ALBERT

Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Ice sheet processes are often simplified in global climate models as changes in ice sheets have been assumed to occur over long time scales compared to ocean and atmospheric changes. However, numerous observations show an increasing rate of mass loss from the Greenland Ice Sheet and call for comprehensive process-based models to explore its role in climate change. Here, we present a new model system, EC-Earth-PISM, that includes an interactive Greenland Ice Sheet. The model is based on the EC-Earth v2.3 global climate model in which ice sheet surface processes are introduced. This model interacts with the Parallel Ice Sheet Model (PISM) without anomaly or flux corrections. Under pre-industrial climate conditions, the modeled climate and ice sheet are stable while keeping a realistic interannual variability. In model simulations forced into a warmer climate of four times the pre-industrial CO〈jats:sub〉2〈/jats:sub〉 concentration, the total surface mass balance decreases and the ice sheet loses mass at a rate of about 500 Gt/year. In the climate warming experiments, the resulting freshwater flux from the Greenland Ice Sheet increases 55% more in the experiments with the interactive ice sheet and the climate response is significantly different: the Arctic near-surface air temperature is lower, substantially more winter sea ice covers the northern hemisphere, and the ocean circulation is weaker. Our results indicate that the melt-albedo feedback plays a key role for the response of the ice sheet and its influence on the changing climate in the Arctic. This emphasizes the importance of including interactive ice sheets in climate change projections.〈/jats:p〉

Description: Land use/land cover change is an important carrier for the study of human-land relationship. Yuxi City is a typical area of with alternating mountain and basin landforms, forming a special human-land system with “mountains” and “basins” as the core elements. Taking 75 towns in Yuxi City, Yunnan Province as a case study, this paper uses a comprehensive evaluation model of land use/land cover change and related analysis methods to analyze the changes of land use pattern in mountainous areas and basin areas respectively from 1995 to 2018, and to reveal their spatial differences and its influencing factors. The results show that: 1) The dynamic evolution of land use in the mountainous area and the basin area presented obvious stage characteristics. From 1995 to 2005, the average comprehensive dynamic degree of land use in the mountainous area was 1.7861, which was significantly higher than the 1.7033 in the basin area. The average comprehensive dynamic degree of land use in mountainous areas from 2005 to 2018 was 1.1284, which was significantly lower than 1.9427 in the basin area. 2) From 1995 to 2018, the land use degree and the comprehensive dynamic degree of land use continued to rise in the basin area, while the mountainous area showed a trend of rising first and then falling. The overall change trend of land use depletion in the mountainous area was consistent with that in the basin area, but the mountainous area was always higher than that in the basin area. 3) The land use change in mountainous areas and basin areas was mainly reflected in the difference of natural factors and socio-economic fators. The radiation and agglomeration functions of the basin area have always attracted people to migrate from the mountains to the basin, which was beneficial to the ecological restoration of the vegetation in the mountains. Since the mountainous area and the basin area are geographically adjacent, the coupling and coordination of the two is the premise and foundation for the sustainable development of the region. This causal relationship of land use changes provides a reliable basis for the regulation of mountain-basin human-land coupling relationship.

Description: Organic matter (OM) is known to be an important reductant in sediment-hosted base metal deposits like the European Kupferschiefer. However, the precise nature of interactions between OM and hydrothermal fluids are still debated as well as how the interconnected reactions develop over geological timescales. This dataset provides for the first time bulk, compositional and stable isotope data of hydrocarbons, biomarkers and organonitrogen, -sulfur and-oxygen (NSO) compounds for the mineralized Kupferschiefer Spremberg-Graustein field in Eastern Germany based on samples from two drill cores. The study aims to help to better understand the role that organic matter plays during the mineralisation and formation of the sedimentary ore deposit within the Kupferschiefer with a focus on stable hydrogen isotope compositions and NSO compositional data to especially address the origin and to assess the oxidative nature of the brines that caused the mineralization in the Spremberg-Graustein field. The data publication includes bulk, compositional and stable isotope data on inorganic metals and organic matter. The data about metal contents were generated using ICP-MS while those on the organic matter were generated using Rock-Eval pyrolysis, a microscope, a Soxhlet apparatus, medium pressure liquid chromatography (MPLC), gas chromatography with flame ionization (GC-FID) and mass spectrometric detection (GC-MS), gas chromatography isotope ratio mass spectrometry (GC-IRMS) and ultrahigh resolution mass spectrometry (Fourier Transform ion cyclotron resonance mass spectrometry, FT-ICR-MS) with Electrospray ionization (ESI) and Atmospheric pressure photoionization (APPI). The full description of samples, methods and data is given in the following sections.

