Ionospheric outflow supplies nearly all of the heavy ions observed within the magnetosphere, as well as a significant fraction of the proton density. While much is known about upflow and outflow energization processes, the full global pattern of outflow and its evolution is only known statistically or through numerical modeling. Because of the dominant role of heavy ions in several key physical processes, this unknown nature of the full outflow pattern leads to significant uncertainty in understanding geospace dynamics, especially surrounding storm intervals. That is, global models risk not accurately reproducing the main features of intense space storms because the amount of ionospheric outflow is poorly specified and thus magnetospheric composition and mass loading could be ill-defined. This study defines a potential mission to observe ionospheric outflow from several platforms, allowing for a reasonable and sufficient reconstruction of the full outflow pattern on an orbital cadence. An observing system simulation experiment is conducted, revealing that four well-placed satellites are sufficient for reasonably accurate outflow reconstructions. The science scope of this mission could include the following: reveal the global structure of ionospheric outflow; relate outflow patterns to geomagnetic activity level; and determine the spatial and temporal nature of outflow composition. The science objectives could be focused to be achieved with minimal instrumentation (only a low-energy ion spectrometer to obtain outflow reconstructions) or with a larger scientific scope by including contextual instrumentation. Note that the upcoming Geospace Dynamics Constellation mission will observe upwelling but not ionospheric outflow.

There is a lot going on in introductory undergraduate science classrooms. Students bring their culture, background, and previous science experiences; instructors bring their knowledge, attitudes, and experience in science and in teaching. Students are there for a variety of reasons, and a substantial proportion will become K-12 teachers: that introductory course may be their primary science experience as an adult learner. How future teachers learn science is of critical importance to how they teach science, but few college science classes reflect the vision of the 2012 Framework for K-12 Science Education, in which “students actively engage in scientific and engineering practices in order to deepen their understanding of crosscutting concepts and disciplinary core ideas” (p. 217). The vision of the Teaching with Investigation and Design in Science (TIDeS) project is that future teachers will learn science as undergraduates the way they are expected to teach science in the K–12 classroom: engaging all students in science investigation and engineering design in a discourse-filled, context-rich, inclusive learning process. TIDeS seeks to catalyze transformation of introductory science courses by supporting faculty in the development and implementation of high-quality, rigorously tested, inclusive curricular materials that focus investigation and design. The project has two broad research questions: (1) How do the beliefs and practices of instructors change with developing and/or implementing new curricular materials? (2) What is the impact of the use of these new materials on diverse students? To address these questions, the TIDeS team developed a suite of research probes aligned with the project’s guiding principles and with each other (see figure). The probes include a semi-structured, pre-/post- faculty interview, a quantitative and qualitative classroom observation protocol, a pre-/post- student survey, a syllabus rubric, and rubrics for the curricular materials and student readings. Our preliminary data suggest that, in combination, the probes will provide a holistic picture of what teaching with investigation and design in introductory college-level science courses looks like, how it differs from an active learning classroom, and how it can support the preparation of future teachers.

AbstractSeveral flood-generating mechanisms could produce high flows in catchments however, AMS/POT sampling is not considering these hydrological processes. Grouping the floods into homogenous samples (in terms of process) has many potential advantages, such as better estimation of return level. This study aims to develop methods to classify and group floods, based on the simple flood hydrograph characteristics, from the daily discharge data. This approach is based on the underlying hypothesis that similar hydrological and catchment conditions lead to similar hydrological responses. We used the Dresden gauge station on the Elbe river, Germany (1950-2019). Flood separation follows four steps: 1. Identification of peaks, i.e., points with a higher streamflow value than its prior and next values, 2. Pruning based on 90th percentile threshold value, 3. Application of independence criterion, 4. Identification of flood starting and ending position. From the separated flood events, six features are extracted for clustering, i.e., peak, volume, timescale, rise to duration ratio, occurrence season and the existence of multi peaks. Extracted flood features include both numerical and categorical variables thus, to deal with these mixed feature datasets, we employed the K-medoids technique for clustering. Further, various cluster validation indices robustly help to identify the optimal number of clusters. We also performed the feature relevancy analysis to understand the hydrograph features’ relative importance. Since hydrometeorological variables are not used for classification, we used the magnitude of the precipitation and snowmelt during the flood duration to characterize the various clusters. Clustering results show that the employed methods are effective in classifying the flood events driven by different flood drivers.Keywords: Flood classification, Flood separation, Flood frequency analysis

