The UCLA Planetarium hosts star shows and lectures on various astronomy topics, educating UCLA and the broader Los Angeles community about science and the wonders of the night sky. It serves over 4000 people per year, as UCLA Astronomy’s largest outreach effort. We host private shows for visiting school groups (30% of our attendees), shows for UCLA astronomy courses (20%), and weekly public shows for the community at large (50%). Our planetarium and its events are run exclusively by graduate students, who also maintain its historic projectors and dome. In the near future, we plan to improve and expand our outreach efforts in two specific ways. Our outreach efforts are free for educational groups, but we currently do not provide travel support for visiting schools. We plan to actively reach out to school groups from underserved communities and hope to raise funds to cover these schools’ field trip and travel expenses. We also plan to improve our science communication effectiveness, with strategies for improving volunteer recruitment, training volunteers on effective public speaking skills, and improving the quality of our existing repository of presentations. Of course, these in person events are on hold due to the ongoing pandemic; in the meantime, we are developing ways to serve our audience virtually. We recently hosted our first “virtual” planetarium show on YouTube Live, with over 1,700 viewers on the livestream and over 7,300 total viewers. We welcome any suggestions or ideas to help us improve our planetarium outreach efforts!

SKB and several other waste management organizations have established the international SKB Task Force on Modeling of Groundwater Flow and Transport of Solutes (TF GWFTS) to support and interpret field experiments. Objectives of the task force are to develop, test and improve tools for conceptual understanding and simulating groundwater flow and transport of solutes in fractured rocks. Work is organized in collaborative modeling tasks. Task 9 focuses on realistic modeling of coupled matrix diffusion and sorption in heterogeneous crystalline rock matrix at depth, e.g. by inverse and predictive modeling of in-situ transport experiments. Posiva’s REPRO (rock matrix REtention PROperties) experimental campaign has been performed at the ONKALO rock characterization facility in Finland. The two REPRO experiments considered were the Water Phase Diffusion Experiment (WPDE), addressing matrix diffusion in gneiss around a single borehole interval (modeled in Task 9A), and the Through Diffusion Experiment, which is performed between sections of three boreholes and addressed by modeling in Task 9C. The Long-Term Diffusion and Sorption Experiment (LTDE-SD) was an in-situ radionuclide tracer test performed at the Swedish Äspö Hard Rock Laboratory at a depth of about 410 m below sea level. The experimental results indicated a possible deeper penetration of sorbing tracers into the rock matrix than expected. The shape of these tracer penetration profiles was difficult to reproduce. This experiment was modeled and interpreted in Task 9B. Task 9D is addressing the possible benefits of detailed models of the in-situ experiments in safety assessment calculations. The task is performed by upscaling of the WPDE models to conditions applicable for nuclear waste repositories. As Task 9 is now in a finalization process, a number of lessons learned from the 4 sub-tasks have been identified. These include: • field tracer experiments can provide surprises even when well designed and executed, • interaction between the experimentalists and modelers is important and mutually beneficial when investigating anomalous results, • differences in conceptual models have the greatest impact on model outcomes, • it is not trivial to go from modeling of field experiments to safety assessment modeling without making substantial simplifications.

Since its formation in 2015, the National Centers for Environmental Information (NCEI) has used disparate, legacy systems spread across several IT networks of the National Environmental Satellite, Data, and Information Service (NESDIS) to fulfill its data-stewardship functions. As part of its modernization and consolidation of these functions, NCEI implemented Common Ingest as the functional component that ingests approximately 200 data streams every month into its enterprise archival information system. In parallel, NESDIS completed the Secure Ingest Gateway Project (SIGP), a pilot project to establish standard-enterprise secure methods for NESDIS and the rest of the National Oceanic and Atmospheric Administration (NOAA) to receive data in a cloud environment from their external partners. SIGP is now transitioning to operations as the Operational Secure Ingest Service (OSIS), which will be the on-ramp to NCEI’s “Common Ingest” functionality when it too moves to the cloud. In addition, this ingest function will populate and use a cloud-based metadata catalog, which will be the beating heart of the NESDIS and NCEI information systems in the cloud environment. The vision is to scale their ingest of environmental data to keep pace with its ever increasing volume, veracity, variety, and velocity. In this presentation to the ocean data community, the authors describe NESDIS and NCEI’s challenges and successes with the implementation of the ingest function of their archival information system in a cloud environment.

