The Affect of Altered Ocean Heat Transports on Climate: Feedback Potential During Periods of Atmospheric Trace Gas Increase

Abstract ATM-9320372 Chandler, Mark A. Martinson, David Gornitz, Vivien M. Rind, David H. Columbia University Title: The Affect of Altered Ocean Heat Transports on Climate: Feedback Potential During Periods of Atmospheric Trace Gas Increase The objective of this project is to investigate the decadal to century-scale affects of ocean heat transports in numerical climate change simulations. The project uses the Goddard Institute for Space Studies atmospheric general circulation model, coupled to an ocean model that includes meridional transport of heat by the oceans, to test directly whether changes in ocean heat transport could enhance or ameliorate the effects of trace-gas-induced global warming. The project is designed as a three year, two phase study: In the first phase, surface heat flux diagnostics from GCM experiments will be used to calculate the potential ocean heat transport associated with historical (20th century) anomalies in sea surface temperatures and sea ice extent. The SST and sea ice anomalies will be acquired from the most comprehensive data sets available including: COADS, Navy/NOAA, Walsh, ESMR, SMMR, and SMM/I, all of which are currently in-house. In addition, ocean heat transports will be calculated from GCM simulations and proxy data from the Little Ice Age (ca. 1700 AD) and Last Glacial Maximum (ca. 18-2lky BP) in order to obtain larger variations of heat fluxes that may be closer to the potential variability of the system. The second phase of the project focuses on simulations of the climatic effects of altered ocean heat transports in conjunction with transient trace gas increase scenarios. Ten 100- year simulations are planned in which the ocean heat values, calculated in phase one, will be used to perturb the normal pattern of climate change associated with the atmospheric trace gas increase. The simulations in phase two will take approximately two years to complete, based on estimates of the current comput ational efficiency of the GISS 4ox5o GCM running on IBM RS/6000-580 workstation. Individual transient experiments will be completed and analyzed at the rate of one every three months. The primary objective of this project is to identify patterns of climate change that are associated with variability in the air/sea/ice system and to estimate the potential ocean energy feedbacks that may accompany climate changes induced by atmospheric trace gas increase. Fingerprinting of such climate patterns will improve our ability to detect the signs of ocean-induced climate change and can improve our ability to distinguish between natural variability and anthropogenic climate change. Furthermore, it will provide us with a quantitative assessment of the oceans ability, through energy transport feedbacks, to alter the climate sensitivity and GCM predictions of future climate change. In lieu of fully coupled atmosphere-ocean-ice models, which are unlikely to reach a reliable predictive capacity in the near future, these experiments provide the realistic alternative for gauging the ability of the oceans to alter GCM future climate diagnoses. This project is funded under the USGCRP NSF Climate Modeling, Analysis and Prediction program.