bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the controlling factors of Ultra-Low Frequency waves and their penetration during geomagnetic storms
Authors: Rae Jonathan , Murphy Kyle , Watt Clare , Sandhu Jasmine , Wharton Samuel , Degeling Alex , Georgiou Marina , Forsyth Colin , Bentley Sarah , Staples Frances , Shi Quanqi
Published: March 2020

Wave-particle interactions play a key role in radiation belt dynamics. Traditionally, Ultra-Low Frequency (ULF) wave-particle interaction is parameterised statistically by a small number of controlling factors for given solar wind driving conditions or geomagnetic activity levels. Here, we investigate solar wind driving of ultra-low frequency (ULF) wave power and the role of the magnetosphere in screening that power from penetrating deep into the inner magnetosphere. We demonstrate that, during enhanced ring current intensity, the Alfvén continuum plummets, allowing lower frequency waves to penetrate deeper into the magnetosphere than during quiet periods. With this penetration, ULF wave power is able to accumulate closer to the Earth than characterised by statistical models. During periods of enhanced solar wind driving such as coronal mass ejection driven storms, where ring current intensities maximise, the observed penetration provides a simple physics-based reason for why storm-time ULF wave power is different compared to non-storm time waves. We demonstrate statistically that the ring current plays a pivotal role in allowing ULF wave energy to access the inner magnetosphere and show a new parameterisation of ULF wave power for radiation belt research purposes that is specifically tuned for geomagnetic storms.
Climate feedbacks in the Black Sea region
Authors: Matov Mirna , Peneva Elisaveta
Published: March 2020

The Black Sea is a large deep water basin on the border between European and Asian continents lying in the continental mid-latitude climate zone. Due to the prevailing westerlies during the year its climatic influence is better pronounced in the eastern border areas, however the sea is an important climatic factor for all borderline countries (Bulgaria, Romania, Ukraine, Russia, Georgia and Turkey). The open plane in north direction enables the propagation of the Siberian High influence in winter. From the other side, the Mediterranean Sea influence is significant through the Mediterranean cyclones passing frequently the area.

The impact of the Black Sea on the surrounding area is analyzed combining data from several different sources: atmospheric data from climate reanalysis and regular synoptic measurements in coastal meteorological stations, marine observations from in situ autonomous profilers and satellite data on ice coverage in winter time. The aim is to investigate the interannual-to-decadal variability of the thermal regime and the exchange of heat between atmosphere and sea. In addition, the relation to the intensity of the main climate centers of action (Siberian High and Mediterranean Low) is analyzed. The winter severity is defined in the different zones around the sea through the number of cold days and the connection with the sea temperature is studied.
Pb, Nd, Sr isotopic composition of the Mesoproterozoic mafic intrusions (Udzha paleorift, Northern Siberia)
Authors: Shpakovich Lidiia , Malyshev Sergey , Savatenkov Valeriy
Published: March 2020

Geodynamic reconstructions are largely based on information contained in mafic igneous rocks, including dykes and sills. The age and isotope-geochemical characteristics of such rocks are inevitable for understanding of geodynamic history of the Proterozoic cratons. The regions in Siberian Craton, where Precambrian mafic dyke swarms are known are following: Anabar Shield and Olenek Uplifts, Aldan-Stanovoi Shield, SE area of Siberian Craton, and smaller Uplifts on the SW margin of Siberian Craton.

The Udzha paleo-rift is located in the northern part of Siberian Craton between Anabar and Olenek Uplifts is also associated with mafic dyke swarm. These dykes cross-cut the pre-Neoproterozoic sedimentary successions. The age of the largest dyke in Udzha paleo-rift (Great Udzha Dyke) presented by medium-grained dolerite was determined to be 1386 ± 30 Ma (Malyshev et al., 2018).

We present new data of Sr, Nd and Pb isotopic composition on the Udzha paleo-rift dykes, determined by TIMS. The initial isotopic composition of Pb in the dykes was obtained using the leaching method by Savatenkov et al., 2019. The Sr isotopic composition of the dykes demonstrates substantial variation (εSr varies from 8.4 to 110.4). We do not consider this fact as a result of crust contamination, because Nd isotopic composition does not vary significantly (εNd varies from -1.4 to 0.7). Obtained results indicate that initial for the Udzha paleo-rift dykes melts were generated from two mantle reservoirs of DM and EMII-type. The initial Pb isotopic composition of the dykes reveals EMII source participation in the melts generation too (206Pb/204Pb varies from 16.133 to 16.266, 207Pb/204Pb varies from 15.343 to 15.458). The presence of enriched component is likely associated with lithospheric mantle, metasomatized by fluids, derived from subducted terrigenous material.

The studies were supported by the Russian Science Foundation project No. 19-77-10048.

