Radiocarbon (Δ¹⁴C) serves as an effective tracer for identifying the origin and cycling of carbon in aquatic ecosystems. Global patterns of organic carbon (OC) Δ¹⁴C values in riverine particles and coastal sediments are essential for understanding the contemporary carbon cycle, but are poorly constrained due to under-sampling. This hinders our understanding of OC transfer and accumulation across the land–ocean continuum worldwide. Here, using machine learning approaches and >3,800 observations, we construct a high-spatial resolution global atlas of Δ¹⁴C values in river–ocean continuums and show that Δ¹⁴C values of river particles and corresponding coastal sediments can be similar or different. Specifically, four characteristic OC transfer and accumulation modes are recognized: the old–young mode for systems with low river and high coastal sediment Δ¹⁴C values; the young–old and old–old modes for coastal systems with old OC accumulation receiving riverine particles with high and low Δ¹⁴C values, respectively; and the young–young mode with young OC for both riverine and coastal deposited particles. Distinguishing these modes and their spatial patterns is critical to furthering our understanding of the global carbon system. Specifically, among coastal areas with high OC contents worldwide, old–old systems are largely neutral to slightly negative to contemporary atmospheric carbon dioxide (CO₂) removal, whereas young–old and old–young systems represent CO₂ sources and sinks, respectively. These spatial patterns of OC content and isotope composition constrain the local potential for blue carbon solutions.

放射性碳 (Δ ¹⁴ C) 可作为识别水生生态系统中碳的来源和循环的有效示踪剂。河流颗粒和沿海沉积物中有机碳 (OC) Δ ¹⁴ C 值的全球模式对于了解当代碳循环至关重要，但由于采样不足而受到很大限制。这阻碍了我们对全球陆地-海洋连续体的有机碳转移和积累的理解。在这里，使用机器学习方法和超过 3,800 个观测值，我们构建了河流-海洋连续体中 Δ ¹⁴ C 值的高空间分辨率全球图集，并表明 Δ ¹⁴ C 值河流颗粒和相应的沿海沉积物可以相似或不同。具体来说，识别了四种特征的OC转移和积累模式：低河流和高沿海沉积物Δ ¹⁴ C值系统的老-年轻模式；具有旧OC积累的沿海系统的年轻-老年和老年-老年模式分别接收具有高和低Δ ¹⁴ C值的河流颗粒；以及针对河流和沿海沉积颗粒的具有年轻 OC 的年轻-年轻模式。区分这些模式及其空间格局对于加深我们对全球碳系统的理解至关重要。具体而言，在全球 OC 含量较高的沿海地区，老-老系统对当代大气二氧化碳 (CO ₂ ) 的去除基本上呈中性至轻微负面影响，而新-老和老-年轻系统则代表 CO < b7> 分别为源和汇。这些 OC 含量和同位素组成的空间模式限制了蓝碳解决方案的局部潜力。