Maximum Sea Surface Temperature Research Articles

Functional traits of ecosystem engineers as predictors of associated fauna

The ongoing combination of global warming and increased anthropogenic pressure is causing latitudinal shifts in marine species, potentially impacting community composition, local richness, and marine trophic webs. This study investigates the factors influencing the distribution and diversity of intertidal seaweed and associated peracarid communities, including their functional traits, and explores various facets of beta diversity (taxonomic and functional). We hypothesize that: 1) abiotic factors such as temperature and anthropogenic pressure significantly influence seaweed distribution and diversity shifts, and 2) changes in seaweed functional diversity have an impact on the diversity and functioning of its associated peracarid communities. The sampling was conducted along a wide latitudinal gradient in the NE Atlantic (27°N - 65°N), encompassing three distinct ecoregions: Northern European coasts, the Iberian Peninsula, and Macaronesia. The identified seaweed and peracarid species were classified functionally, and taxonomic and functional diversity were analysed on a large geographic scale. The northern region exhibited large brown canopy seaweeds and epibiotic isopods, while Macaronesia featured small red, highly branched, and calcareous crust seaweeds with burrower and tube-building tanaids. The Iberian Peninsula acted as a transitional zone, showcasing a mix of green, red, and brown seaweeds, along with Amphipoda peracarids found across all ecoregions. Our findings underscore the impact of geographic distance on total beta diversity, revealing distinct seaweed and peracarid communities across spatial gradients. Environmental variables, particularly pH and maximum sea surface temperature, emerged as significant factors influencing beta diversity patterns of seaweeds, indicating the potential impact of acidification and heat waves on community composition. In addition, seaweed functional traits were shown to be significant in shaping the diversity and abundance of associated peracarid assemblages, impacting both taxonomic and functional beta diversity. These findings provide crucial insights into the factors influencing the biogeography and biodiversity dynamics of intertidal seaweeds and associated peracarids, offering essential implications for conservation and management strategies amid ongoing environmental changes.

Oceanic response to tropical cyclone in the northern South China Sea observed by underwater gliders during 2018 and 2020

In this study, we mainly used in-situ observations from underwater gliders to analyze the ocean response in the northern South China Sea affected by Son-tinh (2018), Mandal et al. (2018) Mangkhut (2018)and Noul (2020). The results showed that these TCs caused 0.6 °C, 1.1 °C and 1.7 °C maximum sea surface temperature cooling respectively, which were weaker than general conditions because of long distance, weak intensity and fast movement speed. Net solar radiation, precipitation, 10-m wind and sea surface heat flux also made contribution in changes of SST. The mixed layer depth (MLD) became shallower after Son-Tinh and Noul passed through, while during Mangkhut it did not change significantly. After TCs passed through, the stratification around MLD became more obvious, with a banded distribution and stronger high-value areas of buoyancy frequency. Within 1 week after the shortest distance, the temperature and salinity responses in the upper ocean were stronger than those at the sea surface, and the gradients of temperature and salinity and their anomalies were more evident in the subsurface layer. The results of this study show that underwater glider observations are important for understanding oceanic responses to tropical cyclones and are useful for studying tropical cyclone activities.

Contribution of El Niño Southern Oscillation (ENSO) Diversity to Low‐Frequency Changes in ENSO Variance

AbstractEl Niño Southern Oscillation (ENSO) diversity is characterized based on the longitudinal location of maximum sea surface temperature anomalies (SSTA) and amplitude in the tropical Pacific, as Central Pacific events are typically weaker than Eastern Pacific events. SSTA pattern and intensity undergo low‐frequency modulations, affecting ENSO prediction skill and remote impacts, and resulting in low‐frequency changes in ENSO variance. Yet, how different ENSO types contribute to these decadal variance changes remains unclear. Here, we decompose the low‐frequency changes of ENSO variance into contributions from ENSO diversity categories. We propose a fuzzy clustering of monthly SSTA to allow for non‐binary event category memberships, where each event can belong to different clusters. Our approach identifies two La Niña and three El Niño categories and shows that the major shift of ENSO variance in the mid‐1970s was associated with an increasing likelihood of strong La Niña and extreme El Niño events.

