Diurnal cycle of runoff

Abstract

Diurnal cycles in runoff are common in mountainous and glacierized basins, but are especially pronounced in glacierized basins during fine summer weather at the peak of the melt season, when large areas of exposed glacier ice generate large volumes of ice melt that is efficiently routed to the glacier terminus by hydraulically efficient subglacial channel networks. The form of runoff cycles is also influenced by the sources of melt and the efficiency with which melt is produced, such that the removal of accumulated winter snowfall from the glacier surface during the summer is a critical control on the timing and extent of runoff cycle evolution, as well as being a significant source of base flow as a result of flow through the snowpack being highly inefficient. The amplitude of the diurnal cycle is critical in many important glacial processes, including the evolution of hydraulically efficient subglacial channels, and rates of basal sliding and sediment evacuation. Nevertheless, as a result of the compexities of runoff sources, the processes that generate melt, and the routing of the resulting runoff, the controls on the form and evolution of key components of the diurnal cycle remain poorly understood.