Ocean Stratification from ongoing Warming Reduces Nutrient Phosphorus Availability Slowing Phytoplankton and Thus the Carbon Sink
In a previous video, I chatted about how the ocean sink for carbon will be reduced with a slowing AMOC (Atlantic Meridional Overturning Circulation). With accelerated ocean warming, and thus stratification of the oceans with less vertical mixing, the nutrients that come from deeper water via upwelling will become more scarce near the surface. I chat about a recent paper that measures the levels of the phosphorus in the shallow ocean waters near the surface, and determines that the phosphorus concentrations essential to phytoplankton proliferation have been reducing over the last several decades.
This is a big risk to the entire marine food web, since phytoplankton are at the vital base of the food chain in the oceans.
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New peer-reviewed scientific paper:
Title: Observed declines in upper ocean phosphate-to-nitrate availability
Abstract
Climate warming is increasing ocean stratification, which in turn should decrease the nutrient flux to the upper ocean. This may slow marine primary productivity, causing cascading effects throughout food webs. However, observing changes in upper ocean nutrients is challenging because surface concentrations are often below detection limits. We show that the nutricline depth, where nutrient concentrations reach well-detected levels, is tied to productivity and upper ocean nutrient availability. Next, we quantify nutricline depths from a global database of observed vertical nitrate and phosphate profiles to assess contemporary trends in global nutrient availability (1972–2022). We find strong evidence that the P-nutricline (phosphacline) is mostly deepening, especially throughout the southern hemisphere, but the N-nutricline (nitracline) remains mostly stable. Earth System Model (ESM) simulations support the hypothesis that reduced iron stress and increased nitrogen fixation buffer the nitracline, but not phosphacline, against increasing stratification. These contemporary trends are expected to continue in the coming decades, leading to increasing phosphorus but not nitrogen stress for marine phytoplankton, with important ramifications for ocean biogeochemistry and food web dynamics.
Link to Open-Source (free) paper: https://www.pnas.org/doi/pdf/10.1073/pnas.2411835122
Uncovering the Mysteries of the Oceans: What is Oceanography and How to Become an Oceanographer
https://www.hydro-international.com/content/article/uncovering-the-mysteries-of-the-oceans
Ocean's Vertical Structure Background
https://oceanmotion.org/html/background/ocean-vertical-structure.htm
Ocean Mixing Study
https://omix.aori.u-tokyo.ac.jp/en/overview/longversion/
Ocean Stratification and Implications
https://ncpor.res.in/pages/view/461/476-science-update---may
Peer-reviewed scientific paper: Comparison of ocean vertical mixing schemes in the Max Planck
Institute Earth System Model (MPI-ESM1.2)
Link: https://gmd.copernicus.org/articles/14/2317/2021/gmd-14-2317-2021.pdf
Peer-reviewed paper: Asymmetrical Ocean Carbon Responses in the Tropical Pacific Ocean to La Niña and El Niño
Abstract
Asymmetrical ocean carbon responses to La Niña and El Niño complicate global carbon budget estimation. Using multiple ocean CO2 data products and an advanced ocean biogeochemical model, we identified significant asymmetries in ocean carbon magnitude, spatial distribution, and duration in the tropical Pacific Ocean. La Niña enhances ocean CO2 outgassing (0.1–0.2 PgC/yr) with a broader poleward extension (15°S–15°N) for up to 3 years, while El Niño reduces outgassing (0.2–0.4 PgC/yr) with a narrower poleward extension (10°S–10°N) for up to 1 year. The air-sea carbon flux anomaly shifts westward during La Niña and eastward during El Niño. These asymmetries are attributed to differing wind, precipitation, and ocean circulation anomalies between La Niña and El Niño. Additionally, the cumulative carbon flux remains slightly imbalanced, impacting the global ocean carbon sink balance. This study provides deeper insights into ocean carbon sink variability and highlights the need for enhanced monitoring of asymmetrical ocean carbon dynamics.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL112039
Please donate to http://PaulBeckwith.net to support my research and videos joining the dots on abrupt climate system mayhem.