References

Malyshev, S. V., Pasenko A. M., Ivanov A. V., Gladkochub D. P., Savatenkov V. M., Meffre S., Abersteiner A., Kamenetsky V. S. & Shcherbakov V. D. (2018): Geodynamic Significance of the Mesoproterozoic Magmatism of the Udzha Paleo-Rift (Northern Siberian Craton) Based on U-Pb Geochronology and Paleomagnetic Data. – Minerals, 8(12), 555

Savatenkov V. M., Malyshev, S. V., Ivanov A. V., Meffre S., Abersteiner A., Kamenetsky V. S., Pasenko A. M. (2019): An advanced stepwise leaching technique for derivation of initial lead isotope ratios in ancient mafic rocks: A case study of Mesoproterozoic intrusions from the Udzha paleo-rift, Siberian Craton. – Chemical Geology, 528, 119253
North Atlantic decadal variability in a coupled global model and relevance to observations
Authors: Kushnir Yochanan , Lee Dog Run (Donna) , Ting Mingfang
Published: March 2020

This study focuses on the decadal time scale variability of the North Atlantic Ocean-Atmosphere system. This time scale is relevant to preparedness and adaptation as society becomes increasingly threatened by the adverse impact of anthropogenic climate change. North Atlantic decadal climate variability has been related to interaction between the subpolar and subtropical gyre and manifested in persistent multi-year SST and heat content anomalies and shifts in the latitude of the Gulf Stream/North Atlantic Current (GS/NAC). We apply a space-time analysis to annual, North Atlantic, upper ocean heat content (OHC) anomalies from the National Center for Atmospheric Research (NCAR), Community Earth System Model (CESM) long pre-industrial control run. The analysis reveals decadal anomalies associated with two patterns: a dipole centered on the GS/NAC, in the western side of the Basin that oscillates quasi-regularly, reversing its sign every of 6 to 7 years. The second pattern is centered in the eastern side of the basin and lags the first by about 5 years, implying that heat is transported between the subtropical and subpolar gyres. Analysis of surface windstress anomalies connected with these OHC fluctuations implies that the latter are forced by stochastic atmospheric variability. Further analysis compares the model patterns with observations to determine their relevance and predictability and assesses their response to climate change.
Recent vegetation composition and above ground biomass change in north-eastern Siberia
Authors: Shevtsova Iuliia , Kruse Stefan , Heim Birgit , Herzschuh Ulrike
Published: March 2020

Climate change is especially prominent in Arctic and sub-Arctic regions. Therefore, it is of great importance to investigate ecosystem processes and the dynamics of its components in the Siberian high latitudes. Plant biomass assessment is essential for estimating carbon stocks and further carbon balance and wildlife habitat modeling. Our study region in central Chukotka (north-eastern Siberia) is one of the least investigated sub-Arctic regions in terms of vegetation dynamics. We quantified changes in four vegetation classes: (1) larch closed-canopy forest, (2) forest tundra and shrub tundra, (3) graminoid tundra, and, (4) prostrate herb tundra and barren areas. We used Landsat spectral indices (Normalised Difference Vegetation Index (NDVI), Normalised Difference Water Index (NDWI), Normalised Difference Snow Index (NDSI)) to map the vegetation classes in four focus areas in 2000/2001 and 2016/2017. In 2016, we collected field data on foliage projective cover (percentage cover) of dominant taxa from 52 sites along the tundra–taiga gradient. We applied constrained ordination for coupling projective cover with corresponding Landsat spectral indices from 2016/2017. Ordination scores were used in a k-means classification. We inferred significant shrubification in the tundra–taiga zone (20%) and in the northern taiga (40%), as well as notable tree infilling in the northern taiga (9%), and, no significant changes in the treeless tundra area. To estimate carbon stocks and its changes within and between differentiated vegetation classes, we aim to upscale above ground biomass across tundra, tundra-taiga and northern taiga zones and derive above ground biomass change for the 15 investigated years. In 2018, another expedition took part to this region with new 38 sites at witch we described projective cover and representatively harvested total above ground biomass (dominant taxa and rest). This data can be projected in the created previously ordination space with the use of projective cover similarities. Using interpolation, we plan to predict above ground biomass  in the whole ordination space. We will further use Landsat data and interpolation results to produce above ground biomass maps for the four focus areas in central Chukotka and derive difference maps from 2000/2001 to 2016/2017.
Assimilation of Aerosol Observations in the NASA GEOS model
Authors: Buchard Virginie , da Silva Arlindo , Holdaway Dan , Todling Ricardo
Published: March 2020

In the GEOS near real-time system, as well as in MERRA-2 which is the latest reanalysis produced at NASA’s Global Modeling Assimilation Office (GMAO), the assimilation of aerosol observations is performed by means of a so-called analysis splitting method. The prognostic model is based on the GEOS model radiatively coupled to GOCART aerosol module and includes assimilation of bias-corrected Aerosol Optical Depth (AOD) at 550 nm from various space-based remote sensing platforms.

