Showing papers by "Korean Ocean Research and Development Institute published in 2021"

Climate model projections from the Scenario Model Intercomparison Project (ScenarioMIP) of CMIP6

Abstract: . The Scenario Model Intercomparison Project (ScenarioMIP) defines and coordinates the primary future climate projections within the Coupled Model Intercomparison Project Phase 6 (CMIP6). This paper presents a range of its outcomes by synthesizing results from the participating global coupled Earth system models for concentration driven simulations. We limit our scope to the analysis of strictly geophysical outcomes: mainly global averages and spatial patterns of change for surface air temperature and precipitation. We also compare CMIP6 projections to CMIP5 results, especially for those scenarios that were designed to provide continuity across the CMIP phases, at the same time highlighting important differences in forcing composition, as well as in results. The range of future temperature and precipitation changes by the end of the century encompassing the Tier 1 experiments (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) and SSP1-1.9 spans a larger range of outcomes compared to CMIP5, due to higher warming (by 1.15 °C) reached at the upper end of the 5–95 % envelope of the highest scenario, SSP5-8.5. This is due to both the wider range of radiative forcing that the new scenarios cover and to higher climate sensitivities in some of the new models compared to their CMIP5 predecessors. Spatial patterns of change for temperature and precipitation averaged over models and scenarios have familiar features, and an analysis of their variations confirms model structural differences to be the dominant source of uncertainty. Models also differ with respect to the size and evolution of internal variability as measured by individual models' initial condition ensembles' spread, according to a set of initial condition ensemble simulations available under SSP3-7.0. The same experiments suggest a tendency for internal variability to decrease along the course of the century, a new result that will benefit from further analysis over a larger set of models. Benefits of mitigation, all else being equal in terms of societal drivers, appear clearly when comparing scenarios developed under the same SSP, but to which different degrees of mitigation have been applied. It is also found that a mild overshoot in temperature of a few decades in mid-century, as represented in SSP5-3.4OS, does not affect the end outcome in terms of temperature and precipitation changes by 2100, which return to the same level as those reached by the gradually increasing SSP4-3.4. Central estimates of the time at which the ensemble means of the different scenarios reach a given warming level show all scenarios reaching 1.5 °C of warming compared to the 1850–1900 baseline in the second half of the current decade, with the time span between slow and fast warming covering 20–28 years from present. 2 °C of warming is reached as early as the late '30s by the ensemble mean under SSP5-8.5, but as late as the late '50s under SSP1-2.6. The highest warming level considered, 5 °C, is reached only by the ensemble mean under SSP5-8.5, and not until the mid-90s.

Underwater Acoustic Sensor Networks With Cost Efficiency for Internet of Underwater Things

Abstract: Despite the potential benefits of Internet of Underwater Things, a number of issues hinder its realization, including the need for communication reliability and cost-effectiveness. This article aims to optimize network design to implement cost-effective underwater acoustic sensor networks (UASNs) with 3D topology while supporting diverse communication quality of service (QoS) requirements. First, we present an analytical framework based on a queueing system that evaluates communication performances of UASNs, wherein each underwater sensor distributed within a 3D space under the sea surface performs fountain code (FC)-based automatic repeat request (ARQ) transmissions under the slotted-Aloha medium access control protocol. Under the proposed framework, we evaluate communication performances given in terms of successful FC-based ARQ transmission probability and the average queueing delay of an underwater sensor. When evaluating the performances, we formulate the service time of each underwater sensor as a function of network parameters, i.e., the density of data sink and amount of redundancy for FC-based ARQ transmission, before solving a function for accurate service time, such that each sensor can be represented by an M/G/1 queue. Further, our analysis can formulate an optimization problem that aims at minimizing total cost incurred to install and operate 3D UASNs, without compromising two communication QoS requirements. To solve this problem, we propose a recursive algorithm to approach an optimal solution in reasonable time. Numerical evaluations demonstrate the validity of the proposed algorithm.

Analysis of environmental organic matters by Ultrahigh-Resolution mass spectrometry—A review on the development of analytical methods

Abstract: Owing to the increasing environmental and climate changes globally, there is an increasing interest in the molecular-level understanding of environmental organic compound mixtures, that is, the pursuit of complete and detailed knowledge of the chemical compositions and related chemical reactions. Environmental organic molecule mixtures, including those in air, soil, rivers, and oceans, have extremely complex and heterogeneous chemical compositions. For their analyses, ultrahigh-resolution and sub-ppb level mass accuracy, achievable using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), are important. FT-ICR MS has been successfully used to analyze complex environmental organic molecule mixtures such as natural, soil, particulate, and dissolved organic matter. Despite its success, many limitations still need to be overcome. Sample preparation, ionization, structural identification, chromatographic separation, and data interpretation are some key areas that have been the focus of numerous studies. This review describes key developments in analytical techniques in these areas to aid researchers seeking to start or continue investigations for the molecular-level understanding of environmental organic compound mixtures.

