East Taiwan Research Articles

Kuroshio path variability inferred from satellite-derived sea surface topography in the northwestern Pacific

The Kuroshio has a fundamental impact on the regional oceanography of the northwestern Pacific. But identification of the Kuroshio path (KP), an abstraction of the course along which the Kuroshio mainstream moves, has not yet been established in a systematic manner. We optimally track the KP and study its variability in the northwestern Pacific south of ~31°N, where eddy activity is rich. An automatic contour method based on maximum surface geostrophic velocity along a given satellite-derived dynamic topographic isoline is applied and its performance is evaluated. Our results are robust and can be further used to derive kinematical, statistical, and spectral properties of the flow field of the Kuroshio upstream. We improve the identification method by tracing two separate KPs in different subdomains. The existence of an alignment or mismatch of these two retrieved KPs hints at the arrival of an approaching eddy. The highly variable and distorted KP east of Luzon Strait and Taiwan is due to eddy impingement. Most of the variability along the KP stems from energy with time scales of ~30–200 days and 1 year. A more consistent KP is seen north of ~26°N, with increasing surface currents of up to ~1 m s−1 before entering through the Tokara Strait. Such regional differences result from the various impacts of impinging mesoscale eddies on the Kuroshio, mainly due to blockage by the Ryukyu Islands. Our optimally determined KP is in line with the historical shipborne subsurface velocity measurements revealing the Kuroshio velocity core and observations of strong surface currents of > ~0.5 m s−1 by shore-based high-frequency radar (HFR) from locations along the east coast of Taiwan. Supportive evidence of concurrent KP distortion shows that HFR-derived vortex-like flow patterns are related to mesoscale eddies impinging from regions east of the radar footprint. Our work has value as a supplement to the data from radar operational routines, and will help interpret and diagnose these complicated HFR observations east of Taiwan.

First telemetry insights into the movements and vertical habitat use of megamouth shark (Megachasma pelagios) in the northwest Pacific

The megamouth shark (Megachasma pelagios) is one of the ocean's largest and most enigmatic elasmobranchs, with only a few hundred individuals ever recorded. Most of what is known about the species comes from rare fishery bycatch, stranding, or sighting events, precluding an in-depth understanding of its movement ecology. Here, we report the results from three megamouth sharks outfitted with pop-up satellite archival transmitting tags to assess the species' horizontal and vertical movement patterns. Deployments of 12, 58, and 244 d in duration provided the first direct evidence of multi-month fidelity to the waters east of Taiwan and seasonal movement out of the region. Depth and temperature data revealed a pattern of normal diel vertical migration, with the majority of the day spent in the mesopelagic zone and night in the epipelagic. Vertical habitat use suggests potential behavioral thermoregulation and was consistent with tracking of migrating mesopelagic prey across diel periods. We discuss the specialized analytical methods needed to reconstruct the spatial habitat use of deep-diving megamouth shark from tag sensor measurements of the magnetic field, as well as avenues for future research on this understudied megaplanktivore.

Kinetic Energy Cascade Induced by the Interaction of Mean Flow, Topography, and Mesoscale Eddies East of Taiwan: A Scale-to-Scale Analysis

