Variability in Sea Ice Melt Onset in the Arctic Northeast Passage: Seesaw of the Laptev Sea and the East Siberian Sea

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. Plain Language Summary Sea ice melt onset is marked by the appearance of liquid water on top of sea ice, which signals the beginning of the melting season in the Arctic. As sea ice reflectivity (albedo) drops after melting, the surface can absorb more heat from the sun and so the ice melts faster, forming the ice‐albedo feedback. As a result, changes in sea ice melt onset may help predict the summer sea ice minimum and be an indicator of climate change. While exploring sea ice melt onset on one vital transport route in the Arctic, the Northeast Passage, we noticed that the sea ice melt onset differs in the Laptev Sea and the East Siberian Sea. For the years 1979–1998, the East Siberian Sea generally experienced a earlier melt onset than the Laptev Sea; however, since 1999, the Laptev Sea usually melts earlier than the East Siberian Sea. We found that the main factors driving these changes include the local wind, surface air temperature, and moisture in the atmosphere, as well as storm tracks, and a large‐scale atmospheric “Barents Oscillation.” This research provides a new perspective into the sea ice system, which may also help improve safe operation in the Arctic Northeast Passage. Key Points Based on the difference in dates of melt onset for the Laptev and East Siber