Isotopic and Ionic Variations in Glacier River Water During Three Contrasting Ablation Seasons

Abstract

The significance of the baseflow component of glacier river discharge in summer vanes with geographical location, altitude, glacier geometry and glacier size. Baseflow is maintained by meltwater generated above the transient equilibrium line and by water released from temporary storage on, in or beneath the glacier. At the Norwegian glacier Austre Okstindbreen, where precipitation is generally high throughout the year and the summers are cool and wet, observations in three successive, but contrasting, years have shown that Na+ ion concentrations in the glacier river water are influenced strongly by the amount of snowmelt. This itself depends on the preceding winter conditions, which determine the amount of accumulation, and on the current summer's weather. The efficiency of the glacier's drainage systems depends on the general progress of summer ablation. The speed with which the systems develop influences ion provision from subglacial sources. Ca2+ ion concentrations are largely determined by subglacial conditions. Oxygen isotope variations in glacier river water reflect the relative contributions made to total discharge by snow meltwater and other sources; the composition of the snow cover, which is a function of winter temperatures, has a strong influence. Ice meltwater has low isotopic variability, but the isotopic composition of rainfall varies markedly. A simple model of mixing of englacial and subglacial waters, each of a constant composition, cannot be applied to a high-latitude glacier of the size and altitudinal range of Austre Okstindbreen.

The Significance of Shifts in Precipitation Patterns: Modelling the Impacts of Climate Change and Glacier Retreat on Extreme Flood Events in Denali National Park, Alaska

“…This suggests that these largest flood events are predominantly rainfall driven [5]. All flood events occur only in summer, when baseflow is elevated due to glacial meltwater contributions [52]. …”

Identifying run‐off contributions during melt‐induced run‐off events in a glacierized alpine catchment

“…Furthermore, the seasonal enrichment of δ 18 O in glacier melt found in our study (Figure b, Table ) could reflect a decreasing proportion of snowmelt water contributions from the upper parts of the glacier reflecting the isotopic composition of snowpack changes between years and of different age (Brown, ). Theakstone and Knudsen () found no isotopic fractionation during ice melting, but they observed marked variations in glacier meltwater hydrochemistry during contrasting summers at Austre Okstindbreen Glacier (Norway). These observations supported our use of monthly samples of glacier melt in HS applications in the Saldur catchment.…”

“…Tracer-based hydrograph separation (HS) for identifying the run-off contributions from different water sources has become a standard tool in numerous catchment hydrology studies (Klaus and McDonnell, 2013). This approach has been broadly applied to identify contributions of event water such as rainwater (Burns et al, 2001;Ladouche et al, 2001;Muir et al, 2011;Soulsby et al, 2003), snowmelt (Sueker et al, 2000;Laudon et al, 2002;Beaulieu et al, 2012) and glacier ice melt (Cable et al, 2011;Maurya et al, 2011;Theakstone and Knudsen, 1996;Xing et al, 2015). However, relatively few studies have focused on identifying snowmelt, ice melt and groundwater contributions at the run-off-event scale in glacierized catchments.…”

Oxygen isotopes in glacier-river water, Austre Okstindbreen, Okstindan, Norway

“…2). Glacier-river discharge is maintained by a baseflow component, the importance of which varies with geographical location, altitude, glacier size and glacier geometry (Theakstone and Knudsen, 1996a). In periods of fine weather, diurnal variations of discharge are superimposed on the baseflow.…”