The U.S. Geological Survey and Sonoma County Water Agency (SCWA) are engaged in a cooperative project to characterize the hydrogeology of southern Sonoma Valley, a groundwater basin in the northern California Coast Ranges where groundwater represents about 60% of the valley’s water supply. The basin lies near the Sonoma volcanic field and major transverse faults of the San Francisco Bay region, resulting in a complex aquifer system comprising volcanic and sedimentary rocks and unconsolidated sediments that are cut by faults and overlain to the south by recent Bay Muds of San Francisco Bay. Geologic sections were constructed using geologic maps and lithologic data from over 1,500 water wells compiled by SCWA to describe the subsurface geologic configuration relative to groundwater pumping wells. This work suggests an aquifer system extending to about 900 feet below land surface (ft bls), consisting of upper and lower aquifer units separated by an intermediate unit with lower hydraulic conductivity, overlying and partly interfingering with a complex suite of volcanic rocks. SCWA constructed a four-layer hydrostratigraphic model of the basin using spatial trends in the lithologic data. The hydrostratigraphic layers defined by SCWA include multiple mapped geologic formations because of heterogeneity and complex interfingering between stratigraphic units. Water from selected wells was analyzed for specific conductance, major and minor ions, nutrients, stable isotopes, carbon isotopes, and tritium. Well data were categorized by completed perforation interval into shallow wells (< 200 ft bls), mid-depth wells (200–500 ft bls), and deep wells (> 500 ft bls). Shallow wells typically have water types related to recent mountain-front recharge, and, near the tidal marshlands north of San Pablo Bay, have high chloride and total dissolved solid concentrations associated with modern saline-water intrusion. Mid-depth and deep wells have water with poor water-quality, likely influenced by connate water from consolidated marine sediments, or a mixture of water from consolidated sediments and thermal water. This cooperative basin characterization of subsurface geology, hydrostratigraphy, and water chemistry will enable SCWA to make strategic water management decisions in Sonoma Valley.

The Astromaterials Data System (AstroMat) is a NASA-funded project, working in close collaboration with the Johnson Space Center (JSC) to provide access to and preserve analytical data from JSC’s astromaterials collections. Meteorite data from close to 1000 peer-reviewed publications, primarily from the JSC Antarctic collections, and data from over 800 lunar publications have been ingested into AstroMat. Data can be explored at the level of reference and sample, or queried interactively through the AstroDB Search (AstroSearch). AstroSearch v 1.0 incorporated lunar and meteorite JSC collections, lunar missions, geofeatures, taxons, analyzed materials, and analysis methods searches. Working closely with domain scientists we have developed AstroSearch v 2.0. This version of the interface enhances the functionality of the original by adding search by chemistry (with comprehensive variable and unit selection), more granular analysis type refinement, and a streamlined customizable data output. The AstroDB Search is paired with the AstroDesk application, where users can login via their ORCiD and save an unlimited number of customized search queries. For researchers who need to submit, archive, and share their data with citable unique identifiers (DOIs) to comply with publisher and funding agency requirements, AstroMat offers a companion service to the AstroDB - the Astromaterials Data Repository (AstroRepo). Through its commitment to long-term data access and preservation, the Astromaterials Data Systems aims to help align cosmochemistry data with the Big-Data Era and reduce time to science for Planetary Sciences researchers by providing FAIR data for next generation scientific applications.

Being in an arid zone that is frequently submitted to high winds, south-central Arizona regularly gets impacted by several blowing dust events or dust storms every year. Major consequences of these events are visibility impairment and ensuing road traffic accidents, and a variety of health issues induced by inhalation of polluted air loaded with fine particulate matter produced by wind erosion. Despite such problems, and thus a need for guidance on mitigation efforts, studies dealing with dust source attribution for the region are largely missing. Furthermore, existing dust models exhibit large uncertainties and deficiencies in simulating dust events, rendering them of limited use in attribution studies or early warning systems. Therefore, to address some of these model issues, we have developed a high-resolution (1 km) dust modeling system by building upon an existing modeling framework consisting of Weather Research and Forecasting (WRF), FENGSHA (a dust emission model), and Community Multiscale Air Quality (CMAQ) models. In addition to incorporating new representations in the dust emission scheme, including roughness correction factor, sandblasting efficiency, and dust source mask, we implemented, in the dust model, up-to-date and very high-resolution data on land use, soil texture, and vegetation index. We used the revised dust modeling system to simulate a springtime dust storm (08–09 April 2013) of relatively long duration that caused a regional traffic incident involving minor injuries. The model simulations compared reasonably well against observations of concentration of particulate matter with a diameter of 10 μm and smaller (PM₁₀) and satellite-derived dust optical depth and vertical profile of aerosol subtypes. Interestingly, simulation results revealed that the anthropogenic (cropland) dust sources contributed more than half (~53 % or 260 µg/m³) of total PM₁₀, during the dust storm, over the region including Phoenix and western Pinal County. Contrary to the conventional wisdom that desert is the main dust source, our findings for this region challenge such belief and suggest that the regional air quality modeling over dryland regions should emphasize an improved representation of dust from agricultural lands as well, especially during high wind episodes. Such representations have the potential to inform decision-making in order to reduce windblown dust-related hazards on public health and safety.

