Data and Code for "Seasonal River Mouth Processes in a Warming Arctic"

The Arctic is warming more than four times the global average, causing rapid change that is threatening the stability of Arctic environments. River mouth zones are especially vulnerable, as these dynamic land–ocean interfaces integrate riverine and oceanic seasonal processes that regulate primary productivity. Spring sea ice melt and summer sediment plume development at river mouths are two seasonal processes that are directly influenced by freshwater, heat, and sediment export from Arctic rivers, yet they remain under-observed. Arctic river discharge directly interacts with coastal sea ice during melting and forms turbid sediment plumes during the open-water season. This study examines six major Arctic river mouths—the Yukon (US), Colville (US), Mackenzie (CA), Ob-Yenisei (RU), Kolyma (RU), and Lena (RU)— to understand the spatial and temporal variability of these processes over sub-seasonal to decadal timescales. I aim to (1) characterize the typical seasonal patterns of coastal sea ice melt and turbid sediment plume dynamics, (2) assess temporal changes over two decades, and (3) compare behaviors across different river systems. I analyzed sea ice and sediment plume behavior using MODIS-derived sea ice data products and MODIS imagery, respectively. Results show that river mouths follow two primary regimes of ice melt, either initiating directly at the shoreline and progressing seaward or initiating at offshore flaw leads and progressing both landward and seaward. As spring temperatures increase and watersheds thaw, bringing sediment to the rivers, turbid plumes develop at the coast. Turbidity typically peaks in early summer with occasional late-season peaks likely driven by storm-related resuspension. Eurasian river mouths show significant trends in sea ice melt over time, with a shortening melt season at the Lena and Ob-Yenisei, and an earlier shift in coastal ice melt at the Kolyma. Across systems, trends indicate earlier riverine sediment delivery to the coast, with significantly earlier plume onset at the Lena, Kolyma, and Mackenzie. The Ob-Yenisei is seeing an increase in sediment plume area. Overall, Arctic river mouth processes are responding to rapid warming, yet the magnitude and timing of these changes vary substantially among river systems, reflecting strong local controls.