bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat-related mortality in Portugal amplified during the COVID-19 pandemic
Authors: Sousa Pedro M. , Trigo Ricardo M. , Russo Ana , Geirinhas João L. , Rodrigues Ana , Silva Susana , Torres Ana
Published: March 2021

The warmest July ever in Portugal was observed during 2020, leading to the highest number of total deaths in July months (10430) since consistent records became available in 2009. This record summed up to the very high death toll throughout the year, characterized by the COVID-19 pandemic. As a combined result of these factors, cumulated deaths during 2020 are also the largest in the records available since 2009 (123753), corresponding to an excess of ~12000 deaths (~11% above the baseline). COVID-19 was responsible for the largest fraction of anomalous mortality during the spring months (62% of the excess during March-May) and from autumn onwards (85% of the excess during October-December). However, during the warmer season, the direct impact of the pandemic decreased substantially (as in the rest of Europe) and other causes were the main trigger for the observed excessive mortality (~3500 versus 553 COVID-19 deaths). Prolonged hot spells, occurring between June 21 and August 7, triggered persistent mortality anomalies in the upper tertile (>310 deaths/day) reaching its peak in mid-July (+45% deaths/day). Two other shorter hot spells occurring outside summer months (May and September) also appear to have contributed to significant mortality anomalies.

July 2020 registered an overall temperature anomaly of +2.6ºC over continental Portugal, and a cumulated anomaly of +127ºC. The lethality rate associated to these cumulated anomalies (+14 deaths per cumulated ºC) was higher than that observed in recent relevant heat-related mortality episodes, even those with higher absolute temperature anomalies, such as in 2013 and 2018. Rates comparable to those observed in 2020 in Portugal are only found far back in tragic heatwaves like those experienced in June 1981 or August 2003. In fact, the 2003 European heatwaves triggered significant changes in public health policies, in order to minimize the mortality burden associated to hot spells, which resulted in lower lethality rates, until 2020. These results are further supported by a statistical model developed to estimate expected deaths due to cold/heat (calibrated for 2009-2019: r=0.84; ME=7%), estimating an amplification of at least 50% in heat-related deaths during 2020 compared to pre-pandemic years. We argue that the significant decrease observed in emergency admissions (ER) and disruption in health-care since the start of the pandemic helps explaining this amplification factor. A ~2/3 decrease in total ERs was observed at the peak of the COVID-19 crisis, never returning to normal pre-pandemic levels. Furthermore, in average cases classified as emergent and very urgent in triage remained below 80% of previous reference levels throughout the 2020 summer, particularly the latter.

The authors would like to acknowledge the financial support  FCT through project UIDB/50019/2020 – IDL.
Absorption of Ocean Heat Along and Across Isopycnals in HadCM3
Authors: Clement Louis , McDonagh Elaine , Gregory Jonathan , Wu Quran , Marzocchi Alice , Nurser George
Published: March 2021

Anthropogenic warming added to the climate system accumulates mostly in the ocean interior and discrepancies in how this is modelled contribute to uncertainties in predicting sea level rise. Temperature changes are partitioned between excess, due to perturbed surface heat fluxes, and redistribution, that arises from the changing circulation and perturbations to mixing. In a model (HadCM3) with realistic historical forcing (anthropogenic and natural) from 1960 to 2011, we firstly compare this excess-redistribution partitioning with the spice and heave decomposition, in which ocean interior temperature anomalies occur along or across isopycnals, respectively. This comparison reveals that in subtropical gyres (except in the North Atlantic) heave mostly captures excess warming in the top 2000 m, as expected from Ekman pumping, whereas spice captures redistributive cooling. At high-latitudes and in the subtropical Atlantic, however, spice predicts excess warming at the winter mixed layer whereas below this layer, spice represents redistributive warming in southern high latitudes.

 

Secondly, we use Eulerian heat budgets of the ocean interior to identify the process responsible for excess and redistributive warming. In southern high latitudes, spice warming results from reduced convective cooling and increased warming by isopycnal diffusion, which account for the deep redistributive and shallow excess warming, respectively. In the North Atlantic, excess warming due to advection contains both cross-isopycnal warming (heave found in subtropical gyres) and along-isopycnal warming (spice). Finally, projections of heat budgets —coupled with salinity budgets— into thermohaline and spiciness-density coordinates inform us about how water mass formation occurs with varying T-S slopes. Such formation happens preferentially along isopycnal surfaces at high-latitudes and along isospiciness surfaces at mid-latitudes, and along both coordinates in the subtropical Atlantic. Because spice and heave depend only on temperature and salinity, our study suggests a method to detect excess warming in observations.
Monitoring of an irrigated olive orchard using C-band backscattering coefficient and interferometric coherence at high temporal frequency: preliminary results
Authors: Chakir Adnane , frison pierre-louis , khabba Said , ezzahar jamal , villard ludovic , ouaadi nadia , ledantec valerie , fanise pascal , jarlan lionel
Published: March 2021

