Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>Temporal changes in seismic velocity estimated from ambient seismic noise can be utilized to infer subsurface properties at volcanic systems. In this study, we process 7 years of continuous seismic noise at Axial Seamount and use cross‐correlation functions to calculate the relative seismic velocity changes (<jats:italic>dv</jats:italic>/<jats:italic>v</jats:italic>) beneath the caldera. We find a long‐term trend of decreasing velocity during rapid inflation, followed by slight increase in velocities as background seismicity increases and inflation rate decreases. Furthermore, we observe small short‐term increases in <jats:italic>dv</jats:italic>/<jats:italic>v</jats:italic> which coincide with short‐term deflation events. Our observations of changes in <jats:italic>dv</jats:italic>/<jats:italic>v</jats:italic> and their correlation with other geophysical data provide insights into how the top ∼1 km of the crust at Axial Seamount changes in response to subsurface magma movement and capture the transition from a period of rapid reinflation to a period where the caldera wall faults become critically stressed and must rupture to accommodate further inflation.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The Gulf of Lion, Northwestern Mediterranean Sea, is one of few oceanic regions where deep convection occurs. We investigate the restratification following a convection event using measurements from an ocean glider equipped with turbulence microstructure sensors. This unique combination of instruments provides a high‐resolution description of the mixed layer with regard to turbulence, stratification and chlorophyll. We observe a rapid restratification process that proceeds over a timescale of days to one week. We find that restratification exerts a leading order control on surface mixed layer turbulence variability, as abrupt changes in turbulence dissipation rates are associated with the formation of near‐surface stratification. The near‐surface formation of stratification occurs through both the diurnal variability in surface buoyancy fluxes and through lateral advective processes. We conclude that daily near‐surface processes that influence stratification control mixed layer turbulence levels, and thus the phytoplankton response in the critical transition period to spring bloom.</jats:p>

<jats:title>Abstract</jats:title><jats:p>An earlier model of the electron distribution function accounts for the pressure anisotropy that develops in the inflow regions during anti‐parallel magnetic reconnection. However, the model is not applicable to the electron diffusion region (EDR), where the electron magnetic moments break as an adiabatic invariant. The earlier model is here generalized through the use of the current‐sheet adiabatic invariant of a 1D current layer, to become applicable also to the EDR. The new generalized model reproduces the main features of the EDR and its vicinity observed in a fully kinetic simulation, formally proving the 1D equilibrium relationship between the upstream electron pressure anisotropy and the EDR electron jets.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Terrestrial gamma ray flashes (TGFs) are short bursts of gamma rays occurring during thunderstorms. They are believed to be produced by relativistic runaway electron avalanches (RREAs). It is usually admitted that the number of high‐energy electrons produced in the brightest TGFs remains mostly confined within a range from 10<jats:sup>17</jats:sup> to 10<jats:sup>19</jats:sup>. To understand the constraints in the development of RREAs, we perform self‐consistent simulations using a newly developed model with a finite acceleration region and various injection rates. We find that RREAs should naturally self‐quench for a fixed total number of runaway electrons, and hence a fixed number of bremsstrahlung photons. From the idea that TGF sources quench themselves, we derive a simple equation controlling the total number of runaway electrons. In this framework, the existence of a saturation in the electron density discovered in a previous work places a lower limit on TGF durations.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Atmospheric Rivers (ARs) are synoptic‐scale conduits for poleward transport of heat and water, often associated with extreme rainfall. Using NASA surface heat flux observations and climate model simulations, we assess whether ARs are “rivers”, transporting heat and moisture over longer distances, or mostly local convergence. The observations indicate that ARs reduce extratropical surface energy fluxes, even during early development. This damping of surface fluxes during ARs is also simulated in the Goddard Institute for Space Studies ModelE, 2.1 (GISS‐E2.1) nudged to (MERRA2) reanalysis winds. Furthermore, water provenance tracers in GISS‐E2.1 identify the moisture source for ∼7,500 ARs globally during 2018–2022 as farther upstream and equatorward compared to climatology. These results quantitatively show that ARs source relatively less moisture from the surface beneath them and more from a greater distance than during non‐AR times.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Deserts play an important role in the climate system, which is closely associated with the emission and transport of dust aerosols. Based on the intensive observation experiment in the Taklimakan Desert, the potential physical processes between the deep convective boundary layer (CBL) and dust emission are revealed in this study. Deep CBL enables the formation of clouds in the late afternoon, leading to significant cooling of surface. Large‐scale buoyant coherent structures thereby transform into the mechanical coherent structures confined near the surface. The responses promote the earlier occurrence of low‐level jet (LLJ) than in cloudless conditions, which allows the downward transport of LLJ momentum and substantially increases surface wind. Therefore, dust emission is initiated by strong wind at dusk and lasts for several hours. The results are useful to predict dust emissions and improve our understanding of distinctive boundary‐layer processes in desert regions.</jats:p>

