Intense Storm Activity Research Articles

Paleostorm redeposition and post-glacial coastal chronology in the eastern Baltic Sea, Latvia

The 494 km long Latvian coast consists of sandy sediments, which serve as an excellent proxy for past coastal events and environment. Our study explores these understudied sediments along the western coast of the Gulf of Riga and combines two sand quartz-wise methods: optically stimulated luminescence (OSL) dating and grain microtextures. We provide a new chronology and microsedimentary results to trace post-glacial storm events and discuss correlations within the Baltic Sea region and elsewhere in Europe. OSL ages reveal a wide time span between 10.38 ± 0.61 ka and 1.04 ± 0.05 ka BP, but their inconsistency in the profiles along with the onshore position of landforms and gravelly horizons argues for sediment relocation due to storm action. A first paleostorm phase is dated to between 7.6 ± 1.2 ka and 4.63 ± 0.27 ka, corresponding with a transgression of the Littorina Sea and the Holocene Thermal Maximum, and with a roughly estimated vertical sediment redeposition above 5 m similar with the recent storms in the region. Sedimentary record from microstudy supports intense storm activity, especially in sediments redeposited after 6.07 ± 0.51 ka, and it is seen through an increased number of cracked quartz grains, shiny grains and fresh surfaces combined with a limited number of V-shaped marks. Weaker storm action, recorded by a lower share of cracked grains in the sediments, occurred between 7.6 ± 1.2 ka and 6.07 ± 0.51 ka.A second storm phase occurred at 1.44 ± 0.21 ka, corresponding with the post-Littorina, again with a performance of a weaker storm. Apart from the palaeostorm records, the beach ridges developed between 5.16 ± 0.33 ka and 4.47 ± 0.31 ka along with drier conditions when aeolian deposition took place twice: at 4.63 ± 0.27 ka and 1.55 ± 0.10 ka.

Cyclone Tauktae Documents a Climate Trend in the Tropics

The western Indian Ocean has been warming at a rate faster than any other region in the tropical oceans, a pattern that is contributing to more frequent and intense storm activity.

SYNOPTYCZNE UWARUNKOWANIA BURZ W PAŹDZIERNIKU 2020 ROKU W POLSCE

The aim of this study is to characterize the occurrence of severe thunderstorms and determine their synoptic conditioning in October 2020 in Poland. In the study, into account were taken three days, i.e. 4, 5 and 10 October, which showed the most intense storm activity. The study considers the number and area of lightning discharges over Poland, the synoptic conditions prevailing in Europe, as well as basic thermodynamic and kinematic indices. The storms in October 2020 were exceptional in comparison to the previous years. They were associated with the migration of cool atmospheric fronts across Poland and the exchange of old polar-marine air masses with polar-marine air masses, which generated the specific thermodynamics and, specifically, the kinetic conditions for the development of thunderstorm cells.

Geomagnetically Induced Currents and Harmonic Distortion: Storm‐Time Observations From New Zealand

AbstractLarge geomagnetic storms are a known space weather hazard to power transmission networks due to the effects of geomagnetically induced currents (GICs). However, research in this area has been hampered by a lack of GIC observations. Previous studies have noted that New Zealand is unusually fortunate in having a comparatively dense, high quality, set of GIC measurements, spanning >60 transformers in >20 substations. However, due to operational reasons these observations are clustered in the mid and lower South Island. In this paper we analyze space weather‐induced GIC impact patterns over the entire country by using a different set of sensors that monitor levels of harmonic distortion, with even and odd harmonics measured separately. GICs lead to half cycle transformer saturation and is one of the few ways in which even harmonics are produced in a well‐run power transmission network. We make use of harmonic distortion measurements at 377 circuit breakers made at 126 separate locations. Focusing on the intense geomagnetic storm activity during 6–9 September 2017, we show how the even harmonic distortion observations provide a useful new picture of GIC‐stressed transformers. These observations demonstrate how GIC effects can be monitored by using even harmonic distortion in locations where no GIC measurements are present (e.g., the most of the North Island). We understand that harmonic distortion measurements are fairly common in electrical networks and could provide a new tool for space weather researchers.

