(S (S (ADVP (RB However)) (COMMA ,) (S (BASENP (NNP Clausen)) (VP (VBZ believes) (SBAR (IN that) (S (BASENP (EX there)) (VP (VBP are) (NP (BASENP (DT no) (JJ current) (NNS systems)) (SBAR (S (VP (TO to) (VP (VP (VB remove) (BASENP (NN oil))) (PP (IN from) (BASENP (JJ icy) (NN ocean) (NNS waters)))))))))))))) (PERIOD .))