Diagnosing CO2 fluxes in the upwelling system off the Oregon-California coast
Diagnosing CO2 fluxes in the upwelling system off the Oregon-California coast
复制标题
诊断俄勒冈-加利福尼亚海岸上升流系统中的二氧化碳通量
DOI：
10.5194/bg-11-6341-2014
复制
发表时间：
2014-01-01
期刊：
影响因子：
4.9
通讯作者：
Feely, R.
中科院分区：
文献类型：
--
作者：
Cao, Z.;Dai, M.;Feely, R.
众所周知，上升流系统中的CO2通量是由地下沃茨通过生物代谢提供的碳和营养盐之间的相互作用决定的。然而，这种相互作用的定量评估是困难的，因为上升流循环和相关的地球化学的动态性质。我们最近提出了一个新的框架，海洋主导的边缘（OceMar），用于半定量诊断海洋边缘在给定时间内的CO2源/汇性质，强调碳和营养物之间的相对消耗决定了碳是否过量（即，CO2源）或不足（即，CO2汇）在海洋边缘的上层沃茨相对于其场外输入从邻近的公海。在本研究中，这样的诊断方法的基础上耦合的物理-地球化学和碳-营养素被应用到解决的CO2通量在著名的上升流系统关闭俄勒冈州和北方加州的美国西海岸，使用的数据收集沿着三个跨陆架断面从内陆架到开放的盆地在2007年春季/初夏。通过研究生物消耗的总碱-盐关系所揭示的水团混合的顶部，我们成功地预测和半解析的CO2通量表现出强烈的吸收从大气中超出近岸区域。这种CO2汇的性质主要是由于较高的利用率的营养盐相对于溶解无机碳（DIC）的基础上，他们从深度的并发输入。另一方面，在俄勒冈州-加利福尼亚州海岸附近的近岸沃茨，对上升流加剧的生物反应较小，在采样期间观察到显著的CO2释气，可以简化CO2通量的解析，而不考虑DIC/营养物消耗，即，上涌和生物消耗之间的脱钩。我们推断OceMar模型中的耦合物理学和地球化学将通过物理传输和生物学改变在可比的时间尺度上假设具有平衡DIC和营养物的稳定状态。
It is generally known that the interplay between the carbon and nutrients supplied from subsurface waters via biological metabolism determines the CO2 fluxes in upwelling systems. However, quantificational assessment of such interplay is difficult because of the dynamic nature of both upwelling circulation and the associated biogeochemistry. We recently proposed a new framework, the Ocean-dominated Margin (OceMar), for semi-quantitatively diagnosing the CO2 source/sink nature of an ocean margin over a given period of time, highlighting that the relative consumption between carbon and nutrients determines if carbon is in excess (i.e., CO2 source) or in deficit (i.e., CO2 sink) in the upper waters of ocean margins relative to their off-site inputs from the adjacent open ocean. In the present study, such a diagnostic approach based upon both couplings of physics-biogeochemistry and carbon-nutrients was applied to resolve the CO2 fluxes in the well-known upwelling system off Oregon and northern California of the US west coast, using data collected along three cross-shelf transects from the inner shelf to the open basin in spring/early summer 2007. Through examining the biological consumption on top of the water mass mixing revealed by the total alkalinity-salinity relationship, we successfully predicted and semi-analytically resolved the CO2 fluxes showing strong uptake from the atmosphere beyond the nearshore regions. This CO2 sink nature primarily resulted from the higher utilization of nutrients relative to dissolved inorganic carbon (DIC) based on their concurrent inputs from the depth. On the other hand, the biological responses to intensified upwelling were minor in nearshore waters off the Oregon-California coast, where significant CO2 outgassing was observed during the sampling period and resolving CO2 fluxes could be simplified without considering DIC/nutrient consumption, i.e., decoupling between upwelling and biological consumption. We reasoned that coupling physics and biogeochemistry in the OceMar model would assume a steady state with balanced DIC and nutrients via both physical transport and biological alterations in comparable timescales.