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A melting world-shaped glacier

A melting world-shaped glacier (Petmal, iStockphoto)

STEM in Context

What is Ocean Warming and Why Does It Matter?

CarolAnne Black

Summary

Oceans absorb the greatest amount of solar radiation on Earth. Ocean warming can lead to glaciers melting and ocean acidification.

The oceans and atmosphere work together to form Earth's climate. However, Earth’s climate is changing. This is partly because of global warming. Global warming affects everything on Earth, including its oceans. When ocean temperatures rise, this causes problems across the planet. Let’s look at some of the ways the ocean is important to global temperature. Then let’s look at why rising ocean temperatures are something to worry about.

How does the ocean help control Earth’s temperature?

Energy from the Sun is called solar radiation. Earth absorbs solar radiation and converts it to thermal energy, or heat. As solar radiation travels through Earth’s atmosphere, some of the energy is reflected. The rest of it is absorbed
 
About half of the solar radiation that enters Earth’s atmosphere is absorbed by the Earth’s surface. The surface includes the land and oceans. The other half is scattered, reflected, or absorbed elsewhere. For example, it might be absorbed by Earth’s atmosphere, or by clouds in the atmosphere.

Oceans absorb the greatest amount of solar radiation that reaches the Earth’s surface. That's because oceans cover 70% of the Earth’s surface! Not only is the ocean good at absorbing solar radiation, it’s also good at doing it while “keeping its cool.” It has to be good at this, because it takes much more energy to change the temperature of the ocean than of the air. This is because of heat capacity.

Heat capacity is the amount of thermal energy it takes to raise the temperature of one gram of a substance by one degree Celsius. The heat capacity of water is 4.186 Joules/gram °C. That is about four times more than the heat capacity of air. This means that ocean water can absorb four times more solar radiation than air before its temperature will rise by one degree.

Did you know?

In order for Earth’s temperature to remain constant, the same amount of solar energy that enters Earth’s atmosphere must leave it. This is called Earth’s energy budget

How is climate change impacting ocean temperatures?

Global temperatures are rising because of climate change. This is partly due to the greenhouse effect caused by greenhouse gas emissions. The greenhouse effect causes more solar radiation to be trapped in the Earth's atmosphere. The atmosphere would be much warmer if it weren't for the oceans. But as global temperatures rise, it becomes more difficult for the oceans to help keep the atmosphere cool.

Since 1955, the oceans have absorbed about 90% of the excess heat in the atmosphere. The US National Oceanic and Atmospheric Administration (NOAA) states that the average ocean surface temperature has risen by 0.07 degrees Celsius every decade for the past 100 years. But it has risen twice as fast since 1985.

Earth’s energy budget including thermal radiation that is reflected and radiated by Earth’s surface, clouds and the atmosphere
Earth’s energy budget including thermal radiation that is reflected and radiated by Earth’s surface, clouds and the atmosphere (© 2019 Let’s Talk Science).

 

Infographic - Text Version

This image shows Earth's energy budget, which includes thermal radiation that is reflected and radiated in various ways.
Of the solar energy that reaches the Earth's atmosphere, 48% is ABSORBED by the Earth's surface. 23% is ABSORBED by Earth's atmosphere. 29% is REFLECTED by the Earth's atmosphere. 18% is RADIATED from the Earth's surface. 25% thermal energy responsible for EVAPORATION. 5% thermal energy responsible through convection. 12% of the thermal energy from the surface reaches space and 59% of the thermal energy from the atmosphere reaches space.

What are the implications of rising ocean temperatures?

As ocean temperatures rise, the glaciers that make up the polar ice caps are melting faster. The polar ice caps are located in the Arctic and in Antarctica. In fact, scientists believe that polar ice has melted faster in the last 20 years than it has in the last 10 000

Because of this rapid melting, sea levels rise as the melt water runs into the ocean. Rising sea levels cause problems for coastal ecosystems. Some examples of problems include:

  • erosion
  • flooding
  • habitat loss
  • saltwater contamination of freshwater sources 

This is a problem for humans as well. As sea levels rise, cities on coasts will experience these problems too!

Since 1992, global sea levels have risen by about 11 millimetres. That might not seem like much. But if the speed of melting continues to increase, sea levels will rise much more quickly! 

