Ocean Circulation Research Articles

Non-contact imaging of terahertz surface currents with aperture-type near-field microscopy

Terahertz (THz) near-field imaging and spectroscopy provide valuable insights into the fundamental physical processes occurring in THz resonators and metasurfaces on the subwavelength scale. However, so far, the mapping of THz surface currents has remained outside the scope of THz near-field techniques. In this study, we demonstrate that aperture-type scanning near-field microscopy enables non-contact imaging of THz surface currents in subwavelength resonators. Through extensive near-field mapping of an asymmetric D-split-ring THz resonator and full electromagnetic simulations of the resonator and the probe, we demonstrate the correlation between the measured near-field images and the THz surface currents. The observed current dynamics in the interval of several picoseconds reveal the interplay between several excited modes, including dark modes, whereas broadband THz near-field spectroscopy analysis enables the characterization of electromagnetic resonances defined by the resonator geometry.

Well-Posedness of the Two-Dimensional Compressible Plasma-Vacuum Interface Problem

We consider the two-dimensional plasma-vacuum interface problem in ideal compressible magnetohydrodynamics (MHD). This is a hyperbolic-elliptic coupled system with a characteristic free boundary. In the plasma region the 2D planar flow is governed by the hyperbolic equations of ideal compressible MHD, while in the vacuum region the magnetic field obeys the elliptic system of pre-Maxwell dynamics. At the free interface moving with the velocity of plasma particles, the total pressure is continuous and the magnetic field on both sides is tangent to the boundary. The plasma-vacuum system is not isolated from the outside world, since it is driven by a given surface current which forces oscillations onto the system. We prove the local-in-time existence and uniqueness of solutions to this nonlinear free boundary problem, provided that at least one of the two magnetic fields, in the plasma or in the vacuum region, is non-zero at each point of the initial interface. The proof follows from the analysis of the linearized MHD equations in the plasma region and the elliptic system for the vacuum magnetic field, suitable tame estimates in Sobolev spaces for the full linearized problem, and a Nash–Moser iteration.

Complex patterns of genetic structure in the sea cucumber Holothuria (Metriatyla) scabra from the Philippines: implications for aquaculture and fishery management

The sandfish Holothuria (Metriatyla) scabra, is a high-value tropical sea cucumber harvested from wild stocks for over four centuries in multi-species fisheries across its Indo-Pacific distribution, for the global bêche-de-mer (BDM) trade. Within Southeast Asia, the Philippines is an important centre of the BDM trade, however overharvesting and largely open fishery management have resulted in declining catch volumes. Sandfish mariculture has been developed to supplement BDM supply and assist restocking efforts; however, it is heavily reliant on wild populations for broodstock supply. Consequently, to inform fishery, mariculture, germplasm and translocation management policies for both wild and captive resources, a high-resolution genomic audit of 16 wild sandfish populations was conducted, employing a proven genotyping-by-sequencing approach for this species (DArTseq). Genomic data (8,266 selectively-neutral and 117 putatively-adaptive SNPs) were used to assess fine-scale genetic structure, diversity, relatedness, population connectivity and local adaptation at both broad (biogeographic region) and local (within-biogeographic region) scales. An independent hydrodynamic particle dispersal model was also used to assess population connectivity. The overall pattern of population differentiation at the country level for H. scabra in the Philippines is complex, with nine genetic stocks and respective management units delineated across 5 biogeographic regions: (1) Celebes Sea, (2) North and (3) South Philippine Seas, (4) South China and Internal Seas and (5) Sulu Sea. Genetic connectivity is highest within proximate marine biogeographic regions (mean Fst=0.016), with greater separation evident between geographically distant sites (Fst range=0.041–0.045). Signatures of local adaptation were detected among six biogeographic regions, with genetic bottlenecks at 5 sites, particularly within historically heavily-exploited locations in the western and central Philippines. Genetic structure is influenced by geographic distance, larval dispersal capacity, species-specific larval development and settlement attributes, variable ocean current-mediated gene flow, source and sink location geography and habitat heterogeneity across the archipelago. Data reported here will inform accurate and sustainable fishery regulation, conservation of genetic diversity, direct broodstock sourcing for mariculture and guide restocking interventions across the Philippines.

