CO2 threshold for millennial-scale oscillations in the climate system: implications for global warming scenarios |
| |
Authors: | Katrin J Meissner Michael Eby Andrew J Weaver Oleg A Saenko |
| |
Institution: | (1) School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Stn CSC, Victoria, BC, V8W 3P6, Canada;(2) Canadian Centre for Climate Modelling and Analysis, Victoria, Canada |
| |
Abstract: | We present several equilibrium runs under varying atmospheric CO2 concentrations using the University of Victoria Earth System Climate Model (UVic ESCM). The model shows two very different
responses: for CO2 concentrations of 400 ppm or lower, the system evolves into an equilibrium state. For CO2 concentrations of 440 ppm or higher, the system starts oscillating between a state with vigorous deep water formation in
the Southern Ocean and a state with no deep water formation in the Southern Ocean. The flushing events result in a rapid increase in atmospheric temperatures, degassing of CO2 and therefore an increase in atmospheric CO2 concentrations, and a reduction of sea ice cover in the Southern Ocean. They also cool the deep ocean worldwide. After the
flush, the deep ocean warms slowly again and CO2 is taken up by the ocean until the stratification becomes unstable again at high latitudes thousands of years later. The
existence of a threshold in CO2 concentration which places the UVic ESCM in either an oscillating or non-oscillating state makes our results intriguing.
If the UVic ESCM captures a mechanism that is present and important in the real climate system, the consequences would comprise
a rapid increase in atmospheric carbon dioxide concentrations of several tens of ppm, an increase in global surface temperature
of the order of 1–2°C, local temperature changes of the order of 6°C and a profound change in ocean stratification, deep water
temperature and sea ice cover. |
| |
Keywords: | Millenial-scale oscillations Climate modelling Nonlinear behavior of the climate system Global warming scenarios Carbon cycle |
本文献已被 SpringerLink 等数据库收录! |
|