Observations using Arecibo Observatory’s highly sensitive Incoherent Scattering Radar (AO-ISR) show ionospheric descending layers from as high as $\sim$400 km, much higher than earlier studies, with continuity down to 90 km. The AO-ISR was operated to observe the ion-line and plasma-line with coded-long-pulse for high temporal and spatial resolution of 35/10 seconds and 300 m, respectively, during 01-06 February 2019. We found multiple layering structures descending from 400 km to 90 km in all these six days. These layers are traditionally called intermediate descending layers (IDLs) ($>$130 km and below F-peak), upper semi-diurnal daytime $\&$ nighttime layers (110 km-130 km), and lower diurnal layers($<$110 km). We have denoted the new daytime descending layers above the hmF2 as top-side descending layers (TDLs). All these layers are collectively named ion descending layers (IonDLs) since all of them are connected with some discontinuity at the F1-peak (i.e., 170 km), except for the daytime lower-diurnal layer. The most pronounced IonDLs occur in the twilight times. IonDLs mainly occur in shear zones of the vertical ion drifts and are favored by downward ion drifts, and their descent speeds increase with increasing altitude. The estimated phase velocities of the waves in the F-region are comparable with the descending speed of the IonDLs. Furthermore, IonDLs/IDLs occur with and without spread-F events but intensified spread-F events raise their beginning altitude. The TDLs and IDLs are driven by gravity waves with time periods of 1.5-4 hours.

We present a comparison of atmospheric transport model simulations for carbonyl sulfide (COS), within the framework of the ongoing atmospheric tracer transport model intercomparison project “TransCom”. Seven atmospheric transport models participated in the inter-comparison experiment and provided simulations of COS mixing ratios in the troposphere over a 9-year period (2010–2018), using prescribed state-of-the-art surface fluxes for various components of the atmospheric COS budget: biospheric sink, oceanic source, sources from fire and industry. Since the biosphere is the largest sink of COS, we tested sink estimates produced by two different biosphere models. The main goals of TransCom-COS are (a) to investigate the impact of the transport uncertainty and emission distribution in simulating the spatio-temporal variability of COS mixing ratios in the troposphere, and (b) to assess the sensitivity of simulated tropospheric COS mixing ratios to the seasonal and diurnal variability of the COS biosphere fluxes. To this end, a control case with state-of-the-art seasonal fluxes of COS was constructed. Models were run with the same fluxes and without chemistry to isolate transport differences. Further, two COS flux scenarios were compared: one using a biosphere flux with a monthly time resolution and the other using a biosphere flux with a three-hourly time resolution. In addition, we investigated the sensitivity of the simulated concentrations to different biosphere fluxes and to indirect oceanic emissions through dimethylsulfide (DMS) and carbon disulfide (CS2). The modelled COS mixing ratios were assessed against in-situ observations from surface stations and aircraft.

Subglacial models represent moulins as cylinders or cones, but field observations suggest the upper part of moulins in the Greenland Ice Sheet have more complex shapes. These more complex shapes should cause englacial water storage within moulins to vary as a function of depth, a relationship not currently accounted for in models. Here, we use a coupled englacial--subglacial conduit model to explore how moulin shape affects depth-dependent moulin water storage and water pressure dynamics within a subglacial channel. We simulate seven different moulin shapes across a range of moulin sizes. We find that the englacial storage capacity at the water level is the main control over the daily water level oscillation range and that depth-varying changes in englacial water storage control the temporal shape of this oscillation. Further, the cross-sectional area of the moulin within the daily oscillation range, but not above or below this range, controls pressures within the connected subglacial channel. Specifically, large cross-sectional areas can dampen daily to weekly oscillations that occur in the surface meltwater supply. Our findings suggest that further knowledge of the shape of moulins around the equilibrium water level would improve englacial storage parameterization in subglacial hydrological models and aid predictions of hydro-dynamic coupling.