In the south Mediterranean region already facing water scarcity, up to 80% of available water is used by irrigated agriculture. This work focuses on the analysis of the C-band response of a tree crop with in situ data acquired with a time step of 15 mns in the final objective of developing water stress detection approaches based on radar data. Focus is put on the daily cycle of the radar-backscattering coefficient and of the interferometric coherence. The site is located in the Chichaoua region (Morocco) was equipped in May 2019 with 6 C-band radar antennas installed on a 20 m tower. In parallel, automatic acquisitions at a half hourly time step of latent and sensible heat fluxes, sapflow, soil moisture and temperature profile together with manual  measurements of LAI, soil roughness and above ground biomass every 15 days were carried out. The preliminary results show a strong daily cycle of the interferometric coherence with a significant drop of the coherence during daytime. The coherence loss at dawn occurred concurrently with the start of the sapflow while minimum values were observed in the afternoon when wind speed is maximum. A significant daily cycle of the backscattering coefficient is also prominent. The amplitude of the daily cycle decreased from the dormancy period in winter from up to 2dB to less than 1dB in summer when physiologic activity of the trees is at its maximum. These first results open perspectives for the monitoring of the hydric status of crops within the frame of future radar missions in geostationary orbit.
Midlatitude cyclones in convection permitting climate simulations: the added value offered for extreme wind speeds and sting-jets
Authors: Manning Colin , Kendon Elizabeth , Fowler Hayley , Roberts Nigel , Berthou Segolene , Suri Dan , Roberts Malcom
Published: March 2021

Extra-tropical windstorms are one of the costliest natural hazards affecting Europe, and windstorms that develop a phenomenon known as a sting-jet account for some of the most damaging storms. A sting-jet (SJ) is a mesoscale core of high wind speeds that occurs in particular types of cyclones, specifically Shapiro-Keyser (SK) cyclones, and can produce extremely damaging surface wind gusts. High-resolution climate models are required to adequately model SJs and so it is difficult to gauge their contribution to current and future wind risk. In this study, we develop a low-cost methodology to automate the detection of sting jets, using the characteristic warm seclusion of SK cyclones and the slantwise descent of high wind speeds, within pan-European 2.2km convection-permitting climate model (CPM) simulations. Following this, we quantify the contribution of such storms to wind risk in Northern Europe in current and future climate simulations, and secondly assess the added value offered by the CPM compared to a traditional coarse-resolution climate model. This presentation will give an overview of the developed methods and the results of our analysis.

Comparing with observations, we find that the representation of wind gusts is improved in the CPM compared to ERA-Interim reanalysis data. Storm severity metrics indicate that SK cyclones account for the majority of the most damaging windstorms. The future simulation produces a large increase (>100%) in the number of storms exceeding high thresholds of the storm metric, with a large contribution to this change (40%) coming from windstorms in which a sting-jet is detected. Finally, we see a systematic underestimation in the GCM compared to the CPM in the frequency of extreme wind speeds at 850hPa in the cold sector of cyclones, likely related to better representation of sting-jets and the cold conveyor belt in the CPM. This underestimation is between 20-40% and increases with increasing wind speed above 35m/s. We conclude that the CPM adds value in the representation of severe surface wind gusts, providing more reliable future projections and improved input for impact models.
Sediment flux across the south-Pyreneean foreland basin. A contribution to the S2S-Future network. 
Authors: Juvany Philémon , Garcés Miguel
Published: March 2021

 

The early Eocene was a period of the intense collision during the formation of the Pyrenees. The flexural response to loading of the overriding European plate led to the formation of an elongated foredeep on the subducting Iberian plate which connected westward to the Atlantic Ocean. A thrust salient formed in the central Pyrenees, where Mesozoic Cover units travelled southwards on top of Triassic salt detachment. This process resulted in the sequencing of the foreland basin in different isolated sub-basins such as the Ripoll basin in the East, the Tremp-Graus and Ainsa-Jaca basins in central and western south Pyrenees and the Ager basin located south of the Tremp-Graus basin.  The precise timing and surface processes associated to this reorganization of the sedimentary routing system remains not totally understood. Indeed, various sedimentary provenance studies show that the sediments of the Tremp-Graus basin were sourced from a different catchment zone than those of the Ager basin. Besides, the Ripoll basin sediments provenance analysis shows major similarities with the Ager basin, suggesting a common catchment area in the Eastern Pyrenees. However, it has been pointed out that the clastic systems feeding the rapidly subsiding sink of the Ripoll through could not find their way towards the shallower Ager basin. In this PhD project we aim at providing further constraints to the paleogeographic reconstruction and sediment routing systems of the South Eastern Pyrenees in the light of a revised chronostratigraphic scheme. A Source-to-Sink approach will be followed to study the sediment Routing Systems and to decode the climatic and tectonic signal from the sedimentary record. It will follow a volumetric quantification of the sediment budget over the entire foreland, and a comparison with eroded rock volumes of the whole Pyrenees. The resulting revised scenario will seek conciliation of all available data from the stratigraphic, structural, petrologic, geochronologic and sedimentologic datasets with new radiogenic isotopes sedimentary provenance analysis.  
Climatic trends of sea surface temperature and sea ice concentration in the Barents Sea
Authors: Mohamed Bayoumy , Nilsen Frank , Skogseth Ragnheid
Published: March 2021

