Letteratura scientifica selezionata sul tema "Sea level South Australia St"

Surficial sediments of Gulf St. Vincent, South Australia, are predominantly bioclastic, cool-temperate carbonates. Benthic foraminifera are abundant and distribution of species is closely related to water depth. For example, Massilina milletti is most common at depths ca. 40 m, while Discorbis dimidiatus is characteristics of shallow, subtidal environments. Elphidium crispum, a shallow-water species, and E. macelliforme, favoring deeper water, provide a useful numerical ratio. Their logarithmic relative abundance, in the sediment size fraction 0.50–0.25 mm, correlates strongly with water depth. Vibrocores SV 4 and SV 5 recovered undisturbed sections of Quaternary strata from the deepest part (ca. 40 m) of Gulf St. Vincent. Amino acid racemization and radiocarbon age determinations show that late Pleistocene sections of the cores were deposited over the time ca. 45,000 to 30,000 yr B.P. Species of fossil foraminifera, recovered from these sections, are mostly extant in modern Gulf St. Vincent, thus allowing paleoecological inferences of late Pleistocene sea levels. These inferred sea-level maxima can be correlated with those determined from study of Huon Peninsula coral reef terraces. Initial estimates of tectonically corrected sea levels for transgressions in Gulf St. Vincent at 40,000 and 31,000 yr B.P. are −22.5 m and −22 m, respectively. The intervening regression lowered sea level to −28 m.

Common dolphins are subject to large-scale fishing activity and tourism operations in South Australia; however, there is a paucity of data on this species. Understanding the behaviour of a population can contribute greatly to our knowledge of a species and how to manage potential population-level threats. This paper describes the behaviour of short-beaked common dolphins (Delphinus delphis) in Australian waters for the first time. Data were collected from 109 independent dolphin groups during boat-based surveys conducted in Gulf St Vincent, South Australia, between September 2005 and May 2008. Activity budgets were used to assess behaviour of common dolphins in relation to diel patterns, season, water depth, sea surface temperature (SST), group size and composition. Foraging (33.9%) and resting (2.8%) were the most and least frequently observed behaviours, respectively. Travelling (33.0%), socialising (20.2%) and milling (10.1%) accounted for the remainder of the activity budget. Diurnal differences were detected, with foraging (59.5%) and socialising (31.8%) groups most frequently observed from 10.00 to 11.59 hours. Behaviour did not vary seasonally or with water depth, SST, group size or composition. Behaviour varied significantly between single- and multispecies aggregations. Foraging was more frequent in multispecies aggregations, as 78.4% of all foraging behaviour observed for common dolphins occurred in the presence of other species. Multispecies aggregations were most frequently observed with flesh-footed shearwaters (Puffinus carneipes), which were present during 29.4% of common dolphin encounters. Behaviour varied significantly during aggregations with shearwaters, as 62.2% of foraging groups occurred in the presence of shearwaters. Resting, milling or socialising was rarely observed in the presence of any other species, indicating that the primary mechanism for aggregations is likely prey-related.

A 50-yr climatology (1957–2007) of subtropical cyclones (STs) in the South Atlantic is developed and analyzed. A subtropical cyclone is a hybrid structure (upper-level cold core and lower-level warm core) with associated surface gale-force winds. The tendency for warm season development of North Atlantic STs has resulted in these systems being confused as tropical cyclones (TCs). In fact, North Atlantic STs are a regular source of the incipient vortices leading to North Atlantic TC genesis. In 2004, Hurricane Catarina developed in the South Atlantic and made landfall in Brazil. A TC system had been previously unobserved in the South Atlantic, so the incidence of Catarina highlighted the lack of an ST climatology for the region to provide a context for the likelihood of future systems. Sixty-three South Atlantic STs are documented over the 50-yr period analyzed in this climatology. In contrast to the North Atlantic, South Atlantic STs occur relatively uniformly throughout the year; however, their preferred location of genesis and mechanisms for this genesis do exhibit some seasonal variability. Rossby wave breaking was identified as the mechanism for the ST vortex initiation for North Atlantic STs. A subset of South Atlantic STs forms via this mechanism, however, an additional mechanism for ST genesis is identified here: lee cyclogenesis downstream of the Andes in the Brazil Current region—an area favorable for convection. This formation mechanism is similar to development of type-2 east coast lows in the Tasman Sea off eastern Australia.

