Inequalities persist in the geosciences. White women and people of color remain under‐represented at all levels of academic faculty, including positions of power such as departmental and institutional leadership. While the proportion of women among geoscience faculty has been cataloged previously, new programs and initiatives aimed at improving diversity, focused on institutional factors that affect equity in the geosciences, necessitate an updated study and a new metric for quantifying the biases that result in under‐representation. We compile a data set of 2,531 tenured and tenure‐track geoscience faculty from 62 universities in the United States to evaluate the proportion of women by rank and discipline. We find that 27% of faculty are women. The fraction of women in the faculty pool decreases with rank, as women comprise 46% of assistant professors, 34% of associate professors, and 19% of full professors. We quantify the attrition of women in terms of a fractionation factor, which describes the rate of loss of women along the tenure track and allows us to move away from the metaphor of the “leaky pipeline.” Efforts to address inequities in institutional culture and biases in promotion and hiring practices over the past few years may provide insight into the recent positive shifts in fractionation factor. Our results suggest a need for 1:1 hiring between men and women to reach gender parity. Due to significant disparities in race, this work is most applicable to white women, and our use of the gender binary does not represent gender diversity in the geosciences.

The importance of both temperature and precipitation as predictors of δ C and δ N values in millets suggests that C plants may be more sensitive to environmental parameters than previously appreciated. Given the high degree of carbon and nitrogen isotope variability among accessions of these species, it is imperative that site-relevant plant isotope ratios are used for making isotope-based paleo-dietary predictions.

Inequalities persist in the geosciences. White women and people of color remain under-represented at all levels of academic faculty, including positions of power such as departmental and institutional leadership. While the proportion of women among geoscience faculty has been catalogued previously, new programs and initiatives aimed at improving diversity, focused on institutional factors that affect equity in the geosciences, necessitate an updated study and a new metric for quantifying the biases that result in under-representation . We compile a dataset of 2,531 tenured and tenure-track geoscience faculty from 62 universities in the United States to evaluate the proportion of women by rank and discipline. We find that 27% of faculty are women. The fraction of women in the faculty pool decreases with rank, as women comprise 46% of assistant professors, 34% of associate professors, and 19% of full professors. We quantify the attrition of women in terms of a fractionation factor, which describes the rate of loss of women along the tenure track and allows us to move away from the metaphor of the 'leaky pipeline'. Efforts to address inequities in institutional culture and biases in promotion and hiring practices over the past few years may provide insight into the recent positive shifts in fractionation factor. Our results suggest a need for 1:1 hiring between men and women to reach gender parity. Due to significant disparities in race, this work is most applicable to white women, and our use of the gender binary does not represent gender diversity in the geosciences.

No abstract

Methane is a globally significant greenhouse gas, energy resource, and it is a product and reactant of microbial metabolisms. Multiple sources and sinks of methane can be challenging to distinguish from each other, thus complicating the understanding of methane budgets and the effects of microbes on mediating Earth’s carbon cycle. The relative abundances of methane isotopologues (e.g., 12CH4, 13CH4, 12CH3D, and 13CH3D) record process-based information about the formation conditions, transport, and fate of methane, and in select environments can serve as a temperature proxy. This geochemical tool is herein applied to methane from marine and lacustrine sediments to test assumptions about prevailing mechanisms of its formation and consumption in these settings. This thesis describes 1) three studies about biogeochemical insights gained by quantifying the relative abundance of clumped methane isotopologue, 13CH3D, in samples from marine and lacustrine sediments, and 2) one foray into method development to improve the quantification of methane in these environments. Chapter 2 presents a global survey of marine gas hydrates where isotope-based temperatures are used to assess whether linkages between methane sources and seepage-associated seafloor features match putative geologic models. Chapter 3 describes two kilometer-scale profiles of methane isotopologues from marine sediments, where the relationship between expected sediment temperature and isotope-based temperature is used to evaluate the temperature limit of microbial processing and abiotic re-equilibration mechanisms. Chapter 4 reports the largest set of methane isotopologue data from ebullition in a single lake basin, which is used to gauge the relative importance of aerobic and anaerobic methane oxidation in the study site and recommend a general sampling strategy to constrain methane source signatures in similar lake settings. Chapter 5 explains the development of a method to quantify the in situ concentration of methane based on ratios of dissolved gases, and its comparison to four other methane quantification methods for surface sediments from marine cold seeps. The findings from this research contribute to ongoing efforts to understand the sedimentary carbon cycle and microbial activity in remote environments.

No abstract

No abstract

No abstract