Diel variations of isotopic and chemical compositions of a stream in King George Island, Antarctica
Abstract
Knowing the flowpath of snowmelt is essential to the understanding of a hydrological system because snowmelt contributes to a significant portion of groundwater and surface water runoff in high latitudes and mountainous regions. Polar regions are under dynamic hydrological conditions due to the presence of active layers, which are seasonally freezing and thawing repeatedly. This study aims to investigate the hydrological process in a stream of a small watershed (<5km2), located in the western part of King George Island in Antarctica. For this, snow and water samples (upstream, midstream, and downstream) were collected and water temperature, electrical conductivity (EC), and flow velocity were measured in-situ for the average of three times per day for 14 days. After that, these samples were analyzed for anion, cations, and water isotopes (18δO and δD). The results showed that the signal of snowmelt source, which is present in the upper stream, was indirectly observed as diel variation in downstream. Based on the results, it was found that the diel cycling is controlled by two different processes depending on the amount of snowmelt. The first mechanism is the runoff dominant flowpath on the surface, and baseflow such as deeper flow pathways is limited in the cooler day. The second mechanism is the dominant flowpath by groundwater on the warmer day. In the first mechanism, the isotopic signal observed in downstream varies depending on whether the snowmelts occurred quickly or slowly in upstream by the isotopic exchange between snow (ice) and snowmelt (liquid). The EC value and chemical signal in downstream is affected by water-rock interaction. In the second mechanism, the isotopic and chemical signal observed in downstream is almost the same as that of groundwater. Besides these factors, the observed diel variation may be explained by the temporal variability of soil thaw as the active layer allows for deeper groundwater to interact with the surface. The development of the active layer on warm temperature resulted in a gradual decrease in runoff contribution to streamflow during snowmelt and streamflow was dominated by pre event water through baseflow. Our study is expected to be used as supplementary information to explain the mechanism for meltwater flowpath in Antarctica with dynamic hydrological conditions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH225...13J
- Keywords:
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- 0736 Snow;
- CRYOSPHERE;
- 0740 Snowmelt;
- CRYOSPHERE;
- 1860 Streamflow;
- HYDROLOGY;
- 1876 Water budgets;
- HYDROLOGY