Bottom water properties in the Australian-Antarctic Basin: A perspective from the Deep-Argo pilot array — Australian Meteorological and Oceanographic Society
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  2. 24(ii) Southern Hemisphere oceans variability and change
  3. Bottom water properties in the Australian-Antarctic Basin: A perspective from the Deep-Argo pilot array

Bottom water properties in the Australian-Antarctic Basin: A perspective from the Deep-Argo pilot array (#28)

Annie Foppert 1 2 , Steve R Rintoul 1 2 , Matthew H England 2 3
  1. CSIRO Oceans and Atmosphere, Battery Point, TAS, Australia
  2. Centre for Southern Hemisphere Oceans Research, Hobart, TAS, Australia
  3. UNSW, Sydney, NSW, AUSTRALIA

The production and export of Antarctic Bottom Water (AABW) regulates the global overturning circulation and ventilates the deep ocean. Roughly 40% of AABW is exported into the Australian Antarctic Basin after being formed in two distinct source regions near East Antarctica: Adelie/George V Land and Ross Sea. Observations from the past several decades show both flavours of AABW freshening, with the highest rates of change near the bottom water sources. A pilot array of Deep-Argo floats capable of profiling to between 4000 and 6000 dbar (depending on float type) was deployed in early 2018 in the Australian Antarctic Basin. As of August 2019, 12 active floats in the region have recorded over 550 profiles, with about 350 bottom-reaching profiles. Calibrated against quasi-contemporaneous shipboard CTD profiles, this array reveals bottom water properties spanning 0.05 psu and nearly 1oC in absolute salinity and conservative temperature, respectively. While Ross Sea sourced AABW is relatively warmer and more saline than that sourced from Adelie/George V Land, the differences are compensated in density. The pilot array of Deep-Argo floats puts the observed changes over the past several decades into a broader spatial context and reveals pathways from two regional sources of AABW.

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