, 4243, doi:10.1029/2002JD002729, 2003

On large variations in atmospheric CO₂ concentration observed over the central and western Pacific Ocean

Shohei Murayama

National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan

Koh Harada

National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan

Kouichi Gotoh

Kansai Environmental Engineering Center Co. Ltd., Osaka, Japan

Takashi Kitao

Kansai Environmental Engineering Center Co. Ltd., Osaka, Japan

Tomonori Watai

Center for Atmospheric and Oceanic Studies, Graduate School of Science, Tohoku University, Sendai, Japan

Susumu Yamamoto

National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan

Abstract

In order to examine distribution of atmospheric CO₂ concentration over the central and western Pacific Ocean and elucidate factors governing the distribution, shipboard measurements were made between 1992 and 1996. Large variations in the concentration were observed in the northernmost and the tropical regions during the cruises. Also, year-to-year differences in the latitudinal CO₂ distribution were detected. To interpret these variations, analyses were performed in terms of atmospheric transport from various source regions using meteorological and climatological data. The following results were obtained: (1) Episodic large CO₂ variations appeared north of 30°N over the central and western Pacific during the periods of ship cruises. These variations were related with exchanges of continental and marine air masses associated with movements of weather systems. (2) Discontinuous changes of CO₂ concentration were observed in the equatorial region during spring cruises, reflecting suppression of interhemispheric air mixing. However, the magnitude, the sharpness, and the location of these discontinuous changes were associated with variations in the strength of air convergence and the movement of enhanced convective areas, and were quite variable. (3) Differences in the latitudinal CO₂ gradient from northern low latitudes to southern low latitudes were found between each spring cruise. Comparison with climatological data suggests that the difference in the CO₂ gradient is related to variation in the anomaly of meridional wind component distribution over the central and western Pacific at low latitudes.

Published 23 April 2003.

Index Terms: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 1610 Global Change: Atmosphere (0315, 0325); 9355 Information Related to Geographic Region: Pacific Ocean.

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Citation: Murayama, S., K. Harada, K. Gotoh, T. Kitao, T. Watai, and S. Yamamoto (2003), On large variations in atmospheric CO₂ concentration observed over the central and western Pacific Ocean, J. Geophys. Res., 108(D8), 4243, doi:10.1029/2002JD002729.

Copyright 2003 by the American Geophysical Union.