Sampling intervals, fluxes, percentages of total flux, organic carbon and lithogen for sediment trap CB9

We combined the analysis of sediment trap data and satellite-derived sea surface chlorophyll to quantify the amount of organic carbon export to the deep sea in the upwelling induced high production area off northwest Africa. In contrast to the generally global or basin-wide adoption of export models, we used a regionally fitted empirical model. Furthermore, the application of our model was restricted to a dynamically defined region of high chlorophyll concentration in order to restrict the model application to an environment of more homogeneous export processes. We developed a correlation-based approximation to estimate the surface source area for a sediment trap deployed from 11 June 1998 to 7 November 1999 at 21.25°N latitude and 20.64°W longitude off Cape Blanc. We also developed a regression model of chlorophyll and export of organic carbon to the 1000 m depth level. Carbon export was calculated for an area of high chlorophyll concentration (>1 mg/m**3) adjacent to the coast on a daily basis. The resulting zone of high chlorophyll concentration was 20,000-800,000 km**2 large and yielded a yearly export of 1.123 to 2.620 Tg organic carbon. The average organic carbon export within the area of high chlorophyll concentration was 20.6 mg/m**2d comparable to 13.3 mg/m**2d as found in the sediment trap results if normalized to the 1000 m level. We found strong interannual variability in export. The period autumn 1998 to summer 1999 was exceeding the mean of the other three comparable periods by a factor of 2.25. We believe that this approach of using more regionally fitted models can be successfully transferred even to different oceanographic regions by selecting appropriate definition criteria like chlorophyll concentration for the definition of an area to which it is applicable.本研究结合沉积物捕获器（sediment trap）数据与卫星反演的海面叶绿素（chlorophyll）浓度数据分析，对西北非洲外海上升流驱动的高生产力海域向深海输出的有机碳总量进行量化。与当前普遍采用的全球或全流域尺度碳输出模型不同，本研究使用了区域拟合的经验模型。此外，为将模型应用限定在输出过程更为均一的环境中，本研究将模型适用范围限定为动态划定的高叶绿素浓度海域。针对1998年6月11日至1999年11月7日在布兰科角外海北纬21.25°、西经20.64°处布放的沉积物捕获器，本研究构建了基于相关性的近似方法以估算其海面源区范围。此外，本研究还建立了叶绿素浓度与1000米深度有机碳输出量之间的回归模型。研究针对沿岸毗邻的高叶绿素浓度海域（>1 mg/m³）以日为单位开展碳输出量计算。最终划定的高叶绿素浓度海域面积介于20000~800000 km²之间，年有机碳输出量为1.123~2.620 太克（Tg）。高叶绿素浓度海域内的有机碳平均输出量为20.6 mg/(m²·d)，若归一化至1000米深度，该结果与沉积物捕获器观测得到的13.3 mg/(m²·d)较为接近。研究发现碳输出存在显著的年际变异性：1998年秋季至1999年夏季的碳输出量是其余三个可比时段平均值的2.25倍。本研究认为，通过选取叶绿素浓度等合适的划定标准来界定模型适用海域，这种采用区域拟合模型的研究思路可成功推广至其他海洋学区域。