Geophysical Research Letters

Abstract Marine cold‐air outbreaks (MCAOs) are key conduits of polar‐to‐midlatitude air‐mass exchange, strongly modulating wintertime air–sea heat fluxes, storm‐track activity, and the development of extreme cold conditions over adjacent continents. The drivers of recent trends of MCAOs in the Northern Hemisphere remain unclear. Using the CESM1 Large Ensemble, we decompose wintertime MCAO frequen…

Abstract Rising‐tone chorus elements are traditionally known to grow from low frequencies and extend to high frequencies. Using high‐resolution waveform measurements from the Van Allen Probes, we report a novel observation: equatorward‐propagating chorus waves at a few degrees in latitude are observed at high frequencies only. As these rising‐tone chorus waves propagate equatorward and approach t…

Abstract The water‐rich mantle transition zone, coupled with the low water storage capacity of the upper mantle, suggests that dehydration melting occurs just above the mantle transition zone near the 410‐km discontinuity. However, the melt fraction produced by the dehydration melting process remains poorly constrained. Here, we investigated the melt fractions of the peridotite +1 wt.% H 2 O syst…

Abstract SWOT resolves sea surface height at spatial scales where geostrophic balance may break down and ageostrophic motions become significant, making identification of the transition scale essential. We test whether wind generated waves provide an independent diagnostic of this transition. WAVEWATCH III was forced with high resolution surface currents decomposed into geostrophic and ageostroph…

Abstract As a key process in magnetosphere‐ionosphere coupling, plasmaspheric refilling is a long‐standing focus in space physics. In this study, we develop a global electron density (GEO‐NE) model based on a CNN‐Transformer architecture, and use the model to investigate plasmaspheric electron density refilling rates. Using global electron density maps reconstructed by the model, we perform stati…

Abstract Accurate and timely reconstruction of sea surface wind fields from available scatterometer‐derived observations is essential for rapid‐response forecasting and operational oceanography. In this study, we explore a novel physics‐guided generative learning network to reconstruct sea surface wind vector fields directly from sparse scatterometer‐like inputs. The proposed method integrates da…

Abstract Atmospheric wind‐pressure covariances (e.g., vertical wind‐pressure covariance, ) affect boundary‐layer energetics and pressure‐related corrections, yet their sign and vertical structure are inconsistently reported. Here, we use a regime‐spanning suite of large‐eddy simulations to quantify how the stability, surface roughness, and wind speed control and its vertical gradient, and to test…

Abstract Extreme vapor pressure deficit (EVPD), representing the 5% hottest and driest surface air conditions, has risen rapidly over the Southern Amazon during the dry season, especially over forested areas. Its frequency has increased by 7 1.5% (or 11 more dry season days) per decade, and its intensity has increased at rates faster than that of mean vapor pressure deficit (VPD), primarily due t…

Abstract Condor Seamount is among the most seismically active regions on the Azores Plateau. In December 2019, an earthquake crisis occurred at the tip of the seamount, which was strongly felt on nearby islands. Two months after the peak of the crisis, we deployed a local network of five ocean‐bottom seismometers around the seamount, recording seismicity over 3 months. Using a machine‐learning‐ba…

Abstract Solar wind (SW) entry into the magnetosphere occurs through several mechanisms, but their dependence on the properties of different ion species is unknown. We compare measurements from Wind‐STICS (magnetosphere) with ACE‐SWICS (L1) to test for any preferential entry between He 2+ and SW heavy ions. We utilize a scaling factor, , between upstream and magnetospheric measurements of [ + + ]…

Abstract The hydroxyl radical (OH) is a key oxidant for methane. Previous studies suggest that OH exhibits interannual variability linked to the El Nino–Southern Oscillation (ENSO), but the sign, magnitude, and underlying mechanisms of this response remain uncertain. We diagnose changes in OH using the CAM‐chem chemistry–climate model with prescribed sea surface temperature composites correspondi…

Abstract Saturn's Kilometric Radiation (SKR) is a powerful non‐thermal radio auroral emission produced by the Cyclotron Maser Instability (CMI), which generates waves close to the local cyclotron frequency in a highly magnetized plasma from mildly relativistic electrons. The source of free energy for SKR was identified by Cassini to be the monoenergetic shell (horseshoe) distributions of 6–12 keV…

Abstract The distinctive pattern of observed Pacific surface temperature trends, with cooling in the east and intensified warming in the west, departs from the more uniform warming anticipated by climate models. The apparent inability of climate models to simulate this warming pattern limits our ability to understand why it is occurring and to predict its wide‐ranging impacts. Here we demonstrate…

Abstract Geological records strongly suggest that, globally, Earth's atmosphere was much dustier than present during the Last Glacial Maximum (LGM) but the explanation is debated, with greater aridity, stronger/gustier winds and less effective washout from a drier atmosphere all invoked. Yet dust deposition can be spatially complex. Both the North Atlantic Ocean and Mediterranean Sea receive dust…

Abstract Seasonal exchange between modified Circumpolar Deep Water (mCDW) and dense shelf water shapes Antarctic Bottom Water in the Ross Sea, making year‐round hydrographic observations indispensable, yet winter observations remain scarce. Miniaturized CTD tags deployed on 64 Weddell seals in Terra Nova Bay during three years relayed 22,661 profiles across the shelf, supplemented by 43 ship‐base…

Abstract An intense seismic swarm started on 27 January 2025 in the Santorini‐Amorgos region and lasted for approximately 45 days. A widely observed seismic tremor on 14 February 2025 suggested a volcanic origin for the 2025 Santorini crisis. Here we present an in‐depth combined seismological analysis of the earthquakes and tremors that occurred during the crisis. We observe two distinct families…

Abstract Among European countries, Italy ranks as one of the most susceptible to flood risk. While this figure is already substantial, climate change and rapid urbanization in flood‐prone areas have been identified as the two main drivers expected to elevate the number of individuals at risk. This study offers a comprehensive assessment of these two drivers of flood risk in Italy over 230 years, …

Abstract Tectonic tremor is a long‐duration noise‐like seismic signal associated with slow fault motion at major plate boundaries. Due to their remarkable sensitivity to stress perturbations, tremors serve as invaluable probes of the mechanical state and stress conditions deep within fault zones. Near the Mendocino Triple Junction, a tremor cluster ceased abruptly following each of three Mw 6.0+ …

Abstract Deep learning hydrological models rely on static catchment attributes to characterize basin heterogeneity, but these traditional descriptors suffer from regional inconsistency and limited temporal representativeness. This study evaluates geospatial foundation model embeddings (from AlphaEarth and StefaLand) as transferable catchment descriptors for rainfall‐runoff modeling. Temporal vali…

Abstract Doppler frequency shifts (DFSs) recorded by continuous wave‐high frequency Doppler sounding systems and ionograms observed by five ionosondes in Taiwan and Japan are used to study three‐dimensionally seismo‐ and tsunami‐traveling ionospheric disturbances (STIDs and TTIDs) triggered by the 29 July 2025 Mw8.8 Kamchatka earthquake. Prominent STIDs in DFSs travel horizontally with the supers…