Salinity changes in the North West Pacific Ocean during the late Pliocene/early Quaternary from 2.73 Ma to 2.52 Ma

Recent research has increasingly advocated a role for the North Pacific Ocean in modulating global climatic
changes over both the last glacial cycle and further back into the geological record. Here a diatom δ18O
record is presented from Ocean Drilling Program Site 882 over the Pliocene/Quaternary boundary from 2.73
Ma to 2.52 Ma (MIS G6-MIS 99). Large changes in δ18Odiatom of c. 4‰ from 2.73 Ma onwards are
documented to occur on a timeframe broadly coinciding with glacial-interglacial cycles. These changes are
primarily attributed to large scale inputs of meltwater from glacials surrounding the North Pacific Basin and
the Bering Sea. Despite these inputs and associated change in surface water salinity, on the basis of existing
opal and Uk
37 temperature data and new modelled water column densities, no evidence exists to suggests a
removal of the halocline stratification or a resumption of the high productivity system similar to that which
prevailed prior to 2.73 Ma. The permanence of the halocline suggests that the region played a key role in
driving global climatic changes over the early glacial-interglacial cycles that followed the onset of major
Northern Hemisphere Glaciation by inhibiting deep water upwelling and ventilation of CO2 to the
atmosphere.