Properties of Oceans

Definition: Salinity is the measure of the concentration of salts in water, typically expressed in parts per thousand (ppt or ‰) or practical salinity units (PSU, g/kg).
Formula:
\text{salinity} = \frac{\text{mass of salt (g)}}{\text{mass of ocean water (kg)}}
Relationship with Density:
- Density is defined as \text{density} = \frac{\text{mass}}{\text{volume}}.
- Higher salinity leads to higher density, while higher temperature leads to lower density.

Increases with Depth: Salinity typically increases with depth in the ocean due to the layering of water masses.
Decreases with Depth: Temperature generally decreases with depth.

Mid-Latitudes: Highest salinity due to higher evaporation rates compared to precipitation, intensified by Hadley circulation.
Equator: Lowest salinity due to high precipitation and river runoff.
Coastlines and Polar Regions: Low salinity due to river runoff and sea ice melt, respectively.

Enhanced by:
- Evaporation: Leads to an increase in salinity as water vapor leaves behind salts.
- Sea Ice Formation: During freezing, salt is expelled from the water, increasing salinity around the ice.
Reduced by:
- Precipitation: Adds freshwater and dilutes ocean salinity.
- River Runoff: Introduces freshwater into oceans.

Global Heat Transport: Helps balance heating differences across the globe by moving cooler water toward the equator and warmer water toward the poles.
Significance: At low latitudes in the Northern Hemisphere, oceanic circulation is more efficient in transporting heat than atmospheric circulation.

Speed: Surface ocean circulation is faster than deep ocean circulation.
Oceanic Gyres:
- Formed by global wind patterns that create surface currents.
- Ekman Spiral: Resulting spiral motion caused by wind friction and Coriolis effects.
Movement:
- Surface water deflects 20-45° from the wind direction due to wind effects.
- Net movement of water is deflected 90° from the initial wind direction.
- Coriolis Effect:
- In the Northern Hemisphere, deflection is right (clockwise gyres).
- In the Southern Hemisphere, deflection is left (counterclockwise gyres).

Caused By: Divergence of surface water masses that pull water away from each other, causing deeper water to rise.
Process: Deep water replaces surface water, leading to nutrient-rich waters that enhance biological productivity.
Location: Typically occurs at the equator (due to trade winds) and at poles.

Caused By: Convergence of surface water masses where water accumulates and sinks.
Process: Surface water accumulates and sinks, generally occurs in the centers of gyres and along coastlines.

Gyres: Formed due to wind patterns pushing water along coastlines, leading to distinct upwelling and downwelling areas.
Great Pacific Garbage Patch: An area of the Northern Pacific Ocean where vast amounts of plastic accumulate due to gyre activity.

Types:
- Western Boundary Currents: Carry warm water from the equator to poles. Faster, deeper, and narrower flow.
- Eastern Boundary Currents: Bring cold water from poles to tropics.
Example: Gulf Stream is a critical component of deep ocean circulation.

Speed: Much slower than surface circulation, often referred to as the "global conveyor belt."
Thermohaline Circulation: Driven by density differences influenced by temperature and salinity, mixing the ocean and impacting climate.
Deep Water Formation Locations:
- North Atlantic: Surface water evaporates, becoming more saline and denser, causing it to sink.
- Antarctica (Weddell Sea): Similar process but results in even denser water due to lower temperatures.
- These processes lead to the formation of North Atlantic Deep Water and Antarctic Bottom Water.

Definition: A coupled ocean-atmosphere climate event occurring in the Equatorial Pacific every 2–7 years, consisting of El Niño and La Niña phases.
Cycle and Features: Each phase has a duration of 9-12 months, marking variations in precipitation patterns, ocean temperatures, and biological productivity.
Trade Winds: Shift from Eastern to Western Pacific along the equator, altering upwelling and thermocline dynamics.
Precipitation Patterns: Driven by warm surface temperatures resulting in rising moist air and contrasting air pressure zones.

Indices:
- Southern Oscillation Index (SOI): Used to detect atmospheric components of ENSO.
- Oceanic Niño Index (ONI): Monitors oceanic components.
Anomalies:
- Negative Anomalies: Indicate El Niño conditions (Eastern Pacific lower than average, Western higher).
- Positive Anomalies: Indicate La Niña conditions (Eastern Pacific higher than average).

Definition: Predicted points where different components of Earth's system undergo irreversible changes, termed the "point of no return."
Intergovernmental Panel on Climate Change (IPCC): An organization responsible for assessing climate change impacts, creating assessment reports to track progress, impacts, and strategies for adaptation.
Climate Models:
- Representative Concentration Pathways (RCPs): Models forecasted global CO2 concentrations over time.
- Shared Socioeconomic Pathways (SSPs): Models the potential impacts of different policies on global temperatures.

Ocean Heat Content: Increases as average temperatures rise due to climate change.
Ocean Acidification: Caused by excess CO2 dissolving in ocean waters, leading to lower pH levels and detrimental effects on marine life, particularly corals.
Oxygen Decreases: Observed in both lakes and oceans, affecting aquatic ecosystems.
Sea Level Rise: Resulting from melting ice caps and thermal expansion of water, increasing storm surge risks.
Changes in ENSO Intensity: Affects global weather patterns and biological productivity.
Coral Bleaching: Leads to the death of symbiotic algae in reef systems, starving coral reefs and threatening marine biodiversity.
Weakening AMOC: Atlantic Meridional Overturning Circulation is less effective in distributing global heat due to changes in ocean circulation.

Sedimentary Rocks (Lithosphere):
- Organic Carbon Compounds: Contain C-C or C-H bonds (e.g., C$2$H$6$O, C$6$H${12}$O$_6$).
- Inorganic Carbon Compounds: No C-C or C-H bonds (e.g., CO$2$, CaCO$3$).
Oceans: Absorb 25% of CO$_2$ released from fossil fuels, leading to ocean acidification.
Fossil Fuels and Soil: Include natural gas, petroleum, coal (organic carbon).
Atmosphere: Contains gaseous CO$_2$.
Organic Biomass: Carbon-containing compounds in living organisms.

Physical Carbon Pump: Transports CO$_2$ across the ocean through thermohaline circulation.
Biological Carbon Pump: Facilitates the cycling of carbon between the atmosphere and oceans through biological processes like photosynthesis and respiration.
Inflow and Outflow:
- Inflow Sources:
1. Respiration (emissions from plants at night).
2. Decay of organic material.
3. Combustion of fossil fuels.
4. Forest fires.
5. Ocean emissions of dissolved CO$_2$.
- Outflow Sources:
1. Terrestrial photosynthesis.
2. Ocean uptake of CO$_2$ through diffusion.