Temporal variability of Antarctic Bottom Water formation and its drivers

Alessandro Silvano, University of Tasmania, Quantitative Marine Science Program, Hobart, TAS, Australia, Annie Foppert, Centre for Southern Hemisphere Oceans Research, CSIRO Oceans and Atmosphere, Hobart, Australia, Hobart, TAS, Australia, Stephen R Rintoul, Commonwealth Scientic and Industrial Research Organization Oceans and Atmosphere, Hobart, TAS, Australia, Paul Holland, British Antarctic Survey, Cambridge, United Kingdom, Pasquale Castagno, Parthenope University of Naples, Naples, Italy, Alberto Naveira Garabato, University of Southampton, Ocean and Earth Science, Southampton, United Kingdom, Alexander Haumann, Princeton University, Atmospheric and Oceanic Sciences Program, Princeton, NJ, United States, Noriaki Kimura, The University of Tokyo, Atmosphere and Ocean Research Institute, Kashiwa, Japan, Takeshi Tamura, NIPR National Institute of Polar Research, Tokyo, Japan and Alison M Macdonald, WHOI, Woods Hole, United States
Antarctic Bottom Water (AABW) is the coldest, densest and deepest water mass of the World Ocean. Formation and renewal of AABW regulate the lower limb of the global overturning circulation, determining the oceanic ability to sequester heat and carbon in the abyss for centuries. Here we show observations collected in the Ross Sea capturing temporal (interannual to decadal) changes in Antarctic Bottom Water properties. We show that a combination of multiple drivers contribute to the observed AABW changes. More specifically, temporal changes in sea ice formation and melting near the Antarctic coast as well as changes in Antarctic Ice Sheet melting regulate the AABW properties. Our observations provide direct evidence that a decrease in sea ice formation and an increase in Antarctic Ice Sheet melting as projected under sustained anthropogenic forcing can cause a dramatic reduction in AABW formation. Further, our observational results highlight that models coupling ocean, sea ice and ice sheet are required to predict future changes in the lower limb of the global overturning circulation.