Sea Surface Temperature Range Research Articles

Effect of environmental drivers on the spatiotemporal distribution of mackerel at age in the Nordic Seas during 2010−20

Abstract A joint spatio–temporal distribution model of mackerel (ages 3–10) was developed to investigate the age-based responses of mackerel to three environmental drivers: sea surface temperature (SST), mixed layer depth, and chlorophyll-a concentration during the summer months 2010–20 in the Nordic Seas. The study showed that SST was the most important variable amongst the ones tested and had the strongest impact on the distribution of the younger age classes (3–5), which had a narrower range of favourable SST and a stronger aversion to cold temperatures than older individuals. Consequently, the impact of SST differed regionally; in the polar front regions, SST explained up to 61% of the variability in the observed density of young individuals, where Arctic water masses likely acted as a barrier to these young individuals. That said, part of it could be confounded with the limited migration capability of young mackerels, which could not reach the furthest frontal regions. In warmer southern waters, the same environmental variables had less explanatory power for mackerel of all ages. Individuals in the south were likely not constrained by temperature and perhaps more influenced by other variables, such as food availability or ocean current (throughout their migration path), for which appropriate data are lacking. Moreover, the model showed that older mackerel were distributed more to the north and west, and their migration pattern changed when the 2013 year-class no longer migrated to the west compared to previous year-classes. Additionally, all-year classes started migrating more eastward from summer 2018.

Sex differences in foraging ecology of a zooplanktivorous little auk Alle alle during the pre-laying period: insights from remote sensing and animal-tracking

BackgroundEnergy and time allocation in seabirds differ between consecutive stages of breeding given various requirements of particular phases of the reproductive period. Theses allocations may also be sex-specific considering differential energetic or nutritional requirements of males and females and/or sexual segregation in foraging niches and/or areas. In this study we investigated the foraging ecology of an Arctic, zooplanktivorous seabird, the little auk Alle alle during the pre-laying period using remote sensing of the environment and GPS-TDR loggers deployed on birds. We compared foraging trips range and habitats of birds with other stages of the breeding period and between sexes.ResultsWe found that little auks during the pre-laying period foraged exclusively in cold sea surface temperature zones (with temperatures < 5 ºC) but in various sea depth zones. They dived to similar depths ranging from -4.0 to -10.9 m, exploring various thermal microhabitats (with mean temperatures values ranging from 2.2 °C in Shelf sea depth zone to 5.9 °C in Deep sea depth zone). The majority of foraging trips and dives characteristics were similar to subsequent phases of breeding. However, home ranges during the pre-laying trips were wider compared to the incubation period. As expected, females exhibited wider foraging niches compared to males (wider range of sea surface temperature and sea depth in foraging locations), which could be explained by sex specific energetic and/or nutritional requirements (females producing an egg). We also delineated local foraging areas important for little auks during their whole breeding season. Protection of these areas is crucial for sustaining the local marine biodiversity.ConclusionsWe found that little auks females during the pre-laying period explored wider foraging niches compared to males. These differences may be attributed to sex-specific nutritional or/and energetical constraints at this stage of breeding. The results of this study also emphasize the importance of shelf Arctic-type water masses as the foraging areas for little auks during successive stages of breeding.

Evaporative controls on Antarctic precipitation: an ECHAM6 model study using innovative water tracer diagnostics

