bluuebunny/crossref_metadata_2025 huggingface dataset:
The Atmosphere and Surface of Mars as Revealed by the Emirates Mars Infrared Spectrometer (EMIRS)
Authors: Edwards Christopher , Smith Michael , Atwood Sam , Badri Khalid , Christensen Philip , Wolff Michael , Osterloo Mikki , Al Tunaiji Eman , Al Mheiri Noora , Yousuf Maryam , Wolfe Chris , Smith Nathan , Anwar Saadat
Published: March 2022

The Emirates Mars Mission (EMM) Emirates Mars Infrared Spectrometer (EMIRS) currently around Mars is acquiring remote measurements of the martian surface (temperature and composition) and lower atmosphere. EMIRS is a FTIR spectrometer covering the range from 6.0-100 µm (1666-100 cm‑1) with a spectral sampling as high as 5 cm-1 with a 5.4-mrad IFOV. The EMIRS optical path includes a flat 45˚ pointing mirror to enable one degree of freedom while the spacecraft provides the other to build up a 2-dimensional array of observations. The primary goals of EMIRS are to characterize the geographic and diurnal variability of key atmospheric constituents (water ice, water vapor, and dust) along with temperature profiles and surface temperature on sub-seasonal timescales

EMIRS acquires data of the full martian disk and thus provides an integrated view of the martian surface and atmosphere in every spectrum. These observations include complete diurnal, seasonal, and geographic coverage of atmospheric properties, surface temperature, and also surface composition/mineralogy at wavelengths not regularly acquired of the martian surface. Due to the unique nature of the EMM orbit, EMIRS also collects data that spans the full local solar time range (all solar incidence angles), at multiple emission angles. These unique observations permit the interrogation of diurnal surface ices/frost, thermophysics (including sub-surface layering from both a seasonal and diurnal skin depth), surface roughness, and rock abundance in addition to the primary science goals.

In this presentation, we provide an overview of the first surface observations, atmospheric retrieval algorithm, and first atmospheric science results from the aphelion-season observations taken by EMIRS over the first several months of EMM Science Phase operations.
Greenhouse gas forcing a necessary, but not sufficient, causation for the northeast Pacific marine heatwaves 
Authors: Barkhordarian Armineh , Nielsen David M. , Baehr Johanna
Published: March 2022

Over the last decade, the northeast Pacific experienced strong marine heatwaves (MHWs) that produced devastating marine ecological impacts and received major societal concerns. Here, we assess the link between the well-mixed greenhouse gas (GHG) forcing and the occurrence probabilities of the duration and intensity of the North Pacific MHWs. We investigate whether GHG forcing was necessary for the North Pacific MHWs to occur and whether it is a sufficient cause for such events to continue to repeatedly occur in the 21st Century. To begin with, we apply attribution technique on the long-term SST time series, and detect a region of systematically and externally-forced SST increase -- the long-term warming pool -- co-located with the past notably Blob-like SST anomalies. We further show that the anthropogenic signal has recently emerged from the natural variability of SST over the warming pool, which we attribute primarily to increased GHG concentrations, with anthropogenic aerosols playing a secondary role.

After we demonstrate that the GHG forcing has a dominant influence on the base climate state in the region, we pursue an event attribution analysis for MHWs on a more localized region. Extreme event attribution analysis reveals that GHG forcing is a necessary, but not sufficient, causation for the multi-year persistent MHW events in the current climate, such as that happened in 2014/2015 and 2019/2020. However, the occurrence of the 2019/2020 (2014/2015) MHW was extremely unlikely in the absence of GHG forcing. Thus, as GHG emissions continue to firmly rise, it is very likely that GHG forcings will become a sufficient cause for events of the magnitude of the 2019/2020 record event.

 

 
Rhizosphere of grassland plants: A hot spot of methanol consumption driven by unusual methylotrophs
Authors: Kanukollu Saranya , Remus Rainer , Rücker Alexander Martin , Kolb Steffen
Published: March 2022

Managed grasslands are global sources of atmospheric methanol, which is one of the most abundant biogenic volatile organic compounds (bVOCs) in the atmosphere and promotes oxidative capacity for tropospheric and stratospheric ozone depletion. The phyllosphere is a favoured habitat of plant-colonizing methanol-utilizing methylotrophs, but their quantitative relevance for methanol consumption and ecosystem fluxes in the rhizosphere is unclear. Methanol utilizers of the plant-associated microbiota are key for the mitigation of methanol emission through consumption. However, information on grassland plant methylotrophs, their biodiversity and, metabolic traits, and thus key actors in the global methanol budget is largely lacking.

Two common plant species (Festuca arundinacea, Taraxacum officinale) of a grassland were investigated in pot experiments using soil as a growth substrate. We used radiotracers (14C-methanol) to evaluate potential methanol oxidation rates and 13C-methanol RNA stable isotope probing (SIP) and metagenomes to identify methanol utilizers.