Along with the progress made in the JCSDA-Joint Effort for Data Assimilation Integration (JEDI) framework, we have developed a prototype including GEOS aerosols as a component of the JEDI framework. Using members produced by the GEOS hybrid meteorological data assimilation system, we are updating the aerosol component of our assimilation system to a variational ensemble type of scheme. In this talk we will examine the impact of replacing the current analysis splitting scheme with this new approach. By including the assimilation of satellite-based single and multi-channel retrievals; we will discuss the impact of this aerosol data assimilation technique on the 3D aerosol distributions by means of innovation statistics and verification against independent datasets such as the Aerosol Robotic Network (AERONET) and surface PM2.5.
Development and evaluation of the xGEOID20 Digital Elevation Model at NGS
Authors: Krcmaric Jordan
Published: March 2020

The U.S. National Geodetic Survey (NGS), an office of the National Oceanic and Atmospheric Administration (NOAA), will release a new vertical datum in 2022, the North American-Pacific Geopotential Datum of 2022 (NAPGD2022). This new datum will be based on a high degree spherical harmonic model of the Earth’s gravitational potential, and will yield a geoid undulation model (GEOID2022) to calculate orthometric heights from GNSS-derived ellipsoid heights.

In preparation for the new vertical datum, NGS has computed annual experimental geoid models (xGEOID) since 2014. This year’s xGEOID model (xGEOID20) will use an updated digital elevation model (DEM) composed of TanDEM-X, 3DEP, MERIT, and other DEMs. The DEMs are merged together to create a seamless elevation model across the extent of the xGEOID20 model. The accuracy of the merged DEM is tested using independent datasets such as GPS on benchmarks and Icesat-2. The effect of the updated DEM on the geoid model is also determined by comparing geoid models computed with previous DEMs to the new xGEOID20 model, and with comparisons to the NGS Geoid Slope Validation Survey lines.
Tracking water pathways and origins in cranberry production: Isotope hydrology application
Authors: Gadomski Jenifer , Gumiere Silvio , Gumiere Thiago , Bordeleau Genevieve , Rousseau Alain
Published: March 2020

New scientific advances based on integrating water management approaches have been developed in order to reduce the environmental footprint. Cranberry production is one of the most influential cultures in Canada, where water is substantial for irrigation, harvesting, and frost control. The cranberry farms are considered closed-circuits. Water is mainly recycled in large pools, increasing the risk of accumulation of chemical substances affecting the quality of irrigation water. The use of isotopic geochemistry provides an additional layer of information for studying hydrological phenomena in agriculture.

The main objective of this project is to identify the sources and sinks of the water in a typical cranberry farm with the help of isotopic hydrology technics and groundwater surveys.

Water samples for stable isotope of the water molecule analysis (16O, 17O, 18O, 1H, 2H)  were collected during the growing season from May to September (from 2017 to 2020). Preliminary results have shown that isotope hydrology technics can be used to trace the water pathway is a cranberry farm by using the mixing model. 

These results can help to implement integrated water management procedures helping to increase fruit yields and to reduce environmental impact. Isotope mixing model also makes it possible to assess water losses by infiltration into the aquifers and by evaporation.
Sensitivity of tides and net water transport in an estuarine network to river discharge, network geometry and sea level rise
Authors: Wang Jinyang , de Swart Huib
Published: March 2020

Quite a number of estuaries are characterised by a complex network of branching channels, in which the water motion is primarily driven by tides and river discharge. Examples are the Berau estuary (Indonesia), the Pearl estuary (China) and the Yangtze estuary (China). Knowledge about tides are required for construction of dikes/harbours, while knowledge about net water transport is important for agriculture, fresh water supply to cities and for quantifying transport of sediment, nutrients and etc.

In this contribution, we present a generic, weakly nonlinear 2DV estuarine network model to study tides and net water transport and to understand the dependence of their along-channel and vertical structure on geometric characteristics and sea level changes. The model will be applied to the Yangtze Estuary for different situations, such as the wet and dry season, with and without a shortcut channel and sea level rise for scenarios for the coming 50 to 100 years.

It will be demonstrated that, for the current conditions, the model results are in good agreement with observations. Both tidal amplitude and current are weaker during the wet season than that during the dry season and the reason for these changes will be explained in terms of river-tide interactions. Effects of local changes in geometry are investigated by creation of a shortcut channel between two main channels. Results show that changes in tides are merely local, but they can be rather strong. Sea level rise (up to 2 meters) causes tides to increase, mainly as a consequence of less friction resulting from larger water depth. Net water transport turns out to be less sensitive to geometry and sea level rise compared to tides.
Tropical precipitation–buoyancy relationship in Convectively Coupled Waves over South America region
Authors: Mayta Victor , Adames Angel
Published: March 2020

