Weathering in the Glacial Foreland of Southern and Western Greenland

Abstract

Glaciers physically grind up underlying rock and create fine-grained sediment that has a high potential for chemical weathering. Subsequent weathering of these sediments produces solutes, including nutrients and radiogenic isotopes, which are transported by streams to the world’s oceans where they can impact primary productivity and record past ice sheet activity. Previous research on the geochemistry of bedrock, bedload sediment and stream waters demonstrated that the extent of chemical weathering varies across a transect in western Greenland due to variations in either exposure age or precipitation (Scribner et al., 2015), and that variations in the extent of weathering associated with retreat of the Greenland Ice Sheet (GrIS) may account for observed trends in solutes during the last deglacial period. This project adds a new study area in southern Greenland that has higher precipitation, more vegetation, a different lithology, and a range of exposure ages, to address the leading factors contributing to the extent of weathering. Based on the relative proportions of cations and percent change between Na+K concentrations of bedload to waters, the southern region is undergoing less extensive weathering than the western transect, which suggests that lithology may be an important driver of weathering, and that exposure age and precipitation are less important factors than expected. The results also suggest there are additional factors that contribute to weathering that were not accounted for in this study, such as dissolved organic matter and microbial activity.