Arne Körtzinger IFM-GEOMAR Leibniz Institute of Marine Sciences Marine Biogeochemistry Kiel, Germany Oceanic oxygen — the oceanographer’s canary bird of climate change WP 10

Joos et al., 2003 Joos, F., G.-K. Plattner, T.F. Stocker, A. Körtzinger, and D.W.R. Wallace (2003). EOS 84(21),

Time series of AOU on isopycnals 26.7, 26.8, 26.9, 27.0, and 27.2 (bottom to top) in the western subarctic Pacific ( ). Annual averaged increase rate of AOU (µmol kg -1 yr -1 ) during the period 1985 to 1999 along 165°E (left) and 47°N (right) lines in the North Pacific. AOU increase: ~0.9 ± 0.5 µmol kg -1 yr -1 AOU increase: up to +5 µmol kg -1 yr -1 Oxygen Trends: What the observations tell... Ono et al., GRL 28, Watanabe et al., GRL 28, 2001.

Kim et al., MTS Journal, 33, ~25 µmol L -1 Oxygen Trends: What the observations tell...

Courtesy of Nicolas Gruber

Oxygen Trends: What the models tell... Oxygen – the oceanographer’s canary bird of climate change

Oxygen Trends: What the models tell... Zonally averaged O 2 changes in the Atlantic Ocean from a transient simulation with the NCAR coupled biogeochemical-climate model (SRES A2 scenario). Joos et al., University of Bern, Physics Institute, Climate and Environmental Physics

“Mirror Image Approach“ – a flawless method to track anthropogenic CO 2 ? Separation of terrestrial and oceanic sinks for anthropogenic CO 2 Oceanic oxygen can improve atmospheric O 2 /N 2 constraint on ocean/land partitioning of anthropogenic CO 2 Complications: O 2 outgassing Local APO signals

O 2 and CO 2 fluxes in upwelling regions – imprint on APO

CO 2 flux [mmol m -2 d -1 ] O 2 flux [mmol m -2 d -1 ] O 2 and CO 2 fluxes in upwelling regions – imprint on APO

(y = x ) slope for pure gas exchange slope for Redfieldian net production observed slope O 2 and CO 2 fluxes in upwelling regions – imprint on APO

The Kiel oxygen float project (since 2002)

The luminophore (organic Pt complex) is immobilized in a sensing foil which is excited with blue light (505 nm) and produces a red luminescence. The intensity and lifetime of the emission depend on the oxygen concentration in the foil and hence the ambient seawater. The dynamic quenching effect can be used to measure oxygen.   = Luminescence lifetime without O 2  = Luminescence lifetime with O 2 The oxygen optode – a major step forward

Körtzinger et al. (2004). The ocean takes a deep breath. Science 306, The Labrador Sea showcase: The ocean‘s breathing quasi-stationary float

The Labrador Sea showcase: The ocean‘s breathing quasi-stationary float Peak convection O 2 inventory builds up with progressing convection Deep O 2 inventory sealed off by low-salinity cap Decay of O 2 inventory through lateral export and respiration

An example from our Weddell Sea oxygen float study 68°S, 0°W APEX float with ice detection alogorithm, O 2 option (optode), and RAFOS option Progressive cooling  freezing O 2 disequilibrium

An example from our Weddell Sea oxygen float study 62°S, 40°W Increasing O 2 saturation Progressive warming APEX float with ice detection alogorithm, O 2 option (optode), and RAFOS option Why is there little anthropogenic CO 2 in the Antarctic Bottom Water? Poisson, A; Chen, C.-T. A. Deep-Sea Research, 34,

Both sensors in good agreement  O 2 = 1.6 µmol/L (p > 800 dbar) Körtzinger et al. (2005). J. Atm. Ocean. Techn. 22, Accuracy: Both sensors off by 17.5 ± 2.5 µmol/L Sensor-to-sensor agreement / Accuracy of sensor batch (optode)

Körtzinger et al. (2005). High-quality oxygen measurements from profiling floats: A promising new technique. J. Atm. Ocean. Techn. 22, Tengberg et al. (2006). Evaluation of a life time based optode to measure oxygen in aquatic systems. Limnol. Oceanogr. Methods 4, Drift check possible through air measurements High long-term stability O 2 = ± 0.7 µmol/L Drift check / Long-term stability

CarboOcean WP10 PROVOR-DOPROVOR-CarboOcean Oxygen sensor PIC sensor March 2007: Delivery of prototype 2 floats from MARTEC company Spring 2007: Testing of floats (vibration, tank, basin) at IFREMER Spring/summer 2007: Sea trials of floats November 2006: Delivery of 2 prototype floats from MARTEC company Nov./Dec. 2006: Testing of floats (vibration, tank, basin) at IFREMER February 2007: Deployment during R/V Poseidon Cruise 348 by IFM-GEOMAR north of the Cape Verde archipelago

Active floats with DO sensor: 65 (measuring profiles from 25 Aug. to Sep. 24) Oxygen floats that are out there …

WHY adding oxygen to ARGO? Objective: To determine seasonal to decadal-time changes in sub-surface oceanic oxygen storage and transport In order to Detect changes in ocean biogeochemistry (Miner's canary bird of climate change) Improve atmospheric O 2 /N 2 constraint on ocean/land partitioning of anthropogenic CO 2 Determine seasonal to interannual net remineralization rates as a proxy for export production Help interpretation of variations in water mass ventilation rates Provide data (initial conditions, evaluation) for ocean bgc models Help interpretation of sparse data from repeat hydrographic surveys