Distinct Distribution Patterns of Dissolved and Particulate Trace Metals in Surface Waters of the Amundsen Sea: From Polynya to Open Waters

Abstract Trace metals regulate Southern Ocean productivity, but their cycling across Antarctic marginal‐sea gradients remains poorly constrained. We measured dissolved, labile particulate, and refractory particulate Mn, Fe, Ni, Cu, Zn, Cd, and Pb across the Amundsen Sea Polynya (ASP), sea‐ice zone (SIZ), and Oceanic Area (OA), alongside iron‐addition incubations. Total Fe, Cu, Zn, and Pb were enriched in the ASP, consistent with vertical and shelf‐derived inputs, whereas the SIZ showed selective Fe enrichment. Phase partitioning was region‐ and element‐specific: Fe and Cu were associated with lithogenic inputs and scavenging, Ni and Cd tracked biological assimilation, and Mn and Zn shifted toward biological association offshore. Dissolved Pb removal was associated with biogenic particles. After 5 days, Fe‐amended chlorophyll‐ a changed little in the ASP but increased in the OA (1.54 ± 0.36‐fold) and variably in the SIZ (2.16 ± 1.96‐fold). Changing shelf and sea‐ice conditions may therefore reshape metal supply, partitioning, and bioavailability.