The Seasonality of Physically Driven Export at Submesoscales in the Northeast Atlantic Ocean
The Seasonality of Physically Driven Export at Submesoscales in the Northeast Atlantic Ocean
复制标题
DOI：
10.1029/2018gb005927
复制
发表时间：
2018-08-01
影响因子：
5.2
通讯作者：
Thompson, Andrew F.
中科院分区：
文献类型：
--
作者：
Erickson, Zachary K.;Thompson, Andrew F.
亚尺度动力学 O(1-100km) 与增强的垂直速度相关，并以类似于生物生产的时间尺度（小时到天）演化。在这里，我们考虑东北大西洋一小片区域（20 x 20 公里）亚尺度动力学的年度周期及其与生产力和出口的关系。在该地区，虽然混合层的间歇性浅滩维持了全年浮游植物的数量，但六月混合层的重新分层引发了春季水华。光学群落指数表明春季大型物种（例如硅藻）占主导地位，冬季微型浮游植物占主导地位。我们回顾了三种类型的亚中尺度不稳定性——混合层（斜压）、重力和对称——并考虑了每种类型对固定碳从表层输出的影响。尽管混合层底部的垂直速度对参数化方案很敏感，但混合层的不稳定性可能会在冬季将物质从混合层中排出。相反，对称不稳定性提供了一种从混合层快速导出的清晰机制。决定出口潜力的一个关键因素是混合层底部的重斜斜强度。出口生产对冬季深层混合层相关的强烈亚中尺度活动和春季重新分层相关的高生产力之间存在的重叠程度很敏感，这意味着物理驱动的固定碳出口可能会在春季的短时间内发生。
Submesoscale dynamics O(1-100km) are associated with enhanced vertical velocities and evolve on a time scale similar to that of biological production (hours to days). Here we consider an annual cycle of submesoscale dynamics and their relation to productivity and export in a small (20 x 20 km) region of the northeast Atlantic Ocean. In this region, a springtime bloom is initiated by restratification of the mixed layer in June, although intermittent shoaling of the mixed layer maintains phytoplankton populations throughout the year. An optical community index suggests a dominance of large species (e.g., diatoms) during spring and picophytoplankton during the winter. We review three types of submesoscale instabilities-mixed layer (baroclinic), gravitational, and symmetric-and consider the impact of each on export of fixed carbon out of the surface layer. Mixed layer instabilities can potentially export material out of the mixed layer during winter, although the vertical velocity across the base of the mixed layer is sensitive to the parameterization scheme. Symmetric instabilities, in contrast, provide a clear mechanism for rapid export out of the mixed layer. A crucial factor determining export potential is the strength of the pycnocline at the base of the mixed layer. Export production is sensitive to the degree of overlap that exists between intense submesoscale activity associated with deep mixed layers in the winter and high productivity associated with the spring restratification, meaning that physically driven export of fixed carbon will likely happen over a short time window during spring.