Seasonal Changes In Sea Surface Temperature Research Articles

CMIP5-Based Projection of Decadal and Seasonal Sea Surface Temperature Variations in East China Shelf Seas

The East China Shelf Seas, comprising the Bohai Sea, the Yellow Sea, and the shelf region of East China Sea, play significant roles among the shelf seas of the Western North Pacific Ocean. The projection of sea surface temperature (SST) changes in these regions is a hot research topic in marine science. However, this is a very difficult task due to the lack of available long-term projection data. Recently, with the high development of simulation technology based on numerical models, the model intercomparison projects, e.g., Phase 5 of the Climate Model Intercomparison Project (CMIP5), have become important ways of understanding climate changes. CMIP5 provides multiple models that can be used to estimate SST changes by 2100 under different representative concentration pathways (RCPs). This paper developed a CMIP5-based SST investigation framework for the projection of decadal and seasonal variation of SST in East China Shelf Seas by 2100. Since the simulation results of CMIP5 models may have degrees of errors, this paper uses hydrological observation data from World Ocean Atlas 2018 (WOA18) for model validation and correction. This paper selects seven representative ones including ACCESS1.3, CCSM4, FIO-ESM, CESM1-CAM5, CMCC-CMS, NorESM1-ME, and Max Planck Institute Earth System Model of medium resolution (MPI-ESM-MR). The decadal and seasonal SST changes in the next 100 years (2030, 2060, 2090) are investigated by comparing with the present analysis in 2010. The experimental results demonstrate that SST will increase significantly by 2100: the decadal SST will increase by about 1.55 °C, while the seasonal SST will increase by 1.03–1.95 °C.

Corals regulate the distribution and abundance of Symbiodiniaceae and biomolecules in response to changing water depth and sea surface temperature

The Scleractinian corals Orbicella annularis and O. faveolata have survived by acclimatizing to environmental changes in water depth and sea surface temperature (SST). However, the complex physiological mechanisms by which this is achieved remain only partially understood, limiting the accurate prediction of coral response to future climate change. This study quantitatively tracks spatial and temporal changes in Symbiodiniaceae and biomolecule (chromatophores, calmodulin, carbonic anhydrase and mucus) abundance that are essential to the processes of acclimatization and biomineralization. Decalcified tissues from intact healthy Orbicella biopsies, collected across water depths and seasonal SST changes on Curaçao, were analyzed with novel autofluorescence and immunofluorescence histology techniques that included the use of custom antibodies. O. annularis at 5 m water depth exhibited decreased Symbiodiniaceae and increased chromatophore abundances, while O. faveolata at 12 m water depth exhibited inverse relationships. Analysis of seasonal acclimatization of the O. faveolata holobiont in this study, combined with previous reports, suggests that biomolecules are differentially modulated during transition from cooler to warmer SST. Warmer SST was also accompanied by decreased mucus production and decreased Symbiodiniaceae abundance, which is compensated by increased photosynthetic activity enhanced calcification. These interacting processes have facilitated the remarkable resiliency of the corals through geological time.

Differences in the reproductive traits of Pacific bluefin tuna Thunnus orientalis among three fishing grounds in the Sea of Japan

Differences in the reproductive traits of Pacific bluefin tunaThunnus orientalis(PBF) in the Sea of Japan (SOJ) were investigated to evaluate the reproductive potential in 3 fishing grounds (i.e. northern, central and southern areas). The size distribution of PBF differed among the fishing grounds, with smaller fish (100-130 cm in fork length, FL) being caught in the central and northern areas of the SOJ. Spawning-capable females were found at sea surface temperatures (SSTs) between 17 and 25°C, with most SSTs >21°C. Seasonal changes in SST differed among the fishing grounds, and the period when SST exceeded 21°C differed in each fishing ground. Spawning-capable females were found at different times among the fishing grounds, and were observed throughout the fishing season in the southern area of the SOJ. The mean ± SD relative batch fecundity was estimated to be 69.8 ± 45.3 and 92.7 ± 43.1 oocytes g-1in the central and southern areas of the SOJ, respectively. The total spawning fraction was 0.2, 0.38 and 0.73 in the northern, central and southern areas of the SOJ, respectively. SST and FL were positively correlated with the batch fecundity. In addition, FL, SST and location affected the probability of occurrence of spawning-capable fish among mature fish. Therefore, the difference in the observed reproductive potential of PBF among fishing grounds in the SOJ can be linked to the differences in seasonal increases in SST and the size distribution of adult fish.

