Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>Surface melt in East Antarctica is strongly correlated with the Southern Annular Mode (SAM) index, but the spatiotemporal variability of the relationship, and the physical processes responsible for it, have not been examined. Here, using melt flux estimates and climate variables from the RACMO2.3p3 regional climate model, we show that a decreasing SAM index is associated with increased melt in Dronning Maud Land primarily owing to reduced precipitation and greater absorption of solar radiation. Conversely, in Wilkes Land, a decreasing SAM index corresponds to increased melt because of greater incoming longwave radiation from a warmer atmosphere. We also demonstrate that SAM‐melt correlations are strongest in December as the melt season develops, and that the SAM’s influence on peak melt intensities in January occurs indirectly through the snowmelt‐albedo feedback. Future work must account for such variability in the physical processes underlying the SAM‐melt relationship to reduce uncertainty in surface melt projections.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Seismic surveys along subduction zones have identified anomalously high ratio of <jats:italic>P</jats:italic>‐ to <jats:italic>S</jats:italic>‐wave velocity (<jats:italic>V</jats:italic><jats:sub><jats:italic>P</jats:italic></jats:sub>/<jats:italic>V</jats:italic><jats:sub><jats:italic>S</jats:italic></jats:sub>) in the subducting oceanic crust that are possibly due to the presence of pore water. Such interpretations postulate that the pore structure is homogeneous at the scale of the seismic wavelength. Here we present the first statistical evidence of a heterogeneous pore structure in oceanic crust at scales larger than laboratory samples. The spatial correlation of measured bulk density profiles of the crustal section of the Samail ophiolite suggests that the pore structure is heterogeneous at scales smaller than ∼1 m. Wave‐induced fluid flow cannot follow the loading during the seismic wave propagation at this estimated heterogeneity, which implies that fluid‐filled microscopic pores and cracks have a limited impact on the observed high <jats:italic>V</jats:italic><jats:sub><jats:italic>P</jats:italic></jats:sub>/<jats:italic>V</jats:italic><jats:sub><jats:italic>S</jats:italic></jats:sub> anomalies in the subducting oceanic crust. Large‐scale cracks may therefore play an important role in shaping these anomalies.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Whether tectonic strain from the early stage India‐Asia collision has synchronously affected the far‐field margin of the Tibetan Plateau is crucial for understanding plateau deformation and growth processes. However, direct evidence for early far‐field deformation remains scarce. Utilizing illite K‐Ar dating of three fault gouge samples, we established the faulting history of the Leibo fault zone (LFZ) at the southeastern margin of the Tibetan Plateau (SEMTP). Consistent authigenic illite ages of 52 ± 2, 54 ± 12 and 55 ± 6 Ma suggest the reactivated thrust faulting of the LFZ in the Early Cenozoic. Positioned ∼700 km east of the collisional boundary and at the intersection of three blocks with distinct lithospheric rheology in strength/viscosity, this event suggests a quasi‐synchronous far‐field tectonic response in the SEMTP to the India‐Asia collision.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The South Asian summer monsoon strongly modulates regional temperature and humidity. While extreme dry heat peaks in the pre‐monsoon season, recent literature suggests that extreme humid heat can continue to build throughout the monsoon season. Here we explore the influence of monsoon onset and subseasonal precipitation variability on the occurrence of extreme wet bulb temperatures (Tw) across South Asia. We find that extreme Tw events often occur on rainy days during the monsoon season. However, the influence of precipitation on Tw varies with the background climatology of surface specific humidity. In climatologically drier areas, positive Tw anomalies tend to occur when precipitation increases due to either early onset or wet spells during the monsoon. In contrast, in climatologically humid areas, positive Tw anomalies occur during periods of suppressed precipitation, including both delayed onset and dry spells during the monsoon.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The baroclinic component of the sea surface height, referred to as steric height, is governed by geostrophically balanced motions and unbalanced internal waves, and thus is an essential indicator of ocean interior dynamics. Using yearlong measurements from a mooring array, we assess the distribution of upper‐ocean steric height across frequencies and spatial scales of O (1–20 km) in the northeast Atlantic. Temporal decomposition indicates that the two largest contributors to steric height variance are large‐scale atmospheric forcing (32.8%) and mesoscale eddies (34.1%), followed by submesoscale motions (15.2%), semidiurnal internal tides (8%), super‐tidal variability (6.1%) and near‐inertial motions (3.8%). Structure function diagnostics further reveal the seasonality and scale dependence of steric height variance. In winter, steric height is dominated by balanced motions across all resolved scales, whereas in summer, unbalanced internal waves become the leading‐order contributor to steric height at scales of O (1 km).</jats:p>

