The article presents changes in the course of ice phenomena on Lake Morskie Oko over 50 years. It comprises detailed data of the course of the main parameters of ice regime of the lake in the years 1963–1970. Such a reference period yielded substantial differences in the obtained values of trends in comparison with the period 1971–2010, which is most common in literature. The trends obtained differed substantially from those describing the years 1971–2010, and the change in the parameters – scaled to a year of the analysed period – was about half the size. Attention was also drawn to the practical aspect of the changes in the duration and thickness of ice cover on the lake. In the years 1963–2012 the period of safe movement on the frozen lake was reduced by only 10 days.
Winter season temperatures are becoming warmer. However, the transformation of the ice regime on the Vistula River in Toruń has also been affected by river engineering. In particular, the construction and operation of the Włocławek Dam had a significant impact on ice processes. The article presents the results of an analysis determining the contribution of natural and anthropogenic factors to the duration of ice phenomena and ice cover on the Vistula River in the city of Toruń. Compared to the end of the nineteenth century, there has been a reduction in the duration of ice phenomena from 88 to 53 days and of ice cover from 40 to 7 days (in the period of 1882-2011). The article compares the duration of ice cover and winter temperature in three different periods: before the completion of river engineering works (1882-1907); for the controlled river (1908-1969), and for the controlled river with the Włocławek Dam upstream of Toruń (1970-2011). The results showed a significant role of these anthropogenic factors in the changes of the ice cover duration on the Vistula River in Toruń.
Our first information of ice cover on the Vistula River in Poland dates from the Middle Ages. However, only since the 19th century have continuous observations been available. This study makes use of a data series, obtained mainly from IMGW (Institute of Meteorology and Water Management), covering the years 1861-2003 for ice phenomena and 1814-2003 for ice cover. Considerable shortening has been observed in the duration of both ice phenomena (from 60-120 days to 30-80 days) and ice cover (from 40-100 days to 20-60 days). These trends correspond well with the trend in winter temperatures becoming warmer. However, the transformation of the ice regime on the Vistula River in Toruń has also been affected by the river control, the construction and operation of the Włocławek Dam and (to a lesser degree than at Korzeniewo) icebreaking activities.
Elżbieta Żądzińska, Iwona Rosset, Czesław Domański, Bogusław Pawłowski and Artur Mikulec
Can economic stress affect secondary sex ratio in Poland?
The ratio of male to female births described as the male proportion is expected to be about 1.06. The secondary sex ratio can be influenced by various stresses experienced by parents (e.g., parents' exposure to chemical and physical pollution, natural phenomena, wars and economic crises). The seminal study in this field speculated that fewer goods and services than needed or desired might sufficiently stress human populations to lower the secondary sex ratio. The main purpose of this study is to examine the relationship between economic stress and the fluctuations of sex ratio at birth in Poland. The statistical analysis was based on annual demographic data obtained from year-books issued by the Central Statistical Office on the overall number of male and female live births in Poland in the years 1956-2005 as well as on the annual data of percentage change in total private consumption. In order to verify the hypothesis that the observed time-series of the secondary sex ratio in Poland declines with deterioration in economic conditions, we constructed mathematical models (ARIMA) of both analyzed phenomena following the statistical procedure proposed by Catalano and Bruckner . We found a statistically significant decline of SSR in Poland over the last 50 years. The decrease appeared to be stronger in villages than in towns. However, the consumption rate as related to the strength of economic stress had no effect on the fluctuation of the sex ratio at birth.