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  • Nature Research
  • Springer Berlin Heidelberg
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  • 1
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    Four millennia of vegetation and environmental history above the Hyrcanian forest, northern Iran (2020)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2024-05-30
    Description: Past vegetation, fire, and climate dynamics, as well as human impact, have been reconstructed for the first time in the highlands of the Gilan province in the Alborz mountains (above the Hyrcanian forest) for the last 4,300 cal yrs bp. Multi-proxy analysis, including pollen, spores, non-pollen palynomorphs, charcoal, and geochemical analysis, has been applied to investigate the environmental changes at 2,280 m a.s.l., above the Hyrcanian forest. Dominant steppe vegetation occurred in the study area throughout the recorded period. The formation of the studied mire deposits, as well as vegetation composition, suggest a change to wetter climatic conditions after 4,300 until 1,700 cal yrs bp. Fires were frequent, which may imply long-lasting anthropogenic activities in the area. Less vegetation cover with a marked decrease of the Moisture Index (MI) suggests drier conditions between 1,700 and 1,000 cal yrs bp. A high proportion of Cichorioideae and Amaranthaceae, as well as the reduction of trees, in particular Fagus and Quercus, at lower elevations, indicate human activities such as intense livestock grazing and deforestation. Soil erosion as the result of less vegetation due to dry conditions and/or human activities can be reconstructed from a marked increase of Glomus spores and high values of K and Ti. Since 1,000 cal yrs bp, the increasing MI, as well as the rise of Poaceae and Cyperaceae together with forest recovery, suggest a change to wetter conditions. The occurrence of still frequent Cichorioideae and Plantago lanceolata along with Sordaria reflect continued intense grazing of livestock by humans.
    Description: Deutsche Forschungsgemeinschaft (DE)
    Description: Georg-August-Universität Göttingen (1018)
    Keywords: ddc:561 ; Late Holocene ; Northern Iran ; Multi-proxy studies ; Hyrcanian mountain vegetation ; Climate change ; Human impact
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    ATOMIX benchmark datasets for dissipation rate measurements using shear probes (2024)
    Nature Research
    Details
    Publication Date: 2024-05-30
    Description: Turbulent mixing in the ocean, lakes and reservoirs facilitates the transport of momentum, heat, nutrients, and other passive tracers. Turbulent fluxes are proportional to the rate of turbulent kinetic energy dissipation per unit mass, ε. A common method for ε measurements is using microstructure profilers with shear probes. Such measurements are now widespread, and a non-expert practitioner will benefit from best practice guidelines and benchmark datasets. As a part of the Scientific Committee on Oceanographic Research (SCOR) working group on “Analysing ocean turbulence observations to quantify mixing” (ATOMIX), we compiled a collection of five benchmark data of ε from measurements of turbulence shear using shear probes. The datasets are processed using the ATOMIX recommendations for best practices documented separately. Here, we describe and validate the datasets. The benchmark collection is from different types of instruments and covers a wide range of environmental conditions. These datasets serve to guide the users to test their ε estimation methods and quality-assurance metrics, and to standardize their data for archiving.
