Arctic Sea Ice Decline Whiplash Events on the Synoptic Time Scale in the Context of Global Warming

Extreme weather events have attracted increasing attention, due to their damaging impacts on natural systems and human communities. “Weather whiplash” describes abrupt transitions from one persistent weather regime to another substantially different one, which is even more disruptive. When we turn our attention to the Arctic sea ice, we observe that the marginal sea ice also undergoes such abrupt declines, which we term as “sea ice decline whiplash”. In this work, we focus on these sea ice decline whiplash events occurring on the synoptic time scale over Barents-Kara Seas (BKS), which are identified based on a daily sea ice tendency index, when the index falls below the 5^th percentile of its probability density function distribution during winters of 1979-2020 for at least three consecutive days. A composite analysis of these sea ice decline whiplash events reveals that there is a significantly positive bottom-amplified temperature anomaly preceding the abrupt sea ice loss. This anomaly is closely associated with a wave train composed of a Ural blocking and an upstream positive phase of the North Atlantic Oscillation. Such a structure is favorable for the transport of warm and moist air into the BKS. As a result, the tropospheric temperature, including the surface air temperature, increases through horizontal warm-temperature advection, specifically through warm advection of the climatological temperature by the anomalous wind. The cooling over the BKS due to the adiabatic effect and vertical mixing opposes the horizontal warm-temperature advection above and below about 900 hPa, respectively. However, an increase in skin temperature prominently results from enhanced downward long-wave radiation, which is also the main contributor to the rapid sea ice loss. Furthermore, we examine how the abrupt sea ice decline events and their associated atmospheric conditions change in the context of global warming. This research sheds further light on the complex processes of Arctic weather and climate change.