Coastal sea level rise with warming above 2 °C Jevrejeva, Svetlana; Jackson, Luke P.; Riva, Riccardo E. M. ...
Proceedings of the National Academy of Sciences - PNAS,
11/2016, Letnik:
113, Številka:
47
Journal Article
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Two degrees of global warming above the preindustrial level is widely suggested as an appropriate threshold beyond which climate change risks become unacceptably high. This “2 °C” threshold is likely ...to be reached between 2040 and 2050 for both Representative Concentration Pathway (RCP) 8.5 and 4.5. Resulting sea level rises will not be globally uniform, due to ocean dynamical processes and changes in gravity associated with water mass redistribution. Here we provide probabilistic sea level rise projections for the global coastline with warming above the 2 °C goal. By 2040, with a 2 °C warming under the RCP8.5 scenario, more than 90%of coastal areas will experience sea level rise exceeding the global estimate of 0.2 m, with up to 0.4 m expected along the Atlantic coast of North America and Norway. With a 5 °C rise by 2100, sea level will rise rapidly, reaching 0.9 m (median), and 80% of the coastline will exceed the global sea level rise at the 95th percentile upper limit of 1.8 m. Under RCP8.5, by 2100, New York may expect rises of 1.09 m, Guangzhou may expect rises of 0.91 m, and Lagos may expect rises of 0.90 m, with the 95th percentile upper limit of 2.24 m, 1.93 m, and 1.92 m, respectively. The coastal communities of rapidly expanding cities in the developing world, and vulnerable tropical coastal ecosystems, will have a very limited time after midcentury to adapt to sea level rises unprecedented since the dawn of the Bronze Age.
Due to the recent development of deep learning techniques applied to satellite imagery, weather forecasting that uses remote sensing data has also been the subject of major progress. The present ...paper investigates multiple hours ahead coastal sea elements forecasting in the Netherlands using UNet based architectures. The hourly satellite image data from the Copernicus observation program spanned over a period of two years has been used to train the models and make the forecasting, including seasonal forecasting. Here, we propose 3D dimension Reducer UNet (3DDR-UNet), a variation of the UNet architecture, and further extend this novel model using residual connections, parallel convolutions and asymmetric convolutions which result in introducing three additional architectures, i.e. Res-3DDR-UNet, InceptionRes-3DDR-UNet and AsymmInceptionRes-3DDR-UNet respectively. In particular, we show that the architecture equipped with parallel and asymmetric convolutions as well as skip connections outperforms the other three discussed models.
Eutrophication-driven hypoxia is one of the reasons for the deterioration of coastal waters, especially those adjacent to densely inhabited urban cities. Thus, effective hypoxia management is ...urgently needed, and quantitative knowledge of factors controlling hypoxia is required. A case in point is the coastal water around Hong Kong, a megacity that has over 7.5 million residents and is located downstream of the large and nutrient-rich Pearl River. The Victoria Harbour (VH) is the core area of Hong Kong water and has been suffering from marine environment deterioration for years because of external biogeochemical influxes from adjacent waters and internal physical and biogeochemical responses. Three channels orienting from south to north (C1), southeast to northwest (C2), and west to east (C3) connect the VH to adjacent waters and serve as the primary exchange pathways for water mass and biogeochemical substances. Using observational data and a coupled physical–biogeochemical model, we showed that the northward transport of low dissolved oxygen (DO) water from the coastal transition zone by the shoreward bottom current mainly through C1 directly contributes to the hypoxia formation in VH. The external influx of anthropogenic nutrients and organic matter through C2 further enhances the bottom water hypoxia in VH by stimulating phytoplankton bloom and microbial consumption of oxygen in water columns and sediments. Although the horizontal oxygen influx to VH is weak, the comparatively strong vertical mixing in C3 facilitates the replenishment of bottom water in the VH, mitigating bottom hypoxia. Locally in the VH, sediment oxygen demand is the dominant biogeochemical contributor (~93%) to hypoxia formation, while the contribution of water column remineralization is relatively minor (~6-7%). In general, vertical diffusion serves as the largest source (~57%) of DO in the VH because of the strong vertical DO gradient, whereas vertical motion ranks the second largest source of DO (~24%) and serves as a critical physical factor regulating the oxygen budget of the entire VH. In the spatial constriction area where the vertical DO gradient is weak, the magnitude of vertical motion exceeds vertical diffusion to become the largest source of DO (~48%).
