Unraveling the Biogeochemical Drivers of Aragonite Saturation State in Baffin Bay: Insights From the West Greenland Continental Shelf

This study investigates the biogeochemical drivers of aragonite saturation state (ΩAr) 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 ΩAr in Baffin Bay; within the upper 200 m, lower ΩAr coincides with increasing fractions of Arctic‐outflow waters, while below 200 m organic matter respiration decreases ΩAr. A temporal analysis comparing historical measurements from 1997 and 2004 with our 2019 data set reveals a significant decrease in the ΩAr of 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 ΩAr. 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. Plain Language Summary Baffin Bay, with its complex interplay of Atlantic and Arctic water masses, is particularly susceptible to ongoing ocean acidification, mainly due to the presence of relatively fresh and low‐alkalinity Arctic waters. To date measurements of the inorganic carbon system in Baffin Bay have primarily been captured at key entrance and exit gateways, and on the Canadian side of the bay, leaving the west Greenland shelf relatively undersampled. This study provides a bay‐wide perspective of the main factors influencing aragonite saturation state (ΩAr; an indicator of ocean acidification impacts on marine calcifying organisms) across Baffin Bay, including the west Greenland shelf. We found that within the upper 200 m, low ΩAr coincides with increased presence of Arctic water