Annual shell growth patterns of three venerid bivalve mollusk species in the subtropical northwestern Pacific as revealed by sclerochronological and stable oxygen isotope analyses

Annual shell growth patterns of the three venerid bivalve species, Gafrarium pectinatum, Pitar citrinus, and Katelysia japonica were investigated based on the results of sclerochronological and stable oxygen isotope analyses of live-caught specimens from the intertidal zone of Iriomote Island, southern Ryukyu Archipelago. In the study area, these three species temporally stopped shell deposition, when sea surface temperature (SST) dropped to 23–26 °C, during the first three years. However, the shutdown temperature for shell growth increased slightly to higher than 26 °C after 6 years old for G. pectinatum combined with a shortening in the length of shell growing period. Seasonal changes in daily shell growth in these species were controlled mainly by SST and primary production. Shell δ18O-derived summer temperatures recorded in the annual increments were higher by 3–5 °C than the highest SST records of the habitat. This data mismatch might be caused by an abrupt decrease in seawater δ18O values during the summer and fall typhoon seasons because of the influx of fresh water into the study area from nearby rivers. This study suggests that in the study area the annual shell growth patterns and shell δ18O values in the three species examined were controlled by mutually related biological and environmental factors such as ontogenetic age and seasonal changes in SST, salinity and primary production.

Spatiotemporal variations in the distribution of round herring eggs in the East China and Japan Seas during 1997–2013

Spawning stock biomass (SSB) and environmental factors, such as water temperature, can affect the size and location of spawning grounds of small pelagic fishes. We examined the effects of SSB, water temperature, and day length on the probability of egg presence of the round herring Etrumeus teres to clarify spatiotemporal variation in its spawning grounds in the Tsushima Warm Current region off the west coast of Japan. Egg presence probability (EPP) was estimated from monthly egg surveys and annual stock assessments from 1997 to 2013. Our results indicated that EPP was positively correlated with sea surface temperature (SST), and increased between 12 and approximately 17 °C, where it became constant, and then decreased when SST exceeded 24 °C. From February to June, locations of the main spawning grounds gradually shifted northeast from the waters off western Kyushu to the Japan Sea as the areas with water temperatures suitable for successful egg development (≥17 °C) expanded. However, few eggs were observed during the season when day length shortened daily, even when SST was suitable. The main spawning grounds expanded more towards northern waters in warmer years than in cooler years. In addition, EPP was positively correlated with SSB, which resulted in an expansion of the spawning grounds into coastal regions in years with high SSB. These results indicate that spawning of the round herring responds to seasonal changes in SST and day length, and interannual fluctuations in SST and SSB in the Tsushima Warm Current region.

Late-Holocene dynamics of sea-surface temperature and terrestrial hydrology in southwestern Africa

