Oxygen minimum zone expansion in the eastern tropical North Pacific during deglaciation

During deglaciation at similar to 17 ka the intensity and footprint of the oxygen minimum zone (OMZ) increased in the Eastern Tropical North Pacific (ETNP) before a subsequent expansion on the California Margin. Evidence for the earlier increase is found in trace metal concentrations, lamination preservation and delta N-15 values from cores located between 540 - 750 m water depth in the Gulf of Tehuantepec, Southern Mexico. These results differ from similar proxies found even 5 degrees N of the site, where there is evidence for OMZ changes related to rapid climate change in the Northern Hemisphere. Instead, OMZ expansion in the Gulf was contemporaneous with changes in sea ice extent and zonal wind shifts around Antarctica, pointing to Subantarctic Mode Water and Antarctic Intermediate Water as likely sources of oxygen-depleted water. These observations reinforce the importance of the Southern Ocean as a primary modulator of northern hemisphere ocean climate, as far as 15 degrees N in the ETNP.