| 1. |
- Lozano, Rafael, et al.
(författare)
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Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
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Tidskriftsartikel (refereegranskat)abstract
- Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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| 2. |
- Murray, Christopher J. L., et al.
(författare)
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Population and fertility by age and sex for 195 countries and territories, 1950–2017: a systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 392:10159, s. 1995-2051
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Tidskriftsartikel (refereegranskat)abstract
- Background: Population estimates underpin demographic and epidemiological research and are used to track progress on numerous international indicators of health and development. To date, internationally available estimates of population and fertility, although useful, have not been produced with transparent and replicable methods and do not use standardised estimates of mortality. We present single-calendar year and single-year of age estimates of fertility and population by sex with standardised and replicable methods. Methods: We estimated population in 195 locations by single year of age and single calendar year from 1950 to 2017 with standardised and replicable methods. We based the estimates on the demographic balancing equation, with inputs of fertility, mortality, population, and migration data. Fertility data came from 7817 location-years of vital registration data, 429 surveys reporting complete birth histories, and 977 surveys and censuses reporting summary birth histories. We estimated age-specific fertility rates (ASFRs; the annual number of livebirths to women of a specified age group per 1000 women in that age group) by use of spatiotemporal Gaussian process regression and used the ASFRs to estimate total fertility rates (TFRs; the average number of children a woman would bear if she survived through the end of the reproductive age span [age 10–54 years] and experienced at each age a particular set of ASFRs observed in the year of interest). Because of sparse data, fertility at ages 10–14 years and 50–54 years was estimated from data on fertility in women aged 15–19 years and 45–49 years, through use of linear regression. Age-specific mortality data came from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 estimates. Data on population came from 1257 censuses and 761 population registry location-years and were adjusted for underenumeration and age misreporting with standard demographic methods. Migration was estimated with the GBD Bayesian demographic balancing model, after incorporating information about refugee migration into the model prior. Final population estimates used the cohort-component method of population projection, with inputs of fertility, mortality, and migration data. Population uncertainty was estimated by use of out-of-sample predictive validity testing. With these data, we estimated the trends in population by age and sex and in fertility by age between 1950 and 2017 in 195 countries and territories. Findings: From 1950 to 2017, TFRs decreased by 49·4% (95% uncertainty interval [UI] 46·4–52·0). The TFR decreased from 4·7 livebirths (4·5–4·9) to 2·4 livebirths (2·2–2·5), and the ASFR of mothers aged 10–19 years decreased from 37 livebirths (34–40) to 22 livebirths (19–24) per 1000 women. Despite reductions in the TFR, the global population has been increasing by an average of 83·8 million people per year since 1985. The global population increased by 197·2% (193·3–200·8) since 1950, from 2·6 billion (2·5–2·6) to 7·6 billion (7·4–7·9) people in 2017; much of this increase was in the proportion of the global population in south Asia and sub-Saharan Africa. The global annual rate of population growth increased between 1950 and 1964, when it peaked at 2·0%; this rate then remained nearly constant until 1970 and then decreased to 1·1% in 2017. Population growth rates in the southeast Asia, east Asia, and Oceania GBD super-region decreased from 2·5% in 1963 to 0·7% in 2017, whereas in sub-Saharan Africa, population growth rates were almost at the highest reported levels ever in 2017, when they were at 2·7%. The global average age increased from 26·6 years in 1950 to 32·1 years in 2017, and the proportion of the population that is of working age (age 15–64 years) increased from 59·9% to 65·3%. At the national level, the TFR decreased in all countries and territories between 1950 and 2017; in 2017, TFRs ranged from a low of 1·0 livebirths (95% UI 0·9–1·2) in Cyprus to a high of 7·1 livebirths (6·8–7·4) in Niger. The TFR under age 25 years (TFU25; number of livebirths expected by age 25 years for a hypothetical woman who survived the age group and was exposed to current ASFRs) in 2017 ranged from 0·08 livebirths (0·07–0·09) in South Korea to 2·4 livebirths (2·2–2·6) in Niger, and the TFR over age 30 years (TFO30; number of livebirths expected for a hypothetical woman ageing from 30 to 54 years who survived the age group and was exposed to current ASFRs) ranged from a low of 0·3 livebirths (0·3–0·4) in Puerto Rico to a high of 3·1 livebirths (3·0–3·2) in Niger. TFO30 was higher than TFU25 in 145 countries and territories in 2017. 33 countries had a negative population growth rate from 2010 to 2017, most of which were located in central, eastern, and western Europe, whereas population growth rates of more than 2·0% were seen in 33 of 46 countries in sub-Saharan Africa. In 2017, less than 65% of the national population was of working age in 12 of 34 high-income countries, and less than 50% of the national population was of working age in Mali, Chad, and Niger. Interpretation: Population trends create demographic dividends and headwinds (ie, economic benefits and detriments) that affect national economies and determine national planning needs. Although TFRs are decreasing, the global population continues to grow as mortality declines, with diverse patterns at the national level and across age groups. To our knowledge, this is the first study to provide transparent and replicable estimates of population and fertility, which can be used to inform decision making and to monitor progress. Funding: Bill & Melinda Gates Foundation.
