Past climate change recorded by annually laminated lake sediments

Project coordinator: Timo Saarinen

Principal Investigator: Eeva Haltia

Energy emitted by the Sun runs the climate system. Low frequency climate modulation at time-scales of 10000-100000 years can be attributed to the orbital theory compiled by M. Milankovitch, but at shorter timescales to solar variation. The activity of the sun is not a constant, but it alternates in periodicities of different duration, one of the best known being the 11-year cycle (Schwabe cycle) of sunspots. Due to the short history of observations, past solar activity has been studied using the production rates of cosmogenic isotopes (e.g. 10Be, 14C) using tree-rings, varved lake sediments and ice cores as a proxy. During periods of high activity, sunspots are abundantly visible on the surface of the sun and the production of cosmogenic isotopes is low and vice versa. Periodicities of various scales found in varve data, often in varve thickness, have been related to modulation in solar activity in different regions of the world. Annually laminated lake sediments are one of the most valuable of terrestrial palaeoclimate records, which may reach back in time in continuous sequences for tens of thousands of years. A varve can be defined as a set of laminae deposited during one year. Because of their precise chronological control and even seasonally discernible laminae, varves provide excellent study material for high-resolution palaeoclimate reconstructions. The climate signal is integrated in lake sedimentation in combination with environmental changes. In favourable circumstances, lake sedimentation may record solar forcing in detail. Our preliminary results suggest that Finnish annually laminated sediments are excellent material to study impact of solar forcing on sedimentation. In this project impact of solar forcing of climate change will be evaluated from precisely dated lake sediment sequences using novel high resolution techniques.

The project is funded by the Academy of Finland (2013-2018)

Climate forcing inferred from varved lake sediments during the last 2000 years: how do varve characteristics represent the variation of precipitation and temperature?

Principal Investigator: Saija Saarni

Climate forcing inferred from varved lake sediments during the last 2000 years: how do varve characteristics represent the variation of precipitation and temperature?

The aim of this project is to analyze the characteristics of the annually laminated sediments from several lakes. The focus is on the physical and chemical composition and composition variation of the varve structures. The high resolution of the varved lake sediments, enable the study of the individual seasons. We can compare summers and winters separately. We observe the past changes in the snow accumulation and precipitation. The main objectives of the project are to better understand the climate forcing in varve characteristics and to present a climate reconstruction for the last 2000 years.

The project is funded by the Kone Foundation.

Development of anoxia in coastal areas of the Archipelago Sea and the Gulf of Finland during the last 2000 years

Principal Investigator: Sami Jokinen

The main objective of this study is to assess how the coastal areas of the northern Baltic Sea respond to natural climate variability such as the Medieval Climatic Anomaly (950‒1250 AD) and the Little Ice Age (1350‒1850 AD). The conventional environmental monitoring programs reach back only the 1970s, when intense human activities in these ecologically sensitive areas were already considerable. Therefore, long-term information on environmental conditions predating the anthropogenic impact is necessary for determining if the spreading of hypoxia is a natural phenomenon in the coastal areas. We use combined sedimentological, ichnological and mineral-specific  in situ microanalyses as indicators of past redox fluctuations in the near-bottom waters. Through detailed understanding of the long-term changes in the coastal depositional environment, forthcoming environmental changes will be anticipated more accurately, facilitating the evaluation of adequate measures that must be taken to ensure a healthier coast.

Modelling the natural leaching of total phosphorus in naturally nutrient-rich areas

Principal researcher: Mira Tammelin

Eutrophication is one of the most pressing environmental problems currently deteriorating our lake water quality. The nutrient load from catchments to lakes consists of natural nutrient leaching and anthropogenic nutrient loading. Estimating the amount of natural leaching is crucial for efficient water protection because it notably varies according to different background geologies. We use diatom-based palaeoecological modelling and mass balance based load-response modelling together with statistical and GIS-based catchment analysis to model the natural leaching of total phosphorus in the Iisalmi watercourse area. Palaeoecological modelling also allows the examination of long-term temporal changes in the diatom assemblages and total phosphorus concentrations of the lakes. The study area, with its shallow, humic and conspicuously eutrophic lakes, has proven challenging for the existing water quality models. Therefore, the results of this study can be utilized to improve these models and also to facilitate water quality target planning, water protection investment allocation and lake restoration.

The project is funded by the Geological Survey of Finland, Finnish Cultural Foundation, Alfred Kordelin Foundation and Olvi Foundation.

Constructing a tephrochronological framework for Finland

Principal researcher: Maarit Kalliokoski

Time-synchronous cryptotephra horizons have been successfully used in dating and correlating stratigraphic sequences in Northern Europe for over 20 years. Robust tephrochronological frameworks, which enable precise dating of palaeoenvironmental records and assessment of inter-regional leads and lags in timing of environmental change, now exist in areas where tephrochronological work has been carried out for a long period of time, such as Ireland, the British Isles and Sweden. Tephra from Icelandic volcano eruptions is known to be carried also to Finland, but no tephra layers have previously been found or reported here. Our main aim is to find and geochemically fingerprint tephra layers in Finnish peat bogs and lake sediments in order to evaluate the possibilities of using tephrochronology as a dating method in environmental research in Finland.

Sedimentation of micro plastic in lacustrine environments

Principal Investigator: Saija Saarni
Plastic is designed to be a durable and resistant material. The low price, high resistance to abrasion and versatility explain the universal and increasing use of plastic. The resistance is a major disadvantage of plastic when the plastic waste is left in the nature. Plastic does not degrade but breaks into smaller and smaller pieces when exposed to ultra violet radiation and mechanic abrasion. As a consequence micro plastic is formed (particle size < 5 mm). The environmental risk caused by micro plastic particles that are enriched in the lakes and oceans has been discovered only recently. The micro size plastics are already found in lake and marine sediments all around the world, even in the deep marine basins. However, the sedimentation processes of micro plastic are not fully understood. The study is carried out at Lake Kallavesi and Lake Haukivesi in eastern Finland, where a four-year sediment monitoring is arranged in a co-operation with the micro-plastic research group of University of Eastern Finland. In addition, a large number of sediment samples will be analyzed in detail during the project. The key objectives of this project is to study the sedimentation of the different plastic types and observe how far from the source of discharge the plastic materials are transported. The aim is to assess the role of seasonal variation in micro plastic sedimentation of different plastic materials. In boreal climate zone the seasonal variation strongly affects the lake sedimentation.