Tackling Oxygen Optode Drift: Near-Surface and In-Air Oxygen Optode Measurements on a Float Provide an Accurate in Situ Reference.

Bittig, Henry C. and Körtzinger, Arne (2015) Tackling Oxygen Optode Drift: Near-Surface and In-Air Oxygen Optode Measurements on a Float Provide an Accurate in Situ Reference. Open Access Journal of Atmospheric and Oceanic Technology, 32 (8). pp. 1536-1543. DOI 10.1175/JTECH-D-14-00162.1.

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Abstract

A yet unexplained drift of (some) oxygen optodes during storage/transport and thus significant deviations from factory/laboratory calibrations have been a major handicap for autonomous oxygen observations. Optode drift appears to be systematic and is predominantly a slope effect due to reduced oxygen sensitivity. A small contribution comes from a reduced luminophore lifetime, which causes a small positive offset. A reliable in situ reference is essential to correct such a drift. Traditionally, this called for a ship-based reference cast, which poses some challenges for opportunistic float deployments. This study presents an easily implemented alternative using near-surface/in-air measurements of an Aanderaa optode on a 10-cm stalk and compares it to the more traditional approaches (factory, laboratory, and in situ deployment calibration). In-air samples show a systematic bias depending on the water saturation, which is likely caused by occasional submersions of the standard-height stalk optode. Linear regression of measured in-air supersaturation against in-water supersaturation (using ancillary meteorological data to define the saturation level) robustly removes this bias and thus provides a precise (0.2%) and accurate (1%) in situ correction that is available throughout the entire instrument’s lifetime.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/312642
Additional Information: WOS:000359565500009
Keywords: Atmosphere-ocean interaction, Chemistry, oceanic, In situ oceanic observations, Profilers, oceanic, Quality assurance/control
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > SFB 754 > A4
OceanRep > The Future Ocean - Cluster of Excellence > FO-R10
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 754
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/JTECH-D-14-00162.1
ISSN: 0739-0572
Projects: E-AIMS, remOcean, O2-Floats, SFB754, Future Ocean
Date Deposited: 18 Aug 2015 08:48
Last Modified: 12 Apr 2017 09:12
URI: http://oceanrep.geomar.de/id/eprint/29393

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