ALBERT

Description: The abyssal ocean circulation is a key component of the global meridional overturning circulation, cycling heat, carbon, oxygen and nutrients throughout the world ocean. The strongest historical trend observed in the abyssal ocean is warming at high southern latitudes, yet it is unclear what processes have driven this warming, and whether it is linked to a slowdown in the ocean's overturning circulation. Furthermore, future change in the abyssal overturning remains uncertain, with the latest CMIP6 projections not accounting for dynamic ice-sheet melt. In this talk I will present new transient forced high-resolution coupled ocean – sea-ice model simulations to show that under a high emissions scenario, abyssal warming is set to accelerate over the next 30 years. We find that meltwater input around Antarctica drives a contraction of Antarctic Bottom Water (AABW), opening a pathway that allows warm Circumpolar Deep Water greater access to the continental shelf. The reduction in AABW formation results in warming and ageing of the abyssal ocean, consistent with recent measurements. In contrast, projected wind and thermal forcing has little impact on the properties, age, and volume of AABW. These results highlight the critical importance of Antarctic meltwater in setting the abyssal ocean overturning, with implications for global ocean biogeochemistry and climate that could last for centuries.

Description: In response to quadrupled CO〈sub〉2〈/sub〉, the Southern Ocean primarily uptakes excess heat around 60°S, which is then redistributed by the northward ocean heat transport (OHT) and mostly stored in the ocean or released back to the atmosphere around 45°S. However, the relative roles of mean ocean circulation and ocean circulation change in the uptake and redistribution of heat in the Southern Ocean remain controversial. Here, a set of climate model experiments embedded with a novel partial coupling technique are used to separate the roles of mean ocean circulation (passive component) and ocean circulation change (active component). For the ocean heat uptake (OHU) response, the mean ocean circulation and ocean circulation change are of equal importance. The OHT response south of 50°S is mainly determined by mean ocean circulation, while the ocean circulation change generates an anomalous southward OHT north of 50°S. A heat budget analysis finds that the divergence of passive OHT acts to balance the passive surface heat gain to the south of ~50°S, while the convergence of active OHT acts to balance the active surface heat loss to the north of ~50°S. Intriguingly, all the increase in ocean heat storage (OHS) is attributable to the passive component, with the ocean circulation change playing almost no role. In the Southern Ocean, both the active and the passive ocean heat transports are overcompensated by the reverse atmospheric heat transport via the Bjerknes compensation.

Description: Precipitable water vapor (PWV), as the most abundant greenhouse gas, significantly impacts the evapotranspiration process and thus the global climate. However, the applicability of mainstream satellite PWV products is limited by the tradeoff between spatial and temporal resolutions, as well as some external factors such as cloud contamination. In this study, we proposed a novel PWV spatio-temporal fusion framework based on the zero-shot super-resolution and the multivariate autoregression models (ZSSR-ARF) to improve the accuracy and continuity of PWV. The framework is implemented in a way that the satellite-derived observations (MOD05) are fused with the reanalysis data (ERA5) to generate accurate and seamless PWV of high spatio-temporal resolution (0.01°, daily) across the European continent from 2001 to 2021. Firstly, the ZSSR approach is used to enhance the spatial resolution of ERA5 PWV based on the internal recurrence of image information. Secondly, the optimal ERA5-MOD05 image pairs are selected based on the image similarity as inputs to improve the fusion accuracy. Thirdly, the framework develops a multivariate autoregressive fusion approach to allocate weights adaptively for the high-resolution image prediction, which primely addresses the non-stationarity and autocorrelation of PWV. The results reveal that the accuracies of fused PWV are consistent with those of the GPS retrievals (r = 0.82–0.95 and RMSE = 2.21–4.01 mm), showing an enhancement in the accuracy and continuity compared to the original MODIS PWV. The ZSSR-ARF fusion framework outperforms the other methods with R2 improved by over 24% and RMSE reduced by over 0.61 mm. Furthermore, the fused PWV exhibits similar temporal consistency (mean difference of 0.40 mm and DSTD of 3.22 mm) to the reliable ERA5 products, and substantial increasing trends (mean of 0.057 mm/year and over 0.1 mm/year near the southern and western coasts) are observed over the European continent. As the accuracy and continuity of PWV are improved, the outcome of this paper has potential for climatic analyses during the land-atmosphere cycle process.

