Global climate and tectonic controls on the denudation of glaciated mountains
Global climate and tectonic controls on the denudation of glaciated mountains
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DOI：
10.1016/j.epsl.2012.01.030
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发表时间：
2012-04
影响因子：
5.3
通讯作者：
B. Yanites;T. Ehlers
中科院分区：
文献类型：
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作者：
B. Yanites;T. Ehlers
高山冰川侵蚀的效率相对于河流和山坡作用存在很大的不确定性。温度的纬度变化对于确定冰川的范围很重要，同样重要的还有影响冰川可能形成的海拔（以及温度）的构造抬升速率。冰川侵蚀对温度的高度敏感性使之前的解释变得复杂，因为温度必须足够低才能维持冰，同时又必须足够热才能让冰川滑动。在这里，我们量化了气候和构造对冰川景观演化的影响，采用了一个冰川、河流和山坡景观演化的耦合模型，该模型系统地探索了岩石隆升率的变化和气候（即冰期-间冰期）在百万年时间尺度上的周期性变化。重点放在了解某一特定气候何时比其冰期前景观更具（例如“电锯”条件）或更少侵蚀性。结果表明，冰川侵蚀效率随纬度控制温度和岩石隆升速率的变化而变化。在某些情况下，局部（河谷底部）侵蚀和短期（一个冰期）冰川作用的速率都有一个数量级的增加。然而，当在整个景观上平均2Ma时，冰川侵蚀的增加通常不到冰期前景观的两倍。在某些情况下，由于小而低效的冰川或广泛的冷基冰川作用，平均冰川侵蚀速率低于冰期前速率。将模型预测与冰川山脉的长期剥蚀率汇编进行比较，表明模型在解释冰川侵蚀效率模式方面表现良好。本文提出的研究结果对冰川对景观演变的影响具有明确的含义，包括：(1)冰川比冰川前速率更具侵蚀性的气候“窗口期”；(2)剥蚀的时空变化可能导致侵蚀脉冲；(3)不同纬度冰川侵蚀效率的预测。我们得出结论，纬度和海拔相关的温度变化控制了冰川剥蚀的效率，并解释了以往研究之间的差异。
Significant uncertainty exists concerning the efficiency of alpine glacial erosion relative to fluvial and hillslope processes. Latitudinal variations in temperature are important for determining the extent of glaciers, as are the rates of tectonic uplift that influence the elevation (and hence temperatures) that glaciers can form. The acute sensitivity of glacial erosion to temperature has complicated previous interpretations because temperatures must be cool enough to maintain ice yet warm enough to allow glacial sliding. Here we quantify the influence of climate and tectonics on glacial landscape evolution with a coupled glacial, fluvial, and hillslope landscape evolution model that systematically explores variations in rock-uplift rate and periodic variations in climate (i.e. glacial–interglacial periods) over million-year time scales. Emphasis is placed on understanding when a particular climate is either more (e.g. “buzzsaw” conditions) or less erosive than its preglacial landscape. Results indicate that the erosional efficiency of glaciers varies as a function of latitudinal controlled temperature and rock-uplift rate. An order of magnitude increase in erosion rates occurs in some scenarios for both localized (valley bottom) erosion and short-term (one glacial period) durations of glaciation. However, when averaged over the entire landscape for 2Ma, increases in glacial erosion are typically less than double that of the preglacial landscape. In some scenarios, average glacial erosion rates are less than preglacial rates due to either small, inefficient glaciers or extensive cold-based glaciation. Model predictions are compared with a compilation of long-term denudation rates from glaciated mountain ranges and indicate models perform well at explaining patterns of glacial erosion efficiency. The findings presented here have clear implications for the impact of glaciations on the evolution of landscapes including: (1) the climatic “window” in which glaciers are more erosive compared to pre-glacial rates; (2) spatial and temporal variations in denudation that can lead to pulses of erosion; and (3) predictions of glacial erosional efficiency at different latitudes. We conclude that latitudinal and elevation dependent variations in temperature control the efficiency of glacial denudation and explain discrepancies between previous studies.