Interannual to Interdecadal CO2 Flux Variability in the Earth System Model
Abstract
Spatio-temporal variability of surface CO2 fluxes in an Earth System Model (ESM) is analyzed. The climate variability modifies both the ocean-atmosphere CO2 flux and the land-atmosphere CO2 flux. The earlier studies, by using observed/assimilated data set, show that tropical oceanic climate variability has strong impacts on the land skin temperature and soil moisture, and there is a negative correlation between the oceanic and terrestrial CO2 fluxes. However, those data set only covers less than recent 20 years and is insufficient for identifying the decadal and longer periodic variabilities. To investigate the possible impact of interannual to interdecadal climate variability upon the CO2 flux exchange, the last 48 years of the ESM output is examined. The global-sum of the terrestrial CO2 anomaly has a variance much greater in amplitude and longer in periodic timescale, compared to that of the oceanic one. In some years terrestrial CO2 anomaly negatively correlates with oceanic one but in other years positively, as the periodic timescale is different between the two. Standard deviation analysis by latitudinal bands shows that anomalous CO2 flux comes 47 percent from tropical continents, 36 percent from northern continents in mid-high latitudes, and 7 percent from tropical oceans, indicating the importance of direct and indirect impact of tropical climate variabilities. To determine the spatial pattern of the variability, a series of composite analyses are performed. As a result, the oceanic CO2 variability peaks when the eastern tropical Pacific has great sea surface temperature anomaly (SSTA). The terrestrial CO2 variability, in contrast, peaks when the SSTA appears in the central tropical Pacific. The former variability quite resembles to the ENSO-mode and the latter to the ENSO-modoki, although the simulated ENSO is much weaker than the real ENSO and the vice versa for the ENSO-modoki, according to the EOF analysis. Our result implies that the oceanic and terrestrial CO2 flux anomalies may correlate either positively or negatively depending on the relative phase of the two oceanic modes in the tropical Pacific.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.U43D..07O
- Keywords:
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- 0428 Carbon cycling (4806);
- 1615 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 4805;
- 4912);
- 1616 Climate variability (1635;
- 3305;
- 3309;
- 4215;
- 4513);
- 1622 Earth system modeling (1225)