Estimating the sea ice floe size distribution using satellite altimetry: theory, climatology, and model comparison
Estimating the sea ice floe size distribution using satellite altimetry: theory, climatology, and model comparison
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DOI：
10.5194/tc-13-2869-2019
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发表时间：
2019-11-08
期刊：
影响因子：
5.2
通讯作者：
Shepherd, Andrew
中科院分区：
文献类型：
--
作者：
Horvat, Christopher;Roach, Lettie A.;Shepherd, Andrew
在海冰覆盖的地区，海冰浮体尺寸分布（FSD）在影响海-冰-海洋-大气耦合系统的许多过程中发挥着重要作用。对 FSD 的观察很少——传统上是通过对冰面摄影的艰苦分析来获取的——并且区域和全球范围内浮冰尺寸的季节性和年际演变在很大程度上是未知的。通常，测量的 FSD 是使用单个数字来评估的，即与观察到的絮凝物尺寸数据最接近的幂律拟合的缩放指数，尽管在缺乏足够的数据集的情况下，对这种“幂律假设”的测试有限。在这里，我们推导并解释了一种数学技术，用于从极轨高度计（具有高沿轨分辨率的次日返回极地地区的卫星）中获取海冰 FSD 统计数据。我们将覆盖 2010 年至 2018 年期间的 CryoSat-2 雷达测高记录应用到其中，并纳入 1100 万个单独的浮冰样本，生成了第一个泛北极气候学和季节周期的海冰浮冰大小统计数据。然后，我们对幂律假说进行了第一次泛北极测试，在摄影观测研究中通常分析的浮冰尺寸范围中发现了有限的支持。我们将观测到的浮冰尺寸的季节性变化与完全耦合的气候模型模拟进行了比较，包括预测浮冰尺寸和厚度分布以及耦合波浪模型，在模拟海洋表面波浪导致海冰破裂的区域中发现了良好的一致性。
In sea-ice-covered areas, the sea ice floe size distribution (FSD) plays an important role in many processes affecting the coupled sea-ice-ocean-atmosphere system. Observations of the FSD are sparse - traditionally taken via a painstaking analysis of ice surface photography - and the seasonal and inter-annual evolution of floe size regionally and globally is largely unknown. Frequently, measured FSDs are assessed using a single number, the scaling exponent of the closest power-law fit to the observed floe size data, although in the absence of adequate datasets there have been limited tests of this "power-law hypothesis". Here we derive and explain a mathematical technique for deriving statistics of the sea ice FSD from polar-orbiting altimeters, satellites with sub-daily return times to polar regions with high along-track resolutions. Applied to the CryoSat-2 radar altimetric record, covering the period from 2010 to 2018, and incorporating 11 million individual floe samples, we produce the first pan-Arctic climatology and seasonal cycle of sea ice floe size statistics. We then perform the first pan-Arctic test of the power-law hypothesis, finding limited support in the range of floe sizes typically analyzed in photographic observational studies. We compare the seasonal variability in observed floe size to fully coupled climate model simulations including a prognostic floe size and thickness distribution and coupled wave model, finding good agreement in regions where modeled ocean surface waves cause sea ice fracture.