3500-year western Pacific storm record warns of additional storm activity in a warming warm pool

Frequent storm surges often cause catastrophic impacts on human lives and the global economy; however, these phenomena are not well understood. In this study, a regional storm reconstruction is performed based on a grain-size analysis and stratigraphic modelling of the accelerator mass spectrometry radiocarbon dates of benthic foraminifera from two neighbouring lagoon cores from Lingyang Reef in the Xisha Islands located in the northern South China Sea of the western Pacific. The dating results from the lagoon cores reveal a ~3500-year depositional history. Three different depositional units are recognized based on a time series of distinct grain-size variations that correspond to the following three stages of storm activity: intense and frequent storms from ~3500 to 3100 cal yr BP and ~1800 cal yr BP to present and weak and infrequent storms from ~3100 to 1800 cal yr BP. A high sedimentation rate remarked by reverse and chaos age is observed from ~2800 to 2600 cal yr BP in both cores, and it was likely associated with a tsunami event. In addition, grain-size variability may be associated with changes over time caused by the synchronous Asian monsoon and may also be correlated with climate records retrieved from the ice cores from Greenland; thus, this variability could indicate pervasive global climatic teleconnections. The overall temporal patterns of the isolated coral branches and shells from the sediment sequences are well correlated with the high sea surface temperatures in the western tropical Pacific. We suggest that increasing sea surface temperatures in the future may lead to more intense storm activity in the western Pacific warm pool as the planet warms.

Long‐Lasting Geomagnetically Induced Currents and Harmonic Distortion Observed in New Zealand During the 7–8 September 2017 Disturbed Period

AbstractSeveral periods of geomagnetically induced currents (GICs) were detected in the Halfway Bush substation in Dunedin, South Island, New Zealand, as a result of intense geomagnetic storm activity during 6 to 9 September 2017. Unprecedented data coverage from a unique combination of instrumentation is analyzed, that is, measurements of GIC on the single‐phase bank transformer T4 located within the substation, nearby magnetic field perturbation measurements, very low frequency (VLF) wideband measurements detecting the presence of power system harmonics, and high‐voltage harmonic distortion measurements. Two solar wind shocks occurred within 25 hr, generating four distinct periods of GIC. Two of the GIC events were associated with the arrival of the shocks themselves. These generated large but short‐lived GIC effects that resulted in no observable harmonic generation. Nearby and more distant magnetometers showed good agreement in measuring these global‐scale magnetic field perturbations. However, two subsequent longer‐lasting GIC periods, up to 30 min in duration, generated harmonics detected by the VLF receiver systems, when GIC levels continuously exceeded 15 A in T4. Nearby and more distant magnetometers showed differences in their measurements of the magnetic field perturbations at these times, suggesting the influence of small‐scale ionospheric current structures close to Dunedin. VLF receiver systems picked up harmonics from the substation, up to the 30th harmonic, consistent with observed high‐voltage increases in even harmonic distortion, along with small decreases in odd harmonic distortion.

Resisting a ‘Doomed’ Fate: an analysis of the Pacific Climate Warriors

The impacts of climate change have been, and are predicted to be, particularly concentrated in tropical areas such as the Pacific Islands. With rising sea levels, more droughts, and more frequent and intense storm activity now evident across the region, scholars have deemed low-lying countries as likely to be uninhabitable in the future. Hugo (1996, 125) made the case early on that ‘[I]nternational relocation may provide an enduring solution’ for small islands. This pragmatic position — of migration being a vital component of an effective adaptation response — was repeated in much of Hugo’s work (see Bardsley and Hugo 2010; Hugo 2010). In this vein, Hugo’s work provided a significant contribution to the complex challenge of uninhabitability in the Pacific Islands region, but it is not the only narrative. A growing number of island nation leaders and civil society groups have vocalised their opposition to a scenario whereby resettlement abroad is considered inevitable. This essay provides details of a grassroots network that defies the inevitability narrative and, like the extensive work of Hugo, offers important and critical contributions to the serious challenges facing the Pacific Islands region now and in the future.

