HYDRANT: Antarctica’s Water Cycle
HYDRANT (HYDRologic system of ANTarctica) aims to investigate the atmospheric part of the Antarctic hydrologic cycle from moisture evaporation and cloud formation to snowfall.
To understand the current and future evolution of the Antarctic ice sheet, and its contribution to sea-level changes, an in-depth knowledge of the surface mass balance (SMB) of these ice sheets (sum of precipitation, sublimation, run-off and snowdrift) is essential. Regional atmospheric models have proven to be suitable tools for studying the SMB, but only if they are realistically representing the meteorological conditions in the region of interest. Therefore, it is absolutely necessary that high-quality measurements are performed to evaluate these models. The HYDRANT project is dedicated to make such measurements in order to evaluate the models accordingly.
Most evaluation studies are restricted to an evaluation of the net accumulation. However, clouds are of importance for an adequate representation of the hydrological cycle. Precipitation and cloud liquid water/ice are coupled and models are found incapable of sustaining high amounts of liquid water without producing precipitation. When atmospheric models are used to study the sensitivity of snowfall to climatic changes, it is important that not only surface precipitation is correctly represented, but also the other processes occurring in the chain from evaporation at the surface to snowfall, which we refer to as the atmospheric branch of the hydrological cycle (ABHC).
There is thus quite a complex system to study. The ice that makes up the vast Antarctic ice sheet comes entirely from accumulated snowfall. However, the distribution of snowfall over the Earth's southernmost continent is widely uneven. The coast receives a lot of snow, whereas the interior of the continent gets about as much precipitation as the Sahara Desert. However, snowfall in the continent's interior stays there for millennia and increases the ice sheet's overall mass balance while the ice sheet loses mass near its edges along the coasts. Each year along the coasts, most of the freshly-fallen snow either sublimes (a direct transition from snow to water vapour), is carried away by the katabatic winds (strong winds carrying high density air from the higher elevations of the interior of the ice sheet down towards the coast under the force of gravity), or simply melts. Ice that forms in the interior of the ice sheet also gets discharged into the sea at the coast.
The HYDRANT project was designed by Prof. Nicole van Lipzig from the Katholieke Universiteit Leuven (KUL). Dr. Irina Gorodetskaya is HYDRANT's project main scientist, and is in charge of setting up instruments to be used for the project at the Princess Elisabeth Station.
Picture: The HYDRANT instruments on the roof of Princess Elisabeth Antarctica - © International Polar Foundation