Description: The eastern margin of the Tibetan Plateau has given rise to much debate about mechanisms of plateau uplift and evolution and, in particular, the role of the lower crust in crustal thickening. Knowledge of the middle to lower crust conditions is critical for evaluating various models of crustal deformation, but data on crustal evolution through time are lacking. Here, we turn to the Gongga Shan granite, an intrusion along the Xianshuihe fault in easternmost Tibet that directly records local Cenozoic crustal conditions. Wepresent 124 U-Pb samples from the Gongga Shan granite (GSG) that prove that the crust has been stepwise producing partial melt from 56 Ma to 4 Ma. According to the age distribution, the GSG can be separated into four major groups with ages of 4–10 Ma, 12–20 Ma, 25–40 Ma, and 43–56 Ma. Combining the timing information with geophysics and lowtemperature thermochronology data, we suggest that events younger than 10 Ma may indicate the onset of recent crustal channel flow in the middle to lower crust. In contrast, the youngest 4 Ma ages indicate the ongoing partial melting of the middle crust. The 12–20 Ma events could be related to an earlier stage of crustal channel flow, consistent with the regional large-scale crustal channel flow in central Tibet.

Description: The Coulomb failure stress (CFS) criterion based on the Mohr-Coulomb friction theory is commonly used to explain physical mechanisms governing injection-induced seismicity. While the CFS criterion can evaluate the onset of fault reactivation caused by fluid perturbations, it cannot tell the kinematic process of fault failure (seismic or aseismic slip). An alternative model for simulating time-dependent earthquake cycles is the rate-and-state friction model, which provides evolving friction depending on slip rate and slip history. To explore the dynamics and stability of fault slip associated with fluid injection, we extend a spring-slider system with a rate-and-state dependent friction law by incorporating the evolving fluid pressure and poroelastic stress. Simulations of continuous constant fluid mass injection rate scenarios using the developed model suggest that injection-induced fault slip behavior is controlled by fault orientation, diffusivity and poroelasticity, and injection rate. Compared to the CFS criterion, our model can offer a temporal component to fault friction and provide new insights on slip, slip rate and trajectory in phase space. We also investigate the relation between cumulative slip displacement versus cumulative injection volume, as well as the event recurrence interval. Our proposed approach has the potential application for evaluating the reactivation of pre-existing faults embedded in the reservoir associated with fluid pressure operations in the field practice.

Description: Highlights • Cadomian continental arc crust of NE Iran was built during ∼15 Myr of magmatism. • Magmatic flare-up in Iran Cadomia occurred over ∼45 Myr; 570 to 525 Ma. • Geochemical differentiation in “hot zones” built the stratified continental crust of Iran. Abstract The generation and differentiation of continental crust by arc magmatism is strongly influenced by episodes of high magmatic flux (“flare-ups”). Magmatic flare-ups encourage the development of deep crustal hot zones where magmatic differentiation and density stratification combine to form the upper felsic and lower mafic continental crust. Such processes, which are responsible for the construction of continental arc crust, are prolonged events, which build a ∼30-40 km arc crust over tens of million years (∼100 Myr). New zircon U-Pb data reveal that the construction of Cadomian crust from NE Iran occurred over ∼15 ± 0.3 Myr. However, compiled zircon U-Pb ages reveal a prolonged magmatic flare-up of ∼45 Myr; ∼570 to 525 Ma. Basement outcrops in NE Iran expose lower- and upper crust that show how magmatic-geochemical differentiation occurred deep beneath a Cadomian continental arc in a crustal hot zone. Isotopic data for igneous rocks produced during this 45 Myr episode reveal interactions between mantle-derived melts and old continental crust. Synthesis of new and published data indicates that this type of interaction is common during periods of high magmatic fluxes. Our results indicate that differentiation of mafic melts in the lower crust during prolonged magmatic flare-ups plays a key role in building a stratified continental crust.

