Insights from the RAPID–MOCHA observation network in the North Atlantic have motivated a recent focus on the South Atlantic, where water masses are exchanged with the neighboring Indian and Pacific ocean basins. Moreover, the South Atlantic meridional overturning circulation basin-wide array (SAMBA) was recently launched to monitor variability in the South Atlantic MOC (SAMOC) at 34.5ºS. In this study, we are interested in understanding the processes which generate volume transport variability that would be observed at this latitude band. To perform this attribution, we compute sensitivities of the SAMOC at 34ºS to atmospheric state variables (e.g. wind stress, precipitation) using the adjoint of a global ocean model which is fit to a vast number of ocean observations over the past 20 years. These sensitivities isolate the impact from each atmospheric variable, and highlight the oceanic mechanisms, such as Kelvin and Rossby waves, which carry atmospheric forcing perturbations to the SAMOC. The domain of influence for the SAMOC is shown to be quite broad, covering neighboring ocean basins even on short time scales. This result differs from what has previously been shown in the North Atlantic, where Atlantic meridional overturning circulation (AMOC) variability is largely governed by dynamics confined to that basin. We convolve historical forcing variability from ERA-Interim with the computed sensitivities in order to attribute seasonal to interannual SAMOC variability to each atmospheric component. The seasonal cycle of the SAMOC is therefore shown to be largely driven by local zonal wind forcing. Interannual variability, however, is shown to have originated from remote locations across the globe, including a nontrivial component originating from the tropical Pacific. We conclude with preliminary results which employ both modeling results and an analysis of modern altimetry observations to show how El Niño Southern Oscillation variability might influence the South Atlantic.

Hurricane Michael in 2018 was one of the strongest storms to impact the coastal U.S. and was unusual given that it occurred in October (i.e., late in the hurricane season) and intensified over the continental shelf. A potential contributor to this extreme event was thought to be anomalously high heat content on the shelf of the Mississippi Bight, a shelf region significantly impacted by freshwater discharge. Using available long-term time series of regional meteorological and oceanic measurements, water column conditions during the run-up to the rapid intensification of Hurricane Michael were compared to historical conditions in the region. Data for the water column heat content in the western Mississippi Bight were available at a mooring site on the 20 m isobath (Site CP) during August-October of 2018. Unusually high heat content was observed, relative to the typical summer conditions of previous years (N = 13), which resulted from the compounding effects of atmospheric events in the preceding months (August and September): a series of smaller mixing events (e.g., passage of Tropical Storm Gordon) in conjunction with a regional heatwave during most of September. Tropical Storm Gordon traveled across the shelf of the Mississippi Bight, disrupting the stratified water column as observed at Site CP. The stratification breakdown mixed the upper water column heat content deeper into the water column and subsequently allowed for the anomalously warm atmospheric conditions in September to effectively transfer heat deeper into the water column. While the mooring site was significantly distant (250 km) from the center of Hurricane Michael, these processes observed in the western Mississippi Bight likely occurred in the eastern portion of the basin as well. As a result of these compounding atmospheric effects, the shelf water column was primed to support the intensification of following tropical storms, which highlights the need for coupled oceanic-atmospheric forecast models to capture the interaction between the ocean and atmosphere and its effect on water column conditions on the shelf.

The mid-to-high latitude North Atlantic features cold temperature anomalies on interannual timescales. For example, in 2015 a region of open ocean southwest of Greenland reached a record low temperature relative to the period 1880-2015. Such rapid drops in upper ocean heat content have been linked to impacts on the North Atlantic Oscillation and European climate (e.g. heat waves induced by changing atmospheric circulation patterns). Despite their potential importance for regional climate, the specific mechanisms that induce these interannual cold anomalies are still not well understood. In particular, the relative importance of changes in surface forcing compared with upwelling of deep ocean cold anomalies (i.e. those below 500 m) in establishing the 2015 cold anomaly is a topic of intense debate. Here we use an observationally-constrained ocean model in adjoint mode to calculate the sensitivities of upper ocean heat content to local and remote surface forcing. Adjoint methods allow us to quantify the relative contributions of wind stress and net heat flux in producing the 2015 cold anomaly. Wind stress contributes to the cold anomaly via both (1) strengthening surface latent and sensible heat losses and (2) inducing changes in ocean circulation. Net heat flux contributes to the cold anomaly by inducing heat loss in both local and upstream waters. We also use adjoint methods to calculate (1) the source waters that contributed to the cold anomaly and (2) regions that may have contributed to the cold anomaly by inducing changes in synoptic-scale ocean circulation. Furthermore, we examine the large-scale context by calculating the sensitivities of subpolar gyre heat content to surface forcing and the ocean state. Our results suggest that surface forcing, particularly the extreme heat loss event in the winter of 2013-2014, played a dominant role in producing the 2015 cold anomaly.