The Kalahari Basin in southern Africa, shaped by subsidence and epeirogeny, features the Okavango Rift Zone (ORZ) as a significant structural element characterized by diffused extensional deformation forming a prominent depocenter. This study elucidates the Pleistocene landscape evolution of the ORZ by examining the chronology of sediment formation and filling this incipient rift and its surroundings. Modeling of cosmogenic nuclide concentrations in surficial eolian sand from distinct structural blocks around the ORZ provides insights into sand’s residence time on the surface. Sand formation occurred from ~2.2 to 1.1 Ma, coinciding with regional tectonic events. Notably, provenance analyses of sand within ORZ’s lowermost block where large alluvial fans are found indicate different source rocks and depositional environments than those of the more elevated eolian sand. This suggests that the major phase of rift subsidence and the following incision of alluvial systems into the rift occurred after eolian dune formation. Luminescence dating reveals that deposition in alluvial fan settings in the incised landscape began not later than ~250 ka, and that a lacustrine environment existed since at least ~140 ka. The established chronological framework constrains the geomorphological effects of the different tectono-climatic forces that shaped this nascent rifting area. It highlights two pronounced stages of landscape development, with the most recent major deformation event in the evolving rift probably occurring during the middle Pleistocene transition (1.2-0.75 Ma). This event is reflected as a striking change in the depositional environments due to the configurational changes accompanying rift progression.

We investigate the evolution of outwardly propagating simple MHD waves in a model of the expanding solar wind using MHD simulations. In order to understand the different evolution of slow, Alfvén and fast modes, the question of wave-action conservation is re-examined theoretically. Using the fluctuation averaged Lagrangian, we discuss the conservation of total wave action and Equi-partition of wave energy for MHD waves. Results show that, even though the wave action for a simple monochromatic wave is subject to loss under resonance/degeneracy condition - conditions that can occur in the expanding solar wind in the regions where plasma ß crosses one, the total wave action possessed by all modes remains conserved, representing a wave action exchange between different degrees of freedom. The Expanding Box simulations demonstrate the results of the theoretical modeling, and reveal further details about mode-mixing, Alfvén resonance and wave steepening. All of these may help to understand the evolution of fluctuations from the inner heliosphere out to Earth orbit and beyond.

The Colorado Rockies were initially raised during the Laramide Orogeny ca. 70-45 Ma. But consensus exists that the range experienced a second, post-Laramide episode of surface uplift; the timing and cause of that post-Laramide surface uplift event remains enigmatic. Low-temperature thermochronologic studies conducted by us and others using apatite (U-Th)/He (AHe), apatite fission track (AFT), and zircon (U-Th)/He (ZHe) techniques reveal that a dome of kilometer-scale exhumation occurred in Colorado’s Elk and West Elk mountains between ca. 18-6 Ma. We call this feature the “Gothic Dome” because it is centered on Gothic Mountain, near the town of Crested Butte. We suggest the ~100-km-diameter Gothic Dome likely experienced Miocene surface uplift, which triggered the dome-shaped exhumation pattern documented by the low-temperature thermochronometry. The exhumation magnitude exceeds 4 km in the center of the dome (as revealed by a 16 Ma ZHe date on an Oligocene pluton) and diminishes toward its perimeter. This diminution of exhumation magnitude toward the perimeter is revealed by progressively older AHe, AFT, and ZHe dates in all directions away from Gothic Mountain. AHe dates for samples that lie outside the perimeter are Laramide-age or older, further documenting the dome-shaped nature of this Miocene exhumation event and illustrating the low magnitude of Miocene to recent exhumation outside the dome’s perimeter. Outcrops of ca. 11 Ma basalt surround the Gothic Dome to the north, west, and south, requiring that Miocene exhumation outside the dome’s perimeter was minimal. A suite of alkaline, low-volume, felsic plutons and ultramafic lamprophyres intruded the Gothic Dome between ca. 18-12 Ma. This alkalic magmatism began either immediately prior to or contemporaneous with the onset of Gothic Dome exhumation, hinting that the same root cause might be responsible for both. Workers elsewhere, including Tibet, the Altiplano, and California’s Sierra Nevada mountains, have attributed small-volume alkalic magmatism, surface uplift, and exhumation to the activity of lithospheric drips. We offer that Miocene activity of such a drip beneath Colorado’s Elk and West Elk mountains is an appealing mechanism to explain the near simultaneity of those same phenomena here.

