North Atlantic Oscillation Index Research Articles

Identifying targets for conservation: the arrival and loss of Common Eider Somateria mollissima ducklings in an estuarine nursery

ABSTRACTCapsuleThe arrival of Common Eider Somateria mollissima ducklings into a reception and nursery area is a measure of breeding success and phenology but reveals gaps in knowledge for effective conservation.AimsEstuarine habitats are important wildlife areas but are continually under threat from human activities. Common Eiders may be an indicator species for monitoring the impacts of development in estuaries used by them as nursery areas. The aim of this study was to understand the arrival and distribution of ducklings in a commercial and recreational estuarine environment.MethodsCoquet Island, Northumberland, is a breeding site for Common Eiders at the southern limit of their range on the east coast of the UK. Numbers of ducklings arriving in the adjacent Coquet Estuary nursery area were monitored daily during the breeding season over a 27-year period from 1995 to 2021 inclusive.ResultsCounts of ducklings were higher overall in less disturbed parts of the estuary, but there were no consistent patterns of habitat use. First-arrival dates varied annually by up to 23 days. Daily arrival counts were affected by tide and, to a lesser extent, rain and wind direction. Observed arrivals each season correlated with counts of breeding females on Coquet Island. There was evidence for links between broader-scale weather conditions (North Atlantic Oscillation indices) and yearly variation in rates of duckling arrival. Arrivals were more synchronous in years when ducklings were late in arriving and supported theoretical predictions from modelling studies. There were high daily rates of duckling loss from the estuary which may have been a consequence of brood movements out of the estuary and loss to predation. There was a positive correlation between counts of ducklings and attendant females.ConclusionsAnnual duckling counts show the value of estuaries for monitoring phenological variation in the breeding of Common Eiders. A better understanding of environmental factors influencing duckling retention or loss in estuaries is needed. Enabling human and wildlife activities to exist together within estuarine environments may promote effective conservation.

Seasonal SIMS δ18O record in Astarte borealis from the Baltic Sea tracks a modern regime shift in the NAO

IntroductionAstarte borealis holds great potential as an archive of seasonal paleoclimate, especially due to its long lifespan (several decades to more than a century) and ubiquitous distribution across high northern latitudes. Furthermore, recent work demonstrates that the isotope geochemistry of the aragonite shell is a faithful proxy of environmental conditions. However, the exceedingly slow growth rates of A. borealis in some locations (<0.2mm/year) make it difficult to achieve seasonal resolution using standard micromilling techniques for conventional stable isotope analysis. Moreover, oxygen isotope (δ18O) records from species inhabiting brackish environments are notoriously difficult to use as paleoclimate archives because of the simultaneous variation in temperature and δ18Owater values.MethodsHere we use secondary ion mass spectrometry (SIMS) to microsample an A. borealis specimen from the southern Baltic Sea, yielding 451 SIMS δ18Oshell values at sub-monthly resolution.ResultsSIMS δ18Oshell values exhibit a quasi-sinusoidal pattern with 24 local maxima and minima coinciding with 24 annual growth increments between March 1977 and the month before specimen collection in May 2001.DiscussionAge-modeled SIMS δ18Oshell values correlate significantly with both in situ temperature measured from shipborne CTD casts (r2 = 0.52, p<0.001) and sea surface temperature from the ORAS5-SST global reanalysis product for the Baltic Sea region (r2 = 0.42, p<0.001). We observe the strongest correlation between SIMS δ18Oshell values and salinity when both datasets are run through a 36-month LOWESS function (r2 = 0.71, p < 0.001). Similarly, we find that LOWESS-smoothed SIMS δ18Oshell values exhibit a moderate correlation with the LOWESS-smoothed North Atlantic Oscillation (NAO) Index (r2 = 0.46, p<0.001). Change point analysis supports that SIMS δ18Oshell values capture a well-documented regime shift in the NAO circa 1989. We hypothesize that the correlation between the SIMS δ18Oshell time series and the NAO is enhanced by the latter’s influence on the regional covariance of water temperature and δ18Owater values on interannual and longer timescales in the Baltic Sea. These results showcase the potential for SIMS δ18Oshell values in A. borealis shells to provide robust paleoclimate information regarding hydroclimate variability from seasonal to decadal timescales.

