Adelicia Johnson

Adelicia Johnson

Years participated in RESESS:

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An Overview

Major: Geology
Academic Affiliation: Cabrillo Community College
Research Mentors: Nikki Lovenduski and Kristin Krumhardt
Communications Mentor: Derek Weller


Adelicia's interest in the geosciences began with the pebbles and cobbles she would pick up while running errands with mom, on a walk to school, or practically anywhere as a young girl. Since then, her interests have lead her to pursue a bachelors degree in Geology at UC Davis with hopes to continue on to get a masters in Geophysics.


Coccolithophore calcium carbonate export in an acidified ocean

Calcifying phytoplankton, known as coccolithophores, play a key role in the ocean’s biological pump by ballasting organic carbon particles and enhancing their transfer from the surface to the deep ocean. The growth and calcification of coccolithophores are uniquely sensitive to the seawater carbon dioxide concentration. Current laboratory studies suggest biomass and calcification have been, and will continue to be, affected by increased atmospheric carbon and the resulting ocean acidification. Here, we assess the impact of increasing surface ocean carbon dioxide concentration on the coccolithophore particulate inorganic carbon (PIC) export using a modified version of the Community Earth System Model where coccolithophores are explicitly represented as a phytoplankton functional group and their growth and calcification vary as a function of seawater carbon dioxide concentration. We analyze output from ocean-ice simulations run under three different atmospheric CO2 concentrations: 280 ppm (preindustrial), 400 ppm (present day), and 900 ppm (end of century) and validate the modeled PIC export with observations collected in sediment traps. From preindustrial to end of century atmospheric CO2conditions, we find a net 18.1% decrease in the globally-integrated PIC export, suggesting a weakening of the biological carbon pump. However, we find a net 3.78% increase in PIC export from preindustrial to present-day atmospheric CO2 conditions. This is most likely due to relief of carbon limitation in coccolithophore photosynthesis leading to a greater biomass and therefore more PIC. We observe large changes in regional PIC export, especially across the subpolar North Atlantic and the great calcite belt in the Southern Ocean. Our results highlight the sensitivity of the biological pump to changing carbon availability and ocean acidity.