The phase-locked effect of north tropical Atlantic SST on the trend-removed 0 °C isotherm elevation along the southern slopes of the Himalayas in pre-monsoon season

This study uses HadISST and ERA5 reanalysis data to investigate the trend-removed variability of the 0 °C isotherm elevation, and the main controls on this variability, along the southern slopes of the Himalayas in pre-monsoon season. Here we show that the sea surface temperature (SST) in the north tropical Atlantic Ocean (NTAO) exerts a phase-locked effect on the anomalous seesaw pattern in the 0 °C isotherm elevation with a node around 84.5°E, after the upward trend in the 0 °C isotherm elevation is removed. When the NTAO SST anomalies are warmer than normal, wave-train-like patterns are forced out over western Africa–southeastern Tibetan Plateau with the same anomalous centers from the lower to upper troposphere. An anomalous temperature dipole associated with this wave-train-like pattern is the direct cause of the rise (fall) in the 0 °C isotherm elevation along the southern slopes of the western (eastern) Himalayas in pre-monsoon season. When the NTAO SST anomalies are colder than normal, the opposite situation develops. This significant phase-locked correlation between NTAO SST and trend-removed isotherm elevation, which persists from the previous autumn to the current pre-monsoon season, will help to both elucidate and mitigate the risks posed by glacier-related hazards such as glacial lake outburst floods and avalanches over the southern Himalayas.