Abstract. Improving our understanding of the controls on Antarctic precipitation is critical for gaining insights into past and future polar and global environmental changes. Here we develop innovative water tracing diagnostics in the atmospheric general circulation model ECHAM6. These tracers provide new detailed information on moisture source locations and properties of Antarctic precipitation. In the preindustrial simulation, annual mean Antarctic precipitation originating from the open ocean has a source latitude range of 49–35∘ S, a source sea surface temperature range of 9.8–16.3 ∘C, a source 2 m relative humidity range of 75.6 %–83.3 %, and a source 10 m wind velocity (vel10) range of 10.1 to 11.3 m s−1. These results are consistent with estimates from existing literature. Central Antarctic precipitation is sourced from more equatorward (distant) sources via elevated transport pathways compared to coastal Antarctic precipitation. This has been attributed to a moist isentropic framework; i.e. poleward vapour transport tends to follow constant equivalent potential temperature. However, we find notable deviations from this tendency especially in the lower troposphere, likely due to radiative cooling. Heavy precipitation is sourced by longer-range moisture transport: it comes from 2.9∘ (300 km, averaged over Antarctica) more equatorward (distant) sources compared to the rest of precipitation. Precipitation during negative phases of the Southern Annular Mode (SAM) also comes from more equatorward moisture sources (by 2.4∘, averaged over Antarctica) compared to precipitation during positive SAM phases, likely due to amplified planetary waves during negative SAM phases. Moreover, source vel10 of annual mean precipitation is on average 2.1 m s−1 higher than annual mean vel10 at moisture source locations from which the precipitation originates. This shows that the evaporation of moisture driving Antarctic precipitation occurs under windier conditions than average. We quantified this dynamic control of Southern Ocean surface wind on moisture availability for Antarctic precipitation. Overall, the innovative water tracing diagnostics enhance our understanding of the controlling factors of Antarctic precipitation.

The Distribution of Oceanographic Parameter Conditions in the Swordfish (Xiphias gladius) Fishing Ground in the Southern Indian Ocean off Java

The Southern Indian Ocean off Java is one of the potential locations for catching swordfish. One crucial factor in improving fishermen's productivity is the availability of information regarding the characteristics of waters related to potential fishing areas. This research aimed to determine the distribution conditions of several oceanographic parameters such as sea surface temperature, salinity, chlorophyll-a, and surface currents using remote sensing data at the swordfish (Xiphias gladius) fishing ground in the Southern Indian Ocean off Java. This research was conducted from April 27, 2022, to December 12, 2022, in the Indian Ocean. Data for several oceanographic parameters were obtained from the data.marine.copernicus.eu website from April 2022 to December 2022, and the coordinates of the swordfish (Xiphias gladius) fishing ground were obtained from KM Lulu Marina 08, which operates in WPPD 57. Data from data.marine.copernicus.eu are the result of reanalysis methods developed by the Copernicus Marine Service (CMS) using multisensor satellite images data such as MODIS-AQUA, NOAA20-VIIRS, NPP-VIIRS, and Sentinel 3A-OLCI. The spatial resolution of the data was standardized to 0.001 degrees using resampling techniques with B-Spline interpolation. The highest sea surface temperature (SST) at each fishing ground was recorded in April 2022 at the fishing ground ST 1, reaching 27.52°C. The lowest SST was observed in November 2022 at fishing ground ST 6, measuring 21.70°C. The lowest salinity values at each fishing ground were recorded in June 2022 at fishing ground ST 1, measuring 34.09 psu, while the highest salinity values were found in April 2022 at fishing ground ST 6, measuring 35.38 psu. The lowest chlorophyll-a concentration values at each fishing ground were recorded in December 2022 at fishing ground ST 6, measuring 0.062 mg/m3, while the highest concentration values were found in September 2022 at fishing ground ST 6, measuring 0.357 mg/m3. The lowest catch was recorded in September 2022, with only 2 fish caught, while the highest catch was recorded in November 2022, with a total of 42 fish caught. The optimal swordfish catch rate falls within the range of SST 23.47-24.74°C, salinity 34.45-34.78 psu, and chlorophyll-a concentration in the range of 0.079-0.124 mg/m3.

Exploring the relationship between environmental drivers and the manifestation of fibropapillomatosis in green turtles (Chelonia mydas) in eastern Brazil.