Genetic-environment associations explain genetic differentiation and variation between western and eastern North Pacific rhinoceros auklet (Cerorhinca monocerata) breeding colonies.

Animals are strongly connected to the environments they live in and may become adapted to local environments. Examining genetic-environment associations of key indicator species, like seabirds, provides greater insights into the forces that drive evolution in marine systems. Here we examined a RADseq dataset of 19,213 SNPs for 99 rhinoceros auklets (Cerorhinca monocerata) from five western Pacific and 10 eastern Pacific breeding colonies. We used partial redundancy analyses to identify candidate adaptive loci and to quantify the effects of environmental variation on population genetic structure. We identified 262 candidate adaptive loci, which accounted for 3.0% of the observed genetic variation among western Pacific and eastern Pacific breeding colonies. Genetic variation was more strongly associated with pH and maximum current velocity, than maximum sea surface temperature. Genetic-environment associations explain genetic differences between western and eastern Pacific populations; however, genetic variation within the western and eastern Pacific Ocean populations appears to follow a pattern of isolation-by-distance. This study represents a first to quantify the relationship between environmental and genetic variation for this widely distributed marine species and provides greater insights into the evolutionary forces that act on marine species.

Different mechanisms for enhanced ocean response and feedback during sequential super typhoons

Relative to a single typhoon, the ocean response and feedback mechanisms during sequential super typhoon process have yet to be fully understood. The upper ocean responses to super typhoons Trami and Kong-Rey that occurred sequentially in autumn 2018 over the northwestern Pacific (NWP) Ocean were investigated using multi satellite and Argo float data. As a slow-moving typhoon, the location of maximum sea surface temperature (SST) cooling induced by Trami was determined by the typhoon's translation speed and the preexisting cyclonic eddy (CE). The most significant SST cooling was observed near the abrupt turning point, where Trami nearly stalled over the ocean, rather than in the CE region, although the CE could enhance the SST cooling. For the subsequent, fast-moving typhoon Kong-Rey, the most significant SST cooling was observed in the CE region. Two different mechanisms (i.e., slow translation and cyclonic eddy) for the enhancement of SST cooling, salinity and chlorophyll-a were also compared. For salinity and chlorophyll-a concentration, slow translation speed plays a more important role than the preexisting cold eddy. Additionally, both typhoons experienced rapid weakening, suggesting that typhoon-induced negative feedback affects not only the intensification of the typhoon itself but also the subsequent typhoon. An analysis of data from Argo floats demonstrated that weak mixing and upwelling contributed to a three-layer structure in the upper ocean temperature on the left side of the typhoon track; strong upwelling played a more important role in the cooling of the whole upper ocean near the typhoon track center; and strong vertical mixing was the dominant factor for the two-layer temperature structure on the right side.

Asian monsoonal temperature and environmental changes since the penultimate deglaciation as revealed by alkenones and alkanes in sediments from the northern South China Sea

A new alkenone sea surface temperature (SST) record from the South China Sea (SCS) over the last 170 ka has been reported here. Our analysis of magnetic susceptibility and AMS 14C dating on the top portion of the core suggests that this record dates to the Marine Isotope Stage (MIS) 6. As indicated in Termination I and II, SST changes are correlated with clear glacial/interglacial cycles and likely dominated by atmospheric CO2 and Western Pacific Warm Pool temperature changes. But the two Terminations were different in magnitude. In Termination I, the minimum and maximum SSTs are 24.5 °C and 27.5 °C, respectively, showing a smaller rise (3 °C) than in Termination II (24–28.3 °C). The n-alkane indices, such as average chain length (ACL) and carbon preference index (CPI), exhibited high/low values during glacial/interglacial periods, and possible more arid climate during MIS 6 than MIS 2. During Termination II, the maximum surface warming in the SCS is accompanied by a progressive lag of approximately 7000 years in relation to maximum summer insolation until Termination I, when they are nearly synchronous. According to the study, SSTs are continuously changing and are influenced by solar insolation, global ice volume changes, and ocean–atmosphere interactions across hemispheres.

