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ARGO FLOATS IN SEASONAL ANTARCTIC ICE

ARGO FLOATS IN SEASONAL ANTARCTIC ICE. Stephen C. Riser, University of Washington. Float deployment from the Aurora Australis in October, 2007. CHARACTERISTICS OF UW ICE FLOATS. (1) A set of ice months are defined for each float (ie, 1,2,3 = January, February, March).

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ARGO FLOATS IN SEASONAL ANTARCTIC ICE

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  1. ARGO FLOATS IN SEASONAL ANTARCTIC ICE Stephen C. Riser, University of Washington

  2. Float deployment from the Aurora Australis in October, 2007

  3. CHARACTERISTICS OF UW ICE FLOATS (1) A set of ice months are defined for each float (ie, 1,2,3 = January, February, March). (2) The ice detection algorithm [(3)-(6)] is only active during the months in this set (the ice months can be changed by command to Iridium floats). (3) When the ice detection algorithm is active, the float estimates the median temperature in real-time as it ascends between 80 and 30 m. (4) If the computed median temperature is below a preset temperature, Ti , it is assumed that ice is present (usually Ti is chosen to be near the freezing point of surface water). If the threshold condition is true, then the buoyancy pump is immediately turned off and the float begins to retract its piston. This usually results in the float beginning its descent at a depth of 10-20 m. At this point, Iridium floats store the measured profile for later transmission. Argos floats do not save the profile. Ti can be changed by command to Iridium floats. (5) If the computed median temperature is not below Ti, then the float continues to ascend to the sea surface as with a normal profile, and the profile data are transmitted. For Iridium floats, if the float cannot find the surface then it stores the profile and begins to descend. (6) For Iridium floats, when (4) is negative after some period of being positive, the float will transmit all stored profiles when it reaches the sea surface. 90% still operational after 1 winter

  4. WMO 2900017 9/16/07  3/10/08

  5. WMO 2900017 (UW 5249)  Profile 7, 10/28/07

  6. WMO 2900017 (UW 5249)  Profile 26, 3/10/08

  7. WMO 2900017 (UW 5249) T/S T/O2

  8. Profiles from WMO 2900118 (UW 5250) Profile 1, 10/7/07 Profile 17, 1/27/08

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