IPCC AR4 모형에서 나타난 전구 순환 변화

Abstract

Four coupled climate models employed in the 4th Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) are used to investigate robust responses of properties and circulation of the global ocean. The sea surface temperature globally and substantially increases, while the sea surface salinity in the Atlantic and Pacific consistently reveals the opposite anomaly at low and mid latitudes, i.e. the surface water of the Atlantic (Pacific) is saltified (freshened). The deep and bottom water in the Southern Ocean not only is warmed, but also is saltified, which indicates that more amount of warm and saline Circumpolar Deep Water are involved in the Antarctic Bottom Water formation. While the Pacific meridional overturning circulation (MOC) remain unchanged, the Atlantic MOC is consistently weakened, the latter of which leads to negative anomalies in the northward (southward), surface (deep) western boundary currents. It implies that changes in the Atlantic Ocean are mainly affected by the anomalous Atlantic MOC, while changes in the Pacific Ocean are mainly attributed to dynamic and thermodynamic atmosphere-ocean interactions. Due to the weakened Atlantic MOC, waters north of the Antarctic Circumpolar Current (ACC) consistently become light, increasing the meridional density gradient across the ACC, and thus enhancing the thermal wind shear. The volume transport of the ACC, i.e. Drake Passage Throughoutflow, appears to consistently increase.