There is a substantial gap between the current emissions of greenhouse gases and levels required for achieving the 2 and 1.5 °C temperature targets of the Paris Agreement. Understanding the implications of a temperature overshoot is thus an increasingly relevant research topic. Here we explore the carbon cycle feedbacks over land and ocean in the SSP5-3.4-OS overshoot scenario by using an ensemble of Coupled Model Intercomparison Project 6 Earth system models. Models show that after the CO2 concentration and air temperature peaks, land and ocean are decreasing carbon sinks from the 2040s and become sources for a limited time in the 22nd century. The decrease in the carbon uptake precedes the CO2 concentration peak. The early peak of ocean uptake stems from its dependency on the atmospheric CO2 growth rate. The early peak of the land uptake occurs due to a larger increase in ecosystem respiration than the increase in gross primary production, as well as due to a concomitant increase in land-use change emissions primarily attributed to the wide implementation of biofuel croplands. The carbon cycle feedback parameters amplify after the CO2 concentration and temperature peaks due to inertia of the Earth system so that land and ocean absorb more carbon per unit change in the atmospheric CO2 change (stronger negative feedback) and lose more carbon per unit temperature change (stronger positive feedback) compared to if the feedbacks stayed unchanged. The increased negative CO2 feedback outperforms the increased positive climate feedback. This feature should be investigated under other scenarios.

We present a near surface air temperature (NSAT) fused data product over the contiguous United States using Level 2 data from the Atmospheric Infrared Sounder (AIRS), on the Aqua satellite, and the Cross-track Infrared Microwave Sounding Suite (CrIMSS), on the Suomi National Polar-orbiting Partnership (SNPP) satellite. We create the fused product using Spatial Statistical Data Fusion (SSDF), a procedure for fusing multiple datasets by modeling spatial dependence in the data, along with ground station data from NOAA’s Integrated Surface Database (ISD) which is used to estimate bias and variance in the input satellite datasets. Our fused NSAT product is produced twice daily and on a 0.25-degree latitude-longitude grid. We provide detailed validation using withheld ISD data and comparison with ERA5-Land reanalysis. The fused gridded product has no missing data; has improved accuracy and precision relative to the input satellite datasets, and comparable accuracy and precision to ERA5-Land; and includes improved uncertainty estimates. Over the domain of our study, the fused product decreases daytime bias magnitude by 1.7 K and 0.5 K, nighttime bias magnitude by 1.5 K and 0.2 K, and overall RMSE by 35% and 15% relative to the AIRS and CrIMSS input datasets, respectively. Our method is computationally fast and generalizable, capable of data fusion from multiple datasets estimating the same quantity. Finally, because our product reduces bias, it produces long-term datasets across multi-instrument remote sensing records with improved bias stationarity, even as individual missions and their data records begin and end.

A document by Saira Hamid. Click on the document to view its contents.

The 2020 California fire season yielded the largest fires in California history. TROPOMI nitrogen dioxide (NO2) and carbon monoxide (CO) ratios (i.e. mole density ratios; MDR) have been previously used to distinguish fire combustion among different vegetation types around the world. Here, we analyze the MDR from TROPOMI overpasses to identify fire characteristics over two regions of California where two wildfires were reported. We show that MDR calculated with TROPOMI NO2 and CO columns can be used to assess fire characteristics at the scale of counties through identifying the smoldering fires of the northern region and flaming fire of the southern region with a shift in the combustion at the end of September resulting from a change in fuel types. Improvement in the land cover maps and use of hourly data could help to better attribute MDR to specific fuel source categories.

The Hunga Tonga-Hunga Ha’apai volcano in the Pacific Ocean erupted on January 15, 2022. The energy released by this submarine eruption caused waves propagating through the lithosphere, ocean and atmosphere. Less than 10 minutes after the eruption, pulsation-like geomagnetic disturbances started at the geomagnetic observatory Apia, approximately 835 km from Hunga Tonga, and lasted for about 2 hours. These disturbances were most prominent in the Y (east) component, with an oscillation amplitude of ~3 nT and dominant periods of 276, 254 and 219 s. Comparable geomagnetic disturbances are absent at neighboring as well as high-latitude geomagnetic observatories, indicating that the disturbances are localized and not related to solar wind energy input. Tide gauge data show that tsunami waves arrived at Apia more than one hour after the eruption. This leaves ionospheric currents as the likely cause of the geomagnetic disturbances.

