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Continental rifts are important sources of mantle carbon dioxide (CO 2 ) emission into Earth’s atmosphere 1 – 3 . Because deep carbon is stored for long periods in the lithospheric mantle 4 – 6 , rift CO 2 flux depends on lithospheric processes that control melt and volatile transport 1 , 3 , 7 . The influence of compositional and thickness differences between Archaean and Proterozoic lithosphere on deep-carbon fluxes remains untested. Here we propose that displacement of carbon-enriched Tanzanian cratonic mantle concentrates deep carbon below parts of the East African Rift System. Sources and fluxes of CO 2 and helium are examined over a 350-kilometre-long transect crossing the boundary between orogenic (Natron and Magadi basins) and cratonic (Balangida and Manyara basins) lithosphere from north to south. Areas of diffuse CO 2 degassing exhibit increasing mantle CO 2 flux and 3 He/ 4 He ratios as the rift transitions from Archaean (cratonic) to Proterozoic (orogenic) lithosphere. Active carbonatite magmatism also occurs near the craton edge. These data indicate that advection of the root of thick Archaean lithosphere laterally to the base of the much thinner adjacent Proterozoic lithosphere creates a zone of highly concentrated deep carbon. This mode of deep-carbon extraction may increase CO 2 fluxes in some continental rifts, helping to control the production and location of carbonate-rich magmas. Carbon dioxide and helium data support lateral advection of carbon-rich cratonic mantle below the East African Rift System, which concentrates deep carbon and causes active carbonatite magmatism near the craton edge.

Continental rifting is influenced by interactions between tectonic, magmatic, and surface processes, with the latter strongly dependent on regional climate. We test the role of regional climate variability on rift system behavior, by investigating fault slip rate changes in the South Turkana Basin (Lake Turkana Rift, northern Kenya) at the end of the African Humid Period. Throw rates on 27 faults examined during the African Humid Period (9,631–5,333 yr BP) and post-African Humid Period (5,333 yr BP–present) exhibit a mean 0.17 ± 0.08 mm/yr increase during the drier, post-African Humid Period. Numerical simulations reveal Coulomb stress changes from two loading sources that may explain these changes: (1) reduced vertical loading from a 100–150 m lake level drop, and (2) increased magmatic loading from enhanced mantle melt production due to reduced lake loading. An increase in magma flux of > 0.1 km 3 /kyr below the South Turkana Basin results in Coulomb stress changes exceeding those expected from a 100–150 m lake level drop. We provide the first empirical evidence of increased fault activity in response to climate-induced lake level changes in the East African Rift System over time scales of 10 3 –10 4  years, and reveal that climate-tectonic interactions are enhanced in magmatically active rift systems.

Mean body size in marine animals has increased more than 100-fold since the Cambrian, a discovery that brings to attention the key life-history parameters of lifespan and growth rate that ultimately determine size. Variation in these parameters is not well understood on the planet today, much less in deep time. Here, we present a new global database of maximum reported lifespan and shell growth coupled with body size data for 1 148 populations of marine bivalves and show that (i) lifespan increases, and growth rate decreases, with latitude, both across the group as a whole and within well-sampled species, (ii) growth rate, and hence metabolic rate, correlates inversely with lifespan, and (iii) opposing trends in lifespan and growth combined with high variance obviate any demonstrable pattern in body size with latitude. Our observations suggest that the proposed increase in metabolic activity and demonstrated increase in body size of organisms over the Phanerozoic should be accompanied by a concomitant shift towards faster growth and/or shorter lifespan in marine bivalves. This prediction, testable from the fossil record, may help to explain one of the more fundamental patterns in the evolutionary and ecological history of animal life on this planet.

Paleoclimate data assimilation (DA) is a tool for reconstructing past climates that directly integrates proxy records with climate model output. Despite the potential for DA to expand the scope of quantitative paleoclimatology, these methods remain difficult to implement in practice due to the multi-faceted requirements and data handling necessary for DA reconstructions, the diversity of DA methods, and the need for computationally efficient algorithms. Here, we present DASH, a MATLAB toolbox designed to facilitate paleoclimate DA analyses. DASH provides command line and scripting tools that implement common tasks in DA workflows. The toolbox is highly modular and is not built around any specific analysis, and thus DASH supports paleoclimate DA for a wide variety of time periods, spatial regions, proxy networks, and algorithms. DASH includes tools for integrating and cataloguing data stored in disparate formats, building state vector ensembles, and running proxy (system) forward models. The toolbox also provides optimized algorithms for implementing ensemble Kalman filters, particle filters, and optimal sensor analyses with variable and modular parameters. This paper reviews the key components of the DASH toolbox and presents examples illustrating DASH's use for paleoclimate DA applications.

