Intrusion Of Masses Research Articles

Exploring near-bottom turbulent mixing across the Challenger Deep based on temperature spectral analysis

The hadal Mariana Trench remains poorly understood. In December 2016, an array of high-resolution temperature loggers, attached to the ocean bottom seismometers (OBSs), was deployed from 1665 to 7520 m for two weeks across the Challenger Deep of the Southern Mariana Trench. The temperature variance spectrum reveals that the bottom water is mildly turbulent and it is mainly modulated by the semidiurnal internal tides. At the second deepest observation station (depth of 7015 m), the viscous subrange is resolved in the high-frequency spectrum. Applying the proposed method with Taylor’s frozen field hypothesis and Kraichnan theoretical spectrum analysis, it is revealed that turbulent dissipation rate ɛ is 7.8×10−10m2/s3 and flow speed U is 8.9 mm/s. Dissipation rates ɛ of all stations vary between 5.9×10−11 and 1.4×10−9m2/s3, with the northern region of Challenger Deep experiencing stronger energy dissipation than the southern one. The vertical distribution of dissipation rate ɛ shows that it decreases with increasing depth from 1000 to 6000 m, but then increases to around 8000 m, which is consistent with previous observations and numerical simulations. The available turbulent mixing data indicates that the energy dissipation is vertically distributed in a distinct multilayer structure in the deep ocean of Challenger Deep, which is proposed to link to the intrusion of water mass in the deep Mariana trench.

Field experiment on thermocline destruction by aerator in dam reservoir (Visualization of water mass intrusion by measuring water temperature)

Field experiment on thermocline destruction by aerator in dam reservoir (Visualization of water mass intrusion by measuring water temperature)

Evolution of Different Types of Eddies Originating from Different Baroclinic Instability Types

This paper investigates the evolution of global eddies and various types of eddies originating from baroclinic instability (BCI) by utilizing satellite altimetry, Argo profiles, and climatology datasets. The structure of global eddies with regard to potential temperature anomalies experiences downward propagation and spreading from the periods of eddy growth to stabilization. However, from the eddy’s stabilization to the decay period, the process of spreading primarily occurs horizontally, and this process is usually accompanied by weakening. By comparing the evolution of eddies in three typical regions dominated by distinct types of BCI, we found that the basic properties of eddies related to different BCI types evolve similarly; however, there are notable differences in their vertical structures and evolution. Eddies associated with Phillips + Charney_s-type, Charney_s-type, and Eady-type BCIs exhibit dual-core, single-core, and dual-core structures, respectively. In particular, the intrusion of the Okhotsk cold water mass into the Northwest Pacific region forms cold-core anticyclonic eddies, resulting in AEs that are significantly distinct from the rest of the ocean. The evolution of surface-layer cores closely resembles that of the global eddies, while the decay of subsurface and bottom-layer cores is comparably sluggish. Additionally, we examine the impact of local oceanic stratification conditions on eddy decay and determine that stronger vertical gradients result in more vigorous eddy decay, accounting for the concentration of eddies at depths where vertical gradients are weaker during their evolution.

Warming waters of the Gulf of Maine: The role of Shelf, Slope and Gulf Stream Water masses