Abstract The scale-to-scale kinetic energy (KE) cascade induced by the nonlinear interaction among topography, the Kuroshio, and mesoscale eddies is systematically investigated in the coarse-graining framework based on simulated data from the well-validated Regional Ocean Model System. The KE transfer exhibits inhomogeneous spatial and temporal distributions and varies with length scale. During current–topography interaction, the KE transfers downscale across larger scales and reversely across smaller scales with an inherent separation scale of 150 km northeast of Taiwan, resulting in a significant positive net KE flux for mesoscale motions. The transfer around Suao Ridge is consistently downscaled with significant seasonal variation that is stronger in summer and weaker in winter. South of Suao Ridge, the transfer is one order of magnitude weaker and changes greatly with time. The cyclonic (anticyclonic) eddy weakens (enhances) KE transfer in most study areas. In particular, the cyclonic eddy reverses the transfer direction around Suao Ridge. The anticyclonic eddy triggers a significant bidirectional transfer south of Suao Ridge. Analyses show that the special arc-shaped topographic feature and northwestward Kuroshio intrusion current are responsible for the nature of bidirectional KE transfer northeast of Taiwan. The direction of mean current relative to the topography gradient determines the Rossby number magnitude and the KE transfer direction. The large-scale circulation determines the transfer intensity by changing the horizontal shear and barotropic instabilities. The KE transfer caused by nonlinear dynamics contributes significantly to the total anticyclonic eddy-induced net KE flux changes. In particular, the inverse KE cascade plays a key role in net KE flux changes in mesoscale motions east of Taiwan. Significance Statement In this work, we clarify the scale-to-scale kinetic energy transfer east of Taiwan. Energy transfer varies in different subareas. It is bidirectional northeast of Taiwan, consistently downscale around Suao Ridge, and weak and variable south of Suao Ridge. These transfer characteristics are closely related to the direction of mean flow relative to the topography gradient. Mesoscale eddies can trigger bidirectional transfer and even reverse the transfer direction. The reverse cascade is as important as the forward cascade for the total mesoscale energy change. This study not only shows an example of KE cascade when strong currents pass through continental slope, sea ridge, and open ocean, but also is of great significance for studying the dynamical and ecological environment variation of marginal sea.

Tropical cyclone activity around Taiwan modulated by El Niño during 1900–1945 and 1970–2015

AbstractTropical cyclone (TC) activity around Taiwan is analysed via typhoon datasets compiled by the Central Weather Administration (CWA) for the pre‐satellite era of 1900–1945 (IE1) and the satellite era of 1970–2015 (IE2). Modulating processes imposed by El Niño years on active and inactive TC activity around Taiwan in the July–September season are examined and compared between IE1 and IE2. Analyses reveal coherent dynamic relationships between TC variability in Taiwan and large‐scale modulating processes; furthermore, modulating processes exhibit similar features between IE1 and IE2. El Niño years tend to have more (less) TC formation in the eastern (western) sector of the western North Pacific (WNP). In both IE1 and IE2, intensified TC activity around Taiwan is associated with northwestward TC tracks from the eastern WNP toward Taiwan assisted by a westward‐elongating cyclonic anomaly across the WNP and South China Sea. When a WNP cyclonic anomaly stretches northwestward toward oceans north of Taiwan, TCs from the tropical eastern WNP generally move northward toward oceans east of Taiwan to result in suppressed TC activity around Taiwan. The westward‐elongating anomalous cyclone is associated with an anomalous divergent centre over the Indian Ocean and an anomalous convergent centre in the tropical eastern Pacific over the 150°–130°W region. The northwestward‐extending anomalous cyclone connects with an anomalous divergent centre over the Maritime Continent and an anomalous convergent centre over the 130°–110°W region. Anomalous divergent and convergent centres displace westward (eastward) for active (inactive) TC types that are related to a more westward (eastward) maximum centre of anomalous warm waters in the tropical eastern Pacific. The above coherent dynamic relationships justify the reliability of TC records compiled by the CWA during IE1 and IE2.

ENSO‐Related Interannual Variability of the Kuroshio in the East China Sea Since the Mid‐2000s

AbstractUsing observational and reanalysis data sets, we investigated interannual variability in the Kuroshio in the East China Sea (ECS‐Kuroshio). We exhibited that the surface velocity and position of the ECS‐Kuroshio were synchronized on a quasi‐3‐year interannual timescale during 2005–2016. We further demonstrated that: (a) during 2005–2016, wind stress curl variability related to the El Niño–Southern Oscillation (ENSO) played a leading role in the interannual ECS‐Kuroshio variability by exciting baroclinic Rossby waves along the subtropical countercurrent (STCC) zone east of Taiwan; (b) mesoscale eddy activities in the STCC zone, especially long‐lived (≥150‐day lifetime) cyclonic eddies, probably played a secondary role in the interannual ECS‐Kuroshio variability. In addition, we showed that the occurrence of the quasi‐3‐year interannual variability of the ECS‐Kuroshio since 2005 was likely linked to the following changes in the ENSO‐related atmospheric circulation: (a) The primary ENSO timescale changed from a quasi‐5‐year period in 1993–2004 to a quasi‐3‐year one in 2005–2016; (b) Over the central equatorial Pacific along with the eastern tropical Indian Ocean, the sea surface temperature in 2005–2016 varied with a more intense amplitude than in 1993–2004, which resulted in a different western North Pacific atmospheric response to the ENSO in 2005–2016 from that in 1993–2004.

