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 2022
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Ocean deep convection and overturning circulation
The deep ocean constitutes the bulk of the oceanic volume and of the climate system heat capacity. However, it has limited interactions with the ocean surface and the overlying climate system. Ocean deep convection is among the main mechanisms of exchanges between the surface and deep ocean, spinning up the so-called global overturning circulation. My research has focused on the representation of deep convection and its role on the global overturning circulation in ocean and climate models.
Dynamical theories of the ocean circulation
The ocean circulation can be reduced to the coupling between the mass and the flow. The oceanic currents redistribute water masses, which in turn exert a pressure force that feeds back onto the circulation. My research has focused on how mass imbalances force the depth-integrated flow, and how this flow interacts with the bottom topography to set up the gyre and overturning circulations.
Ocean mesoscale dynamics
Although mesoscale eddies are ubiquitous and constitute the most energetic ocean circulation feature, their role on the shaping of the mean climate remains unclear. Indeed, accurately representing those eddies in climate models still remains a challenge. However, they are believed to flux heat upward and poleward, and to strongly respond to transient climate forcings. My research has addressed both the explicit representation of mesoscale eddies in regional climate models, and their parameterization in global climate models.
Oceanic energy balance and associated sea level changes
Over 90% of the anthropogenic warming has been absorbed by oceans, causing a sea level rise due to thermal expansion. At the same time, the ocean surface has warmed two thirds as much as continental surfaces, mitigating the global mean warming. This heat buffering capacity is controlled by the oceanic heat budget, itself still poorly understood. My research interests include theories and diagnostics of the oceanic heat budget, and its link to surface warming and thermosteric sea level changes.
Guinaldo, T., Voldoire, A., Waldman R., Saux Picart, S. and Roquet, H. Response of the sea surface temperature to heatwaves during the France 2022 meteorological summer. EGUsphere, https://doi.org/10.5194/egusphere-2022-1119, 2022.
Torres, R., Waldman R., Mak, J. and Séférian, R. Global estimate of eddy dissipation from a diagnostic energy balance GRL, https://doi.org/10.1029/2023GL104688
Gonzalez N., Waldman R., Sannino G., Giordani H., Somot S. Understanding tidal mixing at the Strait of Gibraltar : A high-resolution model approach. PiO, doi : https://doi.org/10.1016/j.pocean.2023.102980
Voldoire A., Roehrig R., Giordani H., Waldman R., Zhiang Y., Xie S., Bouin M-N. Assessment of the sea surface temperature diurnal cycle in CNRM-CM6-1 based on its 1D coupled configuration. GMD, doi : https://doi.org/10.5194/gmd-15-3347-2022
Waldman R., Hirschi J., Voldoire A., Cassou C., Msadek R. (2020) Clarifying the relation between AMOC and thermal wind : application to the centennial variability of the CNRM-CM6 climate model. JPO, doi : https://doi.org/10.1175/JPO-D-19-0284.1 PDF Supplementary
Dunic, N., Vilibic, I., Sepic, J., Mihanovic, H., Sevault, F., Somot, S., Waldman, R., Nabat, P., Arsouze, T., Pennel, R., Jorda, G., Precali, R. (2019) Performance of multi-decadal ocean simulations in the Adriatic Sea. OM, doi : https://doi.org/10.1016/j.ocemod.2019.01.006
Voldoire, A. et al (2019), Evaluation of CMIP6 DECK experiments with CNRM-CM6-1 JAMES, https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019MS001683
Séférian, R. et al (2019). Evaluation of CNRM Earth‐System model, CNRM‐ESM2‐1 : role of Earth system processes in present‐day and future climate. Journal of Advances in Modeling Earth Systems, 11, 4182– 4227. https://doi.org/10.1029/2019MS001791
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
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
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)
Reviewer for the journals Ocean Sciences, Scientific Reports, Journal of Geophysical Research, Remote Sensing, Geophysical Research Letters, Ocean Modelling, Journal of Advances in Modelling the Earth System, Geoscientific Model Development, Journal of Physical Oceanography and Journal of Operational Oceanography.
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.
I have supervised Nicolas Gonzalez’ PhD (2019-2023, co-supervision : Samuel Somot, Hervé Giordani) and am currently the main supervisor of Romain Torres (2021-ongoing, co-supervision : Roland Séférian).
Nicolas has been investigating the role of exhanges at the Strait of Gibraltar as a regulator of the Mediterranean climate. His PhD aimed at improving the understanding of exchanges, and specifically diapycnal mixing, at the Strait of Gibraltar in order to improve their representation in the ocean component of the regional Euro-Mediterranean climate model CNRM-RCSM6. Ultimately, he has characterized the regional climate response to those improved exchanges, under historical climate as well as future climate change scenarios.
Romain focuses on the parametrization of ocean mesoscale eddy transports in climate models. He has developed an approach to estimate eddy energy dissipation from in situ measurements with the use of a diagnostic energetic balance. He is currently developing a novel mesoscale parameterization based on an energy budget in the NEMO ocean model.
Ocean and climate at CNRM - Météo France :
Multi-scale study of oceanic deep convection in the Mediterranean Sea : from observations to climate modelling.
Oceanic deep convection, mesoscale dynamics, intrinsic oceanic variability, ocean modelling, observing system simulation experiment
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.
Le contenu de cette page n’engage que son auteur et en aucune manière la responsabilité du CNRM.