The role of the Dotson Ice Shelf and circumpolar deep water as driver and source of dissolved and particulate iron and manganese in the Amundsen Sea polynya, Southern Ocean
The role of the Dotson Ice Shelf and circumpolar deep water as driver and source of dissolved and particulate iron and manganese in the Amundsen Sea polynya, Southern Ocean
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DOI：
10.1016/j.marchem.2022.104161
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发表时间：
2022-08
期刊：
影响因子：
3
通讯作者：
Mathijs H. van Manen;S. Aoki;C. Brussaard;T. Conway;C. Eich;L. Gerringa;Jinyoung Jung;Tae‐Wan Kim;Sang H. Lee;Youngju Lee;G. Reichart;Hung-An Tian;Flora Wille;R. Middag
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文献类型：
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作者：
Mathijs H. van Manen;S. Aoki;C. Brussaard;T. Conway;C. Eich;L. Gerringa;Jinyoung Jung;Tae‐Wan Kim;Sang H. Lee;Youngju Lee;G. Reichart;Hung-An Tian;Flora Wille;R. Middag
阿蒙森海等南极洲周边沿海地区是微量金属和生物热点的重要来源，但也正在经历气候变化的影响，包括冰盖迅速变薄。在阿蒙森海冰间湖 (ASP) 中部，生物必需的溶解铁 (DFe) 和溶解锰 (DMn) 在地表都被耗尽，表明大量生物吸收和/或沉淀。靠近多特森冰架 (DIS) 的表面 DMn 浓度升高 (>3 nM)，但令人惊讶的是 DFe 浓度却没有升高 (<0.3 nM)。虽然 Fe 结合配体数据表明 DIS 附近的配体丰富，但这些配体很可能不足以战胜清除作用，从而显着增加流出中的 DFe。与溶解相相反，靠近 DIS 的整个水柱以及部分中央 ASP 中的颗粒 Fe (PFe) 和 Mn (PMn) 浓度（不稳定和难熔部分）均升高。我们假设 DFe 从 DIS 中释放出来，并通过（可逆）清除立即与不稳定颗粒 Fe (L-PFe) 池建立平衡，如流出中 L-PFe 和 DFe 之间的正相关性所示。这种清除导致相对较低的 DFe 浓度，但当 DFe 减少时，不稳定的 PFe 池可能会缓冲 DFe 池，例如由于浮游植物的吸收。 DFe 分布还表明，流入的改性环极深水 (mCDW) 和底栖沉积物是 ASP 中 DFe 和 DMn 的明确且重要的来源。难熔的 Fe 和 Mn 可能有成岩来源，而不稳定部分主要是地表水中的生物来源，以及深水（>100 m 深度）中的自生来源。我们比较了不同的吸收率，强调吸收率估计值不一定反映自然变化，最好使用一系列值。未来，气候变化可能会增加 mCDW 的热通量，从而增加 DIS 的融化。这很可能会导致 ASP 中铁和锰的输入增加，从而可能推动 ASP 初级生产力水平的提高。
Coastal areas around Antarctica such as the Amundsen Sea are important sources of trace metals and biological hotspots, but are also experiencing the effects of climate change, including the rapid thinning of ice sheets. In the central Amundsen Sea Polynya (ASP), both bio-essential dissolved Fe (DFe) and dissolved Mn (DMn) were found to be depleted at the surface, indicating substantial biological uptake and/or precipitation. Close to the Dotson Ice Shelf (DIS) there were elevated surface concentrations of DMn (>3 nM) but surprisingly not for DFe (<0.3 nM). While Fe-binding ligand data suggests that ligands were abundant near the DIS, these were most likely not strong enough to outcompete scavenging and thus increase DFe substantially in the outflow. In contrast to the dissolved phase, particulate Fe (PFe) and Mn (PMn) concentrations (both labile and refractory fractions) were elevated over the entire water column close to the DIS and partly in the central ASP. We hypothesize that DFe was released from the DIS and immediately established an equilibrium with the labile particulate Fe (L-PFe)pool, via (reversible) scavenging, as indicated by a positive correlation between L-PFe and DFe in the outflow. This scavenging results in relatively low DFe concentrations, but the pool of labile PFe likely buffers the DFe pool when DFe is decreasing, e.g. due to uptake by phytoplankton. The DFe distribution also shows that inflowing modified circumpolar deep water (mCDW) and benthic sediments are clear and important sources for both DFe and DMn in the ASP. Refractory Fe and Mn likely have a lithogenic source, whereas the labile fractions are mostly biogenic in surface waters, and authigenic in deep waters (>100 m depth). We compared different uptake ratios, underlining that uptake ratio estimates do not necessarily capture natural variability and it is likely better to use a range of values. In the future, climate change may increase the heat flux of mCDW and thereby the melting of the DIS. This will most likely cause an increased input of Fe and Mn into the ASP, which may fuel increased levels of primary productivity in the ASP.