The Coastal Convective Interactions Experiment (CCIE): Understanding the Role of Sea Breezes for Hailstorm Hotspots in Eastern Australia

Abstract Thunderstorm-affected communities develop an awareness of “hotspot” regions that historically experience more frequent or intense storm activity across many years. A scientifically based understanding of this localized variability has significant implications for both the public and industry; however, a lack of sufficiently long and robust observational datasets has limited prior research at the mesogamma spatial scale (2–20 km). This is particularly true for coastal environments, where hotspot activity has been documented in very few locales (e.g., Florida, southern Appalachian coastal plains, and the Iberian Peninsula), despite 45% of the global population living within 150 km of the coast. The Coastal Convective Interactions Experiment (CCIE) focuses on quantifying hailstorm hotspot activity for the coastal South East Queensland (SEQ) region of Australia and understanding the meteorological conditions that result in the spatial clustering of hailstorm activity. An automated thunderstorm identification and tracking technique applied to 18 years of radar data identifies not only the hailstorm hotpots well known to experienced local forecasters but an apparent link between localized maxima and the presence of sea-breeze activity. These climatological findings provided the motivation and guidance for a two-season field campaign to investigate the role of the sea breeze in thunderstorm development. Details of the experiment strategy and equipment specifications are presented alongside preliminary results. Significant complexities were observed within sea-breeze and thunderstorms circulations, limiting the application of standard concepts for idealized gravity current interactions. Furthermore, a multi-instrument case study of a sea-breeze–thunderstorm cold pool interaction identifies the comparatively low sea-breeze buoyancy as the primary contributor toward inhibiting new convective initiation, despite the vorticity balance argument favoring deeper updrafts.

Extreme storms during the last 6500 years from lagoonal sedimentary archives in the Mar Menor (SE Spain)

Abstract. Storms and tsunamis, which may seriously endanger human society, are amongst the most devastating marine catastrophes that can occur in coastal areas. Many such events are known and have been reported for the Mediterranean, a region where high-frequency occurrences of these extreme events coincides with some of the most densely populated coastal areas in the world. In a sediment core from the Mar Menor (SE Spain), we discovered eight coarse-grained layers which document marine incursions during periods of intense storm activity or tsunami events. Based on radiocarbon dating, these extreme events occurred around 5250, 4000, 3600, 3010, 2300, 1350, 650, and 80 years cal BP. No comparable events have been observed during the 20th and 21st centuries. The results indicate little likelihood of a tsunami origin for these coarse-grained layers, although historical tsunami events are recorded in this region. These periods of surge events seem to coincide with the coldest periods in Europe during the late Holocene, suggesting a control by a climatic mechanism for periods of increased storm activity. Spectral analyses performed on the sand percentage revealed four major periodicities of 1228 ± 327, 732 ± 80, 562 ± 58, and 319 ± 16 years. Amongst the well-known proxies that have revealed a millennial-scale climate variability during the Holocene, the ice-rafted debris (IRD) indices in the North Atlantic developed by Bond et al. (1997, 2001) present a cyclicity of 1470 ± 500 years, which matches the 1228 ± 327-year periodicity evidenced in the Mar Menor, considering the respective uncertainties in the periodicities. Thus, an in-phase storm activity in the western Mediterranean is found with the coldest periods in Europe and with the North Atlantic thermohaline circulation. However, further investigations, such as additional coring and high-resolution coastal imagery, are needed to better constrain the main cause of these multiple events.

Making Landfall: Towards a Critical Tempestology of Cyclones in Colonial Australia to 1850

In paleotempestology the mapping of past tropical cyclone activity has been conducted through two principal methods: geological proxy techniques, to gauge the millennial scale incidence of cyclones, and examination of archives, for example, newspapers, ships' logs, diaries, annals, government documents and Chinese historical documentary records which date back over a thousand years (Liu 13-15). The survey of historical sources by paleotempestologists is designed to elicit information about the incidence, intensity and tracks of cyclones and the material damage they have caused. In this essay I turn to Australian colonial newspapers before 1851 digitised by the National Library of Australia for its Trove database. They carried local and overseas reports of hurricane and intense storm activity; poems, letters, and excerpts of travel narratives which represent hurricanes; and local and overseas commentary on current affairs of state.

