Paleotempestology is the study of past
tropical cyclone
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
activity by means of geological proxies as well as historical documentary records. The term was coined by American meteorologist
Kerry Emanuel
Kerry Andrew Emanuel (born April 21, 1955) is an American professor of meteorology currently working at the Massachusetts Institute of Technology in Cambridge. In particular he has specialized in atmospheric convection and the mechanisms acting t ...
.
The usual approach in paleotempestology is the identification of deposits left by storms. Most commonly, these are
overwash Overwash is the flow of water and sediment over a coastal dune or beach crest during storm events (or other situations with high water). 'Overwash' may refer only to the landward flux of water due to overtopping of a dune system while 'washover' may ...
deposits in waterbodies close to the coast; other means are
oxygen isotope
There are three known stable isotopes of oxygen (8O): , , and .
Radioactive isotopes ranging from to have also been characterized, all short-lived. The longest-lived radioisotope is with a half-life of , while the shortest-lived isotope is ...
ratio variations caused by tropical cyclone rainfall in trees or
speleothem
A speleothem (; ) is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on ...
s (cave deposits), and identifying
beach ridge
A beach ridge is a wave-swept or wave-deposited ridge running parallel to a shoreline. It is commonly composed of sand as well as sediment worked from underlying beach material. The movement of sediment by wave action is called ''littoral tra ...
s kicked up by storm waves. The occurrence rate of tropical cyclones can then be inferred from these deposits and sometimes also their intensity – typically the stronger events are the most easily recognizable ones –, by comparing them to deposits left by historical events.
Paleotempestological research has shown that in the
Coast of the Gulf of Mexico and in Australia, the occurrence rate of intense tropical cyclones is about once every few centuries, and there are long-term variations in occurrence which are caused, for example, by shifts in their paths. Common problems in paleotempestology are confounding factors such as
tsunami
A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...
-generated deposits, and the fact that only some parts of the world have been investigated.
Definition and rationale
Paleotempestology is the estimation of tropical cyclone activity with the help of
proxy
Proxy may refer to:
* Proxy or agent (law), a substitute authorized to act for another entity or a document which authorizes the agent so to act
* Proxy (climate), a measured variable used to infer the value of a variable of interest in climate ...
data. The name was coined by
Kerry Emanuel
Kerry Andrew Emanuel (born April 21, 1955) is an American professor of meteorology currently working at the Massachusetts Institute of Technology in Cambridge. In particular he has specialized in atmospheric convection and the mechanisms acting t ...
of the
Massachusetts Institute of Technology
The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...
; the field has seen increased activity since the 1990s and studies were first carried out in the
United States of America
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...
on the
East Coast
East Coast may refer to:
Entertainment
* East Coast hip hop, a subgenre of hip hop
* East Coast (ASAP Ferg song), "East Coast" (ASAP Ferg song), 2017
* East Coast (Saves the Day song), "East Coast" (Saves the Day song), 2004
* East Coast FM, a ra ...
.
The realisation that one cannot rely solely on historical records to infer past storm activity was a major driving force for the development of paleotempestology. The historical record in many places is too short (one century at most) to properly determine the hazard produced by tropical cyclones, especially the rare very intense ones which at times are undersampled by historical records; in the United States, for example, only about 150 years of record are available, and only a small number of hurricanes classified as category 4 or 5 – the most destructive ones on the
Saffir-Simpson scale – have come ashore, making it difficult to estimate the hazard level. Such records may also not be representative for future weather patterns.
Information about past tropical cyclone occurrences can be used to constrain how their occurrences may change in the future, or about how they respond to large-scale climate modes, such as
sea surface temperature
Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air mass ...
changes. In general, the origin and behaviour of tropical cyclone systems is poorly understood, and there is concern that
human-caused global warming will increase the intensity of tropical cyclones and the frequency of strong events by increasing sea surface temperatures.
Techniques
In general, paleotempestology is a complex field of science that overlaps with other disciplines like
climatology
Climatology (from Greek , ''klima'', "place, zone"; and , '' -logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. This modern field of stud ...
and
coastal geomorphology. A number of techniques have been used to estimate the past hazards from tropical cyclones. Many of these techniques have also been applied to studying
extratropical storm
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of ...
s, although research on this field is less advanced than on tropical cyclones.