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| 3. |
- Stanaway, Jeffrey D., et al.
(författare)
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Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks for 195 countries and territories, 1990-2017: A systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 392:10159, s. 1923-1994
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Tidskriftsartikel (refereegranskat)abstract
- Background The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 comparative risk assessment (CRA) is a comprehensive approach to risk factor quantification that offers a useful tool for synthesising evidence on risks and risk-outcome associations. With each annual GBD study, we update the GBD CRA to incorporate improved methods, new risks and risk-outcome pairs, and new data on risk exposure levels and risk- outcome associations. Methods We used the CRA framework developed for previous iterations of GBD to estimate levels and trends in exposure, attributable deaths, and attributable disability-adjusted life-years (DALYs), by age group, sex, year, and location for 84 behavioural, environmental and occupational, and metabolic risks or groups of risks from 1990 to 2017. This study included 476 risk-outcome pairs that met the GBD study criteria for convincing or probable evidence of causation. We extracted relative risk and exposure estimates from 46 749 randomised controlled trials, cohort studies, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. Using the counterfactual scenario of theoretical minimum risk exposure level (TMREL), we estimated the portion of deaths and DALYs that could be attributed to a given risk. We explored the relationship between development and risk exposure by modelling the relationship between the Socio-demographic Index (SDI) and risk-weighted exposure prevalence and estimated expected levels of exposure and risk-attributable burden by SDI. Finally, we explored temporal changes in risk-attributable DALYs by decomposing those changes into six main component drivers of change as follows: (1) population growth; (2) changes in population age structures; (3) changes in exposure to environmental and occupational risks; (4) changes in exposure to behavioural risks; (5) changes in exposure to metabolic risks; and (6) changes due to all other factors, approximated as the risk-deleted death and DALY rates, where the risk-deleted rate is the rate that would be observed had we reduced the exposure levels to the TMREL for all risk factors included in GBD 2017.
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| 4. |
- Kassebaum, Nicholas J., et al.
(författare)
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Global, regional, and national disability-adjusted life-years (DALYs) for 315 diseases and injuries and healthy life expectancy (HALE), 1990-2015 : a systematic analysis for the Global Burden of Disease Study 2015
- 2016
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Ingår i: The Lancet. - 0140-6736 .- 1474-547X. ; 388:10053, s. 1603-1658
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Tidskriftsartikel (refereegranskat)abstract
- Background Healthy life expectancy (HALE) and disability-adjusted life-years (DALYs) provide summary measures of health across geographies and time that can inform assessments of epidemiological patterns and health system performance, help to prioritise investments in research and development, and monitor progress toward the Sustainable Development Goals (SDGs). We aimed to provide updated HALE and DALYs for geographies worldwide and evaluate how disease burden changes with development. Methods We used results from the Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015) for all-cause mortality, cause-specific mortality, and non-fatal disease burden to derive HALE and DALYs by sex for 195 countries and territories from 1990 to 2015. We calculated DALYs by summing years of life lost (YLLs) and years of life lived with disability (YLDs) for each geography, age group, sex, and year. We estimated HALE using the Sullivan method, which draws from age-specific death rates and YLDs per capita. We then assessed how observed levels of DALYs and HALE differed from expected trends calculated with the Socio-demographic Index (SDI), a composite indicator constructed from measures of income per capita, average years of schooling, and total fertility rate. Findings Total global DALYs remained largely unchanged from 1990 to 2015, with decreases in communicable, neonatal, maternal, and nutritional (Group 1) disease DALYs off set by increased DALYs due to non-communicable diseases (NCDs). Much of this epidemiological transition was caused by changes in population growth and ageing, but it was accelerated by widespread improvements in SDI that also correlated strongly with the increasing importance of NCDs. Both total DALYs and age-standardised DALY rates due to most Group 1 causes significantly decreased by 2015, and although total burden climbed for the majority of