A regional hindcast model simulating ecosystem dynamics, inorganic carbon chemistry, and ocean acidification in the Gulf of Alaska
A regional hindcast model simulating ecosystem dynamics, inorganic carbon chemistry, and ocean acidification in the Gulf of Alaska
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DOI：
10.5194/bg-17-3837-2020
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发表时间：
2020-07-29
期刊：
影响因子：
4.9
通讯作者：
Stock, Charles A.
中科院分区：
文献类型：
--
作者：
Hauri, Claudine;Schultz, Cristina;Stock, Charles A.
阿拉斯加湾的沿海生态系统特别容易受到海洋酸化和气候变化的影响。检测这些长期趋势需要对系统的自然状态有很好的理解。GOA是一个高度动态的系统，在亚季节到年际时间尺度上表现出较大的无机碳变化。由于在这一广阔而偏远的地区缺乏观测，对这种变异性了解甚少。本文建立了三维区域海洋模式系统（ROMS）与碳、海洋生物地球化学和低营养（钴）生态系统模型相结合的GOA模型。为了提高我们对该系统的概念理解，我们进行了1980年至2013年的后向模拟。在高分辨率陆地水文模型中，沿海淡水排放量随时间和空间变化而明显改变，从而影响盐度、碱度、溶解无机碳和营养物质浓度。这代表了对以前GOA建模尝试的实质性改进。在这里，我们利用最佳的无机碳观测值在季节到年际时间尺度上对模型进行评估。该模型特别成功地再现了5月和9月分别观测到的近底水文石过饱和和不饱和。该模型最大的缺陷是无法充分模拟春季地表无机碳化学，因为它高估了地表溶解无机碳，从而低估了此时地表文石的饱和状态。我们还利用该模型描述了欠采样月份沿苏厄德线样带的无机碳参数的季节周期和驱动因素。模式输出表明，由于上升流和再矿化作用，6月至1月期间，苏厄德线附近的大部分近底水相对文石季节性不饱和。如此长时间反复出现的文石欠饱和可能对海洋酸化敏感的生物有害。此外，淡水的影响不仅降低了夏秋两季沿海地表水文石饱和状态，同时也降低了表层二氧化碳分压（pCO(2)），从而使文石饱和状态与pCO(2)脱钩。GOA地区的完整季节周期和地理范围采样不足，我们的模式结果为一年中的几个月和缺乏原位无机碳观测的地区提供了新的重要见解。
The coastal ecosystem of the Gulf of Alaska (GOA) is especially vulnerable to the effects of ocean acidification and climate change. Detection of these long-term trends requires a good understanding of the system's natural state. The GOA is a highly dynamic system that exhibits large inorganic carbon variability on subseasonal to interannual timescales. This variability is poorly understood due to the lack of observations in this expansive and remote region. We developed a new model setup for the GOA that couples the three-dimensional Regional Oceanic Model System (ROMS) and the Carbon, Ocean Biogeochemistry and Lower Trophic (COBALT) ecosystem model. To improve our conceptual understanding of the system, we conducted a hindcast simulation from 1980 to 2013. The model was explicitly forced with temporally and spatially varying coastal freshwater discharges from a high-resolution terrestrial hydrological model, thereby affecting salinity, alkalinity, dissolved inorganic carbon, and nutrient concentrations. This represents a substantial improvement over previous GOA modeling attempts. Here, we evaluate the model on seasonal to interannual timescales using the best available inorganic carbon observations. The model was particularly successful in reproducing observed aragonite oversaturation and undersaturation of near-bottom water in May and September, respectively. The largest deficiency in the model is its inability to adequately simulate springtime surface inorganic carbon chemistry, as it overestimates surface dissolved inorganic carbon, which translates into an underestimation of the surface aragonite saturation state at this time. We also use the model to describe the seasonal cycle and drivers of inorganic carbon parameters along the Seward Line transect in undersampled months. Model output suggests that the majority of the near-bottom water along the Seward Line is seasonally undersaturated with respect to aragonite between June and January, as a result of upwelling and remineralization. Such an extensive period of reoccurring aragonite undersaturation may be harmful to ocean acidification-sensitive organisms. Furthermore, the influence of freshwater not only decreases the aragonite saturation state in coastal surface waters in summer and fall, but it simultaneously decreases the surface partial pressure of carbon dioxide (pCO(2)), thereby decoupling the aragonite saturation state from pCO(2). The full seasonal cycle and geographic extent of the GOA region is under-sampled, and our model results give new and important insights for months of the year and areas that lack in situ inorganic carbon observations.