Climate change impacts on the ocean’s biological carbon pump in a CMIP6 Earth System Model:

• Main Author: Walker, Stevie
• Format: Thesis
• Language: English
• Published: Boston College 2021
• Subjects: marine biogeochemistry; ocean carbon cycling; Earth System Models; climate change impacts; biological pump; North Atlantic
• Online Access: http://hdl.handle.net/2345/bc-ir:109224

Thesis advisor: Hilary Palevsky The ocean plays a key role in global carbon cycling, taking up CO2 from the atmosphere. A fraction of this CO2 is converted into organic carbon through primary production in the surface ocean and sequestered in the deep ocean through a process known as the biological pump. The ability of the biological pump to sequester carbon away from the atmosphere is influenced by the interaction between the annual cycle of ocean mixed layer depth (MLD), primary production, and ecosystem processes that influence export efficiency. Gravitational sinking of particulate organic carbon (POC) is the largest component of the biological pump and the aspect that is best represented in Earth System Models (ESMs). I use ESM data from CESM2, an ESM participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), to investigate how a high-emissions climate change scenario will impact POC flux globally and regionally over the 21st century. The model simulates a 4.4% decrease in global POC flux at the 100 m depth horizon, from 7.12 Pg C/yr in the short-term (2014-2034) to 6.81 Pg C/yr in the long-term (2079-2099), indicating that the biological pump will become less efficient overall at sequestering carbon. However, the extent of change varies across the globe, including the largest POC flux declines in the North Atlantic, where the maximum annual MLD is projected to shoal immensely. In the future, a multi-model comparison across ESMs will allow for further analysis on the variability of these changes to the biological pump. Thesis (BS) — Boston College, 2021. Submitted to: Boston College. College of Arts and Sciences. Discipline: Departmental Honors. Discipline: Earth and Environmental Science.