Preliminary paleomagnetic results from PS97 cores from the Drake Passage for the past 110 ka

2020 ◽  
Author(s):  
Jiabo Liu ◽  
Norbert Nowaczyk ◽  
Xufeng Zheng ◽  
Qinsong Liu ◽  
Helge Arz
Keyword(s):  
Southern Ocean ◽  
Geomagnetic Field ◽  
Sediment Cores ◽  
Drake Passage ◽  
Mono Lake ◽  
The Past ◽  
Asymmetric Pattern ◽  
Relative Paleointensity ◽  
Globally Distributed ◽  
Northern And Southern Hemispheres

<p>Paleomagnetic records reconstructed from globally distributed marine sediments have greatly improved our understanding of long-term paleosecular variations and geomagnetic excursions. Nevertheless, questions regarding to the development of the geomagnetic field anomaly in the Southern Atlantic Ocean and the asymmetric geomagnetic field between Northern and Southern Hemispheres are not yet satisfactorily resolved. Paleomagnetic data, particularly from the Southern Hemisphere, is needed to better define the global geomagnetic field configurations spanning paleosecular variations and excursions. In this study, three sediment cores (PS97-085, PS97-84, PS97-079) recovered from the Drake Passage, Southern Ocean were subjected to detailed rock magnetic and paleomagnetic investigations. Preliminary age models were obtained by correlating their magnetic susceptibility to the ẟ<sup>18</sup>O master record from Dome C, Antarctica. In addition, rock magnetic records of the studied PS97 cores were further correlated to that of core PS67/197-1 with AMS <sup>14</sup>C age constraints. The results from PS97 cores are thus continuously covering the past about 110 ka. Rock magnetic results indicate titanomagnetite is the dominant magnetic carrier in the studied PS97 cores. Relative paleointensities (RPI) derived from these PS97 cores are comparable with the regional relative paleointensity records and the South Atlantic paleointensity stack (SAPIS). Additionally, anomalous inclinations at about 41 ka and 35 ka, observed in core PS97-085, are coeval with the Laschamps and the Mono Lake excursions, respectively. This study provides new paleomagnetic records from the Southern Ocean, though further age constrains are needed to consolidate the paleomagnetic interpretations. The up to now obtained paleomagnetic records, together with previous studies from the Southern Ocean, are aiming to clarify the asymmetric pattern of non-dipole geomagnetic field between Northern and Southern Hemispheres.</p>

scholarly journals Relative paleointensity of the geomagnetic field over the last 21,000 years BP from sediment cores, Lake El Trébol (Patagonia, Argentina)

2006 ◽  
Vol 58 (10) ◽  
pp. 1323-1332 ◽  
Author(s):  
C. S. G. Gogorza ◽  
M. A. Irurzun ◽  
M. A. E. Chaparro ◽  
J. M. Lirio ◽  
H. Nunez ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Sediment Cores ◽  
Relative Paleointensity

Relative paleointensity of the geomagnetic field during the past 0.8 Ma from Nihewan Basin, Hebei Province, China

2004 ◽  
Vol 49 (9) ◽  
pp. 948-952 ◽  
Author(s):  
Yong Wang ◽  
Zhenqing Chi ◽  
Tehquei Lee ◽  
Longrui Min ◽  
Huiyair Chu
Keyword(s):  
Geomagnetic Field ◽  
Hebei Province ◽  
The Past ◽  
Nihewan Basin ◽  
Relative Paleointensity

scholarly journals ORBITAL NOISE OF THE EARTH CAUSES INTENSITY FLUCTUATION IN THE GEOMAGNETIC FIELD

2003 ◽  
Vol 03 (01) ◽  
pp. L63-L72 ◽  
Author(s):  
H. S. LIU ◽  
R. KOLENKIEWLCZ ◽  
C. WADE
Keyword(s):  
Geomagnetic Field ◽  
Noise Spectrum ◽  
Outer Core ◽  
The Past ◽  
The Earth ◽  
Spectral Peaks ◽  
Relative Paleointensity ◽  
Intensity Fluctuations ◽  
Composite Curve ◽  
Insight Into

Orbital noise of Earth's obliquity can provide an insight into the core of the Earth that causes intensity fluctuations in the geomagnetie field. Here we show that noise spectrum of the obliquity frequency have revealed a series of frequency periods centered at 250-, 100-, 50-, 41-, 30-, and 26-kyr which are almost identical with the observed spectral peaks from the composite curve of 33 records of relative paleointensity spanning the past 800 kyr (Sint–800 data). A continuous record for the past two million years also reveals the presence of the major 100 kyr periodicity in obliquity noise and geomagnetic intensity fluctuations. These results of correlation suggest that obliquity noise may power the dynamo, located in the liquid outer core of the Earth, which generates the geomagnetic field.

