High-resolution assessment of the Valgu event: conodont diversity and δ18Ophos during the early Telychian (Silurian) in the Baltic Basin

2020 ◽  
Author(s):  
Monica Alejandra Gomez Correa ◽  
Emilia Jarochowska ◽  
Peep Männik ◽  
Axel Munnecke ◽  
Michael Joachimski
Keyword(s):  
Carbon Cycle ◽  
Sea Level ◽  
Global Climate ◽  
Baltic Basin ◽  
Sea Level Fluctuations ◽  
Core Section ◽  
Storm Wave ◽  
The Baltic ◽  
A Minor ◽  
The Impact

<p>The influence of global climate and oceanographic system dynamics over biological patterns throughout Earth’s history is one of the main concerns in paleobiology. Periods that record changes in biodiversity of various magnitude are of particular interest in this field. Previous studies of major Silurian bioevents (e.g. Ireviken, Mulde and Lau) suggest that these events affected different faunas and have been correlated with positive carbon isotope (δ<sup>13</sup>C<sub>carb</sub>) excursions and positive shifts in oxygen isotopes (δ<sup>18</sup>O<sub>phos</sub>) ratios, suggesting there was a disturbance in the carbon cycle, a drop in temperature, and potential glaciations. However, the impact of the biological events has not been fully assessed, and the influence of climate change remains unclear.</p><p>Here, we focus on the Valgu event, a minor episode of proposed environmental and faunistic changes in the early Telychian, which has been recognized in Baltica and Laurentia paleocontinents by changes in conodont succession and a positive excursion in δ<sup>13</sup>C<sub>carb</sub>. In this study, we assess a limestone-marl alternation core section in Estonia deposited below the storm wave base during the Valgu event. We test for a substantial decrease in the biodiversity of conodont communities, for extent perturbation in the carbon cycle, manifest in a positive δ<sup>13</sup>C<sub>carb</sub> excursion, and an abrupt positive δ<sup>18</sup>O<sub>phos</sub> shift, which might be indicative of rapid cooling and a rapid sea-level fall typical for glacio-eustatic cycles. To this aim, we measured bulk-rock δ<sup>13</sup>C<sub>carb</sub> as well as δ<sup>18</sup>O<sub>phos</sub> in monogeneric conodont samples and analyzed the conodont diversity from the event interval.</p><p>The lower part of the investigated section is characterized by shallow-water bioclastic limestones containing green algae. On top of this facies, a pronounced hardground indicates a gap in deposition and marks the boundary between the bioclastic limestones and the overlying sediments composed of nodular limestones and marls, which were deposited below the storm wave base. They show a positive carbon shift of ca. 1.4 ‰ during the Valgu interval, but no indication of an extreme change in the conodont biodiversity is evident. Likewise, the δ<sup>18</sup>O<sub>phos</sub> in conodonts remains constant in the section, arguing against cooling or glacially-driven sea-level fluctuations as drivers for the observed changes.</p>

scholarly journals <i>Lingulodinium machaerophorum</i> expansion over the last centuries in the Caspian Sea reflects global warming

2012 ◽  
Vol 9 (11) ◽  
pp. 16663-16704
Author(s):  
S. A. G. Leroy ◽  
H. A. K. Lahijani ◽  
J.-L. Reyss ◽  
F. Chalié ◽  
S. Haghani ◽  
...  
Keyword(s):  
Sea Level ◽  
Caspian Sea ◽  
Global Climate ◽  
Sediment Cores ◽  
Sea Surface ◽  
Sea Level Changes ◽  
The Caspian Sea ◽  
Sea Level Fluctuations ◽  
Marine Surface ◽  
A Minor

Abstract. We analysed dinoflagellate cyst assemblages in four short sediment cores, two of them dated by radionuclides, taken in the south basin of the Caspian Sea. The interpretation of the four sequences is supported by a collection of 27 lagoonal or marine surface sediment samples. A sharp increase in the biomass of the dinocyst occurs after 1967, especially owing to Lingulodinium machaerophorum. Considering nine other cores covering parts or the whole of Holocene, this species started to develop in the Caspian Sea only during the last three millennia. By analysing instrumental data and collating existing reconstructions of sea level changes over the last few millennia, we show that the main forcing of the increase of L. machaerophorum percentages and of the recent dinocyst abundance is global climate change, especially sea surface temperature increase. Sea level fluctuations likely have a minor impact. We argue that the Caspian Sea has entered the Anthropocene.

