Which Ocean Is The Warmest?

The Indian Ocean has the warmest temperatures of the world's oceans.
The Indian Ocean has the warmest temperatures of the world's oceans.
  • Ocean water temperature is important to understand, as it affects global climate and marine ecosystems.
  • The Indian Ocean is the warmest in the world.
  • Ocean surface temperatures have risen by about 1.6°F over the past 100 years, due to global warming.

Considering how large the Earth is, it may be hard to believe that the world’s oceans cover an estimated 71% of its surface! These five giant bodies of water, consisting of the Pacific, Atlantic, Indian, Southern, and Arctic oceans, hold a whopping 96.5% of the world’s water. The temperature of these waters is important to track and understand, as it affects both the global climate and marine ecosystems.

Measurement of Ocean Surface Temperatures

Ocean surface temperature data is used to create a baseline for comparison with future measurements. The results help monitor temperature trends, which biologists, oceanologists, and climate change experts use in their respective fields.

Ocean surface temperature was originally measured through the input port of ships, and with sensors on buoys, but the results were usually inaccurate because of the ocean's stratification and depth variance. So, temperature measurement techniques evolved to include ocean floats and satellite tools that give more accurate results. Today, scientists use a variety of techniques to measure ocean surface temperature. The layer being measured can go to about 1,200 feet below the ocean’s surface.

Ocean Temperatures

Here are the oceans in order of their temperature:

1. Indian Ocean

This ocean is bordered by Asia, Africa, and Australia and is the warmest in the world. Water temperatures of the Indian Ocean range between 66 and 82 degrees Fahrenheit (19 to 30 Celsius) on the ocean’s upper layer. Since it does not connect to the Arctic Ocean, the coldest ocean on Earth, the Indian Ocean stays pretty warm all year round. The warm waters help foster marine life and, because of this, commercial fishing expeditions are popular.

  • Size: about 27,240,000 square miles, including the Persian Gulf and the Red Sea.
  • Depth: about 12,274 feet deep, on average. Its deepest point is 24,442 feet.
  • Volume: about 63,000,000 cubic miles, which is about 19.8% of the Earth’s ocean volume. 
    Palau Islands, Pacific Ocean. Image credit: BlueOrange Studio/Shutterstock

2. Pacific Ocean

The Pacific Ocean hosts many marine animals and provided 60% of the world’s fish in 1996. As the second warmest ocean, much of its surface temperatures is about 70 to 80 degrees Fahrenheit (21 to 27 Celsius), but near the North and South Poles, this goes down to about 28 Fahrenheit (-2 Celsius).

  • Size: it occupies about 63,800,000 square miles of the Earth’s surface, making it the largest ocean in the world
  • Depth: on average, about 14,040 feet. Its deepest point is the Mariana Trench at 36,201 feet, which is the greatest depth found on Earth.
  • Volume: about 171,000,000 cubic miles, or over 30% of the Earth's surface.

3. Atlantic Ocean

The Atlantic Ocean takes up about 20% of the Earth’s surface and 29% of the planet’s water. This ocean's cooler temperatures compared to the Pacific are due to more contact with Arctic waters, and less water volume at the Equator. This ocean's surface temperatures range from about 28 degrees Fahrenheit to above 84 (-2 to 29).

  • Size: about 41,100,000 square miles. 
  • Depth: about 10,925 feet deep, on average. The deepest point is 27,840 feet, at the Puerto Rico Trench.
  • Volume: 74,471,500 cubic miles.

4. Southern Ocean

The Southern Ocean’s Antarctic waters are extremely cold, while its sub-Antarctic waters are slightly warmer. It has surface temperatures ranging from 28 to 50 degrees Fahrenheit (-2 to 10 degrees Celsius).

  • Size: about 7,849,000 square miles. 
  • Depth: between 13,000 and 16,000 feet. The deepest point is the South Sandwich Trench at 23,740 feet.
  • Volume: 17,225,736 cubic miles. 
    The Arctic Ocean. Image credit: Smit/Shutterstock

5. Arctic Ocean

The Arctic Ocean is the coldest ocean, with average temperatures of about 28°F, but with global warming the arctic is heating twice as fast as the rest of the world. This body of water is also the smallest of the world’s oceans.

  • Size: about 5,427,000 square miles. 
  • Depth: 3,406 feet on average. Its greatest depth is 18,210 feet at the Molloy Hole in the Farm Strait.
  • Volume: 4,498,364 cubic miles.

Impacts of Global Warming on Oceans

Some of the recorded effects of global warming include changes in sea surface temperatures and sea-level changes. Ocean surface temperatures have risen by about 1.6°F over the past 100 years, according to National Oceanic and Atmospheric Administration.

This rising of the ocean temperatures will lead to changes to climate patterns around the world, with potentially devastating consequences to ecosystems underwater and out of it. With each passing year, this phenomenon worsens, and the trend gets harder to reverse.


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