Overwash deposits
Overwash Overwash is the flow of water and sediment over a coastal dune or beach crest during storm events (or other situations with high water). 'Overwash' may refer only to the landward flux of water due to overtopping of a dune system while 'washover' may ...
deposits in
atoll
An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gr ...
s, coastal lakes,
marsh
A marsh is a wetland that is dominated by herbaceous rather than woody plant species.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p Marshes can often be found at ...
es or
reef flat
A fringing reef is one of the three main types of coral reef. It is distinguished from the other main types, barrier reefs and atolls, in that it has either an entirely shallow backreef zone (lagoon) or none at all. If a fringing reef grows direc ...
s are the most important
paleoclimatological
Paleoclimatology (British spelling, palaeoclimatology) is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to ...
evidence of tropical cyclone strikes. When storms hit these areas, currents and waves can overtop barriers, erode these and other beach structures, and lay down deposits in the water bodies behind barriers. Isolated breaches and especially widespread overtopping of coastal barriers during storms can generate fan-like, layered deposits behind the barrier. Individual layers can be correlated to particular storms in favourable circumstances; in addition they are often separated by a clear boundary from earlier sediments. Such deposits have been observed in
North Carolina
North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...
after
Hurricane Isabel
Hurricane Isabel was the strongest Atlantic hurricane since Mitch, and the deadliest, costliest, and most intense hurricane in the 2003 Atlantic hurricane season. Hurricane Isabel was also the strongest hurricane in the open waters of the Atlanti ...
in 2003, for example. The intensity and impacts of the tropical cyclone can also be inferred from overwash deposits by comparing the deposits to these formed by known storms and analyzing their
lithology
The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...
(their physical characteristics). Additionally, thicker sediment layers usually correspond to stronger storm systems. This procedure is not always clear-cut however.
Several techniques have been applied to separate out storm overwash deposits from other sediments:
* Compared to the normal sedimentation processes in such places, tropical cyclone deposits are rougher and can be detected with
sieving
A sieve, fine mesh strainer, or sift, is a device for separating wanted elements from unwanted material or for controlling the particle size distribution of a sample, using a screen such as a woven mesh or net or perforated sheet material. ...
,
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...
-dependent technologies or
x-ray fluorescence
X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis ...
techniques.
* In sediment cores, deposits formed by tropical cyclones may be denser due to a larger proportion of mineral content associated with overwashes, which can be detected with x-ray fluorescence techniques.
* They may contain less organic matter than deposits formed through steady sedimentation, which can be detected by combusting the deposits and measuring the resulting mass loss. This and sediment grain sizes are the most common research tools for sediment cores.
* A little used technique is the analysis of organic material in
sediment core
A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The ...
s; there are characteristic changes in carbon and nitrogen isotope ratios after flooding and the entering of seawater, including a general increase in biological productivity.
* Overwash deposits can contain elements that do not normally occur at the site, such as
strontium
Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...
; this can be detected with x-ray fluorescence techniques.
* Overwash deposits have usually brighter colors than those generated during steady sedimentation.
* Storm surges can transport living structures into such deposits that do not normally occur in these settings.
Drought
A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...
s or the entry of water unrelated to a storm can confound such records, however. Thus, this method is often supplemented with other proxies. The most common living structure employed here are
foraminifera
Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular Ectoplasm (cell biology), ectoplasm for catching food and ot ...
, although
bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...
s,
diatom
A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...
s,
dinoflagellate
The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...
s,
ostracod
Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...
s and
pollen
Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
have also been used. Marine foraminifera, however, are not always present in deposits formed by historical storms.
Generally, sites suitable for obtaining paleotempestology records are not found along the entire length of the coastline, and depending on the properties of the site such as vegetation cover, they might only track storms approaching from a certain direction. Prerequisites for successful correlation of overwash deposits to tropical cyclones are:
* The absence of
tsunami
A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...
s in the region, as their deposits can usually not be easily distinguished from storm deposits.
* The investigation area should have low biological activity, as
bioturbation
Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a pr ...
can otherwise erase evidence of storm deposits. Low biological activity can be found in sites with high salt or low oxygen concentrations.
* A high geomorphic stability of the site.
* High sedimentation rates can facilitate the preservation of storm deposits.
*
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.
Tide t ...
s can destroy layered storm deposits; thus non-tidal waterbodies are ideally used. In tidally active waterbodies, correlations involving various sediment cores can be applied.
Dating and intensity determination
Various dating techniques can then be used to produce a chronology of tropical cyclone strikes at a given location and thus a recurrence rate; for example, at Lake Shelby in Alabama a return period of once every 318 years was determined. The storms in the Lake Shelby record have windspeeds of over as
Hurricane Ivan
Hurricane Ivan was a large, long-lived, Cape Verde hurricane that caused widespread damage in the Caribbean and United States. The cyclone was the ninth named storm, the sixth hurricane and the fourth major hurricane of the active 2004 Atlan ...
which in 2004 made landfall in the region at that intensity did not leave a deposit. Based on geological considerations the minimum windspeed of storms recorded there might be .
For dating purposes
radiometric dating
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares t ...
procedures involving
carbon-14
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...
,
cesium-137
Caesium-137 (), cesium-137 (US), or radiocaesium, is a radioactive isotope of caesium that is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nuclea ...
, and
lead-210
Lead (82Pb) has four stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium ...
are most commonly used, often in combination.
Uranium series
In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations. It is also known as a "radioactive cascade". Most radioisotopes do not decay direct ...
dating,
optically stimulated luminescence
In physics, optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It is used in at least two applications:
* Luminescence dating of ancient materials: mainly geological sediments and sometimes fired pott ...
