We evaluate the mass balance of the Russia High Arctic Archipelago between April 2002 and August 2016 employing independent estimates obtained using time-variable gravity from the NASA/DLR GRACE mission and satellite altimetry data from the NASA ICESat and the ESA CryoSat-2 missions. We present a new algorithm designed to derive ice elevation change maps using altimetry data and we evaluate its performance over the region of interest. Gravimetric and Altimetric observations provide consistent results and show that over the period under analysis, glaciers in the region have lost mass at a rate of 15 +/-7 Gt/yr corresponding to a sea level contribution of 0.039 mm/yr. The mass loss increased after 2010, reaching a maximum rate of 25 +/-7 Gt/yr between 2010 and 2016. The increased mass loss was associated with high thinning rates at low elevations (below 500 m), with marine-terminating glaciers thinning significantly faster than those terminating on land. The mass loss process was associated to a shift in climatic conditions in the region due to enhanced atmospheric and ocean temperatures and decreased sea ice concentrations. These results indicate that glaciers in the region are sensitive to variations of both climatic mass balance and ice discharge.

Social Learning contributes as a guiding proposal for the joint intervention of the local actors and dissemination of methodologies and collaborative activities in socioenvironmental diagnoses. Its principles are active involvement, consultation and public access to participation. Several participatory tools have been developed and have been applied within the principles of Social Learning, such as local socioenvironmental agendas, action research, role playing; world café, participatory monitoring of the streams and socioenvironmental mapping. This article presents the last one applied in different contexts and with different groups of social actors, always aiming to elaborate a participatory diagnosis of the place and reality to identify the wicked problems. Socioenvironmental mapping is a didactic-pedagogical resource used to reflect and rethink about the place. It contributes to elaborate a diagnosis of the local reality and it subsidizes the reflection on the forms of the land use and occupation and its implications for the quality of life of its inhabitants, fostering discussions, possibilities of actions to solve problems and conflicts to improve the quality of life in communities. The map is a product of collective and collaborative construction of the participants. It contributes to transform information into knowledge and establish a bridge between scientific and local knowledge. Consider the following procedures: a) the reality in which the individual lives and how he deals with his immediate environment and his understanding of it, as a starting point; b) the possibility of re-elaborating the individual’s initial understanding of his / her place; c) the way to the development of different types of knowledge for the construction of more elaborate and more critical knowledge. We have applied this methodology with teaching formation, social control and conservation area with positive results of empowering the communities.

Mesoscale convective systems (MCSs) are an important component of our hydrologic cycle as they produce prolific rainfall in the tropics and mid-latitudes. Recent advancements in high-resolution modeling show promise in representing MCSs in regional climate simulations. However, how well do these models represent the complex interactions between convective dynamics and microphysics in MCSs remain unknown. In this study, we take advantage of observations collected during the Midlatitude Continental Convective Cloud (MC3E) experiment to evaluate multi-scale aspects of MCSs in convection-permitting WRF model. We conducted three sets of month-long simulations with Morrison and P3 (1-ice and 2-ice categories) microphysics, respectively, at 1.8 km grid-spacing over the Southern Great Plains. MCSs in observations and simulations were tracked using a newly developed FLEXTRKR algorithm. About 15-20 MCSs were identified in the simulations, consistent with observations. All three simulations underestimate observed monthly total precipitation which are primarily from MCSs, suggesting the biases might be caused by large-scale forcings rather than microphysics. All simulated MCSs overestimate convective area and precipitation amount but underestimate stratiform rain area and precipitation. Simulated MCS convective updraft intensities are comparable with radar retrievals for moderate depths of convective cores, but are too strong for deep cores. The two P3 simulations have smaller mean ice mass aloft but more frequent heavy convective rain rate at the surface than the simulation with Morrison, agreeing better with observations (Figure 1). Simulated stratiform area ice mass in the upper troposphere are generally larger than radar retrievals, but the P3 2-ice category has relatively smaller bias. We will also use polarimetric radar 3-D rain water retrieval to further evaluate the vertical evolution of rainfall to explain differences in simulated surface precipitation.

