Kwon Eun Young, Dunne John P, Lee Kitack
Center for Climate Physics, Institute for Basic Science, Busan 46241, South Korea.
Pusan National University, Busan 46241, South Korea.
Sci Adv. 2024 Mar 29;10(13):eadl0779. doi: 10.1126/sciadv.adl0779.
Marine biogenic calcium carbonate (CaCO) cycles play a key role in ecosystems and in regulating the ocean's ability to absorb atmospheric carbon dioxide (CO). However, the drivers and magnitude of CaCO cycling are not well understood, especially for the upper ocean. Here, we provide global-scale evidence that heterotrophic respiration in settling marine aggregates may produce localized undersaturated microenvironments in which CaCO particles rapidly dissolve, producing excess alkalinity in the upper ocean. In the deep ocean, dissolution of CaCO is primarily driven by conventional thermodynamics of CaCO solubility with reduced fluxes of CaCO burial to marine sediments beneath more corrosive North Pacific deep waters. Upper ocean dissolution, shown to be sensitive to ocean export production, can increase the neutralizing capacity for respired CO by up to 6% in low-latitude thermocline waters. Without upper ocean dissolution, the ocean might lose 20% more CO to the atmosphere through the low-latitude upwelling regions.
海洋生物源碳酸钙（CaCO₃）循环在生态系统以及调节海洋吸收大气二氧化碳（CO₂）的能力方面发挥着关键作用。然而，碳酸钙循环的驱动因素和规模尚未得到很好的理解，尤其是对于上层海洋而言。在此，我们提供了全球尺度的证据，表明沉降的海洋聚集体中的异养呼吸作用可能会产生局部不饱和微环境，碳酸钙颗粒在其中迅速溶解，从而在上层海洋中产生过量碱度。在深海中，碳酸钙的溶解主要由碳酸钙溶解度的传统热力学驱动，随着碳酸钙埋藏通量减少，其进入更具腐蚀性的北太平洋深水区下方的海洋沉积物中。上层海洋的溶解作用对海洋输出生产力敏感，在低纬度温跃层水域中，它可将呼吸产生的二氧化碳的中和能力提高多达6%。如果没有上层海洋的溶解作用，海洋可能会通过低纬度上升流区域向大气中多排放20%的二氧化碳。
