Changes In Wind Patterns Research Articles

Geochemical index of trace metals in the surficial sediments from the western continental shelf of India, Arabian Sea

The present study focuses on the determination and abundance of trace metals (viz. Cu, Ni, Zn, Cr, Co, Cd, Mn and Fe) in the surficial sediments of west coast of Arabian Sea along the Indian subcontinent. Sediment samples were collected from three transects along the western continental shelf of Arabian Sea. The enrichment of Fe and Mn in coastal oxic-sediments indicates the precipitation of these redox sensitive elements as Fe- and Mn-hydroxides and oxides, whereas the low Fe and Mn concentrations in the oxygen deficient sediments of deeper stations reflects the dissolution of their hydroxides and oxides. Concentrations of fairly redox insensitive trace metals like Cu, Ni, Zn, Cr and Cd (with the exceptions of Cr) showed higher values at nearshore sediments, then it decreased towards seaward and again showed a slight increase at oxygen minimum stations in all the three transects. This geochemical variability in their distributional characteristics is mainly associated with the extent to which the precipitation or dissolution of Fe- and Mn-oxides/hydroxides occur since the scavenging or releasing effects of Fe- and Mn-oxides/hydroxides act as significant 'sinks' or 'sources' of heavy metals. The change in wind pattern, coastal upwelling and increased productivity are also the reported factors which influence the biogeochemical cycling of trace metals in the surface sediments of west coast of India. Enrichment factor generally showed a high gradient accumulation from nearshore to shelf.

Sensitivity of Wave Energy to Climate Change

Wave energy will have a key role in meeting renewable energy targets en route to a low carbon economy. However, in common with other renewables, it may be sensitive to changes in climate resulting from rising carbon emissions. Changes in wind patterns are widely anticipated, and this will ultimately alter wave regimes. Indeed, evidence indicates that wave heights have been changing over the last 40 years, although there is no proven link to global warming. Changes in the wave climate will affect wave energy conversion. Where the resource is restricted, there may be reductions in energy exports and, consequently, negative economic impacts. On the other hand, increased storm activity will increase installation survival risks. Here a study is presented that, for the first time, indicates the sensitivity of wave energy production and economics to changes in climate.

Annual changes in sea-ice, chlorophyll a, and primary production in the Ross Sea, Antarctica

Abstract A satellite-based study was conducted to quantify the seasonal-to-interannual changes in phytoplankton production in the southwestern Ross Sea between 1997 and 2001. The size of the Ross Sea polynya from 1992 to 2001 was related to the climate state as expressed by the Multivariate ENSO Index (MEI). These data show that 76% of the variation in sea-ice extent between 1992 and 2000 can be explained by the MEI, with the El Nino year of 1997–1998 exhibiting the greatest sea-ice cover and the La Nina year of 1999–2000 the least. Whether the relationship between ice area and the MEI is caused by interannual changes in wind patterns or changes in the movement of circumpolar deep water onto the Ross Sea continental shelf has yet to be determined. The year 2000–2001 was excluded from the climate analysis, due to the effects of the enormous B-15 iceberg, which inhibited the normal advection pattern of sea-ice out of the Ross Sea, resulting in higher than normal sea-ice conditions. Phytoplankton blooms were markedly less extensive in the heavy sea-ice years of 1997–1998 and 2000–2001 and were significantly delayed in their development, with concentrations of Chl a peaking 2 months later (February) than in reduced sea-ice years (December). Annual production during the 1997–1998 El Nino (27.4 Tg C) was similar to that of the iceberg impacted year 2000–2001 (28.3 Tg C). These annual rates were approximately 40% below values estimated between November 1998 and March 2000 (47.5 Tg C) when open-water area during spring and summer was much greater. This decreased production during heavy sea-ice years is more a function of the delay in the start of the bloom than in the reduction of open water area.

Monitoring North Pacific Heat Content Variability: An Indicator of Fish Quantity?