Spatial and temporal pattern of thermal front in Republic of Indonesia fisheries management area 571 (FMA 571)

Abstract The spatial pattern of thermal front were obtained by processing sea surface temperature (SST) data using the SIED (Single Image Edge Detection) method. The objective of this research is to establish the characteristics of the surface thermal front in the Republic of Indonesia Fisheries Management Area (FMA) 571 based on its spatial and temporal map in the year of 2010-2020. SST & chlorophyll-a of AquaMODIS satellite imagery and FMA 571 bathymetry of the Indonesian Geospatial Information Agency data are used in this research. This research results that the maximum & the minimum average thermal front are found in the southwest monsoon and the first inter-monsoon with values of 135 and 39 events, respectively. The maximum (minimum) SST average is 32.182°C (30.483°C) and the maximum (minimum) average chlorophyll-a concentration value is 0.858 mg/l (0.577 mg/l). The optimum SST is estimated ranges of 30.483°C – 31.831°C for thermal front formation. The Pearson correlation analysis reveals a significant positive correlation coefficient of 0.674 during the northeast monsoon, highlighting the association between thermal fronts and chlorophyll-a concentration. Spatially persistent thermal front always appears in the northern part of FMA 571.

Environmentally-driven variations in reproductive traits in a sandy beach bivalve throughout its geographic range

The yellow clam Amarilladesma mactroides (Reeve, 1854) inhabits the intertidal zone of sandy beaches along the temperate Atlantic coast from Brazil to Argentina (24°-41°S). Over the past decades, there has been a noticeable decline in its abundance, underscoring the importance of understanding their reproductive strategies and phenotypic plasticity for conservation efforts. This study explored large-scale variations in the size at first sexual maturity (SL50), the age at maturity (A50), the vitellogenic oocyte area (VOA), and a reproductive age index (RAI) that combines A50 and the lifespan of each clam population, in relation to local habitat characteristics (e.g., beach morphodynamics) and large-scale environmental variables, such as salinity, sea surface temperature (SST) and chlorophyll-a. Four sandy beach clam populations from Uruguay and Argentina (latitudinal range: 33°45′S - 38°56′S) were sampled monthly between June and August during the reproductive season. SL50 increased linearly with the mean and maximum SST (SSTmean, SSTmax), while VOA and RAI decreased with tidal range and width of intertidal zone, respectively. In beaches that had higher SSTmean and SSTmax, yellow clams reached maturity earlier and spent more than 70% of their lifespan in reproduction. The yellow clam population at the lowest latitude showed the largest oocyte sizes and a shorter lifespan of 3.5 years, while the population at the highest latitude had a longer lifespan (7 years) and the smallest VOA values. Populations at intermediate latitudes showed delayed sexual maturity, a 50–60% investment of their lifespan in reproduction, the longest lifespan (up to 9 years) and intermediate VOA values. The influence of the Rio de la Plata and Bahia Blanca estuaries modified the expected latitudinal gradient in reproductive traits, but local habitat conditions prevailed over large-scale environmental variables as explanatory factors of the reproductive strategy of the yellow clam. Therefore, the species displays phenotypic plasticity in its reproductive aspects to ensure population success.

