Bittig, Henry C.

Claustre, Herve

Fiedler, Björn

Johnson, Ken

Körtzinger, Arne

Poteau, Antoine

Schmechtig, Catherine

OceanRep

Autonomous sensors to quantify remineralization rates and the mesopelagic C fluxOCB summer workshop, Woods Hole, 2014Henry Bittig, Björn Fiedler, Arne Körtzinger (GEOMAR)Antoine Poteau, Catherine Schmechtig, Hervé Claustre (OAO–LOV)Ken Johnson (MBARI)• Chemical approach• Optical approachBittig et al. – OCB summer workshop, WHOI, 22 July 2014Remineralization & C FluxBriggs et al. (2011)• Central Labrador Sea (April – December 2005)• Boundary current (July – November 2006)• Deeply mixed water column after deep convection (vertically homogenized)• AADI optode 3830 calibrated against deployment CTD-O2 castEvolution of Tracer vs. Time → Respiration SignalBittig et al. – OCB summer workshop, WHOI, 22 July 2014Chemical Approach: General ConceptShowcase 1: Labrador Sea Argo-O2after C. Kihm, PhD thesis• O2 utilization along isopycnals• Assumed O2:C ratio (e.g., –1.34:1, Körtzinger et al., 2001)• fit to (differentiated) Martin curve• Integration of C respir. rate → C flux• b exponent higher using OUR than other techniques (Martz et al. 2008)Respiration Signal → C FluxBittig et al. – OCB summer workshop, WHOI, 22 July 2014Chemical Approach: General ConceptShowcase 1: Labrador Sea Argo-O2after C. Kihm, PhD thesisAvailable Sensors• Oxygen O2 sensors most mature, air sea gas exchange• Nitrogen ISUS/SUNA nitrate sensor• Carbon pH, pCO2, indirectly: local AT – S relationshipBittig et al. – OCB summer workshop, WHOI, 22 July 2014Chemical Approach: UtilityAanderaa (AADI)Optode 4330Sea-BirdOptode SBE 63Satlantic SUNA V2MBARI/Satlantic ISUS V3MBARI Deep-Sea DuraFETCONTROSHydroCAvailable Sensors• Oxygen O2 sensors most mature, air sea gas exchange• Nitrogen ISUS/SUNA nitrate sensor• Carbon pH, pCO2, indirectly: local AT – S relationship• Give only net biological signal → sum of production & respiration • Affected by biology and ocean physics (advection, mixing, entrainment) !• Seasonal reset (deep mixing)• „Simple“ hydrographic settingBittig et al. – OCB summer workshop, WHOI, 22 July 2014Chemical Approach: UtilityCaveatRequirement: separate Ocean Physics• Bio-Argo Floats (MBARI/UW) @ 31°40’ N / 064°10’ W (BATS)1  Convective overturn homogenizes water column2  Seasonal net O2 increase (SOM)3  Seasonal net O2 decrease← Productive zone← Respiration zoneBittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 2a: Temporal AspectNorth Atlantic Subtropical Gyre1111112 2 23 33Johnson & Riser (2014), submitted.• Bio-Argo Floats (MBARI/UW) @ 31°40’ N / 064°10’ W (BATS)• Quantify both production & respirationBittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 2a: Temporal AspectNorth Atlantic Subtropical GyreOxygen (μM)200220240260BOxygen (μM)200220240 D2010 2011 2012 2013Oxygen (μM)200220240 F40 – 45 m 105 – 115 m 26.4 kg m-3 (~200 m)← Productive zone← Respiration zone← Respiration zone(1D model incl. gas exchange)O2-basedJohnson & Riser (2014), submitted.• Bio-Argo Floats (remOcean) @ 20° N / 040° W• Shallower mixing, deeper nitracline/productive zone1  Convective overturn2  Seasonal net O2 increase (SOM)No seasonal net O2 decreaseBittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 2b: Temporal AspectNorth Atlantic Subtropical Gyre1 1 1 12 2 ← Productive zone← Respiration zone“steady-state” biological respirationvs.physical diffusion/mixing• Bio-Argo Floats (remOcean) @ 20° N / 040° W• Shallower mixing, deeper nitracline/productive zone• Ocean physics superimposed to biological signal (continuously mixed)Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 2b: Temporal AspectNorth Atlantic Subtropical Gyre← Productive zone← Respiration zone !