Are the older ARGO-Floats more vulnerable to Fouling and Associated Salinity drift compared to that of later deployments?
Abstract
Continued existence of ARGO floats for years together (4 year) make the conductivity cell more vulnerable to fouling and associated drift in salinity measurements In this paper, the authors address this issue by making use of floats deployed in different years Floats deployed in the East/Japan Sea and in the Indian Ocean are examined to find out float-to-float match-ups in such a way that an older float pops up simultaneously with a newer deployment (with tolerable space-time difference) A time difference of less than five days and space difference of less than 100 Km are considered for the match-up data sets For analysis of the salinity drift, observations of the floats from deepest water masses have been used From the float match-ups from the East/Japan Sea and the Indian Ocean, it is found that there is a systematic drift in the older float compared to later deployments All drift results, consistently show negative bias indicating the typical nature of drift from fouled sensors However, the drift is much less than the 0.01 PSU, the specified accuracy of ARGO program.
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