1.2C Positive feedback loops Notes

1. A positive feedback loop occurs when a disturbance amplifies itself, pushing a system further away from equilibrium rather than restoring balance.
2. This can cause rapid and sometimes irreversible changes in natural and human systems.

How Positive Feedback Loops Work

1. Positive feedback amplifies initial disturbances rather than counteracting them.
2. The system experiences self-reinforcing cycles, where outputs act to strengthen the original process.
3. Over time, these loops destabilize the system and may lead to a new equilibrium or even system collapse.
4. Unlike negative feedback, which stabilizes a system, positive feedback accelerates change in either direction (increase or decrease).

Key Characteristics

1. Destabilizing: drives systems away from equilibrium.
2. Amplifying: increases deviation from the initial state.
3. Nonlinear: changes accelerate over time rather than occur proportionally.
4. Common in human and natural systems such as climate processes, population dynamics, and resource depletion.

Melting Ice-Albedo Feedback (Climate System)

Process

1. Global temperatures rise due to greenhouse gas emissions.
2. Ice caps and glaciers melt, reducing surface reflectivity (albedo).
3. Less sunlight is reflected, and more solar radiation is absorbed by darker ocean or land surfaces.
4. Temperatures rise further, accelerating more ice melt.

Result

1. A self-reinforcing cycle of warming and melting that destabilizes the climate system.
2. Leads to positive feedback between energy absorption and temperature increase.

Long-Term Implication

1. The system moves away from its original equilibrium toward a new, warmer climate regime.
2. Melting Arctic sea ice contributes to sea-level rise, ocean circulation changes, and increased climate extremes.

Population Growth and Decline

Population Growth Feedback

1. As population increases, reproductive potential (number of breeding individuals) also increases.
2. This leads to more births, further increasing population size.
3. The larger the population, the faster it grows — an exponential growth loop.