Empirical study on the factors influencing the successful aging of the middle-aged and older adult community volunteers.

The pursuit of successful aging is currently the most important research and policy issue in an aging society. Participating in voluntary services can help middle-aged and older adults recognize the positive value and benefits of social participation, feel a sense of happiness and accomplishment, and improve their overall life satisfaction, which can also contribute to successful aging. This study wants to understand whether the participation motivation and expectation confirmation of middle-aged and older adult volunteering will affect their continuous participation behavior and successful aging because of the satisfaction of actual participation? This study explores the factors related to middle-aged and older adult volunteering participation and their impact on successful aging. Middle-aged and older adult volunteering from the East Taiwan Community Development Association and community care centers were taken as the research objects. Convenience sampling was used to select volunteers who were over 45 years old (inclusive) and have participated in voluntary services over five (inclusive) times in the last 6 months. Respondents completed the questionnaire through self-completion or face-to-face interviews with the interviewer. The measurement tools include engagement motivation, expectation validation, satisfaction, ongoing engagement, and successful aging. A total of 536 questionnaires were distributed of which 498 were valid and 38 invalid. The questionnaire recovery rate was 92.91%. Statistical findings include: (1) Those who perceived that their health was good had a better successful aging status than those who perceived that their health was normal. (2) The volunteering participation motivation and expectation confirmation of middle-aged and older adults significantly affected their volunteer participation satisfaction. (3) Participation motivation and expectation confirmation predicted 50.8% of satisfaction. (4) Satisfaction predicted 47.1% of continuous participation. (5) Continuous participation and satisfaction had a predictive power of 65.1% for successful aging. This study confirms that the motivation and expectation of middle-aged and older adult to participate in volunteering will affect their continuous participation behavior and successful aging status through satisfaction. The research results can be used as a reference for the practical work plan of volunteering.

Impact of physical and social living environments on pro-environmental intentions

The living environment might play an important role in shaping the pro-environmental intentions of the people. However, there was limited research on how the living environments influenced the pro-environmental intentions of people. The objectives of this study are to evaluate the direct effects of physical and social environments on pro-environmental intentions as well as the mediating effects of environmental attitudes and life satisfaction. Structural Equation Modeling was used with data extracted from the 2020 Taiwan Social Change Survey database (n = 1671). Results showed direct positive associations of both physical and social environments with pro-environmental intentions (β = 0.133 and β = 0.076, respectively) as well as indirect positive associations via the life satisfaction-mediating pathway (β = 0.031 and β = 0.044, respectively). The physical environment negatively influenced pro-environmental intentions through the environmental attitude pathway (β = − 0.255) with unpleasant neighborhood enhancing the pro-environmental intentions of residents. Taken together, the overall effect of the physical environment was negative (β = − 0.093) while that of the social environment was positive (β = 0.109). The most important factors for the physical and social environments were disturbance and livability in north, central and south Taiwan, neighborhood pollution and interestingness in east Taiwan. Accordingly, minimizing disturbance and neighborhood pollution of the physical environment could have the highest effect on pro-environmental intentions enhancement in western and eastern Taiwan, respectively. For the social environment, improving livability in the west and interestingness in the east would have an even larger impact on pro-environmental intentions. This study emphasized the importance of neighborhood environment on the environmental intentions of the people. The study also identified the important factors for policymakers to target to achieve the best effect on improving environmental intentions.

Demarchushsui (Coleoptera, Chrysomelidae, Galerucinae, Alticini), a new species from Taiwan, with notes on immatures and biology.

A new species of the little-known genus Demarchus Jacoby was discovered at Pilu, East Taiwan, and is here described as Demarchushsuisp. nov. The larvae and adults utilise showy mistletoes as food plants. Their remarkable biology is described in detail, including egg deposition and leaf mining behaviour. Their biology is compared with that of other members of the genus.