Southwest Africa is an important region for paleo-climatic studies, being influenced by both tropical and temperate climate systems and thus reflecting the interplay of variable controls. The aim of this study was to unravel the interaction of sea-surface temperature (SST) changes in the southernmost Benguela upwelling system with precipitation changes in South Africa’s winter rainfall zone (WRZ) during the late Holocene. Therefore, a marine sediment core from the southernmost Benguela upwelling system was investigated to reconstruct climate changes in this region for the past ~2000 years. Grain size and geochemical analyses were conducted to reconstruct changes in fluvial sediment discharge and weathering intensity, while SST changes were estimated using alkenone paleo-thermometry. Results show that the southernmost Benguela behaves distinctly in comparison with the rest of the Benguela system reflecting amplified SST changes. Decreasing SSTs accompanied increasing river discharge during times of increased precipitation in the WRZ, reflecting northerly shifted westerly winds during austral winter. We infer a control of past SST changes by processes not analogous to modern processes driving seasonal SST changes by changes through upwelling intensity. The findings suggest that late-Holocene SST changes in the southernmost Benguela upwelling system and the precipitation in the WRZ were both driven by latitudinal shifts of the austral westerly wind belt and associated changes in advection of cold sub-Antarctic waters and/or changes in Agulhas leakage of warm Indian Ocean waters.

Assessing elemental ratios as a paleotemperature proxy in the calcite shells of patelloid limpets

Archaeological shell and fish middens are rich sources of paleoenvironmental proxy data. Patelloid limpet shells are common constituents in archaeological middens found along European, African, and South American coastlines. Paleotemperature reconstructions using oxygen isotope ratios of limpet shells depend on the ability to constrain the oxygen isotope ratio of seawater; therefore, alternative proxies are necessary for coastal localities where this is not possible. The study evaluates whether Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li ratios are reliable proxies of sea surface temperature (SST) in the calcite layer of shells of the patelloid limpets, Patella vulgata and Nacella deaurata. We compare Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li ratios to the seasonal variations in contemporaneous δ18Oshell values, which primarily record seasonal changes in SST. Elemental ratios (Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li) show no significant correlations with reconstructed SST in P. vulgata and N. deaurata shells, nor do they show sinusoidal cycles expected from a SST proxy. In addition, shell δ13C values show no significant ontogenetic trends, suggesting that these limpets exhibit little change in metabolic carbon incorporation into the shell with increasing ontogenetic age. Although shell growth rate exhibits a logarithmic decrease with age based on calculated linear extension rates, growth rate does not correlate with elemental profiles in these limpets. Overall, elemental ratios are not reliable recorders of paleotemperature in patelloid limpets.

Occurrence of severe drought conditions in coastal southern California during the medieval climate anomaly inferred from pollen deposited in the Santa Barbara Basin since ∼AD 800

Pollen analyses of the upper 3.95 m from ODP Site 893B from the Santa Barbara Basin (SBB) provide proxy evidence for major climate-driven changes in the vegetation onshore between wAD 800 and AD 1800. Dominance of plant communities adapted to drought conditions of hot, dry southern California summers (chamise chaparral and coastal sage scrub) corresponds with increases in the duration and severity of western U.S. drought identified by Stine (1994) and Cook et al. (2004) and with MacDonald and Case's (2005) interpretation of more negative Pacific Decadal Oscillation variability during the Medieval Climate Anomaly. Extreme drought conditions occur during a period of multi-decadal drought recorded by the high resolution-Ti record between AD 1000-1100 (14C corrected) (Hendy et al., 2011). The shift toward wetter, cooler conditions atwAD 1400 (an increase inmoremesic oak and pine communities such as scrub oak and pine woodland chaparral, or more open grass woodland) coincides with temperature changes in the waters offshore. Correlative diatom and planktonic foraminifera deposited in the SBB during the Little Ice Age suggest increased seasonal sea surface temperature changes with cooler winters and warmer springs, respectively (Barron et al., 2010; Fisler and Hendy, 2008). The distinctive signature of the 19th and 20th century pollen assemblages reflects agricultural and residential impact on the natural vegetation of southern coastal California following European settlement.