Stable parts of the South Australia coast show that the last interglacial sea level was 2 m higher than present, but elsewhere there has been relative subsidence up to 7 m and uplift of 18 m. Estimates of changing sea level, and future projections, should state the time period involved and the tectonic background to be of any use. The coast contains ‘carbonate sand factories’ where organisms produce vast amounts of sand by fixing carbon dioxide as carbonates. Far from dissolving carbonate by acidification, carbon dioxide is an essential part of carbonate production and the continued maintenance and growth of coasts and reefs. Government policies to adapt renewable energy are unlikely to affect the system.

Abstract To determine the possible importance of ENSO events along the coast of South Australia, an exploratory analysis is made of meteorological and oceanographic data and output from a global ocean model. Long time series of coastal sea level and wind stress are used to show that while upwelling favorable winds have been more persistent since 1982, ENSO events (i) are largely driven by signals from the west Pacific Ocean shelf/slope waveguide and not local meteorological conditions, (ii) can account for 10-cm changes in sea level, and (iii) together with wind stress, explain 62% of the variance of annual-averaged sea level. Thus, both local winds and remote forcing from the west Pacific are likely important to the low-frequency shelf edge circulation. Evidence also suggests that, since 1983, wintertime downwelling during the onset of an El Niño is reduced and the following summertime upwelling is enhanced. In situ data show that during the 1998 and 2003 El Niño events anomalously cold (10.5°–11.5°C) water is found at depths of 60–120 m and is more than two standard deviations cooler than the mean. A regression showed that averaged sea level can provide a statistically significant proxy for these subsurface temperature changes and indicates a 2.2°C decrease in temperature for the 10-cm decrease in sea level that was driven by the 1998 El Niño event. Limited current- meter observations, long sea level records, and output from a global ocean model were also examined and provide support for the hypothesis that El Niño events substantially reduce wintertime (but not summertime) shelf-edge currents. Further research to confirm this asymmetric response and its cause is required.

The River Murray Estuary, South Australia exhibits a morphology typical of a wave-dominated estuary and comprises two large, shallow central basin lakes – Lakes Alexandrina and Albert. Contested interpretations of the estuary’s limnological history and uncertainty surrounding the sustainability of current basin water usage practice warrant a robust investigation into how the system has evolved. Here we combine lithostratigraphic, geochemical and sedimentological evidence from a transect of sediment cores to reconstruct the sediment infill history of the system. We uncover multiple stages of sediment infill over the history of the system, associated with (1) the low gradient morphology of the estuary and lower river channel, (2) the mid- to late-Holocene sea-level regression and (3) anthropogenic modifications to the fluvio-estuarine system. We show that while estuarine conditions in the system were fully established during the mid-Holocene highstand (~6.4 kyr BP), central basin facies sedimentation was focussed further inland before prograding with the lowering of base level and shifting of tidal influence as sea-level fell. Central basin facies sedimentation within northern Lake Albert occurred from 5.4 to 4.0 cal kyr BP at ~0.25 cm yr-1. The uppermost accumulation of this unit was eroded by continued reduction in base level until sea-level regression concluded at 3.5 cal kyr BP. Barrage and weir installation (1940 CE) re-initiated and expanded central basin facies sedimentation in the estuary (~0.32 cm yr-1). Recently deposited sediments exhibit geochemical markers of increased trophy and more frequent acid sulfate soil acidification, exposing human impacts on the estuary.

