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

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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)

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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

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Contact: florian.nivert@mercator-ocean.fr

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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