Our presentation represents a brief overview of recent climatic and environmental changes over the Dry Lands of Northern Eurasia. The Dry Land Belt (DLB) in Northern Eurasia is the largest contiguous dryland on Earth. During the last century, changes here have included land use change (e.g., rapid virgin land development in the mid of the 1950s; cf. Figure 1), resource extraction, rapid institutional shifts (e.g., collapse of the Soviet Union), climatic changes, and natural disturbances. These factors intertwine, overlap, sometimes mitigate but sometimes feedback upon each other to exacerbate their synergistic and cumulative effects. Thus, it is important to document properly each of these external and internal factors and to characterize structural relationships among them in order to develop better approaches to alleviating negative consequences of these regional environmental changes. This paper addresses the climatic changes observed over the DLB in recent decades and outlines possible links of these changes (both impacts and feedbacks) with other external and internal factors of contemporary regional environmental change and human activities within the DLB.

Relating seismic anisotropy with mantle flow requires a good understanding of the rock’s microstructural evolution and the development of crystal preferred orientations (CPO), because plastic deformation of olivine is interpreted as the main cause for mantle seismic anisotropy. In this contribution, the influence of deformation history in the microstructure evolution and resulting seismic anisotropy is investigated by means of full-field numerical simulations at the microscale. We explicitly simulate the microstructural evolution of olivine polycrystalline aggregates during dynamic recrystallization up to high strain using the code VPFFT/ELLE (e.g. Griera et al., 2011; 2013; Llorens et al., 2016). Modeling results indicate that the evolution of a CPO is highly sensitive to the initial olivine fabric. When the initial fabric is formed by a random distribution of crystallographic orientations, there is a rapid alignment of the a-axes (or [100]) with the stretching direction of flow. However, when there is an initial CPO inherited from previous deformation, larger strains are required for the a-axes to become re-aligned with the stretching direction. Our numerical results agree with field and experimental observations (e.g. Boneh and Skemer, 2014; Skemer et al., 2012). The analysis of the seismic properties reveals that an increase of the strength of the initial inherited CPO produces a reduction of the azimuthal seismic anisotropy, compared to the case with an initial random fabric. It is concluded that the deformation history significantly influences the development of fabrics. Accordingly, seismic anisotropy interpretations must be carried out with caution in regions with complex deformation histories. References Boneh Y., Skemer P. 2014. EPSL, 406. Griera A, et al. 2011. Geology 39, 275-278. Griera A, et al. 2013. Tectonophysics 587, 4-29. Llorens, M.-G. et al. 2016 EPSL, 450, 233-242. Skemer P. et al. 2012. Geochemistry Geophysics Geosystems, 13:3.

Decision makers and water managers throughout New England desire to understand how development and land-use change, especially under a changing climate, will affect high flows, flooding, and stormwater. We use the New England Landscape Futures (NELF) project to demonstrate the potential for translating participatory scenarios to simulations of land use and land cover and the resulting effects on streamflow. In addition to projecting recent trends, four other landscape scenarios were co-designed through a structured process that engaged over 150 stakeholders and scientists from throughout New England. Daily streamflows were simulated with the Soil and Water Assessment Tool (SWAT) to investigate how high flows vary among the scenarios for the less developed Cocheco River watershed in southeast New Hampshire and the more urbanized Charles River watershed in eastern Massachusetts. The hydrologic response of each land-use scenario was simulated for both historic weather (1999-2017) and downscaled weather for 2049-2067 from the CCSM 4.0-RCP 8.5 model-pathway from the Community Earth System Model. Differences among the land-use scenarios led to no differences in average annual water yield and ET. Loss of forest and increase in urban area reduces the baseflow contribution to streamflow while increasing storm runoff. This shift in partitioning did not affect the frequency of high flows (5% exceedence). The increase in runoff did lead to a concomitant increase in the average annual maximum flow, and the effect is larger in the Charles River watershed than in the Cocheco. Under the future climate, a combination of increased precipitation and decreased potential evaporation results in increased streamflow relative to the scenarios modeled with the historic weather. As a fraction of precipitation, surface runoff remains the same, and baseflow increases. The frequency of high flows increases, with the 5%-exceedence flow (under historical weather) being met or exceeded 8-9% of the days. Annual maximum flows also increased for the future climate, and the effects of land-use change and climate on annual maximum flows are comparable. These water-related results fit into a larger framework for evaluating ecosystem services associated with socially relevant landscape scenarios.

