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Easy virtue : let's misbehave!
A glamorous American woman enters into a spirited battle of wits with her disapproving English mother-in-law.
DVD
OCEANFILMS (Organic Compounds from Ecosystems to Aerosols: Natural Films and Interfaces via Langmuir Molecular Surfactants) sea spray organic aerosol emissions – implementation in a global climate model and impacts on clouds
Sea spray aerosol is one of the major sources of atmospheric particulate matter globally. It has increasingly been recognized that organic matter derived from ocean biological precursors contributes significantly to the composition of submicron sea spray and may modify sea spray aerosol impacts on clouds and climate. This paper describes the implementation of the OCEANFILMS (Organic Compounds from Ecosystems to Aerosols: Natural Films and Interfaces via Langmuir Molecular Surfactants) parameterization for sea spray organic aerosol emissions in a global Earth system model, the Energy Exascale Earth System Model (E3SM). OCEANFILMS is a physically based model that links sea spray chemistry with ocean biogeochemistry using a Langmuir partitioning approach. We describe the implementation details of OCEANFILMS within E3SM, compare simulated aerosol fields with observations, and investigate impacts on simulated clouds and climate. Four sensitivity cases are tested, in which organic emissions either strictly add to or strictly replace sea salt emissions (in mass and number) and are either fully internally or fully externally mixed with sea salt. The simulation with internally mixed, added organics agrees reasonably well with observed seasonal cycles of organic matter in marine aerosol and has been selected as the default configuration of the E3SM. In this configuration, sea spray organic aerosol contributes an additional source of cloud condensation nuclei, adding up to 30 cm−3 to Southern Ocean boundary-layer cloud condensation nuclei concentrations (supersaturation = 0.1 %). The addition of this new aerosol source strengthens shortwave radiative cooling by clouds by −0.36 W m−2 in the global annual mean and contributes more than −3.5 W m−2 to summertime zonal mean cloud forcing in the Southern Ocean, with maximum zonal mean impacts of about −4 W m−2 around 50–60∘ S. This is consistent with a previous top-down, satellite-based empirical estimate of the radiative forcing by sea spray organic aerosol over the Southern Ocean. Through its mechanistic approach, OCEANFILMS offers a path towards improved understanding of the feedbacks between ocean biology, sea spray organic matter, and climate.
Journal Article
The Role of Phytoplankton Biomacromolecules in Controlling Ocean Surface Roughness
Satellite altimetric data routinely map sea surface topography by measuring the ocean return signal. One source of altimeter measurement contamination occurs when the radar ocean backscatter becomes unusually large, a situation termed a Sigma-0 bloom. Past research suggests Sigma-0 blooms are associated with weak wind and natural surface slick conditions where capillary waves at the air–sea interface are suppressed. To date, no explicit connection between these conditions and Sigma-0 bloom presence has been provided. Using a series of simplified equations, our reduced model determines capillary wave heights from estimates of planktonic carbon concentrations and regional wind speed. Our results suggest that the radar signal reflection increases as capillary wave height decreases. This relationship depends on surfactant concentration, surfactant composition, and wind speed. Model sensitivity analysis indicates that the interface reflectivity depends on biological activity and wind speed. Our proposed simplified model provides a method to identify potential Sigma-0 bloom regions. We conclude that because of the demonstrated impact of biological surfactants on ocean roughness, it is necessary to consider the biological activity, i.e., phytoplankton bloom events, when interpreting signals from radar altimetry and when developing ocean hydrology models.
