Atlantic meridional overturning circulation stable over the last 150 years

Albert Parker,Clifford Ollier

doi:10.2478/quageo-2019-0026

Abstract

Abstract The Atlantic Meridional Overturning Circulation (AMOC) describes the northward flow of warm, salty water in the upper layers, and the southward flow of colder water in the deep Atlantic layers. AMOC strength estimates at 41°N latitude based on satellite sea surface height (SSH), and ARGO ocean temperature, salinity and velocity, and finally the difference in between the absolute mean sea levels (MSL) of the tide gauges of The Battery, New York, 40.7°N latitude, and Brest, 48.3°N latitude. Results suggest that the AMOC has been minimally reducing but with a positive acceleration since 2002, has been marginally increasing but with a negative acceleration since 1993, and has not been reducing but only oscillating with clear periodicities up 18 years, 27 years and about 60 years since 1856.

Highlights

The Atlantic Meridional Overturning Circulation (AMOC), is a circulation system characterized by a northward flowing warm, saline water in the upper layers of the Atlantic, a cooling and freshening of the water at higher northern latitudes of the Atlantic in the Nordic and Labrador Seas, and by a southward flowing colder water at depth (Kuhlbrodt et al 2007)
AMOC strength estimates at 41°N latitude based on satellite sea surface height (SSH), and ARGO ocean temperature, salinity and velocity, and the difference in between the absolute mean sea levels (MSL) of the tide gauges of The Battery, New York, 40.7°N latitude, and Brest, 48.3°N latitude
In contrast to the results of Caesar et al (2018), the results provided by Parker (2016) and Parker and Ollier (2016), suggest stability over time windows up to 150 years before present based on the MSL recorded by the tide gauges of The Battery, New York and Brest corrected for absolute land subsidence

Summary

Introduction

The Atlantic Meridional Overturning Circulation (AMOC), is a circulation system characterized by a northward flowing warm, saline water in the upper layers of the Atlantic, a cooling and freshening of the water at higher northern latitudes of the Atlantic in the Nordic and Labrador Seas, and by a southward flowing colder water at depth (Kuhlbrodt et al 2007). Willis and Fu (2008), Willis (2010), Hobbs and Willis (2012) proposed satellite observations of sea surface height (SSH) along with temperature, salinity and velocity from profiling floats to estimate changes in the north-ward flowing, upper limb, of the AMOC at latitudes around 41°N. This overturning had somewhat smaller seasonal and inter-annual variability than at lower latitudes. Inferred from mean absolute sea level, the AMOC has not changed strength since 1856 but only oscillated

Method

Conclusions