Conventional tidal prediction models typically combine constituent lunisolar forcing factors harmonically fit to sets of collected tidal gauge data. A harmonics analysis is favored over a precise orbital ephemeris-based gravitational forcing model, as tides are localized in scope and sensitive to a particular volume geometry. But what happens when the dynamic behavior is much larger in scale? As we have demonstrated previously [1], lunisolar tidal constituents forced by a strong biennial-modulated annual signal will provide a high-quality fit to ENSO – albeit subject to over-fitting of the numerous constituent factors available. Yet as ENSO is a large-scale phenomenon, it should be more amenable to applying a precise set of ephemeris data as the forcing to a Laplace’s tidal equation formulation. This should reflect the underlying physics governing the dynamics more realistically, while severely constraining the degrees of freedom (DOF) in factors which lead to the possibility of over-fitting. We used the NASA JPL Horizons (https://ssd.jpl.nasa.gov/horizons.cgi) ephemeris data for the Sun and Moon as a parametric input to the well-known 1/R^3 gravitational forcing function and verify as good a quality fit as that available from a high-DOF harmonics approach. This extends over the modern-day instrumental record of ENSO but also covers the coral proxy records that span the years from 1650 to 1880. The approach works effectively because the extra DOF (including phases and elliptical nonlinearities in the orbits) needed to precisely define the gravitational forcing are accurately tracked by the Horizons ephemeris algorithm. Importantly, the results are highly sensitive to the relative forcing amplitudes, which is not surprising, since the fast lunisolar cycles are projected over spans of hundreds of years. The challenge is equivalent to attempting to perform a conventional tidal analysis over a similarly lengthy time span, while also dealing with noise and a limited resolution time-series. [1] Pukite, P.R. “Biennial-Aligned Lunisolar-Forcing of ENSO: Implications for Simplified Climate Models.” AGU Fall Meeting, 2017.

Garnet-bearing volcanic rocks are extremely rare at convergent margins, with few known occurrences worldwide [ref 1-2]; however, such rocks are common within the late Miocene volcanic rock suite of the Northern Andean block (NAB) along the Central Cordillera, Colombia [ref 3-5]. They have been linked to pre-existing zones of crustal weakness that channeled magmas to the upper crust in a short period of time [ref 5-6]. Here we present new geochronological and petrographic data to constrain the timing and petrogenesis of these unusual rocks. We obtained mineral chemical analyses from 7 porphyritic-andesite samples from the eastern flank of the Central Cordillera and the Cauca-Patia Basin, Colombia. Garnet phenocrysts are almandine in composition, ranging from 23 to 29 wt.% FeO, 6 to 8 wt.% CaO, and 1 to 4 wt.% MnO. In some samples, garnets are homogeneous with no reaction rims and lacking inclusions; however, in other samples, garnets show re-absorption rims and inclusion assemblages similar to the rock matrix (plag, amph, ± bt) as well as rare plagioclase coronas. The high Ca and low Mn contents of the NAB garnet cores are consistent with crystallization at ~1.2GPa, based on phase equilibrium experiments of [ref 7], while garnet rim assemblages are congruent with a second stage of crystallization at ~0.8GPa under water-undersaturated conditions. Finally, a pre-eruption dehydration stage is evidenced by the presence of breakdown rims in amphibole crystals. Our new U-Pb in zircon ages reveal that NAB garnet-bearing volcanic rocks formed between 9 and 8 Ma. Taken together, our data suggest a rapid ascent of the NAB magmas associated with the onset of regional volcanism and extension, and possibly the development of the Caldas Tear, a slab window within the Nazca Plate. [1] Green & Ringwood (1968) CMP. [2] Harangi et al. (2001) Journal of Petrology. [3] Orrego (1975) UNAL Colombia. [4] García (1983) UNAL Colombia. [5] Bissig et al. (2017) EG. [6] Weber et al. (2018) SGC (in press). [7] Alonso-Pérez et al. (2006) CMP.