Periodically forced self-organization in the long-term evolution of planktic foraminifera

2001 ◽  
Vol 38 (2) ◽  
pp. 293-308 ◽  
Author(s):  
Andreas Prokoph ◽  
Anthony D Fowler ◽  
R Timothy Patterson
Keyword(s):  
Sea Level ◽  
Logistic Map ◽  
Late Eocene ◽  
Self Organization ◽  
Extinction Data ◽  
Sea Level Fluctuations ◽  
Global Sea Level ◽  
Extinction Events ◽  
The Impact

Wavelet transform and other signal analysis techniques suggest that the planktic foraminiferal (PF) long-term evolutionary record of the last 127 Ma can be attributed to complex periodic and nonlinear patterns. Correlation of the PF extinction pattern with other geological series favors an origin of the ~30 Ma periodicity and self-organization by quasi-periodic mantle-plume cycles that in turn drive episodic volcanism, CO2-degassing, oceanic anoxic conditions, and sea-level fluctuations. Stationary ~30 Ma periodicity and a weak secular trend of ~100 Ma period are evident in the PF record, even without consideration of the mass extinction at the K–T boundary. The 27–32 Ma periodicity in the impact crater record and lows in the global sea-level curve, respectively, are ~6.5 Ma and ~2.3 Ma out of phase with PF-extinction data, although major PF-extinction events correspond to the bolide impacts at the K–T boundary and in late Eocene. Another six extinction events correspond to abrupt global sea-level falls between the late Albian and early Oligocene. Self-organization in the PF record is characterized by increased radiation rates after major extinction events and a steady number of baseline species. Our computer model of long-term PF evolution replicates this SO pattern. The model consists of output from the logistic map, which is forced at 30 Ma and 100 Ma frequencies. The model has significant correlations with the relative PF-extinction data. In particular, it replicates singularities, such as the K–T event, nonstationary 2.5–10 Ma periodicities, and phase shifts in the ~30 Ma periodicity of the PF record.

scholarly journals Last Interglacial climate and sea-level evolution from a coupled ice sheet–climate model

2016 ◽  
Vol 12 (12) ◽  
pp. 2195-2213 ◽  
Author(s):  
Heiko Goelzer ◽  
Philippe Huybrechts ◽  
Marie-France Loutre ◽  
Thierry Fichefet
Keyword(s):  
Surface Temperature ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Last Interglacial ◽  
A Minor ◽  
The Antarctic ◽  
The Impact ◽  
And Sea Level

Abstract. As the most recent warm period in Earth's history with a sea-level stand higher than present, the Last Interglacial (LIG,  ∼  130 to 115 kyr BP) is often considered a prime example to study the impact of a warmer climate on the two polar ice sheets remaining today. Here we simulate the Last Interglacial climate, ice sheet, and sea-level evolution with the Earth system model of intermediate complexity LOVECLIM v.1.3, which includes dynamic and fully coupled components representing the atmosphere, the ocean and sea ice, the terrestrial biosphere, and the Greenland and Antarctic ice sheets. In this setup, sea-level evolution and climate–ice sheet interactions are modelled in a consistent framework.Surface mass balance change governed by changes in surface meltwater runoff is the dominant forcing for the Greenland ice sheet, which shows a peak sea-level contribution of 1.4 m at 123 kyr BP in the reference experiment. Our results indicate that ice sheet–climate feedbacks play an important role to amplify climate and sea-level changes in the Northern Hemisphere. The sensitivity of the Greenland ice sheet to surface temperature changes considerably increases when interactive albedo changes are considered. Southern Hemisphere polar and sub-polar ocean warming is limited throughout the Last Interglacial, and surface and sub-shelf melting exerts only a minor control on the Antarctic sea-level contribution with a peak of 4.4 m at 125 kyr BP. Retreat of the Antarctic ice sheet at the onset of the LIG is mainly forced by rising sea level and to a lesser extent by reduced ice shelf viscosity as the surface temperature increases. Global sea level shows a peak of 5.3 m at 124.5 kyr BP, which includes a minor contribution of 0.35 m from oceanic thermal expansion. Neither the individual contributions nor the total modelled sea-level stand show fast multi-millennial timescale variations as indicated by some reconstructions.

