The Various Aspects of the Large- scale Atmospheric Circulation Response to the Northern Hemispheric Ocean Western Boundary Currents

2020 ◽  
Author(s):  
Nour-Eddine Omrani ◽  
Fumiaki Ogawa ◽  
Hisashi Nakamura ◽  
Noel Keenlyside ◽  
Sandro Lubis ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
Western Boundary ◽  
Significant Implication ◽  
Western Boundary Currents ◽  
Near Surface ◽  
Boundary Currents ◽  
The North ◽  
The North Atlantic ◽  
The Impact

<p>Semi-idealized Atmospheric General Circulation-Model (AGCM) experiments are used, in order to study the different aspects of the hemisphere-scale wintertime troposphere/stratosphere-coupled circulation that are maintained by the North Atlantic and Pacific Ocean Western Boundary Currents (OWBCs). Here we show that the North Atlantic and Pacific OWBCs jointly maintain and shape the wintertime hemispheric circulation and its leading mode of variability Northern Annular Mode (NAM). The OWBCs energize baroclinic waves that reinforce quasi-annular hemispheric structure in the tropospheric eddy-driven jetstreams and NAM variability. Without the OWBCs, the wintertime NAM variability is much weaker and its impact on the continental and maritime surface climate is largely insignificant. Atmospheric energy redistribution caused by the OWBCs acts to damp the near-surface atmospheric baroclinicity and compensates the associated oceanic meridional energy transport in agreement with the Bjerknes compensation. Furthermore, the OWBCs substantially weaken the wintertime stratospheric polar vortex by enhancing the upward planetary wave propagation, and thereby affecting both stratospheric and tropospheric NAM-annularity. It is shown that the impact of OWBCs on northern hemisphere circulation has significant implication for stratosphere/troposphere dynamical coupling, time-scales on the NAM, frequency of Sudden stratospheric warming and potential formation of polar stratospheric clouds.</p><p> </p><p>Reference:</p><p>Omrani et al., 2019: Key Role of the ocean Western Boundary currents in shaping the Northern Hemisphere climate, Scientific Reports, https://doi.org/10.1038/s41598-019-39392-y</p><p> </p>

scholarly journals North Atlantic Western Boundary Currents Are Intense Dissolved Organic Carbon Streams

2020 ◽  
Vol 7 ◽  
Author(s):  
Marcos Fontela ◽  
Fiz F. Pérez ◽  
Herlé Mercier ◽  
Pascale Lherminier
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
North Atlantic ◽  
Gulf Stream ◽  
Western Boundary ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
The North ◽  
The North Atlantic

In the North Atlantic, there are two main western boundary currents related to the Atlantic Meridional Overturning Circulation (AMOC): the Gulf Stream flowing northward and the Deep Western Boundary Current (DWBC) flowing southward. Here we analyze data from the OVIDE section (GO-SHIP A25 Portugal-Greenland 40–60°N) that crosses the DWBC and the northward extension of the Gulf Stream, the North Atlantic Current. We show that North Atlantic western boundary currents play a key role in the transport of dissolved organic matter, specifically dissolved organic carbon (DOC). Revisited transports and budgets of DOC with new available data identify the eastern Subpolar North Atlantic (eSPNA) as an important source of locally produced organic matter for the North Atlantic and a key region in the supply of bioavailable DOC to the deep ocean. The East Greenland Current, and its upstream source the East Reykjanes Ridge Current on the eastern flank of the mid-Atlantic ridge, are export pathways of bioavailable DOC toward subtropical latitudes. The fast overturning and subsequent remineralization of DOC produced in the autotrophic eSPNA explains up to 38% of the total oxygen consumption in the deep North Atlantic between the OVIDE section and 24°N. Carbon budgets that do not take into account this organic remineralization process overestimates the natural uptake of carbon dioxide (CO2) from the atmosphere by one third. The inclusion of DOC transports in regional carbon budgets reconciles the estimates of CO2 uptake in the North Atlantic between model and observations.

scholarly journals The Basic Ingredients of the North Atlantic Storm Track. Part II: Sea Surface Temperatures

2011 ◽  
Vol 68 (8) ◽  
pp. 1784-1805 ◽  
Author(s):  
David James Brayshaw ◽  
Brian Hoskins ◽  
Michael Blackburn
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Storm Track ◽  
Horizontal Wind ◽  
Near Surface ◽  
Continental Scale ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
Sst Gradient

