Sentinels Of Climate Change Research Articles

Tibetan lake change linked to large-scale atmospheric oscillations via hydroclimatic trajectory

Lakes are known as sentinels of climate change, but their responses may differ from one to another leading to different strategies in lake protection. It is particularly the case in the Tibetan Plateau (TP) of multiple hydrological processes. We employed the Budyko framework to study Tibetan lakes from two lake-basins of contrasting climates for the period between 1980 and 2022: Taro Co Basin (TCB) in a sub-arid climate, and Ranwu Lake Basin (RLB) in a sub-humid climate. Our results showed that total lake area, surface air temperature, evapotranspiration, and potential evapotranspiration increased in both lake-basins, while precipitation and soil moisture increased in the TCB but decreased in the RLB. In the Budyko space, two basins had contrast hydroclimatic trajectories in terms of aridity and evaporative index. The TCB shifted from wetting to drying trend, while the RLB from drying to wetting in early 2000s. Notably, lake change was generally consistent with the drying/wetting phases in the TCB, but in contrast with that in the RLB, which can be attributed to warming-induced glacier melting. Despite of significant correlation with the large-scale atmospheric oscillations, it turned to be more plausible if lake area changes were substituted with basin's hydroclimatic trajectories. Among the large-scale oscillations, El Niño-Southern Oscillation (ENSO) is the most dominant control of lake trends and their drying/wetting shifts. Our findings offer a valuable insight into lake responses to climate change in the TP and other regions.

Exploratory Analysis Using Deep Learning for Water-Body Segmentation of Peru's High-Mountain Remote Sensing Images.

High-mountain water bodies represent critical components of their ecosystems, serving as vital freshwater reservoirs, environmental regulators, and sentinels of climate change. To understand the environmental dynamics of these regions, comprehensive analyses of lakes across spatial and temporal scales are necessary. While remote sensing offers a powerful tool for lake monitoring, applications in high-mountain terrain present unique challenges. The Ancash and Cuzco regions of the Peruvian Andes exemplify these challenges. These regions harbor numerous high-mountain lakes, which are crucial for fresh water supply and environmental regulation. This paper presents an exploratory examination of remote sensing techniques for lake monitoring in the Ancash and Cuzco regions of the Peruvian Andes. The study compares three deep learning models for lake segmentation: the well-established DeepWaterMapV2 and WatNet models and the adapted WaterSegDiff model, which is based on a combination of diffusion and transformation mechanisms specifically conditioned for lake segmentation. In addition, the Normalized Difference Water Index (NDWI) with Otsu thresholding is used for comparison purposes. To capture lakes across these regions, a new dataset was created with Landsat-8 multispectral imagery (bands 2-7) from 2013 to 2023. Quantitative and qualitative analyses were performed using metrics such as Mean Intersection over Union (MIoU), Pixel Accuracy (PA), and F1 Score. The results achieved indicate equivalent performance of DeepWaterMapV2 and WatNet encoder-decoder architectures, achieving adequate lake segmentation despite the challenging geographical and atmospheric conditions inherent in high-mountain environments. In the qualitative analysis, the behavior of the WaterSegDiff model was considered promising for the proposed application. Considering that WatNet is less computationally complex, with 3.4 million parameters, this architecture becomes the most pertinent to implement. Additionally, a detailed temporal analysis of Lake Singrenacocha in the Vilcanota Mountains was conducted, pointing out the more significant behavior of the WatNet model.

Improving mean water lake surface elevation estimates using dense lidar measurements from the GEDI satellite mission

