Seasonal Air Temperature Research Articles

Study of the feature of the temperature regime of the Mykolaiv and region in the context of the issue of climate change

Climate change is one of the most important and acute environmental problems of our time. It includes a complex of changes, such as rising ambient temperatures, changes in precipitation patterns, rising sea levels, and more frequent extreme weather events. According to the Intergovernmental Panel on Climate Change (IPCC), the average global temperature has risen by about 1.1°C since the late nineteenth century. Projections point to a possible increase of 1.5°C by the middle of this century unless significant measures are taken to reduce greenhouse gas emissions. On the basis of the above, the paper analyzes trends in changes in atmospheric air temperature on the territory of risky agriculture in the South of Ukraine in the Mykolaiv region.The purpose of the study: to determine and substantiate the regularities of changes in the temperature regime of Mykolaiv and Mykolaiv region in the context of climate change.Research results. The values of temperature characteristics for the year and season in Mykolaiv and Mykolaiv region during 1991−2023 are analyzed. In Mykolaiv, about 60-67 days with a negative average daily air temperature and about 32 days with a negative maximum daily air temperature are recorded. The duration of the period with a negative minimum air temperature can be an average of 93 days per year: 64 in winter, 16 in spring and 14 in autumn. At the same time, on a large territory of the Mykolaiv region, autumn is warmer than spring. The average seasonal air temperature is 10.6°C, the average maximum temperature is 15.4°C, and the average minimum temperature is 6.4°C. In the Northern Black Sea region, both maximum and minimum temperatures in autumn are higher than in spring. The dynamics of changes in average annual temperatures in the city of Mykolaiv in the period from 1980 to 2023 are analyzed. A stable linear trend towards a gradual increase in average annual temperatures has been determined. The warmest year for this observation period is 2023, the coldest are 1985 and 1987. It is determined that the rate of increase in average temperature is 0.61°C for every ten years. Maximum temperatures are increasing at a rate of 0.0884°C per year and minimum temperatures are decreasing at a rate of 0.0136°C per year. Every year, the average annual temperature increases by approximately 0.021°С. The largest number of days accompanied by heat stress (up to 90%) is observed in July – August. Thus, changes in air temperature indicate a significant change in the temperature regime of the entire climate system of the region, and the consequences of climate change may be predominantly negative and will intensify in the future.

Exploration of a model driven by climate to simulate pond water temperature in aquaculture systems

IntroductionInterannual climate variability in the Asian mega deltas has been posing a wide range of climate risks in the aquaculture systems of the region. Water temperature variation is one of the key risks related to disease outbreak, fish health, and loss and damage in fish production. However, Climate information can improve the ability to predict changes in pond water quality parameters at the farm level using publicly available weather and climate data. Little research has been done to translate weather data into water temperature forecasts using mechanistic models in order to provide farmers with relevant forecasting information in the context of climate services.MethodsThe advantage of mechanistic models over statistical models is that they are based on physical processes and can therefore be used in a wider range of environmental conditions. In this study, we used an energy balance model to investigate its ability to simulate pond water temperature at daily and seasonal timescales in the southwest and northeast regions of Bangladesh. The model was able to adequately simulate pond water temperature at a daily timescale using publicly available weather data, and the accuracy of the model was lower at the study site with very heavy rainfall events.ResultsSensitivity analyses showed that the model was also able to simulate the impact of air temperature cold and hot spells on the pond water temperature. Connecting the model with seasonal air temperature forecasts resulted in very small variations in the forecasted seasonal pond water temperature, in large part due to the low variability observed in water temperature at seasonal scale in the study sites.DiscussionClimate information can improve the ability to predict changes in pond water quality parameters at the farm level using publicly available weather and climate data. Hence, these improved predictions are important to help fish-farmers make informed decisions for managing associated climate risks.

