NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) laser altimeter launched in Fall 2018, providing an invaluable addition to the polar altimetry record generated by ESA’s CryoSat-2 radar altimeter. The simultaneous operation of these two satellite altimeters enables unique comparison studies of sea ice altimetry, utilizing the different frequencies and profiling strategies of the two instruments. Here, we use freeboard data from ICESat-2 to assess Antarctic snow freeboard retrievals from CryoSat-2. We first discuss updates made to a previously-published CryoSat-2 retrieval process and show how this Version 2 algorithm improves upon the original method by comparing the new retrievals to ICESat-2 in specific along-track profiles as well as on the basin-scale. In two near-coincident along-track profiles, we find mean snow freeboard differences (standard deviations of differences) of 0.3 (9.3) and 7.6 cm (9.6 cm) with 25 km binned correlation coefficients of 0.77 and 0.89. Monthly mean freeboard differences range between -2.9 (10.8) and 6.6 cm (16.8 cm) basin wide, with the largest differences typically occurring in Austral fall months. Monthly mean correlation coefficients range between 0.57 and 0.80. While coincident data show good agreement between the two sensors, they highlight issues related to geometric and frequency sampling differences that can impact the freeboard distributions.

Relating seismic anisotropy with mantle flow requires a good understanding of the rock’s microstructural evolution and the development of crystal preferred orientations (CPO), because plastic deformation of olivine is interpreted as the main cause for mantle seismic anisotropy. In this contribution, the influence of deformation history in the microstructure evolution and resulting seismic anisotropy is investigated by means of full-field numerical simulations at the microscale. We explicitly simulate the microstructural evolution of olivine polycrystalline aggregates during dynamic recrystallization up to high strain using the code VPFFT/ELLE (e.g. Griera et al., 2011; 2013; Llorens et al., 2016). Modeling results indicate that the evolution of a CPO is highly sensitive to the initial olivine fabric. When the initial fabric is formed by a random distribution of crystallographic orientations, there is a rapid alignment of the a-axes (or [100]) with the stretching direction of flow. However, when there is an initial CPO inherited from previous deformation, larger strains are required for the a-axes to become re-aligned with the stretching direction. Our numerical results agree with field and experimental observations (e.g. Boneh and Skemer, 2014; Skemer et al., 2012). The analysis of the seismic properties reveals that an increase of the strength of the initial inherited CPO produces a reduction of the azimuthal seismic anisotropy, compared to the case with an initial random fabric. It is concluded that the deformation history significantly influences the development of fabrics. Accordingly, seismic anisotropy interpretations must be carried out with caution in regions with complex deformation histories. References Boneh Y., Skemer P. 2014. EPSL, 406. Griera A, et al. 2011. Geology 39, 275-278. Griera A, et al. 2013. Tectonophysics 587, 4-29. Llorens, M.-G. et al. 2016 EPSL, 450, 233-242. Skemer P. et al. 2012. Geochemistry Geophysics Geosystems, 13:3.

Our presentation represents a brief overview of recent climatic and environmental changes over the Dry Lands of Northern Eurasia. The Dry Land Belt (DLB) in Northern Eurasia is the largest contiguous dryland on Earth. During the last century, changes here have included land use change (e.g., rapid virgin land development in the mid of the 1950s; cf. Figure 1), resource extraction, rapid institutional shifts (e.g., collapse of the Soviet Union), climatic changes, and natural disturbances. These factors intertwine, overlap, sometimes mitigate but sometimes feedback upon each other to exacerbate their synergistic and cumulative effects. Thus, it is important to document properly each of these external and internal factors and to characterize structural relationships among them in order to develop better approaches to alleviating negative consequences of these regional environmental changes. This paper addresses the climatic changes observed over the DLB in recent decades and outlines possible links of these changes (both impacts and feedbacks) with other external and internal factors of contemporary regional environmental change and human activities within the DLB.

