ABSTRACT
Predicting the solar activity of upcoming cycles is crucial nowadays to anticipate potentially adverse space weather effects on the Earth’s environment produced by coronal transients and ...traveling interplanetary disturbances. The latest advances in deep learning techniques provide new paradigms to obtain effective prediction models that allow to forecast in detail the evolution of cosmogeophysical time series. Because of the underlying complexity of the dynamo mechanism in the solar interior that is at the origin of the solar cycle phenomenon, the predictions offered by state-of-the-art machine learning algorithms represent valuable tools for our understanding of the cycle progression. As a plus, Bayesian deep learning is particularly compelling thanks to recent advances in the field that provide improvements in both accuracy and uncertainty quantification compared to classical techniques. In this work, a deep learning long short-term memory model is employed to predict the complete profile of Solar Cycle 25, thus forecasting also the advent of the next solar minimum. A rigorous uncertainty estimation of the predicted sunspot number is obtained by applying a Bayesian approach. Two different model validation techniques, namely the Train-Test split and the time series k-fold cross-validation, have been implemented and compared, giving compatible results. The forecasted peak amplitude is lower than that of the preceding cycle. Solar Cycle 25 will last 10.6 ± 0.7 yr, reaching its maximum in the middle of the year 2024. The next solar minimum is predicted in 2030 and will be as deep as the previous one.
Tidal measurements from the Italian city of Venice, available since 1872 and constituting the longest sea-level record in the Mediterranean area, indicate that local flooding statistics have ...dramatically worsened during the last decades. Individual flooding episodes are associated with adverse meteorological conditions, and their increased frequency is mainly attributed to the rise of the average local Relative Sea Level (RSL). However, the role of interannual-to-multidecadal modes of average RSL variability in shaping the evolution of Venice flooding is highly significant and can cause sharp increases in the flood frequency episodes. Here, we use local tidal measurements in Venice covering 1872–2020 to deeply inspect the contribution and predictability of the different components characterizing the observed average RSL variability, including a long-term trend and four quasi-periodic modes. Our results demonstrate that the observed increase in flooding frequency is not only due to the average RSL rise but also due to a progressive widening of tidal anomalies around the average RSL, revealed by opposite trends in mean tidal maxima and minima. Moreover, interannual and decadal periodicities are not negligible in modulating the timing of annual mean RSL and flood frequency extremes. This study demonstrates that the last decades experienced an unprecedented sharp increase in sea level, which significantly affected the decadal predictability of RSL with statistical methods. Our work contributes to a deeper understanding of the sources of uncertainty in decadal sea-level variability and predictability in the Venice lagoon.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Transitional coastal zones are subject to high degrees of temporal fluctuation in environmental conditions, with these patterns varying in space. Gaining an in depth understanding of how sessile ...organisms cope with and respond to such environmental changes at multiple scales is needed to i) advance fundamental knowledge, ii) predict how organisms may react to stressors and iii) support the management of halieutic resources in transitional coastal areas. We addressed this question using mussels (Mytilus galloprovincialis) as model system. Valve-gaping sensor were deployed at multiple sites within the southern Venice Lagoon over a period of 6 months, to investigate the existence of periodicity in valve-gaping and its relationship with environmental variables, such as temperature and chlorophyll-a.
Gaping behaviour was found to have periodic rhythms, of ~12 h and ~ 24 h, which were most pronounced in the inner part of lagoon part and were strongest during summer months. In autumn, the dual periodicity became weaker and mostly the 12 h remained. Gaping was closely linked with tide, but the relationship in terms of phasing varied upon location. Surprisingly, no clear direct relationships were found with chlorophyll-a, but food delivery may be mediated by tide itself. The results highlight the heterogeneity of behaviour and the endogenic nature of circadian rhythms in space and time. These findings have important implications for management of transitional areas where tidal alteration may have impacts on key behaviours, and emphasize the importance of characterizing their rhythms before using these as stress indicator. Moreover, the described tidal relationships should be included in growth models of bivalves in these systems.
