A quasi-objective single-buoy approach for understanding Lagrangian coherent structures and sea ice dynamics

Sea ice drift and deformation, namely sea ice dynamics, play a significant role in atmosphere–ice–ocean coupling. Deformation patterns in sea ice can be observed over a wide range of spatial and temporal scales, though high-resolution objective quantification of these features remains difficult. In an effort to better understand local deformation of sea ice, we adapt the trajectory-stretching exponents (TSEs), quasi-objective measures of Lagrangian stretching in continuous media, to sea ice buoy data and develop a temporal analysis of TSE time series. Our work expands on previous ocean current studies that have shown TSEs provide an approximation of Lagrangian coherent structure diagnostics when only sparse trajectory data are available. As TSEs do not require multiple buoys, we find they have an expanded range of use when compared with traditional Eulerian buoy-array deformation metrics and provide local-stretching information below the length scales possible when averaging over buoy arrays. We verify the ability of TSEs to temporally and spatially identify dynamic features for three different sea ice datasets. The ability of TSEs to quantify trajectory stretching is verified by concurrent ice fracture in buoy neighborhoods ranging from tens to hundreds of kilometers in diameter, as well as the temporal concurrence of significant storm events.</p

Direct synthesis of hydrogen peroxide in water at ambient temperature

The direct synthesis of hydrogen peroxide (H2O2) from hydrogen and oxygen has been studied using an Au–Pd/TiO2 catalyst. The aim of this study is to understand the balance of synthesis and sequential degradation reactions using an aqueous, stabilizer-free solvent at ambient temperature. The effects of the reaction conditions on the productivity of H2O2 formation and the undesirable hydrogenation and decomposition reactions are investigated. Reaction temperature, solvent composition and reaction time have been studied and indicate that when using water as the solvent the H2O2 decomposition reaction is the predominant degradation pathway, which provides new challenges for catalyst design, which has previously focused on minimizing the subsequent hydrogenation reaction. This is of importance for the application of this catalytic approach for water purification

Gold as a catalyst for the ring opening of 2,5-Dimethylfuran

The epoxidation of 2,5-dimethyl furan leads to the production of hex-3-ene-2,5-dione via a ring opening rearrangement reaction. A second epoxidation reaction could then enable a further ring closing rearrangement to form 4-hydroxy-2,5-dimethyl-3-furanone (furaneol). In this paper we report the use of gold and gold palladium supported on graphite and titania as catalysts for the ring opening reaction of 2,5-dimethyl furan. We show that by tuning the reaction conditions high selectivity towards hex-3-ene-2,5-dione can be achieved using green chemical methods and mild reaction conditions

Selective hydrogenation of levulinic acid using Ru/C catalysts prepared by sol-immobilsation

A 1% Ru/C catalyst prepared by the sol immobilization method showed a high yield of γ-valerolactone from levulinic acid. We performed an optimization of the catalyst by varying the preparation variables involved in the sol immobilization method and detremined that the ratio of PVA, NaBH4 to Ru and heat treatment conditions play a crucial role in the synthesis of active and selective catalysts. By varying these parameters we have identified the optimum conditions for catalyst preparation by providing well dispersed nanoparticles of RuOx on the carbon support that are reducible under low reaction temperature and in turn gave an enhanced catalytic activity. In contrast to a catalyst prepared without using a PVA stabiliser, the use of a small amount PVA (PVA/Ru = 0.1) provided active nanoparticles, by controlling the steric size of the Ru nanoparticles. An optimum amount of NaBH4 was required in order to provide the reducible Ru species on the surface of catalyst and further increase in NaBH4 was found to cause a decline in activity that was related to the kinetics of nanoparticle formation during catalyst preparation. A variation of heat treatment temperature showed a corresponding decrease in catalytic activity linked with the sintering and an increase in particle size

Anomalous sea-ice reduction in the Eurasian Basin of the Arctic Ocean during summer 2010

Special Issue: The Second International Symposium on the Arctic Research (ISAR - 2

Bicatalytic Multistep Reactions En Route to the One-Pot Total Synthesis of Complex Molecules: Easy Access to Chromene and 1,2-Dihydroquinoline Derivatives from Simple Substrates

By combining nanocatalysis and base-catalysis, a novel one-pot multistep process was found for the synthesis of substituted heterocycles of biological relevance from simple substrates. It is based on an initial Au/O2 oxidation of allylic alcohols followed by a base-catalysed tandem hetero-Michael/aldolisation/crotonisation with ortho-hydroxy or ortho-amino benzaldehydes. The flexibility of the reaction even allowed the benzaldehyde partner to be prepared in situ in an example of one-pot/5-steps process

Preconditioning of the 2007 sea-ice melt in the eastern Beaufort Sea, Arctic Ocean

