scholarly journals Quantifying sea surface temperature ranges of the Arabian Sea for the past 20 000 years

2011 ◽  
Vol 7 (4) ◽  
pp. 1337-1349 ◽  
Author(s):  
G. M. Ganssen ◽  
F. J. C. Peeters ◽  
B. Metcalfe ◽  
P. Anand ◽  
S. J. A. Jung ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Isotope Composition ◽  
Planktonic Foraminifera ◽  
Sediment Cores ◽  
Maximum Temperature ◽  
Physical Parameters ◽  
Seasonal Temperature ◽  
Mean Values ◽  
The Past ◽  
Temperature Ranges

Abstract. The oxygen isotopic composition of planktonic foraminifera tests is one of the widest used geochemical tools to reconstruct past changes of physical parameters of the upper ocean. It is common practice to analyze multiple individuals from a mono-specific population and assume that the outcome reflects a mean value of the environmental conditions during calcification of the analyzed individuals. Here we present the oxygen isotope composition of individual specimens of the surface-dwelling species Globigerinoides ruber and Globigerina bulloides from sediment cores in the Western Arabian Sea off Somalia, inferred as indicators of past seasonal ranges in temperature. Combining the δ18O measurements of individual specimens to obtain temperature ranges with Mg/Ca based mean calcification temperatures allows us to reconstruct temperature extrema. Our results indicate that over the past 20 kyr the seasonal temperature range has fluctuated from its present value of 16 °C to mean values of 13 °C and 11 °C for the Holocene and LGM, respectively. The data for the LGM suggest that the maximum temperature was lower, whilst minimum temperature remained approximately constant. The rather minor variability in lowest summer temperatures during the LGM suggests roughly constant summer monsoon intensity, while upwelling-induced productivity was lowered.

scholarly journals Quantifying sea surface temperature ranges of the Arabian Sea for the past 20 000 years

2010 ◽  
Vol 6 (6) ◽  
pp. 2795-2814 ◽  
Author(s):  
G. Ganssen ◽  
F. Peeters ◽  
B. Metcalfe ◽  
P. Anand ◽  
S. Jung ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Isotope Composition ◽  
Planktonic Foraminifera ◽  
Sediment Cores ◽  
Oxygen Isotopic Composition ◽  
Maximum Temperature ◽  
Physical Parameters ◽  
Seasonal Temperature ◽  
The Past ◽  
Temperature Ranges

Abstract. The oxygen isotopic composition of planktonic foraminifera tests is one of the widest used geochemical tools to reconstruct past changes of physical parameters of the upper ocean. It is common practice to analyze multiple individuals from a mono-specific population and assume that the outcome reflects a mean value of the environmental conditions during calcification of the analyzed individuals. Here we present the oxygen isotope composition of individual specimens of the surface dwelling species Globigerinoides ruber and Globigerina bulloides from sediment cores in the Western Arabian Sea off Somalia inferred as indicators of past seasonal ranges in temperature. Combining the δ18O measurements of individual specimens to obtain temperature ranges with Mg/Ca based mean calcification temperatures allows us to reconstruct temperature extrema. Our results indicate that over the past 20 kyrs the seasonal temperature range has fluctuated from its present value of 16 °C (14 to 30 °C), to 11 °C (15 to 26 °C) during the LGM. The range during the LGM suggests that the maximum temperature was lower, whilst minimum temperature remained approximately constant.

scholarly journals A hundred new eclipsing binary system candidates studied in a near-infrared window in the VVV survey

2020 ◽  
Vol 37 ◽  
Author(s):  
L. V. Gramajo ◽  
T. Palma ◽  
D. Minniti ◽  
R. K. Saito ◽  
J. J. Clariá ◽  
...  
Keyword(s):  
Near Infrared ◽  
Galactic Disk ◽  
Extensive Study ◽  
Eclipsing Binaries ◽  
Physical Parameters ◽  
Eclipsing Binary ◽  
Mean Values ◽  
Median Period ◽  
First Results ◽  
Contact Binaries