In this work, the tropical wave precipitation-buoyancy relationship is revisited by analyzing 4-times daily wave-filtered brightness temperature, reanalysis, and radiosonde datasets over tropical South America during the wet season. Prior studies demonstrated that an integrated measure of buoyancy well-diagnoses precipitation over land and ocean. However, it is an open question whether the buoyancy-based approach can yield a robust relation to precipitation for equatorial wave disturbances. To advance our understanding of this relationship, a comprehensive analysis of their vertical thermodynamic structure and potential interactions with the basic state is also presented. An emphasis is placed on understanding the convection coupling mechanism in convectively coupled Kelvin and inertia-gravity waves. It will be shown that buoyancy is a better predictor of convection for these disturbances than the often-used moist static energy (MSE). Examination of this discrepancy reveals that a cooling of the lower troposphere by gravity wave motions, which reduces MSE, is key to the production of precipitation in these disturbances.
A European groundwater model with variable aquifer thickness derived from spectral analyses of baseflow
Authors: Pujades Estanislao , Houben Timo , Di Dato Mariaines , Kumar Rohini , Attinger Sabine
Published: March 2020

Large-scale groundwater models are needed for assessing impacts of global changes, such as the “Global Warming”, and adapt the groundwater management strategies to ensure its availability. However, the construction of these models presents numerous difficulties, among which the lack of data concerning the properties (hydraulic parameters and geometries) of the subsurface is the most problematic. Although it is possible to find data concerning the hydraulic parameters of the soil (hydraulic conductivity and porosity), there is no realistic information about the saturated aquifer thickness which contributes to the active part of the flow regime. This thickness, which can be named “effective thickness”, is of paramount importance to improve the representativeness of large-scale groundwater models.

Commonly, a constant “effective thickness” is assumed for global models, which provides not a realistic boundary condition. Here, we propose a new approach based on spectral analyses of the baseflow in combination with hydraulic conductivity values to derive the spatial distribution of “effective thickness”. The calculated “effective thickness” can be used to build 2D groundwater models using a transmissivity field or to constrain the thickness in 3D models. The effectiveness of this approach is tested here by constructing Europe-wide groundwater. The representativeness of the model is improved by coupling off-line a mesoscale hydrological model (mHM), which computes near-surface water processes, and the deep groundwater simulation using the numerical model of OpenGeoSys.We demonstrate the implications of our study in conducting large-scale groundwater simulations across Europe for providing continental scale assessment of the impacts of global changes on groundwater system and discussing about the adaptation of different water management strategies affecting the regional groundwater system.
Nonstationary lagged relationships between the Arctic and the midlatitudes
Authors: Kolstad Erik W. , Screen James A. , Årthun Marius
Published: March 2020

Statistical relationships between climate variables are good source of seasonal predictability, but can we trust them to be valid in the future? In two recent papers, we investigated the stationarity of some well-known lagged relationships. The predictors were Arctic sea surface temperatures (SSTs) and sea ice cover during autumn, and the predictands were the North Atlantic Oscillation (NAO) and European temperature in winter. The reason for studying these variables was that in recent decades, reduced sea ice and above-normal SSTs in autumn have often preceded negative NAO conditions and cold temperatures in Northern Europe in the following winter. When we looked further back in time, however, we found that the relationships between SST/ice and NAO/temperatures have been highly changeable and sometimes even the complete opposite to that seen recently. One key finding was that, according to two 20th century reanalyses, the strength of the negative lagged correlation between Barents Sea SST anomalies in fall and European temperature anomalies in winter after 1979 is unprecedented since 1900. An analysis of hundreds of simulations from multiple climate models confirms that the relationships vary with time, just due to natural climate variability. This led us to question the causality and/or robustness of the links between the variables and to caution against indiscriminately predicting wintertime weather based on Arctic sea ice and SST anomalies.
Absolute metal concentrations after calibrating high resolution XRF core scanner data from highly polluted marine deposits offshore Portmán Bay and Barcelona, Spain
Authors: Cerdà-Domènech Marc , Frigola Jaime , Sanchez-Vidal Anna , Canals Miquel
Published: March 2020

X-ray fluorescence core scanners (XRF-CS) allow rapid, non-destructive and continuous high-resolution analyses of the elemental composition of sediment cores. Since XRF-CS analyses are usually performed in fresh untreated materials, elemental intensities can be affected by the physical properties of the sediment (e.g. pore water content, grain size, sediment irregularities and changes in matrix) and the selected excitation parameters. Accordingly, the records of the measured elemental intensity cannot be considered quantitative. Nonetheless, these data can be converted to quantitative data through a linear regression approach using a relatively small number of discrete samples analyzed by techniques providing absolute concentrations. Such conversion constitutes a powerful tool to determine pollution levels in sediments at very high resolution. However, a precise characterization of the errors associated with the linear function is required to evaluate the quality of the calibrated element concentrations.

Here we present a novel calibration of high-resolution XRF-CS for Ti, Mn, Fe, Zn, Pb and As measured in heavily contaminated marine deposits. Three widely applied regression methods have been tested to determine the best linear function for XRF data conversion, which are: the ordinary least-squares (OLS) method, which does not consider the standard error in any variable (x and y), the weighted ordinary least-squares (WOLS) method, which considers the weighted standard error of the vertical variable (y), and the weighted least-squares (WLS) method, which incorporates the standard error in both x and y variables.