Did you know?

Satellite imagery is used to track shrinking glaciers in places like Antarctica and Greenland. 

Another impact of rising ocean temperatures is ocean acidification. As the amount of carbon dioxide in the atmosphere increases, a chemical reaction occurs between carbon dioxide (CO2) and ocean water (H2O). This chemical reaction creates carbonic acid (H2CO3). 

Chemical reaction of carbonic acid and water
Chemical reaction of carbonic acid and water (© 2019 Let’s Talk Science).

On the 14-point pH scale, ocean pH has been at around a slightly basic 8.2 for the past 300 million years. But in the late 18th century, the Industrial Revolution began. Since then, ocean pH has dropped to 8.1. A pH drop of 0.1 may not seem like much. But it represents a 25% increase in ocean acidity over the past 200 years.

Ocean Acidification (2016) by the Alliance for Climate Education (2:51 min.).

Rising ocean temperatures have an impact on many types of marine organisms. For example, carbonic acid can prevent shell growth in animals such as clams, oysters, and snails. 

Higher ocean temperatures have also been blamed for lowering the level of oxygen in the water. This process is called deoxygenation. There are several reasons this might be happening. Warmer water cannot hold as much oxygen. Warming also changes the way oxygen-rich surface water mixes with deeper, oxygen-poor water. 

Rising ocean temperatures directly affect corals. Corals have a symbiotic relationship with a type of algae called zooxanthellae. Zooxanthellae provide corals with nutrients to help them survive. Warmer ocean temperatures cause the corals to expel their algae. This results in a bleaching event. Corals can survive without their algae. But their stress levels go up, which makes them more vulnerable. 

How coral become bleached when their symbiotic algae leave due to stress
How corals become bleached when their symbiotic algae leave due to stress (© 2019 Let’s Talk Science).

The ocean is important for keeping the Earth’s temperature in check. But it can only help so much. We need to understand how climate change is impacting our planet. This includes how greenhouse gases impact the ocean, not just the atmosphere. We have to take care of our planet if we want it to help take care of us!
 

Starting Points

Connecting and Relating
  • Have you gone on a summer vacation to a lake or ocean? Why do you visit these places? 
  • Would you like to visit the Arctic and observe the sea ice? Why or why not? 
  • Do you live in a town or city that is by a large body of water? Has flooding ever occurred there? If so, what impact did it have? 
  • Have you been snorkeling or diving and seen coral up close? Was it healthy, stressed or bleached coral? 
     
Connecting and Relating
  • Have you gone on a summer vacation to a lake or ocean? Why do you visit these places? 
  • Would you like to visit the Arctic and observe the sea ice? Why or why not? 
  • Do you live in a town or city that is by a large body of water? Has flooding ever occurred there? If so, what impact did it have? 
  • Have you been snorkeling or diving and seen coral up close? Was it healthy, stressed or bleached coral? 
     
Relating Science and Technology to Society and the Environment
  • In what ways will climate change affect coastal cities and communities? How might these impacts be felt beyond the coastal regions? 
  • How could a decreasing ocean heat capacity impact ocean food chains? How could this trend impact human food supply? 
     
Relating Science and Technology to Society and the Environment
  • In what ways will climate change affect coastal cities and communities? How might these impacts be felt beyond the coastal regions? 
  • How could a decreasing ocean heat capacity impact ocean food chains? How could this trend impact human food supply? 
     
Exploring Concepts
  • Define heat capacity. What is the heat capacity of water? 
  • What will happen to the ability of oceans to absorb heat as the global climate warms? Why? 
  • How does ocean acidification occur? What are some environmental impacts of ocean acidification? 
     
Exploring Concepts
  • Define heat capacity. What is the heat capacity of water? 
  • What will happen to the ability of oceans to absorb heat as the global climate warms? Why? 
  • How does ocean acidification occur? What are some environmental impacts of ocean acidification? 
     
Nature of Science/Nature of Technology
  • What are some different fields of science that are involved in studying the impacts of climate change on oceans? 
     
Nature of Science/Nature of Technology
  • What are some different fields of science that are involved in studying the impacts of climate change on oceans? 
     
Media Literacy
  • What imagery is often used in media that is focused on climate change and oceans? Does one type/subject of image stand out more than others? What is the purpose of these images? 
     
