During the mission, Arpao “passed the mythical parallel of 66º33’N, which marks the border of the Arctic Circle, as well as the path of the Equator, a suitable landmark for all sailors”, highlighting the fleet, “this mark has not yet been reached by Portuguese submarines”.
“Achieving the objective of sailing under the ice required an intensive preparation and study, in which the crew had to virtually “re-learn” how to operate the vessel as the submarine navigated at high latitudes. The environment, such as icebergs and loose ice, presented noisy conditions and navigational hazards, thus “Many of the normal procedures and techniques normally used by submarines are forced to adapt when sailing in low latitudes,” the Navy statement said.
“Upon completing this mission, the NRP Arpão became one of the very few conventional submarines, if not the first, to travel under the ice, an area normally reserved for nuclear-powered submarines. In total, she remained under the ice. For approximately four (4) days, after World War I, “II has also explored operating in the fringing ice zone, an area where no other western submarine has dared to operate, the denser loose ice, with greater indirect value,” the report added.