<jats:title>Abstract</jats:title><jats:p>We compare abrupt CO<jats:sub>2</jats:sub>‐quadrupling (abrupt‐4xCO2) and ‐doubling (abrupt‐2xCO2) simulations across 10 CMIP6 models. Two models (CESM2 and MRI‐ESM2‐0) warm substantially more than twice as much under abrupt‐4xCO2 than abrupt‐2xCO2, which cannot be explained by the non‐logarithmic scaling of CO<jats:sub>2</jats:sub> forcing. Using an energy balance model, we show that increased warming rates within these two models are driven by both less‐negative radiative feedbacks and smaller global effective heat capacity under abrupt‐4xCO2. These differences are caused by a decrease in low cloud cover <jats:italic>and</jats:italic> shallower ocean heat storage, respectively; both are linked to smaller fractional declines in the Atlantic Meridional Overturning Circulation (AMOC) under abrupt‐4xCO2 (relative to abrupt‐2xCO2). On a global scale, higher climate sensitivity under larger forcing can be explained by a feedback‐temperature dependence; however, we find that forcing‐dependent spatial warming patterns due to AMOC decline are an important physical mechanism which reduces warming in a way that is not captured by a global‐mean framework.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The surface solar irradiance (SSI) is crucial for the land‐atmosphere processes and remarkably affected by the topography over the rugged areas. However, the Coupled Model Intercomparison Project Phase 6 (CMIP6) HighResMIP models adopting the parallel‐plane radiative scheme without considering the sub‐grid terrain solar radiative effects (3DSTSRE) overestimate the SSI in the rugged areas and the overestimation increases with the sub‐grid terrain complexity. To reduce the biases of the SSI simulations, this study offline corrects the SSI simulations of CMIP6 HighResMIP models by a 3DSTSRE scheme. Results show that the SSI biases produced by the HighResMIP models in the rugged regions can be significantly reduced by adopting the 3DSTSRE offline correction, and the improvements increase with the sub‐grid terrain complexity, indicating that considering the 3DSTSRE in the climate models to improve the SSI simulations over rugged areas is necessary.</jats:p>

<jats:title>Abstract</jats:title><jats:p>There is growing evidence that marine microorganisms may influence cloud cover over the ocean through their impact on sea spray and trace gas emissions, further forming cloud droplets or ice crystals. However, evidence of a robust causal relationship based on observations is still pending. In this study, we use 4 years of multi‐instrument satellite data to segregate low‐level clouds into ice‐containing and liquid‐water clouds to obtain clear relationships between cloud types and ocean biological tracers, especially with nanophytoplankton cell abundances. Results suggest that microorganisms may be involved in compensating effects on cloud properties, increasing the frequency of occurrence of warm‐liquid clouds, and decreasing the occurrence of ice‐containing clouds in most regions during springtime. The relationships observed in most regions do not apply to the South Pacific Ocean in the 40°S–50°S latitude band. These results shed light on overlooked potential compensating effects of ocean microorganisms on cloud cover.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Forecast of eruptive activity is a core challenge in volcanology. Here, we present an actual forecast for the end of the 2021 La Palma eruption. Using continuous GNSS data, we identified a co‐eruptive quasi‐exponential deflation trend. Assuming mass conservation, magma upflow from an overpressurized reservoir drives the eruptive process. The forecast was carried out during the eruption, however there was uncertainty in the key percentage of drop in driving pressure necessary to stop this eruption. In hindcast, we explore how forecast uncertainty reduces with increase in ingested near‐real time data. We conclude that precise forecasts could have been possible, but only after twice a characteristic exponential decay time‐scale, providing error estimates of 45% of the actual duration. We verify the mass conservation assumption using eruptive material volumes and propose that the eruption dynamics was controlled by a main reservoir at a depth close to Moho discontinuity beneath Cumbre Vieja volcano.</jats:p>