Climatic conditions deduced from a 150-kyr oxygen isotope–pollen record from the Arabian Sea

Nature ◽  
1982 ◽  
Vol 296 (5852) ◽  
pp. 56-59 ◽  
Author(s):  
E. Van Campo ◽  
J. C. Duplessy ◽  
M. Rossignol-Strick
Keyword(s):  
Oxygen Isotope ◽  
Arabian Sea ◽  
Climatic Conditions ◽  
Pollen Record

scholarly journals Observation of Oceanic Eddy in the Northeastern Arabian Sea Using Multisensor Remote Sensing Data

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
R. K. Sarangi
Keyword(s):  
Remote Sensing ◽  
Arabian Sea ◽  
Chlorophyll Concentration ◽  
Climatic Conditions ◽  
Late Winter ◽  
Surrounding Water ◽  
Noaa Avhrr ◽  
Oceanic Eddy ◽  
Remote Sensing Satellite ◽  
Cold Core

An oceanic eddy of size about 150 kilometer diameter observed in the northeastern Arabian Sea using remote sensing satellite sensors; IRS-P4 OCM, NOAA-AVHRR and NASA Quickscat Scatterometer data. The eddy was detected in the 2nd week of February in Indian Remote Sensing satellite (IRS-P4) Ocean Color Monitor (OCM) sensor retrieved chlorophyll image on 10th February 2002, between latitude 16°90′–18°50′N and longitude 66°05′–67°60′E. The chlorophyll concentration was higher in the central part of eddy (~1.5 mg/m3) than the peripheral water (~0.8 mg/m3). The eddy lasted till 10th March 2002. NOAA-AVHRR sea surface temperature (SST) images generated during 15th February-15th March 2002. The SST in the eddy’s center (~23°C) was lesser than the surrounding water (~24.5°C). The eddy was of cold core type with the warmer water in periphery. Quickscat Scatterometer retrieved wind speed was 8–10 m/sec. The eddy movement observed southeast to southwest direction and might helped in churning. The eddy seemed evident due to convective processes in water column. The processes like detrainment and entrainment play role in bringing up the cooler water and the bottom nutrient to surface and hence the algal blooming. This type of cold core/anti-cyclonic eddy is likely to occur during late winter/spring as a result of the prevailing climatic conditions.

Corrosion Behaviour of Cupronickel 90/10 Alloys in Arabian Sea Conditions and its Effect on Maintenance of Marine Structures

2019 ◽  
Author(s):  
Muntazir Abbas ◽  
Mahmood Shafiee ◽  
Nigel Simms
Keyword(s):  
Corrosion Rate ◽  
Coastal Waters ◽  
Arabian Sea ◽  
Corrosion Behaviour ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Metal Loss ◽  
Natural Seawater ◽  
Marine Structures ◽  
Rate Evaluation

Abstract The composition of seawater plays a very significant role in determining the severity of corrosion process in marine assets. The influential contributors to the general and pitting corrosions in marine structures include temperature, dissolved oxygen (DO), salinity, PH, chlorides, pollutants, nutrients, and microbiological activities in seawater. The Cu-Ni (90/10) alloy is increasingly used in marine applications such as heat exchangers and marine pipelines because of its excellent corrosion resistant properties. Despite the significant advancements in corrosion shielding procedures, complete stoppage of corrosion induced metal loss, especially under rugged marine environments, is practically impossible. The selection of appropriate metal thickness is merely a multifaceted decision because of the high variability in operating conditions and associated corrosion rate in various seawater bodies across the globe. The present research study aims to analyze the early phase of corrosion behavior of Cu-Ni (90/10) alloy in open-sea conditions as well as in pollutant-rich coastal waters of the Arabian Sea. Test samples were placed under natural climatic conditions of selected sites, followed by the mass loss and corrosion rate evaluation. The corrosion rate in the pollutant-rich coastal waters was around five times higher than in the natural seawater. A case study on marine condenser (fitted with of Cu-Ni 90/10 alloy tubes) is presented, and a risk-based inspection (RBI) plan is developed to facilitate equipment designers, operators, and maintainers to consider the implications of warm and polluted seawater on equipment reliability, service life, and subsequent health inspection/ maintenance.

