Alaska glaciers have been shedding about 46 billion tons of ice each year, making America's Arctic state the world's single biggest contributor to glacier-fed sea level rise outside of Greenland or Antarctica, say new estimates published this week in the online edition of the journal of Nature.

Still, Alaska remains a wee player in the global ice frappe, producing only about 8.5 percent of the world's annual glacier shrinkage of 526 billion tons, according to the study, led by a team at the University of Colorado at Boulder.

The total mass ice loss from Greenland, Antarctica combined with all of Earth's other glaciers and ice caps amounted to about 1,000 cubic miles -- about eight times the water volume of Lake Erie, explained UC-Boulder physicist John Wahr in this story about the work.

"The total amount of ice lost to Earth's oceans from 2003 to 2010 would cover the entire United States in about 1 and one-half feet of water," added Wahr, a fellow at the CU-headquartered Cooperative Institute for Research in Environmental Sciences.

Most of Alaska's annual ice loss occurs in the snow-bound coastal ranges that crown the Gulf of Alaska, and it's a huge chunk -- contributing about one third of the 150 billion tons of total annual ice loss from 18 regions around the globe outside of the two much larger continental sources.

Southern Alaskans take note: we are seasonal witnesses to this process. The inexorable retreat of Portage Glacier from view at Portage Lake, and other shrinkage by ice tongues in Anchorage's Chugach State Park, have all made tiny-but measurable-additions to this overall glacier breakdown.

Only shrinkage by the glaciers on Baffin Island (about 35 billion tons) and the Ellesmere Island area (about 34 billion tons) rival the Alaskan retreat, the study reported.

Still, size matters. The loss of ice from Alaska and the Canadian Arctic remains small when compared to the losses seen in the ice sheets of Greenland and Antarctica. Between 2003 and 2010, the continental ice sheets on Greenland dumped 222 billion tons annually, while Antarctica lost 165 billion tons.

Measuring gravity with eyes in the skies

To get the totals, the researchers basically resorted to rocket science, using data gathered by the tandem satellites of the Gravity Recovery and Climate Experiment, or GRACE, a joint effort of NASA and Germany.

Launched in 2002, the GRACE satellites zip around Earth 16 times each day in a 300-mile-high orbit, traveling about 135 miles apart. They dial in tiny changes in the Earth's gravitational pull and keep track of any shifts in the planet's mass caused by melting ice. These ultra-precise measurements have been producing gravity maps about 1,000 times more accurate than previous efforts. For more detail, here is a primer on how GRACE works and the latest fix on its orbit around the globe.

The current study used the satellites to estimate the "mass balance" of the world's glaciers -- the difference between the melt of summer and the growth from snow accumulation during winter. Finding a glacier's mass balance is critical to gauging its health -- whether it's growing or shriveling up -- but can take weeks or months of dangerous, expensive field work spread over many seasons. Only a small fraction of the world's glaciers have been studied on the ground.