Complex imprint of air pollution in the basal area increments of three European tree species

The impact of atmospheric pollution on the growth of European forest tree species, particularly European beech, Silver fir and Norway spruce, is examined in five mesic forests in the Czech Republic. Analyzing of basal area increment (BAI) patterns using linear mixed effect models reveals a complex interplay between atmospheric nitrogen (N) and sulphur (S) deposition, climatic variables and changing CO2 concentrations. Beech BAI responds positively to N deposition (in tandem with air CO2 concentration), with soil phosphorus (P) availability emerging as a significant factor influencing overall growth rates. Fir BAI, on the other hand, was particularly negatively influenced by S deposition, although recent growth acceleration suggests growth resilience in post-pollution period. This fir growth surge likely coincides with stimulation of P acquisition following the decline of acidic pollution. The consequence is the current highest productivity among the studied tree species. The growth dynamics of both conifers were closely linked to the stoichiometric imbalance of phosphorus in needles, indicating the possible sensitivity of exogenous controls on nutrient uptake. Furthermore, spruce BAI was positively linked to calcium availability across sites. Despite enhanced water-use efficiency under elevated CO2, spruce growth is constrained by precipitation deficit and demonstrates weakening resilience to increasing growing season air temperatures. Overall, these findings underscore the intricate relationships between atmospheric pollution, nutrient availability, and climatic factors in shaping the growth dynamics of European forest ecosystems. Thus, incorporating biogeochemical context of nutrient availability is essential for realistic modelling of tree growth in a changing climate.

Trend analysis of air temperature in a megacity between two continents: the synoptic weather station in İstanbul Atatürk Airport

İstanbul is the largest city located in the Mediterranean Basin and has a medium to high risk of climate change and future climate risks. Changes in temperature and other weather variables have had significant impacts on İstanbul. In this context, there is a need for studies on the issues of climate monitoring and climate change vulnerability to reduce the adverse impacts. The aim of this study is to investigate the temperature trends of synoptic weather station in İstanbul Atatürk Airport between 1973 and 2023 to have a general idea about how the temperature has changed over the last half-century and to establish statistically whether a trend is significant or not. The values of minimum (Tmin), maximum (Tmax) and mean (Tmean) temperature related parameters were estimated. Annual, monthly and seasonal temperature trends are also analyzed. The findings of this study indicate a significant (p < 0.001) rise in the mean air temperature (Tmean) of İstanbul over the past 51 years (1973–2023), with an annual warming trend of 0.06 °C. The strongest increasing trend in seasonal mean air temperatures has been observed in the summer season, with an increase of 0.08 °C per year. The trend analysis also shows a statistically non-significant increase in yearly average minimum temperature (Tmin) between 1973 and 2023, with a rate of 0.04 °C per year. However, the annual maximum temperature (Tmax) has shown no changes.

When common recommendations for cultivating in cold soils inadvertently thaw permafrost

When common recommendations for cultivating in cold soils inadvertently thaw permafrost Melissa Ward Jones, details when common recommendations for cultivating in cold soils inadvertently thaw permafrost, starting with the challenges of cultivating at high latitudes. Cultivating crops within cold soils at high latitudes can be challenging. The growing season is short, with the risk of frosts at each seasonal margin, and overall, both air and soil temperatures limit crop options that can be grown. A common recommendation in cultivating cold soils is the use of seasonal extension techniques, such as greenhouses, high tunnels, low tunnels and various mulches (such as plastic and biodegradable like straw and compost) to artificially heat the soil, and depending on the technique used, the air temperature as well (Stevenson et al., 2014).

Seasonal impacts on gut microbial composition of the Eastern subterranean termite (Blattodea: Rhinotermitidae).

Termite hindguts are inhabited by symbionts that help with numerous processes, but changes in the gut microbiome due to season can potentially impact the physiology of termites. This study investigated the impact of seasonal changes on the composition of bacteria and protozoa in the termite gut. Termites were obtained monthly from May to October 2020 at a location in the central United States that typically experiences seasonal air temperatures ranging from < 0 to > 30 °C. The guts of 10 termites per biological replication were dissected and frozen within 1 day after collections. DNA was extracted from the frozen gut tissues and used for termite 16S rRNA mitochondrial gene analysis and bacterial 16S rRNA gene sequence surveys. Phylogenetic analysis of termite 16S rRNA gene sequences verified that the same colony was sampled across all time points. On processing bacterial 16S sequences, we observed alpha (observed features, Pielou's evenness, and Shannon diversity) and beta diversity (unweighted Unifrac, Bray-Curtis, and Jaccard) metrics to vary significantly across months. Based on the analysis of the composition of microbiomes with bias correction (ANCOM-BC) at the genus level, we found several significant bacterial taxa over collection months. In addition, Spearman correlation analysis demonstrated that 41 bacterial taxa were significantly correlated (positively and negatively) with average soil temperature. These results from a single termite colony suggest termite microbial communities go through seasonal changes in relative abundance related to temperature, although other seasonal effects cannot be excluded. Further investigations are required to conclusively define the consistency of microbial variation among different colonies with season.

