The impact of global warming on lake surface water temperature in Poland - the application of empirical-statistical downscaling, 1971-2100

Abstract

The paper presents historical (1971-2015) and scenario-based (2006-2100) changes in surface water temperatures in 10 lakes of Poland. The analysis of historical measurement (1971-2015) showed that mean annual lake surface water temperature (LSWT) was characterised by an increasing tendency by 0.37°C∙dec-1 on average, and was higher by 0.01°C∙dec-1 than air temperature in the analogical period. The highest increase in LSWT was recorded in spring months (April, May) and in summer (July). The future changes in LSWT was based on simulations of 33 AOGCMs available in the scope of CMIP5 project for RCPs: 2.6, 4.5, 6.0, and 8.5. The developed empirical-statistical downscaling models (ESD) use the air temperature field as predictors, with consideration of autocorrelation for two preceding months. ESD models are characterised by high quality of reconstruction of water temperatures in the historical period, with correlation from 0.82 (December, February) to 0.93 (July). The future CMIP5 scenarios for the period 2006-2100 assume an increase in air temperature at the end of the 21st century from +1.8°C (RCP 2.6) to +5.1°C (RCP 8.5) in reference to the period 1971-2005. According to the downscaling models, this corresponds to an increase in water temperature in the analysed lakes ranging from +1.4°C (RCP 2.6) to +4.2°C (RCP 8.5) in the years 2081-2100, respectively, with evident variability between the adopted emission paths beginning from the period 2041-2060. At a monthly scale, water temperature will increase the slowest in February (2081-2100: RCP 2.6 = +0.5°C, RCP 8.5 = +1.8°C). The highest increase in temperature will occur from May to August (RCP 8.5 = +6°C in June).Substantial effects of transformations of the thermal regime are already observed today, e,g. in the reduction of the ice season length. According to developed scenarios, a further considerable increase in water temperature will be the primary factor determining the transformation of lake ecosystems. The obtained results provide a theoretical basis for further research conducted in the scope of many disciplines, among others hydrology, hydrobiology, ecology, water management, energy production, etc. In the case of Poland, issues related to low water resources per capita are particularly important. Contemporary studies concerning changes in water resources showed that the natural factor playing the key role in their reduction is temperature increase and therefore it should constitute for the possibly fast development of multidisciplinary concepts of mitigation policy to potential impact of climate change.

An epilimnion and hypolimnion temperature model based on air temperature and lake characteristics

“…The four-parameter version of the air2water model (Toffolon et al, 2014;Piccolroaz, 2016) is a simplification of the full 8-parameter model by Piccolroaz et al (2013) to estimate the epilimnion temperature of lakes in the temperate region (Piccolroaz et al, 2015;Czernecki and Ptak, 2018;Piccolroaz et al, 2018). It is a semiempirical model that approximates the heat balance from air and water temperature according to:…”

Changes in Potential Evaporation in the Years 1952–2018 in North-Western Poland in Terms of the Impact of Climatic Changes on Hydrological and Hydrochemical Conditions

“…Unlike flowing waters, more unambiguous trends in changes of hydrological conditions have been observed in Polish lakes, in which lowering of the water level has been visible since the second half of the 20th century [18,71]. At the same time, an increase in water temperature was recorded in lakes [72][73][74]. Wang et al [75] forecasted a further global increase in evaporation from lakes and estimate that the global annual lake evaporation will increase by 16% by the end of the century.…”

“…They pointed out that the increase in evaporation could be higher for lakes at low latitudes. Czarnecki and Ptak [72] indicated that a further considerable increase in water temperature of the lakes in Poland will be the primary factor determining the transformation of lake ecosystems. Studies into the impact of climate warming on processes occurring in lakes show that the effects may include changing the mixing type of the lake, extending the period of thermal stratification, shortening the duration of water mixing and increasing the depth and temperature of the epilimnion [70,73,[76][77][78].…”

Characteristics of daily water temperature fluctuations in lake kierskie (West Poland)

“…In a large majority of papers discussing the issue, an increase in water temperature is evident (Naumenko et al 2006, Austin, Colman 2007, Schneider, Hook 2010, Ptak et al 2017, and the scale and rate of the process are dependent on a number of co-occurring factors (climatic conditions, surroundings, lake morphometry, etc.). The transformation of surface waters resulting from climate changes is already evident (Mooij et al 2008, Jeppesen et al 2012, and with the maintenance of the current trend further transformations will proceed, with largely unpredictable effects (Czernecki, Ptak 2018). Such a situation will certainly force undertaking corrective measures reducing the effects of global warming for the functioning of lake ecosystems.…”