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Mineral dust can significantly impact climate and biogeochemical cycles on Earth. To understand dust provenance, an accurate characterization of dust sources and emission regions is required. In this study, we combine rare-earth element patterns, elemental ratios, and radiogenic Sr-Nd-Pb isotopes to discriminate dust sources from key regions in North Africa responsible for similar to 55% of the total dust load emitted annually on Earth. This new dataset, based on fifty-nine analyses of deflatable fine soil material, improves our current knowledge about North African dust sources, especially those underrepresented in Saharan-Sahelian regions. Six potential source areas (PSA) - Libya-Algeria-Mali (PSA(LAM)), Libya-Egypt (PSA(LE)), Bodele Depression (PSA(BD)), Mali Center (PSA(MC)), West African Coast (PSA(WAC)) and Mauritania (PSA(Ma)) - are defined based on several lithogenic tracers as well as on the geological subdivision of North African geological provinces, providing a unique chemical and isotope fingerprint for each PSA. For example, the PSA(BD) - the main dust activation area in North Africa - is clearly distinguished from western African sources using Pb isotopes. Major elements show a large variability within each PSA and are not alone diagnostically useful. Comparison of the newly defined PSA with aerosols collected in remote locations over the North Atlantic shows that their sources are predominantly from western African regions (PSA(LAM) and PSA(WAC)). Bodele-derived dust has a limited impact on the bulk dust transported over the tropical North Atlantic, regardless of the season and altitude of dust transport. The low impact of the Bodele Depression can be explained by a high deposition rate (wet and dry) of aerosols along its southwestward trajectory. A detailed analysis of dust collected over South America during winter will be essential to confirm this observation at a global scale. The present dataset can be efficiently used to track modern dust emiss

During the last African Humid Period (AHP; 15-5 ka), many lakes in the East African Rift System (EARS) experienced pronounced lake-level variations that dramatically transformed the hydrological landscape. Currently dry, saline or marshy-wetland terminal lakes became vast waterbodies, interconnected via overflow sills resulting in the formation of a several thousand-kilometre-long chain of lakes in the EARS. A quantitative, process-based understanding of these hydrological systems can advance our interpretation of past hydroclimate variability from proxy records. Here, we provide a critical modern hydrological dataset for the data-sparse Lake Chew Bahir basin in southern Ethiopia. Driven by modern data, an isotope-enabled hydro-balance model was developed to assess how increases in rainfall modulate delta O-18 and Sr-87/Sr-86 variability. Considering a terminal Lake Chew Bahir scenario, humid conditions resulted in higher lake delta O-18 (similar to+14 parts per thousand) due to increased evaporation and longer water residence times. At the same time Sr-87/Sr-86 Sr decreased from 0.7064 to 0.7061 due to an increased riverine Sr flux characterised by lower, unradiogenic Sr-87/Sr-86 ratios. In a modelling scenario where Lake Chew Bahir became a flow-through system with interconnectivity between lakes Abaya, Chamo, Chew Bahir and Turkana, higher lake delta O-18 (similar to+12 parts per thousand) relative to present was found, but 8 18 0 was lower than in the terminal lake scenario. The lake water Sr-87/Sr-86 ratios (<0.7061) were also slightly lower. A moderate concomitant change in rainfall input delta O-18 of similar to 1 parts per thousand in step with hydrological reorganisation resulted in the lowest lake delta O-18 (similar to+5 parts per thousand). Modelled delta O-18 values were similar to the delta O-18 range of endogenic carbonates from sedimentary cores from Lake Chew Bahir at the onset of the AHP, supporting the validity of our model, and suggesting that ev

Earth’s climatic evolution over the last 5 million years is primarily understood from the perspective of marine mechanisms, however, the role of terrestrial feedbacks remains largely unexplored. Here we reconstruct the last 5 million years of soil moisture variability in Central Asia using paleomagnetism data and isotope geochemistry of an 80 m-thick sedimentary succession at Charyn Canyon, Kazakhstan. We identify a long-term trend of increasing aridification throughout the period, along with shorter-term variability related to the interaction between mid-latitude westerlies and the Siberian high-pressure system. This record highlights the long-term contribution of mid-latitude Eurasian terrestrial systems to the modulation of moisture transfer into the Northern Hemisphere oceans and back onto land via westerly air flow. The response of Earth-surface dynamics to Plio-Pleistocene climatic change in Central Asia likely generated terrestrial feedbacks affecting ocean and atmospheric circulation. This missing terrestrial link elucidates the significance of land-water feedbacks for long-term global climate.

Understanding oceanic cadmium (Cd) cycling is paramount due to its micronutrient-like behavior in seawater, which has been inferred from its similarity to phosphate (PO4) cycling. Cadmium concentrations follow a nutrient-like consumption-regeneration cycle in the top of the water column and are mainly controlled by water mass mixing and circulation in the deep ocean. However, an additional scavenging mechanism through cadmium sulfide (CdS) precipitates, occurring within sinking biogenic particles in oxygen deficient zones (ODZ), has been proposed. In this study, we report Cd stable isotope and concentration data for seven vertical seawater profiles sampled during GEOTRACES cruise GA08 in the northern Cape and Angola Basins, which feature a significant ODZ along their eastern margins. Outside the ODZ, Cd cycling is similar to that previously reported for the South Atlantic. While water mass mixing largely controls deep ocean Cd isotope signatures, Cd isotope fractionation in surface waters can be modeled as an open system at steady state buffered by organic ligand complexation. In the ODZ, stronger Cd depletion relative to PO4 is associated with a shift in delta Cd-114 toward heavier values, which is indicative of CdS precipitation. Our interpretation is supported by experimental CdS precipitation data and a size-resolved particle model involving bacterial sulfate reduction as a precursor of CdS. Our estimates of the CdS flux to the seafloor (10(7) to 10(9) mol/yr) indicate that CdS precipitation is a significant process of Cd removal and constitutes a nonnegligible Cd sink that needs to be better quantified by Cd isotope analyses of marine sediments.

Understanding oceanic cadmium (Cd) cycling is paramount due to its micronutrient-like behavior in seawater, which has been inferred from its similarity to phosphate (PO4) cycling. Cadmium concentrations follow a nutrient-like consumption-regeneration cycle in the top of the water column and are mainly controlled by water mass mixing and circulation in the deep ocean. However, an additional scavenging mechanism through cadmium sulfide (CdS) precipitates, occurring within sinking biogenic particles in oxygen deficient zones (ODZ), has been proposed. In this study, we report Cd stable isotope and concentration data for seven vertical seawater profiles sampled during GEOTRACES cruise GA08 in the northern Cape and Angola Basins, which feature a significant ODZ along their eastern margins. Outside the ODZ, Cd cycling is similar to that previously reported for the South Atlantic. While water mass mixing largely controls deep ocean Cd isotope signatures, Cd isotope fractionation in surface waters can be modeled as an open system at steady state buffered by organic ligand complexation. In the ODZ, stronger Cd depletion relative to PO4 is associated with a shift in delta Cd-114 toward heavier values, which is indicative of CdS precipitation. Our interpretation is supported by experimental CdS precipitation data and a size-resolved particle model involving bacterial sulfate reduction as a precursor of CdS. Our estimates of the CdS flux to the seafloor (10(7) to 10(9) mol/yr) indicate that CdS precipitation is a significant process of Cd removal and constitutes a nonnegligible Cd sink that needs to be better quantified by Cd isotope analyses of marine sediments.