NCDs, age-standardised DALY rates due to NCDs declined. Nonetheless, age-standardised DALY rates due to several high-burden NCDs (including osteoarthritis, drug use disorders, depression, diabetes, congenital birth defects, and skin, oral, and sense organ diseases) either increased or remained unchanged, leading to increases in their relative ranking in many geographies. From 2005 to 2015, HALE at birth increased by an average of 2.9 years (95% uncertainty interval 2.9-3.0) for men and 3.5 years (3.4-3.7) for women, while HALE at age 65 years improved by 0.85 years (0.78-0.92) and 1.2 years (1.1-1.3), respectively. Rising SDI was associated with consistently higher HALE and a somewhat smaller proportion of life spent with functional health loss; however, rising SDI was related to increases in total disability. Many countries and territories in central America and eastern sub-Saharan Africa had increasingly lower rates of disease burden than expected given their SDI. At the same time, a subset of geographies recorded a growing gap between observed and expected levels of DALYs, a trend driven mainly by rising burden due to war, interpersonal violence, and various NCDs. Interpretation Health is improving globally, but this means more populations are spending more time with functional health loss, an absolute expansion of morbidity. The proportion of life spent in ill health decreases somewhat with increasing SDI, a relative compression of morbidity, which supports continued efforts to elevate personal income, improve education, and limit fertility. Our analysis of DALYs and HALE and their relationship to SDI represents a robust framework on which to benchmark geography-specific health performance and SDG progress. Country-specific drivers of disease burden, particularly for causes with higher-than-expected DALYs, should inform financial and research investments, prevention efforts, health policies, and health system improvement initiatives for all countries along the development continuum.
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| 5. |
- Wilson, Harriet L., et al.
(författare)
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Variability in epilimnion depth estimations in lakes
- 2020
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 24:11, s. 5559-5577
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Tidskriftsartikel (refereegranskat)abstract
- The epilimnion is the surface layer of a lake typically characterised as well mixed and is decoupled from the metalimnion due to a steep change in density. The concept of the epilimnion (and, more widely, the three-layered structure of a stratified lake) is fundamental in limnology, and calculating the depth of the epilimnion is essential to understanding many physical and ecological lake processes. Despite the ubiquity of the term, however, there is no objective or generic approach for defining the epilimnion, and a diverse number of approaches prevail in the literature. Given the increasing availability of water temperature and density profile data from lakes with a high spatio-temporal resolution, automated calculations, using such data, are particularly common, and they have vast potential for use with evolving long-term globally measured and modelled datasets. However, multi-site and multi-year studies, including those related to future climate impacts, require robust and automated algorithms for epilimnion depth estimation. In this study, we undertook a comprehensive comparison of commonly used epilimnion depth estimation methods, using a combined 17-year dataset, with over 4700 daily temperature profiles from two European lakes. Overall, we found a very large degree of variability in the estimated epilimnion depth across all methods and thresholds investigated and for both lakes. These differences, manifesting over high-frequency data, led to fundamentally different understandings of the epilimnion depth. In addition, estimations of the epilimnion depth were highly sensitive to small changes in the threshold value, complex thermal water column structures, and vertical data resolution. These results call into question the custom of arbitrary method selection and the potential problems this may cause for studies interested in estimating the ecological processes occurring within the epilimnion, multi-lake comparisons, or long-term time series analysis. We also identified important systematic differences between methods, which demonstrated how and why methods diverged. These results may provide rationale for future studies to select an appropriate epilimnion definition in light of their particular purpose and with awareness of the limitations of individual methods. While there is no prescribed rationale for selecting a particular method, the method which defined the epilimnion depth as the shallowest depth, where the density was 0.1 kg m−3 more than the surface density, may be particularly useful as a generic method.
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| 6. |
- Ayala, Ana I., et al.