Interdecadal variability of meridional tropical cyclone genesis over the western North Pacific and associated modulating processes

AbstractDuring the period 1970–2020, evident interdecadal variability of meridional tropical cyclone (TC) genesis occurs in the western North Pacific (WNP) from September through October (SO). From the periods 1970–1996 (IP1) to 1998–2020 (IP2), TC genesis during SO is enhanced (suppressed) in the region north (south) of 20°N. The large‐scale modulating processes feature a general warming of sea surface temperature (SST) over the WNP and systematic northward displacement in atmospheric circulations. The northward‐shifted Pacific subtropical high and monsoon trough result in an anomalous anticyclone across the subtropical region and an anomalous cyclone across the South China Sea and the northern WNP east of Taiwan. This anomalous cyclone facilitates TC genesis to increase in the northern WNP. Meanwhile, the southeastward‐extending monsoon trough retreats northwestward, leading to an anomalous anticyclone over the tropical eastern WNP and a decrease in TC genesis over the southern region. Correlation analyses indicate that the Pacific Decadal Oscillation (PDO) is more effective than global warming in modulating interdecadal increases of TC genesis in the northern region due to inclusions of both trend and oscillation features. Interdecadal decreases of TC genesis in the southern region exhibit a major oscillation feature and are thus mainly affected by interdecadal oscillation components of PDO. More TCs forming in the oceans east of Taiwan are steered by the overlying anomalous cyclone to recurve northward toward oceans to the northeast and north of Taiwan. TC‐induced rainfall over Taiwan thus increases by 25% from IP1 to IP2, which accounts for about 82% of increased total rainfall in Taiwan, showing the notable impact of interdecadal TC genesis on local climate in the WNP.

Availability of Using Honeybees as Bioindicators of Pesticide Exposure in the Vicinity of Agricultural Environments in Taiwan.

While pollinating, honeybees are subject to exposure to a variety of pesticides; with their characteristics of certain foraging distances, they could serve as bioindicators of pesticide exposure in a neighborhood. We conducted a study to assess availability by collecting and analyzing bee samples from 15 apiaries located in East Taiwan and dust samples from the adjacent environment, and by finding relations between both samples. Seventeen pesticides were selected for the analysis using gas or liquid chromatography coupled with mass spectrometry, and eight (three insecticides, two herbicides, and three fungicides) were more frequently detected from bee or dust samples; the levels of these pesticides were mostly under 1000 ng/g. Significant correlation results (r ≅ 0.8) between residue concentrations in bees and in dust suggest that honeybees could be a good bioindicator for exposure to herbicides and fungicides within certain ranges. The pesticide contents of sick/dead bees were much higher than those of healthy counterparts regarding any pesticide type, with the mean total concentrations of 635 ng/g and 176 ng/g, respectively. We conclude that honeybees could be used as bioindicators of pesticide exposure; sick/dead bees could serve as a warning sign of the severity of pesticide pollution.

Regional discrepancies in the microphysical attributes of summer season rainfall over Taiwan using GPM DPR

Taiwan, an island located in the northwest Pacific region, is influenced by heavy rainfall events during warm seasons, particularly from June to August. Interaction of precipitating clouds with the complex topography results in inhomogeneous and intense rainfall over Taiwan. Hence, the present study investigates the regional discrepancies in the microphysical characteristics of summer season rainfall over (north, south, east, and central) Taiwan using 9 years (2014–2022) of GPM DPR measurements. The results showed clear distinctions in the precipitation and raindrop size distributions over the north, south, east, and central Taiwan. The contoured frequency by altitude diagrams (CFADs) of radar reflectivity, rainfall rate, drop diameter, and concentration clearly infer the dominance of large-size super cooled liquid and ice particles above the melting layer and rain particles below the melting layers in the south and central Taiwan. Central (north) Taiwan is dominated by large-size (small) drops among four regions. Higher concentrations of large drops over central Taiwan (principally from convective precipitation) and south Taiwan (primarily from stratiform precipitation) is attributed to higher rainfall amounts over these two regions than the north and east Taiwan. Furthermore, irrespective of precipitation type and geographic region, summer monsoon rainfall over Taiwan is dominated by coalescence and breakup processes. The microphysical characteristics of summer season rainfall addressed in this study could assist in refining the cloud modeling simulations over complex topography in Taiwan.

