4DANTARCTICA

Ice sheets are a key component of the Earth system, impacting on global sea level, ocean circulation and bio-geochemical processes. Significant quantities of liquid water are being produced and transported at the ice sheet surface, base, and beneath its floating sections, and this water is in turn interacting with the ice sheet itself.

Surface meltwater drives ice sheet mass imbalance; for example enhanced melt accounts for 60% of ice loss from Greenland, and while in Antarctica the impacts of meltwater are proportionally much lower, its volume is largely unknown and projected to rise. The presence of surface melt water is also a trigger for ice shelf calving and collapse, for example at the Antarctic Peninsula where rising air and ocean temperatures have preceded numerous major collapse events in recent decades.

Meltwater is generated at the ice sheet base primarily by geothermal heating and friction associated with ice flow, and this feeds a vast network of lakes and rivers creating a unique bio-chemical environment. The presence of melt water between the ice sheet and bedrock also impacts on the flow of ice into the sea leading to regions of fast-flowing ice. Meltwater draining out of the subglacial system at the grounding line generates buoyant plumes that bring warm ocean bottom water into contact with the underside of floating ice shelves, causing them to melt.  Meltwater plumes also lead to high nutrient concentrations within the oceans, contributing to vast areas of enhance primary productivity along the Antarctic coast.

Despite the key role that hydrology plays on the ice sheet environment, there is still no global hydrological budget for Antarctica. There is currently a lack of global data on supra- and sub-glacial hydrology, and no systems are in place for continuous monitoring of it or its impact on ice dynamics.

The overall aim of 4DAntarctica is to advance our understanding of the Antarctic Ice Sheet’s supra and sub-glacial hydrology, its evolution, and its role within the broader ice sheet and ocean systems. We designed our programme of work to address the following specific objectives:

• Creating and consolidating an unprecedented dataset composed of ice-sheet wide hydrology and lithospheric products, Earth Observation datasets, and state of the art ice-sheet and hydrology models
• Improving our understanding of the physical interaction between electromagnetic radiation, the ice sheet, and liquid water
• Developing techniques and algorithms to detect surface and basal melting from satellite observations in conjunction with numerical modelling
• Applying these new techniques at local sites and across the continental ice sheet to monitor water dynamics and derive new hydrology datasets
• Performing a scientific assessment of Antarctic Ice Sheet hydrology and of its role in the current changes the continent is experiencing
• Proposing a future roadmap for enhanced observation of Antarctica’s hydrological cycle

To do so, the project will use a large range of Earth Observation missions (e.g. Sentinel-1, Sentinel-2, SMOS, CryoSat-2, GOCE, TanDEM-X, AMSR2, Landsat, Icesat-2) coupled with ice-sheet and hydrological models. By the end of this project, the programme of work presented here will lead to a dramatically improved quantification of meltwater in Antarctica, an improved understanding of fluxes across the continent and to the ocean, and an improved understanding of the impact of the hydrological cycle on ice sheet’s mass balance, its basal environment, and its vulnerability to climate change.