scholarly journals Impacts of the Atlantic Multidecadal Variability on North American Summer Climate and Heat Waves

2018 ◽  
Vol 31 (9) ◽  
pp. 3679-3700 ◽  
Author(s):  
Yohan Ruprich-Robert ◽  
Thomas Delworth ◽  
Rym Msadek ◽  
Frederic Castruccio ◽  
Stephen Yeager ◽  
...  
Keyword(s):  
United States ◽  
North Atlantic ◽  
North American ◽  
Heat Waves ◽  
Southern United States ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
Northern Mexico ◽  
The North ◽  
North American Climate

The impacts of the Atlantic multidecadal variability (AMV) on summertime North American climate are investigated using three coupled global climate models (CGCMs) in which North Atlantic sea surface temperatures (SSTs) are restored to observed AMV anomalies. Large ensemble simulations are performed to estimate how AMV can modulate the occurrence of extreme weather such as heat waves. It is shown that, in response to an AMV warming, all models simulate a precipitation deficit and a warming over northern Mexico and the southern United States that lead to an increased number of heat wave days by about 30% compared to an AMV cooling. The physical mechanisms associated with these impacts are discussed. The positive tropical Atlantic SST anomalies associated with the warm AMV drive a Matsuno–Gill-like atmospheric response that favors subsidence over northern Mexico and the southern United States. This leads to a warming of the whole tropospheric column, and to a decrease in relative humidity, cloud cover, and precipitation. Soil moisture response to AMV also plays a role in the modulation of heat wave occurrence. An AMV warming favors dry soil conditions over northern Mexico and the southern United States by driving a year-round precipitation deficit through atmospheric teleconnections coming both directly from the North Atlantic SST forcing and indirectly from the Pacific. The indirect AMV teleconnections highlight the importance of using CGCMs to fully assess the AMV impacts on North America. Given the potential predictability of the AMV, the teleconnections discussed here suggest a source of predictability for the North American climate variability and in particular for the occurrence of heat waves at multiyear time scales.

Beyond the Cold War Chessboard

Worldview ◽  
1974 ◽  
Vol 17 (6) ◽  
pp. 21-22
Author(s):  
John W. Holmes
Keyword(s):  
United States ◽  
Cold War ◽  
North Atlantic ◽  
North American ◽  
The Other ◽  
The North ◽  
Common Interests ◽  
The North Atlantic ◽  
The Cold War

The problem in judging M. Servan-Schreiber's message is that he reaches some sound conclusions on the basis of dubious premises, from which he derives recommendations which could be disastrous.There may be some satisfaction in seeing a Frenchman concerned with le défi, russe instead of le défi américain, but his interpretation of one is as crude as was his interpretation of the other. The shock of revelation that there are common interests of the Atlantic countries in economic as well as strategic matters is understandably more startling to a Frenchman than to others. It was all set out in 1949 in Article 2 of the North Atlantic Treaty and was restated eloquently in 1973 by Mr. Kissinger. But last spring European leaders were included to see the latter as a self-interested plea from a weak United States to a prosperous Europe. The North American countries were reminded that their role in Europe was simply to defend it on request.

scholarly journals Atlantic Multidecadal Variability and the U.K. ACSIS Program

2018 ◽  
Vol 99 (2) ◽  
pp. 415-425 ◽  
Author(s):  
R. T. Sutton ◽  
G. D. McCarthy ◽  
J. Robson ◽  
B. Sinha ◽  
A. T. Archibald ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Heat Content ◽  
Climate Impacts ◽  
Environmental Research ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
The North ◽  
Holistic Understanding ◽  
The North Atlantic