Sensitivity of ocean circulation to warming during the Early Eocene greenhouse

Multiple abrupt warming events ("hyperthermals") punctuated the Early Eocene and were associated with deep-sea temperature increases of 2 to 4 °C, seafloor carbonate dissolution, and negative carbon isotope (δ13C) excursions. Whether hyperthermals were associated with changes in the global ocean overturning circulation is important for understanding their driving mechanisms and feedbacks and for gaining insight into the circulation's sensitivity to climatic warming. Here, we present high-resolution benthic foraminiferal stable isotope records (δ13C and δ18O) throughout the Early Eocene Climate Optimum (~53.26 to 49.14 Ma) from the deep equatorial and North Atlantic. Combined with existing records from the South Atlantic and Pacific, these indicate consistently amplified δ13C excursion sizes during hyperthermals in the deep equatorial Atlantic. We compare these observations with results from an intermediate complexity Earth system model to demonstrate that this spatial pattern of δ13C excursion size is a predictable consequence of global warming-induced changes in ocean overturning circulation. In our model, transient warming drives the weakening of Southern Ocean-sourced overturning circulation, strengthens Atlantic meridional water mass aging gradients, and amplifies the magnitude of negative δ13C excursions in the equatorial to North Atlantic. Based on model-data consistency, we conclude that Eocene hyperthermals coincided with repeated weakening of the global overturning circulation. Not accounting for ocean circulation impacts on δ13C excursions will lead to incorrect estimates of the magnitude of carbon release driving hyperthermals. Our finding of weakening overturning in response to past transient climatic warming is consistent with predictions of declining Atlantic Ocean overturning strength in our warm future.

Econometric Analysis of the Influence of Factors on the Share of Energy From Renewable Sources in the EU

The use of renewable energy is at the core of EU energy policy, reducing dependence on fossil fuels imported from non-EU countries, reducing greenhouse gas emissions and decoupling energy costs from oil prices. Currently, 22.5% of energy consumed in the EU comes from renewable sources. This increase over 2021 is due to strong growth in solar energy. This share is also increasing due to the consumption of non-renewable energy sources in 2022. According to expert forecasts, the share of renewable energy sources in Europe will continue to grow. Achieving the 42.5% target by 2030 will require a deep transformation of the European energy system. The very strong climate and energy policies pursued in the EU for about a dozen years and aimed at limiting emissions of harmful substances into the environment have led to a gradual abandonment of traditional energy sources. Increasing demand for energy while reducing its supply from traditional sources means that in order not to make the economy too dependent on energy imports, the dynamic development of renewable energy is necessary. The EU is therefore taking very extensive operational and strategic actions to use other sources for production, such as wind, solar energy, mechanical water energy, biomass and geothermal energy, as well as tidal waves, ocean heat, wave energy and sea currents. In this study, we assess the impact of energy, economic and environmental factors on the share of renewable energy in the EU. The aim of these studies was to identify the energy, economic and environmental indicators that have the greatest impact on the share of energy from renewable sources in the European Union. The study was conducted using the Statgraphics Centurion software package. The source data for the study was data from the official Eurostat website for the period from 2012 to 2022. The results of this study show that changes in gross domestic product in market prices per capita have a positive impact, as do changes in greenhouse gas emissions per capita negatively affect the share of energy from renewable sources in the EU in the period 2012-2022. This may most likely be due to the fact that EU countries are more likely to invest in renewable energy as they can afford to invest in the development of expensive renewable energy technologies and support subsidies for the promotion and regulation of renewable energy. The negative impact of per capita greenhouse gas emissions on renewable energy development is due to the high share of coal in the EU energy mix, meaning that coal not only has negative environmental impacts, but also negative environmental impacts. development of renewable energy.

