The Western Antarctic Peninsula (WAP) is a rapidly changing region with receding sea-ice cover. This region generally has increased phytoplankton productivity on the continental slope with a decrease observed in off-shelf waters located further northward. This study aims to improve the understanding of the distribution of iron (Fe) in this climatically important oceanic region during early sea-ice retreat, as well as the impact of receding ice cover on Fe concentrations and the importance of Fe and its sources at the beginning of the phytoplankton growth season. Five ocean transects were sampled along the Palmer Long Term Ecological Research (Pal-LTER) grid with an additional oceanward extension to access off-shelf waters during the austral spring (October and November) of 2014. High Fe inputs into the entire water column from ice melt as well as from sediments increased dissolved Fe (DFe) and total dissolvable Fe (TDFe) concentrations across the shelf (off-shelf DFe: 0.38 ± 0.30 nmol/L and TDFe: 2.23 ± 2.95 nmol/L versus shelf DFe: 1.54 ± 1.38 nmol/L and TDFe: 19.47 ± 23.82 nmol/L). The combination of meteoric meltwater and shallow sedimentary sources is strongest over the shelf and increased landward towards the WAP. Additionally, a winter sea-ice formation signature was detected in inner shelf waters that appeared to contribute to DFe concentrations. Relatively warm Circumpolar Deep Water (CDW) that flows onto the shelf through troughs is likely modified by non-reductive sedimentary input of Fe into the water column. The increase in Fe concentrations in WAP waters in early spring could trigger enhanced phytoplankton productivity across the shelf, although the highest productivity levels were observed in off-shelf waters, likely related to improved light conditions following receding sea-ice cover. The relatively high productivity levels in WAP off-shelf waters are presumably caused by two factors: (1) supply from below, and (2) the transport of Fe from the shelf to the off-shelf region. However, 80–90% of Fe introduced into shelf waters was removed from the upper water column prior to reaching off-shelf waters, reducing the influence of the coastal Fe source. Low concentrations of DFe (0.24 ± 0.26 nmol/L) in off-shelf waters (upper 100 m) of the WAP coincide with relatively elevated chlorophyll a concentrations (0.66 ± 0.56 μg/L), implying that uptake of available DFe had already occurred prior to sampling. Our results imply that the horizontal supply of DFe from the shelf as well as total DFe supply into the surface mixed layer might not be sufficiently high to support productivity in the off-shelf waters of the WAP, underlining the development of an Fe deficit early in the growth season.

南极半岛西部 (WAP) 是一个快速变化的地区，海冰覆盖逐渐减少。该地区通常在大陆坡上增加了浮游植物生产力，而在更靠北的陆架水域观察到减少。本研究旨在提高对早期海冰退缩期间这一具有重要气候意义的海洋区域中铁 (Fe) 分布的了解，以及退冰对 Fe 浓度的影响以及 Fe 及其来源在海冰退缩过程中的重要性。浮游植物生长季节的开始。在 2014 年的南方春季（10 月和 11 月）期间，沿着帕默长期生态研究 (Pal-LTER) 网格对五个海洋横断面进行了采样，并额外向海洋延伸以进入近海水域。来自冰融化和沉积物的高铁输入到整个水体中增加了整个架子上的溶解铁 (DFe) 和总溶解铁 (TDFe) 浓度（架外 DFe：0.38 ± 0.30 nmol/L 和 TDFe：2.23 ± 2.95 nmol/L 与货架 DFe：1.54 ± 1.38 nmol/L 和 TDFe：19.47 ± 23.82 nmol/L）。大气融水和浅层沉积源的组合在陆架上最强，向陆向 WAP 增加。此外，在内陆架水域中检测到冬季海冰形成特征，这似乎有助于 DFe 浓度。通过海槽流入陆架的相对温暖的环极深水 (CDW) 很可能被非还原沉积的 Fe 输入水体所改变。早春 WAP 水域中铁浓度的增加可能会引发整个大陆架浮游植物生产力的提高，尽管在大陆架水域观察到最高的生产力水平，这可能与海冰覆盖后改善光照条件有关。WAP 货架外水域相对较高的生产力水平大概是由两个因素造成的：(1) 从下方供应，以及 (2) 铁从货架运输到货架区域。然而，进入陆架水域的 80-90% 的铁在到达陆架水域之前已从上部水体中去除，从而减少了沿海铁源的影响。WAP 的现货水域（上部 100 m）中的低浓度 DFe (0.24 ± 0.26 nmol/L) 与相对升高的叶绿素一致 尽管在近海水域观察到了最高的生产力水平，但这可能与海冰覆盖消退后光照条件的改善有关。WAP 货架外水域相对较高的生产力水平大概是由两个因素造成的：(1) 从下方供应，以及 (2) 铁从货架运输到货架区域。然而，进入陆架水域的 80-90% 的铁在到达陆架水域之前已从上部水体中去除，从而减少了沿海铁源的影响。WAP 的现货水域（上部 100 m）中的低浓度 DFe (0.24 ± 0.26 nmol/L) 与相对升高的叶绿素一致 尽管在近海水域观察到了最高的生产力水平，但这可能与海冰覆盖消退后光照条件的改善有关。WAP 货架外水域相对较高的生产力水平大概是由两个因素造成的：(1) 从下方供应，以及 (2) 铁从货架运输到货架区域。然而，进入陆架水域的 80-90% 的铁在到达陆架水域之前已从上部水体中去除，从而减少了沿海铁源的影响。WAP 的现货水域（上部 100 m）中的低浓度 DFe (0.24 ± 0.26 nmol/L) 与相对升高的叶绿素一致 WAP 货架外水域相对较高的生产力水平大概是由两个因素造成的：(1) 从下方供应，以及 (2) 铁从货架运输到货架区域。然而，进入陆架水域的 80-90% 的铁在到达陆架水域之前已从上部水体中去除，从而减少了沿海铁源的影响。WAP 的现货水域（上部 100 m）中的低浓度 DFe (0.24 ± 0.26 nmol/L) 与相对升高的叶绿素一致 WAP 货架外水域相对较高的生产力水平大概是由两个因素造成的：(1) 从下方供应，以及 (2) 铁从货架运输到货架区域。然而，进入陆架水域的 80-90% 的铁在到达陆架水域之前已从上部水体中去除，从而减少了沿海铁源的影响。WAP 的现货水域（上部 100 m）中的低浓度 DFe (0.24 ± 0.26 nmol/L) 与相对升高的叶绿素一致a浓度 (0.66 ± 0.56 μg/L)，这意味着在采样之前已经吸收了可用的 DFe。我们的结果表明，来自陆架的 DFe 水平供应以及进入表面混合层的总 DFe 供应可能不足以支持 WAP 陆架水域的生产力，这强调了早期铁缺乏的发展生长季节。