Thule, Greenland has been one of the major hubs of Operation IceBridge since the mission began in 2009.
The Thule Air Base, located 750 miles north of the Arctic circle, has been a critical hub of IceBridge Arctic flights during the course of the mission.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0