Atmospheric 14 CO 2 Variations in the Equatorial Region

• Published in: Radiocarbon
• Main Authors: Rozanski, Kazimierz, Levin, Ingeborg, Stock, Jürgen, Guevara Falcon, Raul E., Rubio, Fernando
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1995
• Subjects: General Earth and Planetary Sciences; Archeology; Antarctic; Pacific; Grim; Antarc*
• Online Access: http://dx.doi.org/10.1017/s003382220003099x; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S003382220003099X

We present here first results of 14 CO 2 monitoring at two sampling sites in the equatorial region of the South American continent (station Aychapicho, Ecuador and station Llano del Hato, Venezuela). We also include the data for two other stations representing undisturbed marine atmosphere at mid-latitudes of both hemispheres, far from large continental sources and sinks of CO 2 (station Izaña, Tenerife, Spain and station Cape Grim, Tasmania). Between 1991 and 1993, 14 CO 2 levels in the tropical troposphere were generally higher by 2–5‰ when compared to mid-latitudes of both hemispheres. This apparent maximum of 14 C in the tropics can be explained by two major factors: 1) emissions of 14 C-free fossil fuel CO 2 , restricted mainly to mid-latitudes of the northern hemisphere; and 2) 14 C depletion due to gas exchange with circumpolar Antarctic upwelling water, influencing mainly mid- and high southern latitudes. The δ 14 C record so far available for the Aychapicho station provides direct evidence for a regional reduction of atmospheric 14 CO 2 levels due to gas exchange with 14 C-depleted equatorial surface ocean in the upwelling regions and dilution with the 14 C-depleted CO 2 released in these areas. Recurrent ENSO events, turning on and off the 14 C-depleted CO 2 source in the tropical Pacific, lead to relatively large temporal variations of the atmospheric 14 C level in this region.