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Solute fluxes in Antarctic meltwaters indicate microbial processes influence chemical weathering. Antarctic cyanobacterial mats dominated by Leptolyngbya glacialis enhance weathering rates at 12 °C. Yet, their effects on nutrient fluxes in colder, nutrient-limited conditions, similar to the McMurdo Dry Valleys environments, are unknown. Here, we investigate biotic and abiotic weathering rates of glaciofluvial sediments at 4 °C and compare results to previous experiments at 12 °C. We also examine the effects of nutrient and salt concentrations on weathering fluxes by comparing the effects of different media concentrations (0.1X and 0.001X: 10 and 1000 times diluted) at both temperature conditions. Our results show limited evidence of biologically mediated silica release at 4 °C, yet microbe-mineral interactions still affect nutrient fluxes, particularly for Ca, Mg, Mn, P, and N. However, a higher initial salt concentration (0.1X media) increased the concentration of solutes released under abiotic conditions. These results indicate that aqueous solutes, temperature and microbial processes are all important factors controlling weathering rates and nutrient fluxes in cold settings. [ABSTRACT FROM AUTHOR]

In this study, we have investigated rock weathering phenomena in the central part of Dronning Maud Land, Antarctica. The area is characterized by low mean annual temperatures (−18 °C), strong katabatic winds, and minimal liquid water at the surface. Weathering features, including ventifacts, tafoni, and grus accumulations, are characterized through field observations, rock surface temperature measurements, and microscopic analysis. Abrasion by sand and ice particles transported by strong winds has locally resulted in ridge-shaped ventifacts and rock surfaces with elongated pits, furrows, and grooves. The abrasion-caused features, such as polished facets, keels, and grooves, indicate a northeast-facing wind direction, aligning with the present-day wind regime. The dominant weathering processes in coarse-grained intrusive rocks are oxidation and granular disintegration. Fe-oxidation induces cracking, increasing the porosity and enhancing susceptibility to further weathering. Additionally, temperature fluctuations on rock surfaces caused by solar radiation create thermal stress, which can lead to the formation of microcracks. These microcracks, formed due to thermal expansion, are likely to propagate through subcritical cracking, which is a slow, long-term process. Together, Fe-oxidation, thermal expansion, and subcritical cracking are important mechanisms contributing to long-term weathering and rock decay. Salt weathering, facilitated by snow and ice meltwater, particularly within tafoni, leads to flaking and disintegration of the parent rock. These findings shed light on the complex interactions shaping the geomorphology of central Dronning Maud Land and provide insights into long-term weathering processes operating in Antarctica's extreme environment. • New insights on rock weathering in a remote Antarctic location • Weathering and landscape evolution are greatly influenced by lithological properties. • Coarse grain size and Fe-oxidation control cracking and granular disintegration. • High daily temperature changes lead to thermal stress and subcritical cracking. [ABSTRACT FROM AUTHOR]

The article provides information concerning the processes involved in the growth of tafoni in a cryotic environment, and the relationship of these processes to climate, with particular attention to the thermal regime and the role of wind. The data presented in the study suggested that there is no single key factor that drives the tafoni development. Moreover, the data also confirm that other thermal processes are not really effective for the development of tafoni in this area. The wind speed measured within the tafoni is half that recorded outside, thus favouring snow accumulation within the tafoni and therefore promoting salt crystallization.

Tafoni are one of the most interesting weathering features developed in many areas of the world from tropical areas to polar ones such as Antarctica. Here, we present the results on 4 tafoni in similar conditions (aspect, slope, distance from the sea, elevation) and in the same granite close to the Italian Antarctic station at Mario Zucchelli Station (74°42′S). These tafoni were thermally monitored through infrared thermography and in situ thermistors for an austral summer (2018/19). They were also mineralogically characterized through the image analyses in each tafone sectors (Top, Ceiling, Side and Floor). Salts concentration on the weathered material removed through the scratching was also detected through chemical analyses. Moreover, the weathering rate was calculated through periodic sample weightings of the scratched material from the different tafone sectors. Our results confirmed the importance of the fractures inclination that seem to favor the vertical development of the cavities where basal fractures occurred and the backward development where fractures are vertical. The weathering rates shown that vertical development was always faster than the backward (except for O4) and that the former is statistically linked with the size of the tafone. At mineralogical scale, the higher weathered removal of the quartz concentration could be more closely related to the higher cryogenic weathering of intra-crystal fractures that occur at very low temperatures (−20 °C) in winter than to the thermal stress, thermal shock, or potential freeze-thaw cycles during the summer. Among the different salts, the strong relationship between weathering removals and chlorides suggests that chlorides in this climate are more effective than sulphates. The seasonal trend of weathering matches well with the breaking up of sea ice towards the Tethys Bay and can provide a supply of sea spray that is richer in chlorides (halite) than in sulphates (thenardite, mirabilite). From the analyses of the spatial thermal variability, we could argue that the thermal stress during the summer is not relevant except for the tafone O4. The fact that higher weathering removal were recorded in the innermost (C and S) of the tafoni where thermal variability and AMP were lower suggests that higher moisture content is the crucial factor for a high evaporation flux that can enhance the salt action. [ABSTRACT FROM AUTHOR]