Intact plants unveiled different methanol utilizer communities between plant compartments (phyllosphere, roots, and rhizosphere) but not between plant host species. Methanol utilizers of Gamma- and Betaproteobacteria colonized the phyllosphere. Whereas,Deltaproteobacteria, Gemmatimonadates, and Verrucomicrobiae were predominant in the rhizosphere. Metagenome assembled genomes (MAGs) revealed bacterial methanol dehydrogenases of known but also unexpected genera, such as Methylomirabilis, Methylooceanibacter, Gemmatimonas, and Verminephrobacter. Divergent methanol oxidation rates in both plant species but similarly high rates in the rhizosphere and phyllosphere were determined by 14C-methanol tracing of alive plant material.

Our study revealed eventually the rhizosphere as a hotspot for methanol consumption in grasslands. Differences between the methanol utilizer communities of the two plant species were not evident suggesting a negligible host effect. Our results suggest a model for methanol turnover in which both the sources (plants) and sinks (microbiota) of a bVOC are separated but in the same ecological unit.
The study of detrital zircon geochronology, geochemistry and tectonic-sedimentary significance of Upper Triassic Yanchang Formation in  central and western Ordos Basin
Authors: Wu Ke
Published: March 2022

The Yanchang Formation of the Upper Triassic in the Jiyuan area in the central and western parts of the Ordos Basin is one of the main oil and gas enrichment areas in the basin. However, the tight sandstones of the Yanchang Formation have long been controversial on mineral genesis, formation age and sediment source. The distribution and variation characteristics of detrital zircon ages were studied using LA-ICP-MS dating and geochemistry testing of the detrital zircons from sandstones. The source of detrital zircons of different age components is identified, and difference of tectono-paleogeographic environments is analyzed. The main conclusions can be drawn as follows. Cathodoluminescence images show that most detrital zircon have a zonal structure. Rare Earth Element distribution models show that the sandstone is rich in HREE and is short of LREE, and all of models are left-dipping patterns. The Th/U values of detrital zircon show that most of the values are greater than 0.4, and a few are less than 0.1.The above geochemical testing results show that the source of detrital zircon is mainly magmatic rocks, followed by metamorphic rocks, and the ages of detrital zircons are reliable.The age results show that there exist three age stages of the Yanchang Formation detrital zircons, i.e., 228- 379 Ma, 1650- 1915 Ma, 2400- 2560 Ma, corresponding to the tectonic movements of indosinian, Hercynin, middle- late Lüliang movement and early- middle Wutai movement.By comparing the isotopic ages for the plutons in and around research areas, the tight sandstone of the Yanchang Formation in the central and western parts of the Ordos Basin derive from the Daqing Mountains-Wula Mountains, Yinshan Mountains and Jining areas in the north-northeast of the Ordos Basin.The sedimentary rocks source from gneissic granite in the late Neoarchean, ancient TTG gneiss and granulite in the early Paleoproterozoic, the khondalite belt in the Lüliang Movement, and the magmatic rock in the Indosinian and Hercynian.
Drainage network as an indicator of tectonic evolution of mountain belts: insight from the Middle Atlas (Morocco).
Authors: Yaaqoub Ahmed , Essaifi Abderrahim , Clementucci Romano , Ballato Paolo , Faccenna Claudio
Published: March 2022

In actively deforming regions, the geometry and evolution of fluvial systems are sensitive to surface uplift, style of deformation and erosion processes. The uplift influences drainages via base level changes, drainage reversals, and capture processes. Although drainage development and reorganization might be complex in some cases, it can be used to unravel the tectonic evolution of a region.

The Middle Atlas is an intracontinental fold-and-thrust belt that results from the tectonic inversion of a Triassic to Jurassic continental rift basin. The compressional regime leading to basin inversion has produced limited crustal shortening and thickening in association with the growth of mountain ridges with a wavelength of few km.  These topographic features have been superimposed by a long-wavelength, mantle-driven surface uplift, occurred since the late Cenozoic.

Here, we carry out a topographic and fluvial analysis to investigate at which extent the geomorphic features, mainly the drainage network, reflect the tectonic evolution of the Middle Atlas. Two main drainage divides can be defined in the Middle Atlas: 1) a longitudinal divide that separates an eastern flank draining into the Mediterranean Sea through the Moulouya river from a western flank draining into the Atlantic Ocean through the Sebou and Oum Rbia rivers; 2) a transverse divide that sets apart the catchments of the Sebou and Oum Rbia  rivers. In the eastern flank, where the slopes are steep, the tributaries of the Moulouya river show a parallel pattern and are transversal to the trend of the orogen, whereas in the western flank the rivers are longitudinal and controlled by the tectonic structures. Our results indicate that the topography and drainage are in a disequilibrium condition and in an early stage of evolution. The discrepancy in the rivers network between the two flanks, suggests an asymmetric tectonic uplift history. Specifically the eastern flank of the orogen appears to have accommodated a higher magnitude of late Cenozoic contractional deformation than the western flank
InSAR-based characterization of rock glacier kinematics in the La Sal Mountains, Utah, USA
Authors: Kluetmeier Camryn , Handwerger Alex , Munroe Jeffrey
Published: March 2022

