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WWW.BJERKNES.UIB.NO Modelling the global marine carbon cycle 'end-to-end' Christoph Heinze University of Bergen, Norway Geophysical Institute & Bjerknes Centre for Climate Research Uni-Research Bjerknes AS Outline: 1 Some principles about marine carbon cycling 2 The oceanic anthropogenic-carbon uptake problem is a kinetic problem 3 Models of global ocean biogeochemistry 4 Some recent findings… This is a truncated version of the presenation as given at Brussels on Oct. 4. A more complete version of the talk can be requested for private use from: [email protected] 1 Some principles about marine carbon cycling The ocean is a large carbon reservoir. Small changes in it can induce considerable variations in the atmospheric CO2 content. In the ocean CO2 is highly reactive due to the ability of seawater to disscociate weak acids: 1. Dissociation step: CO2 + H2O HCO3- + H+ 2. Dissociation step: CO32- + H+ Sea water – buffer system! CO2 + H2O + CO32- (1+x)HCO3- + (1-x)CO32- + (1-x)H+ HCO3- CO2 : HCO3- : CO321: 100 : 10 “ocean levers” to change atmospheric CO2: IPCC AR4, ch. 7, after Heinze et al. (1991) Major difficulty: The pristine inorganic carbon system in the ocean has not been measured. “Anthropogenic carbon” (the excess over the natural carbon) has to be reconstructed from present day observations using transfer functions and assumptions. We can illustrate this problem in a model framework, where the “preindustrial” carbon system is known. TCO2 from a model (HAMOOC4) Pre-industrial 1751 Atlantic Ocean Today 2004 TCO2 from a model (HAMOOC4) Pre-industrial 1751 Pacific Ocean Today 2004 TCO2 from a model (HAMOOC4) Pre-industrial 1990 Atlantic Ocean Today 2004 TCO2 from a model (HAMOOC4) Pre-industrial 1990 Pacific Ocean Today 2004 2 The oceanic anthropogenic-carbon uptake problem is a kinetic problem The ocean has the potential to take up large amounts of human produced CO2 but needs time for this. What about biology? 3 Models of global ocean biogeochemistry Ocean models are a key tool for understanding and predicting natural and human induced changes of the carbon cycle. Atlantic Pacific Model HAMOCC2s Observations GEOSECS HAMOCC2s model BSi (opal) CaCO3 org. C clay avg. sediment (model) Atl Pac [CO32-] (model) Heinze, Hamocc2 model BOGCM with NPZD ecosystem model An isopycnic ocean carbon cycle model K. M. Assmann, M. Bentsen, J. Segschneider, and C. Heinze Geosci. Model Dev., 3, 143-167, 2010 BOGCM with NPZD ecosystem model An isopycnic ocean carbon cycle model K. M. Assmann, M. Bentsen, J. Segschneider, and C. Heinze Geosci. Model Dev., 3, 143-167, 2010 Norwegian Earth System Model “old” Will include land use changes “new” NorESM Tjiputra, Assmann, Bentsen, Bethke, Otterå, Sturm, and Heinze, 2010, GMD Will include improved N cycle & river loads 4 Some recent findings… …past ocean, modern ocean, and future challenges Test of parameter changes scaled with EPICA Dome C ice core ∆D signal All parameter changes (low rain ratio, no Redfield ratio change yet). Example, fit currently underway: = observation pCO2 = model Vostok ice core, Antarctica, Barnola et al., 1987, Nature Sediment Core: RC24-07 Verardo&McIntyre Paleoceanography 1994 Lat: -1.35 S Lon: -11.917 W Bottom depth: 3899 m Region: Central eq. Atlantic CaCO3 vs. age vs. depth in core = observation Paleo tracer change Time yr BP Single sequential fits of model to observations, time slice by time slice, time series of maximum likelihood solutions for parameter changes valid for each of the single time slices = observation Paleo tracer change Time yr BP Single sequential fits of model to observations, time slice by time slice, time series of maximum likelihood solutions for parameter changes valid for each of the single time slices = observation Paleo tracer change Continuous fit through entire climatic cycle, Time yr BP optimal T and pCO2 dependent parameters of physical/chemical/biological functional relationship between C cycle (ocean acidification and others) and climate change; less free parameters and system has higher chance to become overdetermined = observation Paleo tracer change one sweep, no sequential time slice consideration Continuous fit through entire climatic cycle, Time yr BP optimal T and pCO2 dependent parameters of physical/chemical/biological functional relationship between C cycle (ocean acidification and others) and climate change; less free parameters and system has higher chance to become overdetermined Ocean internal carbon re-distribution Atmospheric CO2 Upper ocean CO2 intermediate w. CO2 Deep ocean CO2 Eemian 130 kyrBP Last glacial maximum 20 kyrBP Preindustrial 1750 Low CO2 High Ocean internal carbon re-distribution Large external carbon input into ocean Atmospheric CO2 Upper ocean CO2 intermediate w. CO2 Deep ocean CO2 Eemian 130 kyrBP Last glacial maximum 20 kyrBP Preindustrial 1750 Today Low CO2 High Ocean internal carbon re-distribution Large external carbon input into ocean Atmospheric CO2 Upper ocean CO2 intermediate w. CO2 Deep ocean CO2 Eemian 130 kyrBP Last glacial maximum 20 kyrBP Preindustrial 1750 Today Year 20502150 Low CO2 High 3-D is important for air-sea CO2 fluxes !!! Southern Ocean key in anthropogenic CO2 uptake in future Study with Bergen Climate Model (predecessor of NorESM model) Ocean: MICOM (isopycnic) & HAMOCC Uptake Storage Anthropogenic carbon dynamics in the changing ocean J. F. Tjiputra, K. Assmann, and C. Heinze Ocean Sci., 6, 605-614, 2010 = meridional transport into region = uptake form atmosphere Anthropogenic carbon dynamics in the changing ocean J. F. Tjiputra, K. Assmann, and C. Heinze Ocean Sci., 6, 605-614, 2010 C cycle perturbation amplitude 1. Climate Earth system models must reproduce natural system changes and should be calibrated through the paleoclimate record. C cycle perturbation time scale Last glacial cycle, Holocene Anthropocene 1750 - ? C cycle perturbation amplitude 1. Climate Earth system models must reproduce natural system changes and should be calibrated through the paleoclimate record. C cycle perturbation time scale Last glacial cycle, Holocene 2. The “glacial” parameter calibration will help to improve the model skill for long-term and low amplitude changes. Anthropocene 1750 - ? 3. In addition for predicting strong short-term changes are required: C cycle perturbation amplitude (a) Process understanding (qualitative, quantitative) (b) Sustained long-term observations including legacy data sets from NOW. (c) Efficient high resolution Earth system models. (d) Optimisation of coupled models. (e) Development of early warning indicators. 1. Climate Earth system models must reproduce natural system changes and should be calibrated through the paleoclimate record. C cycle perturbation time scale Last glacial cycle, Holocene 2. The “glacial” parameter calibration will help to improve the model skill for long-term and low amplitude changes. Anthropocene 1750 - ? CHANGING CLIMATE International coordination, GEO, GEOSS, GMES Guard rails for policies, mitigation FP6 CARBOOCEAN integrated project Core Theme 2 - Observing systems (Towards ICOS) Core Theme 1 - Key processes, feedbacks, future scenarios, vulnerabilities Global and regional synthesis and synergies with international projects Core Theme 3 - Data model integration IPCC assessments 5 and 6 ICOS global & regional monitoring & prediction systems FP8 Emerging knowledge gaps to be closed Securing our sustainable future Projects on ocean acidification, impacts, ecosystems