The Role of Particle Size, Ballast, Temperature, and Oxygen in the Sinking Flux to the Deep Sea
The Role of Particle Size, Ballast, Temperature, and Oxygen in the Sinking Flux to the Deep Sea
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DOI：
10.1029/2017gb005710
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发表时间：
2018-05-01
影响因子：
5.2
通讯作者：
Deutsch, Curtis
中科院分区：
文献类型：
--
作者：
Cram, Jacob A.;Weber, Thomas;Deutsch, Curtis
有机颗粒从表层到深层的迁移效率是海洋固碳的关键决定因素。近年来，直接观测和地球化学分析揭示了一种系统的输送效率的地理格局，在高纬度地区最高，在副热带环流地区最低。我们使用下沉粒子动力学的力学模型来评估这种模式的可能原因。该模型描述了颗粒的粒度分布、矿物压载、海水温度(影响颗粒沉降速度和微生物代谢率)和氧气的影响。在合理的范围内对参数进行优化，以最大限度地匹配观测约束。我们的模型表明，没有单一因素可以解释观测到的转移率模式，但温度对再矿化速率的生物效应和粒度效应一起可以再现大部分区域变异性，这两个因素都导致副热带环流的低转移率和高纬度的高转移率。矿物压载的颗粒密度与温度和大小具有类似的定向效应，但由于硅酸盐和碳酸钙压载的相反模式，在我们的最佳解决方案中所起的作用要小得多。氧通过抑制再矿化速率，从而提高东热带太平洋的转移效率，对模型拟合产生了一定程度的改善。我们的模型表明，气候驱动的上层海洋温度变化以及与之相关的表层浮游生物大小分布的变化将降低海洋变暖时的碳封存效率。
The transfer efficiency of organic particles from the surface to depth is a critical determinant of ocean carbon sequestration. Recently, direct observations and geochemical analyses have revealed a systematic geographical pattern of transfer efficiency, which is highest in high latitude regions and lowest in the subtropical gyres. We evaluate the possible causes of this pattern using a mechanistic model of sinking particle dynamics. The model represents the size distribution of particles, the effects of mineral ballast, seawater temperature (which influences both particle settling velocity and microbial metabolic rates), and O-2. Parameters are optimized within reasonable ranges to best match the observational constraints. Our model shows that no single factor can explain the observed pattern of transfer efficiency, but the biological effect of temperature on remineralization rate and particle size effects together can reproduce most of the regional variability with both factors contributing to low transfer efficiency in the subtropical gyres and high transfer efficiency in high latitudes. Particle density from mineral ballast has a similar directional effect to temperature and size but plays a substantially smaller role in our optimum solution, due to the opposing patterns of silicate and calcium carbonate ballasting. Oxygen effects modestly improved model fit by depressing remineralization rates and thus increasing transfer efficiency in the Eastern Tropical Pacific. Our model implies that climate-driven changes to upper ocean temperature and associated changes in surface plankton size distribution would reduce the carbon sequestration efficiency in a warmer ocean.