Rock glaciers are perennially frozen bodies of ice and poorly sorted rock debris that flow downslope due to basal shear and deformation of interstitial ice. As common features in high mountain environments, rock glaciers constitute an important component of alpine hydrology and landscape evolution through release of seasonal meltwater and transport of debris downslope. Here, we use satellite-based interferometric synthetic aperture radar (InSAR) from 2015 to 2021 to identify and characterize rock glaciers in the La Sal Mountains of Utah, USA. Following the IPA Action Group guidelines, we created an inventory of 45 active and transitional rock glaciers in the La Sal Mountains based on mean InSAR velocity maps. La Sal Mountain rock glaciers have an average area of 0.09 km2 and are found at a mean elevation of 3187 m, where mean annual air temperature and precipitation are estimated to be 2.44 °C and 1012 mm, respectively. The mean downslope velocity for the inventory is 3.58 ± 1.13 cm yr -1 with individual rock glacier velocities ranging from 1.98 cm yr -1 to 7.54 cm yr -1. Time-dependent deformation of 19 representative rock glaciers shows that rock glacier motion varies seasonally, with rates of up to 38.2 cm yr-1 during the late summer. Average annual rock glacier velocities are also strongly correlated to the overall amount of precipitation received each year (R2 = 0.97). Our results offer insight into environmental factors that may govern rock glacier kinematics, suggesting that rock glacier kinematics are controlled by the availability of liquid water.
The Relationship Between Soil Moisture and Drought Monitoring Using Sentinel-3 SLSTR Data in Lower Eastern Counties of Kenya
Authors: Sahbeni Ghada , Musyimi Peter K. , Székely Balázs , Weidinger Tamás
Published: March 2022

Drought is an extreme climate phenomenon that influences Earth’s water resources and energy balance. It affects hydrological cycle processes such as evapotranspiration, precipitation, surface runoff, condensation, and infiltration. Its extreme and severe occurrences threaten food security and drinking water availability for local populations worldwide. In this regard, this study uses Sentinel-3 SLSTR data to monitor drought spatiotemporal variation between 2019 and 2021 and investigate the crucial role of vegetation cover, land surface temperature, and water vapor amount in influencing drought dynamics over Kenyan’s lower eastern counties. Three essential climate variables (ECVs) of interest were extracted, namely, land surface temperature (LST), fractional vegetation cover (FVC), and total column water vapor (TCWV). These features were processed for four counties between the wettest and driest episodes in 2019 and 2021. The results showed that Makueni county has the highest FVC values of 88% in April and 76% in both periods and years. Machakos and Kitui counties had the lowest FVC estimates of 51% in September for both periods and range between 63% and 65% during dry seasons of both years. The land surface temperature has drastically changed over time and space, with Kitui county having the highest estimates of approximately 27 °C and 29 °C in April 2019 and September 2019, respectively. A significant spatial variation of TCWV was noticed across different counties, with the lowest value of 22 mm in Machakos county during the dry season of 2019, while Taita Taveta county had the highest estimates varying from 30 to 41 mm during the wettest season of 2021. Land surface temperature variation is negatively proportional to vegetation density and soil moisture content, as non-vegetated areas are expected to have lower moisture. A close link between TCWV and soil moisture content has been well established. Overall, Sentinel-3 SLSTR products depict an efficient and promising data source for drought monitoring, especially in cases where in situ measurements are scarce. ECVs produced maps will assist decision-makers in a better understanding of drought events that extremely influence agriculture in Kenya’s arid and semi-arid areas. Similarly, Sentinel-3 products can be used to interpret hydrological, ecological, and environmental changes and implications under different climatic conditions.
Diagnosing the fraction of inter-annual variability of global carbon cycle driven by atmospheric circulation variability
Authors: Li Na , Sippel Sebastian , Winkler Alexander J. , Mahecha Miguel D. , Reichstein Markus , Bastos Ana
Published: March 2022

The inter-annual variability (IAV) of the global carbon cycle (C-cycle) is prone to large uncertainty, which in turn, affects uncertainty in future climate projections. Quantifying the imprint of large-scale atmospheric circulation dynamics and associated carbon cycle responses is a key endeavour to improve our understanding of C-cycle dynamics.

C-cycle IAV mainly results from the balance of carbon uptake by gross primary productivity, carbon release from respiration processes, and other disturbance-induced fluxes. These processes are largely controlled by temperature, water availability, and incoming solar radiation, which are modulated by large-scale modes of atmospheric circulation such as the El Niño/Southern Oscillation (ENSO) or the Pacific Decadal Oscillation (PDO). 