The alluvial wetlands are one of the most important ecosystems of the world and are in abundance in the vast Indo-Gangetic plains. The wetlands of this region are of variable sizes and characteristics but currently face similar problems of drying-out and fragmentation. It is empirical to understand the evolutionary pathways and hydrological connectivity of these wetlands for planning and execution of management and restoration for them. These pathways have been studied for a wetland namely, the Kaabar Tal, situated in the Kosi-Gandak interfan region of the eastern Gangetic plains. Its geomorphic evolutionary pathways have been established using satellite imageries, DEMs, toposheets, and high resolution aerial imagery obtained using unmanned aerial vehicle (UAV). Various geomorphic units characterized by an assemblage of geomorphic features have been mapped for the Kaabar Tal and its surroundings. Seasonal, annual, and decadal variability in the hydrological status of this wetland were estimated for a time-period of 1976-2017 using the historical Landsat datasets. Seasonal variability in hydrological connectivity structure of the wetland with its catchment for the time-period of 1989 to 2017 was estimated in a GIS framework. The structural connectivity was estimated using the technique of diffusion kernel interpolation. The dynamic connectivity was estimated using the Getis-Ord Gi* statistic and Mann-Kendall trend test using the concepts of space-time cubes. The detailed geomorphic mapping revealed that this wetland primarily originated through fluvial processes. A historical reconstruction of its hydrological status revealed that in the recent times the wetland is getting fragmented, and the connectivity potential of different areas of the catchment is a function of the prevalent land-use and land-cover (LULC) pattern and seasonality. Therefore, the heterogeneity and complexity of the geomorphic units of the wetland and the historical LULC patterns of the catchment should be considered in designing any management and restoration plan.

During the mid-Holocene (MH, 6,000 years BP), precessional forcing drove enhanced monsoon rainfall, expanded vegetation cover, and reduced dust emissions throughout the African Sahara. The orbital forcing and feedback of vegetation albedo have been widely studied with climate models, but are found to be insufficient to explain the magnitude and location of rainfall anomalies suggested from proxy reconstructions. The feedback of reduced Saharan dust loading has been less-studied because Paleoclimate Modelling Intercomparison Project (PMIP) Phase 2/3 models did not incorporate the decreased MH Saharan dust emissions. Several recent modeling studies investigated the MH Saharan hydroclimate response to reduced dust loading; however, their models only resolved the direct effect from dust aerosols (i.e. direct radiative forcing), which leaves the contribution from indirect dust aerosol effects (i.e. dust aerosol-cloud interactions) largely unknown. Here we investigate the hydroclimate response due to Saharan dust using CESM CAM5-chem, which includes both the direct and indirect dust aerosol effects. In the simulations, reduced Saharan dust directly increases monsoon season (JJAS) net shortwave radiative flux at the surface, which drives continental warming. Convective clouds and convective precipitation are subsequently enhanced and, due to the overwhelming convective nature of this monsoonal region, total Saharan (20–31°N, 20°W–30°E) precipitation increases by 11.9%. However, indirect dust aerosol effects counteract the increase from convection precipitation. A reduction in Saharan dust decreases cloud nuclei number concentration and increases cloud droplet size, which in turn reduces stratus cloud cover and large-scale stable rainfall. Overall, the decrease in large-scale stable rainfall due to indirect dust effects reduces total precipitation by 12.5%. The total rainfall increase of 0.27 mm/day from reduced dust is significant but smaller than the response to changes in vegetation cover (1.19 mm/day). While these results indicate that less Saharan dust during the MH likely enhanced Saharan rainfall, they also suggest that a reduction in the indirect effects of dust likely dampened the overall response of rainfall to the MH dust forcing.

Tomographic analysis of Pn arrivals times—the guided P-wave propagating within the lithospheric mantle—is ideal for studying the structure of the uppermost mantle. While plate-scale seismic images of Pn wave speeds are common beneath the continents, similar scale studies have not been possible within ocean basins due to the sparsity of seismic stations. The Cascadia Initiative (CI) dataset provides the first opportunity to image spatial variations in lithospheric structure across an entire oceanic plate. We measure 2,862 Pn arrivals from local earthquakes recorded by the CI array. Our dataset provides complete coverage of both the Juan de Fuca (JdF) and deforming Gorda plates. We invert the measured arrival times for 3D variations in anisotropic P-wave velocity and hypocentral parameters. Despite surficial evidence of extensive active faulting, the velocity structure of the Gorda uppermost mantle is remarkably consistent with predictions from a conductive cooling model (attached figure). Limited deformation at mantle depths is supported by seismic anisotropy measurements that show the fast-direction of P-wave propagation rotates in concert with the magnetic anomaly lineations. This rotation may be explained by local plate kinematics without internal deformation and hydration of the shallow mantle. In contrast to Gorda, the seismic velocity structure of the JdF plate does not exhibit a clear age dependence. Three pronounced mantle low-velocity zones are found along the southern edge of the JdF plate near the termini of large pseudofaults that contributed to the formation of the Blanco Transform fault. We attribute these velocity reductions to mantle alteration by seawater. We note that within the interior of the JdF plate pseudofaults do not appear as uniformly slow features in our seismic images. Beneath the central and northern JdF plate, P-wave speeds are ~7.7 km/s out to ~4-5 Myr before abruptly increasing to ~7.9 km/s. Curiously, this transition occurs near the onset of mantle downwelling inferred from teleseismic body wave tomography and attenuation suggesting that mantle flow dynamics may influence the structure of young oceanic lithosphere. Lastly, we note that our results do not suggest a relationship between the structure of the uppermost slab mantle and segmentation of the Cascadia megathrust.

