Journal of Geophysical Research-Oceans最新文献

{"title":"Bottom Stress and Drag on a Shallow Coral Reef","authors":"Elisabeth Boles,&nbsp;Alexandra Khrizman,&nbsp;Jenny Hamilton,&nbsp;David Mucciarone,&nbsp;Robert Dunbar,&nbsp;Jeffrey Koseff,&nbsp;Stephen Monismith","doi":"10.1029/2024JC021528","DOIUrl":"https://doi.org/10.1029/2024JC021528","url":null,"abstract":"<p>Coral reef roughness produces turbulent boundary layers and bottom stresses that are important for reef metabolism monitoring and reef circulation modeling. However, there is some uncertainty as to whether field methods for estimating bottom stress are applicable in shallow canopy environments as found on coral reefs. Friction velocities (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>u</mi>\u0000 <mo>∗</mo>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${u}_{ast }$</annotation>\u0000 </semantics></math>) and drag coefficients (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>C</mi>\u0000 <mi>D</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${C}_{D}$</annotation>\u0000 </semantics></math>) were estimated using five independent methods and compared across 14 sites on a shallow forereef (2–9 m deep) in Palau with large and spatially variable coral roughness elements (0.4–1 m tall). The methods included the following: (a) momentum balance closure, (b) log-fitting to velocity profiles, (c) Reynolds stresses, (d) turbulence dissipation, and (e) roughness characterization from digital elevation models (DEMs). Both velocity profiles and point turbulence measurements indicated good agreement with log-layer scaling, suggesting that measurements were taken within a well-developed turbulent boundary layer and that canopy effects were minimal. However, <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>u</mi>\u0000 <mo>∗</mo>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${u}_{ast }$</annotation>\u0000 </semantics></math> estimated from the DEMs, momentum budget and log-profile fitting were consistently larger than those estimated from direct turbulence measurements. Near-bed Reynolds stresses only contributed about 1/3 of the total bottom stress and drag produced by the reef. Thus, effects of topographical heterogeneity that induce mean velocity fluxes, dispersive stresses, and form drag are expected to be important. This decoupling of total drag and local turbulence implies that both rates of mass transfer as well as values of fluxes inferred from concentration measurements may be proportional to smaller, turbulence-derived values of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>u</mi>\u0000 <mo>∗</mo>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${u}_{ast }$</annotation>\u0000 </semantics></math> rather than to those based on larger-scale flow structure.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Relative Importance of Ocean Advection and Surface Heat Fluxes During the Madden–Julian Oscillation in a Coupled Ocean–Atmosphere Model","authors":"E. Karlowska,&nbsp;A. J. Matthews,&nbsp;B. G. M. Webber,&nbsp;T. Graham,&nbsp;P. Xavier","doi":"10.1029/2024JC021515","DOIUrl":"https://doi.org/10.1029/2024JC021515","url":null,"abstract":"&lt;p&gt;Intraseasonal variability of ocean surface mixed layer temperature (MLT) in the tropics can be linked to the Madden–Julian Oscillation (MJO), the main source of intraseasonal atmospheric variability in the tropics. Here, we conduct a boreal winter mixed layer heat budget using 10-day forecast composites of a coupled ocean–atmosphere Numerical Weather Prediction model of the UK Met Office to reveal that ocean advection plays a major role in modulating intraseasonal anomalies of MLT over the tropical Indian Ocean and the Maritime Continent. Large scale (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 10&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;◦&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) intraseasonal anomalies of MLT (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 0.1 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;◦&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;C) are driven by net surface heat flux. Ocean advection dominates at smaller horizontal scales (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;∼&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 1&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;◦&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;), contributing up to 0.5 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;◦&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${circ}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;C to the intraseasonal MLT anomaly. Prior to the development of the enhanced MJO convection in the western Indian Ocean (phases 8 and 1), ocean advection reinforces the net heat flux warming in this region. However, ocean advection opposes the net heat flux warming in the Maritime Continent prior to the development of suppressed MJO convection in this region. When the MJO convection develops over the central Indian Ocean (phase 3), ocean advection (net surface heat flux) drives the intraseasonal MLT anomalies in the western Indian Ocean (central Indian Ocean and the Maritime Continent). Our results demonstrate the importance of ocean dynamics during the initiation and growth of the MJO, and raise implications for models that do not resolve thes","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021515","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep Mesoscale and Submesoscale Circulations Around the Atlantis II Seamount","authors":"Matthew McKinley,&nbsp;Daoxun