Simulation of the Tropical Thermal Domes in the Atlantic: A Seasonal Cycle

Abstract

A general ocean circulation model is used to analyze seasonal variations in the Guinea Dome and Angola Dome regions. The cold Guinea Dome develops from June through September due to active divergence of heat transport. The cooling is related to upwelling generated by the local wind stress curl associated with the northeast trade winds. The Guinea Dome thus provides an active mechanism of absorbing heat from the atmosphere. The coastal Guinea region experiences semiannual warming in April- July and November-December due to intrusion of coastal downwelling Kelvin waves from the equatorial region. The Angola Dome in the Southern Hemisphere is found to be cooled from March through August. The surface flux plays a major role in the seasonal variation of the heat budget in contrast to the situation of the Guinea Dome in the Northern Hemisphere. The Angola front located at the northern border of the cold Angola Dome becomes distinguishable particularly during the boreal fall because of the intrusion of warm water from the equatorial region. The coastal warming occurs twice a year in both hemispheres mostly due to intrusion of warm water accumulated in the eastern border of the Gulf of Guinea. The semiannual relaxation of the trade winds east of 30 degrees W as well as the semiannual intensification of the eastward component of the West African monsoon is responsible for this remarkable oceanic phenomenon.