The Inter-Tropical Convergence Zone (ITCZ) is a persistent band of organized convection in the tropics that arises due to the surface convergence of the Hadley cells. The location and intensity of the ITCZ is heavily influenced by sea surface temperature and low-level latent heat transport. The ITCZ undergoes an annual march across the equator, and during the summer moves north over India and the Bay of Bengal, affecting the Indian summer monsoon. Occasionally a second parallel band of convection forms to the south, referred to as a double-ITCZ. Double-ITCZs in the tropical east Pacific have been heavily studied, and their development is understood to be linked to seasonal changes in sea-surface temperature. The existence of double ITCZs over the tropical Indian Ocean is well documented, but the underlying mechanism is poorly understood. We develop an algorithm to identify this phenomenon in NOAA outgoing longwave radiation data, and create a thirty-year record of double-ITCZ occurrence. We then use this record to investigate linkages between summer-time double-ITCZ occurrence and intra-seasonal variability in the Indian summer monsoon, and discuss possible physical mechanisms.
Recent observations of warming trends in the Red Sea raise more attention to the response of the basin under a warming climate. Using two remotely sensed datasets, the Hadley Centre Sea Ice and Sea Surface Temperature [HadISST] and Extended Reconstructed Sea Surface Temperature [ERSST.v3], we investigate the reported sudden increase in the Red Sea sea surface temperatures (SST) in terms of average and maximum and assess their relation to multi-decadal climate variability. Prior to the analysis, the two datasets are successfully validated with respect to their ability to reproduce the recent observed and reported trends and their spatial features. Analysis of long-term SST variability revealed a sequence of alternating and similar in amplitude positive and negative trends, characterized by a period of nearly 70 years. Similar oscillations have been reported in other basins and have been related to atmospheric disturbances associated with the Atlantic Multidecadal Oscillation (AMO). A point-by-point spectral analysis of SST evolution shows a significant correlation with the basic modes of the AMO that explains a large fraction of its temporal and spatial variability. Projections on the major modes of the spectral analysis suggest a possible decreasing effect on local SST in the near future. Under this assumption, recent projected trends in the Red Sea may be exaggerated, whilst trends that may be related to anthropogenic influence could be masked by the projected negative influence of the AMO in the near future.
Airborne lidar surveys were used to characterize subsurface layers of phytoplankton in the Arctic Ocean during the latter half of July 2014 and again during the latter half of July 2017. The survey region included US waters in the Beaufort and Chukchi Seas. In 2014, layers were detected in open water and also in openings in pack ice where up to 90% of the surface was covered by ice. The layers in the pack ice were less prevalent, weaker, and shallower than those in open water. Layers were more prevalent in the Chukchi Sea than in the Beaufort Sea. Three quarters of the layers observed were thinner than 5 m. In 2017, ice conditions were significantly different. The ice edge was farther north at the beginning of the measurement period in 2017 and retreated faster during that period. As a result, flights were conducted in the areas surveyed in 2014 in addition to areas near the ice edge. Data analysis of the 2017 flights will be done in the same way as the 2014 data. Low clouds and fog are common in the Arctic. The lidar can operate through optically thin clouds and fog, but at some point, the beam is completely attenuated. Data where the atmospheric attenuation is too great must be removed from consideration by visual inspection. Detection of ice in the lidar return is straightforward, since ice produces a saturated return in the lidar receiver. Subsurface layers will be identified by visual inspection of the data, and the characteristics will be calculated. Subsurface layers are clearly present in the data, and their characteristics will be presented, along with a comparison between 2014 and 2017 results.
The biodiversity of reef fish in the Florida Keys National Marine Sanctuary was evaluated in terms of abundance, biomass, evenness, species richness, Shannon diversity, Simpson diversity, and functional diversity, using observations collected from 1999 – 2016 by the Reef Visual Census program. To compare the different diversity indices, species richness, Shannon diversity, Simpson diversity, and functional diversity were converted into effective number of species. We examined the seven indices by level of protection and type of no-take marine zones and by three habitat strata. The study detected abundance, biomass, and diversity were significantly greater (except evenness) inside no-take marine zones compared to areas open to fishing. Smaller reserves had higher abundance, biomass, and richness values than larger reserves and areas open to fishing, but had moderately higher diversity values. This may be attributed to a few species with many individuals that are dominant inside and outside no-take marine zones. Surprisingly, none of the indices were significantly different (except for functional diversity) between the larger Ecological Reserve and areas open for consumption. This may be due to spillover effects. Furthermore, the no-take marine zones only explained a small proportion of total percent deviance in the indices. Habitat type had a greater influence on patterns in composition and diversity where high relief reef habitats had the greatest abundance, biomass, and diversity indices. Based on our results managers should prioritize preserving high relief reefs through a network of small reserves to enhance reef fish composition and biodiversity.