Lakes are an essential component of the global water cycle and are considered as sentinels of climate change. An accurate estimate of lake's water levels is necessary for reliable continuous monitoring of their water balance. Due to their huge number worldwide, satellite altimetry has been identified as an efficient tool for measuring their temporal variations of water level. This technique can reach an accuracy of a few centimeters for water level estimates over large lakes. Due to the coarse across-track spatial resolution of the radar altimetry missions, their spatial sampling only covers a small part of the lakes surface. To obtain an accurate estimate of the lake water level, it is necessary to apply a correction to account for the small-scale orthometric height undulations occurring on the lake area and not present in the current global geoid models. In this study, the high-density lidar measurements from GEDI are used to estimate the mean lake surface. From the 1,366,211 GEDI data over 1239 tracks acquired over more than 6000 km2 of the surface of Lake Issy-Kul (Kyrgyzstan, Central Asia) between May 2019 and mid-November 2021, 654,592 shots over 843 tracks were selected after a multi-step quality-check and processed to generate a mean lake surface of Lake Issyk-Kul. Comparison between the GEDI-based mean lake surface and GNSS kinematic surveys corrected from the lake level variations exhibit an RMSE of 0.065 m. The principal objective of performing such mean lake surface is to further use it in the framework of the calibration/validation of the Surface Water and Ocean Topography (SWOT) mission.

Geographic redistribution of microcystin hotspots in response to climate warming

High concentrations of cyanobacterial toxins such as microcystin represent a global challenge to water quality in lakes, threatening health, economies and ecosystem stability. Lakes are sentinels of climate change but how warming will affect microcystin concentrations is still unclear. Here we examine how warming impacts the probability of exceeding microcystin water quality thresholds across 2,804 lakes in the United States and show how future warming will alter these probabilities. We find that higher temperatures consistently increase the likelihood of microcystin occurrence but that the probability of microcystin concentrations above water quality thresholds is highest for water temperatures between 20 and 25 °C. Regions with temperatures that promote microcystin will shift to higher latitudes in the coming decades, leading to relative changes in exceedance probabilities of more than 50% in many basins of the United States. High nitrogen concentrations amplify the impact of rising temperatures, calling for increased awareness of a substantial hazard to ecosystems and human health under global warming.

Lake-TopoCat: a global lake drainage topology and catchment database

Abstract. Lakes and reservoirs are ubiquitous across global landscapes, functioning as the largest repository of liquid surface freshwater, hotspots of carbon cycling, and sentinels of climate change. Although typically considered lentic (hydrologically stationary) environments, lakes are an integral part of global drainage networks. Through perennial and intermittent hydrological connections, lakes often interact with each other, and these connections actively affect water mass, quality, and energy balances in both lacustrine and fluvial systems. Deciphering how global lakes are hydrologically interconnected (or the so-called “lake drainage topology”) is not only important for lake change attribution but also increasingly critical for discharge, sediment, and carbon modeling. Despite the proliferation of river hydrography data, lakes remain poorly represented in routing models, partially because there has been no global-scale hydrography dataset tailored to lake drainage basins and networks. Here, we introduce the global Lake drainage Topology and Catchment database (Lake-TopoCat), which reveals detailed lake hydrography information with careful consideration of possible multifurcation. Lake-TopoCat contains the outlet(s) and catchment(s) of each lake; the interconnecting reaches among lakes; and a wide suite of attributes depicting lake drainage topology such as upstream and downstream relationship, drainage distance between lakes, and a priori drainage type and connectivity with river networks. Using the HydroLAKES v1.0 (Messager et al., 2016) global lake mask, Lake-TopoCat identifies ∼ 1.46 million outlets for ∼ 1.43 million lakes larger than 10 ha and delineates 77.5×106 km2 of lake catchments covering 57 % of the Earth's landmass except Antarctica. The global lakes are interconnected by ∼ 3 million reaches, derived from MERIT Hydro v1.0.1 (Yamazaki et al., 2019), stretching a total distance of ∼10×106 km, of which ∼ 80 % are shorter than 10 km. With such unprecedented lake hydrography details, Lake-TopoCat contributes towards a globally coupled lake–river routing model. It may also facilitate a variety of limnological applications such as attributing water quality from lake scale to basin scale, tracing inter-lake fish migration due to changing climate, monitoring fluvial–lacustrine connectivity, and improving estimates of terrestrial carbon fluxes. Lake-TopoCat is freely accessible at https://doi.org/10.5281/zenodo.7916729 (Sikder et al., 2023).

Reservoirs as high-efficacy sentinels of regional atmospheric pollution and precipitation: magnetic and chemical evidence from a typical subtropical reservoir in South China.

