Journal of Geophysical Research-Oceans最新文献

{"title":"Scaling Estimation for Growth Rate and Horizontal Wavelength of Charney-Type Submesoscale Baroclinic Instabilities (C-SBCIs)","authors":"L. Feng,&nbsp;C. Liu,&nbsp;J. C. McWilliams,&nbsp;F. Wang","doi":"10.1029/2024JC022104","DOIUrl":"https://doi.org/10.1029/2024JC022104","url":null,"abstract":"<p>The Charney-type submesoscale baroclinic instabilities (C-SBCIs) originating from the mean ocean state are ubiquitous in the global ocean, characterized by a vertical structure that is surface-intensified and depth-decaying. In a companion study, we examined the geographic distribution and seasonal variation of C-SBCIs, focusing on growth rates, horizontal wavelengths, and Charney depth (or vertical scale). The Charney depth, defined as the depth range of quasi-geostrophic potential vorticity gradient necessary for the instability, serves as an important indicator for energy conversion. In the linear stage, phase change and lateral and vertical eddy buoyancy fluxes are significant above this depth but negligible below it. Based on this, a scaling formula for the growth rate of C-SBCIs is derived using the available potential energy averaged from the surface to the Charney depth; although a scaling formula for the horizontal wavelength of C-SBCIs is derived using the stratification averaged from the surface to the Charney depth. These scaling formulas are analogous to those for the Eady-type instabilities but rely on a self-selected Charney depth instead of the prescribed vertical scale in the Eady model, enhancing their applicability to the complex real ocean state. Additionally, the mechanism underlying phase speeds of C-SBCIs is investigated, which is predominantly controlled by the mean flow averaged from the surface to the Charney depth. The newly derived scaling formulas for the growth rates and horizontal wavelengths of C-SBCIs offer a potential framework for parameterizing the temporal and spatial scale of submesoscale turbulence associated with submesoscale eddies.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085471","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":"Drivers of Chlorophyll-a Variability and Trends in the Agulhas Region: Insights From 25 Years of Satellite Observations","authors":"Prince Prakash,&nbsp;Rahul Mohan,&nbsp;Alvarinho J. Luis","doi":"10.1029/2024JC022149","DOIUrl":"https://doi.org/10.1029/2024JC022149","url":null,"abstract":"<p>The Agulhas Current system in the Indian sector of the Southern Ocean is significant for the climate as well as marine ecosystems. Global warming and alteration in wind patterns are altering the Agulhas region. However, it remains unresolved whether phytoplankton blooms in the Agulhas region show a robust trend in the satellite data era, and if so, what physical mechanisms account for this trend. We used high-resolution satellite-derived chlorophyll-<i>a</i> (Chl-<i>a</i>) data, a proxy for phytoplankton biomass, to examine seasonal and long-term trends and their relationship to sea surface temperature(SST), mixed layer depth (MLD), wind speed, sea surface height, and stratification in the Agulhas Current system between 1998 and 2022. Using Empirical Orthogonal Function analysis, we identified dominant spatial and temporal patterns associated with Chl-<i>a</i> variability. Notable results indicate a significant increase in Chl-<i>a</i> concentrations in the Agulhas Return Current (ARC) and Agulhas Retroflection regions, with increasing trends of 26% and 15% per decade, respectively. In the ARC region, decreased SST, deepened MLD, and intensified wind speeds promoted vertical mixing and nutrient entrainment, supporting increased Chl-<i>a</i> levels. This effect is largely driven by the Southern Annular Mode (SAM), which enhances westerly winds, promoting these physical changes. In contrast, the influence of SAM in the Agulhas Retroflection zone is moderated by the stabilizing presence of Indian Ocean waters. These results highlight the complex interaction between local physical processes and broader climatic variability in driving phytoplankton dynamics in the Agulhas region.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085468","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":"Seasonal Variations in Coral Lipids and Their Significance for Energy Maintenance in the South China Sea","authors":"Shendong Xu,&nbsp;Hongyan Mo,&nbsp;Kefu Yu,&nbsp;Jie Gao,&nbsp;Zheng Men","doi":"10.1029/2024JC021890","DOIUrl":"https://doi.org/10.1029/2024JC021890","url":null,"abstract":"<p>The degradation of coral reef ecosystems caused by coral bleaching has been increasing in recent years. Coral bleaching implies a decrease in the symbiodinianceae, such as endosymbiotic zooxanthellae, which in turn affects the energy supplied to coral hosts. However, as an alternative energy source, the energy supply mechanism of lipids during seasonal changes in zooxanthellae density (ZD) was not well explored and validated. In this study, 66 coral samples of <i>Acropora millepora</i> and <i>Pocillopora damicornis</i> were collected in March, June and October 2020 in Xisha Islands in the South China Sea. The response of lipids to the seasonal variations of ZD and photosynthetic rate was explored by combining physiological parameters (ZD) with geochemical indicators (δ¹³C of zooxanthellae