( ( Two examples ) ( ( are ( ( ( ( ( ocean acidification ) ( caused ( by ( ( increased ( atmospheric concentrations ) ) ( of ( carbon dioxide ) ) ) ) ) ) , ) and ) ( ( the ( long-term melting ) ) ( of ( ( ( ice sheets ) , ) ( which ( contributes ( to ( sea ( level rise ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (CD Two) (NNS examples)) (VP (VBP are) (NP (NP (NP (NN ocean) (NN acidification)) (VP (VBN caused) (PP (IN by) (NP (NP (VBN increased) (JJ atmospheric) (NNS concentrations)) (PP (IN of) (NP (NN carbon) (NN dioxide))))))) (, ,) (CC and) (NP (NP (DT the) (JJ long-term) (NN melting)) (PP (IN of) (NP (NP (NN ice) (NNS sheets)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ contributes) (PP (TO to) (NP (NN sea) (NN level) (NN rise))))))))))) (. .)))
Two examples are ocean acidification caused by increased atmospheric concentrations of carbon dioxide, and the long-term melting of ice sheets, which contributes to sea level rise.
(ROOT (S (NP (NNP Ocean) (NNP acidification)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (NP (JJ excess) (NN carbon) (NN dioxide)) (PP (IN in) (NP (DT the) (NN atmosphere)))) (VP (VBZ causes) (S (NP (DT the) (NNS oceans)) (VP (TO to) (VP (VB become) (NP (NNS acidic))))))))) (. .)))
Ocean acidification occurs when excess carbon dioxide in the atmosphere causes the oceans to become acidic.