Sea ice loss in the Arctic region is an important indicator for climate change. Especially in the Barents Sea, which is expected to be free of ice by the mid of this century (Onarheim et al., 2018). Here, we analyze 38 years (1982-2019) of daily gridded sea surface temperature (SST) and sea ice concentration (SIC) from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) project. These data sets have been used to investigate the seasonal cycle and linear trends of SST and SIC, and their spatial distribution in the Barents Sea. From the SST seasonal cycle analysis, we have found that most of the years that have temperatures above the climatic mean (1982-2019) were recorded after 2000. This confirms the warm transition that has taken place in the Barents Sea over the last two decades. The year 2016 was the warmest year in both winter and summer during the study period.   

Results from the linear trend analysis reveal an overall statistically significant warming trend for the whole Barents Sea of about 0.33±0.03 °C/decade, associated with a sea ice reduction rate of about -4.9±0.6 %/decade. However, the SST trend show a high spatial variability over the Barents Sea. The highest SST trend was found over the eastern part of the Barents Sea and south of Svalbard (Storfjordrenna Trough), while the Northern Barents Sea shows less distinct and non-significant trends. The largest negative trend of sea ice was observed between Novaya Zemlya and Franz Josef Land. Over the last two decades (2000-2019), the data show an amplified warming trend in the Barents Sea where the SST warming trend has increased dramatically (0.46±0.09 °C/decade) and the SIC is here decreasing with rate of about -6.4±1.5 %/decade.  Considering the current development of SST, if this trend persists, the Barents Sea annual mean SST will rise by around 1.4 °C by the end of 2050, which will have a drastic impact on the loss of sea ice in the Barents Sea.   

 

Keywords: Sea surface temperature; Sea ice concentration; Trend analysis; Barents Sea
Quantifying uncertainty in future projections of ice loss from the Filchner-Ronne basin, Antarctica
Authors: Hill Emily , Rosier Sebastian , Gudmundsson Hilmar , Collins Matthew
Published: March 2021

The future of the Antarctic Ice Sheet under climate warming is one of the largest sources of uncertainty for changes in global mean sea level (GMSL). Accelerated ice loss in recent decades has been concentrated in regions where warm circumpolar deep water forces high rates of sub-shelf melt. It is unclear how ice shelves currently surrounded by cold ocean waters with low melt rates will respond to changes in ocean conditions in future. For example, previous studies have shown that if warm water were to infiltrate beneath the Filchner-Ronne ice shelf, it could drastically increase sub-shelf melt rates. However, the inland ice-sheet response to climate-ocean changes remains uncertain. Here, we set out to quantify uncertainties in projections of GMSL from the Filchner-Ronne region of Antarctica over the next two centuries. To do this we take a large random sample from a probabilistic input parameter space and evaluate these parameter sets in the ice-sheet model Úa under four RCP forcing scenarios. We then use this training sample to generate a statistical surrogate model to capture the parameter to projection relationship from our ice-sheet model. Finally, we use sensitivity analysis to identify which parameters drive the majority of uncertainty in our projections.

Our results suggest that accumulation expected with warming is capable of suppressing increases in ice discharge associated with increased ocean-driven sub-shelf melt rates. This could allow the Filcher-Ronne basin to have a negative contribution to GMSL. However, parameters controlling mass accumulation and sub-shelf melting are highly uncertain. Crucially, there is potential within our input parameter space for major collapse and retreat of ice streams feeding the Filchner-Ronne ice shelf and a positive contribution to sea level rise. Further improvements in the representation of accumulation and sub-shelf melt under climate warming in ice-sheet models will help determine the sign of GMSL projections from this region of the ice sheet.
Scale analysis of evapotranspiration estimates from an energy-water balance model and remotely sensed LST
Authors: Paciolla Nicola , Corbari Chiara , Ciraolo Giuseppe , Maltese Antonino , Mancini Marco
Published: March 2021

Remote Sensing (RS) information has progressively found, in recent years, more and more applications in hydrological modelling as a valuable tool for easy and frequent collection of geophysical data. However, this kind of data should be handled carefully, minding its characteristics, spatial resolution and the heterogeneity of the target area.

In this work, a scale analysis on evapotranspiration estimates over heterogeneous crops is performed combining a distributed energy-water balance model (FEST-EWB) and high-resolution remotely-sensed Land Surface Temperature (LST) and vegetation data.