The origin of centennial- to millennial-scale chronological gaps in storm emplaced beach ridge plains

Recent studies of tropical cyclone surge and wave emplaced beach ridge plains have shown that these sequences often contain centennial to millennial scale gaps in their chronologies. Two explanations for the gaps exist — they are due to erosion, or alternatively a cessation or substantial slowing of depositional processes suggestive of a quieter phase in intense storm activity. Differentiating between the two is important for uncovering reliable long-term storm histories from these sequences. We use landform morphology, sediment texture and luminescence chronology to determine the origin of substantial chronological gaps in a plain containing more than 100 shore-parallel ridges composed of fine-grained sand located in northeast Australia. We identify and describe the characteristics associated with both erosional and non-erosional gaps. The erosional gaps are associated with changes in orientation between ridge sets and often a high ridge with hummocky topography that appears to have been disturbed by aeolian activity. River floods likely caused the partial erosion of ridge sets. Non-erosional gaps do not display these morphological characteristics and are likely associated with quiescence in severe tropical cyclone activity. These geomorphic and chronological signatures can be used to identify different sorts of gaps in other ridge plains and are an important tool in the reconstruction of long-term storm histories from these coastal landforms. The data also suggests that fine-grained ridges can, like their coarse-grained counterparts, be predominantly deposited by storm waves and surge and their texture need not necessarily be indicative of the processes responsible for ridge development.

Potential effects of an invasive bivalve, Nuttallia obscurata, on select sediment attributes within the intertidal region of coastal British Columbia

On the west coast of British Columbia, Canada, the varnish clam, Nuttallia obscurata, is a rapidly spreading invasive species that can reach high densities (i.e. 800individualsm−2). A field survey (Tier I) and an in situ mesocosm density manipulation experiment (Tier II) were applied to determine the potential effects of this invasive bivalve on select sediment attributes within the intertidal zone. In situ experiments involved seeding 1m2 mesocosms with varnish clams at four densities; 0 (control), 200 (low), 500 (mid) and 800 (high). Sediment samples were taken 7 times over a three week period and analyzed for organic matter, ammonium and grain size (gravel, coarse silt, fine silt and silt) at three different depths, 0–3cm (surface), 3–6cm (intermediate) and 6–9cm (bottom). Field surveys demonstrated that at natural densities bivalve distribution was best explained by sediment grain size. Contrary to expectations, the in situ manipulations indicated that at high densities varnish clams did not significantly increase sediment organic matter concentrations. Their ability to deposit feed and re-ingest biodeposits may have prevented accumulations. High densities of varnish clams did however result in significantly higher concentrations of sediment ammonium and percent silt, but mostly within the lower sections of the sediment core. Reworking of the surficial sediments due to intense storm activity likely obscured any differences in determined sediment attributes among the 4 treatments. Nitrogen is a limiting nutrient with ammonium preferentially used by phytoplankton and microphytobenthos. These primary producers form the basis of all marine food webs thus increases in amounts of ammonium to shallow coastal seas as a result of high densities of an invasive bivalve within intertidal zones could result in an increased risk of eutrophication within these sensitive regions.

Ionospheric response over South Africa to the geomagnetic storm of 11–13 April 2001

The mid-latitude ionosphere over South Africa is subject to severe F region ionospheric density perturbations during intense geomagnetic storm activity. Communication and navigation systems relying on trans-ionospheric propagation are adversely affected during strong storms. There is a need to compensate for the effects of the sharp ionospheric total electron content (TEC) gradients associated with the storm time disturbance effects at mid-latitudes. The South African ionosonde and Global Positioning System (GPS) database have been used to examine the spatial extent of the electron density structures during the super storm of 11–13 April, 2001. The ionosonde measurements have supported the observed negative (i.e. decreased electron density) and positive (i.e. increased electron density) storm effects over this region. The hmF2 and h'F ionospheric parameters showed higher and reduced values during the main and recovery storm phases respectively. The ionospheric TEC is a widely used parameter in the studies of the near Earth plasma environment. The derived VTEC and their perturbation components revealed TEC fluctuations of magnitude ≥10 TECU during the storm. The storm-induced TEC perturbations on 11–12 April, 2001 revealed a travelling ionospheric disturbance (TID) phenomenon. The source of the irregularities observed over South Africa during this super storm period has been attributed to TIDs generated by gravity waves due to auroral sub-storm activity. The equatorward propagating waves resulted in an uplift of the F2 layer by pushing the ionospheric plasma along magnetic field lines to higher altitudes where recombination is much lower, which in turn leads to plasma density enhancement.

