Ice/snow melt onset (MO) is critical timing for ice-albedo positive feedback in the Arctic. For 1979–1998, the MO in the East Siberian Sea (ESS) occurred earlier than in the Laptev Sea (LS) for 12 of 20 years. However, for 1999–2018, the LS experienced significantly earlier MO than the ESS for 8 of 20 years. We referred to this phenomenon as the MO Seesaw (MOS) and quantified it by the MO difference between the LS and ESS. The MOS is more pronounced since 1999. For positive MOS, storm tracks in May are located south of the ESS and easterly wind prevails, resulting in higher surface air temperature and total-column water vapor and, therefore, earlier MO in the ESS. For negative MOS, storm tracks are located southwest of the LS, and strong southerly/southwesterly winds bring warm air from coastal land toward the LS. When low pressure is centered over the Barents Sea in April, sea ice in the LS has driven away from the coasts, which increases the surface latent heat flux and humidifies the overlying atmosphere, and eventually leads to earlier MO in the LS. Both the local variables and the large-scale atmospheric circulation indices were more related to the MOS for 1999–2018 than for 1979–1998.

中文翻译：

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北极东北航道海冰开始融化的变化：拉普捷夫海和东西伯利亚海的跷跷板

冰/雪融化开始 (MO) 是北极冰反照率正反馈的关键时机。1979-1998 年，东西伯利亚海 (ESS) 的 MO 发生时间早于拉普捷夫海 (LS) 的 20 年中的 12 年。然而，在 1999 年至 2018 年间，LS 经历的 MO 明显早于 ESS 的 20 年中的 8 年。我们将这种现象称为 MO 跷跷板 (MOS)，并通过 LS 和 ESS 之间的 MO 差异对其进行量化。自 1999 年以来，MOS 更为明显。对于正 MOS，5 月的风暴路径位于 ESS 以南，东风盛行，导致较高的地表气温和总柱水汽，因此，ESS 中的 MO 提前。对于负 MOS，风暴路径位于 LS 西南部，强烈的南/西南风将暖空气从沿海陆地带到 LS。4 月，当低压集中在巴伦支海上空时，LS 的海冰已经离开海岸，这增加了地表潜热通量并加湿了上覆的大气，最终导致 LS 中的 MO 提前。与 1979-1998 年相比，1999-2018 年局部变量和大尺度大气环流指数与 MOS 的相关性更大。