Several studies have confirmed the ubiquitous presence of microplastics in marine environments and marine animals at different trophic levels. Understanding how they reach the ocean is crucial for adopting sustainable policies that help mitigate their spread and arrest their detrimental impacts on aquatic ecosystems. Since wastewater treatment plants are considered a potential pathway of microplastics into the marine environment, in this study, we attempted to quantify synthetic microfiber loss during domestic washing. Additionally, we examined the presence of microfibers in water and sediment samples from Newtown Creek and Flushing Bay, because these water bodies receive wastewater from treatment plants that cater to highly urbanized locations of New York City. Fabrics with different percentages and types of polymers were washed with and without detergent. In both variants, Tencel, an organic material, had the biggest mass loss. In addition, clothes shed 50 to 90% more fibers when detergent was used. Likewise, during the drying cycle, fiber loss increased up to 35 times more than the loss during the washing process alone, especially in mixtures containing nylon. Finally, microplastics comprising of fragments, beads, and fibers ranging from to 0.05 mm to 3.5 mm that were encountered were quantified and characterized in the creek and bay water and sediment samples to assess their distribution and fate in the aquatic environment.

Patterns of recruitment are important when determining community dynamics and adult abundance within an ecosystem. Mussels (Mytilus spp.) are an ecologically important foundation species that provide complex habitat for a diverse suite of marine species and are used as biological indicators for environmental pollution. To use mussels as biological indicators, we must understand the timing of mussel dispersal and recruitment. In coastal intertidal zones, mussel populations are kept in check through predation by sea stars, a keystone species, which opens up primary substrate for other sessile invertebrates and algae. Understanding mussel population dynamics is important to make predictions about how intertidal ecosystems will respond to loss of keystone predators through sea star wasting disease. To see if mussel recruitment was impacted by sea star wasting disease, we used tuffy collectors to monitor mussel recruitment in the intertidal at Hopkins Marine Station Marine Life Refuge. After tuffy collectors are filtered and sorted under a dissecting microscope, we will look for changes in mussel recruitment during and after the sea star wasting disease event. We expect higher numbers of mussel recruitment during the peak of the sea star wasting disease from 2013 to 2014.

Tropical cyclones (TCs) are perhaps the most powerful example of air-sea interaction. Although TC-induced energy exchange has been hypothesized to be a signicant agent of ocean heat transport under past and current climates, the margin of uncertainty in both observation and TC-permitting conventional climate models confounds these evaluations. In this study, we introduce a novel approach using simpler climate models, where land geometry is represented by a single strip of pole-to-pole continent, known as the Ridge conguration in previous work. This idealized design is known to represent the large-scale features of atmosphere-ocean general circulation and energy transport, serving to facilitate the physical interpretation of TC-induced energy exchange in the ocean, and its potential role in ocean heat transport. Under the framework of the Community Earth System Model, we congure an idealized, fully coupled Ridge model using Community Atmosphere Model version 4 (CAM4) and Modular Ocean Model version 6 (MOM6) at low horizontal resolutions. After obtaining a quasi-equilibrium climate, we then use the climatological sea surface temperature for forcing a CAM4-only, decadal simulation at TC-permitting resolution. Preliminary results indicate that the formation of a warm pool on the western side of the bounded ocean basin creates a more favorable environment for TC genesis than the cooler eastern side, analogous to observed TC climatology in the Pacic. By comparing ocean-only simulations with and without TCs in the atmospheric forcing, we evaluate the signicance of ocean heat transport attributable to TCs in the idealized atmosphere-ocean climate system. The insights gained through the process- based investigation of TC-induced air-sea interaction in this simpler model framework contribute to an improved understanding of the energetics of TCs, and their role in the climate system.