Fields of modeled sea surface heights and temperatures are used to develop an algorithm to monitor the low-frequency heat content variability of the North Pacific's midlatitudes associated with regime shifts in the circulation patterns of the Alaskan and the California Currents. Data from altimetric and infrared satellites are then used to apply the method using observational measurements. The model shows that the midlatitude Pacific subsurface circulation variability is primarily due to large, low-frequency horizontal north–south gyre movement. The changes may also be due to large-scale atmospheric changes in wind patterns, local mixing, as well as internal dynamics. It is proposed that this type of monitoring might be useful to help with understanding the variability in fisheries.

Temporal variations in surface ozone at Thumba (8.6°N, 77°E)-a tropical coastal site in India

Surface measurements of ozone and meteorological parameters are made at a tropical coastal site, Thumba (8.6°N, 77°E, 2 m) in India from April 1997 to March 1998. Ozone shows a diurnal variation with daytime higher levels and a sharp change in its values during evening time. The evening time change in ozone values with a secondary peak is found to be due to change in wind pattern from sea-breeze to land-breeze at this site. This secondary peak in ozone is weakest during monsoon period. A detailed study of the meteorological parameters shows that during nighttime, polluted air from land side moves to the nearby marine region relatively increasing the levels of ozone and precursor gases. Observations show that the onset time of daytime ozone increase and its rates are related with each other. If onset time of ozone increase is early, its increase rate is slower and vice versa. Maximum ozone levels are observed to be during March, probably due to intense photochemical production. However, this is different when compared to other Indian site like Ahmedabad, where maximum ozone levels are observed during late autumn and early winter. Monthly average ozone levels are observed to be very low (in the range of 13–22 ppbv) at Thumba.

The Laptev Sea as a source for recent Arctic Ocean salinity changes

This study was motivated by observations of significant salinification of the upper Eurasian Basin that began around 1989. Observational data and modeling results provide evidence that increased arctic atmospheric cyclonicity in the 1990s resulted in a dramatic increase of the salinity in the Eurasian Basin. Two mechanisms account for the Laptev Sea salinization: eastward diversion of Russian rivers and increased brine formation due to enhanced ice production in numerous leads in the Laptev Sea ice cover. Both these mechanisms are linked to changes in wind patterns and were essential to the formation of salinity anomalies. The resulting Laptev Sea salinity anomaly was advected to the central Eurasian Basin. The strong salinization over the Eurasian Basin altered the formation of cold halocline waters, weakened vertical stratification, and released heat upward from below the cold halocline layer. Our analysis suggests that local processes in the Laptev Sea may have a basin‐wide impact on the thermohaline structure of the Arctic Ocean.

Palaeobiogeographic aspects of northeast Brazilian basins during the Berriasian before the break up of Gondwana

A complete sedimentary analysis (lithofacies, palaeocurrent pattern, framework composition, biocorrelation) is presented for the northern margin of the Afro-Brazilian Depression, a large, shallow, northeast Brazilian basin that developed during the Berriasian prior to the separation of South America and Africa, the final break up of Gondwana. An understanding of the depositional systems has allowed an interpretation of the fossil record to be made in terms of palaeoclimate as the northern margin became wetter owing to a change in wind patterns. On a local scale, ponds and shallow lakes were surrounded by a rich fauna resembling present-day conditions in African savannahs. The regional behaviour of the fauna indicates migration routes that, although still not fully understood, seem to have changed from the situation that prevailed in southern Africa and South America earlier in the Mesozoic Era.

Atmospheric effects in the Angola‐Benguela frontal zone

The Angola‐Benguela Front is the generic border between, on the one hand, the Benguela Current and the coastal upwelling regime along the southwest African coastline and, on the other hand, the warm, southward flowing Angola Current. This frontal zone has a variable morphology, geographic location, and thermal characteristics. It has been suggested that this variability may be related to changing wind patterns. We have studied the thermal characteristics of the surface expression of the frontal zone for a 74‐day period using daily thermal infrared images and compared these to wind patterns from synoptic weather maps. There is little correlation between the location of the northern and the southern front that form the envelope for this frontal zone. The location of the southern front largely determines the thermal gradient across the entire frontal zone. Large short‐term displacements in the geographic location of the frontal zone as well as short‐term variations in its thermal characteristics are shown to be strongly correlated to the atmospheric pressure gradient of the South Atlantic anticyclone with a 1‐day lag period. This is true irrespective of the latitude changes of the center of the South Atlantic anticyclone.