Private groundwater wells have the potential to be an unmonitored source of contaminants that can harm human health for millions of people throughout the United States. Developing models that predict potential exposure to contaminants, such as nitrate, could guide sampling efforts and allow the residents to take action to reduce their risk. Machine learning models have been successful in predicting nitrate contamination using geospatial information such as proximity to nitrate sources or soil type, but previous models have not considered meteorological factors that change temporally. In this study, we test random forest (regression and classification) and linear regression models to predict nitrate contamination of wells using rainfall and temperature records over the previous 180-days. We trained and tested models for (1) all of North Carolina, (2) each geographic region in North Carolina, (3) a three-county region with high density animal agriculture, and (4) a three-county region with a low density of animal agriculture. All regression models had poor predictive performance (R2 = 0.04) for all areas tested. The random forest classification model for the coastal plain region showed fair agreement (Cohen’s kappa = 0.23) when trying to predict whether contamination occurred. All other classification models had slight or poor predictive performance. Our results show that temporal changes in rainfall and temperature alone are not enough to predict nitrate contamination in most areas of North Carolina but show potential in the coastal plain region.

The inversion of Scholte wave dispersion curves is one of the most important methods employed in the detection of marine sedimentary structures. The measurement methods of Scholte wave dispersion are primarily developed from terrestrial geophysical exploration technologies. Unlike terrestrial seismic source excitation methods, marine exploration typically uses air guns to generate seismic waves in seawater, which will result in strongly dispersed Guided-P waves. We found that the Guided-P waves will truncate the higher-mode dispersive Scholte waves at their lower cutoff frequency. However, a simple individual preprocess of suppressing Guided-P procedure (SGP) before extracting dispersion curves can significantly increase the frequency band and image the full dispersive modes of Scholte waves. The wider frequency band and higher-mode Scholte wave dispersion curves can effectively improve the constraints on the submarine shear wave velocity structure. Based on this, we highly recommend adding this simple step to Scholte wave dispersion imaging.

It has been four decades since Apollo 16 returned the first wide-field UV imagery of the Earth and revealed the vast extent of exospheric hydrogen (H) atoms around the planet. Since that time, appreciation has grown regarding the significance of this outermost atmospheric layer, whose charge exchange interaction with ambient ions dissipates magnetospheric energy, generates the energetic neutral atoms (ENAs) widely used for remote sensing of the ring current dynamics during geomagnetic storms, and accelerates gravitational escape and thus permanent atmospheric evolution. Despite the importance of Earth’s H exosphere to the solar-terrestrial system, however, current understanding of its global structure and dynamical evolution is insufficient, such that the origin of persistent discrepancies between measurements and models remains unresolved. Remote sensing of UV emission from geocoronal H atoms, generated through resonant scattering of solar radiation at 121.6 nm (Lyman-alpha) is the only empirical means available to investigate the terrestrial exosphere. In this work, we present robust tomographic-based techniques we have developed in recent years to estimate the 3-D, global and time-dependent H-density distributions during quiet and storm-time from observations of its optically thin emission at Lyman-α acquired from the Lyman-alpha detectors onboard the NASA TWINS satellites. Several examples of recent 2D and 3D data analyses will be used to demonstrate the current state-of-the-art, reveal surprising exospheric phenomenon, and motivate future work.