scholarly journals High-resolution palaeomagnetic record from Sea of Marmara sediments for the last 70 ka

2020 ◽  
Vol 222 (3) ◽  
pp. 2024-2039
Author(s):  
Özlem Makaroğlu ◽  
Norbert R Nowaczyk ◽  
Kadir K Eriş ◽  
M Namık Çağatay
Keyword(s):  
High Resolution ◽  
Geomagnetic Field ◽  
Ice Core ◽  
Sediment Cores ◽  
Mono Lake ◽  
Sea Of Marmara ◽  
Sea Level Changes ◽  
Geochemical Analyses ◽  
Mineral Magnetic ◽  
High Resolution Reconstruction

SUMMARY Magnetostratigraphic and geochemical analyses were performed on two sediment cores recovered from the Sea of Marmara to investigate geomagnetic field variations over the last 70 ka. A chronology for each of the two cores was developed from eight AMS 14C datings, tephrochronology, and tuning of Ca concentrations with stadials and interstadials observed in Greenland ice core oxygen isotope data. Based on the age models, cores MD01–2430 and MRS-CS19 reach back to 70 and 32 ka, respectively. High average sedimentation rates of 43 cm kyr–1 for core MD01–2430 and 68 cm kyr–1 for core MRS-CS19 allow high-resolution reconstruction of geomagnetic field variations for the Sea of Marmara. Mineral magnetic properties are sensitive to glacioeustatic sea level changes and palaeoclimate variations in this region, reflecting the variable palaeoenvironmental conditions of the Sea of Marmara during last 70 ka. Despite the impairment of the palaeomagnetic record in some stratigraphic intervals due to early diagenesis, relative palaeointensity variations in the Sea of Marmara sediments correlate well with similar records derived from other regions, such as the nearby Black Sea and the GLOPIS-75 stack. The directional record derived from the Sea of Marmara cores exhibits typical palaeosecular variation patterns, with directional anomalies at 41 and 18 ka, representing the Laschamps and postulated Hilina Pali excursions, respectively. Both directional anomalies are also associated with palaeointensity minima. A further palaeointensity minimum at 34.5 ka is likely related to the Mono Lake excursion, with no directional deviation documented in the Sea of Marmara palaeomagnetic record so far.

scholarly journals Calcification and latitudinal distribution of extant coccolithophores across the Drake Passage during late austral summer 2016

2019 ◽  
Vol 16 (19) ◽  
pp. 3679-3702 ◽  
Author(s):  
Mariem Saavedra-Pellitero ◽  
Karl-Heinz Baumann ◽  
Miguel Ángel Fuertes ◽  
Hartmut Schulz ◽  
Yann Marcon ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Austral Summer ◽  
Drake Passage ◽  
Type A ◽  
Polar Front ◽  
Total Alkalinity ◽  
Major Influence ◽  
Limiting Factor ◽  
Assemblage Composition ◽  
Globally Distributed

Abstract. Coccolithophores are globally distributed microscopic marine algae that exert a major influence on the global carbon cycle through calcification and primary productivity. There is recent interest in coccolithophore polar communities; however field observations regarding their biogeographic distribution are scarce for the Southern Ocean (SO). This study documents the latitudinal, as well as in depth, variability in the coccolithophore assemblage composition and the coccolith mass variation in the ecologically dominant Emiliania huxleyi across the Drake Passage. Ninety-six water samples were taken between 10 and 150 m water depth from 18 stations during POLARSTERN Expedition PS97 (February–April 2016). A minimum of 200 coccospheres per sample were identified in the scanning electron microscope, and coccolith mass was estimated with light microscopy. We find that coccolithophore abundance, diversity and maximum depth habitat decrease southwards, marking different oceanographic fronts as ecological boundaries. We characterize three zones: (1) the Chilean margin, where E. huxleyi type A (normal and overcalcified) and type R are present; (2) the Subantarctic Zone (SAZ), where E. huxleyi reaches maximum values of 212.5×103 cells L−1 and types B/C, C and O are dominant; and (3) the Polar Front Zone (PFZ), where E. huxleyi types B/C and C dominate. We link the decreasing trend in E. huxleyi coccolith mass to the poleward latitudinal succession from the type A to the type B group. Remarkably, we find that coccolith mass is strongly anticorrelated to total alkalinity, total CO2, the bicarbonate ion and pH. We speculate that low temperatures are a greater limiting factor than carbonate chemistry in the Southern Ocean. However, further in situ oceanographic data are needed to verify the proposed relationships. We hypothesize that assemblage composition and calcification modes of E. huxleyi in the Drake Passage will be strongly influenced by the ongoing climate change.

