WALDMAN Robin

Chercheur au CNRM (UMR3589 / Météo-France / CNRS / Université de Toulouse)

Centre National de Recherches Météorologiques (depuis 2013)

Groupe de Modélisation Grande Echelle et Climat (GMGEC) / Equipe IOGA

42, avenue Coriolis
31057 Toulouse Cedex 1, France

Tél. +33 (0) 5 61 07 93 36
Office #279 : Bâtiment Navier (CNRM)

courriel : robin (dot) waldman (at) meteo (dot) fr

Curriculum Vitae - Version 2018

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 Web Page Content

Scientific Interests

Projects

Publications

Conferences

Lectures of Physical Oceanography

Outreach

PhD-Thesis



 Scientific interests


Drivers of the thermohaline circulation

"How to solve this chicken-and-egg problem ?"
(a young and naive researcher)

The oceanic thermohaline circulation defines the global overturning that ventilates abyssal waters. It is as paramount for climate and biogeochemistry as it is poorly known due to scarce observations of the deep ocean. A key question, still largely open to date, is that of its main drivers. Is it driven by buoyancy-forced deep convection that drives the downwelling, by diapycnal mixing or Ekman pumping that drive the upwelling, or by horizontal gradients that drive the lateral branches of the overturning ?

My research has up to now mainly focused on the downwelling branch of the Mediterranean thermohaline circulation and in particular on the understanding of the deep convection phenomenon. Some questions addressed in recent studies are : the characterization of deep convection from the 2012-2013 HyMeX/MerMex campaign ; the assessment of its chaotic variability from ensemble simulations ; the sources and drivers of the thermohaline circulation downwelling.


Role of mesoscale dynamics in the oceanic mean state and variability :

"It is such a mess with mesoscale, and do we really care ?"
(a climate researcher)

The oceanic mesoscale is relatively small-scale from a climate system point of view, which raises the question of its importance for climate. Nonetheless, many key water mass and heat transports occur at the mesoscale through the western boundary currents of the wind-driven gyres, the Antarctic circumpolar current and transports through key straits such as Gibraltar. In addition, mesoscale eddies largely dominate the oceanic kinetic energy reservoir and their turbulent nature induces a chaotic self-emerging variability. Although mesoscale dynamics has been in the spotlight of physical oceanography for a few decades now, its role for climate still remains unclear.

My research has up to now mainly focused on the role of mesoscale as a regulator of deep convection and as a source of chaotic oceanic variability. Some questions addressed in recent studies : the role of mesoscale dynamics in the restratification processes ; the chaotic variability of the Mediterranean Sea with ensemble eddying simulations.


Informing observing systems with numerical models

"The issue is with the observations, not with my model, understood ?"
(a young but wise researcher)

Although it is often painful for a modeller to confront to observations, sometimes observations are not reliable enough to evaluate models. The reasons are their inherent uncertainties : spatial and temporal undersampling and instrumental errors. Such errors are for instance evident when trying to estimate trends in the oceanic heat content. A useful way to evaluate and improve an observing network is to perform virtual observations in the "model world". This exercise, called Observing System Simulation Experiments (OSSEs), can help observers design their network but also permits to put errorbars to observed estimations.

My research has up to now focused on : estimating the deep convection and spreading rates in a probabilistic framework with an OSSE on the 2012-2013 HyMeX/MerMex campaign ; evaluating and improving with an OSSE the future PERLE network aimed at documenting the formation and spreading of Levantine Intermediate Waters (LIWs).


The ocean as a regulator of climate :

"At CNRM we do weather and climate, we are not an oceanography lab !"
(anonymous head of lab)

The climate defines the statistical properties of weather, that is the atmosphere. However, the atmosphere has a negligible contribution to the heat content of the climate system and its variability is mostly high-frequency, with little to no memory beyond a few weeks. This role of reservoir and memory of climate is mainly played by the ocean. However, at any given time, only the ocean mixed layer interacts with the atmosphere and climate, meaning that 99% of the ocean volume is isolated from it. By what means does the ocean regulate climate variability and predictability as well as potential future trends and tipping points ? Surely, the longer the period considered, the more abyssal ocean becomes important.

This research activity is recent and should take an increasing fraction of my time in the future. I contribute to the evaluation of the regional climate model CNRM-RCSM6 over the Mediterranean Sea and to the development of its oceanic component. I also contribute to the evaluation of the oceanic component of our global climate models : CNRM-CM6 which is the reference low resolution climate model participating in IPCC/CMIP exercises, CNRM-CM6-HR which is its high-resolution counterpart and CNRM-ESM2 which is its Earth System counterpart. In the future, I am planning to look at the influence of deep ocean processes on climate.



