scholarly journals Paleomagnetic secular variation for a 21,000-year sediment sequence from Cascade Lake, north-central Brooks Range, Arctic Alaska

2021 ◽  
Author(s):  
Douglas P. Steen ◽  
Joseph S. Stoner ◽  
Jason P. Briner ◽  
Darrell S. Kaufman
Keyword(s):  
Secular Variation ◽  
Remanent Magnetization ◽  
Sediment Cores ◽  
Natural Remanent Magnetization ◽  
Companion Paper ◽  
Angular Deviation ◽  
Arctic Alaska ◽  
Geomagnetic Field Models ◽  
Paleomagnetic Secular Variation ◽  
Radiometric Ages

Abstract. Two > 5-m-long sediment cores from Cascade Lake (68.38° N, 154.60° W), Arctic Alaska, were analyzed to quantify their paleomagnetic properties over the past 21,000 years. Alternating-field demagnetization of the natural remanent magnetization, anhysteretic remanent magnetization, isothermal remanent magnetization, and hysteresis experiments reveal a strong, well-defined characteristic remanent magnetization carried by a low coercivity magnetic component that increases up core. Maximum angular deviation values average < 2°, and average inclination values are within 4° of the geocentric axial dipole prediction. Radiometric ages based on 210Pb and 14C were used to correlate the major inclination features of the resulting paleomagnetic secular variation (PSV) record with those of other regional PSV records, including two geomagnetic field models and the longer series from Burial Lake, located 200 km to the west. Following around 6 ka (cal BP), the ages of PSV fluctuations in Cascade Lake begin to diverge from those of the regional records, reaching a maximum offset of about 2000 years at around 4 ka. Several correlated cryptotephra ages from this section (reported in a companion paper by Davies et al., this volume) support the regional PSV-based chronology and indicate that some of the 14C ages at Cascade Lake are variably too old.

Near East Paleomagnetic Secular Variation Recorded in Sediments from the Sea of Galilee (Lake Kinneret)

1985 ◽  
Vol 23 (2) ◽  
pp. 175-188 ◽  
Author(s):  
R. Thompson ◽  
G. M. Turner ◽  
M. Stiller ◽  
A. Kaufman
Keyword(s):  
Magnetic Susceptibility ◽  
Secular Variation ◽  
Similar Pattern ◽  
Remanent Magnetization ◽  
Sediment Cores ◽  
Natural Remanent Magnetization ◽  
Lake Kinneret ◽  
Carbonate Content ◽  
Magnetization Intensity ◽  
Olive Pollen

Paleomagnetic records of declination and inclination from sediments recovered from the bed of Lake Kinneret (32.4°N, 35.7°E) have been dated by radiocarbon techniques. The sediments span the last 5000 yr. The changes in inclination down the sediment cores are more pronounced than the declination fluctuations and are repeatable between the three coring sites, which are several kilometers apart. Magnetic susceptibility logs display 13 maxima in the 5-m-long sequences, with a pronounced susceptibility minimum about 1000 yr B.P. Many of the susceptibility maxima and minima can be easily correlated between coring sites and are shown to be dominantly related to changes in sediment carbonate content. The natural remanent magnetization intensity follows a similar pattern to that of susceptibility, and the natural remanence of the Kinneret sediments is presumed to reside in detrital magnetite grains carried into the lake by the river Jordan from the basalt-rich bedrock of the rift floor and the Golan Heights. The 14C chronology is strongly supported by a pollen study in which pronounced changes in the proportion of olive pollen were interpreted as being due to extensive cultivation of olives around Galilee in the Hellenistic and Byzantine periods. The Kinneret paleosecular variation records, if accurately dated, point to a complex spatial pattern of Holocene secular variation with significant variations over distances as small as 1000–2000 km.

The natural remanent magnetization of sediment cores from the Beaufort Sea

1977 ◽  
Vol 14 (9) ◽  
pp. 2007-2012 ◽  
Author(s):  
G. Vilks ◽  
J. M. Hall ◽  
David J. W. Piper
Keyword(s):  
Remanent Magnetization ◽  
Sediment Cores ◽  
Beaufort Sea ◽  
Natural Remanent Magnetization ◽  
Reasonable Assumption ◽  
High Deposition Rate ◽  
Areal Extent ◽  
Fine Silt ◽  
Geomagnetic Excursion ◽  
Dating Method

Two sediment cores collected from the continental slope of the southeastern Beaufort Sea show zones of stable shallow geomagnetic inclination at close to 0° in contrast with the dipole value of 80°. Although the cores were taken 60 km apart, the shallow inclination sections are sufficiently similar in form to be useful as potential correlation horizons, on the reasonable assumption that the same geomagnetic excursion is recorded in both cores.The cores consist of silt and clay, showing fine silt–clay laminae or structureless mud on X-radiographs. Except for the surface 2.5 m of core 810, foraminifera are sparse everywhere.The 14C dates for total organic carbon place the recorded paleomagnetic event at between 10 000 and 40 000 years BP. According to paleontologic evidence, the event took place between 6 000 and 16 000 years BP. The later dating method is considered to be more reliable. Sediment cores from other high deposition rate areas need to be examined paleomagnetically to determine the areal extent of this Beaufort Sea geomagnetic excursion.

scholarly journals Predictions of the geomagnetic secular variation based on the ensemble sequential assimilation of geomagnetic field models by dynamo simulations

