Argo Buoys Research Articles

Optimizing wave simulation to improve the ocean circulation model in the North Pacific Ocean

In this paper, the simulation performance of two source terms, ST4 and ST6, of the wave model WAVEWATCH III on significant wave heights is investigated in the North Pacific Ocean, and the root mean square error (RMSE), correlation coefficient (R) and mean absolute error (E MAE) were compared between them, and all indices showed that the waves was better modelled by using ST4 in the North Pacific region. Based on the ST4 source term scheme, the Stokes drift is calculated from the wave elements simulated by WAVEWATCH III, and is added to the momentum equation of the SBPOM circulation model with the Stokes drift calculated by spectral integration, and it is found that the sea surface temperature (SST) simulated by the former scheme is better than that by the latter scheme by comparing with that of the Argo buoys, in which the RMSE is reduced by 0.018°C, E MAE is reduced by 0.025°C, and R is improved by 0.007. Finally, by comparing the simulated Langmuir numbers of the two schemes, it is found that in most of the sea area (especially in the deep sea), the simulated Langmuir number of the former scheme is smaller than that of the latter scheme by about 0.1, which indicates the former scheme can be used to enhance seawater mixing, thus improving the accuracy of the coupled WAVEWATCH III-SBPOM model.

Communication Management and Data Compression Algorithm Design of BeiDou Transparent Transmission Terminal for Argo Buoy

The Argo buoy detects marine environmental data by making profile movements in the ocean and transmits the profile detection data to the shore base through the communication terminal. However, due to the large volume of data collected from profile detections and the continuous operation of the terminal, the remote communication of buoys is characterized by lengthy communication times and significant power consumption. A low-power Beidou transparent transmission terminal is designed to solve these problems in this paper. The terminal performs low-power operation management and power management for terminal remote communication. After the end of a communication process, the microcontroller turns the Beidou module power off and enters STOP mode. Before the next communication process begins, the serial port wakes up the microcontroller, which powers up the Beidou module. Before the remote communication, the microcontroller compacts the profile detection data collected by the buoy to reduce the quantity of remote communication data. In this paper, a variety of data compression methods are used to compare the compression rate, and the best compression method is selected according to the format characteristics of the data. The results show that the Beidou transparent transmission terminal of the Argo buoy can realize low power consumption for remote communication in ocean exploration. The terminal reduces power consumption by 77.282% per communication, and the average number of remote communications for each profile detection data are reduced by 55 times. The low-power Beidou transparent transmission terminal improves the battery life and is conducive to the long-term operation of the buoy.

Chlorophyll bloom triggered by tropical storm chedza at the southern tip of madagascar island

Abstract A phytoplankton bloom during the passage of Tropical Storm (TS) Chedza was observed at the southern tip of Madagascar on January 28, 2015. The mechanisms of the chlorophyll bloom were researched with satellite remote sensing data, reanalysis data and Argo buoy data. The results show that there was horizontal transport of chlorophyll-a (Chl-a) with the western coastal current of Madagascar and the South East Madagascar Current (SEMC). At the southern tip of Madagascar, there was a tilted anticyclonic eddy moving westward, which promoted the flow of nitrate at depths from 60 m to 100 m northward into Box A for a month. Simultaneously, the SEMC formed another anticyclonic eddy entering Box C. Following the passage of TS Chedza, cyclone vorticity in Box A increased continuously, and the upwelling became stronger with Ekman pumping. At the same time, the barrier layer weakened, the mixed layer deepened, and the thermocline decreased, which can uplift the nitrate to the upper ocean. After the passage of TS Chedza, sufficient photosynthetically active radiation (PAR) facilitated the Chl-a bloom in Box A. This study contributes to the assessment of the ecological impact of ocean eddies at the southern tip of Madagascar.

