scholarly journals Impacts of the North Atlantic Warming Hole in Future Climate Projections: Mean Atmospheric Circulation and the North Atlantic Jet

2019 ◽  
Vol 32 (10) ◽  
pp. 2673-2689 ◽  
Author(s):  
Melissa Gervais ◽  
Jeffrey Shaman ◽  
Yochanan Kushnir
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Forced Response ◽  
Future Climate ◽  
Climate Projections ◽  
Transient Eddy ◽  
The North ◽  
Climate Simulations ◽  
The North Atlantic ◽  
The Impact

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.

North Atlantic – European weather regimes in a changing climate: present and future

2020 ◽  
Author(s):  
Luise J. Fischer ◽  
Dominik Büeler ◽  
Christian M. Grams ◽  
Urs Beyerle ◽  
David N. Bresch ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Climate Model ◽  
Future Climate ◽  
Climate Projections ◽  
Climate Conditions ◽  
Weather Regimes ◽  
The North ◽  
Surface Weather ◽  
The North Atlantic

<p>We present findings from an analysis of weather regimes over the North Atlantic and Europe in present and future climate conditions. Weather regimes strongly influence the statistical distribution of surface weather variables. We use a recently developed, all-season North Atlantic - European weather regime classification with seven regimes. These regimes were originally identified in ERA-Interim reanalyses and, in this study, we investigate how they are represented in climate simulations using the CESM1 large ensemble for present-day and future (RCP8.5) climate conditions. With these regimes, the classification of the flow conditions in the considered region goes beyond the classical categorization according to the North Atlantic oscillation index; the weather regimes explicitly capture different flavors of strong zonal flows and the occurrence of blocking over Greenland, Scandinavia, and Central Europe, respectively. In ERA-Interim they explain 70% of the variability in geopotential height at 500 hPa year-round. Our analysis quantifies how well CESM1 represents the statistics of the weather regimes in present-day climate and how strongly their frequencies change in the future climate scenario. In addition, we identify statistical relationships between weather regimes and their resulting impacts on spatial patterns of surface variables such as precipitation. We compare those patterns and characteristics of the weather regimes identified in ERA-Interim to their characteristics in simulations of present and future climate conditions.</p><p>This analysis leads to insight into the representation of and changes in atmospheric circulation in one particular climate model, and, at the same time, it quantifies how well the climate model captures the observed link between surface weather and weather regimes. This approach contributes to improving our understanding of atmospheric circulation changes and their impact on a regional scale, and it may benefit the interpretation and communication of climate projections.</p>

scholarly journals Tropical Cyclones in the UPSCALE Ensemble of High-Resolution Global Climate Models*

2015 ◽  
Vol 28 (2) ◽  
pp. 574-596 ◽  
Author(s):  
Malcolm J. Roberts ◽  
Pier Luigi Vidale ◽  
Matthew S. Mizielinski ◽  
Marie-Estelle Demory ◽  
Reinhard Schiemann ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
North Atlantic ◽  
Global Climate ◽  
Future Climate ◽  
Model Resolution ◽  
Central Pacific ◽  
The North ◽  
The Future ◽  
The North Atlantic ◽  
The Impact

Abstract The U.K. on Partnership for Advanced Computing in Europe (PRACE) Weather-Resolving Simulations of Climate for Global Environmental Risk (UPSCALE) project, using PRACE resources, constructed and ran an ensemble of atmosphere-only global climate model simulations, using the Met Office Unified Model Global Atmosphere 3 (GA3) configuration. Each simulation is 27 years in length for both the present climate and an end-of-century future climate, at resolutions of N96 (130 km), N216 (60 km), and N512 (25 km), in order to study the impact of model resolution on high-impact climate features such as tropical cyclones. Increased model resolution is found to improve the simulated frequency of explicitly tracked tropical cyclones, and correlations of interannual variability in the North Atlantic and northwestern Pacific lie between 0.6 and 0.75. Improvements in the deficit of genesis in the eastern North Atlantic as resolution increases appear to be related to the representation of African easterly waves and the African easterly jet. However, the intensity of the modeled tropical cyclones as measured by 10-m wind speed remains weak, and there is no indication of convergence over this range of resolutions. In the future climate ensemble, there is a reduction of 50% in the frequency of Southern Hemisphere tropical cyclones, whereas in the Northern Hemisphere there is a reduction in the North Atlantic and a shift in the Pacific with peak intensities becoming more common in the central Pacific. There is also a change in tropical cyclone intensities, with the future climate having fewer weak storms and proportionally more strong storms.

