A parameterization of Greenland's tip jets suitable for ocean or coupled climate models

Greenland's tip jets are low-level, high wind speed jets forced by an interaction of the synoptic-scale atmospheric flow and the steep, high orography of Greenland. These jets are thought to play an important role in both preconditioning for, and triggering of, open-ocean convection in the Irminger Sea. However, the relatively small spatial scale of the jets prevents their accurate representation in the relatively low resolution (~1 degree) atmospheric (re-)analyses which are typically used to force ocean general circulation models (e.g. ECMWF ERA-40 and NCEP reanalyses, or products based on these). Here we present a method of ‘bogussing’ Greenland's tip jets into such surface wind fields and thus, via bulk flux formulae, into the air-sea turbulent flux fields. In this way the full impact of these mesoscale tip jets can be incorporated in any ocean general circulation model of sufficient resolution. The tip jet parameterization is relatively simple, making use of observed linear gradients in wind speed along and across the jet, but is shown to be accurate to a few m s-1 on average. The inclusion of tip jets results in a large local increase in both the heat and momentum fluxes. When applied to a 1-dimensional mixed-layer model this results in a deepening of the winter mixed-layer of over 300 m. The parameterization scheme only requires 10 meter wind speed and mean sea level pressure as input fields; thus it is also suitable for incorporation into a coupled atmosphere-ocean climate model at the coupling stage

An easterly tip jet off Cape Farewell, Greenland. II: Simulations and dynamics

An easterly tip jet that occurred on 21 February 2007 off Cape Farewell, Greenland, is examined. In Part I of this article aircraft observations were described. Now, in Part II, numerical simulations and an analysis of the dynamical forcing mechanisms are presented. The simulations make use of a limited-area 12 km resolution configuration of the Met Office's Unified Model. Sea-surface temperatures and sea-ice concentrations have been replaced using the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) product, addressing a boundary-layer temperature bias, while roughness lengths over sea ice have been updated, addressing a wind-speed bias. These modifications ensured a reasonably accurate simulation: generally within 1–2 K and 2–3 m s-1 when compared with dropsonde observations. A momentum-budget analysis along a curved locus through the core of the jet has been derived. Off southeast Greenland, the easterly tip jet was in cross-jet geostrophic balance, but was being accelerated downstream by an along-jet pressure gradient. Over the curved part of the locus, as the jet rounded Cape Farewell, a cross-jet residual suggests that the jet was unbalanced at the height of the jet core. This residual decreases with height so that an approximate gradient wind balance applies in the upper part of the jet. The anticyclonic curvature, characteristic of easterly tip jets, was caused by a dramatic decrease in the cross-jet pressure-gradient force at the end of the barrier, after which the jet aligned with the synoptic-scale isobars and returned to approximate geostrophic balance. The momentum budget is shown to be robust and applicable to other cases

The Osmium Isotopic Composition of Seawater: Past and Present

The osmium isotopic composition of seawater (187Os/188Os) reflects a balance between radiogenic continental sources and unradiogenic mantle and extraterrestrial derived sources. Reconstruction of this value has allowed us to unlock vital information about a series of Earth system processes, both today and in Earth’s geological past. This body of work looks to reconstruct the 187Os/188Os of seawater for past and present oceans using the 187Os/188Os composition of shales and macroalgae (seaweed) respectively. The 187Os/188Os composition of Icelandic (0.16 to 0.99) and Japanese (0.16 to 1.09) macroalgae are highly variable, and reflect the mixing between multiple sources. The 187Os/188Os of Icelandic coastal waters is dominated by seawater and local river catchments, and has been utilised to trace the influence of basaltic weathering on the global Os cycle. The 187Os/188Os of Japanese coastal waters is dominated by seawater and river catchments draining Miocene-Holocene continental rocks or anthropogenic sources, and has been utilised to trace mankind’s impact on the global Os cycle. The 187Os/188Os profiles of shales from the Silurian Ireviken, Mulde, Lau and Klonk biovents are similar to those previously recorded for the Hirnantian glaciation. This data suggests the Silurian has been punctuated by several glaciations associated with fluctuations in global temperatures, sea-level and the carbon cycle. When combined with the Li isotopic (δ7Li) composition of carbonates, this study suggests glacial processes caused large changes in oxidative and silicate weathering. This study has successfully utilised macroalgae as a proxy for the 187Os/188Os of seawater and proven it can become a powerful tracer of Earth system processes and human activity. This study has also redefined the Silurian as an icehouse, and suggests the long term decline in atmospheric CO2, due to orogeny, land-plant diversification, volcanic- arc degassing and/or paleogeography, was reversed by periodic glaciations which acted to enhance oxidative weathering whilst suppressing silicate weathering