Mixed Rossby gravity waves at mid-depths of the equatorial Indian Ocean

Abstract This study examines mixed Rossby gravity (MRG) waves at mid-depths (500-2000 m) of the Indian Ocean, using multi-year velocity time series obtained from current meter moorings at 77°, 83°, and 93°E along the equator over the period 2000-2019. These data are analyzed in combination with a high-resolution wind-forced ocean general circulation model. The spectrum of observed meridional velocity showed elevated energy over a wide range of periods from about 10 to 100 days with the spectral peak at a period of about 30 days. The model was able to simulate the characteristics of the observed spectrum. Further diagnostics determined that the detected variability is generally consistent with theoretical MRG waves in a resting ocean. Statistical analysis and a model sensitivity experiment identified distinct variations at three periods, where meridional velocity has sizable energy. The 14-day variability is wind-driven and has a long zonal (∼3300 km) and vertical wavelength (∼4200 m). The 28-day variability is excited by the dynamical instability of the background flow in the equatorial western Indian Ocean near the surface and propagates to the study area. It is characterized by a shorter zonal (∼1100 km) and vertical wavelength (∼2800 m) compared to 14-day variability. The 43-day variability has a zonal wavelength (∼820 km) comparable to the 28-day variability, but does not show the tendency of propagation and is likely generated in situ through nonlinear interactions. These results show that various processes contribute to the excitation of MRG waves at mid-depths of the Indian Ocean.

Third‐Order Structure Functions of Zonal Winds in the Thermosphere Using CHAMP and GOCE Observations

AbstractWe use multi‐year observations of cross‐track winds (u) from the CHAllenging Minisatellite Payload (CHAMP) and the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) to calculate third‐order structure functions in the thermosphere as a function of horizontal separation (s). They are computed using the mean (〈δu3〉) and the median and implemented over non‐polar satellite paths in both hemispheres. On height averages, 〈δu3〉 is shown to scale with s2 for s ≃ 80–1,000 km, in agreement with equivalent estimates in the lower atmosphere from aircraft observations. Conversely, follows an s3 power law for almost the whole s range, consistent with the two‐dimensional turbulence scaling law for a direct enstrophy cascade. These scaling laws appear independent of winds in distinct atmospheric regions. Furthermore, the functions are predominantly positive, indicating a preferential cyclonic motion for the wind.

Season‐Dependent Atmosphere‐Ocean Coupled Processes Driving SST Seasonality Changes in a Warmer Climate

AbstractAmplification of sea surface temperature (SST) seasonality in response to global warming is a robust feature in climate model projections but season‐dependent regional disparities in this amplification and the associated mechanisms are not well addressed. Here, by analyzing large ensemble simulations using Community Earth System Model version 2, we investigate detailed spatiotemporal characteristics of the amplification of SST seasonality focusing on the North Pacific and North Atlantic, where robust changes are projected to emerge around 2050 under SSP3‐7.0 scenario. Our results indicate that atmosphere‐ocean coupled processes shape regional changes in SST seasonality differently between warm (MAMJJAS) and cold seasons (ONDJF). During the warm season, the projected warming tendency is mainly due to increased net surface heat flux and weakening of vertical mixing. On the other hand, in the cold season, the projected cooling tendency is driven by strengthened vertical mixing over the North Pacific associated with the northward shift of storm tracks but weakened horizontal advection and mixing due to changes in ocean currents over the North Atlantic.

Fast reduction of Atlantic SST threatens Europe-wide gross primary productivity under positive and negative CO2 emissions

Climate change mitigation through negative CO2 emissions has been recognized as a crucial strategy to combat global warming. However, its potential effects on terrestrial productivity and agricultural activities remain uncertain. In this study, we utilized large ensemble simulations with an Earth system model of full complexity to investigate the response of Gross Primary Production (GPP) to CO2 forcings. Our findings reveal a significant asymmetry in the GPP response to CO2 ramp-up and symmetric ramp-down model experiments, especially in Europe, suggesting that GPP declines rapidly as CO2 levels decrease. Remarkably, during the CO2 removal period, the North Atlantic Sea surface temperature experienced cooling due to a delayed recovery of the Atlantic Meridional Overturning Circulation (AMOC). This cooling led to precipitation and soil moisture deficits, resulting in a rapid reduction in GPP. This asymmetry in GPP response holds consistent across multi-model simulations. These results underscore the potential implications of delayed recovery in ocean circulation, which could unexpectedly accelerate terrestrial GPP reduction. These insights are crucial for policymakers, aiding them in projecting agricultural activity and formulating targeted GPP control policies specific to the European region.