Here, we use a data-driven approach [1] to quantify the fraction of IAV in atmospheric CO2 growth rate and the land CO2 sink that are driven by atmospheric circulation variability, by using spatio-temporal sea level pressure-a proxy for large-scale atmospheric circulation-as a predictor in ridge regression models of carbon cycle IAV. We use a regularisation approach [1] to curb the problems of overfitting and multicollinearity due to the limited time interval and large number of spatial predictors (spatial gridded time-series of SLP anomalies). We find that the model based on SLP anomalies can achieve high skill in predictions of the IAV in atmospheric growth rate and global land sink, with Pearson correlations between original and predicted test values of 0.7-0.84. The coefficients of the regression indicate two dominant regions contributing to C-cycle IAV: one in the tropical Pacific corresponding to the well-known influence of ENSO, another one located in the western Pacific. We test how the prediction skill depends on the length of the time-series and show that for short time-series (15-20 years) the correlation of predicted vs. observed test values is strongly dependent on the particular period considered, while it is more stable for periods longer than 30 years. These results indicate that the influence of atmospheric circulation variability on IAV of the C-cycle can limit our ability to draw robust conclusions when using short observational records. 

[1] Sippel, S., Meinshausen, N., Merrifield, A., Lehner, F., Pendergrass, A. G., Fischer, E., and Knutti, R.:  Uncovering the Forced Climate Response from a Single Ensemble Member Using Statistical Learning, Journal of Climate, 32(17), 5677–5699, https://doi.org/10.1175/JCLI-D-18-0882.1, 2019.
Surface-atmosphere interactions at an urban site in highly complex terrain
Authors: Ward Helen Claire , Rotach Mathias Walter , Gohm Alexander , Graus Martin , Karl Thomas , Haid Maren , Umek Lukas , Muschinski Thomas
Published: March 2022

We present the first detailed analysis of multi-seasonal near-surface turbulence observations for an urban area in highly complex terrain. Using four years of eddy covariance data collected over the Alpine city of Innsbruck, Austria, we assess the impact of the urban surface, orographic setting and mountain weather on the exchange of energy, momentum and mass. In terms of urban surface controls, findings indicate several similarities with previous studies at city-centre sites (in much flatter terrain). The available energy is used mainly for the net storage heat flux and sensible heat flux, while the lack of vegetation in the source area means latent heat fluxes are small. Observed carbon dioxide fluxes are dominated by anthropogenic emissions from building heating in winter and traffic in summer. The measured annual total carbon dioxide flux corresponds well to both modelled emissions and observations from other sites with a similar proportion of vegetation, but interpretation of seasonal and diurnal patterns is complicated by spatial heterogeneity in the source area combined with distinct temporal trends in flow conditions.

Innsbruck’s mountainous setting impacts atmospheric conditions and surface-atmosphere exchange in multiple ways. Steep valley sides block solar radiation at low sun angles, resulting in a shift in the times of local sunrise and sunset compared to over flat terrain. In the absence of strong synoptic forcing, a thermally driven valley-wind circulation develops with characteristic daily and seasonal flow patterns. Moderate up-valley winds are observed during the afternoon (these are strongest during summer), while weak down-valley winds prevail overnight, in the early morning and during winter. During spring and autumn, downslope windstorms (foehn) can lead to marked increases in temperature, wind speed and turbulence. Sensible heat fluxes in the city are almost always positive (even at night and during winter), however the presence of warm air above cooler surfaces can result in negative sensible heat fluxes during foehn. Furthermore, very low carbon dioxide mixing ratios observed during foehn events illustrate how the intense mixing helps to ventilate the city and reduce pollutant concentrations.

For the first time, the combined influences of the urban environment, complex orography and atmospheric conditions on surface-atmosphere exchange are analysed in order to begin to understand interactions between urban and topographic processes. These results are thus relevant not only for other urbanised Alpine valleys, but for the numerous cities across the globe which are located in some kind of topographic complexity, such as in river valleys or basins, on hilltops or plateaus or along coastlines.
Evidence that invasive earthworms promote bacterial-mediated nitrous oxide emissions in forest ecosystems 
Authors: Villeneuve Clara , Bradley Robert , Beauregard Pascale B.
Published: March 2022

Earthworms are newcomers to South-Eastern Canada, as they were unable to survive the last glaciation period that ended about 11,000 years ago. Since their introduction by Europeans over recent centuries, these exotic earthworm species have substantially affected pedological processes and soil functions. For example, a recent study in the province of Quebec found that earthworms invading native sugar maple (Acer saccharum Marsh.) forests could potentially increase soil nitrous oxide (N2O) emissions by increasing denitrification rates. However, the underlying microbial mechanisms driving the production of this greenhouse gas via denitrification remain unclear. This led us to conduct field and laboratory studies in order to explore whether earthworms preferentially promote bacterial and/or fungal denitrification pathways. We measured earthworm abundance and collected surface mineral soil samples from 38 sugar maple forests, half of which were earthworm-free. In each soil sample, we measured fungal, bacterial and total microbial biomass by substrate-induced respiration, we measured fungal, bacterial and total denitrification by acetylene inhibition, and we quantified the abundance bacterial (nirK, nirS and nosZ) and fungal (P450nor) denitrifying genes by qPCR. Earthworm abundance correlated positively with bacterial as well as fungal biomass, but did not affect the bacterial-to-fungal biomass ratio. Accordingly, bacterial-mediated and fungal-mediated denitrification rates both increased with the abundance of earthworms. However, earthworm abundance correlated positively with the specific bacterial denitrification rate (SBDR = (bacterial-mediated denitrification rate) ÷ (bacterial biomass)), but not with the specific fungal denitrification rate (SFDR = (fungal-mediated denitrification rate) ÷ (fungal biomass)). Moreover, qPCR analyses showed a positive correlation between earthworm abundance and the proportion of all bacterial denitrifying genes in the microbial population, but no such effect on fungal denitrifying genes. Taken collectively, our results suggest that earthworms may increase N2O emissions in sugar maple forest soils by preferentially promoting the bacterial-mediated denitrification pathway.
Main features of the formation and development of the fault zone of the 2011 Tohoku earthquake derived from GPS data
Authors: Vladimirova Irina , Gabsatarov Yurii
Published: March 2022