While there is a general sense that reservoirs can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. Here multiple-proxy analyses including 210Pb, grain size, heavy metals, magnetic parameters, and spheroidal carbonaceous particles (SCPs) were conducted for a sediment core from a typical subtropical reservoir in South China (Huangkeng Reservoir). 210Pb dating revealed that the core spans from ~ 1964 to 2019, with the sedimentary rate increasing during recent years. The sedimentary environment was mainly influenced by natural process (especially precipitation), along with the accumulation of Cr, Ni, Cu, V, As, Sb, and Co and most magnetic particles. However, four heave metals (Cd, Pb, Tl, and Zn) were found mainly from atmospheric deposition from industrial/agricultural activities in Huizhou City, which was also indicated by SCPs, S-ratio, and χARM/SIRM. According to temporal variation of SCPs, the atmospheric pollution history ofnearby city (Huizhou Cityas the most close one) from 1964 was reconstructed. The study shows that reservoir sediments, especially in areas with few or no natural lakes, are high-efficacy and high-resolution achieves for research on environmental evolution in the Anthropocene related to global change and intensifying human activities.

Phytoplankton and zooplankton succession during the dry–refilling cycle: A case study in large, fluctuating soda lakes

Abstract Aquatic ecosystems in arid regions are important habitats for aquatic wildlife and also support species biodiversity. Soda lakes in endorheic drainage basins, so‐called amplifier lakes, are sentinels of climate change and are of scientific significance. Here we present the results of a long‐term study (20 years) of the Torey lakes, Transbaikalia, Russia, including the period from the maximum capacity of the Torey lakes through to aridification, and then to the initial phase of refilling. Our aim was to determine the response of planktonic communities in the lakes to environmental change over this period. We conducted our studies during various parts of the hydrological cycle, including three phases for Lake Zun‐Torey (high [1999, 2003], intermediate [2007, 2011] and low [2014, 2016] water levels) and two phases for Lake Barun‐Torey (high level [1999, 2003] and the initial refilling phase [2014, 2016, 2018, 2020]). Lake Barun‐Torey dried up completely in summer 2009, and since 2013 has been undergoing initial refilling. Lake Zun‐Torey dried up in the autumn of 2017. Temporal variation in planktonic communities differs for each lake. We identified four stages of changes in the planktonic associations during the aridification of Lake Zun‐Torey (the phytoplankton experienced a decrease in abundance and biomass, and was dominated by green algae and diatoms; the zooplankton underwent a decrease in species diversity and an increase in total abundance and biomass, which were caused by an increase in the abundance of some crustacean species) and three stages of changes as the lake level fell and during the initial refilling of Lake Barun‐Torey (the plankton communities increased in species richness and abundance in the transient pools). These results show the complexity of long‐term community dynamics in arid‐zone soda lakes. They have revealed how phytoplankton and zooplankton community diversity and structure can vary with changing environmental conditions and may pass between distinct states related to the stages of the hydroperiod.

Assessing the impact of wildfires on water quality using satellite remote sensing: the Lake Baikal case study

Lakes have been observed as sentinels of climate change. In the last decades, global warming and increasing aridity has led to an increase in both the number and severity of wildfires. This has a negative impact on lake catchments by reducing forest cover and triggering cascading effects in freshwater ecosystems. In this work we used satellite remote sensing to analyse potential fire effects on lake water quality of Lake Baikal (Russia), considering the role of runoff and sediment transport, a less studied pathway compared to fire emissions transport. The main objectives of this study were to analyse time series and investigate relationships among fires (i.e., burned area), meteo-climatic parameters and water quality variables (chlorophyll-a, turbidity) for the period 2003–2020. Because Lake Baikal is oligotrophic, we expected detectable changes in water quality variables at selected areas near the three mains tributaries (Upper Angara, Barguzin, Selenga) due to river transport of fire-derived burned material and nutrients. Time series analysis showed seasonal (from April to June) and inter-annual fire occurrence, precipitation patterns (high intensity in summer) and no significant temporal changes for water quality variables during the studied periods. The most severe wildfires occurred in 2003 with the highest burned area detected (36,767 km2). The three lake sub-basins investigated have shown to respond differently according to their morphology, land cover types and meteo-climatic conditions, indicating their importance in determining the response of water variables to the impact of fires. Overall, our finding suggests that Lake Baikal shows resilience in the medium-long term to potential effects of fires and climate change in the region.

