Recent advances in driving mechanisms of the Arctic amplification: A review

Abstract

Under the influence of recent global warming, the Arctic climate is continuing to experience unprecedented changes. Surface temperatures in the Arctic are increasing at a rate double that of the global average, known as the Arctic amplification. The Arctic amplification has led to a series of consequences locally such as the accelerated sea ice retreat, the continuous permafrost melting and methane release, and the marine and terrestrial ecological dynamics. It also might cause an increased frequency of extreme weather event in mid-latitudes via perturbing the strength of the polar vortex. The Arctic warming is mainly resulted from the imbalance of energy budget at both surface and top of atmosphere. In order to explore the driving mechanism of Arctic amplification, lots of efforts have been made based on model simulations and observations. Several major competing theories and related evidences have been proposed to explain their contributions to the imbalance of energy budget over the Arctic. The sea-ice albedo feedback, caused by the continuously shrinking summer sea ice potentially increasing the absorption of shortwave radiation, is believed to play a critical role in recent Arctic amplification. But certain model simulations have indicated that sea-ice albedo feedback was likely not the dominant factor—robust warming amplification still occurs in the Arctic in the absence of albedo feedback. The positive lapse rate feedback, is also thought to cause greater warming at the Arctic surface through damping the deep convection process at the bottom atmosphere because of the strong temperature inversion in the cold Arctic. However, whether the lapse rate feedback plays a dominant role in the Arctic amplification has not been widely accepted. The Planck feedback—cold region requires larger temperature increase than warm area to balance certain external radiative forcing, is also believed to contribute to the Arctic amplification. But the magnitude of its contribution remains to be further quantified. An enhanced Atlantic meridional overturning circulation (AMOC) transporting extraordinary amounts of heat northward to the Arctic Ocean has been hypothesized to substantially amplify Arctic warming and accelerate summer sea-ice melting in this region. However, evidence has instead shown significant slowing of the AMOC over the last few decades. The enhanced greenhouse effect, resulted from the increased water vapor and cloudiness, has been suggested as an important driver of the Arctic winter warming and summer sea-ice dynamics. However, whether the increased water vapor comes from the strengthened sea surface evaporation or from an enhanced atmospheric northward transportation, is still unclear. This paper elucidates the theoretical basis of all potential mechanisms, and systematically reviews the research progress of these theories. Based on the comprehensive analysis of these studies, we point out that due to the limitation of current study approaches, the data quality problems such as scarce in situ measurements, difficulty in discriminating clouds from snow cover for some remote sensing products, problematic parameterization schemes and model inputs in some reanalsysis and GCM projects, and the lack of systematic analysis for investigating the internal relations between different climate variables, the conclusions from different studies are discrepant, or even contradictory. The causes of the unprecedented climate change in the Arctic remain unclear and are still under heated debate. Therefore, the development of high quality, long-term radiative product, the optimization of the researching approaches and more accurate quantification of these feedback mechanisms, and the systematic analysis of the potential linkage between different climate variables, will help to advance the study of the Arctic amplification and climate change.