Water in glaciers…
For example, glaciologists are using SPOT 5 imagery for the SPIRIT project to map Earth’s polar regions. The satellite’s HRS* instrument acquires 2 images of the same point from different viewing angles, making it possible to map landscape and glacier relief.
“Just as our 2 eyes allow us to see relief, stereopair images enable us to accurately reproduce the surface of glaciers,” explains Etienne Berthier, a glaciologist at French national scientific research centre CNRS. “By acquiring time series of measurements, we can ascertain if the glaciers are getting thicker or thinner.” Such data are vital for gauging the impact of climate change on our planet.
… and groundwater
By measuring fluctuations in the gravity field that holds us on Earth’s surface, the GRACE satellites are helping geophysicists to measure groundwater reserves.
Surprising though it may seem, an increase or drop in gravity at a specific point directly indicates a rise or fall in the amount of water stored underground.
Variation in groundwater in mm (left), variation in gravity in µGal (middle) and vertical ground displacement in mm (right) between 2002 and 2006. The weight of water causes the Earth’s crust to sag. Credits: GLADS/Institut de Physique du Globe de Strasbourg.
Today, as part of the GHYRAF project, field measurements are being pursued from the Sahara to the Gulf of Guinea. “Measurements acquired with gravimeters in the field will allow us to validate satellite data and give us a clearer picture of seasonal variations in water reserves in these regions,” says Jacques Hinderer, director of research at CNRS.
* Relating to the figure (shape and dimensions) of the Earth
** High-Resolution Stereoscopic