At present, there is a general lack of information regarding the spatial genetic architecture and genetic diversity of estuarine and coastal freshwater fish in Australia or about the interacting intrinsic, extrinsic and historical influences responsible for sculpting these patterns. This thesis represented the first investigation of the phylogeographic structure and recent evolutionary histories of teleost fishes from the coastal and estuarine environments of south-western Australia, using the resolution afforded by mtDNA sequence data. Available evidence indicated that, to different degrees, these species have limited potential for dispersal amongst local assemblages from different water bodies. As this theoretically reduces the confounding effects of recent gene flow on extant genetic structure, these fishes were well suited to studying the influences of historical factors. Historical influences were expected to be particularly profound, given that these coastal environments underwent massive modifications during Late Quaternary eustatic fluctuations. The thesis consists of four major components, which explored different aspects of interspecific and intraspecific phylogeny and p hylogeograp hy of three teleost species, based on mtDNA control region and cytochrome b fragments. First, the relationship between the endemic, 'strictly estuarine' Leptatherina wallacei (Atherinidae) and the more widespread, 'estuarine & marine' 6. presbyteroides was examined, with a view to establishing whether 6. wallacei represents a monophyletic or polyphyletic lineage and whether this species was derived recently (i.e. in Holocene estuaries). Second, the phylogeographic structure and genetic diversity of L. wallacei were investigated and compared with data from L. presbyteroides, with a view to using this information to interpret the recent evolutionary histories of each congener. Third, the divergence between assemblages of L. wallacei inhabiting two isolated coastal lakes was used to estimate a maximal substitution rate for the control region, which was then used to infer general time frames for the divergence between the two Leptatherina species and between the major phylogeographic partitions within each species. Fourth, investigations were initiated into phylogeographic patterns and levels of genetic diversity within and among assemblages of Pseudogobius olorum (Gobiidae) from several coastal lakes and an estuary. Phylogenetic analyses indicated that the two Leptatherina species were characterised by exclusive and reciprocally-monophyletic lineages of haplotypes from both mtDNA regions, supporting the monophyletic origins of L. wallacei. Both 6. wallacei and 6. presbyteroides exhibited high levels of genetic diversity and extensive overall subdivision (e.g. Qsr = 0.691 & 0.644 respectively for control region data). There was a profound phylogeographic break in both species between all conspecific assemblages from the lower west coast (LWC phylogroup) and all those from the south coast (SC phylogroup), which suggested the influences of shared extrinsic and/or historical factors. There was limited genetic structuring within the two major phylogroups of either Leptatherina species, apparently reflecting recent connectivity amongst local assemblages, with subsequent fragmentation and insufficient time for lineage sorting. However, two major phylogeographic breaks distinguished monophyletic control region phylogroups of L. wallacei from the isolated coastal Lake Clifton and Lake Walyungup, consistent with their independent evolution following lacustrine entrapment during the Holocene. The divergence between these two isolated lacustrine assemblages of Leptatherina wallaceiformed the basis for an estimate of the maximal substitution rate of the control region. While these data were unable to provide a precise estimate of the actual rate of molecular evolution, all the evidence suggested that it was proceeding very rapidly. The maximal rate estimate of 172.3% lineage-' MY-' was among the fastest ever reported. Based on this rate, the two Leptatherina species diverged at least 1 SKya, thus rejecting a Holocene origin for L. wallacei. The divergence between the LWC and SC phylogroups of L. wallacei has been ongoing for at least GKya, while the equivalent divergence in L. presbyteroides has been ongoing for at least 11 Kya. As the time frames of these divergences were consistent with periods of massive environmental modifications associated with the end-Pleistocene fall in sea level and the HMT, it was likely that these factors have played important roles in sculpting the species' divergence and intra-specific genetic structure. Although useful in temporally scaling genetic divergences within and between the two Leptatherina species, wider application of this rate estimate to questions regarding other taxa was limited. For example, evident rate heterogeneity between the genera precluded its use with even the relatively closely-related atherinid Atherinosoma elongafa. Phylogeographic analyses identified high levels of genetic diversity and extensive genetic subdivision (e.g. st = 0.652 for control region) amongst an estuarine and several lacustrine assemblages of Pseudogobius olorum, although phylogeographic structure was shallower than in either Leptatherina species. There was increased divergence between three assemblages from the lower west coast and two from the south coast, consistent with the profound break evident in the Leptatherina. One lacustrine assemblage appeared to represent a distinct lineage and a preliminary maximal rate estimate (~61.4% lineage-1 MY-1) was calculated based on the minimum divergence of this assemblage from its nearest conspecifics. Although slower than the rate calculated for L. wallacei, this was still high for teleost fishes. Overall, this study indicated that historical environmental factors, especially those related to Quaternary eustatic changes, have played important roles in sculpting the phylogeography and evolution of three teleost species from south-western Australia. Moreover, as these species have differential dependencies on estuarine environments (is. 'strictly estuarine' vs 'estuarine & marine') and represented two different taxonomic groups (i.e. Atherinoidei & Gobioidei), historical environmental factors may have exerted similar influences on other coastal species in the region.