The FEST-EWB model is calibrated on measured LST, based on a procedure where every single pixel is modified independently one from the other; hence in each pixel of the analysed domain the minimum of the pixel difference between modelled RET and satellite observed LST is searched over the period of calibration.

The case study is a Sicilian vineyard, with test dates in the summer of 2008. Meteorological and energy fluxes data are available from an eddy-covariance station, while LST and vegetation data are obtained from low-altitude flights at the high resolution of 1.7 metres.

After a preliminary calibration on LST data and validation on energy fluxes, the scale analysis is performed in two ways: model input aggregation and model output aggregation. Four coarser scales are selected in reference to some common satellite products resolution: 10.2 m (in reference to Sentinel’s 10 m), 30.6 m (Landsat, 30 m), 244.8 m (MODIS visible, 250 m) and 734.4 m (MODIS, 1000 m). First, modelled surface temperature and evapotranspiration are aggregated to each scale by progressive averaging. Then, model inputs are upscaled to the same spatial resolutions and the model is calibrated anew, obtaining independent results directly at the target scale.

The results of the two procedures are found to be quite similar, testifying to the capacity of the model to provide accurate products for a heterogeneous area even at low resolutions. The robustness of the analysis is strengthened by a further comparison with two well-established energy-balance algorithms: the one source Surface Energy Balance Algorithm for Land (SEBAL) and the Two-Source Energy Balance (TSEB) model.
Quantifying competing measures of sediment dynamics on alluvial fans: implications for reconstructing past environmental change
Authors: Whittaker Alexander , Brooke Sam , D'Arcy Mitch
Published: March 2021

The effects of climate change on eroding landscapes and the sedimentary record remains poorly understood. While sediment routing systems at the Earth’s surface should, in principle, record changes in past environmental boundary conditions, the extent to which landscapes are buffered to high-frequency, high-magnitude climate change is contentious. Mountain catchments and alluvial fans offer one way to address this question, as they are accessible sediment routing systems in which source and sink are closely coupled, sedimentation rates are high, and sediment budgets can be closed. Here we consider the extent to which the granulometry of sediment in stream-flow-dominated alluvial fans records changing environmental conditions. We focus on well-constrained field examples in Death Valley, California, such as the Hanaupah Canyon Fan, which have experienced hydroclimate forcing associated with recent glacial-interglacial cycles. Using field-derived measures of grain size, we compare three complementary methods that have recently been used to reconstruct sediment dynamics on alluvial fans. First, we use a self-similarity analysis of sediment calibre to reconstruct sediment mobility on the fan over time. Second, we use a downstream-fining model to evaluate the extent to which different depositional units on the fans record changing sediment fluxes from source catchments. Finally, we adopt a palaeohydrological approach to reconstruct unit discharges, bed shear stresses and instantaneous sediment transport capacities for fans in the study area, based on field measures of hydraulic geometry and grain size. We evaluate the extent to which these three methods provide consistent results, and we quantify the extent to which grain mobility, water and sediment discharge scale with documented variations in the regional climate. Our work shows that alluvial fans are highly sensitive to palaeo-environmental change, but our findings also illustrate the importance of considering which measures of past climate (particularly averages versus variance) are most relevant for landscape responses and sensitivity to climate change. 
Estimation of Uncertainty Contribution of Multiple Sources of GCMs in Hydrological Prediction.
Authors: Sinha Rakesh Kumar , Eldho T.I.
Published: March 2021

The estimation of the impacts of climate change on hydrology at the local level comprises various sources of uncertainty. Especially, global climate models (GCMs) are found to be one of the major sources of uncertainty at the local level and it is important to identify for robust water resource planning and management. Therefore, this study demonstrates the separate and multi-model ensemble GCMs uncertainty for the surface runoff projections for near, mid, and far future under representative concentration pathway (RCP) 4.5 (present condition) and RCP 8.5 (worst condition) at medium level river sub-basins scale in the Western Ghats region of India. The results indicate that considered GCMs are not appropriate for use to prediction of peak surface runoff in the wet season. In addition, uncertainty from ensemble GCMs is closer to actual data than individual GCM because of closely associated with ensemble rainfall data which is maximum influencing the peak surface runoff for the near mid, and far future. Furthermore, findings also suggest that the selection of appropriate GCMs for the study of peak flow analysis at the local level is important for the projection of future surface runoff. Therefore, it is also important to make attention to rainfall data while projecting surface runoff for future time periods in the humid tropic regions.
Late Neogene climatic features recorded by isotope records in the Issyk Kul basin, Kyrgyzstan. 
Authors: Kudriavtseva Anna , Sobel Edward , Codilean Alexandru , Roud Sophie , Wack Michael , Gilder Stuart , Hoke Gregory , Mulch Andreas , Mikolaichuk Alexander , Fink David , Fülöp Réka , Wilcken Klaus
Published: March 2021

We present two carbonate oxygen and carbon isotope records from late Miocene – early Pleistocene stratigraphic sections from the southern flank of the Issyk Kul basin, Kyrgyz Tien Shan. The two sections are 700 and 500 m thick and composed of fluvial and lacustrine sediments. They were dated using magnetostratigraphy (Roud et al., G-Cubed, in review) and 26Al/10Be isochron burial dating (presented here).

