Mechanisms of Atlantic Multidecadal Variability Intiated by Ocean Thermohaline Dynamics

Seminar by Dr. Who Myung Kim from Climate and Global Dynamics Laboratory, National Center for Atmospheric Science

17 July 2019
KST 15:30 – 16:30

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

Atlantic multidecadal variability (AMV) of sea surface temperature (SST) is a key source of climate variability in surrounding regions. Low frequency Atlantic meridional overturning circulation (AMOC) variability is often invoked as a key driving mechanism of AMV. However, some recent studies have argued that AMV is attributable primarily to surface heat fluxes from the atmosphere either through stochastic atmospheric processes or radiative forcing associated with anthropogenic aerosols.

In this presentation, we first review theses recent debates focusing on the recently published studies by the authors that dispute such direct atmospheric surface forcings as prime drivers of AMV. Secondly, using coupled ensemble experiments designed to isolate the climate response to buoyancy forcing associated with the North Atlantic Oscillation in the Labrador Sea, we show that thermohaline circulation changes are the essential drivers of AMV and related climate impacts. Atmospheric teleconnections also play an important role in rendering the full AMV pattern by transmitting the ocean-driven subpolar SST signal into the rest of the basin including the tropical North Atlantic, which has been claimed as the key forcing area for many AMV-related climate impacts. That the atmosphere drives the tropical part of AMV in our experiments calls into question the realism of widely-adopted protocols for AMV pacemaker experiments in which the atmosphere primarily responds to prescribed AMV SST anomalies.