New relative paleointensity results from mafic lava flows erupted in quick succession during four Neogene geomagnetic reversals show that volcanic transition zones can provide a favorable setting for the pseudo-Thellier technique. The most compelling data are from a normal-to-reverse (N-R) transition zone in the 4 my old basaltic lava flows of the Olokele Formation on Kauai (Hawaii). Following stepwise alternating field (AF) demagnetization of each sample’s natural remanent magnetization, an anhysteretic remanent magnetization (ARM) was imparted in a 50 uT bias field and then AF demagnetized. Very similar behavior of the 35 mT to 90 mT coercivity fractions suggest that the NRM (interpreted to be a primary thermoremanent magnetization (TRM)) and ARM reside in the same subpopulation of magnetic grains. With the ARM intensity serving as an analog for TRM susceptibility, the 35 mT-90 mT TRM/ARM ratios provide a relative measure of the ancient field intensity. Good correlation of flow-mean TRM/ARM ratios with a small set of double-heating paleointensities from companion samples allows an approximate scaling of the TRM/ARM ratios to absolute intensity. As the geomagnetic polarity switched, the field strength apparently dropped by 91% compared to the maximum recorded by the flows. This decrease is comparable to that observed in other paleomagnetic studies and numerical simulations. During an interval of NE-down directional stasis recorded by a succession of 10 flows in the lower half of the section, the geomagnetic intensity rose to over 20 uT and then decreased to near 5 uT. This distinctive behavior could mark the waxing and waning of a stationary, inward-directed flux patch on the core mantle boundary centered NE of Kauai. Within-flow variability of relative paleointensity was higher in two other Pliocene transition zones on Kauai (both R-N), and in the R-N transition recorded by 15.2 my old lavas in the Sheep Creek Range (Nevada). Nevertheless, all three records document a reduction in the ancient geomagnetic field intensity similar in magnitude to that seen in the Olokele flows. The relative uniformity of magnetic mineralogy may help explain why the pseudo-Thellier technique was able to capture the large transitional intensity changes recorded by these rapidly-erupted flow sequences.

Northern Mexico is characterized by semiarid climate, where limited precipitation restricts crop production. Therefore, production needs efficient irrigation techniques. Agriculture is a high water consumption activity that in order to become more sustainable, demands knowledge of irrigation efficiencies at the regional scale. In this work we present a method to estimate irrigation efficiencies of croplands based on the crops’ water demand obtained with remote sensing data. The study site is located in an agricultural valley in northern Mexico in an area of cornfields with approximately 47,000 ha under irrigation that lies on top of an overexploited aquifer with a sustained declining water table (averaging 2m/year of drawdown). Using Landsat 8 derived imagery from the METRIC-EEFLUX site for the period between May 16 (emergence season) to Nov 24 (harvest season) during the 2017 agricultural cycle, the Crop coefficient (Kc), the reference Evapotranspiration (ET0) and the actual Evapotranspiration (Eta) were obtained. To obtain daily values of ETa in between the 16 day Landsat images interval, we used Kc obtained from its relation with a normalization of the enhanced vegetation index (EVI), and ET0 calculated using Penmann-Montheit fed with meteorological data from weather stations in the vicinity of the area. Irrigation efficiency was calculated using the quotient between ETa and water applied during the agricultural cycle measured with volumetric gauges at the outlet of the irrigation systems. For this study we monitored 5 parcels of corn with different irrigation systems: two parcels with drip irrigation, one with sprinkler irrigation and two with furrow irrigation. Results from the irrigation efficiencies ranged from 47 % to 71 % and depend on factors like parcel dimensions, irrigation schemes, scheduling and its spatial uniformity. Crop yield data is used to discuss the impacts of these factors on the irrigation efficiencies and the implications of different water use strategies for the sustainability of water resource-compromised regions. This methodology can be replicated in extensive areas requiring knowledge of irrigation efficiencies for more sustainable water management.