 Projects :



International projects

Med–CORDEX : Mediterranean region of the International CORDEX programme (modelling of all the components of the regional climate system, 12 km RCM, fully coupled RCSM). Med-CORDEX is currently the regional climate modelling task of HyMeX (former HyMeX-TTM3) on-going

HyMeX : Study of the Mediterranean hydrological cycle and related extreme events, 2010-2020, on-going

MerMex : Study of the Mediterranean Sea physics, biogeochemistry and marine ecosystems, 2010-2020, on-going

MISTRALS : Meta-programme, also called Chantier Méditerranée, for the integrated study of the Mediterranean at regional and local scales, 2010-2020 on-going. This includes my participation to HyMeX, MerMex, Med-CORDEX, SiMed


French projects

HyMeX-SiMed-3, MISTRALS-SiMed-4 : French coordination for an improved modelling of the Mediterranean Sea using in particular the NEMOMED configurations on-going

ANR-ASICS-MED : Evaluate the role of the ocean meso- and submeso-scale processes in the dense water mass formation in the North-West Mediterranean Sea, follwing the HyMeX-2013 field campaign. finished



 Peer-reviewed publications :



2018

Dunic, N., Vilibic, I., Sepic, J., Mihanovic, H., Sevault, F., Somot, S., Waldman, R., Nabat, P., Arsouze, T., Pennel, R., Jorda, G., Precali, R. Performance of multi-decadal ocean simulations in the Adriatic Sea. OM, in revision

Waldman R., Brüggemann N., Bosse A., Spall M., Somot S., Sevault F. (2018) Overturning the Mediterranean Thermohaline Circulation. GRL, DOI : 10.1029/2018GL078502 PDF Supplementary

M. Peharda, I. Vilibić, B.A. Black, K. Markulin, N. Dunić, T. Džoić, H. Mihanović, M. Gačić, S. Puljas, R. Waldman (2018) Using bivalve chronologies for quantifying environmental drivers in a semi-enclosed temperate sea. Scientific Reports

Waldman R., Somot S., Herrmann M., Sevault F., Isachsen P.E. (2018) On the chaotic variability of deep convection in the Mediterranean Sea. GRL, DOI : 10.1002/2017GL076319 PDF

Testor P., Bosse A., Houpert L., Margirier F., Mortier L., Lego H., Dausse D., Labaste M., Karstensen J., Hayes D., Olita A., Ribotti A., Schroeder K., Chiggiato J., Onken R., Heslop E., Mourre B., D’Ortenzio F., Mayot N., Lavigne H., de Fommervault O., Coppola L., Prieur L., Taillandier V., Durrieu de Madron X., Bourrin F., Many G., Damien P., Estournel C., Marsaleix P., Taupier-Letage I., Raimbault P. Waldman R., Bouin M.-N., Giordani H., Caniaux G., Somot S., Ducrocq V., Conan P. (2018) Multiscale observations of deep convection in the northwestern Mediterranean Sea during winter 2012-2013 using multiple platforms. JGR-Oceans, Special Issue HyMeX-Mermex, doi:10.1002/2016JC012671


2017

Waldman R., Herrmann M., Somot S., Arsouze T., Benshila R., Bosse A., Chanut J., Giordani H., Sevault F., Testor P. (2017b) Impact of the Mesoscale Dynamics on Ocean Deep Convection : The 2012-2013 Case Study in the Northwestern Mediterranean Sea. JGR-Oceans, Special Issue HyMeX-Mermex, sept 2017, doi : 10.1002/2016jc012587 PDF

Waldman R., Somot S., Herrmann M., Bosse A., Caniaux G., Estournel C., Houpert L., Prieur L., Sevault F., Testor P. (2017a) Modelling of the intense 2012-2013 dense water formation event in the northwestern Mediterranean Sea : Evaluation with an ensemble simulation approach. J. Geophys. Res. Oceans, 122, doi:10.1002/2016JC012437, Special Issue HyMeX-Mermex PDF


2016

Waldman R., Somot S., Herrmann M., Testor P., Estournel C., Sevault F., Prieur L., Mortier L., Coppola L., Taillandier V., Conan P., Dausse D. (2016) Estimating dense water volume and its evolution for the year 2012-2013 in the North-western Mediterranean Sea : an Observing System Simulation Experiment approach. JGR-Oceans, 121(9), 6696-6716, doi : 10.1002/2016JC011694, Special Issue HyMeX-MerMex. PDF

Somot S., Houpert L., Sevault F., Testor P., Bosse A., Taupier-Letage I., Bouin M.N., Waldman R., Cassou C., Sanchez-Gomez E., Durrieu de Madron X., Adloff F., P. Nabat, Herrmann M. (2016) Characterizing, modelling and understanding the climate variability of the deep water formation in the North-Western Mediterranean Sea. Climate Dynamics, 1-32, doi : 10.1007/s00382-016-3295-0, (available on-line : http://link.springer.com/article/10.1007/s00382-016-3295-0)


Reviewing

So far, reviewing activity for the journals Ocean Sciences and Scientific Reports.

