The evolution of the North Atlantic Oscillation for the last 700 years inferred from D/H isotopes in the sedimentary record of Lake Azul (Azores archipelago, Portugal).

TheD plant leaf wax variations provide insights on precipitation and evaporation evolution through time. This proxy has been used to reconstruct the temporal evolution of the North Atlantic Oscillation (NAO) climate mode since this mode rules most of the climate variability in the central North Atlantic area. A total lipid extraction preparation and the correspondent analyses in the IRMS have been done for 100 samples from the uppermost 1.5 m of the sedimentary infill of Lake Azul (Azores archipelago, Portugal). According to the chronological model, established by 210Pb profile and 4 AMS 14C dates, this record contains the environmental history of the last 730 years. The reconstructed precipitation variations obtained from D/H isotope values, suggest that this area has suffered significant changes in its distribution and intensity rainfall patterns through time. The end of the Medieval Climate Anomaly (MCA, 1100- 1300 AD) is characterized by a progressive enrichmentof D/H isotope values which meant decreasing arid conditions. These rainfalls’ increase might be interpreted by a shift from positive to negative dominance of the NAO. The Little Ice Age (LIA, 1300 - 1850 AD) was characterized by two humid periods (1300- 1550 AD and 1650 - 1850 AD) separated by a relatively dry period. These precipitation oscillations are clearly visible by marked changes in the D/H isotope values. The LIA was followed by the persistence of the positive NAO mode, exhibited by the depletion of the D/H isotope signal, which indicated an overall decrease of the precipitation in the central North Atlantic area. Surprisingly, the D/H of the last 100 years, characterized by the present global warming and a persistent positive NAO mode, display large fluctuations most possibly linked to an enhancement of the storminess which is in concordance with the data fluctuations observed in the instrumental record for the last 80 years in the archipelago. This climatic evolution is in accordance with other NAO records of the North Atlantic region (Trouet et al., 2012) highlighting the validity of the D/H isotopes as precipitation proxy.Peer Reviewe

Identifying imprints of externally derived dust and halogens in the sedimentary record of an Iberian alpine lake for the past ∼13,500 years – Lake Peixão, Serra da Estrela (Central Portugal)

Iberian lacustrine sediments are a valuable archive to document environmental changes since the last glacial termination, seen as key for anticipating future climate/environmental changes and their far-reaching implications for generations to come. Herein, multi-proxy-based indicators of a mountain lake record from Serra da Estrela were used to reconstruct atmospheric (in)fluxes and associated climatic/environmental changes over the last ∼13.5 ka. Depositions of long-range transported dust (likely from the Sahara) and halogens (primarily derived from seawater) were higher for the pre-Holocene, particularly in the late Bølling-Allerød–Younger Dryas period, compared to the Holocene. This synchronous increase could be related to a recognized dust-laden atmosphere, along with the combined effect of (i) an earlier proposed effective transport of Sahara dust for higher latitudes during cold periods and (ii) the progressive Polar Front expansion southwards, with the amplification of halogen activation reactions in lower latitudes due to greater closeness to snow/sea ice (halide-laden) surfaces. Additionally, the orographic blocking of Serra da Estrela may have played a critical role in increasing precipitation of Atlantic origin at higher altitudes, with the presence of snow prompting physical and chemical processes involving halogen species. In the Late Holocene, the dust proxy records highlighted two periods of enhanced input to Lake Peixão, the first (∼3.5–2.7 ka BP) after the end of the last African Humid Period and the second, from the 19th century onwards, agreeing with the advent of commercial agriculture, and human contribution to land degradation and dust emission in the Sahara/Sahel region. The oceanic imprints throughout the Holocene matched well with North Atlantic rapid climatic changes that, in turn, coincided with ice-rafted debris or Bond events and other records of increased storminess for the European coasts. Positive parallel peaks in halogens were found in recent times, probably connected to fire extinction by halogenated alkanes and roadway de-icing.This work was supported by the Portuguese Foundation for Science and Technology – FCT , through the HOLMODRIVE project ( PTDC/CTA-GEO/29029/2017 ) and P.M.R. grant ( DL57/2016/ICETA/EEC2018/25 ). The Estrela UNESCO Global Geopark is thanked for its support with field activities and permitting. The Parque Natural da Serra da Estrela, ICNF, provided research permits. Pedro J.M. Costa, Alberto Sáez, Santiago Giralt, and personnel of the Estrela UNESCO Global Geopark for fieldwork. Armand Hernández is funded by the Spanish Ministry of Science and Innovation through the Ramón y Cajal Scheme [ RYC2020-029253-I ]. We thank Vitor Magalhães and the EMSO-PT infrastructure project, with grant number POCI-01-0145-FEDER-022157 , for the XRF scanner analysis. A.M.R. and P.L. are supported by the Helmholtz “Changing Earth” program.Peer reviewe

Mid-to-Late Holocene environmental reconstruction on Pico Island (Azores, Portugal) based on multiproxy analysis of Lake Caveiro sediments