Carbonate stable isotope data is useful for reconstruction of climate in Asia over the Cenozoic. Oxygen isotopes are commonly used to detect moisture sources and their interaction with topography. Pedogenic carbon isotopes are used to reconstruct past atmospheric CO2 levels or the spread of C4 vegetation.

The environment of Central Asia is primarily affected by the northern mid-latitude westerlies − winds transporting moisture eastward across Eurasia. Issyk Kul basin is situated on the windward side of the northern Tien Shan. Published data suggest that the Tien Shan mountain ranges interacted with the westerlies since late Oligocene and reorganized Central Asian climate during Neogene (Caves et al., 2017; Charreau et al., 2012; Macaulay et al., 2016; Wang, et al., 2020). The amount of existing published paleoclimate data from northern Central Asia is scarce compared to interior China, and therefore the influence of the Tien Shan uplift on climate in Asia during the Cenozoic is poorly reconstructed.

Our data provide new insight into the role of the range and its interaction with the westerlies in forming climate on the windward side of the northern Tien Shan in the late Neogene. We combine our data with published stratigraphically-older sections nearby (Macaulay et al., 2016) to complete the Neogene stable isotope record of the Issyk Kul basin and study how the evolution of the basin influenced regional climate.

Our d18O and d13C values show slightly positive trends, unlike stratigraphically-older data from the Issyk Kul basin. The preliminary interpretation suggests that the circulation pattern within the range was changed in late Miocene possibly reflecting active tectonic uplift northward of the basin and an increase in aridification.
High spatiotemporal radar observation of the polar summer mesosphere using MAARSY in a MIMO configuration
Authors: Latteck Ralph , Chau Jorge , Urco Miguel , Vierinen Juha , Avsarkisov Victor
Published: March 2021

Atmospheric structures due to gravity waves, turbulence, Kelvin Helmholtz instabilities, etc. in the mesosphere are being studied with a varying of ground-based and satellite-based instruments. At scales less than 100 km, they are mainly studied with airglow imagers, lidars, and radars. Typical radar observations have not been able to resolve spatial and temporal ambiguities due to the strength of radar echoes, the size of the system, and/or the nature of the atmospheric irregularities. In this work we observed spatially and temporally resolved structures of PMSE with unprecedented horizontal resolution, using the improved radar imaging accuracy of the Middle Atmosphere Alomar Radar System (MAARSY) with the aid of a multiple-input multiple output (MIMO) technique. The studies are performed in both the brightness of the mesospheric echoes and their Doppler velocities. The resolutions achieved are less than 1 km in the horizontal direction, less than 300m in altitude, and less than 1 minute in time, in an area of ~15km x 15km around 85km of altitude. We present a couple of wavelike monochromatic events, one drifting with the background neutral wind, and one propagating against the neutral wind. Horizontal wavelengths, periods, and vertical and temporal coverage of the events are described and discussed. A theory of stratified turbulence is employed in the present study. In particular, it is shown that the structure that propagates with the background wind is a large-scale turbulent KHI event.  Some important turbulence characteristics, such as a turbulent dissipation rate, buoyancy Reynolds number, and Froude number, support our conclusion.
Quantitative measurements of pigments in coniferous by the method of differential optical absorption spectroscopy
Authors: Bruchkouski Ilya , Siliuk Volha , Guliaeva Sviatlana , Litvinovich Hleb
Published: March 2021

The relative concentrations of photosynthetic and photoprotective pigments provide important information about the physiological state of the plant and are determined, among other things, by the lighting regime and the presence of nutrients. Relative composition of the pigments is depending on the physiological response of the plant to external influences. In most cases, when an on-line in-situ analysis is required, only the main pigments are measured: Chla, Chlb and a rough estimate of the "total carotenoids" in higher plants, but such an estimate may not always be reliable. Differential Optical Absorption Spectroscopy (DOAS) is known for its applications for the trace gases measurements in the atmosphere sciences; however, no application has been found for the determination of color pigments for plant extracts. For the correct application of the DOAS method, it is necessary to determine the appropriate optical thickness of the sample under study, the fitting intervals for analysis, as well as a set of absorption cross sections for the target pigments.

Purpose of the work is to determine the appropriate settings for the retrieval of concentrations of colored pigments employing the DOAS method by investigating the sample of pine and spruce needles extraction. The relevance of the work consists in the development of a new method for analyzing transmission spectra, which does not require the creation of specialized software, since programs for analyzing spectra by the DOAS method are available.

