Complex sentence: It was in Storglaciären that the first glacier mass balance research program began immediately after World War II, and continues to the present day; this is the longest continuous study of its type in the world.
Split into simpler sentences: It was in Storglaciären that the first mass balance program was initiated immediately after World War II, and continues to the present day. This survey was the initiation of the mass balance record of Storglaciären Glacier, and constitutes the longest continuous study of this type in the world.