Abstract We present the first results obtained from an extensive study of eclipsing binary (EB) system candidates recently detected in the VISTA Variables in the Vía Láctea (VVV) near-infrared (NIR) Survey. We analyse the VVV tile d040 in the southern part of the Galactic disc wherein the interstellar reddening is comparatively low, which makes it possible to detect hundreds of new EB candidates. We present here the light curves and the determination of the geometric and physical parameters of the best candidates found in this ‘NIR window’, including 37 contact, 50 detached, and 13 semi-detached EB systems. We infer that the studied systems have an average of the $K_s$ amplitudes of $0.8$ mag and a median period of 1.22 days where, in general, contact binaries have shorter periods. Using the ‘Physics Of Eclipsing Binaries’ (PHOEBE) interactive interface, which is based on the Wilson and Devinney code, we find that the studied systems have low eccentricities. The studied EBs present mean values of about 5 700 and 4 900 K for the $T_1$ and $T_2$ components, respectively. The mean mass ratio (q) for the contact EB stars is $\sim$ 0.44. This new galactic disk sample is a first look at the massive study of NIR EB systems.

scholarly journals Disruption of the Atlantic Meridional Circulation during Deglacial Climates Inferred from Planktonic Foraminiferal Shell Weights

2021 ◽  
Vol 9 (5) ◽  
pp. 519
Author(s):  
Stergios D. Zarkogiannis
Keyword(s):  
Atlantic Ocean ◽  
Meridional Circulation ◽  
Order Approximation ◽  
Planktonic Foraminifera ◽  
Sediment Cores ◽  
Meridional Overturning Circulation ◽  
Density Structure ◽  
Last Interglacial ◽  
Shell Weight ◽  
The North

Changes in the density structure of the upper oceanic water masses are an important forcing of changes in the Atlantic Meridional Overturning Circulation (AMOC), which is believed to widely affect Earth’s climate. However, very little is known about past changes in the density structure of the Atlantic Ocean, despite being extensively studied. The physical controls on planktonic foraminifera calcification are explored here, to obtain a first-order approximation of the horizontal density gradient in the eastern Atlantic during the last 200,000 years. Published records of Globigerina bulloides shells from the North and Tropical eastern Atlantic were complemented by the analysis of a South Atlantic core. The masses of the same species shells from three different dissolution assessed sediment cores along the eastern Atlantic Ocean were converted to seawater density values using a calibration equation. Foraminifera, as planktonic organisms, are subject to the physical properties of the seawater and thus their shells are sensitive to buoyancy forcing through surface temperature and salinity perturbations. By using planktonic foraminifera shell weight as an upper ocean density proxy, two intervals of convergence of the shell masses are identified during cold intervals of the last two deglaciations that may be interpreted as weak ocean density gradients, indicating nearly or completely eliminated meridional circulation, while interhemispheric Atlantic density differences appear to alleviate with the onset of the last interglacial. The results confirm the significance of variations in the density of Atlantic surface waters for meridional circulation changes.

scholarly journals Absolute seasonal temperature estimates from clumped isotopes in bivalve shells suggest warm and variable greenhouse climate

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Niels J. de Winter ◽  
Inigo A. Müller ◽  
Ilja J. Kocken ◽  
Nicolas Thibault ◽  
Clemens V. Ullmann ◽  
...  
Keyword(s):  
Seasonal Variability ◽  
Sea Water ◽  
Isotope Composition ◽  
Sea Surface ◽  
Mean Annual Temperature ◽  
Seasonal Temperature ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Temperature Reconstructions ◽  
Bivalve Shells