Research on ocean-current-prediction-based virtual mooring strategy for the portable underwater profilers

The Argo Global Ocean Observing Network has remained the preeminent ocean observation network worldwide. Since the Argo buoys lack freedom of lateral movement, their wave-following working characteristics prevent them from completing the long-term observations in the designated sea area. Long-term monitoring of designated waters is often required, for example, to study the impacts of seabed mining on the marine environment in the surrounding sea area. To solve this problem, a portable underwater profiler (PUP) that combines the functionalities of profiling buoys and underwater gliders was devised. The PUP employs a center of gravity adjustment mechanism utilizing the double-weight block approach, enabling the pitch angle adjustment within -90° to 0°. Remarkably, the PUP weighs only 11.25 kg, meeting the requirements for rapid deployment. Furthermore, the prediction method of the ocean current velocity was optimized by employing the full-depth-averaged ocean current velocity instead of the depth-averaged ocean current velocity. To ensure continuous observation operations of the PUP within designated sea areas, a horizontal displacement correction strategy (HDCS) based on the virtual mooring concept is proposed. The effectiveness of the HDCS has been preliminarily validated through simulations and further confirmed through lake trials conducted in Qiandao Lake.

A simulation study of the Argo program-enhanced global ionospheric modeling

The ionospheric total electron content (TEC) is a critical parameter for space weather and Global Navigation Satellite System (GNSS) applications. Since 1998, the Ionospheric Working Group of the International GNSS Service (IGS) has been generating global ionospheric maps using data from hundreds of GNSS stations. However, the uneven geographical distribution of these observations has resulted in significant variations in TEC map accuracy, particularly in marine areas where observations are scarce or absent. In this study, we introduce Argo data as additional observations to enhance the accuracy of global ionospheric modeling. Argo data consists of measurements collected by more than 1,000 robotic floats deployed across the world's oceans. By utilizing the NeQuick model and considering the geographic coordinates of both IGS stations and Argo buoys, we simulate the ionospheric Slant Total Electron Content (STEC). This approach allows us to examine the impact of integrating Argo data into global ionospheric modeling and evaluate its effectiveness. The results indicate a significant improvement in the overall accuracy of the model after incorporating Argo data. Furthermore, by increasing the model's degree, a better global fit is achieved. It eliminates noticeable overestimation or underestimation of TEC, especially evident at a degree of 30. As the availability and uniform distribution of observations improve, the model demonstrates higher accuracy and enhanced global performance.

Sound Velocity Profiles Time Series Prediction Method Based on EMD-NARX Model

To solve the problem of SVP (Sound velocity profiles) representative error caused by the difficulty of obtaining continuous time series SVP in deep-sea operations, an SVP timing prediction method combining EMD (Empirical mode decomposition) and NARX (Nonlinear autoregressive neural network with external input) is proposed. To begin with, the time-series SVP are stratified according to different depths, and the time-series variation curves of sound velocity at different depths are obtained; Furthermore, the EMD is used to decompose the time series variation curve of sound velocity into multiple IMF (Intrinsic mode function) components, each component contains local characteristic signals of different time scales of the original signal. The NARX is used to establish a prediction model for each IMF components, and the prediction values of the sound velocity at different depths are obtained. The EMD-NARX, NARX and polynomial fitting model are analyzed and verified by Argo buoys data in the South China Sea, and the results of the experiment show that EMD-NARX improves the time series prediction accuracy of sound velocity by 32.24% and 65.15% compared with NARX and polynomial fitting, respectively, so EMD-NARX has a good prediction effect on the time series SVP of the deep sea.

Quality Analysis and Correction of Sea Surface Temperature Data from China HY-1C Satellite in Southeast Asia Seas.

China's marine satellite infrared radiometer SST remote sensing observations began relatively late. Thus, it is essential to evaluate and correct the SST observation data of the Ocean Color and Temperature Scanner (COCTS) onboard the China HY-1C satellite in the Southeast Asia seas. We conducted a quality assessment and correction work on the SST of the China COCTS/HY-1C in Southeast Asian seas based on multisource satellite SST data and temperature data measured by Argo buoys. The accuracy evaluation results of the COCTS SST indicated that the bias, Std, and RMSE of the daytime SST data for HY-1C were -0.73 °C, 1.38 °C, and 1.56 °C, respectively, while the bias, Std, and RMSE of the nighttime SST data were -0.95 °C, 1.57 °C, and 1.83 °C, respectively. The COCTS SST accuracy was significantly lower than that of other infrared radiometers. The effect of the COCTS SST zonal correction was most significant, with the Std and RMSE approaching 1 °C. After correction, the RMSE of the daytime SST and nighttime SST data decreased by 32.52% and 42.04%, respectively.

