scholarly journals ENSO feedback drives variations in dieback at a marginal mangrove site

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. M. Hickey ◽  
B. Radford ◽  
J. N. Callow ◽  
S. R. Phinn ◽  
C. M. Duarte ◽  
...  
Keyword(s):  
Sea Level ◽  
Southern Oscillation ◽  
World Heritage Site ◽  
Range Limit ◽  
Tropical Regions ◽  
North West ◽  
Remote Sensing Classification ◽  
The North ◽  
Canopy Area ◽  
Landsat Satellite

AbstractOcean–atmosphere climatic interactions, such as those resulting from El Niño Southern Oscillation (ENSO) are known to influence sea level, sea surface temperature, air temperature, and rainfall in the western Pacific region, through to the north-west Australian Ningaloo coast. Mangroves are ecologically important refuges for biodiversity and a rich store of blue carbon. Locations such as the study site (Mangrove Bay, a World Heritage Site within Ningaloo Marine Park and Cape Range National Park) are at the aridity range-limit which means trees are small in stature, forests small in area, and are potentially susceptible to climate variability such as ENSO that brings lower sea level and higher temperature. Here we explore the relationship between mangrove dieback, and canopy condition with climatic variables and the Southern Oscillation Index (SOI)—a measure of ENSO intensity, through remote sensing classification of Landsat satellite missions across a 29 year period at a north-west Australian site. We find that the SOI, and seasonal mean minimum temperature are strongly correlated to mangrove green canopy (as indicator of live canopy) area. This understanding of climate variations and mangrove temporal heterogeneity (patterns of abundance and condition) highlights the sensitivity and dynamics of this mangrove forest and recommends further research in other arid and semi-arid tropical regions at mangrove range-limits to ascertain the extent of this relationship.

scholarly journals New Insights into Annual and Semiannual Cycles of Sea Level Pressure

2012 ◽  
Vol 140 (4) ◽  
pp. 1347-1355 ◽  
Author(s):  
Ge Chen ◽  
Chengcheng Qian ◽  
Caiyun Zhang
Keyword(s):  
Sea Level ◽  
Southern Oscillation ◽  
Global Ocean ◽  
Boreal Winter ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
Dominant Feature ◽  
The One ◽  
The North Pacific

Sea level pressure (SLP) acts, on the one hand, as a “bridge parameter” to which geophysical properties at the air–sea interface (e.g., wind stress and sea surface height) are linked, and on the other hand, as an “index parameter” by which major atmospheric oscillations, including the well-known Southern Oscillation, are defined. Using 144 yr (1854–1997) of extended reconstructed SLP data, seasonal patterns of its variability are reinvestigated in detail. New features on fundamental structure of its annual and semiannual cycles are revealed in two aspects. First, the spatiotemporal patterns of yearly and half-yearly SLPs are basically determined by a network of “amphidromes,” which are surrounded by rotational variations. Fourteen cyclonic and anticyclonic annual SLP amphidromes (half each and often in pair) are found in the global ocean, while the numbers of the two types of semiannual amphidrome are 11 and 9, respectively. The second dominant feature in SLP variability is the pattern of oscillation or seesaw for both annual and semiannual components. At least eight oscillation zones are identified for the annual cycle, which can be categorized into a boreal winter mode and an austral winter mode. As for the semiannual cycle, the seesaw pattern is geographically divided into three regimes: the North Pacific regime, the North Atlantic regime, and the Southern Ocean regime. These findings serve as a new contribution to characterizing and understanding the seasonality of the global ocean–atmosphere system.

