Browsing by Subject "ilmastonmuutos"

The subarctic ponds of northern Fennoscandia are often clear-water, fish-free and oligotrophic (relatively low primary production). The ponds in the area are useful physical geography research sites, as the human impact in these areas is relatively small. These ponds are often phosphorus-limited and serve as good indicators of air pollution. Understanding and anticipating changes in water chemistry is particularly important for both the people and the ecosystems in the region. Changes in these ecosystems due to the climate change, for example, can be harmful. The effects of the climate change are and will continue to be strongest in arctic and subarctic areas. The current relatively short growing season is lengthening, so habitats and vegetation zones will either relocate or, alternatively, organisms and plants will have to adapt to the changing conditions. Yet many of the cold-water endemic species worldwide will become extinct. The aim of this thesis was to focus on the biomass of benthic algae growing on the rocks of subarctic ponds. These cyanobacteria, green algae, and diatoms are important primary producers in subarctic ponds and an important part of the food web in these waters. The biomass in this thesis refers to the actual amount of benthic biomass expressed by the amount of dissolved nutrients (not their theoretical, potential amount). The aim of the thesis was to find out how well the physical variables (pond area, average water temperature of the last month of measurement and median solar radiation) and chemical variables (water metal and nutrient concentrations, pH, and conductivity) explain the benthic biomass of subarctic ponds. The Kilpisjärvi area is the only area in Finland that belongs to the old Caledonian orogeny range in the northern part of Fennoscandia. All these 39 ponds were studied, and they are located in Kilpisjärvi in Finnish Lapland, in the areas of about 30 km² of Malla Strict Nature Reserve and about 40 km² of Ailakkavaara, at altitudes of 486–882 m a.s.l. Some of the ponds are located above and some below the tree line. Water samples were collected in August 2020, when data from continuous temperature and radiation meters installed in the late summer of 2019 were also read. During the sampling of the ponds, the biomasses of epilithic, rock-bearing benthic algae groups were measured with a BethoTorch field device and a water pH with a YSI PRO field meter. Water samples were analyzed for metal concentrations by ICP-MS and nutrient concentrations by IC. The results obtained after this spectrometric and chromatographic laboratory analyzes were analyzed statistically, including by means of a generalized linear model (GLM). The water chemistry of the ponds and the biomass of benthic algae are affected by many biotic and abiotic factors. Among other things, geographical location, topography, and climate (in the polar region or the equator) affect both water chemistry and pond biomass. The total metal concentrations in the studied ponds ranged from about 20 to 220 μg/l and the nutrient concentrations from about 2 to 17 mg/l. Based on the results, the chemical variables explained the occurrence of 57 % diatoms, 56 % green algae, and 27 % cyanobacteria, and the physical variables explained 28 % diatoms, 8 % green algae, and 4 % cyanobacteria. According to the F-test, of the chemical variables, the metal concentrations in the water played the largest role in the biomass of benthic algae. The pond area had the largest impact from the physical variables. Surprisingly, nutrients did not appear to play much role in the benthic biomass, although the literature suggests that. The warmer the water, the more likely cyanobacteria are the dominant species and the colder the water more likely are diatoms. This is because the growth peak of cyanobacteria coincides with the warmest time of the year, late summer, and diatoms in springtime immediately after the break-up of ice. The advantage of the BenthoTorch instrument was it is ease of use and speed of measurement, but more specific results could have been obtained, for example, by microscopy of the abundance of the benthic species. In the future, special attention should be paid to the stabilization of chlorophyll-a concentrations in the measurement of benthic algae biomasses. This could produce results that are more consistent and comparable.

Tutkielmassa on selvitetty lumensyvyyden muutoksia ERA5-Land-uudelleenanalyysin antamille tuloksille ajanjaksolla 1950-2021. Datan analyysi ja käsittely on toteutettu Pythonilla. ERA5-Land:n etuihin lukeutuu muun muassa parempi erotuskyky kuin ERA5-uudelleenanalyysiin, mikä parantaa aineiston tarkkuutta huomattavasti. ERA5-Land ei suoraan käytä havaintoarvoja vaan lumensyvyys lasketaan muitten sääsuureitten, kuten lämpötilan ja sademäärän, aikasarjoja hyödyntäen. Näin ollen tutkielmassa käsiteltyihin suureisiin on sisällytetty muitakin suureita kuin vain lumensyvyys jotta syitä lumensyvyyden muutoksiin olisi helpompaa hahmottaa. Tutkielmaan valikoitiin kolme tutkimusaluetta; Suomi kokonaisuudessaan, Fennoskandian alueelta Norjan, Ruotsin sekä Suomen yhteinen pinta-ala, sekä Japanista Hokkaidon ja Honshun saarten muodostama maa-alue. Aineiston pohjalta voidaan todeta varsin yksiselitteisesti lumensyvyyden kuukausikeskiarvojen olevan, varsinkin lumensyvyyden huippuarvokuukausina, vertailukaudelle 1991-2020 pienempiä kuin vertailukaudelle 1951-1980. Sama trendi näkyy myös vuotuisten keskiarvojen kehityksessä. Muutosten suuruus on jonkin verran sidoksissa alueellisiin erityispiirteisiin mutta päätrendi on kaikille alueille jokseenkin samansuuntainen; nykyisentyyppinen ilmastollinen kehitystrendi laskee lumensyvyyttä pitkällä aikatähtäimellä. Toisin sanoen ilmastonmuutos vähentää lumimäärää pohjoisella pallonpuoliskolla.