Description: Although the impact of the Indian Ocean on the decaying pace of El Niño events has been documented previously, contrary to the consensus that the Indian Ocean Basin (IOB) mode favors the decay of El Niño via modulating the zonal wind anomalies in the tropical western Pacific, the contribution of the Indian Ocean Dipole (IOD) on the following year’s El Niño remains highly controversial. Through investigating the evolution of fast and slow decaying El Niño events, this study demonstrates that the positive IOD phase with a strong western pole prompts the termination of El Niño, whereas no significant effect of the IOD with a weak western pole. The responsible physical mechanism is that the strong western pole of a positive IOD can lead to a strong IOB pattern along with peaking in the late winter (earlier than normal), enhancing local convection and causing anomalous rising (sinking) motions over the tropical Indian Ocean (western Pacific Ocean). The surface easterly wind anomalies on the western flank of the sinking motions stimulate oceanic upwelling equatorial Kelvin waves, which shoal the thermocline in the equatorial eastern Pacific and rapidly terminate the equatorial warming during El Niño. However, a weak western pole of IOD induces a weak IOB mode that peaks in late spring, and the above cross-basin physical processes will not appear.

Description: In the recent decades, the Ross Ice Shelf (RIS) has experienced frequent summer surface melting, which accelerates ice loss and increases the instability of ice sheets. This study links the interannual variability of surface melting events over the RIS with the northerly wind anomaly over the Ross Sea sector, which is established in association with a quasi-geostrophic barotropic Rossby wave train from subtropical Australia toward West Antarctica. The Rossby wave train is regulated jointly by El Niño and atmospheric heating over western Australia. El Niño provides the major forcing of the atmospheric circulation anomalies over the Ross Sea, and most surface melting events over the RIS happened during El Niño years. In addition, the anomalous atmospheric heating over western Australia is identified as the other significant forcing that triggers the Rossby wave train. The northerly flow is sandwiched between the low and high geopotential height anomalies located respectively over the left-hand and right-hand sides of the Ross Sea, favoring strong poleward moisture and heat transport and leading to surface melting over the RIS.

Description: In July and August of 2022, unprecedented and long-lasting heatwaves attacked central and eastern China (CEC); and the most affected area was in the Yangtze River (YR) basin. The extreme heatwaves and associated drought and wildfire had significant social impacts, but the underlying mechanisms remain unknown. Observational analysis indicates that the heatwaves were regulated by anomalous anticyclone in the mid-upper troposphere over northern CEC. Specifically, the easterly anomalies at the southern flank of the anticyclone caused air isentropic sliding and transported low moist enthalpy (cold and dry) air to the YR basin, contributing to anomalous sinking motions and extreme heatwaves. In comparison, heatwaves were more serious in August than in July due to stronger upper-level anomalous anticyclone and associated easterlies. Importantly, different mechanisms were responsible for the heatwaves in the two months. In July, the relatively weaker anticyclonic anomaly over northern CEC was dominated by the forcing of diabatic heating over northwestern South Asia (NWSA), corresponding with the record-breaking rainfall in and around Pakistan. In August, a powerful anticyclonic condition for the CEC heatwaves originated from an extreme silk road pattern (SRP), superposing the effect of NWSA diabatic heating due to persistent downpour. We notice that another upstream anticyclonic node in the SRP also created heatwaves in Europe. Therefore, the CEC extreme heat was actually associated with other concurrent extremes over the Eurasian continent through large-scale atmospheric teleconnections in 2022.

