Fossilised beached along Cornwall coast help understanding of global warming

Paul Armstrong
Thu, 6 July 2023 

A rocky platform at Bream Cove near Falmouth, one of the beaches visited as part of the research (Image: Sarah Boulton, University of Plymouth)

Fossilised beaches along the Cornwall coastline have enabled scientists to demonstrate for the first time how melting Antarctic ice sheets impacted global sea levels during a period of pronounced climate warming more than 100,000 years ago.

A study developed at the University of Plymouth, and published in the journal Science Advances, analysed ancient sediments from raised beaches - including Bream Cove, Gunwalloe Beach and Pendower Beach - and elsewhere across western Europe.

The scientists involved in the research believe the raised beaches – characterised by flat surfaces, often with fossilised beach sands and stones, and typically found around 4-6 metres above current sea levels – could provide an invaluable insight into the local and global impacts of melting ice sheets in the future.

By combining new and existing data with a series of novel analysis and modelling techniques, the team of researchers from the UK, USA and Canada were able to demonstrate that the melting of the Antarctic ice sheet would have caused a rise in global sea levels of up to 5.7 metres.

They reached this conclusion after determining that the sea level change caused by the melting of northern hemisphere ice sheets was largely offset by the fact that removing an ice sheet causes the land near it to rebound. This meant the sea level change recorded on the beaches could only have come from Antarctica.

The researchers were also able to identify the timescale of this change as occurring between 116,000 and 129,000 years ago, ahead of the melting of any ice sheets in the northern hemisphere.

They believe the warmer polar temperatures during this interglacial period make it an important testing ground for understanding how ice sheets respond to warming.

Dr Matt Telfer, Associate Professor of Physical Geography at the University of Plymouth and a co-author on the research, said: “The South West of England is in a very fortuitous place when it comes to understanding this process. Our findings show that the English Channel is roughly neutral for sea-level change from the northern hemisphere, with the rising sea levels from melt and the rising land from the effects of rebound cancelling each other out. As a result, the historic changes which saw sea levels along the UK coastline rise by up to six metres can be attributed solely to the melting of Antarctic ice.”

Predictions suggest global temperatures will be 2°C warmer than pre-industrial levels by 2100, despite political agreements designed to keep the figure considerably lower.

In a report published in early 2022, the Intergovernmental Panel on Climate Change (IPCC) suggested this could lead to global sea level rises of 0.33 to 1.02 metres.

However, writing in the current study, researchers say there is significant uncertainty around the contribution of melting Antarctic ice to that figure since its fate is governed by more than warming temperatures alone.

Dr Sarah Boulton, Associate Professor in Active and Neotectonics and also a co-author of the study, added: “We know that mass loss from the Greenland Ice Sheet and mountain glaciers track closely to temperature, so we can to some extent predict their fate and the impacts of that change. However, the stability of ice cliffs in the Antarctic are more poorly understood. How much the northern and southern hemispheres have, and will, contribute to future sea-level rise is a really big question when we are trying to understand future climate change. This study gives us some important clues as to how that might play out.”