Intense storm activity during the Little Ice Age on the French Mediterranean coast

Understanding long-term variability in the frequency of intense storm activity is important for assessing whether changes are controlled by climate evolution. Understanding this variability is also important for predicting present and future community vulnerability and economic loss. Our ability to make these assessments has been limited by the short (less than 50years) instrument record of storm activity. Storm-induced deposits preserved in the sediments of coastal lagoons offer the opportunity to study the links between climatic conditions and storm activity on longer timescales. In this study, we present a record of these extreme climatic events that have occurred in the French Mediterrannean coast over the past 1500years. The identification of these extreme events is based on the analysis of sediment cores from Gulf of Aigues-Mortes lagoons that contain a specific sedimentary and geochemical signature associated with intense storms.Overwash deposits do not show any evidence of intense storm landfalls in the region for several hundred years prior to the late 17th century A.D. The apparent increase in intense storms around 250years ago occurs during the latter half of the Little Ice Age, a time of lower continental surface temperatures. Comparison of the sediment record with palaeoclimate records indicates that this variability was probably modulated by atmospheric dynamics. The apparent increase of the superstorm activity during the latter half of the Little Ice Age was probably due to the thermal gradient increase leading to enhanced lower tropospheric baroclinicity over a large Central Atlantic/European domain and leading to a modification of the occurrence of extreme wind events along the French Mediterranean coast. A complete understanding of the relationship between climate fluctuations, storm activity, and the coastal response will be crucial to predicting the impacts of future climate change.

Observed Trends in Summertime Precipitation over the Southwestern United States

Abstract In this paper, the authors evaluate the significance of multidecadal trends in seasonal-mean summertime precipitation and precipitation characteristics over the southwestern United States using stochastic, chain-dependent daily rainfall models. Unlike annual-mean precipitation, trends during the summertime monsoon, covering the period 1931–2000, indicate an overall increase in seasonal precipitation, the number of rainfall events, and the coverage of rainfall events in peripheral regions north of the “core” monsoon area of Arizona and western New Mexico. In addition, there is an increasing trend in intense storm activity and a decreasing trend in extreme dry-spell lengths. Over other regions of the domain, there are no discernible trends found in any of the observed characteristics. These trends are robust to the choice of start dates and, in the case of seasonal-mean precipitation, appear to persist into the current century.

The demise of a major Acropora palmata bank–barrier reef off the southeast coast of Barbados, West Indies

Formerly attributed to human activity, the demise of a bank–barrier reef off southeastern Barbados known as Cobbler’s Reef is now thought to be largely the result of late Holocene, millennial-scale storm damage. Eleven surface samples of the reef crest coral Acropora palmata from nine sites along its 15-km length plot above the western Atlantic sea-level curve from 3,000 to 4,500 cal years ago (calibrated, calendar 14C years). These elevated clusters suggest that the reef complex suffered extensive storm damage during this period. The constant heavy wave action typical of this area and consequent low herbivory maintain conditions favoring algal growth, thereby limiting the reestablishment of post-storm reef framework. Site descriptions and detailed line surveys show a surface now composed mainly of reworked fragments of A. palmata covered with algal turf, macroalgae and crustose coralline algae. The reef contains no live A. palmata and only a few scattered coral colonies consisting primarily of Diploria spp. and Porites astreoides, along with the hydrocoral Millepora complanata. A few in situ framework dates plot at expected depths for normal coral growth below the sea-level curve during and after the period of intense storm activity. The most recent of these in situ samples are 320 and 400 cal years old. Corals of this late period likely succumbed to high turbidity associated with land clearance for sugarcane agriculture in the mid-1600s.

Geomagnetic signatures during the intense geomagnetic storms of 29 October and 20 November 2003

Solar cycle 23 in its declining phase witnessed the most pronounced space weather events during October–November 2003. A series of powerful solar flares and associated geoeffective Coronal Mass Ejections (CMEs) travelling at ∼2000 km/s drove shock fronts that impacted the Earth's magnetic field consecutively on 29 and 30 October, resulting in intense geomagnetic disturbances during 29–31 October. Another intense geomagnetic storm activity occurred during 20–21 November, resulting from a solar flare that had an associated geoeffective CME travelling at a speed of ∼1100 km/s. Digital ground magnetic field measurements from the equatorial and low-latitude locations in the Indian longitude zone, in conjuction with the interplanetary solar wind and magnetic filed parameters, are used to study the characteristics of these storms. Maximum magnitude of the total magnetospheric energy injected into the magnetosphere during the mainphase of the three major storm amounts to approximately 4.5×10 13, 3.6×10 13, 2.8×10 13 W. Another salient feature brought out is the close correspondence between the magnitude of the peak of the southward component of the interplanetary magnetic field B z and the strength of the storm intensity as inferred from the D st and low-latitude digital magnetic records.

