What Is a Positive Feedback Loop and How Does It Destabilize a System?

A positive feedback loop occurs when a disturbance causes effects that amplify the original disturbance. It destabilizes a system by driving it further from equilibrium, potentially toward a tipping point and a new equilibrium.

This is core SL and HL content in IB ESS Subtopic 1.2, Systems. The mechanism works in a repeating sequence:

1. A system experiences an initial disturbance.
2. The disturbance changes one or more system components.
3. Those changes strengthen the original disturbance.
4. Each cycle produces further change, moving the system away from its previous equilibrium.
5. If the system's resilience is exceeded, it may cross a tipping point, where a relatively small additional change produces a large system-wide response.

A major example is the ice-albedo feedback in the Arctic. Rising atmospheric temperatures melt reflective snow and sea ice. The darker ocean or land exposed beneath has a lower albedo, so it absorbs more incoming solar radiation. This causes additional warming, which melts still more ice.

The system can therefore be represented as:

warming increases $\rightarrow$ ice cover decreases $\rightarrow$ albedo decreases $$ solar-energy absorption increases warming increases.