Fibropapillomatosis (FP) is a disease characterized by epithelial tumors that can impede life-sustaining activities of sea turtles, especially green turtles (Chelonia mydas). FP is caused by a herpesvirus, but environmental factors are also thought to play a role in triggering FP tumor growth. In this study, we evaluate the epidemiology of FP tumors in green turtles along the coast of Espírito Santo, Brazil, a region where juvenile green turtles are known to aggregate with high FP prevalence. A dataset comprising 2024 beach-cast green turtles recorded through daily beach surveys on 400 km of coastline from 2018 to 2021 (inclusive) was evaluated. FP tumors were recorded in 40.9% of the individuals in this dataset, and presence of FP tumors was predicted by individual variables (presence of marine leeches, stranding code, curved carapace length, body mass-size residual) and characteristics of the stranding site (distance to nearest metallurgical plant, mean sea surface salinity (SSS), annual range of sea surface temperature (SST)). Additionally, a second dataset comprising detailed information about the size and anatomical distribution of tumors in 271 green turtles with FP from the same region was evaluated. Hierarchical clustering analysis revealed these turtles could be classified in three groups according to the anatomical distribution of their tumors, and in turn the group to which each turtle was assigned could be predicted by the study period (2010-2014 vs. 2018-2022) and by characteristics of the stranding/capture site (green turtle stranding density, mean sea surface chlorophyll-a concentration, mean SSS, mean SST, annual range of SST). These results corroborate that individual and environmental factors play a significant role driving FP epidemiology. Furthermore, the results suggest that rather than behaving as a single entity, FP may be seen as a mosaic of distinct anatomical patterns that are not necessarily driven by the same environmental factors.

Applying deep learning to predict SST variation and tropical cyclone patterns that influence coral bleaching

South Penghu Marine National Park, Taiwan experienced severe coral bleaching in 2020 that may lead to coral mortality. Corals are important animals that enrich marine biodiversity, but several studies have shown that the range of sea surface temperature (SST) corals can survive is narrow, and recovery time can be as long as 10 years. The influences of climate change induced extreme weather should not be underestimated, and it is critical to accurately predict SST variations. In this study, a deep learning model, convolutional long short-term memory (ConvLSTM), which is a newer model suitable for estimating autocorrelated sequences, was built to predict daily SST for the next day, next week, and next two weeks, with the highest achieved 99.22% accuracy and a RMSE values of 0.2579. On the other hand, Penghu was not directly impacted by tropical cyclones in 2020; hence the lack of typhoon-induced SST cooling could be one of the reasons for extensive coral bleaching. The wind intensity, speed, as well as the thickness of ocean mixed layer all affect the variation of SST cooling. The results show that the degree heating weeks (DHWs) near Penghu achieved its highest level in 2020, and according to the analysis of the study, there is a clear association between climate change and coral bleaching risk increase in recent years. Therefore, we applied Random Forest to establish a machine learning model to classify whether a typhoon can trigger significant cooling. Model accuracy achieved 92.90% in the testing set, and empirical orthogonal function (EOF) analysis contributed the most to the SST cooling pattern among typhoons. This study provides a predictive contribution to global coral conservation for relevant institutions to know the risk beforehand, and they can discuss corresponding strategies and early warnings.

Interannual variations of Sargassum blooms in the Yellow Sea and East China Sea during 2017–2021

Golden tide, caused by Sargassum horneri, is becoming another periodic and trans-regional harmful macroalgal bloom in the Yellow Sea (YS) and East China Sea (ECS) other than the green tide. In this study, we employed high-resolution remote sensing, field validations, and population genetics to investigate the spatiotemporal development pattern of Sargassum blooms during the years 2017 to 2021 and explore the potential environmental factors that influence them. Sporadic floating Sargassum rafts could be detected in the middle or northern YS during autumn and the distribution area then occurred sequentially along the Chinese and/or western Korean coastlines. The floating biomass amplified significantly in early spring, reached its maximum in two to three months with an evident northward expansion, and then declined rapidly in May or June. The scale of the spring bloom was much larger than the winter one in terms of coverage, suggesting an additional local source in ECS. The blooms were mostly confined to waters with a sea surface temperature range of 10–16℃, while the drifting pathways were consistent with the prevailing wind trajectory and surface currents. The floating S. horneri populations exhibited a homogenous and conservative genetic structure among years. Our findings underscore the year-round cycle of golden tides, the impact of physical hydrological environments on the drifting and blooming of pelagic S. horneri, and provide insights for monitoring and forecasting this emerging marine ecological disaster.