(författare)
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Analysis of summer heat budget of lakes under a changing climate across a geographic gradient
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Warming surface water temperature is the most direct consequence of climate change in lakes and therefore, predicting the heat exchange at the air-water interface is important to understand how atmospheric forcing will affect lake temperature and thermal structure. Here, we forced a one-dimensional hydrodynamic lake model with outputs from four different climate models under three future greenhouse gas emission scenarios from 1976 to 2099. To investigate the changes in summer (June to August or December to February in the northern or southern hemisphere, respectively) net surface heat flux and the individual flux components for 47 lakes with varying in size and geographic location were analysed. The results show that in the most extreme case (RCP 8.5) summer lake surface temperature is projected to increase by 4.72±0.70 °C by the end of the 21st century, due to increasing absorption of solar radiation (17.40±8.81 W m-2) and of long-wave radiation (33.01±5.44 W m-2). The increased lake surface temperature, also lead to higher heat losses to the atmosphere by outgoing long-wave radiation (27.54±4.07 W m-2) and by latent heat flux (25.10±7.37 W m-2), while a lower heat loss by sensible heat flux is projected (-3.20±1.94 W m-2). Altogether, the net heat balance and thus the accumulation of heat in the lakes over summer remains almost unchanged. However, a shift in the contributions of the individuals heat fluxes is projected, with the latent heat flux gaining relative importance.
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| 7. |
- Ayala, Ana I., et al.
(författare)
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Climate Change Impacts on Surface Heat Fluxes in a Deep Monomictic Lake
- 2023
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 128:11
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Tidskriftsartikel (refereegranskat)abstract
- Turbulent and radiative energy exchanges between lakes and the atmosphere play an importantrole in determining the process of lake-mixing and stratification, including how lakes respond to climate andto climate change. Here we used a one-dimensional hydrodynamic lake model to assess seasonal impacts ofclimate change on individual surface heat flux components in Lough Feeagh, Ireland, a deep, monomictic lake.We drove the lake model with an ensemble of outputs from four climate models under three future greenhousegas scenarios from 1976 to 2099. In these experiments, the results showed significant increases in the radiativebudget that were largely counteracted by significant increases in the turbulent fluxes. The combined change inthe individual surface heat fluxes led to a change in the total surface heat flux that was small, but sufficient tolead to significant changes in the volume-weighted average lake temperature. The largest projected changes intotal surface heat fluxes were in spring and autumn. Both spring heating and autumnal cooling significantlydecreased under future climate conditions, while changes to total surface heat fluxes in winter and summerwere an order of magnitude lower. This led to counter-intuitive results that, in a warming world, there wouldbe less heat not more entering Lough Feeagh during the springtime, and little change in net heating over thesummer or winter compared to natural climate conditions, projected increases in the volume-weighted averagelake temperature were found to be largely due to reduced heat loss during autumn.
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| 8. |
- Ayala, Ana I., et al.
(författare)
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GLOBAL WARMING WILL CHANGE THE THERMAL STRUCTURE OF LOUGH FEEAGH, A SENTINEL LAKE IN THE IRISH LANDSCAPE, BY THE END OF THE TWENTY-FIRST CENTURY
- 2023
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Ingår i: Biology and Environment (Dublin). - : Project MUSE/Royal irish academy. - 0791-7945 .- 2009-003X. ; 123B:3, s. 147-165
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments in impact modelling of global warming on lakes have resulted in a greater understanding of how these vital ecosystems are likely to respond. However, there has been little quantitative analysis of this in an Irish context, despite the importance of lakes in the island's landscape. Here, we explore the impact of global warming on the hydrodynamics and thermal structure of a sentinel Irish lake under future climate scenarios. A 1D lake model, Simstrat, was calibrated and validated using water temperature data collected from Lough Feeagh, a site of long-term ecological research in the west of Ireland. Once validated, the model was then driven by daily climate model projections to generate informative thermal metrics for the time period of 2006-2099. Despite the moderating influence of the Atlantic, projections indicate that global warming will have a marked effect on the thermal structure of Feeagh, with surface water temperatures set to warm by 0.75 degrees C under a more stringent mitigation pathway (RCP 2.6) and 2.42 degrees C under a non-mitigation pathway (RCP 8.5).While warming was projected to be greatest in summer in the epilimnion, winter warming was greater than in other seasons in the hypolimnion. Stratification is projected to become more stable and earlier, and the growing season to be longer by 11 to 47 days, depending on mitigation pathways. Future studies could use a similar modelling workflow to investigate the possible implications of global warming on other Irish lakes, particularly those of specific societal importance or those of conservation interest.
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| 9. |
- Ayala, Ana I.