Climate change is a primary factor influencing alterations in watershed hydrology. Associated changes in temperature and precipitation can influence the fate and transport of non-point source pollution within a watershed, which complicates the application of best management practices (BMPs) for pollution mitigation. Understanding the sensitivity of BMP implementation as climate change is critical for proper management of water resources. The objective of this study is to understand the effects of BMPs on sediment and nutrient yields in the Meramec River watershed in eastern Missouri, U.S.A due to changes in climate. The Soil and Water Assessment Tool (SWAT) was used to model the flow, sediment and nutrient yields across the watershed. Multi-site calibration (1996-2012) and validation (1981-1995; 2012-2014) gave varied results, ranging from very good to acceptable, for the monthly flow, sediment load, total nitrogen (TN) and total phosphorus (TP). Various BMPs were implemented into the calibrated model in conjunction with climate data from four Coupled Model Intercomparison Project Phase 5(CMIP5) projections to estimate the effects of climate change on watershed yields. Implemented BMPs include riparian buffers, vegetated filter strips, terrace, grassed waterway, and tillage. BMPs were implemented in subwatersheds with high sediment and nutrient outputs as well as relatively high ecological value. Results indicate that BMPs could achieve reductions in a range from 2 to 76% for sediment loss, 1 to 64% for TN loss, and 5 to 54% for TP loss. Among the individual BMPs assessed, vegetated filter strips were most effective when considering the reduction in sediment and nutrient loads. This study highlights the effectiveness of a range of BMPs in reducing the sediment and nutrient loads and provides quantitative measures for determining the most effective individual BMP and the optimal combination of BMPs based on current and future climate scenarios.

Permafrost regions store an estimated half of the global belowground organic carbon pool and twice the global atmospheric carbon level. A warming climate results in increased carbon gas emission, therefore knowing more about the amount and composition of organic carbon stored in permafrost regions is crucial for understanding feedbacks on global climate change. Using the Yukon-Kukskowim (YK) Delta, Alaska as a study site, we quantified belowground carbon pools and their potential vulnerability to release into the atmosphere as greenhouse gasses. We identified relevant landcover classes (burned and unburned upland peat plateaus, wetlands, ponds/lakes) in the YK Delta, from which we quantified total belowground carbon pools (30cm) and assessed the composition of the organic matter using Fourier-transform infrared spectroscopy. To characterize the size and distribution of soil carbon pools in the YK Delta, we built a Random Forest Machine Learning model that mapped the spatial distribution of soil carbon to a depth of 30 cm over a 1910 km2 watershed. The map product was produced in Google Earth Engine and used covariates that include, but are not limited to, Worldview2 high-resolution optical imagery (2m), ArcticDEM (5m), and Sentinel-2 level 1C multispectral imagery (10 m), including NDVI. We found substantial variation across landcover classes in soil characteristics that affect organic matter vulnerability, including gravimetric water content, thaw depth, bulk density, and percent carbon. Compared to upland areas, thaw depths were significantly deeper in wetlands and lakes, where we detected no surface permafrost (to 1m). Soil carbon content (%) was greatest in moss-dominated wetlands; however, these areas also had the lowest bulk density. Carbon pools and organic matter characteristics also varied between burned and unburned areas. Therefore, we expect that carbon vulnerability varies by landcover class and that future carbon emissions are driven by total carbon pools, thaw depths, and composition of the carbon stored in organic matter pools. These carbon pool and vulnerability maps will contribute to better understanding the impacts of subarctic warming and are critical for developing a more accurate assessment of carbon cycling feedbacks from permafrost regions on global climate change.

