scholarly journals A record of ozone variability in South Pole Antarctic snow: Role of nitrate oxygen isotopes

2007 ◽  
Vol 112 (D12) ◽  
Author(s):  
Justin R. McCabe ◽  
Mark H. Thiemens ◽  
Joel Savarino
Keyword(s):  
Oxygen Isotopes ◽  
South Pole ◽  
Antarctic Snow

scholarly journals Nitrate Fluctuations in Antarctic Snow and Firn: Potential Sources and Mechanisms of Formation

1982 ◽  
Vol 3 ◽  
pp. 243-248 ◽  
Author(s):  
Bruce C. Parker ◽  
Edward J. Zeller ◽  
Anthony J. Gow
Keyword(s):  
Solar Activity ◽  
Upper Atmosphere ◽  
South Pole ◽  
Ion Concentrations ◽  
Potential Sources ◽  
Long Term Changes ◽  
Antarctic Snow ◽  
Mechanisms Of Formation

We summarize here data on in situ nitrate ion concentrations in snow pits and firn cores over the last ∼3 250 a. Nitrate fluctuations show seasonal, 11 and 22 a periodicities, and long-term changes both at South Pole station and Vostok. High nitrate levels conform to winter darkness and solar activity peaks. Long-term lows and highs conform to solar activity minima and maxima. The data available support the hypothesis that nitrate is fixed in the upper atmosphere by some solar-mediated phenomenon causing a periodicity in East Antarctica snow. Background levels and non-periodic spikes in nitrate come from other sources.

scholarly journals Spatial Distribution of Microparticles Within Antarctic Snow-Fall

1982 ◽  
Vol 3 ◽  
pp. 300-306 ◽  
Author(s):  
Lonnie G. Thompson ◽  
Ellen Mosley Thompson
Keyword(s):  
Size Distribution ◽  
Snow Accumulation ◽  
Distribution Data ◽  
South Pole ◽  
The South ◽  
Near Surface ◽  
Ross Ice Shelf ◽  
Particle Accumulation ◽  
Base Camp ◽  
Antarctic Snow

The concentration and size distribution of water insoluble microparticles were measured in 2 332 snow and firn samples from (a) two sites on the Antarctic Peninsula, (b) the Byrd station strain network, West Antarctica, (c) the Q-13 and base camp sites on the Ross Ice Shelf, and (d) the South Pole and Dome C sites in East Antarctica. These near-surface microparticle studies indicate that, while the number of particles per unit volume of sample remains fairly uniform from site to site, the annual particle accumulation is greatest at locations nearest the coast and decreases rapidly with distance inland. The relationship between particle accumulation and distance from the coast is analogous to a relationship between snow accumulation and distance from the coast. Ten times more particles are deposited annually at stations within 50 km of the coast than at the South Pole and Dome C sites. The size distribution data reveal that, with the possible exception of the Q-13 site, the particulates deposited in Antarctica are well-sorted, indicating little contribution from local sources.

scholarly journals Cumulated insolation: a simple explanation of Milankovitch's forcing on climate changes

2013 ◽  
Vol 9 (5) ◽  
pp. 5553-5568 ◽  
Author(s):  
F. Marra
Keyword(s):  
Northern Hemisphere ◽  
Oxygen Isotopes ◽  
Climate Changes ◽  
Ice Sheets ◽  
Simple Explanation ◽  
Glacial Cycle ◽  
Conditioning Factor ◽  
Summer Insolation ◽  
Satisfactory Answer

Abstract. The occurrence of the sudden melting of the ice sheets during the glacial terminations is explained in this paper as the consequence of the combined role of the minima and the maxima of mean summer insolation on the Northern Hemisphere, providing a new contribution to understand the mechanisms ruling glacial forcing. Indeed, no satisfactory answer has been provided so far to the question why one specific maximum, after a series of consecutive maxima of insolation, has the potentiality to trigger a deglaciation. The explanation proposed in this paper accounts for a pre-conditioning factor, represented by "mild" (warmer) minimum, followed by a sufficiently warm maximum as the conditions that cause the end of a glacial cycle. These conditions are realized whenever the sum of the values of each consecutive minima and maxima ("cumulated insolation") on the curve of mean summer insolation at 65° N exceeds 742 Watt m−2. The comparison of the succession of these cumulated insolation values with the astronomically tuned Oxygen isotopes record provides a satisfactory match with the occurrence of all the glacial terminations in the last 800 ka.

