Rapid climate change recorded in the North Pacific: Triggers, processes and effects

Planktonic foraminiferal isotopic and faunal evidence is presented from a Californian Margin transect (ODP Holes 893A, Santa Barbara Basin; 1017E, San Lucia Slope; and 1014, Tanner Basin) for major climate instability during the latest Quaternary. Differences between all three sites suggest a dramatic response to rapid climate change on the southern Californian Margin inferring relative changes in the contribution of surface water masses via the California Current System produced the large SST changes in the region. Southern California margin surface water conditions recorded by planktonic faunal oscillations also suggest variations in thermocline depth, vertical structure and temperature gradient between interstadials and stadials. Top-down, in situ atmospheric warming of the ocean is implied by differential responses (partial decoupling) in the changes recorded in surface and thermoclinal waters. Surface water conditions demonstrate the rapid response of the California Current System to reorganisation of North Pacific atmospheric circulation during rapid climate change suggesting a bimodal stability in North Pacific surface-ocean circulation organisation.; Synchronous climatic response between north Pacific surface waters and the Greenland ice sheet during D/O cycling is strongly indicated by remarkable similarities in speed, magnitude and character of rapid oceanic and atmospheric reorganizations. As ocean-atmosphere interactions over the North Pacific determine strength and location of surface currents, it follows some global climatic signals were atmospherically transmitted. The oscillatory pattern of climate change during OIS 3 suggests at this time the climate system was close to a threshold, whereby small perturbations were amplified to produce major, rapid climate change. Santa Barbara Basin benthic δ18O oscillations demonstrate North Pacific Intermediate Water temperature instability during submillennial climate change confirming changes in thermolialine circulation. Comparison of benthic and planktonic records provide evidence of differences in temporal response of surface and intermediate waters to rapid climate change. Gradual warming of upper intermediate water compared to abrupt atmospherically transmitted surface water warming suggests mechanistic differences not evident at abrupt coolings. Comparisons suggest North Pacific intermediate water warming preceded the abrupt surface warming by up to 200 years implying a previously undocumented feedback process in the climate system.