For the spectra registration, Solar M150 spectrometer with Hamamatsu S7031-1006S detector has been used, the transmission spectra recorded in the 330 - 750 nm range, and pure acetone employed as a solvent. The paper presents the results of DOAS-analysis of extracts of various coniferous samples, from which it was possible to retrieve the contents of Cha, Chb, B,b-carotene, B,e-carotene, and small amounts of Phaeophytin-a, Neoxanthin. Optimal settings for the DOAS-analysis and experimental setup details for photosynthetic and photoprotective pigments retrieval are discussed.
High resolution palynofacies analysis to understand Holocene Sudanian landscapes. First data from the Bao Bolon middle valley (Senegal).
Authors: Weisskopf Emmanuel , Stern Mathilde , El Madouri Loubna , Landry David , Garnier Aline , Ballouche Aziz
Published: March 2021

Key words: Palaeoenvironments, Holocene, Palynofacies, Microcharcoal, Fire signal, Anthropisation

The Bao Bolon valley, located in a Sudano-Sahelian context and overlapping both the Gambia and Saloum river basins, in western Senegal, is subject to strong seasonal rainfall contrasts. These particular conditions are usually badly appropriate to the good conservation of sedimentary archives. Moreover, this region is well known for his important archaeological heritage which includes the megalithic necropolis of Wanar classified on the UNESCO World Heritage list.

In addition to archaeological research, paleoenvironmental studies have been carried out at the Wanar site. Fluvial archives have been investigated and provide rich sedimentary records covering the entire Holocene period. Thus, the cultural and abiotic contexts of the middle Bao Bolon valley are now well documented (Laporte et al. 2017, Stern et al. 2019). Nevertheless, the biotic aspect, i.e. the landscapes and their evolution, still remains poorly documented in this region. Ongoing studies aim to better understand the Holocene palaeoenvironments and protohistoric agro-sylvo-pastoral systems by reconstituting biotic environments.

Due to the lack of pollen material, we focus on other, more abundant, organic elements recorded in the sedimentary archives. The study of organic matter has been first conducted through the palynofacies analysis. Among the different types of organic particles, we pay special attention to microcharcoals. Microcharcoals are often the longest lasting organic matter because carbonization protects the particles from degradation (except mechanical degradation). Their analysis focuses on the relative and absolute abundance, the morphology and the size of the particles. Microcharcoals are a relevant indicator of fire signals. Fires, whatever their origin, whether they are natural or anthropogenic, contribute to the changing and shaping of environmental landscapes. Therefore, high resolution palynofacies analyses contribute to a better understanding of the physical and anthropogenic transformations of the Holocene landscapes in the Bao Bolon middle valley.

The first results show a relative permanence of the signal of vegetation fires during the Holocene. The fluctuations of this burning activity are still under study. An important change seems to take place in the second half of the twentieth century. Further studies, in particular on phytoliths are under process. They will complete the interpretation of the landscapes dynamics during the Holocene.
On the Use of Satellite Observations to Fill Gaps in the Halley Station Total Ozone Record
Authors: Zhang Lily , Solomon Susan , Stone Kane , Burrows John , Colwell Steve , Eveson Joshua , Haffner David , Jones Anna , Kramarova Natalya , Labow Gordon , Levelt Pieternel , Newman Paul , Shanklin Jonathan , Weber Mark , Wilka Catherine
Published: March 2021

Measurements by the Dobson ozone spectrophotometer at the British Antarctic Survey’s (BAS) Halley research station form a record of Antarctic total column ozone that dates back to 1956. Due to its location, length, and completeness, the record has been, and continues to be, uniquely important for studies of long-term changes in Antarctic ozone. However, a crack in the ice shelf on which it resides forced the station to abruptly close for eight months and [SC-UB1]  led to a gap in its historic record.  We develop and test a method for filling in the record of Halley total ozone by combining and bias-correcting overpass data from a range of different satellite instruments. Tests suggest that our method reproduces the monthly ground-based Dobson total ozone values to within 20 Dobson units.  We show that our approach improves on the overall performance as compared to simply using the raw satellite average or an individual instrument. The method also provides a check on the consistency of the automated Dobson used at Halley after 2018 compared to earlier manual Dobson data, and suggests a significant difference between the two.  The filled Halley dataset provides further support that the Antarctic ozone hole is healing not only during September, but also in January.
Simulation of Instant and Delayed Seismic Triggering Observed After the 30 October 2020 Samos Earthquake at Nearby Faults
Authors: Sopaci Eyup , Özacar Atilla Arda
Published: March 2021

