Oceanic drivers for tropical terrestrial carbon cycle and extreme

Monday, December 10, 2018 - 14:52
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Oceanic variability strongly affects climate regimes and variability in the tropics through multiple teleconnections. The climatic effects of teleconnections include pattern shifts of temperature, precipitation, and clouds, intensity, frequency changes of climatic and weather extremes, and modulations of regional and local water and energy cycles and balances. Hence oceanic variability can significantly influence tropical carbon fluxes and ecosystem dynamics. The El Niño-Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO) and Indian Ocean dipole (IOD), originating from the Pacific, Atlantic and Indian oceans respectively, are three important oceanic variations that generally have important impacts on tropical carbon cycle. There are, however, complicated interactions between the variability in the three oceans and the their associated modes, which in turns can affect their variability and therefore cause large uncertainties in their impacts on tropical climate and terrestrial ecosystems. In this study, we use the Department of Energy (DOE) Energy Exascale Earth System Model (E3SM) to study the oceanic drivers for the tropical terrestrial carbon cycle. We aim to decompose the influences from the Pacific, Atlantic and Indian Oceans on climatic extremes and estimated their attributions to variability of carbon flux and CO2 growth rate. We perform a number of ensemble simulations to assess the model uncertainties. We also run a couple of sensitive experiments to separate the influences of oceanic drivers from different oceans on tropical carbon cycle. Our results show that the ENSO generally plays a dominant role leading to the carbon extremes in the Tropics, but the AMO and IOD may enhance or weaken the effects depending on their modes and geographic locations of extremes.

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