Why does the ocean circulate, and how do currents move heat around the planet?
Explain how ocean surface currents form (winds, the Coriolis effect) and how they redistribute heat, moderate coastal climates and connect to density-driven deep circulation.
A Regents answer on the oceans: how prevailing winds and the Coriolis effect drive surface currents into gyres, how warm and cold currents redistribute heat and moderate coastal climates (for example the Gulf Stream), the difference between surface and density-driven deep circulation, and the link to the water specific heat on the Reference Tables, with worked exam questions.
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What this topic is asking
The Regents wants you to explain how surface ocean currents form (driven by winds and steered by the Coriolis effect), how they redistribute heat and moderate coastal climates, and how they relate to density-driven deep circulation and the high specific heat of water.
How surface currents form
The Reference Tables include a Surface Ocean Currents map showing the major warm and cold currents and the gyres. A common task is to read whether a named current is warm or cold and which way it flows.
How currents move heat and moderate climate
Why water moderates climate: specific heat
This is why coastal areas have milder climates than inland areas at the same latitude: the nearby ocean warms slowly in summer (cooling the coast) and cools slowly in winter (warming the coast), reducing the temperature range. Land, with a low specific heat, heats and cools quickly, giving inland areas larger temperature swings.
Deep, density-driven circulation
Below the wind-driven surface layer, deep currents are driven by density differences set by temperature and salinity. Cold, salty water is denser and sinks; warmer, fresher water is less dense and rises. This thermohaline circulation links the surface and deep oceans in a slow global loop that also moves heat around the planet.
Try this
Q1. State the main force that drives surface ocean currents. [1 point]
- Cue. The prevailing (planetary) winds.
Q2. Explain why a coastal city has a smaller annual temperature range than an inland city at the same latitude. [2 points]
- Cue. Water has a high specific heat, so the nearby ocean warms and cools slowly, moderating coastal temperatures; land heats and cools quickly, so inland areas swing more.
Exam-style practice questions
Practice questions written in the style of NYSED exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Regents (style)1 marksPart A. A warm ocean current flowing along a coast will most likely cause the nearby coastal climate to be (1) cooler and drier (2) warmer and more humid (3) unchanged (4) colder in summer only. Justify your choice.Show worked answer →
A 1-point multiple-choice question. The answer is (2).
A warm current carries warm water poleward and warms the air above it; that air, moving onshore, makes the coastal climate warmer and more humid (warm water evaporates more readily). The Gulf Stream warming western Europe is the classic example. A cold current would make a coast cooler and drier (1). Currents do change coastal climate (3 is wrong). The trap is forgetting that ocean currents transport heat and so moderate the climate of the land they pass.
Regents (style)3 marksPart C. (a) State the main force that sets surface ocean currents in motion. (b) Explain how the Coriolis effect influences the direction of these currents in the Northern Hemisphere. (c) Explain how the high specific heat of water (shown on the Reference Tables) helps the ocean moderate the climate of nearby land.Show worked answer →
A 3-point extended-response question.
(a) 1 point: the prevailing (planetary) winds, which drag the surface water along.
(b) 1 point: Earth's rotation deflects moving water to the right in the Northern Hemisphere (the Coriolis effect), curving the wind-driven currents into clockwise loops called gyres.
(c) 1 point: water has a high specific heat, so it absorbs and releases a great deal of energy with only a small change in temperature; the ocean therefore warms and cools slowly, keeping nearby coastal temperatures milder (cooler summers, warmer winters) than inland areas.
Markers reward winds as the driver, right-deflection/gyres for the Coriolis effect, and the high-specific-heat reasoning for climate moderation.
Related dot points
- Describe the water cycle and its processes, and explain the factors that control infiltration, runoff and groundwater storage (porosity, permeability, slope, saturation and the water table).
A Regents answer on the water cycle and groundwater: evaporation, transpiration, condensation, precipitation and runoff, the factors that control infiltration versus runoff (porosity, permeability, particle size, slope, saturation, vegetation), the water table and zones of saturation and aeration, and the energy that drives the cycle, with worked exam questions.
- Describe the layered structure and composition of the atmosphere and explain how energy is transferred by radiation, conduction and convection, including how surfaces absorb and reflect insolation.
A Regents answer on the atmosphere and energy transfer: the layered structure (troposphere to thermosphere) and temperature profile on the Reference Tables, the composition (nitrogen, oxygen, trace gases), the three modes of heat transfer (radiation, conduction, convection), and how surface color and texture affect the absorption and reflection of insolation, with worked exam questions.
- Explain the factors that control climate (latitude, elevation, proximity to water, ocean currents, mountain barriers and prevailing winds) and distinguish climate from weather.
A Regents answer on climate controls: the difference between weather and climate, how latitude, elevation, proximity to large bodies of water, ocean currents, mountain barriers (orographic effect and rain shadows) and prevailing winds set a region's temperature and precipitation, and why coastal and inland climates differ, with worked exam questions.
- Classify air masses, describe the weather at warm and cold fronts and around high- and low-pressure systems, and interpret weather maps and the Reference Tables station model.
A Regents answer on weather systems: how air masses are classified (maritime/continental, tropical/polar), the weather at cold and warm fronts, high-pressure (clear, sinking, diverging) versus low-pressure (cloudy, rising, converging) systems, the typical west-to-east movement across New York, and how to decode the Reference Tables weather station model, with worked exam questions.
- Explain how the tilt of Earth's axis and its revolution change the angle and duration of insolation through the year, producing the seasons, the solstices and the equinoxes.
A Regents answer on insolation and the seasons: why the 23.5 degree axial tilt and Earth's revolution change the angle and duration of insolation, the solstices and equinoxes, the Sun's path across the sky at New York latitudes, and why summer is warm even though Earth is near aphelion.
Sources & how we know this
- Reference Tables for Physical Setting/Earth Science (2011 edition) — New York State Education Department (2011)
- Regents Examination in Physical Setting/Earth Science — New York State Education Department (2026)