Patterns of Macrofaunal Biodiversity Across the Clarion-Clipperton Zone: An Area Targeted for Seabed Mining

Abstract: Macrofauna are an abundant and diverse component of abyssal benthic communities and are likely to be heavily impacted by polymetallic nodule mining in the Clarion-Clipperton Zone (CCZ). In 2012, the International Seabed Authority (ISA) used available benthic biodiversity data and environmental proxies to establish nine no-mining areas, called Areas of Particular Environmental Interest (APEIs) in the CCZ. The APEIs were intended as a representative system of protected areas to safeguard biodiversity and ecosystem function across the region from mining impacts. Since 2012, a number of research programs have collected additional ecological baseline data from the CCZ. We assemble and analyze macrofaunal biodiversity data sets from eight studies, focusing on three dominant taxa (Polychaeta, Tanaidacea, and Isopoda), and encompassing 477 box-core samples to address the following questions: (1) How do macrofaunal abundance, biodiversity, and community structure vary across the CCZ, and what are the potential ecological drivers? (2) How representative are APEIs of the nearest contractor areas? (3) How broadly do macrofaunal species range across the CCZ region? and (4) What scientific gaps hinder our understanding of macrofaunal biodiversity and biogeography in the CCZ? Our analyses led us to hypothesize that sampling efficiencies vary across macrofaunal data sets from the CCZ, making quantitative comparisons between studies challenging. Nonetheless, we found that macrofaunal abundance and diversity varied substantially across the CCZ, likely due in part to variations in particulate organic carbon (POC) flux and nodule abundance. Most macrofaunal species were collected only as singletons or doubletons, with additional species still accumulating rapidly at all sites, and with most collected species appearing to be new to science. Thus, macrofaunal diversity remains poorly sampled and described across the CCZ, especially within APEIs, where a total of nine box cores have been taken across three APEIs. Some common macrofaunal species ranged over 600-3000 km, while other locally abundant species were collected across <= 200 km. The vast majority of macrofaunal species are rare, have been collected only at single sites, and may have restricted ranges. Major impediments to understanding baseline conditions of macrofaunal biodiversity across the CCZ include: (1) limited taxonomic description and/or barcoding of the diverse macrofauna, (2) inadequate sampling in most of the CCZ, especially within APEIs, and (3) lack of consistent sampling protocols and efficiencies.

Extent of impact of deep-sea nodule mining midwater plumes is influenced by sediment loading, turbulence and thresholds

Abstract: Deep-sea polymetallic nodule mining research activity has substantially increased in recent years, but the expected level of environmental impact is still being established. One environmental concern is the discharge of a sediment plume into the midwater column. We performed a dedicated field study using sediment from the Clarion Clipperton Fracture Zone. The plume was monitored and tracked using both established and novel instrumentation, including acoustic and turbulence measurements. Our field studies reveal that modeling can reliably predict the properties of a midwater plume in the vicinity of the discharge and that sediment aggregation effects are not significant. The plume model is used to drive a numerical simulation of a commercial-scale operation in the Clarion Clipperton Fracture Zone. Key takeaways are that the scale of impact of the plume is notably influenced by the values of environmentally acceptable threshold levels, the quantity of discharged sediment, and the turbulent diffusivity in the Clarion Clipperton Fracture Zone. The extent of impact by midwater discharge plumes from deep-sea nodule mining will be influenced by the quantity of plume sediment, ocean turbulence and acceptable environmental thresholds, according to numerical modelling and direct experiments

Combined effects of heavy metals (Cd, As, and Pb): Comparative study using conceptual models and the antioxidant responses in the brackish water flea.

Abstract: The combined effect of toxic inducers has emerged as a challenging topic, particularly due to their inconsistent impacts on the environment. Using toxic unit (TU) based on LC50 value, we investigated the 48 h acute toxicities of the following combinations: Cd + As, Cd + Pb, As + Pb, and Cd + As + Pb, and binary and ternary combined effects were interpreted using concentration addition (CA) and independent action (IA) model. The molecular effects of these combinations were further examined on the basis of gene expression (four GST and two SOD isoforms) and antioxidant enzymes activity (SOD and GST). The CA-predicted LC50 was similar to the observed results, indicating that the CA model is more applicable for evaluating the combined effects of the metal mixtures. Synergistic effects (ΣTULC50

Improvement of SMAP sea surface salinity in river-dominated oceans using machine learning approaches

Abstract: Sea salinity is one of the indicators of the global water cycle and affects the surface and deep circulation of the ocean. While passive microwave satellite sensors have been used to monitor sea su...

