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Status of O 2 sensors and the O 2 White Paper

Status of O 2 sensors and the O 2 White Paper. Stephen C. Riser, University of Washington. There are presently more than 100 floats with O 2 sensors, and the number is growing. Update to the Friends of Oxygen White Paper.

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Status of O 2 sensors and the O 2 White Paper

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  1. Status of O2 sensors and the O2 White Paper Stephen C. Riser, University of Washington There are presently more than 100 floats with O2 sensors, and the number is growing.

  2. Update to the Friends of Oxygen White Paper • Sensors. SeaBird has continued to develop its IDO sensor and has attempted to improve the drift characteristics. They now claim a drift of 1 micromol/kg/year, an almost undetectable quantity. Experience has shown that with present SBE IDO sensors this is achieved in about 50% of the cases. In the other 50% of IDO sensors the drift is larger (sometimes much larger); overall, SBE seems to be making progress on this problem. SBE also has begun using a more efficient CTD pump, so that the use of an IDO sensor with a SBE 41CP (allowing high resolution O2 sampling) requires essentially no extra energy. Aanderaa is continuing its development of the Optode, with improved response time, lower power electronics, and better calibration. These improvements are supposedly going to be implemented this year. • New field work using large numbers of profiling floats equipped with O2 sensors. (a) Scientists from the EU have proposed a program known as OXYWATCH to examine the low-O2 region off Mauritania in the eastern tropical Atlantic. The program has proposed deploying 50-75 floats with Optode sensors to be used in conjunction with gliders and shipboard measurements to map the low O2 plume in the region. (b) There are discussions within a small US group to propose (8/08) to purchase floats with O2 sensors (as well as to augment Argo floats with O2 sensors) to study the oceanic uptake of O2 and CO2 in the subarctic N. Pacific. • QC of O2 data. Work is beginning but will be difficult.

  3. EU OXYWATCH (floats, gliders, CTD, meteorology, etc.)

  4. Attempts to QC dissolved O2 data from floats:

  5.  4 micromol/kg  9 micromol/kg Time series of O2 from UW float 0894 (WMO 4900093) at the HOT site compared to shipboard Winkler O2 at the sea surface and 2000 m.

  6. UW float 0894 (WMO 3900348) showed a deep-water offset but little drift over a period of 3 years. The float was equipped with a SeaBird IDO O2 sensor. [Results from Annie Wong]

  7. UW float 0035 (WMO 5900952) showed a deep-water offset but little drift over a period of 4 years. The float was equipped with an Aanderaa Optode sensor. [problem: poor O2 climatology in most places]

  8. Scientific results using O2 sensors on floats: Dissolved O2 vs. time and depth for UW float 0894 (WMO 4900093) near the HOT site. The O2 is lowest early in the year when a deep mixed layer is present and then increases below the surface as the water column restratifies in spring. Phytoplankton blooms can be seen in the upper 100 m during autumn, followed by reforming of the mixed layer. [S. Riser and K. Johnson, Nature, 1/17/08]

  9. N. Pacific, HOT S. Pacific, near Tahiti The float O2 data provide a very cost-effective method for estimating new biological production. This calculation could be made from shipboard or moored observations but is prohibitively expensive. [S. Riser and K. Johnson, Nature, 1/17/08]

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