Shahrood et al. (2026) Asymmetric shifts in seasonal transition timing in a sub-Arctic river system under climate warming

Identification

• Journal: ˜The œcryosphere
• Year: 2026
• Date: 2026-08-25
• Authors: Abolfazl Jalali Shahrood, Amirhossein Ahrari, Ali Torabi Haghighi
• DOI: 10.5194/tc-20-4701-2026

Research Groups

• Water, Energy and Environmental Engineering Research Unit, University of Oulu
• Finnish Meteorological Institute
• Finnish Environment Institute

Short Summary

This study analyzes a 59-year daily record from the River Oulankajoki in northeastern Finland to characterize proxy-based seasonal transitions in discharge, snow depth, and air temperature. The analysis reveals earlier shifts in springtime events across snow, discharge, and temperature timings.

Objective

• Investigate how Phase Change Timings (PCTs) shift over a 59-year record from the River Oulankajoki.
• Examine changes in derived Intra-Variable Intervals (IVIs) and Cross-Variable Intervals (CVIs).
• Determine the temporal coupling between thermally-derived PCTs and their surface response.

Study Configuration

• Spatial Scale: Regional, focusing on the River Oulankajoki basin in northeastern Finland.
• Temporal Scale: 59-year record from October 1966 to September 2025.

Methodology and Data

• Models used: RiTiCE (River Ice Timing Characteristics and Extremes) framework.
• Data sources: Daily air temperature, snow depth, and river discharge measurements from the Finnish Meteorological Institute and Finnish Environment Institute.

Main Results

• The six PCTs shifted over the 59-year record, with all three onset-group PCTs shifting to later days of the water year and all three release-group PCTs shifting to earlier days.
• Decadal-binned distributions showed that CCT and CWT had the most consistent directional progression across successive decades.

Contributions

• This study provides a comprehensive analysis of proxy-based seasonal transitions in discharge, snow depth, and air temperature over a 59-year record from the River Oulankajoki.
• The findings contribute to our understanding of the impacts of climate change on Arctic river systems.

Funding

• Not specified.

Citation

@article{Shahrood2026Asymmetric,
  author = {Shahrood, Abolfazl Jalali and Ahrari, Amirhossein and Haghighi, Ali Torabi},
  title = {Asymmetric shifts in seasonal transition timing in a sub-Arctic river system under climate warming},
  journal = {˜The œcryosphere},
  year = {2026},
  doi = {10.5194/tc-20-4701-2026},
  url = {https://doi.org/10.5194/tc-20-4701-2026}
}