Verification of various Island Rules using simulations in application to the Indonesian Throughflow

Abstract

The Indonesian throughflow is an important component of the upper cell of the global overturning circulation. It provides a pathway for warm, fresh waters from the Pacific Ocean to enter the Indian Ocean. Godfrey’s Island Rule states that the transport through the Indonesian Archipelago can be estimated by integrating the surface wind stress around a path enclosing Australia. Study by Feng et al. (2017) suggests the throughflow is also influenced by deep Pacific upwelling and an amended Island Rule is proposed by them. In this thesis, we use simulations to verify both Godfrey’s original Island Rule and the amended Island Rule. For our simulations, we use the four-degree model setup of Veros. Two model runs are conducted, each using different wind forcing. In both cases, we find that the amended Island Rule estimates the actual transport better than Godfrey’s Island Rule does. Our results imply that deep Pacific upwelling does indeed contribute to the strength of the Indonesian throughflow. When studying the future climate under global warming, this should be taken into account to acquire a better estimate of the transport through the Indonesian Archipelago.