The Significance of Anomalies of Atmospheric Circulation Over the North Atlantic in November with Regard to the Temperatures of the Following Winters in New England *

1951 ◽  
Vol 32 (9) ◽  
pp. 319-325 ◽  
Author(s):  
Franz Baur

Seven types are established for forms of the atmospheric circulation in certain portions of “circulation regions” of the middle latitudes of the northern hemisphere. Tendencies of persistence and recurrence are different for each type and are subject to an annual course. Certain rules may be derived from changes in these types.

Science ◽  
1994 ◽  
Vol 263 (5154) ◽  
pp. 1747-1751 ◽  
Author(s):  
P. A. Mayewski ◽  
L. D. Meeker ◽  
S. Whitlow ◽  
M. S. Twickler ◽  
M. C. Morrison ◽  
...  

2010 ◽  
Vol 6 (3) ◽  
pp. 295-303 ◽  
Author(s):  
M. Siddall ◽  
E. J. Rohling ◽  
T. Blunier ◽  
R. Spahni

Abstract. Millennial variability is a robust feature of many paleoclimate records, at least throughout the last several glacial cycles. Here we use the mean signal from Antarctic climate events 1 to 4 to probe the EPICA Dome C temperature proxy reconstruction through the last 500 ka for similar millennial-scale events. We find that clusters of millennial events occurred in a regular fashion over half of the time during this with a mean recurrence interval of 21 kyr. We find that there is no consistent link between ice-rafted debris deposition and millennial variability. Instead we speculate that changes in the zonality of atmospheric circulation over the North Atlantic form a viable alternative to freshwater release from icebergs as a trigger for millennial variability. We suggest that millennial changes in the zonality of atmospheric circulation over the North Atlantic are linked to precession via sea-ice feedbacks and that this relationship is modified by the presence of the large, Northern Hemisphere ice sheets during glacial periods.


2019 ◽  
Vol 32 (10) ◽  
pp. 2673-2689 ◽  
Author(s):  
Melissa Gervais ◽  
Jeffrey Shaman ◽  
Yochanan Kushnir

Abstract In future climate simulations there is a pronounced region of reduced warming in the subpolar gyre of the North Atlantic Ocean known as the North Atlantic warming hole (NAWH). This study investigates the impact of the North Atlantic warming hole on atmospheric circulation and midlatitude jets within the Community Earth System Model (CESM). A series of large-ensemble atmospheric model experiments with prescribed sea surface temperature (SST) and sea ice are conducted, in which the warming hole is either filled or deepened. Two mechanisms through which the NAWH impacts the atmosphere are identified: a linear response characterized by a shallow atmospheric cooling and increase in sea level pressure shifted slightly downstream of the SST changes, and a transient eddy forced response whereby the enhanced SST gradient produced by the NAWH leads to increased transient eddy activity that propagates vertically and enhances the midlatitude jet. The relative contributions of these two mechanisms and the details of the response are strongly dependent on the season, time period, and warming hole strength. Our results indicate that the NAWH plays an important role in midlatitude atmospheric circulation changes in CESM future climate simulations.


2007 ◽  
Vol 3 (2) ◽  
pp. 181-192 ◽  
Author(s):  
F. Kaspar ◽  
T. Spangehl ◽  
U. Cubasch

Abstract. Climate simulations of the Eemian interglacial and the last glacial inception have been performed by forcing a coupled ocean-atmosphere general circulation model with insolation patterns of these periods. The parameters of the Earth's orbit have been set to conditions of 125 000 and 115 000 years before present (yr BP). Compared to today, these dates represent periods with enhanced and weakened seasonality of insolation in the northern hemisphere. Here we analyse the simulated change in northern hemisphere winter storm tracks. The change in the orbital configuration has a strong impact on the meridional temperature gradients and therefore on strength and location of the storm tracks. The North Atlantic storm track is strengthened, shifted northward and extends further to the east in the simulation for the Eemian at 125 kyr BP. As one consequence, the northern parts of Europe experience an increase in winter precipitation. The frequency of winter storm days increases over large parts of the North Atlantic including the British Isles and the coastal zones of north-western Europe. Opposite but weaker changes in storm track activity are simulated for 115 kyr BP.


2009 ◽  
Vol 5 (3) ◽  
pp. 551-570 ◽  
Author(s):  
M. Kageyama ◽  
J. Mignot ◽  
D. Swingedouw ◽  
C. Marzin ◽  
R. Alkama ◽  
...  

Abstract. Paleorecords from distant locations on the globe show rapid and large amplitude climate variations during the last glacial period. Here we study the global climatic response to different states of the Atlantic Meridional Overturning Circulation (AMOC) as a potential explanation for these climate variations and their possible connections. We analyse three glacial simulations obtained with an atmosphere-ocean coupled general circulation model and characterised by different AMOC strengths (18, 15 and 2 Sv) resulting from successive ~0.1 Sv freshwater perturbations in the North Atlantic. These AMOC states suggest the existence of a freshwater threshold for which the AMOC collapses. A weak (18 to 15 Sv) AMOC decrease results in a North Atlantic and European cooling. This cooling is not homogeneous, with even a slight warming over the Norwegian Sea. Convection in this area is active in both experiments, but surprisingly stronger in the 15 Sv simulation, which appears to be related to interactions with the atmospheric circulation and sea-ice cover. Far from the North Atlantic, the climatic response is not significant. The climate differences for an AMOC collapse (15 to 2 Sv) are much larger and of global extent. The timing of the climate response to this AMOC collapse suggests teleconnection mechanisms. Our analyses focus on the North Atlantic and surrounding regions, the tropical Atlantic and the Indian monsoon region. The North Atlantic cooling associated with the AMOC collapse induces a cyclonic atmospheric circulation anomaly centred over this region, which modulates the eastward advection of cold air over the Eurasian continent. This can explain why the cooling is not as strong over western Europe as over the North Atlantic. In the Tropics, the southward shift of the Inter-Tropical Convergence Zone appears to be strongest over the Atlantic and Eastern Pacific and results from an adjustment of the atmospheric and oceanic heat transports. Finally, the Indian monsoon weakening appears to be connected to the North Atlantic cooling via that of the troposphere over Eurasia. Such an understanding of these teleconnections and their timing could be useful for paleodata interpretation.


2008 ◽  
Vol 21 (12) ◽  
pp. 2990-3001 ◽  
Author(s):  
Anastasios A. Tsonis ◽  
Kyle L. Swanson ◽  
Geli Wang

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.


Author(s):  
Les Watling

Exploration of the New England and Corner Rise Seamounts produced four new species of chrysogorgiid octocorals with the spiral iridogorgiid growth form. Three species are described as new in the genus Iridogorgia and one is described in the new genus Rhodaniridogorgia. Both genera have representatives in the Atlantic and Pacific Oceans. Iridogorgia magnispiralis sp. nov., is one of the largest octocorals encountered in the deep sea and seems to be widespread in the Atlantic.


Sign in / Sign up

Export Citation Format

Share Document