Water Can Affect Earth’s Local Gravity Field

In some areas of the world, differences that occur in the amount of precipitations that fall each season can contribute to modifying the local gravity field. The way the water is stored on the landmass can also have the same effect, scientists say.

The planet's water cycle is known to move the chemical around a lot, from the depths of the crust to the oceans and then into the atmosphere. Wind patterns than carry it all over the globe, where it is distributed according to a wide variety of factors.

But few investigators have until now studied the effects that water distribution have on the gravity field our planet exerts at specific locations.

Using the NASA Gravity Recovery and Climate Experiment (GRACE) twin satellites, experts have created a new series of maps of the Western Hemisphere, spanning between July 2009 and June 2010.

The documents show variations in the way water is stored throughout this Hemisphere over the course of a year. The maps also indicate where water is most tied up.

Lakes and rivers, groundwater aquifers, soil moisture, snow, and glaciers are the main storage points for water, the researchers behind the new work explain.

GRACE usually conducts investigations into how the planet's gravity field slowly changes above various regions, and its sensitive sensors made it the primary choice for conducting the new work.

“Among the most serious science and environmental policy issues confronting society are the potential changes in the Earth’s water cycle due to climate change,” says NASA in a recent fact sheet about our planet's water cycle.

“The science community now generally agrees that the Earth’s climate is undergoing changes in response to natural variability, including solar variability, and increasing concentrations of greenhouse gases and aerosols,” the document adds.

“Furthermore, agreement is widespread that these changes may profoundly affect atmospheric water vapor concentrations, clouds, precipitation patterns, and runoff and stream flow patterns. […] Orbiting satellites are now collecting data relevant to all aspects of the hydrologic cycle,” it concludes.

In the attached maps, the color blue is used to indicate areas that have stored higher-than-normal amounts of water over the year-long study. The color brown indicates regions that have lost water.

The differences are expressed in centimeters. Hydrologists usually do this, because their measurements are “expressed as an equivalent water level change, as if all the land's water were ponded on the surface,” says NASA expert Matt Rodell.