Environmental change in coastal and shelf seas provides a challenge to fisheries and aquaculture worldwide. Coupled physical-biogeochemical models can be used to create projections of environmental conditions under different climate scenarios, but models of this type produce a wealth of information covering multiple environmental variables and a range of timescales. It is challenging to synthesize that information into a form which can be quickly and effectively conveyed to stakeholders. I describe how a range of approaches has been used to analyse projections of environmental conditions in European seas, created using a regional model with a resolution of 0.1 degrees. The projections run from the present-day to 2099 and include temperature, primary production, plankton biomass, pH and nutrient and oxygen concentrations for moderate and high carbon concentration scenarios. A range of formats that convey the scale and extent of projected change in the North East Atlantic, the North Sea and the Mediterranean, are included, aiming for simple, visual communication that goes beyond maps of changing sea surface temperature. Colour-coded tables show at a glance which variables are projected to show significant change at a range of locations. Time series and maps are used together to give complementary information. Contours show geographical shifts in conditions. In each case the content can be adjusted to fit the interests of different stakeholder groups: examples from fisheries and aquaculture are included here.

Operational ocean and wave models are used to produce forecasts for navigation but also required for a wide range of services, most of them relying on particle tracking methods. Improving the forecast capabilities and accuracy of a model is then a constant necessity in order to deliver more reliable services. The Marine Institute in Ireland is running several coastal operational models, one of them focuses on the area of Galway Bay in the west coast. At the moment it consists of a stand-alone ocean application, it is the purpose of the work presented here to set-up a coupled application with a wave model. Coupled models are a recent development in ocean modelling, developer teams have included ocean and wave coupling by combining existing models each dedicated to a specific physics. Two theoretical formulations are mostly used for the implementation, both giving the same equations of evolution and interaction terms known as the vortex-force formalism. One approach is using a Lagrangian framework defining an exact averaged operator following the fluid particles, the other approach is Eulerian making use of a multi-scale expansion. In both cases the larger current components are found to be forced by gravity and infra-gravity waves. The Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) modelling system is a widely used code, the vortex-force formalism has been implemented in 2012 coupling the Regional Ocean Modeling System (ROMS) with the Simulation Wave Nearshore wave model (SWAN). The implementation has been validated with academic cases and used in several real case studies in the last decade. The work presented here is making use of COAWST, a coupled model is set-up for Galway Bay running a 1-year hind-cast application for 2017 and preliminary results are shown here. The performance of the coupled model is compared with each stand-alone model, using in-situ data as a reference. In the last releases of COAWST the wave model WAVEWATCHIII has been added and can be used in the coupled system. This new feature is tested and the results are compared against SWAN, both wave codes are solving the same equations but different technical choices have been made resulting in different capabilities.

Ocean primary production constitutes approximately half of global biospheric production, affecting both fisheries productivity and biogeochemical cycling. Although climate change is predicted to affect the ocean's biological productivity, the extent of the global impact is poorly quantified. Assessing changes in the ocean biosphere using remote sensing data is challenged by the relatively short length of the observational record, restricting our ability to disentangle fluctuations in internal variability from forced anthropogenic trends. Additionally, the majority of ocean circulation models with embedded biogeochemistry do not skillfully predict observational records of ocean chlorophyll at ocean time series locations. To overcome these limitations, we have constructed a synthetic ensemble of global ocean chlorophyll concentration. By employing statistical resampling methods to the SeaWiFS and MODIS ocean color datasets and creating surrogate climate modes of ENSO and PDO, we quantify the range of internal climate variability in the 20 year observational record and create multiple alternate realities for the possible evolution of the ocean biosphere over time. Our synthetic ensemble can be used for a variety of purposes, including diagnosing patterns of internal variability and emergence of anthropogenic trends in observed chlorophyll, and validating Earth system model representation of such variability.

