North Atlantic Natural Variability Modulates Emergence of Widespread Greenland Melt in a Warming Climate
North Atlantic Natural Variability Modulates Emergence of Widespread Greenland Melt in a Warming Climate
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DOI：
10.1029/2018gl079682
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发表时间：
2018-09-16
影响因子：
5.2
通讯作者：
Kwon, Y. -O.
中科院分区：
文献类型：
--
作者：
Hahn, L.;Ummenhofer, C. C.;Kwon, Y. -O.
近几十年来格陵兰岛破纪录的融化不仅与气候变化有关，而且与自然变异有关，包括北大西洋涛动负阶段持续的大气高压条件和大西洋数十年振荡正阶段北大西洋温暖的温度。然而，在不同程度的温室强迫下，格陵兰融化的自然变异的相对重要性仍然不清楚。使用再分析数据和一个大的合奏气候模式模拟，我们发现，一个负的北大西洋涛动和积极的大西洋年代际振荡一贯促进夏季融化在各种强迫条件下。此外，广泛的世纪格陵兰融化的时间有很大的不同，由于这些模式的自然变化的不同阶段的合奏成员之间。这些结果表明，在一系列外部强迫条件下，自然变率模式对于年际融化变率和格陵兰岛大面积融化的出现具有重要意义。简明语言摘要格陵兰岛极端冰盖融化部分是由气候变化驱动的，因为温室气体浓度的上升促进了气温的升高，特别是在北极地区。然而，气候系统的自然波动也会促使格陵兰融化。特别是，近几十年来，该区域大气中持续存在的高压系统和北大西洋温暖的温度与格陵兰融化加剧有关。然而，这些自然振荡在过去和未来对融化的重要性仍然不清楚。我们使用一系列气候模型模拟表明，高压条件和温暖的北大西洋在过去和未来的各种变暖情景下，始终促进夏季融化。此外，格陵兰岛在世纪大范围融化的时间取决于这些自然变化模式的时间。
Record-breaking melt over Greenland in recent decades is linked not only to climate change but also to natural variability, including persistent atmospheric high-pressure conditions in the negative phase of the North Atlantic Oscillation and warm North Atlantic Ocean temperatures during the positive phase of the Atlantic Multidecadal Oscillation. However, the relative importance of natural variability for Greenland melt under varying degrees of greenhouse forcing is still unclear. Using reanalysis data and a large ensemble of climate model simulations, we find that a negative North Atlantic Oscillation and positive Atlantic Multidecadal Oscillation consistently promote heightened summer melt under various forcing conditions. Moreover, timing of widespread 21st century Greenland melt varies considerably between ensemble members due to different phasing of these modes of natural variability. These results indicate the importance of natural modes of variability across a range of external forcing conditions for interannual melt variability and the emergence of widespread Greenland melt.Plain Language Summary Extreme Greenland Ice Sheet melt is partly driven by climate change, as rising greenhouse gas concentrations promote warmer temperatures, especially for the Arctic region. However, natural fluctuations in the climate system can also promote Greenland melt. In particular, persistent high-pressure systems in the atmosphere over the region and warm North Atlantic Ocean temperatures have been linked to enhanced Greenland melt in recent decades. Yet the importance of these natural oscillations for melt in the past and future remains unclear. We use a series of climate model simulations to show that high-pressure conditions and a warm North Atlantic Ocean consistently promote heightened summer melt under various warming scenarios for the past and future. Additionally, the timing of widespread Greenland melt in the 21st century depends on the timing of these modes of natural variability.