Estimating the effective elastic thickness of the Arctic lithosphere using the wavelet coherence method: Tectonic implications

Abstract. Many scientists have made use of the wavelet method in analyzing time series, often using popular free software. However, at present there are no similar easy to use wavelet packages for analyzing two time series together. We discuss the cross wavelet transform and wavelet coherence for examining relationships in time frequency space between two time series. We demonstrate how phase angle statistics can be used to gain confidence in causal relationships and test mechanistic models of physical relationships between the time series. As an example of typical data where such analyses have proven useful, we apply the methods to the Arctic Oscillation index and the Baltic maximum sea ice extent record. Monte Carlo methods are used to assess the statistical significance against red noise backgrounds. A software package has been developed that allows users to perform the cross wavelet transform and wavelet coherence (www.pol.ac.uk/home/research/waveletcoherence/).

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The lithospheric effective elastic thickness and its tectonic implications in the Ordos Block and adjacent areas

Geological Journal ◽

10.1002/gj.4335 ◽

2021 ◽

Author(s):

Qing Chen ◽

Franz Neubauer ◽

Yunpeng Dong ◽

Xianfeng Tan ◽

Hao Chen

Keyword(s):

Ordos Block ◽

Tectonic Implications ◽

Effective Elastic Thickness

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Defining Homogeneous Drought Zones Based on Soil Moisture across Japan and Teleconnections with Large-Scale Climate Signals

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-21-0133.1 ◽

2021 ◽

Author(s):

Ke Shi ◽

Yoshiya Touge ◽

So Kazama

Keyword(s):

Soil Moisture ◽

Land Surface ◽

Large Scale ◽

Southern Oscillation ◽

Wavelet Coherence ◽

The Arctic ◽

Surface Model ◽

Drought Prediction ◽

Climate Signals ◽

Wavelet Coherence Analysis

Abstract Droughts are widespread disasters worldwide and are concurrently influenced by multiple large-scale climate signals. This is particularly true over Japan, where drought has strong heterogeneity due to multiple factors such as monsoon, topography, and ocean circulations. Regional heterogeneity poses challenges for drought prediction and management. To overcome this difficulty, this study provides a comprehensive analysis of teleconnection between climate signals and homogeneous drought zones over Japan. First, droughts are characterized by simulated soil moisture from land surface model during 1958-2012. The Mclust toolkit, distinct empirical orthogonal function, and wavelet coherence analysis are used, respectively, to investigate the homogeneous drought zone, principal component of each homogeneous zone, and teleconnection between climate signals and drought. Results indicate that nine homogeneous drought zones with different characteristics are defined and quantified. Among these nine zones, zone-1 is dominated by extreme drought events. Zone-2 and zone-6 are typical representatives of spring droughts, while zone-7 is wet for most of the period. The Hokkaido region is divided into wetter zone-4 and drier zone-9. Zone-3, zone-5 and zone-8 are distinguished by the topography. The analyses also reveal almost nine zones have a high level of homogeneity, with more than 60% explained variance. Also, these nine zones are dominated by different large-scale climate signals: the Arctic Oscillation has the strongest impact on zone-1, zone-7, and zone-8; the influence of the North Atlantic Oscillation on zone-3, zone-4, and zone-6 is significant; zone-2 and zone-9 are both dominated by the Pacific Decadal Oscillation; El Niño-Southern Oscillation dominates zone-5. The results will be valuable for drought management and drought prevention.

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Wavelet Analysis Identifies Carbon Processes in a Subarctic Stream During Snowmelt Spring Flood

10.5194/egusphere-egu21-12676 ◽

2021 ◽

Author(s):

Danny Croghan ◽

Pertti Ala-Aho ◽

Annalea Lohila ◽

Jeffrey Welker ◽

Jussi Vuorenmaa ◽

...

