A document by Fatemeh Karandish. Click on the document to view its contents.

Between 4 and 10 September 2017, multiple solar eruptions occurred from active region AR12673. NOAA and NASA’s well-instrumented spacecraft observed the evolution of these geoeffective events from their solar origins, through the interplanetary medium, to their geospace impacts. The 6 September X9.3 flare was the largest to date for the nearly concluded solar cycle 24 and, in fact, the brightest recorded since an X17 flare in September 2005, which occurred during the declining phase of solar cycle 23. Rapid ionization of the sunlit upper atmosphere occurred, disrupting high frequency communications in the Caribbean region while emergency managers were scrambling to provide critical recovery services caused by the region’s devastating hurricanes. The 10 September west limb eruption resulted in the first solar energetic particle event since 2012 with sufficient flux and energy to yield a ground level enhancement. Spacecraft at L1, including DSCOVR, sampled the associated interplanetary coronal mass ejections minutes before their collision with Earth’s magnetosphere. Strong compression and erosion of the dayside magnetosphere occurred, placing geosynchronous satellites in the magnetosheath. Subsequent geomagnetic storms produced magnificent auroral displays and elevated hazards to power systems. Through the lens of NOAA’s space weather R-S-G storm scales, this event period increased hazards for systems susceptible to elevated “radio blackout” (R3-strong), “solar radiation storm” (S3-strong), and “geomagnetic storm” (G4-severe) conditions. The purpose of this paper is to provide an overview of the September 2017 space weather event, and a summary of its consequences, including forecaster, post event analyst and communication operator perspectives.

The geomagnetic field has an unusual weak spot over South America and the South Atlantic Ocean, called South Atlantic Anomaly (SAA). The magnetospheric particles trapped in this field penetrate deep into the atmosphere over the SAA resulting in lower inner boundary of the radiation belt. Over the past 400 years, the magnetic field in the SAA region has decreased consistently. This study shows that the weakened geomagnetic field has a bearing on the position of the inner boundary of the radiation belt. The present simulation revealed that the inner boundary of the radiation belt over the SAA region is moving earthward at the rate of 4.1$\pm$0.1 km/year and that earthward penetration of energetic particles has increased by $\approx$480 km during period 1900-2020. If the geomagnetic field in the SAA region continues to decrease, the resulting deepening of the radiation belt will pose increased risks to our satellites, life, and climate.

Midlatitude prediction on subseasonal timescales is difficult due to the chaotic nature of the atmosphere and often requires the identification of favorable atmospheric conditions that may lead to enhanced skill (“forecasts of opportunity”). Here, we demonstrate that an artificial neural network can identify such opportunities for tropical-extratropical circulation teleconnections within the North Atlantic (40N, 325E) at a lead of 22 days using the network’s confidence in a given prediction. Furthermore, layer-wise relevance propagation, an ANN explainability technique, pinpoints the relevant tropical features the ANN uses to make accurate predictions. We find that layer-wise relevance propagation identifies tropical hot spots that correspond to known favorable regions for midlatitude teleconnections and reveals a potential new pattern for prediction in the North Atlantic on subseasonal timescales.

The supercontinent cycle explains how landmasses amalgamate into super-plates, which dismember after a ~100 Myr tenure in a quasi-periodic manner controlling Earth’s long-term geodynamics. Pangea, the latest supercontinent, formed ~330 Ma, began to rift ~240 Ma finally broke-up ~200 Ma and it is generally considered the template for all previous supercontinents. The formation of Pangea as a super-plate 330 Ma show a major pitfall: The geologic record between 330-270 Ma predicts >1500km of shortening/extension and shows large volumes of magmatism and metamorphism of unidentified origin. Here I present a tectonic reconstruction that reconciles the inconsistent datasets. In this model, after the initial amalgamation of Pangea the comprising plates kept interacting at least between 320 Ma and 270 Ma, when finally established as a super-plate for a brief period of <70 Myr, which following most recent models would be too short to control the mantle dynamics.

