AbstractThefrequency of natural disasters across the world has been increasing drasticallythroughout recent times, with intense hurricanes taking the lead as one of themost devastating forces of nature.
Thispaper explains the relationship between intense hurricane landfalls and coastalsedimentary deposits, and further describes the methods scientists use todetermine prehistoric hurricane characteristics. 5 scholarly sources were used to explain thethree main points covered and were accompanied by 2 scientific websites thatwere used to explain the basics of hurricanes. Intense hurricanes are classified as any one that reaches and/or exceedscategory 3 on the Saffir-Simpson scale, with sustained winds of 111-129 mph (Hurricane, n.
d.). The frequency and time period of intensehurricane landfalls can be determined using backbarrier sedimentary evidencevia core samples and radiocarbon dating techniques (Donnelly et al., 2001a). The data gathered by the technique of extractingcore samples and dating them can be useful in determining the history ofintense hurricane landfalls in an area, and these discoveries can helpscientists predict the likelihood of an intense storm making landfall again inthe future. Additionally, these methodscan be used to make conclusions on which periods of time experienced high andlow intense storm frequency (Donnelly et al., 2001b).
Relationships can be drawn that explain whatenvironmental characteristics effected the trends most and why each periodexperienced such trends. Finally,sedimentary evidence can be used to describe the correlations between intensehurricane landfall frequency over large areas, such as oceanic masses. This is useful when trying to determinewhether intense storms were only common in one area, or instead across largerdistances (Scileppi & Donnelly, 2007). Overall, this paper explains the significance of sedimentary evidencewhen analyzing the history and future of intense hurricane landfall, andprovides valuable information regarding the tools and methods scientists use toexplain weather trends.Keywords: hurricane, backbarrier,radiocarbon dating, core sample Sedimentary Deposits’ Relationshipto the Past and Future of HurricanesIna world plagued by a rapidly increasing frequency of natural disasters, somereign mightier than others, with the hurricane topping the list in terms ofdestructive capability and power. Hurricanes,also known as tropical cyclones, are rapidly rotating storm systems withlow-pressure centers, strong winds, and a spiral arrangement of thunderstormsthat produce extreme amounts of rain in a short period of time. These storms can grow to over 1,350 mileswide, typically form over large bodies of warm water, and begin rotatingtowards the equator due to the Coriolis effect, or spin of the earth (Hurricanes, 2015). Their strength is separated into fivedifferent categories of increasing violence based on the Saffir-Simpson scale,with category 1 hurricanes having 74-95 mph sustained winds and category 5hurricanes seeing winds in excess of 157 mph.
When a storm reaches the ranking of category 3, it is considered anintense hurricane, with winds of 111-129 mph and the capability to destroyislands, coastlines, and even inland features (Hurricane, n.d.).
Hurricaneshave been forming and wreaking havoc on the world’s coastlines since the dawnof time, so understanding them and their formation is critical when attemptingto predict them in the future. Historicalrecords of these massive, rotating storms only give those studying them a fewhundred years of data to work with, but the geological evidence of intensehurricanes can give researchers a much larger time frame to analyze. While historical records often only go back370 years, sedimentary core samples, aerial photographs, and radiocarbon datingcan be used to analyze a time period’s hurricane activity thousands of years inthe past. These samples can be gathered,radiocarbon dated, and analyzed by researchers in order to establish theprobability of intense hurricane landfalls happening each year, which can helpresearchers better predict future hurricanes (Donnelly, et al., 2001a). Additionally, the use of sedimentary evidencecan yield information that shows what caused different variances in hurricanefrequency throughout specific time periods in history (Liu & Fearn, 2000). Finally, the data collected from radiocarbondating sedimentary samples in one area can be compared to similar samples inanother area, where conclusions can be drawn on a time period’s hurricaneactivity over large areas (Scileppi & Donnelly, 2007).
Sedimentary deposits are a valuable tool inanalyzing prehistoric intense hurricane landfalls, and can give scientists anidea of when a hurricane made landfall, the intensity of the hurricane at thattime, the conditions the hurricane formed under, and the probability of asimilar storm occurring again.Wheninvestigating the past activity of hurricanes, one will find that modernequipment has only helped the National Oceanic and Atmospheric Administrationrecord into the late nineteenth century, and historical records typically onlydate a maximum of 130-370 years into the past (Donnelly et al., 2001a). When glancing at the global geologicaltimeline, these 370 years of the earth’s 4.54 billion years of history isextremely insignificant, making it crucial for researchers to be able to lookfurther into the past to draw valid conclusions. To extend the observation periods forresearch, sediment cores can be drawn from back-barrier areas and radiocarbondated to find a range of dates of deposition.