Keyword(s):

High Resolution ◽

Wavelet Analysis ◽

Carbon Cycle ◽

Wavelet Transforms ◽

Transport Processes ◽

Wavelet Coherence ◽

The Arctic ◽

Spring Flood ◽

Arctic Streams ◽

Wavelet Coherence Analysis

Snowmelt spring floods dominate the annual carbon flux in Arctic streams. However, climate change is altering their timing and magnitude due to changes in snow conditions, further altering the processes controlling the carbon cycle at the catchment scale. Current knowledge is limited by a lack of high-resolution data from Arctic areas. In this study we combine high-resolution biogeochemical-hydro-climatological variables with spectral wavelet analysis for new insights into carbon processes.This study was conducted during the snowmelt spring flood period in a sub-arctic headwater catchment in Pallas-Yll&#228;s national park, Finland (68&#176;02&#8242;N, 24&#176;16&#8242;W). We collected in-stream dissolved organic carbon (DOC), carbon dioxide (C02), and terrestrial C02 flux alongside a suite of hydro-climatological variables measured at 30-minute intervals. Continuous wavelet transformations and wavelet coherence were produced to assess the relationship between hydro-climatological variables and carbon variables at different periodicities.Wavelet transforms indicated that the onset of snowmelt caused the development of significant diel periodicity for in-stream DOC, CO2 and terrestrial CO2 flux, while substantial periods of significant periodicity were observed at multiple day periodicities. Wavelet coherence analysis identified that DOC was consistently lead by flow and conductivity across daily and multiple daily scales suggesting that transport of carbon from the surface and shallow sub-surface pathways to the stream were the predominant processes controlling in-stream DOC. Interestingly for in-stream CO2, groundwater level showed periodic rather than consistent spectral coherence suggesting it is not a consistent control on CO2 in the spring flood. The strongest coherence for in-stream CO2 was with in-stream O2, which may suggest the importance of in-stream metabolism as a control on in-stream CO2 dynamics. Terrestrial CO2 fluxwas controlled by notably different processes than in-stream Carbon and linked strongest to climatological variables. Photosynthetically active radiation (PAR) showed the strongest relationship with CO2 terrestrial flux dynamics.&#160;Our study highlights the unique processes controlling different parts of the carbon cycle in a headwater arctic catchment during the snowmelt spring flood. We highlight in-stream DOC as particularly vulnerable to changes in spring flood magnitude and timing given the importance of snowmelt dominated transport processes to DOC flux. To identify future changes in the Arctic carbon cycle, wavelet analysis shows potential as tool to analyse changes in processes in high-resolution datasets.

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Frequency Associations between East Asian Jet Streams and the Temperature over the Barents–Kara Sea Region/Arctic Oscillation in Winter

Climate ◽

10.3390/cli8100107 ◽

2020 ◽

Vol 8 (10) ◽

pp. 107

Author(s):

Yuefeng Li ◽

Yuxiang Zhu ◽

Wei Song

Keyword(s):

East Asia ◽

Arctic Oscillation ◽

East Asian ◽

Kara Sea ◽

Wavelet Coherence ◽

The Arctic ◽

Jet Stream ◽

Jet Streams ◽

The Arctic Oscillation ◽

Cross Wavelet

The frequency associations between jet streams over East Asia and the Arctic key temperature at 2 m (AKT2m) in the Barents–Kara Sea region (40°–75° E, 66°–82° N) and the Arctic Oscillation in winter are investigated using continuous wavelet transform, cross-wavelet transform, and wavelet coherence. The cross-wavelet transforms between the AKT2m/Arctic Oscillation and the East Asian polar front jet stream (EAPJ) suggest that the EAPJ is closely related to the AKT2m and Arctic Oscillation on an interannual (3–5-year band) timescale, but the variation in the phase angle denotes a complex frequency connection between the EAPJ and Arctic Oscillation. The squared wavelet coherence suggests that weakening of the EAPJ is associated with the rise in AKT2m during the period of abrupt climate change in East Asia. The EAPJ contains more forced components from the Arctic than the East Asian subtropical jet stream. By comparison, the relationship between AKT2m and the EAPJ is closer than that between the Arctic Oscillation and EAPJ, especially during the period of abrupt climate change in East Asia. This suggests that the EAPJ serves as a bridge for Arctic warming to affect the weather and climate over East Asia in winter. By contrast, the Arctic Oscillation does not play an important part, although it also contains information about the Arctic.

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