Researchers are challenged with preparing and complying with data management plans and open data mandates. The ocean science repository community has demonstrated the benefits of providing FAIR (findable, accessible, interoperable, and reusable) data to its researchers through innovative alliances, robust metadata, and semantic connectivity. Challenges still exist in coordinating science policy, and research services across funders, institutions, and publishers that support the researcher’s data management needs. The convenors of this session request abstracts that focus on the value of FAIR data to the research community and the tools that support data discovery, compliance with data management plans, transparency, reproducibility, and research integrity.
Using bibliometric analysis techniques, we trace the evolution of climate and climate-change related articles in major oceanographic journals, 1987-2017. We use these bibliometric tools (network mapping, cluster analysis, alluvial analysis, corpus keyword detection) to document trends in growth, integration and centralization of climate-related research within ocean sciences over the past three decades. Such analysis methods offer an objective and complementary methodology, in contrast to the traditional “expert panel” approach, for guiding long-term strategic science planning. But how does the macro trend compare to scientific outputs supported by large ocean observatory facilities? Have scientists making use of these facilities followed, led or diverged from the general trend? We compare the macro trend to corpora of published science from two such facilities, Australia’s Integrated Marine Observing System (IMOS) and Ocean Networks Canada (ONC). The goal is to discern the extent to which these “big science” ocean observatories have been able to support or lead research that helps inform policy, management and the public about critical societal issues such as long term ocean change.
Chukchi Sea benthic ostracode assemblages collected during a research cruise aboard the USCGC Healy in 2017 are compared to collections from past years, primarily 2009 and 2010, with a goal of understanding recent species changes related to temperature, total organic carbon (TOC) and sediment grain size. The study area includes the continental shelf region influenced by the Alaska Coastal Current and the northward extension of the Bering Sea Shelf waters that flow through Bering Strait. Significant temporal (decadal, interannual) and spatial variability in the proportions of dominant species in the assemblage were observed, including an increase in subarctic species, particularly, Normanicythere leioderma, which is typically dominant in the Bering Sea, but which showed a notable range expansion in 2017 into the Chukchi Sea (20% of the 2017 Chukchi Sea assemblage). Secondary subarctic species with increasing abundance include Schizocythere ikeyai (8%) and Munseyella kiklukhensis (7%). A corresponding decline in dominance of Paracyprideis pseudopunctillata (4%), a common Arctic species in Chukchi, Beaufort and Laptev Sea assemblages, is another significant change. Continued monitoring of temperature-sensitive ostracode species in the Bering and Chukchi Seas is planned to provide additional information on annual and decadal variability in species dominance.
Ocean General Circulation Models (OCGM) have been used for ocean forecasts and reanalysis in the past; successfully reproducing realistic large scale features such as Western Boundary Currents (WBC) which evolve slowly in time. Recent developments of three dimensional OCGM’s include the incorporation of tidal forcing embedded in the numerical integration. With the inclusion of higher frequency tidal forcing it is now possible to study the impact of tides on the larger scale features of the ocean reproduced in the OCGM’s such as WBC’s through comparison of simulations with and without tides. We compare two 1/12.5° simulations of the Hybrid Coordinate Ocean Model (HYCOM) and report on differences in the mean position, transports, and warm/cold core eddy production in the Gulf Stream and Kuroshio Current and their extensions across the Atlantic and Pacific Oceans.
Water sample collection is a simple, but fundamental approach for measuring water properties that cannot currently be sensed in situ with instruments or for conducting experiments requiring water samples. Conventional approaches to water sampling typically employ research vessels which are costly, limited by sea state, and are often restricted by scheduling and other logistics. These factors can limit the ability to sample transient phenomena in inland and coastal waters. They can also restrict sampling frequency for time series measurements. We describe the use of aerial drones and newly developed sampling bottles that allow sub-surface water collection without the use of research vessels. The sampling bottles are similar in operation to conventional Niskin bottles, but with the different methods for closing the bottles. We have experimented with two closing methods. One uses a float and mechanical linkage to close bottles at fixed depths and the other uses pressure sensors to close bottles at programmed depths. Drone-based water sampling is currently employed in the Santa Barbara Coastal Long Term Ecological Research (SBC LTER) project to obtain weekly time series of water samples for pH and total alkalinity at a long-term oceanographic mooring. The water samples are also being used to calibrate pH sensors on the mooring and assess data quality. Drone sampling will be expanded to other SBC LTER moorings in the future. Aerial drones offer a new approach for sampling the coastal ocean and inland waters. Drone-based sampling is in its infancy, but we envision the development of a suite of specialized instrumentation and water collection devices that take advantage of the capabilities of aerial drones. This will allow rapid response for sampling transient events such as harmful algal blooms and toxic spills in a wide range of environmental conditions.
