PMEL Publications Abstract

FY 2010

Evidence of O₂ consumption in underway seawater lines: Implications for air-sea O₂ and CO₂ fluxes

Juranek, L.W., R. Hamme, J. Kaiser, R. Wanninkhof, and P.D. Quay

Geophys. Res. Lett., 37(1), doi: 10.1029/2009GL040423 (2010)

We observed O2 deficits of 0.5 to 2.0% (1 to 4 μmol/kg) in the underway seawater lines of three different ships. Deficits in O2/Ar and isotopic enrichments in dissolved O2 observed in underway seawater lines indicate a respiratory removal process. A 1% respiratory bias in underway lines would lead to a 2.5–5 μatm (2.5–5 μbar) enhancement in surface water pCO2. If an underway pCO2 bias of this magnitude affected all measurements, the global oceanic carbon uptake based on pCO2 climatologies would be 0.5–0.8 Pg/yr higher than the present estimate of 1.6 Pg/yr. Treatment of underway lines with bleach for several hours and thorough flushing appeared to minimize O2 loss. Given the increasing interest in underway seawater measurements for the determination of surface CO2 and O2 fluxes, respiration in underway seawater lines must be identified and eliminated on all observing ships to ensure unbiased data.

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