We present an analysis of a 19-year time series of mooring data (T, S,) collected since 2003 in Jordan Basin in the eastern Gulf of Maine and beginning in 2016, in situ nitrate; we also include hydrographic station data collected by NOAA’s ECOMON Program. Analyses support, in part, conclusions drawn by others that the Gulf of Maine has warmed and continues to warm as a result of long-term and shorter term air-sea heat fluxes. We show that warming is to a large extent a result of changes in advective heat fluxes via lateral exchanges with water masses in neighboring shelf and slope regions (Warm Slope Water and Scotian Shelf Water). Water properties of the source waters and their inflows to the Gulf have been shown to have been changing over time, and now reveal a mix that includes warm, salty, low nutrient Gulf Stream Water. The result is a new baseline in the Gulf of Maine, of warmer temperatures and higher salinities, which appears to have become established after 2010. Annual cycles of spring-to summer water column warming and fall-to-winter cooling and convective mixing are presented and discussed, showing that the maximum depth of convective mixing in the eastern interior Gulf of Maine does not usually exceed 150 m, a depth constrained by the presence a strong vertical density gradient created by layer of high salinity bottom waters. Approximately-six months after the annual late-summer influx to the Gulf of warm and salty water masses at depth and along the bottom, a mass of cold, low salinity Scotian Shelf Water arrives in the upper water layers in winter – these two major water mass fluxes are a half year out of phase with one another, every year. We suggest that these two water mass intrusion events are linked – that the winter-spring inflow of Scotian Shelf Water creates a barotropic pressure gradient in the Gulf that persists into the summer, thereby impeding the inflow of warm and salty Slope, and/or Gulf Stream Water, until that Scotian Shelf Water mass has become sufficiently dispersed in late summer, thereby effectively opening a valve that allows warm and salty deep waters from outside the Gulf to penetrate.

Short-term variability in plankton abundance on the inner shelf off Ubatuba, Brazil

Abstract The interaction between biological and short-term physical processes affects plankton distribution and composition variability, with consequences for the entire ecosystem. Aspects of the plankton distribution at smaller scales have been understudied, mainly in coastal regions where highly variable conditions promote variations in the biophysical environment. This work aimed to investigate the short-term variations in the distribution of plankton along the inner shelf off Ubatuba, Brazil. We quantified the abundance and diversity of the main planktonic taxa (>100 μm) and their spatiotemporal distribution in winter 2018 and summer 2019 using high-resolution sensors and a shadowgraphic imaging system at cross-shore and fixed stations (12 and 24 h). Summer–winter environmental contrast was evident in the water column stability and plankton abundance. In the summer, higher values of plankton abundance and diversity were obtained. Our results suggested that spatiotemporal variations related to wind-induced mixing and water mass intrusions lead to variabilities in plankton populations on a time scale of a few hours, vertically between depth layers and at spatial scales ˂2 km. This study contributes to the knowledge of the mechanisms of biophysical interactions and their spatiotemporal variation, which is crucial for assessing the effects of climate variability on plankton-mediated ecosystem services.

Water Mass Variations in the Maluku Channel of the Indonesian Seas During the Winter of 2018–2019

AbstractAn autonomous underwater glider was deployed in the Maluku Channel during 1 December 2018 through 21 February 2019 to measure temperature and salinity profiles of the upper ∼1,000 m continuously. The measurements suggest intraseasonal variations of the Pacific water mass intrusions into the Maluku Channel, which has not been reported before. The North Pacific Tropical and Intermediate Waters are found to intrude episodically into the eastern Maluku Channel at the depths of 130–180 m and 250–300 m, respectively, during January through February of 2019, each lasting for a few days to a week. The Antarctic Intermediate Water was present in the middle and western Maluku Channel between 600 and 800 m with intraseasonal variability. The South Pacific Subsurface Water was only found to intrude into the eastern Maluku Channel between 250 and 300 m during the first two transections in early December of 2018. Concurrent meter data from three moorings in the Maluku and Talaud‐Halmahera Channels are used to verify the water mass movement. The subsurface and intermediate water mass variations here are found to be closely related to the swing of the Mindanao Current near the Maluku Channel. These intraseasonal water mass intrusions are important aspects of water exchange between the western Pacific Ocean and the Indonesian seas.

