The role of Antarctic sea ice in configuring the global ocean

PLEASE NOTE:  Application deadline date 08 Jan 2024.  Applications are no longer being accepted for this project

Project Overview 

Antarctic sea ice – which has experienced a major decline since 2016 – has recently been proposed to play an important role in shaping the structure and circulation of the global ocean. This project will investigate this role on time scales of seasons to centuries, and assess implications for contemporary climate change.

Project Description 

Antarctic sea ice has recently been proposed to play an important role in configuring the properties and circulation of the global ocean (Klocker et al., 2023). By controlling stratification at high southern latitudes, where mid-depth waters upwell to the surface, Antarctic sea ice governs the structure of the ocean’s main organising feature: the permanent pycnocline (PP). The PP is an interface of elevated stratification – found at 1000-1500 m depth over much of the ocean – that sets apart near-surface waters exchanging heat and carbon with the atmosphere from deeper waters storing those tracers for as long as millennia. Yet, despite its basic underpinning of the ocean’s role in climate, the processes governing the PP’s formation and global impacts remain poorly understood.

This project will determine the mechanisms by which Antarctic sea ice regulates the PP’s establishment across the world ocean, the time scales over which this happens, and the ways in which the PP structures the meridional overturning circulation and ventilation of the global ocean. The student will achieve this by performing and analysing a suite of numerical experiments with perturbed surface forcings (e.g., Antarctic sea ice seasonality or Southern Ocean winds) in an idealised global ocean model (based on Munday et al., 2013), and re-casting the most revealing experiments in a realistic Southern Ocean model constrained by observations (Verdy and Mazloff, 2017). The results will provide new fundamental understanding of the long-term, planetary-scale consequences of the dramatic retreat currently being experienced by Antarctic sea ice.