Using Springs as Sentinels of Climate Change in Nature Parks North and South of the Alps: A Critical Evaluation of Methodological Aspects and Recommendations for Long-Term Monitoring

Spring ecosystems are diverse transition zones between ground- and surface-water habitats. Due to their characteristics and vulnerable species assemblages, springs are considered indicator systems for monitoring environmental change. In particular, climate change is expected to alter spring-ecosystem features, such as water temperature and discharge, affecting otherwise typically stable biotic and abiotic conditions. However, reliable trend-development recognition and analysis require a uniform methodology and comparable data series over long periods of time. Spring research findings in the Berchtesgaden National Park and the Adamello-Brenta Nature Park have been consolidated to develop methodological recommendations to create lasting societal-added value. The successful transfer of the methodology to the Bavarian Forest National Park and the experienced contribution of the Bavarian Association for the Protection of Nature (Bavarian Climate Alliance) strongly improved method validations. Our resulting, newly developed recommendations for long-term spring monitoring have a focus on climate change impacts and aim at providing a decision-making basis for establishing programs in similar ecological and climatic zones. Uniform site-selection criteria and selected climate-sensitive parameters are indicated. This includes documenting the spring’s environment and structure, measuring abiotic parameters, and determining selected floristic and faunistic groups. We recommend measurement and sampling-survey intervals ranging from 3(4) times yearly to every 5 years, depending on the parameter. We further suggest a database system that integrates all monitoring parameters to ensure consistent data management and storage. Analysing the data resulting from our new holistic spring monitoring methodology should provide critical knowledge about putatively changing ecosystems that can then be used as evidence of climate-change impact on spring ecosystems.

Population Status and Ecology of the Steno-Endemic Fairy Shrimp Chirocephalus sibyllae Cottarelli and Mura, 1975 Inhabiting a Mountain Temporary Pond (Central Italy)

High-elevation ephemeral waters are sentinels of climate change, as they quickly respond to decreasing precipitation levels and increasing air temperatures. Fairy shrimps are among the most threatened invertebrates in ephemeral waters, as they are extremely vulnerable to habitat loss. Chirocephalus sibyllae is a fairy shrimp endemic to the Palazzo Borghese temporary pond, located within Sibillini Mountains National Park (Central Italy). The aims of the present study were to: (i) evaluate the physicochemical characteristics of C. sibyllae habitat, with special reference to climate changes over twenty years; (ii) document the life history, size, and abundance of C. sibyllae; and (iii) document the coexisting zooplankton fauna in Palazzo Borghese pond. The zooplankton community was monitored fortnightly, during the filling phases of the pond, from April 2019 to June 2021, using an 80 μm mesh net, within transects of known length. On each sampling occasion, 13 physicochemical parameters were measured, and water-level fluctuations and pond surface area were recorded. Compared to what was reported in the literature, in the last two years the wet phase of the Palazzo Borghese pond was shorter, and the pool dried up much earlier than in the past. The water quality was good and reflected the typical characteristics of high-mountain oligotrophic ponds. Orthophosphates seem to play a key role in zooplankton population abundance, increasing over time during the filling period. According to the extreme unpredictability of environmental features, the zooplankton community was composed of a very limited number of species, adapted to face drought conditions for most of the year. C. sibyllae life-history traits showed a high number of cysts in the broodpouch of ovigerous females (mean ± SD = 66.0 ± 38.9), and a higher mean total length of adults (1.72 cm for females and 1.76 cm for males), in comparison to data reported in the literature. The year 2019 was configured as the season with the most favorable conditions for the development of C. sibyllae; in 2020, the short duration of the pond did not allow the species to complete its life cycle. Climate change seems to pose the main threat to the species, considering that the progressive increase in air temperatures and the decrease in snowfall will, likely, lead to increasingly shorter filling phases of its habitat.