scholarly journals Impact of the radiative forcing on the winter North Atlantic-European atmospheric circulation 

2021 ◽  
Author(s):  
Mireia Ginesta ◽  
Javier García-Serrano ◽  
Guillaume Gastineau
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Radiative Forcing ◽  
Coupled Model ◽  
Forced Response ◽  
Boreal Winter ◽  
Anticyclonic Circulation ◽  
Model Version ◽  
The North ◽  
The North Atlantic

<p><span>The accelerated warming linked to climate change has become a topic of great interest due to its projected impact on ecosystems. In this work, we assess the causes and impacts of the anthropogenic radiative forcing on the North Atlantic-European atmospheric circulation in boreal winter (DJF). To isolate the response to radiative forcing, we have used two approaches, whose simulations follow the historical/scenario concentrations from CMIP6. The first approach consists of three 240-year simulations with the European Consortium – Earth System model version 3.3 (EC-EARTH v3.3) keeping fixed the radiative forcing at 1950, characterizing the Past climate, at 2000, representative of Present-day conditions, and at 2050, projecting the near-Future climate. The second approach makes use of the Large Ensemble (i.e. 24 members) of transient simulations performed with the Institut Pierre-Simon Laplace Coupled Model version 6 (IPSL-CM6), where three 10-year periods have been considered, namely 1949-1959, 1999-2009, and 2049-2059, assuming that the radiative forcing remains relatively constant in each of them. Results show that both approaches yield a consistent forced response, and that it scales linearly with radiative forcing, increasing in amplitude from Present-minus-Past to Future-minus-Present. At low latitudes, in the tropical Atlantic, the forced atmospheric response is characterized by a Gill-type baroclinic structure, where the anomalous anticyclonic circulation at upper levels reinforces the westerly wind at the equatorward flank of the North Atlantic jet. At high latitudes, the forced response is reminiscent of the ‘Arctic Amplification’ linked to sea-ice reduction, and the thermally-driven baroclinic structure can be seen over the Labrador Sea-Hudson Bay region. At mid-latitudes, the forced response shows a barotropic pattern, with a cyclonic (anticyclonic) circulation in the North Atlantic (Euro-Mediterranean) sector, pointing out a role for non-radiative, eddy-related effects.  </span></p>

scholarly journals Assessing the Influence of Sea Surface Temperature and Arctic Sea Ice Cover on the Uncertainty in the Northern Winter Future Climate Projections

2021 ◽  
Author(s):  
Ho Nam Cheung ◽  
Noel Keenlyside ◽  
Torben Koenigk ◽  
Shuting Yang ◽  
Tian Tian ◽  
...  
Keyword(s):  
North Atlantic ◽  
Forced Response ◽  
Arctic Sea Ice ◽  
Climate Projections ◽  
The North ◽  
The Pacific ◽  
Arctic Sea ◽  
Northern Winter ◽  
The North Atlantic ◽  
The North Pacific