On March 11, 2011, the strongest (Mw = 9.0) Tohoku earthquake occurred in northeastern Japan, completing a seismic cycle that lasted nearly 1200 years. We analyzed an extensive set of satellite geodetic, seismological and geological data to determine the geometry of the fault zone, to build an ensemble of models of distributed interseismic, coseismic and postseismic displacements in the source zone, and to study the possible effect of structural inhomogeneities of the medium on the accumulation and release of elastic stresses.

We found that the mechanical coupling immediately before the Tohoku earthquake was relatively high. The interplate coupling coefficient reaches its maximum values near the trench, which could be one of the factors that led to the occurrence of such a devastating tsunami. Near the lower edge of the future fault zone, we found areas of weakened coupling, which probably prevented the downward propagation of the seismic rupture. The area of maximum displacements in the seismic source is, as expected, located in the upper part of the fault zone. The areas of the greatest displacements in the effective postseismic source are concentrated near the lower edge of the seismic rupture, apparently marking the areas where elastic stresses were not released during the earthquake.

Asthenospheric viscosity is one of the key parameters governing the postseismic processes in the vicinity of the source zone of the large subduction earthquake. The study of postseismic deformations caused by the Tohoku earthquake allows us to establish some limitations on the mechanical properties of the asthenosphere under the Japan islands. Our estimate of the effective Maxwell viscosity of the asthenosphere in northeastern Japan is about ten times lower than the average value established for continental subduction zones. According to our forecast, based on the assumption of the constant effective viscosity of the asthenosphere, the prevalence of postseismic displacements in the vicinity of the source will cease approximately 30 years after the Tohoku earthquake.

An integral approach to studying the features of the seismic cycle in subduction zones allows us to establish the relationship between geodynamic processes at different stages of the cycle and to study the influence of regional characteristics of the medium.

This study was supported by Russian Science Foundation (project 20–17-00140).
How does Coastal Gravel get Sorted under Stormy Longshore Transport?
Authors: Eyal Haggai , Enzel Yehouda , Meiburg Eckart , Vowinckel Bernhard , G Lensky Nadav
Published: March 2022

Storm waves transport and sort coarse gravel along coasts. This fundamental process is important under changing sea-levels and increased storm frequency and intensity. However, limited information on intra-storm clast motion restricts theory development for coastal gravel sorting and coastal management of longshore transport. Here, we use ‘smart boulders’ equipped with loggers recording underwater, real-time, intra-storm clast motion, and measured longshore displacement of varied-mass marked boulders during storms. We utilize the unique setting of the Dead Sea shores where rapidly falling water levels allow isolating boulder transport during individual storms. Guided by these observations, we develop a new model quantifying the critical wave height for a certain clast mass mobilization. Then, we obtain an expression for the longshore clast displacement under the fluid-induced pressure impulse of a given wave. Finally, we formulate the sorting enforced by wave-height distributions during a storm, demonstrating how sorting is a direct manifestation of regional hydroclimatology.
Cenozoic relative movements of Greenland and North America by closure of the North Atlantic-Arctic plate circuit: The Labrador Sea, Davis Strait, Baffin Bay, and Eurekan Orogen
Authors: Causer Annabel , Eagles Graeme , Pérez-Díaz Lucía , Adam Jürgen
Published: March 2022

Cretaceous to earliest Oligocene plate motions between Greenland and North America are only modellable at high resolution from a short-lived (61-42 Ma) sequence of magnetic isochrons in the Labrador Sea. Understanding them at other times is hampered by interpretational conflicts and low resolution in geoscientific observations of the Labrador Sea, Davis Strait, Baffin Bay, and Eurekan Orogen. To better contextualize these observations, we build and manipulate models of North America-Eurasia and Eurasia-Greenland divergence in order to depict post-84 Ma North American-Greenland motions at quantified high resolution. Among our findings, we show that the North American-Eurasian plate boundary propagated northwards, leading the continental shelves in the Labrador Sea to separate by 74-72 Ma and in Baffin Bay later, at around 63 Ma, and that field evidence for the Eurekan Orogeny having occurred in two distinct phases is directly related to a 46 Ma change in Greenland-North American plate motion parameters.
The North (Small) Aral Sea after 15 years of recovering: physical and biogeochemical outcomes of the lake-wide conservation experiment.
Authors: Izhitskiy Alexander , Kirillin Georgiy
Published: March 2022