NASA designated Reiner Gamma (RG) as the landing site for the first Payloads and Research Investigations on the Surface of the Moon (PRISM) delivery (dubbed PRISM-1a). Reiner Gamma is home to a magnetic anomaly, a region of magnetized crustal rocks. The RG magnetic anomaly is co-located with the type example of a class of irregular high-reflectance markings known as lunar swirls. RG is an ideal location to study how local magnetic fields change the interaction of an airless body with the solar wind, producing stand-off regions that are described as mini-magnetospheres. The Lunar Vertex mission, selected by NASA for PRISM-1a, has the following major goals: 1) Investigate the origin of lunar magnetic anomalies; 2) Determine the structure of the mini-magnetosphere that forms over the RG magnetic anomaly; 3) Investigate the origin of lunar swirls; and 4) Evaluate the importance of micrometeoroid bombardment vs. ion/electron exposure in the space weathering of silicate regolith. The mission goals will be accomplished by the following payload elements. The lander suite includes: The Vertex Camera Array (VCA), a set of fixed-mounted cameras. VCA images will be used to (a) survey landing site geology, and (b) perform photometric modeling to yield information on regolith characteristics. The Vector Magnetometer-Lander (VML) is a fluxgate magnetometer. VML will operate during descent and once on the surface to measure the in-situ magnetic field. Sophisticated gradiometry allows for separation of the natural field from that of the lander. The Magnetic Anomaly Plasma Spectrometer (MAPS) is a plasma analyzer that measures the energy, flux, and direction of ions and electrons. The lander will deploy a rover that conducts a traverse reaching ≥500 m distance, obtaining spatially distributed measurements at locations outside the zone disturbed by the lander rocket exhaust. The rover will carry two instruments: The Vector Magnetometer-Rover (VMR) is an array of miniature COTS magnetometers to measure the surface field. The Rover Multispectral Microscope (RMM) will collect images in the wavelength range ~0.34–1.0 um. RMM will reveal the composition, texture, and particle-size distribution of the regolith.

Observations of the South Polar Residual Cap suggest a possible erosion of the cap, leading to an increase of the global mass of the atmosphere. We test this assumption by making the first comparison between Viking 1 and InSight surface pressure data that have been recorded with ~40 years of difference. Such a comparison also allows us to determine changes in the dynamics of the seasonal ice caps between these two periods. To do so, we first had to recalibrate the InSight pressure data because of their unexpected sensitivity to the sensor temperature. Then, we had to design a procedure to compare distant pressure measurements. We propose two surface pressure interpolation methods at the local and global scale to do the comparison. The comparison of Viking and InSight seasonal surface pressure variations does not show major changes in the CO2 cycle. Such conclusions are also supported by an analysis of the Mars Science Laboratory (MSL) pressure data. Further comparisons with images of the south seasonal cap taken by the Viking 2 orbiter and MARCI camera do not display significant changes in the dynamic of this cap within ~40 years. Only a possible larger extension of the North Cap after the global storm of MY 34 is observed, but the physical mechanisms behind this anomaly are not well determined. Finally, the first comparison of MSL and InSight pressure data suggests a pressure deficit at Gale crater during southern summer, possibly resulting from a large presence of dust suspended within the crater.