Back-barrier areas are located between barrier islands and the mainlandand can consist of bodies of water such as bays, lagoons, and marshes (Donnellyet al., 2001a). When an intensehurricane occurs, strong storm surges can overtop the barrier island, removingsediment from beaches and nearshore environments and depositing the sedimentsin overwash fans across the back-barrier areas. These sediment depositions are then preserved, and when cores areextracted, the sediments in each overwash layer can be dated to theirrespective time period of deposition (Donnelly et al., 2001a).
Often times, researchers will use aerialphotographs of recorded storms to match the sediments to specific storms, andwhen this occurs, they can begin to look further back, often in excess of 2,000years, and speculate when intense hurricanes struck an area and how strong thehurricanes were. In a study conducted byJeffrey Donnelly at Brown University in 2001, a team of researchers collected14 core samples from the Succotash salt marsh in East Matunuck, Rhode Island,and used these samples accompanied by recorded aerial photographs and data toanalyze the intense hurricane history of the study area (Donnelly et al.,2001a). Initially, the two historicallyrecorded overwash fans were discovered in the stratigraphic record and linkedto intense hurricanes in 1954 and 1938, but an additional four large-scale fanswere found to be deposited in the marsh sediments as well. Of the six total fans the team found, four ofthem were deposited in recent history, and were determined to be the result ofstorms in 1954, 1938, 1815, and 1638 or 1635. The two remaining overwash fans were prehistoric, with no recorded dataof intense hurricanes at the time of deposition. Through radiocarbon dating, the team foundthat the prehistoric fans were deposited in two time periods between 1295-1407and 1404-1446 and were most likely the result of intense hurricanelandfall. Based on the sedimentary coresamples gathered, the correlation of the fans to recorded storms, and theradiocarbon dating of the prehistoric deposits, Donnelly and his team were ableto conclude that a total of 7 intense hurricanes struck the Southern RhodeIsland coast in the past 700 years (Donnelly et al.
, 2001a). By doubling the time period of study fromwhat was recorded, this team of researchers was able to discover two additionalintense hurricanes that were not previously recorded. Although doubling the time frame of what waspreviously recorded is taking a step in the right direction, this method hasmuch more potential, as shown by Kam-biu Liu in a study that looked 7,000 yearsinto the past in order to draw conclusions on coastal environmental changes andcatastrophic hurricane landfalls (Liu & Fearn, 2000). In addition to looking into the past ofintense hurricane landfalls, sedimentary deposits can help researchers lookinto the future as well. When scientistsknow how many intense storms occurred over a long period of time, they cancalculate the probability of a similar intense hurricane happening each year,by dividing the total number of intense storms in the time period by the numberof years the research encompassed (Donnelly et al., 2001b).
In another study conducted by JeffreyDonnelly and his research team from Brown University, the focus was turned onthe number of intense hurricane strikes that effected the Southern New Jerseycoast in the last 700 years. His teamcollected nine samples and found three historic and prehistoric overwashdeposits associated with intense storms over a 700 year period. Of those three intense storms, two weredetermined to be intense hurricanes with the third being the Ash Wednesdaynortheaster which occurred March 5-8, 1962. By knowing the total number of intense hurricanes that made landfall inSouthern New Jersey in the last 700 years, Donnelly’s team concluded that theannual landfall probability for the area was 0.
3%, meaning that one landfall isprobable every 350 years (Donnelly et al., 2001b). Calculating the probability of an intensestorm landfall is relatively simple, and is done by dividing the number ofintense storms by the number of years in the study period, and lastlymultiplying the result times 100 to change the figure into a percentage.
Hypothetically, if there were 7 intensehurricane landfalls in an area over the course of 1,300 years, the probabilityof a similar storm making landfall would be calculated by:This probability figureof .539% means that every year, this certain study area has a .539% chance ofan intense hurricane making landfall. Usingmethods like these, researchers and meteorologists can better prepare forstorms and gain a greater understanding of the frequency of intense hurricanelandfall in a particular area. The useof data to predict probability is another reason why the use of radiocarbondating in sedimentary core samples can be valuable when both analyzing paststorms as well as predicting future ones.Anotheruse of sedimentary evidence when investigating hurricanes is identifying timeperiods of hurricanes and analyzing what climatic factors influenced thespecific period. When investigating thepast intense hurricane activity in a certain area, sedimentary core samples andcarbon dating can also be used to identify times of frequent hurricanes andtimes when there weren’t so many hurricanes (Liu & Fearn, 2000). In a study performed by Kam-biu Liu andMiriam L.