, and correlations to human
land use
Land use involves the management and modification of natural environment or wilderness into built environment such as settlements and semi-natural habitats such as arable fields, pastures, and managed woods. Land use by humans has a long h ...
can also be used in some places.
Beach ridges
Beach ridges and
chenier
A chenier or chénier is a sandy or shelly beach ridge that is part of a strand plain, called a “chenier plain,” consisting of cheniers separated by intervening mud-flat deposits with marsh and swamp vegetation. Cheniers are typically 1 to ...
s form when storm surges, storm waves or tides deposit debris in ridges, with one ridge typically corresponding to one storm. Ridges can be formed by
coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
rubble where
coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
Co ...
s lie at the coast, and can contain complicated layer structures,
shells,
pumice
Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular vol ...
, and
gravel
Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone.
Gravel is classifi ...
. A known example is the ridge that
Cyclone Bebe
Severe Tropical Cyclone Bebe, also known as Hurricane Bebe, was a pre-season storm during October 1972 in the South Pacific Ocean that severely affected Fiji, the Ellice Islands (now Tuvalu), and the Gilbert Islands (now Kiribati).
Meteorologica ...
generated on
Funafuti
Funafuti is the capital of the island nation of Tuvalu. It has a population of 6,320 people (2017 census), and so it has more people than the rest of Tuvalu combined, with approximately 60% of the population. It consists of a narrow sweep of la ...
atoll in 1971.
Beach ridges are common on the
delta
Delta commonly refers to:
* Delta (letter) (Δ or δ), a letter of the Greek alphabet
* River delta, at a river mouth
* D ( NATO phonetic alphabet: "Delta")
* Delta Air Lines, US
* Delta variant of SARS-CoV-2 that causes COVID-19
Delta may also ...
ic shores of China, and are indicative of increased typhoon activity. They have also been found on the
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
n coast facing the
Great Barrier Reef
The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...
and are formed from reworked corals. The height of each ridge appears to correlate with the intensity of the storm that produced it, and thus the intensity of the forming storm can be inferred by
numerical modelling
Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be dete ...
and comparison to known storms and known storm surges. Ridges tend to be older the farther inland they are; they can also be dated through optically stimulated luminescence and
radiocarbon dating
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.
The method was dev ...
. In addition, no tsunami-generated beach ridges have been observed, and tsunamis are important confounding factors in paleotempestology.
Wind-driven erosion or accumulation can alter the elevation of such ridges, and, in addition, the same ridge can be formed by more than one storm event as has been observed in Australia. Beach ridges can also shift around through non-storm processes after their formation and can form through non-tropical cyclone processes. Sedimentary texture can be used to infer the origin of a ridge from storm surges.
Isotope ratios
Precipitation in tropical cyclones has a characteristic
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...
composition with a depletion of heavy
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
isotopes;
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
and
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
isotope data have also been used to infer tropical cyclone activity. Corals can store oxygen
isotope ratio
The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...
s which in turn reflect water temperatures, precipitation and evaporation; these in turn can be related to tropical cyclone activity. Fish
otolith
An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The sa ...
s and
bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...
s can also store such records, as can trees where the oxygen isotope ratios of precipitation are reflected in the
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
of trees, and can be inferred with the help of
tree ring
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
s. However, confounding factors like natural variation and soil properties also influence oxygen isotope ratios of tree cellulose. For these reasons, only the frequency of storms can be reliably estimated from tree ring isotopic records, not their intensity.
Speleothem
A speleothem (; ) is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on ...
s, deposits formed in
cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
s through the dissolution and redeposition of
dolomite Dolomite may refer to:
*Dolomite (mineral), a carbonate mineral
*Dolomite (rock), also known as dolostone, a sedimentary carbonate rock
*Dolomite, Alabama, United States, an unincorporated community
*Dolomite, California, United States, an unincor ...
and
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
, can store isotope signatures associated with tropical cyclones, especially in fast growing speleothems, areas with thin soils and speleothems which have undergone little alteration. Such deposits have a high temporal resolution, and are also protected from many confounding factors although the extraction of annual layers has become possible only recently, with a two-week resolution (two separate layers correlated to two hurricanes that struck two weeks apart) achieved in one case. However, the suitability of speleothems depends on the characteristics of the cave they are found in; caves that flood frequently may have their speleothems eroded or otherwise damaged, for example, making them less suitable for paleotempestology research. Caves where speleothems form mainly during the offseason are also likely to miss tropical cyclones. Very old records can be obtained from oxygen isotope ratios in rocks.
Other techniques
Historical documents such as county
gazette
A gazette is an official journal, a newspaper of record, or simply a newspaper.