Journal Article
Exploring the influence of ancient and historic megaherbivore extirpations on the global methane budget
Globally, large-bodied wild mammals are in peril. Because “megamammals” have a disproportionate influence on vegetation, trophic interactions, and ecosystem function, declining populations are of considerable conservation concern. However, this is not new; trophic downgrading occurred in the past, including the African rinderpest epizootic of the 1890s, the massive Great Plains bison kill-off in the 1860s, and the terminal Pleistocene extinction of megafauna. Examining the consequences of these earlier events yields insights into contemporary ecosystem function. Here, we focus on changes in methane emissions, produced as a byproduct of enteric fermentation by herbivores. Although methane is ∼200 times less abundant than carbon dioxide in the atmosphere, the greater efficiency of methane in trapping radiation leads to a significant role in radiative forcing of climate. Using global datasets of late Quaternary mammals, domestic livestock, and human population from the United Nations as well as literature sources, we develop a series of allometric regressions relating mammal body mass to population density and CH₄ production, which allows estimation of methane production by wild and domestic herbivores for each historic or ancient time period. We find the extirpation of megaherbivores reduced global enteric emissions between 2.2–69.6 Tg CH₄ y−1 during the various time periods, representing a decrease of 0.8–34.8% of the overall inputs to tropospheric input. Our analyses suggest that large-bodied mammals have a greater influence on methane emissions than previously appreciated and, further, that changes in the source pool from herbivores can influence global biogeochemical cycles and, potentially, climate.
Journal Article
“For me, it is for longevity and making sure I am fit and around for my children”: exploring motivations and barriers for weight management among minoritised communities in Medway, England
Background
Migration-related changes in dietary patterns and other structural and individual factors affect weight-related health practices of individuals migrating from low-and-middle-income to high-income countries. Thus, individuals of ethnically diverse backgrounds may be disproportionately affected by poorer health outcomes, including weight-related health issues. Understanding how this community could be supported to adopt weight-related healthy practices such as optimum dietary and exercise behaviour is an important issue for public health research. Against this backdrop, we explored structural and individual factors that facilitate and constrain the uptake of weight management services among members of minority ethnic communities in Medway, England.
Methods
Data were collected from audio-recorded interviews with 12 adult community members from minoritised ethnic communities using a semi-structured interview guide. Participants were recruited through a purposive and convenient sampling technique. Generated data were transcribed, coded into NVivo and analysed using the reflexive thematic analytical technique.
Results
Results showed that social support and health benefits of weight management were the main motivating factors for weight management among the study participants. Conversely, systemic barriers, family commitment and caring responsibilities, changes in dietary patterns post-migration and cultural norms were major factors constraining participants from adopting weight management behaviours.
Conclusion
The results of this study indicate that structural and person-level factors serve as both facilitators and barriers to weight management among ethnically diverse communities in Medway, England. While our study is exploratory and opens doors for more studies among the population, we conclude that these minoritised communities could benefit from more equitable, tailored weight management programmes to support them in adopting weight-related practices.
Journal Article
Demographic Consequences of Predators on Prey: Trait and Density Mediated Effects on Mosquito Larvae in Containers
Predators may affect prey population growth and community diversity through density mediated lethal and trait mediated non-lethal effects that influence phenotypic traits of prey. We tested experimentally the roles of thinning the density of prey (lethality) in the absence of predator cues and density and trait mediated effects (lethality + intimidation) of predatory midge Corethrella appendiculata on competing native and invasive mosquito prey. Predator-mediated reductions in prey and density reductions in the absence of C. appendiculata resulted in lower percent survivorship to adulthood and estimates of the finite rate of increase (λ') for invasive mosquito Aedes albopictus relative to that of controls. In most instances, thinning the density of prey in the absence, but not in the presence, of C. appendiculata cues resulted in lower survivorship to adulthood and λ' for native mosquito Aedes triseriatus relative to that of controls. Together, these results suggested trait mediated effects of C. appendiculata specific to each species of mosquito prey. Release from intraspecific competition attributable to density reductions in the absence, but not in the presence, of C. appendiculata enhanced growth and lengthened adult lifespan relative to that of controls for A. albopictus but not A. triseriatus. These results show the importance of predator-mediated density and trait mediated effects on phenotypic traits and populations of invasive and native mosquitoes. Species-specific differences in the phenotypic responses of prey may be due, in part, to longer evolutionary history of C. appendiculata with A. triseriatus than A. albopictus.
