Kämäri J. 1997. Preface. Boreal Env. Res. 2(1): 1.
Abstract
Vehviläinen, B. & Huttunen, M. 1997. Climate change and water resources in Finland. Boreal Env. Res. 2(1): 3–18.
Abstract
Lepistö A. & Kivinen Y. 1997. Effects of climatic change on hydrological patterns of a forested catchment: a physically based modeling approach. Boreal Env. Res. 2(1): 19–31.
Abstract
Kallio K., Rekolainen S., Ekholm P., Granlund K., Laine Y. Johnsson H. & Hoffman M. 1997. Impacts of climatic change on agricultural nutrient losses in Finland. Boreal. Env. Res. 2(1): 33–52.
Abstract
Frisk T., Bilaletdin Ä. Kallio, K. & Saura, M. 1997. Modelling the effects of climate change on lake eutrophication. Boreal Env. Res. 2(1): 53–67.
Abstract
Lappalainen J. & Lehtonen H. 1997. Temperature habitats for freshwater fishes in a warming climate. Boreal Env. Res. 2(1). 69–84.
Abstract
Lappalainen J., Lehtonen H. & Erm V. 1997. Possible effects of climate warming on the timing of spawning, juvenile abundance and catches of pikeperch, Stizostedion lucioperca (L.). Boreal Env. Res. 2(1): 85–91.
Abstract
Haapala J. & Leppäranta M. 1997. The Baltic Sea ice season in changing climate. Boreal. Env. Res. 2(1): 93–108.
Abstract
Kuikka S. & Varis O. 1997. Uncertainties of climatic change impacts in Finnish watersheds: a Bayesian network analysis of expert knowledge. Boreal Env. Res. 2: 109–128.
Abstract
Kämäri J. 1997. Preface. Boreal Env. Res. 2(1): 1.
Continuous cycling of water in the atmosphere, surface waters, groundwaters and oceans is the basis of present life on Earth. Movement and retention of water around the world are intimately linked to the dynamics of the atmosphere and the global energy budget. Despite the low proportion (some 3%) of fresh waters overall, the fresh water reservoirs are of a crucial importance for biota and mankind.
Vehviläinen, B. & Huttunen, M. 1997. Climate change and water resources in Finland. Boreal Env. Res. 2(1): 3–18.
The effects of climate change on water resources in Finland have been evaluated by conceptual watershed models. The central SILMU scenario is used as a climate change approximation for the future. The evaluated water balance terms are areal corrected precipitation, evapotranspiration, lake evaporation, water equivalent of snow, soil moisture, groundwater and runoff. Changes in the mean values and seasonal distributions of river discharges and lake water levels are also presented. The precipitation and temperature increases assumed by the central SILMU-scenario will not essentially affect annual water balance, but will strongly change the seasonal distribution of runoff and other water balance terms. Snow cover will diminish or almost vanish and its duration will be shortened by one to four months in different scenario runs due to warming. The winters will become wetter and snow-free due to increased precipitation and frequent thawing periods. Spring floods will diminish or vanish and winter floods will occur instead.The summers will become drier due to the longer summer season and increased evapotranspiration and lake evaporation.
Lepistö A. & Kivinen Y. 1997. Effects of climatic change on hydrological patterns of a forested catchment: a physically based modeling approach. Boreal Env. Res. 2(1): 19–31.
Effects of climatic change on hydrological patterns on a catchment scale were evaluated using a semi-distributed, topographic TOPMODEL. The model was calibrated to a forested catchment for the period 1991–92 with a daily time step, using a model version with a snow subroutine. The main criteria in the model calibration were to fit simulated and observed runoff, to obtain an adequate water balance and to compare simulated and observed groundwater depths and water equivalents of snow. The model was tested with data from the years 1993–94, and long-term forecasts of up to 100 years were conducted. Precipitation and temperature input were obtained from the CLIGEN weather generator, which generates stochastic daily time series of these variables, according to the SILMU-policy oriented scenarios high (annual increase in precipitation 1.5%/decade and in temperature 0.6 °C/decade), and low (annual increase in precipitation 0.25%/decade and in temperature 0.1 °C/decade). Ten high scenarios and ten low scenarios were used as an input to TOPMODEL, in order to predict long-term changes of annual averages and interannual variability in runoff, evapotranspiration and average amount of soil water. According to the model runs conducted, first an increase of 4% (12 mm) and then a slight decrease (2–7%, i.e. 6–18 mm) in annual runoff was predicted. The most notable change in runoff was the change from the present spring high flow to a more evenly disributed winter flow. Soil moisture was predicted to increase during the autumn and winter periods and to decrease during summer. A strong reduction of 80–90% in the volume and duration of the snow cover was predicted by the high SILMU scenario during the next 100 years. The reduction by 2050 was predicted to be about 50%. Already at present, three years (1991–93) of the observation period could be considered as ‘future’ winters with very little snow and several distinct, short snow accumulation/melting periods.