VARIATIONS OF δ18О AND δ2H VALUES OF PRECIPITATION IN MOSCOW FROM 2017 TO 2019

To reveal variations in the iso topic composition of O and H in the atmospheric precipitation in Moscow and the processes influencing the isotope composition, all events of precipitation in 2017-2019 were sampled at the Meteorological Observatory of the Moscow State University: 158 samples in 2017, 119 samples in 2018 and 143 samples in 2019. The study is a prolongation of continuous measurements of the isotope composition of precipitation, started by authors in 2014. The study of the isotope composition of precipitation at the MSU Meteorological Observatory was supported by the IAEA and became a part of the Global Network of Isotopes in Precipitation (GNIP) database. It has been found that the intra-annual variability of the isotop e composition of precipitation has a pronounced seasonality. The most isotopically heavy precipitation falls from May to August, and the most isotop ically light precipitation at December-February, mainly due to seasonal air temperature variations. The ratio of the average monthly δ18O values in precipitation and air temperature for the study period varied from 0.34 to 0.39‰/°C, which is consistent with the previously obtained data for precipitation in Moscow. The δ2H-δ18O ratio in precipitation was clos e to that of the Global Meteoric Water Line, pointing to the equilibrium conditions during precipitation formation. It was established that in the summer months isotopic composition is significantly influenced by undercloud evaporation. The deuterium excess va lues in precipitation are not markedly seasonal; however, lower dexc values (below the 3-year average of 11‰) are typical for the summer months (July-August). It is most likely due to undercloud evaporation in conditions of low relative humidity and high air temperatures. Higher dexc values (above 11‰) prevailed from October to April.

Hemeroby Mapping of the Belém Landscape in Eastern Amazon and Impact Study of Urbanization on the Local Climate

This work contributes to the studies on landscape mapping induced by human pressure directly related to the urbanization process, whose approach is based on the concept of hemeroby adapted to the metropolitan area of Belém in the eastern Amazon. The mapping results using 1985 and 2021 Landsat satellite data indicated that the artificial coverage characterized as medium to the high urban system (polyhemerobic and metahemerobic degrees) has increased by almost 17% toward northern districts and Outeiro/Mosqueiro islands, while the natural vegetation cover suppression (ahemerobic degree) was around 11%. In addition, we investigated the impacts of urban expansion on seasonal (WET from January to April and DRY from July to November) surface air temperature (minimum TN and maximum TX) patterns. From statistical comparisons between 18-year samples (2004/2021 to 1985/2002), we find evidence of a current significantly warmer climate, with a notable indication of higher surface temperature over densely urbanized areas compared to lower values over natural areas. In the TX climatology, particularly for the DRY regime, we identified a pattern similar to the classic heat island model with concentric isotherms reaching a maximum center over the more urbanized continental region of Belém and a thermal decrease at the edges. Therefore, the findings of this work are convincing that Belém already faces the direct impacts of urbanization on the local climate, so it is crucial to develop government strategies aimed at taking action to mitigate socioenvironmental risks and threats to the well-being of urban populations.