Global and Regional Discrepancies between Early-Twentieth-Century Coastal Air and Sea Surface Temperature Detected by a Coupled Energy-Balance Analysis

Abstract A major uncertainty in reconstructing historical sea surface temperature (SST) before the 1990s involves correcting for systematic offsets associated with bucket and engine-room intake temperature measurements. A recent study used a linear scaling of coastal station-based air temperatures (SATs) to infer nearby SSTs, but the physics in the coupling between SATs and SSTs generally gives rise to more complex regional air–sea temperature differences. In this study, an energy-balance model (EBM) of air–sea thermal coupling is adapted for predicting near-coast SSTs from coastal SATs. The model is shown to be more skillful than linear-scaling approaches through cross-validation analyses using instrumental records after the 1960s and CMIP6 simulations between 1880 and 2020. Improved skill primarily comes from capturing features reflecting air–sea heat fluxes dominating temperature variability at high latitudes, including damping high-frequency wintertime SAT variability and reproducing the phase lag between SSTs and SATs. Inferred near-coast SSTs allow for intercalibrating coastal SAT and SST measurements at a variety of spatial scales. The 1900–40 mean offset between the latest SST estimates available from the Met Office (HadSST4) and SAT-inferred SSTs range between −1.6°C (95% confidence interval: [−1.7°, −1.4°C]) and 1.2°C ([0.8°, 1.6°C]) across 10° × 10° grids. When further averaged along the global coastline, HadSST4 is significantly colder than SAT-inferred SSTs by 0.20°C ([0.07°, 0.35°C]) over 1900–40. These results indicate that historical SATs and SSTs involve substantial inconsistencies at both regional and global scales. Major outstanding questions involve the distribution of errors between our intercalibration model and instrumental records of SAT and SST as well as the degree to which coastal intercalibrations are informative of global trends. Significance Statement To evaluate the consistency of instrumental surface temperature estimates before the 1990s, we develop a coupled energy-balance model to intercalibrate measurements of sea surface temperature (SST) and station-based air temperature (SAT) near global coasts. Our model captures geographically varying physical regimes of air–sea coupling and outperforms existing methods in inferring regional SSTs from SAT measurements. When applied to historical temperature records, the model indicates significant discrepancies between inferred and observed SSTs at both global and regional scales before the 1960s. Our findings suggest remaining data issues in historical temperature archives and opportunities for further improvements.

Horizontal distribution of chlorophyll-a and water quality on Delta Wulan Estuary, Demak Regency, Central Java, Indonesia

The overflow of water from the Wulan River has an impact on the amount of nutrients and pollutants that enter the Delta Wulan Estuary. Abundant nutrient content greatly affects the level of primary productivity, especially chlorophyll-a content. The study aimed to determine the horizontal distribution of chlorophyll-a and water quality in the Delta Wulan estuary waters. Sampling was carried out in June 2023 at 12 stations on Delta Wulan Estuary. Demak Regency. Based on the analysis results, the highest chlorophyll-a content was found at station 12 (10.59 - 12.20 mg/l). The nitrate content was found at station twelve (9.2 - 10.0 mg/l), and the highest value of phosphate content was found at stations 10 and 12, with a range of 0.22 - 0.25 mg/l. The range of sea surface temperatures ranges from 29.3–33.2°C. The salinity content value has ranged from 30.0 – 32.0 ppt. It can be concluded that water quality data can support the content of chlorophyll-a in the waters of the Wulan Delta Estuary.

Estimation of Albacore Tuna Potential Fishing Grounds in the Southeastern Indian Ocean

To maintain sustainable fisheries, albacore tuna is one of the commercial fish species whose management is regulated globally by the Regional Fisheries Management Organizations. Generally, sea surface temperature (SST) and chlorophyll-a (SSC) are used to determine fish suitability based on the catch data. In this research, we attempt to identify optimal habitats for albacore tuna in the southeastern Indian Ocean by analyzing in situ data based on onboard observers on tuna long line vessels from 2006–2019 and optimum interpolation sea surface temperature from NOAA-Advanced Very High-Resolution Radiometer and sea surface chlorophyll-a from Aqua MODIS satellites. The albacore tuna’s habitat suitability index was examined using the generalized additive model. The results suggested that albacore tuna inhabited waters with an SST range of 15–26 °C and SSC concentration of 0.075–0.125 mg/m3. In the Indian Ocean, most albacore tunas were captured at higher latitudes of 20°-30° S.