The Azores constitutes the most remote archipelago of the North Atlantic Ocean. Both human colonization and natural changes have significantly modified its ecosystems. To assess the impacts of natural and anthropogenic changes over the last 8200 yr, elemental geochemistry on bulk organic matter, diatoms, Cladocera and chironomid remains were analyzed in a 952-cm long sediment (3.7m depth) from Lake Caveiro. From 8200 to 650 cal yr BP, climatic and volcanic forcing seem to have been the main drivers of biological change. Between 8200 and 6000 cal yr BP, the sedimentary sequence was characterized by dominance of volcaniclastic deposits and high abundance of aerophilic diatoms and sparse Cladocera and chironomid remains. This interval has been interpreted as indicative of unstable conditions because of intermittent renewal of lake bottom substratum owing to repetitive tephra sedimentation. Between 6000 and 3500 cal yr BP, fossil assemblages were dominated by benthic species, with an increasing trend of the planktonic/benthic (P:B) ratio, suggesting stable substratum and rising lake levels. An increase in planktonic taxa and the presence of deep-water chironomid species was found between 3500 and 1300 cal yr BP, suggesting a highstand phase. Between 1300 and 650 cal yr BP, a decreasing trend of the P:B ratio was recorded, implying a further lake shallowing. Moreover, the appearance of flowing water species suggests a period characterized by climate instability. From 650 cal yr BP to the present, a significant increase in primary production and a decline in species richness likely reflect anthropogenic impacts, such as forest clearance and the introduction of exotic species. These results highlight the impact that human, volcanic and climatic drivers have had on the environmental evolution of the ecosystems of Pico Island.This research is funded by Spanish projects PaleoNAO (CGL2010-15767), RapidNAO (CGL2013-40608-R) and PaleoModes (CGL2016-75281-C2).Peer Reviewe

Climate Impacts of the Common Era on Aquatic Systems in NW Spain: preliminary results

Poster.-- Clivar 2023, Towards an integrated view of climate, 24-26 January, MadridEcological resistance and resilience of freshwater ecosystems is intimately linked to climate variability. To the extent of our knowledge, this issue has never been addressed using a long-term paleoecological perspective in Galicia (NW Spain). Project IMPACOM (Climate Impacts of the Common Era on Aquatic Systems in NW Spain, Spanish Ministry of Science and innovation, PID2019-107424RB-I00) is intended to study the impacts of changes in the precipitation regime and storm conditions, among other climate forcing factors, on coastal lakes and their enclosing barriers, as well as on bogs and mountain lakes in the region during the Common Era (CE, last 2,000 yr). To identify and precisely date the major ecological transitions of the CE we use a multidisciplinary approach which includes sedimentological facies analysis, inorganic bulk geochemical analyses (from X-ray fluorescence analysis, core scanning, Fourier-transform infrared spectroscopy, estimation of humification indexes, elemental and isotopic analyses of organic matter, biogenic silica), biological proxies (diatoms, pollen, plant macrofossils, testate amoeba and chironomids), as well as a set of geochronological techniques (AMS radiocarbon dating, concentrations of fallout 137Cs, 210Pb, 214Pb and 241Am, OSL dating)The study of the lacustrine sedimentary record of the coastal Lake Doniños, as well as of the sand barrier which encloses this lake and that of the wetland of Pantín, both in A Coruña province, shows a history of breaching and overwashing linked to the intensification of storms and enhanced precipitation over the last 4,500-4,000 yr. For the case of the last 2,000 yr, catastrophic emptying of Lake Doniños took place during the Dark Ages (DA, 350-750 CE) and the Little Ice Age (LIA, 1500-1930 CE). The transition from the Medieval Climate Anomaly (MCA) to the LIA involved in this lake a gradual 200 yr long transformation from an isolated lake to an intermittent tidal lagoon until the LIA breaching episode. Lake Ocelo, an oligotrophic mountain lake located in the Trevinca Massif (Ourense province) shows a net eutrophication trend since the termination of the Subatlantic period. This trend was however interrupted by oligotrophication events in the warm/cold transitions of the Roman Warm Period to the DA, lasting 500 years, and the MCA to LIA, which lasted 600 years. Extended ice cover during the LIA, as suggested by the preliminary diatom data, involved stronger denitrification processes associated to longer periods of anoxia, indicated by the nitrogen isotopic record. Anticipation of the oligotrophication events to the known chronologies for the onset of the DA and the LIA suggests that these two phases occurred approximately 100 and 200 years earlier than expected, according to other mountain lake record of the W Iberian Peninsula. Our preliminary data also show significant discrepancies in the timing of the ecological impacts of Recent Climate Changes (RCCs) taking place in the last 2,000 yr in coastal and mountain areas over a short longitudinal gradient which needs further explorationN

Stream diatom biodiversity in islands and continents—A global perspective on effects of area, isolation and environment

