"10.3189/172756401781818671" . "20th-century sea-ice variations from observational data"^^ . . "33" . "444-448" . "2001"^^ . "10.3189/172756401781818671" . . . _:genid1 . _:genid1 . _:genid1 . _:genid1 . _:genid1 . _:genid2 . _:genid2 . _:genid2 . _:genid2 . _:genid2 . . . . .