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 Rapid and sustained environmental responses to global warming: The Paleocene–Eocene Thermal Maximum in the eastern North Sea

2020 ◽  
Author(s):  
Ella W. Stokke ◽  
Morgan T. Jones ◽  
Lars Riber ◽  
Haflidi Haflidason ◽  
Ivar Midtkandal ◽  
...  
Keyword(s):  
Global Warming ◽  
North Sea ◽  
North Atlantic ◽  
Hydrological Cycle ◽  
Clay Fraction ◽  
The North ◽  
Thermal Maximum ◽  
The North Sea ◽  
The North Atlantic ◽  
The Impact

Abstract. The Paleocene–Eocene Thermal Maximum (PETM; ~ 55.9 Ma) was a period of rapid and sustained global warming associated with significant carbon emissions. It coincided with the North Atlantic opening and emplacement of the North Atlantic Igneous Province (NAIP), suggesting a possible causal relationship. Only a very limited number of PETM studies exist from the North Sea, despite its ideal position for tracking the impact of both changing climate and the NAIP explosive and effusive activity. Here we present sedimentological, mineralogical, and geochemical proxy data from Denmark in the eastern North Sea, exploring the environmental response to the PETM. An increase in the chemical index of alteration and a kaolinite content up to 50 % of the clay fraction indicate an influx of terrestrial input shortly after the PETM onset and during the recovery, likely due to an intensified hydrological cycle. The volcanically derived minerals zeolite and smectite comprise up to 36 % and 90 % of the bulk and clay mineralogy respectively, highlighting the NAIPs importance as a sediment source for the North Sea and in increasing the rate of silicate weathering during the PETM. XRF element core scans also reveal possible hitherto unknown NAIP ash deposition both prior to and during the PETM. Geochemical proxies show that an anoxic environment persisted during the PETM body, possibly reaching euxinic conditions in the upper half with high concentrations of Mo (> 30 ppm), S (~ 4 wt %), and pyrite (~ 7 % of bulk), and low Th/U (

Tropical cloud-radiative changes contribute to robust DJF jet exit strengthening over Europe under global warming

2021 ◽  
Author(s):  
Nicole Albern ◽  
Aiko Voigt ◽  
Joaquim G. Pinto
Keyword(s):  
Climate Change ◽  
North Atlantic ◽  
Storm Track ◽  
Tropical Pacific ◽  
Jet Stream ◽  
The North ◽  
The North Atlantic ◽  
Stream Response ◽  
The Impact ◽  
North Atlantic Jet

<p>During boreal winter (December to February, DJF), the North Atlantic jet stream and storm track are expected to extend eastward over Europe in response to climate change. This will affect future weather and climate over Europe, for example by steering storms which are associated with strong winds and heavy precipitation towards Europe. The jet stream and storm track responses over Europe are robust across coupled climate models of phases 3, 5, and 6 of the Coupled Model Intercomparison Project (CMIP; Harvey et al., 2020, JGR-A, https://doi.org/10.1029/2020JD032701). We show that the jet stream response is further robust across CMIP5 models of varying complexity ranging from coupled climate models to atmosphere-only General Circulation Models (GCMs) with prescribed sea-surface temperatures (SSTs) and sea-ice cover. In contrast to the jet stream response over Europe, the jet stream response over the North Atlantic is not robust in the coupled climate models and the atmosphere-only GCMs.</p><p>In addition to the CMIP5 simulations, we investigate Amip-like simulations with the atmospheric components of ICON-NWP, and the CMIP5 models MPI-ESM-LR and IPSL-CM5A-LR that apply the cloud-locking method to break the cloud-radiation-circulation coupling and to diagnose the contribution of cloud-radiative changes on the jet stream response to climate change. In the simulations, SSTs are prescribed to isolate the impact of cloud-radiative changes via the atmospheric pathway, i.e., via changes in atmospheric cloud-radiative heating, and global warming is mimicked by a uniform 4K SST increase (cf. Albern et al., 2019, JAMES, https://doi.org/10.1029/2018MS001592 and Voigt et al., 2019, J. Climate, https://doi.org/10.1175/JCLI-D-18-0810.1). In all three models, cloud-radiative changes contribute significantly and robustly to the eastward extension of the North Atlantic jet stream towards Europe. At the same time, cloud-radiative changes contribute to the model uncertainty over the North Atlantic. In addition to the jet stream response, we investigate the impact of cloud-radiative changes on the storm track response in ICON-NWP and discuss similarities and differences between the jet stream and storm track responses over the North Atlantic-European region.</p><p>In ICON-NWP, the impact of cloud-radiative changes on the jet stream response is dominated by tropical cloud-radiative changes while midlatitude and polar cloud-radiative changes have a minor impact. A further division of the tropics into four smaller tropical regions that cover the western tropical Pacific, the eastern tropical Pacific, the tropical Atlantic, and the Indian Ocean shows that cloud-radiative changes over the western tropical Pacific, eastern tropical Pacific, and Indian Ocean all contribute about equally to the eastward extension of the North Atlantic jet stream towards Europe because these regions exhibit substantial upper-tropospheric cloud-radiative heating in response to climate change. At the same time, cloud-radiative changes over the tropical Atlantic hardly contribute to the jet response over Europe because changes in atmospheric cloud-radiative heating under climate change are small in this region. As for the impact of global cloud-radiative changes, we also discuss the impact of the regional cloud-radiative changes on the storm track response over the North Atlantic-European region to climate change.</p>

