Changing Seasonal Predictability of Arctic Summer Sea Ice Area in a Warming Climate
Changing Seasonal Predictability of Arctic Summer Sea Ice Area in a Warming Climate
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DOI：
10.1175/jcli-d-19-0034.1
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发表时间：
2019-08-01
影响因子：
4.9
通讯作者：
Vavrus, Steve
中科院分区：
文献类型：
--
作者：
Holland, Marika M.;Landrum, Laura;Vavrus, Steve
我们使用了一个大型的集合模拟和初始化模式预测，以评估从20世纪末到21世纪世纪中期的夏季北极海冰面积的初始值季节可预测性的变化。冰的厚度是一个重要的季节性预测9月冰面积，因为初夏的厚度异常影响有多少融化发生。我们发现，这种预测的作用在气候变暖的变化，导致十年的变化，在9月冰面积的可预测性。在1月初始化的预测实验中，初始化误差随着时间的推移而增长，导致融化季节开始时冰厚的预测误差。在气候变暖的情况下，对夏季融化很重要的地区的冰厚预测误差增长的幅度会减少，这有助于提高可预测性。另一方面，随着气候变暖，初夏厚度异常对夏季融化和由此产生的9月冰面积的影响增加。因此，对于同样量级的初夏冰厚预报误差，9月冰面积异常偏大导致气候变暖，可预报性降低。这些竞争因素的最终结果是，当冰厚预测误差增长适度且这些误差对融化的影响适度时，存在可预测性的最佳点。在我们的模拟中，这种情况发生在2010年左右。夏季冰面积的可预测性较低的前几十年，因为更高的冰厚度预测误差增长，并在以后的几十年，因为更强的影响，冰厚度预测误差对夏季融化。
We use a large ensemble set of simulations and initialized model forecasts to assess changes in the initial-value seasonal predictability of summer Arctic sea ice area from the late-twentieth to the mid-twenty-first century. Ice thickness is an important seasonal predictor of September ice area because early summer thickness anomalies affect how much melt out occurs. We find that the role of this predictor changes in a warming climate, leading to decadal changes in September ice area predictability. In January-initialized prediction experiments, initialization errors grow over time leading to forecast errors in ice thickness at the beginning of the melt season. The magnitude of this ice thickness forecast error growth for regions important to summer melt out decreases in a warming climate, contributing to enhanced predictability. On the other hand, the influence of early summer thickness anomalies on summer melt out and resulting September ice area increases as the climate warms. Given this, for the same magnitude ice thickness forecast error in early summer, a larger September ice area anomaly results in the warming climate, contributing to reduced predictability. The net result of these competing factors is that a sweet spot for predictability exists when the ice thickness forecast error growth is modest and the influence of these errors on melt out is modest. This occurs at about 2010 in our simulations. The predictability of summer ice area is lower for earlier decades, because of higher ice thickness forecast error growth, and for later decades because of a stronger influence of ice thickness forecast errors on summer melt out.