5.1 Driving forces of ocean circulation
3 min read•july 24, 2024
Ocean circulation is driven by a complex interplay of forces. , density differences, and the work together to create surface currents, deep ocean movements, and global circulation patterns. These forces shape the ocean's behavior and impact climate worldwide.
Solar radiation plays a crucial role in ocean density differences. It affects sea surface temperatures, evaporation, and precipitation patterns. These factors influence water density, drive currents, and contribute to the formation of thermoclines, which separate warm surface waters from cooler depths.
Forces Driving Ocean Circulation
Forces driving ocean circulation
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- Wind stress transfers momentum from atmosphere to ocean generating surface currents and waves through friction between wind and ocean surface
- Affects wave height and direction
- Influences ()
- Density differences create pressure gradients driving caused by variations in temperature and salinity
- Impacts deep ocean currents ()
- Influences circulation
- Coriolis effect deflects moving objects due to Earth's rotation influencing direction of ocean currents
- Strength varies with latitude strongest at poles zero at equator
- Causes clockwise rotation in Northern Hemisphere counterclockwise in Southern Hemisphere (Gulf Stream Benguela Current)
Solar radiation in density differences
- Solar radiation absorption varies with latitude and season highest at equator lowest at poles
- Affects sea surface temperature patterns (Caribbean Sea vs )
- Influences atmospheric circulation patterns (Hadley Cells)
- Temperature gradients create warmer waters near equator cooler waters near poles affecting water density
- Drives surface currents ()
- Contributes to thermohaline circulation ( formation)
- Evaporation and precipitation patterns influenced by solar radiation distribution affect salinity and density of surface waters
- High evaporation areas ()
- High precipitation areas ()
- formation separates warmer surface waters from cooler deep waters
- Varies in depth and strength seasonally and geographically (tropical vs polar regions)
- Impacts vertical mixing and nutrient distribution ( zones)
Ocean Circulation and Global Impacts
Heat and nutrient redistribution
- Heat redistribution transports warm water from equator to poles moderating global climate
- Gulf Stream warms Western Europe
- influences climate of Japan
- Nutrient transport through upwelling supports marine ecosystems and productivity
- Coastal upwelling zones ()
- Equatorial upwelling ()
- Oxygen distribution circulates oxygen-rich surface waters to deeper layers sustaining deep-sea life
- (Eastern Tropical Pacific)
- Deep water formation regions (Labrador Sea)
- Carbon cycle regulation absorbs and stores atmospheric CO2 influencing global carbon balance
- CO2 uptake in cold polar regions
- Outgassing in tropical upwelling zones
Atmospheric vs ocean circulation
- Atmospheric pressure systems affect surface ocean currents
- Subtropical high-pressure systems drive ocean gyres
- Aleutian Low influences North Pacific circulation
- drive major surface currents in tropical regions contributing to equatorial upwelling
- North Equatorial Current
- Westerlies influence mid-latitude ocean gyres affecting poleward heat transport
- Monsoons impact regional ocean circulation and mixing
- -Southern Oscillation alters Pacific Ocean circulation and global weather patterns
- El Niño warm phase
- cold phase
- linked to trade winds and equatorial ocean currents
- Normal conditions strengthen equatorial upwelling
- Weakening during El Niño events
Key Terms to Review (27)
Antarctic Bottom Water: Antarctic Bottom Water (AABW) is a dense, cold water mass formed near the Antarctic continent that sinks to the ocean floor and spreads throughout the deep ocean. This water mass plays a crucial role in global ocean circulation, influencing salinity, temperature, and density relationships, as well as driving forces behind ocean currents. Its formation is primarily driven by the combination of sea ice formation and cooling temperatures, leading to a significant impact on thermohaline circulation and deep ocean currents worldwide.
Antarctic Circumpolar Current: The Antarctic Circumpolar Current (ACC) is the world's largest ocean current, flowing around Antarctica and connecting the Atlantic, Pacific, and Indian Oceans. This current plays a crucial role in global ocean circulation, helping to distribute heat and nutrients while also influencing weather patterns and marine ecosystems in the Southern Hemisphere.
