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SUMMARY:The Sensitivity of Antarctic Bottom Water to Changing Surface Buoy
 ancy Fluxes. - Dr. Kate Snow
DTSTART:20160307T110000Z
DTEND:20160307T120000Z
UID:TALK64801@talks.cam.ac.uk
CONTACT:Dr Dave Munday
DESCRIPTION:Processes on the Antarctic continental shelf control the excha
 nge of water masses across the shelf break\, the delivery of heat fluxes t
 o adjacent ice-shelves\, and the formation of Antarctic Bottom Water (AABW
 ). Antarctic Bottom Water controls the abyssal limb of the global overturn
 ing circulation\, and plays an important role in the ocean’s heat and ca
 rbon uptake. Understanding how changing surface buoyancy fluxes influence 
 AABW and Antarctic shelf processes is thus important in defining future cl
 imate change. \n\nUsing a realistic bathymetry coupled ocean-ice sector mo
 del of the Atlantic Ocean\, the sensitivity of AABW to changing surface bu
 oyancy fluxes emulating a changing climate is assessed. The sector model\,
  unlike most climate model\, maintains Dense Shelf Water (DSW) sourced AAB
 W as the dominant mode of AABW formation\, and thus provides a tool to ass
 es feedback's and variability climate models may be lacking. Inclusion of 
 shelf-scoured AABW leads to cooling and freshening of DSW under enhanced s
 urface buoyancy fluxes. The cooling is facilitated via changes in the on-s
 helf/off-shelf exchange and highlights the importance of surface buoyancy 
 fluxes in the exchange process. Such cooling\, in concert with open-ocean 
 warming\, leads to a decadal scale variability of the abyssal ocean.\n\nTh
 e role of buoyancy in controlling the cross shelf exchange and AABW format
 ion is further revealed by analysing unique long-term time series of hydro
 graphic and mooring observation on the Adelie Land continental shelf\, an 
 important AABW formation region.  At seasonal time scales\, changes in sur
 face buoyancy fluxes maintain significant control on the strength of the c
 ross-shelf exchange. With heightened buoyancy losses in winter\, the excha
 nge of DSW and off-shelf waters is an order of magnitude larger than that 
 in summer\, setting up a cyclonic circulation on the shelf. At longer time
  scales\, the calving of the Mertz Glacier Tongue (MGT) and its influence 
 on the freshwater budget in the Adelie region\, provides a unique window i
 nto potential influences of future climate change on AABW formation. Follo
 wing the MGT calving\, DSW formation dramatically decreased\, with the DSW
  available for export as AABW decreasing by 100% in 2011. The reduced DSW 
 export significantly hindered AABW production and suggests that continued 
 changes in surface buoyancy fluxes and the observed freshening around Anta
 rctic may drive dramatic changes in the strength and structure of the abys
 sal limb of the meridional overturning circulation in future decades. \n\n
 In order to understand the role Antarctica and AABW will play in a changin
 g climate\, continued long-term monitoring on the Antarctic region and aby
 ssal ocean is essential\, as is continued development to improve climate m
 odel capability to represent AABW formation processes. 
LOCATION:British Antarctic Survey\, Room 187
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