scholarly journals Seven copepod species considered as indicators of water-mass influence and changes: results from a Northumberland coastal station

2004 ◽  
Vol 61 (4) ◽  
pp. 485-491 ◽  
Author(s):  
D Bonnet ◽  
C Frid
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Water Mass ◽  
Zooplankton Community ◽  
Copepod Species ◽  
Coastal Station ◽  
The North ◽  
North Wall ◽  
The North Atlantic Oscillation

Abstract Zooplankton has been sampled monthly since 1969 at Station Z off the Northumberland coast. Seven copepod species were chosen as potential indicators of specific water masses. Data have been analysed to provide information about seasonal and interannual changes in the zooplankton community with special reference to the indicator taxa and to the possible role of hydrographic and climate drivers, including variations in the position of the Gulf Stream North Wall position and the North Atlantic Oscillation. Results show that, at this Northumberland coastal station, some copepod species are likely to be good indicators of water-mass influence and changes.

The Role of Extratropical Air–Sea Interaction in the Autumn Subseasonal Variability of the North Atlantic Oscillation

2019 ◽  
Vol 32 (22) ◽  
pp. 7697-7712 ◽  
Author(s):  
Yu Nie ◽  
Hong-Li Ren ◽  
Yang Zhang
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Gulf Stream ◽  
Low Frequency ◽  
Mean Flow ◽  
The North ◽  
Subseasonal Variability ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Abstract Considerable progress has been made in understanding the internal eddy–mean flow feedback in the subseasonal variability of the North Atlantic Oscillation (NAO) during winter. Using daily atmospheric and oceanic reanalysis data, this study highlights the role of extratropical air–sea interaction in the NAO variability during autumn when the daily sea surface temperature (SST) variability is more active and eddy–mean flow interactions are still relevant. Our analysis shows that a horseshoe-like SST tripolar pattern in the North Atlantic Ocean, marked by a cold anomaly in the Gulf Stream and two warm anomalies to the south of the Gulf Stream and off the western coast of northern Europe, can induce a quasi-barotropic NAO-like atmospheric response through eddy-mediated processes. An initial southwest–northeast tripolar geopotential anomaly in the North Atlantic forces this horseshoe-like SST anomaly tripole. Then the SST anomalies, through surface heat flux exchange, alter the spatial patterns of the lower-tropospheric temperature and thus baroclinicity anomalies, which are manifested as the midlatitude baroclinicity shifted poleward and reduced baroclinicity poleward of 70°N. In response to such changes of the lower-level baroclinicity, anomalous synoptic eddy generation, eddy kinetic energy, and eddy momentum forcing in the midlatitudes all shift poleward. Meanwhile, the 10–30-day low-frequency anticyclonic wave activities in the high latitudes decrease significantly. We illustrate that both the latitudinal displacement of midlatitude synoptic eddy activities and intensity variation of high-latitude low-frequency wave activities contribute to inducing the NAO-like anomalies.

On the Role of Atmospheric Teleconnections in Climate

2008 ◽  
Vol 21 (12) ◽  
pp. 2990-3001 ◽  
Author(s):  
Anastasios A. Tsonis ◽  
Kyle L. Swanson ◽  
Geli Wang
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
Recent Application ◽  
The North ◽  
The Pacific ◽  
Atmospheric Teleconnections ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The Tropics

Abstract In a recent application of networks to 500-hPa data, it was found that supernodes in the network correspond to major teleconnection. More specifically, in the Northern Hemisphere a set of supernodes coincides with the North Atlantic Oscillation (NAO) and another set is located in the area where the Pacific–North American (PNA) and the tropical Northern Hemisphere (TNH) patterns are found. It was subsequently suggested that the presence of atmospheric teleconnections make climate more stable and more efficient in transferring information. Here this hypothesis is tested by examining the topology of the complete network as well as of the networks without teleconnections. It is found that indeed without teleconnections the network becomes less stable and less efficient in transferring information. It was also found that the pattern chiefly responsible for this mechanism in the extratropics is the NAO. The other patterns are simply a linear response of the activity in the tropics and their role in this mechanism is inconsequential.

scholarly journals Interannual Variability of High-Wind Occurrence over the North Atlantic*

2011 ◽  
Vol 24 (24) ◽  
pp. 6515-6527 ◽  
Author(s):  
Xuhua Cheng ◽  
Shang-Ping Xie ◽  
Hiroki Tokinaga ◽  
Yan Du
Keyword(s):  
Interannual Variability ◽  
North Atlantic ◽  
Gulf Stream ◽  
Storm Track ◽  
Surface Air Temperature ◽  
High Wind ◽  
The North ◽  
The North Atlantic ◽  
The Difference ◽  
The North Atlantic Oscillation

Abstract Interannual variability of high-wind occurrence over the North Atlantic is investigated based on observations from the satellite-borne Special Sensor Microwave Imager (SSM/I). Despite no wind direction being included, SSM/I data capture major features of high-wind frequency (HWF) quite well. Climatology maps show that HWF is highest in winter and is close to zero in summer. Remarkable interannual variability of HWF is found in the vicinity of the Gulf Stream, over open sea south of Iceland, and off Cape Farewell, Greenland. On interannual scales, HWF south of Iceland has a significant positive correlation with the North Atlantic Oscillation (NAO). An increase in the mean westerlies and storm-track intensity during a positive NAO event cause HWF to increase in this region. In the vicinity of the Gulf Stream, HWF is significantly correlated with the difference between sea surface temperature and surface air temperature (SST − SAT), indicative of the importance of atmospheric instability. Cross-frontal wind and an SST gradient are important for the instability of the marine atmospheric boundary layer on the warm flank of the SST front. Off Cape Farewell, high wind occurs in both westerly and easterly tip jets. Quick Scatterometer (QuikSCAT) data show that variability in westerly (easterly) HWF off Cape Farewell is positively (negatively) correlated with the NAO.

scholarly journals Isohaline Salinity Budget of the North Atlantic Salinity Maximum

2015 ◽  
Vol 45 (3) ◽  
pp. 724-736 ◽  
Author(s):  
Frank Bryan ◽  
Scott Bachman
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Mesoscale Eddies ◽  
Surface Fluxes ◽  
Small Scale ◽  
Mixing Processes ◽  
The North ◽  
The North Atlantic ◽  
Averaged Model

AbstractIn this study, the salinity budget of the North Atlantic subtropical salinity maximum region for control volumes bounded by isohaline surfaces is analyzed. The authors provide closed budgets based on output from a high-resolution numerical simulation and partial budgets based on analyses of observational climatologies of hydrography and surface fluxes. With this choice of control volume, advection is eliminated from the instantaneous volume-integrated salt budget, and time-mean advection is eliminated from the budget evaluated from time-averaged data. In this way, the role of irreversible mixing processes in the maintenance and variability of the salinity maximum are more readily revealed. By carrying out the analysis with both near-instantaneous and time-averaged model output, the role of mesoscale eddies in stirring and mixing for this water mass is determined. This study finds that the small-scale mixing acting on enhanced gradients generated by the mesoscale eddies is approximately equal to that acting on the large-scale gradients estimated from climatological-mean conditions. The isohaline salinity budget can be related to water mass transformation rates associated with surface forcing and mixing processes in a straightforward manner. The authors find that the surface net evaporation in the North Atlantic salinity maximum region accounts for a transformation of 7 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) of water across the 37-psu isohaline outcrop into the salinity maximum in the simulation, whereas the estimate based on climatological observations is 9 to 10 Sv.

Sign in / Sign up

Export Citation Format

Share Document