Changes in thermal indices on Herschel Island (Qikiqtaruk), Canada between the periods 1899–1905 and 2008–2014

The paper provides a comparison of minimum air temperature (TN), maximum air temperature (TX), mean air temperature (T mean) and a few derived temperature indices for Herschel Island (Qikiqtaruk) in the Yukon Territory, Canada for the periods 1899–1905 and 2008–2014. A significant increase in the TN was noted at +4.2°C, which was a larger increase than that for both T mean (+3.7°C) and TX (+3.5°C). Air temperature increased the most in October, November, and December. In addition, the length of the frost-free season increased by 26 days and the length of the growing season increased by 25 days from the early 20th century to the early 21st century. The increase in the TN also triggered a change in the plant hardiness zone where Herschel Island is located. However, the daily air temperature range declined over the course of the study period as well as the annual total of heating degree days and the number of exceptionally cold days. No statistically significant change in the number of freeze-thaw days was found for the studied periods.