NOAA/National Ocean Service’s (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) provides users with real-time currents at more than sixty stations, currents predictions at thousands of historic and active stations, and operational currents nowcast and near-term forecast information in navigable estuaries, harbors, rivers, and coastal regions of the United States as an integral part of its safe navigation mission. CO-OPS performs at least one current survey each year to update currents predictions in regions of particular interest to stakeholders. NOS’ Operational Forecast Systems (OFS) operate and maintain fully 3-D hydrodynamic models that provide regional nowcast and forecast (48-60 hours) guidance for water levels, currents, salinity, and temperature. By combining the information available from real-time observations, current surveys, historic current predictions, and OFS output, both the tidal current predictions and the OFS forecast products can be improved. Tidal current predictions are traditionally generated based on analysis of at least one month of six-minute observation data obtained from a physically deployed current meter using harmonic least squares techniques to resolve tidal constituents. By using longer time series and traditional techniques combined with additional statistical methods, a more accurate representation of the tidal flow and a more exact match to the shape of the tidal current curve is obtained. By applying these methods to long-term OFS output at locations where long-term physical observations also exist, tidal current predictions based on model data within the model domain can be verified. Once verified, the number of available “virtual stations” exponentially increases the repository of tidal current predictions. Users can choose any location of interest and receive tidal current predictions that can be incorporated into integrated, user-friendly navigation products and tools. We will evaluate this technique in the lower Chesapeake Bay using output from the Chesapeake Bay Operational Forecast System (CBOFS) and real-time currents data.

Wind is an important driver of large-scale ocean currents, imparting momentum into the ocean at the sea surface. In particular, strong westerly winds help to drive the Antarctic Circumpolar Current, which of key importance for the global climate system. Over the past decades observations established that the strength of the westerlies over the Southern Ocean has increased as a result of climate change forcing. This increase is consistent with global climate model simulations. The future climate state depends strongly on how will the Antarctic Circumpolar Current respond to this strengthening. Eddy saturation is a theoretical regime where the transport of the current remains insensitive to the strengthening of the westerlies. Instead, the strengthening of the westerlies energizes transient eddies. Both satellite observations and numerical simulations suggest that the Antarctic Circumpolar Current is close to the eddy saturated limit. Traditionally eddy saturation has been attributed to baroclinic processes, but recent work suggests that barotropic processes that involve, e.g., standing meanders of the Antarctic Circumpolar Current, can also be responsible for producing eddy-saturated states. Here, we discus the different physical entities of the“usual” baroclinic eddy saturation as well as the recent notion of barotropic eddy saturation. We assess the relative importance of barotropic and baroclinic processes in producing eddy-saturated states using numerical simulations of primitive equations in an idealized setup. Lastly, we discuss potential implications these processes have on global ocean modeling.

Excess sediment is one of the main agents of water pollution, affects the aquatic ecosystem and causes siltation problems in reservoirs and rivers. Bottom sediments are coarse and easily deposited, being the major responsible for morphological alterations in rivers. Therefore, is important to estimate the amount of sediment transported in other to establish mitigation strategies and recovery of affected areas. There are several methodologies for estimating bedload transport: equations, numerical modeling, direct physical sampling, and indirect method measuring dune tracking. Most studies measure bedload transport using the equipment Helley-Smith, generally taken as reference value for other methods. However, Helley-Smith causes changes in the flow field, often resulting in overestimates in sand bed rivers. Those overestimates were not yet described and quantified in detail. This article tries to solve this gap by observing the Helley-Smith sampler at the time of sampling. For this, we used a video camera recording processed by Particle Image Velocimetry (PIV) technique to qualitatively evaluate changes that the intrusive sampler causes in the displacement of bottom sediments in a sand bed river. When the sampler was properly allocated to the bottom, PIV resulting velocity maps of bedload particle transport identified the acceleration of the bottom particles as they approached the mouth of the sampler. We also noticed areas of convergence and vorticity of the sediments towards the sampler’s mouth, which may overestimate sampling. When the sampler’s mouth was disconnected from the bed due to the morphology of the bottom, we find regions of divergence in the displacement of the sediments creating unrealistic results for bedload transport analysis. In addition, the presence of organic matter can be underestimated, which causes difficulties in analyzing the quality of the collections because it is not possible to guarantee an equity in the positioning of the equipment at the bottom of the channel. We thus recommend complementation Helley-Smith measurements with surrogate methods, for example such as using ADCPs or optical methods, as the one described here.