Because remote sensing (RS) data are spatially and temporally explicit and available across the globe, they have the potential to be used for predicting runoff in ungauged catchments and poorly gauged regions, a challenging area of research in hydrology. There is potential to use remotely sensed data for calibrating hydrological models in regions with limited streamflow gauges. This study conducts a comprehensive investigation on how to incorporate gridded remotely sensed evapotranspiration (AET) and water storage data for constraining hydrological model calibration in order to predict daily and monthly runoff in 30 catchments in the Yalong River basin in China. To this end, seven RS data calibration schemes are explored, and compared to direct calibration against observed runoff and traditional regionalization using spatial proximity to predict runoff in ungauged catchments. The results show that using bias-corrected remotely sensed AET (bias-corrected PML-AET data) for constraining model calibration performs much better than using the raw remotely sensed AET data (non-bias-corrected AET obtained from PML model estimate). Using the bias-corrected PML-AET data in a gridded way is much better than using lumped data, and outperforms the traditional regionalization approach especially in headwater and large catchments. Combining the bias-corrected PML-AET and GRACE water storage data performs similarly to using the bias-corrected PML-AET data only. This study demonstrates that there is great potential in using bias-corrected RS-AET data to calibrating hydrological models (without the need for gauged streamflow data) to estimate daily and monthly runoff time series in ungauged catchments and sparsely gauged regions.

The Neoproterozoic Era represents extreme environmental conditions with three major glaciation events. Associated with these glaciation and deglaciation periods are high amplitude positive and negative δ13C excursions which have been observed in the rock records, suggesting perturbations in oceanic biogeochemical cycles. However, whether these isotopic records reflect primary depositional signature and open ocean condition are debated. The Marwar Basin of the Indian Shield preserves one such record of the Ediacaran time period. The magnitude of negative δ13C excursion from the Marwar Basin is comparable with the Shuram excursion.1 We report elemental compositions of sixty-eight carbonate samples collected from five spatially distributed sections from the Bilara carbonates of the Marwar Basin. Selected samples from two of these sections were analyzed for their radiogenic Sr (87Sr/86Sr) and stable Ca (δ44/40Ca) isotopic compositions. Elemental compositions were measured using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS, X series II) while 87Sr/86Sr and δ44/40Ca (reported relative to NIST SRM 915a) values were measured using a Thermal Ionization Mass Spectrometer (TIMS, Triton Plus), both at the CEaS, IISc Bangalore, India. The Bilara Group carbonates are sub-divided into two populations based on non-redox REY anomalies and the Y/Ho ratio. Super-Chondritic Y/Ho (40-52) and positive La anomaly (1.01-2.65) of some samples suggest deposition under open ocean conditions and connectivity to the global ocean. While heterogeneity in δ13C values is evident in samples with low Y/Ho (<40), samples with high Y/Ho (> 40) preserve low δ13C values. No significant correlation has been observed between δ13C and Ce anomaly (Ce/Ce*) suggesting absence of any paleo-redox gradient. The lowest 87Sr/86Sr (~0.7079) observed in the carbonates is comparable with Ediacaran seawater confirming retention of primary depositional signatures in these samples. These carbonates show heavy δ44/40CaSRM915a compositions (1.44‰-2.21‰) typical of Neoproterozoic post-glacial successions2. Our study confirms primary origin and open ocean nature of the late Neoproterozoic δ13C excursions in the Marwar Basin. [1] Ansari et al., (2018) Precambrian Research, [2] Silva-Tamayo et al., (2010) Precambrian Research

