Mississippi River low-flows: context, causes, and future projections
Mississippi River low-flows: context, causes, and future projections
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DOI：
10.1088/2752-5295/acd8e3
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发表时间：
2023-05
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通讯作者：
S. Muñoz;S. Dee;X. Luo;M. R. Haider;M. O'Donnell;B. Parazin;J. Remo
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作者：
S. Muñoz;S. Dee;X. Luo;M. R. Haider;M. O'Donnell;B. Parazin;J. Remo
密西西比河是一条主要的商业水道，河水水位异常低的时期会扰乱河流运输。这些低流量事件周期性发生，最近发生在 2022 年秋季的事件导致驳船运输放缓，并导致河流运输成本急剧增加。在这里，我们将密西西比河下游的仪器河流测量观测与社区地球系统模型 v2 大型集合 (LENS2) 的输出相结合，以评估密西西比河低流量极端值的历史趋势和未来预测，将 2022 年低流量事件置于更广泛的时间背景下，并评估介导低流量发生的水文气候机制。我们发现，1950 年至 1980 年间，随着人工水库的建立，低流量事件的严重程度和持续时间逐渐减少。在过去〜70年的背景下，2022年的低流量事件在阶段或流量最小值方面不如20世纪中后期的其他低流量事件严重。 LENS2 数据集的模型模拟表明，在中高排放情景 (SSP3-7.0) 下，预计到 21 世纪末，低流量事件的严重程度和持续时间将会减少。最后，我们使用 LENS2 数据集提供的大样本量来表明密西西比河的低流量事件与寒冷的热带太平洋强迫（即拉尼娜条件）有关，为厄尔尼诺南方涛动在调解密西西比河极端流量方面发挥关键作用的假设提供了支持。我们预计，描述密西西比河低流量发生的趋势和水文气候机制的研究结果将有助于水资源管理者减少低水位对河流运输的负面影响。
The Mississippi River represents a major commercial waterway, and periods of anomalously low river levels disrupt riverine transport. These low-flow events occur periodically, with a recent event in the fall of 2022 slowing barge traffic and generating sharp increases in riverine transportation costs. Here we combine instrumental river gage observations from the lower Mississippi River with output from the Community Earth System Model v2 Large Ensemble (LENS2) to evaluate historical trends and future projections of Mississippi River low streamflow extremes, place the 2022 low-flow event in a broader temporal context, and assess the hydroclimatic mechanisms that mediate the occurrence of low-flows. We show that the severity and duration of low-flow events gradually decreased between 1950 and 1980 coincident with the establishment of artificial reservoirs. In the context of the last ∼70 years, the 2022 low-flow event was less severe in terms of stage or discharge minima than other low-flow events of the mid- and late-20th century. Model simulations from the LENS2 dataset show that, under a moderate-high emissions scenario (SSP3-7.0), the severity and duration of low-flow events is projected to decrease through to the end of the 21st century. Finally, we use the large sample size afforded by the LENS2 dataset to show that low-flow events on the Mississippi River are associated with cold tropical Pacific forcing (i.e. La Niña conditions), providing support for the hypothesis that the El Niño-Southern Oscillation plays a critical role in mediating Mississippi River discharge extremes. We anticipate that our findings describing the trends in and hydroclimatic mechanisms of Mississippi River low-flow occurrence will aid water resource managers to reduce the negative impacts of low water levels on riverine transport.