Understanding the dynamical behavior of plasma and energetic particles in Earth’s inner magnetosphere requires carefully designed and calibrated instrumentation. The Van Allen Probes Mission included two instruments capable of measuring the proton distribution function in-situ. The Energetic Particle Composition and Thermal Plasma Suite (ECT) – Helium Oxygen, Proton, and Electron (HOPE) spectrometer (Spence et al., 2013; Funsten et al., 2013) used a top-hat detector designed to measure protons from the SC potential through 50 KeV in logarithmic energy steps. The Radiation Belt Storm Probes Ion Composition Detector (RBSPICE) instrument (Mitchell, 2013) used a time of flight and SSD detector design to measure protons from approximately 7 KeV through 650 KeV in logarithmic energy steps. Using the overlap of energy channels between the two instruments, the two instrument teams have worked diligently during the final Phase F of the mission to calibrate the observations so that a continuous distribution function can be resolved on nearly a spin-by-spin basis. During the life of these two instruments calibration changes have been required both on-board the spacecraft as well as within the final production datasets. Manweiler (2018) provided an early report on the intercalibration factors between HOPE and RBSPICE with a nominal factor of two difference between the proton data sets in the energy range between 7 and 50 KeV. With the final production of each of these data sets occurring in Fall 2021, both teams have been worked together to provide for an understanding of the required intercalibration factors to be used so that a full distribution function is available on a spin-by-spin basis. In this poster we report on the final efforts to provide this calibrated set of data products between the two instruments. Details of the intercalibration calculations are presented as well as year by year L by MLT maps of the factors required to match both datasets. Finally, we report on a supplementary data set that is to be made available which contains the spin-by-spin factors required to match the ECT/HOPE and RBSPICE/TOFxPH proton datasets. Funsten, H.O., et al. Space Sci Rev 179, 2013 Manweiler, J. W., et al., 2018 GEM Summer Workshop. Mitchell, D.G., et al., Space Sci. Rev., 179, 2013 Spence, H.E., et al. Space Sci Rev 179, 2013

Nutrient pollution is considered one of America’s most widespread, costly, and challenging environmental problems. Artificial Floating Islands (AFIs), a phytoremediation technology, has been proven as an efficient, environmental-friendly, and cost-effective strategy to address this issue. However, most previous studies of AFIs were done in controlled conditions at mesocosm experiments. In addition, limited information exists on the use of AFIs as a nutrient remediation/prevention strategy in Ohio. This study aims to fill these gaps. We are currently undertaking a combination of mesocosm and natural experiment to assess the nutrient-removal efficiency of AFI systems in the Milliron Research Wetlands (at the Ohio State University Mansfield campus), and establish a performance baseline for two native aquatic plant species, Carex comosa and Eleocharis palustris. In this study, 18 AFIs, 6 planted with Carex comosa, 6 with Eleocharis palustris, and 6 have no plants, were deployed in a section of the Milliron Research Wetlands. Physical and chemical parameters are being monitored bi-weekly. The AFI systems are constructed using PVC pipes to provide buoyance, EVA foam mats as platforms, and nylon nets to cover the system. Each AFI unit has nine luffa sponges, inserted in the foam mat, to hold aquatic plant seedlings, keep the moisture of roots, and enlarge the surface area for bacterial biofilm development. Since nutrient removal from the wetland is affected by numerous natural processes, a mesocosm experiment was set up to assist the quantification of nutrient removal due specifically to the presence of AFIs. The mesocosm experiment mimics the natural experiment at the wetland and contain 12 equal-size tanks containing water pumped directly from the wetland, 3 of which have AFIs with Carex comosa, 3 have Eleocharis palustris, 3 have no plants, and 3 contain just water from the wetland. Physical and chemical measurements (as well as sample collections) are performed weekly in the tanks. Water in the tanks are exchanged bi-weekly. Preliminary results show that the AFI systems quickly developed large root systems and extensive bacterial biofilms. The effects of the associations between plant biomass, biofilm development, and changing chemical and physical conditions will be investigated as the experiment progresses.

