Abstract. Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air-sea carbon dioxide (CO₂) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO₂ whereas mid- and high-latitude shelves act as net sinks. Here, we combine a high-resolution regional model with surface water time-series and repeat transect observations from the Scotian Shelf, a mid-latitude region in the northwest North Atlantic, to determine what processes are driving the temporal and spatial variability of partial pressure of CO₂ (pCO₂). In contrast to the global trend, the Scotian Shelf acts as a net source. Surface pCO₂ undergoes a strong seasonal cycle associated with both a strong biological drawdown of Dissolved Inorganic Carbon (DIC) in spring, and pronounced effects of temperature, which ranges from 0 °C in the winter to near 20 °C in the summer. Throughout the summer, events with low surface-water pCO₂ occur nearshore associated with coastal upwelling. This effect of upwelling on pCO₂ is also in contrast to the general assumption that upwelling increases surface pCO₂ by delivering DIC-enriched water to the surface. Aside from these localized events, pCO₂ is relatively uniform across the shelf. Our model agrees with regional observations, reproduces seasonal patterns of pCO₂, and simulates annual outgassing of CO₂ from the ocean of +1.9 ± 0.2 mol C m⁻² yr⁻¹ for the Scotian Shelf, net neutral CO₂ flux of −0.09 ± 0.16 mol C m⁻² yr⁻¹ for the Gulf of Maine and uptake by the ocean of −0.88 ± 0.4 mol C m⁻² yr⁻¹ for the Grand Banks.

中文翻译：

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生物活性和温度主导的斯科蒂货架上时空p CO ₂变异性的模型研究

摘要。人们认为大陆架受到气候变化的影响最大，并且是全球气海二氧化碳（CO ₂）通量的主要贡献者。经常有报道说，低纬度的架子倾向于充当CO _2的净来源，而中高纬度的架子则充当净汇。在这里，我们将高分辨率的区域模型与地表水时间序列结合起来，并从北大西洋西北部中纬度地区斯科特陆架重复进行横断面观测，以确定哪些过程驱动了分压的时空变化的CO ₂（p CO ₂）。与全球趋势形成鲜明对照的是，斯科蒂尔书架是一个净来源。表面p CO ₂经历了一个强烈的季节性周期，这与春季的溶解无机碳（DIC）的大量生物学下降以及温度的显着影响有关，温度的范围从冬天的0°C到夏天的接近20°C。在整个夏季，地表水p CO ₂较低的事件发生在近岸，与沿海上升有关。向上膨胀对p CO _2的这种影响也与通常的假设相反，该一般假设是通过将富含DIC的水输送到表面来增加表面p CO ₂的。除了这些局部事件外，p CO ₂在整个架子上相对均匀。我们的模型与区域性观测结果吻合，再现了p CO _2的季节性模式，并模拟了斯科舍尔大陆架上+1.9±0.2 mol C m ⁻²  yr ^-1的海洋年度CO ₂脱气，净中性CO ₂流量为−缅因湾为0.09±0.16 mol C m ^-2  yr ^-1，大堤岸为-0.88±0.4 mol C m ^-2  yr ^-1。