The Role of Indian Ocean Internal Processes in Generating Decadal Climate Variability

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

From Indonesia to East Africa, fluctuations of Indian Ocean (IO) sea surface temperature (SST) have been linked to floods, droughts, wildfires, and other disruptive impacts of shifts in rainfall and temperature. These impacts have motivated efforts to characterize IO SST variability and the physical mechanisms that drive it, efforts complicated by the sparsity of observations in the region. A key question in research to date is the extent to which variability of IO SSTs is driven by mechanisms local to the IO and how much is externally forced by El Nino events in the Pacific and other remote influences. Research by the PIs and others has focused on identifying forms of locally-driven IO SST variability and identifying the roles of atmosphere-ocean interactions and subsurface currents and ocean heat storage in generating them. Here the PIs specifically address IO SST fluctuations that take place over a decade or two, which they call the Indian Ocean Decadal Oscillations (IODOs). In its positive phase the IODO features warmer than normal SSTs extending from western Australia to southern Africa accompanied by anomalies in sea level pressure and surface wind. Simulations from the Community Earth System Model (CESM) suggest further anomalies of the subsurface ocean, with higher temperatures to a depth of 200m or so below the region of warm SSTs. The project seeks to investigate the mechanisms of the IODO and explore its impacts on the global climate system through a combination of observational analysis and model simulations. The work is of societal as well as scientific interest given the large populations living in countries surrounding the IO, many of which are quite vulnerable to the impacts of IO variablity as noted above. Results of the work can inform the development of the multi-national IO Observing System (IndOOS) as well as field campaigns organized around it. The project also provides support and training to a graduate student as well as summer support for undergraduates. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.