Includes bibliographical references.
[320] leaves, [29] leaves of plates : ill. (some col., folded), maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1993

Thesis submitted in fulfilment of the academic requirements for the degree of Master of Science. Department of Chemistry University of Witwatersrand, Johannesburg April 2017.
The Mkhuze River discharges into the most northern part of Lake St Lucia, via a contemporary bayhead delta. The delta formed in response to sea level rise during the last deglaciation and today exerts great influence on the functioning of Lake St Lucia, one of the largest estuarine systems in Africa and a globally important conservation area. A sediment core (11.5 m) was extracted from the distal end of the delta to examine the geomorphic evolution of the Mkhuze River Delta and links with variations in Holocene sea level and climate. Radiocarbon and optically-stimulated luminescence dating show that the core captured the entire Holocene infill and documents changes in sedimentation over the last ~13.8 kyr. Grain size and high resolution XRF analysis indicates that initiation of the modern delta occurred since ~7200 cal yr BP , when deglacial sea-level rise reached present-day level. Initial Holocene aged sediments are dominated by clay and silt material that was deposited when seawater intruded into Lake St Lucia via a palaeo-river connection to the ocean at Leven Point. The influx of silt and clay material was accompanied by the emergence of an onshore proto-barrier that created a sheltered lagoonal environment and promoted the accumulation of fine fluvial sediment. The presence of discrete, coarse-grained horizons enriched in zircon identifies a period of increased marine palaeostorm activity between 4700 and 2500 cal yr BP. This period is characterised by the presence of discrete shell fragment accumulations and is interpreted to reflect a strongly positive Indian Ocean dipole anomaly, which resulted in warmer sea surface temperatures and an increase in regional cyclone activity and frequency. The upper part of the core is characterized by generally fine silt and is marked by a decrease in sedimentation rate that corresponds to a phase of lateral delta progradation. The last ~1700 cal yr BP years of the record identify with subtle changes in grain size that can be attributed to a strengthening in El Niño–Southern Oscillation (ENSO) activity, which is known to be associated with prolonged drought and wind erosion in eastern South Africa. This study highlights the usefulness of coastal geochemical records in identifying environmental changes and related climate signals at a regional scale.
GR2018

Booderee National Park at Jervis Bay, 200km south of Sydney, attracts over 450,000 visitors each year. The park has many special features, including dramatic wave cut platforms and sea caves, some of the whitest beach sands in Australia, and very high densities of native predators such as the Powerful Owl and the Diamond Python. This book outlines the biology and ecology of Booderee National Park. Booderee packs an extraordinary level of biodiversity into a small area (roughly 6500 hectares), with more than 260 species of terrestrial vertebrates and over 625 species of plants. It is home to species of significant conservation concern, such as the globally endangered Eastern Bristlebird for which the park is one of its last and most important strongholds. The diversity of vegetation is also astounding: in some parts of the park, it is possible to walk from ankle-high sedgelands, through woodlands and forest and into subtropical rainforest in less than 150 metres. The book highlights how Booderee National Park is a functional natural ecosystem and, in turn, how management practices aim to improve environmental conditions and promote biodiversity conservation. Richly illustrated with colour images from award-winning photographer Esther Beaton, it will delight visitors to the park as well as anyone with an interest in natural history.

The El Niño Modoki/La Niña Modoki (ENSO Modoki) is a newly acknowledged face of ocean-atmosphere coupled variability in the tropical Pacific Ocean. The oceanic and atmospheric conditions associated with the El Niño Modoki are different from that of canonical El Niño, which is extensively studied for its dynamics and worldwide impacts. A typical El Niño event is marked by a warm anomaly of sea surface temperature (SST) in the equatorial eastern Pacific. Because of the associated changes in the surface winds and the weakening of coastal upwelling, the coasts of South America suffer from widespread fish mortality during the event. Quite opposite of this characteristic change in the ocean condition, cold SST anomalies prevail in the eastern equatorial Pacific during the El Niño Modoki events, but with the warm anomalies intensified in the central Pacific. The boreal winter condition of 2004 is a typical example of such an event, when a tripole pattern is noticed in the SST anomalies; warm central Pacific flanked by cold eastern and western regions. The SST anomalies are coupled to a double cell in anomalous Walker circulation with rising motion in the central parts and sinking motion on both sides of the basin. This is again a different feature compared to the well-known single-cell anomalous Walker circulation during El Niños. La Niña Modoki is the opposite phase of the El Niño Modoki, when a cold central Pacific is flanked by warm anomalies on both sides.The Modoki events are seen to peak in both boreal summer and winter and hence are not seasonally phase-locked to a single seasonal cycle like El Niño/La Niña events. Because of this distinction in the seasonality, the teleconnection arising from these events will vary between the seasons as teleconnection path will vary depending on the prevailing seasonal mean conditions in the atmosphere. Moreover, the Modoki El Niño/La Niña impacts over regions such as the western coast of the United States, the Far East including Japan, Australia, and southern Africa, etc., are opposite to those of the canonical El Niño/La Niña. For example, the western coasts of the United States suffer from severe droughts during El Niño Modoki, whereas those regions are quite wet during El Niño. The influences of Modoki events are also seen in tropical cyclogenesis, stratosphere warming of the Southern Hemisphere, ocean primary productivity, river discharges, sea level variations, etc. A remarkable feature associated with Modoki events is the decadal flattening of the equatorial thermocline and weakening of zonal thermal gradient. The associated ocean-atmosphere conditions have caused frequent and persistent developments of Modoki events in recent decades.

