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Geophysical Research Letters
American Geophysical Union
Geophysical Research Letters

American Geophysical Union

0094-8276

Geophysical Research Letters/Journal Geophysical Research LettersSCIISTPAHCIEI
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    Greenland Ice Sheet Rainfall, Heat and Albedo Feedback Impacts From the Mid‐August 2021 Atmospheric River

    Adrien WehrléDirk AsRobert S. FaustoKristian K. Kjeldsen...
    11页
    查看更多>>摘要：Abstract Rainfall at the Greenland ice sheet Summit 14 August 2021, was delivered by an atmospheric river (AR). Extreme surface ablation expanded the all‐Greenland bare ice area to near‐record‐high with snowline climbing up to 788?±?90?m. Ice sheet wet snow extent reached 46%, a record high for the 15–31 August AMSR data since 2003. Heat‐driven firn deflation averaged 0.14?±?0.05?m at four accumulation area automatic weather stations (AWSs). Energy budget calculations from AWS data indicate that surface heating from rainfall is much smaller than from either the sensible, latent, net‐longwave or solar energy fluxes. Sensitivity tests show that without the heat‐driven snow‐darkening, melt at 1,840?m would have totaled 28% less. Similarly, at 1,270?m elevation, without the bare ice exposure, melting would have been 51% less. Proglacial river discharge was the highest on record since 2006 for late August and confirms the melt‐sustaining effect of the albedo feedback.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    Decadal and Long‐Term Variability of Sea Level in the Southwestern Pacific During 1948–2018

    Jingxuan SunLinlin ZhangDunxin Hu
    10页
    查看更多>>摘要：Abstract Decadal and long‐term variability of sea level in the Southwestern Pacific (SWP) was investigated by using tide gauge measurements obtained near New Zealand during 1948–2018 and a 1.5‐layer reduced gravity model. After the removal of the global mean sea level, there still exists a prominent positive trend and strong decadal oscillations in SWP sea level, which are attributed to the Southern Annular Mode (SAM) and Interdecadal Pacific Oscillation (IPO), respectively. On the long‐term time scale, the intensification of local wind stress curl associated with strengthening SAM contributes to SWP sea level rise (SLR) through Ekman convergence. On the decadal scale, locally generated and westward propagating signals induced by IPO exert comparable influences on sea level variations in the SWP. Results from multivariable linear regression suggest that SAM can account for almost all the long‐term SLR, and IPO explains approximately 58% of the decadal variability.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    Distribution of Negative J·E′ in the Inflow Edge of the Inner Electron Diffusion Region During Tail Magnetic Reconnection: Simulations Vs. Observations

    Q. Y. XiongS. Y. HuangM. ZhouZ. G. Yuan...
    9页
    查看更多>>摘要：Abstract Magnetic reconnection is a universal phenomenon existing in the space. Energy conversion is one of the essential parts of reconnection discussed for decades. Positive energy conversion (J·E′?>?0) is usually regarded as the sign of electron diffusion region (EDR), while the negative one (J·E′?<?0) turns out to gather in the outer EDR. Here we report the negative J·E′ appearing in the inflow edge of the inner EDR, based on Magnetospheric Multiscale mission observations and particle‐in‐cell simulations. Both observations and simulations verify that this negative J·E′ is mainly contributed from the electron pressure tensor term in generalized Ohm's law. The energy loss of electrons plays the dominant effect in the electron pressure tensor, and this energy decline is caused by the electric field which is induced by the decreasing magnetic field. Our results provide significant insights to expand the understanding of the reconnection regimes.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    The Rise of Atmospheric Evaporative Demand Is Increasing Flash Droughts in Spain During the Warm Season

    I. NogueraS. M. Vicente‐SerranoF. Domínguez‐Castro
    12页
    查看更多>>摘要：Abstract Flash droughts are characterized by rapid development and intensification, generating a new risk for drought impacts on natural and socio‐economic systems. In the current climate change scenario, the meteorological drivers involved in triggering flash droughts are uncertain. We analyzed the role of meteorological drivers underlying the development of flash droughts in Spain over the last six decades, evidencing that the effect of atmospheric evaporative demand (AED) on flash drought is mainly restricted to water‐limited regions and the warm season. However, the contribution of the AED has increased notably in recent years and particularly in summer (～3.5% per decade), thus becoming a decisive driver in explaining the occurrence of the latest flash droughts in some regions of Spain. Our findings have strong implications for proper understanding of the recent spatiotemporal behavior of flash droughts in Spain and illustrate how this type of event can be related to global warming processes.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    Arrival of New Great Salinity Anomaly Weakens Convection in the Irminger Sea

    T. C. BilóF. StraneoJ. HolteI. A.‐A. Le Bras...
    10页
    查看更多>>摘要：Abstract The Subpolar North Atlantic is prone to recurrent extreme freshening events called Great Salinity Anomalies (GSAs). Here, we combine hydrographic ocean analyses and moored observations to document the arrival, spreading, and impacts of the most recent GSA in the Irminger Sea. This GSA is associated with a rapid freshening of the upper Irminger Sea between 2015 and 2020, culminating in annually averaged salinities as low as the freshest years of the 1990s and possibly since 1960. Upon the GSA propagation into the Irminger Sea over the Reykjanes Ridge, the boundary currents rapidly advected its signal around the basin within months while fresher waters slowly spread and accumulated into the interior. The anomalies in the interior freshened waters produced by deep convection during the 2017–2018 winter and actively contributed to the suppression of deep convection in the following two winters.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    Present‐Day Strike‐Slip Faulting and Thrusting of the Kepingtage Fold‐and‐Thrust Belt in Southern Tianshan: Constraints From GPS Observations

