NASA Says Sea-Level Rise Temporarily Slowed By Aquifers and Lakes

For the first time, scientists can see how water storage on land affects how much and how fast sea levels have risen. An orbiting NASA satellite calculated the amount of water stored on Earth's continents, and the measurements revealed that terrestrial bodies are soaking up an extra 3.2 trillion tons of water, which is briefly mitigating the rise in sea level by approximately 20 percent. This land water is being stored in lakes, underground aquifers and the soil. Researchers from NASA's Jet Propulsion Laboratory (JPL) in Pasadena and the University of California-Irvine published their results in the most recent issue of the journal Science.

The global hydrologic cycle, or water cycle, is when water evaporates from the ocean, then descends to the Earth as precipitation, and then returns to the oceans by way of rivers and land runoff. Regional changes in the water cycle, affected by such things as soil moisture or lake levels, do have an influence on sea levels, changing what scientists would normally predict the sea level to be based on glacial melt rates. But, scientist have known about this connection for some time. What they didn't know, which this new study brings to light, is just how much water is absorbed by land because there was previously no way of precisely gauging the changes in land water amounts on a global scale. Now, they can.

NASA's Gravity Recovery and Climate Experiment (GRACE) twin satellites, which were launched in 2002, are the first instrument able to compute the amount of water stored by land masses. The quantity of water stored on the surface of the Earth changes regionally and that in turn affects the Earth's gravitational pull-something which can be identified by measuring the distance between the twin GRACE satellites, according to NASA. Based on these numbers, the scientists were able to determine just how much change there has been in ice and glacial melt along with changes in liquid water storage on land.

"What we didn't realize until now is that over the past decade, changes in the global water cycle more than offset the losses that occurred from groundwater pumping, causing the land to act like a sponge-at least temporarily," lead author J.T. Reager of JPL said in an official statement released by NASA. "These new data are vital for understanding decadal variations in sea level change. The information will be a critical complement to future long-term projections of sea level rise, which depend on melting ice and warming oceans."

Senior water scientist at JPL and senior author on the study, Jay Famiglietti, said that these figures will help improve global sea level budgets, which in turn will create a reliable estimate to how climate driven changes to hydrology affect sea level changes. These results also indicate that drier areas of the planet are getting drier and moist areas of the planet are getting wetter.

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