Geophysical Research Letters

Fuselier, S. A.; Petrinec, S. M.; Trattner, K. J.; LLera, K.; Burch, J. L.; Gershman, D. J.; Dayeh, M. A.; Schwadron, N.; Funsten, H. O.; McComas, D. J.

doi: 10.1029/2023gl105553pmid: N/A

Combined in situ ion measurements and remote sensing of energetic neutral atoms are used to determine the geocoronal Hydrogen density at large (∼10 RE) distances from the Earth. This method for determining the geocoronal density requires global magnetospheric modeling. Observations in the Earth's subsolar magnetosheath from the Magnetospheric Multiscale mission are used to determine the accuracy of using global models to predict the geocoronal density. On average, gas dynamic and magnetohydrodynamic (MHD) models and observations are in reasonable agreement, with differences <25%. In addition, the MHD model subsolar magnetopause is about 0.5 RE sunward of the observed location. However, variations around averages are large (up to a factor of 2), indicating that global models introduce relatively large uncertainties in geocoronal density estimates. Finally, the critical ion flux in the Interstellar Boundary Explorer IBEX‐Hi energy range is often minimally affected by fluctuations of a factor of 2 in the density.

Gorte, Tessa; Lovenduski, Nicole S.; Nisssen, Cara; Lenaerts, Jan T. M.

doi: 10.1029/2023gl104949pmid: N/A

Multidecadal satellite observations indicate that the Antarctic Ice Sheet (AIS) is losing mass at an accelerating rate, which has the potential to impact many aspects of the climate system. While previous studies demonstrated the importance of AIS freshwater (FW) discharge for regional and global climate processes using climate model experiments, many have applied unrealistic FW forcings. Here, we explore potential Southern Ocean (SO) impacts of realistic AIS mass loss over the 21st century in the Community Earth System Model version 2 by applying observation‐based historical and ice sheet model‐based future AIS FW forcing. The added FW reduces wintertime deep convective area by 72% while retaining 83% more sea ice. Congruent with other studies, we find the increased FW discharge extensively impacts local and remote SO surface and subsurface temperature and stratification. These results demonstrate the necessity of accounting for AIS mass loss in global climate models for projecting future climate.

Orihuela‐Pinto, Bryam; Santoso, Agus; England, Matthew H.; Taschetto, Andréa S.

doi: 10.1029/2023gl103250pmid: N/A

The tropical Pacific Ocean is a key regulator of Earth's climate, with teleconnections that influence remote locations all around the world. Here we use partially coupled climate model experiments to show that tropical Pacific cooling related to an abrupt Atlantic Meridional Overturning Circulation (AMOC) slowdown can strengthen the AMOC by ∼25%. This tropical‐extratropical teleconnection occurs initially via atmospheric Rossby waves propagating from the tropical Pacific to the North Atlantic which alter surface climate conditions locally. These changes facilitate ocean heat loss from the subpolar gyre, favoring enhanced oceanic convection. The AMOC strengthening is subsequently enhanced by anomalous northward salt advection in the Atlantic, with a potential contribution from oceanic wave adjustment triggered by increased Southern Ocean westerly winds. These results highlight the influence of the tropical Pacific on the AMOC on multidecadal timescales and suggest that cold phases of tropical Pacific decadal variability could drive temporary strengthening of the AMOC.

Yin, Jun; Porporato, Amilcare

doi: 10.1029/2023gl105228pmid: N/A

Aridity exerts fundamental controls on terrestrial hydrology with impacts on ecosystems and society. Here we show that the global distribution of dryness index is dominated by the exponential variability of precipitation. The resulting distribution of the dryness index only has one parameter describing the balance between global mean atmospheric water demand and supply. Its shape, with a minus two power‐law tail, is well supported by observations and appears to be robust to future changes in aridity, making it a possible benchmark for Earth System Models.

Chen, Ziming; Zhou, Tianjun; Chen, Xiaolong; Zhang, Wenxia; Zuo, Meng; Man, Wenmin; Qian, Yun

doi: 10.1029/2022gl102124pmid: N/A

Reliable regional temperature projections including heat extremes are essential for climate change adaptation and mitigation. Taking China as an example, simple averages from Coupled Model Intercomparison Project Phase 6 (CMIP6) models project high warming due to sampling many high climate sensitivities in the ensemble. Here, we develop an emergent constraint (EC) framework to obtain constrained mean and daily maximum temperature (TXx) warming over China by using observed global warming and local residual warming. The constrained annual mean and TXx warming over China (2.33°C [1.61–3.05°C] and 2.31°C [1.21–2.99°C]) are 0.65°C [0.04–1.76°C] and 0.63°C [–0.50–2.39°C], respectively, lower than raw projections (2.98°C [1.85–4.22°C] and 2.94°C [2.04–4.39°C]) for 2080–2099 under the intermediate‐emission scenario. Approximately half model uncertainty is reduced after constraint. The land area (population) experiencing temperature extremes in our metric is 78% (85%) of the raw projections. Our results imply a lower impact of extreme heat than implied by current raw CMIP6 projections.

