A chrysophyte-based quantitative reconstruction of winter severity from varved lake sediments in NE Poland during the past millennium and its relationship to natural climate variability

Chrysophyte cysts are recognized as powerful proxies of cold-season temperatures. In this paper we use the relationship between chrysophyte assemblages and the number of days below 4 °C (DB4 °C) in the epilimnion of a lake in northern Poland to develop a transfer function and to reconstruct winter severity in Poland for the last millennium. DB4 °C is a climate variable related to the length of the winter. Multivariate ordination techniques were used to study the distribution of chrysophytes from sediment traps of 37 low-land lakes distributed along a variety of environmental and climatic gradients in northern Poland. Of all the environmental variables measured, stepwise variable selection and individual Redundancy analyses (RDA) identified DB4 °C as the most important variable for chrysophytes, explaining a portion of variance independent of variables related to water chemistry (conductivity, chlorides, K, sulfates), which were also important. A quantitative transfer function was created to estimate DB4 °C from sedimentary assemblages using partial least square regression (PLS). The two-component model (PLS-2) had a coefficient of determination of View the MathML sourceRcross2 = 0.58, with root mean squared error of prediction (RMSEP, based on leave-one-out) of 3.41 days. The resulting transfer function was applied to an annually-varved sediment core from Lake Żabińskie, providing a new sub-decadal quantitative reconstruction of DB4 °C with high chronological accuracy for the period AD 1000–2010. During Medieval Times (AD 1180–1440) winters were generally shorter (warmer) except for a decade with very long and severe winters around AD 1260–1270 (following the AD 1258 volcanic eruption). The 16th and 17th centuries and the beginning of the 19th century experienced very long severe winters. Comparison with other European cold-season reconstructions and atmospheric indices for this region indicates that large parts of the winter variability (reconstructed DB4 °C) is due to the interplay between the oscillations of the zonal flow controlled by the North Atlantic Oscillation (NAO) and the influence of continental anticyclonic systems (Siberian High, East Atlantic/Western Russia pattern). Differences with other European records are attributed to geographic climatological differences between Poland and Western Europe (Low Countries, Alps). Striking correspondence between the combined volcanic and solar forcing and the DB4 °C reconstruction prior to the 20th century suggests that winter climate in Poland responds mostly to natural forced variability (volcanic and solar) and the influence of unforced variability is low

Long-Term Consequences of Water Pumping on the Ecosystem Functioning of Lake Seksu, Latvia

Cultural eutrophication, the process by which pollution due to human activity speeds up natural eutrophication, is a widespread and consequential issue. Here, we present the 85-year history of a small, initially Lobelia-Isoetes dominated lake. The lake's ecological deterioration was intensified by water pumping station activities when it received replenishment water for more than 10 years from a eutrophic lake through a pipe. In this study, we performed a paleolimnological assessment to determine how the lake's ecosystem functioning changed over time. A multi-proxy (pollen, Cladocera, diatoms, and Chironomidae) approach was applied alongside a quantitative reconstruction of total phosphorus using diatom and hypolimnetic dissolved oxygen with chironomid-based transfer functions. The results of the biotic proxy were supplemented with a geochemical analysis. The results demonstrated significant changes in the lake community's structure, its sediment composition, and its redox conditions due to increased eutrophication, water level fluctuations, and erosion. The additional nutrient load, particularly phosphorus, increased the abundance of planktonic eutrophic-hypereutrophic diatoms, the lake water's transparency decreased, and hypolimnetic anoxia occurred. Cladocera, Chironomidae, and diatoms species indicated a community shift towards eutrophy, while the low trophy species were suppressed or disappeared

New sites of laminated lake sediments in Kashubian Lakeland

Annually laminated lake sediments are a very valuable source of paleoecological information because they provide a precise timescale in calendar years and limited post-depositional disturbances. They are formed in specific conditions that enable not only the formation but also preservation of lamination, hence they rarely occur. The goal was to find lakes with annually laminated sediments in Kashubian Lakeland which can provide new high-resolution paleoenvironmental and paleoclimatic data for this part of Europe. Based on statistical analyses including catchment geology and topography, morphometric lake basin features and hydrological parameters, a pre-selection of 22 lakes with water depths ranging from 15 to 35 m was carried out. Gravity cores (30–90 cm long) were obtained from 18 of these lakes during a field survey in 2006. The cores were split lengthwise, photographed digitally and examined carefully. Four of the lakes studied show distinct alternations of pale and dark laminae. For three lakes (Kramsko Duże, Kramsko Małe and BorowoWielkie) such laminations were restricted to sections of the cores only. Lake Suminko was deemed the most promising site with its laminations covering the entire taken core. In all the cases, biochemical varves were developed with pale spring/summer layers composed of autochthonous carbonates and dark fall/winter layers made of organic detritus and minerogenic particles

