Ice sheet retreat controlled by the landscape

India Education Diary: A UK team led by Durham University has found that the geometry of channels beneath the ice can be a strong control on ice behaviour, temporarily hiding the signals of retreat. The findings, which provide the first simulation of past ice-sheet retreat and collapse over a ten-thousand- year period in Antarctica, shed new light on what makes ice stable or unstable and will help refine predictions of future ice extent and global sea-level rise, the researchers say.

The International Panel on Climate Change (IPCC) has stated that one of the main challenges in predicting future sea-level rise is to quantify and model the interactions between evolving ice sheets, oceans, sea level and climate. Significant efforts have been made over the last decade to develop computer models and collect data in order to reduce uncertainties and understand the potential impacts under scenarios of future climate change.

The results of the new research from Durham University, the University of Sheffield, the University of Cambridge, and the British Antarctic Survey are published in the journal Nature Geoscience. Lead author Dr Stewart Jamieson, a glaciologist at the Department of Geography, Durham University, said: “Our research shows that the physical shape of the channels is a more important factor in controlling ice stability than was previously realised. Channel width can have a major effect on ice flow, and determines how fast retreat, and therefore sea-level rise, can happen.

Although climatic and oceanic changes are crucial drivers of ice loss, the research shows that the landscape below the ice strongly controls the speed of any retreat. Dr Jamieson said: "Our results suggest that during an overall phase of retreat an ice stream can appear almost stable when in fact, in the longer-term, the opposite may be the case. Getting a clearer picture of the landscape beneath the ice is crucial if future predictions of change in the ice-sheets and sea level are to be improved.”...

Marine-based ice streams are the fast flowing arteries of ice sheets, draining approximately 90 per cent of the ice that reaches the sea. They flow through large channels where the ice can move thousands of metres in a year. According to the scientists, the unpredictable nature of ice streams makes forecasting ice-sheet retreat extremely difficult. If ice streams speed up they can cause sea level to rise....

Located just 600 miles (970 kilometers) from the North Pole, Franz Josef Land is perpetually coated with ice. Glaciers cover roughly 85 percent of the archipelago’s land masses, and sea ice floats in the channels between islands even in the summertime. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite observed the islands of central Franz Josef Land on August 16 and 19, 2011. (Another sensor on Terra captured a wider view on August 17, 2011.)