The 30 October 2020 Samos Earthquake (Mw=7.0) ruptured a north-dipping offshore normal fault, north of the Samos Island with an extensional mechanism. Aftershocks mainly occurred at the western and eastern ends of the rupture plane in agreement with the Coulomb static stress changes. Mechanism of aftershocks located west of the rupture area supported activation of the neighboring strike-slip fault almost instantly. In addition, a seismic cluster including events with magnitudes reaching close to 4 has emerged fifty hours later at the SE side of Samos Island. This off-plane cluster displays a clear example of delayed seismic triggering that produced small magnitude earthquakes at nearby active faults. In this study, numerical simulations are conducted using rate-and-state friction dependent quasi-static&full-dynamic spring slider model with shear-normal stress coupling to mimic the instant and delayed seismic triggering observed after this event. Coulomb static stress changes and seismic waveforms recorded at nearby strong-motion stations are used as static and dynamic triggers during simulations. According to our results, earthquakes with Mw<3.5 can be triggered almost instantly at the rupture edge and failure time of earthquakes with Mw>3.5 advances for both strike-slip and normal faults which may explain the delayed triggering observed SE of Samos Island. Moreover, simulations revealed that the shear-normal stress coupling increases the triggering potential.
Probability Assessments of an Ice-Free Arctic: Comparing Statistical and Climate Model Projections
Authors: Rudebusch Glenn , Diebold Francis
Published: March 2021

Based on several decades of satellite data, we provide statistical forecasts of Arctic sea ice extent during the rest of this century. The best fitting statistical model indicates that overall sea ice coverage is declining at an increasing rate. By contrast, average projections from the CMIP5 global climate models foresee a gradual slowing of Arctic sea ice loss even in scenarios with high amounts of carbon emissions. Our long-range statistical projections also deliver probability assessments of the timing of an ice-free Arctic. These results indicate almost a 60 percent chance of an effectively ice-free Arctic Ocean sometime during the 2030s—much earlier than the average projection from the global climate models. Our results are also consistent with projections from bivariate regressions of sea ice extent and carbon emissions. 
Causal maps versus correlation maps: visual analysis of tropical-extratropical atmospheric teleconnections using causal discovery
Authors: Di Capua Giorgia , Donner Reik V.
Published: March 2021

In climatology, correlation maps are often used to study the relationships between one 1D time series and a (spatiotemporal) 2D or even 3D field. However, correlation measures do not necessarily capture causal relationships and similarities in correlation maps obtained from different indices may appear if the set of indices contains correlated variables. Causal discovery tools such as the Peter and Clark – Momentary conditional independence (PCMCI) algorithm can help in disentangling spurious from causal links in both linear and nonlinear frameworks. In the linear case considered in the present work, PCMCI extends standard correlation analysis by removing the confounding effects of autocorrelation, indirect links and common drivers. Combining PCMCI and Causal Effect Networks on a 2D field helps identifying, and subsequently discarding the spurious correlations and thereby allows to retain only the causal links. The resulting visualization technique is referred to as a “causal map”.

In this presentation, we illustrate the application of causal maps in combination with maximum covariance analysis to assess how tropical convection interacts with mid-latitude circulation during boreal summer at different intraseasonal timescales. The obtained causal maps reveal the dominant patterns of interaction and highlight specific mid-latitude regions that are most strongly connected to tropical convection. In general, the identified causal teleconnection patterns are only mildly affected by ENSO variability and the tropical-mid-latitude linkages remain similar under different types of ENSO phases. Still, La Niña strengthens the South Asian monsoon generating a stronger response in the mid-latitudes, while during El Niño periods, the western North Pacific summer monsoon pattern is reinforced. Our study paves the way for a process-based validation of boreal summer teleconnections in (sub-)seasonal forecast models and climate models and therefore provides important clues towards improved sub-seasonal and climate projections.

 

Reference: G. Di Capua, J. Runge, R.V. Donner, B. van den Hurk, A.G. Turner, R. Vellore, R. Krishnan, D. Coumou: Dominant patterns of interaction between the tropics and mid-latitudes in boreal summer: Causal relationships and the role of time-scales. Weather and Climate Dynamics, 1, 519-539 (2020)
Tree rings and genetic control of drought resilience
Authors: Isaac-Renton Miriam , Montwé David , Stoehr Michael , Degner Jonathan , Hook Trisha , van der Merwe Lise , Gamal El-Dien Omnia , Daniels Lori , Yanchuk Alvin , Campbell Elizabeth
Published: March 2021

