Eddy activities are particularly prominent in the Southern Ocean due to the instabilities of the Antarctic Circumpolar Current (ACC), which plays a critical role in energy transport of the global ocean. The Indian sector of the Southern Ocean is not only a typical eddy-rich region with strong Eddy Kinetic Energy (EKE) and associated energy conversions among different energy reservoirs (kinetic energy and potential energy of the eddy and mean flow), but also events of extreme EKE. In this study, a systematic energetics analysis framework is employed to examine the notable anomalies of an intensified EKE event observed in the southwest region of the Kerguelen Plateau in 2017 based on a reanalysis product. The EKE anomaly existing at all depths emerges in April, reaches its peak during the austral winter, and persists into the following summer. Energetics analysis indicates that the strong anomalous EKE is primarily determined by baroclinic instability, with distinct governing mechanisms at the surface and in the internal ocean. The anomalous intrusion of warm Circumpolar Deep Water intensifies the baroclinic energy conversion in the subsurface, which contributes to the observed EKE anomalies. Moreover, the anomalous strong wind-induced Ekman pumping serves to amplify the lifting of isopycnals, which enhances the baroclinic instability and subsequently intensifies the EKE anomalies. This study sheds new light on underlying mechanisms governing local polar dynamics and provides insights into the intricate interaction between ocean dynamics and energy distribution in the Antarctic.

Twenty-two sites, subjected to an IZZI-modified Thellier-Thellier experiment and strict selection criteria, recover a paleomagnetic axial dipole moment (PADM) of 62.24$\pm$ 30.6 ZAm$^2$ in Northern Israel over the Pleistocene (0.012 - 2.58 Ma). Pleistocene data from comparable studies from Antarctica, Iceland, and Hawaii, re-analyzed using the same criteria and age range, show that the Northern Israeli data are on average slightly higher than those from Iceland (PADM = 53.8 $\pm$ 23 ZAm$^2$, n = 51 sites) and even higher than the Antarctica average %\cite{asefaw21} (PADM = 40.3 $\pm$ 17.3 ZAm$^2$, n = 42 sites). Also, the data from the Hawaiian drill core, HSDP2, spanning the last half million years (PADM = 76.7 $\pm$ 21.3 ZAm$^2$, n = 59 sites) are higher than those from Northern Israel. These results, when compared to Pleistocene results filtered from the PINT database (www.pintdb.org) suggest that data from the Northern hemisphere mid-latitudes are on average higher than those from the southern hemisphere and than those from latitudes higher than 60$^{\circ}$N. The weaker intensities found at high (northern and southern) latitudes therefore, cannot be attributed to inadequate spatio-temporal sampling of a time-varying dipole moment or low quality data. The high fields in mid-latitude Northern hemisphere could result from long-lived non-axial dipole terms in the geomagnetic field with episodes of high field intensities occurring at different times in different longitudes. This hypothesis is supported by an asymmetry predicted from the Holocene, 100 kyr, and five million year time-averaged geomagnetic field models.

Inlet change along the Virginia barrier islands has been studied on an individual inlet basis. This study evaluated the ten inlets both individually and as a group. Evaluating the inlets as a group allows the discovery of inlet change patterns among the inlets. Inlet width was measured from satellite and aerial images. Width is the straight-line distance from the northernmost fast land to southernmost fast land. Measurements spanned from July 1999 to April 2018 with a frequency of four to eight width measurements per year. Total width change to 2018 was 2 percent to 357 percent. The largest change was to Great Machipongo Inlet. The inlet widened from approximately 800 meters wide in 1999 to 3645 meters wide in 2018. This widening effectively splits the remaining nine inlets into two groups. Inlet widening patterns of the two groups are high rates for the first three or four inlets and a very low rate for the final inlet of the group. Wind direction change also plays a significant role in net inlet widening. Inlet widening has not abated and wider inlets will allow larger waves to affect environmentally and commercially important areas to the west of the barrier island/inlet system.

A document by Jerome Pinti. Click on the document to view its contents.

