Low-latitude (LL) oceans account for up to half of global net primary production and export^1,2,3,4,5. It has been argued that the Southern Ocean dominates LL primary production and export⁶, with implications for the response of global primary production and export to climate change⁷. Here we applied observational analyses and sensitivity studies to an individual model to show, instead, that 72% of LL primary production and 55% of export is controlled by local mesopelagic macronutrient cycling. A total of 34% of the LL export is sustained by preformed macronutrients supplied from the Southern Ocean via a deeper overturning cell, with a shallow preformed northward supply, crossing 30° S through subpolar and thermocline water masses, sustaining only 7% of the LL export. Analyses of five Coupled Model Intercomparison Project Phase 6 (CMIP6) models, run under both high-emissions low-mitigation (shared socioeconomic pathway (SSP5-8.5)) and low-emissions high-mitigation (SSP1-2.6) climate scenarios for 1850–2300, revealed significant across-model disparities in their projections of not only the amplitude, but also the sign, of LL primary production. Under the stronger SSP5-8.5 forcing, with more substantial upper-ocean warming, the CMIP6 models that account for temperature-dependent remineralization promoted enhanced LL mesopelagic nutrient retention under warming, with this providing a first-order contribution to stabilizing or increasing, rather than decreasing, LL production under high emissions and low mitigation. This underscores the importance of a mechanistic understanding of mesopelagic remineralization and its sensitivity to ocean warming for predicting future ecosystem changes.

低纬度 (LL) 海洋占全球净初级生产和出口量的一半^1,2,3,4,5 。有人认为，南大洋主导着低层初级生产和出口⁶ ，这对全球初级生产和出口对气候变化的响应具有影响⁷ 。在这里，我们对单个模型进行了观察分析和敏感性研究，结果表明，72% 的 LL 初级生产和 55% 的出口是由当地中层常量营养素循环控制的。总共 34% 的 LL 输出由南大洋通过更深的翻转单元提供的预制常量营养素维持，浅层预制向北供应，穿过副极地和温跃层水团跨越 30°S，仅维持 LL 的 7%出口。对五个耦合模型比较项目第 6 阶段 (CMIP6) 模型的分析，在 1850 年的高排放低缓解（共享社会经济路径 (SSP5-8.5)）和低排放高缓解 (SSP1-2.6) 气候情景下运行2300，揭示了他们对 LL 初级生产的幅度和符号的预测存在显着的跨模型差异。在更强的 SSP5-8.5 强迫下，随着更显着的上层海洋变暖，解释温度依赖性再矿化的 CMIP6 模型促进了变暖下 LL 中层营养物保留的增强，这为稳定或增加提供了一级贡献，而不是在高排放和低减排条件下，LL 产量不断减少。这强调了中层再矿化的机械理解及其对海洋变暖的敏感性对于预测未来生态系统变化的重要性。