Tropical river discharge dominates riverine carbon export to Australia's coastal waters

Abstract Rivers play a crucial role in the transformation and export of carbon (C) to coastal waters, yet limited observations in Australia have hindered accurate C flux estimates. We compiled 27,696 dissolved inorganic C (DIC), 15,012 dissolved organic C (DOC), and 226 particulate organic C (POC) measurements in Australian rivers and combined these with modeled discharge to estimate Australian‐scale C export. Annual riverine C export was 19.1 (6.1–47.9) × 10 3 Gg C yr −1 , with DIC and DOC exports 2.9 and 2.7 times higher than previous estimates, while POC was 2.6 times lower. The Australian tropics contributed 65%, 39%, and 66% of national DIC, DOC, and POC exports, respectively, despite covering only 11% of exorheic Australia. Within tropical basins, wet‐season C export was 158–423 times higher than dry‐season C export. These findings underscore the dominant influence of tropical rivers and their strong seasonal pulse on Australia's riverine C export.