The Puget Sound is a complex estuarine system within the Salish Sea, fed by both high salinity water from the Pacific Ocean and freshwater from a number of rivers. The Snohomish River is one of the largest of these freshwater inputs, transporting freshwater from the Skykomish and Snoqualmie rivers to Port Gardner Bay off the coast of Everett. At its mouth, the higher density salt water from the Puget Sound intrudes into the freshwater, forming a salt wedge that causes a highly stratified water column which rapidly changes with the tidal cycle. In this stratified water column, little mixing occurs between the different layers of the water, resulting in a lack of nutrients near the surface. This study aims to quantify the amount of mixing occurring at this location in relation to tidal patterns and season and analyze the effect varying levels of mixing have on related chemical properties. This research is being conducted at the Ocean Research College Academy (ORCA), a dual enrollment program through Everett Community College. In cooperation with Gravity Marine Consulting and the Port of Everett, ORCA has permanently moored a SeaBird CTD 3 meters below the surface in the mouth of the Snohomish River. The CTD captures temperature, salinity, chlorophyll, turbidity, and dissolved oxygen measurements at 30-minute intervals. Velocities in 3-dimensions are recorded by a Nortek Aquadopp. This study will define the characteristics of the salt wedge in relation to temperature and salinity and then look at its influence on chlorophyll and turbidity levels.
Marine aggregates are ubiquitous particles formed from the accretion of smaller biogenic and non-biogenic components. Visible aggregates, known as marine snow, are typically in the 0.5 to few mm size range. Aggregates are well recognised as hotspot of microbial and planktonic activities. Aggregates formation is an important pathway for transferring materials and carbon flux from surface to the deep ocean. Because aggregate sinking velocity and carbon mass content is size dependent, understanding the physical mechanism controlling aggregate size distribution is fundamental to determining the biological carbon pump efficiency. Turbulence is a physical mechanism in the aggregates formation and destruction. However, the relative roles of turbulence in aggregates formation and destruction have not been fully tested in observational studies. In this study, we analysed simultaneous in-situ observations of turbulence and aggregate in the various aquatic systems. A microstructure profiler, TurboMAP-L, was used to collect shear data and a digital still logger camera was used to collect images of aggregates. Digital images were subsequently used to determine aggregates abundances and size distributions. Direct comparison of turbulence intensity and aggregate size distributions show that turbulence below 𝜀=10-6[W/kg] enhances aggregation, increasing average particle size; greater turbulence causes particle breakup, limiting the average maximum aggregate size and decreasing the slopes of size distributions. This indicates the role of turbulence controlling aggregate size distributions. We also present fluorescence data collected by TurboMAP-L and focus on difference of aggregates size distributions among different aquatic systems.
The interior of lakes is often quiescent and most of the mixing in a lake occurs at the sloping boundaries, where wind-induced internal waves create turbulence (which leads to mixing) through interactions with the lakebed. To predict the occurrence and strength of turbulence in terms of meteorological forcing and stratification, we investigated the dependence of internal wave type, and their contribution to turbulence on the slope, on the Lake number, which compares the stabilizing tendency of stratification to the destabilizing tendency of the wind. Three thermistor chains and a meteorological station were deployed in West Okoboji Lake (length ~ 9 km, max. depth ~ 40 m) for two weeks. A wavelet analysis was conducted to determine time periods when different wave frequencies were excited, with particular focus on the first vertical mode seiche, the critical frequency with respect to the stratification and slope, and high frequency waves in the band of 1-10 times the buoyancy frequency. We measured the velocities in the bottom boundary layer (BBL) with a high resolution acoustic current profiler (2 MHz Nortek HR Aquadopp) and then computed the turbulent dissipation rate using the structure function method, which uses the spatial correlations of velocity along a beam to estimate the dissipation. This generated a two week time series of turbulent dissipation rate in the BBL which was then compared to the wavelet amplitudes. During the deployment, a strong daily wind forced near constant internal wave activity. The theoretical period of the first vertical mode seiche was ~17 hours, but the diurnal wind forcing interfered with free oscillation of this mode. Although not an obvious natural frequency of the lake, waves of the critical frequency (which had a period of ~11 hours) were activated throughout the measurement period. High-frequency waves were observed in the thermistor chain near the slope at the lowest Lake number wind events. The turbulence observed on the boundary was highest during these events, implying that the low frequency seiching was less important than higher frequency motions in driving turbulence on the slope.