~70 m 26.0 kg m-3 (~140 m)mesoscale• Bio-Argo float (WMO ID 6900632; O2, cp) trapped inside Cyclonic Eddy• Isolated water body → simplified ocean physicsBittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 3: Spatial AspectCyclonic Eddy (CE) off MauritaniaFiedler, unpublished.CEBittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 3: Spatial AspectCyclonic Eddy (CE) off MauritaniaCoastal Open OceanCyclonic EddyNorth of CV FrontMauritanianUpwellingDepth (m)Depth (m)Karstensen et al., in prep.Export production:20 mmol C m-2 d-1lateralintrusion• Chemical approach• Optical approachBittig et al. – OCB summer workshop, WHOI, 22 July 2014Remineralization & C FluxBriggs et al. (2011)General Concept• Establish proxy for POC → Follow C directly• Beam attenuation cp(650)• Particle backscatter bbp(700)• No seasonal system required• SensitivityBittig et al. – OCB summer workshop, WHOI, 22 July 2014Optical ApproachAvailable SensorsRequirementsWET LabsC-RoverWET LabsECO triplet• Separate profile data into baseline & spikes (Briggs et al., 2011)• “Direct” POC observationBittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 1: Profile FocusTrace POC Export (NAB08 experiment)baselinespikesBriggs et al. (2011), Deep Sea Res. I, 58, 1031–1039.• Use mixed layer C inventory changes (Alkire et al., 2012):• TOC (POC & DOC) ~ POC proxy• Production ~ O2 budget / O2-NCP• Difference between production and POC accumulation (in mixed layer)= Export (out of mixed layer)Fsink = FNCP – dPOC/dt – dDOC/dtO2 bbp ./.Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 2: Mixed Layer FocusUse Budget Imbalance (NAB08 experiment)Alkire et al. (2012), Deep Sea Res. I, 64, 157–174.• Med Sea deep bloom → oligotrophic system• Particles settle on transmissiometer: „in-situ sediment trap“• Drift in cp ~ particle flux Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 3: Float Drift FocusSediment Accumulation during DriftPART 1 PART 2 PART 3Claustre et al., in prep.PART 3 PART 2PART 1• Med Sea deep bloom → oligotrophic system• Particles settle on transmissiometer: „in-situ sediment trap“• Drift in cp ~ particle flux Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 3: Float Drift FocusSediment Accumulation during DriftPART 1 PART 2 PART 3Claustre et al., in prep.PART 3 PART 2PART 1PART 1 PART 2PART 3PART 1 PART 2 PART 3• Med Sea deep bloom → oligotrophic system• Particles settle on transmissiometer: „in-situ sediment trap“• Drift in cp ~ particle flux PART 1 PART 2PART 3Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 3: Float Drift FocusSediment Accumulation during DriftClaustre et al., in prep.• Med Sea deep bloom → oligotrophic system• Particles settle on transmissiometer: „in-situ sediment trap“• Drift in cp ~ particle flux Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Showcase 3: Float Drift FocusSediment Accumulation during DriftPART 1 PART 2 PART 3Claustre et al., in prep.PART 1 PART 2 PART 3• Chemical approach• Optical approachBittig et al. – OCB summer workshop, WHOI, 22 July 2014TrendsBriggs et al. (2011)Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Trends: Extended Chemical Capabilities: Inorganic C FloatIridium & ARGOS TelemetryExternal Battery PackpCO2 Sensor [CONTROS HydroC]Oxygen Sensor [Optode]Temperature, Salinity, Pressure[CTD]• CO2-system sensors (pCO2, pH)• Potential to reduce uncertainty in stoichiometric ratios (→ C-overconsumption)• pCO2 nicely anticorrelated to O2Fiedler et al. (2013), J. Atmos. Oceanic Technol., 30, 112–126.• Technological potential for C:N:O Float:simultaneous C, N, and O measurements• e.g., MBARI @ HOT:• pre-SOCCOM:Bittig et al. – OCB summer workshop, WHOI, 22 July 2014Trends: Extended Chemical Capabilities: C:N:O FloatJohnson et al., http://www.mbari.org/chemsensor/floatviz.htm• e.g., lovbio floats (capable to carry heavy load of sensors)• Multitude of information from autonomous platformsBittig et al. – OCB summer workshop, WHOI, 22 July 2014Trends: Chemical & Optical Approaches combined• Chemistry: • sum of production & respiration• if physics can be separated• feasible with deep winter mixing / otherwise simplified system (CE)• Optics:• complementary approach• requires in-situ data for calibration• advent of new / more mature technology to extend capabilities• possibly smart way to separate physics in complex systems (modeling complement)Bittig et al. – OCB summer workshop, WHOI, 22 July 2014SummaryBriggs et al. (2011)

Autonomous sensors to quantify remineralization rates and the mesopelagic C flux

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