Abstract
The purpose of this study is to find connections between the North Atlantic Thermohaline Circulation (NA THC), climate elements, such as cloud cover, precipitation, air temperature, sunshine duration, and relative humidity, and flow of rivers in Poland. The intensity of NA THC was characterized by the DG3L index, which was established to assess changes in the amount of heat transported by NA THC along with the transport of water to the Arctic. The paper explains and discusses the mechanism of impact of the NA THC changeability on the elements of the catchment water balance variability. The positive and negative phases of the DG3L index are strongly correlated with the heat anomalies in the upper layer of the North Atlantic waters. The obtained results show that changes of NA THC have significant impact on weather conditions and selected climate elements in Poland. Statistically significant positive correlations were found between the DG3L index and average annual air temperatures, particularly in April, July, and August, while negative between the DG3L index and the total cloud cover. Consequently, in the years with the positive values of the DG3L index, there are favorable conditions for the strong increase in evaporation and evapotranspiration from the ground surface. This has impact on flow of rivers in Poland, which shows considerable regional differences.
Highlights
Understanding of contemporary changes in climatic conditions and their hydrological consequences is one of the key issues in hydrological and climatological studies
The aim of this paper is to present results of research on determining relationships between the variability of the North Atlantic Thermohaline Circulation (NA THC) intensity and changes of the river flow in Poland, as well as of climatic mechanisms, which allow the impact of NA THC changes to be transferred to the water balance in river catchments
In a given year the impact of the change in the DG3L index on weather conditions extends over the two to three years. The reason for this can be explained by the structure of the index, which takes into account that the THC signal from a given year spreads slowly, and in the North Atlantic waters (50–60◦ N) it appears as still relatively strong only after one year, while in the Arctic waters
Summary
Understanding of contemporary changes in climatic conditions and their hydrological consequences is one of the key issues in hydrological and climatological studies. Research on the impact of climate fluctuations and climate changes on hydrological processes is usually carried out by detecting trends in hydrological and climatological variables, mainly precipitation and air temperature, followed by analysis of their correlations with river flows. Such an analysis can be the starting point for determining the causes of the increase in hydrological anomalies observed in recent years, which in Poland are reflected in extremely low river flows [1,2,3,4]. Labat et al [9]
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