Although the Brown mathematical model is the standard model for waveform retracking over open oceans, coastal waveforms usually deviate from open ocean waveform shapes due to inhomogeneous surface reflections within altimeter footprints, and thus cannot be directly interpreted by the Brown model. Generally, the two primary sources of heterogeneous surface reflections are land surfaces and bright targets such as calm surface water. The former reduces echo power, while the latter often produces particularly strong echoes. In previous studies, sub-waveform retrackers, which use waveform samples collected from around leading edges in order to avoid trailing edge noise, have been recommended for coastal waveform retracking. In the present study, the peaky-type noise caused by fixed-point bright targets is explicitly detected and masked using the parabolic signature in the sequential along-track waveforms (or, azimuth-range echograms). Moreover, the power deficit of waveform trailing edges caused by weak land reflections is compensated for by estimating the ratio of sea surface area within each annular footprint in order to produce pseudo-homogeneous reflected waveforms suitable for the Brown model. Using this method, Jason-2 altimeter waveforms are retracked in several coastal areas. Our results show that both the correlation coefficient and root mean square difference between the derived sea surface height anomalies and tide gauge records retain similar values at the open ocean (0.9 and 20 cm) level, even in areas approaching 3 km from coastlines, which is considerably improved from the 10 km correlation coefficient limit of the conventional MLE4 retracker and the 7 km sub-waveform ALES retracker limit. These values, however, depend on the coastal topography of the study areas because the approach distance limit increases (decreases) in areas with complicated (straight) coastlines.

Geodetic altimeters provide unique observations of the river surface longitudinal profile due to their long repeat periods and densely spaced ground tracks. This information is valuable for calibrating hydraulic model parameters, and thus for producing reliable simulations of water level for flood forecasting and river management, particularly in poorly instrumented catchments. In this study, we present an efficient calibration approach for hydraulic models based on a steady-state hydraulic solver and CryoSat-2 observations. In order to ensure that only coherent forcing/observation pairs are considered in the calibration, we first propose an outlier filtering approach for CryoSat-2 observations in data-scarce regions using simulated runoff produced by a hydrologic model. In the hydraulic calibration, a steady-state solver computes the WSE profile along the river for selected discharges corresponding to the days of CryoSat-2 overpass. In synthetic calibration experiments, the global search algorithm generally recovers the true parameter values in portions of the river where observations are available, illustrating the benefit of dense spatial sampling from geodetic altimetry. The most sensitive parameters are the bed elevations. In calibration experiments with real CryoSat-2 data, validation performance against both Sentinel-3 WSE and in-situ records is similar to previous studies, with RMSD ranging from 0.43 to 1.14 m against Sentinel-3 and 0.60 to 0.73 against in-situ WSE observations. Performance remains similar when transferring parameters to a one-dimensional hydrodynamic model. Because the approach is computationally efficient, model parameters can be inverted at high spatial resolution to fully exploit the information contained in geodetic CryoSat-2 altimetry.

Advancing climate change research requires accurate and traceable measurement of the atmospheric longwave irradiance. Current measurement capabilities are limited to an estimated uncertainty of larger than ± 6 W/ m2 using the interim World Infrared Standard Group (WISG). Two independently designed and calibrated absolute radiometers measuring downwelling longwave irradiance were compared during five outdoor comparisons in 2013, 2015, and 2017 at the Physikalisch Meteorologisches Observatorium Davos/World Radiation Center (PMOD/WRC) and the USA-DOE Atmospheric Radiation Measurement program (ARM) in the Southern Great Planes (SGP). Two Absolute Cavity Pyrgeometers (ACPs) developed by the National Renewable Energy Laboratory (NREL) and four Integrating Sphere Infrared Radiometers (IRISs) developed by PMOD/WRC took part in these intercomparisons. From the five comparisons, the difference between the irradiance measured by the ACPs and IRISs varied from 0.2 W/ m2 to 2.5 W/ m2 based on the atmospheric conditions, which is within the combined stated uncertainties of ±3 W/ m2. The irradiance measured by the WISG is lower than the average irradiance measured by ACPs and IRISs, magnitude of the difference varied from 0.2 W/m2 to 6.6 W/ m2 depending on the integrated water vapor. A concerted effort at the World Meteorological Organization (WMO) Commission for Instruments and Methods of Observation Commission (CIMO) Task Team on Radiation References (TT) started during a meeting from November 15 to 17, 2017 in the National Physical Laboratory (NPL), Teddington, United Kingdom to establish a world reference for measuring the atmospheric longwave irradiance with lower uncertainty and with traceability to SI units by using the ACPs and IRISs as the reference.