We present novel applications of yt, a tool originally designed for analysis of astrophysics datasets, to the geosciences. yt is a python-based platform for volumetric data, which enables semantically meaningful analysis and visualization. As part of a wider effort to bring yt to the geosciences, we present an initial use-case of yt applied to 3D seismic tomography models of the upper mantle from the IRIS Earth Model Collaboration. While the rendering capabilities of yt can in general be applied directly to 3D geoscience data, we add several graphical elements to the 3D rendering to aid in interpretation of volume renderings including latitude/longitude overlays and shapefile suport for plotting political and tectonic boundaries along the Earth’s surface. In this notebook, we focus on tomographic models of North America and the Western U.S., where high resolution models and rapidly varying seismic properties provide a rich dataset to explore systematically at a range of lengthscales. The notebook demonstrates loading and rendering of IRIS netcdf models, highlighting interesting 3D features of the Western U.S. upper mantle, and goes on to demonstrate how having direct control of the transfer functions used in creating the final volume rendering allows for a more systematic exploration of the role of the visualization method in our interpretation of 3D volumetric data. Finally, we conclude by demonstrating some of the semantically-aware capabilities of yt for analysis purposes, and demonstrate how these tools have cross-disciplinary functionality.

Over the last century, runoff from farms and cities, along with land cover and land use changes, have drastically altered the mass balance of nutrients in aquatic systems, affecting both their ecological functioning and the living communities they support. Here we present the results of a multi-year, long-term study designed to assess the control of land-use and hydrology on nutrient fate and transport within a mixed land-use watershed in north-central Ohio. A total of 64 streams (with a mix of urban, cropland, pasture, and forest catchments) have been sampled periodically since the summer of 2008. Hydrological conditions during the study period exhibited marked seasonality, with usually dry winter seasons (average ppt: 23.5±7.4 cm) and wet spring seasons (average ppt: 34.5±8.1 cm). Runoff generation in response to precipitation events is faster in streams draining developed catchments and slowest in forested streams, where runoff is generated only by events > 10 mm/day. Hydrologic connectivity in the watershed appear to be limited, since only about 25% of precipitation inputs were translated into quick flow. There is a significant, positive correlation between runoff and nutrient concentrations (R2 values are: 0.40 for streams draining urban landscapes, 0.34 for forested streams, 0.30 for cropland, and 0.28 for pastureland). We also observed significant inter-annual and seasonal variations on both DIN (p = 0.02) and PO4 concentrations (p < 0.01). Compared to dry years, nutrient fluxes during wetter years are, on average, 16% higher in urban catchments and 47% higher in forested catchments, but 32% lower in pasture-dominated catchments. Baseflow is responsible for only between 20-30% of the annual nutrient export from the watershed.

Inland waters are recognized as a significant source of CO2 to the atmosphere; however, the global magnitude of this flux remains uncertain. In particular, CO2 concentrations and fluxes in stream systems are extremely variable at scales of 10’s to 100’s of meters, complicating monitoring and prediction efforts. Thus, models of pCO2 that capture these scales of spatial variability are necessary for the accurate prediction and monitoring of stream CO2 fluxes. Despite a strong conceptual framework for the hydrologic processes that control stream CO2, predictive models to date have been empirical, based on Strahler stream order and regressions between observed pCO2 and landscape variables. We hypothesize that models incorporating well-described hydrologic processes may lead to new insights into the magnitude of various CO2 sources and improve predictions. Here, we develop and apply a process-based stream network model of CO2 based on NHDplus flowlines and driven by groundwater inputs, hyporheic exchange, water-column metabolism, advective transport, and atmospheric exchange. Model output is compared with 151 measurements of pCO2 (424 - 9718 ppm) collected in August, 2019 across the upper East River watershed in Gothic, CO, a mountainous, high-elevation headwaters system within the Colorado River basin. We find that modeled pCO2 captures observed spatial patterns and predicts measured values with a RMSE of ~250 ppm and R2 of 0.47 (p<10-15). Additionally, our process-based model performs significantly better than a multiple linear regression model between observations and a geomorphic variables (r2=0.35, p<10-7). Estimates from an optimized stream network model give additional insight into CO2 sources, suggesting that groundwater accounts for 70-80% of evasion fluxes, hyporheic processes for 20-30%, and water-column metabolism for ~1% across the East River watershed. The ability of our model to predict pCO2 at the spatial scales of variability may provide an important next step in estimating global CO2 fluxes, and future research will test the predictive power of process-based models at regional and global scales.