AbstractSeasonal variability in sea surface temperatures plays a fundamental role in climate dynamics and species distribution. Seasonal bias can also severely compromise the accuracy of mean annual temperature reconstructions. It is therefore essential to better understand seasonal variability in climates of the past. Many reconstructions of climate in deep time neglect this issue and rely on controversial assumptions, such as estimates of sea water oxygen isotope composition. Here we present absolute seasonal temperature reconstructions based on clumped isotope measurements in bivalve shells which, critically, do not rely on these assumptions. We reconstruct highly precise monthly sea surface temperatures at around 50 °N latitude from individual oyster and rudist shells of the Campanian greenhouse period about 78 million years ago, when the seasonal range at 50 °N comprised 15 to 27 °C. In agreement with fully coupled climate model simulations, we find that greenhouse climates outside the tropics were warmer and more seasonal than previously thought. We conclude that seasonal bias and assumptions about seawater composition can distort temperature reconstructions and our understanding of past greenhouse climates.

scholarly journals Change in mean and extreme temperature at Yingkou station in Northeast China from 1904 to 2017

2021 ◽  
Vol 164 (3-4) ◽  
Author(s):  
Xiaoying Xue ◽  
Guoyu Ren ◽  
Xiubao Sun ◽  
Panfeng Zhang ◽  
Yuyu Ren ◽  
...  
Keyword(s):  
Northeast China ◽  
Extreme Temperature ◽  
Maximum Temperature ◽  
Data Set ◽  
The Past ◽  
Significant Downward Trend ◽  
Cold Events ◽  
Temperature Indices ◽  
Increasing Trends ◽  
Change In Mean

AbstractThe understanding of centennial trends of extreme temperature has been impeded due to the lack of early-year observations. In this paper, we collect and digitize the daily temperature data set of Northeast China Yingkou meteorological station since 1904. After quality control and homogenization, we analyze the changes of mean and extreme temperature in the past 114 years. The results show that mean temperature (Tmean), maximum temperature (Tmax), and minimum temperature (Tmin) all have increasing trends during 1904–2017. The increase of Tmin is the most obvious with the rate of 0.34 °C/decade. The most significant warming occurs in spring and winter with the rate of Tmean reaching 0.32 °C/decade and 0.31 °C/decade, respectively. Most of the extreme temperature indices as defined using absolute and relative thresholds of Tmax and Tmin also show significant changes, with cold events witnessing a more significant downward trend. The change is similar to that reported for global land and China for the past six decades. It is also found that the extreme highest temperature (1958) and lowest temperature (1920) records all occurred in the first half of the whole period, and the change of extreme temperature indices before 1950 is different from that of the recent decades, in particular for diurnal temperature range (DTR), which shows an opposite trend in the two time periods.

scholarly journals Chemical and stable isotope composition of surface and groundwater in the surroundings of the Los Humeros Caldera, Puebla, Mexico

2019 ◽  
Vol 98 ◽  
pp. 07013
Author(s):  
Thomas Kretzschmar ◽  
Matteo Lelli ◽  
Ruth Alfaro ◽  
Juan Ignacio Sanchez ◽  
Yann Rene Ramos
Keyword(s):  
Stable Isotope ◽  
Isotope Composition ◽  
Regression Line ◽  
Sustainable Use ◽  
Geothermal Reservoir ◽  
Maximum Temperature ◽  
Stable Isotope Composition ◽  
Local Fracture ◽  
Hydrogeological Model ◽  
Fracture Systems

It is important to develop a regional hydrogeological model to identify possible recharge and discharge areas for a sustainable use of a geothermal reservoir. The Los Humeros geothermal area is situated within five surficial watersheds and coveres an area of more than 15.000 km2. A total of 208 well and spring samples were collected between June 2017 and November 2018. The stable isotope data for this region define a regression line of δDH2O = 8.032·δ18O + 12 and indicate that groundwater is recharged by regional precipitation. At least 39 groundwater wells, with a maximum temperature of 35 °C, show temperatures above the reported mean average surface temperature of 15 °C. Characteristic elements for geothermal reservoir fluids (B, Li, As) are also present in these groundwaters, indicating a possible connection between the reservoir fluid and the local groundwater through local fracture systems. Concentration of B in these hot wells is between 150 and 35000 ppb.

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