δ¹³C_z, host tissues δ¹³C_h and total lipids δ¹³C_TL). The ZD and δ¹³C_z of <i>Acropora millepora</i> and <i>Pocillopora damicornis</i> (ZD: 28.7% and 28.8%; δ¹³C_z: 0.47 and 0.57‰ respectively) decreased in summer compared to that in spring indicate a decrease in photosynthetic rate of zooxanthellae. Correspondingly, δ¹³C_h decreased by 0.50 and 0.61‰, lipid content decreased by 60.82% and 53.56%, δ¹³C_TL decreased by 2.1 and 2.07‰ respectively. This means that corals can maintain stable energy supply by increasing heterotrophic predation and consuming more lipid when autotrophic photosynthesis decreases in summer. We emphasize that the level of lipid reserves may be an important factor affecting the resistance to environmental stress. Coral species with higher lipid reserves could have a selective advantage and higher resistance to bleaching.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085206","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":"Global Distribution and Seasonal Variations of Charney-Type Submesoscale Baroclinic Instabilities (C-SBCIs)","authors":"L. Feng,&nbsp;C. Liu,&nbsp;J. C. McWilliams,&nbsp;F. Wang","doi":"10.1029/2024JC022103","DOIUrl":"https://doi.org/10.1029/2024JC022103","url":null,"abstract":"<p>Previous studies primarily focused on the upper-ocean submesoscale baroclinic instabilities (SBCIs) influenced by mesoscale eddies. However, both idealized simulations and observations suggest that the mean ocean state may also play an important role in the generation of SBCIs. In this study, we investigate the Charney-type SBCIs (C-SBCIs) using seasonal climatological data, excluding mesoscale eddies, to offer a new perspective on the upper-ocean SBCIs. The C-SBCIs, characterized by surface-intensified and depth-decaying amplitudes, are generated by the opposite-sign quasi-geostrophic potential vorticity gradient at the surface and in the interior. The growth rates of C-SBCIs exhibit a geographic distribution, with substantial enhancement in western boundary currents and a remarkable seasonal variation, being larger in winter than in summer. The horizontal wavelengths of C-SBCIs decrease with increasing latitude, ranging from 2 km poleward of 60<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math>N/S to 30 km equatorward of 10<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math>N/S, and display a pronounced seasonal variation, being longer in winter than in summer. The vertical scale of C-SBCIs, termed the Charney depth, is first identified as the depth range of the potential vorticity gradient necessary for the C-SBCIs. Although the C-SBCIs resemble mixed layer (ML) instabilities in terms of growth rates and horizontal wavelengths, they differ in vertical scales with approximately a 0.2 probability of C-SBCIs extending below the ML depth. These deep-reaching C-SBCIs are caused by strong stratification and strong vertical velocity shear and may account for observed enhanced vertical buoyancy fluxes below the ML.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085207","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":"Disentangling Advection and Lagrangian Evolution of Surface Chlorophyll in a Nearshore Submarine Canyon Using Satellite Remote Sensing and High-Frequency Radar","authors":"Darren C. McKee,&nbsp;Jacquelyn M. Veatch,&nbsp;Maria T. Kavanaugh,&nbsp;Josh T. Kohut,&nbsp;Scott C. Doney","doi":"10.1029/2024JC022101","DOIUrl":"https://doi.org/10.1029/2024JC022101","url":null,"abstract":"<p>Palmer Deep submarine canyon on the western Antarctic Peninsula hosts permanent penguin breeding rookeries and is characterized by elevated chlorophyll-a compared to the surrounding continental shelf. Particle residence times within the canyon are shorter than phytoplankton doubling times, which points to the ecosystem's productivity being tied primarily to advection of externally generated biomass into the canyon. This view is supported by recent observational studies showing alignment of attractive flow structures with phytoplankton patches. While residence times are short, they vary in space and are longer than the timescale for submesoscale instabilities with strong vertical motions (an inertial period), allowing for biological sources to be regionally or episodically important. Here we use measurements of ocean surface velocities (from high-frequency radars) and chlorophyll (from satellites) to calculate the Eulerian, Lagrangian, and horizontal advection terms of the surface chlorophyll budget. The Lagrangian term (including biological sources) is generally comparable in magnitude to advection, but the latter is more important on the canyon's western flank. We then compare joint distributions of relative vorticity and strain conditioned on a particle's net chlorophyll change. In general, parcels experiencing a net increase (decrease) in chlorophyll experience greater cyclonic (anticyclonic) vorticity. Although high-vorticity features significantly influence parcel motion, trajectories generally align with an estimate of the balanced flow, which is often characterized by a cyclone over the central canyon and eastern flank. Without subsurface data we cannot confirm whether the Lagrangian change truly indicates biological accumulation but we offer some interpretations.