Putative Western Lesser Black-backed Gull (Larus fuscus graellsii). It is the first of the two graellsii in Aarhus Harbor today and also the first this summer. Documentation of the second is here.
Judged only on upper part colors we cannot safely dismiss an intergrade between intermedius and graellsii, but it is much paler than a classical Danish breeding intermedius.
It’s at least a 10th calendar year bird as it has been recorded annually in Aarhus Harbor since 2004 when it was in adult plumage, it's present annually from late summer until late autumn. There is an unread metal ring on its right tarsus and the legs are at maximum only slight yellowish in contrast to other adult Lesser Black-backed Gulls present making it easily identifiable from year to year.