Spatial dispersion of ichthyoplankton on Southeastern and Southern Brazilian shelves

The physical–chemical and environmental characteristics of the oceans have the greatest influence on ichthyoplankton. Possible environmental changes affect their structure, determining their abundance and distribution. In this sense, it sought to understand the larval distribution processes, which can provide better manhandling and conservation of the fishery resources of the Southern region of Brazil, from the analysis of the larvae belonging to the families Bregmacerotidae, Myctophidae, Sciaenidae, Sternoptychidae, and Trichiuridae, using the temperature, salinity, and depth variables. The data were collected in the Southeastern and Southern Continental Shelves of Brazil between 1970 and 2010 and partitioned using an agglomerative hierarchical clustering algorithm. Four groups were identified, Group I presented a heterogeneous structure and differentiated itself from the rest. It is evident that Groups I and IV predominated in the shallower water and areas closer to the coast, while Groups II and III represented deeper and further waters, within the maximum depth limit of the platforms. Trichiuridae were distributed throughout the clusters, evidencing their easy acclimation to the different temperatures and salinities found. The temperature and salinity presented a greater influence on the larval distribution for these families, corresponding to the coastal dynamics and intrusion of the different water masses over the past 40 years.

Influence of ocean dynamics on the route of argonauts in the Southeastern Brazil Bight

Argonauts (Cephalopoda: Argonautidae), also known as ‘paper nautilus’, are epipelagic octopuses that are believed inhabit the open ocean despite being rarely encountered alive. Previous studies on the early-life stages of cephalopods have reported unexpectedly high abundances of argonauts in continental shelf areas of the Southeastern Brazilian Bight (SBB). Based on this finding, we explored the potential ocean dynamics driving both seasonal and interannual argonaut paralarvae occurrence in the SBB shelf. A historical archive ofplankton samples (n = 884) collected during 22 survey cruises between 1974 and 2010 covering the northern portion of the SBB was used. Spatiotemporal analysis combining environmental variables and horizontal and vertical abundance maps indicated that high frequency of argonaut paralarvae mostly occurred during summer with a high interannual variability. Horizontal and vertical maps revealed that they were mainly transported from the open ocean into the shelf by the onshore intrusion of water masses promoted by meanders and eddies of the offshore Brazil Current. Furthermore, argonaut occurrence in the southern shelf areas was remarkably influenced by the coastal jet originating from upwelling in the northern SBB. These results suggest that argonauts may be used as indicators of mesoscale processes. The present study provides a novel hypothesis for the route of argonauts from the pelagic realm to the continental shelf.

Composite Analysis of Aerosol Direct Radiative Effects on Meteorology During Wintertime Severe Haze Events in the North China Plain

AbstractPrevious studies on the impacts of severe haze episode on meteorology were generally focused on single episodes. This study aimed to obtain the common features of the influence of aerosol direct radiative effects on meteorology during severe particulate pollution events by composite analyses on model results from the Weather Research and Forecasting Model with online chemistry. Five heavily polluted events (15–17 January 2014, 13–15 January 2015, 8–10 December 2015, 21–23 December 2015, and 29–31 December 2016) in the North China Plain (NCP, 35.4–41.2°N, 113.3–119.3°E) were selected, which were representative of the most frequently observed weather patterns for severe haze. Model results showed that aerosols in the five heavily polluted events led to strong negative changes in radiative flux of 52.1–86.7 W m−2, reductions in the 2‐m temperature by 0.28–0.97°C, and the reductions in planetary boundary layer heights by 23.1–58.5 m, when averaged over the areas with PM2.5 concentrations >150 μg m−3. The magnitudes of aerosol induced changes in the 2‐m temperature were found to be influenced not only by aerosol concentration but also by wind speed, wind direction, and the convergence or divergence of winds. High wind speed diluted the aerosol‐induced cooling, the convergence of wind limited the temperature change to local area, and the intrusion of cold air mass near the surface enhanced the aerosol‐induced cooling. In all the cases, aerosols induced an anti‐cyclone at 500 hPa around NCP and anomalous northerlies or northeasterlies at the surface in the eastern NCP.

