ALBERT

Description: Earth system modelling (ESM) is essential for understanding past, present and future Earth processes. Deep learning (DL), with the data-driven strength of neural networks, has promise for improving ESM by exploiting information from Big Data. Yet existing hybrid ESMs largely have deep neural networks incorporated only during the initial stage of model development. In this Perspective, we examine progress in hybrid ESM, focusing on the Earth surface system, and propose a framework that integrates neural networks into ESM throughout the modelling lifecycle. In this framework, DL computing systems and ESM-related knowledge repositories are set up in a homogeneous computational environment. DL can infer unknown or missing information, feeding it back into the knowledge repositories, while the ESM-related knowledge can constrain inference results of the DL. By fostering collaboration between ESM-related knowledge and DL systems, adaptive guidance plans can be generated through question-answering mechanisms and recommendation functions. As users interact iteratively, the hybrid system deepens its understanding of their preferences, resulting in increasingly customized, scalable and accurate guidance plans for modelling Earth processes. The advancement of this framework necessitates interdisciplinary collaboration, focusing on explainable DL and maintaining observational data to ensure the reliability of simulations.

Description: We use the improved Parker‐Oldenburg's formulas that include a reference depth into the exponential term and employ the Gauss‐fast Fourier transform method to determine Moho depth beneath the Tibetan Plateau. The synthetic models demonstrate that the improved Parker's formula has high accuracy with the maximum absolute error less than 0.25 mGal compared to the analytical solution. Two inversion parameters, that is, the reference depth and the density contrast, are essential for the Moho estimation based on the gravity field, and they need to be determined in advance to obtain correct results. Therefore, the Moho estimates derived from existing seismic studies are used to reduce the nonuniqueness of the gravity inversion and to determine these parameters by searching for the maximum correlation between the gravity‐inverted and seismic‐derived Moho depths. Another critical issue is to remove beforehand the gravity effects of other factors, which affect the observed gravity field besides Moho variations. In addition to the topography, the gravity effects of the sedimentary layer and crystalline crust are removed based on existing crustal models, while the upper mantle impact is determined based on the seismic tomography model. The inversion results show that the Moho structure under the Tibetan plateau is very complex with the depths varying from about 30–40 km in the surrounding basins (e.g., Ganges basin, Sichuan basin, and Tarim basin) to 60–80 km within the plateau. This considerable difference up to 40 km on the Moho depth reveals the substantial uplift and thickening of the crust in the Tibetan Plateau. Furthermore, two visible “Moho depression belts” are observed within the plateau with the maximum Moho deepening along the Indus‐Tsangpo Suture and along the northern margin of Tibet bounding the Tarim basin with the relatively shallow Moho in central Tibet between them. The southern “belt” is likely formed in compressional environment, where the Indian plate underthrusts northward beneath the Tibetan Plateau, while the northern one could be formed by the southward underthrust of the Asian lithosphere beneath Tibet.

Description: Lake Sihailongwan in Jilin province, NE China, provides the first continuous and almost entirely seasonally laminated sediment record on the East Asian mainland comprising the complete Holocene, the Late-glacial period, and large parts of the Last Glacial. Sediment and palynological proxy data provide a finely resolved regional environmental history of the East Asian monsoon. A varve-based chronology (shl-vc2) has been established for the last 65,000 years and allows a detailed comparison with other long regional and global palaeoclimate records. Vegetation density of the study area depends, on the long run, on precessionally forced insolation changes, with superimposed millennial-scale variability during the Last Glacial. Periodic increase of organic carbon content and thermophilous tree species like Ulmus and Fraxinus and contemporary decrease of shrub Alnus precisely mirror millennial-scale climatic variations primarily known from Greenland ice-cores as Dansgaard-Oeschger cycles, as well as Late-glacial period climate changes. Percentages of trees & shrubs pollen and in particular lake productivity-related data reveal substantial differences between interstadial intensities, with those between 50 and 60 ka BP being more pronounced than the following ones.

Description: In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion.

