# Spatio-Temporal Variability of Water Temperature of Arctic Rivers in Russia over the Past 60 Years
## 3 Results
### Change Point Years in Time Series of River Water Temperature
A fairly short period, during which there were violations of homogeneity in the water temperature series across the Russian Arctic, and a large number of significant changes in medium-sized rivers suggest that these changes may be caused by global factors, most likely climatic changes. Years of significant changes in water temperature series (\"change point years\") generally occur later than change point years in time series of annual runoff and maximum runoff data ([PERSON] and [PERSON], 1961). The lag can reach 10-20 years. Lag times between change point years of water temperature time series and air temperature time series are somewhat smaller, mostly below 10 years. Therefore, the changes in the water flow did not significantly affect \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Region** & **Month** & **May** & **June** & **July** & **August** & **September** & **October** \\ \hline Northeast & 43/60\% & 30/43\% & 33/53\% & 37/53\% & 53/80\% & 60/77\% \\ \hline Lena & 33/84\% & 40/73\% & 51/58\% & 26/41\% & 22/58\% & 25/40\% \\ \hline Yenisei & 54/57\% & 65/84\% & 43/66\% & 27/43\% & 22/46\% & 41/65\% \\ \hline North of the West Siberia & 97/77\% & 90/87\% & 23/2\% & 37/50\% & 37/60\% & 63/73\% \\ \hline North of the European part of Russia & 32/60\% & 34/44\% & 7/40\% & 16/44\% & 52/74\% & 71/78\% \\ \hline Karelia & 58/100\% & 17/33\% & 8/58\% & 67/75\% & 100/100\% & 92/100\% \\ \hline Kola Peninsula & 90/90\% & 80/100\% & 20/50\% & 60/100\% & 90/100\% & 70/90\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Percentage of hydrological gauges in hydrographic regions of the Russian Arctic with detected violations of homogeneity of series of mean monthly water temperature in relation to 1990 (in the numerator) and in relation to the Buishand change point year (in the denominator), at \(\alpha=0.05\). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Region** & **Month** & **May** & **June** & **July** & **August** & **September** & **October** \\ \hline Northeast & 1999 & 1994 & 1992 & 1993 & 1999 & 1997 \\ \hline Lena & 2003 & 1999 & 1995 & 1994 & 2002 & 1999 \\ \hline Yenisei & 1999 & 1999 & 1997 & 2002 & 2003 & 1999 \\ \hline North of the West Siberia & 1998 & 1995 & 1995 & 1999 & 2003 & 2002 \\ \hline North of the European part of Russia & 1997 & 1987 & 1995 & 1998 & 1997 & 1997 \\ \hline Karelia & 2003 & 1993 & 1995 & 2000 & 2000 & 1997 \\ \hline Kola Peninsula & 1992 & 1985 & 1997 & 1996 & 1999 & 1993 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mean change point years (according to the Buishand criterion \(\alpha=0.05\)) of water temperature (1961–2021) during warmer months in hydrographic regions of the Russian Arctic. the changes in water temperature. While changes in air temperature appear to be a more significant factor in causing changes in water temperature. The change point years of water temperature are different for different months. The earliest changes in the year occur in summer, mainly for rivers with relatively high flow rates. Geographically, the earliest changes occur on the Kola Peninsula and in the north of the EPR, followed by rivers in the northeast. The change point years of water temperature series of small, medium, and large rivers are similar. The change point years of the rivers in the Russian Arctic occurred earlier in May, June, September, and October during the transitional hydrological and climatological seasons, mainly before 2000, on the Barents Sea, White Sea, and East Siberian Sea and in the Indigirka, Alazeia, and Ob basins. Later, in July and August, they fell on rivers such as the upper reaches of Kolyma and Anadyr and in the Arctic part of Ob basin. In most cases, the change points fell between 1991 and 2010. The greatest number of violations of the homogeneity of series, regardless of the method of their separation, was detected at all gauging stations in May, June, September, and October.