(författare)
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Modelling impact climate-related change on the thermal responses of lakes
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In response to climate-related changes, lakes worldwide have experienced warmer surface water temperatures, shorter ice cover periods and changes in lake stratification. As these aspects of lake dynamics exert substantial control over nutrient availability, oxygenation and biogeochemical cycling, predicting changes in lake water temperature and stratification dynamics can improve our understanding of the consequences of warming on lake ecosystems. This thesis investigates the long-term and short-term (extreme event) effects of climate change on lake thermal dynamics using 1D hydrodynamic lake models.Long-term lake water temperature simulations showed that water temperatures and thermal stratification metrics were projected to clearly shift toward lake thermal conditions that are consistent with a warmer climate at the end of the 21st century, i.e. warmer surface and bottom temperatures and a stronger and longer duration of summer thermal stratification as a result of an earlier onset of stratification and later fall overturn. The simulated lake thermal structure was controlled by energy exchange between the lake surface and the atmosphere (surface heat fluxes) and wind stress. The individual surface heat flux components were projected to change substantially under future climate scenarios. However, the combined changes showed compensating effects, leading to a small overall change in total surface heat flux, that was still sufficient to lead to important changes in whole-lake temperature. On a seasonal scale, spring heating and autumnal cooling were projected to decrease, while only small changes were projected in winter and summer. An extended analysis during summer using 47 lakes showed that while all lakes gained heat during summer under all scenarios, differences in the amount of heat gained during historical and future conditions were small. Additionally, hydrodynamic lake models performed well in reproducing the magnitude and direction of changes in lake temperature and stratification metrics during storms and heatwaves. However, the lake model performance decreased in accuracy compared to non-extreme condition, which should be taken into account. 1D hydrodynamic lake models have been shown to be powerful tools to predict long-term and short-term climate-related changes in lake thermal dynamics, making an in-depth analysis of the surface heat fluxes possible.
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| 10. |
- Ayala, Ana I., et al.
(författare)
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Simulations of future changes in thermal structure of Lake Erken : proof of concept for ISIMIP2b lake sector local simulation strategy
- 2020
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 24:6, s. 3311-3330
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Tidskriftsartikel (refereegranskat)abstract
- This paper, as a part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP2b), assesses the impacts of different levels of global warming on the thermal structure of Lake Erken (Sweden). The General Ocean Turbulence Model (GOTM) one-dimensional hydrodynamic model was used to simulate water temperature when using ISIMIP2b bias-corrected climate model projections as input. These projections have a daily time step, while lake model simulations are often forced at hourly or shorter time steps. Therefore, it was necessary to first test the ability of GOTM to simulate Lake Erken water temperature using daily vs hourly meteorological forcing data. In order to do this, three data sets were used to force the model as follows: (1) hourly measured data, (2) daily average data derived from the first data set, and (3) synthetic hourly data created from the daily data set using generalised regression artificial neural network methods. This last data set is developed using a method that could also be applied to the daily time step ISIMIP scenarios to obtain hourly model input if needed. The lake model was shown to accurately simulate Lake Erken water temperature when forced with either daily or synthetic hourly data. Long-term simulations forced with daily or synthetic hourly meteorological data suggest that by the late 21st century the lake will undergo clear changes in thermal structure. For the representative concentration pathway (RCP) scenario, namely RCP2.6, surface water temperature was projected to increase by 1.79 and 1.36 ∘C when the lake model was forced at daily and hourly resolutions respectively, and for RCP6.0 these increases were projected to be 3.08 and 2.31 ∘C. Changes in lake stability were projected to increase, and the stratification duration was projected to be longer by 13 and 11 d under RCP2.6 scenario and 22 and 18 d under RCP6.0 scenario for daily and hourly resolutions. Model changes in thermal indices were very similar when using either the daily or synthetic hourly forcing, suggesting that the original ISIMIP climate model projections at a daily time step can be sufficient for the purpose of simulating lake water temperature.
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| 11. |
- Bruce, Louise C, et al.
(författare)
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A multi-lake comparative analysis of the General Lake Model (GLM) : Stress-testing across a global observatory network
- 2018
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Ingår i: Environmental Modelling & Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 102, s. 274-291
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Tidskriftsartikel (refereegranskat)abstract
- The modelling community has identified challenges for the integration and assessment of lake models due to the diversity of modelling approaches and lakes. In this study, we develop and assess a one-dimensional lake model and apply it to 32 lakes from a global observatory network. The data set included lakes over broad ranges in latitude, climatic zones, size, residence time, mixing regime and trophic level. Model performance was evaluated using several error assessment metrics, and a sensitivity analysis was conducted for nine parameters that governed the surface heat exchange and mixing efficiency. There was low correlation between input data uncertainty and model performance and predictions of temperature were less sensitive to model parameters than prediction of thermocline depth and Schmidt stability. The study provides guidance to where the general model approach and associated assumptions work, and cases where adjustments to model parameterisations and/or structure are required.