In English and French speaking countries, newspaper publishers have applied the name ''Gazette'' since the 17th century; today, numerous weekly and daily newspapers ...
s in China, diaries,
logbook
A logbook (or log book) is a record used to record states, events, or conditions applicable to complex machines or the personnel who operate them. Logbooks are commonly associated with the operation of aircraft, nuclear plants, particle accelera ...
s of travellers, official histories and old newspapers can contain information on tropical cyclones. In China such records go back over a millennium, while elsewhere it is usually confined to the last 130 years. Such historical records however are often ambiguous or unclear. The frequency of
shipwreck
A shipwreck is the wreckage of a ship that is located either beached on land or sunken to the bottom of a body of water. Shipwrecking may be intentional or unintentional. Angela Croome reported in January 1999 that there were approximately ...
s has been used to infer past tropical cyclone occurrence, such as has been done with a database of shipwrecks that the
Spaniards
Spaniards, or Spanish people, are a Romance peoples, Romance ethnic group native to Spain. Within Spain, there are a number of National and regional identity in Spain, national and regional ethnic identities that reflect the country's complex Hist ...
suffered in the
Caribbean
The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
.
Aside from oxygen isotope ratios, tree rings can also record information on storm-caused plant damage or vegetation changes, such as thin tree rings due to storm-induced damage to a tree canopy, and
saltwater intrusion
Saltwater intrusion is the movement of saline water into freshwater aquifers, which can lead to groundwater quality degradation, including drinking water sources, and other consequences. Saltwater intrusion can naturally occur in coastal aquifers ...
and the resulting slowdown in tree growth. The term "dendrotempestology" is used in this context. Speleothems can also store trace elements which can signal tropical cyclone activity and mud layers formed by storm-induced cave flooding. Droughts on the other hand can cause
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
levels to drop enough that subsequent storms cannot induce flooding and thus fail to leave a record, as has been noted in
Yucatan.
Other techniques:
*
Rhythmite
A rhythmite consists of layers of sediment or sedimentary rock which are laid down with an obvious periodicity and regularity. They may be created by annual processes such as seasonally varying deposits reflecting variations in the runoff cycle, b ...
s in river mouths. These are formed when storms resuspend sediments; the sediments when the storm wanes fall out and form the deposits, especially in places with high sediment supplies. Carbon isotope and chemical data can be used to distinguish them from non-storm sedimentation.
*
Sand dune
A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...
s at coastlines is influenced by storm surge height, and sand splays can be formed when sand is swept off these dunes by storm surges and waves; such deposits however are better studied in the context of tsunamis and there is no clear way to distinguish between tsunami- and storm-formed splays.
* Hummocky deposits in shallow seas, known as
tempestite
Tempestites are storm deposits that can be recognized throughout the geologic record. They are studied in the scientific disciplines of sedimentary geology and paleotempestology. The deposits derive their meaning from the word ''tempest'', a vi ...
s. The mechanics of their formation are still controversial, and such deposits are prone to reworking which wipes out the traces of a storm.
* Boulders and coral blocks can be moved by storms and such moved blocks can potentially be dated to obtain the age of the storm, if certain conditions are met. They can be correlated to storms with the help of oxygen isotope excursions for example. This technique has also been applied to islands formed by storm-moved blocks.
*
Wave
In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (res ...
-driven erosion during storms can create
scarps which can be dated with the assistance of optically-stimulated luminescence. Such scarps however tend to be altered over time – later storms can erode away older scarps, for example – and their preservation and formation is often strongly dependent on the local geology.
* Other techniques involve the identification of
freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
flood deposits by storms such as
humic acid Humic substances (HS) are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). For a long era in the 19th ...
and other evidence in corals, and lack of
bromine
Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simila ...
– which is common in marine sediments – in flood-related deposits, and
oyster
Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not al ...
bed kills caused by sediments suspended by storms (oyster kills however can also be caused by non-storm phenomena).
* Luminescence of coral deposits has been used to infer tropical cyclone activity.
Timespans
A database of tropical cyclones going back to 6,000 BC has been compiled for the western
North Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe an ...
. In the
Gulf of Mexico
The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...
, records go back five millennia but only a few typhoon records go back 5,000–6,000 years. In general, tropical cyclone records do not go farther back than 5,000–6,000 years ago when the Holocene sea level rise levelled off; tropical cyclone deposits formed during sea level lowstands likely were reworked during sea level rise. Only tentative evidence exists of deposits from the
last interglacial. Tempestite deposits and oxygen isotope ratios in much older rocks have also been used to infer the existence of tropical cyclone activity as far back as the
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
.
Results
Paleotempestological information has been used by the
insurance
Insurance is a means of protection from financial loss in which, in exchange for a fee, a party agrees to compensate another party in the event of a certain loss, damage, or injury. It is a form of risk management, primarily used to hedge ...
industry in
risk analysis in order to set insurance rates. The industry has also funded paleotempestological research. Paleotempestology information is further of interest to
archeologist
Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts ...
s,
ecologist
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...
s, and forest and water resource managers.
