Radiocarbon proxies suggest that the deep waters are poorly ventilated, with the old ventilation age, during the Last Glacial Maximum (LGM). Here we use two transient simulations with tracers of radiocarbon and ideal age to show that the deep water ventilation age is not old at the LGM because of the strong Antarctic Bottom Water transport. In contrast, the ventilation age is older during deglaciation, especially in the deep Pacific, mainly caused by reduced transport of Antarctic Bottom Water.

Based on proxy data and modeling, the Arctic temperature has an asymmetric cooling trend with more cooling over the Atlantic Arctic than the Pacific Arctic during the Holocene, dominated by orbital forcing. There is a seasonal difference in the asymmetric cooling trend, which is dominated by the DJF (December, January, and February) temperature variability. The Arctic dipole mode of sea level pressure and sea ice play a major role in asymmetric temperature changes.