25 May 2022
25 May 2022
Status: this preprint is open for discussion.

A modeling framework to understand transient ocean climate change in large coupled ensembles

Yona Silvy1, Clément Rousset1, Eric Guilyardi1,2, Jean-Baptiste Sallée1, Juliette Mignot1, Christian Ethé3, and Gurvan Madec1 Yona Silvy et al.
  • 1LOCEAN-IPSL, Laboratoire d’Océanographie et du Climat: Expérimentation et Approches Numériques, Sorbonne Université/CNRS/IRD/MNHN, Paris, France
  • 2NCAS-Climate, University of Reading, Reading, UK
  • 3IPSL, Institut Pierre-Simon Laplace, Sorbonne Université, CNRS, Paris, France

Abstract. The ocean responds to climate change through modifications of heat, freshwater and momentum fluxes at its boundaries. The role of these contributors in changing the thermohaline structure of the ocean and its circulation has been partly addressed by modeling studies using idealized CO2 forcings. The question of timescales for these individual contributions during transient climate change is however lacking. Here, we propose a novel modeling framework to isolate these contributions during the entire historical period and projections of coupled climate models. We present the framework in the context of the IPSL-CM6A-LR model and its ocean component NEMO3.6. We start by reproducing a coupled pre-industrial control simulation with an ocean-only configuration, forced by fixed fluxes at its interface diagnosed from the coupled model. We then add a perturbation to each flux component, extracted from the historical+ssp ensemble of simulations of IPSL-CM6A-LR. With this configuration, we successfully replicate the ocean's response to transient climate change in the coupled model during 1850–2100. This full response is then decomposed in sensitivity experiments in which the perturbations are applied individually to the heat, freshwater and momentum fluxes. Passive tracers of temperature and salinity are implemented to discriminate the addition of heat and freshwater flux anomalies in the ocean from the redistribution of pre-industrial heat and salt content in response to ocean circulation changes. This framework brings new opportunities to precisely explore the mechanisms driving transient ocean changes within single climate models.

Yona Silvy et al.

Status: open (until 26 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on egusphere-2022-387', Juan Antonio Añel, 16 Jun 2022 reply
  • RC1: 'Comment on egusphere-2022-387', Anonymous Referee #1, 21 Jun 2022 reply
  • RC2: 'Comment on egusphere-2022-387', Anonymous Referee #2, 01 Jul 2022 reply

Yona Silvy et al.

Yona Silvy et al.


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Short summary
A modeling framework is introduced to understand and decompose the mechanisms causing the ocean temperature, salinity and circulation to change since the pre-industrial period and into 21st century scenarios of global warming. This framework aims to look at the response to changes in the winds, and in heat and freshwater exchanges at the ocean interface in global climate models, throughout the 1850–2100 period, to unravel their individual effects on the changing physical structure of the ocean.