Phase Changes of Electromagnetic Oceanic Tidal Signals

Saynisch, Jan; Petereit, Johannes; Irrgang, Christopher; Thomas, Maik

doi:10.1029/2019jc015960

Cited by 3 publications

(2 citation statements)

References 33 publications

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“…As a result, our results represent time averaged estimates over the study period (years 2000.5 - 2023.2). Expanding our approach to temporal variations of the tidal transport amplitudes 23 , e.g., and phases 36 is easily possible and envisioned for further studies.…”

Section: Resultsmentioning

confidence: 99%

“…Second, to calculate EM signals from the tidal electric current density, we use x3dg with the tidal frequencies from Table 1 and by employing a commonly used background conductance environment. The conductance environment (cf., 13 , 36 ) consists of superposed 2D horizontal layers of sediments 8 , 18 and oceans 47 over the vertical 1D mantle conductivity profile of Grayver et al 12 . To estimate the influence of the mantle, we incorporate also the 1D Püthe et al 27 mantle conductivity profile.…”

Section: Approachmentioning

confidence: 99%

See 1 more Smart Citation

Tidal transports from satellite observations of earth’s magnetic field

Saynisch-Wagner,

Baerenzung,

Hornschild

et al. 2023

Sci Rep

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The tides are a major driver of global oceanic mixing. While global tidal elevations are very well observed by satellite altimetry, the global tidal transports are much less well known. For twenty years, magnetic signals induced by the ocean tides have been detectable in satellite magnetometer observations, such as Swarm or CHAMP. Here, we demonstrate how satellite magnetometer observations can be used to directly derive global ocean tidal transports. As an advantage over other tidal transport estimates, our tidal estimates base on very few and very loose constraints from numerical forward models.

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Section: Resultsmentioning

confidence: 99%

Section: Approachmentioning

confidence: 99%

Tidal transports from satellite observations of earth’s magnetic field

Saynisch-Wagner,

Baerenzung,

Hornschild

et al. 2023

Sci Rep

View full text Add to dashboard Cite

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Tide-induced magnetic signals and their errors derived from CHAMP and Swarm satellite magnetometer observations

Saynisch

Baerenzung

Hornschild

et al. 2021

Earth Planets Space

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Satellite-measured tidal magnetic signals are of growing importance. These fields are mainly used to infer Earth’s mantle conductivity, but also to derive changes in the oceanic heat content. We present a new Kalman filter-based method to derive tidal magnetic fields from satellite magnetometers: KALMAG. The method’s advantage is that it allows to study a precisely estimated posterior error covariance matrix. We present the results of a simultaneous estimation of the magnetic signals of 8 major tides from 17 years of Swarm and CHAMP data. For the first time, robustly derived posterior error distributions are reported along with the reported tidal magnetic fields. The results are compared to other estimates that are either based on numerical forward models or on satellite inversions of the same data. For all comparisons, maximal differences and the corresponding globally averaged RMSE are reported. We found that the inter-product differences are comparable with the KALMAG-based errors only in a global mean sense. Here, all approaches give values of the same order, e.g., 0.09 nT-0.14 nT for M2. Locally, the KALMAG posterior errors are up to one order smaller than the inter-product differences, e.g., 0.12 nT vs. 0.96 nT for M2. Graphical Abstract

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On the characterization of tidal ocean-dynamo signals in coastal magnetic observatories

Petereit

Saynisch

Morschhauser

et al. 2022

Earth Planets Space

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Periodic tidal ocean currents induce electric currents and, therefore, magnetic field signals that are observable using spaceborne and ground-based observation techniques. In theory, the signals can be used to monitor oceanic temperature and salinity variations. Tidal magnetic field amplitudes and phases have been extracted from magnetometer measurements in the past. However, due to uncertainties caused by a plentitude of influencing factors, the shape and temporal variation of these signals are only known to a limited extent. This study uses past extraction methods to characterize seasonal variations and long-term trends in the ten year magnetometer time series of three coastal island observatories. First, we assess data processing procedures used to prepare ground-based magnetometer observations for tidal ocean dynamo signal extraction to demonstrate that existing approaches, i.e., subtraction of core field models or first-order differencing, are unable to reliably remove low-frequency contributions. We hence propose low-frequency filtering using smoothing splines and demonstrate the advantages over the existing approaches. Second, we determine signal and side peak magnitudes of the M2 tide induced magnetic field signal by spectral analysis of the processed data. We find evidence for seasonal magnetic field signal variations of up to $$25\%$$ 25 % from the annual mean. Third, to characterize the long-term behavior of tidal ocean dynamo signal amplitudes and phases, we apply different signal extraction techniques to identify tidal ocean-dynamo signal amplitudes and phases in sub-series of the ten-year time series with incrementally increasing lengths. The analyses support three main findings: (1) trends cause signal amplitude changes of up to $$\approx 1~$$ ≈ 1 nT and phase changes are in the order of $${\mathcal {O}}(10^{\circ }$$ O ( 10 ∘ ) within the observation period; (2) at least four years of data are needed to obtain reliable amplitude and phase values with the extraction methods used and (3) signal phases are a less dependent on the chosen extraction method than signal amplitudes. Graphical Abstract

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Phase Changes of Electromagnetic Oceanic Tidal Signals

Cited by 3 publications

References 33 publications

Tidal transports from satellite observations of earth’s magnetic field

Tidal transports from satellite observations of earth’s magnetic field

Tide-induced magnetic signals and their errors derived from CHAMP and Swarm satellite magnetometer observations

On the characterization of tidal ocean-dynamo signals in coastal magnetic observatories

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