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SUMMARY:Reduced overturning and abyssal ventilation in the Australian Anta
 rctic Basin - Kathy Gunn\, CSIRO
DTSTART:20221010T090000Z
DTEND:20221010T100000Z
UID:TALK173741@talks.cam.ac.uk
CONTACT:Dr. Shenjie Zhou
DESCRIPTION:Antarctic Bottom Water (AABW) supplies the lower limb of the o
 verturning circulation and ventilates the abyssal ocean. Observations show
  AABW has warmed\, freshened and contracted. However\, the drivers of thes
 e changes and their impact on abyssal circulation and ventilation are poor
 ly understood. Here we analyse observed changes in AABW properties and tra
 nsport in the well-ventilated Australian Antarctic Basin to assess the cau
 ses and consequences of abyssal ocean change. Freshening of dense shelf wa
 ters reduced the volume transport of AABW by -1.5±0.5 Sv/decade between 1
 994 and 2009. Decreased AABW export reduced oxygen transport into the abys
 sal ocean and caused well-ventilated layers to thin\, driving deoxygenatio
 n of 3 μmol/kg/decade. AABW changes of opposite sign were observed when s
 helf water salinity increased between 2014 and 2018\, confirming the link 
 between shelf water salinity\, AABW formation\, and abyssal ventilation. T
 hese findings suggest that multi-decadal freshening of shelf waters\, whic
 h has been attributed to increased glacial melt\, has driven a marked slow
 down of the deep overturning circulation and rapid deoxygenation of the ab
 yssal ocean.
LOCATION:https://ukri.zoom.us/j/95409884242\; BAS Seminar Room 330b
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