Projections of sea-level rise contributions from West Antarctica’s dynamically thinning ice streams contain high uncertainty because some of the key processes involved are extremely challenging to observe. An especially poorly observed parameter is sub-decadal stability of ice-stream beds. Only two previous studies have made repeated geophysical measurements of ice-stream beds at the same locations in different years, but both studies were limited in spatial extent. Here, we present the results from repeat radar measurements of the bed of Pine Island Glacier, West Antarctica, conducted 3–6 years apart, along a cumulative ~ 60 km of profiles. Analysis of the correlation of bed picks between repeat surveys show that 90 % of the ice-stream bed displays no significant change despite the glacier increasing in speed by up to 40 % over the last decade. We attribute the negligible detection of morphological change at the bed of Pine Island Glacier to the ubiquitous presence of a deforming till layer, wherein sediment transport is in steady state, such that sediment is transported along the basal interface without inducing morphological change to the radar-sounded bed. Significant change was only detected in one 500 m section of the bed where a change in bed morphology occurs with a difference in vertical amplitude of 3–5 m. Given the precision of our measurements, the maximum possible erosion rate that could go undetected along our profiles is 500 mm a-1, far exceeding erosion rates reported for glacial settings from proglacial sediment yields, but substantially below subglacial erosion rates of 1000 mm a-1 previously reported from repeat geophysical surveys in West Antarctica.
By Myriam Ortega/Diálogo March 30, 2017 The training was held in Colombia from February 3rd to 24th with the cooperation of U.S. Southern Command (SOUTHCOM). Its achievements included addressing the training priorities of the Colombian Armed Forces, improving skills in different operations, and sharing best practices with highly qualified military staff from the United States. Some of the courses were taught at the air base of the Military Transport Air Command (CATAM, per its Spanish acronym), while others, including parachuting exercises, airdrops, and medical training took place at the Tolemaida Military Fort. The 24-member work team, which included technicians and logistical support, arrived in a U.S. Army Hercules C-130 aircraft. The group was coordinated by the Mobility Support Advisory Squadron (MSAS), which designed the program and organized the group comprising instructors from the squadron itself and from six squadrons from five U.S. bases. “The MSAS is a squadron that trains Central and South American countries. We maintain a relationship to support the requirements of SOUTHCOM and the U.S. Embassy,” Lieutenant Colonel Ángel “Mango” Santiago, MSAS-Colombia mission commander, told Diálogo. “Normally, the air forces request the type of support they need for each course from the embassy, and the embassy looks at what kinds of teams from the U.S. can do that mission.” Based on Colombia’s needs, a training program was designed that consists of five courses: C-130 Personnel and Airdrop Team, C-130 Medevac Operations, Medical Intelligence, C-130 Maintenance: Propeller Balancing, and Load Preparation: RAMZ (inflatable boats). A total of 92 students from the Colombian Air Force (FAC, per its Spanish acronym), and the Colombian Army attended each course in small groups. During the training program, they used the C-130 aircraft, which can take off and land in rough terrain and has a pressurized cargo hold that can quickly be adapted for passengers, stretchers or troop transport. “The fundamental goal is to improve the capacities of FAC in its tactical mobility platforms, especially [the] C-130 and its capacity to airdrop personnel and cargo,” Major Marcus J. Rodríguez, director of operations of the 571st MSAS Squadron, told Diálogo. The experience of sharing knowledge and joint exercises provides a chance to improve technical capabilities. “We also have this aircraft, as do 69 other countries around the world. So it is an international platform,” said Lt. Col. Santiago, who also pilots that type of plane. The students’ experience Since 2012, this type of training has been offered every six months, more or less, in either Colombia or the United States. This continuity strengthens bi-national bonds of cooperation between partner nations. Participants experienced different styles of training based on the method used and subjects covered. The mass evacuation course gave students the chance to do a drill simulating the transport of injured people at the Tolemaida air base. “We did the drill using a helicopter provided by the Colombian Army. Four wounded individuals were evacuated (…) and transferred immediately, with the engines running, from the helicopter to the U.S. Air Force’s C-130, as the operation would be done,” described participant First Class FAC Technician Boris Polanco, assigned to the Hospital Engineering Division of the Health Department. “That moment was an intense adrenaline rush.” Service Technician Leady Karolina Castro, operator at CATAM’s engine workshop, also attended the course. “This is the first time I’ve taken the propeller course. The Hercules is our mainstay and the propeller course we just took can be applied every day. It’s practically our bread and butter here at the base,” she said. Participants also showed interest in the theory sessions since the content and method were tailored to each group’s needs. “This course, [with] the explanations they gave us, and the hands-on implementation reinforces our experience at work and in the workshop,” added Pastor Ramos Dumar, a junior technician at CATAM’s engine workshop who participated in the training. These courses will help ensure a timely response in a broad range of operations, including responses to natural disasters, humanitarian aid operations, and military operations, which may involve interaction between members of the Colombian Special Forces, Army, Air Force, and Navy.