Mesoscale convective systems (MCSs) are an important component of our hydrologic cycle as they produce prolific rainfall in the tropics and mid-latitudes. Recent advancements in high-resolution modeling show promise in representing MCSs in regional climate simulations. However, how well do these models represent the complex interactions between convective dynamics and microphysics in MCSs remain unknown. In this study, we take advantage of observations collected during the Midlatitude Continental Convective Cloud (MC3E) experiment to evaluate multi-scale aspects of MCSs in convection-permitting WRF model. We conducted three sets of month-long simulations with Morrison and P3 (1-ice and 2-ice categories) microphysics, respectively, at 1.8 km grid-spacing over the Southern Great Plains. MCSs in observations and simulations were tracked using a newly developed FLEXTRKR algorithm. About 15-20 MCSs were identified in the simulations, consistent with observations. All three simulations underestimate observed monthly total precipitation which are primarily from MCSs, suggesting the biases might be caused by large-scale forcings rather than microphysics. All simulated MCSs overestimate convective area and precipitation amount but underestimate stratiform rain area and precipitation. Simulated MCS convective updraft intensities are comparable with radar retrievals for moderate depths of convective cores, but are too strong for deep cores. The two P3 simulations have smaller mean ice mass aloft but more frequent heavy convective rain rate at the surface than the simulation with Morrison, agreeing better with observations (Figure 1). Simulated stratiform area ice mass in the upper troposphere are generally larger than radar retrievals, but the P3 2-ice category has relatively smaller bias. We will also use polarimetric radar 3-D rain water retrieval to further evaluate the vertical evolution of rainfall to explain differences in simulated surface precipitation.

Social Learning contributes as a guiding proposal for the joint intervention of the local actors and dissemination of methodologies and collaborative activities in socioenvironmental diagnoses. Its principles are active involvement, consultation and public access to participation. Several participatory tools have been developed and have been applied within the principles of Social Learning, such as local socioenvironmental agendas, action research, role playing; world café, participatory monitoring of the streams and socioenvironmental mapping. This article presents the last one applied in different contexts and with different groups of social actors, always aiming to elaborate a participatory diagnosis of the place and reality to identify the wicked problems. Socioenvironmental mapping is a didactic-pedagogical resource used to reflect and rethink about the place. It contributes to elaborate a diagnosis of the local reality and it subsidizes the reflection on the forms of the land use and occupation and its implications for the quality of life of its inhabitants, fostering discussions, possibilities of actions to solve problems and conflicts to improve the quality of life in communities. The map is a product of collective and collaborative construction of the participants. It contributes to transform information into knowledge and establish a bridge between scientific and local knowledge. Consider the following procedures: a) the reality in which the individual lives and how he deals with his immediate environment and his understanding of it, as a starting point; b) the possibility of re-elaborating the individual’s initial understanding of his / her place; c) the way to the development of different types of knowledge for the construction of more elaborate and more critical knowledge. We have applied this methodology with teaching formation, social control and conservation area with positive results of empowering the communities.

We evaluate the mass balance of the Russia High Arctic Archipelago between April 2002 and August 2016 employing independent estimates obtained using time-variable gravity from the NASA/DLR GRACE mission and satellite altimetry data from the NASA ICESat and the ESA CryoSat-2 missions. We present a new algorithm designed to derive ice elevation change maps using altimetry data and we evaluate its performance over the region of interest. Gravimetric and Altimetric observations provide consistent results and show that over the period under analysis, glaciers in the region have lost mass at a rate of 15 +/-7 Gt/yr corresponding to a sea level contribution of 0.039 mm/yr. The mass loss increased after 2010, reaching a maximum rate of 25 +/-7 Gt/yr between 2010 and 2016. The increased mass loss was associated with high thinning rates at low elevations (below 500 m), with marine-terminating glaciers thinning significantly faster than those terminating on land. The mass loss process was associated to a shift in climatic conditions in the region due to enhanced atmospheric and ocean temperatures and decreased sea ice concentrations. These results indicate that glaciers in the region are sensitive to variations of both climatic mass balance and ice discharge.