scholarly journals Analysis of moored ship oscillations in waves

2020 ◽  
Author(s):  
Д.П. Ковалев ◽  
П.Д. Ковалев ◽  
А.С. Борисов
Keyword(s):  
Dynamic System ◽  
Sea Level ◽  
Order Differential Equation ◽  
External Excitation ◽  
Impact Oscillator ◽  
Mooring Lines ◽  
Sea Level Fluctuations ◽  
Port Area ◽  
Sea Level Fluctuation ◽  
The Impact

В работе рассмотрены особенности колебаний пришвартованного судна для основных портов Сахалинской области, поскольку качка судна у причала может представлять опасность и приводить к повреждению судна или швартовых линий. По данным натурных измерений морского волнения в портовых бухтах рассчитаны спектры колебаний уровня и определены периоды существующих в них волн для диапазона периодов от 2 с до 30 минут. Произведен расчет периодов собственных колебаний (качки) двух типов судов, преимущественно швартующихся в портах. С учетом полученных результатов выполнено моделирование движения судов при волнении как динамической с системы внешним возбуждающим воздействием на основе дифференциального уравнения второго порядка. Показано влияние коэффициента вязкого демпфирования и жесткости швартовых на реакцию динамической системы без удара о причал и для режима ударного осциллятора. Установлено, что в случае прихода в район порта Корсаков длинноволновой зыби движения судна могут переходить в хаотические. The paper considers the peculiarities of moored vessel oscillations for the main ports of the Sakhalin region, since the pitching of the vessel at the berth can be dangerous and lead to damages of the vessel or mooring lines. Spectra of sea level fluctuations and periods of waves in port bays were calculated using sea level fluctuation measurements obtained in the range from 2 seconds to 30 minutes. Calculations of resonance periods (pitching) of two types of vessels mainly moored in ports were done. Taking into consideration these results the simulation of the vessel movement in waves as a dynamic system with an external excitation was performed on the base of second-order differential equation. The influence of viscous damping coefficient and mooring stiffness on the response of the dynamic system is shown for two cases: for system without impact and for the impact oscillator mode. It is established that in the event of a long-wave swell coming to the Korsakov port area, the vessels movements may become chaotic.

scholarly journals The impact of the 2015/2016 El Niño on global photosynthesis using satellite remote sensing

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170409 ◽  
Author(s):  
Xiangzhong Luo ◽  
Trevor F. Keenan ◽  
Joshua B. Fisher ◽  
Juan-Carlos Jiménez-Muñoz ◽  
Jing M. Chen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Carbon Cycle ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Carbon Sink ◽  
Global Climate ◽  
Prognostic Models ◽  
Positive Anomaly ◽  
The Impact

The El Niño-Southern Oscillation exerts a large influence on global climate regimes and on the global carbon cycle. Although El Niño is known to be associated with a reduction of the global total land carbon sink, results based on prognostic models or measurements disagree over the relative contribution of photosynthesis to the reduced sink. Here, we provide an independent remote sensing-based analysis on the impact of the 2015–2016 El Niño on global photosynthesis using six global satellite-based photosynthesis products and a global solar-induced fluorescence (SIF) dataset. An ensemble of satellite-based photosynthesis products showed a negative anomaly of −0.7 ± 1.2 PgC in 2015, but a slight positive anomaly of 0.05 ± 0.89 PgC in 2016, which when combined with observations of the growth rate of atmospheric carbon dioxide concentrations suggests that the reduction of the land residual sink was likely dominated by photosynthesis in 2015 but by respiration in 2016. The six satellite-based products unanimously identified a major photosynthesis reduction of −1.1 ± 0.52 PgC from savannahs in 2015 and 2016, followed by a highly uncertain reduction of −0.22 ± 0.98 PgC from rainforests. Vegetation in the Northern Hemisphere enhanced photosynthesis before and after the peak El Niño, especially in grasslands (0.33 ± 0.13 PgC). The patterns of satellite-based photosynthesis ensemble mean were corroborated by SIF, except in rainforests and South America, where the anomalies of satellite-based photosynthesis products also diverged the most. We found the inter-model variation of photosynthesis estimates was strongly related to the discrepancy between moisture forcings for models. These results highlight the importance of considering multiple photosynthesis proxies when assessing responses to climatic anomalies. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

scholarly journals Geodetic SAR for Height System Unification and Sea Level Research—Observation Concept and Preliminary Results in the Baltic Sea