First Pediastrum–temperature transfer function and its application to mid-to-late Holocene reconstruction in Central Asia

The green alga Pediastrum is an ecologically significant component of freshwater ecosystems, but its potential as an independent proxy for quantitative paleoenvironmental reconstruction is relatively unexplored. Here we use multivariate statistical analysis to explore the relationship between the Pediastrum composition of lake surface sediments and environmental variables. The findings highlight the mean growing season air temperature between March and October (TMar-Oct) as the most important factor determining the Pediastrum composition. We then establish the first transfer function between the Pediastrum taxa and TMar-Oct, which enables us to provide a quantitative temperature reconstruction for the past ∼8.2 kyr based on sedimentary subfossil Pediastrum records from Bosten Lake in Xinjiang, China. Our findings reveal an exceptionally warm climate during ∼4.8–3.6 kyr, with temperatures ∼4 °C higher compared to those during ∼8.2–4.8 kyr. This unusually warm climate is verified by the carbonate clumped isotopes record of the same core and other paleoclimate records. These findings contribute to our understanding of past temperature changes in Central Asia and provide a basis for future research on long-term lake ecosystem dynamics under past climatic warming.

Analysis of Extreme Temperature Variability in Rwanda

The temperature is one of the most important factors in weather and climate forecasting. Studying its behaviour is crucial to understanding climate variability, which could vary spatially and temporally at local, regional, and global scales. Several recent studies on air temperature findings show that the Earth' s near surface air temperature increased between 0.6 °C and 0.8 °C throughout the twentieth century. Using temperature records from ten meteorological stations, this study examined climate variability in Rwanda from the 1930s to 2014. The air temperature data were collected from Meteo Rwanda. Before making the analysis, the authors used software, such as Excel 2007 and INSTAT to control the quality of the raw data. The analysis of maxima and minima indicated that the trends of maximum air temperature were positive and significant at height meteorological stations, whereas the trends for minimum air temperature were found to be at 10 meteorological stations. For all parameters analysed, Kigali Airport meteorological station indicated the higher significance of the trends. The majority of meteorological stations showed an increase in both hot days and nights, confirming Rwanda' s warming over time. The analysis of average seasonal air temperature showed almost similar trends even though not all were significant. This similarity in trends could be attributed to the fact that Rwanda' s short and long dry seasons coincide with rainy seasons.

Continuous electricity generation from diurnal and seasonal air temperature variation

Limited research has been conducted on green and effective approaches for harnessing thermal energy from diurnal and seasonal air temperature variation. Thermally regenerative electrochemical cycle, with high low-grade heat-to-electricity conversion efficiency, is desirable for generating electricity through periodical temperature variation because of its separate charging and discharging processes. However, the cell merely discharges at a limited period with intermittent power output. Herein, a novel continuous power output system, combining p-type and n-type cells, is proposed and investigated to harness heat from periodical temperature variation and convert it into electricity. In this instance, electricity generation relies solely on the energy derived from air without solar radiation or outer space cooling. Based on operating principles and experiment results, the system concept, operating processes, and mathematic models are well developed. The p-type and n-type cell characteristics, diurnal performance, and seasonal performance are investigated and analysed. The results suggest that the average power density is 0.15 W/kg and 0.69 W/kg in the diurnal and seasonal periodic conditions, respectively, in Urumqi city. This indicates the proposed idea is an effective technology for obtaining electricity continuously from air temperature variation.

The role of temperature in vitality and survival assessments of beam-trawled and discarded European plaice (Pleuronectes platessa).

Thermal stress can influence the recovery of fish released after capture. Vitality assessments using reflex and behavioural responses require that responses can be observed reliably, independent of temperature. Here, we tested whether reflex and behavioural impairment and survival of beam-trawled and discarded European plaice (Pleuronectes platessa) are independent from seasonal air and water temperature deviations. In total, 324 beam-trawled plaice (n = 196 in summer and n = 128 in winter) were exposed to two air temperature treatments and two water treatments (i.e. modified and ambient temperatures for both). The modified treatments (i.e. cooled in summer, warmed in winter) represent the thermal shock a fish may experience when being returned to the water. All reflexes and tested behaviours were affected by ambient temperature, with high impairment noted in summer. None of the reflexes were affected by temperature shocks alone, only body flex was. Body flex was highly impaired under every exposure combination. Fish size and duration of air exposure further influenced impairment of reflexes such as head complex and tail grab. More generally, post-release survival was assessed as 21% [95% CI: 16-28%] in summer and 99% [97-100%] in winter. Beam trawling in summer is likely to induce high reflex impairment and mortality in discarded plaice, and therefore spatial-temporal mitigation approaches should be prioritized over control of on-board temperatures.

