MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
1.7 SOCA3D POC/b, /Chla 
Since July 2020, a new biogeochemical multiyear product 
have been providing global gridded fields of Particulate 
Organic Carbon (POC) and Chlorophyll-a concentration 
(Chla) at depth, two biogeochemical variables still currently 
critically under sampled at all scales. The method relies 
first on a neural network method called SOCA (Satellite 
Ocean-Color merged with Argo) which is inherited from 
the EU H2020 AtlantOS project and R.Sauzede PhD 
thesis. SOCA estimates vertical profiles of backscattering 
coefficient (bbp), a bio-optical proxy for POC, from surface 
ocean color satellite measurement of bbp and additional 
physical drivers (Sauzede et al., 2016). It has been trained 
on high quality bbp data collected from BGC-Argo floats. 
Then, an empirical parameterization is used to infer the 
vertical distribution of Chla from surface ocean color 
satellite observations of Chla and the relative position of 
the mixed layer and euphotic depths (Uitz et al., 2006). 
This parameterization was established from a database 
of Chl profiles acquired by High Performance Liquid 
Chromatography (HPLC), the reference method for such 
measurements. Both methods are developed at LOV/IMEV. 
Two versions of the product have been successively 
veleased. The 1* publication in July 2020 included POC and 
Chla variables, and associated errors on a 1/4° horizontal 
grid over 19 vertical levels from the surface to 1000 m 
depth, at a weekly frequency and for the 1998-2018 period. 
An associated monthly mean climatology is also available. 
The 2°* publication in May 2021 is extended with the year 
2019 and provides bbp with its associated error as new 
variables, an improved bbp to POC relationship and a 
refined vertical resolution with 36 levels. 
2. STATUS AT THE END OF COPERNICUS 
At the end of Copernicus-1, 4 physical, 1 carbon and 2 
biogeochemical products implemented by four groups 
(CLS, CNR, LSCE, LOV/IMEV) composed the MULTIOBS TAC. 
The following products, briefly described in the previous 
section are provided at global scale: 
2D sea surface salinity and sea surface density fields. 
both in NRT and as MYP 
-3D temperature, salinity, geopotential height and 
geostrophic current fields, 2D mixed-layer depth both 
in NRT and as MYP, 
-3D vertical current as MYP, 
2D total surface and near-surface currents, both in 
NRT and as MYP, 
-2D surface carbon fields of flux of CO,, pCO, and pH 
as MYP, 
nutrient vertical distribution (nitrate, phosphate and 
silicate) profiles as MYP. 
3D backscattering coefficient (bbp), Particulate 
Organic Carbon (POC) and Chlorophyll-a (Chl-a) fields 
as MYP 
Service continuity is first ensured by fully operationa 
processing chains and then by daily or weekly operation 
tasks which are performed to produce and then push NRT 
products to the centralized Dissemination Unit. MYP are 
regularly extended, once or twice a year, consistently with 
upstream timeseries temporal extension. MULTIOBS TAC 
products are further used to derive OMlIs for ocean 
Wwarming, ocean acidification and ocean carbon sink which 
timeseries are also regularly extended. All products are 
fully validated and a dedicated QUID (Quality Information 
Document) is associated with each product/OMlI. Results of 
NRT validation metrics for MULTIOBS TAC products are 
also available through Copernicus Marine Service product 
quality Dashboard. In 2020, 1344 users downloaded 
MULTIOBS TAC products. 
3. DOST 2021 PERSPECTIVES 
In the continuity of activities carried out these last years, 
the first perspective will be to ensure the service continuity 
by maintaining the 7 processing chains of the MULTIOBS 
TAC with the four partners. 
System evolution roadmap includes: 
to implement state-of-the-art methods and upstream 
data for which continuous monitoring Is performed, 
-to incorporate and test new or improved products 
from TAC (Sea Level, SST, Ocean Color, Wind, in situ) 
and products currently outside Copernicus Marine 
Service, such as SSS from Aquarius/SMAP and from 
the future Copernicus CIMR (Copernicus Imaging 
Microwave Radiometer) mission, 
to include measurement error and processing 
uncertainty for predictors to reconstruct Surface 
Carbon, 
to test and include additional constraint from climate 
index if possible in ARMOR3D, 
„to improve Information content of products by 
increasing resolution in space (horizontal & vertical) 
and in time for all MULTIOBS products, starting with 
the physical ones, requiring higher resolution (L3/L4) 
products from TAC, 
-to extend OMEGA3D, nutrient profiles and 3D POC/ 
Chla products currently available only as multi- 
year timeseries to near-real-time, providing fully 
consistent multi-year and near-real timeseries for 
almost all MULTIOBS products, 
to improve the representation of physical processes 
such as ageostrophic component (wind-driven, stokes),