2020 ◽  
Vol 12 (22) ◽  
pp. 3747
Author(s):  
Thomas Gruber ◽  
Jonas Ågren ◽  
Detlef Angermann ◽  
Artu Ellmann ◽  
Andreas Engfeldt ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Tide Gauge ◽  
The Baltic Sea ◽  
Early Results ◽  
Height System ◽  
First Results ◽  
The Baltic ◽  
Sea Area ◽  
The Impact

Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national leveling networks and therefore define a height system of a country. One of the main deficiencies to use tide gauge data for geodetic sea level research and height systems unification is that only a few stations are connected to the geometric network of a country by operating permanent GNSS receivers next to the tide gauge. As a new observation technique, absolute positioning by SAR using active transponders on ground can fill this gap by systematically observing time series of geometric heights at tide gauge stations. By additionally knowing the tide gauge geoid heights in a global height reference frame, one can finally obtain absolute sea level heights at each tide gauge. With this information the impact of climate change on the sea level can be quantified in an absolute manner and height systems can be connected across the oceans. First results from applying this technique at selected tide gauges at the Baltic coasts are promising but also exhibit some problems related to the new technique. The paper presents the concept of using the new observation type in an integrated sea level observing system and provides some early results for SAR positioning in the Baltic sea area.

scholarly journals Decomposing Mean Sea Level Rise in a Semi-Enclosed Basin, the Baltic Sea

2019 ◽  
Vol 32 (11) ◽  
pp. 3089-3108 ◽  
Author(s):  
Ulf Gräwe ◽  
Knut Klingbeil ◽  
Jessica Kelln ◽  
Sönke Dangendorf
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Ocean Model ◽  
Spatial Variations ◽  
The Baltic Sea ◽  
Baltic Basin ◽  
Mean Sea Level ◽  
A Value ◽  
Regional Ocean Model ◽  
The Baltic

Abstract We analyzed changes in mean sea level (MSL) for the period 1950–2015 using a regional ocean model for the Baltic Sea. Sensitivity experiments allowed us to separate external from local drivers and to investigate individual forcing agents triggering basin-internal spatial variations. The model reveals a basin-average MSL rise (MSLR) of 2.08 ± 0.49 mm yr−1, a value that is slightly larger than the simultaneous global average of 1.63 ± 0.32 mm yr−1. This MSLR is, however, spatially highly nonuniform with lower than average increases in the southwestern part (1.71 ± 0.51 mm yr−1) and higher than average rates in the northeastern parts (2.34 ± 1.05 mm yr−1). While 75% of the basin-average MSL externally enters the Baltic basin as a mass signal from the adjacent North Sea, intensified westerly winds and a poleward shift of low pressure systems explain the majority of the spatial variations in the rates. Minor contributions stem from local changes in baroclinicity leading to a basin-internal redistribution of water masses. An observed increase in local ocean temperature further adds to the total basinwide MSLR through thermal expansion but has little effect on the spatial pattern. To test the robustness of these results, we further assessed the sensitivity to six different atmospheric surface forcing reanalysis products over their common period from 1980 to 2005. The ensemble runs indicated that there are significant differences between individual ensemble members increasing the total trend uncertainty for the basin average by 0.22 mm yr−1 (95% confidence intervals). Locally the uncertainty varies from 0.05 mm yr−1 in the central part to up to 0.4 mm yr−1 along the coasts.

scholarly journals Impact of Pleistocene Eustatic Fluctuations on Evolutionary Dynamics in Southeast Asian Biodiversity Hotspots

