Now, a new study shows that, from the Florida Keys to southern Alabama, those fluctuations have been intensifying over the past 20 years. Summer peaks have been getting higher and winter troughs dipping lower, potentially increasing flooding from hurricanes and stressing delicate ecosystems, the researchers report.
Sunset Beach on Treasure Island in St. Petersburg, Florida, during Tropical Storm Andrea in June 2013. Increases in summer sea water levels over the past two decades along the eastern Gulf Coast may be boosting storm surge heights, causing more erosion on beaches like this one, according to a new study.
Credit: Thomas Wahl
The additional summer increase in sea levels over the past two decades means storm surges can rise higher than previously thought, increasing how much sea level rise contributes to the flooding risk from hurricanes, according to Thomas Wahl, a postdoctoral researcher from the University of Siegen in Germany who is working at the University of South Florida in St. Petersburg and lead author of the study.
Global sea levels rose by about 5 centimeters (2 inches) from 1993 to 2011 and the newfound trend of summer sea level rise has added approximately 5 centimeters on top of that in the eastern Gulf, the research team reports. Wahl and colleagues from Florida and England published their study last week in Geophysical Research Letters, a journal of the American Geophysical Union.
Conversely, an increasingly downward, winter sea level trend along the eastern Gulf Coast has reduced the flood risk from winter storm surges. At the same time, the growing gap in the region between summer and winter sea levels might be disrupting coastal ecosystems adapted to what was once a relatively stable difference between the seasonal sea levels, Wahl said.
The team studied the entire U.S. Gulf Coast but found the trend toward a greater summer-winter difference only along eastern Gulf shores. Seasonal sea levels in the eastern Gulf of Mexico followed a steady cycle from the beginning of the 1900s to the 1990s, increasing in summer and dropping in winter by roughly the same amount year after year. But, starting in the 1990s, sea levels have gotten both higher in the summer and lower in the winter in the eastern Gulf, causing a significant amplification of the annual cycle, according to the study.
The new work is the first to look at the changes to the sea level cycle for the entire Gulf Coast region in the United States and the first to encounter such a trend, according to Wahl. “This increase over a period of almost 20 years is not found elsewhere in the world,” he said.
Wahl and his colleagues discovered the trend in data from a set of 13 tide gauges stretching from Key West at the tip of Florida to Port Isabel on the Texas coast. Nearly all the tide gauges in the eastern Gulf of Mexico, from Key West to Dauphin Island off the coast of Alabama, showed a significant change in sea level cycle from the 1990s onwards. The change in the sea level cycle was not observed in gauges in the western part of the Gulf, stretching from the Louisiana coast down to the Texas border with Mexico.
The 20-year increase in the annual amplitude, or difference between the high summer levels and low winter levels, was 21 percent on average and as high as 30 percent in some locations, according to the study.
For example, in Key West, the annual amplitude of the sea level cycle for the most recent five-year window was 12.4 centimeters (4.9 inches), 4.5 centimeters (1.8 inches) higher than the average amplitude before 1993, when the change in the seasonal sea level cycle started.
In 2013, when Wahl came to Florida on a fellowship to study the Gulf, he started by looking at the tide gauge record in St. Petersburg. The surprise of seeing a significant increase there in the seasonal cycle during the last few years led him to examine the cycle of the entire U.S. Gulf Coast in the past century.
Although centimeter increases may seem small compared to storm surges measured in meters, the increase means smaller surges have the potential to inundate low-lying areas and cause erosion, Wahl explained. “These indirect effects on storm surges in addition to the global sea level rise are often ignored,” he said.
On the other hand, the decline in sea levels in the winter that was observed in the eastern Gulf reduces the flood risk associated with winter storm surges. However, changes in sea levels in the winter could throw off, for example, the salt balance in sensitive coastal wetlands, Wahl said.
“Very sensitive ecosystems along the Gulf coast depend on the seasonal cycle,” he said. “If there are significant changes in the seasonal cycle then this very likely has an effect” on these ecosystems.
Significant changes in the seasonal cycle might also affect oil spills, although the researchers did not look at this effect, Wahl said. The changes in the seasonal cycle could alter the tides and associated currents, which could in turn influence the mixing of the oil and when it reached land, although the impact would likely be small, he noted.
Unlike global sea level rise, which is driven by temperature and is often cited as an effect of climate change, the annual sea level cycle is driven by a variety of local factors including wind, precipitation, sea level pressure and temperature. The annual cycle varies from region to region, and, until recently, was thought to be constant from year to year. Wahl said it has only been in the past few years that scientists around the world have begun looking at possible changes in regional sea level cycles including in the Baltic Sea, Mediterranean Sea, Chesapeake Bay and the Caribbean.
Coastal engineers need information about baseline sea levels in order to build sea walls to protect coastal communities, said Philip Woodworth, a scientist at the National Oceanography Centre in Southampton in the United Kingdom, who did not contribute to the study.
“A change in the baseline of 5 centimeters could be an important factor,” he said.
Wahl said the changes he and his co-authors saw in the seasonal cycle in the eastern Gulf are driven by changes in air temperature and atmospheric sea level pressure over the past two decades. The researchers found that since 1990, summers have been getting warmer and winters have been getting colder in the region. Atmospheric sea level pressure, which also fluctuates with the seasons, declined more in the summer and increased more in the winter after 1990.
Warmer temperatures and lower sea level pressure in the summer led to the higher water levels being seen in the eastern Gulf, while the lower winter sea levels were driven by the colder temperatures and higher pressure seen during that season, according to the study.Title
Francisco M. Calafat, College of Marine Science, University of South Florida, St. Petersburg, FL, USA; and National Oceanography Centre, Southampton, UK;
Mark E. Luther, College of Marine Science, University of South Florida, St. Petersburg, FL, USA.Contact information for the authors:
Peter Weiss | American Geophysical Union
Further reports about: > Alabama > American Geophysical Union > Baltic Sea > Bompey > Chesapeake Bay > Geophysical > Gulf of Maine region > Marine science > Mobile phone > Oceanography > coastal ecosystem > global sea level > sea level > sea level rise > sea snails > seasonal cycle > storm surges > winter storm > winter storm surge
For a rare prairie orchid, science is making climate change local
12.02.2016 | USDA Forest Service - Northern Research Station
NASA sees Tropical Cyclone Winston form
12.02.2016 | NASA/Goddard Space Flight Center
Today, plants and microorganisms are heavily used for the production of medicinal products. The production of biopharmaceuticals in plants, also referred to as “Molecular Pharming”, represents a continuously growing field of plant biotechnology. Preferred host organisms include yeast and crop plants, such as maize and potato – plants with high demands. With the help of a special algal strain, the research team of Prof. Ralph Bock at the Max Planck Institute of Molecular Plant Physiology in Potsdam strives to develop a more efficient and resource-saving system for the production of medicines and vaccines. They tested its practicality by synthesizing a component of a potential AIDS vaccine.
The use of plants and microorganisms to produce pharmaceuticals is nothing new. In 1982, bacteria were genetically modified to produce human insulin, a drug...
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".
Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...
The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.
Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...
Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.
The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).
Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels
A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...
12.02.2016 | Event News
09.02.2016 | Event News
02.02.2016 | Event News
12.02.2016 | Physics and Astronomy
12.02.2016 | Life Sciences
12.02.2016 | Medical Engineering