Transarctic variant of course is the worst one ...
Maybe they are using it because of this wiki article? http://en.wikipedia.org/wiki/Medal_%22For_the_Defence_of_the_Soviet_Transarctic%22
And again online dictionary http://dictionary.reference.com/browse/transarctic
Although many English-Russian dictionaries will give us simple translation
Transarctical = трансарктический
Another variant of translation is also possible (and some online translators will agree)
Transarctical = заполярный since russian dictionaries define трансарктический as прил., по знач. связанное с сообщением через арктическую или вообще полярную область.