Abstract We investigate the uncertainty (i.e., inter-model spread) in future projections of the northern winter climate, based on the forced response in the CMIP5 RCP8.5 scenario. The uncertainty in the forced response of sea level pressure (SLP) is large in the North Pacific, the North Atlantic, and the Arctic. A major part of these uncertainties (31%) is marked by a pattern with a center in the northeastern Pacific and a dipole over the northeastern Atlantic that we label as the Pacific–Atlantic SLP uncertainty pattern (PAΔSLP). To better understand the nature of PAΔSLP, the associated sea surface temperature (SST) and Arctic sea ice cover (SIC) perturbation patterns are prescribed in experiments with two atmospheric models (AGCMs): CAM4 and IFS.The AGCM experiments indicate more robust SLP response over the North Pacific driven by the SST perturbation, which is associated with the tropical-midlatitude interaction and the Rossby wavetrain. The North Atlantic SLP response is better explained by the joint effect of SST and SIC perturbations, which is partly related to the Rossby wavetrain from the Pacific and the air–sea interactions over the North Atlantic. However, these responses shift westward relative to PAΔSLP, where in CAM4 it is related to the low-frequency transient eddy forcing. The magnitude of these responses in the two AGCMs is largely different. Thus, constraining only the SST and SIC projections might not alone help constrain future climate projections. We should investigate the role of other factors in these uncertainties, such as the atmosphere–SST–SIC coupled dynamics.

scholarly journals Impact of the North Atlantic Warming Hole on Sensible Weather

2020 ◽  
Vol 33 (10) ◽  
pp. 4255-4271 ◽  
Author(s):  
Melissa Gervais ◽  
Jeffrey Shaman ◽  
Yochanan Kushnir
Keyword(s):  
Surface Temperature ◽  
North Atlantic ◽  
Climate Projections ◽  
Subpolar Gyre ◽  
Self Organizing Maps ◽  
Wind Speeds ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
North Atlantic Jet

AbstractIn future climate projections there is a notable lack of warming in the North Atlantic subpolar gyre, known as the North Atlantic warming hole (NAWH). In a set of large-ensemble atmospheric simulations with the Community Earth System Model, the NAWH was previously shown to contribute to the projected poleward shift and eastward elongation of the North Atlantic jet. The current study investigates the impact of the warming hole on sensible weather, particularly over Europe, using the same simulations. North Atlantic jet regimes are classified within the model simulations by applying self-organizing maps analysis to winter daily wind speeds on the dynamic tropopause. The NAWH is found to increase the prevalence of jet regimes with stronger and more-poleward-shifted jets. A previously identified transient eddy-mean response to the NAWH that leads to a downstream enhancement of wind speeds is found to be dependent on the jet regime. These localized regime-specific changes vary by latitude and strength, combining to form the broad increase in seasonal-mean wind speeds over Eurasia. Impacts on surface temperature and precipitation within the various North Atlantic jet regimes are also investigated. A large decrease in surface temperature over Eurasia is found to be associated with the NAWH in regimes where air masses are advected eastward over the subpolar gyre prior to reaching Eurasia. Precipitation is found to be locally suppressed over the warming hole region and increased directly downstream. The impact of this downstream response on coastal European precipitation is dependent on the strength of the NAWH.

scholarly journals Evaluating climate model performance with various parameter sets using observations over the last centuries

2010 ◽  
Vol 6 (2) ◽  
pp. 711-765 ◽  
Author(s):  
M. F. Loutre ◽  
A. Mouchet ◽  
T. Fichefet ◽  
H. Goosse ◽  
H. Goelzer ◽  
...  
Keyword(s):  
North Atlantic ◽  
Climate Model ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Climate Projections ◽  
Freshwater Flux ◽  
The North ◽  
Climate Simulations ◽  
Wide Range ◽  
The North Atlantic

