Trend analysis of temperature, precipitation, and stream flow in the National Petroleum Reserve Alaska

Abstract

Seven hydro-meteorological stations in the National Petroleum Reserve Alaska were analyzed to look at precipitation, discharge, and temperature trends. These hydro-meteorological stations included: Fish Creek, Judy Creek, Ikpikpuk, Ublutuoch, Seabee, Prince, and Otuk. A linear regression was performed on a year-by-year basis to fill in data gaps in the temperature time series, for all six stations with temperature data. The Seasonal Mann-Kendall test and a Modified Seasonal Mann-Kendall test were performed to determine if a trend appeared present in the time series and, if so, how significant the trend was. The Sen's slope analysis was then utilized to determine the magnitude of the trend, if a trend was observed in both analyses. The temperature trends showed an increasing trend in the temperature data for four stations: Judy Creek, Ublutuoch, Fish Creek, and Ikpikpuk. No trend was shown in the remaining station, Otuk station. One station, Prince, was removed from analysis due to a high percentage of missing data. The Modified Seasonal Mann-Kendall tests showed a trend in four of the five stations, and a slight positive trend in one of the five stations. The precipitation data showed 'no trend' in the Seasonal Mann-Kendall analysis. The Modified Seasonal Mann-Kendall test showed a slight trend (Fish Creek), a moderate trend (Otuk), and no trend (Ikpikpuk) for the precipitation data. Using the seasonal Mann-Kendall analysis the discharge data showed no trend in five out of seven stations and two trends (Fish Creek and Seabee). The Modified Seasonal-Mann-Kendall analysis showed and a significant trend twice (Fish Creek and Seabee), a moderate trend three times (Ikpikpuk, Prince, Otuk), a slight trend once (Ublutuoch), and no trend one time (Judy Creek) in the discharge data.