Ideas and perspectives: Sea-level change, anaerobic methane oxidation, and the glacial-interglacial phosphorus cycle
International audience The oceanic phosphorus cycle describes how phosphorus moves through the ocean, accumulates with the sediments on the seafloor, and participates in biogeochemical reactions. We propose a new two-reservoir scenario of the glacial-interglacial phosphorus cycle. It relies on diage...
Published in: | Biogeosciences |
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Main Authors: | , , , |
Other Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2022
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Subjects: | |
Online Access: | https://insu.hal.science/insu-03678658 https://insu.hal.science/insu-03678658/document https://insu.hal.science/insu-03678658/file/bg-19-1421-2022.pdf https://doi.org/10.5194/bg-19-1421-2022 |
Summary: | International audience The oceanic phosphorus cycle describes how phosphorus moves through the ocean, accumulates with the sediments on the seafloor, and participates in biogeochemical reactions. We propose a new two-reservoir scenario of the glacial-interglacial phosphorus cycle. It relies on diagenesis in methane hydrate-bearing sediments to mobilize sedimentary phosphorus and transfer it to the oceanic reservoir during times when falling sea level lowers the hydrostatic pressure on the seafloor and destabilizes methane hydrates. The stock of solid phase phosphorus mobilizable by this process is of the same order of magnitude as the dissolved phosphate inventory of the current oceanic reservoir. The potential additional flux of phosphate during the glacial period is of the same order of magnitude as pre-agricultural, riverine dissolved phosphate fluxes to the ocean. Throughout the cycle, primary production assimilates phosphorus and inorganic carbon into biomass, which, upon settling and burial, returns phosphorus to the sedimentary reservoir. Primary production also lowers the partial pressure of CO 2 in the surface ocean, potentially drawing down CO 2 from the atmosphere. Concurrent with this slow "biological pump", but operating in the opposite direction, a "physical pump" brings metabolic CO 2 -enriched waters from deep-ocean basins to the upper ocean. The two pumps compete, but the direction of the CO 2 flux at the air-sea interface depends on the nutrient content of the deep waters. Because of the transfer of reactive phosphorus to the sedimentary reservoir throughout a glaciation cycle, low-phosphorus and high-CO 2 deep waters reign at the beginning of a deglaciation, resulting in rapid transfer of CO 2 to the atmosphere. The new scenario provides another element to the suite of processes that may have contributed to the rapid glacial-interglacial climate transitions documented in paleo-records. |
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