Aim The species-area relationship (SAR) is one of the most distinctive biogeographic patterns, but global comparisons of the SARs between island and mainland are lacking for microbial taxa. Here, we explore whether the form of the SAR and the drivers of species richness, including area, environmental heterogeneity, climate and physico-chemistry, differ between islands and similarly sized areas on mainland, referred to as continental area equivalents (CAEs). Location Global. Taxon Stream benthic diatoms. Methods We generated CAEs on six continental datasets and examined the SARs of CAEs and islands (ISAR). Then, we compared CAEs and islands in terms of total richness and richness of different ecological guilds. We tested the factors contributing to richness in islands and CAEs with regressions. We used structural equation models to determine the effects of area versus environmental heterogeneity, climate and local conditions on species richness. Results We found a non-significant ISAR, but a significant positive SAR in CAEs. Richness in islands was related to productivity. Richness in CAEs was mainly dependent on area and climate, but not directly on environmental heterogeneity. Species richness within guilds exhibited inconsistent relationships with island isolation and area. Main conclusions Ecological and evolutionary processes shaping diatom island biogeography do not depend on area at the worldwide scale probably due to the presence of distinct species pool across islands. Conversely, area was an important driver of diatom richness in continents, and this effect could be attributed to dispersal. Continents had greater richness than islands, but this was a consequence of differences in environmental conditions such as specific island climatic conditions. We stress the need for more island data on benthic diatoms, particularly from archipelagos, to better understand the biogeography of this most speciose group of algae

Disentangling the geologic, human and climate drivers influencing sediment deposition in volcanic lakes on the Azores Archipelago

IAL-IPA joint meeting "Lakes as Memories of the Landscape", Patagonia, Argentina, 27 November-01 December 2022The Azores Archipelago Western (AAWG) and Central (AACG) groups present a high diversity of tectono-volcanic settings, and, therefore, a wide range of lake-watershed system morphometries. This archipelago has suffered from anthropic impacts, mainly abrupt land-use changes, since medieval times (between 700 and 850 CE), and increasingly after the Portuguese arrival in the 15th century. In this complex geologic and human context, we used a multiproxy approach in sediment records from Lakes Caldeirão (Corvo Island), Funda (Flores Island), and Caveiro (Pico Island) to demonstrate a complex interlinking among several environmental drivers over the last millennia. Paleoenvironmental changes have been defined by a multivariate analysis of sedimentary facies, biogeochemical and mineralogical data. This analysis highlights that the most prominent sedimentary process in the AAWG lakes (Caldeirao and Funda) is hydrological grain size sorting, driven by runoff. Additionally, smooth catchment slopes of the low-gradient lake, Caldeirão, modulated this process by favouring rock grain size diminution through weathering, whereas the steep topographic-bathymetric profile of the high-gradient lake, Funda, do through water-level fluctuations. The frequent volcanic activity of the AACG and the small size of Caveiro lake catchment favoured the deposit of pyroclastic tephra through direct fallout in the lake, over the catchment-sourced inputs, reworked by climate and tectonic activity. The biogeochemical and mineral composition of the sedimentary records present extreme change rates at 1288+28-22-1388+41-32 CE, corresponding with the age of the most intense landscape transformation. Therefore, to obtain robust climate reconstructions from these Azorean lacustrine records, we present a detailed statistical approach to isolate the climate signal from volcano-tectonic, morphometric, and anthropic driversThis research was funded by the Spanish Ministry of Economy and Competitiveness research projects PaleoNAO (CGL2010-15767), RapidNAO (CGL2013-40608-R), PaleoModes (CGL2016-75281-C2), and NEOCLIM (PID2020-113798GB-C33), and through Portuguese Science Foundation (FCT) (DL57/2016/ICETA/EEC2018/25) and the DISCOVERAZORES (PTDC/CTA-AMB/28511/2017)N

The Production and Qualification of Scintillator Tiles for the ATLAS Hadronic Calorimeter

The production of the scintillator tiles for the ATLAS Tile Calorimeter is presented. In addition to the manufacture and production, the properties of the tiles will be presented including light yield, uniformity and stability

Design, Construction and Installation of the ATLAS Hadronic Barrel Scintillator-Tile Calorimeter

The scintillator tile hadronic calorimeter is a sampling calorimeter using steel as the absorber structure and scintillator as the active medium. The scintillator is located in "pockets" in the steel structure and the wavelength-shifting fibers are contained in channels running radially within the absorber to photomultiplier tubes which are located in the outer support girders of the calorimeter structure. In addition, to its role as a detector for high energy particles, the tile calorimeter provides the direct support of the liquid argon electromagnetic calorimeter in the barrel region, and the liquid argon electromagnetic and hadronic calorimeters in the endcap region. Through these, it indirectly supports the inner tracking system and beam pipe. The steel absorber, and in particular the support girders, provide the flux return for the solenoidal field from the central solenoid. Finally, the end surfaces of the barrel calorimeter are used to mount services, power supplies and readout crates for the inner tracking systems and the liquid argon barrel electromagnetic calorimeter