Divergent dynamics of microbial components in two temperate shallow lakes with contrasting steady states in the Southern Hemisphere.

Factors that affect abundances of organisms in water bodies are influenced by extrinsic and intrinsic drivers that operate from outside and within a system. A high temporal coherence in the dynamics of abiotic parameters and biological communities among neighboring lakes evidences a strong extrinsic control operating similarly across lakes, and allows for prediction of ecosystems evolution in the context of global change and intensive land use. The Pampa region (Argentina) encompasses many shallow lakes submitted to different degrees of anthropic influence and showing contrasting alternative states. We studied an eutrophic clear and a hypertrophic turbid shallow lake during an annual cycle in order to evaluate whether they responded similarly to extrinsic factors or these were overridden by the effects of the steady state of each lake. Physical and chemical variables were highly coherent between both lakes, but accounted little for the large disparities among abundances and dynamics of microorganisms. While communities from the clear lake responded to a combination of extrinsic and intrinsic factors, the turbid lake showed a state less prone to be affected by climatic effects. We hypothesize that clear lakes would perform better as sentinels of climate change in the Pampa wetland.

The hydrologic classification of dilute lakes

Dilute lakes, herein defined as having an electrical conductivity ≤25 µS cm−1, are considered valuable culturally, as water and recreational resources; biologically, as unique ecosystems; and scientifically, as sentinels of climate change. However, research and interest has been spread over many disciplines focusing on various issues, making hydrologic comparisons somewhat difficult. Here, 15 dilute lakes are subdivided into lake subtypes based on the dominant hydrologic input and output using annual water balance data. Dilute conditions occur in lakes dominated by all hydrologic inputs (precipitation, surface inflow, and groundwater) and outputs (evaporation, surface outflow, and groundwater), though not all possible input/output combinations produce dilute conditions. Of the nine possible hydrologic lake subtypes (three input by three output fluxes), dilute conditions have been reported in six lake subtypes, not just the traditional seepage and drainage lakes typically suggested in the literature. When annual water balance data are plotted on a “Piper‐type” graph, these six hydrologic lake subtypes are grouped into three hydrologic clusters emphasizing specific hydrologic landscape characteristics and limiting conditions hydrology may impose on naturally dilute lakes. Implications of such a classification system and possible future research questions are discussed.

Cold and wet: Diatoms dominate the phytoplankton community during a year of anomalous weather in a Great Lakes estuary

As sentinels of climate change and other anthropogenic forces, freshwater lakes are experiencing ecosystem disruptions at every level of the food web, beginning with the phytoplankton, a highly responsive group of organisms. Most studies regarding the effects of climate change on phytoplankton focus on a potential scenario in which temperatures continuously increase and droughts intersperse heavy precipitation events. Like much of the conterminous United States in 2019, the Muskegon River watershed (Michigan, USA) experienced record-breaking rainfall accompanied by unusually cool temperatures, affording an opportunity to explore how an alternate potential climate scenario may affect phytoplankton. We conducted biweekly sampling of environmental variables and phytoplankton in Muskegon Lake, a Great Lakes Area of Concern that connects to Lake Michigan. We compared environmental variables in 2019 to the previous eight years using long-term data from the Muskegon Lake Observatory buoy, and annual monitoring excursions provided historical phytoplankton data. Under cold and wet conditions, diatoms were the single dominant division throughout the entire growth season – an unprecedented scenario in Muskegon Lake. In 10 of the 13 biweekly sampling days in 2019, diatoms comprised over 75% of the phytoplankton community in the lake by count, indicating that the spring diatom bloom persisted through the fall. Additionally, phytoplankton seasonal succession and abundance patterns typically seen in this lake were absent. In a world experiencing reduced predictability, increased variability, and regional climate anomalies, studying periods of extreme weather events may offer insight into how natural systems will be affected and respond under future climate scenarios.