Elevational variations of leaf morphological traits and its responses to simulated climate warming in Tibetan alpine meadows

Both climate and environment changes can lead to variations in leaf morphological traits within or among herbaceous species. However, evidence for leaf morphological traits of alpine herbaceous species shifts with elevations, particularly under climate warming, is scarce. A field experimental warming experiment was conducted to address these questions in alpine meadows on the Tibetan Plateau. We measured the leaf morphological traits including leaf length, leaf width, leaf perimeter, leaf area of alpine herbaceous species along a slope of the Nyenqing-Tanggula Mountain (from 4600 m to 5200 m) on the Tibetan Plateau. Our results revealed that warming greatly decreased plant cover, species richness, and plant biomass of alpine meadows, but had no significant effects on soil carbon and nutrients. Leaf area across warming and control treatments was on average larger in low-elevation alpine meadows, and smaller toward the high-elevation alpine meadows, with leaf length and length/width ratio significantly decreased with increasing elevations. Leaf area and leaf length were positively corelated with growing season air temperature and soil temperature, but had no significant relationship with growing season precipitation, soil moisture, and photosynthetically active radiation. The decreasing elevational pattern in leaf size could be mainly attributed to the decreasing in leaf length. In response to experimental warming, our results further revealed that leaf size tended to be larger in warming plots than control plots along the elevational gradient, and the warming effects on leaf size varied greatly with herbaceous species. However, warming greatly decreased community-weighted means leaf area in mid-elevations, but increased that in both lower and higher elevations, which were mainly due to warming-induced variations in species richness and plant coverage. Our findings will fill the knowledge gap and provided valuable observational evidence in exploring elevational pattern of leaf size in Tibetan alpine meadows.

Recent Climate Change in the Republic of Srpska and Bosnia and Herzegovina

The paper gives an overview of the observed climate change in the Republic of Srpska and Bosnia and Herzegovina; primarily the changes in air temperature and precipitation regime. In the period 1961‒2015 the positive trends of mean, maximum and minimum annual and seasonal air temperatures were determined, which were most pronounced in the summer season, whereas in the autumn season there is only a slight upward trend of temperatures. Warming is most pronounced in the northern part of the territory, whereas the increase is much lower in the higher parts of the Herzegovina region. Unlike air temperature, precipitation trends are, both seasonally and regionally, very variable and of different signs (positive and negative), but mostly insignificant. However, in some areas, the interannual variability of precipitation and the frequency of extreme precipitation have increased. In addition, the paper presents the results of research on possible climate change (based on expected changes in air temperature and precipitation) by the end of the 21st century in the Republic of Srpska and Bosnia and Herzegovina according to the climate scenario RCP8.5. The results indicate more pronounced climate change related to increasing annual temperatures up to 5 °C and reducing annual precipitation by up to 30%, whereas the deficit in the summer season (June, July and August) could go up to 40% by the end of the 21st century. Such changes point to the serious problem of drought and water scarcity and the need for more significant integration of climate change issues into planning and strategic documents.

Partiküler Hava Kirliliğinin Bebek Ölümlerine Kısa Dönemdeki Etkisi: 2018-2020 Yılları Ankara İli Örneği

Background: Today, nine out of 10 people on a global scale live in an air pollution environment above the limit values determined. It is predicted that particulate air pollution is a risk factor for 5.3% of deaths under the age of one in Türkiye. In order to examine the causes of infant deaths and take necessary precautions, it is important to investigate air pollution and the possibilities of infant death due to. Aims: This study was carried out to examine the relationship between Particulate Matter (PM) 2.5 and (PM)10 levels observed in Ankara between the years 2018-2020 and infant deaths that occurred at that time. Methods: To examine the relationship poisson regression model, in which the terms formed by the flexible cubic spline function, were mainly used. The effect of each 10 μg/m3 increase in PM2.5 and PM10 on infant mortality, taking into account lags of up to seven days by adjusting for seasonal trends and air temperature effects, was determined by relative risk (RR) and 95% confidence intervals (CI) analyzed by calculation. Results: In the evaluated period, 1295 infant deaths occurred in 754 of 1096 days. The three-year average of the daily average PM2.5 and PM10 levels detected in Ankara is above the limit values. Conclusion: The effect of particulate air pollution on infant mortality in the first week was not detected, this relationship may become detectable when different variables such as possible effect modifiers are included in the models applied. The subject should also be examined under such different conditions.