Abstract The impact of North Atlantic SST patterns on the storm track is investigated using a hierarchy of GCM simulations using idealized (aquaplanet) and “semirealistic” boundary conditions in the atmospheric component (HadAM3) of the third climate configuration of the Met Office Unified Model (HadCM3). This framework enables the mechanisms determining the tropospheric response to North Atlantic SST patterns to be examined, both in isolation and in combination with continental-scale landmasses and orography. In isolation, a “Gulf Stream” SST pattern acts to strengthen the downstream storm track while a “North Atlantic Drift” SST pattern weakens it. These changes are consistent with changes in the extratropical SST gradient and near-surface baroclinicity, and each storm-track response is associated with a consistent change in the tropospheric jet structure. Locally enhanced near-surface horizontal wind convergence is found over the warm side of strengthened SST gradients associated with ascending air and increased precipitation, consistent with previous studies. When the combined SST pattern is introduced into the semirealistic framework (including the “North American” continent and the “Rocky Mountains”), the results suggest that the topographically generated southwest–northeast tilt in the North Atlantic storm track is enhanced. In particular, the Gulf Stream shifts the storm track south in the western Atlantic whereas the strong high-latitude SST gradient in the northeastern Atlantic enhances the storm track there.

scholarly journals A Climatology of Strong Large-Scale Ocean Evaporation Events. Part I: Identification, Global Distribution, and Associated Climate Conditions

2018 ◽  
Vol 31 (18) ◽  
pp. 7287-7312 ◽  
Author(s):  
Franziska Aemisegger ◽  
Lukas Papritz
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Past History ◽  
Spatiotemporal Variability ◽  
Western Boundary ◽  
Near Surface ◽  
Cold Air ◽  
The North ◽  
South Indian ◽  
The North Atlantic

This paper presents an object-based, global climatology (1979–2014) of strong large-scale ocean evaporation (SLOE) and its associated climatic properties. SLOE is diagnosed using an “atmospheric moisture uptake efficiency” criterion related to the ratio of surface evaporation and integrated water vapor content in the near-surface atmosphere. The chosen Eulerian identification procedure focuses on events that strongly contribute to the available near-surface atmospheric humidity. SLOE is particularly frequent along the warm ocean western boundary currents, downstream of large continental areas, and at the sea ice edge in polar regions with frequent cold-air outbreaks. Furthermore, wind-driven SLOE occurs in regions with topographically enforced winds. On a global annual average, SLOE occurs only 6% of the time but explains 22% of total ocean evaporation. An analysis of the past history and fate of air parcels involved in cold season SLOE in the North Atlantic and south Indian Oceans shows that cold-air advection is the main mechanism that induces these events. Extratropical cyclones thereby play an important role in setting the necessary equatorward synoptic flow. Consequently, the interannual variability of SLOE associated with the North Atlantic Oscillation and the southern annular mode reveals a very high sensitivity of SLOE with respect to the location of the storm tracks. This study highlights the strong link between transient synoptic events and the spatiotemporal variability in ocean evaporation patterns, which cannot be deduced from thermodynamic steady-state and climate mean state considerations alone.

scholarly journals Mediterranean heat injection to the North Atlantic delayed the intensification of Northern Hemisphere glaciations

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Stefanie Kaboth-Bahr ◽  
André Bahr ◽  
Christian Stepanek ◽  
Maria Carolina Amorim Catunda ◽  
Cyrus Karas ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
High Latitude ◽  
North Atlantic Ocean ◽  
Proxy Data ◽  
The North ◽  
Enhanced Production ◽  
Mediterranean Outflow ◽  
The North Atlantic ◽  
The Impact

AbstractThe intensification of Northern Hemisphere glaciations at the end of the Pliocene epoch marks one of the most substantial climatic shifts of the Cenozoic. Despite global cooling, sea surface temperatures in the high latitude North Atlantic Ocean rose between 2.9–2.7 million years ago. Here we present sedimentary geochemical proxy data from the Gulf of Cadiz to reconstruct the variability of Mediterranean Outflow Water, an important heat source to the North Atlantic. We find evidence for enhanced production of Mediterranean Outflow from the mid-Pliocene to the late Pliocene which we infer could have driven a sub-surface heat channel into the high-latitude North Atlantic. We then use Earth System Models to constrain the impact of enhanced Mediterranean Outflow production on the northward heat transport in the North Atlantic. In accord with the proxy data, the numerical model results support the formation of a sub-surface channel that pumped heat from the subtropics into the high latitude North Atlantic. We further suggest that this mechanism could have delayed ice sheet growth at the end of the Pliocene.

Which regional cloud-radiative changes are most important for the global warming response of the midlatitude jet streams?