Modulating effect of the divergent and rotational wind induced by mesoscale sea surface temperature perturbations in the Kuroshio Extension

AbstractMesoscale wind stress perturbations induced by sea surface temperature (SST) perturbations have a feedback effect on the ocean by influencing air–sea heat and momentum fluxes. Unlike the thermal feedback mechanism, which is well understood, the momentum feedback still needs to be studied, especially the respective roles of divergent and rotational wind components. In this study, momentum feedback was examined using an ocean model and an empirical equation, which solved wind stress field perturbations from their divergence and curl estimated from time‐evolving downwind and crosswind SST gradients. Through several numerical experiments, it was found that both the divergent and rotational wind can induce positive and negative temperature changes at varying regions and depths. This modulating effect is weak, with a maximum SST change of about 0.4°C on average, but it can reach the deep ocean beyond 1000 m.

Tropical Warming and Intensification of the West African Monsoon During the Miocene Climatic Optimum

AbstractStudying monsoon dynamics during past warm time periods such as the Miocene Climatic Optimum (MCO; ∼16.9–14.5 Ma) could greatly aid in better projecting monsoon intensity, in the context of future greenhouse warming. However, studies on regional MCO temperature change and its effect on the monsoons during this time period are lacking. Here, we present the first high‐resolution, low‐latitude record of sea surface temperature (SST) and paleoceanographic change covering the Miocene Climatic Optimum, in the eastern equatorial Atlantic, at Ocean Drilling Program Site 959, based on TEX86 paleothermometry. SSTs were ∼1.5°C warmer at the onset of the MCO (16.9 Ma) relative to the pre‐MCO (∼18.3–17.7 Ma). This warming was accompanied by a transient increase in %total organic carbon. Prior to the MCO, sediment composition, geochemical proxy data as well as dinoflagellate cyst assemblages imply a productive surface ocean at Site 959. Immediately following the MCO onset (∼16.9–16.5 Ma), we record an intensification of the West African Monsoon (WAM) characterized by higher amplitude variability in all proxy records on precession to obliquity timescales. We interpret increased orbital‐scale SST, biogenic Ba and dinocyst assemblage variability to represent intensification of equatorial upwelling, forced by the WAM strength. Furthermore, higher SSTs during eccentricity maxima correlate to increased relative abundances of the warm and stratification‐favoring dinocyst Polysphaeridium zoharyi, during periods of low WAM intensity. Finally, while long‐term SSTs decline toward the middle Miocene, maximum SSTs and Polysphaeridium zoharyi abundances occur during MCO peak warming at ∼15.6 Ma.

Synoptic Moisture Intrusion Provided Heavy Isotope Precipitations in Inland Antarctica During the Last Glacial Maximum

AbstractStable water isotopes in inland Antarctic ice cores are powerful paleoclimate proxies; however, their relationship with dynamical atmospheric circulations remains controversial. Using a water isotope climate model (MIROC5‐iso), we assessed the influence of the Last Glacial Maximum (LGM; ∼21,000 years ago) sea surface temperatures (SST) and sea ice (SIC) on Antarctic precipitation isotopes (δ18Op) through atmospheric circulation. The results revealed that the synoptic circulation mostly maintained southward moisture transport, reaching inland Antarctica. The steepened meridional SST gradient in the mid‐latitudes increased δ18Op in inland Antarctica with the enhanced baroclinic instability and synoptic moisture transport. In contrast, expanded SIC distribution decreased δ18Op over Antarctica by enhanced preferential removal of heavy isotopes during vapor transport due to the increased transport distance and enhanced surface cooling. These findings propose to use Antarctic ice cores to describe the southern hemisphere atmospheric circulation, represented by the westerly jets, during the LGM and other past climates.

Competition between ocean thermal structure and tropical cyclone characteristics modulates ocean environmental responses in the Yellow and Bohai Seas