Dynamic modeling and switching analysis of all-attitude multimode underwater vehicle for multidimensional data acquisition

This study proposes a unique multimodal underwater observation platform, called all-attitude multimode underwater vehicle (AMUV). AMUV integrates the movement capabilities of Argo buoy, Glider motion modes, and autonomous underwater vehicles (AUVs), enabling comprehensive underwater navigation. To explore the operational rules of individual modes and the changes in actuator and attitude during mode transitions, firstly, a dynamics model of AMUV is established, conforming the operating principles of the Argo buoy, Glider, and AUVs. Secondly, through open-loop simulations of different modes, the feasibility of the dynamic model is verified. Thirdly, through simulation experiments involving three typical mode switching processes, the mechanism of AMUV multi-mode switching is demonstrated. Finally, to examine the ability of the AMUV for multidimensional data acquisition, a simulation task focused on gathering multidimensional data of marine elements is designed. The simulation results indicate that the proposed AMUV has considerable potential for application in monitoring activities requiring the acquisition of multidimensional oceanographic data.

Drastic hydrodynamic changes in the western Bay of Bengal caused by tropical cyclone Nada

To understand the interaction between tropical cyclones (TCs) and the upper ocean in the Bay of Bengal (BoB), TC Nada in 2016 is studied by analyzing ocean reanalysis data, ocean satellite remote sensing data and Argo buoy data. The results show that Nada influenced the anticyclonic eddy (ACE) present at 83.8°E,9.8°N, which propagated westward and formed a new ACE east of Sri Lanka, leading to the EICC bifurcation. An Eastern Sri Lankan Jet (ESLJ) was produced. After the ACE disappeared, the boundary current velocity increased from 1.4 m·s−1 to 1.6 m·s−1. Meanwhile, the main axis of the boundary current is shifted westward. The barrier layer thickness (BLT) was thickened by 33 m at the ACE and thinned by 10 m at the cyclonic eddy (approximately 11°N, 82°E). The mixed layer depth (MLD) became shallower within both the CE and the ACE, which can explain why there were no large-scale phytoplankton blooms in the eddies. Additionally, a part of the sea boundary current intruded into the Palk Strait affected by Nada. The chlorophyll-a (Chl-a) concentration in the Palk Strait increases from 0.08 to 0.67 mg·m−3, causing a phytoplankton bloom. This study helps to estimate the ecological impact of TCs in the western BoB.

Experimental Study on the Efficiency of Dynamic Marine Thermal Energy Generator Based on Phase Change Compensation

Miniaturized detection devices in the ocean generally experience problems such as short endurance and unreliable power supplies. This article aimed to develop a dynamic ocean temperature difference energy collection device to capture ocean temperature difference energy and provide objective electricity for stable detection devices. The main focus was to conduct experimental research on the effectiveness of a dynamic ocean temperature difference energy power generation device. During the research process, the fact that ammonia gas in a working fluid is easy to liquefy and vaporize was utilized. By utilizing the increase in seawater temperature during the floating process of the device, it vaporized and drove the turbine to rotate for power generation. In the structural design, multiple sets of small air chambers were creatively proposed, which could effectively control the air pressure and improve the stability of the airflow. By charging the airflow to impact the turbine, multiple sets of power generation fans were used to form a stable current. Further, the buoyancy of the device could be changed by adding phase change materials between the air chamber and the device shell, and the temperature difference between the two ends of the phase change materials could be used to change the electron density of the material to form a weak current. In this experimental study, concepts such as the structural design of multiple small gas chambers, miniaturization of energy collection devices, compensation power generation of phase change materials, and application scenarios of devices combined with Argo buoys were all proposed for the first time. The results of this experimental study indicate that the overall power generation of the device is about 2A, and its maximum output power amplitude is about 22 W. The cyclic thermal efficiency of the power generation device can be increased from +0.19% to +0.88%. The development of this thermoelectric power generation device can provide a considerable stable power supply for ocean observation devices, especially the buoy device represented by Argo, which can extend the endurance of deep-sea exploration devices.

