Inundation Patterns and Their Effect on the Physical and Hydraulic Properties of Floodplain Soils in the Middle Rio Grande Floodplain

The surface of the floodplain serves as a vadose zone boundary where water infiltrates, evaporates, or returns to the river, and sediments accumulate or are eroded. The discharge of the Middle Rio Grande has been altered by the construction of Cochiti Dam and the implementation of levees. Hydraulic connectivity in the Middle Rio Grande floodplain is perhaps most apparent at a small local wetland and a low-lying trough with a high water table capable of causing seeping floods. The objective of this study was to determine if inundation patterns impact the hydraulic and physical properties of floodplain soils. A study was designed that would test the soil texture, infiltration rates, and hydraulic conductivity at flooding and non-flooding areas within the Middle Rio Grande Floodplain. The statistical difference among the variables with respect to flooding frequency was determined by non-parametric Mann Whitney U tests. No significant difference was found among saturated hydraulic conductivity values or infiltration rates. A greater distinction among flooding and non-flooding areas was noted between the infiltration rates measured under unsaturated conditions than under saturated conditions. The infiltration rates measured under unsaturated conditions were, in general, greater at the non-flooding areas. The difference in the percent of fine particles in flooding and non-flooding areas was significant, suggesting one way in which inundation patterns affect the physical properties of floodplain soils

Changes in the atmospheric CH4 gradient between Greenland and Antarctica during the Holocene

High-resolution records of atmospheric methane over the last 11,500 years have been obtained from two Antarctic ice cores (D47 and Byrd) and a Greenland core (Greenland Ice Core Project). These cores show similar trapping conditions for trace gases in the ice combined with a comparable sampling resolution; this together with a good relative chronology, provided by unequivocal CH4 features, allows a direct comparison of the synchronized Greenland and Antarctic records, and it reveals significant changes in the interpolar difference of CH4 mixing ratio with time. On the average, over the full Holocene records, we find an interpolar difference of 44±7 ppbv. A minimum difference of 33±7 ppbv is observed from 7 to 5 kyr B.P. whereas the maximum gradient (50±3 ppbv) took place from 5 to 2.5 kyr B.P. A gradient of 44±4 ppbv is observed during the early Holocene (11.5 to 9.5 kyr B.P). We use a three-box model to translate the measured differences into quantitative contributions of methane sources in the tropics and the middle to high latitudes of the northern hemisphere. The model results support the previous interpretation that past natural CH4 sources mainly lay in tropical regions, but it also suggests that boreal regions provided a significant contribution to the CH4 budget especially at the start of the Holocene. The growing extent of peat bogs in boreal regions would also have counterbalanced the drying of the tropics over the second half of the Holocene. Finally, our model results suggest a large source increase in tropical regions from the late Holocene to the last millennium, which may partly be caused by anthropogenic emissions

Homogenization of the long-term global ozonesonde records

Póster presentado en: WMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation celebrada del 10 al 13 de octubre de 2022 en París

Observation of large and all-season ozone losses over the tropics” [AIP Adv. 12, 075006 (2022)]

As discussed above, and supported by extensive literature, there is no robust, credible observational evidence for substantial ozone depletion (i.e., an “ozone hole”) in the tropics. It is well known that climatological total ozone in the tropics is much lower than that in the mid-latitudes (e.g., Sahai et al., 2000; Weber et al., 2022). Satellite and ozonesonde measurements indicate a 3%–5% per decade decline of tropical lower stratosphere ozone prior to 2000, far smaller than that reported by L2022. The stronger decline reported by L2022 is caused by inappropriate use of the gap-filled version of the TOST ozone dataset, which is based on sparse tropical ozone sondes before the 1990s. This misuse of data (TOST and total column ozone) shows the importance of collaboratively engaging with groups who obtain the measurements and create climatological datasets before performing such analyses. Furthermore, the study by L2022 has multiple flaws in its discussion of atmospheric chemistry and dynamics, particularly in the proposed, and previously refuted (see Sec. III A), cosmicray- driven electron induced (CRE) mechanism. Evidence for the occurrence of tropical stratospheric clouds, as needed for the tropical CRE mechanism, is lacking, nor do CFC-12 observations show signatures of depletion in the tropical lower stratosphere, which could be associated with dissociative electron attachment-induced loss of CFC-12 on particulate matter (i.e., the CRE mechanism). Finally, it is worth reiterating that the CRE mechanism is also not responsible for polar LS ozone depletion. Polar ozone loss can be well explained by the gas phase and heterogeneous chemistry, based on extensive observations and modeling studies documented in many thousands of scientific papers on the topic [e.g., see WMO (2018) and references therein], which is not acknowledged by L2022. L2022’s research paper is a severely flawed one. There is no tropical ozone hole, and the CRE mechanism does not explain observed changes in stratospheric ozone either in the polar regions or in the tropics