During summer 2007, perennial sea ice in the Beaufort Sea, Arctic Ocean, experienced an unprecedented amount of basal melt. It has previously been shown that this basal melt was linked to an increase in open-water fraction, increasing absorption of solar radiation into the ocean. GPS ice drifters, deployed around the site where the unprecedented basal melt was observed, provide a coincident observation of local divergence. This divergence is used to drive a multi-thickness category thermodynamic sea-ice model. We demonstrate that ∼75% of the observed open-water fraction by midsummer 2007 can be attributed to ice pack divergence during the growth season, preconditioning the ice pack for early melt in summer. Divergence during the melt season explains the remaining 25% of open water. Enhanced ice pack divergence in spring and summer 2007, in response to the increased transport of ice out of the Beaufort Sea, was sufficient to explain the melt observed in summer 2007 and the heat stored in the upper ocean at the end of summer

Improve ocean mixing caused by subgrid-scale brine rejection using multi-column ocean grid in a climate model

Heterogeneous ice pack with sporadic narrow but long leads in the polar oceans was unresolved in typical climate model grid. Although multi-category sea ice thickness distribution was used in one sea ice model grid to calculate separate heat, salt and tracer fluxes through each category, the ocean models use only single-column grid to communicate with the averaged fluxes from all categories. When the lead is resolved by the grid, the added salt at the sea surface will sink to the base of the mixed layer and then spread horizontally. When averaged at a climate-model grid size, this vertical distribution of added salt is lead-fraction dependent. When the lead is unresolved, the model errors were systematic leading to greater surface salinity and deeper mixed-layer depth (MLD). An empirical function was developed to revise the added-salt-related parameter n from being fixed to lead-fraction dependent. Application of this new scheme in climate model showed significant improvement in modeled wintertime salinity and MLD as compared to series of CTD data sets in 1997/1998 and 2006/2007. The results showed the most evident improvement in modeled MLD in the Arctic Basin, similar to that using a fixed n = 5, as recommended by the previous Arctic regional model study, in which the parameter n obtained is close to 5 due to the small lead fraction in the Arctic Basin in winter.This work was funded by NSF ARC-0652838, also supported by International Arctic Research Center through JAMSTEC-IARC Research Agreement

Population-level susceptibility, severity and spread of pandemic influenza: design of, and initial results from, a pre-pandemic and hibernating pandemic phase study using cross-sectional data from the Health Survey for England (HSE)

Background Assessing severity and spread of a novel influenza strain at the start of a pandemic is critical for informing a targeted and proportional response. It requires community-level studies to estimate the burden of infection and disease. Rapidly initiating such studies in a pandemic is difficult. The study aims to establish an efficient system allowing real-time assessment of population susceptibility, spread of infection and clinical attack rates in the event of a pandemic. Methods We developed and appended additional survey questions and specimen collection to the Health Survey for England (HSE) – a large, annual, rolling nationally representative general population survey recruiting throughout the year – to enable rapid population-based surveys of influenza infection and disease during a pandemic. Using these surveys we can assess the spread of the virus geographically, by age and through time. The data generated can also provide denominators for national estimates of case fatality and hospitalisation rates.Phase 1: we compared retrospectively collected HSE illness rates during the first two infection waves of the 2009 pandemic with the Flu Watch study (a prospective community cohort). Monthly and seasonal age-specific rates of illness and proportion vaccinated were compared.Phase 2: we piloted blood specimen and data collection alongside the 2012–13 HSE. We are developing laboratory methods and protocols for real-time serological assays of a novel pandemic influenza virus using these specimens, and automated programmes for analysing and reporting illness and infection rates.Phase 3: during inter-pandemic years, the study enters a holding phase, where it is included in the yearly HSE ethics application and planning procedures, allowing rapid triggering in a pandemic.Phase 4: once retriggered, the study will utilise the methods developed in phase 2 to monitor the severity and spread of the pandemic in real time. Results Phase 1: the rates of reported illness during the first two waves in the HSE underestimated the community burden as measured by Flu Watch, but the patterns of illness by age and time were broadly comparable. The extent of underestimation was greatest for HSE participants interviewed later in the year compared with those interviewed closer to the pandemic. Vaccine uptake in the HSE study was comparable to independent national estimates and the Flu Watch study.Phases 2 and 3: illness data and serological samples from 2018 participants were collected in the 2012–13 HSE and transferred to the University College London Hospital. In the 2013 HSE and onwards, this project was included in the annual HSE ethics and planning rounds. Conclusions The HSE’s underestimation of illness rates during the first two waves of the pandemic is probably due to recall bias and the limitation of being able to report only one illness when multiple illnesses per season can occur. Changes to the illness questions (reporting only recent illnesses) should help minimise these issues. Additional prospective follow-up could improve measurement of disease incidence. The representative nature of the HSE allows accurate measurements of vaccine uptake. Study registration This study is registered as ISRCTN80214280. Funding This project was funded by the NIHR Public Health Research programme and will be published in full inPublic Health Research; Vol. 3, No. 6. See the NIHR Journals Library website for further project information