A determination of air-sea gas exchange and upper ocean biological production from five noble gases and tritiugenic helium-3

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2007The five noble gases (helium, neon, argon, krypton, and xenon) are biologically and chemically inert, making them ideal oceanographic tracers. Additionally, the noble gases have a wide range of solubilities and molecular diffusivities, and thus respond differently to physical forcing. Tritium, an isotope of hydrogen, is useful in tandem with its daughter helium-3 as a tracer for water mass ages. In this thesis, a fourteen month time-series of the five noble gases, helium-3 and tritium was measured at the Bermuda Atlantic Time-series Study (BATS) site. The time-series of five noble gases was used to develop a parameterization of air-sea gas exchange for oligotrophic waters and wind speeds between 0 and 13 m s−1 that explicitly includes bubble processes and that constrains diffusive gas exchange to ± 6% and complete and partial air injection processes to ± 15%. Additionally, the parameterization is based on weeks to seasonal time scales, matching the time scales of many relevant biogeochemical cycles. The time-series of helium isotopes, tritium, argon, and oxygen was used to constrain upper ocean biological production. Specifically, the helium flux gauge technique was used to estimate new production, apparent oxygen utilization rates were used to quantify export production, and euphotic zone seasonal cycles of oxygen and argon were used to determine net community production. The concurrent use of these three methods allows examination of the relationship between the types of production and begins to address a number of apparent inconsistencies in the elemental budgets of carbon, oxygen, and nitrogen.I received funding towards my graduate research from the Department of Defense (NDSEG fellowship), the National Science Foundation (OCE-0221247), and the Scurlock Fund for research

Feminists really do count : the complexity of feminist methodologies

We are delighted to be presenting this special issue on the topic of feminism and quantitative methods. We believe that such an issue is exceptionally timely. This is not simply because of ongoing debates around quantification within the field of feminism and women‟s studies. It is also because of debates within the wider research community about the development of appropriate methodologies that take account of new technological and philosophical concerns and are fit-for-purpose for researching contemporary social, philosophical, cultural and global issues. Two areas serve as exemplars in this respect and both speak to these combined wider social science and specifically feminist methodological concerns. The first is the increasing concern amongst social scientists with how the complexity of social life can be captured and analysed. Within feminism, this can be seen in debates about intersectionality that recognise the concerns arising from multiple social positions/divisions and associated power issues. As Denis (2008: 688) comments in respect of intersectional analysis „The challenge of integrating multiple, concurrent, yet often contradictory social locations into analyses of power relations has been issued. Theorising to accomplish this end is evolving, and we are struggling to develop effective methodological tools in order to marry theorising with necessary complex analyses of empirical data.‟ Secondly, new techniques and new data sources are now coming on line. This includes work in the UK of the ESRC National Data Strategy which has been setting out the priorities for the development of research data resources both within and across the boundaries of the social sciences. This will facilitate historical, longitudinal, interdisciplinary and mixed methodological research. And it may be the case that these developments facilitate the achievement of a longstanding feminist aim not simply for interdisciplinarity but for transdisciplinarity in epistemological and methodological terms

Correlates of Stress and Job Satisfaction: A Quantitative Study of Social Workers in the UK

Background and purpose: Social workers deal with service users in complex life situations and the stress experienced at work has adverse impacts on their mental health and wellbeing. Studies from different countries [e.g., Norway (Nilsen et al., 2023); USA (Rine, 2023); Australia and New Zealand (Alston et al., 2021; India (Stanley &amp; Sebastine, 2023)] suggest high levels of burnout and poor quality of life in social workers. The situation in the UK is much the same. Thematic analysis of interviews in a study of the working conditions and well-being of UK social workers found that workload demands, relationships with peers, management, and service users, and how change was communicated to them were the main difficulties cited about their work environment (Ravalier et al., 2020). Staff shortages and increased work demands owing to the pandemic and its legacy continue (Gillen et al., 2022) and a more recent study by Ravalier et al., (2023), reports a decline in the mental well-being and work-related quality of life in UK based social workers. Methods: Against this background, we conducted an online survey of 98 social workers in the Nort-East region of England to understand the relationship between stress levels and select work correlates as perceived by the respondents. The study was framed with the following three objectives:1.To identify levels of stress manifested in social workers and the extent to which they experienced job satisfaction.2.To determine role ambiguity and role conflict in their work life.3.To determine the nature of the relationship between our four variables of interest (stress, role ambiguity, role conflict and job satisfaction).4.To identify those variables that predicted the manifestation of both stress levels and job satisfaction.The instruments administered were (a) 7 items to assess stress from the Depression, Anxiety and Stress Scale (b) The Short Index of Job Satisfaction (Sinval &amp; Marôco, 2020) (c) The Role Conflict and Ambiguity Scale (Rizzo et al., 1970) and (d) The Perceived Organisational Scale (Apodaca (2010).This quantitative study used a cross-sectional design. Data was analysed using the SPSS package (ver. 24) and findings were generated through statistical procedures (t-tests, Pearson's correlations, and multiple linear regression analysis).Findings: We found high levels of stress and low levels of job satisfaction in the majority of respondents. Stress scores correlated positively with both role conflict and role ambiguity. Significant negative correlations were also obtained for the stress scores in relation to job satisfaction and organisational support. Both stress and role conflict contributed to the experience of job satisfaction while both role ambiguity and job satisfaction explained the experience of stress in the respondents.Conclusions and implications: The post-COVID work scenario for social workers in the UK remains bleak in relation to high stress levels and low job satisfaction. Policies and procedures need to be put in place to ensure that adequate organisational support provisions are put in place and that work roles are presented with greater role clarity and to minimise role conflict.<br/

