Fjord sediments are recognized global hotspots for the burial of organic carbon (OC) and as an integral part of the global carbon (C) cycle. Relative to their spatial extent, more OC is trapped and stored in the sediments of fjords than any other marine sedimentary environment. Until recently, our understanding of the rate at which OC accumulates and is buried in mid-latitude fjord sediments was poor, as these systems have largely been overlooked in favour of their high latitude counterparts. In this study, we quantify and explore the drivers of OC burial in the mid-latitude fjords of Scotland. By examining fifteen sediment cores from ten fjords, it is estimated that on average 57.1 ± 10.9 g C m⁻² yr⁻¹ accumulates in the sediments of Scottish fjords, exceeding observed OC burial in other vegetated fjord systems. When combined with an understanding of the spatial heterogeneity of the fjord sediments, it is estimated that Scottish fjords bury 84,000 t of OC annually, which is equivalent to the whole North Sea sedimentary system, despite the area of the latter being approximately 190 times larger. These findings highlight that mid-latitude fjords play a more significant role in global carbon cycling than previously thought, providing highly effective burial and storage of OC in fjord sediments.

峡湾沉积物是公认的全球有机碳 (OC) 埋藏热点，也是全球碳 (C) 循环的一个组成部分。相对于它们的空间范围，更多的 OC 被捕获和储存在峡湾的沉积物中，而不是任何其他海洋沉积环境。直到最近，我们对 OC 在中纬度峡湾沉积物中积累和掩埋的速度的理解还很差，因为这些系统在很大程度上被忽视了，而有利于它们的高纬度对应物。在这项研究中，我们量化并探索了苏格兰中纬度峡湾 OC 埋葬的驱动因素。通过检查来自 10 个峡湾的 15 个沉积岩心，估计平均 57.1 ± 10.9 g C m ^-2  yr ^-1在苏格兰峡湾的沉积物中积累，超过了在其他植被峡湾系统中观察到的 OC 埋藏量。结合对峡湾沉积物空间异质性的理解，估计苏格兰峡湾每年埋藏 84,000 吨 OC，相当于整个北海沉积系统，尽管后者的面积大约大 190 倍。这些发现强调，中纬度峡湾在全球碳循环中的作用比以前认为的更重要，为峡湾沉积物中的 OC 提供了高效的掩埋和储存。