Description: The rewetting of peatlands is a promising measure to mitigate greenhouse gas (GHG) emissions by preventing the further mineralization of the peat soil through aeration. In coastal peatland, the rewetting with brackish water can increase the GHG mitigation potential by the introduction of sulfate, a terminal electron acceptor (TEA). Sulfate is known to lower the CH4 production and thus, its emission by favoring the growth of sulfate-reducers, which outcompete methanogens for substrate. The data contain porewater variables such as pH, electrical conductivity (EC) and sulfate, chloride, dissolved CO2 and CH4 concentrations, as well as absolute abundances of methane- and sulfate-cycling microbial communities. The data were collected in spring and autumn 2019 after a storm surge with brackish water inflow in January 2019. Field sampling was conducted in the nature reserve Heiligensee and Hütelmoor in North-East Germany, close to the Southern Baltic Sea coast. We took peat cores using a Russian peat corer in addition to pore water diffusion samplers and plastic liners (length: 60cm; inner diameter 10 cm) at four locations along a transect from further inland towards the Baltic Sea. We wanted to compare the soil and pore water geochemistry as well as the microbial communities after the brackish water inflow to the common freshwater rewetting state. Pore water was extracted using pore water suction samplers in the lab and environmental variables were quantified with an ICP. Microbial samples were sampled from the peat core using sterile equipment. We used quantitative polymerase chain reaction (qPCR) to characterize pools of DNA and cDNA targeting total and putatively active bacteria and archaea. qPCR was performed on key functional genes of methane production (mcrA), aerobic methane oxidation (pmoA) and sulfate reduction (dsrB) in addition to the 16S rRNA gene for the absolute abundance of total prokaryotes. Furthermore, we retrieved soil plugs to determine the concentrations and isotopic signatures of dissolved trace gases (CO2/DIC and CH4) in the pore water.

Description: Rewetted peatlands can be a significant source of methane (CH4), but in coastal ecosystems, input of sulfate-rich seawater could potentially mitigate these emissions. The presence of sulfate as an electron acceptor during organic matter decomposition is known to suppress methanogenesis by favoring the growth of sulfate reducers, which outcompete methanogens for substrate. We investigated the effects of a brackish water inflow on the microbial communities relative to CH4 production–consumption dynamics in a freshwater rewetted fen at the southern Baltic Sea coast after a storm surge in January 2019 and analyzed our data in context with the previous freshwater rewetted state (2014 serves as our baseline) and the conditions after a severe drought in 2018 (Fig. 1). We took peat cores at four previously sampled locations along a brackishness gradient to compare soil and pore water geochemistry as well as the microbial methane- and sulfate-cycling communities with the previous conditions. We used high-throughput sequencing and quantitative polymerase chain reaction (qPCR) to characterize pools of DNA and RNA targeting total and putatively active bacteria and archaea. Furthermore, we measured CH4 fluxes along the gradient and determined the concentrations and isotopic signatures of trace gases in the peat. We found that both the inflow effect of brackish water and the preceding drought increased the sulfate availability in the surface and pore water. Nevertheless, peat soil CH4 concentrations and the 13C compositions of CH4 and total dissolved inorganic carbon (DIC) indicated ongoing methanogenesis and little methane oxidation. Accordingly, we did not observe a decrease in absolute methanogenic archaea abundance or a substantial change in methanogenic community composition following the inflow but found that the methanogenic community had mainly changed during the preceding drought. In contrast, absolute abundances of aerobic methanotrophic bacteria decreased back to their pre-drought level after the inflow, while they had increased during the drought year. In line with the higher sulfate concentrations, the absolute abundances of sulfate-reducing bacteria (SRB) increased – as expected – by almost 3 orders of magnitude compared to the freshwater state and also exceeded abundances recorded during the drought by over 2 orders of magnitude. Against our expectations, methanotrophic archaea (ANME), capable of sulfate-mediated anaerobic methane oxidation, did not increase in abundance after the brackish water inflow. Altogether, we could find no microbial evidence for hampered methane production or increased methane consumption in the peat soil after the brackish water inflow. Because Koebsch et al. (2020) reported a new minimum in CH4 fluxes at this site since rewetting of the site in 2009, methane oxidation may, however, take place in the water column above the peat soil or in the loose organic litter on the ground. This highlights the importance of considering all compartments across the peat–water–atmosphere continuum to develop an in-depth understanding of inflow events in rewetted peatlands. We propose that the changes in microbial communities and greenhouse gas (GHG) fluxes relative to the previous freshwater rewetting state cannot be explained with the brackish water inflow alone but were potentially reinforced by a biogeochemical legacy effect of the preceding drought.

