Increasing Importance of Local Hydroclimatology During the Tundra Growing Season in the Yukon–Kuskokwim Delta.

Changing precipitation patterns in the Arctic is a key indicator of climate change, in addition to increasing land and ocean temperatures, but these patterns are not uniform across the circumpolar region. This regional analysis focuses on the Yukon–Kuskokwim Delta in southwestern Alaska and addresses the following questions: (1) What is the baseline hydroclimatology during the growing season on the Yukon–Kuskokwim Delta? (2) What are the seasonal and intraseasonal trends of the hydroclimate variables in the YKD? (3) What are the implications of documented trends for the study region? Utilizing ECMWF's ERA5 reanalysis dataset, we conducted a seasonal analysis for May through September for the years 1982–2022. While no strong trend emerged for total precipitation over the 41-year study period, differing trends were observed for large-scale and convective precipitation. The decline in large-scale precipitation is supported by a decrease in storm counts in the Bering Sea, as well as declining vertically integrated moisture convergence and moisture flux. By contrast, the increase in convective precipitation underscores the growing importance of the local hydrologic cycle, further supported by a significant rise in evaporation. These enhanced local hydroclimatological cycles have significant implications for wildfires and subsistence activities. [ABSTRACT FROM AUTHOR]