    Type: Article , PeerReviewed
    Format: text
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  • 3
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    Diatom-mediated food web functioning under ocean artificial upwelling (2024)
    Nature Research
    Details
    Publication Date: 2024-05-29
    Description: Enhancing ocean productivity by artificial upwelling is evaluated as a nature-based solution for food security and climate change mitigation. Fish production is intended through diatom-based plankton food webs as these are assumed to be short and efficient. However, our findings from mesocosm experiments on artificial upwelling in the oligotrophic ocean disagree with this classical food web model. Here, diatoms did not reduce trophic length and instead impaired the transfer of primary production to crustacean grazers and small pelagic fish. The diatom-driven decrease in trophic efficiency was likely mediated by changes in nutritional value for the copepod grazers. Whilst diatoms benefitted the availability of essential fatty acids, they also caused unfavorable elemental compositions via high carbon-to-nitrogen ratios (i.e. low protein content) to which the grazers were unable to adapt. This nutritional imbalance for grazers was most pronounced in systems optimized for CO 2 uptake through carbon-to-nitrogen ratios well beyond Redfield. A simultaneous enhancement of fisheries production and carbon sequestration via artificial upwelling may thus be difficult to achieve given their opposing stoichiometric constraints. Our study suggest that food quality can be more critical than quantity to maximize food web productivity during shorter-term fertilization of the oligotrophic ocean.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 4
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    A mechanism for reconciling the synchronisation of Heinrich events and Dansgaard-Oeschger cycles (2024)
    Nature Research
    Details
    Publication Date: 2024-05-28
    Description: The evolution of the northern hemispheric climate during the last glacial period was beset by quasi-episodic iceberg discharge events from the Laurentide ice sheet, known as Heinrich events (HEs). The paleo record places most HEs into the cold stadial of the Dansgaard-Oeschger cycle. However, not every Dansgaard-Oeschger cycle is associated with a HE, revealing a complex interplay between the two modes of glacial variability. Here, using a coupled ice sheet-solid earth model, we introduce a mechanism that explains the synchronicity of HEs and Dansgaard-Oeschger cycles. Unlike earlier studies, our mechanism does not require a trigger during the stadial. Instead, the atmospheric warming signal during the interstadial of the Dansgaard-Oeschger cycle causes enhanced ice stream thickening that leads to the HE during the late interstadial. We demonstrate that this mechanism reproduces the key HE characteristics and provides an explanation for synchronous HEs from different regions of the Laurentide ice sheet.
    Type: Article , PeerReviewed
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  • 5
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    Rapid Laurentide Ice Sheet growth preceding the Last Glacial Maximum due to summer snowfall (2024)
    Nature Research
    Details
    Publication Date: 2024-05-28
    Description: There has been extensive research into the nonlinear responses of the Earth system to astronomical forcing during the last glacial cycle. However, the speed and spatial geometry of ice sheet expansion to its largest extent at the Last Glacial Maximum 21 thousand years ago remains uncertain. Here we use an Earth system model with interactive ice sheets to show that distinct initial North American (Laurentide) ice sheets at 38 thousand years ago converge towards a configuration consistent with the Last Glacial Maximum due to feedbacks between atmospheric circulation and ice sheet geometry. Notably, ice advance speed and spatial pattern in our model are controlled by the amount of summer snowfall, which is dependent on moisture transport pathways from the North Atlantic warm pool linked to ice sheet geometry. The consequence of increased summer snowfall on the surface mass balance of the ice sheet is not only the direct increase in accumulation but the indirect reduction in melt through the snow/ice–albedo feedback. These feedbacks provide an effective mechanism for ice growth for a range of initial ice sheet states and may explain the rapid North American ice volume increase during the last ice age and potentially driving growth during previous glacial periods.
    Type: Article , PeerReviewed
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  • 6
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    Global warming due to loss of large ice masses and Arctic summer sea ice (2020)
    Nature Research
    Details
    Publication Date: 2024-05-28
    Description: Several large-scale cryosphere elements such as the Arctic summer sea ice, the mountain glaciers, the Greenland and West Antarctic Ice Sheet have changed substantially during the last century due to anthropogenic global warming. However, the impacts of their possible future disintegration on global mean temperature (GMT) and climate feedbacks have not yet been comprehensively evaluated. Here, we quantify this response using an Earth system model of intermediate complexity. Overall, we find a median additional global warming of 0.43 °C (interquartile range: 0.39−0.46 °C) at a CO 2 concentration of 400 ppm. Most of this response (55%) is caused by albedo changes, but lapse rate together with water vapour (30%) and cloud feedbacks (15%) also contribute significantly. While a decay of the ice sheets would occur on centennial to millennial time scales, the Arctic might become ice-free during summer within the 21st century. Our findings imply an additional increase of the GMT on intermediate to long time scales.
    Type: Article , PeerReviewed
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  • 7
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    A climatology of weather-driven anomalies in European photovoltaic and wind power production (2024)
    Nature Research | Springer
    Details
    Publication Date: 2024-05-28
    Description: Weather causes extremes in photovoltaic and wind power production. Here we present a comprehensive climatology of anomalies in photovoltaic and wind power production associated with weather patterns in Europe considering the 2019 and potential 2050 installations, and hourly to ten-day events. To that end, we performed kilometer-scale numerical simulations of hourly power production for 23 years and paired the output with a weather classification which allows a detailed assessment of weather-driven spatio-temporal production anomalies. Our results highlight the dependency of low-power production events on the installed capacities and the event duration. South-shifted Westerlies (Anticyclonic South-Easterlies) are associated with the lowest hourly (ten-day) extremes for the 2050 (both) installations. Regional power production anomalies can differ from the ones in the European mean. Our findings suggest that weather patterns can serve as indicators for expected photovoltaic and wind power production anomalies and may be useful for early warnings in the energy sector.
