Coupling of Ocean Acidification and Ocean Depletion in the Gulf of Alaska

Abstract

Abrupt deglacial environmental changes are recorded in the North Pacific including the expansion and strengthening of the oxygen minimum zone (OMZ). Previous workers in the North Pacific proposed a link between OMZ intensification and increased ocean acidification. Understanding the relationship between oxygen depletion and ocean acidification during past intervals of climate change is crucial for forecasting and mediating the effects that the modern-day OMZ expansion will have on marine ecology. Here, I use benthic (Uvigerina peregrina) and planktonic (Neogloboquadrina pachyderma) foraminiferal size-normalized shell weights (SNW) from two Gulf of Alaska sediment core records as a proxy for carbonate dissolution, which increases with increasing acidification. If ocean acidification increased during a previously recognized low oxygen event (LOE; ~15-10 kya) should result in lower shell weights due to dissolution if ocean acidification is associated with deoxygenation. At intermediate ocean depths, planktonic SNW were generally lower while high benthic SNW increased, perhaps due to acidification in the water column affecting the planktonics, whereas, dissolution oversaturated pore waters with carbonate ion. SNW of planktonics were heavier in the intermediate than deep site, possibly due to heavier sedimentation rate or more sulfidic conditions in the pore waters at intermediate depths.