Separating human-induced signals from internal variability in the Antarctic Circumpolar Current since 1986
| Tuesday, August 25, 2026 |
| 10:00 AM - 10:15 AM |
Overview
Prof. Nathan Bindoff, IMAS/UTAS
Speaker
Prof. Nathan Bindoff
Professor Of Physical Oceanography And Climate Science
Imas/university Of Tasmania
Separating human-induced signals from internal variability in the Antarctic Circumpolar Current since 1986
Abstract Document
The Antarctic Circumpolar Current (ACC) is the world’s strongest ocean current, transporting more than 150 Sv eastward around Antarctica due to the absence of meridional continental barriers. The ACC is maintained by strong Southern Hemisphere westerlies and meridional density gradients through geostrophic and thermal wind balance. Over recent decades, the westerlies have intensified and shifted poleward, primarily associated with trends in the Southern Annular Mode (SAM) linked to greenhouse gas forcing and stratospheric ozone depletion. However, long-term anthropogenic changes in ACC transport and mesoscale eddy activity remain difficult to detect because of strong internal variability, eddy compensation, and the relatively short observational record.
In this study we apply a novel detection and attribution framework that explicitly accounts for major modes of climate variability (including SAM, ENSO, IPO, IOD and others) to isolate externally forced changes in Southern Ocean heat content and zonal thermal gradients associated with the ACC system.
Preliminary results indicate improved separation of anthropogenic signals from internal variability compared with conventional approaches, with implications for detecting historical changes in ACC structure and circulation over recent decades.
In this study we apply a novel detection and attribution framework that explicitly accounts for major modes of climate variability (including SAM, ENSO, IPO, IOD and others) to isolate externally forced changes in Southern Ocean heat content and zonal thermal gradients associated with the ACC system.
Preliminary results indicate improved separation of anthropogenic signals from internal variability compared with conventional approaches, with implications for detecting historical changes in ACC structure and circulation over recent decades.
Biography
Professor Bindoff is a physical oceanographer in the Institute for Marine and Antarctic Studies (IMAS). His focus is on detecting and understanding the causes of change in the oceans. He was the coordinating lead author for the Fourth and Fifth Assessment Reports from the Inter-Governmental Panel on Climate Change. He led the oceans chapter (2007) and the detection and attribution chapter (2013). Nathan is one of just a few scientists who have been a coordinating lead author twice and contributed to the IPCC winning the Noble Peace Prize in 2007, shared with Al Gore. His research has involved documenting the first evidence for changes in the Indian, North Pacific, South Pacific and Southern Ocean's, and the earth's hydrological cycle from ocean salinity. His most recent work is on documenting the decline in oxygen content of the oceans and projecting the future climate over the Australian continents and impacts. All of these global changes have been attributed to human activity.