<jats:title>Abstract</jats:title><jats:p>Ultra‐low‐frequency (ULF) waves emerge as pivotal factors in elucidating the mechanisms that drive the intricate dynamics of radiation belt electrons within the plasmasphere and plasmaspheric plumes. Utilizing THEMIS data from September 2012 to September 2017, we conducted a comprehensive statistical analysis of Pc4‐5 ULF waves within and outside the plasmaspheric plume. Our findings reveal a distinctive dawn‐dusk asymmetry in occurrence rate and wave power of poloidal mode waves in the absence of the plume, resembling the toroidal mode asymmetry observed. Poloidal mode waves exhibit a higher likelihood of formation within the plume, while the toroidal mode waves show the opposite trend, contributing to the elevated dusk‐side occurrence rate of poloidal mode waves. Moreover, both wave modes within the plume demonstrate lower peak frequencies compared to waves outside the plume. The global distribution of wave power within the plume suggests higher power at noon than on the dusk side.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Climate models suffer from longstanding precipitation biases, much of which has been attributed to their atmospheric component owing to unrealistic parameterizations. Here we investigate precipitation biases in 37 Atmospheric Model Intercomparison Project Phase 6 (AMIP6) models, focusing on the Indo‐Pacific region during boreal summer. These models remain plagued by considerable precipitation biases, especially over regions of strong precipitation. In particular, 22 models overestimate the Asian‐Pacific monsoon precipitation, while 28 models underestimate the southern Indian Ocean Intertropical Convergence Zone precipitation. The inter‐model spread in summer precipitation is decomposed into Empirical Orthogonal Functions (EOFs). The leading EOF mode features an anomalous anticyclone circulation spanning the Indo‐northwest Pacific oceans, which we show is energized by barotropic conversion from the confluence of the background monsoonal westerlies and trade‐wind easterlies. Our results suggest precipitation biases in atmospheric models, though caused by unrealistic parameterizations, are organized by dynamical feedbacks of the mean flow.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Extreme flood events have regional differences in their generating mechanisms due to the complex interaction of different climate and catchment processes. This study aims to examine the capability of climate drivers to capture year‐to‐year variability in global flood extremes. Here, we use a statistical attribution approach to model seasonal and annual maximum daily discharge for 7,886 stations worldwide, using season‐ and basin‐averaged precipitation and temperature as predictors. The results show robust performance of our seasonal climate‐informed models in describing the inter‐annual variability in seasonal and annual maximum discharges regardless of the geographical region, climate type, basin size, degree of regulation, and impervious area. The developed models enable the assessment of the sensitivity of flood discharge to precipitation and temperature changes, indicating their potential to reliably project changes in the magnitude of flood extremes.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Taking advantage of a large ensemble of Convection Permitting‐Regional Climate Models on a pan‐Alpine domain and of an object‐oriented dedicated analysis, this study aims to investigate future changes in high‐impact fall Mediterranean Heavy Precipitation Events at high warming levels. We identify a robust multi‐model agreement for an increased frequency from central Italy to the northern Balkans combined with a substantial extension of the affected areas, for a dominant influence of the driving Global Climate Models for projecting changes in the frequency, and for an increase in intensity, area, volume and severity over the French Mediterranean. However, large quantitative uncertainties persist despite the use of convection‐permitting models, with no clear agreement in frequency changes over southeastern France and a large range of plausible changes in events' properties, including for the most intense events. Model diversity and international coordination are still needed to provide policy‐relevant climate information regarding precipitation extremes.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Subtle bedrock depressions called gnammas allow the water in ephemeral pools to maintain contact with bare rock, thus serving as natural rock‐weathering experiments. Following filling by precipitation, evaporation is often assumed to be the sole process of water loss from gnammas. We evaluated this assumption by monitoring evolving stable isotope compositions of gnamma waters hosted in granite of Colorado's Front Range. Surprisingly, we found that a significant fraction of the water was lost by seepage through the underlying bedrock. Seepage dominated, with only 10%–20% loss by evaporation. We propose a conceptual model of gnamma formation in which enhanced weathering of the bedrock beneath the gnamma increases the water holding capacity and permeability of the underlying rock that in turn promotes efficient water loss through seepage and further weathering of the surrounding rock. This model has implications for bare‐rock weathering and hence the evolution of landscapes over geologic timescales.</jats:p>