Abstract Atlantic multidecadal variability (AMV) is the term used to describe the pattern of variability in North Atlantic sea surface temperatures (SSTs) that is characterized by decades of basinwide warm or cool anomalies, relative to the global mean. AMV has been associated with numerous climate impacts in many regions of the world including decadal variations in temperature and rainfall patterns, hurricane activity, and sea level changes. Given its importance, understanding the physical processes that drive AMV and the extent to which its evolution is predictable is a key challenge in climate science. A leading hypothesis is that natural variations in ocean circulation control changes in ocean heat content and consequently AMV phases. However, this view has been challenged recently by claims that changing natural and anthropogenic radiative forcings are critical drivers of AMV. Others have argued that changes in ocean circulation are not required. Here, we review the leading hypotheses and mechanisms for AMV and discuss the key debates. In particular, we highlight the need for a holistic understanding of AMV. This perspective is a key motivation for a major new U.K. research program: the North Atlantic Climate System Integrated Study (ACSIS), which brings together seven of the United Kingdom’s leading environmental research institutes to enable a broad spectrum approach to the challenges of AMV. ACSIS will deliver the first fully integrated assessment of recent decadal changes in the North Atlantic, will investigate the attribution of these changes to their proximal and ultimate causes, and will assess the potential to predict future changes.

scholarly journals An experimental study of the Atlantic variability on interdecadal timescales

2012 ◽  
Vol 19 (3) ◽  
pp. 335-343 ◽  
Author(s):  
M. Vincze ◽  
I. M. Jánosi ◽  
E. Barsy ◽  
T. Tél ◽  
A. Várai
Keyword(s):  
North Atlantic ◽  
Laboratory Experiments ◽  
Thermal Noise ◽  
Numerical Models ◽  
Low Frequency ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
Sector Model ◽  
The North ◽  
Low Frequency Variability

Abstract. A series of laboratory experiments has been carried out to model the basic dynamics of the multidecadal variability observed in North Atlantic sea surface temperature (SST) records. According to the minimal numerical sector model introduced by te Raa and Dijkstra (2002), the three key components to excite such a low-frequency variability are rotation, meridional temperature gradient and additive thermal noise in the surface heat forcing. If these components are present, periodic perturbations of the overturning background flow are excited, leading to thermal Rossby mode like propagation of anomalous patches in the SST field. Our tabletop scale setup was built to capture this phenomenon, and to test whether the aforementioned three components are indeed sufficient to generate a low-frequency variability in the system. The results are compared to those of the numerical models, as well as to oceanic SST reanalysis records. To the best of our knowledge, the experiment described here is the very first to investigate the dynamics of the North Atlantic multidecadal variability in a laboratory-scale setup.

scholarly journals Evolution of the Atlantic Multidecadal Variability in a Model with an Improved North Atlantic Current

2017 ◽  
Vol 30 (14) ◽  
pp. 5491-5512 ◽  
Author(s):  
Annika Drews ◽  
Richard J. Greatbatch
Keyword(s):  
North Atlantic ◽  
Heat Supply ◽  
Heat Content ◽  
Atlantic Multidecadal Variability ◽  
North Atlantic Current ◽  
Multidecadal Variability ◽  
Eastern Side ◽  
The North ◽  
The North Atlantic ◽  
Atlantic Current

This article investigates the dynamics and temporal evolution of the Atlantic multidecadal variability (AMV) in a coupled climate model. The model contains a correction to the North Atlantic flow field to improve the path of the North Atlantic Current, thereby alleviating the surface cold bias, a common problem with climate models, and offering a unique opportunity to study the AMV in a model. Changes in greenhouse gas forcing or aerosol loading are not considered. A striking feature of the results is the contrast between the western and eastern sides of the subpolar gyre in the model. On the western side, anomalous heat supply by the ocean plays a major role, with most of this heat being given up to the atmosphere in the warm phase, largely symmetrically about the time of the AMV maximum. By contrast, on the eastern side, the ocean anomalously gains heat from the atmosphere, with relatively little role for ocean heat supply in the years before the AMV maximum. Thereafter, the balance changes with heat now being anomalously removed from the eastern side by the ocean, leading to a reduced ocean heat content, behavior associated with the establishment of an intergyre gyre at the time of the AMV maximum. In the warm phase, melting sea ice leads to a freshening of surface waters northeast of Greenland that travel southward into the Irminger and Labrador Seas, shutting down convection and terminating the AMV warm phase.

scholarly journals Changes of decadal SST Variations in the subpolar North Atlantic under strong CO2 forcing as an indicator for the ocean circulation’s contribution to Atlantic Multidecadal Variability