Density banding in corals: barcodes of past and current climate change

The predicted sea surface temperature (SST) rise over the next decades is likely hazardous to coral health because precipitation of the calcareous skeleton depends primarily on SST. Temperature modulates vertical growth and density of the skeleton with seasonal SST changes resulting in an alternation of high-density and low-density bands (HDB and LDB). Notably, growth rates and the timing of the HDBs and LDBs relative to the seasons differ on a global scale within geographic regions. In this contribution, we use combined information of skeletal density and seasonally resolved oxygen isotope SST estimates from massive Porites from a Late Miocene (9 Ma) reef in the eastern Mediterranean Sea (Crete, Greece) to understand reef vulnerability over short and geological periods of time. Three types of HDB–SST relationships have been found: (1) coincidence of HDB with summer, (2) winter or (3) autumn and spring. The latter doubles HDBs in a year and implies maximum calcification is coupled to the taxon-specific optimum SST during the transitional seasons and reduced at its respective critical winter and summer SSTs. Modeling with a nonlinear temperature–calcification relationship reproduces the climate barcode of density bands. The model should be relevant for other poikilothermic carbonate producers in reefs and platforms and has implications for judging geographic distributions and causes of extinctions of corals, benthic carbonate communities and entire carbonate systems. With regard to the causes underlying expansion and demise of carbonate platforms and reefs in geological history, we expect the model predictions to help for a deeper understanding of biotic responses during hyperthermals or coolings and possibly also for identifying regions in the modern ocean where corals are endangered or taking advantage of global warming.

Oxygen isotopic composition of limpet shells from the Beagle Channel: implications for seasonal studies in shell middens of Tierra del Fuego

Shell middens distributed along the coastal areas of the Beagle Channel (Tierra del Fuego) testify the primary role of marine resources in the successful social dynamic of hunter–gatherer–fisher societies (HGF) in extreme high latitude environmental conditions. Intertidal and subtidal limpet species are frequently identified taxa of these archaeological deposits. We investigated whether shell δ18O of the limpet species Nacella deaurata is a valuable record of local sea surface temperature (SST) and ambient water δ18O (δ18Ow) fluctuations, and in turn can be used to estimate the season of its exploitation by Holocene HGF. Sequential shell δ18O of modern species track seasonal changes of SST and δ18Ow. The comparison of shell δ18O profiles of N. deaurata and Nacella magellanica (a coexisting species) suggests the occurrence of distinct growth rate and physiological adaptations between species. Shell δ18O of zooarchaeological specimens of N. deaurata from Lanashuaia II suggests that animals were exploited predominantly in winter and that experienced similar environmental conditions of present day at ∼1320 years BP. Results also indicate that N. deaurata is a valuable candidate for studying past seasonal changes in SST and δ18Ow in this southernmost part of South America.

Distribution and movement of scalloped hammerhead Sphryna lewini and smooth hammerhead Sphyrna zygaena sharks along the east coast of southern Africa

Knowledge of population distribution and movement is crucial for the conservation and management of shark species occurring in coastal waters. From 1984 to 2009, 641 scalloped hammerheads Sphyrna lewini, 1 342 smooth hammerheads Sphyrna zygaena and 1 352 unspecified hammerheads Sphyrna spp. were tagged and released along the east coast of South Africa, with recapture rates of 1.9%, 1.5%, and 0.7% respectively. Maximum and average distance moved was 629 km and 147.8 km (95% CI = 33.0–262.7 km) for S. lewini and 384 km and 141.8 km (95% CI = 99.1–184.5 km) for S. Zygaena respectively. The majority of sharks (68% S. lewini, 74.1% S. zygaena and 33.5% Spyrna spp.) were tagged in the Transkei region, with the largest number tagged in Port St Johns. Across regions, most tagged sharks were >50–100 cm precaudal length (PCL), except in Transkei where more sharks >100–150 cm PCL were tagged. In the Western Cape, Southern Cape and Eastern Cape, few sharks were tagged during the autumn/winter months, whereas in KwaZulu-Natal and Transkei sharks were tagged throughout the year. Large-scale directional movements observed may have been migrations in response to seasonal sea surface temperature changes. We identify coastal locations in Transkei that are of importance to juvenile and subadult hammerhead populations year-round.

