As one of the westernmost stratovolcanoes in the Trans-Mexican Volcanic Belt (TMVB), Ceboruco exhibits a wide range of compositions correlating to its variable eruption style. With around 55,000 people residing within 10 km to the vent, Ceboruco represents an important hazard. Magmatism in the Ceboruco region is the consequence of both compressional and extensional tectonic regimes: the small Rivera plate subducts under North America, and regional crustal extension promotes the formation of three intersecting grabens in western Mexico, one of which hosts Ceboruco. In this tectonic setting, compositions are variable, and types of eruption fluctuate between moderately-effusive ones, like Ceboruco’s 1870-5 CE event, to large Plinian activity, like its caldera-forming eruption 1,060 ± 55 yr BP. Historically documented, the 1870-5 CE eruption led to the formation of a 7.5 km long lava flow, a small plug dome, and a larger dome complex (El Escarabajo). All these lavas exhibit the same trachydacitic composition (~68 wt.% SiO₂, ~9 wt.% Na₂O+K₂O), signaling that they were derived from the same magma batch. As the eruption sequence and the subsurface pre-eruptive conditions remain unexplored, I probe those processes using bulk and mineral compositional analyses, microtextural observations, and phase equilibrium modelling. Higher crystallinity and higher Ba abundance in the dome complex suggest its derivation from the denser, deeper portions of the magma body hinting that El Escarabajo erupted late in the 5-year period. Reverse zoning in plagioclases (An_67-72) and Ca-depleted rims in clinopyroxenes indicate perturbation in Ceboruco’s magmatic system before the event. Phase equilibria modelling suggests re-equilibration of orthopyroxenes approximately in the upper 7 km during magma ascent. The compositional and textural variability indicate magma mixing, which is a common process leading to explosive activity in other TMVB volcanoes such as Popocatépetl and Volcán de Colima.

Mass loss from Alaskan glaciers makes a significant contribution to current sea level rise. The Juneau Icefield (JIF) of southeast Alaska is one of the world's largest, and longest-studied, ice fields, and is currently in a documented state of thinning, retreat, and negative mass balance. The climatological context of this glacial change is critical to understanding its causes, the future of the region, and perhaps that of similar mountain glaciers. Do these changes primarily reflect changes in accumulation or ablation? Are mean air temperatures in the region increasing? If so, during which season, ablation or accumulation, are the changes strongest? Here we investigate the recent temperature history of the Juneau Icefield, using a combination of reanalysis data and in situ temperature observations from the Juneau Icefield Research Program. On the whole we find a significant trend in annual average temperature since the 1950’s of 0.19°C per decade. Interestingly, this warming is entirely a winter-season signal. We find no significant trend in summer-season temperatures, but a winter time trend of nearly 0.5°C per decade, over twice that of the annual average. This pattern is consistent between the reanalysis products and the local temperature observations across the icefield. Using the in situ measurements from stations across the icefield, we find that the magnitude of the winter-season warming (and that of the annual mean warming) depends strongly on surface elevation: the higher the surface elevation, the larger the trend in warming. These results have implications for the cause of recent glacier changes. While there is little evidence for a change in ablation-season temperatures, these results point toward changes in both the length of the ablation season and perhaps the phase of winter precipitation. The elevation-dependence of these trends may have further implications for the future stability of the JIF.

A catastrophic outburst of glacial meltwater into the Labrador Sea 8,200 years ago disrupted worldwide oceanic circulation for more than a century and impacted climate globally. However, there is minimal data regarding the climate response in the tropics - a key region in the global climate system. We will present hydrogen isotopic (²H/¹H) data from sediment cores taken from Jellyfish Lake, Palau, that imply a southward shift of the tropical rainbands during this time. Due to this lake being a uniquely undisturbed area with a high rate of sediment accumulation, the isotopic composition of dinosterol in these sediments can provide a detailed reconstruction of past rainfall in the tropics. Dinosterol is an organic compound that is produced exclusively by dinoflagellates, a taxa of photosynthetic microalgae. Through this “molecular fossil,” we can reconstruct the ²H/¹H ratio of the lake water and its salinity, both of which are directly tied to rainfall in Palau. To identify and purify the dinosterol found in sediment core samples, we use High-Performance Liquid Chromatography (HPLC), Gas Chromatography-Mass Spectrometry (GC-MS), and Gas Chromatography-Flame Ionization Detection (GC-FID) instruments. Using our Gas Chromatography-Isotope Ratio Mass Spectrometry (GC-IRMS), we found large and systematic fluctuations in the ²H/¹H ratios of dinosterol. Thus, our preliminary data demonstrate a trend toward a drier climate in Palau at the time of the glacial meltwater pulse into the North Atlantic 8,200 years ago, implying a southward shift of the rainbands. Over the past century, there has been a substantial increase in glacial melting due to anthropogenically-induced climate change. Our paleoclimatic data has important implications in furthering our understanding of how drastic alterations in ocean circulation could affect climate on a global scale.