Asian-Australian Monsoon System: The Asian-Australian Monsoon System is a climatic phenomenon characterized by seasonal changes in wind patterns and precipitation, primarily affecting the Asian and Australian regions. This system plays a critical role in regulating weather patterns, influencing ocean circulation, and impacting the ecology and economies of countries like India, Indonesia, and Australia.
Bay of Bengal: The Bay of Bengal is a large body of water located in the northeastern part of the Indian Ocean, bordered by India to the west and north, Myanmar to the east, and the Andaman and Nicobar Islands to the southeast. It plays a crucial role in ocean circulation, influencing climate patterns and monsoon weather systems in South Asia.
Coriolis Effect: The Coriolis Effect is the apparent deflection of moving objects, such as air and water, due to the rotation of the Earth. This phenomenon influences large-scale patterns of movement in the atmosphere and oceans, affecting everything from wind patterns to ocean currents, ultimately playing a significant role in climate and weather systems.
Ekman Transport: Ekman Transport refers to the net movement of water at an angle to the wind direction due to the balance of the Coriolis effect and wind stress. This phenomenon is crucial for understanding surface ocean currents and their role in global circulation patterns, linking wind-driven processes with deeper ocean dynamics, particularly in thermohaline circulation.
El Niño: El Niño is a climate pattern that describes the periodic warming of ocean surface temperatures in the central and eastern Pacific Ocean, typically occurring every two to seven years. This phenomenon has significant impacts on weather patterns globally, affecting oceanic and atmospheric conditions, which in turn influence marine ecosystems, global climate systems, and even human activities like agriculture and fishing.
Global conveyor belt: The global conveyor belt is a large-scale ocean circulation system driven by the differences in temperature and salinity of seawater, which influences climate and marine ecosystems worldwide. This continuous movement of ocean water connects surface currents and deep-sea currents, allowing for the transport of heat, nutrients, and gases across vast distances. Understanding this system reveals how physical properties of seawater affect circulation patterns, as well as the driving forces behind ocean currents and thermohaline circulation.
Gulf stream: The Gulf Stream is a powerful warm ocean current originating in the Gulf of Mexico, flowing up the eastern coast of the United States and across the Atlantic Ocean towards Europe. This current significantly influences global climate, ocean circulation patterns, and the distribution of salinity and temperature in ocean waters.
Indian Ocean Monsoon Circulation: Indian Ocean Monsoon Circulation refers to the seasonal wind patterns that significantly affect weather and ocean conditions in the Indian Ocean region, particularly during the monsoon season. This circulation is driven by the differential heating of land and sea, leading to significant changes in atmospheric pressure, which in turn influences ocean currents and climate patterns across the Indian subcontinent and surrounding waters.
Kuroshio Current: The Kuroshio Current is a warm, northward-flowing ocean current located in the western Pacific Ocean, east of Taiwan and Japan. It plays a crucial role in driving ocean circulation patterns, influencing climate, and supporting marine biodiversity in the region, connecting with other major currents in the ocean system.
La Niña: La Niña is a climate pattern characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean. This phenomenon significantly influences global weather patterns, ocean circulation, and climate variability, often causing shifts in precipitation and temperature across various regions of the world.
Labrador Sea: The Labrador Sea is a body of water located between Greenland and Canada, characterized by its cold, nutrient-rich waters that play a vital role in the North Atlantic Ocean's circulation patterns. This sea is significant for its contributions to thermohaline circulation, where variations in temperature and salinity drive deep ocean currents, affecting global climate and marine ecosystems.
Mediterranean Sea: The Mediterranean Sea is a large sea that connects to the Atlantic Ocean and is bordered by Europe to the north, Africa to the south, and Asia to the east. This sea plays a crucial role in ocean circulation, particularly through its unique water properties, salinity levels, and interaction with surrounding landmasses which influence global climate patterns and marine ecosystems.