Projected Future Seasonal Changes in Tropical Summer Climate

Abstract The authors analyze changes in the tropical sea surface temperature (SST), surface wind, and other fields from the twentieth to the twenty-first century in climate projections using the Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel ensemble, focusing on the seasons January–March (JFM) and July–September (JAS). When the annual mean change is subtracted, the remaining “seasonal changes” have robust, coherent structures. The JFM and JAS changes resemble each other very closely after either a change of sign or reflection about the equator. The seasonal changes include an increase in the summer hemisphere SST and a decrease in the winter hemisphere SST. These appear to be thermodynamic consequences of easterly trade winds strengthening in the winter subtropics and weakening in the summer subtropics. These in turn are associated with the weakening and expansion of the Hadley circulation, documented by previous studies, which themselves are likely consequences of changes in extratropical eddies. The seasonal SST changes influence the environment for deep convection: peak precipitation in the summer hemisphere increases by around 10% and convective available potential energy (CAPE) increases by as much as 25%. Comparable fractions of these changes are attributable to the annual mean change and the seasonal changes, though the two have very different spatial structures. Since the annual mean change is marked by relative warming in the Northern Hemisphere compared to the Southern Hemisphere, the seasonal changes oppose the annual mean change in JFM and enhance it in JAS.

Composition of stable isotopes in geoduck ( Panopea abrupta) shells: A preliminary assessment of annual and seasonal paleoceanographic changes in the northeast Pacific

We tested the suitability of using Panopea abrupta (geoduck) shells to evaluate changes in both annual and seasonal sea surface temperature. Geoducks are long-lived and deposit annual growth increments within their shell each winter, making them potentially excellent paleoceanographic archives. Shells were sampled by thin-section from the hinge plate region, where the first 20–30 years of growth provide relatively wide annual increments suitable for sampling for isotopic analysis. The geoducks used in this study were collected in AD 2000 from west of Protection Island, located at the eastern end of the Strait of Juan de Fuca. The isotopic record is compared to the historic instrumental record as well as the thickness of geoduck growth increment measurements, which were also correlated with water temperature [Strom, A., Francis, R.C., Mantua, N.J., Miles, E.L., Peterson, D.L., 2004. North Pacific climate recorded in growth rings of geoduck clams: a new tool for paleoenvironmental reconstruction. Geophysical Research Letters 31, p. LO6206. doi:10.1029/2004GL019440]. The annual average oxygen isotopic values from two geoduck clams, whose first years of growth correspond to the early historic instrumental record (∼AD 1920) appear to be recording trends in sea surface temperature. Intra-annual sampling of annual growth increments indicates that the shells also appear to be recording seasonal changes in sea-surface temperature. Preliminary analysis of carbon isotopic data on both the annual and seasonal timescales indicate the potential for assessing productivity changes in ambient seawater.

Seasonal changes in sea surface temperature of the subtropical North Pacific during the last glaciation

Proxy records of sea surface temperature (SST) near Hawaii in the North Pacific reveal that seasonal changes in SST increased during the Last Glacial Maximum (LGM); the August temperature was about 1°C cooler during the LGM than today, while that for February was 3°C cooler. Here we investigated the causes of the intensified glacial seasonality by considering (1) variations in local heating and cooling due to changes in orbital forcing, (2) variations in the vertical thermal structure of seawater, and (3) changes in the large-scale ocean circulation. Our results suggest that changes in the North Pacific subtropical gyre represent a more plausible cause for the intensified sea sonality than the other two factors.

