Changes in glacier and snow melt contributions to streamflow in James Ross Island, Antarctic Peninsula

Antarctica has been significantly warming in the last decades. According to climate projections, the increase in air temperature is likely to continue in the future, which will affect runoff dynamics due to glacier retreat and changes in snow cover. Despite the large changes in glacier volume in some parts of Antarctica, little is known about streamflow dynamics and contribution of different water sources to total catchment runoff. Therefore, the objective of our research was to 1) describe runoff dynamics in six catchments located in the Ulu Peninsula, James Ross Island, which represents one of the largest deglaciated areas in Antarctica and 2) to assess the inter-annual variations in glacier melt, snowmelt and potentially rain contributions to runoff over the years 2015 – 2021. The study catchments have different glaciation, and thus considerable diurnal regime of streamflow. Streamflow measurements performed in 2018 austral summer were used to describe the streamflow dynamics of the six catchments. Additionally, a conceptual bucket-type catchment model has been set-up for two of the six catchments, first partly glacierized and second without glacier coverage. In-situ measurements of glacier ablations (2015–2019) and daily precipitation and air temperature partly measured directly at automatic weather stations located in the catchments and partly derived from ERA5-land reanalysis were used as model inputs. Since water level and streamflow data are limited for the study area, a genetic algorithm procedure was used to calibrate the model.

Direct streamflow measurements performed in 2018 austral summer showed the largest variations in Triangular and Shark Streams, which represent the most glaciated catchments among all study catchments. The less variable streamflow was found in Algal Stream, a completely deglaciated catchment. Highest streamflow was recorded in late afternoon, whereas minimum streamflow was recorded in late night or early morning which suggests the strong diurnal regime. In glacierized catchments, the streamflow responded fast on increased air temperature and solar radiation during day. In contrast, soil water stored in the active layer and snow patches mostly controlled streamflow dynamics in deglaciated catchments. Besides, the runoff response was somewhat delayed in these catchments compared to glaciated catchments due to temporal subsurface storage. The above findings were proved also by model simulations, which extended streamflow data for the period 2015-2021. Besides, the simulations showed different glacier and snow contributions to total runoff in study catchments and also different times of streamflow responses to changes in meteorological inputs in combination with different catchment storages which influence runoff delays.