Literature widely recognize the strong influence of urban green spaces in the microclimatic regulation and its potential applications to mitigate warming in cities. Promote viable actions to the climate change adaptation from cities through vegetation and help to palliate the urban heat island effect (UHI) to reduce health risk during extreme heat episodes, requires accurate criteria for each context in its different scales. This study presents a multi-scale approach to quantify the influence of urban green spaces on climate behavior of the Viladecans-Gava-Castelldefels conurbation in the metropolitan area of Barcelona. For this purpose, first, air (Ta) and surface (Ts) temperature of 124 points located in the interior and surroundings of seven green spaces are registered through field measurement campaigns during day and night between July 26 and August 4 of 2018. Then, Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) from Landsat 8 and Sentinel 2 data imagery for a clear-sky day nearby to the measurement days are retrieved and complemented with the NDVI of the spring-summer period of 2018 (1m) available in the Cartographic and Geographic Institute of Catalonia (ICGC). Analytical methods departed from the UHI characterization of the three-municipal area, resulted in 1.63°C LST increase in the urban Corine land cover (CLC) in relation with the rural at the whole ambit. Then, an OLS model to predict LST is constructed with NDVI and distance to parks (spaces with NDVI>=0.30) in the whole ambit (R²=0.59) and in the urban area (R²=0.47). At this point, results indicate that increase a tenth of NDVI reduces 1.15°C the LST of the whole ambit and 0.73°C on the urban area (p<0.01); while for each 100m further from parks, the LST rises 0.61°C for the whole ambit and 1.81°C on urban area (p<0.01). Particularly for the seven study cases, field measurements registered coincident spatial distribution with LST and NDVI, as well as highlighted the UHI effect during night. The quantification of the intensity and extent of the cooling effect of the study cases, registered a maximum cooling intensity of 2.7°C with a 300m buffer area; as well as the cooling effect calculation through concentric rings resulted between 40 to 130m extents from the parks boundaries and cooling intensity from 0.29 to 2.15°C. In conclusion, even when the multiple-scale analysis present coincidences and discrepancies between the different approaches, the models and methods applied in this study resulted in values that allow starting to talk about adequate actions to adapt to climate change in the context of the metropolitan area of Barcelona. The present study is part of the “Urban-CLIMPLAN. The urban heat island: effects on climate change and modeling for territorial and urban planning strategies. Application to the metropolitan region of Barcelona”, financed by the Ministry of Economy of Spain (MINECO) and the European Regional Development Fund (ERDF).

This study examines salinity barrier layers (BLs) in the eastern tropical North Pacific in the region of the Salinity Processes in the Upper ocean Regional Studies-2 field campaign. We utilize a high- resolution numerical model to study BLs and their relationship to frontal features and small-scale ocean variability, focusing on two specific events. One is associated with a large outbreak of BL presence near 7°N along 125°W. The other is a relatively isolated but persistent BL that forms near 13°N, again along 125°W. In both cases we find that the BL is proximate to a salinity frontal feature in which isohalines tilt toward the fresh side of the front at its base. The BLs studied are associated with divergent flow at the surface on the fresh side of the front and convergent flow on the salty side. Tilting of the front is invoked to explain this, with an additional mechanism involving a vertical circulation which causes the base of the front to tilt preferentially.

The Ediacaran-aged Shuram excursion was the last and largest of the Neoproterozoic negative carbon isotope anomalies. Recognized in stratigraphic successions around the globe, it precedes diverse evidence for macroscopic, multicellular life, and follows the Cryogenian global glaciations and Ediacaran Gaskiers glaciation. Hypotheses for the cause of the Shuram excursion can be broadly grouped into those that argue for post-depositional diagenetic alteration of the carbon isotope record and those that argue the extremely low δ13C values reflect a primary perturbation to the carbon cycle. Given the timing and magnitude of this event, distinguishing between these disparate hypotheses, or combining them, is critical for reconstructing the environmental conditions under which complex life evolved on Earth. We test specific predictions of each model using a range of stratigraphic observations and micro- and macro-analytical techniques. We find that the type sections in Oman where the Shuram excursion was first described are well preserved and contain a range of features difficult to reconcile with a post-depositional origin. However, many salient features are consistent with an extreme warming event coupled to a carbon cycle perturbation, analogous to the Paleocene-Eocene Thermal Maximum (PETM), and increased middle Ediacaran volcanism. We propose that cooling associated with the recovery was critical for origination rates of macroscopic soft-bodied organisms.

We develop an open source algorithm to apply Transfer learning to Aurora image classification and Magnetic disturbance Evaluation (TAME). For this purpose, we evaluate the performance of 80 pretrained neural networks using the Oslo Auroral THEMIS (OATH) data set of all-sky images, both in terms of runtime and their features’ predictive capability. From the features extracted by the best network, we retrain the last neural network layer using the Support Vector Machine (SVM) algorithm to distinguish between the labels “arc”, “diffuse”, “discrete”, “cloud”, “moon” and “clear sky / no aurora”. This transfer learning approach yields 73% accuracy in the six classes; if we aggregate the 3 auroral and 3 non-aurora classes, we achieve up to 91% accuracy. We apply our classifier to a new dataset of 550,000 images and evaluate the classifier based on these previously unseen images. To show the potential usefulness of our feature extractor and classifier, we investigate two test cases: First, we compare our predictions for the “cloudy” images to meteorological data and second we train a linear ridge model to predict perturbations in Earth’s locally measured magnetic field. We demonstrate that the classifier can be used as a filter to remove cloudy images from datasets and that the extracted features allow to predict magnetometer measurements. All procedures and algorithms used in this study are publicly available, and the code and classifier are provided, which opens possibility for large scale studies of all-sky images.

