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SUMMARY:Drivers and reversibility of abrupt ocean cold-to-warm and warm-to
 -cold transitions in the Amundsen Sea - Justine Caillet\, IGE Géosciences
  Environnement
DTSTART:20240306T140000Z
DTEND:20240306T150000Z
UID:TALK211078@talks.cam.ac.uk
CONTACT:Dr Birgit Rogalla
DESCRIPTION:Ocean warming around Antarctica has the potential to trigger m
 arine ice-sheet instabilities. It has been suggested that abrupt and irrev
 ersible cold-to-warm ocean tipping points may exist\, with possible domino
  effect from ocean to ice-sheet tipping points. A 1/4° ocean model config
 uration of the Amundsen Sea sector is used to investigate the existence of
  ocean tipping points\, their drivers\, and their potential impact on ice-
 shelf basal melting. We apply idealized atmospheric perturbations of eithe
 r heat\, freshwater\, or momentum fluxes\, and we characterize the key phy
 sical processes at play in warm-to-cold and cold-to-warm climate transitio
 ns. Relatively weak perturbations of any of these fluxes are able to switc
 h the Amundsen Sea to an intermittent or permanent cold state\, that is\, 
 with ocean temperatures close to the surface freezing point and very low i
 ce-shelf melt rate. The transitions are reversible\, that is\, canceling t
 he atmospheric perturbation brings the ocean system back to its unperturbe
 d state within a few decades. All the transitions are primarily driven by 
 changes in surface buoyancy fluxes resulting from the freshwater flux pert
 urbation or from modified net sea-ice production due to either heat flux o
 r sea-ice advection anomalies. These changes affect the vertical ocean str
 atification over the continental shelf and thereby the eastward undercurre
 nt at the shelf break\, which both impact ice-shelf melting.
LOCATION:BAS Seminar Room 1\; zoom
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