The shift from denser forests to open, grass-dominated vegetation in west-central North America between 26 and 15 million years ago is a major ecological transition with no clear driving force. This open habitat transition (OHT) is considered by some to be evidence for drier summers, more seasonal precipitation, or a cooler climate, but others have proposed that wetter conditions and/or warming initiated the OHT. Here, we use published (n=2065) and new (n=173) oxygen isotope measurements (δ18O) in authigenic clays and soil carbonates to test the hypothesis that the OHT is linked to increasing wintertime aridity. Oxygen isotope ratios in meteoric water (δ18Op) vary seasonally, and clays and carbonates often form at different times of the year. Therefore, a change in precipitation seasonality can be recorded differently in each mineral. We find that oxygen isotope ratios of clay minerals increase across the OHT while carbonate oxygen isotope ratios show no change or decrease. This result cannot be explained solely by changes in global temperature or a shift to drier summers. Instead, it is consistent with a decrease in winter precipitation that increases annual mean δ18Op (and clay δ18O) but has a smaller or negligible effect on soil carbonates that primarily form in warmer months. We suggest that forest communities in west-central North America were adapted to a wet-winter precipitation regime for most of the Cenozoic, and they subsequently struggled to meet water demands when winters became drier, resulting in the observed open habitat expansion.

It is known that representing wetland dynamics in land surface modeling improves models’ capacity to reproduce fluxes and land surface boundary conditions for atmospheric modeling in general circulation models. This study presents the development of the full coupling between the Noah-MP land surface model (LSM) and the HyMAP flood model in the NASA Land Information System and its application over the Inner Niger Delta (IND), a well-known hot-spot of strong land surface-atmosphere interactions in West Africa. Here, we define two experiments at 0.02º spatial resolution over the 2002-2018 period to quantify the impacts of the proposed developments on IND dynamics. One represents the one-way approach for simulating land surface and flooding processes (1-WAY), i.e., Noah-MP neglects surface water availability, and the proposed two-way coupling (2-WAY), where Noah-MP takes surface water availability into account in the vertical water and energy balance. Results show that accounting for two-way interactions between Noah-MP and HyMAP over IND improves all selected hydrological variables. Compared to 1-WAY, evapotranspiration derived from 2-WAY over flooding zones doubles, increased by 0.8mm/day, resulting in an additional water loss rate of ~18,900km3/year, ~40% drop of wetland extent during wet seasons and major improvement in water level variability at multiple locations. Significant soil moisture increase and surface temperature drop were also observed. Wetland outflows decreased by 35%, resulting in a substantial a Nash-Sutcliffe coefficient improvement, from -0.73 to 0.79. It is anticipated that future developments in global water monitoring and water‐related disaster warning systems will considerably benefit from these findings.

In salt-detached fold-and-thrust belts, contractional modification of salt structures may include decapitation by thrusting, but examples are not well known in the subsurface and unreported in outcrop. Here we present a surface exposure of an intrasalt, sub-horizontal shear zone at the boundary between the Tarcau and Subcarpathian nappes in the Romanian Eastern Carpathians. The Manzalesti diapir forms the largest rock salt outcrop in Europe, with unique salt-karst geomorphology. Numerous wells show that the outcrop is above deep-seated salt of a precursor salt-cored anticline or passive diapir whose base is at > 3500 m. Multiscale observations using UAV-based digital outcrop models, fieldwork, and microstructure analysis show that the outcrop is characterized by sub-horizontal foliation with isoclinal folds, unlike the subvertical fabric of most Romanian diapirs. The halite is rich in clastic inclusions, with a power-law size distribution caused by tectonic reworking of originally dirty salt. Microstructures show that the halite matrix is strongly deformed by dislocation creep, forming subgrains and dynamically recrystallized grains around large porphyroclasts with piezometry indicating relatively high differential stress of around 4 MPa, at pressures sufficient to suppress dilatancy. The observations are best explained by sub-horizontal shear generated by an overriding nappe, overprinting an original coarse-grained salt fabric during decapitation of the salt body.

