EGU25-13255, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-13255
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Changes in ideal age distribution in response to coupled wind/sea ice perturbations in a Southern Ocean channel model 
Nelson Poumaëre1, Graeme MacGilchrist1, and Hemant Khatri2
Nelson Poumaëre et al.
  • 1University of St Andrews, School of Earth and Environmental Sciences, St Andrews, United Kingdom of Great Britain – England, Scotland, Wales (nvjp1@st-andrews.ac.uk)
  • 2University of Liverpool, Department of Earth, Ocean and Ecological Sciences, Liverpool, United Kingdom of Great Britain – England, Scotland, Wales

The Southern Ocean is known as the most prominent oceanic sink of anthropogenic carbon and heat (Khatiwala et al. 2009, Frölicher et al. 2015). Among the processes involved in the region's carbon and heat cycle, ventilation–defined as the transfer of water and tracers from the mixed layer to the stratified pycnocline–is recognised as being of prime significance (Morrison et al. 2022). Recent and future trends in Southern Ocean surface conditions (wind stress and sea ice cover) are likely to impact ventilation patterns and timescales, with concurrent effects on the ocean’s role as a climate mitigator.

Sea ice has been shown to be an important conveyor of heat and salinity throughout the Southern Ocean (Abernathey et al. 2016, Haumann et al. 2016).  Recent modelling (Waugh 2014, Waugh et al. 2019) and data analysis (Cerovečki et al. 2019) studies have revealed the impact of changing surface conditions on ventilation characteristics; however, the contribution of sea ice dynamics and thermodynamics, and their coupled interaction with wind stress changes, have not been specifically addressed.

In this study, we focus on this mechanism by making use of a coupled ocean/sea ice (MOM6/SIS2, Adcroft et al. 2019) reentrant channel model, with generic continental shelf and meridional ridge topography. Quasi-realistic seasonally varying, zonally invariant surface forcing fields of wind stress, heat flux and fresh water are imposed. A meridional overturning circulation is sustained by a sponge region at the domain’s northern boundary. Several diagnostics, including the ideal age, are used to quantify changes in ventilation intensity.

To investigate the impact on ocean ventilation of changing surface conditions and their interactions with sea ice dynamics, we run two configurations of the model: with and without an interactive sea ice component. In both configurations, the model is brought to statistical equilibrium and then perturbed by mimicking a Southern Annular Mode anomaly. By comparing the ventilation characteristics in the two configurations, we isolate and quantify the contribution of the freezing/melting dynamics and their interaction with changes in wind stress forcing. 

How to cite: Poumaëre, N., MacGilchrist, G., and Khatri, H.: Changes in ideal age distribution in response to coupled wind/sea ice perturbations in a Southern Ocean channel model , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13255, https://doi.org/10.5194/egusphere-egu25-13255, 2025.