A modern coastal ocean observing system using data from advanced satellite and in situ sensors – an example

Report of the Ocean Observation Research Coordination Network In-situ-Satellite Observation Working GroupThis report is intended to illustrate and provide recommendations for how ocean observing systems of the next decade could focus on coastal environments using combined satellite and in situ measurements. Until recently, space-based observations have had surface footprints typically spanning hundreds of meters to kilometers. These provide excellent synoptic views for a wide variety of ocean characteristics. In situ observations are instead generally point or linear measurements. The interrelation between space-based and in-situ observations can be challenging. Both are necessary and as sensors and platforms evolve during the next decade, the trend to facilitate interfacing space and in-situ observations must continue and be expanded. In this report, we use coastal observation and analyses to illustrate an observing system concept that combines in situ and satellite observing technologies with numerical models to quantify subseasonal time scale transport of freshwater and its constituents from terrestrial water storage bodies across and along continental shelves, as well as the impacts on some key biological/biogeochemical properties of coastal waters.Ocean Research Coordination Network and the National Science Foundatio

Resolving spatiotemporal characteristics of the seasonal hypoxia cycle in shallow estuarine environments of the Severn River and South River, MD, Chesapeake Bay, USA

AbstractThe nature of emerging patterns concerning water quality stressors and the evolution of hypoxia within sub-estuaries of the Chesapeake Bay has been an important unresolved question among the Chesapeake Bay community. Elucidation of the nature of hypoxia in the tributaries of the Chesapeake Bay has important ramifications to the successful restoration of the Bay, since much of Bay states population lives within the watersheds of the tributaries. Very little to date, is known about the small sub-estuaries of the Chesapeake Bay due to limited resources and the difficulties in resolving both space and time dimensions on scales that are adequate to resolve this question. We resolve the spatio-temporal domain dilemma by setting up an intense monitoring program of water quality stressors in the Severn and South Rivers, MD. Volume rendered models were constructed to allow for a visual dissection of the water quality times series which illustrates the life cycle of hypoxia and anoxia at the mid to upper portions of the tidal tributaries. The model also shows that unlike their larger Virginian tributary counterparts, there is little to no evidence of severe hypoxic water intrusions from the main-stem of the Chesapeake Bay into these sub-estuaries

Explorative coastal oceanographic visual analytics : oceans of data

The widely acknowledged challenge to data analysis and understanding, resulting from the exponential increase in volumes of data generated by increasingly complex modelling and sampling systems, is a problem experienced by many researchers, including ocean scientists. The thesis explores a visualization and visual analytics solution for predictive studies of coastal shelf and estuarine modelled, hydrodynamics undertaken to understand sea level rise, as a contribution to wider climate change studies, and to underpin coastal zone planning, flood prevention and extreme event management. But these studies are complex and require numerous simulations of estuarine hydrodynamics, generating extremely large datasets of multi-field data. This type\ud of data is acknowledged as difficult to visualize and analyse, as its numerous attributes present significant computational challenges, and ideally require a wide range of approaches to provide the necessary insight. These challenges are not easily overcome with the current visualization and analysis methodologies employed by coastal shelf hydrodynamic researchers, who use several software systems to generate graphs, each taking considerable time to operate, thus it is difficult to explore different scenarios and explore the data interactively and visually. The thesis, therefore, develops novel visualization and visual analytics techniques to help researchers overcome the limitations of existing methods (for example in understanding key tidal components); analyse data in a timely manner and explore different scenarios. There were a number of challenges to this: the size of the data, resulting in lengthy computing time, also many data values becoming plotted on one pixel (overplotting). The thesis presents: (1) a new visualization framework (VINCA) using caching and hierarchical aggregation techniques to make the data more interactive, plus explorative, coordinated multiple views, to enable the scientists to explore the data. (2) A novel estuarine transect profiler and flux tool, which provides instantaneous flux calculations across an estuary. Measures of flux are of great significance in oceanographic studies, yet are notoriously difficult and time consuming to calculate with the commonly used tools. This derived data is added back into the database for further investigation and analysis. (3) New views, including a novel, dynamic, spatially aggregated Parallel Coordinate Plots (Sa-PCP), are developed to provide different perspectives of the spatial, time dependent data, also methodologies for developing high-quality (journal ready) output from the visualization tool. Finally, (4) the dissertation explored the use of hierarchical data-structures and caching techniques to enable fast analysis on a desktop computer and to overcome the overplotting challenge for this data