Variability in Global Climatic Circulation Indices and Its Relationship

Global climatic circulation indices play a major role in determining regional and global climate conditions. These atmospheric circulation patterns exhibit substantial variability, covering a wide geographical area and affecting weather-related events. The primary goal of this study was to examine and characterize various global climatic variability indices during the 1950 to 2020 period (El Niño Southern Oscillation, ENSO; Southern Oscillation Index, SOI; North Atlantic Oscillation, NAO; Atlantic Meridional Mode, AMM; and Indian Ocean Dipole, IOD). Also, this article try to investigating the link between these global climatic indices. Trend analysis showed that the ENSO index exhibits the highest recurrence frequency of correlation relationships with the other yearly global indices with significance at the 95% and 99% levels, while the NAO index exhibits the lowest recurrence frequency. On a seasonal basis, most indices demonstrate more abrupt changes during the winter season than during the summer. An increase occurred in events of abrupt changes in these indices over the last two decades (2000 to 2020), especially annually and in summer. The SOI exhibits the largest number of abrupt changes throughout the entire study period, spanning from positive to negative significant trends, whereas the IOD did not exhibit abrupt changes annually. Increasing and decreasing trends in the global climatic circulation indices may be related to natural and anthropogenic causes of climate change. Regarding both the correlation coefficient (CC) and partial correlation results, there existed a highly negative association between the ENSO and SOI in the annual, winter and summer time series. On the other hand, there is no relationship between ENSO and NAO. Furthermore, on an annual basis, there existed a highly negative association between the NAO and AMM and a less negative but still statistically significant association between these indices during the winter and summer seasons, respectively. Therefore, through the Azore high, the NAO could promote AMM. Moreover, when the NAO, AMM, and SOI are held constant, a positive and robust correlation is reached between the ENSO and IOD in winter season. Therefore, a developing IOD is intensified and sustained during the onset of an El Niño event in winter season.

Fluctuations of ice in a lake due to the impact of the North Atlantic Oscillation (1960/61–2009/10) – a case study of Łebsko Lake

The paper represents an attempt to understand the impacts produced by the North Atlantic Oscillation on the ice cover regime of the largest coastal lake in Poland situated in the northern part of the country. The purpose of the study was to estimate the impact of the North Atlantic Oscillation on selected ice cover parameters. The study also attempts to examine other factors that may affect its significant impact on observed changes in the climate. Water temperature data are used to assess temperature conditions in aqueous ecosystems as well as determine the heat absorption capacity of these systems. This allows one to then determine cooling rates in the event of ice cover formation. The data analysis provided in the paper focuses on selected characteristics of ice cover conditions (i.e. dependent variables) including the number of days with ice and maximum ice thickness in relation to NAO index changes (i.e. independent variables) for the reference period 1960/61–2009/10. In addition, the paper divides the studied period into 10-year subperiods in order to capture the weakest and strongest phases of NAO and assess the extent to which they affect the duration of ice cover. A large increase in the mean air temperature (1.8°C) occurred in the years 1960–2010. Trendline analysis indicates that the number of days with ice cover declined by about 60 days and the maximum thickness of ice cover decreased by about 10 cm. Oceanographic research employs satellite image data in order to accurately assess human impact. Therefore, ice cover forecasts generated for consecutive winter seasons may become an important tool in this type of assessment.

Asthma incidence can be influenced by climate change in Italy: findings from the GEIRD study—a climatological and epidemiological assessment

An association between climatic conditions and asthma incidence has been widely assumed. However, it is unclear whether climatic variations have a fingerprint on asthma dynamics over long time intervals. The aim of this study is to detect a possible correlation of the Summer North Atlantic Oscillation (S-NAO) index and the self-calibrated palmer drought severity index (scPDSI) with asthma incidence over the period from 1957 to 2006 in Italy. To this aim, an analysis of non-stationary and non-linear signals was performed on the time series of the Italian databases on respiratory health (ISAYA and GEIRD) including 36,255 individuals overall, S-NAO, and scPDSI indices to search for characteristic periodicities. The ISAYA (Italian Study on Asthma in Young Adults) and GEIRD (Gene Environment Interactions in Respiratory Diseases) studies collected information on respiratory health in general population samples, born between 1925 and 1989 and aged 20–84 years at the time of the interview, from 13 Italian centres. We found that annual asthma total incidence shared the same periodicity throughout the 1957–2006 time interval. Asthma incidence turned out to be correlated with the dynamics of the scPDSI, modulated by the S-NAO, sharing the same averaged 6 year-periodicity. Since climate patterns appear to influence asthma incidence, future studies aimed at elucidating the complex relationships between climate and asthma incidence are warranted.

