Oceanologia最新文献

ARGO program was conceived with an aim to generate near real-time ocean observations as the primary in-situ sources for use in operational oceanography studies. Two decades-long ARGO near-surface temperature data set was used for generating monthly gridded ARGO sea surface temperature (ASST) product on a climatological scale. Data interpolating variational analysis (DIVA) method was employed for generating the product with a spatial resolution of 0.25° x 0.25° for the Tropical Indian Ocean. This monthly ASST product was evaluated using five different climatological SST products derived from in-situ and satellite measurements. Various statistics such as BIAS, RMSE, coefficient of correlation, and skill scores were generated to evaluate the reliability of the ASST product. Further, the ASST product was validated with climatological in-situ SST obtained from RAMA and OMNI moorings deployed in the Indian Ocean. Statistical comparisons showed low BIAS and RMSE, and high correlation and skill scores with most of the buoys locations and the gridded SST products. Results concluded that the near-surface temperature data from ARGO can be used along with other SST data sets in the generation of high-resolution blended SST products.

The upper Gulf of California is one of the most energetic regions owing to its tidal range and strong tidal currents, making the upper gulf and the archipelago zone highly turbulent regions; the abundance of zooplankton should be associated with mixing phenomena. We aimed to determine the latitudinal distribution of zooplanktonic organisms in this region and the influence of the islands on their distribution and abundance using historical data. Distribution of abundance followed the current patterns, the archipelago influences abundance favorably but does not affect diversity. Latitudinal zooplankton richness had a quasi-parabolic shape. A decrease in richness was observed at 27.5°N, in the archipelago region, with maximum richness at 26.5°N and 28.5°N. The distribution of latitudinal ranges is consistent with geometric constraints models; taxa with wide ranges are in the central area, while those with narrow ranges are near the boundaries and the Upper Gulf. Zooplankton responds in some way to the existence of the southern boundary as shown by the decrease of richness in this region. At the whole scale of the Gulf, the distribution of richness followed geometric constraints model, while at smaller scales, distribution and abundance are conditioned by the hydrodynamics of the Gulf. We compared zooplankton spatial distribution with Sea Level Anomaly, Sea Surface Temperature, and Chlorophyll-a concentrations from Copernicus to establish relationships between these factors. We performed Cluster and Redundancy Analysis to characterize similarities between stations in terms of biomass and taxon composition and to assess the importance of environmental variables on the distribution of zooplankton.

Temporal variations in the primary production of the size-fractionated autotrophic plankton community were studied in coastal-estuarine waters of the eutrophic Gulf of Riga, Baltic Sea. The community was net-autotrophic during spring and summer and net-heterotrophic during autumn. The results of the present study clearly demonstrate strong covariation between net primary production (NPP) and <56 µm fractionated community biomass, particularly small-sized (16–33 µm) Mesodinium rubrum, implying that the majority of NPP stems from the lower end of the size spectrum. A pronounced size distribution shift was observed within the M. rubrum population. Large-sized (length ≥34 µm) M. rubrum was the most abundant in the first half of the productive season (until week 24), whereas small-sized M. rubrum dominated during the stratified period.

During an experiment-of-opportunity in July 2019, 27 drift bottles were released in the southern Baltic Sea. Ten of these bottles were found and reported at locations that were surprisingly widespread. In this study, we explore the chances to reproduce these findings with a numerical drift model. While trajectories may be considered as completely deterministic, in practice their prediction as well as reconstruction has a strong stochastic component, because of ubiquitous gradients on even the smallest scales. We illustrate different aspects of uncertainty including specification of leeway, random dispersion, and stretching along Lagrangian coherent structures. By and large, the results of numerical ensemble simulations seem to be in reasonable agreement with the observational evidence available. Some drift bottle findings suggest a bias in simulations, but without knowing the drift bottles’ full drift paths, a basis for more detailed model tuning is missing.

The eastern Great Australian Bight (GAB) is a significant marine ecosystem, featuring a range of marine mammals and large pelagic fish including blue whales, sharks and tuna. Previous research has classified the region as generally oligotrophic, apart from late austral summer months when seasonal upwelling triggers phytoplankton blooms in the region. Based on multi-year field observations, this study analysed the interannual and interdecadal variability of the plankton community structure in this region. Pigment data indicate that nano- and pico-phytoplankton generally dominated the phytoplankton community structure with averages of 39% and 30% of the total biomass, including a relatively large proportion of nanophytoplankton (cryptophytes, haptophytes and prasinophytes) with cell sizes <5 µm, not resolved in microscopic cell counts. Nano- and pico-phytoplankton alone contributed ∼0.3 mg/m³ to the chlorophyll-a signal and therefore sustained an overall mesotrophic environment year-round. Distinct diatom blooms developed during the upwelling season within concentrated subsurface layers where chlorophyll-a concentrations increased to >1 mg/m³, characterising eutrophic conditions. The biomass of diatoms increased from <10% to ∼30% of total biomass. Diatom blooms coincided with relatively high abundances of three dominant zooplankton species (Oithona similis, Penilia avirostris and Microsetella norvegica) and/or the dinophyta Noctiluca scintillans, but events of high zooplankton abundance also occurred outside the upwelling season. The observational findings also show the occurrence of significant subsurface phytoplankton blooms in late spring, not reported before, that may also contribute to the ecosystem functioning of the region.