North Atlantic Deep Water: North Atlantic Deep Water (NADW) is a type of cold, dense water mass that forms in the North Atlantic Ocean, playing a crucial role in global thermohaline circulation. This water mass is characterized by its low temperatures and high salinity, contributing to the vertical mixing of ocean waters and influencing climate patterns around the world. As NADW sinks and flows southward, it drives deep ocean currents and impacts both local and global climate through its interactions with surface waters and the atmosphere.
North Atlantic Drift: The North Atlantic Drift is a powerful warm ocean current that originates from the Gulf Stream and flows across the North Atlantic Ocean towards northwestern Europe. This current plays a crucial role in moderating the climate of regions it passes through, particularly by bringing warmer temperatures to areas like the British Isles and Scandinavia, thus influencing weather patterns and ecosystems in those regions.
North equatorial current: The north equatorial current is a significant surface ocean current that flows westward across the tropical North Atlantic Ocean, situated just north of the equator. This current is primarily driven by the trade winds and plays a crucial role in the overall circulation of ocean waters, influencing weather patterns and marine ecosystems in the region.
Oxygen minimum zones: Oxygen minimum zones (OMZs) are regions in the ocean where oxygen saturation is extremely low, typically found at depths between 200 and 1,000 meters. These zones form as a result of various biological and physical processes, including decomposition of organic matter and limited mixing of water layers, leading to areas where marine life can struggle to survive due to insufficient oxygen levels.
Pacific Equatorial Divergence: Pacific equatorial divergence is a process that occurs in the central and eastern Pacific Ocean where surface waters move apart due to wind patterns, leading to upwelling of deeper, nutrient-rich waters. This phenomenon is essential for understanding ocean circulation as it plays a critical role in the distribution of nutrients and affects marine ecosystems along the equator.
Peru Current: The Peru Current, also known as the Humboldt Current, is a cold oceanic current that flows northward along the western coast of South America, primarily affecting the coastal waters of Peru and Ecuador. This current plays a critical role in influencing local climate, marine biodiversity, and fishing practices due to its nutrient-rich waters, which support a productive marine ecosystem.
South equatorial current: The south equatorial current is a major ocean current that flows westward across the South Pacific Ocean, located between approximately 10°S and 20°S latitude. This current is an important component of the larger system of ocean circulation, influenced primarily by trade winds and the Earth's rotation, and plays a key role in redistributing heat and nutrients across the ocean's surface.
Thermocline: The thermocline is a distinct layer in a body of water where the temperature changes rapidly with depth, separating warmer surface water from the cooler water below. This temperature gradient plays a critical role in ocean circulation, marine life distribution, and climate regulation, influencing everything from nutrient mixing to weather patterns.
Thermohaline circulation: Thermohaline circulation refers to the large-scale movement of ocean water driven by differences in temperature (thermo) and salinity (haline). This process plays a critical role in regulating Earth's climate, affecting deep ocean currents and influencing weather patterns by redistributing heat around the planet.
Trade winds: Trade winds are steady, prevailing winds that blow from east to west in the tropics, typically between 30°N and 30°S latitude. These winds are crucial for ocean circulation, influencing weather patterns and ocean currents, and play a key role in phenomena such as El Niño and La Niña.
Upwelling: Upwelling is the process where deep, cold, nutrient-rich water rises to the ocean surface, replacing the warmer surface water. This phenomenon is crucial for marine ecosystems as it brings essential nutrients to the upper layers of the ocean, supporting a diverse range of marine life and influencing global ocean circulation patterns.
Walker Circulation: Walker Circulation is a large-scale atmospheric circulation pattern that occurs in the tropical Pacific Ocean, characterized by east-to-west trade winds and the rising of warm, moist air over the western Pacific while cooler, drier air descends over the eastern Pacific. This circulation plays a critical role in influencing oceanic and atmospheric conditions, impacting climate and weather patterns globally, particularly during phenomena such as El Niño and La Niña.
Wind stress: Wind stress refers to the force exerted by the wind on the surface of the ocean, influencing the movement of water and playing a crucial role in ocean circulation. This force is primarily a result of friction between the wind and the water surface, which causes surface currents to form and can lead to larger scale oceanic processes such as gyres and upwelling. Understanding wind stress is essential to grasp how wind patterns affect ocean currents and climate systems.