Sun,&nbsp;Mark Kelly,&nbsp;Karim G. Sabra,&nbsp;Annalisa Bracco","doi":"10.1029/2024JC021233","DOIUrl":"https://doi.org/10.1029/2024JC021233","url":null,"abstract":"<p>This study investigates the complex interactions between the North Atlantic Current (NAC) and the New England Seamount chain, focusing on the Atlantis II seamount. Employing a high-resolution submesoscale permitting regional ocean circulation model nested within a basin-wide simulation, it explores three distinct periods, each 2 weeks long, showcasing varied deep mesoscale and submesoscale circulations around the seamount. The analysis includes Eulerian statistics and Lagrangian particle tracing experiments to explore the transport and mixing impacts of the highly dynamic flow around the seamount. The results reveal significant density variations across the water column, attributed to the seamount's influence on local ocean currents. Specifically, mesoscale and submesoscale vortices, a seamount wake, and lee waves form during periods of increased near-bottom current flow. These findings highlight the critical role of topographic features in modulating oceanic flows and ocean mixing, which have implications, among others, for nutrient distribution, acoustic propagation, and climate modeling. The variety and variability of the mesoscale and submesoscale circulations that arise in response to the variability in the NAC strength and position in relation to the New England Seamount Chain demonstrate the difficulty in extrapolating general behaviors from isolated observational campaigns.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021233","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Novel Sea State Classification Scheme of the Global CFOSAT Wind and Wave Observations","authors":"Huimin Li,&nbsp;Bertrand Chapron,&nbsp;Douglas Vandemark,&nbsp;Wenming Lin,&nbsp;Danièle Hauser,&nbsp;Yijun He,&nbsp;Fabrice Collard","doi":"10.1029/2023JC020686","DOIUrl":"https://doi.org/10.1029/2023JC020686","url":null,"abstract":"<p>Ocean waves are essential elements across the air-sea interface, regulating momentum and energy transfer. The mixture of wind sea and ocean swell coupled with surface winds results in diverse sea state conditions that modify the local air-sea interaction. Previous classifications of wind waves and swells are mostly binary that are insufficient to represent the complexity of sea states. In this study, we utilize wind and wave measurements from the China-France Oceanography Satellite (CFOSAT) to construct an observational wind-wave ensemble. Four key parameters: wind speed, significant wave height, inverse wave age, and spectral width are selected out of six variables based on their correlations. Employing the unsupervised learning of k-means clustering, global sea states are categorized into six distinct classes. These classes, characterized by unique centroids and separated in the feature space, represent specific wind regimes and degrees of wave development. Global occurrence highlights that each sea state is region-specific, bridging the spatial gap of swell and wind sea dominated areas, respectively. This new grouping scheme complements the traditional wind sea and/or swell classification by resolving the diversity of wave regimes. The six-class classification enables us to identify transitional states and hybrid conditions that may have been overlooked in the binary classification scheme, which shall help investigate the impact of ocean waves on the air-sea interaction under varying sea states.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JC020686","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of Horizontal Model Resolution on Mixing and Dispersion in the Northeastern Gulf of Mexico","authors":"Nektaria Ntaganou,&nbsp;Eric P. Chassignet,&nbsp;Alexandra Bozec","doi":"10.1029/2024JC021315","DOIUrl":"https://doi.org/10.1029/2024JC021315","url":null,"abstract":"<p>In this paper, the importance of model horizontal resolution in mixing and dispersion is investigated by comparing two data-assimilative high-resolution simulations (4 and 1 km), one of which is submesoscale-permitting. By employing both Eulerian and Lagrangian metrics, upper-ocean differences between the mesoscale-resolving and submesoscale-permitting simulations are examined in the northeastern Gulf of Mexico, a region of high mesoscale and submesoscale activity. Mixing in both simulations is explored by conducting Lagrangian experiments to track the generation of Lagrangian coherent structures (LCSs) and their associated transport barriers. Finite-time Lyapunov exponent (FTLE) fields show higher separation rates of fluid particles in the submesoscale-permitting case, which indicate more vigorous mixing with differences being more pronounced in the shelf regions (depths ≤ 500 m). The extent of the mixing homogeneity is examined using probability density functions (PDFs) of FTLEs with results suggesting that mixing is heterogeneous in both simulations, but some homogeneity is exhibited in the submesoscale-permitting case. The FTLE fields also indicate that chaotic advection dominates turbulent mixing in both simulations regardless of the horizontal resolution. In the submesoscale-permitting experiment, however, smaller scale LCSs emerge as noise-like filaments that suggest a larger turbulent mixing component than in the mesoscale-resolving experiment. The impact of resolution is then explored by investigating the spread of oil particles at the location of the Deepwater Horizon oil spill.