Increased Amazon basin wet-season precipitation and river discharge since the early 1990s driven by tropical Pacific variability

International audienceThe Amazon Basin, the largest watershed on Earth, experienced a significant increase in wet-season precipitation and high-season river discharge from the early 1990s to early 2010s. Some studies have linked the increased Amazon Basin hydrologic cycle to decadal trends of increased Pacific trade winds, eastern Pacific sea surface temperature (SST) cooling, and associated strengthening of the Pacific Walker circulation. However, it has been difficult to disentangle the role of Pacific decadal variability from the impacts of greenhouse gases and other external climate drivers over the same period. Here, we separate the contributions of external forcings from those of Pacific decadal variability by comparing two large ensembles of climate model experiments with identical radiative forcing agents but imposing different tropical Pacific wind stress. One ensemble constrains tropical Pacific wind stress to its long-term climatology, suppressing tropical Pacific decadal variability; the other ensemble imposes the observed tropical Pacific wind stress anomalies, simulating realistic tropical Pacific decadal variability. Comparing the Amazon Basin hydroclimate response in the two ensembles allows us to distinguish the contributions of external forcings common to both simulations from those related to Pacific trade wind variability. For the 1992–2012 trend, the experiments with observed tropical Pacific wind stress anomalies simulate strengthening of the Walker circulation between the Pacific and South America and sharpening of the Pacific–Atlantic interbasin SST contrast, driving increased Amazon Basin wet-season precipitation and high-season discharge. In contrast, these circulation and hydrologic intensification trends are absent in the simulations with climatological tropical Pacific wind stress. This work underscores the importance of Pacific decadal variability in driving hydrological cycle changes and modulating the hydroclimate impacts of global warming over the Amazon Basin

Highly Scalable Multiplication for Distributed Sparse Multivariate Polynomials on Many-core Systems

We present a highly scalable algorithm for multiplying sparse multivariate polynomials represented in a distributed format. This algo- rithm targets not only the shared memory multicore computers, but also computers clusters or specialized hardware attached to a host computer, such as graphics processing units or many-core coprocessors. The scal- ability on the large number of cores is ensured by the lacks of synchro- nizations, locks and false-sharing during the main parallel step.Comment: 15 pages, 5 figure

Allelopathy Effect of the Blue Diatom HasleaOstrearia (Gaillon) Simonsen: Growth Inhibition in Aquaculture Relevant Microalgae

We are well known that the marine pennate diatom Hasleaostrearia (Gaillon) Simonsen produces the blue-green pigment called marennine. Marennine was identified as a polyphenolic compound. This compound is capable to inhibit the growth of herpes simplex virus type 1 (HSV-1) and several bacteria, including pathogens as Vibrio sp. The aim of this study was to determine how strong the allelophatic effect of marennine is generated byH. ostrearia and identifying its minimal concentration that inhibits the growth of other microalgae. The experiment consisted of two phases of research activities. The first phase was biovolumecomparaison between H. ostrearia and microalgae suitable for aquaculture tested to take into account the differences in size of the microalgae tested(Tetraselmissuecica, Chaetocerosgracilis, Skeletonemacostatum, PavlovalutheriandIsochrysisgalbana (T-Iso) in term of H. ostrearia biomass and production of marennine. The second phase was the bioactivity tests, which is include growth kinetics, allelophatic effects and concentration of marennine in the culture medium, measured with spectrophotometer. The results of this study showed that H. ostrearia could inhibit several species of microalgae currently used in aquaculture (T. suecica, C. gracilis and S. costatum). The statistical analysis (One way ANOVA) showed that there are significant differences (P < 0, 05) between treatments andwhen co-cultured with H. ostrearia, these microalgae exhibited a significant growth inhibition. The highest inhibition value was 97.77% (on the treatementH. ostrearia+C. gracilis). In this treatment, the concentration of marennine in the culture was 5.35 mg L-1. According to the results, we can conclude that the supernatant of H. ostrearia with marennine acts as an allelochemical. The minimal concentration is 0.23 mg L-1 and the highest is 5.35 mg L-1. The treatments H. ostreariawithP. lutheri and T-Iso did not performed any inhibition

