Sediment cores from within (570 m) and above (440 m) the modern oxygen minimum zone (OMZ) in the Santa Barbara Basin provide a depth transect of Pacific intermediate water temperature and oxygenation strength during the past 25ky. Intermediate waters (300-2500m) are critically important to the earth’s climate system for the transport of heat and salt around the globe, as well as influencing the carbon cycle via the oxygen minimum zone (OMZ). Oxygen isotopic values of benthic and planktonic foraminifera from these sites reflect a two-step deglaciation (including Terminations IA and IB). Oxygen isotopic values of benthic foraminifera suggest 2-3degC of intermediate water warming during deglaciation.  Records of lamination strength indicate that the OMZ dramatically expanded during the Bolling-Allerod (B/A) extending to above the modern basin sill depth.  Coincident with the sedimentary record of oxygenation changes is evidence for poorly ventilated waters (increase or plateau in ¹⁴C age), increased methane seepage to the basin (tar in sediments and carbon isotopic composition of foraminifera), and response of benthic species assemblages to the environmental changes at this time. These results indicate that intermediate waters experienced changes in temperature, oxygenation, ventilation and methane flux during Termination IA and the B/A. The significant expansion of the OMZ in the North Pacific during the B/A appears to have been forced by an upheaval in local (including surface productivity and methane seepage) and global carbon cycling at this time.