Science Education through Earth Observation for High Schools Module 8: Ocean Currents Measured from Space

Ocean currents influence climate and living conditions for plants and animals, even on land. Like the circulation of air, the global ocean circulation transports energy from the equator towards the poles. Warm surface currents move warm water from the tropics and release heat and moisture into the air at mid to high latitudes. Cold currents move from higher latitudes toward the equator, near the surface and at depth. Water evaporating from warm ocean currents falls on land as rain; hence global vegetation cover is determined by both prevailing winds and the flow of ocean currents. A good knowledge of surface ocean currents is important for reducing the costs of shipping by reducing fuel costs. In the sail-ship era knowing the wind and currents was essential, while today, the round-the-world sailing competitors use surface currents to their benefit. Ocean currents also help to disperse eggs and larvae of many marine life forms, while fronts between different currents are fertile areas, rich in phytoplankton (microscopic marine plants), and important feeding areas for a variety of marine animals. Fishermen the world over know this and take advantage of it, whether they are artisanal fishermen in developing countries, or work from factory ships equipped with the latest satellite technology. The same information is important for environmentalists working to protect endangered species and encourage sustainable development of marine resources.

Ocean currents flow in complex patterns affected by wind, the water's salt and heat content, bottom topography, and the earth's rotation. This module aims at an understanding of the physical principles that drive the global system of surface and deep ocean currents. It shows how our knowledge of ocean circulation may be improved by measuring sea surface topography using satellite altimeters. The module also aims to increase awareness of the role of ocean currents in transporting heat from the equator to the poles, and how cold and warm currents influence our climate by affecting temperature and rainfall in different climate zones.

Ocean currents can be monitored using changes in the sea surface height measured by satellite altimeters. Other remote sensing datasets for example sea surface temperature and chlorophyll concentration, can be used as tracers, following water movement across the oceans.