The overall take-aways from the detailed discussions of sea level in this module are:
- sea levels are not uniform across the planet, so when we talk about mean sea level rise, these averaged numbers used tend to gloss over the fact that some places are experiencing greater or lesser effects, depending on many variables;
- the drivers of sea level changes over the history of the Earth are complex (including intrinsic and extrinsic factors) and feedback loops work to create cycles of sea level rise and fall, while maintaining an overall equilibrium;
- mean global (eustatic) sea level has been rising steadily during the 20th and early 21st Centuries;
- relative sea level rise causes large local differences in rates of sea level rise. Subsidence of the land can exaggerate sea level rise, while geologic uplift can cancel out some of the effects;
- the current rate of global sea level rise is quantified at 3.2 mm/ yr., a number which has increased in recent years, based on strong evidence that the rate of sea level rise is increasing;
- the chief driver for the acceleration in sea level rise in the past one hundred to two hundred years appears to be anthropomorphic in origin and caused by rapidly increasing atmospheric carbon dioxide levels due to fossil fuel combustion;
- paleoclimate research has established that sea levels have been much higher than today for much of the Earth’s history, with many factors at play, but atmospheric carbon dioxide levels appearing to be a chief driver in climate changes;
- glacial and interglacial periods during the past 500,000 years have been responsible for periods of rapid sea level rise, followed by periods of slower sea level fall as climate cools, glaciers form, and water is once again locked up in ice;
- the exact rates of increasing sea level depend on factors, such as rates of ice melt from polar ice caps, that are currently not understood well enough to give accurate projections;
- the Earth system science models are being refined continually, using more exact data from satellites, and will improve the ability of scientists to predict future sea levels;
- current projections for the end of the 21st Century are between 1 and 2 meters of sea level rise;
- a worst-case scenario suggests that if all the ice in Antarctica and the Arctic were to melt, there would result a rise in sea level of 65 meters!
The implications of sea level rise – even the conservative projections – are huge for the millions of people around the world living in coastal communities. In Modules 5 and 6, we will consider how coastal catastrophes impact societies and how these societies are responding.
Reminder - Complete all of the Module 4 tasks!
You have reached the end of Module 4! Double-check the Module 4 Roadmap to make sure you have completed all of the activities listed there before you begin Module 5.
References and Further Reading
The following links are meant to provide suggestions for further investigation into the ever changing landscape of sea level rise.
- Wikipedia: Sea level rise
- Smithsonian National Museum of Natural History: Sea Level Rise
- NASA: Understanding Sea Level - Causes
- NOAA - Climate Change: Global Sea Level
- NOAA National Centers for Environmental Information: What is Paleoclimatology?
- Climate Central: Antarctic Modeling Pushes Up Sea-Level Rise Projections
- NASA: NASA links port-city sea levels to regional ice melt