Positive and negative feedbacks related to the Arctic Oscillation revealed by air-sea heat fluxes

Abstract

The NCEP reanalysis data of surface heat fluxes and other related data are used to study their relationship with the Arctic Oscillation (AO). Positive and negative high correlation regions (HCR) between heat fluxes and the AO within the northern North Atlantic are identified. The main factor influencing heat fluxes is the atmospheric circulation over the Nordic Seas, which produces meridional heat transports and generates ocean circulation variability. Our hypothesis is that there are positive feedbacks that enhance the AO and negative feedbacks that weaken it. Among the three main factors related to the atmospheric circulation in Nordic Seas, meridional wind and ocean circulation result in negative feedbacks. Upward airflow produces three effects: upward advection of warm air, latent heat release by condensation and increased short-wave radiation absorption, which all result in positive feedback to the AO. The region dominated by positive feedback is referred to as Arctic Oscillation Positive Feedback Region (AOPFR). Its area is relative small, but it may have hemispheric effects through the divergence of the airflow. Regarding the driving factor of AO, we find that the upwelled airflow produces the only positive feedback, while oceanic circulation acts as a negative feedback contributor. Both atmospheric and oceanic processes are all important factors governing the evolution of the AO.