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 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.

scholarly journals The North Atlantic Waveguide and Downstream Impact Experiment

2018 ◽  
Vol 99 (8) ◽  
pp. 1607-1637 ◽  
Author(s):  
Andreas Schäfler ◽  
George Craig ◽  
Heini Wernli ◽  
Philippe Arbogast ◽  
James D. Doyle ◽  
...  
Keyword(s):  
North Atlantic ◽  
Subsequent Development ◽  
Jet Stream ◽  
Atmospheric Measurements ◽  
Weather Impact ◽  
The North ◽  
Impact Experiment ◽  
Research Aircraft ◽  
The North Atlantic ◽  
The Impact

AbstractThe North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe.

scholarly journals Response of the Midlatitude Jets, and of Their Variability, to Increased Greenhouse Gases in the CMIP5 Models

2013 ◽  
Vol 26 (18) ◽  
pp. 7117-7135 ◽  
Author(s):  
Elizabeth A. Barnes ◽  
Lorenzo Polvani
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Cmip5 Models ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract This work documents how the midlatitude, eddy-driven jets respond to climate change using model output from phase 5 of the Coupled Model Intercomparison Project (CMIP5). The authors consider separately the North Atlantic, the North Pacific, and the Southern Hemisphere jets. The analysis is not limited to annual-mean changes in the latitude and speed of the jets, but also explores how the variability of each jet changes with increased greenhouse gases. All jets are found to migrate poleward with climate change: the Southern Hemisphere jet shifts poleward by 2° of latitude between the historical period and the end of the twenty-first century in the representative concentration pathway 8.5 (RCP8.5) scenario, whereas both Northern Hemisphere jets shift by only 1°. In addition, the speed of the Southern Hemisphere jet is found to increase markedly (by 1.2 m s−1 between 850 and 700 hPa), while the speed remains nearly constant for both jets in the Northern Hemisphere. More importantly, it is found that the patterns of jet variability are a strong function of the jet position in all three sectors of the globe, and as the jets shift poleward the patterns of variability change. Specifically, for the Southern Hemisphere and the North Atlantic jets, the variability becomes less of a north–south wobbling and more of a pulsing (i.e., variation in jet speed). In contrast, for the North Pacific jet, the variability becomes less of a pulsing and more of a north–south wobbling. These different responses can be understood in terms of Rossby wave breaking, allowing the authors to explain most of the projected jet changes within a single dynamical framework.

Distribution of Jet Streams in the North Atlantic, Europe and the Mediterranean, 1957–8

1961 ◽  
Vol 14 (4) ◽  
pp. 432-445
Author(s):  
A. F. Crossley
Keyword(s):  
North Atlantic ◽  
Critical Speed ◽  
Jet Stream ◽  
Jet Streams ◽  
Once Daily ◽  
Upper Troposphere ◽  
The North ◽  
Four Seasons ◽  
The North Atlantic ◽  
The Mediterranean