Description: While wetlands are the largest natural source of methane (CH4) to the atmosphere, they represent a large source of uncertainty in the global CH4 budget due to the complex biogeochemical controls on CH4 dynamics. Here we present, to our knowledge, the first multi-site synthesis of how predictors of CH4 fluxes (FCH4) in freshwater wetlands vary across wetland types at diel, multiday (synoptic), and seasonal time scales. We used several statistical approaches (correlation analysis, generalized additive modeling, mutual information, and random forests) in a wavelet-based multi-resolution framework to assess the importance of environmental predictors, nonlinearities and lags on FCH4 across 23 eddy covariance sites. Seasonally, soil and air temperature were dominant predictors of FCH4 at sites with smaller seasonal variation in water table depth (WTD). In contrast, WTD was the dominant predictor for wetlands with smaller variations in temperature (e.g., seasonal tropical/subtropical wetlands). Changes in seasonal FCH4 lagged fluctuations in WTD by ~17 ± 11 days, and lagged air and soil temperature by median values of 8 ± 16 and 5 ± 15 days, respectively. Temperature and WTD were also dominant predictors at the multiday scale. Atmospheric pressure (PA) was another important multiday scale predictor for peat-dominated sites, with drops in PA coinciding with synchronous releases of CH4. At the diel scale, synchronous relationships with latent heat flux and vapor pressure deficit suggest that physical processes controlling evaporation and boundary layer mixing exert similar controls on CH4 volatilization, and suggest the influence of pressurized ventilation in aerenchymatous vegetation. In addition, 1- to 4-h lagged relationships with ecosystem photosynthesis indicate recent carbon substrates, such as root exudates, may also control FCH4. By addressing issues of scale, asynchrony, and nonlinearity, this work improves understanding of the predictors and timing of wetland FCH4 that can inform future studies and models, and help constrain wetland CH4 emissions.

Description: The WHU_RL01 GRACE monthly gravity field solutions are produced with the classical dynamic approach at the GNSS Research Center of Wuhan University. Three sets of monthly solutions complete to d/o 60, 90 and 120 are produced without any regularization for the time period from 2002-04 to 2016-07. K-Band range rates with a sampling of 5 seconds and reduced-dynamic orbits with a sampling of 5 minutes are used as observations. To account for the colored noise in the K-Band range-rate measurements, the frequency-dependent data weighting scheme proposed by Ditmar et al. (2007) is adopted. Additionally, a unified weight for the reduced-dynamic orbits is applied based on its a priori precision of 2 cm for each component. The strategy adopted for producing the WHU_RL01 GRACE monthly gravity field models is summarized in Table 1 (please find it in the attached explanatory file). It should be noted that relatively short arcs (6 hours per arc) are used to reduce the resonance effects caused by inaccuracies in initial state vectors and background force models (Colombo, 1984). The reduced-dynamic orbits are also used as observations in our data processing. Although a reduced-dynamic orbit contain certain a priori gravity field information, the resulting bias in the gravity field solutions have been proved to be limited when inverted together with the K-band measurements (Chen et al., 2014; Liu et al., 2010).

Description: The latest generation of GPS satellites, termed Block IIF, provides a new L5 signal. Multi-frequency signals open new prospects for precise positioning and fast ambiguity resolution and have become the trend in Global Navigation Satellite System (GNSS) development. However, a new type of inter-frequency clock bias (IFCB), i.e., the difference between the current clock products computed with L1/L2 and the satellite clocks computed with L1/L5, was noticed. Consequently, the L1/L2 clock products cannot be used for L1/L5 precise point positioning (PPP). In order to solve this issue, the IFCB should be estimated with a high accuracy. Datasets collected at 129 globally distributed Multi-GNSS Experiment (MGEX) stations from 2015 are employed to investigate the IFCB. The results indicate that the IFCB is satellite dependent and varies with the relative sun–spacecraft–earth geometry. Other factors, however, may also contribute to the IFCB variations according to the harmonic analysis of the single-day IFCB time series. In addition, the results show that the IFCB exhibits periodic signal with a notable period of 43,080 s and the peak-to-peak amplitude is 0.023–0.269 m. After considering a time lag of 240 s, the average cross-correlation coefficient between the IFCB series of two consecutive days is 0.943, and the prediction accuracy of IFCB is 0.006 m. A triple-frequency PPP model that takes the IFCB into account is proposed. When using 3-h datasets, the positioning accuracy of triple-frequency PPP can be improved by 19, 13 and 21 % compared with the L1/L2-based PPP in the east, north and up directions, respectively.

