6.2 Ocean Water Properties and Movements
5 min read•august 14, 2024
Ocean water's properties and movements shape Earth's climate and ecosystems. , , and variations create layers in the ocean, influencing global circulation patterns. These factors drive the , a crucial system for heat distribution.
and , opposite phases of a climate pattern, dramatically affect ocean conditions. These events alter sea surface temperatures, wind patterns, and marine life, causing widespread impacts on weather and ecosystems worldwide.
Ocean water properties
Salinity and its influencing factors
Top images from around the web for Salinity and its influencing factors
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
1 of 3
Top images from around the web for Salinity and its influencing factors
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
5.3 Salinity Patterns – Introduction to Oceanography View original
Is this image relevant?
1 of 3
- Salinity is the measure of dissolved salts in ocean water, with an average salinity of 35 parts per thousand (ppt) or 3.5% salt content
- The two main factors affecting ocean water salinity are:
- , which increases salinity by removing fresh water and leaving behind dissolved salts (Mediterranean Sea)
- and freshwater input from rivers, which decrease salinity by adding fresh water to the ocean (Baltic Sea)
- Other factors influencing salinity include sea ice formation and melting, as well as the mixing of water masses with different salinities
Temperature and density variations
- Ocean water temperature varies with depth and latitude
- Warmer temperatures occur near the surface and equator due to increased solar radiation (tropical oceans)
- Colder temperatures are found in deeper waters and near the poles, where there is less solar radiation and more heat loss to the atmosphere (Arctic Ocean)
- Density of ocean water is determined by its salinity and temperature
- Higher salinity and lower temperature result in higher density
- Colder, saltier water is denser than warmer, fresher water, leading to layering of ocean water (Antarctic Bottom Water)
- The relationship between temperature, salinity, and density is described by the equation of state for seawater, which is used to calculate water density based on these properties
Ocean water layering
Stratification based on temperature and salinity
- Ocean water is stratified into layers based on differences in temperature and salinity, which affect water density
- The uppermost layer is the surface mixed layer, which is well-mixed by wind and waves and has relatively uniform temperature and salinity
- The depth of the mixed layer varies seasonally and geographically, typically ranging from 20 to 200 meters (shallower in summer and deeper in winter)
- Below the mixed layer is the thermocline, a region of rapid temperature change with depth, separating the warm surface waters from the colder, denser deep waters
- The depth and strength of the thermocline vary with latitude and season, being shallower and more pronounced in the tropics and during summer (equatorial Pacific)
- The halocline is a layer of rapid salinity change with depth, often found in regions with high freshwater input, such as near river mouths or in polar regions with sea ice melt (Amazon River plume)
Deep ocean characteristics
- Beneath the thermocline and halocline lies the deep ocean, characterized by cold, dense, and relatively homogeneous water
- Deep ocean water has a relatively constant temperature of around 2-4°C and a salinity of about 34.6-35.0 ppt
- The deep ocean is divided into several distinct water masses based on their formation regions and properties, such as North Atlantic Deep Water and Antarctic Bottom Water
- These water masses slowly circulate throughout the global ocean, taking hundreds to thousands of years to complete a full circuit (radiocarbon dating of deep water)
Thermohaline circulation
Driving forces and circulation patterns
- Thermohaline circulation, also known as the global ocean conveyor belt, is the large-scale movement of ocean water driven by differences in temperature and salinity
- The circulation pattern is initiated in the North Atlantic, where cold, dense water sinks and flows southward along the ocean bottom, eventually in the Indian and Pacific Oceans (North Atlantic Deep Water formation)
- The sinking of cold, dense water in the North Atlantic is a key component of the Atlantic Meridional Overturning Circulation (AMOC), which transports warm, salty water northward from the tropics (Gulf Stream)
- In the Southern Ocean, the Antarctic Circumpolar Current (ACC) connects the Atlantic, Indian, and Pacific Oceans, allowing for the global transport of water masses (Drake Passage)
Role in global heat distribution and climate
- Thermohaline circulation plays a crucial role in redistributing heat globally
- Warm carry heat from the equator towards the poles (North Atlantic Current)
- Cold deep currents return cooler water to the tropics (Antarctic Bottom Water)
- The heat transport by ocean currents helps to moderate global climate by reducing the temperature gradient between the equator and the poles
- Changes in thermohaline circulation, such as a slowdown of the AMOC, can have significant impacts on global climate
- A weakening of the AMOC could lead to regional cooling in the North Atlantic and Europe (Younger Dryas event)