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| 12. |
- Engel, Fabian, et al.
(författare)
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Phytoplankton gross primary production increases along cascading impoundments in a temperate, low-discharge river : Insights from high frequency water quality monitoring
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Damming alters carbon processing along river continua. Estimating carbon transport along rivers intersected by multiple dams requires an understanding of the effects of cascading impoundments on the riverine metabolism. We analyzed patterns of riverine metabolism and phytoplankton biomass (chlorophyll a; Chla) along a 74.4-km river reach intersected by six low-head navigation dams. Calculating gross primary production (GPP) from continuous measurements of dissolved oxygen concentration, we found a maximum increase in the mean GPP by a factor of 3.5 (absolute difference of 0.45 g C m−3 d−1) along the first 26.5 km of the study reach, while Chla increased over the entire reach by a factor of 2.9 (8.7 µg l−1). In the intermittently stratified section of the deepest impoundment the mean GPP between the 1 and 4 m water layer differed by a factor of 1.4 (0.31 g C m−3 d−1). Due to the strong increase in GPP, the river featured a wide range of conditions characteristic of low- to medium-production rivers. We suggest that cascading impoundments have the potential to stimulate riverine GPP, and conclude that phytoplankton CO2 uptake is an important carbon flux in the river Saar, where a considerable amount of organic matter is of autochthonous origin.
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| 13. |
- Mesman, Jorrit P., 1993-, et al.
(författare)
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Drivers of phytoplankton responses to summer wind events in a stratified lake : a modelling study
- 2022
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 67:4, s. 856-873
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Tidskriftsartikel (refereegranskat)abstract
- Extreme wind events affect lake phytoplankton amongst others by deepening the mixed layer and increasing internal nutrient loading. Both increases and decreases of phytoplankton biomass after storms have been observed, but the precise mechanisms driving these responses remain poorly understood or quantified. In this study, we coupled a one-dimensional physical model to a biogeochemical model to investigate the factors regulating short-term phytoplankton responses to summer storms, now and under expected warmer future conditions. We simulated physical, chemical and biological dynamics in Lake Erken, Sweden, and found that wind storms could increase or decrease the phytoplankton concentration one week after the storm, depending on antecedent lake physical and chemical conditions. Storms had little effect on phytoplankton biomass if the mixed layer was deep prior to storm exposure. Higher incoming shortwave radiation and hypolimnetic nutrient concentration boosted growth, whereas higher surface water temperatures decreased phytoplankton concentration after storms. Medium-intensity wind speeds resulted in more phytoplankton biomass after storms than high-intensity wind. Simulations under a future climate scenario did not show marked differences in the way wind affects phytoplankton growth following storms. Our study shows that storm impacts on lake phytoplankton are complex and likely to vary as a function of local environmental conditions.
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| 14. |
- Mesman, Jorrit P., 1993-, et al.
(författare)
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Performance of one-dimensional hydrodynamic lake models during short-term extreme weather events
- 2020
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Ingår i: Environmental Modelling & Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 133
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Tidskriftsartikel (refereegranskat)abstract
- Numerical lake models are useful tools to study hydrodynamics in lakes, and are increasingly applied to extreme weather events. However, little is known about the accuracy of such models during these short-term events. We used high-frequency data from three lakes to test the performance of three one-dimensional (1D) hydrodynamic models (Simstrat, GOTM, GLM) during storms and heatwaves. Models reproduced the overall direction and magnitude of changes during the extreme events, with accurate timing and little bias. Changes in volume-averaged and surface temperatures and Schmidt stability were simulated more accurately than changes in bottom temperature, maximum buoyancy frequency, or mixed layer depth. However, in most cases the model error was higher (30-100%) during extreme events compared to reference periods. As a consequence, while 1D lake models can be used to study effects of extreme weather events, the increased uncertainty in the simulations should be taken into account when interpreting results.
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| 15. |
- Mesman, Jorrit P., 1993-, et al.
