Abstract:Statistical characteristics of mesoscale eddies in the Eastern China Sea (ECS) are analyzed using altimetry sea surface height anomaly (SSHA) data from 1993 to 2010. A velocity geometry-based automated eddy detection scheme is employed to detect eddies from the SSHA data to generate an eddy data set. About 1,096 eddies (one lifetime of eddies is counted as one eddy) with a lifetime longer than or equal to 4 weeks are identified in this region. The average lifetime and radius of eddies are 7 weeks and 55 km, re… Show more
“…For example, smaller variances are observed on the persistent Kuroshio path on the western side of the archipelago in the ECS as compared with those on the eastern side. More intensive eddy activity in the east of the archipelago is apparently caused by influences of westward propagating mesoscale eddies as Rossby waves headed toward the eastern side of the chain of the islands (e.g., Liu et al, ; Qin et al, ). In contrast, the other high SSH variances south of Kyushu and in the Kuroshio Extension Region (cf., Kamidaira et al, ; Uchiyama, Suzue, et al, ) correspond to the areas where the Kuroshio path largely meanders, reflecting intrinsic synoptic variability of the Kuroshio.…”
For the preservation and protection of coral habitats along the Nansei Archipelago in the East China Sea, a submesoscale eddy‐resolving synoptic ocean model was developed based on the Regional Oceanic Modeling System coupled with a 3‐D Lagrangian particle tracking model. Millions of neutrally buoyant particles representing coral spawn and larvae were released from 19 major islands and one lagoon every spring from 2012 to 2015. The model results were compared to satellite data, in situ observation, and surface drifters to confirm reasonable agreement. The connectivity matrix across the archipelago was quantified using Lagrangian probability density functions of the modeled particle displacement. Most particles remained near the release areas, while some traveled long distances by the northeastward drifting Kuroshio, leading to notable interisland coral transport across the archipelago that promotes interisland connectivity. A possible mechanism was examined by analyzing the transition from coastal to pelagic transport of the particles released from the Yaeyama Islands, the southernmost area of the archipelago. The Kuroshio trapped the particles released from the northern coast of the islands with considerable temporal variability in the entrainment rate. By contrast, particles released from the southern coast are markedly affected by the eastward current around the release sites, which significantly reduces their entrainment in the Kuroshio and, thus, long‐distance transport. Some entrained particles were expelled abruptly from the Kuroshio, trapped by the southwestward drifting Kuroshio Counter Current developed between the Kuroshio and the archipelago, and subsequently transported eastward to the islands.
“…For example, smaller variances are observed on the persistent Kuroshio path on the western side of the archipelago in the ECS as compared with those on the eastern side. More intensive eddy activity in the east of the archipelago is apparently caused by influences of westward propagating mesoscale eddies as Rossby waves headed toward the eastern side of the chain of the islands (e.g., Liu et al, ; Qin et al, ). In contrast, the other high SSH variances south of Kyushu and in the Kuroshio Extension Region (cf., Kamidaira et al, ; Uchiyama, Suzue, et al, ) correspond to the areas where the Kuroshio path largely meanders, reflecting intrinsic synoptic variability of the Kuroshio.…”
For the preservation and protection of coral habitats along the Nansei Archipelago in the East China Sea, a submesoscale eddy‐resolving synoptic ocean model was developed based on the Regional Oceanic Modeling System coupled with a 3‐D Lagrangian particle tracking model. Millions of neutrally buoyant particles representing coral spawn and larvae were released from 19 major islands and one lagoon every spring from 2012 to 2015. The model results were compared to satellite data, in situ observation, and surface drifters to confirm reasonable agreement. The connectivity matrix across the archipelago was quantified using Lagrangian probability density functions of the modeled particle displacement. Most particles remained near the release areas, while some traveled long distances by the northeastward drifting Kuroshio, leading to notable interisland coral transport across the archipelago that promotes interisland connectivity. A possible mechanism was examined by analyzing the transition from coastal to pelagic transport of the particles released from the Yaeyama Islands, the southernmost area of the archipelago. The Kuroshio trapped the particles released from the northern coast of the islands with considerable temporal variability in the entrainment rate. By contrast, particles released from the southern coast are markedly affected by the eastward current around the release sites, which significantly reduces their entrainment in the Kuroshio and, thus, long‐distance transport. Some entrained particles were expelled abruptly from the Kuroshio, trapped by the southwestward drifting Kuroshio Counter Current developed between the Kuroshio and the archipelago, and subsequently transported eastward to the islands.