Evidence for Extended Hydrogen-Poor CSM in the Three-Peaked Light Curve of Stripped Envelope Ib Supernova

We present multi-band ATLAS photometry for SN 2019tsf, a stripped-envelope Type Ib supernova (SESN). The SN shows a triple-peaked light curve and a late (re-)brightening, making it unique among stripped-envelope systems. The re-brightening observations represent the latest photometric measurements of a multi-peaked Type Ib SN to date. As late-time photometry and spectroscopy suggest no hydrogen, the potential circumstellar material (CSM) must be H-poor. Moreover, late (>150 days) spectra show no signs of narrow emission lines, further disfavouring CSM interaction. On the contrary, an extended CSM structure is seen through a follow-up radio campaign with Karl G. Jansky Very Large Array (VLA), indicating a source of bright optically thick radio emission at late times, which is highly unusual among H-poor SESNe. We attribute this phenomenology to an interaction of the supernova ejecta with spherically-asymmetric CSM, potentially disk-like, and we present several models that can potentially explain the origin of this rare Type Ib supernova. The warped disc model paints a novel picture, where the tertiary companion perturbs the progenitors CSM, that can explain the multi-peaked light curves of SNe, and here we apply it to SN 2019tsf. This SN 2019tsf is likely a member of a new sub-class of Type Ib SNe and among the recently discovered class of SNe that undergo mass transfer at the moment of explosionComment: 23 pages, Comments are welcome, Submitted to Ap

Travelling in time with networks: revealing present day hybridization versus ancestral polymorphism between two species of brown algae, Fucus vesiculosus and F. spiralis

Background: Hybridization or divergence between sympatric sister species provides a natural laboratory to study speciation processes. The shared polymorphism in sister species may either be ancestral or derive from hybridization, and the accuracy of analytic methods used thus far to derive convincing evidence for the occurrence of present day hybridization is largely debated. Results: Here we propose the application of network analysis to test for the occurrence of present day hybridization between the two species of brown algae Fucus spiralis and F. vesiculosus. Individual-centered networks were analyzed on the basis of microsatellite genotypes from North Africa to the Pacific American coast, through the North Atlantic. Two genetic distances integrating different time steps were used, the Rozenfeld (RD; based on alleles divergence) and the Shared Allele (SAD; based on alleles identity) distances. A diagnostic level of genotype divergence and clustering of individuals from each species was obtained through RD while screening for exchanges through putative hybridization was facilitated using SAD. Intermediate individuals linking both clusters on the RD network were those sampled at the limits of the sympatric zone in Northwest Iberia. Conclusion: These results suggesting rare hybridization were confirmed by simulation of hybrids and F2 with directed backcrosses. Comparison with the Bayesian method STRUCTURE confirmed the usefulness of both approaches and emphasized the reliability of network analysis to unravel and study hybridization

Homogenization of the Observatoire de Haute Provence electrochemical concentration cell (ECC) ozonesonde data record: comparison with lidar and satellite observations