Recurrence rates
The
recurrence rate, the time gap between storms, is an important metric used to estimate tropical cyclone risk, and it can be determined by paleotempestological research. In the Gulf of Mexico, catastrophic hurricane strikes at given locations occur once about every 350 years in the last 3,800 years or about 0.48%–0.39% annual frequency at any given site, with a recurrence rate of 300 years or 0.33% annual probability at sites in the Caribbean and Gulf of Mexico;
category 3 or more storms occur at a rate of 3.9–0.1 category 3 or more storms per century in the northern Gulf of Mexico. Elsewhere, tropical cyclones with intensities of category 4 or more occur about every 350 years in the
Pearl River Delta
The Pearl River Delta Metropolitan Region (PRD; ; pt, Delta do Rio das Pérolas (DRP)) is the low-lying area surrounding the Pearl River estuary, where the Pearl River flows into the South China Sea. Referred to as the Guangdong-Hong Kong-Mac ...
(
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
), one storm every 100–150 years at Funafuti and a similar rate in
French Polynesia
)Territorial motto: ( en, "Great Tahiti of the Golden Haze")
, anthem =
, song_type = Regional anthem
, song = " Ia Ora 'O Tahiti Nui"
, image_map = French Polynesia on the globe (French Polynesia centered).svg
, map_alt = Location of Frenc ...
, one category 3 or stronger every 471 years in
St. Catherines Island (
Georgia
Georgia most commonly refers to:
* Georgia (country), a country in the Caucasus region of Eurasia
* Georgia (U.S. state), a state in the Southeast United States
Georgia may also refer to:
Places
Historical states and entities
* Related to the ...
), 0.3% each year for an intense storm in eastern
Hainan
Hainan (, ; ) is the smallest and southernmost province of the People's Republic of China (PRC), consisting of various islands in the South China Sea. , the largest and most populous island in China,The island of Taiwan, which is slightly l ...
, one storm every 140–180 years in
Nicaragua
Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the cou ...
, one intense storm every 200–300 years in the Great Barrier Reef – formerly their recurrence rate was estimated to be one strong event every few millennia – and one storm of category 2–4 intensity every 190–270 years at
Shark Bay
Shark Bay (Malgana: ''Gathaagudu'', "two waters") is a World Heritage Site in the Gascoyne region of Western Australia. The http://www.environment.gov.au/heritage/places/world/shark-bay area is located approximately north of Perth, on the ...
in
Western Australia
Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
. Steady rates have been found for the Gulf of Mexico and the
Coral Sea
The Coral Sea () is a marginal sea of the South Pacific off the northeast coast of Australia, and classified as an interim Australian bioregion. The Coral Sea extends down the Australian northeast coast. Most of it is protected by the Fre ...
for timespans of several millennia.
However, it has also been found that the occurrence rates of tropical cyclone measured with instrumental data over historical time can be significantly different from the actual occurrent rate. In the past, tropical cyclones were far more frequent in the Great Barrier Reef and the northern Gulf of Mexico than today; in
Apalachee Bay
Apalachee Bay is a bay in the northeastern Gulf of Mexico occupying an indentation of the Florida coast to the west of where the Florida peninsula joins the United States mainland. It is bordered by Taylor County, Florida, Taylor, Jefferson Coun ...
, strong storms occur every 40 years, not every 400 years as documented historically. Serious storms in
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
occurred twice in 300 years not once every millennium or less. In general, the area of Australia appears to be unusually inactive in recent times by the standards of the past 550–1500 years, and the historical record underestimates the incidence of strong storms in Northeastern Australia.
Long term fluctuations
Long-term variations of tropical cyclone activity have also been found. The Gulf of Mexico saw increased activity between 3,800 and 1,000 years ago with a fivefold increase of category 4–5 hurricane activity, and activity at St. Catherines Island and Wassaw Island was also higher between 2,000 and 1,100 years ago. This appears to be a stage of increased tropical cyclone activity spanning the region from
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
to
Puerto Rico
Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...
, while the last 1,000 years have been inactive both there and in the Gulf Coast. Before 1400
AD, the Caribbean and the Gulf of Mexico were active while the East Coast of the United States was inactive, followed by a reversal that lasted until 1675 AD; in an alternative interpretation, the US Atlantic coast and the Caribbean saw low activity between 950 AD and 1700 with a sudden increase around 1700. It is unclear whether in the Atlantic hurricane activity is more regionally modulated or basin-wide. Such fluctuations appear to mainly concern strong tropical cyclone systems, at least in the Atlantic; weaker systems have a more steady pattern of activity. Rapid fluctuations over short timespans have also been observed.
In the Atlantic Ocean, the so-called "
Bermuda High
The Azores High also known as North Atlantic (Subtropical) High/Anticyclone or the Bermuda-Azores High, is a large subtropical semi-permanent centre of high atmospheric pressure typically found south of the Azores in the Atlantic Ocean, at the Ho ...
