How Kelvin waves convert East Antarctic winds to West Antarctic ice melt
More Larsen C-type ice shelf collapses likely in future, suggests modelling.
Higher rates of ice melt on the western side of the Antarctic Peninsula – not far from where a large chunk of the Larsen C ice sheet broke off to create one of largest icebergs ever recorded – may be driven by strengthening winds 6,000 kilometres away on the eastern side of the polar continent, suggests new research.
It’s all to do, according to the paper published in Nature Climate Change, with the closer proximity of the peninsula to the warmer water of the Antarctic Circumpolar Current and with Kelvin waves – the giant planetary waves driven by gravity and the inertial motion of the Earth’s rotation (known as the Coriolis force).
Kelvin waves follow along coastlines in a general east-to-west direction, though they will travel north and south when the coast does. When these waves, travelling around the continent at almost 700 km/h, reach the steep underwater topography of the West Antarctic Peninsula, they push warmer water up underneath the ice sheets along the peninsula’s shoreline.
“It is this combination of available warm water offshore, and a transport of this warm water onto the shelf, that has seen rapid ice shelf melt along the West Antarctic sector over the past several decades,” explains lead researcher Paul Spence, of the University of New South Wales. “We always knew warm water was finding its way into this area but the precise mechanism has remained unclear. That remote winds on the opposite side of Antarctica can cause such a substantial subsurface warming is a worrying aspect of the circulation at the Antarctic margin.”
The modelling by Spence and his colleagues, who are associated with the Australian Research Council’s Centre of Excellence for Climate System Science, shows that localised changes in coastal winds off East Antarctica, driven by globalised temperature changes, can produce subsurface temperature anomalies of more than 2°C around much of the continent.
The research contributes to understanding why the the rate of West Antarctic ice mass loss doubled between 2003 and 2014. It also points, given rising global temperatures, to the prospect of more calving of large ice shelves similar to the recent Larsen C event.
Says Spence: “For lack of precise estimates of future change, scientists have remained conservative in what this melting means for the globe, but recent estimates suggest Antarctica could contribute more than a metre to sea-level rise by 2100 and over 15 metres by 2500 under current emissions trajectories.”