The reclaim of the North (Small) Aral Sea is an unprecedented effort on saving of a 2800 km2 large water basin by construction of a dam separating it from the rest of the desiccating Aral Sea area. As a result, the volume of the lake has stabilized at approximately 27.5 km3, the area has increased during 2006-2020 from 2800 km2 to 3400 km2, the salinity has dropped from 15 g kg-1 to 10 g kg-1. The consequences of this unique experiment remain not fully quantified to date and include deep changes in thermal conditions, seasonal stratification, ice regime, dissolved oxygen content and other biogeochemical characteristics. We performed a series of field surveys to the North Aral Sea in 2015-2019 and conducted in situ monitoring of the annual thermal and oxygen regime in 2018-2019 using an autonomous mooring station. The obtained interdisciplinary dataset (supported by modeling and remote sensing data) was used for the first comprehensive analysis of the North Aral system behavior on seasonal to inter-annual scales after its “cold restart”. Freshening of the North Aral waters turned its seasonal mixing regime to dimictic state, close to that existed in the Aral Sea before desiccation. As a result, the lake remains well-oxygenated throughout the year, contrasting to the situation in the hypersaline South (Large) Aral Sea. Concentrations of the dissolved oxygen remain high during the entire ice-covered period, indicating low respiration rates in the cold (~0°C) winter waters of the North Aral. We also discuss the current state of the North Aral Sea with regard to stabilization of its long-term dynamics, as well as consider the possible future projections in view of the global change effects on the regional hydrological regime and potential water management measures.

 
The role of bed morphology and channel curvature in the redistribution of momentum in a series of meander bends, Pearl River, USA
Authors: Konsoer Kory , Rowley Taylor , Rhoads Bruce
Published: March 2022

The process of meandering in alluvial rivers is the result of spatial variability in erosion and deposition that systematically alternates from one side of the channel to the next along sequential meander bends. The localized erosion of outer banks, typically downstream of the bend apex, occurs due to an outward advection of high-momentum fluid leading to an asymmetric lateral distribution of streamwise velocity. Two primary mechanisms are responsible for the lateral flux of streamwise momentum within meander bends. The first is an increasing bed elevation along the inner bank in the form of a point bar that causes a shoaling effect, steering fluid mass and momentum from the inner bank toward the outer bank. The second mechanism is curvature-driven secondary circulation that leads to helical motion of flow through the bend and an outward advection of high-momentum near-surface flow. While these two mechanisms have been studied previously, their relative contribution to the net redistribution of momentum within a series of consecutive bends have not yet been fully documented. For this study, we obtained three-dimensional velocity measurements using a boat-mounted acoustic Doppler current profiler along regularly spaced cross-sections for six consecutive meander bends on the Pearl River (Louisiana, USA) during two different discharge conditions. Velocity data were processed using the Velocity Mapping Toolbox in Matlab, and calculations were performed to evaluate the lateral flux of streamwise momentum due to topographic steering and secondary circulation using the Rozovskii frame of reference. These momentum flux terms are systematically compared to spatial series of curvature, bed elevation, and channel width to elucidate the interactions between form and flow structure. Results show that lateral flux of streamwise momentum is primarily driven by topographic steering, and that values of momentum flux due to curvature-driven secondary circulation are on average an order of magnitude lower. The spatial pattern of these flux components through the bends show that momentum redistribution due to topographic steering is highest at the entrance to the bend, and momentum redistribution due to secondary circulation is typically highest downstream of the apex.  The results of this study emphasize the important role that interaction between process and form play in dynamics of natural meandering rivers.  Point bars form through spatial variations in bed-material transport capacity within curved channels, but, once in place, these bars reinforce their own persistence through their influence on the lateral redistribution of streamwise momentum. 
Suprathermal populations and small scale fluctuations in the solar wind
Authors: Lazar Marian , Lopez Rodrigo , Shaaban Hamd , Poedts Stefaan , Fichtner Horst , Yoon Peter
Published: March 2022

In the last decade, studies of solar wind plasma have shown that suprathermal populations (up to a few keV) are closely linked to wave turbulence and fluctuations at small (or kinetic) scales. We aim to identify those types of wave fluctuations observed at these scales scales, for which existing theories predict a major implication in particle acceleration and formation of suprathermal tails in the velocity distributions of plasma particles. On the other hand, it is currently believed that fluctuation power (magnetic, density, velocity) measured at ion scales and lower are generated by the turbulent cascade but also wave instabilities. Therefore, we also intend to discuss a number of recent results describing the kinetic instabilities driven by the anisotropy of velocity distributions (e.g., temperature anisotropy, field-aligned drifts), and how are these instabilities influenced by the suprathermal populations. These results help to understand the energy exchanges between particles and electromagnetic fields, not only in the solar wind but also in the coronal plasma ejections, with consequences for the space weather and terrestrial magnetosphere.
Deep basin record evolution of chemical weathering and physical erosion as response to the tectonic uplift of the South African Plateau during the upper Cretaceous
Authors: Gaitan Valencia Camilo Esteban , Pucéat Emmanuelle , Pellenard Pierre , Blondet Justine , Guillocheau François , Robin Cécile , Bayon Germain , Adatte Thierry
Published: March 2022