The diurnal cycles of near-surface shear and stratification, also known as diurnal jet and diurnal warm layer (DWL), are ubiquitous in the tropical oceans, affecting the heat and momentum budget of the ocean surface layer, air-sea interactions, and vertical mixing. Here, we analyse the presence and descent of near-surface diurnal shear and stratification in the upper 20 m of the equatorial Atlantic as a function of wind speed using ocean current velocity and hydrographic data taken during two trans-Atlantic cruises along the equator in autumn 2019 and spring 2022, data from three types of surface drifters, and data from PIRATA moorings along the equator. The observations during two seasons with similar wind speeds but varying net surface heat fluxes reveal similar diurnal jets with an amplitude of about 0.11 m s-1 and similar DWLs when averaging along the equator. We find that higher wind speeds lead to earlier diurnal peaks, deeper penetration depths, and faster descent rates of DWL and diurnal jet. While the diurnal amplitude of shear is maximum for intermediate wind speeds, the diurnal amplitude of stratification is maximum for minimal wind speeds. The presented wind dependence of the descent rates of DWL and diurnal jet is consistent with the earlier onset of deep-cycle turbulence for higher wind speeds. The DWL and the diurnal jet not only trigger deep-cycle turbulence but are also observed to modify the wind power input and thus the amount of energy available for mixing.

Long-term carbon dioxide (CO2) flux measurements between the atmosphere and the ecosystem have been made since 1993 at a cool-temperate deciduous forest site (Takayama) in Japan influenced by Asian Monsoon, constituting the longest dataset among all the AsiaFlux sites. Interannual variations (IAVs) and trends of the annual carbon budget components and their environmental factors were examined. Annual net ecosystem production (NEP) (mean ± 1σ) during the period of eddy covariance measurement in 1999-2021 was 265 ± 86 gC m-2 yr-1, and its IAV was dependent more on gross primary production (GPP) than on ecosystem respiration. IAVs in annual NEP and GPP were correlated with the IAVs of the monthly mean NEP, GPP and leaf area index (LAI) from June to September, as well as with that of the length of the net carbon uptake period. Significant increasing and decreasing trends in the annual NEP and GPP were detected during 2004-2013 and 2013-2021, respectively; the increasing trends were mainly caused by the vegetation recovery from typhoon disturbances while the decreasing trends were partly influenced by recent extreme weather events. Significant positive correlations of the IAVs between the start and the end of the net carbon uptake period, and between the leaf expansion and leaf fall were found. These may be attributed to biological functions and interseasonal relationship of meteorological parameters associated with ENSO events that can also influence IAVs in annual NEP and GPP.

Attenuation of ocean waves by ice is a crucial process of the interaction between waves and sea ice in marginal ice zone (MIZ), while such interaction can contribute to the retreating of sea ice in the Arctic. Based on the retrieved two-dimensional ocean wave spectra by spaceborne SAR, we investigated the attenuation of ocean waves in the MIZ in Svalbard and Greenland. The results show that the energy attenuation rate ranges from \(0.126\times10^{-4}\)/m to  \(0.618\times10^{-4}\)/m . Quantitative analysis suggests that the attenuation rate is significantly related to wave height and peak wave period of coming waves. It is further found that the waves decay faster in the area with ice thickness exceeding 0.5 m. We compared the derived wave attenuation rates in the present study with those in previous studies based on in situ measurements, which reveals that waves are becoming less attenuated by sea ice in the Arctic in recent decades.

