7 November, 2018

Fresh water freezing onto the bottom of the Greenland and Antarctic Ice Sheets leads to the formation of spectacular plume-shaped features, according to new research published today (7th November) in Nature Communications.

Understanding how ice sheets grow and evolve over time is important for predicting future ice sheet responses to climate change. The huge ice structures, observable using ice-penetrating radar, extend from the base of the ice sheet up to a maximum height of 1000 metres – half the thickness of the ice sheets – and can be tens of kilometres in length. Until now, it has been unclear how these unusual features are formed and how they grow to such sizes.

A team of scientists from University of Zurich and British Antarctic Survey used computer simulations to show that these features could be reproduced by the “freeze-on” of fresh water running beneath the ice sheet.

This freeze-on process of adding ice to the base of the ice sheet protects original older ice from melting. This is important as locating these structures could help scientists identify suitable sites for future ice core drilling projects.

Observed (a) and interpreted (b) layer structures in radar image together with simulated (c) layer structure for basal freeze-on. (Radar imagery from the NASA IceBridge MCoRDS L1B instrument, courtesy NASA NSIDC DAAC, NSF and CReSIS, Kansas)

Lead author, Dr Gwendolyn Leysinger Vieli, from University of Zurich says:

“This study highlights that in areas with a rugged bedrock surface, water freezing on to the base of an ice sheet can cause it to grow. The frozen-on ice is expected to behave differently from the surrounding ice, and it is vital to understand its control on ice-dynamics. The properties of this ice would affect how glaciers respond to climate change.”

Dr Richard Hindmarsh, British Antarctic Survey (BAS), adds:

“As well as its importance for understanding current and future ice sheet dynamics, discovering how these structure form is significant for future ice-core drilling projects. Identifying sites where older ice is preserved is crucial for extending knowledge of past climate, stored within the ice, beyond current records. International work involving BAS scientists is already underway in East Antarctica to identify sites and organise drilling projects to extend the ice core record.”

Read the paper here.