In recent years we have seen a veritable ‘explosion’ in the use of the sea for a growing variety of marine leisure activities. This is now a truly global phenomenon that can be seen from Iceland to South Africa, Australia to Florida. Activities in the sea have always been part of coastal tourism, from paddling and swimming to sailing and diving to angling and boat trips. However, in the past decade or two we have seen the invention of new activities and the developments of variations on traditional marine activities. We now have coasteering, wild swimming, paddle-boarding, RIB and banana boats and sea kayaking, all giving tourists further opportunities to get pleasure from the marine environment. Many of these activities also reflect a change in marine leisure with an increase in active rather than passive activities and an increase in adventure activities. This has, inevitably, increased the risk level of sea-based leisure activities in some ways. Several of the more adventurous new activities also involve travelling further from land or to less developed areas of coast, increasing the risk further. Interestingly, it appears that many tourists become ‘hooked’ on some sea-based leisure activities once they have experienced them on vacation. From that point onwards their desire to continue to participate in an activity will often influence their choice of vacation destination. The innovative developments we have seen in terms of sea-based leisure activities have led to a huge increase in participation in marine leisure activities. This has been stimulated by, and reflected in, the investment made in equipment and infrastructure for such activities by governments, commercial operators, and hotels and resorts.

Several physical features combine to make Southeast Asia one of the most distinct and unique coastal regions in the world. The mainland or continental part of Southeast Asia consists of a number of peninsulas extending south and southeast from the Asian continent and separated by gulfs and bays. The world’s two largest archipelagos form the islands of Southeast Asia. During much of the Pleistocene, a large part of the South China Sea was dry land, and the islands of Sumatra, Java, and Borneo were linked to the mainland by the exposed shallow Sunda Shelf. Southeast Asia comes under the influence of the monsoons, or seasonal winds, which have an important impact on its coasts. The region is also a high biodiversity zone, characterized by its rich coral reefs and mangroves. This chapter examines the coastal environments of Southeast Asia in three stages. First, the major elements that make the coastal environments of Southeast Asia distinctive are discussed. The focus is on the coastal processes, as the geological framework and Quaternary have been covered in earlier chapters. Secondly, the various coastal environments in the region (excluding estuaries and deltas discussed in Chapter 13) are described next in terms of their extent, characteristics, and significance, with sufficient examples given to show their variability. Finally, the chapter ends with an assessment of the major environmental problems facing the region’s coastal environments—coastal erosion and rising sea level associated with climate change. Overall, this chapter provides the physical basis for a better appreciation of coastal development in Southeast Asia. The coastal environments of Southeast Asia bear the impact of significant geological and climatic factors. Geologically, the core of the region is an extension of the Eurasian Plate meeting the Indo-Australian and the Pacific Plates and two lesser ones (Philippines and Molucca Sea) with mountain chains trending in a general north–south direction. The island of New Guinea is part of the Indo-Australia Plate. Island arcs have developed along the convergent margins, and many are volcanically active and also associated with shallow to deep earthquakes.

The term “tropics” refers to the continuously warm and frost-free zone of the world that lies approximately between the Tropic of Cancer (or latitude 23.5° north of the equator) and the Tropic of Capricorn (or latitude 23.5° south of the equator). The tropical region comprises approximately 36% of the world’s land surface. Geographically, the tropics encompasses the entire region of Southeast Asia, Central America, the islands in the South Pacific and the Caribbean Basin, a major part of Africa, South America, a large portion of the Indian subcontinent, and a small part of northern Australia. Within a tropical region, natural vegetation and agriculture vary with elevation and rainfall regime. Within the tropical belt, mean annual temperature at sea level is about 26 °C, and it decreases approximately 0.6 °C with every 100 m increase in elevation. On the basis of elevation, the tropics may be further divided into • lowland tropics (areas below 600 m), • midaltitude tropics (areas between 600 and 900 m), and • high-altitude tropics or tropical highlands (areas above 900 m). Tropical highlands account for 23% of the tropics whereas the low- and midaltitude regions together comprise about 87% of the total area. Tropical highlands usually have cool air temperatures with a mean annual temperature of 20 °C or lower. Rainfall on tropical highlands can be extremely variable within a short distance. Because of the year-round comfortable temperature, areas of tropical highlands with favorable rainfall and fertile soils are usually densely populated and hence intensively cultivated. Climates in the lowland and midaltitude tropics generally share three common features, namely, a year-round warm temperature, rainfall of high intensity and short duration, and a high rate of evaporation. Climates are characterized principally by mean monthly air temperature, and the amount and distribution of rainfall.