Solar photovoltaic (PV) energy is one of the most preferred and fastest growing emission-free energy sources in Australia. However, the dependency of PV generation on climatological factors can impact future power generation. Considering the future large-scale deployment of PV systems, accurate climate information is essential for PV site selection, stable grid regulation, planning and energy output projections. In this study, the effect of projected changes in shortwave downwelling radiation, temperature and wind speed on the performance of PV systems over Australia is examined using regional climate projections. Results indicate a small, but significant decline in future PV potential over Australia due to reduced insolation and increased temperature. Under a high emission scenario, the cell temperature is predicted to increase 2.5°C by 2070 leading to increased periods of significantly reduced cell efficiency (6-13 days/year) mostly in Western and central Australia.

ICESat-2 carries NASA’s next-generation laser altimeter, ATLAS, (Advanced Topographic Laser Altimeter System), designed to measure changes in ice sheet height, sea ice freeboard, and vegetation canopy height. ATLAS contains a photon-counting lidar which transmits green (532-nm) pulses at 10kHz. Each pulse is split into 3 pairs of beams (one strong and one weak). Approximately 1014photons per pulse travel from ATLAS through the atmosphere to reflect off the Earth’s surface. Some return back into the ATLAS telescope where they are recorded. Photons from sunlight and instrument noise at the same wavelength are also recorded. The flight software time tags all photons within a 500m to 6 km range window and generates histograms. Using the histograms, it selects a telemetry window which varies from 20m over flat surfaces to hundreds of meters over rougher terrain. ATL03 contains the time, height (relative to the WGS-84 ellipsoid), latitude and longitude of every photon within the telemetry window. The basic challenge is to determine which of these photons were reflected off the surface. We have developed an algorithm that identifies these signal photons and assigns a confidence level (low, medium, or high) to each signal photon based on the signal to noise ratio. We present an overview of the signal identification algorithm and show the results on actual ICESat-2 data over ice sheet, sea ice, vegetated, and water surfaces. Higher level ATLAS products work with aggregations of the photons in order to determine the ellipsoidal height of the Earth, canopy height and structure, and other quantities of geophysical interest.

The growth of the marine internal boundary layer (MIBL, height ℎ𝑖 ) with the shore-normal distance 𝑥, is a topic of continuing interest because of its applications in coastal dispersion, offshore wind farm siting, coastal air-sea fluxes and in evaporative ducting. Available data on MIBL are only scarce, given the difficulty to measurements and variability of coastal winds. During Coupled Air-Sea Processes and Electromagnetic Research (CASPER)-West campaign, from September 27 to October 27, 2017, an array of instrumentation was deployed on the Californian coast at Point-Mugu and on the research vessel Sally Ride. A state-of-art triple Doppler Lidar system was used to map the flow field up to 500 m in height above sea level and to a distance of ~ 4 kilometers from the coast with a spatial resolution of 30 m. Triple Doppler Lidar provides simultaneous vertical profiles of all three velocity components in the atmospheric boundary layer. A 20 m flux tower was used to characterize the atmospheric surface layer, especially its stability. The temporal variability of MIBL growth measured by the triple Doppler Lidar near the coast every 15 minutes were synthesized by its offshore wind direction and atmospheric stability. Over 5 unique case-studies of MIBL offshore development provided some useful general conclusions on the MIBL growth. Measurements also from a state-of-art motion-stabilized coherent Doppler Lidar and microwave radiometer on Sally Ride also showed the growth of offshore internal boundary layer several kilometers from the coast.

