Influence of Spatial Rainfall Gradients on River Longitudinal Profiles and the Topographic Expression of Spatially and Temporally Variable Climates in Mountain Landscapes
Influence of Spatial Rainfall Gradients on River Longitudinal Profiles and the Topographic Expression of Spatially and Temporally Variable Climates in Mountain Landscapes
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DOI：
10.1029/2021jf006183
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发表时间：
2021-03
期刊：
影响因子：
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通讯作者：
Joel S. Leonard;K. Whipple
中科院分区：
文献类型：
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作者：
Joel S. Leonard;K. Whipple
山地景观具有动态气候，与构造过程一起影响其地形演变。降雨的空间和时间变化在这些环境中是普遍存在的，因为地形降水模式随着气候变化和地形而演变。尽管重要的影响，这种变化对河流切割，其影响是研究不足。在这里，我们调查降雨模式的变化应如何影响稳定状态的形式和瞬态演变的河流剖面在流域尺度上使用流功率模型。我们发现，空间变化的降雨模式可以复杂的稳定状态之间的关系，平均降雨量，通道陡度和河流救济，这取决于降雨集中在集水区，并导致意外的瞬态行为，如果他们被忽略。具体而言，降雨模式的变化会导致多阶段的瞬态响应，这些响应与降雨均匀变化的响应不同。经历不同降雨条件的河流，特别是干支河流的不同响应，也是理解整个流域对气候变化响应的重要因素。因此，在采样策略和地形分析中考虑到这种差异，对于检测和量化气候在景观演变中的作用至关重要。最后，我们将展示如何明确占通道陡度指数的降雨模式，从而侵蚀效率的空间变化，可能会提前了解景观对气候的敏感性。这些结果有重要的影响，检测瞬态响应降雨模式（更广泛的气候）的变化，在稳态和瞬态景观的形态计量学的解释，量化的敏感性景观和侵蚀速率气候。
Mountain landscapes have dynamic climates that, together with tectonic processes, influence their topographic evolution. Spatial and temporal variations in rainfall are ubiquitous in these settings as orographic precipitation patterns evolve with climate change and topography. Despite important implications such changes have for river incision, their influence is understudied. Here, we investigate how changes in rainfall pattern should affect both the steady state form and transient evolution of river profiles at the catchment scale using the stream power model. We find that spatially varied rainfall patterns can complicate steady state relationships between mean rainfall, channel steepness and fluvial relief, depending on where rainfall is concentrated in catchments, and lead to unexpected transient behavior if they are neglected. Specifically, changes in rainfall pattern cause multi‐stage transient responses that differ from responses to uniform changes in rainfall. Disparate responses by rivers that experience different rainfall conditions, particularly trunk and tributary rivers, are also an important factor in understanding catchment‐wide responses to climate change. Accounting for such disparities in sampling strategies and topographic analyses may, therefore, be vital for detecting and quantifying climate's role in landscape evolution. Lastly, we show how explicitly accounting for rainfall patterns in channel steepness indices, and thus spatial variations in erosional efficiency, may advance understanding of landscape sensitivity to climate. These results have important implications for detecting transient responses to changes in rainfall pattern (and more broadly climate), interpretation of morphometrics in steady state and transient landscapes, and quantifying the sensitivity of landscapes and erosion rates to climate.