Recent abatement of easterly winds in the northern Adriatic

Easterly winds from the northern Adriatic contribute, together with atmospheric depressions, and the often decisive southerly winds from the southern and middle Adriatic, to produce damaging sea surges in the Gulf of Venice. A new statistical analysis of 3-hourly wind records from Trieste for the period 1951–1996, has shown a clear decline in the frequency and strength of Bora and other easterlies. This abatement is not accompanied by a strengthening of winds from other directions, but by more frequent calm situations (from 26% of total observations in the 1950s, to 44% during the last 10 years, and even to over 60% during the early 1980s). Similar (although weaker) declining trends for the easterlies have been recorded at other stations in the northern Adriatic (Ronchi, Venice). An inspection of previously published data from Trieste suggests that such trends may have been going on, possibly with minor fluctuations, since at least the beginning of regular instrumental records, in the late 1860s. Such changes in wind pattern, which have favourable effects on the frequency of coastal flooding, may be due, at least in part, to interdecadal climate variability. However, the persistence of certain trends suggests a climatic shift, with, in particular, less-frequent situations, with strong atmospheric pressure gradients between highs in central/eastern Europe and lows in southern Italy or in the Adriatic area. Such situations may be a consequence of recent global warming and of less-frequent drifts of polar cold air towards middle latitudes. Copyright © 1999 Royal Meteorological Society

Vulnerability of oceanic dune systems under wind pattern change scenarios in Uruguay

The dynamics of the large dune systems adjacent to lowlands and to the oceanic coastline in Uruguay is likely to be affected both by sea level rise and wind circulation patterns. A simple eolian sand transport model, which relates wind friction, frequency and direction to sand transport, was used to estimate annual sand transport as a measure of the impact of potential climate changes on the stability of dune systems and beaches. The model was adjusted to local conditions using real wind-matrix and eolian-transport data from the past 5 decades. The climate change scenarios considered assume a positive or negative 10% change in the frequency of the South Atlantic Anticyclone winds, since its position determines the near-surface wind circulation pattern. Results obtained at the Cabo Polonio study area indicate that, in the medium and long term, coastal recession is likely to occur due to a decrease in coastal dunefield activity induced by changes in wind pattern. It was also observed that, should current anthropogenic impact in the area remain unchanged, the situation would be equally serious even under a non-climate-change scenario. This is due to the fact that the forestation process that has taken place over the past 20 yr has caused the immobilization of a significant portion of the dune system, preventing natural sand transfer to the coast. In recent years a still insufficient deforestation effort, intended to stop coastline recession, has taken place.

Southern Oscillation Signal in South American Palaeoclimatic Data of the Last 7000 Years

During strong El Niño events, rainfall anomalies and changes in wind patterns are observed in different regions of South America. Along the central Brazilian coast, during the 1983 El Niño year, the frontal systems were blocked to the south, provoking a reversal of the longshore sand transport. Long-duration reversals of longshore transport were also recorded in Holocene beach-ridge terraces from the Rio Doce coastal plain. This led to the formulation of a model relating these reversals of longshore transport to El Niño-like conditions. El Niño-like conditions are past average climate situations that generate the same perturbations as the strong El Niño events observed during the last decade. They are likely to correspond to the long-duration low phase of the Southern Oscillation. To confirm this hypothesis we compared the Holocene beach-ridge record with other palaeoenvironmental records from regions where strong El Niño events would have a substancial signal as well: (1) water-level fluctuations of Lake Titicaca, (2) a pollen and sediment record in an eastern Amazonian lake, (3) changes of the Rio Xingu discharge in eastern Amazonia, and (4) variations of sand supply at the Rio Piura and Rio Chira outlets in the Sechura Desert. The occurrences of El Niño-like conditions were numerous before 3900-3600 yr B.P., absent between 39003600 and 2800-2500 yr B.P., and infrequent after 2800-2500 yr B.P.