Temperature (T) is a key parameter controlling the rheology of lava flows. Since hazardous behavior of eruptions prevents direct measurements of hot magmatic bodies [1], the temperature is mostly retrieved by measuring the infrared (IR) radiance of the lava flow [2, 3]. The determination of T is however subjected to important errors related to the poor knowledge of one of the most critical parameters, namely spectral emissivity (ε). In this study, we explored the temperature–emissivity relationship for basaltic magmas, mostly from the 2014–2015 Holuhraun eruption. We performed in situ spectral emissivity measurements at relevant magmatic temperatures (from room temperature up to 1800 K) over a wide spectral range (400–8000 cm−1) covering TIR, MIR and SWIR regions, using a non-contact IR emissivity apparatus [4]. To unravel the complex radiative behavior of basalts with temperature evolution, structural, chemical and textural analyses (SEM, EMPA, Raman spectroscopy, DSC, XRD, and TEM) were systematically performed. Our results show that spectral emissivity varies accordingly with temperature, wavenumber, and is greatly affected by micro-scale crystallization, emphasizing the effect of small change in silicate structure on magma radiative properties. Because of the multiphase nature of lava, each constitutive phase (glass, melt, crystal, vesicles) contribute differently to the spectral emissivity. The evaluation and quantification of the impact of these phases on effective thermal radiative properties is a key point to improve the accuracy of lava T determination. These new data will ultimately improve our knowledge of the complex lava flow properties that are crucial in thermo-rheological models for hazard assessment [5]. References: [1] Kolzenburg et al. 2017. Bull. Volc. 79:45. [2] Harris, A. 2013: Cambridge University press. 728. [3] Rogic et al. 2019 Remote Sens., 11, 662 [4] De Sousa Meneses et al. 2015. Infrared Physics & Technology 69. [5] Thompson and Ramsey, 2021, Bulletin of Volcanology, 83:41. Keywords: Spectral emissivity, temperature, IR spectroscopy, rheology, basalt

Lava flows are one of the main hazards related to effusive basaltic volcanism. To minimize their impact during emplacement, we use lava flow potential distance-to-run predicted by propagation models. These models are partly based on infrared (IR) measurements of lava radiative heat fluxes by remote sensing (RS) methods (ground-based or satellite-based detectors) [1]. These results are however subjected to important errors related to the poor knowledge of spectral emissivity (ε), commonly considered constant by these well-established techniques[2, 3]. This oversimplification is an important source of uncertainties in derived temperatures, which restrain our capacity to accurately model active lava flows. In this study, we developed new algorithms that take into account the effect of spectral emissivity for calculating radiative heat fluxes. We describe the temperature-emissivity relationship with equations established at two wavelengths of interest for RS (10.9 μm and 1.6 μm) that are retrieved from in situ measurements of spectral emissivity for basaltic magma from the 2014–2015 Holuhraun eruption. Spectral emissivity data were systematically acquired over a wide spectral range (400–8000 cm−1) covering TIR, MIR and SWIR, and up to 1473 K [4]. Our results show that spectral emissivity varies linearly with temperature in TIR (10.9 μm), and nonlinearly in SWIR (1.6 μm). We confronted our lab-based results to the field IR data retrieved by [5] and found that temperature precision increases compared to data using constant emissivity value. These new insights will ultimately improve the thermo-rheological models of lava flows [6] in order to support hazard assessment in volcanic systems. References: [1] Kolzenburg et al. 2017. Bull. Volc. 79:45. [2] Harris, A. 2013: Cambridge University press. 728. [3] Rogic et al. 2019 Remote Sens., 11, 662 [4] De Sousa Meneses et al. 2015. Infrared Physics & Technology 69. [5] Aufaristama et al. 2018, Remote Sens, 10,151. [6] Thompson and Ramsey, 2021, Bulletin of Volcanology, 83:41. Keywords: Spectral emissivity, temperature, IR spectroscopy, remote sensing, basalt

