Sebastian Tyszkowski

Site-specific sediment responses to climate change during the last 140 years in three varved lakes in Northern Poland

Accurate dating and unambiguous chronological correlation using cryptotephras provide a powerful tool to compare the varved sediment records of the lakes Głęboczek (JG), Czechowskie (JC) and Jelonek (JEL) (north-central Poland). For the last 140 years, micro-facies analyses and µ-XRF element scanning at seasonal resolution, as well as bulk elemental analyses (organic matter, carbonate) at sub-decadal to decadal resolution, were conducted for all three lakes records. All lakes are located in a region with low population density, and therefore, anthropogenic influences are negligible or only minor. The varve chronologies have been established independently for each record and were synchronized with the Askja AD 1875 cryptotephra. Comparison with monthly temperature data since 1870 and daily temperature data since 1951 revealed different responses of lake deposition to recent climate change. Varves are well preserved over the entire 140 years only at JG, while in the JC record two faintly varved intervals are intercalated and in the JEL record two non-varved intervals occur at the base and top of the profiles. These differences likely are due to variations in lake characteristics and their influence on lake-internal responses. JG is the smallest and best wind-sheltered lake, which favours varve preservation. JC’s attenuated sediment responses can likely be linked to lake productivity changes with respect to climate warming. JEL is lacking a direct sedimentological response to the observed temperature increase, which can be linked to lake size and water depth superimposing regional climate changes. Climate changes at the demise of the ‘Little Ice Age’ around 1900 and the recent warming since the 1980s are expressed in sediment proxies in the lakes with different response times and amplitudes. This detailed comparison study on three nearby lakes demonstrates the influence of local parameters such as lake and catchment size and water depth superimposed on more regional climate-driven changes.

Geology, permafrost, and lake level changes as factors initiating landslides on Olkhon Island (Lake Baikal, Siberia)

Permafrost decline, observed in the last few decades as a result of climate change, causes an activation of cryogenic landslide processes. This study on Olkhon Island in Lake Baikal (Eastern Siberia), located within the discontinuous permafrost zone, was aimed to determine how strongly the landslide forms found there are associated with climatic conditions and if they can react to climate change. It was also important to identify which type of landslides in this area is the most sensitive indicator of the observed changes and to what extent they can react to them. For this purpose, landslides were identified, and their morphology, geological structure, and thermal parameters were assessed. The results show that the key process is the increase in thickness of the active layer, partly due to the presence of Miocene lake clays and changes in water level in Lake Baikal.

The Application of Box–Cox Transformation to Determine the Standardised Precipitation Index (SPI), the Standardised Discharge Index (SDI) and to Identify Drought Events: Case Study in Eastern Kujawy (Central Poland)

Abstract The article presents the results of research into the transformation of series of hydro-meteorological data for determining dry periods with the Standardised Precipitation Index (SPI) and the Standardised Discharge Index (SDI). Time series from eight precipitation stations and five series of river discharge data in Eastern Kujawy (central Poland) were analysed for 1951–2010. The frequency distribution of the series for their convergence with the normal distribution was tested with the Shapiro–Wilk test and homogeneity with the Bartletts test. The transformation of the series was done with the Box–Cox technique, which made it possible to homogenise the series in terms of variance. In Poland, the technique has never been used to determine the SPI. After the transformation the distributions of virtually all series complied with the normal distribution and were homogeneous. Moreover, a statistically significant correlation between the δ transformation parameter and the skewness of the series of monthly precipitation was observed. It was similar for the series of mean monthly discharges in the winter half-year and the hydrological year. The analysis indicates an alternate occurrence of dry and wet periods both in case of precipitation and run-offs. Drought periods coincided with low flow periods. Thus, the fluctuations tend to affect the development of agriculture more than long-term ones.