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•It is necessary to understand how organisms respond to environmental changes.•Transitional coastal areas are great model systems.•Mussels behaviour was monitored long-term and in continuous in three sites.•It followed the tidal rhythm particularly in more internal site and in summer.•Responses to small scale changes are important for management and for predictions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, we apply multichannel singular spectrum analysis (MSSA), a data-adaptive, multivariate, non-parametric technique that simultaneously exploits the spatial and temporal correlations of ...the input data to extract common modes of variability, to investigate the intermediate quasi-periodicities of the Fe
xiv
green coronal emission line at 530.3 nm for the period between 1944 and 2008. Our analysis reveals several significant mid-term periodicities in a range from about one to four years that are consistent with the so-called quasi-biennial oscillations (QBOs), which have been detected by several authors using different data sets and analysis methods. These QBOs display amplitudes varying significantly with time and latitude over the six solar cycles (18 to 23) covered by this study. A clear North–South asymmetry is detected both in their intensity and period distribution, with a net predominance of spectral power in the active-region belt of the northern hemisphere. On the other hand, while the QBOs with periods
≳
1.7
years are particularly intense around the polar regions and therefore related to the global magnetic field, the ones with shorter periods are mainly generated at mid-latitudes, in correspondence with the emergence of active regions. Our findings indicate that the North–South asymmetry manifested in the uneven latitudinal distribution of QBOs is a fundamental, albeit puzzling, characteristic of solar activity.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The German Bight is a shallow area in the southeastern North Sea. Atmospheric forcing, particularly wind stress, plays an essential role in the sea circulation dynamics in the area as a source of ...momentum and consequent driver of the variability on seasonal to interannual timescales. Westerly and SouthWesterly winds constitute the mean state of this forcing over the North Sea due to the persistent pressure gradients between the Icelandic Low and the Azores High. Consequently, the transport in the North Sea is primarily cyclonic. Nevertheless, the presence of land influences wind stress in the coastal regions (in terms of both intensity and direction). Moreover, distant locations respond differently to the action of the atmospheric pressure centers. Therefore, studies characterizing wind statistics in specific regions are mandatory for understanding and numerically simulating the sea circulation patterns in such areas. We present a detailed analysis of wind patterns in the German Bight, specifically in the Marine Protected Areas and Helgoland Island, using ERA5 reanalysis atmospheric data. We define and catalog area‐specific “events” according to their typical duration and magnitude and analyze their seasonality and interannual variability. We investigate the most recurrent locations and intensities of the high‐ and low‐pressure dipoles causing specific wind patterns over the German Bight during the different periods of the year. We show how, besides Westerly and SouthWesterly winds, NorthWesterly flows are a recurrent pattern in the area; winds from the East are less frequent but can be extremely persistent over the same site in the spring.
Plain Language Summary
Winds significantly affect the sea circulation in the German Bight, in the southeastern part of the North Sea. Typical winds come from the West and SouthWest, causing a general anticlockwise transport in the area. However, because of the presence of land, winds in coastal regions can significantly differ from the mean flow over the North Sea basin. This study provides a definition and complete catalog of significant wind events in the German Bight, specifically in the Marine Protected Areas and Helgoland Island, selected for their socioeconomic and scientific relevance. We describe which winds are more frequent during the year since, besides the Westerly and SouthWesterly winds, those from the NorthWest are also frequent. We report which events are more intense and which have the highest probability of persisting for several days, like the Easterly winds in spring. We also show how the frequency of the events has changed in the last decades. Finally, we also show the characteristic features of the mean sea level pressure centers originating the various wind events because these local phenomena derive from atmospheric systems over a large area.