Whole atmosphere models that fully capture the propagation of wave dynamics from lower to upper atmosphere are believed sufficient to reproduce the type of short-term variability in the neutral upper atmosphere that produces observed variations in ionospheric parameters. However, recent studies suggest that upper atmospheric observations are needed to accurately represent short-term variability in both planetary-scale mass transport and tidal behavior crucial to representing the structure of the thermosphere and the wind-dynamo coupling in the ionosphere. To address this, we use atmospheric specifications from the prototype High-Altitude Navy Global Environmental Model (HA-NAVGEM) from the ground to 92 km to nudge the Whole Atmosphere Community Climate Model extended version (WACCM-X) coupled to the Navy Highly Integrated Thermosphere Ionosphere Demonstration System (Navy-HITIDES) ionospheric model. The HA-NAVGEM data assimilation/forecast system is run in two configurations: a reference experiment for the time period December 2012-March 2013, where satellite-based middle atmospheric observations (SABER temperature retrievals; Aura MLS temperature, ozone, and water vapor retrievals; and SSMIS microwave radiances) are included between 20-90 km; and a perturbed experiment, during the same time period, in which the middle atmospheric observations are removed. The resulting nudged simulations using WACCM-X coupled to Navy-HITIDES are used to study the impact of upper atmospheric observations in reproducing the observed short-term variability in the thermosphere-ionosphere system, both in terms of the thermospheric structure and the ionospheric response via wind-dynamo coupling. The role of solar thermal and lunar gravitational tides is discussed, as well as the impact of observations on the weather of the day in the lower thermosphere.

Continental shelves are important land-ocean interfaces where natural and anthropogenic processes, as well as sediment geochemistry regulate the sequestration of organic matter (OM) in the sediment. In the Northern Gulf of Mexico, along the Louisiana shelf, the Mississippi River discharge asserts strong seasonal controls over primary production and sedimentary reserves of minerals. Recent studies have shown the importance of mineral-organic matter interactions in the sedimentary OM preservation, both of which are abundant in this region. Thus, the major objective of this work is to understand the spatial and temporal variability of the sediment organic carbon (OC) directly bound to the reactive iron (rFe) mineral phases such as goethite, ferrihydrite, lepidocrocite and hematite. Sediment samples were collected from five sites along the river plume during periods of low (August/September 2016) and high (May 2017) river discharge. Average rFe content in the top 20 cm of sediment was significantly higher at all sites in May (6.9 ±1.5 mg gdw-1) compared to August (4.3± 0.6 mg gdw-1), while particulate OC content in these sediments was higher in August (11.9 ± 3.7 mg gdw-1) compared to May (7.4± 4.7 mg gdw-1). However, the bulk OC bound to rFe in these sediments did not vary significantly between the two seasons and ranged between 2.3 - 3.4 mg gdw-1. Molar OC: Fe ratios in the OC associated with rFe ranged between 0.9-6.2, with higher ratios in the deeper sediment sections (5-20 cm) than at the top (0-5 cm). Our results indicate that 27- 32% of the total OC in sediment is associated with rFe phase and preserved in these recent shelf sediments. A combination of X-ray diffractometry and Fe-K Edge X-ray absorption near edge structure spectroscopy analyses were carried out to identify the mineralogical composition of rFe bound to the organic carbon in the sediments. Preliminary findings indicate that most of the iron is found as non-reactive iron in clay mineral smectite, but the dominant form of rFe associated with OC is goethite.

Timing errors are a notorious problem in seismic data acquisition and processing. We present a technique that allows such time shifts to be detected and corrected in a systematic fashion. The technique relies on virtual-source surface-wave responses retrieved through the crosscorrelation of ambient seismic noise. In particular, it relies on the theoretical time-symmetry of these time-averaged receiver-receiver crosscorrelations. By comparing the arrival time of the surface waves at positive time to the arrival time of the surface waves at negative time for a large a number of receiver-receiver pairs, relative timing errors can be determined in a least-squared sense. The time-symmetry of the receiver-receiver crosscorrelations, however, is contingent on a uniform surface-wave (noise) illumination pattern. In practice, the illumination pattern is often not uniform. We therefore show that weighting different receiver-receiver pairs differently in the inversion allows timing errors to be determined more accurately. The weights are based on the susceptibility of different receiver pairs to illumination-related travel-time errors. The proposed methodology is validated using both synthetic data and field data. The field data consists of recordings of ambient seismic noise by an array of stations centered around the tip of the Reykjanes peninsula, southwest Iceland (some of these stations exhibit time shifts of an unknown nature).