Understanding a flammable planet – climate, fire and global vegetation patterns

Understanding a flammable planet – climate, fire and global vegetation patterns

Records of prehistoric hurricanes on the South Carolina coast based on micropaleontological and sedimentological evidence, with comparison to other Atlantic Coast records

Research Article| September 01, 2003 Records of prehistoric hurricanes on the South Carolina coast based on micropaleontological and sedimentological evidence, with comparison to other Atlantic Coast records D.B. Scott; D.B. Scott 1Centre for Marine Geology, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada Search for other works by this author on: GSW Google Scholar E.S. Collins; E.S. Collins 1Centre for Marine Geology, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada Search for other works by this author on: GSW Google Scholar P.T. Gayes; P.T. Gayes 2Center for Marine and Wetland Studies, Coastal Carolina University, Conway, South Carolina 29526, USA Search for other works by this author on: GSW Google Scholar E. Wright E. Wright 2Center for Marine and Wetland Studies, Coastal Carolina University, Conway, South Carolina 29526, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2003) 115 (9): 1027–1039. https://doi.org/10.1130/B25011.1 Article history received: 16 Aug 2001 rev-recd: 20 Feb 2003 accepted: 21 Feb 2003 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D.B. Scott, E.S. Collins, P.T. Gayes, E. Wright; Records of prehistoric hurricanes on the South Carolina coast based on micropaleontological and sedimentological evidence, with comparison to other Atlantic Coast records. GSA Bulletin 2003;; 115 (9): 1027–1039. doi: https://doi.org/10.1130/B25011.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Singleton Swash on the South Carolina coast provides an extended record of storm events for this coast. We used experience gained by looking at storm traces detected as layers of offshore foraminifera intercalated with marsh sediments from a known storm in the area (Hugo, which occurred in 1989) to detect storm horizons from the sediments that have been accumulating in Singleton Swash since 5700 yr B.P. We suggest here that the most intense storm activity occurred in the 0–1000 yr B.P. interval (six storms); only three occurred in the 1000–2000 yr B.P. interval and two in the 2000–3000 yr B.P. time interval (calibrated radiocarbon years). There was one giant storm in the pre–5000 yr B.P. interval; a sea-level oscillation in the 3500–5000 yr B.P. interval appears to have destroyed most records during that period.Previous work suggests that the position of the Bermuda (or Azores) High influences the direction of general storm paths for major North Atlantic hurricanes: a position of the Bermuda High farther to the south tends to force storms into the Gulf of Mexico, whereas a northern position allows them to track up the Atlantic Coast. Results here combined with results of other workers on the Gulf Coast suggest a more southern position for the Bermuda High, causing more storms on the Gulf Coast in the interval of 1000–3400 yr B.P. Conversely, a more northern position during the past 1000 yr is suggested to have contributed to higher frequencies of storms on the Atlantic Coast in that period. To test this hypothesis, modern records of the movement of the North Atlantic Oscillation (NAO, which controls the position of the Bermuda High) have been compared with historical records of hurricane tracks over the twentieth century. There does appear to be a strong correlation between the position of the NAO and the track the storms have pursued in modern times. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Studies of the Influence of Graded Storm Layers on 210Pb and Heavy Metals Profiles in Great Barrier Reef Sediments

Intense storm activity can resuspend surficial sediments in coastal regions resulting in the formation of graded layers in the sediment. This occurs in the Great Barrier Reef area of northeastern Australia where tropical cyclones are common. The vertical redistribution of 210Pb and heavy metals in these graded sediment layers has been examined mathematically using a model based on Stokes's Law of settling and experimentally using laboratory simulations. The vertical profiles of 210Pb and heavy metal concentrations show an increase with the increasing proportion of fine particles toward the sediment−water interface. The calculated and experimental results mimic 210Pb-depth profiles produced where there has been a constant rate of sedimentation. The use of 210Pb as a geochromometer in sediments including unidentified graded storm layers may yield incorrect sedimentation rates and false geochronologies. The redistribution of heavy metals is similar and may incorrectly suggest recent increases in heavy metal inputs. This misinterpretation is significant where the results are used in making environmental management decisions.