Martian aeolian features and deposits: Comparisons with general circulation model results

The development of a general circulation model (GCM) of Mars' atmosphere allows questions to be addressed concerning the relationships between near‐surface winds and the distribution of wind‐related features and deposits. Predictions of wind surface stress as a function of season and dust optical depth are used to investigate the distribution and orientation of wind streaks, yardangs, and rock abundance on the surface. The occurrence and orientation of bright streaks are well accounted for by the GCM. Results suggest that bright streaks form during southern hemisphere summer by Hadley cell circulation, in which dust is raised in the southern hemisphere, carried northward at high altitudes, then deposited in the wake of craters and other topographic obstacles by the descending Hadley cell. The reduction in the number of bright streaks southward from 30°N is interpreted to reflect the depletion of dust by near‐surface winds blowing to the south. Although the winds responsible for the formation of the dark streaks are not well reproduced in all areas by GCM simulations, a band of high wind surface stresses in the southern subtropics corresponding to the latitude band where most of the dark streaks are found are predicted at the height of the dust storm season (southern hemisphere summer). Yardang orientations do not match the GCM simulations for any season; their orientation is attributed to either structural control in the rocks (such as joint patterns) or to a change in wind patterns from the time when the yardangs formed. The global distribution of rocks on the surface is correlated well with predicted wind stress, particularly during dust storm season; the rocky areas are sites of strong winds, suggesting that fine material is swept away by the wind, leaving rocks and coarser material behind.

The Ash-Fall Pattern of the Fire Clay Tonstein, Central Appalachian Basin: Paleogeographic and Plate Tectonic Implications

Thickness data for the Fire Clay tonstein bed (Middle Pennsylvania, Breathitt Formation) of Kentucky and its correlatives in West Virginia, Virginia, and Tennessee show a moderately complex ash-fall pattern across the central Appalachian basin. Within the tonstein bed are four or possibly more distinct graded units, which may represent multiple ash-fall events. The mineralogical and chemical signatures for all tonstein beds are similar and suggest a single magmatic source. The absence of coal or non-ash-fall detrital bands between the individual graded units demonstrates that the events occurred in rapid succession. The ash-fall deposits are elongated and thin generally from southwest to northeast. The longest and thickest part of the deposits lies along the southeastern side of the basin, where the deposit's southwestern end is up to 12 in. thick. The areal distribution indicates ash deposition on unstable surfaces and probably changes in wind patterns. Paleogeographic interpretation suggest that the Fire Clay ash fall or falls were deposited from a western source near the paleoequator. This source is thought to be on the Yucatan block, which was involved in collisional tectonics and eastward-directed subduction during the Middle Pennsylvanian. The block contained a volcanic chain from which the deposits may have originated.more » This composite ash-fall bed, which became the Fire Clay tonstein, formed the most important isochron in the Middle Pennsylvanian of North America.« less

Applications of tonsteins to coal geology: some examples from western United States

Applications of tonsteins to coal geology: some examples from western United States

Pb isotopic tracers of the Cretaceous‐Tertiary extinction event

The global excess of Ir in sediments at the Cretaceous‐Tertiary (K‐T) boundary has been attributed to either a meteorite impact or enhanced volcanism (e.g. Deccan Traps). The isotopic composition of Pb associated with this Ir provides a test of these hypotheses because meteoritic Pb is isotopically quite distinct from Pb of volcanic or continental origin. Pb abundances and isotopic compositions of pelagic oozes from DSDP Site 577A (Shatsky Rise, NW Pacific) measured in this study show little change over the deposition interval of Ir‐rich sediment (∼10 cm). However, a Pb enriched layer with a more radiogenic isotopic composition is found in the basal ∼0.5 cm of the Tertiary. These observations appear to preclude the Ir excess in these sediments originating as impact fallout from a stony meteorite although an iron meteorite impactor cannot be excluded. Any Pb flux accompanying Ir in volcanogenic aerosols from the Deccan Traps should be considerable. However, the boundary Pb ‧spike‧ does not isotopically resemble known Deccan Trap lavas. There is isotopic overlap with coal ash although the lack of correlation between soot and Pb abundance precludes any simple relationship between the two. Overall, any wind pattern changes following the K‐T ‧event‧ were apparently short‐lived as neither airborne sources of Pb nor their magnitude to the then central Pacific were affected while the Ir enriched sediments were being laid down.

