---
title: "Ocean Conveyor Belt — AP Enviro Definition & Exam Guide"
description: "The ocean conveyor belt is the global current system that moves heat around the planet. Learn how it shows up in AP Enviro Unit 9 climate change questions."
canonical: "https://fiveable.me/ap-enviro/key-terms/ocean-conveyor-belt"
type: "key-term"
subject: "AP Environmental Science"
unit: "Unit 9"
---

# Ocean Conveyor Belt — AP Enviro Definition & Exam Guide

## Definition

In AP Environmental Science, the ocean conveyor belt is the global system of oceanic currents (thermohaline circulation) that carries heat throughout the world's oceans, and disruptions to it can significantly shift regional and global climate patterns.

## What It Is

The ocean conveyor belt is essentially Earth's central heating system, but instead of pipes it uses seawater. Warm surface [water](/ap-enviro/unit-6/hydrogen-fuel-cell/study-guide/VBHYpOxkIwXQuPkI6px8 "fv-autolink") flows from the tropics toward the poles, cools, gets saltier and denser, sinks, and then creeps back along the deep ocean floor before rising again somewhere else. That whole loop is driven by differences in temperature and [salinity](/ap-enviro/key-terms/salinity "fv-autolink"), which is why it's also called **thermohaline circulation** (thermo = heat, haline = salt).

The key idea in essential knowledge STB-4.F.5 is that these currents move heat around the planet. When the currents speed up, slow down, or change course, [climate](/ap-enviro/unit-1/terrestrial-biomes/study-guide/itE0pooQYg0jGiYtQnws "fv-autolink") changes with them. A classic example: melting Greenland ice dumps cold freshwater into the North Atlantic. That fresh water is less dense, so it doesn't sink as easily, which can slow the whole conveyor down and cool the regions that depended on that warm water delivery (like Western Europe).

## Why It Matters

This term lives in **[Unit 9](/ap-enviro/unit-9 "fv-autolink"): Global Change**, specifically topic **9.5 Global Climate Change**, and it backs learning objective **[AP Enviro](/ap-enviro "fv-autolink") 9.5.A** (explain how short- and long-term climate changes impact ecosystems). It sits right next to essential knowledge STB-4.F.4 about atmospheric circulation, so the CED wants you to see the ocean and the atmosphere as two heat-moving systems working together. The big-picture theme is that climate isn't just about average temperature, it's about the circulation patterns that distribute heat, and disrupting those patterns has ecosystem and regional consequences.

## Connections

### Hadley cells and the jet stream (Unit 9)

Think of these as the atmosphere's version of the conveyor belt. [Hadley cells](/ap-enviro/key-terms/hadley-cells "fv-autolink") and the jet stream move heat through the air the way ocean currents move it through water, and the CED pairs them in STB-4.F.4 and STB-4.F.5. Climate change can knock both off their usual patterns.

### Glacier melt and positive feedback loops (Unit 9)

Melting Greenland and polar ice pours [freshwater](/ap-enviro/unit-5/irrigation-methods/study-guide/Kr9Iykj8aAtyXWOCln7c "fv-autolink") into the North Atlantic, which dilutes the salty water that's supposed to sink. Less sinking means a slower conveyor, which can amplify regional cooling, a feedback chain you should be able to trace start to finish.

### Photic zone and marine ecosystems (Unit 9)

The conveyor belt connects to STB-4.F.3 because currents carry nutrients and heat that [marine ecosystems](/ap-enviro/key-terms/marine-ecosystems "fv-autolink") depend on. Shifting currents and sea level change which communities still sit in the sunlit photic zone where photosynthesis happens.

## On the AP Exam

Expect this term in Unit 9 multiple-choice stems built around cause-and-effect chains. A very common setup gives you freshwater from melting Greenland ice flowing into the North Atlantic and asks what happens to thermohaline circulation (answer: it slows, because added freshwater reduces density and weakens the sinking that drives the loop). Other stems ask how a conveyor slowdown affects coastal climates, or ask you to distinguish ocean circulation from atmospheric circulation. On FRQs, you'd use this term to explain a mechanism: how heat gets redistributed, why a disruption cools or warms a region, and what that does to marine ecosystems. Be ready to walk through the steps, not just name the term.

## ocean conveyor belt vs Atmospheric circulation (Hadley cells / jet stream)

Both move heat around the globe, but the ocean conveyor belt does it through water using temperature and salinity (thermohaline) differences, while atmospheric circulation does it through air using Hadley cells and the jet stream. A question asking for 'atmospheric circulation affecting climate' wants the air system, not the ocean currents.

## Key Takeaways

- The ocean conveyor belt, also called thermohaline circulation, is the global current system that moves heat through the world's oceans.
- It's driven by differences in temperature and salinity: warm water cools, gets saltier and denser, and sinks, then flows back along the deep ocean.
- Freshwater from melting ice (like Greenland) dilutes the salty water, reduces its density, and can slow the whole conveyor down.
- A slowdown cools regions that depend on warm-water delivery, which is why Western Europe is the classic example.
- It connects to learning objective AP Enviro 9.5.A and pairs with atmospheric circulation (Hadley cells, jet stream) as Earth's two heat-moving systems.

## FAQs

### What is the ocean conveyor belt in AP Environmental Science?

It's the global system of oceanic currents, also called thermohaline circulation, that carries heat throughout the world's oceans. It shows up in Unit 9, topic 9.5, under essential knowledge STB-4.F.5.

### Does melting ice speed up or slow down the ocean conveyor belt?

It slows it down. Freshwater from melting ice is less dense than salty seawater, so it doesn't sink as easily, which weakens the sinking that drives the whole conveyor loop.

### How is the ocean conveyor belt different from atmospheric circulation?

Both move heat around the globe, but the conveyor belt uses ocean water driven by temperature and salinity, while atmospheric circulation uses air through Hadley cells and the jet stream. Watch the wording on a question to know which one it's asking about.

### How does a slowdown in the ocean conveyor belt affect climate?

It changes how heat is distributed regionally. Areas that rely on warm-water delivery, like Western Europe, can cool down even as the planet overall warms, which is why circulation disruption is a big deal in climate questions.

### Is thermohaline circulation the same thing as the ocean conveyor belt?

Yes. Thermohaline circulation is the technical name, and it describes the same global current system. 'Thermo' refers to heat and 'haline' refers to salt, the two factors that drive it.

## Related Study Guides

- [9.5 Global Climate Change](/ap-enviro/unit-9/global-climate-change/study-guide/7uD60uqTmhzrFIlNVpw9)

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