Lakes as sentinels of climate change on the Tibetan Plateau

Lakes as sentinels of climate change on the Tibetan Plateau

LA RICOLONIZZAZIONE DELL’ANTARTIDE: STORIE DI PINGUINI E FOCHE, SENTINELLE DEI CAMBIAMENTI CLIMATICI NEGLI ULTIMI 10 MILA ANNI

The re-colonization of Antarctica: stories of penguins and seals, sentinels of climate change in the last ten thousand years. During the Late Pleistocene the Antarctic glacial system expanded and advanced on the coastal margin of the continent forcing penguins, seals and other animals nesting in the deglaciated areas to migrate toward refuge areas located at northern latitudes. The deglaciation that followed the last glacial maximum, in the Ross Sea area, was accomplished around 8000 years ago, freeing the Antarctic coasts that were re-colonized by Adélie penguins and elephant seals. These two species have coexisted, even alternating, in the deglaciated areas of the coastal strip for several millennia. In the ornithogenic soils of the abandoned penguin colonies and in the breeding sites of the elephant seals, recently discovered on the Holocene raised beaches, a precious heritage of organic remains is preserved, allowing us to study different aspects of recent environmental history. The phases of colonization and coexistence between penguins and elephant seals are very complex and reflect the climatic-environmental variations that have characterized the Antarctic scenario for several thousand of years. Penguins and elephant seals, sensitive sentinels of the Antarctic ecosystem, are now playing an important role in the Southern Ocean scenario, interpreting the dramatic role of bellwether of climate change.

Multinational, integrated approaches to forecasting and managing the impacts of climate change on intertidal species

Marine biodiversity and ecosystem functioning are facing unprecedented pressures in the Anthropocene, with climate change being a primary stressor. To understand the biological response mechanisms along coastlines, the international scientific community requires coordinated action, integrating obervations through observatory networks and spatially extensive experiments using standardized approaches over broad geographic scales. Currently, however, a multinational, integrated approach is lacking, with little application of standard methodologies or data sharing across countries. Changes in the abundance, distribution and competitive dominance of rocky intertidal organisms are useful sentinels of climate change because these communities are easy to observe and long-term time series exist. Europe is in a prime position to lead by example, building on the extensive history of sustained observations and experimental research to establish an integrated network of studies and monitoring programmes. These will improve our understanding of how organismal responses translate into biogeographic range shifts, and generate more biologically realistic predictions of future climate change impacts with which to design mitigation, adaptation and conservation strategies

Gentoo penguins as sentinels of climate change at the sub-Antarctic Prince Edward Archipelago, Southern Ocean

Some upper trophic level predators, such as marine mammals, seabirds and large predatory fish have been shown to be useful sentinels for marine ecosystems. Through their demography, diet and foraging behaviour, ecosystem changes associated with climate change can be monitored. The local marine ecosystem at the Prince Edward Archipelago in the Southern Indian Ocean is heavily influenced by the position of the dynamic sub-Antarctic front (SAF) that varies inter-annually in terms of its influence on the local environment. If the SAF migrates southwards, as climate change models have predicted, the abundance of autochthonous and allochthonous prey found within the vicinity of the archipelago will decrease and increase, respectively. We investigated the diet of an inshore forager at the archipelago, the gentoo penguin Pygoscelis papua, as a possible sentinel to the expected changes in the prey assemblages in local waters, due to the southward migration of the SAF. We collected stomach content samples from gentoo penguins, using the water off-loading technique, monthly over three years (1994–1996) and then annually during 2012, 2014 and 2015. Prey assemblages within the diet was found to coincide with the proximity of the SAF to the Prince Edward Archipelago as well as the annual life cycles of prey. Due to the plasticity these penguins exhibit in their diet and foraging behaviour, we suggest that they are important sentinel species for the local marine ecosystem of the Prince Edward Archipelago. Regular sample collection from these birds, albeit stomach content samples and/or tissues for stable isotope analysis, should be collected so that variability in the ecosystem can be easily monitored.

