A "critical" climatic evaluation of last interglacial (MIS 5e) records from the Norwegian Sea

Sediment cores from the Norwegian Sea were studied to evaluate interglacial climate conditions of the marine isotope stage 5e (MIS 5e). Using planktic forminiferal assemblages as the core method, a detailed picture of the evolution of surface water conditions was derived. According to our age model, a step-like deglaciation of the Saalian ice sheets is noted between ca. 135 and 124.5 Kya, but the deglaciation shows little response with regard to surface ocean warming. From then on, the rapidly increasing abundance of subpolar forminifers, concomitant with decreasing iceberg indicators, provides evidence for the development of interglacial conditions sensu stricto (5e-ss), a period that lasted for about 9 Ky. As interpreted from the foraminiferal records, and supported by the other proxies, this interval of 5e-ss was in two parts: showing an early warm phase, but with a fresher, i.e., lower salinity, water mass, and a subsequent cooling phase that lasted until ca. 118.5 Kya. After this time, the climatic optimum with the most intense advection of Atlantic surface water masses occurred until ca. 116 Kya. A rapid transition with two notable climatic perturbations is observed subsequently during the glacial inception. Overall, the peak warmth of the last interglacial period occurred relatively late after deglaciation, and at no time did it reach the high warmth level of the early Holocene. This finding must be considered when using the last interglacial situation as an analogue model for enhanced meridional transfer of ocean heat to the Arctic, with the prospect of a future warmer climate

Predicting risk of rupture and rupture-preventing reinterventions following endovascular abdominal aortic aneurysm repair.

BACKGROUND: Clinical and imaging surveillance practices following endovascular aneurysm repair (EVAR) for intact abdominal aortic aneurysm (AAA) vary considerably and compliance with recommended lifelong surveillance is poor. The aim of this study was to develop a dynamic prognostic model to enable stratification of patients at risk of future secondary aortic rupture or the need for intervention to prevent rupture (rupture-preventing reintervention) to enable the development of personalized surveillance intervals. METHODS: Baseline data and repeat measurements of postoperative aneurysm sac diameter from the EVAR-1 and EVAR-2 trials were used to develop the model, with external validation in a cohort from a single-centre vascular database. Longitudinal mixed-effects models were fitted to trajectories of sac diameter, and model-predicted sac diameter and rate of growth were used in prognostic Cox proportional hazards models. RESULTS: Some 785 patients from the EVAR trials were included, of whom 155 (19·7 per cent) experienced at least one rupture or required a rupture-preventing reintervention during follow-up. An increased risk was associated with preoperative AAA size, rate of sac growth and the number of previously detected complications. A prognostic model using predicted sac growth alone had good discrimination at 2 years (C-index 0·68), 3 years (C-index 0·72) and 5 years (C-index 0·75) after operation and had excellent external validation (C-index 0·76-0·79). More than 5 years after operation, growth rates above 1 mm/year had a sensitivity of over 80 per cent and specificity over 50 per cent in identifying events occurring within 2 years. CONCLUSION: Secondary sac growth is an important predictor of rupture or rupture-preventing reintervention to enable the development of personalized surveillance intervals. A dynamic prognostic model has the potential to tailor surveillance by identifying a large proportion of patients who may require less intensive follow-up

Pulses of carbon dioxide emissions from intracrustal faults following climatic warming

Carbon capture and geological storage represents a potential means of managing atmospheric carbon dioxide levels. Understanding the role of faults, as either barriers or conduits to the flow of carbon dioxide, is crucial for predicting the long-term integrity of geological storage sites. Of particular concern is the influence of geochemical reactions on the sealing behaviour of faults and the impact of seismicity and stress regime on fault stability. Here, we examine a 135,000-year palaeorecord of carbon dioxide leakage from a faulted, natural carbon dioxide reservoir in Utah. We assess the isotope and trace-element composition of U-Th-dated carbonate veins, deposited by carbon-dioxide-rich fluids. Temporal changes in vein geochemistry reveal pulses of carbon dioxide injection into the reservoir from deeper formations. Surface leakage rates increase by several orders of magnitude following these pulses. We show that each pulse occurs around 100-2,000 years after the onset of significant local climatic warming, at glacial to interglacial transitions. We suggest that carbon dioxide leakage rates increase as a result of fracture opening, potentially caused by changes in groundwater hydrology, the intermittent presence of a buoyant gas cap and postglacial crustal unloading of regions surrounding the fault

The British Late Middle Palaeolithic: An Interpretative Synthesis of Neanderthal Occupation at the Northwestern Edge of the Pleistocene World