Felsic continental crust is unique to the Earth in the solar system, but it still remains controversial regarding its formation, accretion and reworking. The plate tectonics theory has been significantly challenged in explaining the origin of continents as Archean continents rarely preserve hallmarks of plate tectonics. In contrast, growing evidence emerges to support mantle plume-derived oceanic plateau models as the models can reasonably explain the origin of bimodal volcanic assemblages and nearly coeval emplacement of tonalite-trondjhemite-granodiorite (TTG) rocks, presence of ~1600ºC komatiites and dominant dome structures, and lack of ultra-high-pressure rocks, paired metamorphic belts and ophiolites in Archean continents. Although plate tectonics seems to fail in explaining the origin of continents, it has been successfully applied to interpret the accretion or outgrowth of continents along subduction zones where new mafic crust is generated at the base of continental crust through partial melting of the mantle wedge with addition of H2O-dominant fluids from the subducted oceanic slabs, and partial melting of the juvenile mafic crust results in the formation of new felsic continental crust, leading to the outside accretion of continents. Subduction processes also cause the softening, thinning and recycling of continental lithosphere due to the vigorous infiltration of volatile-rich fluids and melts especially along weak layers or weak belts, leading to the widespread reworking and even destruction of continental lithosphere. Reworking of continents also occurs in continental interiors due to plume-lithosphere interactions, which, however, leads to much less degrees of lithospheric modification than subduction-induced craton destruction.

A document by Navid Hosseini. Click on the document to view its contents.

Here we assess to what extent the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM) can reproduce the climatological variations of vertical Total Electron Content (vTEC) in the Canadian sector. Within the auroral oval and polar cap, E-CHAIM is found to exhibit Root Mean Square (RMS) errors in vTEC as low 0.4 TECU during solar minimum summer but as high as 5.0 TECU during solar maximum equinox conditions. These errors represent an improvement of up to 8.5 TECU over the errors of the International Reference Ionosphere (IRI) in the same region. At sub-auroral latitudes, E-CHAIM RMS errors range between 1.0 TECU and 7.4 TECU, with greatest errors during the equinoxes at high solar activity. This represents an up to 0.5 TECU improvement over the IRI during summer but worse performance by up to 2.4 TECU during the winter. Comparisons of E-CHAIM performance against in situ measurements from the European Space Agency’s Swarm mission are also conducted, ultimately finding behaviour consistent with that of vTEC. In contrast to the vTEC results, however, E-CHAIM and the IRI exhibit comparable performance at Swarm altitudes, except within the polar cap, where the IRI exhibits systematic underestimation of electron density by up to 1.0e11 e/m^3. Conjunctions with mid-latitude ionosondes demonstrate that E-CHAIM’s errors appear to result from compounding same-signed errors in its NmF2, hmF2, and topside thickness at these latitudes. Overall, E-CHAIM exhibits strong performance within the polar cap and auroral oval but performs comparably to the IRI at sub-auroral latitudes.

Many physical processes in the field of rock physics are influenced by the presence of fractures and microcracks. Therefore, intact rock samples are often used for reproducible experimental studies, and cracks are artificially created by various methods. For this, one possibility is the use of thermal treatments. In this work, twelve thermal treatments, differing in the applied maximum temperature and the applied cooling condition (slow versus fast cooling) are experimentally studied for dry Bianco Carrara marble under ambient conditions. Two sizes of cylindrical core samples are investigated to identify a potential size effect. As effective quantities on the core-scale, the bulk volume, the bulk density, and the P- and S-wave velocities, including shear wave splitting, are examined. To obtain a three-dimensional insight into the mechanisms occurring on the micro-scale level, micro X-Ray Computed Tomography (micro-XRCT) imaging is employed. For both cooling conditions, with increasing maximum temperature, the bulk volume increases, and the propagation velocities significantly drop. This behavior is amplified for fast cooling. The bulk volume increase is related to the initiated crack volume as micro-XRCT shows. Based on comprehensive measurements, a logarithmic relationship between the relative bulk volume change and the relative change of the ultrasound velocities can be observed. Although there is a size effect for fast cooling, the relationship found is independent of the sample size. Also the cooling protocol has almost no influence. A model is derived which predicts the relative change of the ultrasound velocities depending on the initiated relative bulk volume change.