The Combined Effect of Atmospheric and Solar Activity Forcings on the Hydroclimate in Southeastern Europe

The purpose of this study was to analyze the influence of solar activity described by the sunspot number (SSN) on certain terrestrial variables that might impact the Southeastern European climate at different spatio-temporal scales (the North Atlantic Oscillation Index, NAOI, and the Greenland–Balkan Oscillation Index, GBOI—on a large scale; the Palmer Hydrological Drought Index, PHDI—on a regional scale; the Danube discharge at the Orsova (lower basin), Q, representative of the Southeastern European climate—on a local scale). The investigations were carried out for the 20th century using the annual and seasonal averages. To find the connections between terrestrial (atmospheric and hydrological) parameters and SSN, the wavelet coherence were used both globally and in the time–frequency domain. The analyses were carried out for the time series and considered simultaneously (in the same year or season), as well as with lags from 1 to 5 years between the analyzed variables. For the annual values, the type of correlation (linear/non-linear) was also tested using elements from information theory. The results clearly revealed non-linear links between the SSN and the terrestrial variables, even for the annual average values. By applying the wavelet transform to test the solar influence on the terrestrial variables, it was shown that the connections depend on both the terrestrial variable, as well as on the considered lags. Since, in the present study, they were analyzed using wavelet coherence, but only the cases in which the coherence was significant for almost the entire analyzed time interval (1901–2000) and the terrestrial variables were in phase or antiphase with the SSN were considered. Relatively few results had a high level of significance. The analysis of seasonal averages revealed significant information, in addition to the analysis of annual averages. Thus, for the climatic indices, the GBOI and NAOI, a significant coherence (>95%) with the solar activity, associated with the 22-year (Hale) solar cycle, was found for the autumn season for lag = 0 and 1 year. The Hale solar cycle, in the case of the PHDI, was present in the annual and summer season averages, more clearly at lag = 0. For the Danube discharge at Orsova, the most significant SSN signature (~95%) was observed at periods of 33 years (Brüuckner cycle) in the autumn season for lags from 0 to 3 years. An analysis of the redundancy–synergy index was also carried out on the combination of the terrestrial variables with the solar variable in order to find the best synergistic combination for estimating the Danube discharge in the lower basin. The results differed depending on the timescale and the solar activity. For the average annual values, the most significant synergistic index was obtained for the combination of the GBOI, PHDI, and SSN, considered 3 years before Q.

Spatial Effects of NAO on Temperature and Precipitation Anomalies in Italy

The NAO teleconnective pattern has a great influence on the European climate; however, the exact quantification of NAO pattern in the different areas is sometimes lacking, and at other times, highlights even large differences between the various studies. This motivation led to the identification of the aim of this research in the study of the relationship between the NAO index and temperature and precipitation anomalies over the period 1991–2020, through the analysis of 87 rain gauges and 86 thermometric stations distributed as homogeneously as possible over the Italian territory. The results were sometimes at odds with the scientific literature on the subject, as significance was also found outside the winter season, e.g., in the spring for temperatures and in the autumn for precipitation, and in some cases, correlations were found, especially in August, even in southern Italy, which is usually considered a poorly correlated area. In addition, the linear relationship between the NAO index and temperature and precipitation anomalies was verified, with many weather stations obtaining significant coefficients of determinations as high as 0.5–0.6 in December, with 29 degrees of freedom, and a p-value set at 95%. Finally, for both climatic parameters, the presence of clusters and outliers at seasonal and monthly levels was assessed, obtaining a spatial distribution using the local Moran index, and summarising them in maps. This analysis highlighted important clusters in Northern and Central Italy, while clusters in the summer months occur in the South. These results provide information that may further elucidate local atmospheric dynamics in relation to NAO phases, as well as encourage future studies that may link other teleconnective indices aimed at better explaining the variance of climate parameters.

