1943-2023 annual freezing and thawing indices based on mean daily air temperatures from Kotzebue, Alaska and nearby 2012-2019 Mt NOAK remote automated weather station.

Daily mean air temperature values in "Kotzebue_DailyAirT.csv" were used to calculate thermal indices in "Freezing_Thawing_Thermal_Indices.csv" for 1943-2023.Located on the Chukchi Sea, the weather station (Wx) in Kotzebue, AK, Station No. 2616: 66.8857, -162.6068, 3 m above sea level (asl) has the longest running air temperature record in northwest Alaska, useful for its length and because it captures climate dynamics associated with the Chukchi Sea that affect the Brooks Range environment[58]. We downloaded the 1897-2023 Kotzebue daily record of instrumental temperatures from the National Atmospheric and Oceanographic Administration’s (NOAA) National Centers for Environmental Information (NCEI) (https://www.ncei.noaa.gov/) and calculated the mean daily air temperature as T = (max daily temperature + min daily temperature)/2.Note that mean daily air temperature from 1 May to 9 Sep 2019 was estimated using multiple regression (month as fixed factor) based on "Mt Noak DailyT 2012_2018.csv" air temperature as recorded at a nearby remote automated weather station (Mt. Noak RAWS, 33 km NNW of Kotzebue 67.1413, -162.994, 255 m asl). The regression was then applied to values from "MtNoakRAWS_2019.csv".Other details are in the "ReadMe.txt" file.