Fearn of Lousiana State University and the University of SouthAlabama, sediment cores were taken from Western Lake, FL and used to provide a7,000 year record of coastal environmental changes and catastrophic hurricanelandfalls along the Gulf Coast. Usingthe sedimentary record provided by various core samples from the lake, the pairconcluded that there were few intense hurricanes during the periods of 5000-3400years ago and 1000 years ago to present. Oppositely, it was determined that a period of frequent, intensehurricane landfalls occurred between 3400 and 1000 years ago. These assumptions were drawn based on theoverwash sediment depositional layers in the lake combined with radiocarbondating of the samples.
From theirresearch, Liu and Fearn concluded that the fluctuations in hurricane frequencyand intensity were related to shifts in the positions of the Jet Stream andBermuda High, instead of changes in climate (Liu & Fearn, 2000). This information can be useful inunderstanding the origins of these storms, what causes them, and can also helpscientists better understand how changing climate affects the severity andfrequency of intense hurricanes. It haslong been proposed that hurricane frequency is directly related to the increasein surface water temperatures in the ocean, but some scientists refute thisproposal, claiming that instrumental record is too short and inconsistent toshow definitive trends in data.
Sedimentary core samples can be used to study the correlations betweenclimatic conditions and hurricane activity on substantially longer time scalesthan instrumental record can show, allowing researchers to determine whatclimatic factors influence hurricane formation and frequency the most (Donnelly& Woodruff, 2007). In a studyconducted by Jeffrey Donnelly and Jonathan Woodruff, the pair looked more intothe relationship between climate and intense hurricanes by researching 5,000years of intense hurricane activity based on sedimentary deposits from aCaribbean lagoon. Core samples ofsedimentary deposits in the lagoon were extracted and radiocarbon dated so thatthe two researchers could formulate a historical timeline pertaining to intensehurricane landfall. They found thatintense hurricane landfall has varied throughout the last 5,000 years oncentennial to millennial scales, which triggered the pair to dig further intothe data. When the sediment record wascompared to the paleo-climate records, it was determined that intense hurricanelandfall frequency was not varied by climate change, but instead by variancesin atmospheric conditions. The twoinfluential atmospheric dynamics Donnelly and Woodruff found to be causing thevariances were the El Niño current and the varying strength of the West Africanmonsoon. They concluded that sea surfacetemperatures as high as ones in the present day are not necessary to supportperiods of increased intense hurricane frequency, and that in order toaccurately predict changes in hurricane frequency, it is crucial to understandatmospheric dynamics such as the El Niño and West African monsoon (Donnelly& Woodruff, 2007). Research andconclusions encompassing the climatic conditions that have historically causedincreases and decreases in intense hurricane landfall frequency are yet anothervaluable result of using sedimentary evidence to analyze intense stormaction.
The relationships betweenhurricanes and climate are of special importance in the present day consideringthat the Earth is experiencing a warming period faster than ever before. By understanding the effects of climate onpast intense storm systems, scientists can better understand why patterns ofintense storm landfall are increasing in the present day.Finally,sedimentary evidence can be used to discover correlations between different stronghurricane landfalls over large areas such as oceans, but only when similar datais collected and compared from the separate study areas. When data is used in this way, the similaritiesand differences in climatic and storm characteristics can be explained betweendifferent coastal points that share the same oceanic mass, and conclusions canbe drawn regarding the intense hurricane activity in that specific ocean perunit time (Scileppi & Donnelly, 2007). This data is particularly useful when trying to understand the overallpresence of intense hurricanes in an area throughout a specific period. The process begins when sedimentary coresamples are taken and analyzed, where researchers are looking for evidence ofoverwash fans and attempting to link these sedimentary deposits to specifictime periods via radiocarbon dating. From here, researchers can further make conclusions on what time periodscontained high or low hurricane frequency, and link these conclusions tospecific climatic events or cycles.
Onceall of the data is acquired and overall conclusions are drawn based on onespecific coastal point, similar records of data can be pulled from differentcoastline points that share the same ocean, and comparison can begin to takeplace (Scileppi & Donnelly, 2007). Often,similarities are seen in the data from different areas, which helps researchersgain a better understanding of the consistency of hurricanes as well as whatcauses the different cycles of high and low storm frequencies. One specific study conducted by ElyseScileppi and Jeffrey Donnelly used overwash deposits, radiocarbon dating, anddocumented data to analyze the correlation between intense hurricane landfallsin New York City, the Gulf Coast, and the Caribbean coast. They began their study by recovering evidenceof strong hurricane landfall in the New York City area from historical records,and furthered their investigations by looking for evidence of prehistoric stormlandfall in the backbarrier sediments of the area.