Super-Earth and super-Venus exoplanets may have similar bulk compositions, but their surface conditions and mantle dynamics are vastly different. Vigorous convection within their metallic cores may produce dynamos and thus magnetospheres if the total heat flow out of the core exceeds a critical value. Earth has a core-hosted dynamo because plate tectonics cools the core relatively rapidly. In contrast, Venus has no dynamo and its deep interior probably cools slowly, potentially due to a lack of plate tectonics. It is not fully known how or if magnetic fields affect habitability, but the size of a magnetosphere might indirectly constrain the habitability of a surface. In this study, we developed scaling laws for how planetary mass affects the minimum heat flows required to sustain both thermal and chemical convection, which we compared to a simple model for the actual heat flow of both super-Earth and super-Venus exoplanets conveyed by solid-state mantle convection. We calculated three critical thresholds for heat flow based on varying the size of an inner core, the rate at which light elements precipitate at the core-mantle boundary, and the thermal conductivity of the core. We found that the required heat flows increase with planetary mass (to a power of ~0.8–0.9), but the actual heat flows of both super-Earths and super-Venuses could increase even faster (to a power of ~1.6) (Figure 1). Massive super-Earths are likely to host a dynamo in their metallic cores if their silicate mantles are entirely solid. Super-Venuses with relatively slow mantle convection could host a dynamo if their mass exceeds ~1.5 (with an inner core) or ~4 (without an inner core) Earth-masses. However, the mantles of massive rocky exoplanets might not be completely solid. Basal magma oceans may reduce the heat flow across the core-mantle boundary and smother any core-hosted dynamo. Detecting a magnetosphere at an Earth-mass planet probably signals Earth-like geodynamics. In contrast, magnetic fields may not reliably reveal if a massive exoplanet is a super-Earth or a super-Venus. We eagerly await direct observations in the next few decades. Published in JGR, doi:10.1029/2020JE006739

Magnetic trackline data are of central importance in estimating relative plate motions, have allowed a detailed apparent polar wander path to be determined for the Pacific Plate from skewness analysis, and provide important constraints for many other geophysical investigations. Interpreting trackline data typically requires processing, which often involves dividing tracks into quasi-linear segments. Here we present a method for automating this processing step by adapting the Ramer-Douglas-Peucker (RDP) algorithm, originally developed for polygonal approximation and cartographic generalization, for use on trackline data on a sphere and demonstrate its ability to segment data into quasi-linear (i.e., great circle-like) sections quickly based on two intuitive parameters. The new procedure is largely automated and requires minimal effort. As a test and proof of concept, we apply this method to estimate an angular velocity for motion between the Pacific and Rivera plates since 0.781 Ma using data from the NCEI geophysical trackline database. Our modified RDP algorithm identified 400+ track segments that intersected the Rivera Rise, of which more than 50 provided useful Pacific-Rivera spreading rates, which is roughly twice the 26 rates used to estimate Pacific-Rivera motion in the MORVEL set of geologically current plate relative angular . We compare the resulting angular velocity to previous estimates of Pacific-Rivera angular velocity and explore implications for Pacific-North America and Pacific-Cocos relative motion and Rivera absolute motion.

The paleolatitude distribution of paleoclimate proxies and contintential landmass is an important constraint for modeling and understanding paleoclimate. True polar wander (TPW), which can produce large, potentially rapid changes in paleolatitude, is a necessary component in paleolatitude reconstructions. Prior workers, e.g., van Hinsbergen et al. (2015), have created paleolatitude frameworks from global continental apparent polar wander paths (APWPs) drawn from running means of continental paleomagnetic studies (e.g., Torsvik et al. 2012). These are limited by the precision of the running mean, poor age resolution amplified by use of a running mean, and the uncertainties and the unknowns of ancient plate motion circuits. In particular, the Pacific Plate is linked to the global plate circuit through Antarctica. Early paleomagnetic tests of this circuit (Suarez & Molnar, 1980; Gordon & Cox 1980; Acton & Gordon 1994) indicated inconsistency of the circuit with paleomagnetic data such that the reconstructed Pacific plate did not move as far north as indicated by its indigenous paleomagnetic data. Some later work has asserted, however, that updated paleomagnetic data and plate reconstructions no longer indicate the inconsistency found before (Doubrovine & Tarduno 2008). Important progress has also been made in estimating the motion between East and West Antarctica from seafloor data (e.g. Granot & Dyment 2018). We revisit these questions here. We test the predictions of the global paleolatitude framework at points across the Pacific Plate using a well-constrained observed APWP constructed from indigenous Pacific plate data from skewness analysis of marine magnetic anomalies (Schouten & Cande 1976; Cox & Gordon 1980) and locations of paleo-equatorial sediments (Moore et al. 2004; Woodworth & Gordon 2018), which uniquely determine Pacific Plate paleolatitude independent of plate circuits. The misfit between the observed and predicted paleolatitude varies with longitude across the plate and is as large as ~10±3°, with the largest misfit occurring between 40 and 60 Ma. Implications of this discrepancy will be discussed and an improved paleolatitude framework for the Pacific plate will be presented.

