Cross-Shore Flow and Implications for Carbon Export in the California Current Ecosystem: A Lagrangian Analysis
Cross-Shore Flow and Implications for Carbon Export in the California Current Ecosystem: A Lagrangian Analysis
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DOI：
10.1029/2020jc016611
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发表时间：
2021-02-01
影响因子：
3.6
通讯作者：
Ohman, M. D.
中科院分区：
文献类型：
--
作者：
Chabert, P.;d'Ovidio, F.;Ohman, M. D.
东部边界上升流系统是初级生产量和碳出口增加的地区，因此在全球碳循环中发挥核心作用。在这些区域，营养物质上升流发生在靠近海岸的狭窄区域，但初级生产和碳输出通常在更广泛的区域内观察到。多产水域进入公海这一事实对生物碳泵具有重要影响，因为这种输送将靠近海岸的营养源与近海的深层碳汇连接起来。然而，这种离岸运输的许多方面仍然未知。在这里，我们用卫星资料推断的水平输送的拉格朗日诊断方法，研究了加利福尼亚海流生态系统(CCE)中与上升流相关的跨岸水流的季节和年际变化。我们将平流年龄定义为水团在500米等深线附近流动的时间。我们发现，高Chl-a水域的离岸延伸与近岸水团的年龄相关，并与中尺度环流相一致。老水域近海范围的年际变化主要是由中尺度变化驱动的，并伴随着ENSO和NPGO的大尺度强迫。现场新生产的测量比率：碳出口也随着水龄的变化而变化，在较年轻的水域往往为1，在较老的水域更平衡。我们的结果可能有助于将FineScale在上升区碳输出中的作用参数化，用于气候解析模式。简单语言摘要加州当前生态系统(CCE)是一个沿海上升流强烈、有机质生产增加、碳通量高进入深海的地区，在全球碳循环中具有潜在的影响。此前的研究表明，CCE的产量和下沉并不平衡：靠近海岸的产量比下沉多，近海的下沉比生产多。我们的研究使用卫星测量来分析CCE的跨岸流动，并评估水、营养物质和浮游生物的水平运输是否可以协调这种空间失衡。通过跟踪水团轨迹，我们发现，从海岸到近海的水团被运输到近海的时间是预测该水团是有机质的净来源(新增产量大于沉降量)还是净沉降量(大于新增产量)的指标。我们发现，水输送的离岸距离每年变化很大，并与已知的气候强迫源有关，包括厄尔尼诺-南方涛动和北太平洋环流。由于与这些气候指数的协变性，可以估计未来海岸和近海之间的有机物质交换。
Eastern Boundary Current Upwelling Systems are regions of elevated primary production and carbon export and thus play a central role in the global carbon cycle. In these regions, nutrient upwelling occurs in a narrow region close to the coast, but primary production and carbon export are typically observed across a broader region. The fact that productive waters reach the open ocean has important consequences for the biological carbon pump, because such transport connects nutrient sources close to the coast to the deep carbon sinks of the offshore ocean. However, many aspects of this offshore transport are still not known. Here we address seasonal and interannual variability of upwelling-related cross-shore flows in the California current ecosystem (CCE) by employing Lagrangian diagnostics of horizontal transport inferred from satellite data. We define an advective age as the time a water parcel flowed offshore of the 500 m isobath. We find that the offshore extension of high Chl-a waters covaries with the age of a coastal water parcel, and is consistent with mesoscale circulation. Interannual variability in the offshore extent of older waters is primarily driven by mesoscale variability and covaries with large scale forcing by both ENSO and the NPGO. The measured ratio of in-situ new production: carbon export also covaries with water age, and tends to be 1 in younger and more balanced in older waters. Our results may help to parameterize the role of the finescale on the export of carbon in upwelling regions for climate resolving models.Plain Language Summary The California current ecosystem (CCE) is a region of strong coastal upwelling, elevated organic matter production and high carbon flux into the deep ocean, and potentially influential in the global carbon cycle. Previous studies have suggested that production and sinking are not balanced in the CCE: there is more production than sinking close to the coast and more sinking than production offshore. Our study uses satellite measurements to analyze cross-shore flows in the CCE and assess whether horizontal transport of water, nutrients, and plankton can reconcile this spatial imbalance. By following water parcel trajectories, we find that the time since a water parcel is transported from the coast to the offshore is a predictor of whether the water parcel is a net source of organic matter (greater new production than sinking) or a net sink (greater sinking than new production). We find that the offshore distance of water transport varies strongly from year to year and is related to known sources of climate forcing, including El Nino-Southern Oscillation and the North Pacific Gyre Oscillation. Future organic matter exchanges between the coast and the offshore can be estimated thanks to covariability with these climate indices.