Seasonal Variability of Eddy Kinetic Energy along the Kuroshio Current

Abstract The seasonal variability of the eddy kinetic energy (EKE) along the Kuroshio Current (KC) is examined using outputs from an eddy-resolving (1/10°) ocean model. Using a theoretical framework for climatological monthly mean EKE, the mechanisms governing the seasonal cycle of upper-ocean EKE are investigated. East of Taiwan, the EKE shows two comparable peaks in spring and summer in the surface layer; only the spring one is evident in the subsurface layer. The seasonality is determined by mixed barotropic (BTI) and baroclinic (BCI) instabilities. Northeast of Taiwan, the EKE is also elevated during spring–summer but with a sole peak in summer, which is dominated by the meridional EKE advection by the KC. In the middle part of the KC in the East China Sea, the mesoscale (>150 km) EKE (EKEMS) is relatively strong during spring–summer, whereas the submesoscale (50–150 km) EKE (EKESM) is significantly enhanced during winter–spring. The seasonal cycles of EKEMS and EKESM are primarily controlled by the external forcing and BCI, respectively. In particular, the higher EKEMS level in summer is mainly due to the increased wind work. West of the Tokara Strait, the EKE exhibits a prominent peak in winter and has its minimum in summer, which is regulated by the BCI. As the submesoscale signals are partially resolved by the model, further studies with higher-resolution simulations and observations are needed for a better understanding of the EKESM seasonality and its contribution to the seasonally modulating EKEMS along the KC.

Near-inertial waves generated by typhoon MITAG under the influence of anticyclonic eddy east of Taiwan

Based on subsurface mooring observations and HYCOM data, a complete investigation was conducted of the near-inertial waves (NIWs) caused by Typhoon MITAG to the east of Taiwan. HYCOM data were mainly used to reveal the role played by anticyclonic eddies in the propagation of NIWs. The results show that most typhoon-generated NIWs propagate towards negative vorticity, and NIWs near the edge gradually accumulated towards the eddy center and down to 800 m. NIWs propagating through the thermocline to the deep ocean were mainly concentrated in the eddy, and the near-inertial energy flux showed a significant enhancement from 400 to 600 m. Moreover, the downwards propagation of NIWs in the eddy enhanced the kinetic energy of background flow. NIWs outside the anticyclonic eddy dissipated quickly, while inside the eddy, there were high value areas of e-folding time. Dynamic mode decomposition illustrates that the anticyclonic eddy mainly captures higher modes of NIWs, and the state of continuous energy growth of higher modes can be maintained for more than a week. In addition, NIWs can also be carried westwards by the advection of the mean background flow at the eddy’s edge.

Three-dimensional structure of mesoscale eddies and their interaction with Kuroshio based on observations from a CPIES array

Mesoscale eddies are widespread in the oceans; however, tracking and observing them remains a challenge. Additionally, there are few studies of eddy–Kuroshio interactions based on large-scale in situ data. Data from a large array of 39 CPIESs deployed around the Luzon Strait in 2018–2019 (12 deployed east of Taiwan within a 3 × grid) were used to reveal the three-dimensional structure of mesoscale eddies and their interaction with Kuroshio. The results show a strengthening (weakening) of the tilt of the pycnocline, which has also caused a deeper (shallower) pycnocline in eastern Taiwan following an anticyclonic (cyclonic) interaction with Kuroshio, which resulted in a strengthening (weakening) of the Kuroshio. During the anticyclonic eddy impinging Kuroshio, the downward (upward) movement at the center of the anticyclonic eddy (Kuroshio) results in a positive (negative) anomaly structure for temperature, with corresponding positive (negative) anomalies for salinity above 600 m in the intermediate layer and negative (positive) anomalies below 600 m. In contrast, when the cyclonic eddies interact with the Kuroshio, the temperature and salinity anomalies change simultaneously, with the temperature showing an overall negative anomaly and the salinity showing a negative and positive anomaly above and below 600 m, respectively. The research in this study provides the basis for further research on energy exchange during eddy–Kuroshio interactions.