Sea ice plays a significant role in the global climate, but the details of summer melt processes remain poorly resolved. Sustained low-wind events over the Arctic Ocean have been observed to correspond to high salinity and temperature stratification in sea-ice leads, consequently increasing lateral melt rates during summer. Such an effect is currently unaccounted for in leading climate models, and appropriate parameterization could potentially reduce error in projections. We used a wind reanalysis dataset produced by the National Center for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) to study wind patterns in the Arctic. We focused on daily variation in oceanic regions at latitudes above 65 degrees during Summer (May 1 - September 30) over 2010-2019. An index of low-wind events was extracted from the reanalysis data and these events were classified according to length of event and geographical extent. Our results suggest that low wind events are frequent throughout the summer, but are not equally distributed spatially across the basin. Low-wind events were compared to other climate data, including sea-ice extent, on a spatial and temporal basis. Our results were compared to climate model output and differences were examined. We propose a basic parameterization of the effect of low-wind events on sea ice melt, and suggest further collection of observational data to improve physical representation in climate models.

Oceanic biogeochemical pathways, and particularly nitrogen, play a large role in global carbon cycling. Oxygen Deficient Zones (ODZs) such as the Eastern Tropical North Pacific (ETNP) have microbes that use distinct metabolic pathways for energy and nutrients in the absence of oxygen. These ODZ pathways shape the global inventory of nutrients and are thought to be responsible for around half of marine bioavailable nitrogen losses. While some of these pathways such as canonical denitrification and the more recently discovered anaerobic ammonia oxidation have been studied, there are also other potentially significant pathways. Trimethylamine N-oxide (TMAO), a small nitrogen-containing organic molecule with pathways that connect into other nitrogen cycle pathways, was seen to be diminished to nonexistence in ODZs which suggested it was being utilized. While studied in other environments, microbial utilization of TMAO in ODZs has not been significantly studied. We mapped metagenome reads collected from the ETNP ODZ onto a phylogenetic tree annotated with genes for TMAO degradation found outside the ODZ. We were able to confirm the presence of genes for TMAO degradation pathways and identified a range of organisms involved. We also examined the distribution of these genes and organisms across the different depths we sampled from to create a more complete picture of nitrogen cycling in ODZs.

People living in rural Northern Tanzania are highly dependent on their natural environment for their health and livelihood. Consequently, they are a vulnerable population with regard to the potential negative effects of climate change. In this study, a semi-structured interview questionnaire was used to interview inhabitants of the Laja, Getamock and Kaza Roho villages, and measure their perception of the effect of climate change on their livelihood, health, and gender roles in the Manyara and Arusha regions of rural Tanzania. A total of 226 interviewees were asked about their perceptions of rainfall patterns, natural resource availability, disease rates, gender roles, and birth control use. The majority of respondents perceived a decrease in the frequency of rainfall and an increase in the frequency of drought. Moreover, 89% of the respondents were determined to be pastoralists or farmers that are directly affected by reduced precipitation, which decreases natural resource availability and crop yield, and increases rates of disease in humans and livestock. Respondents also reported shifts in gender roles to accommodate the rise of health, natural resource, and financial burdens stemming from climate change; for example, men are increasingly responsible for gathering drinking water because sources nearby villages have dried up and only men can drive motorbikes and ox carts now required to travel such long distances. Lastly, it was found that contraception usage has increased in younger, more educated groups in conjunction with a decreased number of desired children. Because family planning are associated with girls achieving higher levels of education and economic growth, improved family planning presents a potential solution to the financial hardship imposed by climate change. Considering the challenge of mitigating the inimical effects of climate change to developed nations, solutions to these problems are critically important to vulnerable groups that are highly dependent on natural resources for their health and livelihood.

A growing body of work suggests that we are experiencing widespread reductions in insect biodiversity and abundance. Habitat restoration is one possible way to combat these declines, but we don’t have a full understanding of if or how effectively restoration positively affects insect populations. My research considers taxonomic and geographic biases in existing insect restoration studies. I defined an insect restoration study as any study that considers both habitat restoration and associated insect populations. I hypothesized that insect restoration studies would show a significant bias towards 1) northern hemisphere studies and 2) some insect orders over others. Northern hemisphere bias – a subset of geographic bias – seems likely because there is a much higher percentage of prominent research institutions in the northern hemisphere than in the southern hemisphere while species are distributed much more evenly between the two hemispheres. Indeed, a preliminary analysis of my data suggests there may be a bias towards northern hemisphere studies. Taxonomic bias seems likely because some orders of insects such as the butterfly and moth order are widely seen as more charismatic than others. Additionally, some types of insects are easier to study than others for pragmatic reasons. To test my hypotheses, I found taxonomic and geographic data for roughly 200 insect restoration studies and compared that data to expected values. I chose to examine these questions because the scope of restoration studies impacts both our knowledge of restoration processes and the extent of future restoration efforts. By considering such biases carefully, we may be able to protect more insect species in more geographic locations from various threats such as anthropogenic climate change via our restoration attempts.