A Systematic Review and Meta-Analysis of Free Triiodothyronine (FT3) Levels in Humans Depending on Seasonal Air Temperature Changes: Is the Variation in FT3 Levels Related to Nonshivering Thermogenesis?

Thyroid hormones play a crucial role in regulating normal development, growth, and metabolic function. However, the controversy surrounding seasonal changes in free triiodothyronine (FT3) levels remains unresolved. Therefore, the aim of this study was to conduct a systematic review and meta-analysis of variations in FT3 levels in relation to seasonal air temperatures in the context of current knowledge about its role in nonshivering thermogenesis. Ten eligible articles with a total of 336,755 participants were included in the meta-analysis. The studies were categorized into two groups based on the air temperature: "Cold winter", where the winter temperature fell below 0 °C, and "Warm winter", where the winter temperature was above 0 °C. The analysis revealed that in cold regions, FT3 levels decreased in winter compared to summer (I2 = 57%, p < 0.001), whereas in warm regions, FT3 levels increased during winter (I2 = 28%, p < 0.001). These findings suggest that seasonal variations in FT3 levels are likely to be influenced by the winter temperature. Considering the important role of the FT3 in the nonshivering thermogenesis process, we assume that this observed pattern is probably related to the differences in use of thyroid hormones in the brown adipose tissue during adaptive thermogenesis, which may depend on intensity of cold exposure.

High Arctic channel incision modulated by climate change and the emergence of polygonal ground

Stream networks in Arctic and high-elevation regions underlain by frozen ground (i.e., permafrost) are expanding and developing in response to accelerating global warming, and intensifying summertime climate variability. The underlying processes governing landscape dissection in these environments are varied, complex and challenging to unravel due to air-temperature-regulated feedbacks and shifts to new erosional regimes as climate change progresses. Here we use multiple sources of environmental information and physical models to reconstruct and understand a 60-year history of landscape-scale channelization and evolution of the Muskox Valley, Axel Heiberg Island. A time series of air photographs indicates that freeze-thaw-related polygon fields can form rapidly, over decadal time scales. Supporting numerical simulations show that the presence of polygons can control how surface runoff is routed through the landscape, exerting a basic control on channelization, which is sensitive to the timing, duration and magnitude of hydrograph events, as well as seasonal air temperature trends. These results collectively highlight that the occurrence and dynamics of polygon fields modulate channel network establishment in permafrost-rich settings undergoing changes related to a warming climate.

СЕЛЕКЦИЯ, ПОДСОЛНЕЧНИК, УРОЖАЙ

The results of long-term studies (1955-2022) carried out on typical chernozems of the Tambov region, the northernmost border of sunflower cultivation, are presented. The aim of the research is to create very early and early varieties of sunflower with a growing season of 85-95 days, ripening without the use of desiccants. The effect of moisture availability during the growing season and average air temperature on the productivity potential of various sunflower varieties bred by the Tambov Research Institute of Agriculture - branch of the Federal State Budget Scientific Institution “FSC named after I.V. Michurin" was studied. The negative impact of increased temperature and reduced precipitation on the yield capacity of sunflower varieties has been established. Over the years of research work on sunflower breeding, 19 varieties and 1 sunflower hybrid have been created. Currently, the State Register of Breeding Achievements approved for cultivation in the agricultural production of the Central Chernozem (5) and Middle Volga (7) regions contains 5 varieties: Spartak, Chakinsky 931, Chakinsky 77, PK 05, Chakinsky 100 and one sunflower hybrid Nadezhda, created jointly with OOO “Agroplazma”. In 2021, a new sunflower variety Zagrei 21 was submitted for the State Variety Test.