Compared to herpetological population adjustment patterns in North America (sec Holman, 1995c), the patterns in Britain and central and northern Europe seem to be rather straightforward. Basically, (1) very few herpetological species were present in ice-free areas during full glacial times, and (2) formerly glaciated areas were reinvaded by species from the south during warming cycles. Moreover, during climatic optimal warm times, several southern species existed well north of their present ranges. The invasion of southern Europe by northern populations in cold times is taken for granted (e.g., Rocek, 1995), although, as addressed in this chapter, it is difficult to document this in the fossil record. As indicated by geological and fossil evidence, the British Islands were connected to continental Europe during much of the Pleistocene. Although sea level changes in the British late Pleistocene arc a subject of some controversy (Stuart, 1982), it is generally agreed that Britain first separated from Ireland and then from the continent early in the Holocene. The classic idea is that the very depauperate British heretofauna of the cold part of the Devensian (last glacial stage) became somewhat, but not fully enriched by herpetological species during a warming trend that began about 10,000 ybp and lasted until about 8,500 ybp. The fact that Ireland has a much poorer modern herpetofauna (Triturus vulgaris, the rare Bufo calamita, Rana temporaria, and Lacerta vivipara) than Britain, which has six native species of amphibians and six native species of reptiles (Fra/,er, 1983; Smith, 1964), is attributed to Ireland's early separation from Britain. The Irish herpetofauna suggests that this separation occurred rather soon after the final withdrawal of the Devensian (last glacial) ice sheet. One of the most common questions asked about snakes, especially near St. Patrick's Day, is, "Have there ever been any snakes in Ireland?" No fossil snakes have ever been found in Ireland. But since Ireland lacks a terrestrial fossil record during most of the time that snakes have existed, it would seem that snakes could have lived in Ireland during some part of geological time. As far as I am aware, the few Pleistocene deposits containing herpetological remains in Ireland represent very late Devensian (last glacial) times.

The basic climatic characteristics of the major mountain ranges in the United States—the Appalachians, the Coast Range, the Alaska Range, the Cascade Range, the Sierra Nevada, and the Rocky Mountains—can be described in terms of the four factors discussed in chapter 1. The mountains of North America extend latitudinally all the way from the Arctic Circle (66.5°N) to the tropic of Cancer (23.5°N) (figure 2.1). There are significant differences in day length and angle of solar radiation over this latitude belt that result in large seasonal and diurnal differences in the weather from north to south. Elevations in the contiguous United States extend from below sea level at Death Valley to over 14,000 ft (4270 m) in the Cascade Range, the Sierra Nevada, and the Rocky Mountains. Several prominent peaks along the Coast Range in Alaska and Canada (e.g., Mount St. Elias and Mount Logan) reach elevations above 18,000 ft (5486 m). Denali (20,320 ft or 6194 m) in the Alaska Range is the highest peak in North America. The highest peak in the Canadian Rockies is Mt. Robson, with an elevation of 12,972 ft (3954 m). The climates of the Coast Range, the Cascade Range, and the Sierra Nevada, all near the Pacific Ocean, are primarily maritime. The Appalachian Mountains of the eastern United States are subject to a maritime influence from the Atlantic Ocean and the Gulf of Mexico, but they are also affected by the prevailing westerly winds that bring continental climatic conditions. Only the climate of the Rocky Mountains, far from both the Pacific and Atlantic Oceans, is primarily continental. Each of the mountain ranges is influenced by regional circulations. For example, the Appalachians are exposed to the warm, moist winds brought northward by the Bermuda-Azores High and to the influence of the Gulf Stream. Similarly, the Coast Range feels the impact of the Pacific High, the Aleutian low, and the Japanese Current. A mountain range, depending on its size, shape, orientation, and location relative to air mass source regions, can itself affect the regional climate by acting as a barrier to regional flows.