The coral Li/Mg temperature proxy is revisited through an in-depth trace element analysis of scleractinians collected live from tropical to polar environments. The dataset consists of Li/Ca, Mg/Ca, ...Sr/Ca and Li/Mg ratios from 64 coral specimens belonging to 8 different taxa, including both reef-building zooxanthellate and cold-water non-zooxanthellate species, from a wide range of water temperature (−1 to 29.5 °C), salinity (34.71 to 38.61), and depth (3 to 670 m).
Our results showed that the reliability of the Li/Mg temperature proxy is strongly limited by the organic matter associated with the coral skeleton, which is most evident within the green bands observed in tropical corals. Organic-rich bands can double the Mg content otherwise present in the skeleton, which may ultimately lead to a temperature overestimation exceeding 15 °C. We found that this bias can be overcome by the treatment of coral skeletons with a specific oxidizing cleaning protocol. We also detected the presence of calcite deposits within the aragonite skeleton of some Antarctic living coral specimens, which strongly affects the robustness of the Li/Mg proxy given its temperature sensitivity of ~1.5 °C/1% calcite. Therefore, to obtain reliable reconstructions a correction needs to be applied when organic matter and/or calcite contamination is present, which requires the scrupulous assessment of the integrity of the aragonite prior to geochemical analyses. Given that some species entrap more organic matter than others, and that some are more prone to calcite contamination, a taxon-related effect is apparent. Here we show that the tropical species Porites spp., Pseudodiploria strigosa and Orbicella annularis, and the cold-water species Madrepora oculata, Caryophyllia antarctica and Flabellum impensum, are all suitable candidates for reconstructing seawater temperatures.
The integrated results across a wide temperature range, from extreme cold to tropical shallow waters, yield an overall precision for the Li/Mg-temperature proxy of ±1.0 °C, as quantified by the standard error of estimates. If calculated from the 95% prediction intervals, the uncertainty of the temperature estimates is ±0.9 °C at 1 °C, ±1.5 °C at 12 °C and ± 2.6 °C at 25 °C. However, the uncertainty for the tropical corals (e.g. Porites) can be reduced to ±0.6 °C if a Li/Mg and Sr/Ca multi-regression approach is applied.
Central Asia is positioned at a crossroads linking several zones important to hominin dispersal during the Middle Pleistocene. However, the scarcity of stratified and dated archaeological material ...and paleoclimate records makes it difficult to understand dispersal and occupation dynamics during this time period, especially in arid zones. Here we compile and analyze paleoclimatic and archaeological data from Pleistocene Central Asia, including examination of a new layer-counted speleothem-based multiproxy record of hydrological changes in southern Uzbekistan at the end of MIS 11. Our findings indicate that Lower Palaeolithic sites in the steppe, semi-arid, and desert zones of Central Asia may have served as key areas for the dispersal of hominins into Eurasia during the Middle Pleistocene. In agreement with previous studies, we find that bifaces occur across these zones at higher latitudes and in lower altitudes relative to the other Paleolithic assemblages. We argue that arid Central Asia would have been intermittently habitable during the Middle Pleistocene when long warm interglacial phases coincided with periods when the Caspian Sea was experiencing consistently high water levels, resulting in greater moisture availability and more temperate conditions in otherwise arid regions. During periodic intervals in the Middle Pleistocene, the local environment of arid Central Asia was likely a favorable habitat for paleolithic hominins and was frequented by Lower Paleolithic toolmakers producing bifaces.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present radiocarbon and neodymium isotope records from accurately dated (U-series) live and fossil (<2 ka, 17.5 to 29.6 ka BP) deep-water corals, collected between 675 and 1788 m from the Perth ...Canyon, offshore southwest Australia. These records provide the first insights into recent and last glacial intermediate-deep water circulation and ventilation histories from the poorly represented southeast Indian Ocean. Ocean ventilation fluctuated significantly during the last glacial period, being highly ventilated during early Marine Isotope Stage 2 and the early deglaciation, yet less ventilated and more stratified during the Last Glacial Maximum. Furthermore, the Perth Canyon corals recorded a major and rapid (∼300 years) perturbation at 25 ka, indicating that mid-depth waters were exposed to poorly ventilated, unradiogenic Nd deeper waters. We link this to similar, age equivalent changes at geographically disparate sites from the southeast Atlantic to the Southern Ocean south of Tasmania, together with fluctuations in Antarctic sea-ice, oceanic fronts, and Atlantic Meridional Overturning Circulation (AMOC). This widespread Southern Ocean event indicates a transient breach in upper and lower ocean cell boundaries of the MOC, providing further evidence for the non-steady state, zonal dynamics of the glacial Southern Ocean.
Epilepsy Action is the UK's leading epilepsy organisation, providing advice, information and social opportunities to people with epilepsy, their families and carers. Here, Pete Scott explains how ...Epilepsy Action is engaging in social research, campaigns for positive change and promoting quality care to key decision makers in order to secure a better future for people with epilepsy in the UK.
Although SpaceWire 1 is fast approaching its 20 th anniversary, the requirements for equipment to test and develop new SpaceWire devices and networks continues to evolve and push the capabilities of ...commercial technology. STAR-Dundee has developed a new PCI Express product, the SpaceWire PCIe Mk2, to take advantage of the higher data rates offered in newer generations of the PCIe standard. The device features three SpaceWire ports capable of operating at 400 Mbit/s link speeds, and a PCIe Gen-3 interface that enables transmitting and receiving from/to software at the maximum rate on all links concurrently. This high throughput is achieved through improvements to the STAR-System software suite 2, which also includes other new features to support the latest requirements for SpaceWire test and development. As well as new graphical applications providing functionality such as the ability to operate as a Remote Memory Access Protocol (RMAP) 3 initiator, support for ARM targets and the Python scripting language is also included. This paper describes the advancements present in the SpaceWire PCIe Mk2 board and the STAR-System software suite, which simplify test and development activities while also providing higher throughput and lower latency transmission and reception of data.
The Hi-SIDE project 1 is a European Union project carried out by several leading aerospace organisations from across Europe. It aims to develop satellite data-chain technologies for future Earth ...observation and Telecommunication systems. Hi-SIDE has made substantial advances in the major elements of the data chain including networking, processing, compression, and downlink transmission to support the next generation of data intensive missions. The data chain elements are interconnected via a SpaceFibre network 2. This paper introduces SpaceFibre and the Hi-SIDE project and then describes the STAR-Tiger SpaceFibre routing switch which forms the heart of the SpaceFibre network.
The original STAR-Dundee SpaceWire-USB Brick has provided a simple yet powerful interface to SpaceWire networks for a number of years. STAR-Dundee's SpaceWire Brick Mk3 provides all the features of ...the original Brick, but with better performance, better software, better documentation and the same high quality support. It will replace the Brick with a product which can be used to very easily perform numerous SpaceWire test and development activities, and at very high speeds.
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