Reassessing Methanesulfonic Acid as a Sea Ice Proxy: An Example From the Weddell Sea Sector

Abstract Antarctic sea ice has declined since 2015, but placing this trend in a longer‐term context remains challenging. Ice core methanesulfonic acid (MSA) offers a potential record of sea ice variability beyond the instrumental period, yet its applicability in sectors including the Weddell Sea remains unclear. We present an MSA record from the Gomez ice core on the southwest Antarctic Peninsula and combine air mass back‐trajectories and satellite observations to reassess the MSA‐sea ice relationship. Trajectory and spatial correlation analyses identify the central Weddell Sea as the dominant MSA source. We show that traditional correlations with northernmost sea ice extent are misleading in this region due to spatially complex seasonal ice dynamics; instead, the timing of autumn–winter ice advance and consolidation influences MSA formation during the following spring–summer. These findings highlight both the complexity of the MSA‐sea ice relationship and its potential for reconstructing seasonal sea ice variability.