To study the environmental responses of tropical cyclones (TCs) in continental shelf regions, TCs passing over the Yellow Sea and Bohai Sea (YBS) during 2002–2020 were investigated, with a special focus on how competition between ocean thermal structure and TC characteristics modulates ocean surface changes. The spatial distributions of the climatic mixed layer depth (MLD), accumulated wind forcing power index (WPi), accumulated sea surface temperature (SST) changes and accumulated chlorophyll (Chl-a) changes in the YBS were calculated. The linear regressions indicate that both the TC-induced SST cooling and TC-induced Chl-a increase are correlated with the TC wind speed rather than the translation speed, especially when the TC forcing depth (Zmixing) is greater than the MLD. Otherwise, both the changes in SST and Chl-a are correlated with the TC translation speed when Zmixing is shallower than the MLD. Further study has shown that whether TCs can break the MLD is also a key condition for oceanic responses. In the southern YBS, which has a deep-sea basin and MLD, the TC wind speed is the major factor affecting SST cooling and Chl-a increase, as TCs need more strength to reach the MLD. However, in the northern YBS, which has the shallowest sea basin and MLD, even weak TCs can easily break the MLD and reach the seabed; thus, ocean surface changes are associated mainly with the TC translation speed. The composite results reveal that both the maximum SST cooling center (1.64 °C) and the maximum Chl-a increasing center (0.14 log10(mg/m3)) are located on the right and behind the TC center, respectively. In addition, TC-induced SST cooling and Chl-a increase were initiated two days prior to TC passage and then reached their maximum values after 1 day. It takes approximately 7–8 days for the Chl-a concentration to recover, but it takes a much longer time (>15 days) for the SST to recover.

Variable Rainfall over Steady SST: The Effect of the Free Troposphere on Surface Pressure in the East Pacific

Abstract Surface winds and precipitation over the tropical oceans are related to sea surface temperature (SST) through multiple mechanisms. Greater SST is associated with greater conditional instability, which in turn is more conducive to deep convection. The associated mass and flow responses can extend to the surface, via associated pressure gradients imprinted on the top of the planetary boundary layer (PBL). SST also influences surface pressure and wind directly through its control over PBL temperature, as explained by Lindzen and Nigam. The authors examine the relative magnitudes of these two influences over the eastern tropical Pacific on subseasonal precipitation variability during northern summer, when and where SST gradients are largest and the direct influence via PBL temperature is expected to be strongest. Geopotential at 1000 hPa is partitioned into two components: the geopotential at the PBL top (the PBL top is chosen to be 850 hPa, supported by an analysis of the vertical structure of geopotential and temperature) and the PBL thickness. These fields are composited on quintiles of daily ITCZ precipitation both with and without a high-pass filter that isolates subseasonal time scales. The PBL thickness varies little between the highest and lowest precipitation quintiles, while the PBL top geopotential varies much more. This supports a view in which the direct contribution of SST to the surface pressure and flow fields, including the associated PBL convergence over sharp SST maxima, can be viewed as a steady forcing on the rest of the column, while free-tropospheric transients contribute most of the variability associated with precipitation on subseasonal time scales.

Porcelaneous larger foraminiferal responses to Oligocene–Miocene global changes

Sea surface temperatures (SST) have been identified as a main controlling factor on larger benthic foraminifera (LBF) living in tropical to sub-tropical shallow-water carbonate and mixed siliciclastic‑carbonate platforms. Changes in SST, along with those in ocean acidification and nutrient content recorded in the global oceans throughout their history will not only continue but also be amplified in the future at an unprecedented rate of change possibly reaching levels found in the geological record. This study focuses on the Oligocene (mean SST 8 °C higher than present) and the Miocene (SST 5–8 °C higher than present) epochs which were characterized by a higher richness in porcelaneous LBF (pLBF) than today. A systematic re-assessment and comprehensive literature survey of stratigraphic ranges and palaeogeographic distribution in the Western Tethyan (Mediterranean) and Indo-Pacific regions are used to evaluate the impact of changes in SST, seawater pCO2 and pH on the biodiversity of the Oligocene–Miocene pLBF Alveolinella, Austrotrillina, Borelis, Bullalveolina, Flosculinella, and Praebullalveolina. Two peaks in species richness were identified during the Aquitanian and Langhian–Serravallian. These peaks occurred when SST was ∼29 °C, with pCO2 of ∼400 ppm and pH > 7.8. These values are comparable to those of today. The minima in species richness recorded in the Rupelian–early Chattian, in the Burdigalian and from the Tortonian onward can be correlated to the detrimental effects of both minimum (< 26 °C) and maximum (> 31 °C) SST thresholds. High pCO2 (> 600 ppm) values, which are limited to the Rupelian–early Chattian, are also detrimental to species richness. Seawater pH higher than 7.7 did not negatively affect species richness. These historical trends have serious implications for the future diversity of pLBFs with the increasing likely scenario of rising SST and pCO2 and lowering of pH values in the near future. These developments can potentially lead to diversity decrease and even extinction of pLBFs. However, the resilience of present-day pLBF species to rising SST and pCO2 levels is underpinned by the evolutionary histories of their fossil counterparts during climate variations, albeit at much different rates of change.

