Application of a barotropic model to North Atlantic synoptic sea level variability

A barotropic, shallow-water model of the North Atlantic is used to investigate variability in adjusted sea level on time scales of a few days to a few months (by “adjusted,” we mean that the inverse barometer is removed from both the model-computed sea level and the observations). The model has 1/3° × 0.4° resolution in latitude and longitude, respectively, and is forced using atmospheric pressure and wind stress data derived from European Centre for Medium Range Weather Forecasts (ECMWF, 1994) analyses. The model results are compared with coastal tide gauge data. Along the western boundary, from St. John\u27s, Newfoundland, to Fernandina Beach, Florida, coherence squared between model and data is greater than 0.5 in the period range 3 to 10 days. South of Cape Hatteras, the model underestimates the amplitude seen in the data, with much better agreement north of the Cape. Model performance on the eastern boundary is generally poor. We suggest this is because on the eastern boundary, the shelf width is much narrower, compared to the internal radius of deformation, than on the western boundary. In addition, the model resolution is insufficient to adequately represent the shelf on the eastern boundary. The poorer agreement south of Cape Hatteras may be due Gulf Stream effects not accounted for by the model dynamics. Finally, we discuss the model-computed variability in the ocean interior

Interaction between the tidal and seasonal variability of the Gulf of Maine and Scotian Shelf Region

As part of a broader study of ocean downscaling, the seasonal and tidal variability of the Gulf of Maine and Scotian shelf, and their dynamical interaction, are investigated using a high-resolution (1/36°) circulation model. The model’s seasonal hydrography and circulation, and its tidal elevations and currents, are compared with an observed seasonal climatology, local observations, and results from previous studies. Numerical experiments with and without density stratification demonstrate the influence of stratification on the tides. The model is then used to interpret the physical mechanisms responsible for the largest seasonal variations in the M2 surface current that occur over, and to the north of, Georges Bank. The model generates a striation pattern of alternating highs and lows, aligned with Georges Bank, in the M2 surface summer maximum speed in the Gulf of Maine. The striations are consistent with observations by a high-frequency coastal radar system and can be explained in terms of a linear superposition of the barotropic tide and the first-mode baroclinic tide, generated on the north side of Georges Bank, as it propagates into the Gulf of Maine. The seasonal changes in tidal currents in the well-mixed area on Georges Bank are due to a combination of increased sea level gradients, and lower vertical viscosity, in summer

Seasonal variation of the deep limb of the Pacific Meridional Overturning circulation at Yap-Mariana junction

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wang, J., Ma, Q., Wang, F., Lu, Y., & Pratt, L. J. Seasonal variation of the deep limb of the Pacific Meridional Overturning circulation at Yap-Mariana junction. Journal of Geophysical Research: Oceans, 125(7), (2020): e2019JC016017, doi:10.1029/2019JC016017.This study reveals the seasonal variability of the lower and upper deep branches of the Pacific Meridional Overturning Circulation (L‐PMOC and U‐PMOC) in the Yap‐Mariana Junction (YMJ) channel, a major gateway for deep flow into the western Pacific. On the western side of the YMJ channel, mooring observations in 2017 and in 1997 show the seasonal phase of the L‐PMOC at depths of 3,800–4,400 m: strong northward flow with speed exceeding 20 cm s−1 and lasting from December to next May and weak flow during the following 6 months. On the eastern side of the channel, mooring observations during 2014–2017 show two southward deep flows with broadly seasonal phases, one being the return flow of L‐PMOC below ~4,000 m and with the same phase of L‐PMOC but reduced magnitude. The second, shallower, southward deep flow corresponds to the U‐PMOC observed within 3,000–3,800 m and with opposite phase of L‐PMOC, that is, strong (weak) southward flow appearing during June–November (December–May). Seasonal variations of the L‐PMOC and U‐PMOC are accompanied by the seasonal intrusions of the Lower and Upper Circumpolar Waters (LCPW and UCPW) in lower and upper deep layers, which change the isopycnal structure and the deep currents in a way consistent with geostrophic balance.This study is supported by the National Natural Science Foundation of China (grants 91958204 and 41776022), the Strategic Priority Research Program of the Chinese Academy of Sciences (grant XDA22000000), the Key Research Program of Frontier Sciences, CAS (grant QYZDB‐SSW‐SYS034). F. Wang thanks the support from the Scientific and Technological Innovation Project by Qingdao National Laboratory for Marine Science and Technology (grant 2016ASKJ12), the National Program on Global Change and Air‐Sea Interaction (grant GASI‐IPOVAI‐01‐01), and the National Natural Science Foundation of China (grants 41730534 and 41421005). L. Pratt gratefully acknowledges the support by NSF (grant OCE‐1657870). Jianing Wang and Qiang Ma contributed equally to this work

