Do atmospheric circulation patterns explain variability and trends in the seasonality of Oulu-Hailuoto ice road in Northern Finland?
Kiani, Sepideh; Irannezhad, Masoud; Ronkanen, Anna-Kaisa; Ahmadi, Behzad; Moradkhani, Hamid; Klöve, Björn
Kiani, Sepideh; Irannezhad, Masoud; Ronkanen, Anna-Kaisa; Ahmadi, Behzad; Moradkhani, Hamid; Klöve, Björn (2016), Do atmospheric circulation patterns explain variability and trends in the seasonality of Oulu-Hailuoto ice road in Northern Finland?, Abstract C43B-0760 presented at 2016 Fall Meeting, AGU, San Francisco, Calif., 11-15 Dec.
In cold climate regions, ice roads are engineered as temporary winter transportation routes on the frozen seas, lakes and rivers. The ice road season parameters (start, end and length) are principally dependent on the thickness of ice, which is naturally controlled by temperature in terms of freezing (FDDs) and thawing (TDDs) degree-days. It has been shown that the variations in FDDs and TDDs are influenced by large-scale atmospheric circulation patterns (ACPs). Therefore, this study aims at understanding the role of ACPs in variability and trends in the seasonality of Oulu–Hailuoto ice road in northern Finland during 1974–2009. The Mann-Kendall nonparametric trend test determined significant shortening in the length of ice road season over the study period of 1974–2009, which can be attributed to later start and earlier end days. In the study area, the maximum ice thickness of the Baltic Sea also showed significant declines over time. Such sea ice thinning can be associated with the wintertime temperature warming manifested by the decreasing trend found in the cumulative FDD during October-January in the water year (September–August). The increased cumulative TDD during February-April also reflects warmer climate in spring, which has resulted in the earlier end day of the ice road season. Measuring the Spearman’s rank correlation identified the Arctic Oscillation as the most significant ACP influencing variations in the cumulative FDD, and accordingly in the ice thickness and the start day. However, the cumulative TDD during February–April shows significant positive correlation with the East Atlantic (EA) pattern, which appears to control the end day of the Oulu–Hailuoto ice road season.
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