As the sea-ice modeling community is shifting to advanced numerical frameworks, developing new sea-ice rheologies, and increasing model spatial resolution, ubiquitous deformation features in the Arctic sea ice are now being resolved by sea-ice models. Initiated at the Forum for Arctic Modelling and Observational Synthesis (FAMOS), the Sea Ice Rheology Experiment (SIREx) aims at evaluating current state-of-the-art sea-ice models using existing and new metrics to understand how the simulated deformation fields are affected by different representations of sea-ice physics (rheology) and by model configuration. Part I of the SIREx analysis is concerned with evaluation of the statistical distribution and scaling properties of sea-ice deformation fields from 35 different simulations against those from the RADARSAT Geophysical Processor System (RGPS). For the first time, the Viscous-Plastic (and the Elastic-Viscous-Plastic variant), Elastic-Anisotropic-Plastic, and Maxwell-Elasto-Brittle rheologies are compared in a single study. We find that both plastic and brittle sea-ice rheologies have the potential to reproduce the observed RGPS deformation statistics, including multi-fractality. Model configuration (e.g. numerical convergence, atmospheric forcing, spatial resolution) and physical parameterizations (e.g. ice strength parameters and ice thickness distribution) both have effects as important as the choice of sea-ice rheology on the deformation statistics. It is therefore not straightforward to attribute model performance to a specific rheological framework using current deformation metrics. In light of these results, we further evaluate the statistical properties of simulated Linear Kinematic Features (LKFs) in a SIREx Part II companion paper.

Indian plate passed over four plumes during its way towards Eurasian plate. These interactions with plumes certainly affected the upper mantle and crust of Indian plate as manifested by its thinned lithosphere and relatively low shear velocities both in crust and upper mantle, but the depth extent of these effects of plume-lithosphere interaction remains ambiguous. In this study, we investigate the mantle transition zone beneath Indian shield using P-to-S receiver functions computed at 24 stations covering the entirety of the Indian shield to investigate the depth extent of the imprints of the plume-lithosphere interaction as well as to study the lateral variations of transition zone beneath a stable intraplate setting like the Indian shield. Our results show good agreement with the results of previous studies as well as with the tomographic models in terms of the average apparent depths of the 410 and 660 discontinuities and the transition zone thickness. However, unlike previous studies, we find a compelling evidence of a persistent mid transition zone discontinuity beneath all the stations and a low velocity layer beneath some regions. We also investigated the frequency dependence of amplitudes of receiver functions and found most of the stations showed strong dependence of amplitudes on frequency. Based on the evidence from our investigation, we demarcate the regions potentially containing relatively more weight percentage of water inside the otherwise considered ‘dry’ mantle transition zone. These regions should be further investigated in detail by a dense seismic network and a realistic 3-D velocity model.

Studies reconstructing surface paleoproductivity and benthic conditions allow us to measure the effectiveness of the biological pump, an important mechanism in the global climate system. In order to assess surface productivity changes and their effect on the seafloor, we studied the core SAT-048A, recovered from the continental slope of the southernmost Brazilian continental margin, in the western South Atlantic. We assessed the sea surface productivity, the organic matter flux to the seafloor and the dissolution effects, based on micropaleontological (benthic and planktonic foraminifers, ostracods), geochemical (benthic and planktonic δ13C isotopes) and sedimentological data (carbonate and bulk sand content). Superimposed on the climate-induced changes related to the last glacial-interglacial transition, the reconstruction indicates paleoproductivity changes synchronized with the precessional cycle. From the reconstructed data, it was possible to identify high (low) surface productivity, high (low) organic matter flux to the seafloor, and high (low) dissolution rates of planktonic Foraminifera tests during the glacial (postglacial). Furthermore, within the glacial, enhanced productivity was associated with higher insolation values, explained by increased NE summer winds that promoted meandering and upwelling of the nutrient-rich South Atlantic Central Water. Changes in the Atlantic Meridional Overturning Circulation and the reorganization of bottom water masses could also have changed the CO3 2- saturation levels and have influenced the carbonate preservation. However, changes in the Uvigerina spp. δ13C values are very likely linked to the organic matter flux and not to the sea bottom dissolved inorganic matter δ13C values.