Subfootprint variability (SFV), or representativeness error, is variability within the footprint of a satellite that can impact validation done by comparison of in situ and remote sensing data. This study seeks to determine the size of the SFV as a function of footprint size in two regions that were heavily sampled with in situ data. The SPURS-1 (Salinity Processes in the Upper-ocean Regional Studies) experiment was conducted in the subtropical North Atlantic in 2012-2013, whereas the SPURS-2 study was in the tropical eastern North Pacific in 2016-2017. SFV was also computed using a high-resolution regional model based on ROMS (Regional Ocean Modeling System). We computed SFV at footprint sizes ranging from 20-100 km for both regions. SFV is strongly seasonal, but for different reasons in the two regions. In the SPURS-1 region, the meso- and submesoscale variability seemed to control the size of the SFV. In the SPURS-2 region, the SFV is much larger than SPURS-1 and controlled by patchy rainfall.

Computational Oceanography is the study of ocean phenomena by numerical simulation, especially dynamical and physical phenomena. Progress in information technology has driven exponential growth in the number of global ocean observations and the fidelity of numerical simulations of the ocean in the past few decades. The growth has been exponentially faster for ocean simulations, however. We argue that this faster growth is shifting the importance of field measurements and numerical simulations for oceanographic research. It is leading to the maturation of Computational Oceanography as a branch of marine science on par with observational oceanography. One implication is that ultra-resolved ocean simulations are only loosely constrained by observations. Another implication is that barriers to analyzing the output of such simulations should be removed. Although some specific limits and challenges exist, many opportunities are identified for the future of Computational Oceanography. Most important is the prospect of hybrid computational and observational approaches to advance understanding of the ocean.

The drivers of the efficiency in organic carbon (OC) burial are still poorly understood despite their key role in reliable projections of future climate trends. Here we shed new light on this question by presenting paleoclimate time series including OC content in sediments from Lake Veliko jezero, Croatia. The Sr/Ca ratios of the bulk sediment mainly derives from Sr and Ca concentrations of needle like aragonite in Core M1-A and was used as a palaeotemperature and palaeohydrology indicator. Four major and six minor cold and dry events were detected in the 8.3 to 2.6 cal ka BP interval. The combined assessment of Sr/Ca ratios, OC content, C/N ratios, δ13C data, and modelled proxies for palaeoredox conditions and aeolian input reveals that cold and dry climate state promoted anoxic conditions in the lake enhancing preservation of organic matter and leading to increased OC burial efficiency. Our study contributes to that projected future increase of temperature might play an important role in OC burial efficiency of meromictic lakes.

We present a re-examination of mass spectral data obtained from the Pioneer Venus Large Probe Neutral Mass Spectrometer. Our interpretations of differing trace chemical species are suggestive of redox disequilibria in Venus’ middle clouds. Assignments to the data (at 51.3 km) include phosphine, hydrogen sulfide, nitrous acid, nitric acid, carbon monoxide, hydrochloric acid, hydrogen cyanide, ethane, and potentially ammonia, chlorous acid, and several tentative PxOy species. All parent ions were predicated upon assignment of corresponding fragmentation products, isotopologues, and atomic species. The data reveal parent ions at varying oxidation states, implying the presence of reducing power in the clouds, and illuminating the potential for chemistries yet to be discovered. When considering the hypothetical habitability of Venus’ clouds, the assignments reveal a potential signature of anaerobic phosphorus metabolism (phosphine), an electron donor for anoxygenic photosynthesis (nitrite), and major constituents of the nitrogen cycle (nitrate, nitrite, ammonia, and N2).