Description: Most arcs show systematic temporal and spatial variations in magmatism with clear shifts in igneous rock compositions between those of the magmatic front (MF) and those in the backarc (BA). It is unclear if similar magmatic polarity is seen for extensional continental arcs. Herein, we use geochemical and isotopic characteristics coupled with zircon U‐Pb geochronology to identify the different magmatic style of the Iran convergent margin, an extensional system that evolved over 100 Myr. Our new and compiled U‐Pb ages indicate that major magmatic episodes for the NE Iran BA occurred at 110–80, 75–50, 50–35, 35–20, and 15–10 Ma. In contrast to NE Iran BA magmatic episodes, compiled data from MF display two main magmatic episodes at 95–75 and 55–5 Ma, indicating more continuous magmatism for the MF than for the BA. We show that Paleogene Iran serves as a useful example of a continental arc under extension. Our data also suggest that there is not a clear relationship between the subduction velocity of Neotethyan Ocean beneath Iran and magmatic activity in Iran. Our results imply that the isotopic compositions of Iran BA igneous rocks do not directly correspond to the changes in tectonic processes or geodynamics, but other parameters such as the composition of lithosphere and melt source(s) should be considered. In addition, changes in subduction zone dynamics and contractional versus extensional tectonic regimes influenced the composition of MF and BA magmatic rocks. These controls diminished the geochemical and isotopic variations between the magmatic front and backarc.

Description: Networks of identical coupled oscillators display a remarkable spatiotemporal pattern, the chimera state, where coherent oscillations coexist with incoherent ones. In this paper we show quantitatively in terms of basin stability that stable and breathing chimera states in the original two coupled networks typically have very small basins of attraction. In fact, the original system is dominated by periodic and quasi-periodic chimera states, in strong contrast to the model after reduction, which can not be uncovered by the Ott-Antonsen ansatz. Moreover, we demonstrate that the curve of the basin stability behaves bimodally after the system being subjected to even large perturbations. Finally, we investigate the emergence of chimera states in brain network, through inducing perturbations by stimulating brain regions. The emerged chimera states are quantified by Kuramoto order parameter and chimera index, and results show a weak and negative correlation between these two metrics.

Description: As China ramped-up coal power capacities rapidly while CO2 emissions need to decline, these capacities would turn into stranded assets. To deal with this risk, a promising option is to retrofit these capacities to co-fire with biomass and eventually upgrade to CCS operation (BECCS), but the feasibility is debated with respect to negative impacts on broader sustainability issues. Here we present a data-rich spatially explicit approach to estimate the marginal cost curve for decarbonizing the power sector in China with BECCS. We identify a potential of 222 GW of power capacities in 2836 counties generated by co-firing 0.9 Gt of biomass from the same county, with half being agricultural residues. Our spatially explicit method helps to reduce uncertainty in the economic costs and emissions of BECCS, identify the best opportunities for bioenergy and show the limitations by logistical challenges to achieve carbon neutrality in the power sector with large-scale BECCS in China.

Description: With the outbreak of COVID-19, great loss and damage were brought to human society, making the study of epidemic spreading become a significant topic nowadays. To analyze the spread of infectious diseases among different areas, e.g., communities, cities, or countries, we construct a network, based on the epidemic model and the network coupling, whose nodes denote areas, and edges represent population migrations between two areas. Each node follows its dynamic, which describes an epidemic spreading among individuals in an area, and the node also interacts with other nodes, which indicates the spreading among different areas. By giving mathematical proof, we deduce that our model has a stable solution despite the network structure. We propose the peak infected ratio (PIR) as a property of infectious diseases in a certain area, which is not independent of the network structure. We find that increasing the population mobility or the disease infectiousness both cause higher peak infected population all over different by simulation. Furthermore, we apply our model to real-world data on COVID-19 and after properly adjusting the parameters of our model, the distribution of the peak infection ratio in different areas can be well fitted. Network spreading dynamics is a significant issue in network science. Outbreaks of COVID-19 make research on disease transmission even more important and strategies for epidemic prevention are usually proposed from a regional level. Therefore, this paper establishes an epidemic model considering epidemic spreading among areas. In our model, a network is constructed where nodes represent areas, and edges denote migrations between two areas. For each node in the network, there is a dynamic transition among susceptible, infected, and recovered individuals. We give a proof of the stability at the final state of the system and find that the final solution is only related to the infected transition rate and recovery rate. Based on our model, we put forward the peak infected ratio as a significant index to measure the epidemic in different areas and analyze its property by simulation with statistical methods. By changing the structure of the network, we observe different properties of indexes. In addition, the influence of the connection strength of coupling between areas and the infection rate in the Susceptible-Infected-Recovered (SIR) epidemic model on the infected ratio is also investigated. Additionally, we utilize our model to fit epidemical spreading data in the real world.