With datasets of Global Land Data Assimilation System (GLDAS) NOAH land surface model, GPCC monthly mean rainfall and NCAR/NCEP global monthly mean reanalysis from 1948 to 2010, by using methods of filtering, composite and linear regression and correlation, characteristics of Eurasian snow depth anomalies in El Niño mature winter, its influences on soil moisture after snow melting, and finally on East Asian summer monsoon are investigated, and the main conclusions are as follows: In El Niño mature winter, snow depth in regions of the Iranian Plateau, the northeast of Lake Balkhash and the southern Tibetan Plateau increase remarkably, so are the related snow melting and soil moisture. The above-mentioned three regions are identified as the key regions for snow depth to store and extend the El Niño signals. In spring, the snow begins to melt, and the soil moisture increases correspondingly, thus the El Niño signals are transmitted from winter snow depth to soil moisture in spring. As a result, sensible heat flux decreases and latent heat flux increases, and the atmospheric circulations are greatly influenced. The anomalous soil moisture in the Iranian plateau is most important for the East Asian summer monsoon in El Niño decaying summer, since it has similar impact pattern on the anomalous summer precipitation as the El Niño composite. The spring and summer soil moisture in both the southern Tibetan plateau and the northeast of Lake Balkhash increase simultaneously, which significantly contribute to the increased precipitation in North China. Therefore, to investigate and predict the East Asian summer monsoon variabilities by using El Niño signal, the roles of snow depth in storing and modulating El Niño impacts in those key regions should be considered.

We present a comparison of the detailed present-day crust to upper-mantle (400km) structure in the Western Mediterranean along two transects in Alboran and Algerian domains. The transect across the Alboran domain is NW-SE oriented crossing the Betics and the Alboran Basin and the northern margin of Africa between the Tell and Rif mountains. The Algerian domain transect is also NW-SE oriented crossing the Valencia Trough, the Balearic Promontory, the Algerian basin and ending in the Tell-Atlas Mountains in the northern margin of Africa. The structure is computed using integrated geophysical-petrological modelling tool (LitMod2D) which combines petrological, geochemical and geophysical dataset in a self-consistent framework. We model thermal, compositional, density and seismological structure, also incorporating slabs imaged by seismic tomography, constrained by simultaneously fitting elevation, gravity, geoid, surface heat flow and seismic tomography models to reduce the uncertainties in the modelling. Preliminary results suggest that crust is thickest beneath the Betics and thins beneath the Alboran basin within a distance of ~100 km. Farther SE, crust gradually thickens beneath the north margin of Africa, between Tell and Rif mountains over ~300 km distance. The LAB shows a similar trend though it is affected by the presence of the slab underneath Betics. For the Algerian domain transect, maximum crustal thickness occurs beneath the Tell-Atlas Mountains with noticeable variations across the Algerian basin, Balearic Promontory and Valencia Trough, the LAB showing a similar tendency. Comparing the modelled geometries suggests that both transects have opposite trends with the deepest Moho and LAB in the NW side of the Alboran transect and in the SE side of the Algerian transect, imposing important restrictions on the geodynamic evolution of the Western Mediterranean.

In the last decades, volcano monitoring capabilities have increased enormously, thanks to geochemical and geophysical airborne and surface measurements that have steadily improved their accuracy and time resolution. Such a wealth of data is routinely used to track volcanic unrest and eruption evolution, although precise causative links with underground processes are often missing. Modeling of magmatic and volcanic systems has also leaped forward, thanks to the increased availability of computer power and development of numerical models. Capturing the complexity of magmatic system evolution at all scales is nonetheless still a challenge: the crystal- and bubble-size processes need to be taken into account in order to resolve the reservoir-scale dynamics detected by the monitoring networks. We have developed a robust numerical model to solve the thermo-fluid dynamics of magmatic mixtures, that includes pressure-, temperature and melt composition-dependent, locally (space-time) defined properties and constitutive equations of multi-component magmas. The model has been applied to a variety of scenarios related to magma dynamics in underground volcanic systems, including magma arrival from depth into shallow reservoirs. Model results include the space-time evolution of density, pressure, velocity and composition within the domain, that can be used as sources of synthetic geodetic and seismic datasets, akin to those recorded by monitoring networks. The synthetic and monitoring time series can thus be compared and their similarities can be exploited to detect the underground dynamics causing well-defined time and spectral patterns: we are building a physically sound reference for the interpretation of volcanic unrest signals and their relationships with the deep magma dynamics. This approach has been successfully used to detect shallow magma arrival from strainmeter records at Campi Flegrei during the ongoing unrest phase; it is also being applied to evaluate how precise gravity surveys at Mount Etna can help in detecting any shift in the eruptive sequence.