Evidence of 8.2-ka event in Southeast Asia inferred from marginal marine sediments off Kallang River Basin, Singapore

2021 ◽  
Author(s):  
Yama Dixit ◽  
Stephen Chua ◽  
Yu Ting Yan ◽  
Adam Switzer
Keyword(s):  
River Basin ◽  
Marine Sediments ◽  
Large Scale ◽  
Southern Oscillation ◽  
Signal Propagation ◽  
Warm Pool ◽  
Seasonal Migration ◽  
Monsoon Circulation ◽  
Tropical Regions ◽  
The North

<p>The Maritime Continent (MC) is located within the Indo-Pacific Warm Pool, which is known as the largest area of warm sea surface temperatures with the highest rainfall on Earth that drives the global atmospheric and hydrologic circulation. The complex climatic system of the MC is controlled by large-scale phenomena such as the seasonal migration of the Intertropical Convergence Zone which causes the northwest and southeast monsoon circulation in the region as well as tropical Indo-Pacific climate phenomena, the Indian Ocean Dipole in the west and the El Niño-Southern Oscillation operating to the east of the MC. In addition to interactions of these climate phenomena, their influence varies across the region due to island topography and ocean–atmosphere fluxes. Despite dedicated efforts, a comprehensive picture of the impacts of abrupt climate events such as the ‘8.2 ka event’ during the Holocene on the MC has proved elusive. Here we use sedimentology and stable isotopes of benthic foraminifera collected from the marginal marine sediments off the Kallang River Basin, Singapore to reconstruct paleoenvironmental history of the early-mid Holocene. Owing to the high sedimentation rate (~4.4 mm/yr), the timing and nature of the ‘8.2 ka event’ was examined in detail in this region making this an invaluable and unique archive to study up to sub-centennial changes. Comparison of the Kallang record with other high-resolution marine and absolutely dated terrestrial archives speleothems revealed that the timing of the onset of ‘8.2 ka event’ in the western IPWP region lags the cooling in the North Atlantic and that of Asian and Indian monsoon failure, by ~100years possibly implying a north-south signal propagation. The termination of the ‘8.2 ka event’, however may have occurred near synchronously between high and low tropical regions at ~7.96ka BP possibly linked via both atmospheric and oceanic processes.</p><p> </p>

Temporal patterns in distributions of tropical fish larvae on the North West Shelf of Australia

2004 ◽  
Vol 55 (5) ◽  
pp. 473 ◽  
Author(s):  
A. Sampey ◽  
M. G. Meekan ◽  
J. H. Carleton ◽  
A. D. McKinnon ◽  
M. I. McCormick
Keyword(s):  
Southern Oscillation ◽  
Fish Larvae ◽  
Early Stage ◽  
Larval Survival ◽  
Zooplankton Biomass ◽  
Tropical Fish ◽  
North West ◽  
Larval Fishes ◽  
The North ◽  
Abundance And Diversity

Information on the temporal distributions of tropical fish larvae is scarce. Early stage larval fishes were sampled using towed bongo plankton nets at sites on the southern North West Shelf of Australia (21°49′S, 114°14′E), between October and February of 1997/98 and 1998/99. The first summer was characterised by El Niño–Southern Oscillation-driven upwelling and high primary productivity, whereas in the second summer water temperatures were warmer and primary production was lower. Benthic percoid shorefishes dominated surface assemblages in both summers and this pattern may be typical of tropical shelf environments.The abundance and diversity of larval fishes were lowest in October and increased from November through to February. Assemblages displayed weak cross-shelf patterns, with a few taxa being more abundant at inshore sites (e.g. monacanthids), whereas others were more abundant offshore (e.g. scombrids). Although the composition of assemblages remained relatively consistent, many taxa (e.g. pomacentrids and carangids) showed differences in abundance between summers. Multivariate analyses found no relationships between abundance patterns of larval fishes and biophysical variables, such as temperature, salinity, and zooplankton biomass. Thus, seasonal changes in abundance may reflect differences in the spawning activities of adult fishes and/or larval survival.

