Impact of Remineralization Profile Shape on the Air‐Sea Carbon Balance

• Published in: Geophysical research letters Vol. 48; no. 7; pp. e2020GL091746 - n/a
• Main Authors: Lauderdale, Jonathan Maitland, Cael, B. B.
• Format: Journal Article
• Language: English
• Published: United States John Wiley and Sons Inc 16-04-2021
• Subjects: Abrupt/Rapid Climate Change; Air/Sea Constituent Fluxes; Air/Sea Interactions; Atmosphere; Atmospheric; atmospheric CO2; Atmospheric Composition and Structure; Atmospheric Effects; Atmospheric Processes; Avalanches; Benefit‐cost Analysis; Biogeochemical Cycles, Processes, and Modeling; Biogeochemical Kinetics and Reaction Modeling; Biogeochemistry; Biogeosciences; biological pump; Biosphere/Atmosphere Interactions; carbon cycle; Carbon Cycling; Climate and Interannual Variability; Climate Change and Variability; Climate Dynamics; Climate Impact; Climate Impacts; Climate Variability; Climatology; Computational Geophysics; Cryosphere; Decadal Ocean Variability; Disaster Risk Analysis and Assessment; Earth System Modeling; Earthquake Ground Motions and Engineering Seismology; Effusive Volcanism; Evolution of the Atmosphere; Evolution of the Earth; Explosive Volcanism; export fluxes; General Circulation; Geodesy and Gravity; Geological; Global Change; Global Change from Geodesy; Gravity and Isostasy; Hydrological Cycles and Budgets; Hydrology; Impacts of Global Change; Informatics; Land/Atmosphere Interactions; Marine Geology and Geophysics; Martin Curve; Mass Balance; Modeling; Mud Volcanism; Natural Hazards; Numerical Modeling; Numerical Solutions; Ocean influence of Earth rotation; Ocean Monitoring with Geodetic Techniques; Ocean/Atmosphere Interactions; Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions; Oceanic; Oceanography: Biological and Chemical; Oceanography: General; Oceanography: Physical; Oceans; Paleoceanography; Physical Modeling; Policy Sciences; Radio Oceanography; Radio Science; Regional Climate Change; Regional Modeling; Research Letter; Risk; Sea Level Change; Sea Level: Variations and Mean; Seismology; Solid Earth; structural uncertainty; Surface Waves and Tides; Tectonophysics; Theoretical Modeling; Tsunamis and Storm Surges; Volcanic Effects; Volcanic Hazards and Risks; Volcano Monitoring; Volcano Seismology; Volcano/Climate Interactions; Volcanology; Water Cycles; atmospheric CO2; Martin Curve; carbon cycle; biological pump; export fluxes; structural uncertainty
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL091746

The ocean's “biological pump” significantly modulates atmospheric carbon dioxide levels. However, the complexity and variability of processes involved introduces uncertainty in interpretation of transient observations and future climate projections. Much research has focused on “parametric uncertainty,” particularly determining the exponent(s) of a power‐law relationship of sinking particle flux with depth. Varying this relationship's functional form introduces additional “structural uncertainty.” We use an ocean biogeochemistry model substituting six alternative remineralization profiles fit to a reference power‐law curve, to systematically characterize structural uncertainty, which, in atmospheric pCO2 terms, is roughly 50% of parametric uncertainty associated with varying the power‐law exponent within its plausible global range, and similar to uncertainty associated with regional variation in power‐law exponents. The substantial contribution of structural uncertainty to total uncertainty highlights the need to improve characterization of biological pump processes, and compare the performance of different profiles within Earth System Models to obtain better constrained climate projections.
Plain Language Summary
The ocean's “biological pump” regulates atmospheric carbon dioxide levels and climate by transferring organic carbon produced at the surface by phytoplankton to the ocean interior via “marine snow,” where the organic carbon is consumed and respired by microbes. This surface to deep transport is usually described by a power‐law relationship of sinking particle concentration with depth. Uncertainty in biological pump strength can be related to different variable values (“parametric” uncertainty) or the underlying equations (“structural” uncertainty) that describe organic matter export. We evaluate structural uncertainty using an ocean biogeochemistry model by systematically substituting six alternative remineralization profiles fit to a reference power‐law curve. Structural uncertainty makes a substantial contribution, about one‐third in atmospheric pCO2 terms, to total uncertainty of the biological pump, highlighting the importance of improving biological pump characterization from observations and its mechanistic inclusion in climate models.
Key Points
Six alternative flux profiles fit to a Martin Curve yield large differences in atmospheric carbon
Structural uncertainty comprises one‐third of total uncertainty in the ocean's biological pump
Varying particle attenuation with depth may account for half of the biological pump's overall carbon drawdown