Topography and canopy cover influence soil organic carbon composition and distribution across a forested hillslope in the discontinuous permafrost zone

AbstractTopography and canopy cover influence ground temperature in warming permafrost landscapes, yet soil temperature heterogeneity introduced by mesotopographic slope positions, microtopographic differences in vegetation cover, and the subsequent impact of contrasting temperature conditions on soil organic carbon (SOC) dynamics are understudied. Buffering of permafrost‐affected soils against warming air temperatures in boreal forests can reflect surface soil characteristics (e.g., thickness of organic material) as well as the degree and type of canopy cover (e.g., open cover vs. closed cover). Both landscape and soil properties interact to determine meso‐ and microscale heterogeneity of ground warming. We sampled a hillslope catena transect in a discontinuous permafrost zone near Fairbanks, Alaska, to test the small‐scale (1 to 3 m) impacts of slope position and cover type on soil organic matter composition. Mineral active layer samples were collected from backslope, low backslope, and footslope positions at depths spanning 19 to 60 cm. We examined soil mineralogical composition, soil moisture, total carbon and nitrogen content, and organic mat thickness in conjunction with an assessment of SOC composition using Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). Soils in the footslope position had a higher relative contribution of lignin‐like compounds, whereas backslope soils had more aliphatic and condensed aromatic compounds as determined using FT‐ICR‐MS. The effect of open versus closed tree canopy cover varied with the slope position. On the backslope, we found higher oxidation of molecules under open cover than closed cover, indicating an effect of warmer soil temperature on decomposition. Little to no effect of the canopy was observed in soils at the footslope position, which we attributed, in part, to the strong impact of soil moisture content in SOC dynamics in the water‐gathering footslope position. The thin organic mat under open cover on the backslope position may have contributed to differences in soil temperature and thus SOC oxidation under open and closed canopies. Here, the thinner organic mat did not appear to buffer the underlying soil against warm season air temperatures and thus increased SOC decomposition as indicated by the higher oxidation of SOC molecules and a lower contribution of simple molecules under open cover than the closed canopy sites. Our findings suggest that the role of canopy cover in SOC dynamics varies as a function of landscape position and soil properties, namely, organic mat thickness and soil moisture. Condition‐specific heterogeneity of SOC composition under open and closed canopy cover highlights the protective effect of canopy cover for soils on backslope positions.

Lake Dynamics Modulate the Air Temperature Variability Recorded by Sedimentary Aquatic Biomarkers: A Holocene Case Study From Western Greenland

AbstractQuantitative temperature reconstructions from lacustrine organic geochemical proxies including branched glycerol dialkyl glycerol tetraethers (brGDGTs) and alkenones provide key constraints on past continental climates. However, estimation of air temperatures from proxies can be impacted by non‐stationarity in the relationships between seasonal air and water temperatures, a factor not yet examined in strongly seasonal high‐latitude settings. We pair downcore analyses of brGDGTs and alkenones measured on the same samples through the Holocene with forward‐modeled proxy values based on thermodynamic lake model simulations for a western Greenland lake. The measured brGDGT distributions suggest that stable autochthonous (aquatic) production overpowers allochthonous inputs for most samples, justifying the use of the lake model to interpret temperature‐driven changes. Conventional calibration of alkenones (detected only after 5.5 thousand years BP) suggests substantially larger temperature variations than conventional calibration of brGDGTs. Comparison of proxy measurements to forward‐modeled values suggests variations in brGDGT distributions monotonically reflect multi‐decadal summer air temperatures changes, although the length of the ice‐free season dampens the influence of air temperatures on water temperatures. Drivers of alkenone variability remain less clear; potential influences include small changes in the seasonality of proxy production or biases toward specific years, both underlain by non‐linearity in water‐air temperature sensitivity during relevant seasonal windows. We demonstrate that implied temperature variability can differ substantially between proxies because of differences in air‐water temperature sensitivity during windows of proxy synthesis without necessitating threshold behavior in the lake or local climate, and recommend that future studies incorporate lake modeling to constrain this uncertainty.