WATER (OCEANS)

Hydrological Cycle

Water is a cyclical source which we can use and re uses it. Water has to go through a cycle from oceans to land and land to Oceans

The Hydrological cycle describes the movement of water on, in and above the earth, it has been working since billion years and all the life on earth depends on it

Next to Air, water is the most important element. Water is distributed uneven on the earth

The Hydrological cycle is the circulation of water within the earth’s hydrosphere in different forms- liquid, gases, solids

The hydrological cycle, also known as the water cycle, describes the continuous movement and exchange of water between the Earth's surface, atmosphere, and various reservoirs, driven by solar energy and gravity. It involves a series of processes that ensure the circulation and distribution of water across the planet.

Key components and processes of the hydrological cycle include:

1. Evaporation: Solar energy heats water bodies (oceans, lakes, rivers, and soil moisture), causing water to evaporate and change from liquid to vapor, rising into the atmosphere.

2. Transpiration: Plants absorb water from the soil through their roots and release it as vapor through small openings in their leaves in a process called transpiration.

3. Condensation: As water vapor rises in the atmosphere, it cools and condenses to form clouds. This process occurs when water vapor changes back into liquid water droplets or ice crystals.

4. Precipitation: When condensed droplets become heavy enough, they fall from clouds to the Earth's surface as precipitation. This includes rain, snow, sleet, or hail.

5. Runoff: Precipitation that doesn't infiltrate into the soil flows over the land surface, forming streams, rivers, and eventually reaching oceans or other bodies of water. Runoff also recharges groundwater.

6. Infiltration: Some precipitation infiltrates into the soil, where it is stored as soil moisture or percolates downward to become groundwater.

7. Storage: Water is stored in various reservoirs such as oceans, ice caps, glaciers, rivers, lakes, groundwater aquifers, and as moisture in the soil.

8. Sublimation and Melting: Sublimation occurs when ice or snow changes directly into water vapor without melting. Melting is the process where ice or snow changes into liquid water.

9. Human Impact: Human activities, including agriculture, urbanization, damming of rivers, deforestation, and pollution, can alter the natural balance of the hydrological cycle, affecting water quality, availability, and distribution.

The hydrological cycle is essential for sustaining life, supporting ecosystems, regulating climate, and shaping landscapes. Understanding this cycle helps manage water resources, predict weather patterns, and address environmental challenges related to water scarcity, flooding, and drought

Relief of the Ocean Floor

Oceans are confined to the great depressions of the earth’s outer layer

Oceans like to merge into one another by themselves not like continents and it is hard to demarcate them

Geographers have divided the oceanic part of the earth into five oceans namely

1. Pacific ocean
2. Atlantic Ocean
3. Indian Ocean
4. Southern Ocean
5. Arctic Ocean

A major portion of the ocean floor is found between 3 to 6km below the sea-level

The relief of the ocean floor refers to its topography or the landscape features found beneath the water surface. The ocean floor is not a uniform plain but contains various formations, including:

1. Mid-Ocean Ridges: These are extensive underwater mountain ranges with volcanic activity where new oceanic crust is formed through seafloor spreading. Examples include the Mid-Atlantic Ridge and the East Pacific Rise.

2. Trenches: Deep, elongated depressions in the ocean floor formed where one tectonic plate is forced beneath another in a process called subduction. The Mariana Trench in the Pacific Ocean is the deepest known trench on Earth.

3. Abyssal Plains: Vast, flat areas of the ocean floor found at considerable depths. They are typically covered by fine sediment and are the flattest regions on Earth's surface. Abyssal plains cover a significant portion of the ocean floor.

4. Seamounts and Guyots: Seamounts are underwater mountains that rise steeply from the ocean floor but do not reach the surface. Guyots are flat-topped seamounts that were once above the surface but have since subsided.

5. Oceanic Plateaus: Large, relatively flat areas of elevated seafloor, often associated with volcanic activity. They are formed by the eruption of large volumes of basaltic lava.

6. Continental Shelves, Slopes, and Rises: Near continents, the ocean floor transitions from the continental shelf (a shallow, gently sloping area extending from the shoreline) to the continental slope (a steeper descent to the abyssal plain) and finally to the continental rise (a gentle slope leading to the abyssal plain).

These features of the ocean floor are the result of various geological processes, including plate tectonics, volcanic activity, erosion, and sedimentation. Mapping and understanding the relief of the ocean floor are crucial for oceanographers, geologists, and marine scientists to study marine ecosystems, ocean currents, seafloor habitats, and the Earth's geological history

Division of Ocean floors

The ocean floors are broadly divided into different regions based on their geological features, depths, and proximity to continents. These divisions help scientists understand the diverse characteristics of the ocean basins. Here are the primary divisions:

1. Continental Margins:

   • Continental Shelf: The shallow, gently sloping area extending from the shore to the shelf break. It's rich in marine life and resources and is typically less than 200 meters (656 feet) deep.
   • Continental Slope: A steeper descent from the shelf break to the ocean floor. It marks the boundary between the continental crust and the oceanic crust.
   • Continental Rise: A gentle incline that leads from the base of the continental slope to the abyssal plain. It's formed by the accumulation of sediments.