We examine the role of transient and standing eddies in an idealized model with a Southern Ocean analog and two basins in the Southern hemisphere. We use the new MOM6 code base in an entirely adiabatic configuration, which allows for full equilibrium integration in only 100 years of simulation time. Fine resolution eddy-resolving simulations at 1/16- and 1/8-degree resolutions are performed in cases with and without continental barriers and/or bottom roughness. A time- and zonal-Reynolds averaging approach is used to decompose eddy fluxes into transient eddies and standing meanders. For a flat bottom channel the wind driven overturning circulation is balanced by transient eddies, consistent with previous studies. However, when continental barriers or bottom roughness are present, we find that standing meanders are dominant in the Southern Ocean.
Mesoscale eddies are ubiquitous in the ocean, and typically exhibit different characteristics to their surroundings, allowing them to transport properties such as heat, salt and carbon around the ocean. This takes place everywhere in the world’s ocean and at all latitude bands. Most of mesoscale eddies energy is generated by instabilities of the mean flow, and by air-sea interactions. Mesoscale dynamics can feed energy and momentum back into the mean flow and help drive the deep ocean circulation. Their suspected importance in transporting and mixing water properties as they propagate in the ocean, play a significant role in the global budgets of these tracers and climate. Increasing evidences point out at intense air-sea interaction at smaller scale than synoptical, especially in the extratropics that can strongly affect the Troposphere. However we do not have yet neither a global quantitative assessments nor a theoretical understanding of these processes. We will present new results from a recently developed eddy-atlas (ToEddies) that includes eddies merging and splitting. In particular, we will discuss properties of Agulhas Rings in the South Atlantic derived from satellite altimetry and the colocalization of these eddies with Argo floats. Our results show that these eddies are, in the South Atlantic, associated with strong thermal and haline anomalies. These are essentially due to Mode Waters (Agulhas Rings Mode Water: ARMW) formed in the core of the rings in the southeastern Cape Basin, just west of the Agulhas Retroflection, after intense air-sea interactions that can last for more than an entire season. These eddies are then advected in the South Atlantic and are responsible of an important flux of heat and salt into this basin (Laxenaire et al. 2018a,b). We corroborate such findings with full depth hydrography of selected eddies and very high-resolution modelling studies.
We present a data-derived, ecosystem mapping approach for the global ocean as commissioned by the Group on Earth Observations (GEO) and as a contribution to the Marine Biodiversity Observation Network (MBON). These ecological marine units (EMUs) are comprised of a global point mesh framework, created from over 52 million points from NOAA’s World Ocean Atlas with a spatial resolution of 1 by 1 degree (∼27 x 27 km at the equator) at 44 varying depths and a temporal resolution that is currently decadal. Each point carries attributes of chemical and physical oceanographic structure (temperature, salinity, dissolved oxygen, nitrate, silicate, phosphate) as likely drivers of many marine ecosystem responses. We used a k-means statistical clustering algorithm to identify physically distinct, relatively homogenous, volumetric regions within the water column (the EMUs). Backwards stepwise discriminant analysis determined if all of six variables contributed significantly to the clustering, and a pseudo F-statistic gave us an optimum number of clusters worldwide at 37. A major intent of the EMUs is to support marine biodiversity conservation assessments, economic valuation studies of marine ecosystem goods and services, and studies of ocean acidification and other impacts. As such, they represent a rich geospatial accounting framework for these types of studies, as well as for scientific research on species distributions. To further benefit the community and facilitate collaborate knowledge building, data products are shared openly and interoperably via www.esri.com/ecological-marine-units. This includes provision of 3D point mesh and EMU clusters at the surface, bottom, and within the water column in varying formats via download, web services or web apps, as well as generic algorithms and GIS workflows that scale from global to regional and local. Work is in progress to delineate EMUs at finer spatial and temporal resolutions and to include ocean currents and various biodiversity observations. A major aim is for the ocean science community members to move the research forward with higher-resolution data from their own field studies or areas of interest, with the original EMU project team assisting with GIS implementation (especially via a new online discussion forum), and hosting of additional data products as needed.