Description: Rewetted peatlands can be a significant source of methane (CH4), but in coastal ecosystems, input of sulfate-rich seawater could potentially mitigate these emissions. The presence of sulfate as electron acceptor during organic matter decomposition is known to suppress methanogenesis, by favoring the growth of sulfate-reducers, which outcompete methanogens for substrate. We investigated the effects of a brackish water inflow on the microbial communities relative to CH4 production-consumption dynamics in a freshwater rewetted fen at the southern Baltic Sea coast after a storm surge in January 2019 and analyzed our data in context with the previous freshwater rewetted state (2014 serves as our baseline) and the conditions after a severe drought in 2018. We took peat cores at four previously sampled locations along a brackishness gradient to compare soil and pore water geochemistry as well as the microbial methane and sulfate cycling communities with the previous conditions. We used high-throughput sequencing and quantitative polymerase chain reaction (qPCR) to characterize pools of DNA and cDNA targeting total and putatively active bacteria and archaea. Furthermore, we measured CH4 fluxes along the gradient and determined the concentrations and isotopic signatures of trace gases in the peat. We found that both, the inflow effect of brackish water and in parts also the preceding drought increased the sulfate availability in the surface and pore water. Still, peat soil CH4 concentrations and the 13C compositions of CH4 and total dissolved inorganic carbon (DIC) indicated ongoing methanogenesis and little methane oxidation. Accordingly, we did not observe a decrease of absolute methanogenic archaea abundance or a substantial change in methanogenic community composition following the inflow, but found that the methanogenic community had mainly changed during the precedent drought. In contrast, absolute abundances of aerobic methanotrophic bacteria decreased back to their pre-drought level after the inflow while they had increased during the drought year. In line with the higher sulfate concentrations, the absolute abundances of sulfate reducing bacteria (SRB) increased – as expected – by almost three orders of magnitude compared to the freshwater state and also exceeded abundances recorded during the drought by over two orders of magnitude. Against our expectations, methanotrophic archaea (ANME), capable of sulfate-mediated anaerobic methane oxidation, did not increase in abundance after the brackish water inflow. Altogether, we could find no microbial evidence for hampered methane production or increased methane consumption in the peat soil after the brackish water inflow. Because Koebsch et al. (2020) reported a new minimum in CH4 fluxes at this site since rewetting of the site in 2009, methane oxidation may, however, take place in the water column above the peat soil or in the lose organic litter on the ground. This highlights the importance to consider all compartments across the peat-water-atmosphere continuum to develop an in-depth understanding of inflow events in rewetted peatlands. We propose that the changes in microbial communities and GHG fluxes relative to the previous freshwater rewetting state cannot be explained with the brackish water inflow alone, but was potentially reinforced by a biogeochemical legacy effect of the precedent drought.

Description: Sedimentary ancient DNA-based studies have been used to probe centuries of climate and environmental changes and how they affected cyanobacterial assemblages in temperate lakes. Due to cyanobacteria containing potential bloom-forming and toxin-producing taxa, their approximate reconstruction from sediments is crucial, especially in lakes lacking long-term monitoring data. To extend the resolution of sediment record interpretation, we used high-throughput sequencing, amplicon sequence variant (ASV) analysis, and quantitative PCR to compare pelagic cyanobacterial composition to that in sediment traps (collected monthly) and surface sediments in Lake Tiefer See. Cyanobacterial composition, species richness, and evenness was not significantly different among the pelagic depths, sediment traps and surface sediments (p 〉 0.05), indicating that the cyanobacteria in the sediments reflected the cyanobacterial assemblage in the water column. However, total cyanobacterial abundances (qPCR) decreased from the metalimnion down the water column. The aggregate-forming (Aphanizomenon) and colony-forming taxa (Snowella) showed pronounced sedimentation. In contrast, Planktothrix was only very poorly represented in sediment traps (meta- and hypolimnion) and surface sediments, despite its highest relative abundance at the thermocline (10 m water depth) during periods of lake stratification (May–October). We conclude that this skewed representation in taxonomic abundances reflects taphonomic processes, which should be considered in future DNA-based paleolimnological investigations. View Full-Text