(Table 3) Interannual variability of total mass flux at the deep sediment trap site CBmeso between 1988 and 2006

This article will review major features of the 'giant' Cape Blanc filament off Mauritania with regard to the transport of chlorophyll and organic carbon from the shelf to the open ocean. Within the filament, chlorophyll is transported about 400 km offshore. Modelled particle distributions along a zonal transect at 21°N showed that particles with a sinking velocity of 5 m d**-1 are advected offshore by up to 600 km in subsurface particle clouds generally located between 400 m and 800 m water depth, forming an Intermediate Nepheloid Layer (INL). It corresponds to the depth of the oxygen minimum zone. Heavier particles with a sinking velocity of 30 m d**-1 are transported from the shelf within the Bottom Layer (BL) of more than 1000 m thickness, largely following the topography of the bottom slope. The particles advected within the BL contribute to the enhanced winter-spring mass fluxes collected at the open-ocean mesotrophic sediment trap site CB-13 (200 nm offshore), due to a long distance advection in deeper waters. The lateral contribution to the deep sediment trap in winter-spring is estimated to be 63% and 72% for organic carbon and total mass, respectively, whereas the lateral input for both components on an annual basis is estimated to be in the order of 15%. Biogenic opal increases almost fivefold from the upper to the lower mesotrophic CB-13 trap, also pointing to an additional source for biogenic silica from eutrophic coastal waters. Blooms obviously sink in smaller, probably mesoscale-sized patches with variable settling rates, depending on the type of aggregated particles and their ballast content. Generally, particle sinking rates are exceptionally high off NW Africa. Very high chlorophyll values and a large size of the Cape Blanc filament in 1998-1999 are also documented in enhanced total mass and organic carbon fluxes. An increasing trend in satellite chlorophyll concentrations and the size of the Cape Blanc filament between 1997 and 2008 as observed for other coastal upwelling areas is not documented.

本文将围绕毛里塔尼亚外海巨型布兰科角丝状流（Cape Blanc filament）的核心特征展开综述，聚焦其叶绿素与有机碳从陆架向开阔大洋的输运过程。该丝状流可将叶绿素输送至离岸约400 km的海域。在21°N纬向断面上的模拟粒子分布结果显示，沉降速率为5 m·d⁻¹的粒子会被平流输送至离岸最远600 km的次表层粒子云区，此类云团通常分布于400 m至800 m水深区间，进而形成中间浑浊层（Intermediate Nepheloid Layer, INL），其深度与氧最低区一致。沉降速率为30 m·d⁻¹的较重粒子则通过厚度超1000 m的底层（Bottom Layer, BL）从陆架向外输运，整体沿海底坡度地形运动。由于在深层水中发生了长距离平流输运，底层内输送的粒子会促成位于离岸200海里的开阔大洋中营养级沉积物捕集器站位CB-13处收集到的冬春季增强质量通量。冬春季期间，该站位的侧向贡献占比分别为有机碳63%、总质量72%；而年际尺度下，两种组分的侧向输入占比均约为15%。生物成因蛋白石在从中营养级CB-13捕集器的上层至下层的样品中增幅近五倍，这也表明富营养化近岸海域可为生物成因硅提供额外来源。水华显然以小型、大概率为中尺度尺度的团块形式沉降，其沉降速率因凝聚态颗粒类型与压载含量而异。整体而言，西北非外海的粒子沉降速率极高。1998-1999年期间，布兰科角丝状流的叶绿素浓度极高且规模庞大，这一现象也在总质量与有机碳通量的增强中得到印证。1997至2008年间，卫星观测到的叶绿素浓度与布兰科角丝状流规模并未呈现出与其他沿岸上升流区一致的增长趋势。