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SUMMARY:Two talks on Ice-Ocean interaction in East Antarctica - Takeshi Ta
 mura (National Institute of Polar Research) and  Daisuke Hirano (Institute
  of Low Temperature Science)
DTSTART:20190320T103000Z
DTEND:20190320T113000Z
UID:TALK121804@talks.cam.ac.uk
CONTACT:Dr Ryan Patmore
DESCRIPTION:Anybody wishing to attend from outside BAS please email the se
 minar organiser beforehand. The talk details are as follows:\n\n\n\n*Resea
 rch of Ocean-ice BOundary InTeraction and Change around Antarctica (ROBOTI
 CA): a strategy to explore ice-ocean interactions in East Antarctica*\n\nT
 akeshi Tamura (National Institute of Polar Research)\n\nAntarctica and the
  surrounding Southern Ocean are changing. Acceleration of ice mass loss an
 d the warming of the coastal ocean in West Antarctica have substantial imp
 acts on the global climate system. In East Antarctica\, which has been con
 sidered to be stable and attracted relatively less attention\, regional ch
 aracteristics of interactions among climate subsystems have recently been 
 revealed\, and evidence of variations on time scales from decadal to mille
 nnial\, has been accumulating. Totten Glacier Ice Shelf\, Wilkes Land\, ha
 s an ice discharge rate known to be accelerating. A potential pathway for 
 warm water access to the cavity beneath this ice shelf has been discovered
 \n\nRecent rapid progress in the techniques of remote autonomous observati
 on and satellite communication are improving our ability to observe this s
 ystem. Under the project called ROBOTICA within the Japanese Antarctic Exp
 edition six-year plan (2016-2023)\, we plan to utilize state-of-the-art un
 manned observations such as under-ice oceanographic\, seafloor and cryosph
 eric observations using ROV and geodetic network observations of ice/ocean
  motion and deformation using GPS/GNSS. In combination with conventional a
 nd robust observational techniques this will enable us to acquire detailed
  temporal and spatial datsets. Implementation of this project can provide 
 a big step forward for realization of the dream of a sustained observation
  system around Antarctica. As part of preliminary studies\, during the 201
 6-17 and 17-18 seasons we targeted ice ocean interactions in Lutzow-holm B
 ay in front of Shirase Glacier.\n\n\n\n*Strong ice-ocean interaction at Sh
 irase Glacier Tongue\, East Antarctica*\n\nDaisuke Hirano (Institute of Lo
 w Temperature Science)\n\nShirase Glacier Tongue (SGT) is a thick floating
  slab of ice that forms where the glacier flows down onto the ocean surfac
 e at the southern closed-section of Lützow-Holm Bay (LH Bay) off Enderby 
 Land\, East Antarctica. Compared with other major ice shelves/tongues arou
 nd Antarctica\, SGT is small in area but\, estimated at ~7 m per year\, it
 s basal melt rate is relatively high (Rignot et al.\, 2013)\, presumably a
 s a result of the presence of warm deep water. LH Bay is usually covered b
 y heavy sea ice\, even during the summer\, and so hydrographic observation
 s are extremely limited. To explore in detail the SGT-ocean interaction\, 
 summer comprehensive hydrographic observations in LH Bay were conducted du
 ring JARE58th in 2017 under the project called ROBOTICA.\nLH Bay has a dee
 p glacial trough in its center\, connecting the shelf break to SGT. Cold\,
  fresh\, and oxygen-rich Winter Water (WW: remnant of winter mixed layer) 
 overlies warm\, saline\, and oxygen-poor modified Circumpolar Deep Water (
 mCDW) along the trough. This indicates mCDW inflow beneath the SGT\, with 
 the inflowing mCDW temperature exceeding the in-situ freezing point by mor
 e than 2.7oC. In the surface/sub-surface layers\, the water becomes warmer
 \, with lower oxygen content toward the ice front. In d18O-salinity space\
 , this anomalous warm and oxygen poor layer at the ice front is distribute
 d along the line connecting mCDW with glacier end-members\, with glacial m
 elt water fraction estimated to be 0.5-1.7%. In addition\, the anomalous l
 ayer contains relatively high mCDW fraction even at surface/sub-surface la
 yers\, indicating the glacial melt water outflow beneath the SGT as a mixt
 ure with mCDW.\nThe observational results suggest a 3-dimensional circulat
 ion\, associated with SGT-ocean interaction (i.e.\, basal melting of SGT b
 y mCDW)\, that comprises: (1) warm mCDW flows southward at the deep layer 
 of glacial trough leading into the region beneath SGT\, (2) mCDW meets to 
 melt the base of SGT\, then a mixture of glacial melt water and mCDW is tr
 ansported upward as a buoyant melt plume\, and (3) the mixture exports nor
 thward at surface/sub-surface layers. As is the case with Totten Ice Shelf
 \, the SGT is characterized as a warm ice cavity\, atypical in East Antarc
 tica\, as a result of the absence of a coastal polynya as well as the pres
 ence of a deep trough serving as a pathway for mCDW toward the SGT in LH B
 ay. In this talk\, preliminary results from our recent observations off To
 tten Ice Shelf in 2018 are also presented.\n\n\n\n\n\n\n\n
LOCATION:British Antarctic Survey\, Innovation Centre\, Seminar Room 1
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