Severe drought events are affecting forests around the world, even in temperate climates. A viable climate change adaptation strategy may involve planting forests with trees more resilient to drought. The majority of the 300 million seedlings planted annually in western Canada are genetically-selected trees derived from tree breeding programs. Since tree breeding populations supply the seed that is deployed on the landscape, it is important to closely examine the degree of genetic control of drought resilience in these populations – yet methods for evaluating drought responses in mature experimental trials are limited. We evaluated the potential to use tree rings to infer genetic adaptation to drought. Specifically, we used annual growth increments to evaluate the genetic component behind variation in drought resilience. We also quantified potential genetic trade-offs between drought resilience and growth in long-term progeny trials. We worked with two economically and ecologically valuable sympatric conifers, coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) and western redcedar (Thuja plicata). Annual growth increment and tree height data were obtained from 1980 coastal Douglas-fir trees (93 polycross families on two well-replicated sites at age 19) and 1520 western redcedar trees (26 polycross families on three well-replicated sites at age 18). All trees showed substantial reduction in growth under drought, but there was clear variability in the longer-term response of families within each breeding population. The heritability (h2) of such drought resilience, or proportion of this variation explained by genetics, was high for Douglas-fir (h2 = 0.26, SE = 0.07) and moderate for redcedar (h2 = 0.13, SE = 0.04). Preliminary genetic correlations between tree height and drought resilience were also positive for both species (Douglas-fir: rg = 0.77, SE = 0.18; redcedar: rg = 0.62, SE = 0.17). Families that were both high-yielding and drought resilient could also be identified. Since growth response to drought is a variable and heritable trait, these traits are therefore under the control of the tree breeder. Moreover, the positive genetic correlations between tree height and an adaptive growth response to drought suggest that historic selection for tree height did not compromise drought resilience of planted seedlings. Tree rings appear to be an effective tool to screen these populations for drought resilience, which will help ensure that planted trees will remain healthy and productive under climate change.
Effect of ambient water conditions on microbial communities on the artificially produced aggregates: Evidence from experiments using two different seawater cultures
Authors: Weinbauer Markus , Motegi Chiaki , Migon Christophe , Mari Xavier
Published: March 2021

Microbial communities on marine aggregates could be influenced by ambient water conditions; however, empirical data are scarce. In this study, we used fingerprint analysis of PCR-amplified 16S rRNA gene fragment to examine how microbial communities on aggregates change in response to different conditions of ambient water. We conducted two experiments using seawater cultures from surface waters of the lagoon and the anthropogenically influenced bay of Nouméa, New Caledonia: a transplant experiment in which the artificially produced aggregates from one station was added to ultra-filtered seawater culture of another station, and a water-flow experiment in which the artificially produced aggregates placed in the ultra-filtered seawater culture with or without water-flow. In a transplant experiment, bacterial community composition (BCC) on the bay and lagoon water aggregates were significantly different (p < 0.05, ANOSIM) at the beginning of experiment. After 11 days of incubation, BCC on the lagoon water aggregates were significantly different (p < 0.05) from transplanted communities. Transplantation effect was also observed in the bay water treatments. In a water-flow experiment, BCC on the bay and lagoon water aggregates were significantly different (p < 0.05) at the beginning of the experiment. BCC on the lagoon and bay water aggregates with and without water-flow treatments were significantly different (p < 0.05) at the end of incubation, and effect of water-flow on BCC were observed in the bay and lagoon water treatments. Our experimental studies suggest that changes in ambient water conditions potentially influence microbial communities on aggregates in the Bay of Nouméa.
Comparative study of chemical stimulation at geothermal wells in the carbonates of the upper jurassic in the Bavarian Molasse Basin
Authors: Kaplar Felicitas , Baumann Thomas
Published: March 2021

Chemical stimulation of geothermal wells to remove drilling mud and to increase the connection to the reservoir are state of the art. There is hardly any deep geothermal well in the carbonates of the upper jurassic in the pre alpine foreland basin which was not developed using one or more pulses of acid. Several tons of acid are injected into the borehole and followed by a chaser to push the acid into the reservoir. Given the wide use of chemical stimulation measures, mass balance data for the stimulation is rare. This might be due to a rather simple reaction mechanism and the assumption that there is a full stoichiometric reaction and all injected acid is recovered. The efficiency of the stimulation is assessed based on the hydraulic properties derived from the short-term pumping tests following the stimulation.

This project compares the full mass balance for chemical stimulation measures and the temporal development of the concentration of relevant ions during the pumping test after stimulation. The data was collected at several sites with a temporal resolution of down to 30 mins. The data includes multiple stimulations as well as stimulation with varying acids and different setup. Using this data set we want to answer the questions whether the acid is fully recovered, whether the assumption of full stochiometric reaction is valid, whether there is a difference in the transport of reactive and conservative ions, what additional value a hydrochemical analysis could add and whether on-site measurements could substitute costly measurements.

The evaluation shows a distinct behaviour of the temporal development of the chloride concentration (after stimulation with hydrochloric acid) which can be described by a bi-exponential fit. The fitting parameters of the two exponential terms are getting closer with each stimulation indicating a reduced heterogeneity along the accessible flow paths around the borehole. A comparison of the full scale analysis with on-site sensors was sometimes not possible because the sensors showed a drift during the experiment or were poorly calibrated. As calcium, magnesium, and chloride ion concentrations showed different behaviour, electrical conductivity is not able to cover the full development. The mass balance indicates that a full recovery of the injected acid might take significantly longer than the short term pumping tests.

Hydrochemical monitoring provides additional and relevant data about the reservoir in the surrounding of the borehole and allows important predictions about the long-term behaviour, especially if the borehole is used as injection well. For routine applications improved sensors and fast (and cheap) on-site analysis is required.