The Impact of Tropical Sea Surface Temperatures on the Chemistry and Dynamics of the Stratosphere in the GEOSCCM

Simulations of past and future climate were conducted using the GEOS coupled chemistry/climate model (CCM). These runs were conducted using 1) Hadley Center observed, 2) Hadley Center Global Environmental Model, Version 1 (HadGEM1) predicted, and 3) NCAR CCSM predicted sea surface temperatures (SSTs). Significant differences in the chemistry and dynamics are seen between these simulations. HadGEM1 SSTs, which have a cold bias, produce significant differences in the age-of-air, ozone, methane oxidation, and tropopause pressure compared to those produced using NCAR CCSM SSTs which are more consistent with observations. The quantitative differences in age-of-air can be related to differences in tropical SSTs. This has implications as to the cause of the increased tropical upwelling seen in this as well as almost all other models simulating our future climate. We will discuss some of the possible causes of these changes and the importance of properly simulating SSTs as we move in the future toward fully coupled chemistry/climate/ocean general circulation models.