Cyclostratigraphy’s near 100% success rate in statistical cycle identification suggests confirmation bias; absence of cyclicity is not regarded as a possible outcome. Vaughan et al 2011 (VBS) showed that the usual methods of estimating confidence levels (CLs) admit numerous false cycle detections, but in subsequent debate it is asserted that the corrections recommended by VBS do not apply in cyclostratigraphy because they lead to rejection of the expected orbital periods. Is there a deeper problem? VBS particularly criticised universal failure to correct CLs for the unavoidably multiple nature of significance tests of power spectra. However, the multiple-test problem is compounded by assumptions of unlimited freedom to vary procedures to allow for properties of individual datasets. Statistical analysis in cyclostratigraphy operates in a large variable-space, both of target hypotheses (many orbital cycles and combinations thereof), and of procedures (many pre- and syn-processing options). Each of the many data-contingent choices made before and during spectral analysis and significance-testing implies the existence of alternatives: in effect, the reported analysis is only one of many. Given that multiple experiments will eventually achieve a positive result purely by chance, unadjusted significance thresholds will result in large numbers of spurious cycle identifications, a possible explanation for observed success rates. Additional multiplicity is implied by the practice of treating CLs as a guide, rather than as a definitive signal:noise discriminator; treating CLs as movable (or even optional) negates the concept that the particular dataset is just one realisation of many permitted by the noise model; without pre-selection of a CL the statistics are meaningless. Suggestions for practical improvements include: better hypothesis formulation (with attention to the prior probability of signal preservation in an unreliable recording medium); more care in discriminating between the exploratory (hypothesis-setting) and confirmatory (hypothesis-testing) modes of data analysis; advance definition of analytical protocols; and publication of all results whether positive or negative. Reference: Vaughan et al 2011: doi:10.1029/2011PA002195.

The world has changed, and the role and responsibilities of scientists have changed as a consequence. Not only is there an increasingly urgent need for scientifically informed multi-scale responses to the global problems we face, but there is also a need to address to the obstructive attitudes toward evidence accumulated and presented through scientific activities. What skills will allow future scientists to continue extending the frontiers of knowledge, to cooperate in response to the wicked problems we face, and negotiate the complexities of denialism? These questions go to the very heart of what it means, and is likely to mean in future, to be a scientist. This in turn goes to the heart of the educational process that will deliver graduates able to address these conundrums. The implications of these considerations will be explored from curriculum design, learning outcomes, and pedagogic perspectives. We start by considering the value of longitudinal curricula, problem based learning approaches and authentic assessment strategies. We demonstrate the utility of an enhanced graduate profile framework as a tool for planning educational interventions across the scales at which they occur -- institution, programme, module, session and individual learner. Based on our experiences in formal teaching, informal student support, and research training at both undergraduate and post-graduate levels, we will reflect on the value of such an approach to science education in this brave new post-truth world.

Atmospheric drag is one of the primary sources of error in the orbit determination and prediction of satellites in the low altitude LEO regime. Accurate modeling of the drag force is limited by uncertainties in the atmospheric density model used in the filter and the assumption of a constant drag coefficient, the so-called ‘cannonball’ model. Over the last two decades, various advances in density and drag-coefficient modeling have been made possible through the development of empirical and physics-based dynamical calibration techniques and machine-learning methods respectively. But even with high-fidelity models for density and drag coefficient, systematic uncertainties can remain in both due to the lack of temporal and spatial resolution of data and insufficient knowledge of parameters that feed into these models. In this work, we develop an estimation-based Fourier expansion model that can provide corrections to the nominal values of density and drag coefficient during the orbit determination process. In an earlier work (Ray et al., 2018), we demonstrated improved orbit prediction performance over the standard cannonball model with Fourier series expansions of the drag coefficient in body frame and orbit frame of a satellite. Whereas a body-fixed Fourier model captures the dependence of the drag coefficient on satellite attitude, the orbit-fixed model corrects for periodic changes in the gas-surface interaction in orbit. Since changes in the gas-surface interaction parameters in orbit are highly correlated with atmospheric density, any existing errors in the density are absorbed in the estimated orbit-fixed coefficients. Here, we derive a body-orbit Fourier model such that the orbit-fixed terms provide corrections for combined error variations of density and drag coefficient in orbit while the body-fixed terms account for the drag coefficient attitude dependence. We analyze the performance of the proposed approach with various atmospheric models such as NRLMSISE-00 (Picone et al., 2002), JB08 (Bowman et al., 2008), HASDM (Storz et al., 2002) and densities derived by Mehta et al. (2017) for varying geomagnetic conditions for the GRACE satellite.

