Persistent influence of precession on northern ice sheet variability since the early Pleistocene.

Prior to ~1 million years ago (Ma), variations in global ice volume were dominated by changes in obliquity; however, the role of precession remains unresolved. Using a record of North Atlantic ice rafting spanning the past 1.7 million years, we find that the onset of ice rafting within a given glacial cycle (reflecting ice sheet expansion) consistently occurred during times of decreasing obliquity whereas mass ice wasting (ablation) events were consistently tied to minima in precession. Furthermore, our results suggest that the ubiquitous association between precession-driven mass wasting events and glacial termination is a distinct feature of the mid to late Pleistocene. Before then (increasing), obliquity alone was sufficient to end a glacial cycle, before losing its dominant grip on deglaciation with the southward extension of Northern Hemisphere ice sheets since ~1 Ma.

Cost-effectiveness of stroke unit care followed by early supported discharge.

BACKGROUND AND PURPOSE: Stroke places a significant burden on the economy in England and Wales with the overall societal costs estimated at pound7 billion per annum. There is evidence that both stroke units (SUs) and early supported discharge (ESD) are effective in treating patients with stroke. This study assesses the cost-effectiveness of the combination of these 2 strategies and compares it with the care provided in SU without ESD and in a general medical ward without ESD. The objective of this study was to model the long-term (10 years) cost-effectiveness of SU care followed by ESD. METHODS: The study design was cost-effectiveness modeling. The study took place in SUs in the coverage area of the South London Stroke Register, UK. The modeled population was incident ischemic stroke cases (N=844) observed between 2001 and 2006. SU care followed by ESD was compared with SU care without ESD and general medical ward care without ESD. Main outcome measures were health service and societal costs and cost per quality-adjusted life-year gained. RESULTS: Using the cost-effectiveness threshold of pound30000, as commonly used in the UK, SU care followed by ESD is the cost-effective strategy compared with the other 2 options. The incremental cost-effectiveness ratio of SU care followed by ESD is pound10661 compared with the general medical ward without ESD care and pound17721 compared with the SU without ESD. CONCLUSIONS: SU care followed by ESD is both an effective and a cost-effective strategy with the main gains in years of life saved.

Glacial-interglacial changes in moisture sources for greenland: influences on the ice core record of climate.

Large, abrupt shifts in the (l8)O/(16)O ratio found in Greenland ice must reflect real features of the climate system variability. These isotopic shifts can be viewed as a result of air temperature fluctuations, but determination of the cause of the changes-the most crucial issue for future climate concerns-requires a detailed understanding of the controls on isotopes in precipitation. Results from general circulation model experiments suggest that the sources of Greenland precipitation varied with different climate states, allowing dynamic atmospheric mechanisms for influencing the ice core isotope shifts.

Isotopic evidence for reduced productivity in the glacial southern ocean.

Records of carbon and nitrogen isotopes in biogenic silica and carbon isotopes in planktonic foraminifera from deep-sea sediment cores from the Southern Ocean reveal that the primary production during the last glacial maximum was lower than Holocene productivity. These observations conflict with the hypothesis that the low atmospheric carbon dioxide concentrations were introduced by an increase in the efficiency of the high-latitude biological pump. Instead, different oceanic sectors may have had high glacial productivity, or alternative mechanisms that do not involve the biological pump must be considered as the primary cause of the low glacial atmospheric carbon dioxide concentrations.

Oxygen isotopes in biogenic silica: global changes in ocean temperature and isotopic composition.

A record of oxygen isotopes in biogenic silica from a deep-sea sediment core from the Southern Ocean reveals that marine diatoms retain their primary isotopic composition after burial. As a result, the marine diatom record can be combined with data on coexisting planktonic foraminifera to monitor past surface temperature and isotopic composition of seawater. The coupling of these two records allows the solution of two paleotemperature equations for each core interval. Data from a South Atlantic core show that the average delta(18)O during the glacial period at this site was higher by about 1.3 per mil than average Holocene values, and that average glacial-age temperatures were not significantly different from average Holocene values.