(top of the page)



 International conferences



2018

11th HyMeX workshop – Lecce, Italy
Waldman R., Bruggemann N., Bosse A., Sevault F., Somot S., Spall M., "Overturning the Mediterranean Thermohaline Circulation." (talk)

11th HyMeX workshop – Lecce, Italy
R. Waldman, F. d’Ortenzio, X. Durrieu de Madron, F. Dumas, V. Taillandier, "Evaluating PERLE network with an Observing System Simulation Experiment" (poster)

Ocean Sciences conference 2018 – Portland, USA
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, « On the chaotic variability of the Mediterranean Thermohaline Circulation. » (poster)

DRAKKAR workshop 2018 – Grenoble, France
Waldman, R., N. Brüggemann, S. Somot, F. Sevault, « Where does the downwelling of the Mediterranean thermohaline circulation take place ? » (talk)


2017

10th International HyMeX Workshop – Barcelona, Spain
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, « Does intrinsic ocean variability impact ocean deep convection ? Answers from eddy-resolving ensemble simulations of the Northwestern Mediterranean Sea. » (talk)

10th International HyMeX Workshop – Barcelona, Spain
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, G. Caniaux, P. Testor, H. Giordani, R. Benshila, T. Arsouze, A. Bosse, R. Benshila, J. Chanut, « How does mesoscale impact ocean deep convection ? Answers from ensemble Northwestern Mediterranean Sea simulations. » (poster)

2017 European Geosciences Union Meeting – Vienna, Austria
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, « Does intrinsic ocean variability impact ocean deep convection ? Answers from eddy-resolving ensemble simulations of the Northwestern Mediterranean Sea. » (talk)

2017 European Geosciences Union Meeting – Vienna, Austria
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, G. Caniaux, P. Testor, H. Giordani, R. Benshila, T. Arsouze, A. Bosse, R. Benshila, J. Chanut, « How does mesoscale impact ocean deep convection ? Answers from ensemble Northwestern Mediterranean Sea simulations. » (poster)


2015

9th International HyMeX Workshop – Mikonos, Greece
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, G. Caniaux, P. Testor, C. Estournel, H ; Giordani, R. Benshila, Q. Akuetevi, T. Arsouze, « Impact of mesoscale eddies on ocean deep convection in the Northwestern Mediterranean sea. » (talk)

9th International HyMeX Workshop – Mikonos, Greece
Waldman, R. ; S. Somot, M. Herrmann, C. Estournel, « An uncertainty framework to estimate dense water formation rates : case study in the Northwestern Mediterranean. » (poster)

2015 European Geosciences Union Meeting – Vienna, Austria
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, G. Caniaux, P. Testor, C. Estournel, H. Giordani, R. Benshila, Q. Akuetevi, T. Arsouze, « Ocean deep convection in the Mediterranean sea : 2012-2013 case study in the Gulf of Lions, from observations to modelling. » (talk)

2015 European Geosciences Union Meeting – Vienna, Austria
Waldman, R. ; S. Somot, M. Herrmann, P. Testor, C. Estournel, « An uncertainty framework to estimate uncertainty in dense water formation rates : case study in the Northwestern Mediterranean. » (poster)


2014

8th International HyMeX Workshop – Valetta, Malta
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, G. Caniaux, P. Testor, L. Houpert, L. Coppola, C. Estournel, « Ocean deep convection in the Mediterranean sea : 2012-2013 case study in the Gulf of Lions, from observations to modelling. » (talk)

8th International HyMeX Workshop – Valetta, Malta
Waldman, R. ; S. Somot, M. Herrmann, P. Testor, C. Estournel, « An Observing System Simulation Experiment (OSSE) to assess uncertainty in MOOSE large-scale estimates. » (poster)

3rd International MedCordex Workshop – Palaiseau, France
Waldman, R. ; S. Somot, M. Herrmann, F. Sevault, G. Caniaux, P. Testor, L. Houpert, L. Coppola, « Ocean deep convection in the Mediterranean sea : 2012-2013 case study in the Gulf of Lions, from observations to modelling. » (talk)


2012

2012 European Geosciences Union Meeting – Vienna, Austria
Waldman, R. ; Mignot, J. ; Frankignoul, C. « Seasonal AMOC variability at 26.5°N in two coupled models and a forced ocean model : comparison with observations. » (poster)


2009

2009 American Geophysical Union Fall Meeting – San Francisco, USA
Bonelli, S ; Ramstein, G. ; Donnadieu, Y. ; Dumas, C. ; Ritz, C. ; Waldman, R. « Relation between the occurrence of major glaciations of Antarctica and Greenland and the atmospheric CO2:a modelling approach. » (talk)



