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SUMMARY:Lagrangian pathways for sub-Antarctic Mode Water (SAMW) formation 
 and carbon uptake - Bieito Fernandez Castro (University of Southampton)
DTSTART:20230511T140000Z
DTEND:20230511T150000Z
UID:TALK200506@talks.cam.ac.uk
CONTACT:Dr Michael Haigh
DESCRIPTION:Sub-Antarctic Mode Waters (SAMW)\, forming in the deep winter 
 mixed layers in the Sub-Antarctic Zone to the north of the Antarctic Circu
 mpolar Current (ACC)\, connect the ocean thermocline with the atmosphere\,
  contributing to ocean carbon and heat uptake and transporting high-latitu
 de nutrients northward\, to fuel primary production at lower and northern 
 latitudes. The important climatic role of SAMW is controlled by the rate o
 f fluid subduction from the deep winter mixed layers and the the mixed lay
 er properties at the end of winter. These concentrations depend on a range
  of processes\, both physical and biogeochemical\, whose relative contribu
 tions are very poorly understood. With a Lagrangian particle-tracking expe
 riment in a data-assimilative coupled physico-biogeochemical model of the 
 Southern Ocean (B-SOSE)\, we assessed the origin of the waters leading to 
 SAMW formation and the physico- and biogeochemical transformations occurri
 ng along their pathways. Our results revealed two main pathways for SAMW f
 ormation: a "classical" pathway originating from the upwelling of Circumpo
 lar Deep Waters south of the ACC and a subtropical pathway with waters acc
 essing the ACC at the intersection with the subtropical western boundary c
 urrents. The two pathways are characterised by contrasting transit times\,
  degree of ventilation and range of processes controlling the final SAMW p
 roperties. The number particles joining each pathway was also different be
 tween the Indian and Pacific SAMW varieties. These findings have implicati
 ons for our understanding of the Southern Ocean overturning circulation an
 d its role on the sequestration of heat\, nutrients and carbon dioxide.
LOCATION:BAS Seminar Room 330b\; https://ukri.zoom.us/j/91474458573
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