Atlantic Thermohaline Circulation and its Response to Increasing CO2 in a Coupled Atmosphere—Ocean Model

PDF: http://data.dhkim.info/monograph/GRL/2001GL013325.pdf


GEOPHYSICAL RESEARCH LETTERS, VOL. 28, NO. 22, PAGES 4223–4226, 2001

Atlantic Thermohaline Circulation and its Response to Increasing CO2 in a Coupled Atmosphere—Ocean Model

Shan Sun

NASA Goddard Institute For Space Studies, New York, New York

Rainer Bleck

Los Alamos National Laboratory, Los Alamos, New Mexico

Abstract

We discuss aspects of the Atlantic thermohaline circulation (THC) and its response to increased greenhouse gas concentration, using a coupled atmosphere-ocean general circulation model (AOGCM) whose oceanic component is a new hybrid-isopycnal model. Two 200-year model integrations are carried out — a control run assuming fixed atmospheric composition and a perturbation run assuming gradual doubling of CO2. We employ no flux corrections at the air-sea interface, nor do we spin up the ocean prior to coupling. The surface conditions in the control run stabilize after several decades. When doubling CO2 at the rate of 1% per year, the model responds with a 2°C increase in global mean surface air temperature (SAT) after 200 years and a virtually unchanged Atlantic meridional overturning circulation. The latter is maintained by a salinity increase that counteracts the effect of global warming on the surface buoyancy. © 2001 American Geophysical Union

Index Terms: 1620 Global Change: Climate dynamics (3309); 1630 Global Change: Impact phenomena; 4215 Oceanography: General: Climate and interannual variability (3309); 4255 Oceanography: General: Numerical modeling.