Changes of Antarctic Bottom Water in the central region (near 115°E) of the Australia-Antarctic Basin

Changes of AABW in the central region (near 115°E) of the Australia-Antarctic Basin were examined mainly with historical hydrographic surveys and recent observations of deep floats. For several decades AABW there had decreased its thickness and its (isothermal) salinity; the average rates were accelerated gradually in time: from about 12 m yr^-1 and 0.3 ×10^-3 yr^-1 for 1965-2019 to about 16 m yr^-1 and 0.5 ×10^-3 yr^-1 for 1990-2019, respectively. In the recent years, however, the AABW seemed to have changed differently from what it used to be; the AABW thickness decreased rapidly by about 30 m yr^-1 and its salinities on isothermal surfaces showed almost no clear trend after 2013. The recent modulations of the AABW changes were expected to be derived from the smaller supply of Dense Shelf Water due to the smaller sea ice production off the Adélie/George V Land coast, and ultimately the collapse of Mertz Glacier Tongue in February 2010.