Under-Ice Light Field in the Western Arctic Ocean During Late Summer
Under-Ice Light Field in the Western Arctic Ocean During Late Summer
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DOI：
10.3389/feart.2021.643737
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
G. Veyssière;G. Castellani;J. Wilkinson;M. Karcher;Alexander Hayward;J. Stroeve;M. Nicolaus;Joo‐Hong Ki
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文献类型：
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作者：
G. Veyssière;G. Castellani;J. Wilkinson;M. Karcher;Alexander Hayward;J. Stroeve;M. Nicolaus;Joo‐Hong Ki
北极不再是一个由厚的多年冰（MYI）主导的地区，而是由更薄，更动态的第一年冰（FYI）主导的地区。这种向季节性冰盖的转变对冰下光场产生了影响，因为海冰及其积雪是影响辐射传输的主要因素，因此也是影响冰内和冰下生物活动的主要因素。这项工作描述了在2018年8月和2019年8月对楚科奇海进行的两次考察期间，通过不同类型的海冰（MYI和FYI）进行的光透射的原位测量，以及对冰微生物系统生物状态的简单表征。我们的分析表明，在夏末，两种不同的状态FYI存在于该地区：1）FYI在一个增强的衰减状态，和2）强大的FYI，更有可能生存的融化季节。两种FYI类型的平均冰厚不同：0.74 ± 0.07 m（N = 9）和0.93 ± 0.11 m（N = 9），透射率的平均值不同：0.15 ± 0.04和0.09 ± 0.02，冰消光系数不同：1.49 ± 0.28和1.12 ± 0.19 m−1。在MYI上进行的测量呈现出不同的特征，平均冰厚为1.56 ± 0.12 m，透射率较低（0.05 ± 0.01），冰消光系数为1.24 ± 0.26 m−1（N = 12）。所有类型的冰都显示出持续的低盐度，叶绿素a浓度和营养物质，这可能与测量的时间和融水通过冰的冲刷有关。随着北极持续变暖，夏季冰将继续消退，FYI的衰变变体具有更高的光散射，但厚度减小，导致整体透光率更高，可能成为更相关的冰类型。我们的研究结果表明，在这种情况下，更多的光将到达冰内部和海洋上层。
The Arctic is no longer a region dominated by thick multi-year ice (MYI), but by thinner, more dynamic, first-year-ice (FYI). This shift towards a seasonal ice cover has consequences for the under-ice light field, as sea-ice and its snow cover are a major factor influencing radiative transfer and thus, biological activity within- and under the ice. This work describes in situ measurements of light transmission through different types of sea-ice (MYI and FYI) performed during two expeditions to the Chukchi sea in August 2018 and 2019, as well as a simple characterisation of the biological state of the ice microbial system. Our analysis shows that, in late summer, two different states of FYI exist in this region: 1) FYI in an enhanced state of decay, and 2) robust FYI, more likely to survive the melt season. The two FYI types have different average ice thicknesses: 0.74 ± 0.07 m (N = 9) and 0.93 ± 0.11 m (N = 9), different average values of transmittance: 0.15 ± 0.04 compared to 0.09 ± 0.02, and different ice extinction coefficients: 1.49 ± 0.28 and 1.12 ± 0.19 m−1. The measurements performed over MYI present different characteristics with a higher average ice thickness of 1.56 ± 0.12 m, lower transmittance (0.05 ± 0.01) with ice extinction coefficients of 1.24 ± 0.26 m−1 (N = 12). All ice types show consistently low salinity, chlorophyll a concentrations and nutrients, which may be linked to the timing of the measurements and the flushing of melt-water through the ice. With continued Arctic warming, the summer ice will continue to retreat, and the decayed variant of FYI, with a higher scattering of light, but a reduced thickness, leading to an overall higher light transmittance, may become a more relevant ice type. Our results suggest that in this scenario, more light would reach the ice interior and the upper-ocean.