- Alterations in thermohaline circulation patterns may also affect the distribution of nutrients and marine productivity (upwelling regions)
El Niño vs La Niña
El Niño characteristics and impacts
- El Niño is the warm phase of the El Niño-Southern Oscillation (ENSO), characterized by weakening of the easterly trade winds and a shift of warm surface water towards the eastern Pacific
- During an El Niño event, sea surface temperatures in the eastern Pacific increase, leading to a decrease in upwelling of cold, nutrient-rich water along the coast (Peruvian anchovy fishery collapse)
- The increased sea surface temperatures during El Niño can lead to changes in global weather patterns
- Increased rainfall in the eastern Pacific and along the west coast of South America (flooding in Peru and Ecuador)
- Drought in the western Pacific, including Australia and Indonesia (bush fires)
- El Niño events can also cause coral bleaching due to increased water temperatures, and alter the distribution and abundance of marine species (Great Barrier Reef bleaching events)
La Niña characteristics and impacts
- La Niña is the cool phase of ENSO, characterized by stronger-than-normal easterly trade winds and a shift of warm surface water towards the western Pacific
- During a La Niña event, sea surface temperatures in the eastern Pacific decrease, leading to increased upwelling of cold, nutrient-rich water along the coast (enhanced Peruvian anchovy fishery)
- The cooler sea surface temperatures during La Niña can result in opposite weather patterns compared to El Niño
- Increased rainfall in the western Pacific, including Australia and Indonesia (flooding)
- Drier conditions in the eastern Pacific and along the west coast of South America (drought in Peru and Ecuador)
- La Niña events can also enhance the formation of tropical cyclones in the Atlantic basin due to reduced wind shear and cooler upper-ocean temperatures (active Atlantic hurricane seasons)
Key Terms to Review (22)
Benthic zone: The benthic zone is the ecological region at the lowest level of a body of water, including the sediment surface and sub-surface layers. This zone plays a crucial role in the ocean ecosystem as it is where various organisms live, feed, and interact with the ocean floor. It is significant for nutrient cycling and is affected by factors such as light availability, water pressure, and sediment composition.
Chlorinity: Chlorinity is a measure of the concentration of chloride ions in seawater, typically expressed in parts per thousand (ppt). It is an important parameter that helps in understanding the salinity and overall composition of ocean water, influencing various properties such as density and buoyancy. By assessing chlorinity, scientists can gain insights into ocean circulation, the distribution of marine organisms, and the chemical processes occurring in the ocean.
Coral reefs: Coral reefs are underwater structures formed by the accumulation of coral polyps, tiny marine animals that secrete calcium carbonate to create a hard skeleton. These vibrant ecosystems are among the most diverse habitats on Earth, providing essential services to marine life and coastal communities while also being highly sensitive to environmental changes.
CTD Casts: CTD casts refer to a method used to collect data on the physical and chemical properties of ocean water, specifically measuring conductivity, temperature, and depth. This technique is essential for understanding the ocean's structure and dynamics, as it helps identify variations in salinity, temperature gradients, and other characteristics that influence ocean currents and ecosystems.
Density: Density is the measure of mass per unit volume of a substance, usually expressed in grams per cubic centimeter (g/cm³) for solids and liquids, and in kilograms per cubic meter (kg/m³) for gases. It plays a crucial role in understanding how materials interact in different states, influencing phenomena such as buoyancy in fluids and the behavior of Earth's layers.
El Niño: El Niño is a climate pattern characterized by the periodic warming of sea surface temperatures in the central and eastern Pacific Ocean. This phenomenon has far-reaching impacts on weather and climate across the globe, influencing rainfall patterns, atmospheric circulation, and oceanic conditions.
Evaporation: Evaporation is the process by which liquid water transforms into vapor, primarily driven by heat energy from the sun. This process plays a crucial role in regulating the Earth's climate and contributes to the movement of water through different systems, such as rivers, groundwater, and oceans. It also acts as a key mechanism in the water cycle, facilitating the transition of water from liquid form into the atmosphere, which ultimately influences weather patterns and precipitation.
Jacques Cousteau: Jacques Cousteau was a French naval officer, explorer, conservationist, and filmmaker who is best known for his pioneering work in marine conservation and oceanography. He co-invented the Aqua-Lung, which revolutionized underwater diving, allowing scientists to study ocean water properties and movements in greater depth and detail. His commitment to the exploration and preservation of marine environments has left a lasting impact on ocean science and environmental awareness.