scholarly journals A new high-resolution pollen sequence at Lake Van, Turkey: insights into penultimate interglacial–glacial climate change on vegetation history

2017 ◽  
Vol 13 (6) ◽  
pp. 689-710 ◽  
Author(s):  
Nadine Pickarski ◽  
Thomas Litt
Keyword(s):  
High Resolution ◽  
Climate Variability ◽  
Eastern Mediterranean Region ◽  
Climatic Conditions ◽  
Semiarid Region ◽  
The Black Sea ◽  
Pollen Record ◽  
Lake Van ◽  
Last Interglacial ◽  
Pollen Records

Abstract. A new detailed pollen and oxygen isotope record of the penultimate interglacial–glacial cycle, corresponding to the marine isotope stage (MIS) 7–6, has been generated from the Ahlat Ridge (AR) sediment core at Lake Van, Turkey. The presented Lake Van pollen record (ca. 250.2–128.8 ka) displays the highest temporal resolution in this region with a mean sampling interval of  ∼  540 years.The integration of all available proxies shows three temperate intervals of high effective soil moisture availability. This is evidenced by the predominance of steppe-forested landscapes (oak steppe-forest) similar to the present interglacial vegetation in this sensitive semiarid region between the Black Sea, the Caspian Sea, and the Mediterranean Sea.The wettest and warmest stage, as indicated by highest temperate tree percentages, can be broadly correlated with MIS 7c, while the amplitude of the tree population maximum during the oldest penultimate interglacial (MIS 7e) appears to be reduced due to warm but drier climatic conditions. The detailed comparison of the penultimate interglacial complex (MIS 7) to the last interglacial (Eemian, MIS 5e) and the current interglacial (Holocene, MIS 1) provides a vivid illustration of possible differences in the successive climatic cycles. Intervening periods of treeless vegetation can be correlated with MIS 7d and 7a, in which open landscapes favor local erosion and detrital sedimentation. The predominance of steppe elements (e.g., Artemisia, Chenopodiaceae) during MIS 7d indicates very dry and cold climatic conditions. In contrast, the occurrence of higher temperate tree percentages (mainly deciduous Quercus) throughout MIS 7b points to relatively humid and mild conditions, which is in agreement with other pollen sequences in southern Europe.Despite the general dominance of dry and cold desert-steppe vegetation during the penultimate glacial (broadly equivalent to MIS 6), this period can be divided into two parts: an early stage (ca. 193–157 ka) with higher oscillations in tree percentages and a later stage (ca. 157–131 ka) with lower tree percentages and subdued oscillations. This subdivision of the penultimate glacial is also seen in other pollen records from southern Europe (e.g., MD01-2444 and I-284; Margari et al., 2010; Roucoux et al., 2011). The occurring vegetation pattern is analogous to the division of MIS 3 and MIS 2 during the last glacial in the same sediment sequence. Furthermore, we are able to identify the MIS 6e event (ca. 179–159 ka) as described in marine pollen records, which reveals clear climate variability due to rapid alternation in the vegetation cover.In comparison with long European pollen archives, speleothem isotope records from the Near East, and global climate parameters (e.g., insolation, atmospheric CO2 content), the new high-resolution Lake Van record presents an improved insight into regional vegetation dynamics and climate variability in the eastern Mediterranean region.