The Upper and Lower Quinn River subbasins (HUC-8 16040201,16040202) comprise one of the largest single drainages in northwest Nevada. The sub-basins cover approximately 1.7 million hectares. The Quinn river originates in the Montana Mountains and Santa Rosa Range and drains to the Black Rock Desert Playa. The elevational gradient ranges from 2000 m to 1100 m. Sagebrush and perennial grasses dominate the higher elevations, with the lowlands being dominated by greasewood, saltbrush, and desert scrub. This presentation examines the human habitation in the sub-basins over the past 13,000 years in context to the palaeoclimatic records from the sub-basins and adjoining areas. Over 1100 prehistoric sites exist in the study area, with 19 sites having been excavated and yielding 108 radiocarbon dates. Palaeoclimate proxies from the study area include the Mud Meadows and Summit Lake pollen cores, and the Jackson Mountain tree ring widths. While the radiocarbon record shows numerous gaps between 13 kBP and 5 kBP, the summed probability distribution of calibrated radiocarbon dates suggests continuous occupation from 5 kBP to 1 kBP with exponential growth. Based on the abundance of Chenopodiaceae pollen in the Summit Lake core, the study area is drier than today during the Late Holocene Drought (LHD, ca. 2.5 to 1.9kBP). During the LHD, sites south of 41N are abandoned or see no growth; northwards, sees site growth. Despite contrasting climatic conditions, the Late Antique Little Ice Age (LALIA) and the Medieval Climatic Anomaly (MCA) are both periods of site occupation and growth across the sub-basins. Occupied sites are found throughout the sub-basins during the LALIA, and during the MCA site occupation is focused at Trego hot springs and at higher elevations. As evidenced by the three palaeoclimate proxies from the sub-basins, the Little Ice Age is a period of cooler temperatures and increased moisture. Despite the ameliorated conditions, the number of dated sites significantly decreases. This may reflect a more dispersed settlement pattern with lower numbers of residents during the Terminal Prehistoric period.

Water is one of the most important substances for plants. Limited water supplies directly influence crop yield, which eventually leads to food scarcity to humans. In this present study, we quantify the dynamics of a fluttering leaf as a function of the days without water. The deformation and vibration of a plant leaf can be induced by dropping an object or tapping with a finger. Using multiple cameras, the 3D motion of a leaf can be measured. We found that the frequency of a leaf increases with water stress. In terms of natural frequency, it tends to increase when moisture stress is applied to leaves. These results suggest that the stiffness of leaves according to moisture stress is related, so it can be used as an indicator of the overall performance of plants. This would lead to a nondestructive way to measure water stress through leaf stiffness.

Rapid changes of magnetic fields associated with nighttime magnetic perturbation events (MPEs) with amplitudes |ΔB| of hundreds of nT and 5-10 min periods can induce geomagnetically-induced currents (GICs) that can harm technological systems. In this study we compare the occurrence and amplitude of nighttime MPEs with |dB/dt| ≥ 6 nT/s observed during 2015 and 2017 at five stations in Arctic Canada ranging from 75.2° to 64.7° in corrected geomagnetic latitude (MLAT) as functions of magnetic local time (MLT), the SME and SYM/H magnetic indices, and time delay after substorm onsets. Although most MPEs occurred within 30 minutes after a substorm onset, ~10% of those observed at the four lower latitude stations occurred over two hours after the most recent onset. A broad distribution in local time appeared at all 5 stations between 1700 and 0100 MLT, and a narrower distribution appeared at the lower latitude stations between 0200 and 0700 MLT. There was little or no correlation between MPE amplitude and the SYM/H index; most MPEs at all stations occurred for SYM/H values between -40 and 0 nT. SME index values for MPEs observed more than 1 hour after the most recent substorm onset fell in the lower half of the range of SME values for events during substorms, and dipolarizations in synchronous orbit at GOES 13 during these events were weaker or more often nonexistent. These observations suggest that substorms are neither necessary nor sufficient to cause MPEs, and hence predictions of GICs cannot focus solely on substorms.

Extreme heat events are one of the most dangerous climate hazards and they are projected to increase in frequency, intensity and duration as this century progresses. Change in future exposure to extreme heat events depends not only on climate change, but also on changes to future population size and the areas this population inhabits. This study explores exposure to the heat event known as a tropical night. Using a CMIP6 multi-model ensemble, coupled with population projections, this study projects exposure for the four alternative futures described by SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. Exposure is quantified annually at both the global and regional scale, relative to a preindustrial baseline. By the end of the twenty-first century global annual exposure to tropical nights will total 1338-2674 billion person-days depending on the pathway followed. Of the four pathways, globally change in exposure from the pre-industrial is avoided most under SSP1-2.6, which, when compared to SSP3-7.0 which projects the greatest change, is a reduction of 1336 billion person-days annually. Exposure reduction varies at the regional level, yet in the majority of cases, SSP1-2.6 remains the more desirable future in terms of minimising future exposure. Moreover, this study finds that changes in climate versus changes in population do not equally influence changes in exposure, and their contributions vary regionally. Irrespective of the future pathway followed, human exposure is set to increase at the global scale and for the vast majority of regions.