 Lectures of Physical Oceanography, UNAM, Mexico (November 2018)



Lectures

1 - Introduction to Ocean Circulation.
Online videos :
https://www.youtube.com/watch?v=zMoCY3qVnsA
https://www.youtube.com/watch?v=qftbniNmc58

2 - The Equations of Ocean Circulation and Ocean Modelling.
Online videos :
https://www.youtube.com/watch?v=pZoUb9I7Y2g
https://www.youtube.com/watch?v=XtvA0LuvP1I

3 - The Wind-Driven Oceanic Circulation.
Online videos :
https://www.youtube.com/watch?v=bZm2NGAbOnA
https://www.youtube.com/watch?v=eNSLm7asr1c


Talks

1 - Introduction to Ocean Circulation.
2 - The Equations of Ocean Circulation and Ocean Modelling.
3 - The Wind-Driven Oceanic Circulation.


Quizzes

1 - Prerequisite.
2 - On lecture 1.
3 - On lecture 2.
4 - On lecture 3.


Tutorials

1 - Paper analysis.
Students’ talks :
- Abrupt cooling over the subpolar North Atlantic.
- The Atlantic Meridional Overturning Circulation.
- Abyssal mixing in the South Atlantic.
- Sverdrup and nonlinear dynamics in the Tropical Pacific.

2 - Regional ocean modelling.

3 - Global ocean climate modelling.



 Outreach


Ocean and climate at CNRM - Météo France :
https://www.facebook.com/CentrodeCienciasdelaAtmosferaUNAM/videos/252171518811435/



 PhD thesis


TITLE :

Multi-scale study of oceanic deep convection in the Mediterranean Sea : from observations to climate modelling.

KEYWORDS :

Oceanic deep convection, mesoscale dynamics, intrinsic oceanic variability, ocean modelling, observing system simulation experiment

ABSTRACT :

The northwestern Mediterranean sea, also named the Liguro-Provençal basin, is one of the few places where ocean deep convection occurs. This localized and intermittent phenomenon is one of the main modes of interaction between the deep ocean and the climate system. It is of paramount importance for the vertical redistribution of heat, carbon dioxyde and biogeochemical elements, and therefore for climate and marine biology. The PhD has been carried out in the framework of HyMeX programme, it aims at characterizing the ocean deep convection phenomenon in the Liguro-Provençal basin from the year 2012-2013 case study and at understanding the role of mesoscale dynamics and of the resulting intrinsic ocean variability on deep convection.
The PhD work has first focused on characterizing the ocean deep convection phenomenon from observations collected during the 2012-2013 case study. We estimated the winter deep convection and spring restratification rates and an Observing System Simulation Experiment (OSSE) was developed to estimate the associated observation error. We conclude on the validity of MOOSE network observations to estimate the deep convection and restratification rates in the period 2012-2013. We characterize the period as exceptionally convective with a winter deep water formation rate of 2.3±0.5Sv (1Sv=10⁶m³/s) and we estimate for the first time a spring deep water restratification rate of 0.8±0.4Sv.
Two novel numerical approaches were developped during the PhD to characterize the roles of mesoscale dynamics and of intrinsic variability in the deep convection phenomenon. We implemented AGRIF grid refinement tool in the northwestern Mediterranean Sea within NEMOMED12 regional model to document the impact of mesoscale on deep convection and on the Mediterranean thermohaline circulation. In addition, we carried out perturbed initial state ensemble simulations to characterize the impact of ocean intrinsic variability on convection.
After extensively evaluating the realism of deep convection in NEMOMED12 numerical model thanks to the 2012-2013 observations, we study with this model the impact of intrinsic variability on deep convection. During the case study as well as in the 1979-2013 historical period, intrinsic ocean variability largely modulates the mixed patch geography, particularly in the open-sea domain. At climatic timescales, intrinsic variability modulates largely the deep convection rate interannual variability. On average over the historical period, it also modulates the mixed patch geography, but it impacts marginally its magnitude and the properties of the deep water formed.
Finally, we study with AGRIF tool the impact of mesoscale dynamics on deep convection and on the thermohaline circulation. In the 2012-2013 case study, mesoscale improves the realism of the simulated convection. We show that it increases the deep convection intrinsic variability. In this period as well as during the 1979-2013 historical period, it decreases the mean deep convection rate and it reduces deep water transformations. We mainly relate its impact on convection to the modifincation of the stationary circulation characterized by a relocation and an intensification of boundary currents and the presence of a stationary Balearic Front meander. Also, in the historical period, exchanges with the Algerian basin are increased, which modifies water mass climatological properties. Finally, the surface signature of mesoscale is likely to alter air-sea interactions and the coastal to regional Mediterranean climate.

DEFENSE :
Friday, December 16th 2016



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