The Water’s Getting Higher. . . and Lower

by Philip Luther

The sunset over the Gulf of Mexico from the west coast of Florida

The sunset over the Gulf of Mexico from the west coast of Florida (Wikipedia)

Researchers at the University of South Florida College of Marine Science have made an astonishing discovery: the Gulf of Mexico is getting higher. If you have been following any of the recent news about climate change, this revelation probably isn’t that surprising. It’s relatively common knowledge that there has been a measurable rise in ocean level over the past few years. Some would argue that this is caused by climate change, but that’s a topic that is better discussed elsewhere.

What may be surprising to many is that the Gulf is also getting lower. This probably sounds pretty confusing. How can the ocean be getting higher and lower at the same time? The answer is it isn’t really.

The ocean undergoes a seasonal cycle of high and low water levels. This is like the daily tides, but instead of a daily cycle, it’s on a yearly cycle. Oceanographers quantify these levels by amplitude, or the difference between the normal sea level and the peak sea level in this cycle.

What the researchers found is quite alarming. Using a model created from tide gauge data from around the Gulf of Mexico, they discovered that in the time period since 1990, the maximum sea level amplitude during any given year was as much as 30% higher than that of the years before 1990. This means that this sea level cycle has become more extreme over recent years, with higher peaks in sea level and lower lows.

According to the researchers, this increase could present a real danger in the future. When the increase in seasonal amplitude is combined with the overall world increase in sea level, it presents a much higher risk for flooding along coastal. Areas that were normally high and dry in a storm surge may now be completely underwater during times of peak sea level. It’s not all bad, though. When the sea level is at its lowest, flooding potential is greatly reduced.

Hurrican pic

Higher summer sea levels may lead to more flood damage from hurricanes like 2012’s Isaac shown here. (Nasa)

This may sound like it would pretty much even out: More flooding at sometimes and less at others. The fact is that it doesn’t. The highest sea levels occur during the late summer months, the dead middle of hurricane season. Storm surges are much more likely to occur then than in winter months when sea levels are at their lowest. This unequal balance results in more overall damage to coastal areas.

While this study only concerned the Gulf of Mexico, it wouldn’t be a far stretch to say that this is most likely a global trend. The researchers don’t directly state what is causing this change, but it wouldn’t surprise me if climate change were to blame, as it seems to be for just about everything these days.

If you live on the Gulf Coast, my suggestion is to invest in a boat, because the water is rising, and it doesn’t look like it will stop anytime soon.

Works Cited

Wahl, T.F. M. Calafat, and M. E. Luther (2014), Rapid changes in the seasonal sea level cycle along the US Gulf coast from the late 20th centuryGeophys. Res. Lett.41491498, DOI:10.1002/2013GL058777.

writing in the natural sciences