| Summary: | Analysis of stable oxygen isotope (δ 18 O) characteristics is a useful tool to investigate water provenance in glacier river systems. In order to attain knowledge on the diversity of spatio-temporal δ 18 O variations in glacier rivers, we have examined three glacierized catchments in Greenland with different areas, glacier hydrology and thermal regimes. At Mittivakkat Gletscher River, a small river draining a local temperate glacier in southeast Greenland, diurnal oscillations in δ 18 O occur with a three-hour time lag to the diurnal oscillations in runoff. Throughout the peak flow season the δ 18 O composition is controlled by the proportion between snowmelt and ice melt with episodic inputs of rainwater and occasional storage and release of a specific water component due to changes in the subglacial drainage system. At Kuannersuit Glacier River on the island Qeqertarsuaq, the δ 18 O characteristics were examined after the major 1995–1998 glacier surge event. Despite large variations in the δ 18 O values of glacier ice on the newly formed glacier tongue, there were no diurnal oscillations in the bulk meltwater emanating from the glacier in the post-surge years 2000–2001. In 2002 there were indications of diurnal oscillations, and in 2003 there were large diurnal fluctuations in δ 18 O. At Watson River, a large catchment at the western margin of the Greenland Ice Sheet, the spatial distribution of δ 18 O in the river system was applied to fingerprint the relative runoff contributions from sub-catchments. Spot sampling indicates that during the early melt season most of the river water (64–73 %) derived from the Qinnguata Kuussua tributary, whereas the water flow on 23 July 2009 was dominated by bulk meltwater from the Akuliarusiarsuup Kuua tributary (where 7 and 67 % originated from the Russell Glacier and Leverett Glacier sub-catchments, respectively). A comparison of the δ 18 O compositions from glacial river water in Greenland shows distinct differences between water draining local glaciers (between −17.4 and −13.7 ‰), large ice caps (between −23.0 and −17.8 ‰) and the Greenland Ice Sheet (between −29.9 and −23.2 ‰).
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