Construction of a deltaic strandplain during the Roman period in the Tavoliere di Puglia plain and palaeoclimatic implications

In response to the accidental exhumation of three ancient trees by farmers, we conducted a multidisciplinary study based on the stratigraphic analysis of boreholes, carbon-14 dating, aerial photo interpretation, and analysis of palaeobotanical and archaeological evidences. We reconstructed the formation and evolution during Roman times of a first “continuous” and then “discontinuous” deltaic strandplain at the mouth of the Carapelle Stream in the Tavoliere di Puglia Plain—the second-largest plain in Italy. Ttwo main phases can be recognised in the evolution of the Carapelle deltaic strandplain: 1) a first phase, lasted until ca. the birth of Christ, was characterised by a regular and continuous construction of sand ridges one leaning against the other; 2) a second phase, lasted more or less from the birth of Christ to the termination of the construction of the deltaic strandplain, was characterised by the discontinuous construction of sand ridges/coastal barriers with the isolation of lagoons/ponds, and by evidences of alluvial events. The most probable climatic–environmental scenario to have formed the Roman-period deltaic strandplain implied that: 1) the first phase was triggered by a higher total amount of precipitations, but with less extreme alluvial events; 2) the second phase was triggered by a total amount of precipitation lower than the previous period, but with higher occurrence of extreme alluvial events and/or by extreme alluvial events separated by longer period of low precipitations. This second phase was enhanced by the opening of vegetation. The passage between the first and second phase of the Carapelle deltaic strandplain coincides with the passage from overall negative NAO index to an overall positive NAO index.

Dolphin social phenotypes vary in response to food availability but not the North Atlantic Oscillation index.

Social behaviours can allow individuals to flexibly respond to environmental change, potentially buffering adverse effects. However, individuals may respond differently to the same environmental stimulus, complicating predictions for population-level response to environmental change. Here, we show that bottlenose dolphins (Tursiops truncatus) alter their social behaviour at yearly and monthly scales in response to a proxy for food availability (salmon abundance) but do not respond to variation in a proxy for climate (the North Atlantic Oscillation index). There was also individual variation in plasticity for gregariousness and connectedness to distant parts of the social network, although these traits showed limited repeatability. By contrast, individuals showed consistent differences in clustering with their immediate social environment at the yearly scale but no individual variation in plasticity for this trait at either timescale. These results indicate that social behaviour in free-ranging cetaceans can be highly resource dependent with individuals increasing their connectedness over short timescales but possibly reducing their wider range of connection at longer timescales. Some social traits showed more individual variation in plasticity or mean behaviour than others, highlighting how predictions for the responses of populations to environmental variation must consider the type of individual variation present in the population.

Exploring NAO influence on waterbirds abundance through hydrological changes in a Mediterranean coastal wetland

Predicting how waterbird populations may respond to climate change is a major challenge for conservation, which could be addressed by understanding the effects of large-scale climate oscillations, such as the North Atlantic Oscillation (NAO), on breeding population size. Here, we explore the relationship between the NAO position and the abundance of waterbird breeding pairs in a protected Mediterranean coastal wetland (Mouth of the Guadalhorce River, Málaga, southern Iberian Peninsula). We found a significant and negative relationship between the winter NAO index and the abundance of grebes (r=-0.72, N=15, p<0.01), rails (r=-0.74, N=15, p<0.01), diving ducks (r=-0.56, N=15, p<0.05) and dabbling ducks (r=-0.54, N=15, p<0.05). Our results suggest that this relation is mediated by the NAO indirect effects on wetland flooded surface via changes in winter precipitation and Mediterranean sea level. These results should be considered to design appropriate environmental management strategies devoted to preventing or mitigating potential deleterious effects of the NAO variability on Mediterranean wetlands ecosystems and preserving their valuable waterbird communities.

Synchronous Impact of the North Atlantic Oscillation (NAO) and Southern Oscillation Index (SOI( Poles on Temperature and Rain Over Iraq

Background: This study is an attempt to analyze the correlation of the impact of the North Atlantic Oscillation( NAO )and Southern Oscillation Index( SOI ) on the climate of Iraq. Method: This has been conducted based on the highest and lowest recorded values of the mentioned oscillations. The values of temperature and rain for the stations of Mosul, Baghdad, Rutba, Basrah and for a major climatic cycle from 1950-2018 were also relied upon. On the statistical analytical approach to find the correlation relationship between the studied oscillations and depending on the Pearson Correlation Coefficient. Results: The results brought to light that there is a strong and statistically significant correlation between the oscillations. The time series of oscillations were also analyzed during the fall season, due to the absence of a single effect of oscillations on the studied elements. Therefore, the analysis of the simultaneous behavior of oscillations on the climatic elements during the autumn was relied upon. In the meantime, four cases of simultaneous behavior for selected years of the study were found, recording the highest oscillations’ values. Such four cases were compared with the values of the elements for those years. Conclusion: It became clear from the four cases that there are two cases that show a regular behavior of the influence, as it became clear when the poles are NAO +, SOI - and vice versa that the climatic elements are affected more clearly with the oscillation's indicators and that the climate of Iraq has become more affected by the oscillations.

