Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Harbingers of increased Atlantic hurricane activity identified

14.08.2009
Reconstructions of past hurricane activity in the Atlantic Ocean indicate that the most active hurricane period in the past was during the "Medieval Climate Anomaly" about a thousand years ago when climate conditions created a "perfect storm" of La Niña-like conditions combined with warm tropical Atlantic waters.

"La Niña conditions are favorable for hurricanes because they lead to less wind shear in the tropical Atlantic," said Michael E. Mann, professor of meteorology, Penn State. When combined with warm tropical Atlantic ocean temperatures, a requirement for hurricanes to form, conditions become ideal for high levels of activity."

During an El Niño, the more familiar half of the El Niño Southern Oscillation (ENSO), there is more wind shear in the Caribbean and fewer hurricanes. The low Atlantic hurricane activity so far during this current season is likely related to the mitigating effects of an emerging El Niño event.

"Hurricane activity since the mid-1990s is the highest in the historical record, but that only goes back a little more than a century and is most accurate since the advent of air travel and satellites in recent decades," said Mann. "It is therefore difficult to assess if the recent increase in hurricane activity is in fact unusual."

Mann, working with Jonathan D. Woodruff, assistant professor of geosciences, University of Massachusetts; Jeffrey P. Donnelly, associate scientist, Woods Hole Oceanographic Institution, and Zhihua Zhang, postdoctoral assistant, Penn State, reconstructed the past 1,500 years of hurricanes using two independent methods. They report their results in today's (Aug. 13) issue of Nature.

One estimate of hurricane numbers is based on sediment deposited during landfall hurricanes. The researchers looked for coastal areas where water breached the normal boundaries of the beaches and overwashed into protected basins. Samples from Puerto Rico, the U.S. Gulf coast, the Southern U.S. coast, the mid-Atlantic coast and the southeastern New England coast were radiocarbon dated and combined to form a history of landfall hurricanes.

The other method used a previously developed statistical model for predicting hurricane activity based on climate variables. They applied the model to paleoclimate reconstructions of tropical Atlantic sea surface temperature, the history of ENSO and another climate pattern called the North Atlantic Oscillation (NAO), which is related to the year-to-year fluctuations of the jet stream. Warm waters are necessary for hurricane development, ENSO influences the wind shear and the NAO controls the path of storms, determining whether or not they encounter favorable conditions for development.

The researchers compared the results of both hurricane estimates, taking into account that the sediment measurements only record landfall hurricanes, but that the relationship between landfall hurricanes and storms that form and dissipate without ever hitting land can be estimated.

Both hurricane reconstructions indicate similar overall patterns and both indicate a high period of hurricane activity during the Medieval Climate Anomaly around AD 900 to 1100.

"We are at levels now that are about as high as anything we have seen in the past 1,000 years," said Mann.

The two estimates of hurricane numbers do not match identically. The researchers note that they do not know the exact force of a storm that will breach the beach area and deposit sediments. They are also aware that the relationship between landfalling hurricanes and those that remain at sea is not uniform through all time periods. However, they believe that key features like the medieval peak and subsequent lull are real and help to validate our current understanding of the factors governing long-term changes in Atlantic hurricane activity.

One thing the estimates show is that long periods of warm Atlantic ocean conditions produce greater Atlantic hurricane activity.

"It seems that the paleodata support the contention that greenhouse warming may increase the frequency of Atlantic tropical storms," said Mann. "It may not be just that the storms are stronger, but that there are there may be more of them as well."

The National Science Foundation and the Bermuda Institute for Ocean Sciences supported this work.

A'ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>