Modeling the seasonal evolution of the Arctic sea ice floe size distribution
Modeling the seasonal evolution of the Arctic sea ice floe size distribution
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DOI：
10.12952/journal.elementa.000126
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发表时间：
2016-09
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通讯作者：
Jinlun Zhang;H. Stern;B. Hwang;A. Schweiger;M. Steele;M. Stark;H. Graber
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作者：
Jinlun Zhang;H. Stern;B. Hwang;A. Schweiger;M. Steele;M. Stark;H. Graber
为了更好地模拟北极海冰的季节性演变，特别是边缘冰区，海冰模型的冰厚度，浮冰大小和焓的分布实施到泛北极冰-海洋模拟和同化系统（PIOMAS）。将浮冰尺寸分布（FSD）和冰厚分布（ITD）理论耦合起来，以同时显式地模拟多类FSD和ITD分布。扩展的PIOMAS然后被用来估计2014年北极FSD的季节演变，当FSD观测可用于模型校准和验证。结果表明，模拟的FSD，通常被等效地描述为累积浮冰数量分布（CFND），一般遵循幂律跨越空间和时间，并同意来自TerraSAR-X卫星图像的CFND观测。模拟的幂律指数也与使用MODIS图像得到的指数相关，平均偏差为-2%。在边缘冰区，模拟的CFND显示了大量的小浮冰在冬季，因为更强的风作用于薄，弱的第一年冰在冰边缘地区。在春季中期和夏季，CFND类似于上截幂定律，最大的浮冰大多被分解成较小的浮冰;然而，小浮冰的数量低于冬季，因为小尺寸的浮冰或第一年的冰很容易融化。在冰包内部有较少的浮冰在晚秋和冬季比在夏季，因为许多浮冰“焊接”在一起成为更大的浮冰在冻结条件下，导致一个相对平坦的CFND与低幂律指数。模拟的所有冰雪覆盖地区的平均浮冰尺寸显示出明显的年周期，冬季较大，夏季较小。然而，没有明显的年周期的平均浮冰大小平均在边缘冰区。将FSD纳入PIOMAS的结果减少冰的厚度，主要是在边缘冰区，这提高了模拟的冰的范围，并产生一个更早的冰撤退。
To better simulate the seasonal evolution of sea ice in the Arctic, with particular attention to the marginal ice zone, a sea ice model of the distribution of ice thickness, floe size, and enthalpy was implemented into the Pan-arctic Ice–Ocean Modeling and Assimilation System (PIOMAS). Theories on floe size distribution (FSD) and ice thickness distribution (ITD) were coupled in order to explicitly simulate multicategory FSD and ITD distributions simultaneously. The expanded PIOMAS was then used to estimate the seasonal evolution of the Arctic FSD in 2014 when FSD observations are available for model calibration and validation. Results indicate that the simulated FSD, commonly described equivalently as cumulative floe number distribution (CFND), generally follows a power law across space and time and agrees with the CFND observations derived from TerraSAR-X satellite images. The simulated power-law exponents also correlate with those derived using MODIS images, with a low mean bias of –2%. In the marginal ice zone, the modeled CFND shows a large number of small floes in winter because of stronger winds acting on thin, weak first-year ice in the ice edge region. In mid-spring and summer, the CFND resembles an upper truncated power law, with the largest floes mostly broken into smaller ones; however, the number of small floes is lower than in winter because floes of small sizes or first-year ice are easily melted away. In the ice pack interior there are fewer floes in late fall and winter than in summer because many of the floes are “welded” together into larger floes in freezing conditions, leading to a relatively flat CFND with low power-law exponents. The simulated mean floe size averaged over all ice-covered areas shows a clear annual cycle, large in winter and smaller in summer. However, there is no obvious annual cycle of mean floe size averaged over the marginal ice zone. The incorporation of FSD into PIOMAS results in reduced ice thickness, mainly in the marginal ice zone, which improves the simulation of ice extent and yields an earlier ice retreat.