Exploration: Ocean Thermal Expansion Notes
Thermal Expansion
A blanket of gases called the atmosphere surrounds the Earth's surface.
Energy from the sun passes through the atmosphere, and about half is absorbed by the Earth's surface.
Some heat energy is reflected back into the atmosphere and absorbed by gases present there.
Greenhouse gases: Carbon dioxide, methane, and nitrogen oxides are examples of heat-absorbing gases.
Greenhouse gases occur naturally, but humans have increased their concentration by burning fossil fuels and wood.
More greenhouse gases lead to increased heat absorption, resulting in a temperature increase known as global warming.
Global Warming: Increase in the Earth's average temperature.
The average temperature in 1990 was 53.4°F.
In 2022, the average temperature was 56.3°F, the highest recorded.
In 1995, scientists predicted a 2 to 3.5°C (3.6-6.3°F) increase in global temperature over the next 100 years (IPCC).
This rate of warming is the highest seen in the last 10,000 years.
As temperature increases, thermal expansion causes sea level to rise.
Warmer temperatures may cause mountain glaciers and ice sheets (Greenland and Antarctica) to melt, further contributing to sea level rise.
Sea Level Rise
A small temperature increase of 0.1°C can result in a significant rise in sea level, only from thermal expansion.
Melting of ice sheets and glaciers also contributes to sea level rise.
Over the last 25 years, the sea level has been rising by about 3 mm per year, based on satellite data, and this rate is accelerating.
Sea Level Definition
Sea level is the average height of the ocean between high and low tide.
Sea level has fluctuated throughout Earth's history.
During ice ages, sea level was lower due to much water being frozen in glaciers.
Most of the increase in sea level due to global warming results from the thermal expansion of the oceans.
Thermal expansion: Seawater expands due to higher temperature.
Oceans absorb heat from the atmosphere, causing them to warm.
Warm seawater has a greater volume than cold seawater.
As ocean temperature increases, so does total ocean volume, causing sea levels to rise.
Over the next 100 years, sea level is expected to rise from 15 to 95 centimeters.
This is significantly different from the 6 to 37 centimeters rise observed over the last 100 years!
In general, for every 1 centimeter of sea level rise, 1 meter of coastal land is lost.
Places with flat coasts, like Florida, could lose up to 300 meters of coastal land.
Coastal Flooding Consequences
If sea level rises as predicted, several consequences are expected:
Freshwater contamination with saltwater (including drinking water).
Destruction of ports.
Flooding or ruin of coastal cities.
Damage to wetlands and swamps.
Accelerated coastal erosion.
Death of large numbers of plants and animals.
Increased intensity and number of hurricanes.
Changes in precipitation patterns, leading to droughts in some areas.
Tourism and recreational businesses dependent on coastal areas will collapse.
The economic impacts of rising sea level due to global warming will be devastating.
Rising sea level will severely affect humans and other organisms.
Review Questions:
Why does global heating lead to a rise in sea levels?
Global heating leads to a rise in sea levels primarily through two mechanisms: thermal expansion and melting of ice sheets and glaciers. Thermal expansion occurs because warmer water occupies a larger volume. As the oceans absorb heat from the atmosphere, the water temperature increases, leading to an expansion of the water and a rise in sea level. Additionally, global warming causes ice sheets and glaciers to melt at an accelerated rate, adding more water to the oceans and further contributing to sea level rise.
How will populations living near the coasts be affected by a rise in sea level?
Populations living near the coasts will be affected in numerous ways:
Increased Flooding: Coastal areas will experience more frequent and severe flooding, leading to displacement of residents and damage to infrastructure.
Saltwater Intrusion: Rising sea levels can cause saltwater to contaminate freshwater sources, including drinking water supplies, making them unusable.
Coastal Erosion: Higher sea levels will accelerate coastal erosion, leading to loss of land and property.
Damage to Infrastructure: Ports, roads, and other coastal infrastructure will be damaged by flooding and erosion, disrupting transportation and commerce.
Loss of Wetlands: Coastal wetlands, which provide important ecosystem services such as storm protection and habitat for wildlife, will be inundated and destroyed.
Economic Impacts: Tourism and recreational businesses that depend on coastal areas will suffer, leading to job losses and economic decline.
Increased Storm Damage: Rising sea levels can exacerbate the impacts of hurricanes and other coastal storms, leading to greater property damage and loss of life.
With a constant rise of 3.3 mm a year, how much higher will the sea level be in the year 2100?
To calculate the sea level rise by the year 2100 with a constant rise of 3.3 mm per year, we need to determine the number of years between the current year and 2100, then multiply that by the annual rate of sea level rise. Assuming the current year is 2024, there are 76 years between 2024 and 2100. Therefore, the total sea level rise would be:
Converting this to centimeters:
Thus, the sea level would be approximately 25.08 cm higher in the year 2100, given a constant rise of 3.3 mm per year.