Ventilation and buffering capacity effects on ocean acidification in low oxygen environments

Area of Science:

• Oceanography
• Marine Chemistry
• Climate Science

Background:

• Ocean acidification is driven by anthropogenic carbon dioxide (CO₂) uptake.
• The Revelle factor (RF) quantifies buffering capacity, influencing acidification rates.
• The impact of RF on acidification in low-oxygen zones remains poorly understood.

Purpose of the Study:

• To compare changes in ocean acidification metrics between oxygen minimum zones (OMZs) and well-ventilated regions.
• To investigate the role of ventilation and buffering capacity in OMZs.
• To assess how different acidification indicators respond in these environments.

Main Methods:

• Comparison of preindustrial to present changes in CO₂ partial pressure (pCO₂), [H⁺], pH, aragonite saturation state (Ω_ara), and RF.
• Analysis focused on permanent OMZs versus adjacent well-ventilated areas.
• Evaluation of the influence of ventilation on CO₂ delivery and subsequent acidification.

Main Results:

• Acidification is minimal in poorly ventilated, lower OMZs but detectable in moderately ventilated upper OMZs.
• In upper OMZs, pCO₂ and [H⁺] increase faster, while Ω_ara, pH, and RF change slower than in well-ventilated regions.
• Limited CO₂ delivery by ventilation constrains acidification in low-oxygen regions.

Conclusions:

• Poorly ventilated, low-oxygen regions experience less ocean acidification than well-ventilated areas.
• Different acidification metrics ([H⁺] vs. Ω_ara) exhibit distinct responses due to their sensitivities.
• Ventilation is a key factor controlling the extent of ocean acidification in OMZs.