Key Points
This study provides the definition and catalog of wind events in four sites in the German Bight
The events are classified according to their persistence, mean intensity, seasonality, and interannual variability
The events' local features are analyzed and discussed in the context of the large‐scale pressure systems that originated them
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Sea‐level rise is one of the most critical consequences of global warming, with potentially vast impacts on coastal environments and societies. Sea‐level changes are spatially and temporally ...heterogeneous on multiannual‐to‐multidecadal timescales. Here, we demonstrate that the observed rate of winter sea‐level rise in the Italian city of Venice contains significant multidecadal fluctuations, including interdecadal periods of near‐zero trend. Previous literature established a connection between the local sea‐level trend in Venice and over the broad subpolar and eastern North Atlantic. We demonstrate that for multidecadal variations in sea‐level trend such connection holds only since the mid‐20th Century. Such multidecadal sea‐level fluctuations relate to North Atlantic sea‐surface temperature changes described by the Atlantic multidecadal variability, or AMV. The link is explained by combined effect of AMV‐linked steric variations in the North Atlantic propagating in the Mediterranean Sea, and large‐scale atmospheric circulation anomalies over the North Atlantic with a local effect on sea level in Venice. We discuss the implications of such variability for near‐term predictability of winter sea‐level changes in Venice. Combining available sea‐level projections for Venice with a scenario of imminent AMV cooling yields a slowdown in the rate of sea‐level rise in Venice, with the possibility of mean values remaining even roughly constant in the next two decades as AMV effects contrast the expected long‐term sea‐level rise. Acknowledging, understanding, and communicating this multidecadal variability in local sea‐level rise is crucial for management and protection of this world‐class historical site.
Plain Language Summary
Environmental and socioeconomic impacts of sea‐level rise are one of the major concerns of global warming. Here, we consider the case of the Italian city of Venice, one of the iconic locations for the potentially dramatic effects of sea‐level rise. We show that the sea‐level evolution in Venice during the past ∼150 years contains strong multidecadal fluctuations, so that periods of more than two decades when there is little or no trend occurred even in the recent past. We link these fluctuations with sea‐level and climatic variations in the North Atlantic. In particular, we focus on the phenomenon known as Atlantic multidecadal variability, or AMV, which describes the alternation over multidecadal periods of warm and cold phases of the North Atlantic surface. Our results indicate that warm AMV phases are linked to faster sea‐level rise in Venice and vice versa. Accordingly, we build sea‐level rise scenarios for Venice until 2035 by considering an imminent AMV cooling as suggested by recent studies. The scenarios yield a temporary slowdown of sea‐level rise as the AMV contrasts the effects of global warming. This sea‐level variability can strongly impact on the management of protective measures against flooding currently operative in Venice.
Key Points
The historical rate of sea‐level rise in Venice contains large multidecadal fluctuations and interdecadal periods of near‐zero trend
Multidecadal sea‐level trend variations in Venice follow those in the subpolar North Atlantic since the mid‐20th Century
Atlantic multidecadal variability paves the way for the exploration of decadal predictability of sea‐level rise in Venice
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
On 1996 December 19, the Ultraviolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO) conducted a special high-cadence sit-and-stare observation in the O vi 1032 ...Å spectral line above a polar coronal hole at a heliocentric distance of 1.38 R⊙. The ~ 9-h dataset was analyzed by applying advanced spectral techniques to investigate the possible presence of propagating waves. Highly significant oscillations in O vi intensity (P = 19.5 min) and Doppler shift (P = 7.2 min) were detected over two different portions of the UVCS entrance slit. A cross-correlation analysis between the O vi intensity and Doppler shift fluctuations shows that the most powerful oscillations were in phase or anti-phase over the same portions of the slit, thus providing a possible signature of propagating magnetosonic waves. The episodic nature of the observed oscillations and the large amplitudes of the Doppler shift fluctuations detected in our observations, if not attributable to line-of-sight effects or inefficient damping, may indicate that the observed fluctuations were produced by quasi-periodic upflows.