Impacts of model resolution on simulation of meso-scale eddies in the Northeast Pacific Ocean

The model simulated meso-scale eddies in the Northeast Pacific Ocean, using two models with nominal horizontal resolutions of 1/12° and 1/36° in latitude/longitude (grid spacing of 7.5 km and 2.5 km), respectively, are presented. Compared with the 1/12° model, the 1/36° model obtains (1) similar variance and wavenumber spectra of  the sea level anomaly and water temperature anomaly, and (2) increases in the level of the domain-averaged total kinetic energy, eddy kinetic energy (EKE), and variance of horizontal gradient of water temperature. In the interior basin of the southern region, both models show stronger eddy frontal activities, represented by EKE, temperature and its horizontal gradient, in summer and fall than in winter and spring. The challenge of evaluating the realism of high-resolution ocean models with conventional satellite remote sensing observations is discussed

Pathways, volume transport, and seasonal variability of the lower deep limb of the Pacific Meridional Overturning Circulation at the Yap-Mariana Junction

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wang, J., Wang, F., Lu, Y., Ma, Q., Pratt, L. J., & Zhang, Z. Pathways, volume transport, and seasonal variability of the lower deep limb of the Pacific Meridional Overturning Circulation at the Yap-Mariana Junction. Frontiers in Marine Science, 8, (2021): 672199, https://doi.org/10.3389/fmars.2021.672199.The lower deep branch of the Pacific Meridional Overturning Circulation (L-PMOC) is responsible for the deep-water transport from Antarctic to the North Pacific and is a key ingredient in the regulation of global climate through its influence on the storage and residence time of heat and carbon. At the Pacific Yap-Mariana Junction (YMJ), a major gateway for deep-water flowing into the Western Pacific Ocean, we deployed five moorings from 2018 to 2019 in the Eastern, Southern, and Northern Channels in order to explore the pathways and variability of L-PMOC. We have identified three main patterns for L-PMOC pathways. In Pattern 1, the L-PMOC intrudes into the YMJ from the East Mariana Basin (EMB) through the Eastern Channel and then flows northward into the West Mariana Basin (WMB) through the Northern Channel and southward into the West Caroline Basin (WCB) through the Southern Channel. In Pattern 2, the L-PMOC intrudes into the YMJ from both the WCB and the EMB and then flows into the WMB. In Pattern 3, the L-PMOC comes from the WCB and then flows into the EMB and WMB. The volume transports of L-PMOC through the Eastern, Southern, and Northern Channels all exhibit seasonality. During November–April (May–October), the flow pathway conforms to Pattern 1 (Patterns 2 and 3), and the mean and standard deviation of L-PMOC transports are −4.44 ± 1.26 (−0.30 ± 1.47), −0.96 ± 1.13 (1.75 ± 1.49), and 1.49 ± 1.31 (1.07 ± 1.10) Sv in the Eastern, Southern, and Northern Channels, respectively. Further analysis of numerical ocean modeling results demonstrates that L-PMOC transport at the YMJ is forced by a deep pressure gradient between two adjacent basins, which is mainly determined by the sea surface height (SSH) and water masses in the upper 2,000-m layer. The seasonal variability of L-PMOC transport is attributed to local Ekman pumping and westward-propagating Rossby waves. The L-PMOC transport greater than 3,500 m is closely linked to the wind forcing and the upper ocean processes.This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (grant XDA22000000), the National Natural Science Foundation of China (grants 91958204 and 41776022), the Key Research Program of Frontier Sciences, CAS (grant QYZDB-SSW-SYS034), and the International Partnership Program of CAS (grant 133137KYSB20180056). FW thanks the support from the National Natural Science Foundation of China (grants 41730534 and 41421005). QM thanks the support by the National Natural Science Foundation of China (grant 42006003)

Carbon Nanotubes Enabling Highly Efficient Cell Apoptosis by Low-Intensity Nanosecond Electric Pulses via Perturbing Calcium Handling.