Subsurface dispersion path and travel time of radiocesium from Fukushima by Mode Water

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on March 11, 2011 resulted in the release of immense amounts of radioactive materials into the ocean. However, the dispersion of radioactive materials in the subsurface has not yet been clarified due to the spatiotemporal limitation of observations. Thus, herein, a tracer experiment was implemented using a three-dimensional numerical model to estimate the dispersion path of 137Cs released directly from the FDNPP and its travel time in the subsurface of the North Pacific Ocean from 2011 to 2020. The results show that the subsurface 137Cs spreads by two mode waters, namely, Sub-Tropical Mode Water (STMW) and Central Mode Water (CMW). Subsurface 137Cs primarily spreads clockwise in the sub-tropical region, while a portion driven by STMW is dispersed southward. The clockwise dispersion path of 137Cs released into the ocean by STMW is relatively shallower and inward than that by CMW. The 137Cs that was spread clockwise reached the east of Taiwan and the Philippines via STMW and CMW nine years after the accident, respectively. The model described in this study is applicable for estimating the water path and travel time of tritium water planned to be discharged from Fukushima.

Diurnal Sea Surface Temperature Warming Along the Kuroshio off Taiwan Under Easterly Wind Conditions

AbstractWe carry out the Lagrangian diurnal warm layer (DWL) observations, supplemented by satellite products, along the strong Kuroshio east of Taiwan, where the boundary terrain modifies the winds and the advection effect is significant. The synoptic easterly wind bifurcates as it encounters Taiwan's coast, forming the southward‐blowing and the northward‐blowing branches in the southern and northern regions of the bifurcation, respectively. The two branches produce areas with enhanced and weakened apparent wind speed relative to the northeastward flowing Kuroshio. The DWL can reach 5 m in the south of the bifurcation due to the shear instability‐induced mixing. Sea surface temperature (SST) enhancement occurs around and in the north of the wind bifurcation, where the solar heat is only trapped in the upper 2 m due to the absence of instability, forming inhomogeneous SST along the Kuroshio. The synoptic wind variations and Kuroshio advection further modulate the location of SST enhancement.

Influence of mesoscale eddies on the cross-shelf phosphate transport of the Kuroshio Current northeast of Taiwan: A modeling study

The Kuroshio Current flows northeastward along the East China Sea (ECS) shelf break, carrying a large amount of nutrients, and is thus an important source of nutrients for the ECS. The mainstream and transport of the Kuroshio Current are significantly affected by mesoscale eddies. However, the influence of mesoscale eddies on the Kuroshio nutrient input into the ECS is unknown. We add constructed cyclonic and anticyclonic eddies to a hydrodynamic model to explore the influence of mesoscale eddies on cross-shelf Kuroshio phosphate input into the ECS. This model suitably reproduces the fate of mesoscale eddies and the variation in the Kuroshio Current during eddy-current interactions. The simulation results reveal that during the strong interaction between the Kuroshio Current and mesoscale eddy east of Taiwan, the cyclonic eddy reduces the on-shelf phosphate flux, while the anticyclonic eddy increases the Kuroshio phosphate input to the ECS. When the anticyclonic eddy moves to the Okinawa Trough, it reduces the Kuroshio phosphate input into the ECS.These basic features are not sensitive to the initial latitude of the eddy center east of Taiwan. The change in cross-shelf phosphate flux is caused by the changes in cross-shelf velocity and phosphate concentration along the shelf. Momentum balance analyses suggest that the change in cross-shelf velocity is mainly caused by the change in the pressure gradient term due to eddy-induced changes in sea surface height in the horizontal direction and isotherm tilting in the vertical direction. The advection-diffusion equation analysis shows that the change in phosphate concentration along the shelf is attributed to changes in the upper horizontal advection and lower vertical advection of phosphate, which are induced by the upper phosphate change and vertical velocity change along the shelf, respectively. This study has important implications for the possible response of the ECS ecosystem to mesoscale eddies that are partly triggered by enhanced typhoons east of Taiwan under global warming.