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021315","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142574064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"More Than Deoxygenation: Linking Iodate Reduction to Nitrogen, Iron, and Sulfur Chemistry in Reducing Regimes","authors":"Natalya Evans,&nbsp;Emma Johnson,&nbsp;Amanda Taing,&nbsp;Alexi A. Schnur,&nbsp;Peter J. Chace,&nbsp;Samantha Richards,&nbsp;Dalton S. Hardisty,&nbsp;James W. Moffett","doi":"10.1029/2024JC021013","DOIUrl":"https://doi.org/10.1029/2024JC021013","url":null,"abstract":"<p>A striking feature of Oxygen Deficient Zones (ODZs) on the eastern boundary of the Pacific Ocean are large subsurface plumes of iodide. Throughout the oceans, iodate is the predominant and thermodynamically favored species of dissolved iodine, but iodate is depleted within these plumes. The origin of iodide plumes and mechanism of reduction of iodate to iodide remains unclear but is thought to arise from a combination of in situ reduction and inputs from reducing shelf sediments. To distinguish between these sources, we investigated iodine redox speciation along the Oregon continental shelf. This upwelling system resembles ODZs but exhibits episodic hypoxia, rather than a persistently denitrifying water column. We observed elevated iodide in the benthic boundary layer overlying shelf sediments, but to a much smaller extent than within ODZs. There was no evidence of offshore plumes of iodide or increases in total dissolved iodine. Results suggest that an anaerobic water column dominated by denitrification, such as in ODZs, is required for iodate reduction. However, re-analysis of iodine redox data from previous ODZ work suggests that most iodate reduction occurs in sediments, not the water column, and is also decoupled from denitrification. The underlying differences between these regimes have yet to be resolved, but could indicate a role for reduced sulfur in iodate reduction if the sulfate reduction zone is closer to the sediment-water interface in ODZ shelf sediments than in Oregon sediments. Iodate reduction is not a simple function of oxygen depletion, which has important implications for its application as a paleoredox tracer.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142561689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanisms Regulating Coccolithophore Dynamics in the Great Calcite Belt in the Southern Ocean in the Community Earth System Model","authors":"H. Oliver,&nbsp;K. M. Krumhardt,&nbsp;D. J. McGillicuddy Jr.,&nbsp;C. Mitchell,&nbsp;W. M. Balch","doi":"10.1029/2024JC021371","DOIUrl":"https://doi.org/10.1029/2024JC021371","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>The Great Calcite Belt (GCB) is a region of elevated particulate inorganic carbon (PIC) generated by coccolithophore growth that spans the subantarctic Southern Ocean. The GCB is thought to play an important role in the global carbon cycle. Coccolithophores, however, are sensitive to multiple climate-related environmental factors. To understand these controls on Southern Ocean coccolithophores comprising the GCB, we explore its major bottom-up and top-down processes using the Community Earth System Model (CESM). We find that coccolithophore biomass accumulates where both macronutrients and iron are available at concentrations greater than ∼50% of their half-saturation constants, and temperature is more limiting than both light and nutrients. Coccolithophore biomass is decoupled from growth rates due to top-down control. At higher temperatures and lower latitudes, microzooplankton grazing outpaces coccolithophore growth. This occurs because the temperature dependence of grazing is parameterized with an exponential (Q₁₀) function, whereas coccolithophore growth is parameterized with a power function; these temperature curves diverge at higher temperatures. While the extent of the GCB is primarily controlled by temperature, its magnitude is most strongly controlled by environmental factors affecting iron concentrations. Our results suggest that (a) the temperature relationships for both coccolithophore growth and its loss terms are critical for resolving a GCB in CESM, and (b) the spatial extent of Southern Ocean coccolithophores may be sensitive to continued increases in sea surface temperatures.</p>\u0000 </section>\u0000 </div>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142561630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sources and Fates of Sedimentary Polycyclic Aromatic Hydrocarbons in the East Siberian Arctic Shelf: Implications for Input Pathways and Black Carbon Constraint","authors":"Wenxiu Yu,&nbsp;Limin Hu,&nbsp;Yuying Zhang,&nbsp;Jiazong Du,&nbsp;Yazhi Bai,&nbsp;Tian Lin,&nbsp;Huimin Yu,&nbsp;Zhigang Guo,&nbsp;Alexander Bosin,&nbsp;Anatolii Astakhov,&nbsp;Xuefa Shi","doi":"10.1029/2024JC021234","DOIUrl":"https://doi.org/10.1029/2024JC021234","url":null,"abstract":"<p>The Arctic region is experiencing more rapid climate changes than the other parts of the world and serves as a sink for semi-volatile persistent organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), which can be utilized as molecular markers for pyrogenic carbon, such as black carbon (BC). As the sea ice retreats and increased terrestrial inputs with widespread wildfires, the PAH concentrations in the Arctic Ocean are rising. In this study, the sources and fates of PAHs together with BC in surface sediments from the East Siberian Arctic Shelf (ESAS) were analyzed. Positive matrix factorization (PMF) elucidated a mixed petrogenic and pyrogenic sources and distinct PAH fates associated with diverse input pathways including coastal permafrost erosion contribution (∼30%), petrogenic-related emission (∼34%), fossil fuel combustion (∼26%), and biomass burning (∼10%). Correlation analysis indicated that BC plays a key role in affecting the behavior and fates of PAHs. In the Chukchi Sea, PAHs are closely associated with soot-BC, whereas in the Laptev Sea (LS) and west East Siberian Sea (W-ESS), they exhibit a coupling process with char-BC. The presence of these carbonaceous materials in the sediments of CS is likely influenced by atmospheric deposition and biological activity, whereas the LS and W-ESS regions are mainly affected by long-distance river transport and direct deposition from coastal permafrost. As global warming continues, permafrost thawing induces the remobilization and retranslocation of PAHs, thereby becoming a significant PAH contributor and input pathway in the rapidly changing Arctic coastal margin.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142561738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strengthening of the Equatorial Pacific Upper-Ocean Circulation Over the Past Three Decades","authors":"Franz Philip Tuchen,&nbsp;Renellys C. Perez,&nbsp;Gregory R. Foltz,&nbsp;Michael J. McPhaden,&nbsp;Rick Lumpkin","doi":"10.1029/2024JC021343","DOIUrl":"https://doi.org/10.1029/2024JC021343","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Thirty years (1993–2022) of concurrent satellite and in-situ observations show a long-term strengthening of the equatorial Pacific upper-ocean circulation. Enhanced southeasterly and cross-equatorial winds have caused an annual mean, basin-wide acceleration of the equatorial westward near-surface currents by ∼20% and an acceleration of poleward flow north (south) of the equator by ∼60% (∼20%). Additional moored velocity data reveal a deepening of the Equatorial Undercurrent (EUC) core at 170°W and significant shoaling at 140°W and 110°W, but no significant changes in EUC core velocity. The strongest subsurface zonal velocity trends are observed above the EUC core in the central to eastern Pacific and occur before and after the seasonal maximum of EUC core velocity, causing enhanced upper-ocean vertical current shear. Consistent with trends of the 20°C isotherm depth along the equatorial Pacific, a significant basin-wide steepening of the equatorial thermocline is observed. Both the accelerating equatorial current system and the enhanced thermocline slope are consistent with an observed steepening of the zonal sea surface height gradient due to increased wind-driven westward mass transport at the surface. During February-March, both surface and subsurface currents along the equator show eastward velocity trends, in contrast to westward near-surface current trends during the remainder of the year. The trend reversal is attributed to both a long-term shift in equatorial Kelvin wave activity and to the impact of strong interannual variability due to El Niño Southern Oscillation and other modes of natural variability on decadal to multidecadal time scales.</p>\u0000 </section>\u0000 </div>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021343","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142561728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nonlinear Tide-River-Surge Interactions and Their Impacts on Compound Flooding During Typhoon Hato in the Pearl River Delta","authors":"Haoxuan Du,&nbsp;Kai Fei,&nbsp;Liang Gao","doi":"10.1029/2023JC020673","DOIUrl":"https://doi.org/10.1029/2023JC020673","url":null,"abstract":"<p>In coastal areas, multiple hydrodynamic processes co-occur, including the astronomical tide, river discharge, and storm surge. Their propagation and interaction within coastal tidal river result in strong nonlinear behavior in inland areas. This study employed a hydrodynamic model and continuous wavelet transform analysis to investigate the complex tide-river-surge interactions and their impacts on compound flooding in the West River of the Pearl River Delta during an extreme typhoon event. Validated model outputs provided insights into the spatial and temporal variations of river discharge, water levels, and currents. Wavelet analysis revealed river discharge modulates tidal properties, causing nonstationary tides and asymmetries, with high flows suppressing tidal ranges but facilitating energy transfers to overtides. During Typhoon Hato, storm surges dominated high-frequency water level fluctuations that rapidly propagated upstream. Crucially, strong high-frequency tide-river-surge coupling induced significant water level amplifications, with interaction intensities increasing landward. In upstream areas where riverine and coastal drivers converged, flood risks exceeded typical estimates due to this vigorous multi-driver compounding. Findings highlighted how existing flood mitigation approaches over simplistically superposing individual sources may severely underestimate flood levels by neglecting such nonlinear interactions. A comprehensive accounting of the cumulative, multiplicative effects of tides, discharge, storm surge, and sea level rise is imperative. This quantitative unraveling of key physical drivers offers transferable insights applicable to compound flood risk evaluations and policy guidance for enhancing resilience in other estuary and delta regions. Future work should focus on holistically modeling multivariate extremes and their interactions.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"129 11","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JC020673","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142555327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}