Future intensification of extreme Aleutian low events and their climate impacts

K Giamalaki,C Beaulieu,H Kassem,S A Henson,D Faranda,A P Martin

doi:10.1038/s41598-021-97615-7

Abstract

Extreme Aleutian Low (AL) events have been associated with major ecosystem reorganisations and unusual weather patterns in the Pacific region, with serious socio-economic consequences. Yet, their future evolution and impacts on atmosphere–ocean interactions remain uncertain. Here, a large ensemble of historical and future runs from the Community Earth System Model is used to investigate the evolution of AL extremes. The frequency and persistence of AL extremes are quantified and their connection with climatic variables is examined. AL extremes become more frequent and persistent under the RCP8.5 scenario, associated with changes in precipitation and air temperature patterns over North America. Future changes in AL extremes also increase the variability of the sea surface temperature and net heat fluxes in the Kuroshio Extension, the most significant heat and energy flux region of the basin. The increased frequency and persistence of future AL extremes may potentially cause substantial changes in fisheries and ecosystems of the entire Pacific region as a knock-on effect.

Highlights

The Aleutian Low (AL) pressure system is a major climatic feature in the North Pacific, formed over the Aleutian Islands during boreal winter
AL variability is primarily linked to the North Pacific decadal climate v ariability[23,24], which is a major source of uncertainty in the near-future model SLP projections[49]
Observational and modelling studies have demonstrated that internal variability alone can generate El Niño–Southern Oscillation (ENSO)-like responses in the North Pacific atmospheric s ystem[50]

Summary

Introduction

The Aleutian Low (AL) pressure system is a major climatic feature in the North Pacific, formed over the Aleutian Islands during boreal winter. The magnitude of the AL pressure anomalies and the duration of AL events affect the North Pacific ocean conditions by altering the wind stress curl and wind speed (e.g.11–13), with knock-on effects on sea surface temperature (SST), sea surface height and net heat flux. The Kuroshio Extension SST and net heat flux variability both drive, and are significantly driven by, the North Pacific atmospheric c irculation[19,20]. ENSO and its associated SST variability in the North Pacific have been considered a precursor to changes in precipitation[27,28] and surface air temperature (SAT) p atterns[29] over the west coast of the United States. To consider wider impacts due to future changes of the AL, its relationship with precipitation and SAT over North America, and the SST and net heat flux over the North Pacific is examined. We quantify the oceanic and atmospheric response that follows the atmospheric extremes by evaluating the change in the dominant period of common variability of the AL SLP and each one of these climate parameters

Methods

Results

Conclusion