Contrasting interannual atmospheric COsub2/sub variabilities and their terrestrial mechanisms for two types of El Ni?os

摘要

El Ni?o has two different flavors, eastern Pacific?(EP) and central Pacific (CP) El Ni?os, with different global teleconnections. However, their different impacts on the interannual carbon cycle variability remain unclear. Here we compared the behaviors of interannual atmospheric COsub2/sub variability and analyzed their terrestrial mechanisms during these two types of El Ni?os, based on the Mauna Loa?(MLO) COsub2/sub growth rate (CGR) and the Dynamic Global Vegetation Model's?(DGVM) historical simulations. The composite analysis showed that evolution of the MLO CGR anomaly during EP and CP El Ni?os had three clear differences:?(1) negative or neutral precursors in the boreal spring during an El Ni?o developing year (denoted as yr0 ), (2)?strong or weak amplitudes, and (3)?durations of the peak from December (yr0) to April during an El Ni?o decaying year (denoted as yr1 ) compared to October (yr0) to January (yr1) for a CP El Ni?o, respectively. The global land–atmosphere carbon flux (FsubTA/sub) simulated by multi-models was able to capture the essentials of these characteristics. We further found that the gross primary productivity (GPP) over the tropics and the extratropical Southern Hemisphere (Trop + SH) generally dominated the global FsubTA/sub variations during both El Ni?o types. Regional analysis showed that during EP El Ni?o events significant anomalous carbon uptake caused by increased precipitation and colder temperatures, corresponding to the negative precursor, occurred between 30° S and 20° N from January (yr0) to June (yr0). The strongest anomalous carbon releases, largely due to the reduced GPP induced by low precipitation and warm temperatures, occurred between the equator and 20° N from February (yr1) to August (yr1). In contrast, during CP El Ni?o events, clear carbon releases existed between 10° N and 20° S from September (yr0) to September (yr1), resulting from the widespread dry and warm climate conditions. Different spatial patterns of land temperatures and precipitation in different seasons associated with EP and CP El Ni?os accounted for the evolutionary characteristics of GPP, terrestrial ecosystem respiration?(TER), and the resultant FsubTA/sub. Understanding these different behaviors of interannual atmospheric COsub2/sub variability, along with their terrestrial mechanisms during EP and CP El Ni?os, is important because the CP El Ni?o occurrence rate might increase under global warming.