The results, derived from the analysis of metal-polluted sediments from offshore Portmán Bay and Barcelona, in the Mediterranean Sea off Spain, demonstrate that the applied calibration procedure improves the quality of the linear regression for any of the three regression methods (OLS, WOLS, and WLS), thus increasing correlation coefficients, which are higher than r2=0.94, and reducing data deviation from the linear function. Nonetheless, the WLS appears as the best regression method to minimize errors in the calibrated element concentrations. Our results open the door to use calibrated XRF-CS data to evaluate marine sediment pollution according to the sediment quality guidelines (SQG) with errors lower than 0.4% to 2% for Fe, 1% to 7% for Zn, 3 to 14% for Pb, and 5% to 16% for Mn, which highlight the robustness of the calibration procedure here presented. Our study incorporates and evaluates for the first time the analytical and statistical errors of XRF-CS data calibration, and evidences that the errors of the calibrated element concentrations must be properly assessed in future calibration efforts.
Growth of carbonate platforms controlled by salt tectonics (Northern Calcareous Alps, Austria)
Authors: Strauss Philipp , Ruh Jonas , Huet Benjamin , Granado Pablo , Muñoz Josep Anton , Pelz Klaus , König Michael , Roca Eduard , Wilson Elizabeth P
Published: March 2020

The Mid Triassic section of the Northern Calcareous Alps (NCA) is dominated by carbonate platforms, which grew diachronously on the Neo-Tethys shelf beginning in the Middle Anisian and ending in Lower Carnian times. The platforms grew isolated in previous deeper marine settings with high growth rates reaching 1.5 to 2 mm per year. The concept of self-controlled growth of carbonate systems on salt changes the understanding of Mid-Triassic NCA sedimentology. Conceptual models of the carbonate platform growth were done based on field observations, construction of cross-sections and subsidence analysis of selected carbonate mini-basins. To satisfy the observed boundary conditions of platforms growth in respect of timing, water depth and basin evolution, fast accumulation rates have to be assumed best represented by salt deflation and down-building of carbonate minibasins. A feedback loop of carbonate growth (creating a load gradient) and subsidence by salt evacuation initiates once the pre-kinematic layer reaches the sea level and the first layer of carbonate is produced. An initial phase of fast carbonate aggradation ends once the salt below the platform is fully evacuated and the minibasin is primary welded.

To further analyse and quantify boundary conditions necessary for the observed carbonate mini basin evolution, a series of thermo-mechanical numerical experiments were conducted. The density and rheological parameters for rock salt applied in the experiments were mainly gathered from observations and mechanical experiments on salt from salt mines and from an exploration well by OMV in the Vienna Basin. The numerical simulations essentially support the concept of down-building carbonate platforms. Self-controlled growth of carbonate systems on salt allows a completely new perspective to understand Mid-Triassic NCA carbonate platforms and their boundary conditions, such as the accumulation of thick carbonates (>1.5 km) without basement faulting, the isolated growth of platforms, or the transition of aggradational to progradational growth.
Tidal processes and their spatial and temporal variability in the mid-field Guadalquivir ROFI
Authors: Serrano Maria Angeles , Díez-Minguito Manuel , Ortega-Sánchez Miguel , Losada Miguel Ángel
Published: March 2020

In the Region Of Freshwater Influence (ROFI), located between sea exposure and estuary, characteristic physical processes of both estuarine and shelf seas overlap and impact on shelf circulation, sediment transport and ecosystem (Simpson, 1997). Although freshwater discharge typically exhibits the highest variability (Horner-Devine et al., 2015), this work focus on the tidal variability within the ROFI, which is often overlooked. This work addresses the spatial and temporal variability of tidal elevations and currents at the mid-field Guadalquivir ROFI (SW Spain), which is semidiurnal in character. Observations from five current-meter profiles, which were moored pointing upwards from June 2008 to December 2009 are analyzed. These instruments were placed along an arc, from south to north, and closing the estuary mouth.  

 

The analysis of the observations indicates that tides in the Guadalquivir ROFI have a close-to standing wave behavior. This is induced by the reflection at the continental margin of the northward-propagating tidal Kelvin wave. Regarding the M2 and M4 tidal constituents, which are relevant for residual sediment transport, their relative phase difference shows that, although the inner estuary is flood-dominant, in the mid-field ROFI zone ebb currents are slightly stronger than flood currents. Fortnightly variations are observed in the ratio of the M4 and M2 tidal amplitudes. Remarkably, the minimumvalues occur during the transition periods from neap to spring tides, whereas the maximum values are observed during neap tides. These results might suggest that there is still some influence of the tidal jet in this region.