Children and Domestic Homicide

In England and Wales, Domestic Homicide Reviews (DHRs) are completed following domestic homicides. They provide multi-agency accounts of families living with domestic violence and abuse (DVA) and their interactions with services. This study addressed children’s involvement in domestic homicide. We analysed all DHRs where there were children under eighteen among those published in 2011–16. This yielded a sub-sample of fifty-five DHRs from a total of 142 reports. The extent of children’s exposure to homicide varied, with some directly witnessing the homicide, viewing the aftermath or calling for help. DHRs provided limited information on children’s needs or their future care and children were only rarely involved in the review process itself. Nearly a third of reports identified that children had previous experience of DVA and contact emerged as a means of sustaining control and intimidation. There was evidence of blinkered vision among professionals who missed indicators of DVA and failed to engage with perpetrators or listen to children. Practitioners need training and assessment tools that direct their attention onto children and knowledge of resources that enables identification of need and appropriate referrals. Law and practice should address children’s involvement in the DHR process and the risks embedded in child contact

Quantifying photosynthetic rates of microphytobenthos using the triple isotope composition of dissolved oxygen

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography: Methods 11 (2013): 360-373, doi:10.4319/lom.2013.11.360.Microphytobenthos are important mediators of nutrient and carbon fluxes in coastal environments. However, quantifying production rates by microphytobenthos is difficult, and existing methods necessitate perhaps erroneous assumptions that dark respiration equals light respiration. Here we present a new method for quantifying photosynthetic rates of microphytobenthos, i.e., gross primary production, by using the triple isotope composition of dissolved oxygen in benthic flux chambers. Because the triple oxygen isotope signature is sensitive to photosynthesis, but not to respiration, this method allows quantification of gross photosynthetic oxygen fluxes by microphytobenthos without assumptions about respiration. We present results from field experiments in Waquoit Bay, Massachusetts, that illustrate the method.We gratefully acknowledge funding for this work by the Coastal Ocean Institute of Woods Hole Oceanographic Institution and the National Science Foundation (OCE-82964400). EH was supported by a National Defense Science and Engineering Graduate Fellowship award

Vulnerable, recalcitrant and resilient: a Foucauldian discourse analysis of risk and older people within the context of COVID-19 news media

Risk is an innate and integral part of everyday life and is present in simple, everyday occupations and complex actions. Age-related stereotypes can mean older people have little opportunity to engage in activities that present some degree of risk. The present study explores the discourse around risk and older people in the context of the COVID-19 pandemic. We investigated news media as a reflection of the dominant public discourse around older people\u27s behaviour to identify how risk is represented in relation to occupational engagement. Texts relating to older people and COVID-19 were sourced from the West Australian newspaper for a period of two months. Seventy texts were subject to Foucauldian discourse analysis to identify subject positions, location of risk and discursive features. Findings indicate that older people were segregated from the rest of society, with their behaviours framed in mostly negative ways. We identified three areas of discourse: vulnerable, and in need of protection; recalcitrant, and in need of management; and resilient, deserving of respect. While we recognise competing representations, implicit within the dominant discourse was the premise that older people were not capable of mediating risks and required ‘management’. These findings highlight the role of surveillance in restricting occupational engagement for older people and carry implications for older people, the public and therapists

Rates of summertime biological productivity in the Beaufort Gyre : a comparison between the low and record-low ice conditions of August 2011 and 2012

© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Marine Systems 147 (2015): 29-44, doi:10.1016/j.jmarsys.2014.04.006.The Arctic Ocean is changing rapidly as the global climate warms but it is not well known how these changes are affecting biological productivity and the carbon cycle. Here we study the Beaufort Gyre region of the Canada Basin in August and use the large reduction in summertime sea ice extent from 2011 to 2012 to investigate potential impacts of climate warming on biological productivity. We use the gas tracers O2/Ar and triple oxygen isotopes to quantify rates of net community production (NCP) and gross oxygen production (GOP) in the gyre. Comparison of the summer of 2011 with the summer of 2012, the latter of which had record low sea ice coverage, is relevant to how biological productivity might change in a seasonally ice-free Arctic Ocean. We find that, in the surface waters measured here, GOP in 2012 is significantly greater than in 2011, with the mean basin-wide 2012 GOP = 38 ± 3 mmol O2 m− 2 d− 1 whereas in 2011, mean basin GOP = 16 ± 5 mmol O2 m− 2 d− 1. We hypothesize that this is because the lack of sea ice and consequent increase in light penetration allows photosynthesis to increase in 2012. However, despite the increase in GOP, NCP is the same in the two years; mean NCP in 2012 is 3.0 ± 0.2 mmol O2 m− 2 y− 1 and in 2011 is 3.1 ± 0.2 mmol O2 m− 2 y− 1. This suggests that the heterotrophic community (zooplankton and/or bacteria) increased its activity as well and thus respired the additional carbon produced by the increased photosynthetic production. In both years, stations on the shelf had GOP 3 to 5 times and NCP 2 to 10 times larger than the basin stations. Additionally, we show that in 2011, the NCP/GOP ratio is smallest in regions with highest ice cover, suggesting that the microbial loop was more efficient at recycling carbon in regions where the ice was just starting to melt. These results highlight that although satellite chlorophyll records show, and many models predict, an increase in summertime primary production in the Arctic Basin as it warms, the net amount of carbon processed by the biological pump during summer may not change as a function of ice cover. Thus, a rapid reduction in summertime ice extent may not change the net community productivity or carbon balance in the Beaufort Gyre.We thank our funding sources: the National Science Foundation (PLR 1304406, PLR-0856531) and the support of Fisheries and Oceans Canada

The triple oxygen isotope tracer of primary productivity in a dynamic ocean model

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycle 28 (2014): 538–552, doi:10.1002/2013GB004704.The triple oxygen isotopic composition of dissolved oxygen (17Δdis) was added to the ocean ecosystem and biogeochemistry component of the Community Earth System Model, version 1.1.1. Model simulations were used to investigate the biological and physical dynamics of 17Δdis and assess its application as a tracer of gross photosynthetic production (gross oxygen production (GOP)) of O2 in the ocean mixed layer. The model reproduced large-scale patterns of 17Δdis found in observational data across diverse biogeographical provinces. Mixed layer model performance was best in the Pacific and had a negative bias in the North Atlantic and a positive bias in the Southern Ocean. Based on model results, the steady state equation commonly used to calculate GOP from tracer values overestimated the globally averaged model GOP by 29%. Vertical entrainment/mixing and the time rate of change of 17Δdis were the two largest sources of bias when applying the steady state method to calculate GOP. Entrainment/mixing resulted in the largest overestimation in midlatitudes and during summer and fall and almost never caused an underestimation of GOP. The tracer time rate of change bias resulted both in underestimation of GOP (e.g., during spring blooms at high latitudes) and overestimation (e.g., during the summer following a bloom). Seasonally, bias was highest in the fall (September-October-November in the Northern Hemisphere, March-April-May in the Southern), overestimating GOP by 62%, globally averaged. Overall, the steady state method was most accurate in equatorial and low-latitude regions where it estimated GOP to within ±10%. Field applicable correction terms are derived for entrainment and mixing that capture 86% of model vertical bias and require only mixed layer depth history and triple oxygen isotope measurements from two depths.We acknowledge support from Center for Microbial Oceanography Research and Education (CMORE) (NSF EF-0424599) and NOAA Climate Program Office (NA 100AR4310093).2014-11-2

Quantifying seasonal air-sea gas exchange processes using noble gas time-series : a design experiment

Author Posting. © Sears Foundation for Marine Research, 2006. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 64 (2006): 267-295, doi:10.1357/002224006777606452.A multi-year time-series of measurements of five noble gases (He, Ne, Ar, Kr, and Xe) at a subtropical ocean location may allow quantification of air-sea gas exchange parameters with tighter constraints than is currently available by other methods. We have demonstrated this using a one-dimensional upper ocean model forced by 6-hourly NCEP reanalysis winds and heat flux for the Sargasso Sea near Bermuda. We performed ensemble model runs to characterize the response of the modeled noble gas saturation anomalies to a range of air-sea gas exchange parameters. We then used inverse calculations to quantify the sensitivity of the parameters to hypothetical observations. These calculations show that with currently achievable measurement accuracies, noble gas concentrations in the Sargasso Sea could be used to constrain the magnitude of equilibrium gas exchange to ±11%, the magnitude of the total air injection flux to ±14%, and the magnitude of net photosynthetic oxygen production to ±1.5 mol O2 m−2 y−1. Additionally, we can use noble gases to quantify the relative contributions of bubbles that are partially dissolved to bubbles that are completely dissolved. These constraints are based on idealized assumptions and may not fully account for some of the uncertainties in the meteorological data, in lateral transport processes, and in the solubilities of the noble gases. As a limited demonstration, we applied this approach to a time series of He, Ne, Ar, and O2 measurements from the Sargasso Sea from 1985 to 1988 (data from Spitzer, 1989). Due to the limited number of gases measured and the lower accuracy of those measurements, the constraints in this example application are weaker than could be achieved with current capabilities.This work was supported by the National Science Foundation Chemical Oceanography program (OCE-0221247) and by the Department of Defense (graduate fellowship to RHRS)