A 20-year perspective of dissolved organic matter distribution in the Arctic Ocean

About This Grant

The Arctic atmosphere has been warming 3-4 times faster than the rest of the planet and receives large amounts of river freshwater from the watersheds surrounding the Arctic Ocean. This study is mapping the distribution of freshwater and its organic matter content in the Arctic Ocean with unprecedented spatial detail. In addition, the new data set is being compared to historical data collected by the researchers in 2005 and 2015 to create a 20-year perspective for these observations. Combining the information on organic matter composition and distribution with other parameters like salinity, temperature, and the isotopic composition of water molecules is allowing the investigators to identify sources and distribution of freshwater in the Arctic Ocean and advance understanding of freshwater sources (rivers, ice melt, precipitation) and their variability. The organic matter entering the Arctic from surrounding continents can be used as a tracer for the formation of the halocline, a water layer in the Arctic Ocean that isolates the sea ice on the surface from the much warmer subsurface Atlantic layer. Understanding the stability of the Arctic halocline is essential to predict future changes to sea ice cover and regional climate in the Arctic. This project is training undergraduate and graduate students and exposing them to international and multidisciplinary research through participation in expeditions and data workshops with collaborators. Undergraduate students are writing newspaper columns in the local newspapers and team members are presenting the research to the public during parent weekend events at the College of Marine Sciences and Maritime Studies at Texas A&M University. The Arctic receives a high volume of river discharge and large amounts terrigenous dissolved organic matter (DOM). Data from the last 20 years have demonstrated the important roles of river input and sea ice processes in the distribution of DOM, the formation of the halocline, and freshwater dynamics in the Arctic Ocean system. At the same time, analyses of existing data on DOM and water isotopes have led to inconsistent conclusions. This study aims to resolve these inconsistencies by analyzing optical properties and lignin phenols at high spatial resolution. Data are being analyzed from several icebreaker expeditions, including one on the German research icebreaker Polarstern (completed in Fall 2024) and others on the US Coast Guard Cutter Healy (2025 and 2026). In combination with hydrographic, water isotope, and nutrient data collected by collaborators, new information about the distribution and molecular composition of terrigenous biomarker lignin phenols will: 1). advance understanding of the circulation of surface waters, halocline formation, and fluxes, origin, and distribution of freshwater and carbon; and 2). create of a 20-year perspective of changes in Arctic Ocean biogeochemistry, surface circulation, and halocline variability during a time of rapid warming in the Arctic region, providing the modeling community with data to validate numerical simulations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.