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Sabrina Sanchez ◽  
Johannes Wicht ◽  
Julien Bärenzung
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Geomagnetic Field ◽  
Wave Number ◽  
Main Magnetic Field ◽  
Candidate Model ◽  
Uncertainty Estimates ◽  
Geomagnetic Field Models ◽  
Dipole Configuration

Abstract The IGRF offers an important incentive for testing algorithms predicting the Earth’s magnetic field changes, known as secular variation (SV), in a 5-year range. Here, we present a SV candidate model for the 13th IGRF that stems from a sequential ensemble data assimilation approach (EnKF). The ensemble consists of a number of parallel-running 3D-dynamo simulations. The assimilated data are geomagnetic field snapshots covering the years 1840 to 2000 from the COV-OBS.x1 model and for 2001 to 2020 from the Kalmag model. A spectral covariance localization method, considering the couplings between spherical harmonics of the same equatorial symmetry and same azimuthal wave number, allows decreasing the ensemble size to about a 100 while maintaining the stability of the assimilation. The quality of 5-year predictions is tested for the past two decades. These tests show that the assimilation scheme is able to reconstruct the overall SV evolution. They also suggest that a better 5-year forecast is obtained keeping the SV constant compared to the dynamically evolving SV. However, the quality of the dynamical forecast steadily improves over the full assimilation window (180 years). We therefore propose the instantaneous SV estimate for 2020 from our assimilation as a candidate model for the IGRF-13. The ensemble approach provides uncertainty estimates, which closely match the residual differences with respect to the IGRF-13. Longer term predictions for the evolution of the main magnetic field features over a 50-year range are also presented. We observe the further decrease of the axial dipole at a mean rate of 8 nT/year as well as a deepening and broadening of the South Atlantic Anomaly. The magnetic dip poles are seen to approach an eccentric dipole configuration.

scholarly journals Paleomagnetic secular variation at the Azores during the last 3 ka

2012 ◽  
Vol 117 (B7) ◽  
pp. n/a-n/a ◽  
Author(s):  
Anita Di Chiara ◽  
Fabio Speranza ◽  
Massimiliano Porreca
Keyword(s):  
Secular Variation ◽  
Paleomagnetic Secular Variation

Natural remanent magnetization studies of a layered Breccia Boulder from the lunar highland region

The Moon ◽  
1975 ◽  
Vol 14 (3-4) ◽  
pp. 473-481 ◽  
Author(s):  
S. K. Banerjee ◽  
G. Swits
Keyword(s):  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Highland Region

A full-vector paleomagnetic secular variation record from 55,000 to 33,000 cal. years BP from Río Valdéz glaciolacustrine outcrop (Tierra Del Fuego, Argentina)

2021 ◽  
pp. 106768
Author(s):  
Pedro Palermo ◽  
Claudia Gogorza ◽  
María J. Orgeira ◽  
María De Bernardi ◽  
María A. Irurzun ◽  
...  
Keyword(s):  
Secular Variation ◽  
Tierra Del Fuego ◽  
Paleomagnetic Secular Variation ◽  
Full Vector

Contributions of Cretaceous Quiet Zone natural remanent magnetization to Magsat anomalies in the Southwest Indian Ocean

1994 ◽  
Vol 99 (B6) ◽  
pp. 11923-11936 ◽  
Author(s):  
Lawrence G. Fullerton ◽  
Herbert V. Frey ◽  
James H. Roark ◽  
Herman H. Thomas
Keyword(s):  
Indian Ocean ◽  
Remanent Magnetization ◽  
Natural Remanent Magnetization ◽  
Southwest Indian Ocean

scholarly journals An Arctic watershed observatory at Lake Peters, Alaska: weather–glacier–river–lake system data for 2015–2018

2019 ◽  
Vol 11 (4) ◽  
pp. 1957-1970 ◽  
Author(s):  
Ellie Broadman ◽  
Lorna L. Thurston ◽  
Erik Schiefer ◽  
Nicholas P. McKay ◽  
David Fortin ◽  
...  
Keyword(s):  
Data Center ◽  
National Science Foundation ◽  
Thermal Structure ◽  
Sediment Cores ◽  
Pressure Sensors ◽  
Sediment Traps ◽  
Lake System ◽  
Arctic Alaska ◽  
Monitoring Effort ◽  
System Data

Abstract. Datasets from a 4-year monitoring effort at Lake Peters, a glacier-fed lake in Arctic Alaska, are described and presented with accompanying methods, biases, and corrections. Three meteorological stations documented air temperature, relative humidity, and rainfall at different elevations in the Lake Peters watershed. Data from ablation stake stations on Chamberlin Glacier were used to quantify glacial melt, and measurements from two hydrological stations were used to reconstruct continuous discharge for the primary inflows to Lake Peters, Carnivore and Chamberlin creeks. The lake's thermal structure was monitored using a network of temperature sensors on moorings, the lake's water level was recorded using pressure sensors, and sedimentary inputs to the lake were documented by sediment traps. We demonstrate the utility of these datasets by examining a flood event in July 2015, though other uses include studying intra- and inter-annual trends in this weather–glacier–river–lake system, contextualizing interpretations of lake sediment cores, and providing background for modeling studies. All DOI-referenced datasets described in this paper are archived at the National Science Foundation Arctic Data Center at the following overview web page for the project: https://arcticdata.io/catalog/view/urn:uuid:df1eace5-4dd7-4517-a985-e4113c631044 (last access: 13 October 2019; Kaufman et al., 2019f).

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