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Large-scale climate modes such as the El Niño/Southern Oscillation (ENSO), the Asian monsoon, and the Arctic Oscillation are responsible for much of the Earth’s climate variability. Despite the importance of these modes, we have limited understanding of how they vary on long (multidecadal to millennial) timescales due to the short length of instrumental climate records. Fortunately, climate information stored in natural archives can provide us with information on how these modes varied in the more distant past. Lake sediments are an ideal climate archive since they are continuous, have high temporal resolution, and contain many potential climate proxies. In the present study, I use lake sediment records to assess past climate and environmental changes associated with the El Niño/Southern Oscillation, the Asian monsoon, and the Arctic Oscillation. Exploring modern precipitation variability across the Asian monsoon region, I found that precipitation within this broad area is not coherent, which holds implications for paleorecords that are hypothesized to represent monsoon variability, including many lake sediment records on the Tibetan Plateau. Monsoon precipitation in the Arabian Sea is distinct from precipitation in India and China, and increased precipitation in the Arabian Sea coincides with decreased precipitation in the western North Pacific. Furthermore, only precipitation in southwestern Tibet responds to the Southwest monsoon, whereas precipitation in southeastern Tibet responds to the western North Pacific monsoon. In southwestern Tibet, I have reconstructed dust variability over the last millennium using the lake sediment record from Kiang Co. The sediment record shows a trend toward increasing dust over the 20th century, and our hypothesized dust proxy is positively correlated with the June-November Arctic Oscillation Index. A trend toward more positive Arctic Oscillation Index values as well as higher temperatures over the 20th century likely drove increased dustiness in southwestern Tibet, due the influence of temperature on glaciofluvial sediment availability in the Himalayas. Sediment trap, sediment core data, and modern measurements of local climate and lake water variables at Genovesa Crater Lake, Galápagos, indicate the lake and its sediments respond to local climate variability, with carbonate-rich sediments forming during prolonged dry periods (La Niña events), and organic-rich sediment forming during the warm season and El Niño events. The ratios of silica to calcium and strontium to calcium also reflect cool season SST. Thus, this lake sediment record has potential to provide a record of both seasonal and ENSO variability spanning the Holocene.

Wind erosion and associated dust emissions play a fundamental role in many ecological processes, yet most ecological studies do not explicitly consider dust-driven processes despite the growing body of evidence suggesting that wind erosion is a key driver of land surface dynamics and many other environmentally relevant processes such as desertification. This study provides explicit support for a pervasive underlying but untested desertification hypothesis by showing that at the vegetation patch scale shrubs are significantly more efficient at capturing wind-blown sediment and other resources such as nutrients than grasses and that this difference is amplified following disturbance. At the landscape scale, the spacing and shape of woody plants were found to be a major determinant of dryland aeolian sediment transport processes in grasslands, shrublands, woodlands and forests, particularly following disturbance. This study also found that disturbance such as fire can have a significant influence on background dust emissions, which can have important consequences for many basic ecological and hydrological processes. Potential interactions between aeolian and fluvial processes were also evaluated in this study, and a new conceptual framework was developed that highlights important differences and similarities between the two processes as a function of scale-dependencies, mean annual precipitation, and disturbance. This study also explicitly evaluates the effect of climatic extremes and alternate land management practices on the absolute and relative magnitudes of wind and water erosion. Notably, results indicate that wet/dry climatic extremes and grazing can increase the wind-to-water erosion ratio, whereas burning disproportionally increases water erosion relative to wind erosion.

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