Sea Level Changes in the Southeastern United States
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Material Information

Title:
Sea Level Changes in the Southeastern United States Past, Present, and Future
Creator:
Mitchum, Gary T.
Affiliation:
University of South Florida
Publisher:
Florida Climate Institute
Publication Date:
Language:
English

Subjects

Subjects / Keywords:
Climate change ( lcsh )
Florida ( lcsh )
Sea level rise ( lcsh )
Oceanography ( lcsh )

Notes

Summary:
This paper is about past, present, and future sea level changes in the southeastern United States. It is aimed at non-scientists and scientists who are not specialists in sea level change. Although this report is about our specific part of the world, sea level change in any region is best viewed in the context of global sea level changes. This should be seen as encouraging, though, since measuring and predicting global sea level change is a much easier problem than predicting the changes at any particular location along a coastline. Global sea level measures the volume of the oceans. This volume can change only if we add or remove water, or if we change the mean density of the water in the oceans. The most likely way to change the density is to warm or cool the oceans. For example, warmer water is less dense and therefore takes up more space, thus raising the sea level. So determining global sea level change is a relatively easy problem since we only have to determine how much water is added or subtracted from the oceans, or how much the oceans on average are warmed or cooled. Regional and local relative sea level changes, on the other hand, are strongly influenced by land motion. Many people do not realize that the land we are standing upon is also slowly moving up and down. If the land is sinking, then the sea level appears to be rising, and vice versa. Also, even if the oceans are globally warming, that does not mean that the associated sea level increase will be felt everywhere uniformly. If our region is warming at an anomalously high rate, then we will see a higher rate of sea level change. Similarly, if the water added from ice melt does not immediately spread out over the entire ocean, then we may see higher or lower rates of sea level change. At present we do not know if our region is set to be a winner or a loser in this game. Fortunately, though, the present sea level changes in the southeastern US region can be accounted for largely by the global changes once we take into account the local and regional land motions. The latter are small at most stations in our region, but nonetheless need to be accounted for. In some areas along our coastlines the land motions are in fact dominant. I will suggest that the best projection of the future is about 80 centimeters of global sea level increase by 2100, an increase we need to plan for in our region. This is somewhat larger than the most recent global assessment from the Intergovernmental Panel on Climate Change, but I will argue that it is likely our present best guess. Unfortunately, the uncertainties in these analyses lead me to conclude that the probability of a larger increase is more likely than the chance that it will be substantially smaller. It may seem a bit tangential, but I will also suggest that episodic changes due to changes in storm tracks, frequencies, and intensities should not be ignored. Climate change will almost certainly be felt most strongly as changes in what we call weather. Such changes are potentially the most important thing that we need to predict in the coming decades. Finally, I will say that we can likely reduce the uncertainty in sea level rise rates over the next 10 years, but only if we maintain the superb observational system that we have in place now. We are now able to determine sea level change from the global scale, to the regional scale, and down to the local scale. If we simply continue to make the observations that we are making now for another decade, then we will most likely be able to intelligently inform the public about the real risks that might be associated with climate change. ( English )

Record Information

Source Institution:
Florida International University
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