地球科学最新文献

Riverine dissolved organic carbon (DOC), primarily sourced from soil organic carbon (SOC), plays a crucial role in regional and global carbon cycles. However, the complexities of the underlying mechanisms and limited observations present significant challenges for predictive understanding of DOC at regional or larger scales. Recently, we developed a machine learning-based (ML) map of DOC transformation rates, bridging the gap between SOC and DOC leaching flux and simplifying terrestrial DOC representation. Building on this advancement, we introduce ELM-MOSART-DOC, a DOC module integrated into the riverine component of the Energy Exascale Earth System Model (E3SM)—the Model for Scale Adaptive River Transport (MOSART). ELM-MOSART-DOC simulates DOC transport and transformation across both headwater streams and river networks, including those managed. Model validation demonstrates the ability of ELM-MOSART-DOC to accurately capture long-term average DOC concentrations, with Kling-Gupta Efficiency (KGE) scores of 0.58 and 0.76 at large and local stations, respectively. We further assess the impact of reservoirs through different simulation schemes, revealing that reservoirs significantly alter DOC fluxes by regulating streamflow patterns and promoting DOC mineralization. Model simulations indicate that reservoirs reduce total DOC flux from the Mississippi River into the ocean by 7.5%, with the long-term average annual export decreasing from 3.34 to 3.14 teragrams (Tg) per year. ELM-MOSART-DOC integrates process-based modeling with ML parameterization to enhance the predictive understanding of riverine biogeochemical processes. This approach reduces uncertainties in modeling regional and global carbon cycle ESMs and provides new insights into carbon cycling and its implications for global environmental change.

Located in the northernmost part of Central Asia, the western foothills of the Altai Mountains (Western Siberia) represent to date the easternmost known boundary of Neanderthal distribution, far from their main cultural areas currently known in Western Eurasia. This geographic situation suggests the possibility of distinct cultural and biological traits in Altai Neanderthals. In this region, Chagyrskaya Cave contains the most substantial paleoanthropological collection, with 75 remains, including 20 craniodental elements attributed to at least eight individuals of varying ages (22 permanent teeth and four deciduous teeth), dating to between approximately 59 and 51 ka BP. Previous paleogenetic analyses suggest several individuals from this site are closely related. Our study is the first to comprehensively analyze the morphology of the entire set of dentognathic elements. In this study, we document the phenotypic variability of the Chagyrskaya's individuals by examining the dimensions and proportions of the crown and root tissues, the nonmetric traits of the outer enamel surface, and the enamel-dentine junction of the 26 teeth from this site and by comparing them to published data of both fossil and more recent material. Furthermore, we explore aspects related to their lifestyle and behavior describing the antemortem lesions affecting their dentognathic elements. Our results show that the dental traits of these human remains fall within the known Neanderthal phenotypic variability while also presenting certain specificities, the origins of which we discuss. In addition, the identification of several lesions on some of these fossils allows us to document their oral health and the use of their teeth for paramasticatory activities.