 

Regarding the vertical structure of tidal currents, the M2 inclination varies with depth, being maximum near the bottom at all moorings. Tidal currents inclination also varies with time in the southern part of the ROFI. Moreover, in the southern part of the ROFI, current ellipses in the upper layer of the water column rotate clockwise whereas near the bottom currents rotate anti-clockwise, as revealed by the sign of the eccentricity. However, the eccentricity of tidal ellipses is uniform throughout the water column in the northern part of the ROFI. This along-coast variability of the vertical structure of the tidal ellipses suggests that the buoyant outflow circulates preferentially southwards, most likely driven by the prevailing winds.
Water Mass Characteristics and Distribution Adjacent to Larsen C Ice Shelf, Antarctica
Authors: Hutchinson Katherine , Deshayes Julie , Sallee Jean-Baptiste , Dowdeswell Julian , de Lavergne Casimir , Ansorge Isabelle , Luyt Hermann , Henry Tahlia , Fawcett Sarah
Published: March 2020

The physical oceanographic environment, water mass mixing and transformation in the area adjacent to Larsen C Ice Shelf (LCIS) are investigated using hydrographic data collected during the Weddell Sea Expedition 2019. The results shed light on the ocean conditions adjacent to a thinning LCIS, on a continental shelf that is a source region for the globally important water mass, Weddell Sea Deep Water (WSDW). Modified Weddell Deep Water (MWDW), a comparatively warmer water mass of circumpolar origin, is identified on the continental shelf and is observed to mix with local shelf waters, such as Ice Shelf Water (ISW), which is a precursor of WSDW. Oxygen measurements enable the use of a linear mixing model to quantify contributions from source waters revealing high levels of mixing in the area, with much spatial and temporal variability. Heat content anomalies indicate an introduction of heat, presumed to be associated with MWDW, into the area via Jason Trough. Furthermore, candidate parent sources for ISW are identified in the region, indicating the potential for the circulation of continental shelf waters into the ice shelf cavity. This highlights the possibility that offshore climate signals are conveyed under LCIS. ISW is observed within Jason Trough, likely exiting the sub-ice shelf cavity en route to the Slope Current. This onshore-offshore flux of water masses links the region of the Weddell Sea adjacent to northern LCIS to global ocean circulation and Bottom Water characteristics via its contribution to ISW and hence WSDW properties. 

What remains to be clarified is whether MWDW found in Jason Trough has a direct impact on basal melting and thus thinning of LCIS. More observations are required to investigate this, in particular direct observations of ocean circulation in Jason Trough and underneath LCIS. Modelling experiments could also shed light on this, and so preliminary results based on NEMO global simulations explicitly representing the circulation in under-ice shelf seas, will be presented. 
Vertical Atmospheric Coupling during the September 2019 Antarctic Sudden Stratospheric Warming
Authors: Yamazaki Yosuke , Matthias Vivien , Miyoshi Yasunobu , Stolle Claudia , Siddiqui Tarique , Kervalishvili Guram , Laštovička Jan , Kozubek Michal , Ward William , Themens David , Kristoffersen Samuel , Alken Patrick
Published: March 2020

A sudden stratospheric warming (SSW) is an extreme wintertime meteorological phenomenon occurring mostly over the Arctic region. Studies have shown that an Arctic SSW can influence the whole atmosphere including the ionosphere. In September 2019, a rare SSW event occurred in the Antarctic region, following strong wave-1 planetary wave activity. The event provides an opportunity to investigate its broader impact on the upper atmosphere, which has been largely unexplored in previous studies. Ionospheric data from ESA's Swarm satellite constellation mission show prominent 6-day variations in the dayside low-latitude region during the SSW, including 20-70% variations in the equatorial zonal electric field, 20-40% variations in the electron density, and 5-10% variations in the top-side total electron content. These ionospheric variations have characteristics of a westward-propagating wave with zonal wavenumber 1, and can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi-6-day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard NASA's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere at this time, which is one of the strongest in the record. These results suggest that an Antarctic SSW can lead to ionospheric variability by altering middle atmosphere dynamics and propagation characteristics of large-scale waves from the middle atmosphere to the upper atmosphere.
Multi-Array Multi-Phase Back-Projection: Improving the imaging of earthquake rupture complexities
Authors: Vera Felipe , Tilmann Frederik , Saul Joachim
Published: March 2020

We present a back-projection method capable of being parameterized with multiples arrays. The rupture imaging is weighted to restrict uncertainties induced by non-symmetric azimuthal coverage of seismic arrays. The strategy also exploits the differences in time delays between P and depth phase (pP) waveforms by assuming them as proxies of the rupture that can be simultaneously back-projected. Surprisingly, this helps to improve the final results, even when depth phases overlap with the direct arrivals due to the rupture time exceeding the pP-P delay. Thus, the approach heightens the spatiotemporal resolvability enough to image rupture complexities. The rupture image of two large events demonstrates its robustness. The first one is the 14 November 2007 Mw 7.7 Tocopilla earthquake in northern Chile. The high-frequency rupture (0.5 - 2.0 Hz) encircles two asperities while the short-period energy radiated predominates up-dip of the coseismic slip. We propose the contribution of asperity rupture complexities and along-dip barriers to high-frequency emissions beyond the megathrust frictional structure. The second one is the Mw 7.5 Palu strike-slip earthquake, which occurred on 28 September 2018 in Sulawesi island. The back-projection reveals a prominent supershear rupture at a speed of 4.5 km/s. The result correlates with space geodesy data highlighting the successful recovery of fault structures. Finally, we discuss the potential and challenges of automating this analysis for near-real-time applications, including near-source back-projection with strong-motion data.
Bishop coefficients in elastic and plastic regimes of unsaturated soils
Authors: Pereira Jean-Michel , Dangla Patrick
Published: March 2020