Observations reveal end of summer Arctic sea ice extent is declining at an accelerating rate. Model projections underestimate this decline and continue to have a broad spread in forecasted September sea ice extent. This suggests some important summer processes, such as melt pond formation and evolution, may not be properly represented in current models. Melt ponds form on the sea ice surface as snow melts, and pools in low lying areas on the sea ice surface. The evolution of the ponds depends on snow depth, ice thickness, and surface conditions. Melt water may spread across a level surface, or be confined to depressions between sea ice ridges. Ponds decrease the albedo of the surface and enhance the positive ice albedo feedback, accelerating further melt. Until recently, Arctic-wide observations of individual melt ponds were not available. ICESat-2, a photon counting laser altimeter launched in 2018, provides high resolution detail of sea ice and snow topography due to its unique combination of a small footprint (~12 m) and high-resolution along-track sampling (0.7 m). The green laser (532 nm) is able to penetrate water, enabling melt pond depth measurements. We have developed methods to track the melt pond surface and bathymetry in ICESat-2 data to determine melt pond depth. We also track melt pond evolution through application of a sea ice classification algorithm to 10 m resolution Sentinel-2 imagery. The combination of these two datasets allows for an evolving, three-dimensional view of the melting sea ice surface. We focus on the evolution of summer melt on multiyear ice in the Central Arctic north of Greenland and Canada in 2020. Our findings are put in context of existing literature on melt pond depth, volume, and evolution. We also discuss our results in relation to the melt pond fraction north of the Fram Strait, where we expect different ice conditions in the vicinity of the 2020 MOSAiC field studies. Observational data products comprising melt pond fraction and pond depth are being developed for public distribution. These products may be of interest to those studying under-ice light and biology, as well as modelers who are interested in understanding the evolution of melt pond parameters for model initialization and validation.

Sediment grain size links sediment production, weathering, and fining from fractured bedrock on hillslopes to river incision and landscape relief. Yet, models of sediment grain size delivery to rivers remain unconstrained due to a scarcity of field data. We analyzed how bedrock fracture spacing and hillslope weathering influence landscape-scale patterns in surface sediment grain size across gradients of erosion rate and hillslope bedrock exposure in the San Gabriel Mountains (SGM) and northern San Jacinto Mountains (NSJM) of California, USA. Using ground-based structure-from-motion photogrammetry models of 50 bedrock cliffs, we showed that fracture density is ~5× higher in the SGM than the NSJM. 274 point count surveys of surface sediment grain size measured in the field and from imagery show a drainage area control on sediment grain size, with systematic downslope coarsening on hillslopes and in headwater colluvial channels transitioning to downstream fining in fluvial channels. In contrast to prior work and predictions from a hillslope weathering model, grain size does not increase smoothly with increasing erosion rate. For soil-mantled landscapes, sediment grain size increases with increasing erosion rates; however, once bare bedrock emerges on hillslopes, sediment grain size in both the NSJM and SGM becomes insensitive to further increases in erosion rate and hillslope bedrock exposure, and instead reflects fracture spacing contrasts between the NSJM and SGM. We interpret this threshold behavior to emerge in steep landscapes due to efficient delivery of coarse sediment from bedrock hillslopes to channels and the relative immobility of coarse sediment in fluvial channels.

The 2020 Mw 6.8 Elazig earthquake was the largest along the Eastern Anatolian Fault (EAF) in over a century, providing valuable insights into its rupture behavior. We use satellite geodesy and seismology to detail the mainshock rupture, postseismic deformation and aftershocks. The mainshock propagated mostly westwards at 2 km/s from a nucleation point on an abrupt 10° fault bend. Only one end of the rupture corresponds to an established EAF segment boundary, and the earthquake may have propagated into the slip zone of the 1874 M 7.1 Golcuk Golu earthquake. It exhibits a pronounced (80%) shallow slip deficit, only a small proportion of which is recovered by early aseismic afterslip. The slow rupture velocity, shallow slip deficit and low afterslip are characteristic of earthquakes hosted by faults of low-to-intermediate structural maturity, indicating that faults continue to evolve in important ways even as they accrue cumulative off sets of tens of kilometers