Origin and transformation of morainic landscape in NW part of Lubawa Upland Origin and transformation of morainic landscape in NW part of Lubawa Upland

The paper presents the investigation results concerning the origin and transformation of the morainic landscape in the northwest part of Lubawa Upland. Detailed sedimentological studies of the sediments within the morainic hill in Rożental and the reconstruction of their depositional and deformational processes are presented. We proposed a model of landscape formation and transformation in examined area. The reconstruction of the palaeogeographical conditions which have been prevailed during the late Pleistocene is also proposed. Collected data show that morainic landscape in the northwestern part of Lubawa Upland reveal landforms of an older origin. It is suggested that relief of examined area consist some features of "palimpsest landscape". The older glacial landforms, formed before the last ice advance, can exist here

Palimpsest terminal moraines in NW part of Lubawa Upland : structure and mechanisms of formation

W artykule przedstawiono wyniki badań litofacjalnych i strukturalnych osadów budujących przetrwałe moreny czołowe na NW skłonie Garbu Lubawskiego. Uzyskane rezultaty wskazują na złożoną genezę badanych wzgórz oraz na wyraźne cechy świadczące o ich przetrwałości. Zaproponowano modele genetyczne dla analizowanych form, prezentujące główne etapy ich formowania oraz mechanizmy sprzyjające ich zachowaniu w strefie subglacjalnej. Analiza budowy badanych form sugeruje ich „palimpsestowy” charakter oraz możliwy wpływ wieloletniej zmarzliny na procesy przetrwania wzgórz pod ostatnim lądolodem skandynawskim.This article presents the results of lithofacies and structural studies of deposits in the palimpsest terminal moraines on the NW slope of Lubawa Upland. The results document a complex origin of these hills and some distinct features suggesting their palimpsest nature. We propose genetic models highlighting the main stages of their formation as well as the mechanisms of their preservation in the subglacial system. The inner structure of the hills suggests a crucial role of permafrost in preservation protecting the hills from erosion under the last Scandinavian Ice Sheet

Chrysophyte-based reconstruction of number of days below 4°C from sediment traps of Lake Zabinskie in northeastern Poland

Chrysophyte cysts are recognized as powerful proxies of cold-season temperatures. In this paper we use the relationship between chrysophyte assemblages and the number of days below 4 °C (DB4 °C) in the epilimnion of a lake in northern Poland to develop a transfer function and to reconstruct winter severity in Poland for the last millennium. DB4 °C is a climate variable related to the length of the winter. Multivariate ordination techniques were used to study the distribution of chrysophytes from sediment traps of 37 low-land lakes distributed along a variety of environmental and climatic gradients in northern Poland. Of all the environmental variables measured, stepwise variable selection and individual Redundancy analyses (RDA) identified DB4 °C as the most important variable for chrysophytes, explaining a portion of variance independent of variables related to water chemistry (conductivity, chlorides, K, sulfates), which were also important. A quantitative transfer function was created to estimate DB4 °C from sedimentary assemblages using partial least square regression (PLS). The two-component model (PLS-2) had a coefficient of determination of R**2cross = 0.58, with root mean squared error of prediction (RMSEP, based on leave-one-out) of 3.41 days. The resulting transfer function was applied to an annually-varved sediment core from Lake Żabińskie, providing a new sub-decadal quantitative reconstruction of DB4 °C with high chronological accuracy for the period AD 1000–2010. During Medieval Times (AD 1180–1440) winters were generally shorter (warmer) except for a decade with very long and severe winters around AD 1260–1270 (following the AD 1258 volcanic eruption). The 16th and 17th centuries and the beginning of the 19th century experienced very long severe winters. Comparison with other European cold-season reconstructions and atmospheric indices for this region indicates that large parts of the winter variability (reconstructed DB4 °C) is due to the interplay between the oscillations of the zonal flow controlled by the North Atlantic Oscillation (NAO) and the influence of continental anticyclonic systems (Siberian High, East Atlantic/Western Russia pattern). Differences with other European records are attributed to geographic climatological differences between Poland and Western Europe (Low Countries, Alps). Striking correspondence between the combined volcanic and solar forcing and the DB4 °C reconstruction prior to the 20th century suggests that winter climate in Poland responds mostly to natural forced variability (volcanic and solar) and the influence of unforced variability is low