DataSheet_1_A first estimate of the effect of offshore wind farms on sedimentary organic carbon stocks in the Southern North Sea.xlsx

Offshore wind farms (OWFs) can increase the transfer and stock of organic carbon (OC) in the surrounding sediments during their operational phase, while their construction and decommissioning release carbon. To answer the question whether sediments of OWFs trap more OC than they release, we estimate the net carbon effect over the entire life cycle (construction, operational and decommissioning phases) of OWFs in the Southern North Sea. Based on existing studies we compare the increased OC flux due to the colonization of organisms at the foundations of wind turbines and the OC loss due to sediment-disturbing activities during construction and decommissioning. Our results show that the areal intensity of carbon release in the disturbed areas is about 43.5 times higher than that of carbon trapping in the entire area of the OWFs. However, since the disturbed areas only account for about 0.50 ± 0.06% of the total area of the OWFs, in absolute terms about 4.6 ± 1.4 times more carbon is trapped in the sediment of the OWFs than is released. Due to limited data availability and the resulting need for extensive assumptions, our estimates only represent orders of magnitude. We therefore provide sensitivity estimates that define the limits of our calculations in terms of disturbance depth, remineralisation ratio, scour protection measures and heterogenous OC contents. In addition, we identify shortcomings of our extrapolation. Further research, especially more advanced impact assessments of construction and decommissioning processes must follow to improve the understanding of impacts of OWFs on sedimentary OC.

海上风电场（Offshore wind farms, OWFs）可在运行阶段提升周边沉积物中有机碳（organic carbon, OC）的迁移量与储量，但其建设与退役过程会释放碳。为解答海上风电场沉积物固存有机碳的量是否高于其释放量这一问题，我们针对北海南部海域海上风电场的全生命周期（包括建设、运行与退役阶段）估算其净碳效应。基于现有研究，我们对比了风力涡轮机基座处生物定植引发的有机碳通量增量，以及建设与退役阶段沉积物扰动活动造成的有机碳损失。研究结果显示，扰动区域的单位面积碳释放强度约为海上风电场全域碳固存强度的43.5倍。但由于扰动区域仅占海上风电场总海域面积的0.50±0.06%，从绝对总量来看，海上风电场沉积物固存的碳量约为其释放量的4.6±1.4倍。由于可用数据有限，且需依托大量假设前提，本研究的估算仅能反映碳效应的数量级范围。据此，我们提供了敏感性估算结果，以明确本研究计算在扰动深度、再矿化率、冲刷防护措施以及非均质有机碳含量等维度上的边界。此外，我们还指出了本次外推分析存在的不足。后续需开展进一步研究，尤其是针对建设与退役环节的精细化影响评估，以深化对海上风电场对沉积有机碳影响机制的认知。