2021 ◽  
Author(s):  
Arni Sholihah ◽  
Erwan Delrieu-Trottin ◽  
Fabien L Condamine ◽  
Daisy Wowor ◽  
Lukas Rüber ◽  
...  
Keyword(s):  
Southeast Asia ◽  
Sea Level ◽  
Evolutionary Dynamics ◽  
Biodiversity Hotspots ◽  
Freshwater Biodiversity ◽  
Climatic Fluctuations ◽  
Ample Evidence ◽  
Sea Level Fluctuations ◽  
The Impact ◽  
Eustatic Fluctuations

Abstract Pleistocene Climatic Fluctuations (PCF) are frequently highlighted as important evolutionary engines that triggered cycles of biome expansion and contraction. While there is ample evidence of the impact of PCF on biodiversity of continental biomes, the consequences in insular systems depend on the geology of the islands and the ecology of the taxa inhabiting them. The idiosyncratic aspects of insular systems are exemplified by the islands of the Sunda Shelf in Southeast Asia (Sundaland), where PCF-induced eustatic fluctuations had complex interactions with the geology of the region, resulting in high species diversity and endemism. Emergent land in Southeast Asia varied drastically with sea level fluctuations during the Pleistocene. Climate-induced fluctuations in sea level caused temporary connections between insular and continental biodiversity hotspots in Southeast Asia. These exposed lands likely had freshwater drainage systems that extended between modern islands: the Paleoriver Hypothesis. Built upon the assumption that aquatic organisms are among the most suitable models to trace ancient river boundaries and fluctuations of landmass coverage, the present study aims to examine the evolutionary consequences of PCF on the dispersal of freshwater biodiversity in Southeast Asia. Time-calibrated phylogenies of DNA-delimited species were inferred for six species-rich freshwater fish genera in Southeast Asia (Clarias, Channa, Glyptothorax, Hemirhamphodon, Dermogenys, Nomorhamphus). The results highlight rampant cryptic diversity and the temporal localization of most speciation events during the Pleistocene, with 88% of speciation events occurring during this period. Diversification analyses indicate that sea level-dependent diversification models poorly account for species proliferation patterns for all clades excepting Channa. Ancestral area estimations point to Borneo as the most likely origin for most lineages, with two waves of dispersal to Sumatra and Java during the last 5 Myr. Speciation events are more frequently associated with boundaries of the paleoriver watersheds, with 60%, than islands boundaries, with 40%. In total, one-third of speciation events are inferred to have occured within paleorivers on a single island, suggesting that habitat heterogeneity and factors other than allopatry between islands substantially affected diversification of Sundaland fishes. Our results suggest that species proliferation in Sundaland is not wholly reliant on Pleistocene sea-level fluctuations isolating populations on different islands.

scholarly journals Designing global climate and atmospheric chemistry simulations for 1 and 10 km diameter asteroid impacts using the properties of ejecta from the K-Pg impact

2016 ◽  
Vol 16 (20) ◽  
pp. 13185-13212 ◽  
Author(s):  
Owen B. Toon ◽  
Charles Bardeen ◽  
Rolando Garcia
Keyword(s):  
Optical Depth ◽  
Atmospheric Chemistry ◽  
Forest Fires ◽  
Global Climate ◽  
Three Dimensional ◽  
Minor Component ◽  
Mass Extinctions ◽  
Mass Extinction Event ◽  
A Minor ◽  
The Impact

