Volcanogenic fluxes of iron from the seafloor in the Amundsen Sea, West Antarctica
Volcanogenic fluxes of iron from the seafloor in the Amundsen Sea, West Antarctica
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DOI：
10.1016/j.marchem.2023.104250
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发表时间：
2023-06
期刊：
影响因子：
3
通讯作者：
L. Herbert;A. Lepp;Santiago Munevar Garcia;Arianne Browning;Lauren E. Miller;J. Wellner;S. Severmann;C. Hillenbrand;Joanne S. Johnson;R. Sherrell
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文献类型：
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作者：
L. Herbert;A. Lepp;Santiago Munevar Garcia;Arianne Browning;Lauren E. Miller;J. Wellner;S. Severmann;C. Hillenbrand;Joanne S. Johnson;R. Sherrell
位于西南极洲太平洋部分的阿蒙森海接受着南极冰川消融最快的融水，其沿海冰穴拥有南极大陆架上观察到的最高的单位面积初级生产力。Polynya生产力提供了一个强大的，多样化的生态系统的基础，并主要由光和微量营养素铁（Fe）的可用性控制。虽然在该地区的铁的来源还不确定，铁可以在修改的环极深水（mCDW），侵入逆行的货架和冰架腔，在那里它获得浮力通过添加冰川融水和注入到上层水柱时，它退出了腔。因此，溶解铁从海底流入mCDW通量可能最终是铁的真光层在阿蒙森海的来源。为了调查表层沉积物的地球化学和潜在的一个显着的底栖铁通量的沃茨上的阿蒙森海陆架，沉积物岩心收集在两个网站接近的崩解前的松岛和Thwaites冰川冰架。分析孔隙水的微量元素含量，并分析沉积物的物理和化学性质，包括有机碳和微量元素。使用一种新的方法的基础上假设的铁形态和胶体颗粒半径，理论铁通量计算孔隙水梯度和孔隙度。通量揭示了一个空间可变的铁输入到较低的水柱，最终可以施肥初级生产力。地球化学和物理证据的支持下，我们得出结论，海底风化的火山玻璃颗粒观察和量化的海底沉积物中的松岛网站驱动器非还原铁通量是100倍以上的Thwaites网站。这项研究突出表明，需要进一步调查阿蒙森海地区的底栖-中上层耦合，这可能会在未来几十年受到冰川融化加速的影响。
The Amundsen Sea in the Pacific sector of West Antarctica receives meltwater from the fastest retreating Antarctic glaciers, and its coastal polynyas host the highest primary productivity per unit area observed on the Antarctic continental shelf. Polynya productivity provides the base for a robust, diverse ecosystem and is controlled primarily by light and the availability of the micronutrient iron (Fe). While the sources of Fe in the region are not yet certain, Fe could be transported within modified Circumpolar Deep Water (mCDW) that intrudes onto the retrograde shelf and into ice shelf cavities, where it gains buoyancy through the addition of glacial meltwater and is injected into the upper water column when it exits the cavity. Thus, fluxes of dissolved Fe from the seafloor into in-flowing mCDW may ultimately be a source of Fe to the euphotic zone in the Amundsen Sea. To investigate the surface sediment biogeochemistry and the potential for a significant benthic flux of Fe to the waters on the Amundsen Sea shelf, sediment cores were collected at two sites close to the calving fronts of the Pine Island and Thwaites Glacier ice shelves. Pore water was analyzed for trace element content, and sediment was analyzed for physical and chemical properties including organic carbon and trace elements. Using a novel approach based on hypothesized Fe speciation and colloidal particle radius, theoretical Fe fluxes were calculated from pore water gradients and porosity. The fluxes reveal a spatially variable Fe input to the lower water column that could ultimately fertilize primary productivity. Supported by geochemical and physical evidence, we conclude that submarine weathering of volcanic glass grains observed and quantified in seabed sediments at the Pine Island site drives nonreductive Fe fluxes that are 100-fold higher than at the Thwaites site. This study highlights the need for further investigations of benthic-pelagic coupling in the Amundsen Sea region, which will likely be impacted in coming decades by accelerating glacial melting.