2020 ◽  
Author(s):  
Ralf Hand ◽  
Jürgen Bader ◽  
Daniela Matei ◽  
Rohit Ghosch ◽  
Johann Jungclaus
Keyword(s):  
Heat Transport ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Ocean Dynamics ◽  
Atlantic Multidecadal Variability ◽  
Ocean Heat Transport ◽  
Multidecadal Variability ◽  
The North ◽  
Sst Variability ◽  
Co2 Forcing

<p>The question, whether ocean dynamics are relevant for basin-scale North Atlantic decadal temperature variability is subject of ongoing discussions. Here, we analyze a set of simulations with a single climate model, consisting of a 2000-year pre-industrial control experiment, a 100-member historical ensemble, and a 100-member ensemble forced with an incremental CO2 increase by 1%/year. Compared to previous approaches, our setup offers the following advantages: First, the large ensemble size allows to robustly separate internally and externally forced variability and to robustly detect statistical links between different quantities. Second, the availability of different scenarios allows to investigate the role of the background state for drivers of the<br>variability. We find strong evidence that ocean dynamics, particularly ocean heat transport variations, form an important contribution to generate the Atlantic Multidecadal Variability (AMV) in the Max Planck Institute Earth System Model (MPI- ESM). Particularly the Northwest North Atlantic is substantially affected by ocean circulation for the historical and pre-industrial simulations. Anomalies of the Labrador Sea deep ocean density precede a change of the Atlantic Meridional Overturning Circulation (AMOC) and heat advection to the region south of Greenland.<br>Under strong CO2 forcing the AMV-SST regression pattern shows crucial changes: SST variability in the north western part of the North Atlantic is strongly reduced, so that the AMV pattern in this scenario is dominated by the low-latitude branch. We found a connection to changes in the deep water formation, that cause a strong reduction of the mean AMOC and its variability. Consequently, ocean heat transport convergence becomes less important for the SST variability south of Greenland.</p>

NOTES ON SOME TROPICAL NOCTUIDS IN NORTH AMERICA

1937 ◽  
Vol 69 (10) ◽  
pp. 218-219
Author(s):  
A. Glenn Richards
Keyword(s):  
United States ◽  
North America ◽  
North American ◽  
Southern United States ◽  
Tropical Species ◽  
The North

The following notes are written to place on record certain authentic records of tropical species taken in the southern United States. Most of these species are not at present recorded in the North American lists. Unless otherwise stated all specimens are in the author's collection.

scholarly journals The Atlantic Multidecadal Variability phase-dependence of teleconnection between the North Atlantic Oscillation in February and the Tibetan Plateau in March

2021 ◽  
pp. 1-40
Author(s):  
Jingyi Li ◽  
Fei Li ◽  
Shengping He ◽  
Huijun Wang ◽  
Yvan J Orsolini
Keyword(s):  
Tibetan Plateau ◽  
Rossby Wave ◽  
North Atlantic ◽  
Wave Train ◽  
The Tibetan Plateau ◽  
Atlantic Multidecadal Variability ◽  
Multidecadal Variability ◽  
The North ◽  
Rossby Wave Train ◽  
The North Atlantic

AbstractThe Tibetan Plateau (TP), referred to as the “Asian water tower”, contains one of the largest land ice masses on Earth. The local glacier shrinkage and frozen-water storage are strongly affected by variations in surface air temperature over the TP (TPSAT), especially in springtime. This study reveals that the relationship between the February North Atlantic Oscillation (NAO) and March TPSAT is unstable with time and regulated by the phase of the Atlantic Multidecadal Variability (AMV). The significant out-of-phase connection occurs only during the warm phase of AMV (AMV+). The results show that during the AMV+, the negative phase of the NAO persists from February to March, and is accompanied by a quasi-stationary Rossby wave train trapped along a northward-shifted subtropical westerly jet stream across Eurasia, inducing an anomalous adiabatic descent that warms the TP. However, during the cold phase of the AMV, the negative NAO can not persist into March. The Rossby wave train propagates along the well-separated polar and subtropical westerly jets, and the NAO−TPSAT connection is broken. Further investigation suggests that the enhanced synoptic eddy and low frequency flow (SELF) interaction over the North Atlantic in February and March during the AMV+, caused by the enhanced and southward-shifted storm track, help maintain the NAO anomaly pattern via positive eddy feedback. This study provides a new detailed perspective on the decadal variability of the North Atlantic−TP connection in late winter−early spring.

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