Spatial variations of sea surface pCO₂ in the tropical Western Pacific near Guam

Abstract

The ocean sequesters carbon through solubility and biological pumps. It serves a critical role in the sequestration of the atmosphere’s carbon dioxide (CO₂). Understanding the extent of its sequestration role is an essential tool in tackling climate change policies and protecting the oceans. This study aims to understand the small-scale variabilities with increased levels of anthropogenic CO₂ on the ocean’s role as a sink of CO₂. This was done by collecting underway temperature, salinity, sea surface partial pressure of CO₂ (pCO₂), atmospheric pCO₂ and conditions continuously on the 2024-2025 University of Washington Oceanography Senior Thesis Cruise between 4 °N-16 °N, 148 °E-149 °E. Small-scale spatial features of pCO₂ concentrations will be analyzed to find correlations with other parameters (temperature, salinity, bathymetry) to find the driving process of the variations in pCO₂. Highest pCO₂ concentrations were measured around the deepest sections of the Nam-2 Atoll and the furthest south. In contrast, the lowest pCO₂ concentrations were measured around the Namonuito Guyot and directly north of the 4 °N peaks, at 5.5 °N-6.2 °N. It was found that seamounts have a great influence on pCO₂ concentrations. Since pCO2 is relatively consistent in its vertical distribution, local mixing due to currents accelerating against the seamount structures stirs higher concentrations of pCO2 into the mixed layer. This makes these areas with seamounts sources of pCO₂. This will put the atmospheric pCO₂ concentrations into even higher saturation.