Arctic concentration–discharge relationships for dissolved organic carbon and nitrate vary with landscape and season
Arctic concentration–discharge relationships for dissolved organic carbon and nitrate vary with landscape and season
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DOI：
10.1002/lno.11682
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发表时间：
2020-12
影响因子：
4.5
通讯作者：
Arial J. Shogren;J. Zarnetske;Benjamin W. Abbott;F. Iannucci;Alexander Medvedeff;Samuel T Cairns;M. Duda;W. Bowden
中科院分区：
文献类型：
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作者：
Arial J. Shogren;J. Zarnetske;Benjamin W. Abbott;F. Iannucci;Alexander Medvedeff;Samuel T Cairns;M. Duda;W. Bowden
气候变化正在加剧北极的水文循环，可能会加速碳和营养物质从永久冻土地貌向河流的释放。然而，有足够频率和持续时间的有限的河流流量和溶质数据来测试季节性和集水区景观特征如何影响北极河网的碳和营养物质的生产和运输。我们在阿拉斯加北极三个源头的出水口进行了为期3年的高频水化学动力学测量。这些集水区代表了北极常见的地貌：低坡度冻土带、低坡度和受湖泊影响的冻土带以及高坡度高山冻土带。使用现场分光光度计，我们在2017年、2018年和2019年的流季每隔15分钟测量一次溶解有机碳(DOC)和硝酸盐(NO3−)的浓度。这些高频数据使我们能够量化整个汛期各个风暴事件期间的浓度-排放(C-Q)响应。不同流域C-Q响应的差异表明，景观和季节对横向DOC和NO3−通量有很强的控制作用。对于两个低梯度冻土带流域，我们在流动事件中观察到了一致的DOC浓缩(输送限制)和N3−稀释(来源限制)。相反，我们在高梯度高山集水区发现了一致的N3DOC浓缩和−稀释。我们的分析揭示了高流量事件对这些北极河流下游出口的不成比例贡献。由于流动季节的持续时间预计将延长，北极风暴的强度预计将增加，因此了解流量和溶质浓度是如何耦合的，对于了解快速变化的永久冻土生态系统中的碳和营养动态至关重要。
Climate change is intensifying the Arctic hydrologic cycle, potentially accelerating the release of carbon and nutrients from permafrost landscapes to rivers. However, there are limited riverine flow and solute data of adequate frequency and duration to test how seasonality and catchment landscape characteristics influence production and transport of carbon and nutrients in Arctic river networks. We measured high frequency hydrochemical dynamics at the outlets of three headwater catchments in Arctic Alaska over 3 years. The catchments represent common Arctic landscapes: low‐gradient tundra, low‐gradient and lake‐influenced tundra, and high‐gradient alpine tundra. Using in‐situ spectrophotometers, we measured dissolved organic carbon (DOC) and nitrate (NO3−) concentrations at 15‐min intervals through the flow seasons of 2017, 2018, and 2019. These high‐frequency data allowed us to quantify concentration–discharge (C‐Q) responses during individual storm events across the flow season. Differences in C‐Q responses among catchments indicated strong landscape and seasonal controls on lateral DOC and NO3− flux. For the two low‐gradient tundra catchments, we observed consistent DOC enrichment (transport‐limitation) and NO3− dilution (source‐limitation) during flow events. Conversely, we found consistent NO3− enrichment and DOC dilution in the high‐gradient alpine catchment. Our analysis revealed how high flow events may contribute disproportionately to downstream export in these Arctic streams. Because the duration of the flow season is expected to lengthen and the intensity of Arctic storms are expected to increase, understanding how discharge and solute concentration are coupled is crucial to understanding carbon and nutrient dynamics in rapidly changing permafrost ecosystems.