Rapid Climate Change in the Cenozoic: Insights from Geochemical Proxies

Studying the mean state and variability of past climate provides important insight into the dynamically coupled climate system, directly aiding projections of future climate. Reconstruction of past climate conditions can be achieved using geochemical proxies including the novel clumped isotope paleothermometer. In this thesis I use multiple proxies to study climate variability during the last glacial period and at the onset of Antarctic glaciation. Greenland ice cores record repeated millennial-scale fluctuations in climate during the last glacial period known as Dansgaard-Oeschger (DO) cycles. We measure 18O of bulk sediment and planktonic foraminifera (Neogloboquadrina Pachyderma) in sediment cores from the North Atlantic to investigate fluctuations in sediment properties on the timescale of DO cycles. We find evidence of episodic deposition of carbonate ice-rafted debris near Iceland. Integrating these observations with published data and modeling studies, we propose a new hypothesis to explain DO cycles. We suggest that a large ice shelf in the Nordic Seas acted in concert with sea ice to set the slow and fast timescales of DO cycles. The ice shelf was periodically removed by subsurface warming with the timescale of shelf regrowth setting the duration of each interstadial. We utilize the clumped isotope proxy to reconstruct the climate history during a key period of the Cenozoic - the onset of Antarctic glaciation. To facilitate this work, a new inlet is developed to streamline sample preparation and reduce sample size requirements. We decrease the required sample size from 5-8mg to 1-2mg per replicate, while still achieving external precision of 0.005-0.010o/oo, equivalent to previous methods. This new capability increases the range of possible applications for the clumped isotope paleothermometer, specifically in the field of paleoceanography. We apply the clumped isotope paleothermometer to thermocline-dwelling foraminifera (Subbotina angiporoides and Subbotina utilisindex) from the Southern Ocean core ODP689 across the Eocene-Oligocene transition. With the clumped isotope paleothermometer we separate the contributions of near- surface temperature change and ice sheet growth on the ~1o/oo increase in 18O observed in planktonic foraminifera from this site. We measure no change in temperature, and 0.8±0.2o/oo change in 18Osw, equivalent to 124-140% of the modern Antarctic ice sheet volume.Earth and Planetary Science

Clumped Isotope Measurements of Small Carbonate Samples Using a High-Efficiency Dual-Reservoir Technique

Rationale: The measurement of multiply substituted isotopologues of CO2 derived from carbonate has allowed the reconstruction of paleotemperatures from a single phase (CaCO3), circumventing uncertainty inherent in other isotopic paleothermometers. Traditional analytical techniques require relatively large amounts of carbonate (3–8 mg per replicate), which limits the applicability of the clumped isotope proxy to certain geological materials such as marine microfossils, commonly used for paleoclimate reconstructions. Methods: Clumped isotope ratio measurements of small samples were made on a new, high-efficiency, dual-reservoir sample-preparation inlet system attached to a Thermo-Finnigan MAT 253 mass spectrometer. Sample gas produced on the inlet is introduced from a 10 mL reservoir directly into the source via a capillary. Reference gas fills an identical 10 mL reservoir installed between the reference bellows and the capillary. The gas pressures in the two reservoirs are initially balanced, and are allowed to decrease together over the run. Results: Carbonate samples from 1 mg to 2.6 mg produced Δ47 values equivalent to those from the traditional two-bellows method with identical single-sample precision (1 SE = 0.005–0.015‰) and external standard error (SE = 0.006–0.015‰, n = 4–6). The size of sample needed to achieve good precision is controlled by the sensitivity of the mass spectrometer and the size of the fixed reservoirs and adjacent U-trap installed on our inlet. Conclusions: The high-precision clumped isotope measurements of small aliquots of carbonate obtained in this method allows for the application of this proxy to a wider range of geological sample materials, such as marine microfossils, that until now have been nearly impossible to analyze given sample size limitation.Engineering and Applied Science