CPUE Estimation and Standardization Based on VMS: A Case Study for Squid-Jigging Fishery in the Equatorial of Eastern Pacific Ocean

Different fisheries, even the same fishery, use different ways of quantifying fishing efforts such as the number of vessels, days, voyages, and hooks. In squid-jigging fisheries, fishing hours, fishing days, and the number of vessels are valid units for calculating the catch per unit effort (CPUE). A vessel monitoring system (VMS) provides vessel position data with high spatial and temporal resolution and offers the possibility to quantify the CPUE at a finer scale. Using the squid fishery in the equatorial waters of the eastern Pacific as a case study, the CPUE was evaluated and standardized based on VMS data. The drifting operating points of the squid fishing vessels were filtered by the speed threshold, solar radiation, and operating time setting methods, leading to the number of fishing hours per day, and the nominal CPUE was calculated by combining the catch data obtained from logbooks. Then, the generalized linear model (GLM) and generalized additive model (GAM) were applied to conduct CPUE standardization considering spatiotemporal factors and environmental variables including sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), and chlorophyll-a (Chl_a). The results showed that month, latitude, SST, SSH, and Chl-a all have a high significant effect on CPUE as demonstrated through the significance test conducted by GLM. The GAM including the significant factors was judged to be the best model according to the AIC guidelines. The latitude range for high CPUE in the fishery was 3°S~0°S, SST range 24~25 °C, SSH range 4~8 m, and Chl_a range 0.15~0.20 mg/m3. In addition, the nominal and standardized CPUEs were compared based on fishing hours and fishing days. The results indicated that the two types of CPUEs were highly related hence there was no significant difference.

SEASONAL AND INTERANNUAL DYNAMICS OF THE ABUNDANCE OF THE BLACK SEA ALIEN SPECIES &lt;i&gt;PSEUDODIAPTOMUS MARINUS&lt;/i&gt; SATO, 1913 (COPEPODA, CALANOIDA, PSEUDODIAPTOMIDAE) IN THE CRIMEAN COASTAL WATERS: INFLUENCE OF THE TEMPERATURE FACTOR

Observation on the occurrence of the Black Sea alien species Pseudodiaptomus marinus were initiated since this species was reported in the coastal waters of Crimea, in 2016. Current study is focused on the 170-500 µm microplankton fraction represented by nauplii and the first copepodite stages. These data were complemented by the mesoplankton fraction abundance contributed by copepodite stages II-V and adults. Samples were collected by plastic bottles at the sea surface and by Juday and Apstein plankton nets in the upper 10 m layer. Nauplial stages of P. marinus were observed during the first three years after species invasion, in September, at the sea surface temperature range from 21.1 to 25.5 C. From 2019 to 2020, specimens appeared in July, at temperatures from 25.8 to 26.0C. The presence of specimens in samples has been observed by the end of November or December, at sea surface temperature of 13.1 or 8.6C, respectively. The maximal abundance was observed in the inner part of the Sevastopol Bay. The correlation value of 0.7-0.9 was estimated between the abundance and sea surface temperature throughout the year. Inter-annual variations of the abundance were associated with an integrative indicator of temperature (in particular, the sum of active temperatures).

The physical oceanography of Fortune Bay, an overview

This paper describes the physical oceanography of Fortune Bay, a broad, mid-latitude fjord located in Newfoundland (Canada). Fortune Bay is subject to a strong seasonal stratification (0–16 °C sea-surface temperature range with up to 1 °C/m vertical gradient) influenced by local freshwater runoff, wind forcing and shelf inputs. Sea-ice is seldom present in the bay and unlikely to be of importance on the seasonal stratification and mixing processes. Fortune Bay is warmer than its adjacent shelf both at the surface (by about 2 °C) and at intermediate depths (by about 1 °C from 50–150 m). While the former is likely due to local freshwater runoff stratification influence, the latter is probably related to the warm, deep water input occurring in winter below sill depth and subsequently mixed with the intermediate layer via the input of a colder water mass flowing in summer and which eventually reaches the bottom as well. Currents are dominated by the ‘weather band’ (2–20 d) and characterized by energetic pulses associated with downwelling and upwelling events. Mean circulation is rather weak and the seasonal pattern obtained here did not reveal either the presence of a distinct estuarine circulation nor a strong influence of the main coastal current. Tidal currents are weak also and no inertial signal was observed. Estimates of water exchange between the inner and outer part of the bay were calculated using several methods and led to residence times of the order of a few to several months for the upper layers and of the order of a year for the bottom layer with a probable strong seasonal variability (larger residence time in summer for the upper layers). The “baroclinic pumping” processes, which include the downwelling/upwelling events, appear to be important players but more work is needed to better understand their nature and actual contribution.