Kallio K., Rekolainen S., Ekholm P., Granlund K., Laine Y. Johnsson H. & Hoffman M. 1997. Impacts of climatic change on agricultural nutrient losses in Finland. Boreal. Env. Res. 2(1): 33–52.
Changes in nitrate and particulate phosphorus losses from agricultural areas in Finland were estimated in a new equilibrium climate assuming an increase of 4.7 °C in temperature and 12% in precipitation as compared to the present climate. The assessment was mainly based on the use of mathematical simulation models. Process-oriented soil profile and field-scale models (SOIL/SOILN and modified CREAMS) were used to estimate potential nutrient losses for typical combinations of slopes, soils, crops and climatic regions in Finland. These model results were then combined with the geographical data sets to produce regional estimates of the impact of climate change. In addition, a simple drainage basin scale model based on the HBV runoff model was used to estimate the changes in nutrient losses from a typical agricultural drainage basin. The modeling results were compared with the observations of nutrient fluxes from normal years and years with exceptionally mild winters in an agriculturally loaded river. On the basis of the model estimations and the observations, the predicted increases in precipitation and temperature will most probably increase the nitrogen loss from agricultural areas to surface waters. The increase was predicted to be highest in south-western Finland. The main reasons for the increase are the acceleration of organic matter mineralization in agricultural soils and the increased water flow through the soil column. Particulate phosphorus losses showed a mean decrease for all agricultural land in Finland. The main causes for the decrease are the shorter period of frozen soil and the reduced snowfall, both of which reduce surface runoff. The regional differences in phosporus losses can be explained by differences in soil and crop composition and in the proportion of steeply sloping fields in different regions. The estimates of changes in nitrogen losses by the SOIL/SOILN model were generally in good agreement with estimates obtained by the drainage basin model. In the case of changes in phosphorus losses the CREAMS model gave a considerable reduction, whereas the drainage basin model predicted an increase. Observations from the years with exceptionally mild winters indicated an increase in nitrogen losses and no change in phosphorus losses. The assessment was based on the assumption that no changes in cropping patterns and cultivars would take place. Furthermore, a possible increase in yields was only partly taken into account.
Frisk T., Bilaletdin Ä. Kallio, K. & Saura, M. 1997. Modelling the effects of climate change on lake eutrophication. Boreal Env. Res. 2(1): 53–67.
The effects of climate change on lake eutrophication were studied using a dynamic simulation model. The climate scenarios of the Finnish Research Programme on Climate Change (SILMU) were applied. As the model, a modified version of the Swedish PROBE was used. The description of water quality and growth of plankton was included in the model in Finland. There were three case study lakes: Lake Villikkalanjärvi in southern Finland and Lakes Kalliojärvi and Längelmävesi in central Finland. The model was successfully calibrated to all three lakes. According to the simulations the effects of climate change on the trophic status of the lakes will not be great. An increase in the spring peak of phytoplankton is expected, but the average biomasses will remain the same as at present. However, on the basis of the modelling results we can conclude that climate change may cause a risk for eutrophication in some lakes.
Lappalainen J. & Lehtonen H. 1997. Temperature habitats for freshwater fishes in a warming climate. Boreal Env. Res. 2(1). 69–84.
The effects of global warming on the six freshwater fish species, whitefish (Coregonus lavaretus (L.)), brown trout (Salmo trutta L.), bream (Abramis brama (L.)), roach (Rutilus rutilus (L.)), perch (Perca fluviatilis L.), and pikeperch (Stizostedion lucioperca (L.)), were studied on the basis of temperature scenarios made by the weather generator and the PROBE model. Two theoretical indices were used to evaluate the effects of warming on the fish species: temperature sum of growth habitat and the number of days when water temperature was above the lowest stress level. The results showed that cool- and warmwater species will benefit from warming in the whole of Finland while the habitats of coldwater species will shrink primarily in southern Finland. For all the selected species the growing season will start earlier, but for the coldwater species (whitefish and brown trout) epilimnic temperatures will rise above stress levels during the summer. This may cause population collapses of these species in the shallow lakes of southern Finland. The range of bream and pikeperch may shift northward to cover the whole of Finland by 2060.
Lappalainen J., Lehtonen H. & Erm V. 1997. Possible effects of climate warming on the timing of spawning, juvenile abundance and catches of pikeperch, Stizostedion lucioperca (L.). Boreal Env. Res. 2(1): 85–91.
The effects of climate warming on the population dynamics and exploitation of pikeperch (Stizostedion lucioperca (L.)) were studied in the Baltic Sea and its drainage area. In southern (61°N) and in central Finland (64°N) the average spawning period will be about one month earlier due to climate warming in the year 2050. In Pärnu Bay, Estonia (58°N, 24°E), the juvenile abundance of 0+ pikeperch will be higher, and higher abundances and warmer waters will also enhance fishermens catches.