The British Middle Palaeolithic is divided into two discrete periods of occupation: the Early Middle Palaeolithic (MIS 9–7, ~330–180 ka BP) and the Late Middle Palaeolithic (MIS 3, ~59–36 ka BP), separated by a long hiatus. Owing to the relative poverty of the record and historical difficulties in dating and correlating archaeological sites, the British Late Middle Palaeolithic has, until recently, received scant attention, and has largely been regarded as the poor man of Europe, especially by British archaeologists. Indeed, there has been more discussion of the absence of humans from Britain than of what they did when they were present. We aim here to redress that situation. Following from recent considerations of the Early Middle Palaeolithic (White et al. in J. Quat. Sci. 21:525–542, 2006; Scott, Becoming Neanderthal, Oxbow, Oxford, 2010), we offer an interpretative synthesis of the British Late Middle Palaeolithic, situating ‘British’ Neanderthals in their chronological, environmental and landscape contexts. We discuss the character of the British record, and offer an account of Neanderthal behaviour, settlement systems and technological practices at the northwestern edge of their known Upper Pleistocene range. We also examine the relationship of the enigmatic Early Upper Palaeolithic leafpoint assemblages to Neanderthals

Nesseltalgraben, a new reference section of the last glacial period in southern Germany

In the northern Alpine region only a few lacustrine sediment sequences are known from the period of the last glacial, regionally assigned as Würmian. Even less is known about Alpine palaeoenvironments prior to the last glacial maximum (LGM). The recently discovered sediment sections at the Nesseltalgraben site (northern Alps, southern Germany) presented here, comprise an approximately 27-m-high, predominantly lacustrine composite profile below coarse clastic sediments assigned to the LGM and underlain by Permian–Triassic evaporitic and sandy clayey sediments of the Haselgebirge and Werfen-Formation. The Würmian lake sediments consist of carbonate mud layers representing cooler phases, and organic rich layers (compressed peat, organic mud), that were deposited during warmer periods. Bulk organic geochemical analyses suggest that predominantly algal organic matter was deposited during the cooler periods, while higher fractions of terrestrial vascular plants were admixed during warmer phases. A diamict represents an erosional unconformity and cuts the sediment sequence into a lower and an upper part. Paleomagnetic, palynostratigraphic and radiocarbon analyses place the lower part into the Marine Isotope Stage (MIS) 5c (Lower Würmian), while the upper part covers at least the period from 45 to 31 ka cal BP (MIS 3, Middle Würmian). Different explanations for the origin and spatiotemporal extent of the palaeolake are discussed. The most plausible sedimentary deposition is the formation of the small-scaled lake in a sinkhole in the evaporitic Haselgebirge Formation. The results highlight the significance of the Nesseltalgraben site as a new reference section of the last glacial period in the Northern Calcareous Alps and call for the necessity of further geochronological and paleoenvironmental studies at that site

Evolution of the Indo-Pacific Warm Pool and Hadley-Walker Circulation Since the Last Deglaciation

The Indo-Pacific warm pool (IPWP), East Pacific cold tongue, and deep overturning atmospheric Hadley (meridional) and Walker (zonal) circulations form a tightly coupled system. In this chapter, we explore the concept of the Hadley circulation as the fundamental driver of changes in this system, and examine its possible impact on global climates of the past. Recent modeling studies indicate that the Hadley circulation is sensitive to Milankovitch forcing, dominated by the precession cycle (22,000 years) in the tropics. It is well established that the increasing Northern Hemisphere summer insolation during the post-glacial transition enhanced nor-them summer monsoon rainfall, particularly across the Asian landmass. Based on the results of modeling studies, it is probable that the northward asymmetry in tropical beating led to asymmetrical intensification of the Hadley circulation during the early Holocene. The response of the tropical ocean to the intensification of the Hadley circulation is given by foraminiferal Mg/Ca and coral Sr/Ca sea surface temperature (SST) reconstructions, which show that ocean-atmosphere feedbacks drove the tropical Pacific into a westward-concentrated La Nina-like state (warming in the west, cooling in the east) between similar to 11,000 and similar to 4,000 years ago. At the same time, air temperatures reconstructed from Southern Hemisphere high-altitude tropical ice cores also equal or exceed late Holocene values. The widespread warming of the tropical middle troposphere during the early Holocene suggests that the additional flux of water vapor and heat from the warmer IPWP during the La Nina state overwhelmed any atmospheric cooling brought about by the expansion of the East Pacific cold tongue. However, the expanded cold tongue area could also play a role in the early Holocene warming through enhanced Taken together, the paleoclimate records indicate that a post-glacial strengthening of the Hadley circulation initiated ocean-atmosphere feedbacks that altered the energy budget of the tropics to amplify early Holocene warming. Synchronous warming of the Southern Hemisphere high latitudes, as indicated by Antarctic ice core records, may be the result of southward-directed dynamical heating produced by the asymmetrical Hadley circulation. The demise of the early Holocene warming in the tropics and Southern Hemisphere similar to 4,000 through 7,000 years ago correlates with decreasing Northern Hemisphere summer insolation, a southward migration of the Intertropical Convergence Zone (ITCZ), and the onset of modem El Nino/Southern Oscillation (ENSO) variability