Oral

IACS

JMCP19 - Biogeochemical interactions across the atmosphere-ice-ocean interface

Unraveling Dimethyl Sulfide Hotspots in Polar Oceans

Dimethyl sulfide (DMS), a key biogenic trace gas, plays a crucial role in atmospheric chemistry and climate regulation through its contribution to cloud condensation nuclei (CCN) formation. Recent observations have revealed unexpectedly high DMS concentrations in Arctic melt ponds and Southern Ocean polynyas, challenging conventional understanding of DMS dynamics in polar environments. This study synthesizes findings from recent field campaigns and observational data to elucidate the processes governing DMS production, distribution, and climate feedbacks in polar regions. Field observations from the Arctic Ocean indicate that melt ponds, once considered minor contributors to atmospheric DMS, can exhibit concentrations up to 33 nM, ten times higher than adjacent open waters (typically <3 nM), driven by microbial activity and organic matter accumulation. In the Southern Ocean, the presence of abundant microzooplankton has been linked to ultrahigh DMS levels of up to 400 nM during seasonal phytoplankton blooms, highlighting complex trophic interactions that influence DMS cycling. Such localized DMS hotspots have the potential to have a significant impact on regional cloud properties by increasing the formation of sulfate aerosols, which, in turn, modulate radiative forcing and feedback mechanisms. Moreover, recent high-frequency underway observations conducted in the Southern Ocean demonstrate that DMS variability is influenced by factors such as sea ice retreat, nutrient availability, and biological productivity. Notably, in regions experiencing rapid ice melt, such as the Amundsen Sea Polynya, high DMS fluxes reaching up to 50.8 mmol m�� d?�� coincide with increased primary productivity, contributing to enhanced air-sea gas exchange and atmospheric processing. In conclusion, DMS hotspots in polar regions represent an important, yet underappreciated, component of the global sulfur cycle. Also, current climate models might underestimate DMS emissions due to limited observational data and complex biogeochemical feedbacks. Continuous monitoring and interdisciplinary research are essential for better capturing the evolving dynamics of DMS production in the rapidly changing Arctic and Antarctic environments. Further efforts integrating field observations, remote sensing, and modeling will be crucial for improving our understanding of their impact on atmospheric processes and future climate scenarios.