Description: The main formation of the Yinggehai Basin has been related to the rotation of the Indochina block, resulting in large-scale strike-slip motion along the Red River Fault Zone (RRFZ). Transrotational tectonics played a key role in the evolution of the Yinggehai Basin. In this study, we present analog experiments with a preexisting basal velocity discontinuity boundary, rotation of crustal blocks concerning vertical axes, and syntectonic sedimentations to evaluate how the transrotational tectonics controls the evolutionary process of the Yinggehai Basin. Particle image velocimetry (PIV) was used to monitor the deformation of the model surface. Four successive poles of rotation have been applied to the model. The basin evolution underwent two phases. An early phase of deformation is characterized by the nucleation of the main internal faults above the velocity discontinuity boundary and segmented en echelon border fault systems. In the early phase, the internal and boundary faults mainly accommodated large-scale strike-slip displacement. During progressive extension, the main internal faults deactivated, and tectonic activity is localized along the boundary and secondary internal faults in the late phase. The boundary faults in the rotating block play a dominant role in the widening and deepening of the rift zone at an accelerating rate. The model surface morphology shows similarities to the Yinggehai Basin, which is wide in the middle and converges toward the northwest and southeast. In addition, experimental profiles have been compared with seismic profiles in the Yinggehai Basin. The model results also indicate that the rotation of the Indochina block combines with strong strike-slip motion. The similarities between modeling and nature provide support for ∼250 km sinistral displacement along the RRFZ between ∼32 and ∼21 Ma.

Description: This data publication includes standard rock magnetic data related to concentration, coercivity and magneto-mineralogy versus depth from six sediment cores (M72/5-22GC3, M72-5-22GC4, M72-5-22GC6, M72-5-22GC8, M72-5-24GC3, M72-5-25GC1), collected at the Arkhangelsky Ridge in the Southeastern Black Sea during the marine expedition M72/5 of the German research vessel RV METEOR (in May 2007). The data are related to publications by Liu et al. (2018, 2019, 2020), Liu (2019) and Nowaczyk et al. (2012, 2013, 2018, 2021a, b). Sediment cores were recovered using gravity corers. For paleo- and rock magnetic analyses clear plastic boxes of 20×20×15 mm were pressed into the split halves of the generally 1 m long sections of the sediment cores. Data are provided as six ASCII files (.dat, one for each core) with metadata header, followed by 12 data columns and are decribed in the associated data description file (pdf).

Description: This data publication includes standard rock magnetic data related to concentration, coercivity and magneto-mineralogy versus depth from twelve sediment cores recovered from the Arkhangelsky Ridge in the Southeastern Black Sea, German RV Maria S. Merian expedition MSM33 in 2013: MSM33-51-3, MSM33-52-1, MSM33-53-1, MSM33-54-3, MSM33-55-1, MSM33-56-1, MSM33-57-1, MSM33-60-1, MSM33-61-1, MSM33-62-2, MSM33-63-1, MSM33-64-1. The data are related to publications by Liu et al. (2018, 2019, 2020), Liu (2019) and Nowaczyk et al. (2012, 2013, 2018, 2021a, b). Sediment cores were recovered using gravitiy and piston corers. For paleo- and rock magnetic analyses clear plastic boxes of 20×20×15 mm were pressed into the split halves of the generally 1 m long sections of the sediment cores. Data are provided as 12 ASCII files (.dat, one for each core) with metadata header and are decribed in the associated data description file (pdf).