BIOMER1/4-V1 and BIOMER1/4-V2 (week average, from 04/01/15 to 04/07/15), GLOBCOLOUR 2014 and CLIM WOA 2005 (April average). Up to the bottom: Chlorophyll, Nitrate, Phosphate, Silicate, and Iron surface concentration F e S i P O 4 BIOMER1/4-V1 and BIOMER1/4-V2 (week average, from 04/01/15 to 04/07/15), GLOBCOLOUR 2014 and CLIM WOA 2005 (April average) of vertical longitudinal of nutrients along the Pacific Ocean (100° W) B I O M E R 1 / 4 - V 2 Integration of Biogeochemistry into the MERCATOR OCEAN global eddy resolving and forecasting system PSY4 F. Nivert, A. El Moussaoui, C. Perruche, C. Bricaud and J. Paul This work reports few results of some compartments designed to improve the future Mercator Ocean global biogeochemical forecasting system forced by PSY4 physics. A particular focus is first placed on the degradation tool which must conserve the mesoscale physical properties produced by PSY4 in order to improve their impact on the biogeochemical fields. At the beginning, a resolution of 1° was applied (BIOMER1, El Moussaoui et al. 2011). Then we increased the resolution of BIOMER to 1/4° using PSY3 1/4° physical forcing. We now plan to use a new physical forcing: PSY4 (1/12°) degraded to 1/4°. We needed to degrade the PSY4 physics because PISCES is currently running on 1/4° due to computer limits. In this context we have been performing two experiences to analyze the impact of the physical forcing on the biogeochemical model. Both experiences started from the same initial state and were carried out with PISCES forced by PSY3 (BIOMER1/4-V1) and by PSY4 Degraded (BIOMER1/4-V2). PISCES is a biogeochemical model simulating the marine biological productivity and describing the biogeochemical cycles of carbon and of the main nutrients (P, N, Si, Fe). It has currently 24 compartments with 5 modelled limiting nutrients (Nitrate, Ammonium, Phosphate, Silicate and Iron). In addition to the ecosystem model, PISCES also simulates 2 phytoplankton growths, 2 zooplanktons, 3 non-living compartments, carbon, and oxygen cycles. We first constructed degraded physics from PSY4. Active Tracers are averaged onto “squares” of three boxes longitudinally by three boxes latitudinally. We calculate degraded velocity fields by conserving the fluxes at the boundaries. Fluxes at the boundaries (velocity and thus tracer fluxes) and tracers quantities are conserved (Levy et al, 2012). We can observe that the degradation is efficient and conserves the main structures. We also observe that PSY3 and PSY4 physics are different, particularly for the vertical velocity which could affect the biogeochemical model. Day average (04/01/15) of vertical longitudinal of salinity (psu) in the Atlantic Ocean along the 26° W and vertical longitudinal of vertical velocity (m.day -1 ) in the Pacific Ocean along the 168.8° W. Representation of the physical and biogeochemical parameters of an area in the North-eastern part of the Atlantic Ocean (55°N to 60°N; 27°W to 30°W) for PSY3, PSY4 deg, BIOMER1/4-V1 and BIOMER1/4- V2 from November 2014 to May 2015. On the Equatorial band we observe that the BIOMER1/4-V2 simulation is largely closer to observations and CLIM simulation than BIOMER1/4-V1 for chlorophyll and nutrients. It’s even more obvious for the silicate surface concentration. The oligotrophic subtropical gyres are better reproduced in BIOMER1/4-V2 than in BIOMER1/4-V1. At the Equator and in the Austral Ocean, BIOMER1/4-V2 is closer to observations than BIOMER1/4-V1. The physical forcing (Lellouche et al, 2013) is more realistic in the BIOMER1/4-V2 simulation. In the North Atlantic area, the physical parameters of PSY3 and PSY4 deg are close, even if PSY4 deg provides a deeper mixed layer than PSY3. At regional scale, nutrients and chlorophyll surface concentration are higher in BIOMER1/4-V2 than BIOMER1/4-V1, especially during the bloom period. BIOMER1/4-V2 is also closer to observations. We usually observe a bloom in March (Mercator Ocean QUID, 2014), but here, we observe it at the end of February. The increase of the chlorophyll surface concentration during the last weeks of April may refer to the observed high temperature along the same period. PISCES: an advanced Biogeochemical model Degradation approach Conclusion BIOMER1/4-V1 GLOBCOLOUR BIOMER1/4-V2 Nitrate Phosphate Silicate Iron B I O M E R 1 / 4 - V 1 C L I M Contact: [email protected] C H L N O 3 PSY4 (1/12°) PSY4 deg (1/4°) PSY3 (1/4°) CLIM WOA 2005 Introduction BIOMER1/4-V1 BIOMER1/4-V2 PISCES model (Aumont et al, 2006) Results Aumont O and Bopp L, 2006, Globalizing results from ocean in situ iron fertilization studies, Global Biogeochemical Cycles, Vol. 20 El Moussaoui A et al. 2011, Integration of biogeochemistry into Mercator Ocean systems. Mercator Ocean newsletter 40:3 Levy et al. 2012, Grid degradation of submesoscale resolving ocean models: Benefits for offline passive tracer transport Lellouche et al. 2013, Evaluation of global monitoring and forecasting systems at Mercator Ocean, Ocean Sci., 9, 57-81 Mercator Ocean QUID, 2014, Quality Information Document – Global Analysis Forecast BIO 001_014