Thermodynamics of the 3-flavor NJL model : chiral symmetry breaking and color superconductivity

Employing an extended three flavor version of the NJL model we discuss in detail the phase diagram of quark matter. The presence of quark as well as of diquark condensates gives raise to a rich structure of the phase diagram. We study in detail the chiral phase transition and the color superconductivity as well as color flavor locking as a function of the temperature and chemical potentials of the system.Comment: 27 pages, 7 figure

Arctic troposphere warming Driven by external radiative forcing and modulated by the Pacific and Atlantic

During the past decades, the Arctic has experienced significant tropospheric warming, with varying decadal warming rates. However, the relative contributions from potential drivers and modulators of the warming are yet to be further quantified. Here, we utilize a unique set of multi-model large-ensemble atmospheric simulations to isolate the respective contributions from the combined external radiative forcing (ERF-AL), interdecadal Pacific variability (IPV), Atlantic multidecadal variability (AMV), and Arctic sea-ice concentration changes (ASIC) to the warming during 1979–2013. In this study, the ERF-AL impacts are the ERF impacts directly on the atmosphere and land surface, excluding the indirect effects through SST and SIC feedback. The ERF-AL is the primary driver of the April–September tropospheric warming during 1979–2013, and its warming effects vary at decadal time scales. The IPV and AMV intensify the warming during their transitioning periods to positive phases and dampen the warming during their transitioning periods to negative phases. The IPV impacts are prominent in winter and spring and are stronger than AMV impacts on 1979–2013 temperature trends. The warming impacts of ASIC are generally restricted to below 700 hPa and are strongest in autumn and winter. The combined effects of these factors reproduce the observed accelerated and step-down Arctic warming in different decades, but the intensities of the reproduced decadal variations are generally weaker than in the observed. © 2022. The Authors

Massive quark propagator and competition between chiral and diquark condensate

The Green-function approach has been extended to the moderate baryon density region in the framework of an extended Nambu--Jona-Lasinio model, and the thermodynamic potential with both chiral and diquark condensates has been evaluated by using the massive quark propagator. The phase structure along the chemical potential direction has been investigated and the strong competition between the chiral and diquark condensate has been analyzed by investigating the influence of the diquark condensate on the sharp Fermi surface. The influence of the diquark condensate on the quark properties has been investigated, even though the quarks in the color breaking phase are very different from that in the chiral breaking phase, the difference between quarks in different colors is very small.Comment: Revtex, 34 pages, 7 figures, section V revised, accepted by PR

Seismic stratigraphy and sediment cores reveal lake-level fluctuations in Lake Iznik (NW Turkey) over the past ∼70 ka

Our study aims to understand the palaeohydrological history of Lake Iznik and unravel the complex interplay between climatic, tectonic, and environmental factors that have shaped this Turkish basin. Through the analysis of seismic stratigraphy and sediment cores, we reveal a significant lowstand, indicating a lake level 60 m lower than today at ∼70 ka BP. Subsequently, a major phase of stepwise transgression is evidenced by 13 buried palaeoshorelines between ∼70 and 45 ka BP. From 45 to ∼10 ka cal BP, strong currents controlled the sedimentation in the lake, as evidenced by the occurrence of contourite drifts. Between ∼14 and 10 ka cal. BP, a major lowstand indicating a drier climate interrupted the current-controlled sedimentation regime. From ∼10 ka cal. BP, the subsequent increase in lake level occurred at the same time as the reconnection between the Mediterranean and Black seas. Archaeological evidence, including submerged structures of a basilica, establishes a link between lake-level changes and human settlement during the last millennium. The level of Lake Iznik has since continued to fluctuate due to climate change, tectonic events, and human activity