[PAOCQ] Andrew Babbin (MIT)

“Mechanisms and climate consequences of shallow carbonate dissolution in the ocean”

Evidence for the shallow cycling of calcium carbonate in the global ocean is mounting, but the mechanisms driving the dissolution of thermodynamically stable carbonates like aragonite and calcite in the surface ocean remain unconstrained. Here, we quantify how microbial metabolism creates acidic microenvironments in marine particles that enhance local dissolution despite supersaturated conditions in bulk waters. A temporal decoupling of particle deoxygenation and acidification suggests that respiration-derived carbon dioxide is not the sole driver of the observed undersaturation. Rapid dissolution occurs in particles exhibiting bacterial growth, with rates exceeding abiotic dissolution at the same saturation state by more than an order of magnitude. We observe the highest particle-associated dissolution rates at intermediate settling velocities, suggesting a tradeoff between elevated mass transfer due to settling and bacterial respiration. Translation of our experiments to the water column suggests that microbially-driven undersaturation in marine particles may dissolve a significant fraction of calcite in the mesopelagic ocean, extend particle transit times, and reduce the efficiency of organic carbon sequestration by eliminating this vital ballast mineral.

— This week’s talk is in-person only. 

PAOC Colloquium —

Interdisciplinary seminar series that brings together the whole PAOC (Program in Atmospheres, Oceans, and Climate) community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, as well as talks about societal impacts of climatic processes.

Contact: paoc-colloquium-comm@mit.edu