Three North African dust source areas and their geochemical fingerprint

North Africa produces more than half of the world’s atmospheric dust load. Once entrained 24 into the atmosphere, this dust poses a human health hazard locally. It also modifies the 25 radiative budget regionally, and supplies nutrients that fuel primary productivity across the 26 North Atlantic Ocean and as far afield as the Amazonian Basin. Dust accumulation in deep 27 sea and lacustrine sediments also provides a means to study changes in palaeoclimate, 28 particularly those associated with rainfall climate change. Systematic analysis of satellite 29 imagery has greatly improved our understanding of the trajectories of long-range North 30 African dust plumes, but our knowledge of the dust-producing source regions and our ability 31 to fingerprint their contribution to these export routes is surprisingly limited. Here we 32 report new radiogenic isotope (Sr and Nd) data for sediment samples from known dust33 producing substrates (dried river and lakes beds), integrate them with published isotope 34 data and weight them for dust source activation. We define three isotopically distinct 35 preferential dust source areas (PSAs): a Western, a Central and an Eastern North African 36 PSA. More data are needed, particularly from the Western PSA, but our results show a 37 change in PSA dust source composition to more radiogenic Nd- and less radiogenic Sr38 isotope values from west to east, in line with the overall decreasing age of the underlying 39 bedrock. Our data reveal extreme isotopic heterogeneity within the Chadian region of the 40 Central PSA, including an extremely distinctive geochemical fingerprint feeding the Bodélé 41 Depression, the most active dust source on Earth. Our new analysis significantly improves 42 the reliability by which windblown dust deposits can be geochemically fingerprinted to their 43 distant source regions

A two million year record of low-latitude aridity linked to continental weathering from the Maldives

Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial periods with periodicities closely linked to variations in Earth’s orbital parameters. However, processes that control wet versus dry, i.e. aridity cyclical periods on the orbital time-scale in the low latitudes of the Indian-Asian continent remain poorly understood because records over millions of years are scarce. The sedimentary record from International Ocean Discovery Program (IODP) Expedition 359 provides a well-preserved, high-resolution, continuous archive of lithogenic input from the Maldives reflecting on low-latitude aridity cycles. Variability within the lithogenic component of sedimentary deposits of the Maldives results from changes in monsoon-controlled sedimentary sources. Here, we present X-ray fluorescence (XRF) core-scanning results from IODP Site U1467 for the past two million years, allowing full investigation of orbital periodicities. We specifically use the Fe/K as a terrestrial climate proxy reflecting on wet versus dry conditions in the source areas of the Indian-Asian landmass, or from further afield. The Fe/K record shows orbitally forced cycles reflecting on changes in the relative importance of aeolian (stronger winter monsoon) during glacial periods versus fluvial supply (stronger summer monsoon) during interglacial periods. For our chronology, we tuned the Fe/K cycles to precessional insolation changes, linking Fe/K maxima/minima to insolation minima/maxima with zero phase lag. Wavelet and spectral analyses of the Fe/K record show increased dominance of the 100 kyr cycles after the Mid Pleistocene Transition (MPT) at 1.25 Ma in tandem with the global ice volume benthic δ 18 O data (LR04 record). In contrast to the LR04 record, the Fe/K profile resolves 100-kyr-like cycles around the 130 kyr frequency band in the interval from 1.25 to 2 million years. These 100-kyr-like cycles likely form by bundling of two or three obliquity cycles, indicating that low-latitude Indian-Asian climate variability reflects on increased tilt sensitivity to regional eccentricity insolation changes (pacing tilt cycles) prior to the MPT. The implication of appearance of the 100 kyr cycles in the LR04 and the Fe/K records since the MPT suggests strengthening of a climate link between the low and high latitudes during this period of climate transition. The Correction to this article has been published in Progress in Earth and Planetary Science 2019 6:21 - https://doi.org/10.1186/s40645-019-0259-

Sea-surface temperature, productivity and hydrological changes in the Northern Indian Ocean (Maldives) during the interval similar to 575-175 ka (MIS 14 to 7)