Phosphorus (P) is hypothesised to be the main nutrient limiting forest productivity in tropical forests, but more recent evidence suggests that multiple nutrients could regulate forest functioning. Root functional trait expression represents a trade-off between maximising the acquisition of limiting resources and minimising root tissue construction and maintenance. Therefore, if the limiting soil nutrient supply is increased, plant investment in root biomass and nutrient uptake strategies should decrease. To test this hypothesis we investigated how fine root traits associated with nutrient acquisition responded to large-scale nutrient additions of nitrogen, phosphorus and cations in a slow-growing mature tropical forest established on low fertility soils in the Central Amazon. To evaluate short-term responses to nutrient addition 6 months after fertilisation commenced, we sampled young fine roots (<2mm diameter), measuring root biomass and productivity, root morphological traits (root diameter, specific root length, specific root area and root tissue density) and root phosphatase enzyme activity. We hypothesised that if tropical forests are P limited, responses to P addition would be strongest, resulting in i) a decrease in root production; ii) a shift in root morphology from acquisitive to more conservative traits by increased root diameter and decreased specific length and area and iii) decrease in the investment in phosphatase enzyme. As expected, root phosphatase activity decreased by ~13% with P addition. Among the root morphological traits, root diameter increased, mainly for the 0-10 cm soil layer, with the addition of cations and P, but there were no significant effects on other root morphological traits. Contrary to expectations, root productivity was >50% higher in plots where cations were added, with no effects of P addition. Although we found support for the hypothesis that P limits some aspects of plant functioning in this Central Amazon forest, the results also suggest that cations could play an important role in controlling the expression of root traits. We conclude that multiple nutrients may limit belowground process in Central Amazon forests and that even slow-growing tropical forest can respond very rapidly to changes in soil nutrient availability.

Lightning plays a major role in tropospheric oxidation, and its role on modulating tropospheric chemistry was thought to be emissions of nitrogen oxides (NOx). Recent field and laboratory measurements demonstrate that lightning generates extremely large amounts of oxidants, including hydrogen oxides (HOx) and O3. We here implement the lightning-produced oxidants in a global chemical transport model to examine its global impact on tropospheric composition. We find that lightning-produced oxidants can increase global mass weighted OH by 0.3-10%, and affect CO, O3, and reactive nitrogen substantially, depending on the emission strength of oxidants from lightning. Our work highlights the importance and uncertainties of lightning-produced oxidants, as well as the need for rethinking the role of lightning in tropospheric oxidation chemistry.

The cold and fresh upper water column of the Arctic Ocean (AO) is separated from warm and saline subsurface Atlantic Waters (AW) by the strong vertical stratification. Recent rapid declining of sea ice and increasing storms in the region makes the AO more vul nerable to the vertical mixing. Here we report significant impact of storms on the re-distribution of AW in an Arctic fjord, Kongsfjorden, using the hydrography observations and numerical simulations. During storm events high-frequency currents and near-inertial waves are observed which induce large vertical shear in the water column. This leads to enhanced vertical mixing, re-distributing subsurface AW and warming of the mixed layer. Near inertial wave induced mixing also leads to enhanced primary productivity in the upper water column. Numerical experiments further confirm the role of storms in inducing vertical mixing and resulting mixed layer warming. This study also points out the possible impact of near-inertial waves on the primary productivity in the fjords in ice-free condition. The findings of the study indicates that storm induced vertical re-distribution of AW in the AO can become more important in future with declining sea ice cover and increasing storm activity in the Arctic.