Shannon Information of the geomagnetic field during the excursions

2021 ◽  
Author(s):  
Saioa A. Campuzano ◽  
Angelo De Santis ◽  
Martina Orlando ◽  
F. Javier Pavón-Carrasco ◽  
Alberto Molina-Cardín
Keyword(s):  
Information Content ◽  
Spherical Harmonic ◽  
Geomagnetic Field ◽  
Scalar Potential ◽  
Mono Lake ◽  
Shannon Information ◽  
Statistical Measure ◽  
The Past ◽  
Maximum Value ◽  
Smoothing Effects

<p>The Shannon Information or Information Content is a statistical measure of a system characterising its properties of organisation (maximum value) or disorder (minimum value). Once it is introduced the scalar potential of the geomagnetic field in terms of a spherical harmonic expansion, it is straightforward to define the Shannon Information by an expression including the Gauss coefficients [De Santis et al., EPSL, 2004]. Some recent models of the past geomagnetic field, including also the two most recent excursions, i.e. Laschamp (~41 ka) and Mono Lake (~34 ka) events, allow us to calculate the Shannon Information in the periods of those events and compare each other. It is expected that when approaching to excursions, the Shannon Information decreases, i.e. the disorder of the system increases. From the behaviour in time of the Shannon Information calculated from the Gauss coefficients of three geomagnetic field reconstructions that span the last excursions, i.e. IMOLE, GGF100k and LSMOD2, it is observed a decrease of the Shannon Information that seems to anticipate the occurrence of the impending excursions some time in advance. This result must be taken with caution because the reconstructions used are based on sedimentary data, which could present some smoothing effects related to the acquisition of the magnetisation mechanism.</p>

scholarly journals Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400 ka

2021 ◽  
Author(s):  
María H. Toyos ◽  
Gisela Winckler ◽  
Helge W. Arz ◽  
Lester Lembke-Jene ◽  
Carina B. Lange ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Drake Passage ◽  
Accumulation Rates ◽  
Export Production ◽  
The Core ◽  
The Past ◽  
Iron Fertilization ◽  
The Pacific ◽  
Mass Accumulation Rates ◽  
Mass Accumulation

Abstract. Changes in Southern Ocean export production have broad biogeochemical and climatic implications. Specifically, iron fertilization likely increased subantarctic nutrient utilization and enhanced the efficiency of the biological pump during glacials. However, past export production in the subantarctic Southeast Pacific is poorly documented, and its connection to Fe fertilization, potentially related to Patagonian Ice Sheet dynamics is unknown. We report on biological productivity changes over the past 400 ka, based on a combination of 230Thxs-normalized and stratigraphy-based mass accumulation rates of biogenic barium, organic carbon, biogenic opal, and calcium carbonate as indicators of paleo-export production in a sediment core upstream of the Drake Passage. In addition, we use fluxes of iron and lithogenic material as proxies for terrigenous matter, and thus potential micronutrient supply. Stratigraphy-based mass accumulation rates are strongly influenced by bottom-current dynamics, which result in variable sediment focussing or winnowing at our site. Carbonate is virtually absent in the core, except during peak interglacial intervals of the Holocene, and Marine Isotope Stages (MIS) 5 and 11, likely caused by transient decreases in carbonate dissolution. All other proxies suggest that export production increased during most glacial periods, coinciding with high iron fluxes. Such augmented glacial iron fluxes at the core site were most likely derived from glaciogenic input from the Patagonian Ice Sheet promoting the growth of phytoplankton. Additionally, glacial export production peaks are also consistent with northward shifts of the Subantarctic and Polar Fronts, which positioned our site south of the Subantarctic Front and closer to silicic acid-rich waters of the Polar Frontal Zone, as well as a with a decrease in the diatom utilization of Si relative to nitrate under Fe-replete conditions. However, glacial export production near the Drake Passage was lower than in the Atlantic and Indian sectors of the Southern Ocean, which may relate to complete consumption of silicic acid in the study area. Our results underline the importance of micro-nutrient fertilization through lateral terrigenous input from South America rather than aeolian transport, and exemplify the role of frontal shifts and nutrient limitation for past productivity changes in the Pacific entrance to the Drake Passage.

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