Effective induction of targeted cancer cells apoptosis with minimum side effects has always been the primary objective for anti-tumor therapy. In this study, carbon nanotubes (CNTs) are employed for their unique ability to target tumors and amplify the localized electric field due to the high aspect ratio. Highly efficient and cancer cell specific apoptosis is finally achieved by combining carbon nanotubes with low intensity nanosecond electric pulses (nsEPs). The underlying mechanism may be as follows: the electric field produced by nsEPs is amplified by CNTs, causing an enhanced plasma membrane permeabilization and Ca2+ influx, simultaneously triggering Ca2+ release from intracellular storages to cytoplasm in a direct/indirect manner. All the changes above lead to excessive mitochondrial Ca2+ uptake. Substructural damage and obvious mitochondria membrane potential depolarization are caused subsequently with the combined action of numerously reactive oxygen species production, ultimately initiating the apoptotic process through the translocation of cytochrome c to the cytoplasm and activating apoptotic markers including caspase-9 and -3. Thus, the combination of nanosecond electric field with carbon nanotubes can actually promote HCT116 cell death via mitochondrial signaling pathway-mediated cell apoptosis. These results may provide a new and highly efficient strategy for cancer therapy

Model-observations synergy in the coastal ocean

Integration of observations of the coastal ocean continuum, from regional oceans to shelf seas and estuaries/deltas with models, can substantially increase the value of observations and enable a wealth of applications. In particular, models can play a critical role at connecting sparse observations, synthesizing them, and assisting the design of observational networks; in turn, whenever available, observations can guide coastal model development. Coastal observations should sample the two-way interactions between nearshore, estuarine and shelf processes and open ocean processes, while accounting for the different pace of circulation drivers, such as the fast atmospheric, hydrological and tidal processes and the slower general ocean circulation and climate scales. Because of these challenges, high-resolution models can serve as connectors and integrators of coastal continuum observations. Data assimilation approaches can provide quantitative, validated estimates of Essential Ocean Variables in the coastal continuum, adding scientific and socioeconomic value to observations through applications (e.g., sea-level rise monitoring, coastal management under a sustainable ecosystem approach, aquaculture, dredging, transport and fate of pollutants, maritime safety, hazards under natural variability or climate change). We strongly recommend an internationally coordinated approach in support of the proper integration of global and coastal continuum scales, as well as for critical tasks such as community-agreed bathymetry and coastline products

Weather sensitivity of maritime activities on Chinese Shelf

Master's thesis in Offshore technologyThe objective of the thesis is to discuss the weather sensitivity of maritime activities, inter alia, with respect to the aspects of passage planning, load plan-making, and ship maneuvering. As maritime activities represent a high risk industry, the risk analysis is not only a mandatory requirement of the administration but also a need during practice. A risk analysis will also be carried out in this thesis. With the improvement of the state of technology, a myriad of state-of-art technologies and equipment have been applied in oil field service realm, for example, shuttle tankers with DP2 (Dynamic Position System) have been used extensively in the North Sea area of Norway. However, there is none of this kind of shuttle tankers in Chinese costal area yet, therefore, this thesis will also discuss the prospect that such shuttle tanker will be used in Chinese costal area. In recent years, the global climate is getting increasingly unstable. Extreme weather, like typhoons, abnormal temperature, and storm occur frequently. According to a survey, in 2011, the US lost 50 billion dollars and in the recent 17 years, China mainland lost in average 185.9 billons RMB every year due to the damage of weather. Numerous professions，for example the oil field service and shipping industry, which we are engaged in, were affected mostly. When it comes to the Chinese costal area, it is also one of the most famous zones of heavy storms and waves in the world. Up to this day, I still remember clearly that on 4th Nov, 2004, due to hash weather, two cargo ships went down in the Bohai Bay, and 44 members of the crew lost their life. At that time, I experienced the rescue activity in personal as the chief officer of a rescue boat. Therefore, there is a need to analyze the weather system and its influence on marine transportation on the Chinese Shelf. The final goal is to lower the risk of a marine operation by use of its advantages and avoidance of its disadvantages. In addition, in order to integrate methodology with practice closely, in the process of the thesis writing, the ships and the business of the Marine and Transportation (M&T) department of COSL will be referenced in discussing subtopics