Nonstationary thermodynamic and dynamic contributions to the interannual variability of winter sea ice growth in the Kara–Laptev Seas

The Kara–Laptev Seas (KLS), known as the ‘Ice Factory of the Arctic’, witnesses rising instead of falling winter sea ice growth (WSIG) under the shrinkage of Arctic ice. However, knowledge of the large year-to-year variation is still unclear. Combining a seasonal ice concentration budget, a composite analysis, and a typical case study, we study both the interannual variability of WSIG in the KLS and the associated air-sea forcings during 1985–2021. Results quantitatively reveal that, during 1985–2021, thermodynamic melt in the melting season (April–August) contributed 80.3% to the interannual ice loss difference and promoted the subsequent WSIG by the recovery mechanism in the KLS. This consistent thermodynamic melt is caused by the strengthened summer Beaufort High, transporting heat and introducing a locally positive ice-albedo feedback. However, since 2010, the dynamic growth during the freezing season (October–February) has increasingly stimulated the WSIG. Typical cases in 2013 and 2017 indicate that the overlying anticyclonic atmospheric regime restricts the ice drift from the KLS and contributes to the dynamic growth of 41.6% of the WSIG difference, while the turbulent-heat-induced thermodynamic growth in winter is down to 58.4%. In short, we reveal an unstable relationship between the summer ice loss and the subsequent WSIG under the background of Arctic warming. Our study points out that the distinct dynamic ice growth driven by surface winds or ocean currents during the freezing season is likely to increase in the near future, with thinner and more mobile seasonal ice predominating in the Arctic.

The Role of Surface Potential Vorticity in the Vertical Structure of Mesoscale Eddies in Wind-Driven Ocean Circulations

Abstract The vertical structure of ocean eddies is generally surface-intensified, commonly attributed to the dominant baroclinic modes arising from the boundary conditions (BCs). Conventional BC considerations mostly focus on either flat- or rough-bottom conditions. The impact of surface buoyancy anomalies—often represented by surface potential vorticity (PV) anomalies—has not been fully explored. Here, we study the role of the surface PV in setting the vertical distribution of eddy kinetic energy (EKE) in an idealized adiabatic ocean model driven by wind stress. The simulated EKE profile in the extratropical ocean tends to peak at the surface and have an e-folding depth typically smaller than half of the ocean depth. This vertical structure can be reasonably represented by a single surface quasigeostrophic (SQG) mode at the energy-containing scale resulting from the large-scale PV structure. Due to isopycnal outcropping and interior PV homogenization, the surface meridional PV gradient is substantially stronger than the interior PV gradient, yielding surface-trapped baroclinically unstable modes with horizontal scales comparable to or smaller than the deformation radius. These surface-trapped eddies then grow in size both horizontally and vertically through an inverse energy cascade up to the energy-containing scale, which dominates the vertical distribution of EKE. As for smaller horizontal scales, the EKE distribution decays faster with depth. Guided by this interpretation, an SQG-based scale-aware parameterization of the EKE profile is proposed. Preliminary offline diagnosis of a high-resolution simulation shows the proposed scheme successfully reproducing the dependence of the vertical structure of EKE on the horizontal grid resolution.

Regional Fluctuations in the Eastern Tropical North Pacific Oxygen Minimum Zone during the Late Holocene