2. Abyssal Plain:

   • Abyssal plains are vast, relatively flat areas of the ocean floor found in the deep ocean basins. They cover a significant portion of the Earth's surface underwater and are often covered by fine sediments.

3. Mid-Ocean Ridges:

   • Extensive mountain ranges that run through the middle of the ocean basins, characterized by volcanic activity and seafloor spreading. They mark divergent plate boundaries.

4. Trenches and Deep-Sea Trenches:

   • Deep, elongated depressions formed at subduction zones where one tectonic plate is forced beneath another. The Mariana Trench is the deepest known trench.

5. Seamounts and Guyots:

   • Underwater mountains that rise above the ocean floor, with seamounts having peaks below the ocean surface and guyots having flat tops due to erosion.

6. Oceanic Plateaus:

   • Large, flat, elevated regions of the ocean floor typically associated with volcanic activity and formed by massive eruptions of basaltic lava.

Each of these divisions plays a significant role in oceanography, affecting marine life, currents, geological processes, and resource exploration. The study of these divisions helps scientists understand the dynamics and features of the world's oceans

Minor relief features

The ocean floor hosts various minor relief features that contribute to its diverse topography and habitats. These features, while smaller in scale compared to major divisions like mid-ocean ridges or abyssal plains, are essential in understanding specific areas of the ocean. Some minor relief features include:

1. Rift Valleys: Found along some mid-ocean ridges, these are smaller valleys formed as a result of the spreading of tectonic plates.

2. Hydrothermal Vents: These are fissures on the ocean floor near mid-ocean ridges where superheated, mineral-rich water emerges from beneath the Earth's crust. They support unique ecosystems and are home to specialized organisms.

3. Cold Seeps: Similar to hydrothermal vents, cold seeps are areas where fluids rich in methane, sulfide, and other hydrocarbons seep from the seafloor. They also sustain specific biological communities.

4. Submarine Canyons: Deep, steep-sided valleys cut into the continental slope and sometimes extend across the continental shelf. They're formed by erosion from sediment flows, currents, or tectonic activity.

5. Tidal Rips and Eddies: These are smaller-scale oceanographic features caused by the interaction of tides, currents, and differing water densities. They can create areas of turbulent water.

6. Pockmarks: Indentations or craters on the seafloor caused by the release of gas, often methane, from beneath the seafloor.

7. Sand Waves and Ripples: Formed by the movement of currents, these small-scale features are akin to sand dunes on the seafloor.

8. Mud Volcanoes: Similar to terrestrial volcanoes, these formations release mud, gases, and water instead of lava. They can create small conical structures on the seafloor.

These minor relief features contribute to the overall complexity and biodiversity of the ocean environment. They're crucial in providing habitats for various marine organisms, influencing local oceanography, and shaping specific ecological niches in the ocean

Temperature of ocean waters

The temperature of ocean waters can vary significantly based on several factors, including location, depth, season, and ocean currents. Generally, the temperature of ocean waters can be categorized as follows:

1. Surface Temperatures:

   • Tropical Regions: Near the equator and in tropical regions, surface water temperatures can be relatively warm, typically ranging from 20°C (68°F) to 30°C (86°F) or higher. These warmer waters are characteristic of the tropics and contribute to the formation of tropical climates and diverse marine ecosystems.

   • Temperate Regions: In temperate zones, which are farther from the equator, surface water temperatures vary seasonally. They can range from around 0°C (32°F) in winter to 20°C (68°F) or higher in summer.

   • Polar Regions: Near the poles, especially in the Arctic and Antarctic regions, surface water temperatures are generally cold, often close to or below the freezing point, particularly in the winter months. During the summer, temperatures might rise but still remain relatively cold compared to other regions.

2. Depth and Thermocline:

   • Ocean temperatures decrease with depth. The uppermost layer of the ocean, the epipelagic zone or the sunlit zone, typically has warmer surface temperatures. As depth increases, temperatures drop significantly, reaching cooler conditions in the deeper layers.

   • The thermocline is a boundary layer in the ocean where there's a rapid change in temperature with depth. Below the thermocline, temperatures are relatively stable and cold.

3. Ocean Currents:

   • Ocean currents play a significant role in transporting warm or cold water across different regions. For example, warm ocean currents, like the Gulf Stream in the North Atlantic, can raise water temperatures in the regions they flow through, while cold currents bring cooler waters from polar regions to lower latitudes.