Sclerochronological characteristics of Orbicella faveolata in Cayo Arenas, a remote coral reef from the Gulf of Mexico.

During coral calcification in massive scleractinian corals, a double annual banding of different densities (high- and low-density) is formed in their skeletons, which can provide a retrospective record of growth and the influence of environmental conditions on the coral's lifespan. Evidence indicates that during the last decades, the reduction in coral calcification rate is attributed to the combination of global stress factors such as Sea Surface Temperature (SST) and local anthropic stressors. Yet, coral growth trajectories can vary between regions and coral species, where remote locations of coral reefs can act as natural laboratories, as they are far from the harmful effects of direct anthropogenic stressors. The present study reports historical chronology over a 24-year period (1992-2016) of coral extension rate (cm yr-1), skeletal density (g cm-3), and calcification rate (g cm-2 yr-1) of the reef-building coral Orbicella faveolata at the remote reef Cayo Arenas, Campeche Bank, in the south-eastern Gulf of Mexico. The relationships between the three sclerochronological features show that O. faveolata uses its calcification resources to build denser skeletons. Chronological trends indicate that coral extension increased, skeletal density and calcification rate decreased (33% calcification rate) over time. The results reveal that despite the remoteness of the locality the maximum SST has been increased, and the coral calcification rate decreased over time. If the temperature continues to rise, there is a conceivable risk of experiencing a decline in reef-building coral species. This scenario, in turn, could pose a significant threat, endangering not only the framework of coral reefs but also their ecological functionality, even within remote Atlantic reef ecosystems.

Massive SST-front anomaly in the tip of Sumatra waters triggered by extreme positive IOD 2019 event

ABSTRACT Western Sumatra typically accepts intense radiation throughout the year, affecting the alteration of sea surface temperature (SST) in the area. This study examines a widespread SST-front in the northeastern Tropical Indian Ocean (NETIO) which is not an essential area of the anomalies that was not predicted by previous studies. The data processing method is based on a remote-sensing approach with SST-front analysis utilizing gradient magnitude (GM). This study reveals the anomaly finding and its mechanism as the impact of extreme positive IOD (IODp) 2019 event modulating the strong ocean–atmosphere interactions in late 2019 to early 2020. However, similar massive phenomena were not found during IODp 2006 or 2015 events. The tip of Sumatra waters showed a high value of GM with more than 0.2°C km−1 in the wide area and well-shaped lengthened towards the Indian Ocean. It has corresponded to cold fronts with minimum SST around 26.0°C and maximum SST reaching 30.0°C, respectively. Cooler SST is associated with an upwelling process that is influenced by reflective upwelling Rossby waves with the speed of 0.24 m s−1, anticyclonic circulation in the Andaman Sea, and strong northeast monsoonal wind with a speed of around 8.0 m s−1 forming a divergent area at NETIO. The correlation of wind component with SST-front is about −0.56(−0.71) for u(v) component. Meanwhile, warmer SST was generated by the local-monsoon shift in influencing the downwelling of the southeast Tropical Indian Ocean (SETIO) by the end of the IODp event. This upwelling–downwelling process is also illustrated by the contrasting sea surface height, which differs by about 0.3 m. It is highlighted that the strong upwelling (NETIO) as the result of the end of extreme IODp 2019 event and downwelling (SETIO) caused an abrupt alteration of water mass in the tip of Sumatra, leading to a massive SST-front.

