Two modes of bottom water in the Australian‐Antarctic Basin

Recent data from the deep Australian‐Antarctic Basin show that waters colder than about −0.4°C are fresher by as much as 0.02 than data collected prior to 1994. It is possible that the freshening represents a fundamental change in the sources of bottom water for the basin, but it is more likely that the fresh mode recurs periodically and is underrepresented in the historical database. The freshening may be caused by a change in fresh bottom water input from the Antarctic coast between 120°E – 160°E or by a reduction in the outflow of saline Ross Sea Bottom Water.