Liu, Jann‐Yenq; Kao, Tzu‐Hsun; Liu, Tien‐Chi; Huang, Bor‐Shouh; Lee, Po‐Han; Sun, Yang‐Yi; Chen, Chieh‐Hung; Hattori, Katsumi; Liao, Po‐Han; Lee, I.‐Te; Su, Ching‐Lun; Terng, Chuen‐Teyr; Huang, Treng‐Shi

doi: 10.1029/2023gl105393pmid: N/A

Intense eruptions of the Tonga volcano activated prominent traveling atmospheric disturbances (TADs) at 04:05UT on 15 January 2022. Himawari‐8 satellite images depict that TADs of the tropospheric Lamb wavefront propagate with a speed of 315 m/s and arrive in Taiwan at 11:30UT. Networks of 98 barometers, 28 tide gauges, an ionosonde, and 10 magnetometers are used to study the responses of magnetic fields to TADs in Taiwan. The horizontal components in magnetic field changes of the Taiwan magnetometers all point toward and away from the Tonga volcano at 11:00–12:00UT upon the tropospheric Lamb wavefront arrival and at 22:00–23:00UT when the thermospheric Lamb wavefront with speeds of 487 m/s coming, respectively. Analyses of the raytracing and beamforming techniques on the horizontal components in magnetic field changes of 69 INTERMAGNET magnetometers show that both tropospheric and thermospheric Lamb waves efficiently activate traveling ionospheric disturbances and modify ionospheric currents of the globe.

Ren, Qiang; Zhang, Shihong; Sukhbaatar, Turbold; Hou, Mingcai; Wu, Huaichun; Yang, Tianshui; Li, Haiyan; Chen, Anqing

doi: 10.1029/2023gl104881pmid: N/A

The timing of formation of the Hegenshan suture is crucial to understanding the evolution of the Central Asian Orogenic Belt (CAOB). Here we present a well‐dated paleomagnetic pole (103 samples from 15 sites, 36.7°N/29.2°E, A95 = 3.3°) that passed a positive fold test, a reversal test, and a conglomerate test from the ∼250 Ma upper Gunbayn Formation andesites in the southeastern Mongolia Block (MOB). The high‐quality paleomagnetic database may demonstrate that the MOB drifted rapidly southward and collided with the Xilinhot–Songliao Block between 256 and 250 Ma, resulting in the closure of the Hegenshan Ocean at ∼250 Ma. The Hegenshan suture and the Solonker suture were formed almost simultaneously and marked the final closure of the Paleo‐Asian Ocean.

Wang, Xi; Lu, Jianyong; Wang, Ming; Zhou, Yue; Hao, Yufei

doi: 10.1029/2023gl105270pmid: N/A

To analyze the influence of high‐speed jets (HSJs) on the position of the magnetopause during long‐term radial interplanetary magnetic fields (IMFs), we report three events of magnetopause expansions and indentions by HSJs observed by Time History of Events and Macroscale Interactions during Substorms. In these events, the upstream solar wind condition is stable and the IMF direction is quasi‐radial, characterized by the cone angle less than 30°. Actually, such upstream conditions are rare, especially when the HSJ is observed near the magnetopause crossing time. The actual positions of the magnetopause in these three cases are further away from Earth than that shown by the empirical models. A local indention in the magnetopause caused by HSJ is inferred by the inward movement of the magnetopause from the compression of HSJ. It is the first time to report the simultaneous magnetopause expansion under radial IMF and magnetopause indention caused by HSJ.

Block, Grant A.; Roy, Mousumi; Graves, Emily; Grapenthin, Ronni

doi: 10.1029/2023gl105689pmid: N/A

Surface deformation plays a key role in illuminating magma transport at active volcanoes, however, unambiguous separation of deep and shallow transport remains elusive. The Socorro Magma Body (SMB) lacks an upper crustal magma transport system, allowing us to link geodetic measurements with predictions of numerical models investigating rheologic heterogeneities and magma‐mush interaction in the mid‐/lower crust. New InSAR observations confirm that a pattern of central surface uplift surrounded by a region of subsidence (previously coined “sombrero” deformation) has persisted over >100 years at the SMB. Our models suggest this pattern may reflect the presence of a large (>100 km width), weaker‐than‐ambient, compliant region (CR) surrounding the mid‐crustal magma body. Interactions between a pressurizing (e.g., due to melt injection and/or volatile exsolution) sill‐like magma body and CR drive the sombrero pattern, depending on both viscoelastic relaxation and pressurization timescales, explaining its rare observation and transient nature.

Wang, Ning; Sun, Fubao; Koutsoyiannis, Demetris; Iliopoulou, Theano; Wang, Tingting; Wang, Hong; Liu, Wenbin; Sargentis, G.‐Fivos; Dimitriadis, Panayiotis

doi: 10.1029/2023gl105064pmid: N/A

Comprehending the correlation between alterations in human‐flood distance and flood fatalities (as well as displacements) is pivotal for formulating effective human adaptive strategies in response to floods. However, this relationship remains inadequately explored in existing global analyses. To address this gap, we examine 910 flood events occurring from 2000 to 2018, resulting in significant numbers of fatalities and displacements. We find that in 53% of countries, humans tend to distance from floods, particularly in the Middle East. Such distancing greatly mitigates flood fatalities and displacements. Simultaneously, in areas with increased flood protection level (FPL), humans are less likely to move away from floods. Furthermore, FPL and human‐flood distance have decreased in regions affected by ice jam‐ and hurricane‐induced floods from 2000 to 2018. Notably, regions with human‐flood distance slightly below the average for a given flood type experience more severe flood fatalities.