Northward range expansions are not the full story: A case study of Sabellaria alveolata in Great Britain

Warming oceans are causing changes in the distribution of numerous species. If greenhouse gas production continues to follow current trends, further distribution changes will result. It is often assumed that range shifts into higher latitudes may mitigate threats to susceptible species. Sabellaria alveolata is an important intertidal ecosystem engineer and protected by the UK Biodiversity Action Plan. In this study we created a habitat suitability model for S. alveolata around Great Britain and quantified changes in coastal suitability with increasing sea surface temperatures (SST) using Representative Concentration Pathway (RCP) scenarios modelled by the International Panel on Climate Change. The model included maximum and minimum SST, substrate, slope, kinetic energy due to waves and currents, photosynthetically active radiation, and the coefficient of light attenuation. The model performed very well (AUC = 0.932, 50.2% of deviance explained) and all variables explaining comparable deviance (up to 10%). Recent SST was then combined with predicted SST increases, leading to suitable habitat locations expanding across the southern and western GB coastlines and resulting in larger patches, hence potential for connectivity. Some northern extension was observed; however, this was limited and patchy. The greatest extensions were seen on the south coast, with most of the south coast becoming a continuous network with excellent suitability. With an increase of 1.2 °C, the extent of coast in the excellent suitability class was increased by 5.75% compared to 2020, and by 38.1% with 3.2 °C. Despite the importance of winter temperature in driving S. alveolata distribution, over-riding environmental constraints prevented any major northward migration. The assertion that potential for range shifts to higher latitudes may mitigate the effects of climate change depends on niche availability which may not always be realised.

ENSO effects in the southern Gulf of California estimated from satellite data

This study assessed the impact of ENSO events in the seasonal and interannual variability of the sea surface temperature (SST) and phytoplankton biomass (expressed as chlorophyll-a, Chl-a levels) obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products from June 2002 to December 2018, in two contrasting regions of the southern Gulf of California, the connection between the gulf and the Pacific Ocean, and the coastal region off Mazatlán. The generated dataset was compared with the El Niño–Southern Oscillation (ENSO) indices and a local wind-derived coastal upwelling index (CUI) computed in the coastal region off Mazatlán from the ERA5 monthly average wind. In this region, the results showed that the prevailing northwesterly winds reached 4 m s−1; however, southwesterly winds were observed during summer, mainly from June to August. The CUI showed values of up to 35 m3 s−1 per 100 m of coastline. The prevailing winds induce upwelling most of the year, with peaks in winter more intense during La Niña than during the El Niño event. Regarding SST and Chl-a levels, changes were observed with clear seasonal, semiannual, annual, and interannual variability, with 2.8 and 3.7 years of periodicities. In the coastal zone, seasonal values were maximum SST values (30–31 °C) during the summer and minimum values (20–22 °C) during the winter. The Chl-a levels showed an inverse trend, with minimum values (0.1–1.00 mg m−3) during summer and maximum values (>2 mg m−3) during winter. In the P1 site, in the connection between the gulf and the Pacific Ocean, the results showed during summer maximum SST values (29.5–31 °C) and minimum Chl-a (<0.2 mg m−3), while during winter minimum SST values (21–23 °C) and maximum Chl-a (0.3–2.0 mg m−3). Changes were also observed in both parameters owing to El Niño (high SST, low Chl-a levels) and La Niña (low SST, high Chl-a levels) conditions, which were confirmed by spectral and wavelet analyses. During the study period, La Niña conditions occurred during 2005/2006, 2007/2008, a multiyear event in 2010/2012, and 2017/2018, while El Niño conditions occurred during 2002/2003, 2006/2007, 2009/2010, and a multiyear event 2014/2016. Regarding their frequency, La Niña event occurred twice with a frequency corresponding to two years, and El Niño had a recurrence interval of between three and four years.