Decadal Scale Variability of Larsen Ice Shelf Melt Captured by Antarctic Peninsula Ice Core

In this study, we used the stable water isotope record (δ18O) from an ice core drilled in Palmer Land, southern Antarctic Peninsula (AP). Utilizing δ18O we identified two climate regimes during the satellite era. During the 1979–1998 positive interdecadal Pacific oscillation (IPO) phase, a low-pressure system north of the Weddell Sea drove southeasterly winds that are associated with an increase in warm air mass intrusion onto the Larsen shelves, which melted and a decreased sea ice concentration in the Weddell Sea/increase in the Bellingshausen Sea. This climate setting is associated with anomaly low δ18O values (compared with the latter IPO period). There is significantly more melt along the northern AP ice shelf margins and on the Larsen D and southern Larsen C during the 1979–1998 IPO positive phase. The IPO positive climatic setting was coincidental with the Larsen A ice shelf collapse. In contrast, during the IPO negative phase (1999–2011), northerly winds caused a reduction in sea ice in the Bellingshausen Sea/Drake Passage region. Moreover, a Southern Ocean north of the Weddell Sea high-pressure system caused low-latitude warm humid air over the tip and east of the AP, a setting that is associated with increased northern AP snowfall, a high δ18O anomaly, and less prone to Larsen ice shelf melt.

Quantification of the Seasonal Intrusion of Water Masses and Their Impact on Nutrients in the Beibu Gulf Using Dual Water Isotopes

AbstractA new data set of seasonal stable water isotopes (δD and δ18O) and temperature‐salinity profiles was applied to improve our understanding of water mass distributions and their impact on the environment of the Beibu Gulf (BG). Our study revealed that the coastal current (CC), West‐Guangdong coastal current (WGCC), and South China Sea water (SCSW) were the three dominant water masses in the BG, and their influence was exhibited in seasonal variations. The CC was the dominant contributor to the BG water during summer (43%) and fall (45%), while it changed to the intrusion of SCSW with higher salinity in winter (57%). The contribution of WGCC to the BG was relatively stable during the three seasons (24%–31%). In addition, the nutrients in the BG were greatly affected by different water mixing occurring in the gulf. The nutrients mainly originated from the CC in summer (52%–68%) and fall (32%–69%), while the dominant source shifted to the WGCC in winter (36%–69%). Moreover, the contribution of SCSW to the nutrients loading (15%–49%) in the BG was relatively high due to its high contribution (57%) to the BG water during winter. These indicated that the BG has a stable input of external nutrients from different water masses to sustain primary production in the BG. Our study uses dual water isotopes to quantify the seasonal intrusion of water masses and their impact on nutrients, providing a new method to study the impact of the distribution of water masses on nutrients in the gulf.

Geothermal Mechanism and Reservoir Characterization with Multiscale Analysis of the Potential Field and MT Profile in the Yanqing-Huailai Basin, North China

Abstract Geothermal energy has attracted increasing attention worldwide due to its abundant reserves, stability, and sustainability. Based on the survey of geothermal resources in the Yanqing-Huailai Basin, this paper conducts comprehensive data study, demonstrates geothermal distribution and multiscale characteristics, and constructs the geothermal mechanism and conceptual model to promote regional geothermal energy development and utilization. Our study proposes to characterize geothermal reservoirs using geophysical data ranging from the representative geothermal field scale to the basin scale. Hydrochemical samples were also collected. According to the results of multiscale analysis and interpretation, combined with field geological and geothermal investigations, it is concluded that the Dahaituo pluton is composed of acid granite and monzonite granite, with low gravity and high magnetic anomaly. Its intrusion and development are responsible for the local geothermal anomaly. Multiscale analysis and source depth estimation of potential field data and MT profile interpretation were carried out. The regional thermal structure and reservoir characteristics were demonstrated from the deep to the shallow. In addition, according to the regional geological background and geophysical interpretation, a three-dimensional geological model is constructed to characterize the distribution law and genetic mechanism of geothermal anomalies. The study shows that strong Cenozoic tectonic movement and the intrusion and development of rock mass are the main factors causing local geothermal anomaly. The development of regional deep and major faults and extensional structures, as well as the channels and space formed by the breaking of rocks at the intersection of faults, provides advantageous conditions for the upwelling, migration, and convergence of geothermal fluids. The recharge of surface water in the intermountain basin and thermal convection drive the circulation of the geothermal system.

