Modeling the effects of the Indonesian Throughflow on the Indian Ocean.

摘要

This dissertation explores the spreading characteristics of the Indonesian Throughflow (ITF) water within the Indian Ocean and the responses of the Indian Ocean to the transport variability of the ITF.; In Chapter 2, using a comprehensive observational data set and a three dimensional Lagrangian trajectory experiment in an ocean general circulation model (OGCM), we find that, for the thermocline ITF water north of the South Equatorial Current, upwelling and the concomitant southward Ekman transport provides an important escape pathway towards the southern boundary of the Indian Ocean. In the upper thermocline the ITF crosses the Indian Ocean in 10 years, and reaches the Arabian Sea on a time scale of over 20 years.; In Chapter 3, we find that the transport profile of the ITF is important in regulating the stratification and surface heat fluxes of the Indian Ocean. With the same total ITF transport, a thermocline-intensified ITF, relative to a surface-intensified ITF, not only cools the surface layer of the Indian Ocean while warming the Indian Ocean below the thermocline, but also induces negative temperature anomalies at the sea surface throughout the Indian basin. As a consequence of this surface effect the net heat gain of the Indian Ocean is increased. The results suggest that it is necessary to properly represent the vertical profile of ITF transport within ocean and climate numerical models.; In Chapter 4, we study the Indian Ocean meridional overturning circulation (MOC) and heat budget, and their sensitivity to the ITF transport variability using an OGCM. We find that the deep cell of the MOC (below 1500 m) is insensitive to the ITF transport variation. The effects of the ITF net transport variation on the Indian Ocean net surface heat flux depend on the ITF transport profile. The magnitude of the decrease in net ocean heat gain from the atmosphere can vary significantly if the ITF transport profile is altered as it total transport varies, with larger reduction in net Indian Ocean heat gain if the ITF becomes more surface-intensified.