Section 1_ Ocean Surface Currents (2024~2025; CP).txt

Ocean Surface Currents Overview

One World Ocean and Ocean Basins

• There is one global ocean that is divided into five major ocean basins.

• A Pacific-Centered Map can be used to visualize these.

Formation of the Oceans

1. Volcanic Outgassing Theory: It is theorized that the oceans formed from volcanic eruptions. These eruptions released water vapor into the atmosphere, which later condensed into clouds as the Earth cooled. Over millions of years, this led to rain, filling low points on Earth through watersheds.

2. Comet and Asteroid Theory: Another theory suggests that ice from comets and asteroids crashed into Earth and melted, contributing to the formation of oceans.

How Did the Oceans Become Salty?

• Rainwater dissolves Halite (sodium chloride) deposits on land, and surface runoff carries this dissolved salt into the oceans.

Ocean Surface Currents

1. Ocean Current : An ocean current is the flow of ocean water driven by several factors, including global winds, the Coriolis effect, land placement, and the gravitational pull from the moon, Earth, and sun, as well as differences in water density.

2. Surface Current: This is a stream of water flowing in the upper 100-400 meters of the ocean, primarily caused by wind.

3. Key Component - Angle of Insolation: This refers to the angle at which the sun’s rays strike Earth. The angle affects heating—higher angles (like at the Equator) mean warmer air, while lower angles (like at the poles) result in cooler air.

Global Winds and Currents

• Warm Air Movement: Air at the Equator heats up due to higher solar radiation, rises, and then spreads out at the tropopause (the boundary between the troposphere and the stratosphere).

• 30° Latitude and Beyond: The air cools and sinks at around 30° latitude, creating what are known as Hadley Cells (between the equator and 30°) and Ferrel Cells (between 30° and 60°) along with Polar Cells at the poles.

• Coriolis Effect: Earth's rotation causes winds to bend; thus, winds in the Northern Hemisphere curve to the right, while those in the Southern Hemisphere curve to the left.

Gyres

• A gyre is a large circular flow of ocean surface water influenced by global winds.

• There are five major gyres in the ocean: North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean.

• Gyres in the Northern Hemisphere generally rotate clockwise, while those in the Southern Hemisphere rotate counterclockwise.

Tracking Ocean Currents

• Events like the spilling of shipping containers (e.g., Rubber Duckies, Nike Shoes) into the ocean have been used to track surface ocean currents.

Great Pacific Garbage Patch (GPGP)

• Discovered in 1997 by oceanographer Charles Moore, this cluster of microplastics is found in the Northern Pacific Gyre. Similar patches can be found in all five gyres.

• Plastics pose significant threats to marine life; for example, marine animals can get entangled and suffer deformities due to plastic ingestion.

• NASA has been mapping plastic pollution to understand its impacts better.