The variation of climate sensitive tidal ocean-dynamo signals on sub-decadal and seasonal time scales

Motional induction describes the induction of electric currents through charged particles moving perpendicular to an ambient magnetic field. A well-known device that uses motional induction to induce electric currents is the bicycle dynamo. The induction of electric currents in the ocean due to the motion of saltwater within the ambient geomagnetic field is, by contrast, lesser-known; this phenomenon is called the ocean-dynamo effect which indicates the similarity of both phenomena. The electromagnetic field signals emitted by ocean-dynamo induced electric currents are primarily sensitive to three factors: 1. the number of moving charged particles, 2. the magnetic field strength of the ambient field, and 3. the velocity with which the particles move perpendicular to said magnetic field. The amount of electrically charged particles in the seawater, a saline solution, is measured with the electrical seawater conductivity σ. σ is determined by the saline solution's chemical equilibrium, which in return is predominantly defined by the physical properties of seawater temperature and salinity. Thus, changes in the spatial distribution of seawater temperature and salinity cause changes in the spatial distribution of electrical seawater conductivity, which in return affect the ocean-dynamo signals. In theory, ocean-dynamo signals are therefore suitable for ocean observation applications. Out of all ocean-induced electromagnetic signals, signals induced by ocean tides play a unique role. The signatures of the periodic tidal flow are the only ocean-dynamo signals that have been successfully observed in magnetometer observations, space-borne and land-based. In addition to the proven measurability, the signals are also modelled with sufficient accuracy so that, on a global scale, observed tidal ocean-dynamo signatures agree well with model predictions. These two preconditions allow for an investigation of the relationship between ocean dynamics and tidal ocean-dynamo signals, a much-needed advancement towards practical ocean observation applications. In the past, sensitivity studies of tidal ocean-dynamo signals have focused mainly on changes on long time scales. By contrast, the present cumulative thesis examines the influence of ocean dynamics on tidal ocean-dynamo signals on short and intermediate time scales. In particular, it investigates the mechanisms and effects of ocean dynamics and recent seawater temperature and salinity changes on tidal ocean-dynamo signals. Furthermore, it investigates the detectability and measurability of short-term variations of said signals in magnetometer observations. Out of the presented three research studies, the first is a model-based characterization of tidal ocean-dynamo amplitude variations attributed to the El Niño/Southern Oscillation (ENSO). The study shows that tidal ocean-dynamo signal changes precede the onset of warm and cold ENSO phases and attributes these findings to the underlying oceanic processes. Furthermore, the study provides an assessment of the measurability of ENSO-induced tidal ocean-dynamo amplitude variations. The second study covers a time series analysis of modeled tidal ocean-dynamo amplitudes on a global scale. Here, the amplitudes were modeled based on existing oceanic seawater temperature and salinity observations. Based on the analysis of the underlying in-situ data, the study assesses recent developments in signal amplitudes to resolve a conflict between existing model-based sensitivity studies. Furthermore, the study identifies the heightened sensitivity of coastal tidal ocean-dynamo signals and provides a physical explanation for this fact. The third study focuses on local ocean phenomena and analyses time series of coastal island magnetometer observations. It presents evidence for seasonal amplitude variations and trends in amplitudes and phases of tidal ocean-dynamo signals. The advancements in the field contribute to the transition from retrospective or model-based analysis to an actual inference of the oceanic temperature and salinity dynamics from magnetometer observations

Towards a Global Perspective of the Marine Microbiome

Marine microbes play fundamental roles in nutrient cycling and climate regulation at a planetary scale. The field of marine microbial ecology has experienced major breakthroughs following the application of high-throughput sequencing and cultureindependent methodologies that have pushed the exploration of the marine microbiome to an unprecedented scale. This chapter overviews how the advances in gene- and genome-centric approaches as well as in culturing and single cell physiological methodologies in conjunction with global oceanographic circumnavigation expeditions and long-term time series are fueling our understanding of the biogeography, temporal dynamics, functional diversity, and evolutionary processes of microbial populations. We discuss how the joint effort of all those integrative approaches will help to boost our knowledge of the marine microbiome to reach a predictive understanding of how it is going to evolve in future scenarios.Versión del edito

3-D Global Induction in the Oceans and Solid Earth: Recent Progress in Modeling Magnetic and Electric Fields from Sources of Magnetospheric, Ionospheric and Oceanic Origin

Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic and electric fields. The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes: (a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth's main magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans, crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly (in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations both on the ground and at satellite altitude

Mechanisms of fast-ice development in the south-eastern Laptev Sea: a case study for winter of 2007/08 and 2009/10

Accurate representation of fast ice in numerical models is important for realistic simulation of numerous sea-ice and ocean variables. In order to simulate seasonal and interannual variability of fast-ice extent, the mechanisms controlling fast-ice development need to be thoroughly understood. The objective of this paper is to investigate mechanisms contributing to the advance of fast-ice edge to its winter location in the south-eastern Laptev Sea. The study is based on time series of synthetic aperture radar (SAR) imagery for winter 2007/08 and 2009/10. A detailed examination of SAR-based ice drift showed that several grounded ice features are formed offshore prior to fast-ice expansion. These features play a key role in offshore advance of the fast-ice edge and serve as stabilizing points for surrounding pack ice as it becomes landfast. Electromagnetic ice thickness measurements suggest that the grounded ice ridges over water depths of ca. 20 m water might be responsible for interannual variations in fast-ice edge position. Contrary to previous studies, we conclude that grounding is a key mechanism of fast-ice development in the south-eastern Laptev Sea

The Influence of Model Resolution on Dispersal and Retention in Oregon Coastal Waters

Lagrangian particle tracking (LPT) models are used to explore how physical processes influence the transport of particles (e.g., eggs, larvae, or propagules) in the ocean. On the Oregon continental shelf and slope, the Northern California Current System (CCS) is influenced by spatially and temporally variable coastal currents driven by weather, tides, and topography. Nearshore waters, which are sites for recreational, cultural, and economic activities, are essential to coastal communities. In Oregon coastal waters, there are five marine reserves (MRs) which range in size from 3 km2 (e.g., Otter Rock) to 37 km2 (e.g., Cape Perpetua) and average maximum depths of 18 m (e.g., Otter Rock) to 55 m (e.g., Cape Falcon, Cape Perpetua). To date, the dispersal and retention potential of these coastal MRs is poorly characterized, in part because of limited modeling studies conducted at scales that are not consistent with the size and spacing of these MRs. In past LPT model studies, particle residence times in the Oregon nearshore and shelf are less than three weeks. However, the retention of particles in the nearshore may depend on the accurate representation of smaller-scale physical processes that are not resolved in those modeling studies. In chapter 2, I developed a LPT model to examine how the spatial resolution of a Regional Ocean Modeling System (ROMS) at 2 km and 250 m affects dispersal and retention characteristics on the Oregon coast. Further, I compared the predictions of temperature, salinity, and current velocities from the 250 m ROMS to oceanographic data collected in situ to corroborate the overall trends between the model and observations. In chapter 3, I characterize particle dispersal along the Oregon nearshore, particularly in and out of the Oregon MRs, using ROMS of different spatial resolutions (2 km, 250 m). In chapter 2, I found that along-shelf and cross-shelf velocities are similar between the 250 m ROMS and in situ data for a majority of the domain, with the ROMS velocity higher at Heceta Bank and Cape Blanco. The 250 m ROMS tends to overestimate upwelling salinity and underestimate temperature, which may be due to an overestimation of upwelling strength (i.e., vertical velocity) in the 250 m ROMS model. A possible explanation is that the winds used to force the ROMS are higher than the observations. However, the winds at station NWPO3 are stronger than the winds used to force the ROMS (e.g., NOAA North American Mesoscale Model forecasts), making it unlikely that the higher salinity and lower temperature of the ROMS are driven by higher wind stress and consequently stronger upwelling. In simulations forced with the 250 m ROMS, particles have more meandering, a higher percentage of retention in the domain at the end of the simulation, and a greater depth range than in simulations forced with the 2 km ROMS. In chapter 3, similarly to chapter 2, a higher percentage of particles are retained in the domain, and particles exhibit a greater depth range when forced with the 250 m ROMS. Particles forced with the 250 m ROMS travel less distance in the latitudinal direction (e.g., alongshore) and greater retention than the 2 km ROMS. However, the general spatial patterns of particle retention for the three years examined are similar between the two models, showing that it may suffice to use a lower resolution model when asking questions related to areas that retain or source particles. This study has provided a better understanding of the influence of physical processes on particle dispersal and retention in Oregon coastal areas. The information gained by understanding regions in the Oregon nearshore that retain and disperse particles is important for the management and evaluation of the Oregon MR system