Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

Role of long-term Indian Ocean warming in modulating tropical atmospheric circulation (#206)

Shreya Dhame 1 2 , Katrin Meissner 1 2 , Andréa Taschetto 1 2 , Agus Santoso 1 3
  1. Climate Change Research Centre, Sydney, NSW, Australia
  2. ARC Centre of Excellence for Climate Extremes, Sydney, NSW, Australia
  3. Centre for Southern Hemisphere Oceans Research, CSIRO Oceans and Atmosphere, Hobart, TAS, Australia

Indian Ocean (IO) warming has been suggested to play a role in the recent strengthening of Pacific trade winds by rearranging the Walker Circulation. Under increasing greenhouse gases conditions, this warming is likely to continue, resulting in an inter-basin warming contrast. To see the impacts of the long-term IO warming on changes in Walker Circulation and the associated rainfall patterns, two sets of experiments are performed. In the first experiment, the sea surface temperatures (SSTs) are increased only over the Indian Ocean in an atmospheric general circulation model, resembling the observed trend from 1950 to 2017. In the second experiment, the warming structure is kept uniform. This shows to what extent the spatially heterogenous warming pattern in the Indian Ocean matters for regional and remote large-scale atmospheric circulation, temperature and precipitation patterns. Preliminary results show that the observed SST warming drives anomalous low-level convergence, upward motion and divergence at upper troposphere over western Indian Ocean, with subsidence over South America extending into the tropical Atlantic. This suggests the Indian Ocean warming intensifies the Pacific Walker circulation and also affects the local Atlantic Walker cell.