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Source: AGU Advances

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

众所周知，二氧化碳（CO2）浓度上升会导致地球大气温度升高。但缓慢的反馈过程，包括海洋的热量储存和碳循环的变化，意味着这种温度变化有时不会立即显现；地球可能需要数十年甚至数千年才能达到平衡。

然而，不同的气候模型对于何时达到这种平衡的预测却大相径庭。造成这些差异的原因之一是“模态效应”，即海面温度的不均匀变化会形成不同的海洋变暖模式，进而影响大气环流，最终影响云量、降水和热量传递。这些因素之间的复杂相互作用会加剧或减缓变暖，并影响气候对温室气体的敏感性。

帮助预测长期变暖模式的一种方法是回顾过去。挖掘古气候数据中的模式，特别是来自地球气候温暖时期的数据，可以为未来的变暖模式提供线索。刘小庆、张一歌等人分析了过去1000万年的海洋表面温度记录，以确定在二氧化碳浓度上升的情况下，不同海洋区域的相对升温情况。

该研究以地球上最大、最温暖的表层水体——西太平洋暖池为参考点，将其海表温度数据与其他17个海洋站点的海表温度数据进行比较，从而建立全球变暖模式。

随后，研究人员随后将这些古气候数据中显示的升温情况与几个模拟模型的结果进行比较，这些模型模拟了二氧化碳浓度相对于工业化前水平突然增加四倍的情况。他们发现，古气候数据和模型结果显示出相似的千年尺度升温模式，尤其是在高纬度地区。然而，当两者与过去160年的海表温度测量数据进行比较时，升温模式出现了显著的差异。受海洋热吸收的影响，现代升温仍处于过渡状态，而古气候模式则代表了完全的平衡响应。

研究人员指出，要达到新的平衡需要数千年的时间。该研究表明，与目前的瞬时气候变化相比，未来在中高纬度地区，包括北太平洋、北大西洋和南大洋的升温模式将更为显著。这种高纬度地区的升温幅度可能超过之前的估计，并且在千年尺度上的预测比在百年尺度上的预测更为明显。(AGU Advances, https://doi.org/10.1029/2025AV001719, 2025)

—科学撰稿人Rebecca Owen (@beccapox.bsky.social)

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AbstractThe rheological properties of the mantle govern plate tectonics and mantle convection, yet constraining the rheological parameters remains a significant challenge. Laboratory experiments are usually performed under different temperature-pressure-strain-rate conditions than those of natural environments, leading to substantial uncertainties when extrapolating the parameters to real-world conditions. While traditional Bayesian inversion with Monte Carlo sampling methods offers sufficient exploration of the parameter space and accurate inversion results, the excessive computational cost limits its practical application to complex nonlinear problems. To address these limitations, we integrate finite-difference-based geodynamic forward modeling with Automatic Differentiation (AD) to build a framework to invert non-linear rheological parameters. By incorporating multisource observational data, including surface velocities and topography, we are able to invert critical rheological parameters of the lithosphere and mantle, including the viscosity pre-exponential factor, activation energy, stress exponent, yield stress, and plate-interface viscosity. To validate the method, a series of models with different levels of complexity from single- to multiple-subduction systems and consideration of data noises are designed to generate synthetic data that are further used for inversion. Our method can successfully restore the rheological parameters under various conditions, with minimal errors between predicted and true values, underscoring its stability and broad applicability. In general, this study introduces a highly efficient and practical geodynamic forward and inverse modeling approach that can be used to infer the rheology of the mantle.

AbstractSeismic waveforms are essential for deciphering the subsurface structures of the Earth. Traditional methods for seismic waveform selection rely heavily on manual identification by experienced seismologists, which can be inconsistent and challenging when complex structures or huge amount of seismic data volumes are involved. Recent advancements in machine learning, particularly supervised learning techniques, have shown promising progress in addressing these challenges; however, their dependence on large labeled datasets limits their application to weak or rare seismic phases. In this study, we propose a new strategy using hierarchical clustering for seismic waveform identification, which does not need labeled dataset and minimizes extensive parameter settings. Our strategy is especially powerful when dealing with multiple waveform phases that may shift according to epicentral distance or may be distorted due to attenuation or other factors. We apply our strategy to identify various seismic wave of both P and S phases, especially those sampling deep Earth such as SKS-SKPdS and ScP phases. The results show that the strategy performs excellently and can identify different anomalous signals. Our approach empowers researchers to conduct more detailed studies in previously overlooked regions or datasets, thereby leading to a better understanding of deep Earth’s structures.

SUMMARYRock glaciers are specific landforms consisting of a mixture of rock debris, ice, liquid water, and air. In the Alps, active rock glaciers are generally found at high elevations above 2500 m. Active rock glaciers creep and can develop anomalous slide-like behaviors called destabilization. Induced polarization is a non-intrusive geophysical method that has proven to be sensitive to the hydrogeological properties of porous media. In August 2023, we performed four induced polarization profiles at Plan-du-Lac (Vanoise, France), on a multi-unit rock glacier complex with a front located at a low altitude of 2200 m). Our goal was to determine its architecture and its water and ice contents in relation with its activity rate. The survey included two transverse high-resolution profiles with a 5 m spacing between the electrodes and two other longitudinal profiles with a 20 m spacing between the electrodes allowing a depth of investigation of roughly 200 m to image the rock glacier from its terminal front up to its root. The conductivity and normalized chargeability tomograms were inverted and then used to get the water content and cation exchange capacity (a proxy for the clay content) tomograms. In most of the units, ice has disappeared and the landforms associated with the former rock glacier were characterized by low water and clay contents with respect to the basement. This was consistent with these units being mostly formed by rock debris with a low water saturation except at their bases, which are water-saturated. Ice remains were found at the roots of the rock glacier, with a volume content up to ∼10 per cent (vol. per cent) for profile P2 and 16 per cent for profile P4. The roots of the rock glacier complex were still creeping as shown by InSAR data. This case study demonstrates the usefulness of the induced polarization method to quantitatively characterize gravitational instabilities associated with coarse materials and transitional rock glaciers.