    Type: Article , PeerReviewed
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  • 8
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    Strong temperature gradients in the ice age North Atlantic Ocean revealed by plankton biogeography (2023)
    Nature Research
    Details
    Publication Date: 2024-05-28
    Description: The cold Last Glacial Maximum, around 20,000 years ago, provides a useful test case for evaluating whether climate models can simulate climate states distinct from the present. However, because of the indirect and uncertain nature of reconstructions of past environmental variables such as sea surface temperature, such evaluation remains ambiguous. Instead, here we evaluate simulations of Last Glacial Maximum climate by relying on the fundamental macroecological principle of decreasing community similarity with increasing thermal distance. Our analysis of planktonic foraminifera species assemblages from 647 sites reveals that the similarity-decay pattern that we obtain when the simulated ice age seawater temperatures are confronted with species assemblages from that time differs from the modern. This inconsistency between the modern temperature dependence of plankton species turnover and the simulations arises because the simulations show globally rather uniform cooling for the Last Glacial Maximum, whereas the species assemblages indicate stronger cooling in the subpolar North Atlantic. The implied steeper thermal gradient in the North Atlantic is more consistent with climate model simulations with a reduced Atlantic meridional overturning circulation. Our approach demonstrates that macroecology can be used to robustly diagnose simulations of past climate and highlights the challenge of correctly resolving the spatial imprint of global change in climate models.
    Type: Article , PeerReviewed
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  • 9
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    Climate effects on archaic human habitats and species successions (2022)
    Nature Research
    Details
    Publication Date: 2024-05-28
    Description: It has long been believed that climate shifts during the last 2 million years had a pivotal role in the evolution of our genus Homo 1–3 . However, given the limited number of representative palaeo-climate datasets from regions of anthropological interest, it has remained challenging to quantify this linkage. Here, we use an unprecedented transient Pleistocene coupled general circulation model simulation in combination with an extensive compilation of fossil and archaeological records to study the spatiotemporal habitat suitability for five hominin species over the past 2 million years. We show that astronomically forced changes in temperature, rainfall and terrestrial net primary production had a major impact on the observed distributions of these species. During the Early Pleistocene, hominins settled primarily in environments with weak orbital-scale climate variability. This behaviour changed substantially after the mid-Pleistocene transition, when archaic humans became global wanderers who adapted to a wide range of spatial climatic gradients. Analysis of the simulated hominin habitat overlap from approximately 300–400 thousand years ago further suggests that antiphased climate disruptions in southern Africa and Eurasia contributed to the evolutionary transformation of Homo heidelbergensis populations into Homo sapiens and Neanderthals, respectively. Our robust numerical simulations of climate-induced habitat changes provide a framework to test hypotheses on our human origin.
    Type: Article , PeerReviewed
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  • 10
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    Recent European drought extremes beyond Common Era background variability (2021)
    Nature Research
    Details
    Publication Date: 2024-05-24
    Description: Europe’s recent summer droughts have had devastating ecological and economic consequences, but the severity and cause of these extremes remain unclear. Here we present 27,080 annually resolved and absolutely dated measurements of tree-ring stable carbon and oxygen (δ13C and δ18O) isotopes from 21 living and 126 relict oaks (Quercus spp.) used to reconstruct central European summer hydroclimate from 75 BCE to 2018 CE. We find that the combined inverse δ13C and δ18O values correlate with the June–August Palmer Drought Severity Index from 1901–2018 at 0.73 (P 〈 0.001). Pluvials around 200, 720 and 1100 CE, and droughts around 40, 590, 950 and 1510 CE and in the twenty-first century, are superimposed on a multi-millennial drying trend. Our reconstruction demonstrates that the sequence of recent European summer droughts since 2015 CE is unprecedented in the past 2,110 years. This hydroclimatic anomaly is probably caused by anthropogenic warming and associated changes in the position of the summer jet stream.
    Type: Article , PeerReviewed
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    Format: other
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