Glacial Meltwater Promotes Biological Productivity and Subsequent Dissolved Organic Carbon Accumulation in the Eastern Ross Sea: Evidence From the Austral Summer of 2023

Abstract The Ross Sea, a critical region for global carbon cycling, receives increasing glacial meltwater from West Antarctica, yet the impact on regional carbon cycling remains poorly understood. A key uncertainty is how this meltwater influences dissolved organic matter (DOM), particularly in the historically inaccessible eastern Ross Sea. This study provides the first comprehensive analysis of meltwater‐driven DOM dynamics during exceptional 2023 low sea ice conditions. By analyzing dissolved organic carbon (DOC) concentrations, DOM optical properties, and biogeochemical parameters across 42 stations, we examined associations between glacial meltwater, DOM, and regional carbon cycling. DOC concentrations varied regionally, with the eastern Ross Sea exhibiting significantly higher levels (75 ± 20 μM C) than the central (65 ± 16 μM C) and western regions (52 ± 10 μM C). In the eastern Ross Sea, high meltwater fractions were associated with elevated iron (Fe) concentrations (0.54 ± 0.18 nM) and enhanced biological production, evidenced by nutrient depletion and elevated particulate organic carbon, which subsequently promoted DOC accumulation. Modified Circumpolar Deep Water (mCDW) intrusion through the Hayes Bank creates a hydrographic boundary confining DOC‐rich waters. Accumulated DOM undergoes microbial processing, as indicated by optical properties showing low‐molecular‐weight characteristics and biological breakdown. These processes contribute to the deep water microbial loop and suggest that accelerating West Antarctic ice loss may alter Southern Ocean carbon sequestration by creating regional carbon hotspots that enhance the biological carbon pump. The 2023 observations provide critical insights into how glacial meltwater inputs during low sea ice conditions could influence regional carbon cycling patterns.