Relationship between surface-water temperature and ice-sheet expansion during the middle Miocene

A three-fold expansion of the Antarctic ice sheet at 13.60, 12.82, and 11.60 Ma has been inferred from δ18O maxima analyzed in planktonic and benthic foraminiferal tests, although accompanying changes in sea surface temperature have not been detailed. We present estimated changes in middle Miocene surface-water temperatures based on analysis of δ18O in planktonic foraminifera collected at mid-latitude Deep Sea Drilling Project sites in the North Atlantic and South Pacific oceans. We also identify periods of ice-sheet growth based on comparisons of benthic and planktonic foraminiferal δ18O values. Our results indicate: (1) a distinct cooling of the sea surface from 13.6 to 13.5 Ma immediately following a peak in ice volume at 13.6 Ma, (2) a cooling of the sea surface during a period of increasing ice volume from 13.2 to 13.0 Ma, and (3) a development of the Antarctic ice sheet during a period of cooling of the sea surface centered at 11.6 Ma.