Dissecting mesopelagic particulate organic carbon budgets in the North Atlantic: A mechanistic diagnosis and evaluation of PISCESv2_RC
- 1Barcelona Supercomputing Center (BSC), Plaça d’Eusebi Güell, 1–3, 08034 Barcelona, Catalonia, Spain; Universitat Politècnica de Catalunya (UPC), UPC Campus Nord, Carrer de Jordi Girona, 1–3, Les Corts, 08034 Barcelona, Catalonia, Spain; Institut de Ciències del Mar (ICM), Pg. Marítim de la Barceloneta, 37, Ciutat Vella, 08003 Barcelona, Catalonia, Spain
- 2Barcelona Supercomputing Center (BSC), Plaça d’Eusebi Güell, 1–3, 08034 Barcelona, Catalonia, Spain
- 3Institut de Ciències del Mar (ICM), Pg. Marítim de la Barceloneta, 37, Ciutat Vella, 08003 Barcelona, Catalonia, Spain
Abstract
Biogeochemical and physical processes in the mesopelagic layer regulate long-term carbon storage in the ocean interior. However, uncertainties in particulate organic carbon (POC) budgets limit quantitative understanding of the biological carbon pump and its representation in models. Here we analyse POC budgets simulated by the NEMO4–PISCESv2_RC model in the upper 1000 m of the North Atlantic over a climatological seasonal cycle, evaluating model performance and diagnosing the mechanisms that regulate POC export and transfer efficiency. Comparison with satellite, Argo-float, shipboard, and sediment-trap data indicates generally realistic POC stocks and fluxes. However, the model exhibits systematic biases, including (i) excessive diatom dominance at mid–high latitudes, (ii) compensation between too-low primary production and excessive epipelagic export in the subtropics, and (iii) underestimated mesopelagic POC stocks at mid and low latitudes. In the model, the mesopelagic POC supply driven by gravitational export and large detritus increases poleward, while winter–spring mixing supplies an additional 37 % in the subpolar region. Up to 60 % of mesopelagic POC supply is intercepted by zooplankton, yet most is recycled to detritus through fragmentation and trophic processing. This detrital loop modulates particle size, sinking speed, and degradation pathways, and is seasonally reinforced at mid–high latitudes. The lability of exported POC increases with latitude, whereas temperature-driven decay rates decrease with latitude. These opposing gradients result in maximal mesopelagic POC flux attenuation at midlatitudes, coincident with peak productivity. Small detritus plays a central role in the model, accounting for ∼ 55 % of mesopelagic POC decay and driving 33 %–50 % of vertical flux at 1000 m. These large modelled contributions reflect substantial biological supply and a pronounced vertical decline in lability, together favouring mesopelagic transfer of small POC. We propose POC budget analysis as a mechanistic framework for identifying structural biases and constraining inter-model spread in projections of the biological particulate carbon pump.
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BibTeX
@article{orihuelagarcia2026dissecting,
title = {{Dissecting mesopelagic particulate organic carbon budgets in the North Atlantic: A mechanistic diagnosis and evaluation of PISCESv2_RC}},
author = {M. Andrea Orihuela-García and Yohan Ruprich-Robert and Vladimir Lapin and Saskia Loosveldt Tomas and Raffaele Bernardello and Margarida Samsó-Cabré and Pierre-Antoine Bretonnière and Miguel Castrillo and Martí Galí},
journal = {Biogeosciences},
year = {2026},
month = jun,
doi = {10.5194/bg-23-4083-2026},
url = {https://doi.org/10.5194/bg-23-4083-2026},
note = {CC BY},
}
RIS
TY - JOUR
TI - Dissecting mesopelagic particulate organic carbon budgets in the North Atlantic: A mechanistic diagnosis and evaluation of PISCESv2_RC
AU - M. Andrea Orihuela-García
AU - Yohan Ruprich-Robert
AU - Vladimir Lapin
AU - Saskia Loosveldt Tomas
AU - Raffaele Bernardello
AU - Margarida Samsó-Cabré
AU - Pierre-Antoine Bretonnière
AU - Miguel Castrillo
AU - Martí Galí
PY - 2026
DA - 2026/06/01
JO - Biogeosciences
DO - 10.5194/bg-23-4083-2026
UR - https://doi.org/10.5194/bg-23-4083-2026
AB - Biogeochemical and physical processes in the mesopelagic layer regulate long-term carbon storage in the ocean interior. However, uncertainties in particulate organic carbon (POC) budgets limit quantitative understanding of the biological carbon pump and its representation in models. Here we analyse POC budgets simulated by the NEMO4–PISCESv2_RC model in the upper 1000 m of the North Atlantic over a climatological seasonal cycle, evaluating model performance and diagnosing the mechanisms that regulate POC export and transfer efficiency. Comparison with satellite, Argo-float, shipboard, and sediment-trap data indicates generally realistic POC stocks and fluxes. However, the model exhibits systematic biases, including (i) excessive diatom dominance at mid–high latitudes, (ii) compensation between too-low primary production and excessive epipelagic export in the subtropics, and (iii) underestimated mesopelagic POC stocks at mid and low latitudes. In the model, the mesopelagic POC supply driven by gravitational export and large detritus increases poleward, while winter–spring mixing supplies an additional 37 % in the subpolar region. Up to 60 % of mesopelagic POC supply is intercepted by zooplankton, yet most is recycled to detritus through fragmentation and trophic processing. This detrital loop modulates particle size, sinking speed, and degradation pathways, and is seasonally reinforced at mid–high latitudes. The lability of exported POC increases with latitude, whereas temperature-driven decay rates decrease with latitude. These opposing gradients result in maximal mesopelagic POC flux attenuation at midlatitudes, coincident with peak productivity. Small detritus plays a central role in the model, accounting for ∼ 55 % of mesopelagic POC decay and driving 33 %–50 % of vertical flux at 1000 m. These large modelled contributions reflect substantial biological supply and a pronounced vertical decline in lability, together favouring mesopelagic transfer of small POC. We propose POC budget analysis as a mechanistic framework for identifying structural biases and constraining inter-model spread in projections of the biological particulate carbon pump.
SN - 1726-4170
SN - 1726-4189
ER -