Influence of the Atlantic meridional overturning circulation on the U.S. extreme cold weather

Jianjun Yin,Ming Zhao

doi:10.1038/s43247-021-00290-9

Abstract

Due to its large northward heat transport, the Atlantic meridional overturning circulation influences both weather and climate at the mid-latitude Northern Hemisphere. Here we use a state-of-the-art global weather/climate modeling system with high resolution (GFDL CM4C192) to quantify this influence focusing on the U.S. extreme cold weather during winter. We perform a control simulation and the water-hosing experiment to obtain two climate states with and without a vigorous Atlantic meridional overturning circulation. We find that in the control simulation with an overturning circulation, the U.S. east of the Rockies is a region characterized by intense north-south heat exchange in the atmosphere during winter. Without the northward heat transport by the overturning circulation in the hosing experiment, this channel of atmospheric heat exchange becomes even more active through the Bjerknes compensation mechanism. Over the U.S., extreme cold weather intensifies disproportionately compared with the mean climate response after the shutdown of the overturning circulation. Our results suggest that an active overturning circulation in the present-day climate likely makes the U.S. winter less harsh and extreme.

Highlights

Due to its large northward heat transport, the Atlantic meridional overturning circulation influences both weather and climate at the mid-latitude Northern Hemisphere
In this study, we use a state-of-the-art global weather/climate modeling system with high resolution to investigate the influence of Atlantic Meridional Overturning Circulation (AMOC) on extreme winter weather
Located at the upwind direction of the North Atlantic, mean winter temperatures over the U.S are thought to be less influenced by the AMOC compared with the downwind European side (Fig. 5a and Supplementary Fig. 3b)

Summary

Introduction

Due to its large northward heat transport, the Atlantic meridional overturning circulation influences both weather and climate at the mid-latitude Northern Hemisphere. Without an AMOC and associated northward heat transport, northern and western Europe could be much colder[1,2,5,6,9], the Arctic sea ice could expand[1], the InterTropical Convergence Zone (ITCZ) could shift southward[3,5,9], and sea level along the East Coast of North America could be higher[12] Compared with these changes in the mean climate, the impact of AMOC on extreme weather has not been investigated systematically and sufficiently far. As lowfrequency high-impact events, extreme cold snaps could be disastrous (https://www.ncdc.noaa.gov/billions/), for the U.S southern states with typical mild temperatures during winter[24,25]

Methods

Results

Conclusion