Warming Climate Shortens Ice Durations and Alters Freeze and Breakup Patterns in Swedish Water Bodies

• Main Authors: Hallerbäck, Sofia, Huning, Laurie S., Love, Charlotte, Persson, Magnus, Stensen, Katarina, Gustafsson, David, AghaKouchak, Amir
• Format: Text
• Language: English
• Published: 2021
• Subjects: Northern Sweden
• Online Access: https://doi.org/10.5194/tc-2021-304; https://tc.copernicus.org/preprints/tc-2021-304/

Increasing air temperatures reduce the duration of ice cover on lakes and rivers, altering their water quality, ecology, biodiversity, and physical, economical and recreational function. Using a unique in-situ record of freeze and breakup dates, including records dating back to the beginning of the 18th century, we analyze changes in ice duration (i.e., first freeze to last breakup), freeze and breakup patterns across Sweden. Results indicate a significant trend in shorter ice duration (62 %), later freeze (36 %) and earlier breakup (58 %) dates from 1913–2014. In the latter 3 decades, the mean observed ice durations have decreased by about 11 days in northern (above 60N) and 28 days in southern Sweden, whereas the average freeze date occurred about 10 days later and breakup date about 17 days earlier in southern Sweden. The rate of change is roughly twice as large in southern Sweden as in its northern part. Sweden has experienced an increase in occurrence of years with an extremely short ice cover duration (i.e., less than 50 days), which occurred about eight times more often in southern Sweden than previously observed. Our analysis indicates that even a 1 °C increase in air temperatures in southern (northern) Sweden results in a mean decrease of ice duration of 22.5 (7.6) days. Given that warming is expected to continue across Sweden during the 21st century, we expect increasingly significant impacts on ice cover duration and hence, ecology, water quality, transportation, and recreational activities in the region.