The diamondback terrapin (Malaclemys terrapin), the official state reptile of Maryland, is an estuarine turtle found along the eastern and Gulf coasts of the United States. The diamondback terrapin may experience risks due to increasing global temperatures because they display temperature-dependent sex determination (TSD). Terrapins, through TSD, produce more female offspring than male offspring if their nest temperatures are relatively warm, leading to ecological issues should global temperatures get too high. This study used temperatures from several individual field, monitored nests, along with air temperatures at the nesting site, recorded in the summer of 2018, to select a predictive model with the R software package rstanarm. The model was then used to predict the average nest temperature in the same nesting site using air temperatures that were recorded during the summer of 2019. This prediction was then compared to temperatures recorded from five nests within the nesting site in 2019 to evaluate its predictive capabilities. A regression spline mixed model (RSMM) was selected for having the lowest leave-one-out information criterion at 50905.95 LOOIC, with a standard error of 0.64 LOOIC. The prediction of average nest temperature developed by the RSMM was given a predictive interval of 95%. We found that the actual temperature of the average nest in 2019 had a prediction coverage of 92.97% from the prediction model, with a root squared mean error of 1.89oC and a predictive mean absolute error of 2.10oC. Benefits of the study involve the ability to predict the future diamondback terrapin nest temperatures within a specific nesting site so long as future air temperatures within that site are known.

Whereas scientific explanations have expanded our understanding of nature, they are often inappropriate for communicating the relevance of science to a lay audience. The arts avert these intellectual hurdles in permitting people to appreciate nature, while also informing scientific endeavors. This project combines the art of sculpture with the technology of electro mineral accretion (EMA) and the science of coral reef restoration. A DNA-inspired sculpture permits the transmission of a minimal DC current that extracts minerals from seawater and deposits them on the steel surface, thus creating a habitat for transplanted corals or settling larvae. Live streaming video (via a webcam) of these processes and related ocean data is sent out worldwide from this underwater art installation in Cozumel, Mexico. Snorkelers can visit the developing reef and students can participate in planting corals or monitoring conditions in the surrounding seawater. Divers and dive instructors have shown an interest in the project, which focuses on generating, rather than exploiting, reefs and welcomes curious locals and tourists. Mineral accretion reefs can adopt a range of shapes, sizes and arrangements on the ocean floor, thus facilitating an evaluation of how different designs influence the coral recruitment, growth, and survival, as well as how the evolving ecosystem protects shorelines and mitigates sea level rise. Research indicates that neighboring reefs are interconnected in many ways (as a network), contributing to their resilience. This sculpture serves as an artificial reef patch among the damaged natural reefs and could eventually contribute larvae from selected species. It is also an example of integrative emergence inasmuch as it substitutes for the natural growth of a reef’s substrate. In uniting wildlife preservation, marine science/education and ecotourism, the project exemplifies the nexus of functional art and environmental solutions.

As already presented at previous conferences, we have developed an innovative technique for ocean wave observations from space: A dedicated reprocessing of spotlight-mode synthetic aperture radar (SAR) data enables us to produce a series of images covering a total time interval of a few seconds, in which moving wave patterns become visible. In most cases, the duration and quality of the image series is sufficient for computing a wavenumber-frequency spectrum and applying a dispersion relation filter to separate signatures of actual ocean waves from contributions of other physical phenomena and noise. Then the extracted wave signatures can be inverted into surface slope and displacement fields (in the space-time domain) and / or spectra (in the wavenumber-frequency domain) by applying relatively simple linear modulation transfer functions. Altogether this process is much more straightforward than traditional wave retrieval techniques for SAR images, and we think it produces more accurate results, although a full quantitative validation is still to be completed. This presentation at Ocean Sciences 2020 will not focus on the waves themselves, but on secondary information that can be retrieved from the moving wave patterns: Since the dispersion relation of ocean waves depends on water depth and surface current, these two parameters need to be tuned to fit the shape of the “dispersion shell” to the observed spectral energy distribution in each subwindow of a SAR image for which the wave field is analyzed. Accordingly, depth and surface current are obtained as additional outputs of the dispersion relation filter. This methodology is well established in the marine radar community, but has not been applied to satellite data before, where it presents a range of new opportunities as well as specific challenges. We will discuss the potential of the proposed method for practical applications and show first examples of retrieved nearshore wave, depth, and surface current fields.