During the upper Cretaceous the South African Plateau underwent an uneven uplift period that coincided with the onset of a long-term climate cooling. This uplift recorded two pulses, an early pulse during the Turonian that affected the eastern margin and a later pulse occurred during the Campanian affecting the western margin (van der Beek et al., 2002; Braun et al., 2014; Baby et al., 2020). We aim here to determine the response of physical erosion and chemical weathering to this tectonic event, that may have played a role in the long-term climate cooling by promoting silicate weathering and associated atmospheric CO2 drawdown. In this study we targeted the IODP 361 site located in the Cape Basin. We applied a new proxy (DeHf) of chemical weathering intensity based on the coupled Lu-Hf and Sm-Nd isotopic systems in clay fractions of the sediments. This approach is combined with X-ray diffraction analyses to determine the concomitant evolution of clay mineralogical assemblages, which in active tectonic settings can provide insights on the evolution of mechanical erosion.

Twenty-two samples were analyzed for Hf-Nd isotopic compositions and 99 samples were analyzed for X-ray diffraction analyses. Clay eNd values remain relatively stable throughout the studied interval, mainly within -8 to -9 e-units, but down to -10 e-units in the Maastrichtian, suggesting a relatively stable source of the sediments. These values are coherent with a sediment source from the Karoo basin and/or the Cape Belt (Dia, 1990; Garzanti et al., 2014). Clay mineral assemblages are dominated by smectite (about 65 to 98%) but show an increase in illite proportions during the Campanian-Maastrichtian, up to about 25%. This increase in primary clay minerals may point to an increase in mechanical erosion, that could be linked to the uplift pulse affecting the western south African margin at that time. DeHf values represent the departure of eHf from the clay array (Bayon et al., 2016), and display a marked increase during the Campanian-Maastrichtian as well, suggesting concomitant enhanced weathering of the nearby margin at that time.

Altogether, our data suggest a coupled response of mechanical erosion and chemical weathering of the southwestern African margin during the upper Cretaceous tectonic uplift of the margin, which also may have played as an active CO2 consumption mechanism. 
ULF waves upstream and downstream of interplanetary shocks
Authors: Blanco-Cano Xochitl , Kajdic Primoz , Rojas-Castillo Diana , Preisser Luis , Jian Lan , Russell Christopher , Luhmann Janet
Published: March 2022

Interplanetary (IP) shocks can be driven in the solar wind by fast coronal mass ejections and by the interaction of fast solar wind with slow streams of plasma. These shocks can be preceded by extended wave and suprathermal ion foreshocks. We use STEREO data to study wave modes upstream and downstream of IP shocks. Understanding these waves is important because they contribute to shock acceleration processes and modify the solar wind as the shocks propagate in the heliosphere. We find that upstream regions can be permeated by whistler waves (f ~ 1 Hz) and/or ultra low frequency (ULF) right-handed waves (f~10-2–10-1 Hz). While whistlers appear to be generated at the shock, the origin of ULF waves is most probably associated with local kinetic ion instabilities. In contrast with planetary bow shocks, most IP shocks have a small Mach number (<4) and most of the upstream waves studied here are mainly transverse and no steepening occurs. Downstream of the shocks ion cyclotron and mirror mode waves can grow due to temperature anisotropy. The waves observed downstream of IP quasi-parallel shocks have larger amplitudes than waves in the regions downstream of quasi-perpendicular shocks. A variety of waves can be found in the sheath regions of IP shocks, even when IP shocks are weak, mostly for quasi-perpendicular shocks. These include ion cyclotron waves (ICW) with well defined peaks in frequency, broad spectra ICW, and mirror mode storms, which tend to occur for higher plasma beta.
Hydrological processes in undisturbed northern peatlands: Relative impact on water conservation and streamflow
Authors: Nijp Jelmer , Huseby Karslen Reinert , Nilsson Mats , Bishop Kevin
Published: March 2022

The hydrology of peatlands is a crucial control on peatland ecosystem functions, including greenhouse gas emission, biogeochemistry, biodiversity and energy balance partitioning. Undisturbed peatlands contain numerous hydrological feedbacks that stabilize the internal water balance, hence ecosystem functioning. Besides affecting the peatland water balance internally, peatlands are renowned for their capacity to regulate streamflow. Nevertheless, the impact of peatlands on flow regulation remains inconclusive. Some studies suggest that peatlands reduce floods, whereas others conclude that there is no impact or even increased risk of flooding. Such contrasting results can largely be explained by the wide range of peatland ecosystem characteristics, or differences in local geohydrology, climate, and landscape configuration that control hydrological response. No two catchment are the same, making it difficult to discern whether observed differences between catchments originate from peatland hydrological processes or catchment dissimilarities. This seriously hampers understanding the effect of peatlands on streamflow in general and also the setting of priorities in peatland restoration projects.

