MERCATOR OCEAN JOURNA, 
SEPTEMBER 2021 
Mean Sea Level: Global Ocean 
retten ltr hr 
Datatype : Observations 
Credit : E.U. Copernicus Marine Service Informatic ” "opernicus Climate Service 
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‚igure 3: OM| GLOBAL_OMI_SL_area_averaged_anomalies. Gives the evolution of the mean sea level since January 1993 (in cm) computed from 
satellite altimeter observations (L4 gridded product). Timeseries has been low-pass filtered, the annual and semi-annual periodic signals have beer 
adjusted, and the curve has been corrected for the GIA using the ICE5G-VM2 GIA model (Peltier, 2004). During 1993-1998, the dashed line shows 
an estimate of the global mean sea level corrected for the TOPEX-A instrumental drift, based on comparisons between altimeter and tide gauges 
measurements (Ablain et al.. 2017) 
1.3 Preparation of next generation products 
Finally, The SL-TAC also prepared the next generation of 
products by integrating the R&D from space Agencies, 
H2020 or Service evolution projects in order to better 
address end-user needs. 
The improvement of the product resolution and spatial 
coverage were notably addressed and supported by CNES 
R&D activities in synergy with CMEMS long term evolution 
plan. 
First, an along-track L3 product was defined with a higher 
spatial sampling (i.e., about 1 km) than the conventional 
(about 7 km) product already present in the SL-TAC 
catalogue. It leveraged the full rate altimeter measurement. 
Specific Innovative processing and corrections were 
applied in order to reduce the residual noise signal and led 
to a more accurate observation of the small mesoscale 
signal (up to -55 to -35 km according to the mission 
considered) with this new product. Indeed, a reduction by 
at least one third compared to the capability of the 
conventional product over the North East Atlantic Ocean 
was achieved. This demonstrative production was 
proposed to different MFCs for assimilation a/o0 validation 
test. Enjoyably, the assimilation of this product 
significantly reduced the model forecast errors as 
discussed by Benkiran et al., (2017). Authors underlined a 
7% reduction of RMSD between the model forecast and 
>bservations. This result was also enhanced (additional 2 
to 5%) when the altimeter physical content is fully 
zompatible with model characteristics, thanks to the 
different geophysical variables available. The operational 
processing chain able to generate the new L3 product ir 
NRT conditions has been developed during years 2020- 
2021. The new corresponding NRT product line is expectec 
sarly 2022 in the Copernicus Marine Service catalogue 
Then, experimental gridded products dedicated to the 
Arctic areas were also developed with support from CNES. 
‚hey aim to estimate the sea level height in areas covered 
by sea ice. This Is possible thanks to specific processing 
that enables the exploitation of the altimeter measurement 
ın “ice leads” areas. As usual, this product was proposed to 
Arctic and Global MFCs for independent assessment. 
In addition to the scientific work, SL-TAC was also active to 
ijormulate recommendations and requirements to 
upstream provider (Eumetsat) in order to prepare its future 
transition to operation. SL-TAC is notably represented In 
the Sentinel-3 Quality Working Group.