Dynamical connection between the stratospheric Arctic vortex and sea surface temperatures in the North Atlantic

Abstract

We used two long-term reanalysis datasets and time-slice simulations to examine the decadal relationship between the stratospheric Arctic vortex (SAV) and sea surface temperature anomalies (SSTAs) in the North Atlantic and the dynamic mechanisms involved in the linkage between the two. Our results show that there is a significant decadal linkage between SSTAs over the North Atlantic and the SAV, where warmed (cooled) SSTAs over the North Atlantic in association with its principal mode correspond to a weakened (strengthened) SAV. The warmed North Atlantic SSTAs tend to result in a weakened SAV via two dynamic processes: (1) constructive interference at high latitudes with a ridge in the Atlantic sector and a trough in the Pacific accompanied by a negative North Atlantic Oscillation-like pattern over the North Atlantic and a weakened Aleutian low over the North Pacific; and (2) more wavenumber-1 waves propagated into the Arctic stratosphere by modifying the baroclinic term of the zonal mean background state and altering the propagating conditions around the tropopause over the Arctic. Results from reanalysis and model simulations both suggest that a strengthening wave intensity in the high-latitude troposphere and more upward propagation of the planetary wavenumber-1 wave in response to the warmed North Atlantic SSTAs conjunctly contribute to the increased planetary wave flux in the Arctic stratosphere, facilitating a weakened SAV. These results provide a new understanding of what dynamic processes control the SAV, and will help to predict the stratosphere on decadal timescales.