Spatial and temporal variation in precipitation at the start of the rainy season in tropical Australia

2010 ◽  
Vol 32 (2) ◽  
pp. 215 ◽  
Author(s):  
S. T. Garnett ◽  
G. Williamson
Keyword(s):  
Seed Germination ◽  
El Niño ◽  
Rainy Season ◽  
El Nino ◽  
Southern Oscillation ◽  
Temporal Trends ◽  
Spatial And Temporal Variation ◽  
Economic Implications ◽  
North West ◽  
The North

The patterns of rainfall early in the rainy season vary substantially across northern Australia, even in sites with the same annual average. This has biophysical and economic implications in terms of land and infrastructure management, resource availability and capacity, and access. Daily patterns in long-term rainfall records in Australia north of 23°S subject to regular monsoonal rainfall were compared with threshold levels for dryland and wetland seed germination, initiation of the growing season, patterns of gaps between early storms and the heaviness of the first falls, correlations between thresholds, spatial variation in correlation with the Southern Oscillation Index (SOI) and temporal trends in mean threshold dates. The earliest rains sufficient to cause seed germination or generate fresh fodder occur in the north-west of the Northern Territory with the average date being later to the south, east and west. Initial falls of the rainy season are heaviest, however, on Cape York Peninsula so that the time between first falls and saturation is shortest in the east. The probability of extended gaps between rainfall events increased from north to south. When the SOI is taken into account, no change in timing could be detected at the few sites with records of sufficient duration. However, because of changes in SOI frequency, rains are tending to start earlier in the drier parts of the north and north-west and later in the east. This may be because anthropogenic climate change is resulting in fewer classical El Niño Southern Oscillation events and more frequent El Niño Modoki climate anomalies.

scholarly journals The impact of sea-level rise on tidal characteristics around Australia

Ocean Science ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 147-159 ◽  
Author(s):  
Alexander Harker ◽  
J. A. Mattias Green ◽  
Michael Schindelegger ◽  
Sophie-Berenice Wilmes
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Tidal Dissipation ◽  
North West ◽  
The North ◽  
Tidal Changes ◽  
Tidal Characteristics ◽  
The Impact

Abstract. An established tidal model, validated for present-day conditions, is used to investigate the effect of large levels of sea-level rise (SLR) on tidal characteristics around Australasia. SLR is implemented through a uniform depth increase across the model domain, with a comparison between the implementation of coastal defences or allowing low-lying land to flood. The complex spatial response of the semi-diurnal M2 constituent does not appear to be linear with the imposed SLR. The most predominant features of this response are the generation of new amphidromic systems within the Gulf of Carpentaria and large-amplitude changes in the Arafura Sea, to the north of Australia, and within embayments along Australia's north-west coast. Dissipation from M2 notably decreases along north-west Australia but is enhanced around New Zealand and the island chains to the north. The diurnal constituent, K1, is found to decrease in amplitude in the Gulf of Carpentaria when flooding is allowed. Coastal flooding has a profound impact on the response of tidal amplitudes to SLR by creating local regions of increased tidal dissipation and altering the coastal topography. Our results also highlight the necessity for regional models to use correct open boundary conditions reflecting the global tidal changes in response to SLR.

The Excavation of Nympsfield Long Barrow, Gloucestershire

1938 ◽  
Vol 4 (1) ◽  
pp. 188-213 ◽  
Author(s):  
Elsie M. Clifford
Keyword(s):  
Sea Level ◽  
Rural District ◽  
North West ◽  
The North

The Nympsfield long barrow is situated in the parish of Frocester, but is less than a mile to the north-west of Nympsfield village. The boundaries of the Parish, the Rural District and the Union, run from north to south down the centre of the field, called ‘Buckholt End,’ in which it lies. The position of the barrow is latitude 51° 42′ 35″ and longitude 2° 17′ 54″ (six-inch O.S., Gloucs. XLIX S.W.) and its height 750 feet above sea level. Ninety yards to the east of the barrow there is a road, marked by Grundy as a ‘ridgeway,’ which now runs from Selsley Hill to Uley (fig. 1). The underlying rock is the Inferior Oolite, a formation separable into numerous sub-divisions, here including, in descending order, Clypeus Grit, Upper Trigonia Grit and Upper Freestone. The greater part of the barrow, if not the whole of it rests on Clypeus Grit.