Climate and juvenile recruitment as drivers of Arctic cod (Boreogadus saida) dynamics in two Canadian Arctic seas

Arctic cod (Boreogadus saida) is the most abundant forage fish species in Arctic seas and plays a pivotal role in the transfer of energy between zooplankton and top predators. The dominance of Arctic cod and the Arctic’s relatively low biodiversity interact such that changing population dynamics of Arctic cod have cascading effects on whole Arctic marine ecosystems. Over the last decades, warming in the Arctic has led to a decline in Arctic cod populations in the Barents Sea, but in the Canadian Arctic these conditions have been correlated with up to a 10-fold higher biomass of age-0 Arctic cod at the end of summer. However, whether this enhanced larval survival with warmer waters endures through age-1+ populations is unknown. A better understanding of spatial variation in the response of Arctic cod populations to environmental conditions is critical to forecast future changes in Arctic ecosystems. Here, we rely on a 17-year time series of acoustic-trawl surveys (2003–2019) to test whether ice-breakup date, sea surface temperature, zooplankton density, and Arctic climate indices during early life stages affect the subsequent recruitment of age-1+ Arctic cod in the Beaufort Sea and Baffin Bay. In the Beaufort Sea, the biomass of age-1+ Arctic cod correlated with both Arctic Oscillation indices and age-0 biomass of the previous year. In Baffin Bay, the biomass of age-1+ Arctic cod correlated with previous-year North Atlantic Oscillation indices and the timing of ice breakup. This study demonstrates that climate and environmental conditions experienced during the early life stages drive the recruitment of the age-1+ Arctic cod population and helps to quantify spatial variation in the main environmental drivers.

Analysis of mesoscale Eddy in the Nordic seas and Barents Sea using multi-satellite data

Under the background of climate change, the characteristics of meso-scale eddies (radius > 20 km) in the Nordic Sea are worthy of further study. In this study, the daily sea level anomaly (SLA) product provided by archiving, validation, and interpretation of satellite oceanographic data (AVISO) and the daily sea surface temperature (SST) data provided by remote sensing systems (REMSSs) were collected from January 2003 to December 2021. The collected data were daily averaged with a spatial grid resolution of 0.25°. The large-scale eddies with a radius of >80 km and activity intensity (EKE) values of >0.02 m2/s were more detectable using SST data Moreover, the spatial distribution between the SLA-based and SST-based eddies had the opposite correlation with respect to the water depth. The SST-based eddies were more sensitive to seasonal variations. The long-term variations in the eddy parameters and the North Atlantic Oscillation Index (NAOI) during 2003–2021 were studied, and it was found that the radius of the SLA-based eddies was likely consistent with the NAOI and the EKE of the SLA-based eddies has the highest correlation (=0.2) with the NAOI, however, the correlation between eddy parameters and the NAOI is not significant. Collectively, SLA data has good performance on eddy identification in most cases, while SST data is suitable for investigating the activities of mesoscale eddies with large radius (> 80 km) and strong EKE (>0.02 m2/s).