The Impact of Typhoon “In-Fa” (2021) on Temperature, Salinity, and Chlorophyll-a Concentration in the Upwelling Area of Northwestern East China Sea

Severe typhoon “In-Fa” passed through the northwestern region of East China Sea (ECS) in July 2021, affecting oceanic variables such as seawater temperature, salinity, and chlorophyll-a (Chl-a) concentration over the upwelling area. In this study, we analyzed the influence of the passage of typhoon “In-Fa” on the marine environment over the Upwelling Area off the Yangtze River Estuary (UAYRE) and the Upwelling Area of Zhoushan (UAZS). The results showed a significant decrease in sea surface temperature (SST) during the “In-Fa” typhoon, with maximum SST reductions of 2.98 °C in the UAYRE and 1.46 °C in the UAZS, which showed a “right bias” (indicating a greater cooling effect on the right side of the typhoon path compared to the left side). “In-Fa” influenced the temperature and salinity structure of the study areas and deepened the mixed layer depth (MLD). The MLD varied from the shallowest values of 2.02 m (18 July) to the deepest values of 19.4 m (26 July) in the UAYRE and from 2.43 m (18 July) to 16.79 m (25 July) in the UAZS. Furthermore, “In-Fa” led to an increase in sea surface Chl-a concentration, with a maximum Chl-a concentration enhancement of 285.58% (from 20 July to 28 July) in the UAYRE and 233.33% (from 20 July to 27 July) in the UAZS. The Ekman suction effect of “In-Fa” strengthened the upwelling, facilitating the transport of deep-sea nutrients to the upper ocean and providing favorable conditions for the growth of phytoplankton, thus benefiting the reproduction and survival of zooplankton, fish, and shrimp. This study contributes to understanding the mechanisms by which typhoons impact the ocean environment in upwelling area and provides valuable insights for the sustainable development of marine fisheries resources.

Enhanced upper ocean response within a warm eddy to Typhoon Nakri (2019) during the sudden-turning stage

The passage of typhoons usually induces a pronounced upper ocean response that is not only determined by typhoon attributes but also modulated by pre-existing mesoscale eddies. Here we examined the upper ocean response to Typhoon Nakri (2019) in the South China Sea, which first passed over a cold eddy following a straight path and then made a sudden turning over a warm eddy, on the basis of satellite observations and HYbrid Coordinate Ocean Model (HYCOM) reanalysis datasets in addition with numerical experiments. Two cold and salty patches with remarkable sea surface temperature (SST) cooling and sea surface salinity (SSS) increase emerged after Typhoon Nakri's passage in the pre-existing cold-eddy and warm-eddy regions. Particularly, the maximum SST cooling and SSS increase induced by Typhoon Nakri reached 6.6 °C and 1.6 psμ in the pre-existing warm-eddy region, which were even more pronounced than those in the pre-existing cold-eddy region (6.0 °C and 1.3 psμ). Typhoon Nakri enlarged the cold eddy and weakened the warm eddy significantly, with the maximum sea surface height reduction (up to 43 cm) appearing in the pre-existing warm eddy, which even disappeared after Nakri. Furthermore, Nakri induced phytoplankton blooms with a chlorophyll-a concentration increase reaching 2 mg m−3. The subsurface temperature (salinity) was also reduced (increased) significantly in the pre-existing warm-eddy region. The more pronounced ocean response in the warm-eddy region was largely attributed to the sudden turning of Nakri's track, prolonging the forcing time of typhoon winds. By employing the three-dimensional Price–Weller–Pinkel model, the results of numerical experiments demonstrated that typhoon's track turning as well as the accompanied slow translation speed during Nakri's sudden-turning stage, played a predominate role in resulting in the remarkable SST cooling within the warm-eddy region. These results highlight the important role of sudden track turning in modulating the upper ocean response to typhoons.