The South Asian Monsoon (SAM) drives seasonal changes in the atmospheric and ocean circulation of the tropical Indian Ocean, affecting precipitation on land and oceanic primary productivity. This work examined sediments from the International Ocean Discover Program (IODP) Site U1467 (IODP Expedition 359) located in the Maldives Inner Sea (Northern Indian Ocean) at a water depth of 487 m. The Maldives Inner Sea is a perfect location to study past changes in tropical climate and ocean circulation related to monsoon dynamics in the Equatorial Indian Ocean. This study focuses on the similar to 575-175 ka interval, from Marine Isotope Stage (MIS) 14 to 7, an important period for human evolution and dispersal to Eurasia. We reconstructed sea-surface temperature (SST), based on alkenone unsaturation index (U-37(K')), hydrological changes, based on terrestrial input of n-alkanes, and past surface ocean productivity, based on total C-37 alkenones concentration. The U-37(K')-SST record shows a difference of about 1.5 degrees C between glacial and interglacial periods, clearly showing all stages and substages from MIS 14 to 7, and revealing a connection between ice sheets extension and SST at the equatorial region. The n-alkanes concentration and average chain length index indicate vegetation changes at the Indian Peninsula with drier conditions generally associated with glacial periods. Precipitation increases abruptly at the end of terminations, lasting for a variable time interval in each interglacial period, except for MIS 13. However, other mechanisms superimposed to the glacial-interglacial forcing, such as the Indian Ocean Dipole (IOD) mode, have been invoked to explain shorter-scale variability in precipitation over India. The total alkenone concentration record indicates that primary productivity at Site U1467 is strongly associated with orbital changes, probably related to the summer inter-tropical insolation gradient (SITIG, 23N-23S on June 21st). High primary productivity occurred during intervals of low SITIG, which resulted in strong inter-monsoon (April-May and October-November) Indian Ocean Equatorial Westerlies (IEW) and reduced precipitation in the equatorial region. This mechanism may also be related to the IOD, which affects the strength of the IEW.FCTPortuguese Foundation for Science and Technology [UID/Multi/04326/2019, PTDC/CTA-GEO/29897/2017, SFRH/BPD/96960/2013, SFRH/BPD/108600/2015]NSFNational Science Foundation (NSF) [OCE-1326927

Edoxaban versus warfarin in patients with atrial fibrillation

Contains fulltext : 125374.pdf (publisher's version ) (Open Access)BACKGROUND: Edoxaban is a direct oral factor Xa inhibitor with proven antithrombotic effects. The long-term efficacy and safety of edoxaban as compared with warfarin in patients with atrial fibrillation is not known. METHODS: We conducted a randomized, double-blind, double-dummy trial comparing two once-daily regimens of edoxaban with warfarin in 21,105 patients with moderate-to-high-risk atrial fibrillation (median follow-up, 2.8 years). The primary efficacy end point was stroke or systemic embolism. Each edoxaban regimen was tested for noninferiority to warfarin during the treatment period. The principal safety end point was major bleeding. RESULTS: The annualized rate of the primary end point during treatment was 1.50% with warfarin (median time in the therapeutic range, 68.4%), as compared with 1.18% with high-dose edoxaban (hazard ratio, 0.79; 97.5% confidence interval [CI], 0.63 to 0.99; P<0.001 for noninferiority) and 1.61% with low-dose edoxaban (hazard ratio, 1.07; 97.5% CI, 0.87 to 1.31; P=0.005 for noninferiority). In the intention-to-treat analysis, there was a trend favoring high-dose edoxaban versus warfarin (hazard ratio, 0.87; 97.5% CI, 0.73 to 1.04; P=0.08) and an unfavorable trend with low-dose edoxaban versus warfarin (hazard ratio, 1.13; 97.5% CI, 0.96 to 1.34; P=0.10). The annualized rate of major bleeding was 3.43% with warfarin versus 2.75% with high-dose edoxaban (hazard ratio, 0.80; 95% CI, 0.71 to 0.91; P<0.001) and 1.61% with low-dose edoxaban (hazard ratio, 0.47; 95% CI, 0.41 to 0.55; P<0.001). The corresponding annualized rates of death from cardiovascular causes were 3.17% versus 2.74% (hazard ratio, 0.86; 95% CI, 0.77 to 0.97; P=0.01), and 2.71% (hazard ratio, 0.85; 95% CI, 0.76 to 0.96; P=0.008), and the corresponding rates of the key secondary end point (a composite of stroke, systemic embolism, or death from cardiovascular causes) were 4.43% versus 3.85% (hazard ratio, 0.87; 95% CI, 0.78 to 0.96; P=0.005), and 4.23% (hazard ratio, 0.95; 95% CI, 0.86 to 1.05; P=0.32). CONCLUSIONS: Both once-daily regimens of edoxaban were noninferior to warfarin with respect to the prevention of stroke or systemic embolism and were associated with significantly lower rates of bleeding and death from cardiovascular causes. (Funded by Daiichi Sankyo Pharma Development; ENGAGE AF-TIMI 48 ClinicalTrials.gov number, NCT00781391.)