Flow-topography interactions in the western tropical Atlantic boundary off Northeast Brazil

Flow-Topography Interaction can be considered as a particular set of processes resulting of the currents interaction with a topographic gradient, specially associated with submarine canyon areas, which are important morphological features with potential to upwelling and cross-isobath transport on the continental margins. The South Pernambuco Continental Shelf (SPCS) and Pernambuco Plateau located on the Southwestern Tropical Atlantic (SWTA), present incised morphological features, highlighting the shelf valleys and blind canyons, which do not have a connection to the shelf or an onshore river system. They are likely features for interactions between the dominant along-shelf flow represented by the strong western boundary North Brazil Undercurrent. We investigated potential canyon induced upwelling and the respective mechanisms at the late spring/early fall context. CTD and reanalysis data from GLORYS12V1, and in situ bathymetric measurements were used to characterise the hydrodynamics and canyon morphology, respectively. Then, we combined both to obtain dimensionless numbers from dynamical scale analysis to infer possible imbalances of the acting forces. Reanalysis data evidenced uplift at the slope not related to the blind canyons. CTD data indicated a seasonal variation of the intrusion of water masses, especially at the shelf-break for the Middle shelf valley and Campas shelf valley. A temperature difference of 2.5 °C (2.0 °C) between surface and deep waters was observed during the late spring. A stepwise temperature structure was present in both seasons, indicating instability below the mixed layer depth, the uplifting of isotherms, and the corrosion of the lower portion of the surface mixed layer. The dimensionless parameters analysis reveals highest Rossby values during the fall, mainly in Zieta shelf valley (R0=130.87) and Csv (R0=111.71), and lower values for the canyons of the Pernambuco Plateau. Our hypothesis is that the shelf valleys might play a role in conducting the uplifted slope water coast-ward. For the blind canyons, although no related upwelling was observed, reanalysis revealed the presence of a deep anti-cyclonic eddy at one of the blind canyon's mouth. Rossby and Burger numbers indicate a weak geostrophic balance at the canyon rim, and instability of the horizontal length scale of the pressure gradient force, with tendency to vorticity control. While the paradigm that shelf and coastal waters off north-eastern Brazil are mostly oligotrophic in the surface is true, our observation of shallow (<60 m) subsurface uplift should be considered in future works in the SWTA.

Cases of mass development of intrusions in Lake Baikal and the correlation of intrusions with atmospheric circulation processes

Abstract. The cases of the development of mass intrusions in some basins of Lake Baikal were reviewed based on the measurements of water temperature and dissolved oxygen in water in 1993-2022. It was shown that in Southern, Middle and Northern Baikal during the development of intrusions in the spring-summer period, the heat deficit value was within 0.5-103.0, 3.1-15.8, 0.2-3.6 MJ/m2, dissolved oxygen amount was 0.2-161.3, 14.7-46.0, 0.6-6.3 g/m2 and the renewed bottom layer thickness was 36-318, 48-176, 38-94 m respectively. In winter in Southern Baikal, the heat deficit value varied within 0.8-5.2 MJ/m2, the amount of dissolved oxygen was 9.9-19.2 g/m2, and the thickness of the renewed bottom layer was 24-124 m. Analysis of the correlation between the heat deficit values and the circulation indices revealed that mass intrusions in Southern and Northern Baikal during the spring-summer period were associated with the prevailing meridional transport of air masses from the Eastern Atlantic and blocking zonal transport of air masses from the Atlantic and Pacific Oceans. On the contrary, in Middle Baikal, mass intrusions during the spring-summer period were developing under the conditions of zonal transport of air masses simultaneously from the Eastern Atlantic and northern and western areas of the Pacific Ocean. The development of mass intrusions in Southern Baikal in winter was related to the intensification of circumpolar circulation and zonal transport of air masses from the Atlantic Ocean.