To trace the Gulf Stream (GS) path across five decades from 1965 to 2017, we mapped the annually averaged positions of the Gulf Stream North Wall (GSNW) defined by the 15°C isotherm at 200 m depth computed using in situ seawater temperature records from the World Ocean Database 2018 (WOD18). Inter-annual GSNW variability is noticeably different west and east of ~50°W. There are two distinct variability zones west and east of that longitude—a zone with a rather narrow envelope (~3° of latitude-wide) west and a zone with a twice as wide envelope (~ 6° of latitude-wide) east of that longitude. The more disperse annual pathways are near the Mid-Latitude Transition Zone. Moreover, within the ~50-year timeline, the quasi-decadal period of 2005–2017 is marked by far larger spread in the annual GSNW positions than the previous decades, especially between 50°W and 40°W. The principal conclusion of our analysis, is that the GS between Cape Hatteras and the Grand Banks (west of 50°W) is not only stiff but maintains its position with astounding resiliency. The GSNW average position along that stretch of longitudes migrates slowly northward as a whole, but it is unlikely that such a slow and spatially insignificant migration could cause substantial changes in the Atlantic Meridional Overturning Circulation (AMOC). In contrast, near the Grand Banks (east of 50°W), the GSNW northward shift is quite noticeable—over 2.6° in latitude over ~50 years—and thus could have some impacts on the AMOC long-term dynamics. There are significant correlations between the GSNW and Ocean Heat Content (OHC) variability east of 50°W that may be critical for the GS path resilience and its future changes over decadal and longer time scales. Furthermore, the significant correlations between OHC and GSNW in the extension zone rose from r=0.5 for annual to r=0.8 for pentadal to r=0.9 decadal time scales. We assert that the OHC may become the best indicator of the GS path’s variability on decadal and longer time scales.

The isotopic composition of water vapor (e.g. its Deuterium content) evolves along the water cycle as phase changes are associated with isotopic fractionation. In the tropics, it is especially sensitive to convective processes. Consequently the isotopic composition of precipitation recorded in paleoclimate archives has significantly contributed to the reconstruction of past hydrological changes. It has also been suggested that observed isotopic composition of water vapor could help better understand convective processes and evaluate their representation in climate models. Yet, water isotopes remain rarely used beyond the isotopic community to answer today’s pressing climate questions. A prerequisite to better assess the strengths and weaknesses of the isotopic tool is to better understand what controls spatio-temporal variations in water vapor isotopic composition through the tropical atmosphere. A first step towards this better understanding is to understand what controls the isotopic composition of the sub-cloud layer water vapor over the ocean. Isotopic measurements show that the water vapor is the most enriched in trade-wind regions, and becomes more depleted as precipitation increases. To understand this pattern, we use global simulations with the isotope-enabled general circulation model LMDZ, large-eddy simulation in radiative-convective equilibrium and with large-scale ascent or descent, with the isotope-enabled model SAM and simple analytical models. We show that increased precipitation rate is associated with increased isotopic depletion if it is associated with stronger large-scale ascent, but with decreased isotopic depletion if it is associated with warmer surface temperature. As large-scale ascent increases, the isotopic vertical gradient in the lower troposphere is steeper, which makes downdrafts and updrafts more efficient in depleting the sub-cloud layer water vapor. The steeper gradient is caused mainly by the larger quantity of snow falling down to the melting level, forming rain whose evaporation depletes the water vapor.