Paleotemperature proxy data form the cornerstone of paleoclimate research and are integral to understanding the evolution of the Earth system across the Phanerozoic Eon. Here, we present PhanSST, a database containing over 150,000 data points from five proxy systems that can be used to estimate past sea surface temperature. The geochemical data have a near-global spatial distribution and temporally span most of the Phanerozoic. Each proxy value is associated with consistent and queryable metadata fields, including information about the location, age, and taxonomy of the organism from which the data derive. To promote transparency and reproducibility, we include all available published data, regardless of interpreted preservation state or vital effects. However, we also provide expert-assigned diagenetic assessments, ecological and environmental flags, and other proxy-specific fields, which facilitate informed and responsible reuse of the database. The data are quality control checked and the foraminiferal taxonomy has been updated. PhanSST will serve as a valuable resource to the paleoclimate community and has myriad applications, including evolutionary, geochemical, diagenetic, and proxy calibration studies.Measurement(s)sea surface temperature proxy valuesTechnology Type(s)variousSample Characteristic - OrganismPlanktonic Foraminifera • Brachiopoda • Mollusca • Conodonta • Thaumarchaeota • HaptophyteSample Characteristic - Environmentmarine biomeSample Characteristic - Locationglobal

Mean body size in marine animals has increased more than 100-fold since the Cambrian, a discovery that brings to attention the key life-history parameters of lifespan and growth rate that ultimately determine size. Variation in these parameters is not well understood on the planet today, much less in deep time. Here, we present a new global database of maximum reported lifespan and shell growth coupled with body size data for 1148 populations of marine bivalves and show that (i) lifespan increases, and growth rate decreases, with latitude, both across the group as a whole and within well-sampled species, (ii) growth rate, and hence metabolic rate, correlates inversely with lifespan, and (iii) opposing trends in lifespan and growth combined with high variance obviate any demonstrable pattern in body size with latitude. Our observations suggest that the proposed increase in metabolic activity and demonstrated increase in body size of organisms over the Phanerozoic should be accompanied by a concomitant shift towards faster growth and/or shorter lifespan in marine bivalves. This prediction, testable from the fossil record, may help to explain one of the more fundamental patterns in the evolutionary and ecological history of animal life on this planet.

Climate change is arguably the most important issue facing modern society. One of the best tools we have for constraining future climate conditions comes from looking at warm and transitional intervals in Earth’s geologic past, such as the Eocene Epoch (~56-34 Ma). The Eocene Epoch was a time of large-scale global climate change, bookended by both the warmest temperatures of the Cenozoic (i.e., the Paleocene-Eocene Thermal Maximum) and the onset of southern hemisphere glaciation (i.e., the Eocene-Oligocene Transition). While mean global climatic conditions across the Eocene, inferred from a compilation of oxygen isotopes of benthic foraminifera, are well constrained and document a clear cooling trend, the few and geographically disparate records of local sea surface temperature (SST) from this interval are often conflicting and difficult to reproduce with climate models. Likewise, multi-proxy studies from the same location frequently yield diverging SST estimates. These inconsistencies within the climate record inhibit our ability to identify the mechanisms responsible for late Eocene cooling, and call into question our understanding of fundamental aspects of climate dynamics and the underlying assumptions guiding our interpretation of proxy data. Further, they highlight one of the dominant shortcomings of paleoclimate studies; namely the propensity to express climate variability in terms of global or latitudinal averages, while overlooking local and regional scale climate heterogeneity. Distilling global climate to single numbers (e.g., the 2oC global warming threshold) or metrics (e.g., meridional temperature gradients) is appealing, as it allows for direct comparison of different climate states, however oversimplifying conditions by ignoring natural spatial heterogeneity may lead to erroneous paleoclimate interpretations and contribute to the frequent need to set unrealistic boundary conditions in climate modelling studies. In fact, inspection of modern SST data reveal abundant variability along individual latitudinal bands. This contradicts the simplifying assumption of homogenous zonal paleotemperatures and suggests that improving our understanding on the controls on modern SSTs may hold the key to better understanding ancient climate systems. The ultimate goal of my dissertation is to provide the tools to facilitate a more robust evaluation of ancient climate dynamics, and thereby improve the fidelity of proxy-based paleoclimate reconstructions and future climate predictions. In Chapter 2, I use analyses of modern SST data to identify sampling biases in the paleo record and propose a new framework within which to more meaningfully interpret annually- and seasonally-resolved SST proxy data. In Chapter 3, I develop a bivalve growth rate model, which accounts for variable intra-annual growth rates and facilitates the temporal alignment of serially-sampled geochemical proxy data, increasing the reliability and applicability of paleo-seasonality interpretations. In Chapters 4 and 5, I apply these approaches to reconstruct seasonal changes in nearshore waters off the eastern margin of the Antarctic Peninsula between the middle and late Eocene. Proxy data are evaluated using climate models and modern analog analyses, supplemented with seasonal precipitation data, and contextualized with existing SST data from the Eocene Southern Ocean, resulting in a holistic assessment of climatic conditions during this critical time interval. The findings of these studies: 1) demonstrate the utility of seasonal data in distinguishing between the mechanisms responsible for large-scale climate change and identifying seasonal biases in other SST proxy data, 2) suggest that initial late Eocene Antarctic cooling was driven by changes in ocean circulation, rather than pCO2, 3) reveal how sampling location biases can generate spurious climate interpretations, and 4) illustrate that recognition of and correction for these biases can allow for a more comprehensive and accurate understanding of ancient climate dynamics conditions.