The Heifangtai area is commonly known as the museum of loess landslides in China. Irrigation-induced loess flowslides frequently recur along the margin cliffs of the Hefaingtai terrace, causing 42 fatalities and significant economic losses, as well as major ecological and environmental problems, such as increased soil erosion rate. The initiation and mobility of these irrigation-induced loess flowslide recurrences remain undetermined. On three typical recurrences of the loess flowslides, we performed joint geophysical detection using electrical resistivity tomography (ERT) and multichannel analysis of surface waves (MASW), and also tested loess basic properties by field profile sampling. In addition, we examined the shear behaviors of saturated loess utilizing an undrained ring shear apparatus. The geophysical signatures and in-situ loess property profiles showed that hydrogeological conditions are key to the initiation of recurring loess flowslides. The results also demonstrated that liquefaction shear behaviors of saturated loess control the mobility of after-failure of the loess flowslides. Rapid criteria of liquefaction susceptibility evaluation are suggested to provide a better understanding of the dynamic mechanisms of loess flowslides. These findings shed substantial light on long-runout flowslides that occur in fine-grain soil and their implications for landslide hazard mitigation.

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.

Large storms are considered to be influential drivers of morphologic change on open sandy coasts. Whereas storm-driven morphologic changes and the recovery processes that typically follow have been robustly documented, less well understood is the concept of storm-driven coastal behavior over seasonal to annual timescales, which integrates multiple storm response and recovery cycles. In this study, storm controls on coastal evolution are evaluated using a topographic dataset containing monthly measurements of the intertidal and subaerial beach for 5 years (2009-2014) along a 10 km reach of open sandy coast fronting NASA-Kennedy Space Center near Cape Canaveral, Florida. In addition to shoreline and volume change analyses, a novel Empirical Orthogonal Function (EOF) analysis has been applied to these data to extract dominant spatial and temporal patterns of morphologic change over the full beach surface, as opposed to being applied over individual cross-shore transects or alongshore contours as previously practiced. Results indicate that the most dominant pattern of morphologic evolution within these data describes an isolated change of state to this system initiated by the impact of Hurricane Sandy (2012). This is exhibited physically as a southward migration of a previously stable cuspate foreland beginning immediately after the storm, resulting in nearly 600 m of propagation over the following 1.5 yr observation interval. Additionally, remaining dominant patterns describe a seasonal erosion cycle linked to storm driven seasonality in nearshore water levels, and a spatially variable berm formation cycle on inter-storm timescales likely driven by storm-induced variations in sediment storage locations and associated availability to non-storm hydrodynamics. These results illustrate that coastal response to an individual storm may control the recovery processes that follow by shifting morphologic equilibria such that processes of recovery drive the beach toward a configuration unlike its pre-storm state. Because these post- event processes influence morphologic response to the next event, the results presented here highlight a largely unexplored coupling between storm response and recovery that may be considered a dominant control on interannual-scale coastal evolution in storm-prone regions.

This study observed seasonal trends and inferred drivers of CO2 biogeochemistry at the air-water interface of Lake Superior. Underway carbon dioxide partial pressure pCO2 was measured in surface water during 69 transects spanning ice free seasons of 2019-2022. These data comprise the first multiannual pCO2 time series in the Laurentian Great Lakes. Surface water pCO2 was closely tied to increasing atmospheric pCO2 by a 100 day CO2 equilibration timescale, while seasonal variability was controlled equally by thermal and biophysical drivers during the ice-free season. Comparison to previous modeling efforts indicates that Lake Superior surface pCO2 increased at a similar rate as the atmosphere over the preceding two decades. Spatial heterogeneity in CO2 dynamics was highlighted by a salinity-based delineation of “riverine” and “pelagic” regimes, each of which displayed a net CO2 influx over Julian days 100-300 on the order of 30 Gmol C. These findings refine previous estimates of Lake Superior C fluxes, support predictions of anthropogenic CO2 invasion, point to new observation strategies for large lakes, and highlight an urgent need for studies of changes to lacustrine C cycling.