A Multi-Sensor and Modeling Approach for Mapping Light Under Sea Ice During the Ice-Growth Season
A Multi-Sensor and Modeling Approach for Mapping Light Under Sea Ice During the Ice-Growth Season
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DOI：
10.3389/fmars.2020.592337
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发表时间：
2021-02
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影响因子：
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通讯作者：
J. Stroeve;M. Vancoppenolle;G. Veyssière;Marion Lebrun;G. Castellani;M. Babin;M. Karcher;J. Landy;G. Liston;J. Wilkinson
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作者：
J. Stroeve;M. Vancoppenolle;G. Veyssière;Marion Lebrun;G. Castellani;M. Babin;M. Karcher;J. Landy;G. Liston;J. Wilkinson
北极海冰正在从全年海冰转变为季节性海冰。通过北极海冰范围的缩小和厚度的变薄，这种巨大的转变影响了进入上层海洋的光量。这反过来又影响冰下藻类的生长和相关的生态系统动态。实地活动为了解冰雪特性如何影响北极固定地点的光穿透提供了宝贵的见解，但为了了解冰下光场的空间变化，需要扩大到泛北极水平。将卫星信息与最先进的参数化相结合是实现这一目标的一种方法。这项研究结合了卫星和建模数据产品，绘制了 2011 年至 2018 年每月时间尺度的冰下光线图。主要限制在于卫星衍生的海冰厚度的可用性，对于雷达测高来说，该厚度仅在海冰生长季节可用。我们清楚地表明，雪深的逐年变化以及薄冰的比例对于进入北冰洋的光量起着关键作用。这在四月份尤其重要，在某些地区，这恰逢冰下藻华的开始，而我们发现冰厚度是十月融化季节结束时冰下光照可用性的主要驱动因素。由于北极变暖导致融化季节延长，意味着积雪减少，这导致通过雪的光传输呈积极趋势。再加上更薄的冰层，夏季冰下有效光合有效辐射也会增加。
Arctic sea ice is shifting from a year-round to a seasonal sea ice cover. This substantial transformation, via a reduction in Arctic sea ice extent and a thinning of its thickness, influences the amount of light entering the upper ocean. This in turn impacts under-ice algal growth and associated ecosystem dynamics. Field campaigns have provided valuable insights as to how snow and ice properties impact light penetration at fixed locations in the Arctic, but to understand the spatial variability in the under-ice light field there is a need to scale up to the pan-Arctic level. Combining information from satellites with state-of-the-art parameterizations is one means to achieve this. This study combines satellite and modeled data products to map under-ice light on a monthly time-scale from 2011 through 2018. Key limitations pertain to the availability of satellite-derived sea ice thickness, which for radar altimetry, is only available during the sea ice growth season. We clearly show that year-to-year variability in snow depth, along with the fraction of thin ice, plays a key role in how much light enters the Arctic Ocean. This is particularly significant in April, which in some regions, coincides with the beginning of the under-ice algal bloom, whereas we find that ice thickness is the main driver of under-ice light availability at the end of the melt season in October. The extension to the melt season due to a warmer Arctic means that snow accumulation has reduced, which is leading to positive trends in light transmission through snow. This, combined with a thinner ice cover, should lead to increased under-ice PAR also in the summer months.