Media Literacy
  • What imagery is often used in media that is focused on climate change and oceans? Does one type/subject of image stand out more than others? What is the purpose of these images? 
     
Teaching Suggestions
  • This article can be used to support teaching and learning of Environmental Science, Climate Change, Earth Science, Oceans, Physics, Heat and Energy and Climate related to oceans, heat transfer, the greenhouse effect, solar radiation, climate change, acids & bases and glaciers & ice caps. Concepts introduced include climate, global warming, solar radiation, thermal energy, reflected, absorbed, heat capacity, climate change, greenhouse effect, greenhouse gas, glaciers, polar ice caps, ocean acidification, pH scale and symbiotic relationship. 
  • After reading this article, teachers could have students complete a Concept Definition Web for the concept of heat capacity. Ready-to-use. Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • For a hands on exploration and/or simple demonstration of ocean acidification, teachers could have students try an investigation such as this Ocean Acidification in a Cup (Khan Academy) or Blowing bubbles to Acidify Water (Montessori Muddle) or Ocean Acidification Experiment (Ocean Wise). 
  • To go further after reading this article, teachers could have students consider the various consequences of ocean warming due to climate change, using a Consequence Mapping learning strategy. Resources from Learn More section above could also be used for additional research. Ready-to-use Consequence Mapping reproducibles for this article are available in [Google doc] and [PDF] formats.
Teaching Suggestions
  • This article can be used to support teaching and learning of Environmental Science, Climate Change, Earth Science, Oceans, Physics, Heat and Energy and Climate related to oceans, heat transfer, the greenhouse effect, solar radiation, climate change, acids & bases and glaciers & ice caps. Concepts introduced include climate, global warming, solar radiation, thermal energy, reflected, absorbed, heat capacity, climate change, greenhouse effect, greenhouse gas, glaciers, polar ice caps, ocean acidification, pH scale and symbiotic relationship. 
  • After reading this article, teachers could have students complete a Concept Definition Web for the concept of heat capacity. Ready-to-use. Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • For a hands on exploration and/or simple demonstration of ocean acidification, teachers could have students try an investigation such as this Ocean Acidification in a Cup (Khan Academy) or Blowing bubbles to Acidify Water (Montessori Muddle) or Ocean Acidification Experiment (Ocean Wise). 
  • To go further after reading this article, teachers could have students consider the various consequences of ocean warming due to climate change, using a Consequence Mapping learning strategy. Resources from Learn More section above could also be used for additional research. Ready-to-use Consequence Mapping reproducibles for this article are available in [Google doc] and [PDF] formats.

Learn more

 

Sea Level Rise & Global Warming Infographics (2014)

Infographics from the Union of Concerned Scientists that illustrate rising ocean temperatures and their impacts (focused on the United States).

Climate Change Indicators: Sea Surface Temperature (2016)

Heat map from the Environmental Protection Agency documenting the average rise in ocean surface temperatures from 1901 - 2015.

Hard Coral Bleaching Time Lapse (2018)

Short time lapse video (1:05 min.) by Peter Kragh of hard corals undergoing the bleaching process

Ocean Acidification (2018)

A detailed description of ocean acidification and its effects on various invertebrates from the Smithsonian Ocean Portal Team.

References

Dahlman, L., & Lindsey, R. (2018). Climate change: Ocean heat content. National Oceanic and Atmospheric Administration

Kushnir, Y. (2000). Solar radiation and the Earth's energy balance. European Economic and Social Committee.

Leon, N. D. (2001). Specific heat and heat capacity. Indiana University.

National Centers for Environmental Information. (2018). Global climate report - January 2018.

National Geographic. (2017). Ocean acidification.

North Carolina Climate Office. (n.d.). Earth's energy balance.

Nunez, C. (2019). Sea level rise, explained. National Geographic.

Ocean Scientists for Informed Policy. (n.d.). Ocean warming.

CarolAnne Black

As a masters student in the Department of Oceanography at Dalhousie University, CarolAnne Black studies how ice forms and gets moved by the currents in the Bay of Fundy in Nova Scotia. She tries to spend as much time as possible outside, playing ultimate frisbee, cycling, hiking and camping. She and her brother biked through the Rockies from Vancouver to Calgary last summer.