Understanding the cause of sea level rise along coastal zone for 2005–2021

Understanding the coastal sea level budget (SLB) is essential to revealing the causes of sea level rise and predicting future sea level change. Here we present the coastal SLB based on multiple sets of sea level observations, including satellite altimetry, satellite gravimetry, and Argo floats over 2005 to 2021. The coastal zone is defined within 500 km from the coast and covered by all Argo products. We find that sea level observations enable a closure for the coastal SLB for 2005-2015. However, since 2016, the coastal SLB shows a substantially larger discrepancy, consistent with the global mean SLB. The coastal SLB is unclosed for 2005-2021, with a mean sea level rise of 4.06 ± 0.27 mm yr−1, a 0.74 ± 0.21 mm yr−1 rate for ocean mass, and a 2.27 ± 0.53 mm yr−1 for the steric component. Systematic Argo buoy salinity drift after 2016 is the main cause for the non-closure of coastal SLB over 2005-2021. Ignoring the suddenly unrealistic coastal salinity trends, the global coastal SLB from 2005 to 2021 is closed with a residual trend of 0.46 ± 0.63 mm yr−1. Our results confirm that the coastal 500 km range does not need to be deliberately masked and ignored in global SLB research.

Effects of Anticyclonic Eddies on the Unique Tropical Storm Deliwe (2014) in the Mozambique Channel

The unique tropical storm (TS) Deliwe (2014) occurred in the northern Mozambique Channel on 17 January 2014 and turned right during its whole life cycle, moving south along the west coast of Madagascar Island. During the development of the TS, the anticyclonic eddies in the Mozambique Channel had an important influence on the intensity and track of Deliwe, which existed for months. In this study, multisource reanalysis, conductivity temperature depth (CTD) and Argo buoy data were used to investigate the mechanism of dynamics. The results showed that the anticyclonic eddies in the Mozambique Channel were a major cause of Deliwe strengthening, weakening and then deflection to the right. On 17 January, the maximum latent heat flux of anticyclonic eddy W1 reached 103.1 w/m2. After Deliwe passed, the tropical cyclone heat potential (TCHP) of anticyclonic eddy W1 was significantly reduced by 3 kJ/cm2. The mixed layer of anticyclonic eddy W1 was deeper than the surrounding waters, supporting the development of Deliwe. As the TS intensity decreased, the low-pressure center of 500 hPa moved above anticyclonic eddy W2, and the westerly wind belt moved northward to form a westerly trough of low pressure, which caused the TS to keep turning right and formed a unique TS track. This study provides a new understanding of the influence of marine anticyclonic eddies on the development of tropical cyclones (TCs) in the Mozambique channel.

Decreased surface and bottom salinity and elevated bottom temperature in the Northern Baltic Sea over the past six decades

Temperature and salinity are key factors in controlling marine habitats and gas fluxes. Finnish and Swedish temperature and salinity monitoring data from the northern Baltic Sea since the 1960s, and Argo buoy data from the eastern Gotland Basin and the Bothnian Sea from 2012 to 2021 were examined using linear trend analysis. Since the 1960's near-bottom temperature has increased by 0.75–2.9 °C (0.013–0.115 °C/a) and surface salinity declined by 0.31–1.14 units (0.005–0.019/a). Surface temperature trends at monitoring stations were negative (16 cases out of 33) but deemed unreliable. Near-bottom salinity has declined by 0.35–1.45 units (0.007–0.025/a), except in the northern Baltic Proper and the central-eastern Gulf of Finland. Most rapid increases in near-bottom temperature have occurred after 1993, especially in the northern Baltic Proper and the Gulf of Finland. Argo data corroborated declining surface salinity in the eastern Gotland Basin, increasing deep-water temperature in the eastern Gotland Basin and the Bothnian Sea and increasing deep-water salinity in the eastern Gotland Basin. Argo data from 2013 to 2021 indicated deep-water temperature increase in the Gotland basin was more rapid than the concomitant salinity increase and is probably related to global change.