We developed a novel ice-core laser melting sampler (LMS) to measure the stable water isotope ratios (δ18O and δD) as temperature proxies at ultra-high depth resolutions. In this LMS system, a 2-mm diameter movable evacuation nozzle holds an optical fiber through which a laser beam irradiates the ice core. The movable nozzle intrudes into the ice core, the laser radiation meanwhile melting the ice cylindrically, and the meltwater is pumped away simultaneously through the same nozzle and transferred to a vial for analysis. To avoid isotopic fractionation of the ice-core components by vaporization, the laser power is adjusted to ensure that the temperature of the meltwater is always kept well below its boiling point. Internal contamination and cross-contamination were both found to be negligible using this LMS. A segment of a Dome Fuji shallow ice core (Antarctica), using the LMS, was then demonstrated to have been discretely sampled with a depth-resolution as small as 3 mm: subsequent measurements of δ18O and δD were reasonably consistent with results obtained by hand segmentation. The LMS will thus enable us to seek the past temperature variations that may appear even in sub-centimeter resolutions in ice cores.

On 14 October 2023, an annular eclipse took place between 1503 UT and 2055 UT. It affected both North and South America. In this study, we used multiple ground-based and space-borne instruments, and we analysed ionospheric, thermospheric, magnetic and electrodynamic responses to this eclipse. In the vertical total electron content (VTEC) maps, at mid-latitudes, we observed a 40% depletion shortly after the Moon's shadow arrival. When the eclipse reached the low latitude region and the northern crest of the equatorial anomaly, we observed only 20-25% VTEC decrease in the vicinity of the eclipse path. However, after the Moon shadow crossed the magnetic equator, the low-latitude VTEC depletion reached 40%. The latter can be explained by the eclipse weakening the equatorial electric fields and, consequently, the equatorial fountain. In the topside VTEC and in the in-situ electron density measurements from Swarm B and C satellites we observed 40-50% decrease over the area affected by the eclipse. In the thermosphere, the eclipse produced a noticeable drop in the neutral mass density (7-18%) at 490-510 km of altitude, and changed the thermospheric composition in the vicinity of the eclipse path by 25-35%. Finally, the eclipse also clearly affected the geomagnetic field, especially at low and equatorial latitudes. Shortly after the umbra's arrival, we observed a clear decline in the total intensity F and the horizontal component H at all equatorial stations in South America. Whereas, in the variations of the vertical magnetic component Z no common pattern was observed during the eclipse. Key points:  the eclipse caused 40% depletion in total electron content, and it produced 40-50% decrease in electron density in the topside ionosphere  satellites show 7 to 20% decrease in the neutral mass density and 25-35% change in the thermospheric composition due to the eclipse  magnetic measurements show a clear decrease in the total intensity and horizontal component at low latitudes during the eclipse

The UK Polar Data Centre (PDC, https://www.bas.ac.uk/data/uk-pdc/) is the focal point for Antarctic environmental data management in the UK. Part of the Natural Environmental Research Council’s (NERC) network of environmental data centres and based at the British Antarctic Survey (BAS), the PDC coordinates the management of polar data from UK-funded research. In the last two years, the geophysics team at the PDC has made significant progress to improve the management of BAS aerogeophysics data, a challenging task considering that the British Antarctic Survey is one of the largest acquisitors of airborne geophysics data over Antarctica. In 2020, we published bedrock elevation data for fourteen airborne radar surveys over the continent, and more than thirty airborne gravity and magnetics datasets. This year, we will release large swaths of processed airborne radar data collected by BAS since the early 2000s, including extensive surveys over Pine Island (2004-05) and Thwaites (2018-20) glaciers, as well as the large surveys covering the Wilkes subglacial basin (2005-06) and the South Pole (2015-16), amongst others. Considerable effort has been made to curate these datasets to make them up-to-date and comply with the FAIR (Findable, Accessible, Interoperable and Re-usable) principles. In doing so, we believe that these datasets will be a valuable asset to future geophysical and glaciological studies over the Antarctic. Our aim here is to show our progress in re-processing and publishing these datasets and, for the first time, showcase our new Polar Aerogeophysics Data Portal which will serve as a user-friendly interface to discover and download the newly-published aerogeophysics data deposited on BAS’s data catalogue.