WACO, Texas — A federal judge Friday sentenced Pfc. Naser Jason Abdo to two consecutive life sentences, plus 60 years in prison for plotting to bomb and shoot Fort Hood soldiers in 2011.

Abdo, who represented himself at the sentencing hearing after dismissing his court-appointed lawyers last month, told U.S. District Judge Walter Smith that he remains committed to “jihad,” an Arabic word meaning struggle, that in some Islamic contexts can mean holy war.

He was arrested in July 2011 at a motel outside Fort Hood after a Killeen gun store clerk called police to report that Abdo had been acting suspiciously — wearing dark sunglasses, acting aggressively and seeming to know little about the items he was purchasing, including 6 pounds of gunpowder and shotgun ammunition. A search of his room and backpack found bomb-making equipment, a pistol and an article on assembling bombs from an English-language al-Qaida magazine.

Abdo, a Muslim involved in a highly publicized battle to obtain conscientious objector status while stationed at the Fort Campbell Army post in Kentucky, later told investigators that his attack was in response to what he considered the U.S. military’s wrongful treatment of the people of Iraq and Afghanistan. Abdo was absent without leave from Fort Campbell when he was arrested.

Greenland’s ice sheet thinning at uneven pace, scientists find

LOS ANGELES — The Greenland ice sheet, the second-largest ice body in the world, has lost its ice in fits and starts — with short bursts of dramatic ice loss separated by periods of stability, a study has found.

Scientists predict that if Greenland’s entire ice sheet were to melt, sea levels would rise more than 20 feet. But though recent observations have shown dramatic losses, they cannot easily predict what the pace of future loss is likely to be.

One of the issues is how far the data go back. Scientists track ice mass patterns via satellites in space, but such images date only to 2000, making predictions tentative. The new study, published Aug. 3 in Science, extended the time period for which Greenland’s ice can be observed by using photographs taken from airplanes dating back to the 1980s.

Kurt Kjaer, science director at the Natural History Museum of Denmark, and colleagues used the aerial data to create a map of ice sheet elevations in Northwest Greeland. Using digitally produced models of the area’s elevation, the scientists found high amounts of ice thinning — up to about 490 feet in some places — had occurred in fits and starts on the ice sheet during the last 25 years .

Uniformed Afghan kills 3 U.S. troops in apparently premeditated assault

KABUL, Afghanistan — A gunman in an Afghan uniform shot and killed three American service members in southern Afghanistan, the U.S. military said Friday, in the latest of an intensifying spate of so-called green-on-blue attacks.

An Afghan official in Helmand province, where the shooting took place, said the three men killed were members of the U.S. special operations forces, and that they were deliberately lured to their deaths by a police commander who invited them to dinner Thursday night at his checkpost. The Taliban claimed responsibility and said the gunman had defected to the insurgency.

The apparently premeditated nature of the attack added an alarming new dimension to the phenomenon of Afghan police and soldiers turning their weapons on Western mentors. The NATO force has disclosed 28 such deaths so far this year, and the latest shooting, in Helmand’s Sangin district, was the second of its kind this week.

The attacks pose a quandary for Western military officials, because the training of Afghan police and soldiers is a crucial part of plans to wind down the NATO force’s combat role and hand over security responsibilities to Afghan forces. Such mentoring requires Western troops to live and work in close quarters with Afghan counterparts.