On this poster we explore how well global HYbrid Coordinate Ocean Model (HYCOM) simulations predict (semidiurnal) internal tides and their decay. We explore two important factors that govern the internal tide predictability: model resolution (8 km vs. 4 km) and wave drag. We validate these simulations with internal-tide sea-surface height amplitudes from altimetry, surface-tide dissipation rates estimated from an altimetry-constrained model, finestructure and microstructure dissipation rates, and modal-conversion rates computed from analytical models. To compare HYCOM to various altimetry data sets, we derive a spatially varying correction factor that accounts for the effect of time series duration on non-stationarity. We perform tidal energy balances and decompose the M2 internal tides into vertical modes.

Greater public, and research, focus on oceanic and atmospheric oxygen budgets is needed. Oceans are “losing their breath”; there has been a 1-2% loss, 77-154 gigatons (GT) of total oceanic oxygen (O2) 7,700GT (est.), over the last 50 years. Low O2 ocean areas occur more frequently and more widely; O2 minimum zone (OMZ) depths are rising; and sulphidic events are more common. Where is lost ocean oxygen ‘gO2ing’? Oxygen (O2) is recharged by phototropic O2 producing organisms in both the oceans and on land. Pre-human activity, O2, and CO2 (190-260ppm.) levels likely oscillated within a relatively stable band, for 800,000 years or more. Thus, O2 usage by volcanism, fires, and soil and sea biomes, must have balanced ocean and land based photosynthetic O2 production, as cyclically regulated by ‘Gaian’ feedback. Therefore, additive anthropogenic related increases in CO2 production, must result in net atmospheric O2 loss, including ocean outgassing. Importantly, exchange of oxygen between the oceans and atmosphere is determined by ‘Henry’s Law’, as influenced by oceanic temperature change (warmer waters dissolve less oxygen), and also salinity. Undissolved oxygen concentrations within upper ocean layers, will be higher due to the water pressure gradient, so less oxygen being dissolved at lower pressures. Thus, subject to usage by sea life forms; and thermoclines and haloclines; will likely be replenished from below, tending to surface saturation, even if the OMZs are rising so decreasing in depth? Henry’s law dictates, as anthropogenic reduction of atmospheric O2 reduces partial pressure, dissolved ocean oxygen will equilibrate, releasing stored oxygen to the atmosphere. Thus, over time, if atmospheric O2 continues to fall due to anthropogenic usages, irrespective of other factors, oceanic O2 will arguably be diminished year on year; ultimately will oceans become sufficiently anoxic to be unstable? Research suggests risk of species extinction type events of varying severity strongly correlate to anoxic ocean events. Due to Henry’s Law; will continued anthropogenic oxygen including fossil fuel use, inevitably lead to oceanic oxygen outgassing depletion, and absent change, ultimately an extinction event risk? Is a global Manhattan type project needed to find viable non-carbon-based, non-oxygen using, energy sources?

Seagrasses provide a multitude of ecosystem services: they alter water flow, cycle nutrients, stabilize sediments, support the food web structure, and provide a critical habitat for many animals. However, due to threats to seagrass meadows and their associated ecosystems, these habitats are declining globally. Acoustical methods can be a powerful remote sensing tool to efficiently monitor seagrass meadows, alleviating the problem of space and time aliasing associated with traditional spot measurements. The acoustic field is highly sensitive to the presence of gas bubbles in liquids, which result in acoustic dispersion, absorption, and scattering. The biological processes and physical characteristics associated with seagrass result in trapped gases, which are present in the aerenchyma of seagrass leaves, roots, and rhizomes as well as in freely floating bubbles in the water. To investigate the use of acoustical methods to monitor ecosystem health, an experiment was conducted in the Lower Laguna Madre where the seabed was covered by a dense growth of Thalassia testudinum. During the experiment, a combustive sound source was used to produce broadband signals at ranges of 25 m to 400 m from an array of receivers. The data were collected over a period of one day to assess the diurnal effects of photosynthetic activity on the acoustic measurements. An additional set of measurements were collected in a nearby sparsely vegetated site to provide a baseline data set for comparison. Supporting measurements of irradiance, dissolved oxygen, and water temperature were acquired at the experiment site. The acoustic data were analyzed for the purposes of inferring environmental parameters in the seagrass meadow, including the gas volume present in the environment. An effective medium model for gas bubbles in liquids was used to characterize the frequency-dependency of sound speed and attenuation in the waveguide. [Work sponsored by ARL:UT IR&D and ONR.]

