In one recent study, Sullivan and colleagues investgated the remote Salmon River watershed in northwest Alaska - a region known for its pristine wilderness - and assessed how thawing permafrost is exposing sulfide minerals to weathering and thereby releasing metals (iron, aluminum, cadium, nickel, copper, zinc) into aquatic ecosystems. They found that most tributaries and the mainstem of the Salmon had metal concentrations exceeding U.S. EPA chronic exposure thresholds for aquatic organisms, and that many of the once “gin-clear” streams are now running orange and turbid. The degradation is not only aesthetic but has important ecological implications, as the research team found declines in macroinvertebrate abundance and degraded fish habitat quality in the affected waters.

In another recent study, Dr. Sullivan and his collaborators combined extensive wilderness field sampling, tree-ring analysis, and synthesis of 82 previous circumpolar studies to reveal that retreating Arctic sea ice is fueling enhanced growth of the world's northernmost trees and their advance into Arctic tundra. They found that open water from retreating sea ice correlates more strongly with increased tree growth and recruitment than air temperature alone - likely via indirect effects like warmer winter temperatures, deeper snowpacks, and greater nutrient availability from warmer winter soils. Spatially, treelines closer to regions of rapid sea ice loss were more likely to have advanced into the tundra than those where sea ice extent has been more resistant to change. 

Dr. Sullivan is dedicated to mentoring the next generation of ecologists and environmental scientists. He actively involves graduate students in every stage of research - from field sampling and instrument deployment to data analysis and publication. He cultivates hands-on learning and scientific curiosity, preparing students for careers in environmental science, resources management, and climate research. Dr. Sullivan's leadership at ENRI continues to expand the institute's capacity for interdisciplinary collaboration, advancing understanding of Alaska's environment in a time of unprecedented change. 

This project was designed to address persistent health equity gaps in Alaska by co-developing practical tools with and for communities most affected by wildfire smoke and intersecting climate hazards. These populations include Alaska Native communities, older adults, people living in remote areas without road access, and those experiencing chronic health conditions. Through a unique partnership between UAA, UAF, University of Washington, Alaska Native communities, Alaska Native Tribal Health Consortium, Alaska Fire Sciece Consortium, Alaska Department of Health, and Anchorage Health Department, this project developed essential decision-support tools to help Alaska communities access real-time air quality data, short-term smoke forecasts, long-term flammability projections, and health and demographic information. These tools help Alaskans make informed choices to safely recreate, hunt, fish, and work during wildfire events. Additionally, the long-term planning tools help communities advocate for funding and decide what kind of infrastructure or programs they need to protect health and welfare in future wildfire seasons. The project supports health equity by making relevant climate and health data accessible and actionable for these populations, enabling locally driven adaptation and response.

Two publicly available tools were enhanced through this work:

• Alaska Wildfire Explorer - Now includes real-time and forcast air quality data to help users better understand smoke impacts. 
• Northern Climate Reports - Updated to include health and demographic information to support community-specific adaptation planning. Learn more and access the comic book user guides for the tools here (coming in June).

This initiative addresses critical data gaps and highlights locally relevant solutions to protect vulnerable populations across Alaska. Learn more in Dr. Hahn's project abstract on the EPA's website.