Tropical Pacific influences on the North Atlantic Thermohaline Circulation

M Latif M Latif

doi:10.4401/ag-3392

Abstract

Most global climate models simulate a weakening of the North Atlantic thermohaline circulation (THC) in response to enhanced greenhouse warming. Both surface warming and freshening in high latitudes, the so-called sinking region, contribute to the weakening of the THC. Some models simulate even a complete breakdown of the THC at sufficiently strong forcing. Here results from a state-of-the-art global climate model are presented that does not simulate a weakening of the THC in response to greenhouse warming. Large-scale air-sea interactions in the tropics, similar to those operating during present-day El Ninos, lead to anomalously high salinities in the tropical Atlantic. These are advected into the sinking region, thereby increasing the surface density and compensating the effects of the local warming and freshening. The results of the model study are corroborated by the analysis of observations.

Highlights

The Atlantic Thermohaline Circulation (THC) is an important component of the global climate system (Broecker, 1991)
The THC is forced partly by convection at high latitudes, which causes dense surface waters to sink to deeper ocean layers, forming the so-called North Atlantic Deep Water (NADW)
The range of this internal THC variability is consistent with that simulated by other global climate models (Delworth et al, 1993; Timmermann et al, 1998)

Summary

Introduction

The Atlantic Thermohaline Circulation (THC) is an important component of the global climate system (Broecker, 1991). It transports about 1 PW of heat poleward in the North Atlantic, thereby warming Western Europe. Mojib Latif shown that flux correction may cause misleading results (e.g., Neelin and Dijkstra, 1995). It should be noted, that many studies addressing the stability of the THC have been conducted with flux-corrected models (e.g., Manabe and Stouffer, 1994). The effects of anthropogenic sulfate emissions are not included in the simulation

Results

Further modeling and observational evidence

Concluding remarks