A High‐Resolution Atlas of the Eastern Tropical Pacific Oxygen Deficient Zones

AbstractOxygen deficient zones (ODZs) are important biogeochemical provinces of the global oceans wherein standing dissolved oxygen concentrations decrease to nanomolar levels. Despite their confinement, these regions are disproportionally important to the ocean's role in modulating Earth's climate through the interactions between the marine nitrogen cycle and that of carbon. Moreover, the spatial domain of low oxygen regions of the ocean is predicted to change as a consequence of ocean warming, increased stratification, and changes in circulation and productivity. However, the expanse of the modern ODZs is poorly resolved due to a dearth of direct sampling compounded with errors that arise in the processing and gridding of the sparse measurements that do exist. Here, we take a novel approach to map the horizontal and vertical extent of the two major ODZs of the eastern tropical Pacific via analysis of meter‐scale resolution electrode sensors from both ship casts and Argo profiles, rather than from discretized bottle measurements. The resulting three‐dimensional data product is based on a compendium of nearly 15 million measurements taken across three decades and provides the precise locations of low oxygen water, elucidating the ODZs' three‐dimensional structures. It can be utilized by researchers to validate models, plan cruise occupations, and as a comparison for future change. Calculations made with this high‐resolution atlas also provide the volumes, layers of maximal areal extent, and other descriptive statistics for both Pacific ODZs. Finally, the atlas reveals fine‐scale features of oxygenated water mass intrusions and regional differences across these anoxic zones.

Analysing the Media Consumer Trends During the COVID-19 Period-The Rise of Otts in India

In the wake of an unprecedented COVID-19 widespread, there is a massive development in the media and entertainment industry through OTT (Over-the-Top) platforms which offer video streaming directly to viewers via the internet without cable, broadcast, and satellite television supports. During the self-isolation period, OTTs have increased the overall media consumption to a real high and are now gradually becoming mainstream entertainment destination amidst the growing internet users. This mass intrusion has given an opportunity for many independent platforms to grow and run alongside the likes of already established biggies, Netflix and Amazon Prime. The telecom operators chipped in this aspect and are extensively working on optimizing their operations with advertising revenue and bringing in effective content strategies in order to reach out to more people. The present study focuses on this new development by using the technique of quantitative content analysis in order to know the cause of this sudden increase in OTT channels' viewership among millennials during the lockdown period in India and its impact on traditional modes of communication.

Behaviour and distribution of arsenic in seawater and suspended particulate matter in the adjacent area of the Changjiang Estuary during summer and autumn

Water and suspended particulate matter (SPM) were collected from the Changjiang Estuary and its adjacent areas during summer (July) and autumn (October) to study the distributions and partitioning of arsenic. The dissolved arsenic (DAs) and particulate arsenic (PAs) concentration distributions were strongly affected by inputs from riverine discharge and water masses in the East China Sea, generally exhibiting a decreasing trend from inshore to offshore. The DAs concentration was higher in the surface water due to the influence of seawater stratification in summer, but it was not obvious in autumn. DAs and PAs concentrations in the estuary were significantly higher in autumn than in summer. Seasonal variations in arsenic were due to seasonal differences in riverine input (mainly the Changjiang River) and the intrusion of water masses. PAs showed a positive correlation with both SPM and turbidity. The highest PAs concentration was observed in the northern Changjiang Estuary affected by the YSCC, with higher turbidity during autumn. The higher concentration of PAs in autumn was affected by the high SPM input and resuspension of sediment. The water-particulate distribution coefficient of As in summer showed an increasing tendency with salinity, which might be caused by the decrease in the diameter of suspended particles in the open sea.

