A Baroclinic Teleconnection Between the Mozambique Channel and the Makassar Strait

Abstract

The Mozambique Channel and the Makassar Strait are very important for the large scale circulation in the Indian Ocean and the water and climate signal exchange between the Indian Ocean and its surrounding oceans. Up to 2004, very little long-term data on transport was available, so it was unknown how it varies and how it is driven. In order to get this data, the LOCO (Mozambique) and INSTANT (Makassar) mooring networks were installed. The data answered many questions, but also brought in new questions. One of these questions is why the Mozambique Channel transport transits from low net and highly variable transport to high net and little varying transport in May 2006. A second question is why at Makassar Strait similar changes occurred in July 2006 and, even though the general flow direction in the Indian Ocean is westward, why the Mozambique Channel transport transits earlier than the transport through Makassar Strait. A Sverdrup model on the flow around an island shows that changing wind patterns can play a role. The velocity field is analysed for the case that wind is blowing over the full ocean, only over the western half and only over the eastern half. For the case that wind stress acts on the entire ocean surface, the velocity field is analysed for different choices of the latitude of minimum wind curl. By analysing data, the influence of the Indian Ocean Dipole and El Nino Southern Oscillation on the wind, the position of the Indian Ocean Subtropical Gyre, the South Equatorial Current and the sea level is investigated. From this, it is found that the transports are significantly determined by equatorial dynamics rather than by the local wind patterns near the Mozambique Channel and Makassar Strait.