Haapala J. & Leppäranta M. 1997. The Baltic Sea ice season in changing climate. Boreal. Env. Res. 2(1): 93–108.
The ice pack is an important and highly sensitive component in the climatology of the Baltic Sea, which has been examined with a coupled ice-ocean model. The observed Baltic ice climate variability is well reproduced by the model. Future ice season are simulated as follows: in an average winter in 2050 ice is formed only in the Bay of Bothnia, the Archipelago Sea, the east of Gulf of Finland and on the Estonian west coast. The freezing date has been shifted about 20 days later and the break-up date 10 earlier. The ice thickness is 20 cm thinner. Locally such degrees of change could also be obtained using a simple analytic model. The coupled ice-ocean modeled 30 year’s ice statistics centered on 2050 gives a 30–65 cm range for the annual maximum ice thickness in the Bay of Bothnia. The length of the ice season varied from 3.5–6 months. The latest freezing occurred in January and the ice break-up happened at the earliest in April. Some ice would still be formed in 2100 at Kemi.
Kuikka S. & Varis O. 1997. Uncertainties of climatic change impacts in Finnish watersheds: a Bayesian network analysis of expert knowledge. Boreal Env. Res. 2: 109–128.
Climatic change impact studies are among the most complicated and uncertain environmental assessments scientists have ever faced. Not only are possible scenarios on key changes and impacts needed, but also estimates of their probabilities, which are of particular relevance to policy making. In modeling, the key uncertainties lie in inaccuracies and errors in parameters, and above all (but often not fully discussed) in assumed causalities (model structure). In the present study, the views of eight Finnish experts on interactions between climatic and aquatic systems were analyzed. They were asked to assess the states of 24 key variables in the climate-water system in southern Finland, using subjective probability distributions and the causalities between those variables. The methodological approach used was based on Bayesian belief networks. The highest uncertainties were seen in the changes of floods, water pH and oxygen concentrations, problems to constructions, and the recreational value of watersheds. Positive impacts can be expected on transportation and hydropower production. The relative importance of different causalities was analyzed separately for hydrological, limnological, and interest variables. The causalities between climate and hydrology did not appear very important from the interest standpoint, because uncertainty deriving from other sources masked their effects. The causality between temperature and precipitation was important throughout the model, while expected changes in temperature and precipitation were also important in the case of most variables.
The surface waters within the Boreal Zone, with their small water volumes, naturally high contents of organic matter and long ice-cover period, are particularly susceptible to changes due to external loading induced by climate change. Even small changes in the external loading can severely effect the structure and function of the northern lacustrine ecosystems. Moreover, the Baltic Sea, the world’s largest brackish water basin, is also vulnerable to changes in loading of nutrients.
There is clear evidence of the possible effect of climate change on waters in the Boreal Zone. The approaches used in different research programmes on climate change vary from palaeoecological methods reconstructing past climatic changes based on lake sediments and time series analysis of hydrological observations to dynamic modeling of hydrology, material fluxes and ecological responses of lakes, as well as to experimental studies of temperature effects on the rates of biological processes. These different approaches strongly complement each other. Without experimental work, the parameterization of the models would be very uncertain. On the other hand, modeling can reveal gaps in our knowledge and thus direct experimental work to the most relevant questions.
The Boreal Environment Research presents highlights of the symposium on “Climate Change and Waters in the Boreal Zone”, held in Kuhmo, Finland, 21–24 November 1995, and organized by the Finnish Climate Change Research Programme (SILMU). The objectives of the Symposium were (i) to assess the current understanding of the processes controlling leaching of elements to surface waters in a changing climate, (ii) to assess the current understanding of the potential ecological effects in both fresh water and marine ecosystems due to climate change, (iii) to discuss the potential of presently available models for describing the dynamics of the impact on surface waters, and (iv) to discuss various scenarios produced by available predictive impact models for analyzing the climate change impact on surface waters.
The main bulk of the results of the Symposium are included in the present issue. However, one paper (Regier et al.: “Likely responses to climatic change of fish associations in the laurentian Great Lakes Basin: concepts, methods and findings”) was already published in the former issue (Boreal Env. Res. 1: 1–16). Four papers accepted by the Boreal Environment Research will be published in the next issue: Gottschalk and Krasovskaia: “Climate change and river runoff in Scandinavia; approaches and problems”, Zhang et al.: “Variability of climate and ice conditions in the Bohai Sea, China”, Forsius et al.: “Impacts of climate change on material leaching from forests”, and Inkala et al.: “Modelling the effect of climate change on nutrient loading, temperature regime, and algal biomass in the Gulf of Finland”.
The SILMU programme of the Academy of Finland is greatfully acknowledged for sponsoring the Symposium and the publication of the papers in the Boreal Environment Research.