Paleoclimatic Reconstruction in Northern Oman Based on Carbonates from Hyperalkaline Groundwaters

1990 ◽  
Vol 33 (3) ◽  
pp. 320-336 ◽  
Author(s):  
Ian D. Clark ◽  
Jean-Charles Fontes
Keyword(s):  
Late Pleistocene ◽  
Radiocarbon Dating ◽  
Arabian Sea ◽  
Flow System ◽  
Climatic Conditions ◽  
Current Phase ◽  
Groundwater Flow System ◽  
Paleoclimatic Reconstruction ◽  
The Past ◽  
Lacustrine Deposits

AbstractA paleoclimatic reconstruction for the past 35,000 years for northern Oman is based on an unusual approach using travertines and fracture calcites associated with hyperalkaline springs. High-pH groundwaters (pH up to 11.9) discharge from the mantle sequence of the Oman Ophiolite as the product of modern, low-temperature serpentinization. Under arid climatic conditions, hyperalkaline discharge occurs at the surface. Uptake of atmospheric CO2precipitates characteristic laminated travertines, accompanied by strong kinetic depletion of13C and18O. Pluvial climates supporting a shallow bicarbonate-groundwater flow system and vegetation are recorded by fracture calcites with equilibrium stable isotope contents and calcite-replaced roots and stems. All such carbonates have modern initial14C contents, allowing radiocarbon dating and paleoclimatic reconstruction for the late Pleistocene and Holocene. Our reconstruction shows a dominantly wet late Pleistocene up to 19,000 yr B.P., when a phase of climatic deterioration began, leading to a period of hyperaridity which dominated from ca. 16,300 to 13,000 yr B.P. The early Holocene pluvial occurred from 12,500 to ca. 6500 yr B.P. and was followed by renewed climatic deterioration and the current phase of hyperaridity. Comparison of this paleoclimatic reconstruction with that for lacustrine deposits from the A'Rub al Khali of central Saudi Arabia and the summer insolation-driven monsoon record of east Africa and the Arabian Sea is remarkably good.

Neotropical Ostracodes as Indicator for Paleo-Hurricanes - High-temporal Calcification Periods traced by Oxygen Isotopes

2021 ◽  
Author(s):  
Claudia Wrozyna ◽  
Thomas C. Brachert ◽  
Martin Dietzel ◽  
Stefan Geyer ◽  
Markus Reuter ◽  
...  
Keyword(s):  
Life Cycle ◽  
Oxygen Isotope ◽  
Temporal Resolution ◽  
Lake Water ◽  
Environmental Control ◽  
Isotope Composition ◽  
Coastal Lagoons ◽  
Climatic Conditions ◽  
High Temporal Resolution ◽  
Precipitation Seasonality

<p>Overwash deposits in coastal lagoons are most commonly utilized for the identification of past hurricane landfalls. These deposits have a small spatial distribution and a limited preservation potential. Thus, geochemical approaches to indicate palaeo-hurricanes, such as δ<sup>18</sup>O signatures of carbonate deposits, are rare besides most archives do not provide the requested high temporal resolution. Ostracodes are ideally suited for the application of paleo-hurricanes since they calcify new valves within hours to few days – fast enough to document a rainstorm event. But, information on the ostracode life cycle and influences on modern oxygen isotope compositions are limited, especially in tropical regions.    </p><p>This study investigates the relationship between hydrochemistry, climate, and valve geochemistry (δ<sup>18</sup>O, δ<sup>13</sup>C) of living populations of the common Neotropical ostracode <em>Cytheridella </em>on a large geographical range. Since most of the regions in the Neotropics are sparsely covered by hydrochemical data, especially with respect to stable isotopes (δ<sup>18</sup>O and δ<sup>13</sup>C), the present approach is based on estimation of δ<sup>18</sup>O<sub>eq</sub> values calcites at isotope equilibrium as references for the interpretation of oxygen isotope distribution of ostracodes.</p><p>As postulated in other studies δ<sup>18</sup>O<sub>precipitation</sub> and temperature are the most important controls on lake water and, consequently, ostracode δ<sup>18</sup>O.</p><p>Oxygen isotope composition reveals inferences to be drawn on calcification periods of <em>Cytheridella </em>within its geographical distribution. Offsets between <em>Cytheridella </em>δ<sup>18</sup>O and δ<sup>18</sup>O<sub>eq</sub> values vary throughout the year and coincide only during spring (April/May) and autumn (October) which indicates that <em>Cytheridella </em>calcifies seasonally in all investigated regions. This implies a synchronous life cycle of <em>Cytheridella </em>in all investigated regions. Since the regions differ in climatic conditions (i.e., precipitation seasonality and amounts, temperature gradients) an environmental control on Cytheridella´s life cycle can be excluded.</p><p>The above approach yields in an improved understanding of geochemical (i.e., δ<sup>18</sup>O, δ<sup>13</sup>C) signatures of ostracode valves on a seasonal basis especially in regions where few information on lake water hydrochemistry is available and points to δ18O values of ostracode species to be used for the identification of hurricane-related precipitation extremes by their high-temporal resolution of seasonal calcification.</p>