The pair found that the overwash deposits inthe area were related to the documented landfalls of the area’s most intensehurricanes in 1893, 1821, 1788, and 1693. They also found a large gap in the frequency of intense hurricanelandfall in the area that started directly before recorded history began, andconcluded based on sedimentary evidence from multiple sites, that a period ofinfrequent intense storm landfall possibly occurred between 900 years ago and250 years ago (Scileppi & Donnelly, 2007). Adding to these findings, their research found that the lower seasurface temperatures caused by the back end of the Little Ice Age did not deterintense storm landfall. Instead of adecrease in landfall with lower sea surface temperatures than today, the areaexperienced an increase in overall intense hurricane landfall. When the team compared their researchfindings to findings from similar studies performed in different areas, theywere able to conclude that intense hurricane landfalls in the New York Cityarea were roughly synchronous with similar landfalls observed on the CaribbeanCoast and Gulf Coast. Finally, theydetermined that the changes in landfall frequency were experienced across theNorth Atlantic Ocean instead of just at their research site of the New YorkCity area (Scileppi & Donnelly, 2007).
Studies like the one conducted by this research pair are crucial whenattempting to understand the relationship between environmental factors andintense storms, and they can often illustrate different trends experienced inprehistoric eras. By understanding howthe trends in data such as climate, sea surface temperatures, and sea levelrelate to intense hurricane landfall, meteorologists and scientists can notonly better understand the environmental factors of the past, but can also drawrelationships to the present and future. As sea level trends and climate continue to change, it is of the utmostimportance for the science community and coastal population to understand howthe frequency of intense storm landfall will change.Inconclusion, sedimentary evidence can be an extremely powerful tool to use whenanalyzing the past, present, and future of intense hurricane landfall. Core samples from backbarrier areas coupledwith radiocarbon dating techniques can reveal an overwhelming amount ofinformation about hurricane landfalls, and specifically about those thatoccurred far before the beginning of recorded history.
Since recorded history only goes back about370 years, there are no documents or evidence of hurricane landfalls beforethis point in time, so sedimentary evidence is often the only proof availablethat intense storm landfall occurred at all (Donnelly et al., 2001a). Researchers can use this sedimentary evidenceto analyze prehistoric storm landfalls, and they can further use it to betterpredict hurricanes moving into the future. Also, sedimentary evidence can be used to estimate time periods of frequentintense storm landfall as well as periods of lower frequency storm landfall(Donnelly et al., 2001b). This is alsoimportant when attempting to draw relationships between past conditions andpresent ones moving into the future. Finally, sedimentary evidence can be used to form relationships betweendifferent locations of landfalls spread out across large areas such as oceanicmasses.
This is done by using similarresearch methods at different locations and then comparing data and conclusionsin search of a correlation between the locations. If data is relatively synchronous between thedifferent locations, it can be concluded that the entire area had experiencedhigher or lower than normal intense storm landfall, instead of just onespecific location. From here, researcherscan make conclusions as to what climatic conditions were occurring at the timeand how they relate to the formation and landfall of intense storms (Scileppi& Donnelly, 2007). Overall,sedimentary deposits are a valuable tool in analyzing prehistoric intensehurricane landfalls, and they can help give scientists and researchers adetailed outline of when a hurricane made landfall, how intense it was, theclimatic conditions the earth was experiencing at the time, and the probabilityof a similar storm occurring in the near or distant future. References(2015). Hurricanes: Science and Society.
Retrieved from http://www.hurricanescience.org/science/science/hurricanestructure/ Donnelly, J.P., Bryant, S.S., Butler, J.
, Dowling,J., Fan, L., Hausmann, N., . . . Webb III, T. (2001).
700 yr sedimentary record of intensehurricane landfalls in Southern New England. Geological Society of America, 113(6), 714-727.Donnelly,J.P., Roll, S.
, Wengren, M., Butler, J., Lederer, R., Webb III, T. (2001). Sedimentary evidence of intense hurricanestrikes from New Jersey.
Geological Survey of America, 29(7), 615-618.Donnelly,J.P., Woodruff, J.D.
(2007). Intensehurricane activity over the past 5,000 years controlled by El Niño and the WestAfrican monsoon. Nature Publishing Group, 447, 465-468. https://www.researchgate.net/publication/6309528Liu,K.
B., Fearn, M.L. (2000). Reconstructionof Prehistoric Landfall Frequencies of Catastrophic Hurricanes in NorthwesternFlorida from Lake Sediment Records. Quaternary Research, 54(2), 238-245.Scileppi,E.
, Donnelly, J. P. (2007). Sedimentaryevidence of hurricane strikes in western Long Island, New York. GeochemistryGeophysics Geosystems, 8(6), 1-25.TheColumbia Encyclopedia, 6th ed.
Hurricane. Retrieved from http://www.encyclopedia.com/earth-and-environment/atmosphere-and-weather/weather-and-climate-terms-and-concepts/hurricane