La Niña: La Niña is a climate pattern characterized by cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean, which influences global weather patterns. This phenomenon can lead to significant changes in atmospheric circulation and wind systems, often resulting in increased rainfall in some regions and droughts in others, affecting both local climates and oceanic conditions.
Marine biodiversity: Marine biodiversity refers to the variety of life forms found in ocean environments, including species diversity, genetic diversity, and ecosystem diversity. This rich tapestry of life is crucial for maintaining healthy ocean ecosystems, supporting food webs, and providing essential services such as carbon sequestration and nutrient cycling.
Matthew Maury: Matthew Maury was a pioneering American oceanographer and navigator, often referred to as the 'Father of Oceanography.' He made significant contributions to the understanding of ocean water properties and movements by mapping ocean currents and developing the first comprehensive oceanographic charts, which greatly advanced maritime navigation and scientific knowledge of the seas.
Neritic zone: The neritic zone is the part of the ocean that extends from the low tide mark to the edge of the continental shelf, typically reaching depths of about 200 meters. This area is characterized by relatively shallow waters that are rich in nutrients and support a diverse array of marine life, making it one of the most productive zones in the ocean. The neritic zone plays a vital role in ocean water movements and properties, influencing temperature, salinity, and biodiversity.
Nutrient Cycling: Nutrient cycling refers to the movement and exchange of organic and inorganic matter back into the production of living matter. This process is essential for ecosystems as it ensures that vital nutrients like carbon, nitrogen, and phosphorus are continuously recycled through various biogeochemical cycles, sustaining life. The cycling of nutrients connects the various components of ecosystems, including living organisms, soil, water, and the atmosphere, maintaining their productivity and health.
Ocean stratification: Ocean stratification is the layering of water in the ocean due to differences in temperature, salinity, and density. This layering affects how water moves, mixes, and interacts within the ocean, leading to distinct layers such as the surface layer, thermocline, and deep water. Understanding ocean stratification is crucial because it influences marine life, nutrient distribution, and overall ocean circulation patterns.
Pelagic zone: The pelagic zone refers to the open ocean environment that extends from the surface down to the ocean floor, excluding coastal and benthic regions. This vast area is crucial for understanding ocean water properties, including temperature, salinity, and currents, as well as supporting a diverse range of marine ecosystems and organisms that contribute to overall ocean biodiversity.
Precipitation: Precipitation refers to any form of water, liquid or solid, that falls from the atmosphere and reaches the Earth's surface. This process plays a crucial role in replenishing water sources, influencing river systems, and impacting climate patterns.
Salinity: Salinity refers to the concentration of dissolved salts in water, typically measured in parts per thousand (ppt) or practical salinity units (PSU). It plays a crucial role in influencing water density, ocean circulation, and marine ecosystems. Variations in salinity can affect the distribution of marine life and the physical properties of seawater, making it a fundamental factor in understanding oceanic processes and the behavior of water bodies.
Surface currents: Surface currents are the horizontal movement of ocean water occurring primarily in the upper 400 meters of the ocean, driven by wind, the Coriolis effect, and the gravitational pull of the moon and sun. These currents are crucial for regulating global climate, distributing heat across the oceans, and influencing weather patterns. They play a key role in transporting nutrients and marine organisms, impacting both ocean ecosystems and human activities.
Temperature: Temperature is a measure of the average kinetic energy of the molecules in a substance, indicating how hot or cold that substance is. In oceanography, temperature plays a critical role in determining ocean water properties, influencing everything from density to circulation patterns. Understanding temperature is essential because it affects marine life, climate systems, and ocean movements.
Thermohaline circulation: Thermohaline circulation is a global system of ocean currents driven by differences in water temperature and salinity, which influence water density. This circulation plays a crucial role in regulating the Earth’s climate by redistributing heat and nutrients across the oceans, impacting marine ecosystems and weather patterns. It is often referred to as the 'global conveyor belt' due to its extensive network of currents that connect various ocean basins.
Tide gauges: Tide gauges are instruments used to measure the change in sea level caused by tides, as well as other phenomena such as storm surges and long-term sea level rise. These devices provide crucial data that helps in understanding ocean water properties and movements, allowing scientists to analyze tidal patterns, predict coastal flooding, and monitor climate change effects on sea levels.
Upwelling: Upwelling is a process in which deep, cold, and nutrient-rich water rises to the surface of the ocean. This phenomenon occurs primarily along coastlines and can significantly impact marine ecosystems by providing essential nutrients that support the growth of phytoplankton, the base of the oceanic food web. Upwelling zones are often associated with high biological productivity, making them vital for fisheries and other marine life.