The finite element method is used to investigate the ultimate lateral pressure of snowflake pile group in undrained clay in this paper. The parametric analyses are performed to study the effects of the geometry of cross-section, the pile-soil adhesion coefficient, the loading direction, and the normalized pile spacing on the ultimate lateral pressure and the damage mechanism of the snowflake pile. The analysis results show that the ultimate lateral pressure of snowflake pile group decreases with the increasing of the length-thickness ratio of the pile flange and increases with the increasing of the pile-soil adhesion coefficient. When the loading direction is considered, the snowflake pile group with the number of piles of 4 is less affected by the loading direction, it has a larger ultimate lateral pressure. The ultimate lateral pressure of the pile group significantly decreases with the increasing of the number of piles. When the pile spacing is smaller, the decreasing of the ultimate lateral pressure is more obvious with the increasing of the number of piles. On the basis of finite element analysis, the empirical formula of ultimate lateral pressure of snowflake pile group is proposed and calibrated with the finite element results.

Study region: The Qinghai Lake basin, including China's largest saltwater lake, is located on the Qinghai-Tibetan Plateau (QTP). Study focus: This study focuses on the hydrological changes between the past (1971-2010) and future period (2021-2060) employing the distributed hydrological model in the Qinghai Lake basin. Lake evaporation, lake precipitation, and water level changes were estimated using the simulations driven by corrected GCM data. The impacts of various factors on the lake water levels were meticulously quantified. New hydrological insights: Relative to the historical period, air temperatures are projected to rise by 1.72 degrees C under SSP2-4.5 and by 2.21 degrees C under SSP5-8.5 scenarios, and the future annual precipitation will rise by 34.7 mm in SSP2-4.5 and 44.1 mm in SSP5-8.5 in the next four decades. The ground temperature is projected to show an evident rise in the future period, which thickens the active layer and reduces the frozen depth. The runoff into the lake is a pivotal determinant of future water level changes, especially the runoff from the permafrost degradation region and permafrost region dominates the future water level changes. There will be a continuous rapid increase of water level under SSP5-8.5, while the water level rising will slow down after 2045 in the SSP2-4.5 scenario. This study provides an enhanced comprehension of the climate change impact on QTP lakes.

Lakes are commonly accepted as a sensitive indicator of regional climate change, including the Tibetan Plateau (TP). This study took the Ranwu Lake, located in the southeastern TP, as the research object to investigate the relationship between the lake and regional hydroclimatological regimes. The well-known Budyko framework was utilized to explore the relationship and its causes. The results showed air temperature, evapotranspiration and potential evapotranspiration in the Ranwu Lake Basin generally increased, while precipitation, soil moisture, and glacier area decreased. The Budyko space indicated that the basin experienced an obviously drying phase first, and then a slightly wetting phase. An overall increase in lake area appears inconsistent with the drying phase of the basin climate. The inconsistency is attributable to the significant expansion of proglacial lakes due to glacial melting, possibly driven by the Atlantic Multidecadal Oscillation. Our findings should be helpful for understanding the complicated relationships between lakes and climate, and beneficial to water resources management under changing climates, especially in glacier basins.

Numerous endorheic lakes in the Qinghai-Tibet Plateau (QTP) have shown a dramatic increase in total area since 1996. These expanding lakes are mainly located in the interior regions of the QTP, where permafrost is widely distributed. Despite significant permafrost degradation due to global warming, the impact of permafrost thawing on lake evolution in QTP has been underexplored. This study investigated the permafrost degradation and its correlation with lake area increase by selecting four lake basins (Selin Co, Nam Co, Zhari Namco, and Dangqiong Co) in QTP for analysis. Fluid-heat-ice coupled numerical models were conducted on the aquifer cross-sections in these four lake basins, to simulate permafrost thawing driven by rising surface temperatures, and calculate the subsequent changes in groundwater discharge into the lakes. The contribution of these changes to lake storage, which is proportional to lake area, was investigated. Numerical simulation indicates that from 1982 to 2011, permafrost degradation remained consistent across the four basins. During this period, the active layer thickness first increased, then decreased, and partially transformed into talik, with depths reaching up to 25 m. By 2011, groundwater discharge had significantly risen, exceeding 2.9 times the initial discharge in 1988 across all basins. This increased discharge now constitutes up to 17.67 % of the total lake water inflow (Selin Co). The dynamic lake water budget further suggests that groundwater contributed significantly to lake area expansion, particularly since 2000. These findings highlight the importance of considering permafrost thawing as a crucial factor in understanding the dynamics of lake systems in the QTP in the context of climate change.