A fine-resolution barotropic model of the North Atlantic driven by wind and atmospheric pressure forcing

We investigate the response of the North Atlantic to wind and atmospheric pressure forcing with a two-dimensional, fine-resolution barotropic model. The model domain extends from the equator to 65ﾟN and from 100ﾟ W to 14ﾟE with a resolution of 1/3ﾟ in latitude and 2/5ﾟ in longitude. The forcing field to drive the model is the twice-daily wind and atmospheric pressure data from the European Center for Medium Range Weather Forecasts (ECMWF). The model results are compared with sea level observed at coastal tide gauges, volume transport derived from voltage measurements made using a submarine cable across the Florida Straits, and bottom pressure data collected on the Labrador and Newfoundland Shelf. The time scales being studied range from several days to seasonal. -- The primary model experiment is a two-year (1985-1986) run driven by both wind and atmospheric pressure forcing. Three one-year runs are used to determine the contributions from the individual forcing, and the influence of Hudson Bay on the Labrador Shelf. Model results show the best agreement with observed sea level data at locations with broad shelves where the stratification is weak. Significant coherence between observed and modeled adjusted sea level is obtained at periods beyond ~3 days, at four representative stations along the western boundary. Contributions from atmospheric pressure forcing are not important for periods beyond ~2-3 days. The primary model experiment explains the observed volume transport variation through the Florida Straits at synoptic time scales, which is mainly due to wind. The model captures the variation at longer time scales in 1985, but not in 1986. The exclusion of advection by the mean flow may be the reason for the drop of coherence at ~10 days in the case of the Florida Straits volume transport and at ~12 days in the case of sea level at Fernandina Beach, Florida. -- Model output is also coherent with the observed bottom pressure data from the Labrador and Newfoundland Shelf. The significant non-iostatic response in the observational data at synoptic time scales in reproduced by model experiments with the Hudson Bay-Hudson Strait system included, with energy peaks at ~2-6 days. The contribution from atmospheric pressure forcing is only important in generating the energy peak at ~2-6 days when the Bay/Strait system is included, verifying the Helmholtz-like resonance mechanism proposed by former researchers. Wind forcing dominates over atmospheric pressure forcing at synoptic time scales. In particular, the wind over Hudson Bay-Hudson Strait is shown to be important

Layered mixing on the New England Shelf in summer

The article of record as published may be located at http://dx.doi.org/10.1002/2014JC009947The layered structure of stratification and mixing on the New England Shelf (NES) in summer is examined by analyzing a comprehensive set of observations of hydrography, currents and turbulence. A clear distinction in mixing characteristics between the midcolumn water (consisting of subsurface stratification, middepth weak stratification and lower-layer stratification) and a well-mixed bottom boundary layer (BBL) is revealed. The combination of subtidal Ekman onshore bottom transport and cross-shore density gradient created a lower-layer stratification that inhibited the upward extension of the BBL turbulence. The BBL mixing was related to strong shear generated by bottom stress, and the magnitude and periodic variation of BBL mixing was determined by both the tidal and subtidal flows. Mixing in the midcolumn water occurred under stably stratified conditions and showed correspondence with the occurrence of near-inertial and semidiurnal internal waves. Positive correlations between buoyancy frequency squared (N2) and shear variance (S2), S2 and dissipation rate (e), N2 and e are established in the midcolumn, but not in the BBL. The midcolumn e was reasonably described by a slightly modified MacKinnon-Gregg (MG) model.The field component of this program was jointly supported by the US Office of Naval Research (grants N00014-95-1-1030, N00014-95-1-0373, and N00014-96-1- 0953) and Fisheries and Oceans of Canada