Dynamic Planet SSSS Notes 2021

The six most abundant ions of seawater include:
- Chloride (Cl−)
- Sodium (Na+)
- Sulfate (SO₄²−)
- Magnesium (Mg²+)
- Calcium (Ca²+)
- Potassium (K+)
These ions comprise about 99 percent of all sea salts by weight.
Other major dissolved substances include inorganic carbon, bromide, boron, strontium, and fluoride.
Notable minor dissolved constituents:
- Inorganic phosphorus
- Inorganic nitrogen (important for the growth of marine organisms)
Seawater also contains atmospheric gases: nitrogen, oxygen, argon, and carbon dioxide.
Dissolved organic substances include carbohydrates and amino acids primarily in the upper 100 meters of the ocean, where photosynthesis converts inorganic carbon to organic matter.
Carbon dioxide from the atmosphere forms weak carbonic acid, which dissolves minerals, creating ions that contribute to salinity.
While water evaporates from the ocean, the salt remains, making up only 3.5% of seawater's weight (the other 96.5% is freshwater).
To create artificial seawater, key compounds to add include NaCl, MgCl₂, Na₂SO₄, and CaCl₂.
Weights of common elements per kg of seawater:
- Cl: 0.9989 g/kg
- Na: 0.556 g/kg
- S: 0.14 g/kg
- Mg: 0.068 g/kg
- Ca: 0.02125 g/kg

The concentration of salt in seawater (salinity) averages about 35 parts per thousand, or 3.5% of seawater's weight.
If all ocean salt was spread evenly across the Earth's land, it would form a layer over 500 feet thick.
Forchhammer's Principle (or the Principle of Constant Proportions) states that major salt proportions remain consistent across different oceanic locations.
Sources of ocean salt include:
- Rocks on land
- Sediment runoff from rivers
- Weathering of continents
- Hydrothermal vents
- Volcanic eruptions and undersea volcanoes.
Rainwater, slightly acidic due to dissolved carbon dioxide, erodes rocks, creating ions that are carried to the ocean through runoff.
The predominant ions in seawater are chloride and sodium, which together account for over 90% of dissolved ions.

Shortwave radiation is part of the visible light spectrum and carries higher energy than longwave radiation.
This radiation from the sun travels through the atmosphere with minimal obstruction, but ozone layer degradation allows more to reach Earth.
When shortwave radiation hits the ground, it is converted into longwave infrared energy due to Earth's cooler temperature.
Energy loss occurs as longwave radiation reflects back into the atmosphere and space as heat waves.
Some greenhouse gases (CO₂, CH₄, N₂O, H₂O) can trap certain radiation wavelengths, increasing atmospheric temperatures.
Light penetration in seawater: Blue light penetrates the deepest, followed by green light.

Latent heat flux refers to heat transfer related to water's evaporation and condensation cycles. It can be calculated using:
$ext{Latent heat flux} = rac{( ext{wind speed} imes ext{latent heat of evaporation} imes ext{heat transfer coefficient} imes ext{density of air} imes ext{specific humidity gradient})}{1000}$
Latent heat is the energy needed for phase changes, with water’s latent heat of vaporization at 22.6 x 10⁵ J/kg, meaning that much energy is needed to convert 1 kilogram of water at 100°C from liquid to gas.
The overall heat transfer coefficient is key for estimating heat transfer through walls or various materials based on their properties and the adjacent fluids.

Wind-driven surface currents are typically confined to the uppermost 100m of the ocean, often referred to as the mixed layer.
- These currents are affected by wind, precipitation, and temperature changes.
The pycnocline is characterized by rapid density changes due to temperature and salinity shifts; it usually extends between 500 to 1000 m depth.
Deep ocean layer:
- Cold, dark waters below the pycnocline where density increases gradually.
Thermocline exists in warmer regions where temperature variations create density differences.

Epipelagic Zone (Surface/Sunlight Zone): 0-656 feet with ample light; contains most marine life and is crucial for photosynthesis.
Mesopelagic Zone (Twilight Zone): 656-3281 feet, some light penetration; unique species adaptations.
Bathypelagic Zone (Midnight Zone): 3281-12124 feet; little to no light.
Abyssopelagic Zone: 13124-19686 feet; cold, dark, high-pressure environments with limited life.
Hadalpelagic Zone (Trenches): Below 19686 feet; extreme conditions, difficult for organisms to survive.

Heat and density differences drive ocean currents; thermohaline circulation describes this process where cold, dense water sinks.
Ekman transport describes how winds influence surface currents, creating net water movement at angles to wind direction.

Tidal currents are influenced by the gravitational interplay between the Moon and Earth, characterized by alternating periods of high (flood) and low (ebb) tides.
Tidal amplitude varies cyclically due to factors like the position of the moon and sun in relation to Earth.
Wave heights and frequencies are characterized as follows:
- Wave height: vertical distance from crest to trough.
- Wavelength: horizontal distance between crests or troughs.
- Wave steepness: height relative to wavelength.

Sonar uses sound waves to measure underwater distances and map topographical features.
Various instruments measure temperature, salinity, oxygen levels, and other oceanic conditions, including:
- Hydrometer: measures salinity based on water density.
- Drogues: track currents over long distances.
- ADCP: Acoustic Doppler Current Profiler, maps water velocity at varying depths.

Biogenous sediments originate from the remains of marine organisms, notably plankton, contributing significantly to ocean floor composition.
Hydrogenous sediments form through precipitation processes within seawater.

Global currents like the Gulf Stream influence regional climates by transporting warm water northward; conversely, cold currents like the Humboldt Current impact coastal cooler temperatures.
El Niño and La Niña variations significantly affect global weather patterns and climatic conditions.

Understanding both physical and biological oceanic processes can aid in predicting climate change impacts, driving policies that address the consequences of rising sea levels, and protecting marine life under changing atmospheric conditions.