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SUMMARY:Mixing at the fringes of a rapidly melting Antarctic ice shelf - A
 lberto Naviera-Garabato (National Oceanography Centre\, Southampton)
DTSTART:20151130T130000Z
DTEND:20151130T140000Z
UID:TALK61541@talks.cam.ac.uk
CONTACT:Doris Allen
DESCRIPTION:The processes regulating the physical exchanges across the fro
 nt of the Pine Island Ice Shelf (one of the most rapidly melting Antarctic
  ice shelves) in the Amundsen Sea are investigated through the analysis of
  an extensive set of full-depth hydrographic\, velocity and microstructure
  measurements\, obtained as part of the ISTAR expedition in February 2014\
 , and an idealised high-resolution numerical circulation model. The outflo
 ws of Ice Cavity Water (ICW)\, which contains elevated concentrations of m
 eltwater from the ice shelf\, are shown to be subject to very intense smal
 l-scale turbulent mixing within 5 kilometres of the ice front. The rates o
 f turbulent kinetic energy dissipation and diapycnal mixing in the outflow
 s are enhanced by up to four orders of magnitude relative to those in surr
 ounding waters\, which are characterised by turbulence levels typical of t
 he open ocean. An investigation of the causes of the intensified turbulenc
 e reveals that it is sustained by centrifugal instability of the ICW outfl
 ows. The instability drives a secondary ageostrophic circulation that indu
 ces rapid lateral mixing between ICW and pycnocline waters offshore\, ther
 eby preventing the ICW outflows from reaching the upper-ocean mixed layer 
 and directly influencing surface climate in the region. The significance o
 f this process for the fate of meltwater outflows from other Antarctic ice
  shelves will be discussed.
LOCATION:MR5\, Centre for Mathematical Sciences
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