Conduit roughness and dye-trace breakthrough curves: why slow velocity and high dispersivity may not reflect flow in distributed systems
Conduit roughness and dye-trace breakthrough curves: why slow velocity and high dispersivity may not reflect flow in distributed systems
复制标题
导管粗糙度和染料痕量突破曲线：为什么慢速和高分散性可能无法反映分布式系统中的流动
作者：
Jason Gulley;Jason Gulley;P. Walthard;P. Walthard;Jonathan B. Martin;Alison F. Banwell;Alison F. Banwell;Douglas I. Benn;Douglas I. Benn;G. Catania
摘要染料示踪穿透曲线（BTC），通过融化季节的速度增加和分散性降低已被解释为指示从分布式到导管冰下排水系统的开关，但这种解释尚未得到验证的冰川排水系统配置是独立已知的。为了测试冰下排水系统的配置变化以外的过程是否会产生类似的BTC，我们测量了斯瓦尔巴特群岛Rieperbreen下的一个持久的、映射的冰下管道的BTC，该管道缺乏分布式系统，因为它被冻结在床上。这种管道产生缓慢和高度分散的BTCs早在融化季节时，融水输送率低，快速和急剧峰值BTCs后，积雪已经撤退过去的注射冰臼。在Rieperbreen，BTC的季节性演变是由管道粗糙度的降低控制的，因为融水输送速率的增加增加了管道底板上岩石的相对淹没深度。由于粗糙度的季节性变化可以产生缓慢和高度分散的BTC，染料示踪研究可能无法唯一地识别冰下排水系统的配置。因此，导管可能会在融化季节比以前认识到的更早形成。
Abstract Dye-trace breakthrough curves (BTCs) that increase in velocity and decrease in dispersivity through a melt season have been interpreted as indicating a switch from a distributed to a conduit subglacial drainage system, but this interpretation has not been validated in glaciers where the drainage system configuration was independently known. To test if processes other than a change in the configuration of the subglacial drainage system could produce similar BTCs, we measured BTCs from a persistent, mapped subglacial conduit beneath Rieperbreen, Svalbard, which lacks a distributed system because it is frozen to its bed. This conduit produced slow and highly dispersed BTCs early in the melt season when meltwater delivery rates were low, and fast and sharply peaked BTCs after the snowpack had retreated past the injection moulin. At Rieperbreen, the seasonal evolution of BTCs was controlled by decreases in conduit roughness as increased rates of meltwater delivery increased the relative submergence depths of rocks on the conduit floor. Because seasonal changes in roughness can produce slow and highly dispersed BTCs, dye-tracing studies may not be capable of uniquely identifying subglacial drainage system configurations. As a result, conduits may form earlier in melt seasons than previously recognized.