International audienceThe Observatoire de Haute Provence (OHP) weekly electrochemical concentration cell (ECC) ozonesonde data have been homogenized for the pe- riod 1991–2021 according to the recommendations of the Ozonesonde Data Quality Assessment (O3S-DQA) panel. The assessment of the ECC homogenization benefit has been carried out using comparisons with other ozone-measuring ground-based instruments at the same station (lidar, surface measurements) and with colocated satellite observations of the O3 vertical profile by Microwave Limb Sounder (MLS). The major differences between uncorrected and homoge- nized ECC data are related to a change of ozonesonde type in 1997, removal of the pressure dependency of the ECC background current and correction of internal pump tem- perature. The original 3–4 ppbv positive bias between ECC and lidar in the troposphere is corrected with the homoge- nization. The ECC 30-year trends of the seasonally adjusted ozone concentrations are also significantly improved in both the troposphere and the stratosphere after the ECC homogenization, as shown by the ECC/lidar or ECC/surface ozone trend comparisons. A −0.19 % yr−1 negative trend of the normalization factor (NT) calculated using independent measurements of the total ozone column (TOC) at OHP disappears after homogenization of the ECC data. There is, however, a remaining −3.7 % negative bias in the TOCwhich is likely related to an underestimate of the ECC concentrations in the stratosphere above 50 hPa. Differences between TOC measured by homogenized ECC and satellite observations show a smaller bias of −1%. Comparisons between homogenized ECC and OHP stratospheric lidar and MLS observations below 26 km are slightly negative (−2 %) or positive (+2 %), respectively. The comparisons with both lidar and satellite observations suggest that homogenization increases the negative bias of the ECC to values lower than −6 % above 28 km. The reason for this bias is still unclear, but a possible explanation might be related to freezing or evaporation of the sonde solution in the stratosphere

Miles down for lunch: deep-sea in situ observations of Arctic finned octopods Cirroteuthis muelleri suggest pelagic–benthic feeding migration

Deep-sea cephalopods are diverse, abundant, and poorly understood. The Cirrata are gelatinous finned octopods and among the deepest-living cephalopods ever recorded. Their natural feeding behaviour remains undocumented. During deep-sea surveys in the Arctic, we observed Cirroteuthis muelleri. Octopods were encountered with their web spread wide, motionless and drifting in the water column 500–2600 m from the seafloor. Individuals of C. muelleri were also repeatedly observed on the seafloor where they exhibited a repeated, behavioural sequence interpreted as feeding. The sequence (11–21 s) consisted of arm web spreading, enveloping and retreating. Prey capture happened during the enveloping phase and lasted 5–49 s. Numerous traces of feeding activity were also observed on the seafloor. The utilization of the water column for drifting and the deep seafloor for feeding is a novel migration behaviour for cephalopods, but known from gelatinous fishes and holothurians. By benthic feeding, the octopods benefit from the enhanced nutrient availability on the seafloor. Drifting in the water column may be an energetically efficient way of transportation while simultaneously avoiding seafloor-associated predators. In situ observations are indispensable to discover the behaviour of abundant megafauna, and the energetic coupling between the pelagic and benthic deep sea

Unsupervised data to content transformation with histogram-matching cycle-consistent generative adversarial networks

The segmentation of images is a common task in a broad range of research fields. To tackle increasingly complex images, artificial intelligence-based approaches have emerged to overcome the shortcomings of traditional feature detection methods. Owing to the fact that most artificial intelligence research is made publicly accessible and programming the required algorithms is now possible in many popular languages, the use of such approaches is becoming widespread. However, these methods often require data labelled by the researcher to provide a training target for the algorithms to converge to the desired result. This labelling is a limiting factor in many cases and can become prohibitively time consuming. Inspired by the ability of cycle-consistent generative adversarial networks to perform style transfer, we outline a method whereby a computer-generated set of images is used to segment the true images. We benchmark our unsupervised approach against a state-of-the-art supervised cell-counting network on the VGG Cells dataset and show that it is not only competitive but also able to precisely locate individual cells. We demonstrate the power of this method by segmenting bright-field images of cell cultures, images from a live/dead assay of C. elegans, and X-ray computed tomography of metallic nanowire meshes.ISSN:2522-583