Precipitation anomalies have a significant impact on both natural environmental and human activity. Long lasting drought analysis has received great attention on a global and regional scale while prolonged rainy periods so far have been much less studied. However, long-term precipitation events are also important and threatening. The situation around the Baltic Sea in 2017 revealed that such periods could cause significant losses in agriculture.

The rainy periods of 30, 60, and 90 consecutive days in a given year during which the maximum precipitation amount was recorded in the eastern part of the Baltic Sea region were analysed in this study. Daily precipitation amount data from the E-OBS gridded dataset was used. The investigation covered a period from 1950 to 2019. The changes in magnitude and timing of such rainy periods were evaluated.

It was found that the annual precipitation in the eastern part of the Baltic Sea region increased significantly during the analysed period. Positive changes were observed throughout the year except during April and September. The amounts of precipitation during rainy periods of different duration also increased in most of the investigated areas but changes were mostly insignificant. Consequently, a decrease in the ratio of precipitation amount during the rainy period to annual precipitation was observed. It was also found that the rainy periods occurred earlier, especially in the case of the rainy periods of 60- and 90-days durations. Such tendencies pose an increasing threat to agriculture.

The marginal seas are in the transition zone between land and ocean and are often subject to extensive human activities causing multiple stresses on the marine environment and its ecosystems. A large gap between our scientific knowledge and our treatment of the sea illustrates a weak coupling between facts and values. The aim of this work is to initiate a discussion of how to improve the human relationship with the sea. Research into the UN 2030 Agenda with its ambition to transform our world into a sustainable and healthy physical and mental environment creates an opportunity to deepen our understanding of human behaviour and values and how they impinge on the physical world. Together with improved communication and transdisciplinary initiatives, these efforts should be vital in better understanding the marginal sea system and generating a new relationship with the ocean.

There is a pressing need to change the human relationship with the ocean and its marginal seas. Connecting the natural and human sciences can improve our awareness of the sea's state and support behavioural change. Such transdisciplinary development requires training in broad thinking and communication. It is time for natural science to “open the human black box”, adding values to facts.

We modelled changes in relative sea level (RSL) in the Beibu Gulf region, South China Sea, caused by the melting of the Pleistocene ice sheets, i.e., glacial isostatic adjustment (GIA). Both the temporal evolution of RSL between the last glacial maximum and present day as well as present-day rates were derived. The interplay of changing ocean water volume, gravitational induced water redistribution and solid Earth deformations due to the varying surface loads is accounted for by means of the sea-level equation. The modelled RSL curves for the Beibu Gulf region reveal the shape typical for regions far away from the former centres of glaciation, exhibiting a pronounced Holocene sea-level highstand between 4 and 5 kyr before the present. A general good agreement was found between modelled and empirical RSL curves, although differences in the timing and magnitude of the highstand were revealed. In addition to GIA-induced RSL, we also modelled the effect of RSL variations due to sediment accumulation during marine isotopic stages MIS 4 to MIS 1 descending mainly from Hainan Island, but also other terrestrial sources from the Chinese (and Vietnamese) mainland. Estimates for the sediment loading originate from seismic surveys and dated sediment cores. We found that RSL changes caused by sediment loading are at least three orders of magnitude smaller than those induced by GIA. The present-day rates of both RSL effects are too small to be detectable by geodetic observations and cannot be discriminated from prominent tectonic signals.

Glacio-isostatic adjustment (GIA) corrected limiting non-marine and marine sea-level data from the western Baltic Sea indicate a rapid relative sea-level (RSL) rise of 18 m for the first phase of the Littorina transgression using a linear age-elevation model. This accelerated RSL rise occurred in the time period 8.57 to 8.0 ka before present (BP) with an RSL rise rate of 31.5 mm/year. RSL rose from 28 m to 10 m below the mean relative sea level (bmrsl) during the time period of less than 600 years. The first phase of Littorina transgression documents the last big meltwater pulse (MWP), which has been reported also from various other regions in the world as a consequence of the final decay of the Laurentide ice sheet and additional meltwater sources from Antarctica.