Anthropogenic Controls: Humans and Sea Level

When it comes to sea level change, it is clear that natural intrinsic and extrinsic processes can contribute to major changes in sea levels. The scales of sea level change recorded by sediments, and ice demonstrate how sea level change can change on the order of 100s of feet over 100,000s of years. So, how can human activities impact sea level change?

There is little doubt that when we dam rivers, we limit the amount of sediment delivered to our coastlines. When we do this, we impair the river's ability to provide sediments to deltas, salt marshes, and barrier island coastlines. Without these precious sediments, many of the coastal landforms that depend on these sediments struggle to exist. Salt marshes and barrier islands are thus disappearing globally as they gradually sink into the sea.

However, an even more disturbing impact occurs due to the connection between human-produced greenhouse gases and our climate system. When carbon dioxide and other pollutants enter the atmosphere in non-natural concentrations, they interfere with the transmission and exchange of solar and thermal energies. Thus, when the concentration of these compounds increase in the atmosphere, so, too, do global temperatures as greenhouse gases limit the escape of long-wave radiation (thermal energy). The end result is that a warmer climate means more glacial ice is being melted. When combined with more water released into the ocean, warmer ocean waters also expand in volume and results in higher sea levels. In the discussion that follows, we will explore these ideas a bit more together.

• Humans and Sea Level Change Over the Last 11,000 Years
• Instrumental Records: Direct Measurements of Environmental Change
• Learning Check Point
• Feedback in Action: Sea Level Rise and Coastal Subsidence