A case study of the westward transport of Chorophyll-a entrained by ocean eddies during a tropical cyclone

During the passage of tropical cyclone (TC) ARB O1, a westward transport of Chlorophyll-a (Chl-a) enhancement was identified south of the Indian Peninsula. The features and underlying dynamics were investigated with high-resolution satellite remote sensing, reanalysis, and Argo buoy data. From January 12 to January 19, 2006, the phytoplankton bloom propagated westward with two ocean anticyclonic eddies, which were enhanced after the passage of the TC. The surface average maximum Chl-a concentration with an inertia period of approximately 4–5 days occurred in the four boxes. The maximum average concentration of Chl-a on January 16 (21) was 0.4 mg•m−3 (0.53 mg•m−3) in Box B, which was caused by a cyclonic eddy and Ekman pumping triggered by the TC (horizontal current transport). However, the maximum average concentration of Chl-a was 0.32 mg•m−3 in Box D, which was caused by an anticyclonic eddy and Ekman pumping triggered by the TC. After passage of the TC, the mixing layer deepened, and the upper ocean stratification weakened, which promoted an uplift of phytoplankton from the deeper layer to the upper layer. In addition to horizontal current transport, westward phytoplankton transport was produced under the joint influence of eddy entrainment and Ekman pumping triggered by the TC. This study can aid with assessing the biological responses of future typhoons.

Seasonal and Interannual Variability of the Thermohaline Structure of the Bengel Upwelling Based on the Argo Buoys Data

Seasonal and Interannual Variability of the Thermohaline Structure of the Bengel Upwelling Based on the Argo Buoys Data

Reconstructing Sound Speed Profile From Remote Sensing Data: Nonlinear Inversion Based on Self-Organizing Map

By establishing a linear regression relationship between the projection coefficient of the empirical orthogonal function (EOF) of the sound speed profile (SSP) and remote sensing parameters of the sea surface, the single empirical orthogonal function regression (sEOF-r) method was used to reconstruct the underwater SSP from satellite remote sensing data. However, because the ocean is a complex dynamical system, the parameters of the surface and the subsurface did not conform to the linear regression model in strict sense. This paper proposes a self-organizing map (SOM)-based nonlinear inversion method that used satellite observations to obtain anomalies in data on the sea surface temperature and height, and combined them with the EOF coefficient from an Argo buoy to train and generate a map. The SSP was then reconstructed by obtaining the best matching neuron. The results of SSP reconstruction in the northern part of the South China Sea showed that the relationship between the parameters of the sea surface and the subsurface could be adequately expressed by the nonlinear neuronal topology. The SOM algorithm generated a smaller inversion error than linear inversion and had better robustness. It improved the average accuracy of reconstruction by 0.88 m/s and reduced the mean-squared reconstruction error to less than 1.19 m/s. It thus offered significant promise for acoustic applications.

An Arctic Gridded Sea Surface Temperature Product Constructed from Spaceborne Radiometer Data

Sun, W.; Zhang, J.; Meng, J.; Li, Y., and Cao, K., 2020. An arctic gridded sea surface temperature product constructed from spaceborne radiometer data. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Geospatial Research of Coastal Environments. Journal of Coastal Research, Special Issue No. 102, pp. 280-286. Coconut Creek (Florida), ISSN 0749-0208.A sea surface temperature (SST) record with a grid size of 0.1° for the Arctic region is presented by fusing satellite-derived SST products from three passive-microwave (WindSat, AMSR-E and ASMR2) and four infrared (AVHRR, MODIS onboard Terra and Aqua, and VIIRS) radiometers (RMs). In this study, optimum interpolation (OI) is used to construct the dataset. The fused SST data of Arctic covering the regime north of 60°N span from 2010 to 2018, available with the format of NetcDF. The accuracy of the gridded Arctic SST product was assessed with the drifting buoy measurements. Comparisons with the measurements from Argo buoys show that the Root Mean Squared Errors (RMSE) of the fusion SST data obtained in this study is relatively stable with values ranging from 0.54 to 0.75 °C. This gridded SST data set is characterized with a high spatiotemporal resolution and an assured accuracy.

