| Abstract: The presence of low-latitude
circumglobal passage from the late Jurassic (~160 Ma) through the
Miocene (~14 Ma) provides a possible mechanism for increased poleward
ocean heat transport during periods of warm climate and may help explain
low meridional temperature gradients of the past. Experiments using an
ocean general circulation model (GCM) with an energy-balance atmosphere
and idealized bathymetry reveal that, like the modern Drake Passage, a
circumglobal Tethyan Passage might have induced high rates of
wind-driven upwelling of relatively cold and deep water, but at low
latitudes. With no change in radiative forcing, a low-latitude
circumglobal passage increases simulated northern high-latitude
temperatures by 3°–7°C, while tropical temperatures cool by up to 2°C
relative to a scenario with solid meridional boundaries. Combining this
mechanism of heat transport with increased radiative forcing allows
substantial warming of northern high latitudes by 7°–11°C, while
tropical temperatures remain within 3°C of present-day temperatures. |