We review the characteristics of sea level variability at the coast focussing on how it differs from the variability in the nearby deep ocean. Sea level variability occurs on all timescales, with ...processes at higher frequencies tending to have a larger magnitude at the coast due to resonance and other dynamics. In the case of some processes, such as the tides, the presence of the coast and the shallow waters of the shelves results in the processes being considerably more complex than offshore. However, ‘coastal variability’ should not always be considered as ‘short spatial scale variability’ but can be the result of signals transmitted along the coast from 1000s km away. Fortunately, thanks to tide gauges being necessarily located at the coast, many aspects of coastal sea level variability can be claimed to be better understood than those in the deep ocean. Nevertheless, certain aspects of coastal variability remain under-researched, including how changes in some processes (e.g., wave setup, river runoff) may have contributed to the historical mean sea level records obtained from tide gauges which are now used routinely in large-scale climate research.
The marginal Bohai Sea, connected to the northwestern Pacific Ocean, is threatened by human activity. The Yellow River, the second largest river in China, drains large amounts of water, silts, and ...polycyclic aromatic hydrocarbons (PAHs) into the southern Bohai Sea; however, to what extent the Yellow River inputs influence the spatial distributions and partitions of PAHs in the southern Bohai Sea is not well known. Therefore, this study collected surface water, bottom water, and sediment samples from the southern Bohai Sea and analyzed them to examine the spatial distributions and partitions of 15 priority PAHs. The results showed that PAH concentrations ranged from 26.9 to 50.1 ng L-1 in surface water, 18.8 to 44.1 ng L-1 in bottom water, and 7.4 to 143.9 ng g-1 in sediment, with higher proportions of four-, five-, and six-ring PAHs in sediment than in water. PAH inputs from the Yellow River and sea coastal currents determined the spatial distribution of PAH concentrations in water and sediment, with an overall decrease from the estuary to the southeast. However, the solid dilution effect of input silts from the Yellow River and the liquid dilution effect of water from the Yellow River and Yellow Sea led to lower PAH concentrations in the water and sediment of the southern Bohai Sea than those in other areas of the Bohai Sea. PAH exchange between the atmosphere and seawater led to significantly higher individual PAH concentrations (except for acenaphthylene) in the surface water than in the bottom water, with ratios significantly related to the PAH n-octanol-water partition coefficient, organic carbon-water partition coefficient, and Henry's law constants. These parameters also determined PAH partitioning between the bottom water and sediment. Individual and total PAH concentrations in the sediment were significantly correlated with organic matter, clay, and silt contents. Therefore, the partitions and spatial distributions of PAHs in the southern Bohai Sea comprehensively depend on PAH properties, PAH inputs from the Yellow River and the atmosphere, sea currents, and seawater and sediment properties. The ecological risks posed by individual PAHs in both water and sediment were negligible or acceptable.
A power law velocity profile for engineering application was obtained based on the field data set of flow velocity and sediment concentration in coastal areas of Jinzhou, Nantong, and Zhoushan. Using ...theoretical analyses, van Rijn's formula for sediment concentration profile was modified. Tests of the new power-law velocity profile and the modified formula of suspended sediment concentration against a large data set were performed. The results show a good fit to the data and that these two formulae could demonstrate the basic principles of vertical distribution of flow velocity and suspended sediment concentration, respectively.
Suspended particulate matter (SPM) dynamics and exchange fluxes at the interface between a macrotidal estuary and its adjacent coastal sea were investigated from long-term high-frequency in situ ...observations. Optical and acoustic measurements were coupled to calculate SPM concentration over the whole water column using an existing acoustic inversion algorithm. A method was developed to distribute over the water column the surface and bottom calibrated equivalent particle diameters based on complementary ship-based surveys. Surface and bottom SPM show similar patterns in response to main forcings (tide, river discharge and waves), but present significantly higher concentrations near the bed. Increasing tidal ranges were responsible for higher tidal-median SPM concentrations, with spring/neap SPMC ratio varying from 2 to 3. This increase is driven by local resuspension during flood phase at the bottom, and low salinity turbid water flushed out from the estuary from mid-ebb to low tide at the surface. Increasing river discharge implies a downward shift of the estuarine turbidity maximum from the inner estuary to the mouth, and yields a 2-fold increase in both surface and bottom tidal-median concentration. Waves generated strong resuspension, with the highest SPM concentration recorded both at the surface and near the bed. Analysing SPM residual fluxes highlighted large up-estuary fluxes from low to moderate tidal ranges (below 6 m), and exporting seaward fluxes for higher tidal ranges, due to stronger mixing during spring tides. High river discharge enhanced stratification at the mouth and strengthened density circulation and up-estuary residual bottom circulation, resulting in larger up-estuary fluxes for all tidal ranges. Larger SPM concentrations along the tidal cycle during wave events yield high exporting fluxes.