This study presents a high-resolution record of δ15Nsed, which serves as a proxy for water column denitrification and oxygen minimum zone (OMZ) intensity, from the Soledad Basin in the Eastern Tropical North Pacific OMZ. The Soledad Basin δ15Nsed record is compared to the Pescadero Slope and Santa Barbara Basin (SBB) δ15Nsed records to gain insight into regional variations in the ETNP OMZ. During the Medieval Climate Anomaly (MCA; 950–1250 CE), Soledad Basin, Pescadero Slope, and SBB records exhibit coherent trends suggesting that there was general water column oxygenation stability. During the Little Ice Age (LIA; 1350–1850 CE), Soledad Basin and SBB showed a similar decreasing trend in δ15Nsed values while the Pescadero Slope δ15Nsed exhibited an increasing trend until values abruptly declined between 1740 and 1840 CE. We suggest that increased δ15Nsed variability and the different trends at the Pescadero Slope during the LIA are due to the influence of the North American monsoon (NAM), which can suppress upwelling when enhanced and result in OMZ contraction. The decoupling between the Soledad Basin, SBB, and the Pescadero Slope could also be due to the increased influence of enriched 15NO3− subarctic waters in the California Current System. Since each site is influenced by local productivity, basin morphology, and regional atmospheric and ocean circulation patterns, we suggest that assessing OMZ fluctuations from multiple sites provides a more comprehensive view of regional OMZ dynamics in response to climate variations.

Regional Sea Level Response to External Forcings from the Twentieth to the Twenty-First Century

Abstract Using a range of Detection and Attribution Model Intercomparison Project (DAMIP) simulations from phase 6 of Coupled Model Intercomparison Project (CMIP6), we study the response of dynamic sea level (DSL) to external anthropogenic climate forcing [greenhouse gases (GHGs), aerosols, and stratospheric ozone] with a focus on the differences over the twentieth and twenty-first century. In the second half of the twentieth century, the DSL nonuniformity in the Northern Hemisphere (NH) was relatively small due to a cancellation between the effects of increasing GHGs and aerosols. In contrast, the DSL signal in the Southern Hemisphere (SH) over this period was large because stratospheric ozone depletion reinforced the effects of increasing GHGs. In the twenty-first century, the DSL response has been intensified in the NH because the warming effects of diminishing aerosols have acted to reinforce the effects of increasing GHGs. Meanwhile, the distribution of SH DSL has also become uneven although stratospheric ozone recovery has partially offset the effects of rising GHGs. Using a global ocean circulation model, we decompose the changes in the twenty-first century DSL into distinct responses to surface forcings including sea surface temperature, salinity, and wind stress. Our results show that the dipole-like pattern of DSL in the North Pacific can be attributed largely to sea surface warming, while the dipole-like pattern in the North Atlantic is attributed to subpolar surface salinity freshening. The belted pattern of DSL changes in the Southern Ocean is induced by both surface warming and intensifying/poleward-shifting westerly winds.

Environmental Influences on Illex argentinus Trawling Grounds in the Southwest Atlantic High Seas

To understand the spatial temporal distribution characteristics of Illex argentinus caught by trawl fishing vessels in the Southwestern Atlantic Ocean and their relationship with key marine environmental factors, this study analyzed the temporal and spatial changes in the fishing ground center of trawl vessels at the ten-day scale from December 2019 to May 2022, combining Chinese trawl fishing log data marine environmental data with satellite remote sensing marine environmental data. Utilizing the Maxent model, ten-day intervals were used as the temporal scale, and ten marine environmental factors, including sea surface temperature, sea surface height, sea surface salinity, chlorophyll concentration, temperature at 50 m and 100 m depth, and the meridional and zonal velocities of ocean currents were quantitatively analyzed to explore the correlation between the spatial distribution of catch and environmental factors. The study reveals that the trawl fishing grounds for Illex argentinus are divided into southern and northern grounds. The southern grounds first appear near 45°20′ S in December, gradually moving southeastward in February and March. The northern grounds do not appear until April, near 42° S in the high seas. On the ten-day time scale, the central fishing grounds of Illex argentinus show significant spatial variability but minor interannual differences. The Maxent model results indicate that sea surface temperature and chlorophyll a concentration are the key environmental factors influencing the spatial and temporal variability of the high seas trawl fishing grounds for most of the time, with high environmental contribution rates during the fishing season. While the range of suitable habitats with an HSI > 0.6 identified by the Maxent model varies significantly between years, a pattern is observed where the range expands at the start and end of the fishing season and contracts during the peak fishing season. This suggests that a more concentrated range of suitable habitats is conducive to accurate predictions of trawl fishing grounds, enabling efficient fishing operations.