(författare)
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Timing of spring events changes under modelled future climate scenarios in a mesotrophic lake
- 2024
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Ingår i: Hydrology and Earth System Sciences. - : European Geosciences Union (EGU). - 1027-5606 .- 1607-7938. ; 28:8, s. 1791-1802
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Tidskriftsartikel (refereegranskat)abstract
- Lakes experience shifts in the timing of physical and biogeochemical events as a result of climate warming, and relative changes in the timing of events may have important ecological consequences. Spring, in particular, is a period in which many key processes that regulate the ecology and biogeochemistry of lakes occur and also a time that may experience significant changes under the influence of global warming. In this study, we used a coupled catchment–lake model forced by future climate projections to evaluate changes in the timing of spring discharge, ice-off, the spring phytoplankton peak, and the onset of stratification in a temperate mesotrophic lake. Although the model explained only part of the variation in these events, the overall patterns were simulated with little bias. All four events showed a clear trend towards earlier occurrence under climate warming, with ice cover tending to disappear at the end of the century in the most extreme climate scenario. Moreover, relative shifts in the timing of these springtime events also occurred, with the onset of stratification tending to advance more slowly than the other events and the spring phytoplankton peak and ice-off advancing faster in the most extreme climate scenario. The outcomes of this study stress the impact of climate change on the phenology of events in lakes and especially the relative shifts in timing during spring. This can have profound effects on food web dynamics as well as other regulatory processes and influence the lake for the remainder of the growing season.
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| 16. |
- Moras, Simone, et al.
(författare)
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Historical modelling of changes in Lake Erken thermal conditions
- 2019
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Ingår i: Hydrology and Earth System Sciences. - : COPERNICUS GESELLSCHAFT MBH. - 1027-5606 .- 1607-7938. ; 23:12, s. 5001-5016
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Tidskriftsartikel (refereegranskat)abstract
- Historical lake water temperature records are a valuable source of information to assess the influence of climate change on lake thermal structure. However, in most cases such records span a short period of time and/or are incomplete, providing a less credible assessment of change. In this study, the hydrodynamic GOTM (General Ocean Turbulence Model, a hydrodynamic model configured in lake mode) was used to reconstruct daily profiles of water temperature in Lake Erken (Sweden) over the period 1961-2017 using seven climatic parameters as forcing data: wind speed (WS), air temperature (Air T), atmospheric pressure (Air P), relative humidity (RH), cloud cover (CC), precipitation (DP), and shortwave radiation (SWR). The model was calibrated against observed water temperature data collected during the study interval, and the calibrated model revealed a good match between modelled and observed temperature (RMSE = 1.089 degrees C). From the long-term simulations of water temperature, this study focused on detecting possible trends in water temperature over the entire study interval 1961-2017 and in the sub-intervals 1961-1988 and 1989-2017, since an abrupt change in air temperature was detected in 1988. The analysis of the simulated temperature showed that epilimnetic temperature increased on average by 0.444 and 0.792 degrees C per decade in spring and autumn in the sub-interval 1989-2017 Summer epilimnetic temperature increased by 0.351 degrees C per decade over the entire interval 1961-2017. Hypolimnetic temperature increased significantly in spring over the entire interval 1961-2017, by 0.148 and by 0.816 degrees C per decade in autumn in the subinterval 1989-2016. Whole-lake temperature showed a significant increasing trend in the sub-interval 1989-2017 during spring (0.404 degrees C per decade) and autumn (0.789 degrees C per decade, interval 1989-2016), while a significant trend was detected in summer over the entire study interval 1961-2017 (0.239 degrees C per decade). Moreover, this study showed that that changes in the phenology of thermal stratification have occurred over the 57-year period of study. Since 1961, the stability of stratification (Schmidt stability) has increased by 5.365 J M-2 per decade. The duration of thermal stratification has increased by 7.297 d per decade, corresponding to an earlier onset of stratification of similar to 16 d and to a delay of stratification termination of similar to 26 d. The average thermocline depth during stratification became shallower by similar to 1.345 m, and surface-bottom temperature difference increased over time by 0.249 degrees C per decade. The creation of a daily time step water temperature dataset not only provided evidence of changes in Erken thermal structure over the last decades, but is also a valuable resource of information that can help in future research on the ecology of Lake Erken. The use of readily available meteorological data to reconstruct Lake Erken's past water temperature is shown to be a useful method to evaluate long-term changes in lake thermal structure, and it is a method that can be extended to other lakes.
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