The authors implemented the Regional Ocean Modelling System (ROMS) to coastal waters on the west coast of Ireland. The Connemara model has c.200 m horizontal resolution and has 20 vertical sigma levels and stretches from 10.8oW to 8.9oW and from 52.95oN to 53.73oN. It has three open ocean boundary conditions in the north, south and west, and several rivers are included at the head of Galway Bay. Both 3D and 2D configurations have been set up; with the aim of the 2D configuration being the prediction of storm surges. The 3D configuration has been running in the operational forecasting mode for approximately the last decade and produce weekly hindcasts and 3-day forecasts. Details of the operational system will be presented. Most recent developments include the implementation of wetting/drying algorithm with a critical depth of 0.25 m. It has undergone a testing phase and the authors will report on the findings in terms of the computational efficiency and in terms of the changes to the model skill. Details of the set-up of each configuration, as regards the forcing functions, the choice of boundary conditions, atmospheric forcing, advection schemes, turbulence schemes, will be presented. The predictive skill of various configurations have been assessed by means of root mean square error (RMSE) differences and correlations with data collected from the Marine Institute’s observational network in Galway Bay. The observational platforms comprise of 5 tide gauges, 4 x ADCPs and temperature and salinity sensors. The harmonic analysis has been carried out on the data from the tide gauges and the corresponding model predictions in order to validate the tidal signal. The tidal signal in the Sea Surface Height (SSH) data is dominated by three semi-diurnal constituents (i.e. constituents with a period of approx. 12 to 12.5 hours), M2, S2 and N2, and three diurnal constituents, K1, O1 and Q1. At Galway Port tide gauge, the M2 magnitude error between the model and data is 0.07 m. The surge component is calculated for observed and modelled data at the locations of tide gauges. The authors will present the skill of the model as regards the prediction of storm surges to include the comparison between a 3D and 2D configuration.

The mechanisms by which time-dependent wind stress anomalies at mid-latitudes can force variability in the meridional overturning circulation at low latitudes are explored. It is shown that winds are effective at forcing remote variability in the overturning circulation when forcing periods are near the mid-latitude baroclinic Rossby wave basin-crossing timescale. Remote overturning is required by an imbalance in the mid-latitude mass storage and release resulting from the dependence of the Rossby wave phase speed on latitude. A heuristic theory is developed that predicts the strength and frequency-dependence of the remote overturning well when compared to a two-layer numerical model. The theory indicates that the variable overturning strength, relative to the anomalous Ekman transport, depends primarily on the ratio of the meridional spatial scale of the anomalous wind stress to its latitude. For strongly forced systems, a mean deep western boundary current can also significantly enhance the overturning variability at all latitudes. For sufficiently large thermocline displacements, the deep western boundary current alternates between interior and near-boundary pathways in response to fluctuations in the wind, leading to large anomalies in the volume of North Atlantic Deep Water stored at mid-latitudes and in the downstream deep western boundary current transport.

“Eddy saturation” is the regime in which the total time-mean volume transport of an oceanic current is relatively insensitive to the wind stress forcing and is often invoked as a dynamical description of Southern Ocean circulation. We revisit the problem of eddy saturation using a primitive-equations model in an idealized channel setup with bathymetry. We apply only mechanical wind stress forcing; there is no diapycnal mixing or surface buoyancy forcing. Our main aim is to assess the relative importance of two mechanisms for producing eddy saturated states: (i) the commonly invoked baroclinic mechanism that involves the competition of sloping isopycnals and restratification by production of baroclinic eddies, and (ii) the barotropic mechanism, that involves production of eddies through lateral shear instabilities or through the interaction of the barotropic current with bathymetric features. Our results suggest that the barotropic flow-component plays a crucial role in determining the total volume transport.