Vertical land motion (VLM) from past and ongoing glacial changes can amplify or mitigate ongoing relative sea level change. We present a high resolution VLM-model for the wider Arctic, that includes both present-day ice loading (PDIL) and glacial isostatic adjustment (GIA). The study shows that the non-linear elastic uplift from PDIL is significant (0.5-1 mm/y ) in most of the wider Arctic and exceeds GIA at 15 of 54 Arctic GNSSsites, including sites in non-glaciated areas of the North Sea region and the east coast of North America. Thereby the sea level change from PDIL (1.85 mm/y) is significantly mitigated from VLM caused by PDIL. The combined VLM-model was consistent with measured VLM at 85% of the GNSS-sites (R=0.77) and outperformed a GIA-only model (R=0.64). Deviations from GNSS-measured VLM can be attributed to local circumstances causing VLM.

Evaluating flood risk is an essential component of understanding and increasing community resilience. A robust approach for quantifying flood risk in terms of average annual loss (AAL) in dollars at the community level is needed to provide valuable information for stakeholder decision-making. This research develops a computational framework to evaluate AAL at the community level by owner/occupant type (i.e., homeowner, landlord, and tenant) for increasing first-floor heights. The AAL values are calculated here by numerically integrating loss-exceedance probability distributions to represent economic annual flood risk to the building, contents, and use. A case study for a census block in Jefferson Parish, Louisiana, reveals that homeowners bear a mean AAL of $4,390 at the 100-year flood elevation (E_100), compared with $2,960, and $1,590 for landlords and tenants, respectively, because the homeowner incurs losses to building, contents, and use, rather than only two of the three, as for the landlord and tenant. The results of this case study show that increasing first-floor heights reduces AAL proportionately for each owner/occupant type, and that two feet of additional elevation above E_100 may provide the most economically advantageous benefit. The modeled results suggest that Hazus Multi-Hazard (Hazus-MH) output underestimates the AAL by 11% for building and 15% for contents. Application of this technique to the community level while partitioning the owner/occupant types will improve planning for improved resilience and assessment of impacts attributable to the costly flood hazard.

Tree-ring series from ENSO rainfall impact regions reconstruct the tropical Pacific SST field with a high degree of skill back to 1100 CE. 2. Two very different reconstruction methods produce similar results and each can only reconstruct the leading EOF mode of SST variability. 3. Reconstructions extending back 1100 CE do not reveal any clear increase in El Niño variability, but do show a recent overall SST warming.

Despite strong impacts that aerosols have on climate and air quality, significant gaps remain in our knowledge concerning their long-range transport, especially extreme transport events. With this consideration in mind and by leveraging the “atmospheric river” concept, this work develops an objective global algorithm for detecting aerosol atmospheric rivers (AARs), shows a climatology of AARs, elucidates their contributions to major global aerosol transport pathways, and illustrates how AARs can drive extreme cases of poor air quality conditions. Our methodology separately accounts for dust, carbonaceous (accounting for organic and black carbon separately where appropriate), sea salt and sulfate aerosols. Findings show there are a number of long-range regional transport pathways where AARs account for a sizable fraction (40-80%) of the total transport in relatively few events (20-40 AAR days/year). This study highlights the role of AARs in establishing source-receptor relationships that can drive regional air-quality and extremes.