Seasonality of the Somali Current/Undercurrent system

The connected western boundary current system in the Arabian Sea plays an important role in the exchange of heat, mass, and freshwater and their distribution. Nonetheless, the dynamics and time scales of the processes and characteristics of this boundary current are not well understood because most prior measurements were only for a limited period or only resolved the surface circulation. Seasonality of the Somali Current (SC)/Undercurrent (SUC) system is investigated using a multi-decadal time series of ocean temperature and salinity profiles. The SC is driven principally by the seasonal monsoon winds, flowing southwestward in the winter monsoon (January–March), then reverses to northeastward in the summer monsoon (June–September). The subsurface southwestward SUC is found during the transition seasons in April–June and again in September–November. A vertical normal mode decomposition shows that the surface SC is mainly controlled by the seasonally varying first baroclinic mode and the barotropic component (a combined 86.5% of the total variance), while the SUC variations can be explained by the superimposition of the first and second baroclinic modes (a combined 75.9% of the total variance). Here we show that the occurrence of the countercurrent is not only due to the baroclinic adjustment caused by the wind forcing, but also a response to the complex salinity structure caused by the intrusion of high salinity water masses. Specifically, the presence of the salty water masses from the northern Arabian Sea during the boreal summer monsoon inhibits the southwestward flowing SUC and results in a baroclinic structure that supports a subsurface northeastward flow, aligned with the surface current. This suggests that salinity dynamics play a fundamental role in the circulation of the boundary current system of the Arabian Sea.

Quantifying upwelling in tropical shallow waters: A novel method using a temperature stratification index

AbstractUpwelling has profound effects on nearshore tropical ecosystems, but our ability to study these patterns and processes depends on quantifying upwelling dynamics in a repeatable and rigorous manner. Previous methods often lack the ability to identify individual cold‐pulse events within temperature time series data or require several user‐defined parameters, and therefore previous hydrographic knowledge of the study site. When unavailable, parameters are chosen arbitrarily or from previous studies potentially conducted under different environmental contexts. Previous methods also require the user to manually separate upwelling‐induced cold‐pulse events from those caused by other physical mechanisms like surface downwelling. Here, we present a novel method that uses a temperature stratification index (TSI) to detect upwelling‐induced cold‐water intrusions in tropical waters. We define a cold pulse as a continuous period having an abnormally low TSI, with this criterion based on a climatological threshold of the temperature profile at the study site calculated from the National Centers for Environmental Prediction's Global Ocean Data Assimilation System (GODAS) reanalysis product. Our TSI method is therefore automatically tuned for the study site in question, removing biases associated with user‐defined input parameters. The method also automatically determines the directional origin of the cold‐water mass to isolate upwelling‐induced cooling and can achieve overall cold‐pulse detection rates 10–14.2% higher than previous methods. Our new TSI method can easily be adapted to detect a range of physical processes in shallow waters, including intrusion of water masses through upwelling, downwelling, and horizontal advection.

Temporal Variability of Oceanic Mesoscale Events in the Gulf of California

Oceanic mesoscale events such as eddies, coastal upwelling, filaments and fronts created by water mass intrusion present properties allowing them to concentrate, transport and disperse salt, nutrients and plankton, among other important constituents in the ocean. The use of satellite images enables the continuous monitoring of the ocean dynamics at different temporal and spatial scales, aiding the study of its variability. This study focuses on the identification of these mesoscale events in the Gulf of California (GC) by means of sea surface temperature (SST) and chlorophyll a (Chl a) fronts (edge) detection by processing 5-day satellite images from the 1998–2019 period. The annual occurrence or frequency and duration of each event was identified; the interannual variability was evaluated and underlying correlations with the Multivariate El Niño Index (MEI) and the Pacific Decadal Index (PDOI) were assessed via Principal Component Analysis. Most events showed a seasonal variability due to the seasonal behavior of forcing agents (i.e., Pacific Ocean and winds) that stimulate their formation or presence in the GC; seasonality was more evident in the northern region than in the southern region. The interannual variability of their frequency or duration was associated with strong and intense El Niño and La Niña conditions (positive or negative MEI values) together with positive or negative phases of the PDOI. The use of SST and Chl a satellite images with a 5-day temporal resolution allowed to better identify and quantify the annual frequency and duration of each mesoscale event. It allowed to detect a seasonal behavior of these events in the northern region, followed by the central region. The southern region, due to the interaction of different water masses with unique characteristics, exhibited a less evident seasonality in the frequency of eddies, and no apparent association between their interannual frequency and duration with the MEI and PDOI. Constantly monitoring these oceanic events and their variability will help in the understanding of how the different regions of this large marine ecosystem respond to these variations in the long term.