Predicting the impacts of climate change on aquatic ecosystems in the Subarctic is challenging due to the presence of permafrost and the wide range of geomorphologic conditions found across this heterogeneous landscape. To accurately predict how fish and wildlife will be impacted by climate change, it is critical to identify the habitat requirements of important prey such as macroinvertebrates. To better understand spatial heterogeneity in macroinvertebrate populations and identify key habitat requirements, we compared taxonomic richness, relative abundance, and density of macroinvertebrate populations in seven different lake basin types, spanning a large latitudinal and elevational gradient of subarctic Alaska. We used nonparametric statistics and NMDS to relate macroinvertebrate community metrics to landscape characteristics such as sedimentary deposit type, permafrost extent, geomorphology, and lake basin type, as well as chemical conditions within the lakes. Macroinvertebrate richness was highest in areas with continuous permafrost, largely driven by richness in dipterans. Lake water chemistry influenced taxa richness, relative abundance, and densities of both macroinvertebrates and microcrustaceans. Invertebrate densities were greatest in regions (parks) with higher nutrient concentrations and specific conductance, with higher relative abundance of dipterans in older landscape terrains (Yedoma) while a higher relative abundance of microcrustaceans was found in landscapes with little peat accumulation (sand dunes). As climate-driven permafrost thaw continues across the subarctic, shifts in pH, specific conductance, and calcium are likely to occur due to changes in active layer thickness and surface and groundwater flow paths that drive nutrient and solute delivery. Changes in invertebrate relative abundance and density are most likely to occur in ETOC and Diptera, two of the most ecologically important invertebrate groups found in subarctic lakes.

Permafrost thaw has the potential to release ancient particulate and dissolved organic matter that had been stored for thousands of years. Previous studies have shown that dissolved organic matter from permafrost is very labile and can be used by heterotrophic microbes close to the thaw area. However, it is unknown if ancient particulate organic matter can also be utilized. This study aims to investigate whether arctic microbial communities (bacteria and Archaea) incorporate ancient organic matter potentially released from thawing permafrost into their biomass. We compare and contrast the radiocarbon signatures of microbial lipids and higher plant biomarkers (representing terrestrial organic matter) from five soil profiles and seven deltaic lake sediment cores from the Mackenzie River drainage basin, Arctic Canada. In the surface soils, modern to post-modern short-chain fatty acids (SCFA) ages indicate in situ microbial production, with differential rates of organic carbon (OC) cycling depending on soil moisture. In contrast, SCFA in deeper soils display millennial ages, which likely represent the microbial necromass preserved through mineral association. In deltaic lakes that are disconnected from the river, generally old SCFA suggests the uptake of pre-aged OC by bacteria. In perennially connected lakes, pre-aged SCFA could originate from in situ microbial uptake of old OC or from the Mackenzie River. Higher plant-derived long-chain fatty acids (LCFA) present older radiocarbon ages, reflecting mineral stabilization during either pre-aging in soils (for high closure lakes) or riverine transport (for no and low closure lakes). Archaeal lipids are younger than SCFA and LCFA in high closure lakes, and older in low and no closure lakes, mirroring bulk radiocarbon signatures due to their heterotrophic production. These radiocarbon signatures of bacterial biomarker lipids may therefore reflect microbial incorporation of ancient OC (e.g., derived from permafrost thaw) or exceptional preservation (e.g., through mineral stabilization). Hence, even in relatively high OC environments such as arctic aquatic ecosystems, microbes can rely on ancient OC for their growth.

Magnesium phosphate cement (MPC), renowned for its rapid hardening, low water demand, low-temperature hydration capability, and excellent wear resistance, is an ideal construction material for the extreme lunar environment, characterized by high vacuum, low gravity, and severe temperature fluctuations. In this study, by-product B-MgO from lithium extraction in salt lakes was utilized to develop four types of phosphate cement systems: ammonium magnesium phosphate cement (MAPC), sodium magnesium phosphate cement (MSPC), calcium magnesium phosphate cement (MCPC), and potassium magnesium phosphate cement (MKPC). Through a comparative analysis of the physical and mechanical properties of these systems at varying calcination temperatures of MgO, MKPC was identified as the most suitable for lunar construction. Further investigations examined the influence of the water-to-binder ratio (W/B) and the mass ratio of raw materials (M/P) on MKPC performance, alongside a detailed analysis of its phase composition and microstructure. The results revealed that the optimal MKPC performance is achieved at an MgO calcination temperature of 1000 degrees C, an M/P ratio of 1:1 to 2:1, and a W/B ratio of 0.2 to 0.25. Additionally, MKPC was employed as a cementitious material to produce MKPC-simulated lunar regolith concrete with regolith contents of 30 %, 53 %, and 70 %. The fabricated concrete met the required mechanical properties and 3D printability standards under lunar environmental conditions. Even at high regolith content, the concrete maintained satisfactory mechanical performance. These findings provide an efficient and reliable material solution for lunar infrastructure construction. (c) 2024 Published by Elsevier B.V. on behalf of COSPAR.

