Anthropogenic temperature and salinity changes in the Southern Ocean

• Published in: Journal of Climate
• Main Authors: Hobbs, WR, Roach, C, Roy, T, Sallee, J-B, Bindoff, N
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Meteorological Soc 2020
• Subjects: Southern Ocean; attribution; climate change; coupled models; model comparison; Antarctic; Antarc*
• Online Access: https://eprints.utas.edu.au/42279/; https://eprints.utas.edu.au/42279/2/141607%20-%20Anthropogenic%20temperature%20and%20salinity%20changes%20in%20the%20Southern%20Ocean.pdf

In this study, we compare observed Southern Ocean temperature and salinity changes with the historical simulations from 13 models the Coupled Model Intercomparison Project version 5 (CMIP5), using an optimal fingerprinting framework. We show that there is an unequivocal greenhouse gas-forced warming in the Southern Ocean. This warming is strongest in the Sub-Antarctic Mode Waters, but is also detectable in denser watermasses which has not been shown in previous studies. We also find greenhouse gas-forced salinity changes, most notably a freshening of Antarctic Intermediate Waters. Our analysis also shows that non-greenhouse gas anthropogenic forcings - anthropogenic aerosols and stratospheric ozone depletion – have played an important role in mitigating the Southern Ocean’s warming. However, the detectability of these responses using optimal fingerprinting is model-dependent, and this result is therefore not as robust as for the greenhouse gas response.