Seasonality in the Amplitude of Decadal Variability

Abstract As the understanding of decadal variability in climate systems deepens, there is a growing interest in investigating the decadal variability of seasonal-mean or monthly mean variables. This study aims to understand the seasonality observed in the amplitude of decadal variability. To accomplish this, we analyze the decadal variability of the monthly mean North Atlantic Oscillation (NAO) index and North Pacific index (NPI) over the past decades using two different calculating processes: the full smoothing (F) process and the seasonal-specific (SS) process. Our findings suggest that the F process only captures the decadal variability of annual-mean variables, whereas the SS process is suited for capturing the seasonality of decadal variability. We find that the seasonality in decadal variability aligns with the seasonality in interannual variability. Additionally, we explore the seasonality in decadal variability in atmospheric and oceanic variables. The seasonality in oceanic decadal variability, including sea surface temperature and salinity, is found to be weak and small. The amplitude of decadal variability in the Pacific decadal oscillation (PDO) is similar across different months, indicating weak seasonality in the PDO. On the other hand, decadal variability of lower-tropospheric atmospheric circulation, including horizontal wind, geopotential height, and surface air temperature, exhibits significant seasonality in the extratropics, with the strongest decadal variability occurring in winter. Moreover, the significant seasonality in decadal variability of precipitation is observed in the tropics, with the strongest decadal variability occurring in summer. Our study provides insights into understanding the seasonality of decadal variability, which can aid in the improvement of decadal prediction of climate variability. Significance Statement The amplitude of decadal variability of seasonal-mean or monthly mean variables exhibits seasonality. Our results show that the seasonality in decadal variability is consistent with the seasonality in interannual variability. We also identified that the seasonality in oceanic decadal variability is weak and smaller than that in atmospheric decadal variability. Decadal variability of lower-tropospheric atmospheric circulation exhibits significant seasonality in the extratropics, with the strongest decadal variability occurring in winter. However, the significant seasonality in decadal variability of precipitation occurs in the tropics, with the strongest decadal variability occurring in summer. Our study provides insights into the seasonality of decadal variability in climate systems.

The possible links between the Barents–Kara sea‐ice area, Ural blocking, and the North Atlantic Oscillation

AbstractWe investigated the possible links between the Barents–Kara sea‐ice area (SIA), Ural blocking, and the North Atlantic Oscillation (NAO) in December–January (DJ) and February–March (FM) using the ERA5 data for the period December 1979–March 2022. The Barents–Kara SIA loss in December is correlated with an increase in geopotential height at 500 hPa (), mean sea‐level pressure (MSLP), and the frequency and intensity of blocking over the Ural in DJ. The Barents–Kara SIA loss in December is also associated with the weakening of the stratospheric polar vortex in FM (particularly in mid‐February) and the negative NAO index. However, our results show that persistent Ural blocking occurs during the transition from a neutral or positive NAO index to its negative phase. Indeed, a significant decrease in NAO index leads to the development of an area of instantaneous blocking (IB) and positive anomalies over the Ural. Persistent Ural blocking contributes significantly to Barents–Kara SIA loss, with a peak decline about seven days after the onset of Ural blocking. The onset of persistent Ural blocking also precedes the weakening of the stratospheric polar vortex by about one month. This implies that the negative correlation between the Barents–Kara SIA loss in December and the NAO index in FM might be caused by the weakening of the stratospheric polar vortex, which itself is induced by persistent Ural blocking. We conclude that the Barents–Kara SIA loss in December can be viewed as a sign rather than the cause of changes in atmospheric circulation over the high‐latitude North Atlantic in succeeding months, because the Barents–Kara SIA also largely responds to Ural blocking and the NAO.

Population Density of European Hare Predicts Risk of Tularemia Infection, Czech Republic, 2006-2022.

Background: Over 200 different animal species are susceptible to infection by tularemia, highly infectious disease caused by Francisella tularensis. Hares (Lepus sp.) and small rodents, such as common vole (Microtus arvalis), have been acknowledged as the most significant sources of human tularemia infection in most European countries. Our objective was to verify ability of these species in predicting incidence of human tularemia in a Central European country, the Czech Republic. Materials and Methods: We used 17 years of data on densities of European hare (Lepus europaeus) and common vole, and climate variability to test effects of these factors on temporal dynamics of tularemia incidence. The data were obtained from annual reports available from online e-repositories. Results: The analysis showed that 33% of the yearly variation in human tularemia incidence was explained solely by the abundance of European hare in the Czech Republic during 2007-2022. Density of common vole and North Atlantic Oscillation index, a measure of climate variability, did not significantly explain tularemia incidence. While hare population declined severely during 1993-2022, we did not detect any clear accompanied decrease in the prevalence of tularemia in humans and hares. Conclusion: Contrary to expectations, only hares proved capable in predicting yearly dynamics in human tularemia incidence in the Czech Republic. We call for continued monitoring of infection rates in hares and advocate the use of hunter estimates of hare abundance as a cheap and effective means of predicting the risk of tularemia.

