[A-CG42] 地球規模環境変化の予測と検出

[ACG42-09] The Energy Exascale Earth System Model version 2 (E3SMv2) Global Ocean Biogeochemical Simulations: Effects of Vertical Mixing on the Ocean Carbon Cycle

★Invited Papers

*高野 陽平¹、Maltrud Mathew²、Nissen Cara³、Smith Katherine²、Lovenduski Nicole³、Gray Alison⁴、Christensen Katy³、Conlon LeAnn²、Falcinelli Kristen⁴、Jeffery Nicole²、Petersen Mark²、Sauvé Jade⁴、Sinha Anirban⁵、Wolfe Jonathan² (1.英国南極観測局、2.ロスアラモス国立研究所、3.コロラド大学、4.ワシントン大学、5.ピカロ)

キーワード：地球システムモデル、全球海洋炭素循環、鉛直混合

Ocean biogeochemistry models have large uncertainties in simulating changes in the observed ocean carbon sink in recent decades. Vertical mixing is one of the major physical processes that is critical for controlling the exchange of biogeochemical tracers between the upper and deep ocean. This process is parameterized in ocean biogeochemistry models, which contributes to uncertainties in simulating the ocean carbon sink. We present ocean–sea ice–biogeochemical simulations based on the Department of Energy's Energy Exascale Earth System Model version 2 (E3SMv2-BGC), with a particular focus on the simulated historical ocean carbon cycle and the model’s latest features. The E3SMv2-BGC incorporates the Marine Biogeochemistry Library (MARBL) and additional improvements to the representation of ocean physics, the most significant being background vertical mixing in ocean biogeochemistry simulations. We performed forced ocean biogeochemistry simulations with and without background vertical mixing. A comparison of the two simulations suggests that additional vertical mixing improves the representation of the spatial patterns of air–sea CO₂ flux, nutrients, and dissolved oxygen in the thermocline. Moreover, enhanced thermocline mixing through additional background vertical diffusion leads to a slower accumulation of modeled dissolved inorganic carbon in the upper ocean over recent decades, contributing to enhanced ocean carbon uptake in subtropical and mid-latitude regions. The results highlight the importance of incorporating background vertical diffusion for improved ocean biogeochemistry and carbon cycle simulations.