Analysis of Sea and River Water Quality Standards Due to Operations and Domestic Activities in the Sanur Port Area, Bali

The development of an area has impacts, both positive and negative impacts. The positive impact is in the form of regional economic growth, employment and development of the surrounding regions. The negative impact is the disruption of the environmental ecosystem and a decrease in environmental quality due to waste generated from development operations, in the form of solid waste (garbage) and liquid waste. The increasing pollution load is also caused by public awareness and business activities in upstream areas that do not manage waste properly, which ultimately leads to all of the waste accumulating in water bodies and causing changes in water quality standards. Sanur Port, which is one of the development centers in its operations, is very vulnerable to environmental pollution impacts. The pollution mechanism originates from activities around Sanur Port and domestic activities which are discharged into rivers and seas in the Sanur area. This research aims to analyze the quality of river water and sea water caused by activities around Sanur Port and community activities based on Decree of the Minister of Environment Number 51 of 2004 and determine the pollution index. Water quality standards use Bali Governor Regulation no. 16 of 2016 concerning Environmental Quality Standards and Quality Standard Criteria for Environmental Damage. This research uses a quantitative approach by collecting primary data from direct observations in the field and secondary data based on previous research reports and government reports. The research results show that TDS in the rainy season tends to be lower than in the dry season, both in the results of testing samples of Abianbase river water, the results of testing samples of sea water in front of the Mak Beng Restaurant and sea water samples in the Sanur Port Pool. In front of Mak Beng, ammonia levels during the rainy season are higher than during the dry season. Ammonia levels in the Abianbase River and sea water in front of Sanur port are lower during the rainy season compared to the dry season. The presence of Coliform bacteria and E. coli shows a tendency to decrease during the rainy season. This decrease is thought to be caused by leaching by rainwater entering marine waters and retailing and changes in ocean currents during the rainy season.

Primary Drivers of the Recent Changes Observed in Global Ocean Circulation Patterns in Mozambique

Purpose: The aim of the study was to examine the primary drivers of the recent changes observed in global ocean circulation patterns in Mozambique Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study revealed that primary drivers of the recent changes observed in global ocean circulation patterns are involving a combination of natural variability and anthropogenic influences. Key factors identified include global warming, alterations in wind patterns, sea surface temperature anomalies, and increased freshwater input from melting ice caps and glaciers. These elements interact in intricate ways to influence the dynamics of ocean currents, which are critical for regulating Earth's climate and supporting marine ecosystems. Unique Contribution to Theory, Practice and Policy: Bronfenbrenner's Ecological Systems Theory & Abraham Maslow's Hierarchy of Needs may be used to anchor future studies on primary drivers of the recent changes observed in global ocean circulation patterns in Mozambique. Increase investment in global ocean monitoring systems, such as Argo floats, satellite missions, and autonomous underwater vehicles, to collect high-resolution data on temperature, salinity, and currents. This data is crucial for validating models and understanding the current state and trends of ocean circulation. Strengthen international cooperation to address global warming, a primary driver of changes in ocean circulation. This includes adhering to and expanding commitments under the Paris Agreement to reduce greenhouse gas emissions.

Undervalued dry riverbeds: A key factor in equating intermittent river CO2 emissions to perennial rivers

Intermittent rivers in semiarid and arid regions, constituting over half of the world's rivers, alternate the carbon cycle interactions among the biosphere, hydrosphere, and atmosphere. Inadequate quantification of flow duration and river water surface area, along with overlooked CO2 emissions from dry riverbeds, result in notable inaccuracies in global carbon cycle assessments. High-resolution remote sensing images combined with intensive field measurements and hydrological modelling were used to estimate and extract the flow duration, river water surface area and dry riverbed area of Huangfuchuan, an intermittent river watershed that acts as a major tributary of the Yellow River in semiarid Northwest China. CO2 emission rates and partial pressures in water and air across the watershed were in-situ measured. In 2018, the flow duration of Huangfuchuan increased from less than 5 days in the first-order tributary to 150 days in the sixth-order mainstream. River water surface area estimated by remote sensing extraction plus the hydrodynamic model simulation varied from 3.9 to 88.6 km2 under 5 %–95 % discharge frequencies. CO2 emissions from the water-air interface and dry riverbed in 2018 were estimated at 582.3 × 103 and 355.2 × 103 ton, respectively. The estimated total annual emission (937.5 × 103 ton) aligns closely with the range of emissions (67.3 × 103–1377.2 × 103 ton) calculated for the water-air interface alone, derived using DEM river length and hydraulic geometry method. This similarity can be attributed to the overestimation of flow duration and flow velocity, as well as the over- or under-estimation of river water surface area and slope. The new method proposed in this study has large potential to be applied in estimating CO2 emissions from data-scarce intermittent rivers located in mountainous regions and provides a standardized solution in the estimation of CO2 emission. Results of this research reveal the spatiotemporal distribution of CO2 emissions along an intermittent river system and highlight the substantial role of dry riverbed in carbon cycle.

