Legacy from CCI projects “Sea Level”

A. Cazenave1, JF. Legeais2, G. Larnicol2, J. Benveniste3, M. Ablain2, B. Meyssignac1, J. Johannessen4, M. Scharffenberg5, G. Timms6, P. Knudsen7, O. Andersen7, P. Cipollini8, M. Roca9, S. Rudenko10, J.

Fernandes11, M. Balmaseda12, G. Quartly13, L. Fenoglio14-15, A. Ambrozio3 , M. Restano3, M. Passaro16

1LEGOS, 2CLS, 3ESA, 4NERSC, 5University of Hamburg, 6CGI, 7DTU, 8NOCS, 9IsardSAT, 10GFZ,

11 University of Porto, 12ECMWF, 13PML, 14TUD, 15University of Bonn , 16University of Munich

Question 1: What was the status of the

« sea Level » landscape at the start of the CCI programme?

Landscape à - International collaboration - Developement of networks - Cross project activities ……

Responses to question 1

q  Satellite altimetry was an already mature technique à high precision altimetry era started in the early 1990s q  International collaboration already well established v  within Europe (à ERS-1/2 & Envisat ESA missions) v  between USA and Europe (àTopex/Poseidon & Jason series)

q  Networks of altimetry users & sea level scientists worldwide already existed (in particular thanks to the yearly working meetings called « OSTST/Ocean Surface Topography Science Team » handled by CNES and NASA) q  However, in spite of continuous progress in altimetry data processing between

1990 and 2010, still important differences remained between « Sea Level » products provided by the main processing groups (AVISO, Univ. Colorado, NASA/GSFC, NOAA, CSIRO) à negative consequences on scientific interpretation

q  GCOS accuracy requirements not satisfied; no error characterisation à Errors and uncertainties either not estimated or not well described

- Cross project activities : poorly developped

Question 2: What is the status of the « Sea

Level » landscape at the end of the 6 years of CCI?

Responses to question 2

q  International collaboration reinforced: v  The CCI Sea Level project involved 15 European partners that met at least

twice a year during the past 5-6 years v  An international panel of experts was invited to assess the CCI sea level activities

à contributed to the visibility of the CCI project and led to the development of a significant number of scientific collaborations

(e.g., between altimetry experts and ocean modelers)

q  Innovation in data processing methodology (i.e. Round Robin exercise): v  A formal protocol of validation has been set up, allowing the evaluation of the numerous

altimeter standards (corrections) and algorithms v  Selection of algorithms obtained through a consensus between Earth Observation experts

and climate scientists

q  Development of cross project activities v  Very positive synergy

v  Contribution to a European network of expertise v  Emergence of collaboration between sea level experts and climate modelers (via CMUG)

v  At the origin of a new integrated project (“Sea Level Closure Budget”)

Newproject:“CCISeaLevelBudgetClosure”Background

Sea level is an integrative indicator of climate change.

Given the improvement of ECVs achieved by the CCI, the ISSI Workshop ”Integrative Study of Sea Level Budget”, (Bern, 02/2015) discussed •  the closure of the sea level budget •  the study of regional variabilities and their attribution and recommended to ESA to launch a related activity.

Projectobjec>ves

•  Investigate in a coherent way the closure of the sea level budget. Thereby assess the quality of CCI products

•  Study and analyze the regional variability of sea level and its steric and mass components. The Arctic Ocean is chosen as study region.

•  Prepare the way to more comprehensive and more operational assessments of the global and regional sea level budget

à2-yearproject,inprepara>on,tobestartedwithinthenextmonths

Question 3: What are the activities in CCI

that have served to change from status 1 to status 2?

Responses to question 3

q  Annual collocation meetings at ESRIN à Development of cross project activities

q  Regular meetings (work meetings, annual meetings, etc.) within the project à Increased group collaborations at the European level

q  Opportunity for increased relationship with international organizations (e.g., GCOS, WCRP, ISSI, IPCC….)

à Increased visibility of the CCI programme towards the climate community and other users of EO data

q  Innovation in ECV data processing methodology à New protocol of algorithm selection and validation

Question 4: What are the lessons learned

from CCI to provide to future projects?

Responses to question 4

q Acccording to the « Sea level » consortium, the CCI project has reached most of its objectives à Sea Level ECV ready for operational production (Production Service to be implemented within the Copernicus Climate Change Service /C3S)

q Round Robin framework should be used by future CCI+ projects

Comments and questions q But, still work to do to fully reach the GCOS requirements in

terms of accuracy and stability, reconcile sea level records produced by the different groups (including the CCI), include new satellites (CryoSat, Sentinel-3, Jason-3, …), insure continuity of the sea level record for climate research, develop useable coastal sea level products, etc.

q  Coordination required between “space components” and

Services (C3S, CMEMS) to manage: R&D vs operational, and the reprocessing activities, especially for the historical missions (e.g., Topex/poseidon)

q More generally, what will be the fate of the CCI ECVs?

Source: Ablain et al., 2015, 2016

Spatial Scales Temporal Scales GCOS Requirements

Errors of CCI products

Global Mean Sea Level

Long-term trend <0.3 mm/yr <0.5 mm/yr

Interannual signals 0.5 mm over 1 year

< 2 mm over 1 year

Regional Sea Level

Long-term trend <1 mm/yr <3 mm/yr

Current Sea Level Uncertainties «ESA Climate Change Initiative/CCI» products

GCOS: Global Climate Observing System

Difference between different global mean sea level time series and the ESA « Climate Change Initiative/CCI » sea level product

2011 LA

NINA

Copernicus Climate Change Service

Challenges: -  Quality assessment -  Account for improved corrections and

new missions -  Reprocessing -  …..

Continuity of the « sea level » record….

Who will take care of that?

Thanks for your attention