陆源入海碳通量

        河流有机碳通量定义为一定时间内水平通过河流某垂直断面的有机碳总量,即某断面有机碳浓度函数与流量函数的乘积相对于时间、深度、宽度的积分。河流有机碳浓度遥感反演机理与海洋有机碳反演相似,但存在一定难度。一方面,常用公里级分辨率的SeaWiFS、MERIS、MODIS等传统水色资料很难用于只有几百米至几公里宽度的河流。随着遥感技术的发展,如2012年韩国发射的世界上第一颗静止轨道水色传感器(Geostationary Ocean Color Imager, GOCI),空间分辨率为500 m、时间分辨率为1 h,是河流及高动态变化河口区域有机碳反演的良好数据源。另一方面,TM/Landsat和ETM+/Landsat等陆地传感器,虽然空间分辨率达30 m,但其宽波段及低信噪比设计很难从低水体信号中区分水体成分浓度差异。

        海洋遥感技术创新团队在长江大通水文站断面和长江河口分别开展了月尺度和季节尺度的光学-化学同步现场观测,利用多源遥感和实测资料估算了长江有机碳通量:(1)基于表征流域生态特征的关键参数(流量、遥感耕地面积比和总初级生产力等),构建了长江大通DOC浓度的多层回馈神经网络估算模型,并结合大通实测流量估算了2000-2013年长江大通水文站的DOC月平均通量。 (2)构建了适用于Landsat数据的POC浓度遥感算法,结合大通流量,估算了大通2000-2016年POC月平均通量。(3)构建了基于GOCI数据的POC浓度遥感算法,利用大通水文站的流量,估算了徐六泾断面的2015-2016年POC月平均通量。

        值得注意的是,河流入河口有机碳通量并不等同河流输运有机碳的有效入海通量。河流输运的有机碳会在河口冲淡水区发生转化、分解、沉降等,从而使最终能真正进入海洋的河流有机碳显著减少,这涉及到复杂的河口过程以及陆架有机碳的侧向输运。


部分代表性文章:

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