Flare suprathermal ions with enhanced 3He and heavy-ion abundances are an essential component of the seed population accelerated by CME-driven shocks in gradual solar energetic particle (GSEP) events. However, the mechanisms through which CME-driven shocks gain access to flare suprathermals and produce spectral and abundance variations in GSEP events remain largely unexplored. We report two recent GSEP events: one observed by Solar Orbiter on 2020 Nov 24 (the first GSEP event on Solar Orbiter) and the other by ACE on 2021 May 29 (the most intense GOES proton event in the present solar cycle). The events were preceded by impulsive SEP (ISEP) events. Abundances and energy spectra are markedly different in the examined events at < 1 MeV/nucleon. For example, in the May event, Fe/O is typical of ISEP events, a factor of 100 to 10 higher than Fe/O in the November event. 3He abundance in the November event is high, typical of ISEP events, while in the May event, it is much lower, though finite. The May event shows a hard 4He spectrum with a power-law index of −1.6, and the November event a soft spectrum with an index of −3.5. The events were associated with halo CMEs with speeds around 900 km/s. The November event was also measured by Parker Solar Probe and the May event by STEREO-A and Solar Orbiter. This paper discusses the origin of vastly different abundances and spectral shapes in terms of variable remnant population from preceding ISEP events. Furthermore, we discuss a possible direct contribution from parent flares.

Modeling studies have predicted that the acoustic resonance of the atmosphere during geophysical events such as earthquakes and volcanos can lead to an oscillation of the geomagnetic field with a frequency of about 4 mHz. However, observational evidence is still limited due to scarcity of suitable events. On January 15, 2022, the submarine volcano Hunga Tonga-Hunga Ha’apai (20.5˚S, 175.4˚W, Tonga) erupted in the Pacific Ocean and caused severe atmospheric disturbance, providing an opportunity to investigate geomagnetic effects associated with acoustic resonance. Following the eruption, geomagnetic oscillation is observed at Apia, approximately 835 km from Hunga Tonga, mainly in the Pc 5 band (150-600 s, or 1.7-6.7 mHz) lasting for about 2 hours. The dominant frequency of the oscillation is 3.8 mHz, which is consistent with the frequency of the atmospheric oscillation due to acoustic resonance. The oscillation is most prominent in the eastward (Y) component, with an amplitude of ~3 nT, which is much larger than those previously reported for other events (<1 nT). Comparably large oscillation is not found at other stations located further away (>2700 km). However, geomagnetic oscillation with a much smaller amplitude (~0.3 nT) is observed at Honolulu, which is located near the magnetic conjugate point of Hunga Tonga, in a similar wave form as at Apia, indicating interhemispheric coupling. This is the first time that geomagnetic oscillations due to the atmospheric acoustic resonance are simultaneously detected at magnetic conjugate points.

Research interest in the Kinki region, southwestern Japan, has been aroused by the frequent occurrence of microearthquake activity that do not always coincide with documented active fault locations. Previous studies in the Kinki region focused mainly on deep, large-scale structures and could not efficiently resolve fine-scale (~10 km) shallow crustal structures. Hence, characterization of the upper crustal structure of this region at an improved spatial resolution is required. From the cross-correlation of the vertical components of the ambient seismic noise data recorded by a densely-distributed seismic array, we estimated Rayleigh wave phase velocities using a frequency domain method. Then, we applied a direct surface wave tomographic method for the measured phase velocity dispersion data to obtain the 3D S-wave velocity model of the Kinki region. The estimated velocity model reveals a NE-SW trending low-velocity structure coinciding with the Niigata-Kobe Tectonic Zone (NKTZ) and the active Biwako-seigan Fault Zone (BSFZ). Also, we identified fine-scale low-velocity structures coinciding with known active faults on the eastern side of the NKTZ, as well as sets of low-velocity structures across the Tanba region, that may be attributable to the weathering effects or activity of unidentified concealed fault zones. Furthermore, sedimentary basins manifest as low-velocity zones extending to depths ranging from ~1.5 to 2 km, correlating with those reported in previous studies. Our results therefore contribute towards fundamental understanding of earthquake faulting as well as tectonic boundary and will be useful for hazard assessment and disaster mitigation.