Journal Article
Large-scale modeling of primary production and ice algal biomass within arctic sea ice in 1992
An ice ecosystem model was coupled to a global dynamic sea ice model to assess large‐scale variability of primary production and ice algal biomass within arctic sea ice. The component models are the Physical Ecosystem Model (PhEcoM) ice ecosystem model and the Los Alamos Sea Ice Model (CICE). Simulated annual arctic sea ice primary production was 15.1 Tg C; within the range of 9 to 73 Tg C estimated using in situ data. The amount of C fixed was >3 Tg C month−1 for March, April, and May. The Bering Sea, Arctic Ocean basins, and the Canadian Archipelago/Baffin Bay were the most productive regions on an annual basis, contributing approximately 24, 18, and another 18%, respectively. High production in the Bering Sea was due to high daily production rates, while the large sea ice coverage in the Canadian Archipelago/Baffin Bay and, in particular, the Arctic Ocean basins resulted in their considerable contribution to sea ice primary production. The simulated trends, patterns, and seasonality of ice algae agree reasonably well with very limited observations. In the model, ice growth rate controls the availability of nutrients to sea ice algae, such that ocean nutrient supply is of secondary importance to ice algal growth. The numerical model results suggest that ice melt rate, which determines the proportional rate of ice algal release, controls the termination of the bloom on large scales. The model described advances the role of sea ice algae in biogeochemical cycling within global climate models. Key Points Simulation results are reasonable compared with in situ observations First large‐scale modeling of pan‐Arctic sea ice primary production High annual production is due to either high daily rates or large ice coverage
Journal Article
Contribution of oceanic gas hydrate dissociation to the formation of Arctic Ocean methane plumes
Vast quantities of methane are trapped in oceanic hydrate deposits, and there is concern that a rise in the ocean temperature will induce dissociation of these hydrate accumulations, potentially releasing large amounts of carbon into the atmosphere. Because methane is a powerful greenhouse gas, such a release could have dramatic climatic consequences. The recent discovery of active methane gas venting along the landward limit of the gas hydrate stability zone (GHSZ) on the shallow continental slope (150 m to 400 m) west of Svalbard suggests that this process may already have begun, but the source of the methane has not yet been determined. This study performs 2‐D simulations of hydrate dissociation in conditions representative of the Arctic Ocean margin to assess whether such hydrates could contribute to the observed gas release. The results show that shallow, low‐saturation hydrate deposits, if subjected to recently observed or future predicted temperature changes at the seafloor, can release quantities of methane at magnitudes similar to what has been observed, and that the releases will be localized near the landward limit of the GHSZ. Both gradual and rapid warming is simulated, along with a parametric sensitivity analysis, and localized gas release is observed for most of the cases. These results resemble the recently published observations and strongly suggest that hydrate dissociation and methane release as a result of climate change may be a real phenomenon, that it could occur on decadal timescales, and that it already may be occurring. Key Points Seafloor warming can dissociate hydrates and cause methane release Shallow hydrates alone may contribute to significant release Methane release may occur under a wide range of sediment conditions
Journal Article
Ocean Contributions to the Marine Boundary Layer Aerosol Budget
[...]uncertainty in the origin, number size distribution, and chemical composition of background aerosol complicates the assessments of direct and indirect anthropogenic aerosol forcing and makes it difficult for Earth system science models to accurately predict 21st century climate change. Because effects on climate are estimated from the differences between model simulations with present-day and preindustrial aerosol and precursor emissions, concerns over the global aerosol budget in the absence of anthropogenic influence have sparked renewed interest in the natural emissions of trace gases (acting as particle precursors) and aerosols. A reduction of the uncertainties in the representation of natural aerosols in climate models requires an improved quantification of their number, size distribution, chemical composition, and hygroscopic properties in the marine boundary layer (MBL). Studies have shown that the production rates and physiological properties of SSA and the resulting efficacy to act as CCN or INP can be strongly influenced by the ocean’s biogeochemical state (nutrient availability, pH, bacterial and phytoplankton abundance, eco-physiological factors, and evolutionary drivers). By combining Moderate Resolution Imaging Spectroradiometer (MODIS) and Aerosol Robotic Network (AERONET) AOD retrievals with 2 m wind speed data, the study develops a new power–law relationship between AOD and surface–wind over the oceans.
Journal Article