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At the end of its second decade, the Surface Ocean-Lower Atmosphere Study (SOLAS) continues to expand critical collaborations in Earth system research, opening new gateways between the disciplines of oceanic and atmospheric science. The collection of papers in this Special Feature highlights important recent advances in air-sea interaction science, emphasizing emerging priorities and critical challenges. Since the last SOLAS synthesis in 2014, the community has gained a more nuanced understanding of the variety of marine sources of atmospheric aerosols; the influence of chemical speciation on atmospheric deposition and resulting biogeochemical impacts in the ocean; the mechanistic microscale controls of aerosol production and gas exchange at the sea surface; and also how air-sea exchange processes are influencing and responding to climate change, among numerous other advances. At the same time, SOLAS scientists have engaged more directly with socio-economic networks and in the development and evaluation of environmental and policy decisions. In addition to substantial contributions to improved understanding of the global cycling of greenhouse gases, SOLAS scientists are examining the impacts of new shipping regulations and contributing to development of frameworks for climate intervention research and governance. However, challenges remain, including characterizing the variability in air-sea gas exchange, particularly in coastal regions, and identifying mechanisms by which marine emissions influence cloud dynamics and thereby coupled marine and atmospheric feedbacks to climate change. Addressing these and other challenges requires development of innovative scientific tools (e.g., chemical sensors, expanded and integrated observational networks, machine learning algorithms), and also new inter- and trans-disciplinary collaborations, to ensure that air-sea exchange research continues to transcend boundaries in tackling current and emerging global challenges. 

Abstract This study investigates the biogeochemical drivers of aragonite saturation state (Ω_Ar) in Baffin Bay, with a focus on the relatively undersampled west Greenland shelf. Our findings reveal two main depth‐dependant processes controlling the spatial distribution of Ω_Arin Baffin Bay; within the upper 200 m, lower Ω_Arcoincides with increasing fractions of Arctic‐outflow waters, while below 200 m organic matter respiration decreases Ω_Ar. A temporal analysis comparing historical measurements from 1997 and 2004 with our 2019 data set reveals a significant decrease in the Ω_Arof Arctic‐outflow waters, coinciding with reduced total alkalinity (TA). However, no discernible anthropogenic ocean acidification signal is identified. Significant Arctic water fractions (20%–40%) are found to be present on the west Greenland shelf, associated with reduced TA and Ω_Ar. A numerical modeling simulation incorporating a passive tracer demonstrates that periodic changes in wind direction lead to a switch from onshore to offshore Ekman transport along the Baffin Island current, transporting Arctic waters toward the west Greenland shelf. This challenges the conventional understanding of Baffin Bay's circulation and underscores the need for further research on the region's physical oceanography. Based on salinity‐TA relationships, surface waters on the west Greenland shelf have a significantly lower meteoric TA end‐member compared to waters of the Baffin Island Current in western Baffin Bay. The low eastern TA freshwater end‐member agrees well with recent glacial meltwater TA measurements, suggesting that glacial meltwater is the main freshwater source to surface waters on the west Greenland shelf.