Understanding the exposure of business characteristics like its location, sector, size, age, and owner demographics and structure to building damages from an earthquake can inform business continuity planning and broader community and regional programs and policies for business recovery. A baseline analysis was performed for the HayWired scenario (Wein, Haveman and others, 2019) using business characteristic data from the National Establishment Time Series (NETS) which showed that location and sector are strong differentiators of disruptive building damage risk, while minority ownership, branch ownership structure, and low revenue are other above average differentiators. The HayWired analysis was limited by damage information at the census tract scale for occupancy classes (per the Federal Emergency Management Agency Hazus software). In this study, we expand the analysis to multiple earthquake scenarios and apply machine learning techniques to generate building level assessments instead of census tract level. Association of business characteristics with building damages by location increases the analysis resolution providing more nuanced understanding and analyzing across multiple scenarios shows the variability of business characteristic exposure to different earthquakes for the region and across communities. Anne Wein, Jon Haveman, Cynthia Kroll, Jeff Peters. 2019. Characteristics of Businesses disrupted by Building Damages from the HayWired Scenario Mainshock, in press.

Rising summer temperatures are expected to increase tree mortality rates across the western United States. Here, we analyze subfossil wood samples from Colorado dating to the last interglacial to assess the response of two common conifers to a previous warm period. The trees experienced comparable growth rates and water use efficiency during the interglacial relative to modern despite evidence from model simulations of a ~30% increase in evaporative demand during the peak of the growing season. High-resolution isotopic analysis of the wood samples show an enrichment in the late season cellulosic δ18O relative to modern samples, which we find was associated with increased reliance on summer rain. The data are consistent with other proxy data and climate model simulations showing the interglacial was associated with wetter summers across the western US. We propose enhanced summer rain during this warm period compensated for drought stress imposed by higher evaporative demand.

Meridional gradients in CO2 forcing are known to drive increases in poleward heat transport (Huang and Zhang 2014, Huang et al. 2017). However, the climate factors which control these meridional forcing gradients are not well understood. Building upon the work of Wilson (2012), we build a first-principles, analytical model for CO2 forcing which requires as input only the temperatures at the surface and roughly 30 hPa, as well as column relative humidity. This model quantitatively captures global variations in clear-sky CO2 forcing, and shows that the meridional forcing gradient is directly attributable to the meridional surface temperature gradient.

Familiarity with the use of face coverings to reduce the risk of respiratory disease has increased during the coronavirus pandemic; however, recommendations for their use outside of the pandemic remains limited. Here, we develop a modeling framework to quantify the potential health benefits of wearing a face covering or respirator to mitigate exposure to severe air pollution. This framework accounts for the wide range of available face coverings and respirators, fit factors and efficacy, air pollution characteristics, and exposure-response data. Our modeling shows that N95 respirators offer robust protection against different sources of air pollution, reducing exposure by more than a factor of 14 when worn with a leak rate of 5%. Synthetic-fiber masks offer less protection with a strong dependence on aerosol size distribution (protection factors ranging from 4.4 to 2.2.), while natural-fiber and surgical masks offer reductions in exposure of 1.9 and 1.7, respectively. To assess the ability of face coverings to provide population-level health benefits to wildfire smoke, we perform a case study for the 2012 Washington state fire season. Our models suggest that although natural-fiber masks offer minor reductions in respiratory hospitalizations attributable to smoke (2-11%) due to limited filtration efficiency, N95 respirators and to a lesser extent surgical and synthetic-fiber masks may lead to notable reductions in smoke-attributable hospitalizations (22-39%, 9-24%, and 7-18%, respectively). The filtration efficiency, bypass rate, compliance rate (fraction of time and population wearing the device) are the key factors governing exposure reduction potential and health benefits during severe air pollution events.