BackgroundIsolated non-specific ST-T abnormalities (NSSTTAs), a common finding on ECGs, were associated with an increased risk of coronary heart disease (CHD) and stroke. However, their association with heart failure (HF) is not well documented.MethodsThis analysis included REasons for Geographic and Racial Differences in Stroke participants who were free of HF, CHD or major ECG abnormalities at baseline (2003–2007). NSSTTAs were defined from baseline ECG using the standards of Minnesota ECG classification. Incident HF events through 2020 were determined from a physician-adjudicated review of hospitalisation medical records and cause of death. Participants with ejection fraction (EF) ≥50% were considered to have HF with preserved EF (HFpEF), and the rest with EF <50% represented HF with either reduced or mildly reduced EF (HFrEF/HFmrEF). Multivariable Cox proportional hazards models examined the association between isolated NSSTTAs and HF. Separate, cause-specific Cox models were used to examine the association with HF subtypes, treating them as competing risks.ResultsAmong 13 914 participants (mean age: 63.1±9.0 years; 60.1% women; 40.0% black), 3859 (28%) had isolated NSSTTAs. Over a median follow-up of 13.5 years (IQR: 7.9–15.6), isolated NSSTTAs were associated with an increased risk of incident HF (HR: 1.83, 95% CI 1.53 to 2.19). Isolated NSSTTAs were associated with an increased risk of both HFrEF/HFmrEF (HR: 2.19; 95% CI 1.64 to 2.93) and HFpEF (HR: 1.66; 95% CI 1.23 to 2.24).ConclusionsIsolated NSSTTAs were associated with an increased risk of developing both HFrEF/HFmrEF and HFpEF. These findings challenge the assumption that NSSTTAs are benign and suggest their potential role in HF risk stratification.

Soil-transmitted helminth infections (STH) are associated with substantial morbidity in low-and-middle-income countries, accounting for 2.7 million disability-adjusted life years annually. Current World Health Organization guidelines recommend controlling STH-associated morbidity through periodic deworming of at-risk populations, including children and women of reproductive age (15-49 years). However, there is increasing interest in community-wide mass drug administration (cMDA) which includes deworming adults who serve as infection reservoirs as a method to improve coverage and possibly to interrupt STH transmission. We investigated determinants of cMDA coverage by comparing high-coverage clusters (HCCs) and low-coverage clusters (LCCs) receiving STH cMDA in three countries. A convergent mixed-methods design was used to analyze data from HCCs and LCCs in DeWorm3 trial sites in Benin, India, and Malawi following three rounds of cMDA. Qualitative data were collected via 48 community-level focus group discussions. Quantitative data were collected via routine activities nested within the DeWorm3 trial, including annual censuses and coverage surveys. The Consolidated Framework for Implementation Research (CFIR) guided coding, theme development and a rating process to determine the influence of each CFIR construct on cMDA coverage. Of 23 CFIR constructs evaluated, we identified 11 constructs that differentiated between HCCs and LCCs, indicating they are potential drivers of coverage. Determinants differentiating HCC and LCC include participant experiences with previous community-wide programs, communities' perceptions of directly observed therapy (DOT), perceptions about the treatment uptake behaviors of neighbors, and women's agency to make household-level treatment decisions. The convergent mixed-methods study identified barriers and facilitators that may be useful to NTD programs to improve cMDA implementation for STH, increase treatment coverage, and contribute to the successful control or elimination of STH. The parent trial was registered at clinicaltrials.gov (NCT03014167).

High mortality after discharge from hospital following acute illness has been observed among children with Severe Acute Malnutrition (SAM). However, mechanisms that may be amenable to intervention to reduce risk are unknown. We performed a nested case-control study among HIV-uninfected children aged 2–59 months treated for complicated SAM according to WHO recommendations at four Kenyan hospitals. Blood was drawn from 1778 children when clinically judged stable before discharge from hospital. Cases were children who died within 60 days. Controls were randomly selected children who survived for one year without readmission to hospital. Untargeted proteomics, total protein, cytokines and chemokines, and leptin were assayed in plasma and corresponding biological processes determined. Among 121 cases and 120 controls, increased levels of calprotectin, von Willebrand factor, angiotensinogen, IL8, IL15, IP10, TNFα, and decreased levels of leptin, heparin cofactor 2, and serum paraoxonase were associated with mortality after adjusting for possible confounders. Acute phase responses, cellular responses to lipopolysaccharide, neutrophil responses to bacteria, and endothelial responses were enriched among cases. Among apparently clinically stable children with SAM, a sepsis-like profile is associated with subsequent death. This may be due to ongoing bacterial infection, translocated bacterial products or deranged immune response during nutritional recovery.