Quantifying sources, pathways, and controls on sediment transport dynamics in two rivers on James Ross Island, Antarctica

Abstract

The Antarctic Peninsula is now warming again after a hiatus in temperatures, and ice masses are receding at an enhanced rate, resulting in the enlargement of proglacial regions. Despite the importance of proglacial regions as sediment sources in polar environments, few studies focus on the Antarctic and sub-Antarctic fluvial sediment dynamics and even fewer have explored the spatio-temporal variability in sediment delivery or compiled a comprehensive source-to-sink description of sediment transportation. Proglacial rivers are shaped by the interplay of glacial meltwater, which erodes, transports, and deposits sediment, and hillslope activity, which provides new sediment to the riverine system during mass transport events. Active layer soils can be an additional source of water and sediment when ground temperatures are above freezing; particularly in catchments with low glacier cover. In this study, we aim to discuss how different environmental factors, such as air temperature, active layer thaw, and precipitation affect sediment yields in two rivers on James Ross Island, Antarctica. Based on field data collected at the start of 2022, we used a multi-disciplinary approach to quantify the spatio-temporal variability in sediment yields across the river catchments of the Algal and Bohemian Streams and their key environmental controls. Additionally, we discuss how X-ray fluorescence and infrared spectroscopy have provided an insight into how sediment composition and, potentially, source change downstream in each stream. We estimate that the annual sediment yield for the Bohemian Stream in the austral summer of 2021/2022 was 400 tonnes/year/ km2 and 530 tonnes/year/ km2 for the Algal Stream. While the Algal Stream has a higher estimated yield, its daily sediment yield values are highly variable and the Bohemian Stream typically exports more sediment into the Southern Ocean. Our results show that the active layer is an important driver of sediment yield variability in the Algal catchment. In contrast, sediment yield from the Bohemian catchment is more sensitive to air temperature. Both catchments are sensitive to changes in precipitation. The differences in sediment yield from the two catchments likely stem from differences in glacier and snowfield coverage. These sediment yield values are exceptionally high by Antarctic standards, and are comparable to that from catchments on Svalbard, although they remain low by global standards. Our identification of the controls on sediment yield provides insight into how other fluvial sedimentary systems across the Antarctic Peninsula could respond as glaciers lose mass in a warming climate.