These variations in ocean temperatures influence global climate patterns, marine life distribution, and weather systems. Understanding ocean temperatures is crucial for studying marine ecosystems, predicting weather patterns, and monitoring climate change's impact on ocean temperatures and currents

Factors affecting Temperature distribution

The distribution of temperature across the Earth's surface, including oceans, is influenced by various factors, creating diverse climate patterns and temperature variations globally. Some key factors affecting temperature distribution include:

1. Latitude:

   • Temperature generally decreases from the equator towards the poles. Near the equator, where sunlight is more direct, temperatures tend to be warmer, while at higher latitudes, sunlight is less direct, resulting in cooler temperatures.

2. Altitude:

   • Higher elevations experience lower temperatures. As you move higher in the atmosphere, air pressure decreases, and the air becomes less dense. Due to adiabatic cooling, temperatures drop by about 6.5°C per 1,000 meters (3,280 feet) of elevation gained.

3. Proximity to Water Bodies:

   • Areas near large bodies of water, such as oceans and seas, tend to have more moderate temperatures. Water has a higher specific heat capacity than land, so coastal regions often experience less temperature variability compared to inland areas.

4. Ocean Currents:

   • Ocean currents transport warm or cold water across the globe, influencing nearby coastal climates. Warm currents raise temperatures in adjacent regions, while cold currents have the opposite effect.

5. Prevailing Winds:

   • Wind patterns can affect temperature distribution. For instance, wind blowing from a warm region can raise temperatures in a cooler area, while wind coming from a cold region can lower temperatures.

6. Topography:

   • Features such as mountains, valleys, and coastlines can influence local temperature patterns. Mountains can block or redirect wind, leading to different temperatures on either side (leeward vs. windward sides). Valleys can trap cold air, creating temperature inversions. Coastal areas experience moderated temperatures due to the ocean's influence.

7. Land and Vegetation Cover:

   • Different land surfaces and vegetation types absorb and reflect sunlight differently, affecting local temperatures. Urban areas with concrete and asphalt tend to absorb more heat (urban heat island effect) compared to rural areas with more vegetation.

These factors interact in complex ways to create regional climate variations and contribute to the diversity of temperatures observed across the Earth's surface. Understanding these influences is crucial for predicting climate patterns, studying ecosystems, and assessing the impact of climate change

Horizontal and vertical distribution of Temperature

The temperature-depth profile for the ocean shows how the temperature decreases with the increase in the depths

The boundary usually begins at 100-400m below the sea surface and extends several hundred meters downward

The boundary from where there is a rapid decrease in temperature is called thermocline

About 90% of the total volume of water is found below the thermocline in the deep ocean

Temperature structure of oceans over middle and lower latitudes can be described in three layers

Salinity of waters

The salinity of ocean waters refers to the concentration of dissolved salts, primarily sodium chloride (table salt), and other minerals in seawater. It's typically measured in parts per thousand (ppt) or practical salinity units (PSU), representing the amount of salt dissolved in seawater.

Key points about ocean salinity:

1. Average Salinity: The average salinity of the world's oceans is around 35 parts per thousand (ppt) or 35 PSU. This means that for every 1,000 grams of seawater, approximately 35 grams are dissolved salts.

2. Factors Affecting Salinity:

   • Evaporation and Precipitation: Regions with high evaporation rates and low precipitation tend to have higher salinity because water evaporates, leaving salts behind.
   • River Runoff: Freshwater from rivers and streams can dilute seawater, reducing its salinity, especially near river mouths and coastal areas.
   • Ice Formation/Melting: During freezing, seawater's salinity increases as the ice formed is mostly freshwater, leaving behind higher concentrations of salts in the remaining liquid.
   • Ocean Currents: Ocean currents can transport water with different salinity levels across regions, affecting local salinity.

3. Salinity Variation: Salinity can vary across different ocean regions. For example, the Red Sea has higher salinity due to high evaporation rates and limited freshwater input, while areas near the poles might have lower salinity due to melting ice adding freshwater.

4. Halocline: The ocean often exhibits layers of varying salinity, known as haloclines, where abrupt changes in salinity occur with depth. These layers can affect ocean currents and marine life distribution.

5. Importance of Salinity: Salinity plays a crucial role in ocean density, which influences ocean currents and circulation. It also affects the freezing point and buoyancy of seawater, impacting marine organisms' survival and distribution.

6. Impact of Climate Change: Climate change can influence ocean salinity patterns due to changes in precipitation, melting ice, and alterations in ocean circulation, potentially affecting marine ecosystems.

Maintaining a balance in ocean salinity is vital for the health of marine ecosystems, as many organisms have specific tolerances to salinity levels. Monitoring changes in ocean salinity helps scientists understand the impacts of climate change and human activities on marine environments