‘MERIT’ Working Group Plans for a New Earth Rotation Service

During the past 80 years, classical astronomical techniques have been used to determine polar motion (the variation of the direction of the spin axis of the earth with respect to a coordinate system fixed in the earth). The motion, which includes an Eulerian motion of about 0.3″ amplitude with a 430‐day period and a somewhat smaller seasonal variation, is also subject to effects of geophysical processes that cannot be detected reliably because of the 0.01–0.02″ uncertainty (averaged over 5 days) in the astronomical determinations of pole position. The rate of the earth's rotation about its spin axis, measured to about 1‐ms accuracy by astronomical techniques, also has seasonal variations of tens of milliseconds, variations of a few milliseconds over time periods of 2–4 months because of changing wind patterns, and currently undetectable effects as a result of tectonic processes. Higher accuracy and higher frequency determinations of polar motion and the earth–s rotation are required if the data are to be used to learn more about the internal constitution of the earth and earthquake processes.

Sodium, magnesium, potassium and calcium concentrations in ice cores from the Law Dome, Antarctica

The concentrations of Na, Mg, K and Ca have been determined in three ice cores drilled along a flow line on the Law Dome, Antarctica. Average cationic concentrations in the upper sections of the cores show a marked decrease in concentration with increasing distance from the coast. A depth profile of the core drilled 5 km from the coast near Cape Folger indicates that the ice below 260 m was precipitated in a colder climate regime, probably towards the end of the Wisconsin stage. The depth profile of the core located at the summit of the dome, 110 km from the coast, shows an unexpected steady increase in the concentration of cations with depth. This may indicate an increase in precipitation, or a gradual change in wind patterns on the dome over recent centuries.

Effects of the August 1972 solar particle events on stratospheric ozone

The spatial extent and the ionization profiles within the extended oval‐shaped regions irradiated by the intense solar particle events (SPE) of August 1972 have been derived from high‐energy proton data obtained with the 1971‐089A polar‐orbiting satellite and from several balloon flights. The particle ionization during the most intense 10‐hour period of the event on August 4 greatly enhanced the concentrations of short‐lived HOx and long‐lived NOx constituents, which in turn were responsible for the creation of a polar ozone cavity (POC) that has been identified and tracked with the backscattered ultraviolet (BUV) ozone sensors on the Nimbus 4 satellite. At the end of the peak irradiation period the ozone concentrations within the northern hemisphere POC were reduced by 46, 16, and 4% at altitudes of 49.5, 41, and 32 km, respectively. The total columnar ozone is estimated to have been reduced by ∼2% at this time. Above ∼45 km the ozone recovered on the time scale of several days. At 38.7 km in the northern hemisphere, however, the POC persisted and rotated as a semirigid mass in an east‐to‐west direction for some 53 days until the autumnal changes in wind patterns finally prevented further tracking. Time‐dependent chemistry calculations have been performed to explain the cause, magnitude, and temporal features of the ozone reductions. Using the calculated diurnal and particle‐induced behavior of the ozone during the SPE, the changes in heating rate and temperature expected in the stratosphere have been estimated. As a result of the initial large HOx‐caused ozone reduction, the temperature at 45 km should have decreased by ∼4°K several days after the event. Attempts to verify the predicted temperature changes have been unsuccessful due to limitations in the temperature measurement techniques.

Wind-induced upwelling, coastal currents and sea-level changes

The problem of coastal and equatorial upwelling induced by changing wind patterns is considered. In each case, the solution of the linearized problem can be expressed as a sum of modes, the amplitude of each satisfying a first order wave equation. Such equations can be integrated by simple procedures and may be of use for forecasting upwelling. The response at a particular point depends on the wind stress at earlier times at other positions along the coast. Procedures which might be employed for predictions are discussed. When topography and stratification are both present, a model shows that movements of the thermocline are correlated with changes of sea-level at the coast. This suggests that information about upwelling and coastal currents can be obtained from tide gauges.

A statistical approach to the relationship between coastal erosion and changes in wind patterns at byron bay, N.S.W.

(1967). A statistical approach to the relationship between coastal erosion and changes in wind patterns at byron bay, N.S.W. Australian Geographer: Vol. 10, No. 4, pp. 275-285.