Preston Cosslett Kemeny

Addressing the challenges facing students and researchers in academia requires reimagining academic traditions to make research and teaching more equitable and effective. Kemeny et al. (2024, https://doi.org/10.1029/2024cn000240 ) proposed 14 alternative academic practices, focused on the physical sciences in the United States, designed to launch discussion. These proposals spanned the graduate student experience, faculty careers, evaluation methods, peer review and publication, and conference norms. It is important to gauge levels of support for these practices in order to inform strategies for implementation. To assess support for the proposed alternative practices, Kemeny et al. included a survey that invited readers to share their quantitative and qualitative evaluations. The survey was open for 18 months and received 83 unique responses. Most practices received mean ratings above neutral, though only six were significantly above the scale midpoint after correction for multiple comparisons. The practice with the highest support was anonymous manuscript review (#9), followed by teaching‐focused faculty leading courses (#2), free conference attendance (#14), a lottery system for grant review (#7), decentralized graduate training by departments (#3), and rotating faculty editing appointments at journals (#10). Women were significantly more likely than men to support the practice of conferences not serving alcohol or hosting bar‐related events ( p , FDR‐corrected = 0.017). Respondents were also invited to propose alternative academic practices, most of which focused on reforms to the graduate student experience. While understanding public perceptions of reimagined academic practices is necessary, institutional constraints, cost, legality, and cultural resistance must also be considered when assessing implementation feasibility.

Quantitative analysis of dissolved river chemistry underlies study of the chemical weathering reactions that stabilize the global carbon cycle over geological timescales. Because different chemical sources have distinct implications for the impact of weathering on biogeochemical cycles, interpreting fluvial chemistry requires constraining the fraction of each solute derived from separate lithologic or process end-members. The task of allocating river solute loads among end-member sources is commonly accomplished through inversion calculations. However, the process of sampling end-member chemical values for use within river inversion models was recently made much more complex by a shift away from normalizing chemical values to sodium and toward normalizing chemical values to a sum of parameters. Given that variables normalized to a sum must themselves sum to one, the updated normalization imposes constraints on the selection of end-member chemical ratios that have previously been overlooked. Here we demonstrate that the end-member selection process employed in the initial version of the MEANDIR model, which is an open-source program for conducting river inversion calculations, does not optimally sample end-member chemistry and results in artificially high end-member chemical variances that generate excess variance in inversion results. To correct this shortcoming, we present a new variance-targeting algorithm for sum-constrained sampling of Gaussian chemical distributions. The new approach is first demonstrated for normal distributions with a constant variance, then for three normal distributions with arbitrary variances, and finally a general case is presented for an arbitrary number of normal distributions with arbitrary variances. The final case operates by numerically calculating matrix components to maximize the absolute value of the matrix determinant subject to variance-based optimization constraints; rather than employing a user-defined covariance matrix, the algorithm maximizes the joint entropy of the vector of end-member chemical ratios. The algorithm is implemented in MEANDIR and used to invert a global river chemistry dataset. The updated sampling strategy reduces the compositional range of the end-member priors relative to the initial approach and results in modest-to-large reductions in the 95th-5th percentile range of accepted results for the fraction of carbonate mineral weathering. In contrast, the median inversion result does not change substantially under the new sampling algorithm. Overall, the variance-targeting and sum-constrained sampling algorithm improves the MEANDIR model by bringing end-member chemical priors into closer alignment with user-supplied distributions.

Degradation of Arctic permafrost is altering biogeochemical dynamics by exposing previously frozen sediment to water, acids, and oxidants. While thaw-driven enhancement of carbonate and silicate mineral weathering results in drawdown of atmospheric carbon dioxide (pCO2), acting as a negative feedback on modern climate change, enhancement of sulfide mineral oxidation increases pCO2 and acts as a positive feedback. The net balance of these chemical weathering reactions sets the sign of the permafrost mineral weathering feedback and partially underlies predictions for the impacts of Arctic landscape change on pCO2 over decadal timescales. This work inverts historical river observations using the MEANDIR model (v1.4) and interprets those results with a new polar conceptual framework to demonstrate that increases in carbonate weathering and silicate weathering since 1980 have fully compensated for increases in sulfide oxidation within the Mackenzie River catchment (sampled upstream of its confluence with the Arctic Red River). Despite declines in the ratio of weathering-derived alkalinity to weathering-derived carbon, permafrost degradation has not yet significantly modified the impact of inorganic chemical weathering on pCO2 within this major Arctic catchment. Within smaller and steeper sedimentary systems, such as the Peel River, enhanced sulfide oxidation has reduced CO2 drawdown. Likewise, increases in carbonate weathering and silicate weathering within the Yukon River have not been sufficient to compensate for increases in sulfide mineral oxidation through time. The relative importance of thaw-driven mineral exposure, couplings among weathering reactions, and changes in the length of flow paths collectively determine how each weathering system responds to decadal permafrost thaw; such processes are expected to vary across geomorphic setting and ecosystem structure. Non-linearity in the magnitude of chemical weathering required to compensate for changes in the ratio of weathering-derived alkalinity to weathering-derived carbon suggests that it will be increasingly difficult to avoid further reductions in CO2 drawdown over the coming decades.