" hypothesis stipulates that changes in the position of this
anticyclone
An anticyclone is a weather phenomenon defined as a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere as viewed from abov ...
can cause storm paths to alternate between
landfall
Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...
s on the East Coast and the
Gulf Coast
The Gulf Coast of the United States, also known as the Gulf South, is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Texas, Louisiana, Mississ ...
but also Nicaragua. Paleotempestological data support this theory although additional findings on
Long Island
Long Island is a densely populated island in the southeastern region of the U.S. state of New York (state), New York, part of the New York metropolitan area. With over 8 million people, Long Island is the most populous island in the United Sta ...
and Puerto Rico have demonstrated that storm frequency is more complex as active periods appear to correlate between the three sites. A southward shift of the High has been inferred to have occurred 3,000–1,000 years ago, and has been linked with the "hurricane hyperactivity" period in the Gulf of Mexico between 3,400 and 1,000 years ago. Conversely a decrease in hurricane activity is recorded after the mid-millennium period and after 1,100 the Atlantic changes from a pattern of widespread activity to a more geographically confined one. Between 1,100-1,450 the Bahamas and the Florida Gulf Coast were frequently struck while between 1,450-1,650 activity was higher in New England. Furthermore, a tendency to a more northerly storm track may be associated with a strong
North Atlantic Oscillation
The North Atlantic Oscillation (NAO) is a weather phenomenon over the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High. Through fluctuations in the ...
while the
Neoglacial
The neoglaciation ("renewed glaciation") describes the documented cooling trend in the Earth's climate during the Holocene, following the retreat of the Wisconsin glaciation, the most recent glacial period. Neoglaciation has followed the hypsither ...
cooling is associated with a southward shift. In West Asia, high activity in the
South China Sea
The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...
coincides with low activity in
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
and vice versa.
Role of climate modes
The influence of natural trends on tropical cyclone activity has been recognized in paleotempestology records, such as a correlation between
Atlantic hurricane tracks and activity with the status of the
ITCZ
The Intertropical Convergence Zone (ITCZ ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the thermal ...
; position of the
Loop Current
A parent to the Florida Current, the Loop Current is a warm ocean current that flows northward between Cuba and the Yucatán Peninsula, moves north into the Gulf of Mexico, loops east and south before exiting to the east through the Florida Stra ...
(for Gulf of Mexico hurricanes); North Atlantic Oscillation; sea surface temperatures and the strength of the
West African Monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscill ...
; and Australian cyclone activity and the
Pacific Decadal Oscillation
The Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. O ...
. Increased
insolation
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre (W/m ...
– either from
solar activity
Solar phenomena are natural phenomena which occur within the atmosphere of the Sun. These phenomena take many forms, including solar wind, radio wave flux, solar flares, coronal mass ejections, coronal heating and sunspots.
These phenomena are ...
or from
orbit
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...
al variations – have been found to be detrimental to tropical cyclone activity in some regions. In the first millennium AD, warmer sea surface temperatures in the Atlantic as well as more restricted anomalies may be responsible for stronger regional hurricane activity. The climate mode dependency of tropical cyclone activity may be more pronounced in temperate regions where tropical cyclones find less favourable conditions.
Among the known climate modes that influence tropical cyclone activity in paleotempestological records are
ENSO phase variations, which influence tropical cyclone activity in Australia and the Atlantic, but also their path as has been noted for typhoons. More general global correlations have been found, such as a negative correlation between tropical cyclone activity in Japan and the North Atlantic and correlation between the Atlantic and Australia on the one hand and between Australia and French Polynesia on the other hand.
Influence of long-term temperature variations
The effect of general climate variations have also been found. Hurricane and typhoon tracks tend to shift north (e.g.
Amur Bay
Amur Bay (russian: Амурский Залив, ''Amurskiy Zaliv''), a major bay within Peter the Great Gulf of the Sea of Japan, has an approximate length of , a width of to , and a depth of . It is part of a larger bay formed with Ussuri B ...
) during warm periods and south (e.g.
South China
South China () is a geographical and cultural region that covers the southernmost part of China. Its precise meaning varies with context. A notable feature of South China in comparison to the rest of China is that most of its citizens are not n ...
) during cold periods, patterns that might be mediated by shifts in the
subtropical anticyclone
The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as subtropical ridges, or highs. It is a high-pressure ...
s. These patterns (northward shift with warming) has been observed as a consequence of human-induced
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
and the end of the Little Ice Age but also after volcanic eruptions (southward shift with cooling); some volcanic eruptions have been linked to decreased hurricane activity, although this observation is not universal.
The
Dark Ages Cold Period
Darkness, the direct opposite of lightness, is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black or brown.
Human vision is unable to distinguish colors in conditions of very low lu ...
has been linked to decreased activity off Belize. Initially the
Medieval Climate Anomaly
The Medieval Warm Period (MWP), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly, was a time of warm climate in the North Atlantic region that lasted from to . Climate proxy records show peak warmth occurred at differe ...
featured increased activity across the Atlantic, but later activity decreased along the US East Coast. During the 1350 to present interval in the
Little Ice Age
The Little Ice Age (LIA) was a period of regional cooling, particularly pronounced in the North Atlantic region. It was not a true ice age of global extent. The term was introduced into scientific literature by François E. Matthes in 1939. Ma ...