scholarly journals A 1200-year history of environmental changes in Bay Jimmy area, coastal Louisiana, USA

The Holocene ◽  
2019 ◽  
Vol 30 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Lawrence M Kiage
Keyword(s):  
Environmental Changes ◽  
Forest Disturbance ◽  
Climatic Conditions ◽  
Ice Age ◽  
Pollen Record ◽  
Ambrosia Pollen ◽  
Paleoenvironmental Changes ◽  
European Settlement ◽  
Red Mangrove ◽  
Coastal Louisiana

Paleoecological studies from the northern Gulf of Mexico (GOM) have mostly aimed at understanding long-term paleoenvironmental changes. Only a few studies have been performed in the southern United States focusing on paleoenvironmental changes during the common era. This study investigated paleoenvironmental changes in coastal Louisiana over the past 1200 years by utilizing proxy data, including loss-on-ignition (LOI) and pollen from a sediment core collected from a wetland in Bay Jimmy. The results indicate that the marsh in the study area was formed at ca. AD 1090 and has been primarily shaped by prevailing climatic conditions, including rare extreme events. At least four major hurricanes impacted the site over the 1200 years, including two that made landfall in recent times. The findings show that coastal Louisiana was warm and dry during the ‘Medieval Warm Period’ (ca. AD 950–1250). The environment after AD 1090 contained scattered Pinus and Juglans vegetation communities that were later succeeded by a closed forest that included Quercus and Morus. Red mangrove ( Rhizophora) was established in the vicinity of Bay Jimmy until shortly after cal AD 1450 and 1640. The pollen record indicates that the ‘Little Ice Age’ period (AD 1550–1850) was cold and dry, characterized by a more open vegetation community. There is evidence of forest disturbance that is marked by a rise in Ambrosia pollen in the 1700s, coinciding with the time of European settlement in North America. The presence of Ambrosia and Cheno/Am pollen throughout the record suggests that anthropogenic influence has been part of the fabric of the southern Louisiana landscapes throughout the 1200 years.

scholarly journals Three millennia of vegetation and environmental dynamics in the Lagunas de Mojanda region, northern Ecuador

2017 ◽  
Vol 57 (2) ◽  
pp. 407-421 ◽  
Author(s):  
Andrea Villota ◽  
Hermann Behling ◽  
Susana León-Yánez
Keyword(s):  
Vegetation Type ◽  
Montane Forest ◽  
Climatic Conditions ◽  
Climate Dynamics ◽  
Peat Bog ◽  
Pollen Record ◽  
Vegetation Composition ◽  
Human Occupation ◽  
Vegetation And Climate ◽  
Montane Rainforest

AbstractThe pollen record from Lagunas de Mojanda, located at 3748 m a.s.l. (northern Ecuadorian Andes) reflects the vegetation and climate dynamics for the last ca 3400 cal yr BP. Páramo vegetation has been the main vegetation type since the beginning of the record. At Lagunas de Mojanda, from the last ca 3400 to 2200 cal yr BP, grass páramo was well represented mainly by Poaceae (40%) and the occurrence ofValeriana(5%), while montane forest taxa were poorly represented and subpáramo taxa were rare. The vegetation composition suggests cool and humid conditions. Between ca 2200 and ca 1300 cal yr BP, montane rainforest and subpáramo taxa had a higher presence but páramo taxa remained the main vegetation type in the study area, suggesting cool climatic conditions. From ca 1300 to ca 500 cal yr BP, páramo vegetation remained stable, with higher presence ofPhlegmariurusandIsoetes, suggesting cool and humid conditions. The last ca 500 cal yr BP generally show lower frequency of montane rainforest and subpáramo taxa. Páramo vegetation reached the highest share, with the presence of Poaceae,PlantagoandRanunculussuggesting a trend of peat bog drying. Fires were present during the whole record, perhaps human-caused, but the study area does not show great disturbance except from ca 1300 to 500 cal yr BP, a period of an evident higher influx of charcoal particles coincidentally with nearby ancient human occupation.