Chemical weathering produces alkalinity that, in conjunction with marine carbonate burial, mediates the return of carbon from planetary volcanism, metamorphism, and sedimentary recycling. However, clay formation during chemical denudation can result in reduced alkalinity fluxes. Because the ⁷ Li/ ⁶ Li ratio of dissolved lithium in river water (δ ⁷ Li _river ) traces the degree of clay mineral formation following silicate dissolution at the watershed scale, fluvial Li isotope ratios and their expression in sedimentary archives can potentially convey the strength of silicate weathering-driven CO ₂ drawdown. However, little attention has been given to the coupled dynamics that emerge when also considering the weathering of coexisting non-silicate minerals, such as carbonate and sulfide phases, that also modify alkalinity and carbon fluxes to the global ocean-atmosphere system. These additional phases potentially complicate attempts to relate δ ⁷ Li _river values to changes in the partial pressure of atmospheric carbon dioxide (pCO ₂ ). Here we address this complexity by compiling a global dataset of δ ⁷ Li _river values and major and trace ion concentrations (n = 413), attributing solutes among lithologic sources and clay sinks with the MEANDIR inversion model and comparing numerical results to watershed properties. The analyses demonstrate that δ ⁷ Li _river values correlate with alkalinity consumption by clay formation but do not simply relate to the net impact of weathering on atmospheric pCO ₂ due to the weathering of carbonate and sulfide minerals. However, other weathering indices, like river Li/Na ratios, may more directly relate to pCO ₂ change. A simple regolith model demonstrates that mineral supply, driven by bedrock composition and uplift, impacts the balance of sulfuric and carbonic acid weathering, the degree of clay mineral formation, and the fraction of Li incorporated from solution into clays. As a result, where measured or calculated δ ⁷ Li _river trends have previously been interpreted in terms of clay mineral formation, we interpret δ ⁷ Li _river as reflecting mineral supply modulated by climate.

Some fraction of the total carbon (C) transported by rivers can enter the atmosphere as CO ₂ via gas evasion as water transits from source to sink. Quantifying this evaded portion can be challenging due to the need to constrain chemical and physical parameters along an entire stream network using a limited number of point measurements. To address this challenge, we employed an tracer‐enabled (C and ²²² Rn) reactive transport model to simulate CO ₂ evasion along an entire stream network in the Little Deschutes River in the Eastern Cascades, Oregon, USA. We sampled the river network in distinct lanscape regimes and measured potential C sources including soil gas, groundwater springs, and wetland waters. Using these data, we first evaluated the reactive transport model using empirical gas transfer scaling relationships and measured groundwater chemistry. We then employed a Monte‐Carlo optimization using riverine observations of , C and ²²² Rn, which yielded more accurate estimates of CO ₂ evasion by improving estimates of spatially‐averaged groundwater pCO ₂ and generating a site‐specific gas transfer scaling relationship. Our results demonstrate that riparian wetlands contribute to 19% of the computed CO ₂ evasion flux. Lastly, we find that CO ₂ evasion only accounts for 12% of the total riverine C flux, with the remaining fraction contributed by advective flux of DIC (50%) and DOC (38%) through the watershed outlet.

How glaciation affects drawdown by chemical weathering influences the weathering‐climate feedback strength, which controls the exogenic carbon cycle and planetary habitability. However, the role of glaciers remains elusive as glaciation alters multiple factors controlling weathering, the net effect of which is ambiguous even in directionality. To isolate and quantify the effect of glaciers, we developed a novel multi‐proxy system for constraining catchment‐scale weathering fluxes in the past. This approach utilizes the correlation between Ge/Si and Si isotope ratios in modern rivers and the preservation of these signals in lacustrine sediments. Reconstructed weathering fluxes in two Icelandic catchments with different glacial histories during the past 10,000 years show that chemical weathering fluxes are roughly 10 times higher when a catchment is glaciated versus ice‐free. The synchronous variations in weathering fluxes with the expansion and contraction of glaciers indicate that glaciation may rapidly amplify climatic variations via a positive feedback.

The evolution of modern academic practices, analogous to the evolution of biological systems, reflects the influence of both contingency and determinism. From a theoretical perspective, how then could academic practices differ from those that were inherited? Would any alternative outcomes be more just, equitable, diverse, or inclusive? Here we present 14 alternative academic practices that might be attained upon replaying the tape of academia and evaluate their benefits and drawbacks. Oriented primarily around the physical sciences within the United States, these alternative practices reconsider common activities within the broad categories of the graduate student experience, faculty careers, evaluation methods, peer review and publication, and conference norms. Consideration of these alternative practices can guide within‐system change and large‐scale restructuring of academia to address the myriad challenges facing researchers and students. Conversely, alternative practices may introduce new issues or exacerbate existing problems. These alternative practices are meant to be imaginative, not prescriptive, and we hope their underlying ideas spur reflection and conversation on the existing practices embedded within academic culture. Readers are encouraged to complete a brief survey regarding their impressions of the alternative practices, available at the following link: rebrand.ly/AlternativePractices2024.