Heat transports in the Indian Ocean estimated from TOPEX/POSEIDON altimetry and model simulations

Estimates of the heat budget of the Indian Ocean computed using TOPEX/Poseidon (T/P) sea-level anomalies and the Miami Isopycnal Coordinate Ocean Model are compared to study the redistribution of heat in the Indian Ocean. In particular, the horizontal heat transport and heat storage are used because they typically change on time scales of months or years or longer, and are therefore a predictable element of the climate system. The results show that T/P-derived heat storage is weaker than that derived from the model but has similar spatial structure and temporal evolution. Complex principal component analysis shows that there are two main modes of heat content redistribution in the Indian Ocean. The most dominant mode has an annual signal peaking in the boreal summer, and depicts the response to strong southwest monsoon winds. This involves offshore propagation of heat in the northern Indian Ocean and southward propagation of heat across the equator. The other main mode of heat content redistribution in the Indian Ocean results from westward propagating equatorial Rossby waves. This process is prominent in the boreal fall to spring, and represents the dynamic readjustment of the Indian Ocean to near-equatorial wind forcing. This mode indirectly relates to the dipole mode index in the Indian Ocean. The minima of this time series coincide with the occurrence of the anomalous dipole structure in the equatorial Indian Ocean.