The definition of a suitable effective stress to model the behaviour of unsaturated soils has been questioned for decades. This issue is still a matter of debate in the community. Recently, Alonso et al. (2010) have shown that this coefficient might depend on the microstructure of the soil and that fine plastic soils are characterised by a Bishop coefficient tending to deviate from the commonly used assumption according to which it is equal to the degree of saturation. On the other hand, Coussy et al. (2010) have shown that this coefficient deviates from the latter assumption if the isodeformation of all pores is not satisfied. They also showed that the Bishop coefficient might be different in elastic and plastic regimes, respectively.

In this work, we take advantage of experimental data available in the literature covering, for each soil, both elastic and plastic regimes at various saturation states and including the water retention curve together with microstructure data. We conclude that the Bishop coefficient depends on the deformation regime and that, in particular, distinct values might be used depending whether the plastic regime is active or not.

References:

Alonso, E. E., Pereira, J. M., Vaunat, J., & Olivella, S. (2010). A microstructurally based effective stress for unsaturated soils. Géotechnique, 60(12), 913–925. https://doi.org/10.1680/geot.8.P.002

Coussy, O., Pereira, J. M., & Vaunat, J. (2010). Revisiting the thermodynamics of hardening plasticity for unsaturated soils. Computers and Geotechnics, 37(1–2), 207–215. https://doi.org/10.1016/j.compgeo.2009.09.003
Towards a new trait-based framework bringing together terrestrial and marine ecosystems in Earth system models.
Authors: Pellerin Felix , Porada Philipp , Hense Inga
Published: March 2020

The climate on Earth arises from multiple interactions between the different spheres, including the biosphere. Within the biosphere, the organisms composing the various types of ecosystem are characterized by a set of traits involved in biological processes that can influence the climate system. Identifying and integrating these traits into models such as earth system models (ESM) is thus crucial to predict the future of earth climate. While an important number of biological processes are similar, the amount and the type of traits considered to represent these processes can vary considerably among ecosystem types in current ESMs. Such inconsistencies could bias our perception of the global influence of biosphere on climate dynamics. Here we first list the biological traits that have been included in the terrestrial and oceanic modules of the CMIP5 Earth system models. By comparing the traits and associated processes, we reveal consistencies and inconsistencies in trait representation among both ecosystem types. Based on a critical evaluation we propose a new conceptual framework that allows to describe the climate relevant traits in a consistent way in terrestrial and oceanic modules of ESMs. This framework can also be used to identify new traits characterizing terrestrial and/or marine ecosystems, and to integrate them in ESMs.
Thermodynamic and Kinetic controls to the ice nucleation rate
Authors: Barahona Donifan
Published: March 2020

Ice nucleation is a necessary step for the formation of ice clouds in the atmosphere. It has become clear that its correct representation is critical for the accurate description of atmospheric processes, and for the reliable prediction of the effect of anthropogenic activities on climate. This is accomplished in most cases using empirical models. Although a simple way to parameterize ice nucleation they provide limited information on the nature of ice formation and may not represent all atmospheric conditions.  Theoretical approaches used in cloud models are typically based on the Classical Nucleation Theory (CNT).  There is however a large uncertainty in key parameters of the theory which in most cases are fitted to reproduce observed rates. This talk details recent efforts to go beyond the formulation of CNT to describe ice nucleation. It shows that it is possible to define uncertain parameters like the ice-liquid interfacial tension and the activation energy over a pure thermodynamic basis, hence only as a function of the bulk thermodynamic properties of water. This approach is extended to describe heterogeneous ice nucleation mediated by immersed ice nucleating particles (INPs). It is shown that INPs that significantly reduce the work of ice nucleation also pose strong limitations to the growth of the nascent ice germs. This leads to the onset of a new ice nucleation regime, called spinodal ice nucleation, where the dynamics of ice germ growth instead of the ice germ size determines the nucleation rate. Nucleation in this regime is characterized by an enhanced sensitivity to particle area and cooling rate. Finally a new approach to extract intrinsic nucleation rates from droplet-freezing experiments is used to compare of predicted ice nucleation rates against experimental measurements, for a diverse set of species relevant to cloud formation. This comparison suggests that spinodal ice nucleation may be common in nature, and shows a considerable skill of the new theory in predicting measured ice nucleation rates. 
Evaluation of calibrations for limb scattering sensors
Authors: Kramarova Natalya , Bhartia Pawan , Jaross Glen , Chen Zhong
Published: March 2020