This paper compares and contrasts UAS-based Structure from Motion (SfM) and TLS survey methods as applied to evaluate the impacts of, and recovery from, the extreme El Niño 2015-16 on the seasonal geomorphic and sediment budget responses of an embayed, high-energy beach-dune system on the central coast of British Columbia, Canada. TLS and UAS mapping campaigns over a two-year period provided seasonal bare-earth digital terrain models (DTMs) and orthophoto mosaics. Spatial-temporal change detection methods were used to quantify volumes of significant erosion and deposition within the beach-dune system. The frequency and magnitude of erosive events and aeolian activity were also estimated from oblique, time-lapse photography. During the 2015-16 El Niño season, elevated water levels and storm waves eroded the foredune and lowered the beach surface by ~ 1m. Erosion was greatest in the middle of the beach with dune scarping of over 2m where wave energy was focused. Minor accretion occurred during the summer of 2016 on the upper beach, and ramp rebuilding was observed mostly from slumping and avalanching of existing dune sands. The following winter 2017 storm season led to minor erosion on the beach and extensive incipient dune development and sand ramp recovery fronting the foredune to an extent close to pre-El Niño elevations. Comparison of change surfaces between methods revealed limitations in the SfM method, namely due to vegetation effects on DTM generation, which limit its ability to detect change in the coastal environment. The costs, time, logistics, and accuracy for both SfM and TLS survey methodologies for coastal geomorphic change detection analysis is also evaluated. Combined, the UAS and SfM workflow provides a competitive solution to more expensive and time-consuming survey methods, such as TLS and aerial LiDAR, but its utility and accuracy is highly dependent on research objectives and post-processing techniques.
Stanford University offers a wide variety of opportunities for its students to engage in substantive, meaningful academic and professional experiences at the interface of ocean science and policy. As a student studying interdisciplinary environmental science, these programs have been transformative for how I see myself academically and professionally. The opportunities are made possible by collaborations with other academic institutions, non-governmental organizations, and governments. For instance, the Stanford at SEA program partners with the Sea Education Association to introduce students to marine biology and oceanography alongside sail handling and celestial navigation aboard a tall ship. While dissecting fish stomachs on the ship, I became more comfortable identifying myself as a scientist and fell in love with being at sea. Outside of courses, Stanford provides students with myriad ways to undertake significant work experiences. The Stanford in Washington program, for example, matches undergraduates with government offices or nonprofit organizations in Washington, D.C., for full-time internships during the school year. Students also take classes in the evening to complement their work experiences. I interned at the Department of Justice in the Environment and Natural Resources Division, which gave me a unique perspective on how federal agencies enforce environmental statutes. The Haas Center for Public Service and Stanford in Government, a student organization, also provide stipends for hundreds of summer fellowships. With SIG funding, I worked at the Center for Ocean Solutions and contributed significantly to a coastal adaptation policy project and planning for a new small-scale fisheries initiative. My experience with Stanford's programs have allowed me to substantively contribute to my learning about the ocean and to the missions of my host organizations while also giving me a sense of direction for my plans post-graduation.
In closed sea areas in the world the eutrophication is being progressed day by day. Nowadays in closed sea areas in Japan it is hard to control the seawater quality in deep areas because of the poor oxygen seawater or the anoxic seawater. Aerobic microorganisms can contribute to decompose organic compounds in the seawater as long as they live to consume oxygen. As a result the oxygen decreases in deep areas. It is necessary to maintain that the seawater is clean and rich in nature for the sustainable development. One of methods is this sustainable seawater purification system built in quays and piles using purifying functions of microorganisms and the tidal energy (Dan et al. 2017). It is shown that this system can decrease Chemical Oxygen Demand (CODMn) in the seawater experimentally and can be utilized in order to purify the seawater from the depth to the shallows using this system built in piles partially around a pile and using this system built in quays widely along a quay. This system has following advantages. 1.Using the tidal energy –> “ecosystem” 2.Using the purifying functions of microorganisms, decomposing organic materials –> “ecological and natural without chemicals”, 3.Capable of purifying the seawater in the shallow area, especially also in the deep area –> “useful” in closed sea areas 4.This system built in piles or quays is simple. Not to construct new quays but to construct the purifying room additionally. It costs less. –> “economical” The initial CODMn is almost 8 by putting sugar adequately in seawater and mixing (Fig. 9 and 10). The changing process of CODMn is checked by measuring CODMn according to JIS K 0102 (Japanese industrial Standards). In the case of seawater purification system CODMn is becoming smaller and it is found that this system can reduce CODMn in seawater. In future in order to construct this system built in piles or in quays in the field following procedure is considered, ①When the field site to construct this system is selected and the tidal range z is given. ②Because the velocity v in the vessel through gravels is sufficiently small for microorganisms to decompose organic compounds then v