“…1). From both observational analysis 1 and statistical detection results from various satellite data sets 2, 3 , abundant eddies occur along the Kuroshio path. Most studies of such eddies (in terms of generation or interaction) are related to the Kuroshio meandering path in some specific regions, e.g., in the northern Okinawa Trough 4, 5 , between the Tokara Strait and south of Kyushu 6 , in the northeast of Taiwan Island 7 , and in the Luzon Strait 8 .Figure 1The study area: East China Sea area with boundaries marked out by the dashed line.…”
Section: Introductionmentioning
confidence: 99%
“…Because the mean horizontal shear (a source for barotropic instability) is an important dynamic mechanism of eddy generation, we speculate that the MPK should produce mesoscale or sub-mesoscale eddies along its two sides and with eddy size constrained by the width of MPK. These eddies are not easily visualized in the low-resolution satellite images 2 , 3 , so the drifter data and high-resolution model output are employed to detect these eddies.…”
From the analysis of oceanic eddies detected in the drifter trajectories of the Global Drifter Program (GDP) data set, it was found that oceanic eddies are asymmetrically distributed across the Kuroshio in the East China Sea: predominant cyclonic (anticyclonic) eddies are on the western (eastern) sides of Kuroshio. This distribution is confirmed by high-resolution numerical modeling output as well. Most of these eddies are 5~20 km in radius, less than the local first baroclinic deformation radius, thus categorized as submesoscale. The generation mechanism of these submesoscale eddies is speculated to be related to the horizontal velocity shear of the Kuroshio when it flows northeastward along the shelf break in the East China Sea. The budget analysis of eddy kinetic energy shows that both the horizontal shear and vertical buoyancy flux are important energy sources for eddy generation on the two sides of Kuroshio axis. The finding highlights the unique feature of oceanic eddies along the western boundary currents.
“…The mechanism of eddy generation and dissipation is diverse in different sea areas. Based on previous studies such as those conducted by Liu et al [58] that found eddies in the north Pacific subtropical band are generated through baroclinic instability and wind stress, the Qin et al [60] analysis which shows that CEs in the East China Sea are mainly affected by Kuroshio transport in addition to interference from the surrounding ocean and orographic wind blockage, and the discovery of Ji et al [59] that eddies are generated near the Kuroshio Extension Region due to horizontal shear instability, it is apparent that for different regions, eddies are generated through a wide variety of mechanisms. For example, and relevant to the current subject, Chen et al [21] suggest that for BOB eddies, baroclinic instability and the influence of wind stress are the principal mechanisms for eddy interannual variability.…”
Section: The Mechanisms For Eddy Generation and Dissipationmentioning
Mesoscale eddies are important to ocean circulation due to their roles in the transport of mass, energy, and heat. This study employs a combination of data sources to initiate a statistical analysis of eddy spatiotemporal characteristics in the Bay of Bengal (BOB) to elucidate the sea surface and vertical structures of the eddies and their impacts on sea surface chlorophyll (Chl) distributions. The results suggest that 1237 cyclonic eddies (CEs) and 1121 anticyclonic eddies (AEs) were detected in 26 years. The number of two eddy polarities was almost the same, and most of them spread to the west or southwest direction. The vertical change of temperature (T) and salinity (S) caused by the eddies is studied and the anomalous eddies, i.e., a CE (AE) eddy with warm (cold) water at the center, are mainly distributed on the northeast side of the Island of Sri Lanka. Furthermore, CEs are found to increase Chl concentration in the surrounding sea by approximately 11.15%, while AEs decrease concentrations also by approximately 11.25%. Changes in Chl concentrations occur most rapidly during the mature and intensification eddy phases. Observations also indicate that the strong local current and wind fields are the primary mechanisms in eddy generation.
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