Impact of aquaculture on distribution of dissolved organic matter in coastal Jeju Island, Korea, based on absorption and fluorescence spectroscopy

Abstract: In Jeju Island, multiple land-based aquafarms were fully operational along most coastal region. However, the effect of effluent on distribution and behaviours of dissolved organic matter (DOM) in the coastal water are still unknown. To decipher characteristics of organic pollution, we compared physicochemical parameters with spectral optical properties near the coastal aquafarms in Jeju Island. Absorption spectra were measured to calculate the absorption coefficient, spectral slope coefficient, and specific UV absorbance. Fluorescent DOM was analysed using fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were measured using high-temperature catalytic oxidation. The DOC concentration near the discharge outlet was twice higher than that in natural groundwater, and the TDN concentration exponentially increased close to the outlet. These distribution patterns indicate that aquafarms are a significant source of DOM. Herein, principal component analysis was applied to categorise the DOM origins. There were two distinct groups, namely, aquaculture activity for TDN with humic-like and high molecular weights DOM (PC1: 48.1%) and natural biological activity in the coastal water for DOC enrichment and protein-like DOM (PC2: 18.8%). We conclude that the aquafarms significantly discharge organic nitrogen pollutants and provoke in situ production of organic carbon. Furthermore, these findings indicate the potential of optical techniques for the efficient monitoring of anthropogenic organic pollutants from aquafarms worldwide.

Mechanical behavior of waste fishing net fiber-reinforced cementitious composites subjected to direct tension

Abstract: In this study, we investigated the mechanical behavior of waste fishing net (WFN) fiber-reinforced cementitious composites (FRCCs) subjected to direct tension to evaluate the possibility of using WFN fibers as reinforcement in cementitious composites. Three different WFN fibers, two commercial (C) polypropylene (PP) fibers, and two fiber volumes (0.5 and 1.0%) were considered as test variables to explore the effect of adding WFN fiber to a cement mortar. As the fiber volume was increased, both the compressive and first cracking strengths decreased, while the post-cracking strength increased. Reinforced samples (WFN3-FRCCs) with a 0.5% fiber volume exhibited the highest compressive strength, while those with a fiber volume of 1.0% had the highest post-cracking strength. The compressive and post-cracking strengths of WFN3-FRCCs were 6–10% and 2–13% higher than those of C-FRCCs, respectively. Therefore, WFN-fibers consisting of twisted yarns, which generate mechanical bonds during fiber pull-out, are appropriate for reinforcing cement mortar, thereby improving their strength and ductility under tensile loads.

Zooming on dynamics of marine microbial communities in the phycosphere of Akashiwo sanguinea (Dinophyta) blooms.

Abstract: Characterizing ecological relationships between viruses, bacteria and phytoplankton in the ocean is critical to understanding the ecosystem; however, these relationships are infrequently investigated together. To understand the dynamics of microbial communities and environmental factors in harmful algal blooms (HABs), we examined the environmental factors and microbial communities during Akashiwo sanguinea HABs in the Jangmok coastal waters of South Korea by metagenomics. Specific bacterial species showed complex synergistic and antagonistic relationships with the A. sanguinea bloom. The endoparasitic dinoflagellate Amoebophrya sp. 1 controlled the bloom dynamics and correlated with HAB decline. Among nucleocytoplasmic large DNA viruses (NCLDVs), two Pandoraviruses and six Phycodnaviruses were strongly and positively correlated with the HABs. Operational taxonomic units of microbial communities and environmental factors associated with A. sanguinea were visualized by network analysis: A. sanguinea-Amoebophrya sp. 1 (r = .59, time lag: 2 days) and A. sanguinea-Ectocarpus siliculosus virus 1 in Phycodnaviridae (0.50, 4 days) relationships showed close associations. The relationship between A. sanguinea and dissolved inorganic phosphorus relationship also showed a very close correlation (0.74, 0 day). Microbial communities and the environment changed dynamically during the A. sanguinea bloom, and the rapid turnover of microorganisms responded to ecological interactions. A. sanguinea bloom dramatically changes the environments by exuding dissolved carbohydrates via autotrophic processes, followed by changes in microbial communities involving host-specific viruses, bacteria and parasitoids. Thus, the microbial communities in HAB are composed of various organisms that interact in a complex manner.