A Mechanism for Abrupt Climate Change Associated with Tropical Pacific SSTs*
- 15 January 2006
- journal article
- Published by American Meteorological Society in Journal of Climate
- Vol. 19 (2) , 242-256
- https://doi.org/10.1175/jcli3608.1
Abstract
The tropical Pacific’s response to transiently increasing atmospheric CO2 is investigated using three ensemble members from a numerically efficient, coupled atmosphere–ocean GCM. The model is forced with a 1% yr−1 increase in CO2 for 110 yr, when the concentration reaches 3 times the modern concentration. The transient greenhouse forcing causes a regionally enhanced warming of the equatorial Pacific, particularly in the far west. This accentuated equatorial heating, which is slow to arise but emerges abruptly during the last half of the simulations, results from both atmospheric and oceanic processes. The key atmospheric mechanism is a rapid local increase in the super–greenhouse effect, whose emergence coincides with enhanced convection and greater high cloud amount once the SST exceeds an apparent threshold around 27°C. The primary oceanic feedback is greater Ekman heat convergence near the equator, due to an anomalous near-equatorial westerly wind stress created by increased rising (sinking) air to the east (west) of Indonesia. The potential dependence of these results on the specific model used is discussed. The suddenness and far-ranging impact of the enhanced, near-equatorial warming during these simulations suggests a mechanism by which abrupt climate changes may be triggered within the Tropics. The extratropical atmospheric response in the Pacific resembles anomalies during present-day El Niño events, while the timing and rapidity of the midlatitude changes are similar to those in the Tropics. In particular, a strengthening of the Pacific jet stream and a spinup of the wintertime Aleutian low seem to be forced by the changes in the tropical Pacific, much as they are in the modern climate.Keywords
This publication has 58 references indexed in Scilit:
- An Orbitally Driven Tropical Source for Abrupt Climate Change*Journal of Climate, 2001
- Closing of the Indonesian seaway as a precursor to east African aridification around 3–4 million years agoNature, 2001
- Evidence for a time‐varying pattern of Greenhouse warming in the Pacific OceanGeophysical Research Letters, 2000
- Simulated impacts of historical land cover changes on global climate in northern winterClimate Dynamics, 2000
- The NCAR Climate System Model, Version One*Journal of Climate, 1998
- Sea Surface Temperature and Large-Scale Circulation Influences on Tropical Greenhouse Effect and Cloud Radiative ForcingJournal of Climate, 1997
- An Ocean Dynamical ThermostatJournal of Climate, 1996
- Climatic Equilibrium of the Atmospheric Convective Boundary Layer over a Tropical OceanJournal of the Atmospheric Sciences, 1989
- Analysis of General Circulation Model Sea-Surface Temperature Anomaly Simulations Using a Linear Model. Part I: Forced SolutionsJournal of the Atmospheric Sciences, 1985
- ATMOSPHERIC TELECONNECTIONS FROM THE EQUATORIAL PACIFIC1Monthly Weather Review, 1969