UMass scientist tracks climate changes in the North Atlantic
A University of Massachusetts scientist has conducted research along with others in the scientific community that demonstrates a correlation between changes in the climate and frequency of hurricane activity in the North Atlantic Ocean.
Jon Woodruff, a UMass professor of geosciences, is part of a project that has used geographical data from sedimentary deposits in salt marshes and coastal ponds from eight main locations from Puerto Rico to Massachusetts.
Their data has allowed them to construct a 1,500-year history of hurricane activity in the region.
“The main finding was that there are two times in recent history – the last 1,500 years – of climate anomalies,” said Woodruff.
About 1,000 years ago, sea surface temperatures were higher – much like today. During this period, hurricane activity increased.
Similarly, during what is called the “little ice age” that occurred around 500 years ago, the study found that hurricane frequency decreased.
In an August 13 publication of “Nature,” Woodruff, along with Michael Mann, a professor at Penn State and the lead author of the study along with two others, published their findings.
“[We] now have a critical mass of landfall hurricane estimates,” said Mann.
While sea surface temperature was found to be a major indicating factor in hurricane frequency, El Niño and La Niña conditions were also found to be critical.
The El Niño effect refers to the slight warming of the waters in the South Eastern Pacific. The phenomenon tends to occur every three to eight years and often coincides with milder hurricane seasons because of increased wind shear.
La Niña years tend to have an opposite effect. La Niña periods tend to be more intense after a period of slightly cooler sea temperatures in the South Eastern Pacific.
“A perfect storm [would be] relatively warm sea surface temperatures and La Niña,” said Mann.
This appears to be the kind of conditions that occurred during the medieval period about 1,000 years ago. During this period, El Niño-like conditions were less frequent, and sea surface temperatures were higher.
Sediment data was collected for their research along the Eastern seaboard of the United States and in Puerto Rico. Eight major sites were examined.
In some salt marshes and coastal ponds, there is a barrier beach that protects the system from the ocean – sediment accumulates steadily and reliably through time.
According to Woodruff, “Episodically, the whole game changes when these hurricanes come through.”
By examining the “inundated” barrier after heavy sediment deposits are made, Woodruff was able to record a history of hurricane activity.
Woodruff collected much of the solid geographical data along with Jeffrey Donnelly from the Woods Hole Oceanographic Institute in Massachusetts. This data was used, along with information from past studies, to construct a model.
A major implication of this study concerns the impact of global warming on hurricane activity.
With sea surface temperatures rising, a big question asked is how this will affect storm frequency.
“We are not there yet,” said Woodruff. “The big unknown is how El Niño will respond in the future.”
This is a major point of contrast because some models, according to Woodruff, show El Niño becoming stronger, which would probably result in a future with fewer hurricanes.
The next step for Woodruff is to collect more data.
Only about one-tenth of cyclone activity worldwide takes place in the North Atlantic, and Woodruff is looking to do more research in the Western North Pacific where almost a third of worldwide cyclone activity occurs.
“The Western North Pacific responds very different to El Niño and sea surface temperature activity,” said Woodruff. “What we are saying is just about the North Atlantic.”
Woodruff and his colleagues have been developing records since 2001. The research is not without some discrepancies in the data between the physical findings and the model that was used.
“Some of the signal we see could very well be a result of a change in barriers,” he said.
Yet consistency across locations allows them to remain confident in their findings.
Woodruff also acknowledged that the model might not be using the entire climate phenomenon that could affect hurricane activity.
Mann called the study a “proof of concept” that his kind of link between the state of the climate and the frequency of hurricanes could be established.
Both Mann and Woodruff focused on the future potential of their research into hurricane activity. The hope is that more data and even better models will provide more accurate predictions of future hurricane patterns.