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC022101","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085472","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":"Sheltering of Sea Ice Ridges in the Ice-Ocean Drag Force: Implications From Idealized Laboratory Experiments","authors":"S. Wang,&nbsp;P. Lu,&nbsp;M. Leppäranta,&nbsp;Y. Zu,&nbsp;Q. Wang,&nbsp;Z. Li,&nbsp;P. Hao","doi":"10.1029/2024JC020884","DOIUrl":"https://doi.org/10.1029/2024JC020884","url":null,"abstract":"<p>Sea ice ridge keels enhance the turbulent mixing beneath ice and the ice-ocean drag coefficient. However, densely distributed keels suppress drag through the sheltering effect, which has not been specifically examined. To this end, we investigated whether and how this sheltering should be incorporated into form drag parameterization for sea ice-ocean momentum exchange. Through conducted water tank experiments, the form drag on artificial keels with varying shapes was measured at different flow velocities. Particle image velocimetry was employed to capture the wake characteristics and vertical mixing induced by keel-flow interactions. Sheltering reduced the downstream keel drag, which reversed at dimensionless spacing <i>L</i>/<i>H</i> (keel spacing-to-depth ratio) less than 5. Sheltering decreased exponentially with <i>L</i>/<i>H</i> and increased following a power law with the keel slope angle, independent of the flow velocity. We propose a new sheltering function that incorporates the effects of these keel properties, fitting observational data. It affects the ice-ocean drag coefficient in a nonmonotonic way, arising from the competition between the keel form drag and sheltering. Compared with this function, the previous <i>L</i>/<i>H</i>-dependent exponential/power sheltering functions overestimated/underestimated the drag coefficient by 33%/17%, respectively, for <i>L/H</i> &lt; 100 with an angle less than 50°. We present findings from nonstratified flows with a dimensionless water depth-to-keel depth ratio (<i>D</i>/<i>H</i>) ranging from 3.75 to 22.50. Therefore, our results are not applicable to large parts of the polar oceans where <i>D</i> ≫ <i>H</i>. However, our findings provide fundamental insights into the shallow limit case, serving as a benchmark for ice-ocean momentum flux parameterizations.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085469","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":"Semidiurnal Inner Shelf Flow in the Southern California Bight","authors":"K. Okun,&nbsp;A. Desai,&nbsp;P. E. Parnell,&nbsp;E. Masunaga,&nbsp;A. J. Lucas,&nbsp;J. Lerczak,&nbsp;G. Pawlak","doi":"10.1029/2024JC021591","DOIUrl":"https://doi.org/10.1029/2024JC021591","url":null,"abstract":"<p>Semidiurnal variability of alongshore currents on the inner shelf of the Southern California Bight is investigated using a 7-year velocity and pressure time series. Analysis reveals that the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${M}_{2}$</annotation>\u0000 </semantics></math>-frequency alongshore current varies significantly over spatial scales of O(10 km), inconsistent with the expected progressive surface tide. Instead, the observed variability is attributed to the influence of a northward-propagating, superinertial baroclinic coastal trapped wave (CTW) that generates a quasi-barotropic flow, defined as the portion of the depth-averaged alongshore current that is not directly driven by the surface tide. A superinertial CTW model, forced by realistic bathymetry and stratification conditions, suggests that the dominant mode of variability is likely a mode-1 CTW with a wavelength of approximately 40 km. The observations and model also reveal that seasonal changes in stratification modulate the wavelength and phase speed of the CTW, leading to a seasonal pattern in the phasing of the quasi-barotropic alongshore flow. These findings provide a new perspective on the complex dynamics governing semidiurnal variability of alongshore currents on the inner shelf of the Southern California Bight and highlight the importance of considering the effects of superinertial CTWs when examining coastal dynamics.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021591","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144085470","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":"Heterogeneous Mixing Processes Observed in the Dotson Ice Shelf Outflow, Antarctica","authors":"Tiago S. Dotto,&nbsp;Peter M. F. Sheehan,&nbsp;Yixi Zheng,&nbsp;Rob A. Hall,&nbsp;Gillian M. Damerell,&nbsp;Karen J. Heywood","doi":"10.1029/2024JC022051","DOIUrl":"https://doi.org/10.1029/2024JC022051","url":null,"abstract":"<p>We present the first observations of ocean turbulent mixing rate in front of the Dotson Ice Shelf, where meltwater-enriched water leaves the cavity. The observations showed elevated turbulent kinetic energy dissipation rates (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>ε</mi>\u0000 </mrow>\u0000 <annotation> $varepsilon $</annotation>\u0000 </semantics></math>; ∼10⁻⁷ W kg⁻¹) and turbulent diapycnal diffusivities (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>κ</mi>\u0000 </mrow>\u0000 <annotation> $kappa $</annotation>\u0000 </semantics></math>; ∼10⁻² m² s⁻¹) near the seabed and in middepth layers, which are three orders of magnitude above background values away from the outflow. Elevated diapycnal fluxes of heat and salt were observed in regions of high mixing, moving vertically on average O ∼ 10 W m⁻² and O ∼ 10⁻⁶ kg m⁻² s⁻¹, respectively, toward shallow depths. At middepth layers, the overturning instabilities are characterized by shear-driven symmetric and centrifugal instabilities. Our observations provide an understanding of mixing in front of fast-melting ice shelves and are key to developing better parameterizations and representations of mixing in climate models.