Geomagnetic field evolution during the Laschamp excursion

Leonhardt, Roman; Fabian, Karl; Winklhofer, Michael; Ferk, A.; Làj, C.; Kissel, Catherine

doi:10.1016/j.epsl.2008.11.028

Cited by 49 publications

(68 citation statements)

References 46 publications

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“…All these results are in agreement with early stages of a dipole collapse in the numerical dynamo model by Olson et al (2009). In a detailed study of the Matuyama-Brunhes polarity reversal (Leonhardt and Fabian, 2007) and Laschamp excursion (Leonhardt et al, 2009) the field instability starts when reverse flux patches appear in low or mid latitude regions at the CMB and then move poleward. In contrast, Aubert et al (2008) found a mixed behavior, with reversals and excursions initiated by reversed flux generated both outside and inside the tangent cylinder.…”

Section: Introductionsupporting

confidence: 74%

Toward a possible next geomagnetic transition?

Santis

Qamili

2013

Nat. Hazards Earth Syst. Sci.

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Abstract. The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering that: (a) in the last 83 million yr the typical average time between one reversal and the next (the so-called chron) is around 400 000 yr, (b) the last reversal occurred around 780 000 yr ago, (c) more excursions (rapid changes in polarity) can occur within the same chron and (d) the geomagnetic field dipole is currently decreasing, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards that are really global. The South Atlantic Anomaly (SAA) is a great depression of the geomagnetic field strength at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterized by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power law or logarithmic functions in reverse time, also decorated by logperiodic oscillations, whose final singularity (a critical point t c ) reveals a great change in the near future (2034 ± 3 yr), when the SAA area reaches almost a hemisphere. An interesting aspect that has recently been found is the possible direct connection between the SAA and the global mean sea level (GSL). That the GSL is somehow connected with SAA is also confirmed by the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033 ± 11 yr) agrees, within the estimated errors, with the value found for the SAA. From this result, we point out the intriguing conjecture that t c would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

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Section: Introductionsupporting

confidence: 74%

Toward a possible next geomagnetic transition?

Santis

Qamili

2013

Nat. Hazards Earth Syst. Sci.

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“…Similarly, a short full reversal of 0.4-0.8 ka, superimposed on a background of low relative paleointensity that lasted 1.5-2 ka, is reported from cores from the Blake Ridge (Bourne et al, 2013), the Bermuda Rise (Kissel et al, 1999;Channell et al, 2012), Irminger Basin (Channell, 2006), northwest of Iceland, and the southern Indian Ocean (Laj et al, 2006). These paleomagnetic data are consistent with cosmogenic nuclide production rates from sediment and ice cores (e.g., Muscheler et al, 2005;Ménabréaz et al, 2011;Nilsson et al, 2011), and are supported by Bayesian inversion of geomagnetic field evolution during the Laschamp in North America (Leonhardt et al, 2009). Bayesian inversion also suggests that the timing and duration of the Laschamp may vary according to locality (Leonhardt et al, 2009).…”

supporting

confidence: 71%

“…Information regarding the anatomy, timing, and duration of excursions can serve to calibrate magnetohydrodynamic modeling of outer core flow dynamics on centennial to millennial scales, thus helping us to understand the intrinsic behavior of Earth's dynamo (Gubbins, 1999). In addition, accurate and precise high-resolution time series of geomagnetic excursions are critical for dating geologic phenomena, climatic episodes, astronomical events, or paleontologic and anthropologic stratigraphic markers (Leonhardt et al, 2009;Richards and Andersen, 2013;Singer, 2014).…”

Section: Introductionmentioning

confidence: 99%

Age of the Laschamp excursion determined by U-Th dating of a speleothem geomagnetic record from North America

Lascu

Feinberg

Dorale

et al. 2016

Geology

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The Laschamp geomagnetic excursion was the first short-lived polarity event recognized and described in the paleomagnetic record, and to date remains the most studied geomagnetic event of its kind. In addition to its geophysical significance, the Laschamp is an important global geochronologic marker. The Laschamp excursion occurred around the time of the demise of Homo neanderthalensis, in conjunction with high-amplitude, rapid climatic oscillations leading into the Last Glacial Maximum, and coeval with a major supervolcano eruption in the Mediterranean. Thus, precise determination of the timing and duration of the Laschamp excursion would help in elucidating major scientific questions situated at the intersection of geology, paleoclimatology, and anthropology. Here we present a North American speleothem geomagnetic record of the Laschamp excursion that is directly dated using a combination of high-precision 230 Th dates and annual layer counting using confocal microscopy. We have determined a maximum excursion duration that spans the interval 42.25-39.70 ka B.P., and an age of 41.10 ± 0.35 ka B.P. for the main phase of the excursion, during which the virtual geomagnetic pole was situated at the southernmost latitude in the record. Our chronology provides the first age bracketing of the Laschamp excursion using radioisotopic dating, and improves on previous age determinations based on 40 Ar/ 39 Ar dating of lava flows, and orbitally tuned sedimentary and ice-core records.

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“…Since the last reversal, there have been several geomagnetic excursions, during which the dipolar field significantly weakened without undergoing a complete reversal [6,34]. For example, during the Laschamp excursion 40 000 years ago, the surface field over most of Europe and northwest Africa was as weak as 4 mT (see [7], on the basis of the model by Leonhardt et al [35]). Our present data suggest that the avian magnetic compass based on radical-pair processes would have been able to cope with such low fields.…”

Section: Discussionmentioning

confidence: 99%

Avian magnetic compass can be tuned to anomalously low magnetic intensities

Winklhofer

Dylda²,

Thalau³

et al. 2013

Proc. R. Soc. B.

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The avian magnetic compass works in a fairly narrow functional window around the intensity of the local geomagnetic field, but adjusts to intensities outside this range when birds experience these new intensities for a certain time. In the past, the geomagnetic field has often been much weaker than at present. To find out whether birds can obtain directional information from a weak magnetic field, we studied spontaneous orientation preferences of migratory robins in a 4 mT field (i.e. a field of less than 10 per cent of the local intensity of 47 mT). Birds can adjust to this low intensity: they turned out to be disoriented under 4 mT after a pre-exposure time of 8 h to 4 mT, but were able to orient in this field after a total exposure time of 17 h. This demonstrates a considerable plasticity of the avian magnetic compass. Orientation in the 4 mT field was not affected by local anaesthesia of the upper beak, but was disrupted by a radiofrequency magnetic field of 1.315 MHz, 480 nT, suggesting that a radical-pair mechanism still provides the directional information in the low magnetic field. This is in agreement with the idea that the avian magnetic compass may have developed already in the Mesozoic in the common ancestor of modern birds.

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Geomagnetic field evolution during the Laschamp excursion

Cited by 49 publications

References 46 publications

Toward a possible next geomagnetic transition?

Toward a possible next geomagnetic transition?

Age of the Laschamp excursion determined by U-Th dating of a speleothem geomagnetic record from North America

Avian magnetic compass can be tuned to anomalously low magnetic intensities

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