With this blog post, we inaugurate a new section on our site: scientific papers made easy! Often complicated, specialized and full of scientific jargon, these papers are rarely readable for the general public, or sometimes even for scientists working in a different field. But we strongly believe that discoveries and research should be accessible to everyone! Therefore, APECS Belgium thought that you might like to read the publications of our members with a clearer and more accessible vocabulary. For this first post, we take you to the white continent to attempt to answer a tricky question:
How can we predict the contribution of Antarctica to sea level rise in a context of global warming?
Centered on the South pole, Antarctica is a continent of 13,3 million square kilometers (around 433 times the surface of Belgium) covered by 2 kilometers of ice on average which weights 25,4 million Gigatons of ice. This huge quantity of ice on the ground is called ice sheet and the floating ice platforms coming from the ice sheet are called ice shelves. The boundary separating them is called the grounding line. Ice sheet and ice shelves are formed from fresh water unlike sea ice which is formed from sea water. Actually, Antarctica represents the biggest fresh water stock in the world and its future possible contribution to the global sea level in the current context of global warming is really uncertain. If all the ice in Antarctica was to disappear, the estimation of the sea level rise is about 57m. That would mean we would have a beach in Brussels.
Uncertainties about future projections in the Antarctic ice-sheet behaviors come from different sources including basal conditions. As you can imagine, it is difficult to know what happens at the base of the continent below kilometers of ice thickness which make direct observations impossible. Different basal parameters like nature of the bedrock and presence of water could play a role in the sensitivity of the Antarctic ice-sheet in a context of global warming. We focus our study on the uncertainties brought by the subglacial water control. The subglacial water in Antarctica comes from the basal melting of the ice. Basal melting is produced by the ice fusion below high pressure applied by kilometers of ice in contact with a bedrock with a certain geothermal flux. This water lubricates the interface between ice and bedrock and permits soil deformation under ice pressure. These two phenomena are responsible for the ice slipping over the bedrock but with an unknown intensity.
In this recently published paper, thanks to a numerical ice-sheet model, we evaluate different plausible subglacial water representations to investigate their impact on the future contribution of the Antarctic ice-sheet to global mean sea level by comparison with a scenario without subglacial consideration. To link these to basal sliding we will use two consistent parameters: the subglacial water flux and the subglacial water pressure between ice and bed or inside the till[1] which will impact the effective pressure (ice pressure reduced by the subglacial water pressure) determining the ice buoyancy. All our simulations start from the Antarctic ice-sheet geometry of 2015 and end in 2100. Simulations evaluate different climate scenarios until the end of the Century.
[1] Name given to the unstratified soil deposited by a glacier.
Figure 1: Schematic presentations and steady-state subglacial characteristics for the Antarctic ice-sheet according to the different subglacial models.
The results show that the subglacial hydrology representation modulates basal sliding response of the Antarctic ice-sheet to realistic climate scenarios by several centimeters of sea-level contribution at the end of the Century. Generally, this increases the ice sheet sensitivity, especially when the subglacial water pressure is increased in grounded zone or even more near the grounding line. As subglacial water considerations bring their share of uncertainties, the subglacial water pressure parameter determination is crucial in Antarctic projections.
Do you want to read more? Check out the full paper:
Written by Elise Kazmierczak