Skip to main content

Changes

View changes from to

On October 22, 2024, 1:48:16 PM UTC, Gravatar ckan_admin:

  • Updated description of Fe-binding ligands in Fram Strait and over the Northeast Greenland shelf - cruise PS100 from

    Here we investigate the potential sources, distribution, properties and transport of natural Fe-binding ligands in Fram Strait and over the Northeast Greenland shelf. Our results indicate that the main sources of organic ligands to surface waters of Fram Strait were Fe-binding ligands associated with primary productivity together with ligands from the Arctic Ocean. We calculated a total Fe-binding ligand concentration, [Lt], in Polar Surface Water from the western Fram Strait of 1.65??0.4 nM eq. Fe. This value is intermediate compared to the reported values for the Arctic and the North Atlantic Ocean, confirming the suggestion of a previous study that [Lt] decreases southward from the Arctic Ocean. The differences between ligand sources in different biogeochemical provinces, result in distinctive ligand properties and distributions that are reflected in [Lt], the binding strength (log K_(FeL,Fe')^cond) and the reactivity (log ??_FeL) of the ligands. Higher [Lt] was present near the Nioghalvfjerdsfjorden (79N) glacier terminus and in the Westwind Trough (median of [Lt]=2.17 nM eq. Fe; log K_(FeL,Fe')^cond=12.3; log ??_FeL =3.4) than in the Norske Trough (median of [Lt]=1.89 nM eq. Fe; log K_(FeL,Fe')^cond=12.8; log ??_FeL =3.8) and in Fram Strait (median of [Lt]=1.38 nM eq. Fe; log K_(FeL,Fe')^cond=13; log ??_FeL =3.9), but they were weaker and therefore less reactive. Our findings reveal the fundamental mechanism on how organic Fe-binding ligands determined dissolved-Fe (DFe) transport from the 79N glacier to Fram Strait. The lower ligand binding strength result in a higher inorganic Fe concentration, [Fe`], which is more prone to precipitation and/or scavenging than Fe complexed with ligands. Accordingly, a portion of the glacial DFe will not be transported over the shelf into the ocean, indicating that organic ligands are an important factor regulating DFe export. The ongoing changes in the Arctic and subarctic will influence the sources of Fe binding ligands and therefore have consequences for Fe solubility.
    to
    There is a paucity of data on Fe-binding ligands in the Arctic Ocean. Here we investigate the distribution and chemical properties of natural Fe-binding ligands in Fram Strait and over the northeast Greenland shelf, shedding light on their potential sources and transport. Our results indicate that the main sources of organic ligands to surface waters of Fram Strait included primary productivity and supply from the Arctic Ocean. We calculated the mean total Fe-binding ligand concentration, [Lt], in Polar Surface Water from the western Fram Strait to be 1.65 ± 0.4 nM eq. Fe. This value is in between reported values for the Arctic and North Atlantic Oceans, confirming reports of north to south decreases in [Lt] from the Arctic Ocean. The differences between ligand sources in different biogeochemical provinces, resulted in distinctive ligand properties and distributions that are reflected in [Lt], binding strength (log K′) and competing strength (log α) of ligands. Higher [Lt] was present near the Nioghalvfjerdsfjorden (79 N) Glacier terminus and in the Westwind Trough (median of [Lt] = 2.17 nM eq. Fe; log K′ = 12.3; log α = 3.4) than in the Norske Trough (median of [Lt] = 1.89 nM eq. Fe; log K′= 12.8; log α = 3.8) and in Fram Strait (median of [Lt] = 1.38 nM eq. Fe; log K′ = 13; log α = 3.9). However, organic ligands near the 79 N Glacier terminus and in the Westwind Trough were weaker, and therefore less reactive than organic ligands in the Norske Trough and in Fram Strait. Our findings reveal the fundamental mechanism that underpin transport of dissolved-Fe (DFe) from the 79 N Glacier to Fram Strait, less reactive ligands will reduce Fe solubility. Accordingly, a portion of the glacial DFe will not be transported over the shelf into the ocean. The lower ligand binding strength in the outflow results in a higher inorganic Fe concentration, [Fe´], which is more prone to precipitation and/or scavenging than Fe complexed with stronger ligands. Ongoing changes in the Arctic and sub-Arctic Oceans will influence both terrestrially derived and in-situ produced Fe-binding ligands, and therefore will have consequences for Fe solubility and availability to microbial populations and Fe cycling in Fram Strait.


  • Changed the version of Fe-binding ligands in Fram Strait and over the Northeast Greenland shelf - cruise PS100 to 3 (previously 2)