14 DAY TRIAL // Scientists studying the planet's gravity say that ices melting from Greenland and the Antarctic are influencing this field, something that wasn't even suspected before. The new discovery could finally reveal why the two ice-rich areas began melting so fast over the past few decades.
Furthermore, the data might help climate scientists refine models seeking to explain how global ocean levels will rise once these two massive ice sheets lose most of their mass. This is bound to happen unless politicians step up their game, which they are unlikely to do in time.
Land-based ice has the highest potential of all ice types of raise global sea levels. When this happens, the phenomenon will threaten millions of people living in cities close to the ocean. Such cities include large metropolises like New York, Los Angeles, Rotterdam, Tokyo and so on.
Interestingly, it would appear that the weight glaciers put on mountains in Antarctica and Greenland was preventing the latter from raising. However, as the ice melts, the process is picking up speed, forcing a rearrangement of the mass underneath the continental masses.
Earth's continental and oceanic crusts are not uniformly distributed on the surface of the planet, so Earth's gravity field was not uniform in the first place. Now that the heavy weight of glaciers is lifted, and equally distributed over the ocean's surface, the field is changing, experts say.
“Although these changes are very small, they can be detected by satellites,” University of Colorado in Boulder (UCB) satellite geodesist and researcher R. Steven Nerem explains. The geodesic dome is the shape Earth's oceans would take if no continents were in place to constrain and redirect them.
Satellites such as the European Space Agency's (ESA) Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) are extremely well-suited for studying this dome, and their data are now pouring in from very low-Earth orbit (LEO).
Gravity field maps were also produced by the Gravity Recovery and Climate Experiment (GRACE) satellite, which has been studying the planetary surface for more than 20 years. The data this spacecraft produce also indicate a minor shift in the planet's gravitational pull.
“Glaciologists know that Greenland and Antarctica are melting, but it is harder for them to pin down when the melting started to change – they just don't have much data prior to the mid-1990s,” Nerem told Our Amazing Planet in a recent interview.
“Our study helps narrow the time uncertainty somewhat – it says that the mid-1990s is roughly when the behavior of the ice sheets started to change,” the expert concludes.