Analysis of Past Temperature Changes in Ice Layers and the Ocean Based on the Ratios of Argon, Krypton, and Xenon with Nitrogen

New research methods are being developed to get a broad picture of the temperature changes throughout the World Ocean. A permanent global network of oceanographic stations based on Argo profiling buoys was created about 20 years ago. The main purpose of Argo profiling buoys is to measure the vertical profiles of the water temperature and salinity as they rise from the depth of the ocean to the surface. A fundamentally new method to determine changes in the mean temperature in the ocean began to be developed in the early 2000s. It is based on the use of the elemental and isotopic ratios of Ar with N2 and the heavy inert (noble) gases Kr and Xe with N2 contained in ice cores captured from the atmosphere by air bubbles. The use of these new methods gives scientists unique opportunities for the continuous monitoring of the state of the World Ocean. The work focuses on estimates of ocean temperature changes based on the available direct, historical data and indirect, experimental data, as well as data obtained with the aforementioned new methods. The reconstructions of temperatures for different time intervals are analyzed, and reconstructions of the global surface temperatures and ocean temperatures after the retreat of the last ice age, which were obtained from model and indirect experimental data, are compared.

The assessment of salinity impact on surface water mass transformation in the North Atlantic

In this study, we investigate sensitivity of total surface water transformation to salinity from different data sources. Here we use surface salinity from NCEP CFSv2 reanalysis, GLORYS ocean reanalysis, Aquarius satellite data and ISAS-15 (product of optimal interpolation of ARGO buoys) as well as heat and freshwater fluxes from NCEP CFSv2 reanalysis. The largest spread in estimates of salinity is observed for Aquarius satellite in subpolar regions. The best correspondence between transformation computed using salinity from different datasets is observed for subtropical waters. Model-based products (CFSv2 and GLORYS) are the most consistent in estimates of surface water transformation and the largest discrepancies between these datasets are observed in the regions with high freshwater fluxes.

Decadal Spatiotemporal Halocline Analysis by ISAS15 Due to Influx of Major Rivers in Oceans and Discrepancies Illustrated Near the Bay of Bengal

The discharge from rivers is one of the major factors of regional salinity perturbations in addition to precipitation, evaporation, and circulation of the ocean, whereas simulations regarding the marine environment are dominantly affected by ocean salinity. Moreover, perturbations in the timing and quantity of freshwater cause salinity fluctuations, which in turn, affect the communities of both plant and fauna. In this regard, the study ingeniously employs In Situ Analysis System-15 (ISAS15) data, which is freely available online, to ascertain the salinities in proximity of the major rivers around the globe. Such computations are multilayered, i.e., for 1, 3, 5, and 10 m, and conducted along major freshwater influxes, i.e., the Amazon River, Bay of Bengal (BoB), and Yangtze River, on decadal scales, i.e., in 2004 and in 2014. Depending upon the location and availability of ISAS-15 data, the area in proximity of the Amazon is analyzed horizontally, vertically, and obliquely, whereas the areas in proximity of the BoB and Yangtze estuary are analyzed vertically and obliquely. Similarly, the study analyzed the freshwater influx at the aforementioned locations both for the maxima and minima, i.e., during the particular months that observed the maximum and minimum influx into the ocean from the above-mentioned freshwater sources in 2004, as well as in 2014. The detailed analysis proved the outcomes to be conforming with the documented literary data along the Amazon and Yangtze estuaries. However, the computed analysis illustrated the anomalous values in proximity of the BoB. The study proceeds to discuss an ingenious approach of computing, as well as extrapolating, the salinities, temperatures, and sound speed profiles (SSPs) by employing in situ deep Argo data in order to counter such anomalies, as well as conjoin it with ISAS data, to investigate such regions with broader spatiotemporal capabilities for the future course of action. For this particular study, this method is employed on certain Argo buoys in order to prove the efficacy of the aforementioned novel approach.