•Long term high frequency observations were analyzed to investigate the sediment dynamics at the estuary - bay interface•An original approach was developed to unify and inverse acoustic backscatter signal to suspended sediment concentration•Sediment fluxes at the estuary mouth were analyzed to apprehend sediment exchange in response to riverine and oceanic forcings
This study investigates the propagation of coastal trapped waves (CTWs) along the Brazilian continental shelf between 34°S and 11°S using in situ data combined with the outputs from a high-resolution ...ocean simulation with HYCOM. The CTWs generation area covers a wide region ranging from the Patagonian shelf to the southern Brazilian shelf. The spectral analysis of coastal sea level series between 54°S and 10.5°S shows three bands of high energy associated with periods from 5 to 12 days, 15–22 days, and 25–40 days. The energy of the CTWs decreases along their propagation for all frequency bands, showing a drastic reduction north of 22°S, due to abrupt variations in the width and depth of the continental shelf between Tubarão Bight and Abrolhos Bank. Their phase speed propagation varies along the coast, being faster (>25 m/s) in the southernmost region (between 42°S and 41°S), reaching ~11 m/s north of 41°S, and reducing to ~3 m/s further north (equatorward of 24°S). The free Continental Shelf Wave theory supports the notion that the intense deceleration north of 24°S can be explained by the narrowing of the continental shelf. The stratification parameter indicates that the Brazilian continental shelf has a barotropic response to wind-generated disturbances.
Identifying physical processes responsible for historical coastal sea-level changes is important for anticipating future impacts. Recent studies sought to understand the drivers of interannual to ...multidecadal sea-level changes on the United States Atlantic and Gulf coasts. Ocean dynamics, terrestrial water storage, vertical land motion, and melting of land ice were highlighted as important mechanisms of sea-level change along this densely populated coast on these time scales. While known to exert an important control on coastal ocean circulation, variable river discharge has been absent from recent discussions of drivers of sea-level change. We update calculations from the 1970s, comparing annual river-discharge and coastal sea-level data along the Gulf of Maine, Mid-Atlantic Bight, South Atlantic Bight, and Gulf of Mexico during 1910–2017. We show that river-discharge and sea-level changes are significantly correlated (p < 0.01), such that sea level rises between 0.01 and 0.08 cm for a 1 km³ annual river-discharge increase, depending on region. We formulate a theory that describes the relation between river-discharge and halosteric sea-level changes (i.e., changes in sea level related to salinity) as a function of river discharge, Earth’s rotation, and density stratification. This theory correctly predicts the order of observed increment sea-level change per unit river-discharge anomaly, suggesting a causal relation. Our results have implications for remote sensing, climate modeling, interpreting Common Era proxy sea-level reconstructions, and projecting coastal flood risk.
Coastal areas can represent an ecological transition zone with the function of biodiversity conservation, and good water quality is fundamental to maintaining this function. In this study, we ...analyzed data from 2011 to 2020 to reveal the variation in dissolved oxygen (DO) and the aquatic biological response in China's coastal seas. Results showed that DO in coastal waters exhibited an upward trend from 2011 to 2020 because of reduction in terrestrial anthropogenic pollutant (TAP) input. In comparison with DO in other seas, the DO content in the East China Sea was lower owing to higher TAP input, i.e., the proportion of DO of <5 mg L−1 accounted for approximately 60% of the total. Species numbers, density, and the species diversity index of phytoplankton, zooplankton, and macrobenthos were different in the different sea areas because phytoplankton, zooplankton, and macrobenthos have different responses to changes in DO. In comparison with the species numbers of zooplankton and macrobenthos, the species numbers of phytoplankton were more significantly related to DO, and showed a negative linear relationship with a better DO environment (DO ≥ 5 mg L−1; r2 = 0.39, p < 0.01) and positive correlation with a poor DO environment (DO < 3 mg L−1; r2 = 0.52, p < 0.01). A better DO environment is conducive to increased density of macrobenthos. Studies have shown that a good DO environment contributes to coastal ecosystem health, and continuous control of TAP input is an effective means of ensuring DO recovery.
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•DO in the coastal seas has improved from 2011 to 2020.•East China Sea has worse DO than that in other seas due to more TAP input.•The responses of aquatic organisms to DO changes were different.•Further control TAP input benefit for DO recovery and coastal ecosystem protection.
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