Coastal North Carolina experienced 36 tropical cyclones (TCs), including three floods of historical significance in the past two decades (Hurricanes Floyd-1999, Matthew-2016 and Florence-2018). These events caused catastrophic flooding and major alterations of water quality, fisheries habitat and ecological conditions of the Albemarle-Pamlico Sound (APS), the second largest estuarine complex in the United States. Continuous rainfall records for coastal NC since 1898 reveal a period of unprecedented high precipitation storm events since the late-1990s. Six of seven of the “wettest” storm events in this > 120-year record occurred in the past two decades, identifying a period of elevated precipitation and flooding associated with recent TCs. We examined storm-related freshwater discharge, carbon (C) and nutrient, i.e., nitrogen (N) and phosphorus (P) loadings, and evaluated contributions to total annual inputs in the Neuse River Estuary (NRE), a major sub-estuary of the APS. These contributions were highly significant, accounting for > 50% of annual loads depending on antecedent conditions and storm-related flooding. Depending on the magnitude of freshwater discharge, the NRE either acted as a “processor” to partially assimilate and metabolize the loads or acted as a “pipeline” to transport the loads to the APS and coastal Atlantic Ocean. Under base-flow, terrestrial sources dominate riverine carbon. During storm events these carbon sources are enhanced through the inundation and release of carbon from wetlands. These findings show that event-scale discharge plays an important and, at times, predominant role in C, N and P loadings. We appear to have entered a new climatic regime characterized by more frequent extreme precipitation events, with major ramifications for hydrology, cycling of C, N and P, water quality and habitat conditions in estuarine and coastal waters.

中文翻译：

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北卡罗来纳州（美国）热带气旋 (TC) 最近降雨和洪水的增加：对沿海流域有机物质和养分循环的影响

北卡罗来纳州沿海地区经历了 36 次热带气旋 (TC)，其中包括过去 20 年中具有历史意义的 3 次洪水（Hurricanes Floyd-1999、Matthew-2016 和 Florence-2018）。这些事件导致了美国第二大河口综合体 Albemarle-Pamlico Sound (APS) 的灾难性洪水和水质、渔业栖息地和生态条件的重大改变。自 1898 年以来沿海北卡罗来纳州的连续降雨记录揭示了自 1990 年代后期以来前所未有的高降水风暴事件时期。在这个超过 120 年的记录中，七次“最潮湿”风暴事件中有六次发生在过去 20 年，确定了与近期 TC 相关的降水和洪水增加的时期。我们检查了与风暴相关的淡水排放、碳 (C) 和养分，即 氮 (N) 和磷 (P) 负荷，并评估了对 APS 主要子河口 Neuse River Estuary (NRE) 年总投入的贡献。这些贡献非常显着，根据先前条件和与风暴相关的洪水，占年负荷的 50% 以上。根据淡水排放量的大小，NRE 要么充当“处理器”以部分吸收和代谢负荷，要么充当“管道”将负荷输送到 APS 和大西洋沿岸。在基流下，陆地来源主导河流碳。在风暴事件期间，这些碳源通过淹没和从湿地释放碳而增强。这些发现表明，事件规模的排放在 C、N 和 P 负载中起着重要的作用，有时也起主导作用。