Distribution characteristics of terrestrial and marine lipid biomarkers in surface sediment and their implication for the provenance and palaeoceanographic application in the northern South China Sea

Multi biolipids, including plant wax, algal biomarkers, and glycerol dialkyl glycerol tetraethers (GDGTs), were studied in surface sediments of the northern South China Sea (SCS). Unusual elevated contents of odd n-alkanes (C27, C29, C31) and even n-alkanols (C22, C24, C26) derived from terrestrial plant wax in the outer shelf areas indicated the strong influence of deep-water counter current in redistributing and deposition of Taiwan Island sourced organic matter (OM) in the northern SCS. The spatial distribution of dinosterol and brassicasterol (corresponding to dinoflagellates and diatoms of high competitive advantage for nutrients), respectively, displayed a high abundance near the Pearl River Estuary (PRE), southwest off Taiwan Island, and southeast off Hainan Island, in contrast to the relatively high biomass of C37-alkenones, C30-diol/ketol and isoprenoid GDGTs (iGDGTs) in the outer shelf oligotrophic areas, indicating their feasibility in marine productivity reconstruction. The observed high contents of alkenones than brassicasterol in the sediment, albeit the overall dominance of diatoms in the SCS surface water, showed differences in the degradation and/or preservation efficiency of different organic lipids in sediments. The influences of season, source organisms, and different regression methods on the sea surface temperatures (SST) reconstruction were also evaluated in the region extending from shelf to deep water. The reconstructed SSTs based on U37K' mainly reflected spring SSTs, indicating the influence of growing seasons on the source organism. The reconstructed TEX86 SST corresponded more with the mean annual SST in the northern SCS, mainly in the deep-water regions. Changes in the total composition of the archaeal community and population is suggested to be the major factor causing the unusually low and wide range of TEX86 SSTs in the nearshore areas. The combination of the two organic paleothermometers offers complementary information on SST developments in the northern SCS. Multi-biomarkers study in the present work indicates the feasibility of lipids in paleoecology and paleoclimate reconstruction. However, care must be taken in palaeoceanographic reconstruction due to complex hydrological and biological influence, i.e., the deep lateral current on the continental matter transportation, the differential degradation of various organic lipids, and the different seasonal and/or source organism community bias on the organic thermometer in the study area.

Multi-Sensor Sea Surface Temperature Products from the Australian Bureau of Meteorology

Sea surface temperature (SST) products that can resolve fine scale features, such as sub-mesoscale eddies, ocean fronts and coastal upwelling, are increasingly in demand. In response to user requirements for gap-free, highest spatial resolution, best quality and highest accuracy SST data, the Australian Bureau of Meteorology (BoM) produces operational, real-time Multi-sensor SST level 3 products by compositing SST from Advanced Very-High-Resolution Radiometer (AVHRR) sensors on Meteorological Operational satellite (MetOp)-B and National Oceanic and Atmospheric Administration (NOAA) 18, along with SST from Visible Infrared Imaging Radiometer Suite (VIIRS) sensors on the Suomi National Polar-orbiting Partnership (Suomi NPP) and NOAA 20 polar-orbiting satellites for the Australian Integrated Marine Observing System (IMOS) project. Here we discuss our method to combine data from different sensors and present validation of the satellite-derived SST against in situ SST data. The Multi-sensor Level 3 Super Collated (L3S) SSTs exhibit significantly greater spatial coverage and improved accuracy compared with the pre-existing IMOS AVHRR-only L3S SSTs. When compared to the Geo Polar Blended level 4 analysis SST data over the Great Barrier Reef, Multi-sensor L3S SST differs by less than 1 °C while exhibiting a wider range of SSTs over the region. It shows more variability and restores small-scale features better than the Geo Polar Blended level 4 analysis SST data. The operational Multi-sensor L3S SST products are used as input for applications such as IMOS OceanCurrent and the BoM ReefTemp Next-Generation Coral Bleaching Nowcasting service and provide useful insight into the study of marine heatwaves and ocean upwelling in near-coastal regions.

