The National Aeronautics and Space Administration (NASA) announced on Wednesday that an intensive satellite study has determined that the melting of land-based ice from 2003 to 2010 has added 4.3 trillion tons of water to the Earth’s oceans and has increased worldwide ocean and sea levels by approximately half an inch over that time period.
In reaching these conclusions, a scientific team led by University of Colorado at Boulder Professor John Wahr used data collected from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE). In its research, the team studied not only ice melt from Greenland’s glaciers and Antarctica, but also completed a detailed study of other glaciers across the Earth.
According to a NASA press release, Professor Wahr remarked, “Earth is losing a huge amount of ice to the ocean annually, and these new results will help us answer important questions in terms of both sea rise and how the planet’s cold regions are responding to global change.” Continuing, he said, “The strength of GRACE is it sees all the mass in the system, even though its resolution is not high enough to allow us to determine separate contributions from each individual glacier.”
The results of the study determined that approximately 25 percent of the land ice melt occurred outside Greenland and Antarctica. The data further indicates that higher elevations have not been as drastically affected by global warming as previously thought, particularly mountain ranges in Asia, possibly due to previous studies being conducted at lower altitudes.
Remarking on the unexpected data at higher elevations, Wahr explained, “One possible explanation is that previous estimates were based on measurements taken primarily from some of the lower, more accessible glaciers in Asia and extrapolated to infer the behavior of higher glaciers. But unlike the lower glaciers, most of the high glaciers are located in very cold environments and require greater amounts of atmospheric warming before local temperatures rise enough to cause significant melting. This makes it difficult to use low-elevation, ground-based measurements to estimate results from the entire system.”
While sea ice melt has occurred heavily over the past 30 years it has much less of an effect on water levels, as sea ice already displaces water. However land ice melt is of highly critical concern, as it adds significantly to rising water levels.
The two GRACE satellites, launched on March 16, 2002, orbit the Earth at an altitude of approximately 311 miles. Their mission is to collect data on Earth’s gravity field as well as Earth’s water system. Of primary interest is studying how the movement of Earth’s water affects Earth’s gravity field.