scholarly journals Precipitação na América do Sul: Médias Climáticas e Padrões da Variabilidade no Período entre 1979 e 2008

2016 ◽  
Vol 9 (1) ◽  
pp. 032
Author(s):  
Éder Leandro Maier ◽  
Juliana Costi ◽  
Sandra Barreira ◽  
Jefferson Cardia Simões
Keyword(s):  
South America ◽  
North Atlantic ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Principal Component ◽  
Monthly Precipitation ◽  
Tropical Regions ◽  
The North ◽  
North Atlantic Variability

Este artigo discute os principais padrões médios e anômalos da precipitação sobre a América do Sul no período 1979–2008. Para isso foram manipulados dados mensais da precipitação observada em 890 estações meteorológicas localizadas na Argentina, Bolívia, Brasil, Paraguai e Uruguai ao longo desse período de trinta anos. As médias climáticas foram subtraídas das amostras, originando as anomalias, as quais foram agrupadas por meio da Análise das Componentes Principais em dois modos. No modo T se identificou 6 componentes principais, que explicam 35% da variância e representam 12 padrões espaciais anômalos originados, principalmente, pelo fenômeno El Niño–Oscilação Sul (ENOS) e pela variabilidade do Atlântico Norte. No modo S foram identificadas 8 zonas em que a variabilidade temporal das séries anômalas é semelhante, sendo que o ENOS prevalece no controle das anomalias nas zonas situadas na região equatorial e extratropical, além disso, a variabilidade do Atlântico Norte pode maximizar ou minimizar os impactos do ENOS. A frequência de recorrência desses estresses hídrico variam entre 20 e 60 meses.  This article discusses mean and anomalous rainfall patterns over South America in the period 1979–2008. For that we handled monthly precipitation data observed at 890 meteorological stations located in Argentina, Bolivia, Brazil, Paraguay and Uruguay over this thirty years period. Climatic means were subtracted from the data, resulting in anomalies that were grouped by Principal Component Analysis in two modes. We identified 6 main components in the T mode, which explain 35% of the variance and represent 12 anomalous spatial patterns originated mainly by El Niño–Southern Oscillation (ENSO) phenomenon and the North Atlantic variability. In mode S, we identified eight zones where the series temporal variability is also anomalous, and the ENOS prevails as the anomalies controller in the equatorial and extra tropical regions. Further, North Atlantic variability may maximize or minimize the ENSO impact. The frequency of these recurrent water stresses range from 20 to 60 months. Keywords: Precipitation, South America, PCA  

Ritual Inscriptions from Uzundara

2021 ◽  
pp. 250
Author(s):  
Nigora D. Dvurechenskaya
Keyword(s):  
Sea Level ◽  
Natural Boundary ◽  
Crucial Point ◽  
North West ◽  
The North ◽  
Archaeological Materials

The paper presents three Greek votive graffiti from the excavations of citadel of Fortress Uzundara (Uzbekistan) and describes their archaeological context. This fortress is located on the North-West Border of Ancient Bactria, and represents the crucial point in the tens–kilometers long borderline fortification system in this area. It is built at altitude of 1700 meters above the sea level. The fortress stands on the narrow (220 meters) neck between the precipitous walls of the natural boundary Kara-Kamar and the canyon Uzundara, and locks the pass for the equestrian troops intent to bypass the borderline wall of Darband in 7 kilometers northward. It consists of the principal rhomboid castle, a detached and adjacent triangular citadel, same sections of the external walls, and of three external towers. The main goal of this fortress was the warning of the sudden attack of nomads from the Karshin steppes. A military garrison was stationed in the Uzundara fortress – a Seleucid frurion in the first quarter of the 3rd century BC. Apparently at this time it consisted of Macedonians and Greeks. This is clearly evidenced by archaeological materials, including epigraphic ones. We analyze three artefacts voted to Demeter of the Mountains and the Borderline, Zeus–Mitra, and Zoroastrian Deity Srosh. The most complete inscription – votive to Demeter – persists on the three fragments of tagora (luterium) which could be used for the ritual ablution. They were founded in different years and in different places around the ovoid cellar on the rocky complex of the citadel Uzundara.