Abstract. Many sources of uncertainties limit the accuracy and precision of climate projections. Here, we focus on the parameter uncertainty, i.e. the imperfect knowledge of the values of many physical parameters in a climate model. We use LOVECLIM, a global three-dimensional Earth system model of intermediate complexity and vary several parameters within their range of uncertainty. Nine climatic parameter sets and three carbon cycle parameter sets are identified. They all yield present climate simulations coherent with observations and they cover a wide range of climate responses to doubled atmospheric CO2 concentration and freshwater flux in the North Atlantic sensitivity experiments. They also simulate a large range of atmospheric CO2 concentrations in response to prescribed emissions. Climate simulations of the last millennium are performed with the 27 combinations of these parameter sets. A special attention is given to the ability of LOVECLIM to reproduce the evolution of several climate variables over the last few decades, for which observations are available. The model response, even its ocean component, is strongly dominated by the model sensitivity to an increase in atmospheric CO2 concentration but much slightly by its sensitivity to freshwater flux in the North Atlantic. The whole set of parameter sets leads to a wide range of simulated climates. Although only some parameter sets yield simulations that reproduce the observed key variables of the climate system over the last decades, all of them could be used to characterise extreme climate projections.

Impact of the North Atlantic Warming Hole on Sensible Weather

2020 ◽  
Author(s):  
Melissa Gervais ◽  
Jeffrey Shaman ◽  
Yochanan Kushnir
Keyword(s):  
Surface Temperature ◽  
North Atlantic ◽  
Climate Projections ◽  
Subpolar Gyre ◽  
Self Organizing Maps ◽  
Wind Speeds ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
North Atlantic Jet

<p>In future climate projections there is a notable lack of warming in the North Atlantic subpolar gyre, known as the North Atlantic warming hole (NAWH). The NAWH has been previously shown to contribute to a poleward shift and eastward elongation of the North Atlantic jet that constitutes an additional important driver of future changes in the North Atlantic jet using a set of large-ensemble atmosphere simulations with the Community Earth System model.  The current study investigates the impact of the warming hole on sensible weather, particularly over Europe using the same simulations. North Atlantic jet regimes are classified within the model simulations by applying self-organizing maps to winter daily wind speeds on the dynamic tropopause. The NAWH is found to increase the prevalence of jet regimes with stronger and more poleward jets.  A previously identified transient eddy-mean response to the NAWH that leads to downstream enhancements of wind speeds is found to be dependent on the jet regimes. These localized regime-specific changes vary by latitude and strength, combining to form the broad increase in seasonal mean wind speeds over Eurasia. Impacts on surface temperature and precipitation within the various North Atlantic jet regimes are also investigated. A large decrease in surface temperature over Eurasia is found to be associated with the NAWH in regimes where air masses are advected over the subpolar gyre.  Precipitation is found to be locally suppressed over the warming hole region and increased directly downstream. The impact of this downstream response on coastal European precipitation is dependent on the strength of the NAWH.</p>

Preaching and Sermons

2017 ◽  
Author(s):  
Robert H. Ellison
Keyword(s):  
Eighteenth Century ◽  
North Atlantic ◽  
Religious Revival ◽  
Early Nineteenth Century ◽  
Denominational Identity ◽  
The North ◽  
The North Atlantic ◽  
The One ◽  
The Impact

Prompted by the convulsions of the late eighteenth century and inspired by the expansion of evangelicalism across the North Atlantic world, Protestant Dissenters from the 1790s eagerly subscribed to a millennial vision of a world transformed through missionary activism and religious revival. Voluntary societies proliferated in the early nineteenth century to spread the gospel and transform society at home and overseas. In doing so, they engaged many thousands of converts who felt the call to share their experience of personal conversion with others. Though social respectability and business methods became a notable feature of Victorian Nonconformity, the religious populism of the earlier period did not disappear and religious revival remained a key component of Dissenting experience. The impact of this revitalization was mixed. On the one hand, growth was not sustained in the long term and, to some extent, involvement in interdenominational activity undermined denominational identity; on the other hand, Nonconformists gained a social and political prominence they had not enjoyed since the middle of the seventeenth century and their efforts laid the basis for the twentieth-century explosion of evangelicalism in Africa, Asia, and South America.

Sign in / Sign up

Export Citation Format

Share Document