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SUMMARY:Antarctic Coastal Polynyas: Do Measurements of Winter Processes gi
 ve clues to modeling Improvements and better model fidelity? - Stephen Ack
 ley (University of Texas at San Antonio)
DTSTART:20171005T123000Z
DTEND:20171005T131500Z
UID:TALK84161@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:The PIPERS cruise to the Terra Nova Bay (TNB) and Ross Ice She
 lf (RIS) polynyas during April-June 2017 focused on joint measurements of 
 air-ice-ocean wave interaction in these polynyas.  In Terra Nova Bay\, mea
 surements were taken during intense katabatic wind events with sustained w
 inds over 35 meters per second and air temperatures of -15C or below.  Des
 pite a relatively short fetch\, intense wave fields with wave amplitudes o
 f over 2m and 7-9 sec periods built and large amounts of frazil ice crysta
 ls grew.  The frazil ice gathered initially into short plumes that eventua
 lly were added laterally to create longer\, wide streaks.   The wave field
  within the wider streaks was dampened and enhanced the development of pan
 cake ice.  Eventually\, the open water areas sealed off between the streak
 s\, developing a uniform pancake ice cover of 100 percent concentration.  
 The pancakes continued to grow in diameter and thickness\, further attenua
 ting  the wave field and the pancake ice growt h then ceased.  While the w
 aves died off however\, katabatic wind velocities were sustained and resul
 ted in a wide area of concentrated\, rafted\, pancake ice that was rapidly
  advected downstream until the end of the katabatic event.  The equilibriu
 m thickness of the ice was typically 30 to 40 cm in the pancake ice.  High
  resolution TerraSar-X radar satellite imagery showed the length of the ic
 e area produced in one single event extended over 300km or ten times the l
 ength of the open water area during the polynya event.    The TNB polynya 
 is therefore an &ldquo\;ice factory&rdquo\; where frazil ice is manufactur
 ed into pancake ice floes that are then pushed out of the assembly line an
 d advected\, rafted and occasionally piled up into &ldquo\;dragon skin&rdq
 uo\; ice\, until  the katabatic wind dies off at the coastal source.
LOCATION:Seminar Room 1\, Newton Institute
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