Characteristics of anchoveta (Engraulis ringens) schools in the optimum zone and the physiological stress zone of its distribution between 2011 and 2021

AbstractThis study has considered anchoveta acoustic data from the Pelagic Resources Hydroacoustic Assessment Surveys carried out by the Peruvian Sea Institute (IMARPE) and free access satellite data (HYCOM and MODIS from the USA) of some oceanographic variables between the period 2011 and 2021, to know the oceanographic conditions, characteristics of schools and size structure in the optimum zone (OZ) and in the physiological stress zone (PSZ), of their total distribution. The OZ is determined by the extent of the Cold Coastal Waters (CCW), and the PSZ is determined by the mixing of waters, to the north by the CCW‐ESW (Equatorial Surface Waters) and to the west between the CCW‐SSW (Subtropical Surface Waters). The range of sea surface temperature and salinity in the PSZ (16.1–25.0°C and 34.65–35.29, respectively) was wider than in the OZ (14.5–24.0°C and 34.65–35.20, respectively), where a higher number of schools were recorded. Our analyses showed that the morphometric and energetic acoustic descriptors of anchoveta schools in the summer were higher during summers compared to springs. In terms of positional characteristics, the mean depth of the schools in the PSZ was slightly greater than in the OZ. The total size structure of anchoveta in the OZ consisted mainly of juvenile specimens (less than 12 cm total length) in the summer of 2011 and 2013–2014 and in the spring between 2014–2017 and 2021. In the PSZ, adult specimens (greater than 12 cm total length) predominated in summer between 2011–2013, 2015, 2018, and 2021 and in spring between 2011–2013, 2015, and between 2018–2021. However, specimens greater than 10 cm in total length were found in the PSZ. Knowledge of the location of this zone away from the coast will allow a high probability of anchoveta capture of adult specimens during fishing periods.

Controls on the Boundary Between Thermally and Non‐Thermally Driven pCO2 Regimes in the South Pacific

AbstractRegional and temporal patterns of air–sea carbon exchange are strongly linked to the surface ocean partial pressure of carbon dioxide (pCO2), which varies with sea surface temperature (SST), salinity, dissolved inorganic carbon (DIC), and alkalinity. It is well‐known that temperature controls the pCO2 seasonal cycle in the subtropics, whereas DIC dominates at high latitudes. The balance of mechanisms governing the boundary between these regimes, however, are not well characterized due to lack of year‐round pCO2 data. Here, we use autonomous biogeochemical float measurements from the South Pacific to investigate the processes that control meridional variations in pCO2 seasonality. We find that the transition between pCO2 regimes is linked to the poleward decrease in SST seasonal cycle amplitude, which is closely associated with the northern boundary of deep winter mixed layers. Processes that determine the annual SST range are, therefore, central to the response of oceanic carbon uptake to anthropogenic forcing.

