Assimilating water column and satellite data for marine export production estimation
Assimilating water column and satellite data for marine export production estimation
复制标题
同化水柱和卫星数据以估算海洋出口产量
DOI：
--
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
R. Schlitzer
中科院分区：
文献类型：
--
作者：
Xiaoping Yao;R. Schlitzer
摘要。卫星检索方法的最新进展现在允许直接从基于卫星的光学数据估计海洋表层水中特定的有机碳（POC）浓度。由于覆盖范围广，这些数据揭示了小尺度的时空浓度梯度，记录了整个季节地表水POC的演变以及潜在的驱动生物地球化学过程。水柱养分数据也揭示了生物地球化学活动。然而，由于数据的缺乏，在海洋的大部分地区不可能推导出颗粒产生和输出的时间变化。在这里，我们提出了一项结合两种数据流的新研究的第一个结果，从而利用卫星光学传感器的地表POC浓度的高时空分辨率，水柱营养数据覆盖较少，但提供了整个水柱的信息。我们使用了一个具有稳态三维环流的中分辨率全球模型，该模型通过拟合大量水文参数和示踪剂（包括CFCs和天然放射性碳）进行了优化。允许POC的生产和出口每月变化，每月出口通量的大小是通过使用伴随方法将模型拟合卫星POC数据以及水柱养分数据来确定的。研究了两种情况：(1)POC的产量被设定为与出口产量（EP）成正比，并且假定季节变化是正弦的（经向变化的幅度和相位），以及(2)POC的产量与初级产量有关（文献）。两种情况下运行相同的初始状态和模型设置，并显示总成本函数分别下降了12%和95%。单是POC失配项就分别减少了75%和99.8%。这两种情况下的全球POC年综合出口量分别为9.9亿吨和12.3亿吨。总体而言，两种解决方案的剩余POC和磷酸盐错配被认为太大，不同的领域仍然表现出显著的系统性地理格局。这表明，目前的模型运行过于简单，不能完全解释数据。此外，还需要更精细的模型设置。
Abstract. Recent advances in satellite retrieval methodology now allow for estimation of particular organic carbon (POC) concentration in ocean surface waters directly from satellite-based optical data. Because of the good coverage, these data reveal small-scale spatial and temporal concentration gradients and document the evolution of surface water POC as well as the underlying driving biogeochemical processes throughout the seasons. Water column nutrient data also reveal biogeochemical activity. However, because of the scarcity of data, the deduction of temporal changes of particle production and export is not possible in most parts of the ocean. Here we present first results from a new study combining both data streams, thereby exploiting the high spatio-temporal resolution of surface POC concentrations from satellite optical sensors with water column nutrient data having sparser coverage but providing information throughout the entire water column. We use a medium-resolution global model with steady-state 3-D circulation that has been optimized by fitting to a large number of hydrographic parameters and tracers, including CFCs and natural radiocarbon. Production and export of POC is allowed to vary monthly, and the magnitudes of the monthly export fluxes are determined by fitting the model to satellite POC data as well as water column nutrient data using the adjoint method. Two cases have been investigated: (1) the production rate of POC is set to be proportional to export production (EP) and the seasonal changes are assumed sinusoidal (meridionally varying amplitude and phase), and (2) the POC production rate is linked to primary production rates (literature). Both cases were run with the same initial state and model settings, and show total cost function decreases of 12 and 95%, respectively. The POC misfit term alone decreased by 75 and 99.8%. The integrated annual global POC exports of the two cases are 9.9 and 12.3 Gt C yr−1, respectively. Overall, the remaining POC and phosphate misfits of both solutions are considered too large, and the difference fields still exhibit significant systematic geographical patterns. This indicates that the present model runs are too simplistic and do not fully explain the data. Further, more refined model setups are needed.