The underlying mechanisms for Arctic sea ice decline can be categories as those directly related to changes in atmospheric circulations (often referred to as dynamic mechanisms) and the rest (broadly characterized as thermodynamic processes). An attribution analysis based on the self-organizing maps (SOM) method is performed to determine the relative contributions from these two types of mechanisms to the Arctic sea ice decline in August–October during 1979–2016. The daily atmospheric circulations represented by daily 500-hPa geopotential height anomalies are classified into 12 SOM patterns, which portray the spatial structures of the Arctic Oscillation and Arctic Dipole, and their transitions. Due to the counterbalance between the opposite trends among the circulation patterns, the net effect of circulation changes is small, explaining only 1.6% of the declining trend in the number of August–October sea ice days in the Arctic during 1979–2016. The majority of the trend (95.8%) is accounted for by changes in thermodynamic processes not directly related to changes in circulations, whereas for the remaining trend (2.6%) the contributions of circulation and non-circulation changes cannot be distinguished. The sea ice decline is closely associated with surface air temperature increase, which is related to increasing trends in atmospheric water vapor content, downward longwave radiation, and sea surface temperatures over the open ocean, as well as to decreasing trends in surface albedo. An analogous SOM analysis extending seasonal coverage to spring (April–October) for the same period supports the dominating role of thermodynamic forcing in decadal-scale Arctic sea ice loss.

北极海冰下降的潜在机制可以归为与大气环流变化直接相关的那些机制（通常称为动力机制），而与其余部分（广泛地称为热力学过程）有关。进行了基于自组织图（SOM）方法的归因分析，以确定这两种类型的机制对1979-2016年8月至10月北极海冰下降的相对贡献。每天由500hPa地势高度异常代表的每日大气环流分为12个SOM模式，描绘了北极涛动和北极偶极子的空间结构及其过渡。由于流通模式之间相反趋势之间的平衡，流通变化的净效应很小，仅作解释1。1979年至2016年期间，北极8月至10月海冰天数下降趋势的6％。趋势的大部分（95.8％）是由与循环变化不直接相关的热力学过程变化引起的，而其余趋势（2.6％）则无法区分循环变化和非循环变化的贡献。海冰的下降与地表气温的升高密切相关，这与大气水蒸气含量的增加趋势，向下的长波辐射和公海的海面温度的上升以及地表反照率的下降有关。类似的SOM分析将同一时期的季节覆盖范围扩展到春季（4月至10月），这支持了热力学强迫在年代际北极海冰损失中的主导作用。