In the context of global warming, landscapes with ice-rich permafrost, such as the Qinghai-Tibet Plateau (QTP), are highly vulnerable. The expansion of thermokarst lakes erodes the surrounding land, leading to collapses of various scales and posing a threat to nearby infrastructure and the environment. Assessing the susceptibility of thermokarst lakes in remote, data-scarce areas remains a challenging task. In this study, Landsat imagery and human-computer interaction were employed to improve the accuracy of thermokarst lake classification. The study also identified the key factors influencing the occurrence of thermokarst lakes, including the lake density, soil moisture (SM), slope, vegetation, snow cover, ground temperature, precipitation, and permafrost stability (PS). The results indicate that the most susceptible areas cover 19.02% of the QTP's permafrost region, primarily located in southwestern Qinghai, northeastern Tibet, and the Hoh Xil region. This study provides a framework for mapping the spatial distribution of thermokarst lakes and contributes to understanding the impact of climate change on the QTP.

The stability of arctic permafrost and the carbon it contains are currently threatened by a rapidly warming climate. Burial Lake, situated in northwestern arctic Alaska, is underlain by continuous permafrost and has a uniquely rich set of paleoclimate proxy data that comprise a 40-ka record of climate and environmental change extending well into Marine Isotope Stage (MIS) 3. Here, we examine the relationship between erosion, subsurface hydrology, and primary productivity from the Burial Lake sediments to improve our understanding of the links between climate, hydrology, sediment transport, and carbon mobility. The record is developed with radiocarbon (14C) age-offsets from two independent methods used to date the lake sediments: 1) 14 C measurements on paired bulk sediment and plant macrofossils from the same stratigraphic layer of lake sediment and 2) ramped pyrolysis- oxidation (RPO) 14 C analysis that separates fractions of organic carbon (OC) from a single bulk sediment sample based on thermochemical differences through continuous heating. As lakes capture and archive OC transported from the watershed, changes in the amount and relative age of permafrost-derived OC mobilized during past climatic variations can be documented by examining how age-offsets change over time. The Burial Lake sediment revealed higher age-offsets during the cold Last Glacial Maximum (LGM; 29-17 ka) than the comparatively warmer post-glacial ( 17 ka-present) and the MIS 3 interstadial ( 40-29 ka) periods. The relatively warm, wet climate of the post-glacial period promoted both terrestrial and aquatic productivity, resulting in increased OC deposition, and it likely favored transport via subsurface flow of dissolved OC (DOC) sourced from soils. This resulted in a greater flux of contemporary OC relative to ancient OC into the lake sediment, lowering the average age offset to 2 ka. In contrast, the low-productivity conditions of the LGM resulted in slow soil accumulation rates, leaving ancient OC in a shallower position in the soil profile and allowing it to be easily eroded in the form of particulate OC (POC). Although the amount of total OC deposited in the lakebed during the LGM is small relative to post-glacial deposition, the majority is ancient, which leads to a relatively high average age offset of 9 ka. Finally, climate and environmental conditions of the MIS 3 interstadial were intermediate between those of the post-glacial and the LGM. As with post-glacial sediments, a relatively large amount of OC is present; however, the vast majority of it is ancient (more similar to the LGM), and it produces an average age offset of 6 ka. The Burial Lake radiocarbon record demonstrates the complexities of the thaw and mobilization of permafrost OC in arctic Alaska, including the balance between production, transport, deposition, remobilization, and preservation. This record highlights the importance of considering factors that both enhance and inhibit erosion (i.e. vegetation cover, lake level, precipitation) and the mechanisms of OC transport (i.e. subsurface flow or erosion) in predictions of future permafrost response to changes in climate.

Lake sediments record the environment during the lake sedimentation whose characteristics can infer environmental changes and human activities. In this study, the Pb-210 chronologies and sedimentation rate of the sediment core in Honghu Lake were calculated by the Constant Rate of Supply model. The characteristics of the sedimentary environment were analysed by using physical and chemical indicators. Four stages were divided as follows: Stage A (before 1900): The relatively low sedimentation rate and nutrient content indicated an extremely stable sedimentary environment. Stage B (1900-1949): With the growth of population, the intensity of land use began to increase, with an averaged sedimentation rate of 0.252 gcm(-2)a(-1). Stage C (1949-1980): The sedimentation rate and nutrient content increased markedly. The intense human activity has damaged the surrounding vegetation leading to soil erosion and accelerated sedimentation rate. With the deterioration of the lake water environment, the organic matter source was mainly the internal source represented by algae and bacteria. Stage D (1980-2011): Influenced by the difference in land use types along the coast, the sedimentation rate of HH-A (0.570 gcm(-2)a(-1)) is higher than that of HH-B (0.445 gcm(-2)a(-1)). The results are of significance to the management of rural lakes and reservoirs.