Radiolarian fluxes from the southern Bay of Bengal: sediment trap results

A study of radiolarian fluxes collected during 1991–93 from time-series sediment traps deployed at 1071 and 3010 m water depth in the southern Bay of Bengal (SBBT) yielded 40 species/groups of radiolarians. Among the order Polycystina, the species of sub-order Spumellaria were by far the most abundant (∼95%) followed by sub-order Nassellaria (5%). This is contrary to reports from the Atlantic and Pacific Oceans and is attributed to the prevailing hyposaline condition resulting from the monsoonal rainfall. Higher radiolarian fluxes occurred during March–May, when moderate salinity and a high sea surface temperature (SST) regime prevailed at the trap site. R-mode cluster analysis of the radiolarian flux data revealed three assemblages represented by the cooler (A) and warmer (C) surface dwelling fauna (0–50 m) dominated by spumellarians, and a deeper dwelling (B) sub-surface fauna (50–100 m) associated with deep dwelling (>100 m) nassellarian species. Spongaster tetras tetras, a surface water radiolarian species, exhibited its preference for high SST and moderate salinity conditions during the pre-monsoon season (March–May). Radiolarian fluxes responded to seasonal changes in SST and salinity variations due to the monsoonal precipitation, and the freshwater runoff from the Indian rivers causing a hyposaline condition in the Bay of Bengal. Results imply that the radiolarian assemblages in the down core data may reveal the monsoonal history in the geological past.

Seasonal changes in sea surface temperature and salinity during the Little Ice Age in the Caribbean Sea deduced from Mg/Ca and 18O/16O ratios in corals

Abstract The oxygen isotopic composition ( δ 18 O) of coral skeletons reflects a combination of sea surface temperature (SST) and the δ 18 O of seawater, which is related to sea surface salinity (SSS). In contrast, the magnesium/calcium (Mg/Ca) ratio of a coral skeleton reflects SST independent of salinity. By using the relationships among coral Mg/Ca ratios, coral δ 18 O, seawater δ 18 O and SST, it is possible to determine past SST and SSS uniquely. Such determinations were made and calibrated using the Mg/Ca ratio and the δ 18 O of the modern part of a 3 m long coral core ( Montastrea faveolata ), collected from the southwest coast of Puerto Rico in the Caribbean Sea where both SST and SSS changes seasonally and the seawater δ 18 O measured at the coral site. Our results yielded three relationships (coral Mg/Ca–SST, δ 18 O coral – δ 18 O water -SST, and δ 18 O water –SSS). With these calibration equations seasonal changes in SST and SSS during the little ice age (LIA) in the Caribbean Sea were reconstructed. The δ 18 O and Mg/Ca ratio of the coral skeleton between 1699 and 1703 suggests that the SST during the LIA was approximately 2°C cooler than present with the SSS showing greater seasonal changes as well. These results are in good agreement with climate-based reconstruction from corals based on oxygen isotopes, although the possibility of some uncertainty remain in our estimation including long-term decadal scale trends in climate.

Copepod Community Structure at Bahia Magdalena, Mexico during El Niño 1983–84

Changes in the community structure and distribution patterns of 71 species of copepods collected during eight oceanographic surveys at Bahia Magdalena, Mexico were analysed. From March 1983 to January 1985, the responses of the copepod community structure to the seasonal environmental conditions and temporal changes during the peak warming of the El Niño event 1982–83, the relaxation phase in 1984, and the winter 1984–85 cooler period were studied. As in other estuaries and bays, the copepod community had a few dominant species, which have a seasonal succession throughout the year related to seasonal changes in sea-surface temperature. There are two major successional stages in the annual cycle of zooplankton development. During the warming period (July–October of 1983 and 1984), Acartia lilljeborgiiGiesbrecht and Acartia tonsaDana (tropical affinity) were the dominant species in the copepod community. During the cooler period (December–June), the dominant species was Paracalanus parvus(Claus). During Summer and Autumn 1983 (El Niño peak), an unusual increase of tropical-equatorial copepod species were found, that are regularly found offshore. The resident species Acartia clausiGiesbrecht was replaced by A. tonsa. Despite these changes in the species composition because of El Niño, seasonal succession is the general rule in Bahia Magdalena and was only enhanced by the presence of several tropical species during the warmest period.