LSU School of Coast & Environment professor works to understand prehistoric storms in order to better predict future activity
Kam-Biu Liu, George W. Barineau III Professor in the LSU Department of Oceanography and Coastal Sciences, and an international alliance of contributing researchers at Skidmore College and the University of Costa Rica recently received a $300,000 grant extension from the Inter-American Institute for Global Change Research, or IAI, and the National Science Foundation, or NSF, to continue research focused on reconstructing ancient hurricane history.
The new grant is a performance-based continuation of funding for Liu and collaborators’ project to reconstruct hurricane activities and hazards in the Caribbean region based on geologic records. To read more about the original project, visit IAI’s website.
“This enhancement of funding allows us to expand on our achievements based on our ongoing project,” Liu said. “We are trying to understand the mechanisms and patterns of hurricanes in the Caribbean islands, and, now, along the Pacific Coast of Mexico.”
With the grant extension funded by the IAI and NSF, Liu and his international team of paleotempestology researchers plan to continue their work in reconstructing hurricane activities in the Caribbean Basin over the last several thousand years as well as begin constructing records for the Eastern North Pacific, or ENP, Basin. As the second most active hurricane basin in the world, the ENP is even more active than the Atlantic side. The coasts of Central America suffer from what Liu calls “double jeopardy,” with hurricane impacts approaching from both the East and the West.
“We are lucky here on the Gulf Coast. We only have to watch one side,” Liu said. “This opens up a completely new front of paleotempestology. Nothing has been done before on reconstructing ancient hurricane activity in the Easter North Pacific basin. Tropical cyclone activities inflict lots of damage to the west coast of Mexico.”
Liu’s group and collaborators on the project are currently producing geological records of hurricane activity from three areas along the west coast of Mexico, including the Mexican states of Baja California, Jalisco, and Guerrero. With a tectonic plate boundary running along the west coast of Mexico, Liu’s research team is also looking into ancient earthquakes and tsunami records.
Tropical cyclones are a major cause of environmental catastrophes in many coastal regions of the world today. According to Liu, many people living in coastal regions are uncertain about the risks of hurricane damage in their region and do not have clear conceptualizations of their vulnerability to major storms. Adding to this uncertainty is a lack of reliable information on return periods for the rare but extreme hurricane such as Hurricane Katrina in 2005.
Without Liu and collaborators’ work on creating worldwide ancient hurricane records from geological histories, disaster planners could not be sure if the Hurricane Katrina scale of storm is a 50-year, 100-year, or 500-year event for New Orleans. Instrumental records simply do not date back far enough to provide reliable return periods for the largest and most damaging storms.
“The only way to understand present and future risks is to look into the past,” Liu said.
Liu’s ongoing paleotempestology project has important implications for understanding what factors control overall hurricane activity in the Atlantic Basin and other hurricane basins around the world. Informed by research conducted under the auspices of the ongoing project, Liu has pioneered an explanation of hurricane patterns in the Atlantic Basin known as the Bermuda High Hypothesis.
According to the Bermuda High Hypothesis, there exist millennial scale patterns of hurricane activity superimposed on the more familiar multi-decadal hurricane activity fluctuations that result from a semi-permanent area of high pressure located in the North Atlantic Ocean, called the Bermuda High. This area of high pressure, which migrates east and west depending on atmospheric pressure conditions, promotes a clockwise circulation of air that controls the path of tropical cyclones that approach the Gulf of Mexico or the East Coast of the U.S. By studying the Bermuda High, Liu is trying to understand the factors that affect what track hurricanes take as they approach the coasts of the U.S.
“Most hurricanes are produced south of the Bermuda High, which steers storms toward the Gulf Coast and the Atlantic Coast,” Liu said. “It acts like a gardener holding and steering a garden hose. The Bermuda high pressure system, like the gardener, controls the path of hurricanes and where they go. Our data show that hurricane activity is not the same everywhere. When one region of the Atlantic Basin is quiet, another region could be very active.”
Liu’s work on explaining the Bermuda High Hypothesis is helping hurricane researchers understand both the temporal and geographical patterns of hurricane activity and the climate mechanisms that control hurricane activity and location of hurricane hits. Such information is important to help policy-makers and coastal residents better prepare for the future.
Liu, known as the “Father of Paleotempestology,” is also famous for his development of research methods to uncover ancient hurricane history from sedimentary records. Liu was the first to devise a methodology to reconstruct hurricane activities based on analysis of storm deposits in coastal sediments, created when hurricane winds and storm surge force sand from natural coastal barriers into normally dark-sediment lakes. By dating sand layers found in lake sediment cores, Liu’s team can recreate the properties of hurricanes of the ancient past.
As a part of the ongoing IAI-funded project, Liu and his co-investigators Samuel J. Bentley, associate professor in the LSU Department of Geology and Geophysics, and Amy Frappier, assistant professor of Paleoclimatology at Skidmore College, are devising new methods of reconstructing past storm activities. Bentley is developing new groundbreaking methodology based on sediment cores extracted from the bottom of the Blue Hole in Belize. A large submarine sinkhole, the Blue Hole is a normally quiet basin surrounded by coral reefs.
“The Blue Hole is like a deep bucket in the ocean,” Liu said. “Sediment accumulates in seasonal layers, leaving a record like tree rings.”
The laminated sediment deposition that forms summer and winter layers at the bottom of the Blue Hole are extremely rare throughout the world in that, being contained in such as isolated deep water environment, they are not affected by waves, burrowing sea creatures and plants or even hurricane turbulence. However, hurricane conditions can knock sand from the edges of the Blue Hole’s coral walls, producing sand layers that scientists can use to determine the occurances of ancient hurricanes.
“Coarse grain layers can be produced by hurricanes that erode coral sands from the walls of the Hole,” Liu said. This only happens under very rough conditions produced by hurricanes.”
Thanks to ongoing research at LSU, the Blue Hole is producing a 1,200 year useful history of hurricanes in the region.
“This is a completely new record,” Liu said. “Nobody has done this kind of work before. We are sharpening the tools in paleotempestology.”
In addition to looking to geological records to uncover hurricane records otherwise obscured by time, Liu is working with co-investigator Nina Lam, professor in the LSU Department of Environmental Sciences, to develop indices of vulnerability in the Caribbean region and most recently along the Pacific Coast of Mexico, superimposing maps of roads, storm surge height, coastal topography and population data to layers of hurricane data to inform planning and evacuation procedures.
“I think that the most powerful part of our research is our ability to integrate the social sciences into our natural science information about hurricane activity, temporal and geographical distribution,” Liu said.
The team’s vulnerability models informed by ancient hurricane records have consequences for planning and assessing hurricane impacts to various regions and are helping coastal societies around the world better understand their vulnerability to extreme weather.
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BY Paige Brown