Hallitustenvälinen ilmastonmuutospaneeli IPCC määrittelee Pohjois-Atlantin subpolaaripyörteen ilmaston käänne-elementiksi, joka voi joutua ilmaston muutoksen seurauksena toiseen tilaan. Tässä työssä tarkastellaan ensin tieteellisten artikkelien pohjalta subpolaaripyörrettä ja sen vuorovaikutusta muun meren, sekä ilmakehän kiertoliikkeen kanssa. Sen jälkeen muodostetaan CMIP5-projektin (Coupled Model Intercomparison Project 5) ilmastomallien pohjalta kaksi malliryhmää. Toisessa on kolme mallia, joissa subpolaaripyörteen syvänveden muodostus romahtaa, toinen on vertailuryhmä. Subpolaaripyörteen romahdus näyttää todennäköisemmältä kuin CMIP5-malliryhmien kokoa vertailemalla voisi päätellä ja romahdus voi tapahtua jo pienimmällä RCP2.6-skenaariolla. Suunnilleen yhtä todennäköistä, kuin yksi romahdus, on useampi nopea subpolaaripyörteen heikkeneminen, joiden välissä subpolaaripyörre voimistuu uudelleen. Tämä ilmiö voi lisätä tulevaisuuden ilmastossa vaikeasti ennakoitavaa vuosikymmenten välistä vaihtelua. Subpolaaripyörteen romahduksen ilmastovaikutukset ovat suurimmat arktisella alueella, Pohjois-Atlantilla ja Euroopassa. Se heikentäisi pohjoisen napa-alueen lämpenemistä, joka muuten on paljon voimakkaampaa kuin maapallon keskimääräinen lämpeneminen. Euroopassa ilmiö hillitsee ilmastonmuutoksen aiheuttamaa lämpenemistä ja voi muuttaa ilmakehän keskimääräistä kiertoliikettä. Suurimmat vaikutukset keskittyvät kuitenkin subpolaaripyörteen alueelle.

A significant amount of carbon has been stored in the northern peatlands during the Holocene. These peatlands are an important part of global carbon cycle by sequestering and releasing carbon dioxide (CO2) and methane (CH4) into the atmosphere. The development of high-latitude peatlands begun at the beginning of the Holocene, about 11,700 years ago after the retreat of the continental ice. To some extend, the carbon accumulation rate history has followed Holocene climate phases. Due to the high primary production during the warm periods, their carbon sequestration has been high and lower during the colder periods as primary production decreased. Perhaps the most important factor determining peatland carbon dynamics moisture conditions, i.e. water table depth. The climate is predicted to warm much faster in the north than elsewhere, making the northern peatlands particularly vulnerable to the effects of climate change. In the future, climate change is expected to change the humidity and temperature conditions, which likely affecting the carbon dynamics of the peatlands. However, the ultimate effects are not yet fully known. This thesis studies changes in the hydrological conditions of the subarctic Lompolojänkkä peatland in Finnish Lapland over the past 900 years. Based on a testate amoeba analysis of two peat profiles, a quantitative water table depth reconstruction was created using a transfer function based on the surface samples reference data. The supporting plant macrofossil data was available supplemented by chronology based on radiocarbon and lead dating. The results show that the hydrology of Lompolojänkkä has adapted changes in climate conditions over the past 900 years and the data show that the surface of the peatland is now drying. The observed current trend towards drier conditions is in line with previous observations from northern peatlands. Changes in the Lompolojänkkä's plant community indicate extensive peatland lateral growth as well as a small-scale development resembling fen-bog-transition. In contrast to prevailing understanding, changes in the testate amoeba community followed changes in the plant community. This may be due to relative change in water level whereas a result of warming the plant growth accelerated and peat accumulation increased, which resulted in deepening of water table depth. The number of testate amoebae in different peat layers gives the slightly conflicting indications of the development of the carbon sequestration capacity of the peatland over the time studied, and there are some uncertainties associated to applicability of such data. However, the observed vegetation shift suggests future increase in carbon sequestration potential in Lompolojänkkä.