scholarly journals Variations in the distributions of Centropages chierchiae and Temora stylifera (Copepoda: Calanoida) in the north-eastern Atlantic Ocean and western European shelf waters

2005 ◽  
Vol 62 (5) ◽  
pp. 869-877 ◽  
Author(s):  
J.A. Lindley ◽  
S. Daykin
Keyword(s):  
North Atlantic ◽  
Seasonal Cycles ◽  
Frequency Of Occurrence ◽  
English Channel ◽  
The North ◽  
Edge Current ◽  
Eastern Atlantic Ocean ◽  
North Eastern ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Centropages chierchiae and Temora stylifera occurred rarely in the Continuous Plankton Recorder (CPR) survey in the Bay of Biscay, Celtic Sea, and English Channel before 1988. By 2000 they were found frequently and in abundance. The seasonal cycles of abundance of these species differ, C. chierchiae occurring mainly in the summer while T. stylifera was found most frequently in late autumn or winter towards the northern limits of its distribution. The increase in abundance of both species is related to temperature. However, in the years when it was found in the samples, the frequency of occurrence of C. chierchiae was correlated positively with the strength of the shelf edge current and negatively with the North Atlantic Oscillation (NAO) while the reverse was true for T. stylifera.

scholarly journals Persistent Circulation Regimes and Preferred Regime Transitions in the North Atlantic

2011 ◽  
Vol 68 (12) ◽  
pp. 2809-2825 ◽  
Author(s):  
Christian Franzke ◽  
Tim Woollings ◽  
Olivia Martius
Keyword(s):  
North Atlantic ◽  
Wave Breaking ◽  
Teleconnection Pattern ◽  
Jet Stream ◽  
Frequency Of Occurrence ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
Regime Transitions

Abstract The persistent regime behavior of the eddy-driven jet stream over the North Atlantic is investigated. The North Atlantic jet stream variability is characterized by the latitude of the maximum lower tropospheric wind speed of the 40-yr ECMWF Re-Analysis (ERA-40) data for the period 1 December 1957–28 February 2002. A hidden Markov model (HMM) analysis reveals that the jet stream exhibits three persistent regimes that correspond to northern, southern, and central jet states. The regime states are closely related to the North Atlantic Oscillation and the eastern Atlantic teleconnection pattern. The regime states are associated with distinct changes in the storm tracks and the frequency of occurrence of cyclonic and anticyclonic Rossby wave breaking. Three preferred regime transitions are identified, namely, southern to central jet, northern to southern jet, and central to northern jet. The preferred transitions can be interpreted as a preference for poleward propagation of the jet, but with the southern jet state entered via a dramatic shift from the northern state. Evidence is found that wave breaking is involved in two of the three preferred transitions (northern to southern jet and central to northern jet transitions). The predictability characteristics and the interannual variability in the frequency of occurrence of regimes are also discussed.

Regime behaviour in the Atlantic-Eurasian Arctic related to sea ice and sea surface temperature changes

2020 ◽  
Author(s):  
Ralf Jaiser ◽  
Mirseid Akperov ◽  
Alexander Timazhev ◽  
Erik Romanowsky ◽  
Dörthe Handorf ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Sea Surface ◽  
The Arctic ◽  
Frequency Of Occurrence ◽  
Temporal Behaviour ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

<p>Climate change in the Arctic is embedded in the global climate system leading to phenomenon like Arctic Amplification and linkages to the mid-latitudes. A major forcing emerges from changed surface conditions like declining sea ice cover (SIC) and rising sea surface temperatures (SST). We performed time-slice model experiments with the global atmosphere-only model ECHAM6 and changed SIC and SST to either high or low states, respectively. These experiments are compared to reanalysis data and analysed aiming at a separation between the influences of SIC and SST, while focusing on linkages between the Arctic and mid-latitudes in winter.</p><p>We identify five significant regimes in the Atlantic-Eurasian sector with the k-means clustering method. The regimes include different blocking patterns, situation with strong low pressure influence and the North Atlantic Oscillation in its two phases. Their frequency of occurrence is discussed for winter months. In the reanalysis we observe an increase of blocking patterns in early winter of the most recent decades. This is reproduced by our experiments with increased SST, where blocking becomes more dominant overall. In late winter, an increased frequency of occurrence of the North Atlantic Oscillation in its negative phase is observed. This and the overall temporal behaviour of regimes in recent years is best represented if SST and SIC are changed to their more recent state simultaneously. Therefore, our results suggest that increased SSTs and reduced SIC together act on observed linkages between polar regions and mid-latitudes.</p>

scholarly journals Influence of the North Atlantic oscillation on the atmospheric levels of benzo[a]pyrene over Europe