Controls of climate, catchment erosion and biological production on long-term community and functional changes of chironomids in High Arctic lakes (Svalbard)

Arctic freshwater basins are diversity hotspots and sentinels of climate change, but their long-term variability and the environmental variables controlling them are not well defined. We examined four available lake sediment sequences from High Arctic Svalbard for their subfossil Chironomidae communities, biodiversity and functional traits and assessed the influence of climatic and limnological variability on the long-term ecological dynamics. Our results indicated that collector-filterers had an important role in the oligotrophic sites, whereas collector-gatherers dominated the nutrient-enriched sites with significant bird guano inputs. In the oligotrophic sites, benthic production, taxon richness and taxonomic and functional diversity were highest during the early Holocene, when temperatures showed a rapid increase. An increase in subfossil abundance and diversity metrics was also found in recent samples of the oligotrophic sites, but not in the bird-impacted sites, where the trends were decreasing. When partitioning out the environmental forcing on chironomid communities, the influence of climate was significant in all the sites, whereas in-lake production (organic matter) was significant in two of the sites and catchment erosion (magnetic susceptibility) had only minor influence. The findings suggest that major changes in Arctic chironomid assemblages were driven by climate warming with increasing diversity in oligotrophic sites, but deteriorating ecological functions in environmentally stressed sites. We found that although taxonomic and functional diversity were always coupled, taxonomical and functional turnovers were coupled only in the oligotrophic sites suggesting that the ecological functions operated by chironomids in these low-productivity sites may not be as resilient to future environmental change.

Influence of recent climatic events on the surface water storage of the Tonle Sap Lake

Lakes and reservoirs have been identified as sentinels of climate change. Tonle Sap is the largest lake in both the Mekong Basin and Southeast Asia and because of the importance of its ecosystem, it is has been described as the “heart of the lower Mekong”. Its seasonal cycle depends on the annual flood pulse governed by the flow of the Mekong River. This study provides an impact analysis of recent climatic events from El Niño 1997/1998 to El Niño 2015/2016 on surface storage variations in the Tonle Sap watershed determined by combining remotely sensed observations, multispectral images and radar altimetry from 1993 to 2017. The Lake's surface water volume variations are highly correlated with rainy season rainfall in the whole Mekong River Basin (R = 0.84) at interannual time-scale. Extreme droughts and floods can be observed when precipitation deficit and excess is recorded in both the Tonle Sap watershed and the Mekong River Basin during moderate to very strong El Niño/La Niña events (R = −0.70) enhanced by the Pacific Decadal Oscillation (R = −0.68). Indian and Western North Pacific Monsoons were identified as having almost equal influence. Below normal vegetation activity was observed during the first semester of 2016 due to the extreme drought in 2015.

Parameter sensitivity analysis of a 1-D cold region lake model for land-surface schemes

Abstract. Lakes might be sentinels of climate change, but the uncertainty in their main feedback to the atmosphere – heat-exchange fluxes – is often not considered within climate models. Additionally, these fluxes are seldom measured, hindering critical evaluation of model output. Analysis of the Canadian Small Lake Model (CSLM), a one-dimensional integral lake model, was performed to assess its ability to reproduce diurnal and seasonal variations in heat fluxes and the sensitivity of simulated fluxes to changes in model parameters, i.e., turbulent transport parameters and the light extinction coefficient (Kd). A C++ open-source software package, Problem Solving environment for Uncertainty Analysis and Design Exploration (PSUADE), was used to perform sensitivity analysis (SA) and identify the parameters that dominate model behavior. The generalized likelihood uncertainty estimation (GLUE) was applied to quantify the fluxes' uncertainty, comparing daily-averaged eddy-covariance observations to the output of CSLM. Seven qualitative and two quantitative SA methods were tested, and the posterior likelihoods of the modeled parameters, obtained from the GLUE analysis, were used to determine the dominant parameters and the uncertainty in the modeled fluxes. Despite the ubiquity of the equifinality issue – different parameter-value combinations yielding equivalent results – the answer to the question was unequivocal: Kd, a measure of how much light penetrates the lake, dominates sensible and latent heat fluxes, and the uncertainty in their estimates is strongly related to the accuracy with which Kd is determined. This is important since accurate and continuous measurements of Kd could reduce modeling uncertainty.