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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. 

Abstract The hundreds of tidewater glaciers found in the Canadian Arctic Archipelago have the potential to enhance delivery of nutrients and other material to the surface ocean. Despite this, their influence on marine ecosystems, specifically phytoplankton, is poorly characterized. Here we developed and applied a quantitative mass spectrometry‐based approach to measure phytoplankton ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) concentrations to examine differences in productivity in glacierized and non‐glacierized marine systems in Jones Sound, Nunavut, within Inuit Nunangat. Comparisons to chloroplast 16S rRNA gene amplicon sequencing data suggested that these measurements detect the majority of Rubisco produced in Jones Sound. Because Rubisco catalyzes carbon fixation, we used these measurements to estimate total and group‐specific primary production potential, which were within the range of historical primary production measurements made using classical methods in this region. Our measurements also revealed that up to 2% of total protein in the water column is Rubisco, and that Rubisco concentrations are correlated with chlorophyll fluorescence, with maxima near the nitracline. Rubisco produced by diatom generaChaetocerosandThalassiosirawere higher in marine regions influenced by glaciers, while Rubisco fromMicromonas(Chlorophyta) was greater in non‐glacierized regions. This suggests that future climate scenarios may favor smaller phytoplankton groups, likeMicromonas, with consequences for food webs and carbon cycling. This study broadens our understanding of how tidewater glaciers will impact phytoplankton communities, now and in a warmer future, and lays the foundation for using this mass spectrometry‐based approach to quantify phytoplankton group‐specific carbon fixation potential in other marine regions. 

Abstract. Marine diazotrophs convert dinitrogen (N2) gas intobioavailable nitrogen (N), supporting life in the global ocean. In 2012, thefirst version of the global oceanic diazotroph database (version 1) waspublished. Here, we present an updated version of the database (version 2),significantly increasing the number of in situ diazotrophic measurements from13 565 to 55 286. Data points for N2 fixation rates, diazotrophic cellabundance, and nifH gene copy abundance have increased by 184 %, 86 %, and809 %, respectively. Version 2 includes two new data sheets for the nifH genecopy abundance of non-cyanobacterial diazotrophs and cell-specific N2fixation rates. The measurements of N2 fixation rates approximatelyfollow a log-normal distribution in both version 1 and version 2. However,version 2 considerably extends both the left and right tails of thedistribution. Consequently, when estimating global oceanic N2 fixationrates using the geometric means of different ocean basins, version 1 andversion 2 yield similar rates (43–57 versus 45–63 Tg N yr−1; rangesbased on one geometric standard error). In contrast, when using arithmeticmeans, version 2 suggests a significantly higher rate of 223±30 Tg N yr−1 (mean ± standard error; same hereafter) compared to version 1(74±7 Tg N yr−1). Specifically, substantial rate increases areestimated for the South Pacific Ocean (88±23 versus 20±2 Tg N yr−1), primarily driven by measurements in the southwestern subtropics,and for the North Atlantic Ocean (40±9 versus 10±2 Tg N yr−1). Moreover, version 2 estimates the N2 fixation rate in theIndian Ocean to be 35±14 Tg N yr−1, which could not be estimatedusing version 1 due to limited data availability. Furthermore, a comparisonof N2 fixation rates obtained through different measurement methods atthe same months, locations, and depths reveals that the conventional15N2 bubble method yields lower rates in 69 % cases compared tothe new 15N2 dissolution method. This updated version of thedatabase can facilitate future studies in marine ecology andbiogeochemistry. The database is stored at the Figshare repository(https://doi.org/10.6084/m9.figshare.21677687; Shao etal., 2022).