Pliocene carbonate accumulation along the California margin

Recent modeling studies call on increased ocean heat transport to explain high-latitude warming observed for intervals throughout the middle Pliocene. Possible vehicles for ocean heat transport are the poleward arms of the subtropical gyres. Sites from the California margin (Ocean Drilling Program Leg 167) provide monitors of wind field within the eastern arm of the gyre which may be an indication of basin-wide subtropical gyral strength. At most sites (water depths from 1106 to 4212 m) CaCO₃ mass accumulation rate (MAR) was highest in the middle Pliocene (3.5-2.0 Ma). This high CaCO₃ MAR "event" is attributed primarily to higher CaCO₃ production due to higher offshore upwelling associated with the zone of the greatest wind stress curl. Thus, in the middle Pliocene, there was enhanced wind stress curl along the California margin, and possibly enhanced North Pacific sub-tropical gyral circulation and meridional ocean heat advection.