Sensitivity of inter-annual variation of CO2 seasonal cycle at Mauna Loa to atmospheric transport (original) (raw)
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Seasonal and interannual variations of atmospheric CO2 and climate
Tellus Series B-chemical and Physical Meteorology, 1998
Interannual variations of atmospheric CO2 concentrations at Mauna Loa are almost masked by the seasonal cycle and a strong trend; at the South Pole, the seasonal cycle is small and is almost lost in the trend and interannual variations. Singular-spectrum analysis (SSA) is used here to isolate and reconstruct interannual signals at both sites and to visualize recent decadal changes in the amplitude and phase of the seasonal cycle. Analysis of the Mauna Loa CO2 series illustrates a hastening of the CO2 seasonal cycle, a close temporal relation between Northern Hemisphere (NH) mean temperature trends and the amplitude of the seasonal CO2 cycle, and tentative ties between the latter and seasonality changes in temperature over the NH continents. Variations of the seasonal CO2 cycle at the South Pole differ from those at Mauna Loa: it is phase changes of the seasonal cycle at the South Pole, rather than amplitude changes, that parallel hemispheric and global temperature trends. The seasonal CO2 cycles exhibit earlier occurrences of the seasons by 7days at Mauna Loa and 18days at the South Pole. Interannual CO2 variations are shared at the two locations, appear to respond to tropical processes, and can be decomposed mostly into two periodicities, around (3years)
1 and (4years)1, respectively. Joint SSA analyses of CO2 concentrations and tropical climate indices isolate a shared mode with a quasi-triennial (QT) period in which the CO2 and sea-surface temperature (SST) participation are in phase opposition. The other shared mode has a quasi-quadrennial (QQ) period and CO2 variations are in phase with the corresponding tropical SST variations throughout the tropics. Together these interannual modes exhibit a mean lag between tropical SSTs and CO2 variations of about 6 8months, with SST leading. Analysis of the QT and QQ signals in global gridded SSTs, joint SSA of CO2 and δ13C isotopic ratios, and SSA of CO2 and NH-land temperatures indicate that the QT variations in CO2 mostly reflect upwelling variations in the eastern tropical Pacific. QQ variations are dominated by the CO2 signature of terrestrial-ecosystem response to global QQ climate variations. Climate variations associated with these two interannual components of tropical variability have very different effects on global climate and, especially, on terrestrial ecosystems and the carbon cycle.
Interannual variability of the atmospheric CO2 growth rate: roles of precipitation and temperature
Biogeosciences
The interannual variability (IAV) in atmospheric CO<sub>2</sub> growth rate (CGR) is closely connected with the El Niño–Southern Oscillation. However, sensitivities of CGR to temperature and precipitation remain largely uncertain. This paper analyzed the relationship between Mauna Loa CGR and tropical land climatic elements. We find that Mauna Loa CGR lags precipitation by 4 months with a correlation coefficient of −0.63, leads temperature by 1 month…
Geophysical Research Letters, 2007
Using a 3-dimensional atmospheric transport model driven by the ECMWF winds and the non-interannually varying seasonal biospheric flux from the CASA global ecosystem model, we show that a significant change in the downward-zero crossing day (DZCD) of the atmospheric CO2 seasonal cycle in the Northern Hemisphere above 30°N latitude can be obtained by year-to-year changes in the atmospheric transport alone. The transport model is able to reproduce both the trend and standard deviation of DZCD observed at Pt. Barrow. With only atmospheric transport changing from year to year, eastern North Atlantic, Europe, southern Eurasia, southeastern United States and western North America show DZCD starting earlier by 5-10 days after 21 years of model integration. If DZCD obtained from CO2 monitoring stations is going to be used as a proxy for determining the growing season length, then it is important to take into account of that portion caused by the atmospheric transport.