In this research we take a modelling approach to quantify the relative impact of hydrological self-regulating processes in undisturbed northern peatlands on the internal peatland water balance and streamflow. By doing so, the confounding effects of local hydroclimatological settings can be excluded. Specifically, we set up a modular model to quantify the relative impact of (1) reduced lateral groundwater losses at deeper groundwater levels and (2) elastic storativity owing to the high compressibility of peat and (3) reduced evapotranspirative water losses at deeper groundwater levels. Landscape position was accounted for by adding or subtracting an extra efflux of water.

Our results indicate that hydrological self-regulation in natural peatlands is an important means to maintain the functionality of peatland vegetation in the face of changing hydroclimatological conditions. Part of the stored water is used for evapotranspiration. A significant part, however, is slowly released as discharge, resulting in maintaining downstream streamflow.

This study provides insight on the relative importance of hydrological processes and properties in northern peatlands in affecting internal peatland hydrology and downstream water availability. This information can be used for effective and targeted hydrological restoration of peatlands. With this research we contribute to a more solid scientific basis for the impact of peatlands on streamflow. Moreover, this work highlights the importance of undisturbed peatland processes for catchment behaviour. 
Evaluating modeled snow cover dynamics over Fennoscandia using Earth observations
Authors: Yılmaz Yeliz A. , Aalstad Kristoffer , Filhol Simon , Gascoin Simon , Pirk Norbert , Remmers Janneke , Stordal Frode , Tallaksen Lena M.
Published: March 2022

The snow cover is an essential part of the climate system in cold regions through its effects on the terrestrial water, energy, and carbon balance. Due to the high spatiotemporal variability of snow, it is challenging to resolve snow cover dynamics in models. Thus, our ability to improve the representation of these dynamics in Earth System Models (ESMs) leans heavily on the accuracy and representativeness of the observational data sets used for model evaluation.

The big picture provided by the long-term climate data record from satellites helps us to monitor changes in land cover over large areas. At the same time, rapidly developing drone and terrestrial imaging technology provides higher resolution information over specific areas. This complimentary information from spaceborne, airborne, and terrestrial Earth observations is invaluable for better understanding the complex processes in the climate system. In our work, we are currently exploiting estimates of snow-covered area from different optical sensors onboard polar orbiting satellites that are imaging the Nordic region. Drone and terrestrial images are being explored as a source of validation and calibration data for the satellite products. 

Having representative snow cover maps enables us to better evaluate the terrestrial component of the Norwegian Earth System Model (NorESM), namely the Community Land Model (CLM5). With a focus on snow processes, we are conducting an analysis using satellite-based estimates of snow-covered area (MODIS, Sentinel-2, and Landsat 8), snow simulations from CLM5, snow variables from several climate reanalyses (ERA5, ERA5-Land, and MERRA-2), and in-situ data from eddy covariance stations (LATICE flux sites). Two offline CLM5 simulations are conducted with different atmospheric forcing, namely the default data set (GSWP3) and ERA5. We are investigating trends in the snow cover phenology, which we characterize using snow cover duration, first and last days of the snow cover, and consecutive snow cover days for each snow season over the last two decades. This work illuminates a path to integrate Earth observations with Earth system modeling in cold environments to both identify and constrain sources of uncertainty.

Acknowledgement: This ongoing study is supported by the LATICE (Land-ATmosphere Interactions in Cold Environments) strategic research initiative funded by the University of Oslo, and the project  EMERALD (294948) funded by the Research Council of Norway.
Machine learning to quantify cloud responses to aerosols from satellite data
Authors: Gonzalez Jessenia , Sourdeval Odran , Camps-Valls Gustau , Quaas Johannes
Published: March 2022

The Earth's radiation budget may be altered by changes in atmospheric composition or land use. This is called radiative forcing. Among the human-generated influences in radiative forcing, aerosol-cloud interactions are the least understood. A way to quantify a key uncertainty in this regard, the adjustment of cloud liquid water path (LWP), is by the ratio (sensitivity) of LWP to changes in cloud droplet number concentration (Nd). A key problem in quantifying this sensitivity from large-scale observations is that these two quantities are not retrieved by operational satellite products and are subject to large uncertainties. 

In this work, we use machine learning techniques to show that inferring LWP and Nd directly from satellite observation data may yield a better understanding of this relationship without using retrievals, which may lead to large and systematic uncertainties. In particular, we use supervised learning on the basis of available high-resolution ICON-LEM (ICOsahedral Non-hydrostatic Large Eddy Model) simulations from the HD(CP)² project (High Definition Clouds and Precipitation for advancing Climate Prediction) and forward-simulated radiances obtained from the radiative transfer modeling (RTTOV, Radiative Transfer for TOVS) which uses MODIS (Moderate Resolution Imaging Spectroradiometer) data as a reference. Usually, only two channels from the reflectance of MODIS can be used to estimate the LWP and Nd. However, having access to 36 bands allows us to exploit data and find other patterns to get these parameters directly from the observation space rather than from the retrievals. A machine learning model is used to create an emulator which approximates the Radiative Transfer Model, and another machine learning model to directly predict the sensitivity of LWP - Nd from the satellite observation data.