Geophysical Fluid Dynamics [chapter]

2012 Fluid Mechanics  
The potential for sea ice-albedo feedback to give rise to nonlinear climate change in the Arctic Ocean region -defined as a nonlinear relationship between polar and global temperature change or, equivalently, a time-varying polar amplification -is explored in IPCC climate models. Five models supplying SRES A1B ensembles for the 21 st century are examined and very linear relationships are found between polar and global temperatures (indicating linear polar region climate change), and between
more » ... e), and between polar temperature and albedo (the potential source of nonlinearity). Two of the climate models have Arctic Ocean simulations that become annually sea ice-free under the stronger CO 2 increase to quadrupling forcing. Both of these runs show increases in polar amplification at polar temperatures above -5 o C and one exhibits heat budget changes that are consistent with the small ice cap instability of simple energy balance models. Both models show linear warming up to a polar temperature of -5 o C, well above the disappearance of their September ice covers at about -9 o C. Below -5 o C, effective annual surface albedo decreases smoothly as reductions move, progressively, to earlier parts of the sunlit period. Atmospheric heat transport exerts a strong cooling effect during the transition to annually ice-free conditions, counteracting the albedo change. Specialized experiments with atmosphere-only and coupled models show that the main damping mechanism for sea ice region surface temperature is reduced upward heat flux through the adjacent icefree oceans resulting in reduced atmospheric heat transport into the region.
doi:10.1016/b978-0-12-382100-3.10013-7 fatcat:fb2n3h4lcnbxpli5hdcoa54s3i