    Jie LiYuan YaoRui LiSulitan Yusan...
    11页
    查看更多>>摘要：Abstract Across inherited complex fold‐and‐thrust belts (FTBs), shortening may be accommodated at different rates depending on structural style variations; such cases have rarely been documented We present the example of the Kepingtage FTB in southern Tianshan, which is bisected by the NNW‐trending left‐lateral strike‐slip Piqiang Fault (PQF) into eastern and western segments. The 1.45?±?0.31–2.10?±?0.42?mm/a shortening rate of the eastern segment is accommodated in a diffuse‐deformation pattern within the five‐row thrust‐anticlinal zone and the 2.36?±?0.23–3.70?±?0.59?mm/a shortening rate of the western segment is accommodated within the two‐row thrust‐anticlinal zone at the FTB front. To accommodate the latitudinal variability, the PQF exhibits a 2.30?±?0.20–4.10?±?0.40?mm/a segmentation strike‐slip rate. The 2.35?±?0.33–4.20?±?0.45?mm/a shortening rate of the Kepingtage FTB and southern Tianshan Fault is one‐third of the total convergence rate between the Tarim Basin and Kazakh Platform at 77°–79°E; hence, the complex Tianshan deformation occurred mainly at the FTB.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    Issue Information

    2页
    查看更多>>摘要：No abstract is available for this article.
      原文链接:
    • NSTL

    Early‐to‐Late Winter 20th Century North Atlantic Multidecadal Atmospheric Variability in Observations, CMIP5 and CMIP6

    Thomas J. Bracegirdle
    9页
    查看更多>>摘要：Abstract The strong multidecadal variability in North Atlantic (NA) winter atmospheric circulation is poorly understood and appears too weak in climate models. Recent research has shown peak atmospheric multidecadal variability over the NA in late winter, particularly March, linked to Atlantic multidecadal variability (AMV) of the ocean. Here a range of NA atmospheric circulation indices are assessed to provide a comprehensive picture of early‐to‐late winter low‐frequency variability and its representation in the latest generation of climate models (Coupled Model Intercomparison Project Phase 6 [CMIP6]). As found for CMIP5, CMIP6 models exhibit too‐weak multidecadal NA atmospheric variability compared to reanalysis data over the period 1862–2005. Consistent with previous research, the eastern part of the NA westerly jet (U700NA) exhibits peak low‐frequency variability in March. However, for NA‐wide jet speed and the NAO, low‐frequency variability and model‐reanalysis discrepancies are strongest in January and February, associated with too‐weak NA ocean‐atmosphere linkages.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    Reconstruction of Violent Tornado Environments in Europe: High‐Resolution Dynamical Downscaling of ERA5

    Natalia PilgujMateusz TaszarekMaciej KryzaHarold E. Brooks...
    12页
    查看更多>>摘要：Abstract Approximately 1–3 violent tornadoes hit Europe each decade. We use the ERA5 reanalysis and WRF model to reconstruct environments for 12 cases between 1957 and 2021. Violent tornadoes in Europe occur in a variety of synoptic and mesoscale patterns, but they share environmental similarities with significant tornadoes from the United States. Downscaling simulations to 3?km grid‐spacing showed the added value of improved resolution in representing local convective environments. In 8 out of 12 simulations, the model indicated updraft helicity (UH) tracks in a favorable convective environment in spatial (+/?50?km) and temporal (+/?3?hr) proximity to the tornado report. Tornadoes were accompanied by a mean 0–6?km wind shear of 24.3?m?s?1 and mean convective available potential energy of 1678?J kg?1. The combination of UH tracks with convective environments offers promising results for operational forecasting in Europe, and should be explored in future studies.
      原文链接:
    • NSTL
    • Amer Geophysical Union

    A Semi‐Empirical Approach for Tsunami Inundation: An Application to the Coasts of South Italy

    Lorenzo MelitoFrancesco LalliMatteo PostacchiniMaurizio Brocchini...
    12页
    查看更多>>摘要：Abstract Tsunamis in the Mediterranean Sea have been increasingly investigated recently due to past destructive events. We present a novel operational approach for evaluating tsunami‐induced inundation, based on a generalization of Green's law and a chain of intermediate and small‐scale simulations. At the intermediate level, simulations with a linear solver are made to identify the distribution of a novel parameter, namely α, condensing all nearshore wave transformations other than shoaling. α represents a proxy for coastal susceptibility to the tsunami impact. Small‐scale modeling of coastal flooding performed at locations for which a DTM is freely available, at the Esaro river estuary (Calabria) and in Bari (Apulia), yields inundation levels that compare well with those obtained via intermediate‐scale modeling, with a saving in computational time of about 41%. This demonstrates the value of α to “scale” the offshore wave input and reduce computational effort to evaluate flooding at regional scale.
      原文链接:
    • NSTL
    • Amer Geophysical Union