, there were more but weaker storms in the Gulf of Mexico while hurricane activity did not decrease in western Long Island. Colder waters may have impeded tropical cyclone activity in the Gulf of Mexico during the Little Ice Age. Increased hurricane activity during the last 300 years in the Caribbean may also correlate to the Little Ice Age. The Little Ice Age may have been accompanied by more but weaker storms in the
South China Sea
The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...
relative to preceding or following periods.
The response of tropical cyclones to future global warming is of great interest. The
Holocene Climatic Optimum
The Holocene Climate Optimum (HCO) was a warm period that occurred in the interval roughly 9,000 to 5,000 years ago BP, with a thermal maximum around 8000 years BP. It has also been known by many other names, such as Altithermal, Climatic Optimu ...
did not induce increased tropical cyclone strikes in
Queensland
)
, nickname = Sunshine State
, image_map = Queensland in Australia.svg
, map_caption = Location of Queensland in Australia
, subdivision_type = Country
, subdivision_name = Australia
, established_title = Before federation
, established_ ...
and phases of higher hurricane activity on the Gulf Coast are not associated with global warming; however warming has been correlated with typhoon activity in the
Gulf of Thailand
The Gulf of Thailand, also known as the Gulf of Siam, is a shallow inlet in the southwestern South China Sea, bounded between the southwestern shores of the Indochinese Peninsula and the northern half of the Malay Peninsula. It is around in l ...
and marine warming with typhoon activity in the South China Sea, increased hurricane activity in
Belize
Belize (; bzj, Bileez) is a Caribbean and Central American country on the northeastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a wate ...
(which increased during the
Medieval Warm Period
The Medieval Warm Period (MWP), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly, was a time of warm climate in the North Atlantic region that lasted from to . Proxy (climate), Climate proxy records show peak warmth oc ...
) and during the
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
when
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
caused warming episodes such as the
Toarcian
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
The Toarcian ...
anoxic event
Oceanic anoxic events or anoxic events ( anoxia conditions) describe periods wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic (anoxic and sulfidic) waters. Although anoxic events have not ...
.
After-effects of tropical cyclones
A correlation between hurricane strikes and subsequent
wildfire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...
activity and vegetation changes has been noted in the
Alabamian and
Cuba
Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...
n paleotempestological record. In St. Catherines Island, cultural activity ceased at the time of increased storm activity, and both
Taino settlement of the Bahamas and
Polynesian expansion across the Pacific may have been correlated to decreased tropical cyclone activity. Tropical cyclone induced alteration in oxygen isotope ratios may mask isotope ratio variations caused by other climate phenomena, which may thus be misinterpreted.
On the other hand, the
Classic Maya collapse
In archaeology, the classic Maya collapse is the decline of the Classic Maya civilization and the abandonment of Maya cities in the southern Maya lowlands of Mesoamerica between the 7th and 9th centuries. At Ceibal, the Preclassic Maya e ...
may coincide with, and have been caused by, a decrease in tropical cyclone activity. Tropical cyclones are important for preventing
drought
A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...
s in the southeastern US.
Other patterns
Sites in the Bahamas show more strong storms in the northern Bahamas than the southern ones, presumably because storms approaching the southern Bahamas have passed over the
Greater Antilles
The Greater Antilles ( es, Grandes Antillas or Antillas Mayores; french: Grandes Antilles; ht, Gwo Zantiy; jam, Grieta hAntiliiz) is a grouping of the larger islands in the Caribbean Sea, including Cuba, Hispaniola, Puerto Rico, Jamaica, and ...
before and have lost much of their intensity there. Atmospheric conditions favourable for tropical cyclone activity in the "main development region" of the Atlantic are correlated to unfavourable conditions along the East Coast. The anti-correlation between Gulf of Mexico and Bahamas activity with the US East Coast activity may be due to active hurricane seasons - which tend to increase storm activity in the former - being accompanied by unfavourable climatological conditions along the East Coast.
Problems
Paleotempestological reconstructions are subject to a number of limitations, including the presence of sites suited for the obtainment of paleotempestological records, changes in the hydrological properties of the site due to e.g.
sea level rise
Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...
which increases the sensitivity to weaker storms and "false positives" caused by for example non-tropical cyclone-related floods, sediment winnowing, wind-driven transport, tides, tsunamis, bioturbation and non-tropical storms such as
nor'easter
A nor'easter (also northeaster; see below), or an East Coast low is a synoptic-scale extratropical cyclone in the western North Atlantic Ocean. The name derives from the direction of the winds that blow from the northeast. The original use o ...
s or
winter storm
A winter storm is an event in which wind coincides with varieties of precipitation that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain. In temperate continental climates, these storms are not necessar ...
, the latter of which however usually result in lower surges. In particular, tsunamis are a problem for paleotempestological studies in the
Indian
Indian or Indians may refer to:
Peoples South Asia
* Indian people, people of Indian nationality, or people who have an Indian ancestor
** Non-resident Indian, a citizen of India who has temporarily emigrated to another country
* South Asia ...
and
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
; one technique that has been used to differentiate the two is the identification of traces of runoff which occurs during storms but not during tsunamis.