2020 ◽  
Author(s):  
Nicole Albern ◽  
Aiko Voigt ◽  
David W. J. Thompson ◽  
Joaquim G. Pinto
Keyword(s):  
Global Warming ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Radiative Heating ◽  
Jet Stream ◽  
Jet Streams ◽  
The North ◽  
The North Atlantic ◽  
The Impact

<p>Clouds and the midlatitude circulation are strongly coupled via radiation. Previous studies showed that global cloud-radiative changes contribute significantly to the global warming response of the midlatitude circulation. Here, we investigate the impact of regional cloud-radiative changes and identify which regional cloud-radiative changes are most important for the impact of global cloud-radiative changes. We show how tropical, midlatitude and polar cloud-radiative changes modify the annual-mean, wintertime and summertime jet stream response to global warming across ocean basins. To this end, we perform global simulations with the atmospheric component of the ICOsahedral Nonhydrostatic (ICON) model. We prescribe sea surface temperatures (SST) to isolate the impact of cloud-radiative changes via the atmospheric pathway, i.e. changes in atmospheric cloud-radiative heating, and mimic global warming by a uniform 4K SST increase. We apply the cloud-locking method to break the cloud-radiation-circulation coupling and to decompose the circulation response into contributions from cloud-radiative changes and from the SST increase.</p><p>In response to global warming, the North Atlantic, North Pacific, Northern Hemisphere and Southern Hemisphere jet streams shift poleward and the North Atlantic, Northern Hemisphere and Southern Hemisphere jets strengthen. Global cloud-radiative changes contribute to these jet responses in all ocean basins. <span>In the annual-mean and DJF, tropical and midlatitude cloud-radiative changes contribute significantly to the poleward jet shift in all ocean basins. </span><span>P</span><span>olar cloud-radiative changes shift the jet streams </span><span>poleward </span><span>in the northern hemispheric ocean basins </span><span>but</span> <span>equatorward </span><span>in the Southern Hemisphere. In JJA, the poleward jet shift is small in all ocean basins. In contrast to the jet shift, the global cloud-radiative impacts on the 850hPa zonal wind and jet strength responses </span><span>result predominantly from </span><span>tropical cloud-radiative </span><span>changes</span><span>.</span></p><p><span>The cloud-radiative impact on the jet shift can be related to changes in upper-tropospheric baroclinicity via increases in upper-tropospheric meridional temperature gradients, enhanced wave activity and increased eddy momentum fluxes. However, the response of the atmospheric temperature to cloud-radiative heating is </span><span>more difficult to understand because it is modulated by other small-scale processes such as convection and the circulation.</span><span> Our results help to understand the jet stream response to global warming and highlight the importance of regional cloud-radiative changes for this response, </span><span>in particular those in the tropics</span><span>.</span></p>

scholarly journals Connectivity of climatic variations in the North Atlantic and North Pacific

Trudy VNIRO ◽  
2020 ◽  
Vol 180 ◽  
pp. 23-43
Author(s):  
A. S. Krovnin
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Northwestern Part ◽  
Teleconnection Patterns ◽  
Climatic Variations ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
The North Pacific

Based on the analysis of changes in the spatial structure of climatic variations in the Northern Hemisphere before and after the climatic regime shift in the 1980s, the modes of interaction between climatic processes in the North Atlantic and North Pacific have been identified. The first (“western”) mode prevailed until the late 1980s, reflected the impact of the North Pacific climatic processes on the North Atlantic climate as a result of interaction of two mutually independent Pacific teleconnection patterns (Pacific/North American and Tropical/Northern Hemisphere patterns) with the West Atlantic pattern. The pronounced eastward shift of the North Atlantic Oscillation (NAO) centers from the late 1970s resulted in establishment of the “eastern” mode of interaction between the aquatories under consideration. The climatic changes originated in the North Atlantic basin propagated in the western half of the North Pacific via the system of atmospheric teleconnection patterns over Eurasia (“atmospheric bridge”). The establishment of the “eastern” mode became obviously one of the reasons of sharp warming of surface waters in the western and central areas of the North Pacific from the end of the 1980s, which favored the beginning of a new “salmon epoch” in its northwestern part. Along with the synchronous relationships between the Eurasian atmospheric modes and North Pacific sea surface temperature anomalies, an asynchronous response in the ocean to longitudinal shifts in position of the NAO centers, was found. The atmospheric signal associated with its southern center propagated eastward along the equatorial zone and appeared in the southwestern sector of the North Pacific 5–6 years later.

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.

REGIONAL SECURITY DYNAMICS IN NORTHERN EUROPE (ON THE EXAMPLE OF NORWAY) IN THE LIGHT OF RECENT CHANGES

2020 ◽  
Vol 73 (1) ◽  
pp. 103-111
Author(s):  
D. Kalibekuly ◽  
◽  
Y.S. Chukubayev ◽  
Keyword(s):  
North Atlantic ◽  
Member Country ◽  
Security Policy ◽  
Security System ◽  
Regional Security ◽  
Northern Europe ◽  
The North ◽  
The North Atlantic ◽  
The Impact

The paper examines the dynamics of regional security in Norway as a part of Northern Europe. Being a political and geographical part of the Euro-Atlantic security system. Northern Europe, in its turn, is experiencing the impact of the confrontation between Russia and NATO. Norway's security policy analyzed from the perspective of a regional leader, as a NATO member country participating in the operations of the North Atlantic Alliance and as NATO's northern wing.

Sign in / Sign up

Export Citation Format

Share Document