Introduzione. Scienza, esplorazione ed eroismo: Robert Falcon Scott al Polo Sud

2012 ◽  
pp. 5-15
Author(s):  
Nicoletta Brazzelli
Keyword(s):  
Twentieth Century ◽  
Scientific Research ◽  
South Pole ◽  
The South ◽  
Scientific Exploration ◽  
Antarctic Expedition ◽  
Polar Research Institute ◽  
Return Journey ◽  
The Antarctic

The centenary of Scott’s arrival at the South Pole in 1912 and of his tragic death during the return journey has been celebrated through exhibitions and conferences, while a general reassessment of Scott’s figure has been provided by several scholars. In particular, the scientific role of the 1910-12 British Antarctic expedition is now emphasized: Scott’s aim was not only to reach the Pole but especially to collect data and geological specimens of a completely unknown continent. This introduction focuses on the scientific dimension of Scott’s enterprise, giving special attention to the role of photography, employed during the expedition as a tool of scientific exploration, and to the crucial impact of photographs on the modern perception of the Antarctic. Another important point concerns the Scott Polar Research Institute (Cambridge, UK), founded in 1920 to commemorate Scott, that laid the foundations of Polar studies and pioneered scientific research throughout the twentieth century.

The role of contamination in the tightrope of Gran Canaria felsic magma differentiation

2020 ◽  
Author(s):  
Edgar Alejandro Cortes Calderon ◽  
Ben Ellis ◽  
Julia Neukampf ◽  
Chris Harris ◽  
Darren Mark ◽  
...  
Keyword(s):  
Oxygen Isotopes ◽  
Major And Trace Elements ◽  
Crustal Assimilation ◽  
Gran Canaria ◽  
Liquid Line ◽  
Ar Geochronology ◽  
Liquid Line Of Descent ◽  
Differentiation Trend ◽  
Alkali Feldspars

<p>Peralkaline magmatism is mostly sustained by extensive feldspar fractionation from mafic parents at shallow depths in intraplate settings. In this case, silica saturation is critical as it controls the differentiation trend that a peralkaline magma follows. SiO<sub>2</sub>-oversaturated parents fractionate towards rhyolites, and SiO<sub>2</sub>-undersaturated towards phonolitic compositions. The Miocene post-shield stage of Gran Canaria records both differentiation trends, which has previously been ascribed to changes in the mantle source. Such stage has been divided in the Mogan and Fataga Group based on silica saturation. Here, we propose that contamination plays a key role in the differentiation of Gran Canaria volcanics. This assumption is supported with new <sup>40</sup>Ar/<sup>39</sup>Ar geochronology, mineral, glass and juvenile clast chemistry (oxygen isotopes, major and trace elements) merged with a detailed stratigraphy. Two types of contaminants were identified, one being cogenetic feldspar-dominated cumulates and the second one being sediments within the island crust. We propose that barium-rich trachytic magmas with positive europium anomalies are linked to melting of the feldspar cumulates left after extensive fractional crystallisation. The chemistry of such trachytes does not follow a liquid line of descent and contains reverse-zoned alkali-feldspars. The shift in silica saturation took less than 1 Ma and is marked by an increase in peralkalinity from 0.9 to 1.5 and a decrease in oxygen isotopes ratio from 7.0 to 5.0 ‰. We interpret these observations as the consequence of maturation of the shallow magma reservoir towards less sediment contamination. Such assimilation of sediments is limited thermally, and compositionally because the system should remain alumina deficient. Crustal assimilation in Gran Canaria did not produce voluminous silicic melts by itself but allowed the deviation of the differentiation trend of a more primitive, initially SiO<sub>2</sub>-undersaturated magma. The tightrope of differentiation is represented by the thermal divide between the granite and phonolite minima (i.e. feldspar join in petrogeny’s residua system). Contamination by sediments produces a transient SiO<sub>2</sub>-oversaturated system (Mogan Group). Cogenetic assimilation of cumulates by thermal rejuvenation of the reservoir attracts the magma towards the thermal divide (ubiquitous during the peralkaline stage). Armouring against sediment assimilation through time relaxes the system back to the initial SiO<sub>2</sub>-undersaturated conditions (Fataga Group).</p>

scholarly journals Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

2011 ◽  
Vol 287 (1-2) ◽  
pp. 54-65 ◽  
Author(s):  
V.D. Wanless ◽  
M.R. Perfit ◽  
W.I. Ridley ◽  
P.J. Wallace ◽  
C.B. Grimes ◽  
...  
Keyword(s):  
Oxygen Isotopes ◽  
Ocean Ridges ◽  
Spreading Centers

Oxygen Isotopes Unravel the Role of Microorganisms in Phosphate Cycling in Soils

2012 ◽  
Vol 46 (11) ◽  
pp. 5956-5962 ◽  
Author(s):  
Federica Tamburini ◽  
Verena Pfahler ◽  
Else K. Bünemann ◽  
Kathi Guelland ◽  
Stefano M. Bernasconi ◽  
...  
Keyword(s):  
Oxygen Isotopes
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