Terrestrial inputs of nutrients and dissolved organic carbon to the Arctic Ocean and their influence on primary production.

The Arctic region, warming at approximately four times the global average, is experiencing rapid climatic shifts that could result in a summer ice-free Arctic Ocean by mid-century. This review compiles recent studies on Arctic biogeochemistry, highlighting the significant role of continental runoff-including rivers, permafrost, and glaciers-in nutrient cycling, carbon dynamics, and pelagic primary production. Particularly in the East Siberian Shelf, terrestrial inputs substantially contribute to the export of dissolved organic carbon (DOC) and nutrients, thus impacting regional ecosystems and primary productivity. Subsea permafrost emerges as a key DOC exporter, with estimated fluxes reaching 700 to 1000 Tg yr under extreme scenarios. In the Arctic's low-light environment, photodegradation plays a vital role in transforming terrestrial dissolved organic matter (DOM) into nutrients. Notably, phytoplankton levels in the Arctic Ocean have surged by about 30 % since the 1990s. Projections indicate that by this century's end, the Arctic Net Primary Productivity (NPP) could approach 700 Tg C yr, with a more significant increase in the Eurasian Arctic than in the American and Barents Sea regions. This trend is mainly due to terrestrial inputs and permafrost thawing effects. Research in the Arctic, particularly on biogeochemistry and phytoplankton dynamics in response to climate change, faces challenges from extreme weather, data scarcity, and complex environmental processes. Therefore, continuous monitoring and targeted research, especially in the East Siberian Shelf and subsea permafrost regions, are crucial for overcoming these challenges and improving our understanding of the changing Arctic Ocean ecosystem.