A New Mechanism for Dansgaard-Oeschger Cycles

[1] We present a new hypothesis to explain the millennial-scale temperature variability recorded in ice cores known as Dansgaard-Oeschger (DO) cycles. We propose that an ice shelf acted in concert with sea ice to set the slow and fast timescales of the DO cycle, respectively. The abrupt warming at the onset of a cycle is caused by the rapid retreat of sea ice after the collapse of an ice shelf. The gradual cooling during the subsequent interstadial phase is determined by the timescale of ice-shelf regrowth. Once the ice shelf reaches a critical size, sea ice expands, driving the climate rapidly back into stadial conditions. The stadial phase ends when warm subsurface waters penetrate beneath the ice shelf and cause it to collapse. This hypothesis explains the full shape of the DO cycle, the duration of the different phases, and the transitions between them and is supported by proxy records in the North Atlantic and Nordic Seas.Engineering and Applied Science

Biogenic carbonate mercury and marine temperature records reveal global influence of Late Cretaceous Deccan Traps

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155784/1/Meyer_et_al_2019_Biogenic_carbonate_mercury.pd

Cardiovascular Remodeling Experienced by Real-World, Unsupervised, Young Novice Marathon Runners.

Aims: Marathon running is a popular ambition in modern societies inclusive of non-athletes. Previous studies have highlighted concerning transient myocardial dysfunction and biomarker release immediately after the race. Whether this method of increasing physical activity is beneficial or harmful remains a matter of debate. We examine in detail the real-world cardiovascular remodeling response following competition in a first marathon. Methods: Sixty-eight novice marathon runners (36 men and 32 women) aged 30 ± 3 years were investigated 6 months before and 2 weeks after the 2016 London Marathon race in a prospective observational study. Evaluation included electrocardiography, cardiopulmonary exercise testing, echocardiography, and cardiovascular magnetic resonance imaging. Results: After 17 weeks unsupervised marathon training, runners revealed a symmetrical, eccentric remodeling response with 3-5% increases in left and right ventricular cavity sizes, respectively. Blood pressure (BP) fell by 4/2 mmHg (P < 0.01) with reduction in arterial stiffness, despite only 11% demonstrating a clinically meaningful improvement in peak oxygen consumption with an overall non-significant 0.4 ml/min/kg increase in peak oxygen consumption (P = 0.14). Conclusion: In the absence of supervised training, exercise-induced cardiovascular remodeling in real-world novice marathon runners is more modest than previously described and occurs even without improvement in cardiorespiratory fitness. The responses are similar in men and women, who experience a beneficial BP reduction and no evidence of myocardial fibrosis or persistent edema, when achieving average finishing times

Peer sexual harassment in adolescence: Dimensions of the sexual harassment survey in boys and girls

The phenomenon of adolescent sexual harassment is a topic that has taken on special relevance in recent decades. However, general consensus regarding its nature, prevalence and dimensions has yet to emerge. This study used a representative sample of 3,489 Andalusian adolescents from the second stage of Compulsory Secondary Education (E.S.O.) and the Spanish Baccalaureate (Bachillerato), and it is primarily focused on two main objectives: to test the factor structure of the "sexual harassment" scale in boys and girls, and to analyzethe prevalence of hte sexual harassment among adolescent students. Descriptive analyses andconfirmatory factor analysis (CFA) were performed, allowing us to explore the nature of the phenomenon and to describe its prevalence. The results obtained revealed a two-dimensionalstructure of this scale in both boys and girls: one dimension reflecting visual-verbal forms of sexual harassment and the second dimension including physical forms. Regarding to prevalence,the outcomes shown a high prevalence of sexual harassment involvement across both sexes during adolescence. However, boys were more involved in victimization and aggression than girls. The importance of analyzing the phenomenon in greater depth is also highlighted

Validation of the revised IPSS at transplant in patients with myelodysplastic syndrome/transformed acute myelogenous leukemia receiving allogeneic stem cell transplantation

The International Prognostic Scoring System has been revised (IPSS-R) to predict prognosis of patients with myelodysplastic syndromes at diagnosis. To validate the use of the IPSS-R assesse

Nutritional cognitive neuroscience of aging: Focus on carotenoids and cognitive frailty

The term „nutritional cognitive neuroscience” was recently established to define a research field focusing on the impact of nutrition on cognition and brain health across the life span. In this overview, we summarize the robust evidence on the role of carotenoids as micronutrients with different biological properties in persons with cognitive (pre)frailty. As neurodegenerative processes during aging occur in a continuum from brain aging to dementia, we propose the name „nutritional cognitive neuroscience of aging“ to define research on the role of nutrition and micronutrients in cognitive frailty. Further studies are warranted which integrate carotenoid interventions in multidomain, personalized lifestyle strategies