scholarly journals I.—The Kishon and Jordan Valleys

1904 ◽  
Vol 1 (12) ◽  
pp. 575-582 ◽  
Author(s):  
T. G. Bonney
Keyword(s):  
Sea Level ◽  
Difficult Problem ◽  
The South ◽  
North West ◽  
The North ◽  
South West ◽  
Western Side ◽  
Physical Geology

That broad trench through the Palestine Highlands, an ancient highway and battlefield of nations—the plain of Esdraelon or the valley of Megiddo, together with the plain of Acre—has for long presented to me a difficult problem in Physical Geology, for it seemed inexplicable by subaerial denudation under existing conditions. Its floor varies roughly from five to eight miles in breadth; running approximately from south-east to north-west, it is bounded on the more western side by the limestone mountains of Samaria and on the more eastern by those of Galilee. The former descend from the ridge of Carmel (1,742 feet at highest) with a fairly steep escarpment, which becomes a little less regular as we follow it to the bastion-mass of Mount Gilboa; the latter correspond in their general outlines with those of the eastern portion of Samaria, but the advance of a lower spur towards the south-west divides the plain of Esdraelon from that of Acre, by a kind of strait in which, so far as I could see, there is but little level ground on either side of the Kishon. This spur, however, of the northern hills, hardly does more than interrupt the floor of the Kishon valley, for above it the great trench is continued between two hill masses, much of these ranging from thirteen to sixteen hundred feet above sea-level. Beyond the strait the upper basin (plain of Esdraelon) quickly broadens out, extending towards the south-east for about fifteen or sixteen miles, where it is divided into two arms by Jebel Duhy (Little Hermon) (1,690 feet), which is thus isolated from Tabor (1,846 feet) on the north, and from Gilboa (1,698 feet) on the south; a broad, rather shallow, grassy valley descending from the last-named mass to lose itself in the plain.

Further Discoveries of Flint Implements in the Brown Boulder Clay of North-West Norfolk

1932 ◽  
Vol 6 (4) ◽  
pp. 306-315 ◽  
Author(s):  
J. Reid Moir
Keyword(s):  
Sea Level ◽  
Geological Survey ◽  
Prehistoric Archaeology ◽  
East Anglia ◽  
North West ◽  
Terminal Moraine ◽  
The North ◽  
Boulder Clay ◽  
Western Portion ◽  
North Western

Since my original paper on the flint implements found in the Brown Boulder Clay of north-west Norfolk, I have continued my researches in that region, and now wish to give some account of these, and of the further specimens which have been discovered in this most recent boulder clay of East Anglia. I would take this opportunity of thanking the Trustees of the Percy Sladen Fund for their kindness in supporting this research with a money grant, and so enabling me to continue my examination of an era of much interest and importance to prehistoric archæology. I am also very grateful to my friends, Mr. J. B. Calkin, Mr. Guy Maynard, and Mr. J. S. Fisher, for the valuable help they have given me in carrying out the investigation of the Brown Boulder Clay.As is now widely known, this deposit, so far as Norfolk is concerned, is confined to the north-western portion of that county, and many years ago was examined and reported upon by the Geological Survey in two of their memoırs. The Brown Boulder Clay occurs approximately at sea-level at Hunstanton, while at Brancaster, as reported by Mr. Clement Reid, the deposit is exposed at low water upon the foreshore, underlying the ‘submerged forest’ which he saw there. At other places, such as Holkham brickfield, and the remarkable formation (probably a terminal moraine) in Hunstanton Park, the boulder clay rests at about 50 ft, above O.D.

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