A084-0001
Abnormal volume transport during the 1990s in the Banda Sea: a causal analysis using a box model
Abstract:
Yiwei Zhang, PhD student at the University of Sheffield
Supervisor: Prof Grant Bigg
The Indonesian Throughflow (ITF) is the only tropical connection between the Pacific and Indian Ocean. Most mass and energy are transported by the wind-driven current in the surface layer of the Indonesian Seas. The Pacific input contains a mix of fresher and cooler water from the north Pacific, via the Mindanao Current, and the relative saltier and warmer water from the south Pacific, via the New Guinea Coastal Current. As the deepest basin in the Indonesian Seas, the Banda Sea is not only an important fishing area but also permits most of the thermohaline transport of the ITF.
Utilizing the SODA 3.7.2 reanalysis dataset, an abnormal volume transport shift has been found during the 1990s in the Banda Sea. The vertical distribution of the horizontal volume transport over the Banda Sea presents a main pattern of transport direction as “north-south-north” as depth increasing. In the early 1990s, this pattern shifted to shallower depth, with this change persisting to 2000. Therefore, although the ENSO activity influences the ITF, the time scale of this anomaly indicates ENSO may not have caused this shift.
The anomaly was studied using a simple idealized 3 box model (Stommel, 1961). The results suggest that this persistent anomaly was caused by changes in the ratio of the input waters from the north and south Pacific. There was more water from the south Pacific involved than average, which led this anomaly shitf happened.
STOMMEL, H. (1961), Thermohaline Convection with Two Stable Regimes of Flow. Tellus, 13: 224-230. doi:10.1111/j.2153-3490.1961.tb00079.x