Surface currents shape protist community structure across the Indo-Pacific.

Biogeographic structure in marine protist communities is shaped by a combination of dispersal potential and environmental selection. High-throughput sequencing and global sampling efforts have helped better resolve the composition and functions of these communities in the world's oceans using both molecular and visual methods. However, molecular barcoding data are critically lacking across the Indo-Pacific, a region widely considered the epicenter of marine biodiversity. To fill this gap, we characterized protist communities in four sampling regions across Indonesia that represent the latitudinal, longitudinal, and human population gradients of the region: Lombok, Wakatobi, Misool, and Waigeo. We show high spatial structuring in marine protist communities across Indonesia, and biotic factors appear to play little role in driving this observed structure. Our results appear to be driven by abiotic factors linked to surface current patterns across the Indo-Pacific as a result of: (1) a choke point in circulation at the Indonesian Throughflow leading to low diatom diversity in Lombok, Wakatobi, and Misool; (2) an increase in nutrient availability at the edge of the Halmahera Eddy in Waigeo, leading to an increase in diatom diversity; and/or (3) seasonal variations in protist communities in line with shifts in velocity of the Indonesian Throughflow. Overall, our results highlight the importance of abiotic factors in shaping protist communities on broad geographic scales over biotic, top-down pressures, such as grazing from higher trophic levels.

Unveiling Regional Climate Patterns Through Global Subsurface Ocean Temperature Data: An AI Multi-Layer Analysis Framework

AbstractRegional-scale climate variability has far-reaching implications for both local and global climate systems, impacting factors like temperature, precipitation patterns, oceanic circulation, and the occurrence of extreme weather events. However, despite these influences, there is currently no universal methodology for the automated identification of regional-scale variability modes, including those less dominant globally, and for simultaneously exploring the influence of various ocean depth layers in characterizing these modes and diagnosing regional sea level variations. The presented innovative approach addresses these critical region-specific needs by assisting in the extraction of novel regional depth-layered variability modes and establishing their correlation with regional sea level fluctuations, employing tailored machine-learning techniques. This dual-purpose is achieved through the utilization of an optimized k-means clustering method for the automatic identification of regions with shared variability patterns across all global oceans, revealing previously unexplored regional variability modes. Additionally, guided by an EOF/PC analysis, the approach facilitates an automatic exploration of depth layers that significantly contribute to explaining sea level variability, providing insights into diverse climatic regions. Furthermore, the methodology is specifically designed for a multi-scale analysis, enabling the examination of climate variability spanning from months to several years. The results obtained through this approach have the potential to support informed decision-making regarding local climate-related changes.

Increasing impacts of ocean acidification on coral reefs under global warming

The rapid increase in atmospheric CO2 concentration in recent decades has influenced the marine system to a great extent with ocean acidification being one of the consequences. Ocean acidifications impact on calcifying marine organisms has long been the subject of scientific studies. To determine the effect of ocean acidification on hard coral reefs, we analyzed five ocean coastal regions, comparing the trend in regional surface hydrogen ion activity with the change in hard coral coverage. In each region, we included both historical measured data and predicted data using RCP models as an implication of the potential future. The outcome does not provide substantial evidence to confirm the hypothesis linking the two variables. Additionally, the direct association between these variables cannot be ascertained due to the influence of uncontrolled factors such as local pollution, ocean warming, and ocean currents.