Where to Look for Recent Decadal Ocean Temperature and Salinity Changes: a CMIP Model Density Analysis
[18-Dec-2014] Guilyardi, E., Durack, P., and Gleckler, P.
Presented at the 2014 AGU Fall Meeting
Multi-decadal ocean temperature and salinity changes, a key element of climate variability and change, is not well constrained by available observations. Recent observed assessments have highlighted coherent long-term temperature and salinity changes that appear consistent with CMIP multi-model mean assessments, however there are discrepancies in the absolute magnitude of these observed and simulated changes. In this study, we use global climate models (from the CMIP5 and CMIP3 model suites) and a number of available observational analyses to investigate the global and regional distribution of temperature and salinity changes in neutral density space. Unlike the classical fixed-depth diagnostics, isopycnal analysis provides a lagrangian view of ocean property changes that can be directly related to surface fluxes and upper ocean water mass transformation, while essentially ignoring isopycnal heave. The comparison of pre-industrial and historical (1860-2005) simulations allows us to precisely describe where the heat and salt is stored as a result of modified forcing, leveraging off a large suite of similarly forced simulations. We also evaluate the modeled global and regional isopycnal climatologies against recent (ARGO) observations with better spatio-temporal coverage, to investigate model performance.