2021 ◽  
Author(s):  
Pedro Jiménez-Guerrero ◽  
Nuno Ratola
Keyword(s):  
Spatial Pattern ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Transport Model ◽  
Regional Scale ◽  
The South ◽  
Climatic Fluctuations ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

AbstractThe atmospheric concentration of persistent organic pollutants (and of polycyclic aromatic hydrocarbons, PAHs, in particular) is closely related to climate change and climatic fluctuations, which are likely to influence contaminant’s transport pathways and transfer processes. Predicting how climate variability alters PAHs concentrations in the atmosphere still poses an exceptional challenge. In this sense, the main objective of this contribution is to assess the relationship between the North Atlantic Oscillation (NAO) index and the mean concentration of benzo[a]pyrene (BaP, the most studied PAH congener) in a domain covering Europe, with an emphasis on the effect of regional-scale processes. A numerical simulation for a present climate period of 30 years was performed using a regional chemistry transport model with a 25 km spatial resolution (horizontal), higher than those commonly applied. The results show an important seasonal behaviour, with a remarkable spatial pattern of difference between the north and the south of the domain. In winter, higher BaP ground levels are found during the NAO+ phase for the Mediterranean basin, while the spatial pattern of this feature (higher BaP levels during NAO+ phases) moves northwards in summer. These results show deviations up to and sometimes over 100% in the BaP mean concentrations, but statistically significant signals (p<0.1) of lower changes (20–40% variations in the signal) are found for the north of the domain in winter and for the south in summer.

Polar motion and the North Atlantic Oscillation

1997 ◽  
Vol 42 (11) ◽  
pp. 927-931 ◽  
Author(s):  
Yonghong Zhou ◽  
Dawei Zheng ◽  
Benjamin Fong Chao
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Polar Motion ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

scholarly journals Global drivers effect in multi-annual variability of runoff

2014 ◽  
Vol 62 (3) ◽  
pp. 169-176 ◽  
Author(s):  
Miriam Fendeková ◽  
Pavla Pekárová ◽  
Marián Fendek ◽  
Ján Pekár ◽  
Peter Škoda
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Coherence Function ◽  
Climatic Conditions ◽  
Base Flow ◽  
Quasi Biennial Oscillation ◽  
The North ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
Biennial Oscillation

Abstract Changes in runoff parameters are very important for Slovakia, where stream-flow discharges, being supplied by precipitation and groundwater runoff, are preferentially influenced by climatic conditions. Therefore, teleconnections between runoff parameters, climate parameters and global atmospheric drivers such as North Atlantic Oscillation, Southern Pacific Oscillation, Quasi-biennial oscillation and solar activity were studied in the Nitra River Basin, Slovakia. Research was mostly based on records of 80 years (1931-2010) for discharges and baseflow, and 34 years for groundwater heads. Methods of autocorrelation, spectral analysis, cross-correlation and coherence function were used. Results of auto- correllograms for discharges, groundwater heads and base flow values showed a very distinct 11-year and 21-year periodicity. Spectrogram analysis documented the 11-year, 7.8-year, 3.6-year and 2.4-year periods in the discharge, precipitation and air temperature time series. The same cycles except of 11-years were also identified in the long-term series of the North Atlantic Oscillation and Southern Pacific Oscillation indices. The cycle from approximately 2.3 to 2.4-years is most likely connected with Quasi-biennial oscillation. The close negative correlation between the North Atlantic Oscillation winter index and the hydrological surface and groundwater parameters can be used for their prediction within the same year and also for one year in advance.

scholarly journals Seasonal Predictability of the North Atlantic Oscillation and Zonal Mean Fields Associated with Stratospheric Influence in JMA/MRI-CPS2

SOLA ◽  
2017 ◽  
Vol 13 (0) ◽  
pp. 209-213 ◽  
Author(s):  
Naoaki Saito ◽  
Shuhei Maeda ◽  
Tosiyuki Nakaegawa ◽  
Yuhei Takaya ◽  
Yukiko Imada ◽  
...  
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Seasonal Predictability ◽  
The North ◽  
Mean Fields ◽  
The North Atlantic ◽  
The North Atlantic Oscillation
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