We found the signatures of the multiple prompt penetration electric fields (PPEF) and the disturbance dynamo (DD) electric field having impacts on the East Asian sector ionosphere along the meridional chain thoroughly from the equator, low-mid to high latitudes during the space weather event of 03-05 November 2021. The observation is made on GPS-TEC, digisonde, and magnetometer stations. In the main phase of the storm, intense modulations of VTEC (vertical total electron content) and foF2 (critical frequency) are observed as coherently fluctuating with IEF (interplanetary electric field) and IMF Bz reorientations. It is diagnosed that the oscillations in the DP2 (disturbance polar current 2) current system directly penetrate meridianally from high to equatorial latitudes, leading to the significant changes in ionospheric electrodynamics that governs the density fluctuations. The wavelet spectra of VTEC, foF2, h’F (virtual height), H-components and IEF give a result of common and dominant periodicity occurring at ~1hr. This result suggests that the wavelike oscillations of VTEC and foF2 and H component are associated with PP electric fields.

Current methods of root sampling typically only obtain small or incomplete sections of root systems and do not capture their true complexity. To facilitate the visualization and analysis of entire, full sized root systems of crop plants, mesocosm growth containers were developed with an internal volume of 45 ft3 (1.27 m3). Mesocosms allow for unconstrained root growth, excavation and preservation of 3-dimensional RSA, and modularity that facilitates the use of a variety of sensors. Sensors arrays monitoring matric potential, temperature and CO2 levels are buried in a grid formation at depths of 1.25, 2.75, & 4.25 ft to assess environmental fluxes at regular intervals. Additionally, 3-dimensional water availability can be measured using ERT inside of root mesocosms. Methods of 3D data visualization of fluxes were developed to allow for comparison with root architectural traits. Following harvest, the recovered root system can be digitally reconstructed through photogrammetry, which is an inexpensive method requiring only an appropriate studio space and a digital camera. Initial metrics inferred from the 3D models include root system biomass (occupied voxels), volume, flatness, convex hull volume and solidity with depth. Root systems are finally dissected and biomass measurements are made in a 3-dimensional matrix of the growth zone, while the crown is saved for X-ray CT analysis.

Coral oxygen isotopes (δ18O) from the central equatorial Pacific provide monthly-resolved records of El Niño-Southern Oscillation (ENSO) activity over past centuries to millennia. However, calibration studies using in situ data to assess the relative contributions of warming and freshening to coral δ18O records are exceedingly rare. Furthermore, the fidelity of coral δ18O records under the most severe thermal stress events is difficult to assess. Here, we present six coral δ18O records and in situ temperature, salinity, and seawater δ18O data from Kiritimati Island (2°N, 15°W) spanning the very strong 2015/16 El Niño event. Local sea surface temperature (SST) anomalies of +2.4±0.4°C and seawater δ18O anomalies of -0.19±0.02‰ contribute to the observed coral δ18O anomalies of -0.58±0.05‰, consistent with a ~70% contribution from SST and ~30% from seawater δ18O. Our results demonstrate that Kiritimati coral δ18O records can provide reliable reconstructions even during the largest class of El Niño events.

Basal melting of ice shelves is fundamental to Antarctic Ice Sheet mass loss, yet direct observations are sparse. We present the first melt record (2017 to 2021) from a phase-sensitive radar at Fimbulisen, East Antarctica, one of the fastest flowing ice shelves in Dronning Maud Land. The observed long-term mean ablation below the central part of the ice shelf was 1.0 ±0.4 m yr–1, marked by substantial sub-weekly variability ranging from 0.3 to 3.8 m yr–1. 36-h filtered fluctuations in basal melt exhibit a close alignment with ocean velocity, revealing shear-driven turbulent heat transfer as the predominant driver of melt variability at sub-weekly to monthly timescale. Seasonally, basal melt rates are highest in the austral summer, when ocean temperature is higher. Our observed in-situ melt rates show threefold lower amplitudes and a 3-month delay in seasonality compared to satellite-derived melt rates, however, the long-term multi-year mean is of similar magnitude (1.0 m yr–1 vs 0.8 m yr–1). Our detailed ice–ocean observations provide essential validation data for remote sensing and numerical models aiming to measure and project ice-shelf response to ocean forcing. In-situ measurements and continued monitoring are crucial for accurately assessing and modelling future basal melt rates, as well as understanding the complex dynamics driving ice-shelf stability and sea-level change.