SUMMARYIn October 2023, an earthquake sequence comprising four ∼ MW 6.0 events struck Herat Province in northwestern Afghanistan, causing severe casualties and property losses. The geometry of seismogenic faults and the mechanisms of the earthquake sequence are essential for regional seismic hazard assessment, but still remain poorly constrained. With Interferometric Synthetic Aperture Radar (InSAR) techniques, we extracted high-resolution co- and early post-seismic deformations of the events. Through a two-step inversion method, we inferred the geometry of the causative faults and the distributed slip models. The earthquake sequence ruptured two intersecting low-dip thrust faults, indicating that the complex geometry may have played a key role in controlling the propagation of the events. The ruptures of the four major events are clearly imaged at depths of 1-10 km without reaching the surface, showing a pattern of first spreading westwards, then jumping eastwards to the bend segment, and finally rupturing an adjacent fault. Post-seismic deformation further reveals reactivation of a secondary fault splay which underwent afterslip. Shallow afterslip up-dip of the co-seismic rupture dominates post-seismic deformation during 10 months following the earthquake sequence. Relying on the evolution of afterslip, we infer that significant rate-strengthening property in the shallow bend section may have hindered further co-seismic rupture propagation. Combining obtained results and the complex geological setting of the Herat region, we suggest that the earthquake sequence reflects N-S crustal shortening between two branches of the western Herat Fault System.

SUMMARYIn the last decade, the Dynamic Stern Layer (DSL) model has proven to be a reliable petrophysical model to comprehend induced polarization data at various scales from the representative elementary volume of a porous rock to the interpretation of field data. Preliminary works have demonstrated that such model can be extended to understand the induced polarization properties of ice-bearing rocks and to interpret field-acquired induced polarization data in the context of permafrost. That being said, the direct effect of ice was let aside. We first review the DSL model in presence of ice and discuss the role of ice as an interfacial protonic dirty semi-conductor in the complex conductivity spectra with an emphasis on the role of the complex-valued surface conductivity of ice crystals above 1 Hz. We propose a new combined polarization model including indirect and direct ice effects. By direct effects, we mean the effects associated with change in the liquid water content and salinity of the pore water. By direct effect, we mean the role of the interfacial properties of the ice surface and liquid water is still present in the pore space of the porous composite. In this case, the electrical current is not expected to cross the ice crystals. Instead, it would polarize the surface of the ice crystals and generate a very high chargeability that can reach one depending on the value of the volumetric content of ice. We apply the DSL model to a new set of complex conductivity spectra obtained in the frequency range 10 mHz-45 kHz using a collection of 25 rock samples including metamorphic and sedimentary rocks in the temperature range + 15/+20°C to -10/-15°C. We observe that the model explains very well the observed data in the low-frequency range (10 mHz-1 Hz) without any direct contribution of ice. In the high frequency range (above 1 Hz), we observe a weak contribution possibly associated with the contribution of ice crystals. We establish under what conditions the direct contribution of ice can be neglected. We also investigate the role of porosity, cation exchange capacity, and freezing curve parameters on the complex conductivity spectra of crystalline and non-crystalline rocks during freezing. Laboratory experiments demonstrate that in most field conditions including permafrost conditions, surface conductivity associated with conduction on the surface of clay minerals (and alumino-silicates in general) is expected to dominate the overall conductivity response. Therefore Archie’s law cannot be used as a conductivity equation in this context because of the contribution of surface conductivity. A large experimental and field dataset at the Aiguille du Midi (3842 m a.s.l., French Alps) for the resistivity versus temperature data of granitic rocks demonstrates the role of surface conductivity in the overall conductivity of the rock.

A research group led by Prof. Sun Xiaobing from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, investigated the impact of multiangular polarimetry on the quantification of marine aerosol remote sensing applications.

If you know what diatoms are, it's probably because of their beauty. These single-celled algae found on the ocean floor have ornate glassy shells that shine like jewels under the microscope.

Melting of the Antarctic ice sheet due to global warming has long-term, irreversible societal impacts with important implications for people around the world. Spatial patterns of sea level change from ice sheet mass loss vary in cause, and have worldwide impacts.

Tulane University researchers, collaborating with an international team of scientists, have discovered why some parts of Earth's crust remain strong while others give way, overturning long-held assumptions about how continents break apart.

An international study presents the first global assessment of blue carbon accumulated in the living parts of seagrass plants. According to the results, their leaves, rhizomes and roots store up to 40 million tons of carbon worldwide.

For nearly a decade, Leigh Stearns and collaborators aimed a laser scanner system at Greenland's Helheim Glacier. Their long-running survey reveals that Helheim's massive calving events don't behave the way scientists once thought, reframing how ice loss contributes to sea-level rise.

Three new high-profile studies led by Dr. Yi Yao (Vrije Universiteit Brussel and ETH Zurich) show that while irrigation may be seen as a tool to dampen heat extremes, its benefits will come with adverse impacts.

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