Late glacial vegetation and climate oscillations on the southeastern Tibetan Plateau inferred from the Lake Naleng pollen profile

2010 ◽  
Vol 73 (2) ◽  
pp. 324-335 ◽  
Author(s):  
Annette Kramer ◽  
Ulrike Herzschuh ◽  
Steffen Mischke ◽  
Chengjun Zhang
Keyword(s):  
Tibetan Plateau ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Pollen Record ◽  
Tree Line ◽  
Climate Trends ◽  
Southeastern Tibetan Plateau ◽  
Alpine Steppe ◽  
Effective Moisture ◽  
Climatic Cooling

We present a late glacial pollen record (17,700 to 8500 cal yr BP) from a Lake Naleng sediment core. Lake Naleng is located on the southeastern Tibetan Plateau (31.10°N 99.75°E, 4200 m) along the upper tree-line. Variations in the summer monsoon are evident from shifts in vegetation that correspond to late glacial climate trends from other monsoon-sensitive regions. Alpine steppe was recorded between 17,700 and 14,800 cal yr BP, indicating low effective moisture at the study site. Expansion of alpine meadows followed by advances in the position of tree-line around Lake Naleng suggest that climate became warmer and wetter between ∼ 14,800 and 12,500 cal yr BP, probably representing an enhancement of the Asian monsoon. Climatic cooling and reduced effective moisture are inferred from multivariate analysis and the upward retreat of tree-line between ∼ 12,500 and 11,700 cal yr BP. The timing and nature of these shifts to warm, wet and then cold, dry climatic conditions suggest that they correspond to the Bølling/Allerød and Younger Dryas intervals. Abies-Betula forests, representing warm and moist conditions, spread during the early Holocene.

Palynologie et morphogenèse récente dans le bassin du Grizzly Creek (Territoire du Yukon)

1983 ◽  
Vol 20 (10) ◽  
pp. 1543-1553 ◽  
Author(s):  
J. C. Bourgeois ◽  
M.-A. Geurts
Keyword(s):  
Pollen Analysis ◽  
Volcanic Ash ◽  
Climatic Conditions ◽  
Yukon Territory ◽  
Pollen Record ◽  
Pollen Production ◽  
Present Climate ◽  
White River ◽  
Geomorphological Evolution ◽  
Great Accumulation

Pollen analysis of three sections from the Grizzly Creek basin, Yukon Territory was undertaken in order to reconstruct the paleoecology of the region over the last two millennia.Diagrams for two sites show three well defined pollen zones, whose boundaries are based on fluctuation of pollen spectra. The oldest zone corresponds to vegetation comparable to that of the present and a climate similar to or a little colder than the present climate. In zone 2, the strong decline of Picea is interpreted as a break in pollen production caused by a decrease in precipitation and a warming of the climate. The forest survived for several centuries in a state of degeneration, which favoured the development of a stratum of shrubs and herbaceous plants. Zone 3 reflects a return to vegetation and to climatic conditions similar to those of zone 1.The positions of two layers of volcanic ash, dated at approximately 1230 and 1890 years BP and corresponding to two lobes of White River Ash, indicate the rhythm of sedimentation. The presence of loess in the sediments helps explain the great accumulation of sediment before 1250 years BP and supports an increase in aridity during this period. The pollen record also suggests that the deposition of volcanic ash had an influence on the geomorphological evolution of the area.

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