Not all of the world has been investigated with paleotempestological methods; among the places thus researched are Belize, the
Carolinas
The Carolinas are the U.S. states of North Carolina and South Carolina, considered collectively. They are bordered by Virginia to the north, Tennessee to the west, and Georgia to the southwest. The Atlantic Ocean is to the east.
Combining Nort ...
of North America, northern coasts of the Gulf of Mexico, the northeastern United States, (in a lesser measure) the
South Pacific islands and tropical Australia. Conversely China, Cuba,
Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
,
Hispaniola
Hispaniola (, also ; es, La Española; Latin and french: Hispaniola; ht, Ispayola; tnq, Ayiti or Quisqueya) is an island in the Caribbean that is part of the Greater Antilles. Hispaniola is the most populous island in the West Indies, and th ...
,
Honduras
Honduras, officially the Republic of Honduras, is a country in Central America. The republic of Honduras is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Oce ...
, the
Lesser Antilles
The Lesser Antilles ( es, link=no, Antillas Menores; french: link=no, Petites Antilles; pap, Antias Menor; nl, Kleine Antillen) are a group of islands in the Caribbean Sea. Most of them are part of a long, partially volcanic island arc betwe ...
and
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
north of
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
are poorly researched. The presence of research institutions active in paleotempestology and suitable sites for paleotempestological research and tropical cyclone landfalls may influence whether a given location is researched or not. In the Atlantic Ocean, research has been concentrated on regions where hurricanes are common rather than more marginal areas.
Paleotempestology records mostly record activity during the
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
and tend to record mainly catastrophic storms as these are the ones most likely to leave evidence. In addition, there has been little effort in making comprehensive databases of paleotempestological data or in attempting regional reconstructions from local results. Different sites have different intensity thresholds and thus capture different storm populations.
Also, paleotempestological records, especially overwash records in marshes, are often grossly incomplete with questionable geochronology. Deposition mechanism are poorly documented, and it is often not clear how to identify storm deposits. The magnitude of overwash deposits is fundamentally a function of storm surge height, which, however, is not a function of storm intensity. Overwash deposits are regulated by the height of the overwashed barrier and there is no expectation that it will remain stable over time; tropical cyclones themselves have been observed eroding such barriers and such barrier height decreases (e.g. through storm erosion or sea level rise) may induce a spurious increase of tropical cyclone deposits over time. Successive overwash deposits can be difficult to distinguish, and they are easily eroded by subsequent storms. Storm deposits can vary strongly even a short distance from the landfall point, even over few tens of metres, and changes in tropical cyclone activity recorded at one site might simply reflect the stochastic nature of tropical cyclone landfalls. In particular, in core tropical cyclone activity regions weather variations rather than large-scale modes may control tropical cyclone activity.
Application to non-tropical storms
Paleotempestological research has been mostly carried out in low-latitude regions but research in past storm activity has been conducted in the
British Isles
The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...
, France and the
Mediterranean
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...
. Increases in storm activity on the European Atlantic coast have been noted AD 1350–1650, AD 250–850, AD 950–550, 1550–1350 BC, 3550–3150 BC, and 5750–5150 BC. In southern France, a recurrence rate of 0.2% per year of catastrophic storms has been inferred for the last 2,000 years.
Storm records indicate increased storm activity during colder periods such as the Little Ice Age,
Medieval Dark Age
In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the Post-classical, post-classical period of World history (field), global history. It began with t ...
and
Iron Age Cold Epoch. During cold periods, increased temperature gradients between the polar and low-latitude regions increase
baroclinic
In fluid dynamics, the baroclinity (often called baroclinicity) of a stratified fluid is a measure of how misaligned the gradient of pressure is from the gradient of density in a fluid. In meteorology a baroclinic flow is one in which the densi ...
storm activity. Changes in the North Atlantic Oscillation may also play a role.
Examples
See also
*
Tropical cyclone
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
*
Tropical cyclone observation
Tropical cyclone observation has been carried out over the past couple of centuries in various ways. The passage of typhoons, hurricanes, as well as other tropical cyclones have been detected by word of mouth from sailors recently coming to port ...
*
Tropical cyclones and climate change
Climate change can affect Tropical cyclone, tropical cyclones in a variety of ways: an intensification of rainfall and wind speed, a decrease in overall frequency, an increase in the frequency of very intense Storm, storms and a poleward extensio ...
Notes
References
Citations
General sources
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Further reading
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*{{cite news , first=Andrew C. , last=Revkin , author-link=Andrew Revkin , title=Experts Unearth a Stormy Past , url=https://www.nytimes.com/2001/07/24/science/experts-unearth-a-stormy-past.html , work=The New York Times , date=July 24, 2001 , ref=none
External links
Western North Atlantic Basin 8,000 Year palaeotempestology Database 2018palaeotempestology Resource CenterShipwrecks, tree rings and hurricanes
Tempestology
Tropical cyclone meteorology
Paleoclimatology