Assessing the ecological loss of mining areas in Taiwan.

Mines are mostly located in the mountains and national forestlands in Taiwan. The development and use of mines have severely damaged the environment. Despite the long history of mining, the value of forest ecological services lost during mining operations have not yet been incorporated into the expenses borne by miners, and miners are not liable for compensation for ecological damage. This study evaluated the forest ecosystem service benefits lost since mining began, with the aim of providing future reference for calculating ecological damage related to mining. We investigated Mount Taibai mines in Yilan (northeast Taiwan) and Mount Yongshi mines in Hualian (east Taiwan), which are richly forested areas. According to Article 13 of the Mining Act in Taiwan, mining rights have a limitation of 20years, and the two mines in this study have been in operation for 20years. By using four ecological services-forest production, carbon sequestration, water resource replenishment, and forest recreation-we estimated the loss of ecological values in both mining regions. The result indicated that the loss of total forest production benefits over 20years was 7,498.6k New Taiwanese dollars (NTD) in Mount Taibai mines and 6,543.1k NTD for Mount Yongshi mines, while the loss for the total carbon sequestration benefits over 20years was 19,950k NTD in Mount Taibai mines and 17,400k NTD in Mount Yongshi mines. The loss of value for the total water conservation benefits over 20years was 11,160k NTD in Mount Taibai mines and 5,070k NTD in Mount Yongshi mines. The loss value of forest recreation over 20years was 1,443,855k NTD for the two mines.

Influence of Differences in the Density of Seawater on the Measurement of the Underwater Gravity Gradient.

In preparing gravity gradient reference maps for navigation purposes, researchers have tended to use a constant value for the density of seawater. However, the actual seawater density at a particular location may vary due to the effects of longitude, latitude and bathymetry. In this study, the right rectangular prism method was used to calculate the disturbing gravity gradient caused by the mass deficiency of seawater for three different seawater profiles in an area east of Taiwan. For this purpose, two seawater density models were used as alternatives to the constant seawater density model, and the alteration in the gravity gradient was calculated to quantify the error in the gravity gradient as a result of using a constant seawater density. The results demonstrated that the error in the gravity gradient can reach 1E for water at large depths. Moreover, the difference between the amplitude of the error of the corrected thermocline and that for the uncorrected seawater density model was found to be quite small. If a gravity gradient reference map with accuracy better than 1E is to be realized, the seawater density cannot be taken as constant during forward modeling.

Eddy Deformation and Kinetic Energy Conversion During the Eddy‐Kuroshio Interaction East of Taiwan

AbstractEddy‐mean flow interactions have always been of interest to researchers because they are among the causes of energy cascades. Different from most previous studies, this research concentrates on the Kuroshio Current's effect on an eddy during multiple independent elliptical eddy‐Kuroshio interactions. Eddy deformation during the eddy‐Kuroshio interaction is applied as the statistical criterion to select the typical eddies that interact with the Kuroshio east of Taiwan. There are 9 anticyclonic eddies (AEs) and 15 cyclonic eddies (CEs) that satisfy the criteria from the 1993 to 2018 satellite altimeter data. The blocking effect caused by the anti‐phase velocity at the contact interface of the CE and Kuroshio results in the eddy kinetic energy (EKE) at the CE edge being obviously inhomogeneous, while the AE does not result in the same effect. Moreover, the temporal variation in EKE during the eddy‐Kuroshio interaction precedes the AE/CE deformation by approximately 0.55/0.27 interaction cycles. The Kuroshio has different modulation mechanisms for different eddy polarities. Barotropic and baroclinic instabilities contribute to the generation of EKE, with barotropic instabilities providing more than 10 times as much as baroclinic instabilities for the AE and 4 times as much for the CE. The advection effect of the AE on the Kuroshio is in anti‐phase with the effect of the Kuroshio on the AE, which eventually makes the AE shrink. They are in phase for the CE and lead the CE to eventually become meandering.