Increasing river alkalinity slows ocean acidification in the northern
Gulf of Mexico
Abstract
Ocean acidification (OA) progression is affected by multiple factors,
such as ocean warming, biological production, and runoff. Here we used
an ocean-biogeochemical model to assess the impact of river runoff and
climate variability on the spatiotemporal patterns of OA in the Gulf of
Mexico (GoM) during 1981-2014. The model showed the expected pH and
aragonite saturation state (ΩAr) decline, due to the increase in
anthropogenic carbon, with trends close to values reported for the
Subtropical North Atlantic. However, significant departures from the
basin-averaged pattern were obtained in part of the northern GoM shelf,
where pH and ΩAr increased. Model sensitivity analyses showed that OA
progression was counteracted by enhanced alkalinity from the
Mississippi-Atchafalaya River System. Our findings highlight that river
alkalinity is a key driver of carbon system variability in
river-dominated ocean margins and emphasize the need to quantify
riverine chemistry to properly assess acidification in coastal waters.