Arctic coastal landscapes, like those in northernmost Alaska, are often characterized by saline permafrost which is prone to thawing. We studied six sediment cores to understand how thawing and salinity affect organic matter breakdown and landscape change. Our results show that salinity accelerates organic matter degradation when permafrost thaws. This highlights the overlooked risk of salinity in shaping Arctic landscapes and carbon mineralization as the climate continues to warm.

In a mesocosm study, the investigation of colored and fluorescent dissolved organic matter provided information on its transformation, enrichment, and exchange processes within the sea-surface microlayer and the underlying water. Photodegradation was suggested as the main sink, exceeding microbial alteration, and indicating that light and biological processes, such as the induced phytoplankton bloom, jointly shaped organic matter composition under strong vertical mixing.