Abstract. About 66 million years ago, an asteroid about 10 km in diameter struck the Yucatan Peninsula creating the Chicxulub crater. The crater has been dated and found to be coincident with the Cretaceous–Paleogene (K-Pg) mass extinction event, one of six great mass extinctions in the last 600 million years. This event precipitated one of the largest episodes of rapid climate change in Earth's history, yet no modern three-dimensional climate calculations have simulated the event. Similarly, while there is an ongoing effort to detect asteroids that might hit Earth and to develop methods to stop them, there have been no modern calculations of the sizes of asteroids whose impacts on land would cause devastating effects on Earth. Here, we provide the information needed to initialize such calculations for the K-Pg impactor and for a 1 km diameter impactor. There is considerable controversy about the details of the events that followed the Chicxulub impact. We proceed through the data record in the order of confidence that a climatically important material was present in the atmosphere. The climatic importance is roughly proportional to the optical depth of the material. Spherules with diameters of several hundred microns are found globally in an abundance that would have produced an atmospheric layer with an optical depth around 20, yet their large sizes would only allow them to stay airborne for a few days. They were likely important for triggering global wildfires. Soot, probably from global or near-global wildfires, is found globally in an abundance that would have produced an optical depth near 100, which would effectively prevent sunlight from reaching the surface. Nanometer-sized iron particles are also present globally. Theory suggests these particles might be remnants of the vaporized asteroid and target that initially remained as vapor rather than condensing on the hundred-micron spherules when they entered the atmosphere. If present in the greatest abundance allowed by theory, their optical depth would have exceeded 1000. Clastics may be present globally, but only the quartz fraction can be quantified since shock features can identify it. However, it is very difficult to determine the total abundance of clastics. We reconcile previous widely disparate estimates and suggest the clastics may have had an optical depth near 100. Sulfur is predicted to originate about equally from the impactor and from the Yucatan surface materials. By mass, sulfur is less than 10 % of the observed mass of the spheres and estimated mass of nanoparticles. Since the sulfur probably reacted on the surfaces of the soot, nanoparticles, clastics, and spheres, it is likely a minor component of the climate forcing; however, detailed studies of the conversion of sulfur gases to particles are needed to determine if sulfuric acid aerosols dominated in late stages of the evolution of the atmospheric debris. Numerous gases, including CO2, SO2 (or SO3), H2O, CO2, Cl, Br, and I, were likely injected into the upper atmosphere by the impact or the immediate effects of the impact such as fires across the planet. Their abundance might have increased relative to current ambient values by a significant fraction for CO2, and by factors of 100 to 1000 for the other gases. For the 1 km impactor, nanoparticles might have had an optical depth of 1.5 if the impact occurred on land. If the impactor struck a densely forested region, soot from the forest fires might have had an optical depth of 0.1. Only S and I would be expected to be perturbed significantly relative to ambient gas-phase values. One kilometer asteroids impacting the ocean may inject seawater into the stratosphere as well as halogens that are dissolved in the seawater. For each of the materials mentioned, we provide initial abundances and injection altitudes. For particles, we suggest initial size distributions and optical constants. We also suggest new observations that could be made to narrow the uncertainties about the particles and gases generated by large impacts.

scholarly journals Ordovician reef and mound evolution: the Baltoscandian picture

2016 ◽  
Vol 154 (4) ◽  
pp. 683-706 ◽  
Author(s):  
BJÖRN KRÖGER ◽  
LINDA HINTS ◽  
OLIVER LEHNERT
Keyword(s):  
Sea Level ◽  
Climatic Conditions ◽  
Late Ordovician ◽  
Reef Growth ◽  
Baltic Basin ◽  
Reef Development ◽  
The Baltic ◽  
Oceanographic Conditions ◽  
Main Factor

AbstractThe widespread growth of reefs formed by a framework of biogenic constructors and frame-lacking carbonate mounds began on Baltica during Ordovician time. Previously, Ordovician reef and mound development on Baltica was considered to be sporadic and local. A review of all known bioherm localities across the Baltic Basin reveals a more consistent pattern. Ordovician bioherms grew in a wide E–W-aligned belt across the Baltic Basin and occur in several places in Norway. Substantial reef development began simultaneously across the region during the late Sandbian – early Katian interval and climaxed during the late Katian Pirgu age. The current spatiotemporal distribution of bioherms is a result of interdependent factors that involve original drivers of reef development such as relative sea level, climate during the time of deposition and effects of post-depositional erosion. Oceanographic conditions were likely more favourable during times of cooler global climates, low sea level and glacial episodes. At the same time, the likelihood that bioherms are preserved from long-term erosion is higher when deposited during low sea level in deeper parts of the basin. A main factor controlling the timing of the reef and mound evolution was Baltica's shift toward palaeotropical latitudes during Late Ordovician time. The time equivalence between initial reef growth and the Guttenberg isotope carbon excursion (GICE) suggests that global climatic conditions were important.

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