Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Century of data shows sea-level rise shifting tides in Delaware, Chesapeake bays

25.01.2018

The warming climate is expected to affect coastal regions worldwide as glaciers and ice sheets melt, raising sea level globally. For the first time, an international team has found evidence of how sea-level rise already is affecting high and low tides in both the Chesapeake and Delaware bays, two large estuaries of the eastern United States.

The team combined a computer model with 100 years of observations to tease out the fact that global sea-level rise is increasing the tidal range, or the distance between the high and low tides, in many areas throughout each bay.


A tide level gauge that has been bolstered to withstand hurricanes. Researchers have shown that sea-level rise is changing patterns of the tides in the Delaware and Chesapeake bays.

Credit: NOAA

Tides, or the rising and falling of the ocean's surface, occur on regular intervals and result from numerous factors, the biggest of which is the gravitational pull from the sun and moon. For centuries, people have documented and predicted the daily high and low tides because they can impact ocean navigation. Tides can also affect ocean life, flooding risk, fishing, the weather, and some energy sources such as hydroelectric power.

In 2015, Andrew Ross, meteorology doctoral student, Penn State, noticed an odd pattern emerging while testing a numerical computer model for tidal research. Adding one meter of sea-level rise to the model resulted in a distinct pattern of changes to the high and low tides throughout the Chesapeake Bay.

"We weren't sure why it was there, but it was unique enough that we thought it should show up in observations, too, if it was actually real," said Ross, now a postdoctoral research associate, Princeton University. "So we started looking at the observations, doing more comparisons."

Ross began working with a team that included his adviser, Raymond Najjar, professor of oceanography, Penn State, to pinpoint the precise effects of sea-level rise by subtracting other forces that affect changes to the tidal range. Some of these forces are predictable, including the 18.61 years it takes for the moon's orbit around the Earth to oscillate.

Other forces are less predictable, like the effect from dredging a bay to create a wider, deeper space for container ships. The team analyzed tidal gauge records from 15 locations in the Delaware and Chesapeake bays, the oldest of which dates back to 1901. They also studied nearby cities outside of each bay to control for larger changes affecting the ocean more broadly.

Once they isolated sea-level rise's influence on the tides using the tide gauge records, they compared this information with a computer model in which they could adjust the overall sea level, simulating the effects of the past or future. They reported, in the Journal of Geophysical Research: Oceans, that both the tide gauge data and the model generally agreed on the main effects of sea-level rise on tides. The analysis showed that one meter of sea-level rise increased the tidal range by up to 20 percent in some areas. The exact amount of change from sea-level rise varied based on physical characteristics such as the shape of the bay.

"In the Delaware Bay, as you go upstream toward Philadelphia, the shore lines are converging in a sort of funnel shape, and so we see that amplifies sea-level rise's effects on the tides," said Ross. "That amplification gets magnified the farther you go upstream."

By contrast, the shape of the Chesapeake Bay resulted in a different pattern of effects, in some cases slightly decreasing the tidal range. Compared to the Delaware Bay, the Chesapeake Bay is longer and has less of a funnel shape. After a wave enters the Chesapeake Bay from the ocean, it eventually hits the end of the bay and reflects back towards the ocean, either adding to or subtracting from the heights of waves it contacts. Because waves travel faster in deeper water, a higher sea level results in a faster wave speed. This changes where incoming and outgoing waves interact with each other, which has a cascading effect on tide patterns throughout the bay.

"When people think about flooding associated with sea-level rise, they often think everything will just go up, including the tides, but the reality is that in some cases, the tidal range may stay the same or decrease," said Najjar. "It all depends on the geometry of the bay and the speed of waves, which we know are affected by rising sea levels."

###

Collaborators include Ming Li, Fan Zhang, and Wei Liu, Horn Point Lab, University of Maryland, and Serena Blyth Lee, Griffith University, Australia.

The National Science Foundation supported this research.

Media Contact

A'ndrea Elyse Messer
aem1@psu.edu
814-865-9481

 @penn_state

http://live.psu.edu 

A'ndrea Elyse Messer | EurekAlert!

More articles from Earth Sciences:

nachricht A promising target in the quest for a 1-million-year-old Antarctic ice core
24.05.2018 | University of Washington

nachricht Tropical Peat Swamps: Restoration of Endangered Carbon Reservoirs
24.05.2018 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>