Warming amplification over the Arctic Pole and Third Pole: Trends, mechanisms and consequences

Warming amplification over the Arctic Pole (AP hereafter) and Third Pole (Tibetan Plateau, TP hereafter) can trigger a series of climate responses and have global consequences. Arctic amplification (AA) and Tibetan amplification (TA) are the most significant characteristics of climate change patterns over the two Poles. In this study, trends, mechanisms and consequences of both AA and TA are compared. Based on ERA5 reanalysis during 1979–2020, both AP and TP have undergone significant warming with an annual rate of 0.72 °C/decade and 0.34 °C/decade respectively, which exceeds the rates for the Northern Hemisphere (0.29 °C/decade) and the global means (0.19 °C/decade) over the same period. Based on 22 Coupled Model Intercomparison Project Phase 6 models, AA over the AP is warming at a rate almost four times than the global means and twice as fast over the TP. Although both AA and TA are projected to continue in the future, currently there is no consensus on the dominant mechanisms for AA or TA over the two Poles. Proposed mechanisms of AA can be divided into two types: local climate factors (sea ice-albedo feedback, Planck feedback, temperature gradient feedback, cloud feedback, and water vapor feedback); and poleward heat and moisture transport from lower latitudes (atmospheric circulation effect, ocean circulation effect, and modulation of Pacific and Atlantic SST). Consequences of AA include decline of sea ice cover, retreat of the Greenland ice sheet, permafrost degradation, accelerated disturbances in marine and terrestrial ecosystems, and influences on extreme climate events at lower latitudes. Anthropogenic greenhouse gas emission, snow/ice-albedo feedback, cloud-radiation interactions, water vapor and radiative flux feedbacks, local forcing and feedback processes, land use changes and reduction in total ozone, are generally considered to be the main mechanisms causing TA. TA has caused significant change within the atmosphere and cryosphere over the TP and its surroundings, such as changes in climate extremes, snow cover, the retreat of glaciers, and permafrost degradation. Similarities and differences of warming amplifications over the two Poles are proposed, and the relative contribution of each mechanism to the warming amplifications and how the specific consequences may compare over the two Poles remain unclear and under continuing investigation.