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EPOCA WP9: From process studies to ecosystem models. Participants involved: LOV, UiB, IFM-GEOMAR, GKSS, KNAW, UGOT, UNIVBRIS (a.o. J.-P. Gattuso, R. Bellerby, M. Schartau, J. Middelburg, A. Oschlies). Motivation: Current parameterisations of calcification.
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EPOCA WP9:From process studies to ecosystem models Participants involved: LOV, UiB, IFM-GEOMAR, GKSS, KNAW, UGOT, UNIVBRIS (a.o. J.-P. Gattuso, R. Bellerby, M. Schartau, J. Middelburg, A. Oschlies)
Motivation: Current parameterisations of calcification • PIC prod. ~ Prim.Prod. (of some PFT, possibly modulated by ) • PIC prod. ~ Detritus prod. • Essentially all current parameterisations employ Eppley’s temperature dependence.
Calcification & temperature(according to current models) low T high T low PP, slow microbial loop high PP, fast microbial loop low PIC prod. large PIC prod. low PIC export large PIC export irrespective of nutrient supply, export production, grazing…
Example: calcification & temperature UVic model: temperature dependence helps to get latitudinal distribution of rain ratio “right”: (Schmittner et al., 2008)
Example: calcification & temperature Does this give meaningful results in global-warming runs? PICprod PICprod Increase in PIC production closely linked to temperature-driven increase in Prim.Prod. PP EP (Schmittner et al., 2008)
General problem with empirical models • May work well under empirical conditions • No guarantee that this will continue under new environmental conditions • higher temperatures • higher CO2 • … Aim for mechanistic models
Objectives • Integration & Synthesis Efficient knowledge transfer experiments models Feedback to efficiently reduce uncertainty
Approach • Analysis experiments models Coherent data base (organisms, ecosystems) Meta-analysis (model assumptions, parameterisations) T9.1 T9.3 Meta-analysis (mesocosm, microcosm) T9.2
Approach • Modelling of micro- and mesocosm experiments • Model improvement: balance complexity, performance, portability • Assessment and recommendations for incorporation into global-scale models experiments models T9.4 Data-assimilative parameter estimation T9.5 T9.6
Deliverables • D9.1: advice/guidance: data storage/documentation/protocol (month 2, R, PU) • D9.2: structured data base (month 12, R, PP) • D9.3: Mesocosm meta-analysis, guidance to future experiments (month 12, R, PP) • D9.4: Identification of physiological/ecological processes that contribute most to uncertainties in ecosystem models (month 24, R, PU) • D9.5: Improved model formulation for pH-sensitive processes -> Earth system models (month 40, R, PU) • D9.6: Uncertainty analysis (month 48, R, PU)
Example 1Calibration by chemostat/turbidostat data Chain model of N, P, light colimitation (Pahlow & Oschlies, subm.)
Example 2Calibration by mesocosm data (Schartau et al., 2007)
Example 3: Transfer to global models 50% increase in suboxic volume (<5mmol/m3) 350 ppm 700 ppm 1050 ppm (Riebesell et al., 2007) (Oschlies et al., subm.)
Questions from model study & feedback to experimentalists • Temperature effects vs. pH effects? • Observational evidence of pCO2-sensitive C:N ratios in the ocean? • What is the mechanism for export of excess C?