The Ozone Mapping and Profiler Suite represents a new generation of the US ozone measuring instruments aimed to monitor the ozone recovery associated to the reduction in levels of man-made ozone depleting substances regulated by the Montreal protocol. The first OMPS was launched on board of the Suomi NPP satellite in October 2011. The Limb Profiler is a part of the OMPS instrumental suite, and it collects solar radiances scattered from the atmospheric limb in the UV and VIS spectral ranges. The next OMPS Limb Profiler is scheduled to launch in 2022 on board of NASA/NOAA JPSS-2 mission. These limb scattering measurements allow to retrieve vertical ozone profiles from the tropopause up to the mesosphere with a high vertical resolution (~2 km). The expected ozone recovery is almost three times slower than the ozone loss observed in 1980s and 1990s. To detect such small trends in ozone concentration, the instrument calibrations should be extremely accurate. Comparisons of ozone retrievals from OMPS LP with the correlative satellite measurements from Aura MLS and ISS SAGE III revealed that OMPS LP retrievals accurately characterize the vertical ozone distribution in different atmospheric regions which are most sensitive to changes in the stratospheric composition and dynamics. Between 18 and 42 km the mean differences between LP and correlative measurements are within ±10%, except for the northern high latitudes where between 20 and 32 km biases exceed 10% due to the measurement errors. We also found a small positive drift of ~0.5%/yr against MLS with a pattern that is consistent with the ~150-meter drift (over 7 years) in sensor pointing detected by one of our altitude resolving methods. The spatial patterns in the ozone biases and drifts suggest that remaining errors in the LP ozone retrievals are due to errors in altitude registration and instrument calibrations. We present a study where we evaluate calibrations of the OMPS LP by converting ozone differences between OMPS LP and Aura MLS into differences in radiances. Then these radiance differences are compared with the LP measured radiances to determine errors in OMPS LP calibrations. Since the OMPS LP has three slits, some of the errors, like a drift in the altitude registration, should be common across all three slits, but other errors will be unique for each slit, helping to isolate different sources of errors. This approach can be extended to earlier ESA’s limb scattering missions, like SCIAMACHY and OSIRIS, since MLS has long overlap with the ENVISAT and Odin missions.
Towards tackling ice-sheet ocean interaction with Finite Element Methods
Authors: Ottolenghi Stefano , Ahlkrona Josefin
Published: March 2020

Ice sheet-ocean interaction is important to properly understand phenomena such as ice sheet melting and ocean circulation. While the long term goal of this project is to fully couple the ice and ocean in one single numerical framework, we here start by modelling the ocean. We use the full non-hydrostatic equations in order to accurately model the complex ocean dynamics near the ice sheets. As numerical method, we employ finite element methods due to their capability of representing a complex fjord geometry and locally refining the mesh in the areas which require more careful handling, and its strong mathematical foundation. This will allow to overcome classical problems such as representing a moving ice shelf in a discretized setting. We here present an example of modeled fjord circulation obtained simulating the model with the FEniCS computing platform.
Leaf functional diversity is not equivalent to canopy functional diversity: Mapping whole canopy traits with imaging spectroscopy and lidar fusion
Authors: Kamoske Aaron , Dahlin Kyla , Serbin Shawn , Stark Scott
Published: March 2020

Foliar nitrogen concentration (foliar N) and leaf mass per area (LMA) have been identified as key drivers of plant functional diversity and are strongly correlated with photosynthetic carbon assimilation in terrestrial ecosystems. However, these traits are not static between and among species, instead tradeoffs between light interception, photosynthetic capacity, and construction costs (e.g. leaf economics spectrum) lead to significant variation across landscapes. This diversity in leaf traits can lead to considerable differences in carbon assimilation rates at the leaf level, which is difficult to quantify  at ecosystem scales without advanced technologies. Much of our current understanding of landscape-scale heterogeneity in functional traits has come from airborne imaging spectroscopy, which can be linked with foliar trait data to map functional diversity across entire ecosystems. Yet, these remote sensing platforms primarily measure processes occurring in leaves at the top of the canopy, thus ignoring critical information about the three-dimensional structure of forest canopies. Moreover, there is a critical relationship between forest structure and function which drives ecological processes such as carbon assimilation, resource use and efficiency, and woody growth. With traditional remote sensing platforms assuming a 2D world, this leads to an important question in ecosystem functioning: Do total canopy foliar N patterns match top of canopy N concentrations, or are these patterns different? In the United States, the National Ecological Observatory Network’s Airborne Observation Platform (NEON AOP) provides a unique opportunity to address this question by collecting airborne lidar and hyperspectral data in unison across a variety of ecoregions. With a fusion of hyperspectral and lidar data from the NEON AOP and field collected foliar trait data, we show that top of canopy leaf-level and whole canopy foliar N represent fundamentally different measurements regardless of spatial resolution, which could have critical impacts when scaled to landscape, continental, and global models. In addition, we examine the influence of topography, geology, and management regimes on these two measurements of functional diversity at a NEON site consisting of patches of open longleaf pine and dense broadleaf deciduous forests. By understanding how these measurements are linked to abiotic gradients and management regimes, we show that top of canopy functional diversity is more closely related to environmental gradients, reflecting species differences, while whole canopy functional diversity is more evenly distributed, which is a reflection of N availability and utilization across this ecosystem.