SKIPJACK TUNA FISHING SEASON AND ITS RELATIONSHIP WITH OCEANOGRAPHIC CONDITIONS IN PALABUHANRATU WATERS, WEST JAVA

Skipjack tuna (Katsuwonus pelamis) is the main catch species in Indonesian Palabuhanratu waters. The dynamics of skipjack fishing areas are influenced by oceanographic parameters such as sea surface temperature and chlorophyll-a concentration. This study aims to predict the skipjack fishing season, analyze the dynamics of oceanographic conditions, especially the distribution of sea surface temperature and the distribution of chlorophyll-a, and determine the relationship between skipjack fishing season and the dynamics of the distribution of sea surface temperature and the distribution of chlorophyll-a in the waters of Palabuhanratu, West Java. Catch per unit effort analysis was used to determine the fishing season index, while the dynamics of sea surface temperature and distribution of chlorophyll-a were analyzed from MODIS image data. The results showed that skipjack fishing season in Palabuhanratu waters was from July to November. Monthly sea surface temperatures range from 26-30℃ with an average value of 29℃. The distribution value of chlorophyll-a concentration ranged from 0.09 mg/m3 to 0.51 mg/m3 with an average value of 0.23 mg/m3. Skipjack tuna production tends to increase when sea surface temperatures are low and chlorophyll-a concentrations increase.

Paleoclimate Records of the Middle Okinawa Trough Since the Middle Holocene: Modulation of the Low-Latitude Climate

The ubiquity of glycerol dibiphytanyl glycerol tetraethers (GDGTs) and their temperature sensitivity make them one of the most effective tools for paleoclimate reconstruction. High- and low-latitude climates influence the Okinawa Trough (OT). It receives diverse inputs from the East China Sea, the western Pacific, and the Kuroshio Current, providing good conditions for paleoclimate studies. Here, isoprenoid GDGTs (isoGDGTs), branched GDGTs, and hydroxylated GDGTs (OH-GDGTs) were studied to reconstruct the sea surface temperature (SST) of the central OT for the past 8.2 kyr using the tetraether index of 86 carbon atoms at low latitudes (TEXH86) and the ring index of OH-GDGTs (RI-OH). The GDGT-0/crenarchaeol ratios ranged from 0.39 to 0.98. The branched and isoprenoid tetraether index and the methane index values were lower than 0.1 and 0.5, respectively, indicating that the isoGDGTs were mainly derived from marine Thaumarchaeota and that TEXH86 could be used to reconstruct the paleotemperatures. The TEXH86 SSTs ranged from 21.6 to 27.2°C during 8.2 kyr. The overall range of TEXH86 SSTs is close to the UK’37 SST of the middle OT and reflects the mean annual SST. In contrast, RI-OH temperatures varied from 17.4 to 26.0°C, showing a lower trend than TEXH86 SSTs. The core top RI-OH temperature is 24.1°C, in line with the mean annual seawater temperature at 40 m (24.2°C) in the study area, which likely reflects the subsurface temperature in this case. The small overall warming trend of TEXH86 SSTs agrees with the increasing intensity of the Kuroshio Current during the last 8.2 kyr, indicating that the SST evolution is governed by the Kuroshio Current that transports heat from the western tropical Pacific. The decreasing temperature differences between TEXH86 and RI-OH and between UK’37 and RI-OH showed increased mixing of the upper water column, which was in good accordance with the increasing low-latitude winter insolation decoupling from the East Asian summer monsoon. The cold event that occurred at 7.4–6.6 kyr was magnified (∼5°C) at the TEXH86 and RI-OH temperatures and possibly caused by tephra’s significant input (∼7.3 kyr).

Immense variability in the sea surface temperature near macro tidal flat revealed by high-resolution satellite data (Landsat 8)

Sea surface temperature (SST) is crucial for understanding the physical characteristics and ecosystems of coastal seas. SST varies near the tidal flat, where exposure and flood recur according to the tidal cycle. However, the variability of SST near the tidal flat is poorly understood owing to difficulties in making in-situ observations. The high resolution of Landsat 8 enabled us to determine the variability of SST near the macro tidal flat. The spatial distribution of the SST extracted from Landsat 8 changed drastically. The seasonal SST range was higher near the tidal flat than in the open sea. The maximum seasonal range of coastal SST exceeded 23 °C, whereas the range in the open ocean was approximately 18 °C. The minimum and maximum horizontal SST gradients near the tidal flat were approximately − 0.76 °C/10 km in December and 1.31 °C/10 km in June, respectively. The heating of sea water by tidal flats in spring and summer, and cooling in the fall and winter might result in a large horizontal SST gradient. The estimated heat flux from the tidal flat to the seawater based on the SST distribution shows seasonal change ranging from − 4.85 to 6.72 W/m2.