The Southwest Indian Ocean Thermocline Dome Simulated In CMIP5 Models And Its Response To Global Warming

Comparing 20 models outputs of Coupled Model Intercomparison Project phase 5 (CMIP5) with observations, the simulation of the southwest Indian ocean (SWIO) thermocline dome (i.e. Seychelles dome, SD) is evaluated in this study. The analysis of historical run (1950-1999) outputs indicates that most models show deepening biases in climatological SD simulation due to easterly wind biases along the equator. Such a thermocline bias further influences IO basin mode (IOBM), which is the first mode of IO interannual variability.A model with a deep (shallow) climatological SWIO thermocline shows an weakened (enhanced) interannual amplitude of sea surface temperature (SST) in the SWIO during March-April-May (MAM), as well as the tropical IO (TIO) antisymmetic mode and amplitude of the north IO (NIO) SST during June-July-August (JJA), leading to a significant negative correlation between the thermocline depth of SD and interannual amplitude of IOB mode among the models. Furthermore, the simulation of the amplitude of El Nino-Southern Oscillation (ENSO) in CMIP5 models also influences the IOB amplitude. Its relationship with IOB amplitude is even more significant than that of SD.This thesis further explores the response of the mean state of SD to global warming in CMIP5 models. Over the TIO region, an easterly wind trend along the equator induces IOD-like SST warming pattern and deepend thermocline. However, the magnitude of thermocline deepening shows no signifcant change of IOB amplitude under global warming, suggesting a decreasing effect of the deepening SWIO thermocline dome on the change in IOB mode in the future.