4-Year Outcome Analysis of Endoscopic Vein Harvesting for Coronary Artery Bypass Grafting

Objective. Despite increasing recognition that endoscopic vein harvesting (EVH) is associated with decreased leg wound morbidity, improved cosmetic results, and enhanced patient satisfaction, concerns persist regarding the safety and efficacy of EVH. This study compares in-hospital and midterm outcomes for EVH and open vein harvesting (OVH) at our institution. Methods. 772 patients with EVH were propensity matched to 772 patients who had OVH. Their data were prospectively entered into the cardiac surgery database (PATS; Dendrite Clinical Systems, Ltd., Oxford, UK) and analyzed, retrospectively. The mean duration of followup was 26.4 ± 10.3 months. Results. EVH was associated with a significant reduction in rate of donor site infection compared to OVH (0.39% versus 3.9%, ). Short- and medium-term vein graft patency was similar. After adjusting for clinical covariates, EVH did not emerge as an independent predictor of readmission to hospital for cardiac causes (odds ratio (OR) 1.19, 95% confidence interval (CI) 0.96–1.58, and ), medium-term mortality (hazard ratio (HR) 1.28, 95% CI 1.09–1.42, and ), and need for reintervention (HR 1.21, 95% CI 0.98–1.32, and ). Risk-adjusted survival was 94% for EVH patients and 93% for OVH patients () during the medium-term followup. Conclusion. Our analysis confirms the short- and midium-term safety and efficacy of EVH.</jats:p

Oral Care after Stroke: Where are we now?

Purpose There appears to be an association between poor oral hygiene and increased risk of aspiration pneumonia – a leading cause of mortality post-stroke. We aim to synthesise what is known about oral care after stroke, identify knowledge gaps and outline priorities for research that will provide evidence to inform best practice. Methods A narrative review from a multidisciplinary perspective, drawing on evidence from systematic reviews, literature, expert and lay opinion to scrutinise current practice in oral care after a stroke and seek consensus on research priorities. Findings Oral care tends to be of poor quality and delegated to the least qualified members of the caring team. Nursing staff often work in a pressured environment where other aspects of clinical care take priority. Guidelines that exist are based on weak evidence and lack detail about how best to provide oral care. Discussion Oral health after a stroke is important from a social as well as physical health perspective, yet tends to be neglected. Multidisciplinary research is needed to improve understanding of the complexities associated with delivering good oral care for stroke patients. Also to provide the evidence for practice that will improve wellbeing and may reduce risk of aspiration pneumonia and other serious sequelae. Conclusion Although there is evidence of an association, there is only weak evidence about whether improving oral care reduces risk of pneumonia or mortality after a stroke. Clinically relevant, feasible, cost –effective, evidence based oral care interventions to improve patient outcomes in stroke care are urgently needed

Osmium and lithium isotope evidence for weathering feedbacks linked to orbitally paced organic carbon burial and Silurian glaciations

The Ordovician (∼487 to 443 Ma) ended with the formation of extensive Southern Hemisphere ice sheets, known as the Hirnantian glaciation, and the second largest mass extinction in Earth History. It was followed by the Silurian (∼443 to 419 Ma), one of the most climatically unstable periods of the Phanerozoic as evidenced by several large scale (> 5‰) carbon isotope (δ13C) perturbations associated with further extinction events. Despite several decades of research, the cause of these environmental instabilities remains enigmatic. Here, we provide osmium (187Os/188Os) and lithium (δ7Li) isotope measurements of marine sedimentary rocks that cover four Silurian δ13C excursions. Osmium and Li isotope records resemble those previously recorded for the Hirnantian glaciation suggesting a similar causal mechanism. When combined with a new dynamic carbon-osmium-lithium biogeochemical model we suggest that astronomical forcing of the marine organic carbon cycle, as opposed to a decline in volcanic arc degassing or the rise of early land plants, resulted in drawdown of atmospheric CO2, triggering continental scale glaciation, intense global cooling and eustatic sea-level lows recognised in the geological record. Lower atmospheric pCO2 and temperatures during the Hirnantian and Silurian glaciations suppressed CO2 removal by silicate weathering, driving 187Os/188Os and δ7Li variability, supporting the existence of climate-regulating feedbacks