Chemical Weathering Processes Leading to Soil Development in Arctic Glacial Forefields

Few Arctic forefields have been studied previously for their role in soil formation and in the carbon cycle. Yet, despite their prevailing polar climate, their soils may develop quickly and be extensive. Rock water residence times are prolonged in glacial tills that contain a rock flour component with high surface area and reactive that amasses in the forefields of glaciers as they retreat. Rapid sulfide oxidation and carbonate dissolution could be a potential CO2 source to the atmosphere, while silicate-weathering and soil organic carbon accumulation a CO2 sink. The extent of these sink-source reactions, and the soil forming processes that affect these, were tested over a century of Arctic forefield soil formation. In young, subglacial till-based moraine soils, the rapid depletion of accessory sulfide and carbonates minerals in the initial, and up to about 60-years of exposure, reflected widespread sulfide oxidation and carbonate dissolution. Defining young forefield soils as a potential transient CO2 source to the atmosphere, since potential CO2 sinks, namely calcium silicate mineral weathering and soil organic carbon accumulation were retarded, and limited to the older moraine soils. The slow onset of biological evolution in Arctic forefields and proton consumption by carbonates, present in the forefield lithologies, are suggested as the principal reasons for the limited silicate weathering and in turn soil formation. The results from this thesis may have new implications for the carbon cycle. Given glacial–interglacial cycles that have waxed and waned throughout Earth history, and carbonate and sulfide minerals are common in most lithologies made up of low to medium grade metamorphic and metasedimentary rocks. However, higher resolution temporal (diurnal to seasonal) and spatial field studies are needed in-order to more confidentially up-scale these findings beyond a glacier catchment scale.