Solar wind models are highly dependent on global magnetic fields at the solar surface as their inner boundary condition, and the lack of global field data is a significant problem plaguing solar wind modeling. Currently, only direct observations of the near-side magnetic field exist and far-side approximations are incapable of predicting growth of existing active regions or new magnetic flux emergence. To fill this data gap, we develop a method that calibrates far-side helioseismic images, which are calculated using near-side Doppler observations, to far-side magnetic flux maps. The calibration employs multiple machine-learning methods that use EUV 304 Å data as a bridge. These algorithms determine a relation 1) between the near-side AIA 304 Å data and HMI magnetic field data, and 2) between STEREO 304 Å data and far-side helioseismic images obtained from a newly developed time-distance helioseismic far-side imaging method. The resulting magnetic flux maps have been further calibrated using maps produced by a flux transport model. The various data products from this work — far-side acoustic maps, far-side STEREO EUV-derived magnetic flux maps, and near-real-time acoustically-driven far-side magnetic flux maps, along with maps of the associated uncertainties — are being made available to enable a synchronic global magnetic flux input into coronal and solar wind models.

Volcanic aerosols reduce global mean precipitation in the years after major eruptions, yet the mechanisms that produce this response have not been rigorously identified. Volcanic aerosols alter the atmosphere's energy balance, with precipitation changes being one pathway by which the atmosphere acts to return towards equilibrium. By assessing the atmosphere's energy budget in climate model simulations, we here show that global precipitation reduction is largely a consequence of Earth's surface cooling in response to volcanic aerosols reflecting incoming sunlight. In addition, these aerosols also directly add energy to the atmosphere by absorbing outgoing longwave radiation, and this is a major cause of precipitation decline in the first post-eruption year. We also identify mechanisms that oppose the post-eruption precipitation decline, and provide evidence that our results are robust across climate models.

We present an analysis of in-situ thermal ion measurements from a cusp auroral sounding rocket. Using a forward modeling procedure, we find most-probable thermal ion temperature and parallel (field-aligned) bulk flow velocity along the trajectory. Spatially and temporally intermittent fine-scale structure in upflowing/downflowing features in the dayside cusp ionosphere are presented. We show that the observed ion temperatures are consistent with Joule heating expectations if spatially and temporally intermittent drivers and responses in the dynamic cusp environment are considered. Additionally, a forward modeling procedure for the ion data interpretation is improved and a sensitivity analysis is presented.

The Plankton, Aerosol, Cloud, and Ocean Ecosystem (PACE) mission is NASA’s next great investment in Earth Science, continuing NASA’s legacy of over forty years of satellite ocean color measurements. PACE, expected to launch in 2023, will advance our Earth-observing and monitoring capabilities through hyperspectral imaging and multi-angle polarimetric observations of ocean, atmosphere, and land ecosystems. PACE will give us an unprecedented view of our home planet and will support user-driven environmental applications through research and applied science to address societal challenges and inform decision-making. An integral component of actionable applied science is Design Thinking - an iterative, problem-solving framework that integrates human perspectives, needs, and experiences at every step of process. In this session, we will present the design process, collaborative activities, and outcomes of the 2021 PACE Applications Water Quality community focus session. A Design Thinking methodology was used in event planning as well as during day-of ideation breakout sessions. To foster empathy and better illuminate the goals, concerns, and needs of the diverse PACE user community, eight draft user personas were created to represent a range of water industry users from research to government to the private sector. Attendees worked together to complete the various personas by identifying different user challenges and pain points, ideal data experiences, and realistic, tailored Earth Observation and PACE Mission specific solutions and opportunities to satisfy users’ needs and goals. As a result, the eight archetype personas and co-production of knowledge will help ensure that PACE data are usable and accessible for a variety of possible users, thereby expanding the eventual reach and societal benefit of PACE. Lastly, we will highlight how Design Thinking will inform future stakeholder engagement efforts and actionable science via the PACE Mission.