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FMFMET, NUK, UL, UM, UPUK
Typical reconstructions of historic heliospheric magnetic field (HMF) BHMF are based on the analysis of the sunspot activity, geomagnetic data or on measurement of cosmogenic isotopes stored in ...terrestrial reservoirs like trees (14C) and ice cores (10Be). The various reconstructions of BHMF are however discordant both in strength and trend. Cosmogenic isotopes, which are produced by galactic cosmic rays impacting on meteoroids and whose production rate is modulated by the varying HMF convected outward by the solar wind, may offer an alternative tool for the investigation of the HMF in the past centuries. In this work, we aim to evaluate the long-term evolution of BHMF over a period covering the past twenty-two solar cycles by using measurements of the cosmogenic 44Ti activity (τ1∕2 = 59.2 ± 0.6 yr) measured in 20 meteorites which fell between 1766 and 2001. Within the given uncertainties, our result is compatible with a HMF increase from 4.87-0.30+0.24 $4.87^{+0.24}_{-0.30}$ 4.87-0.30+0.24 nT in 1766 to 6.83-0.11+0.13 $6.83^{+0.13}_{-0.11}$ 6.83-0.11+0.13 nT in 2001, thus implying an overall average increment of 1.96-0.35+0.43 $1.96^{+0.43}_{-0.35}$ 1.96-0.35+0.43 nT over 235 years since 1766 reflecting the modern Grand maximum. The BHMF trend thus obtained is then compared with the most recent reconstructions of the near-Earth HMF strength based on geomagnetic, sunspot number, and cosmogenic isotope data.
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FMFMET, NUK, UL, UM, UPUK
Climate change effects on coastal ecosystems vary on large spatial scales, but can also be highly site dependent at the regional level. The Wadden Sea in the south-eastern North Sea is warming faster ...than many other temperate coastal areas, with surface seawater temperature increasing by almost 2 °C over the last 60 years, nearly double the global ocean mean increase. Climate warming is accompanied by rising sea levels, which have increased by approximately 2 mm yr
−1
over the last 120 years. For this sedimentary coast, the predicted acceleration of sea-level rise will have profound effects on tidal dynamics and bathymetry in the area. This paper synthesises studies of the effects of ocean warming and sea level rise in the northern Wadden Sea, largely based on research conducted at the Wadden Sea Station Sylt of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research. An increasing rate of sea level rise above a critical threshold will lead to coastal erosion and changes in sediment composition, and may cause the transition from a tidal to lagoon-like environment as tidal flats submerge. This involves changes to coastal morphology, and the decline of important habitats such as muddy tidal flats, salt marshes and seagrass meadows, as well as their ecological services (e.g. carbon sequestration). Ocean warming affects plankton dynamics and phenology, as well as benthic community structure by hampering cold-adapted but facilitating warm-adapted species. The latter consist mostly of introduced non-native species originating from warmer coasts, with some epibenthic species acting as ecosystem engineers that create novel habitats on the tidal flats. Warming also changes interactions between species by decoupling existing predator–prey dynamics, as well as forming new interactions in which mass mortalities caused by parasites and pathogens can play an understudied but essential role. However, Wadden Sea organisms can adapt to changing abiotic and biotic parameters via genetic adaptation and phenotypic plasticity, which can also be inherited across generations (transgenerational plasticity), enabling faster plastic responses to future conditions. Important research advances have been made using next-generation molecular tools (-omics), mesocosm experiments simulating future climate scenarios, modelling approaches (ecological network analysis), and internet-based technologies for data collection and archiving. By synthesising these climate change impacts on multiple levels of physical and biological organisation in the northern Wadden Sea, we reveal knowledge gaps that need to be addressed by future investigations and comparative studies in other regions in order to implement management, mitigation and restoration strategies to preserve the uniqueness of this ecosystem of global importance.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The analysis of two historical time series of temperature and precipitation in Northeast China, spanning, respectively, 1870-2004 and 1841-2004, performed by continuous wavelet transform and other ...classical and advanced spectral methods, is presented here. Both variables show a particular trend and oscillations of about 85, 60, 35 and 20 years that are highly significant, with a phase opposition at the centennial scale and at the 20-year scale. The analysis of the four temperature series relative to single seasons shows that the 20-year cycle is typical of the summer monsoon season, while the 35-year cycle is most evident in winter. The cycles of ~ 60 years and longer are present in all seasons. The centennial variation of temperature and precipitation describes well the 1970-1980 transition between a period of relatively strong East Asian Summer Monsoon (EASM), corresponding to high precipitation and relatively cool temperatures in Northeast China, and a conditions of weak EASM (low precipitation and warm temperatures). The connection of the detected local variations with large-scale climatic variability is deduced from the comparison with different climatic records (Northern Hemisphere temperature, Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation indexes).
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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