Discriminant Analysis of the Solar Input on the Danube’s Discharge in the Lower Basin

This paper presents the extent to which the combination of extra-atmospheric and hydroclimatic factors can be deciphered to record their contribution to the evolution and forecasting of the Danube discharge (Q) in the lower basin. A combination of methods such as wavelet filtering and deep learning (DL) constitutes the basic method for discriminating the external factors (solar activity through Wolf numbers) that significantly contribute to the evolution and prediction of the lower Danube discharge. An ensemble of some of the most important factors, namely, those representing the atmospheric components, i.e., the Greenland-Balkan Oscillation Index (GBOI) and the North Atlantic Oscillation Index (NAOI); the hydroclimatic indicator, the Palmer Hydrological Drought Index (PHDI); and the extra-atmospheric factor, constitutes the set of predictors by means of which the predictand, Q, in the summer season, is estimated. The external factor has to be discriminated in the Schwabe and Hale spectra to make its convolutional contribution to the Q estimation in the lower Danube basin. An interesting finding is that adding two solar predictors (associated with the Schwabe and Hale cycles) to the terrestrial ones give a better estimation of the Danube discharge in summer, compared to using only terrestrial predictors. Based on the Nash–Sutcliffe (NS) index, a measure of performance given by the extreme learning machine (ELM), it is shown that, in association with certain terrestrial predictors, the contribution of the Hale cycle is more significant than the contribution of the Schwabe cycle to the estimation of the Danube discharge in the lower basin.

О согласованности океанического переноса тепла через северные моря: баланс океанического тепла и его межгодовая изменчивость

The Atlantic Water is the main source of heat and salt in the Arctic. Properties of the Atlantic Water inflow regionally affect sea ice extent and deep water formation rate. The Atlantic Water heat transported into the Nordic Seas has a significant impact on the local climate and is investigated here along with its inter-annual variability. We use the ARMOR3D dataset, which is a collection of 3D monthly temperature, salinity and geostrophic velocities fields, derived from in situ and satellite data on a regular grid available since 1993. We compare the heat transport across seven zonal transects in the eastern part of the Nordic seas, from Svinøy section (65°N) to the Fram Strait (78.8°N). 
 The correlations of the interannual variations of the advective heat fluxes rapidly drop from Svinøy to Jan Mayen sections and between Bear Island and Sørkapp sections. This is a result of different tendencies over the latest decades in the southern and the northern parts of the study region, as well as of a differential damping of the observed periodicities along the Atlantic Water path on its way north (the amplitude of 5–6 year oscillations drops significantly faster than that of 2–3 year oscillations). 
 A certain link between the heat fluxes and the North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and East Atlantic (EA) indices is observed only for the southern sections. On the other hand, the heat fluxes at all sections show a consistent increase during the dominance of western weather type W and a decrease – of meridional weather type C. The link is explained by the variations of the wind fields, favourable for the sea-level build-up (Ekman pumping) east of the branching of the Norwegian Current for type W and an opposite tendency for type C.

The North Atlantic Oscillation influence on the Debeli Namet Glacier

This article presents the relationship between climate variables in the Durmitor Massif (Montenegro) and the North Atlantic Oscillation (NAO). A new climate standard for temperatures and precipitation over the last 30 years has been presented. The Debeli Namet Glacier is an indicator of climate change. We have shown that the size of this glacier is affected by the NAO which mainly affects the precipitation in the accumulation period from December to March. During the ablation period from June to September, the influence of the NAO on precipitation and temperatures is less pronounced. El Niño and La Niña events are significant, especially in years with a low NAO index. The relationship between El Niño/La Niña and the NAO is still a subject of scientific debate.

Nonstationary flood and its influencing factors analysis in the Hanjiang River Basin, China

Due to the impact of climate change and human activities, flood disasters have occurred frequently in the Hanjiang River Basin (HRB) in recent years, and the stationary behavior of its flood fluctuation has been disrupted. In this study, we used Generalized Additive Models for Location, Scale, and Shape (GAMLSS) to analyze the nonstationary changes of annual maximum runoff in the HRB and its influencing factors. It has also been complemented with a stationary model for comparative analysis. We found that the annual maximum runoff has a significant decreasing trend. The top four factors influencing this runoff change are the local changes in precipitation and temperature, and the regional climate oscillations as reflected by the North Atlantic Oscillation index (NAO) and the Pacific North American Index (PNA). The nonstationary model had better simulation effect than the stationary model. The stationary model could not reflect the impact of explanatory variables on annual maximum runoff, while the nonstationary model could well analyze the impact of single and dual explanatory variables. The results of this study provide some new insights in support of flood prevention and control in the HRB.