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Oulun yliopiston väitöskirjat

PAST, PRESENT, AND FUTURE OF RIVER FLOW REGIME IN NORDIC REGION FOCUSING ON RIVER ICE BREAK-UP EVENTS ACTA UNIVERSITATIS OULUENSIS C Technica 907

ISBN-13:	978-952-62-3871-5
Kieli:	englanti
Kustantaja:	Oulun yliopisto
Painosvuosi:	2023
Sidosasu:	pehmeäkantinen
Tekijät:	Abolfazl Jalali Shahrood

25.00 €

This thesis aims to enhance the current body of research on arctic flow regimes by conducting a thorough analysis of the long-term fluctuations in cold hydrologic extremes. The study will specifically concentrate on examining the inter-annual variability in low and high flows, ice processes, and overall river dynamics, including morphological parameters. It provides new perspectives on changes in river hydrology, specifically snow-melt patterns and their relationship to streamflow hydrology and aims to assess the long-term effects of extreme flow events, including both high and low flows, across different seasons. Furthermore, the research has yielded valuable insights pertaining to the determination of ice break-up dates by means of analyzing hydrographs. This contribution enhances our comprehension of river ice dynamics and its impact on climate change. One of the goals of the RiTiCE was to identify the break-up date (BUD) of ice by analyzing daily hydrographs. Moreover, the study has developed indices with the intention of analyzing the exceptional values, patterns, and changes in flow attributes over a period. The examination of BUD and Temperature Transition Point (TTP) at each station yields insights into the interplay between temperature dynamics and river ice behavior. The timing offset that has been observed serves to emphasize the connection between these variables and emphasizes the necessity for additional research into this captivating interaction. The investigation has revealed a notable degree of consistency in trends observed across various indices, indicating that modifications in river flow patterns can be used as reliable indicators of shifts in climate patterns. In contrast to the prevailing consensus, it is uncommon for floods and droughts to occur simultaneously in the majority of rivers, suggesting a lack of uniformity in the modification of extreme hydrological events. The results validate the substantial influence of climate change and global warming on Arctic hydrology, specifically in relation to the decreasing trends observed in annual maximum flow. Keywords: arctic rivers, break-up, cold climate, hydrology, ice processes, remote sensing, river ice jam

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