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC022051","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074552","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":"Interdisciplinary Applications for Identifying and Quantifying Modern Storm Washover Deposits on Pea Island, North Carolina, USA","authors":"Shara L. Gremillion,&nbsp;Davin J. Wallace,&nbsp;Eve R. Eisemann","doi":"10.1029/2024JC021695","DOIUrl":"https://doi.org/10.1029/2024JC021695","url":null,"abstract":"<p>Hurricanes and nor'easters annually threaten or impact the North Carolina (NC) Outer Banks, generating significant destruction to infrastructure, habitat, and life, while costing taxpayers thousands to billions of dollars. The geologic record (i.e., washover deposits) of these storms can be used to better understand past frequency and magnitudes, and aid in resource cost estimations for post-storm recoveries and clean-ups. Therefore, understanding washover rates and their influences on barrier island evolution is of critical importance. To identify and map recent storm washover deposition on Pea Island (PI), NC, for the period of 2003–2019, meteorological records, aerial photographs, lidar digital elevation models, ground penetrating radar (GPR) data, and sediment from trenches and cores were collected and analyzed. Hurricanes Isabel (2003), Irene (2011), and Sandy (2012), and three nor'easters (2006, 2009, and 2018) impacted PI during the study period, yielding washover deposits to the backbarrier. To quantify the storms' washover sedimentology and annual sand deposition rates, radiocarbon ages, washover thicknesses, and volumes were utilized on three distinct PI washover fans. These six storms yielded ∼9 × 10⁴ m³ of total washover in the study areas combined, with Isabel contributing 38.4%, Sandy contributing 35.8%, and the remaining storms contributing 25.8%. The washover deposition rate was at least ∼5.6 × 10³ m³/yr for the study period, an increase of 40% over the previous period of 1996–1999 at two comparative sites. This research highlights PI's vulnerability to repeated future storm impacts and provides stakeholders with quantifiable data with which to allocate future post-storm resources.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143949821","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":"Seasonal Salinification of the US Northeast Continental Shelf Cold Pool Driven by Imbalance Between Cross-Shelf Fluxes and Vertical Mixing","authors":"Lukas L. Taenzer,&nbsp;Ke Chen,&nbsp;Albert J. Plueddemann,&nbsp;Glen G. Gawarkiewicz","doi":"10.1029/2024JC021270","DOIUrl":"https://doi.org/10.1029/2024JC021270","url":null,"abstract":"<p>The US Northeast continental shelf “cold pool” comprises winter-cooled Shelf Water that is trapped below the warm surface layer during the stratified season. The regional ecosystem relies on the preservation of winter temperatures within the cold pool throughout the year. Here, we present first evidence of a significant increase in the cold pool's salt content on the US Northeast continental shelf throughout the stratified season, suggesting that shelfbreak exchange contributes strongly to the seasonal erosion of the cold pool. Cold pool salinification rates of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>0.18</mn>\u0000 <mspace></mspace>\u0000 <mtext>PSU/month</mtext>\u0000 </mrow>\u0000 <annotation> $0.18,text{PSU/month}$</annotation>\u0000 </semantics></math> remain steady throughout the stratified season, leading to salinity differences of over <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>1</mn>\u0000 <mspace></mspace>\u0000 <mtext>PSU</mtext>\u0000 </mrow>\u0000 <annotation> $1,text{PSU}$</annotation>\u0000 </semantics></math> between April and October. A cold-pool salinity budget reveals that the observed salinification is caused by an imbalance between cross-shelf salt fluxes, which deposit salt into the cold pool at all times of year, and the strong seasonal cycle of vertical mixing. During the stratified season, vertical mixing is inhibited and no longer counteracts the cross-shelf flux, leading to net salinification of the cold pool over the summer. Along-shelf freshwater advection from upstream is only present in the fall and contributes some additional freshening to shut down the salinification trend. Seasonal variability in the position of the US Northeast shelfbreak front is too small and out of phase to contribute to the salinity increase. The strong relationship between the seasonal cycle of cold pool modification and seasonal stratification points toward the importance of the timing of spring re- and fall de-stratification on near-bottom continental shelf temperature and salinity.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JC021270","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143949825","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}