From an inspection of upper-air contour charts for 300 and 200 mb., the location of the axis of jet streams of 80 kt. or more has been assessed once daily over the two years 1957–8. Results are presented for each of the four seasons by means of isopleths of frequency (Fig. 1) and also by means of frequency-roses in areas of 5 degrees of latitude by 10 degrees of longitude (Figs. 2–5); each rose shows the number of occasions of direction of the axis from the eight compass points. The area covered extends from latitude 30° N. to 70° N., and from longitude 60° W. to 30° E. An Appendix contains some discussion of the technique of locating the axis of jet streams on contour charts.The characteristics of jet streams were described in a paper by Chambers in this Journal for July/October 1959. The present paper goes a stage further by giving the number of occurrences of jet streams per season over a two-year period in an area from the North Atlantic to the Mediterranean. The number of occurrences depends very much on the chosen definition, about which there is no general agreement. Whilst a jet stream may be fairly described as a fast-moving stream of air in the upper troposphere with great extension in the direction of the wind and persistence of the order of days, for statistical purposes it is necessary to be more precise. In this paper a critical speed of 80 kt. is required at the 300- or 200-mb. level in order that the stream shall qualify as a jet stream. Further discussion of this point is given in the Appendix, but any definition is largely subjective and it does not matter a great deal what definition is used provided the reader is aware of the limits to which the statistics refer.

scholarly journals Rapid and sustained environmental responses to global warming: the Paleocene–Eocene Thermal Maximum in the eastern North Sea

2021 ◽  
Vol 17 (5) ◽  
pp. 1989-2013
Author(s):  
Ella W. Stokke ◽  
Morgan T. Jones ◽  
Lars Riber ◽  
Haflidi Haflidason ◽  
Ivar Midtkandal ◽  
...  
Keyword(s):  
Global Warming ◽  
North Sea ◽  
North Atlantic ◽  
Silicate Weathering ◽  
Environmental Response ◽  
The North ◽  
Thermal Maximum ◽  
The North Sea ◽  
The North Atlantic ◽  
The Impact

Abstract. The Paleocene–Eocene Thermal Maximum (PETM; ∼ 55.9 Ma) was a period of rapid and sustained global warming associated with significant carbon emissions. It coincided with the North Atlantic opening and emplacement of the North Atlantic Igneous Province (NAIP), suggesting a possible causal relationship. Only a very limited number of PETM studies exist from the North Sea, despite its ideal position for tracking the impact of both changing climate and NAIP activity. Here we present sedimentological, mineralogical, and geochemical proxy data from Denmark in the eastern North Sea, exploring the environmental response to the PETM. An increase in the chemical index of alteration and a kaolinite content up to 50 % of the clay fraction indicate an influx of terrestrial input shortly after the PETM onset and during the recovery, likely due to an intensified hydrological cycle. The volcanically derived zeolite and smectite minerals comprise up to 36 % and 90 % of the bulk and clay mineralogy respectively, highlighting the NAIP's importance as a sediment source for the North Sea and in increasing the rate of silicate weathering during the PETM. X-Ray fluorescence element core scans also reveal possible hitherto unknown NAIP ash deposition both prior to and during the PETM. Geochemical proxies show that an anoxic to sulfidic environment persisted during the PETM, particularly in the upper half of the PETM body with high concentrations of molybdenum (MoEF > 30), uranium (UEF up to 5), sulfur (∼ 4 wt %), and pyrite (∼ 7 % of bulk). At the same time, export productivity and organic-matter burial reached its maximum intensity. These new records reveal that negative feedback mechanisms including silicate weathering and organic carbon sequestration rapidly began to counteract the carbon cycle perturbations and temperature increase and remained active throughout the PETM. This study highlights the importance of shelf sections in tracking the environmental response to the PETM climatic changes and as carbon sinks driving the PETM recovery.

scholarly journals The Impact of Land-Ocean Contrast on The Seasonal To Decadal Variability of The Northern Hemisphere Jet Stream

2021 ◽  
Author(s):  
Samantha Hallam ◽  
Simon Josey ◽  
Gerard McCarthy ◽  
Joel Hirschi
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
North Pacific ◽  
Jet Stream ◽  
Latitude Range ◽  
The North ◽  
Regional Basis ◽  
The North Atlantic ◽  
The North Pacific

Abstract Seasonal to decadal variations in Northern Hemisphere jet stream latitude and speed over land (Eurasia, North America) and oceanic (North Atlantic, North Pacific) regions are presented for the period 1871 – 2011 from the Twentieth Century Reanalysis dataset. Significant regional differences are seen on seasonal to decadal timescales. The ocean acts to reduce the seasonal jet latitude range from 20° over Eurasia to 10° over the North Atlantic where the ocean meridional heat transport is greatest. The mean jet latitude range is at a minimum in winter (DJF), along the western boundary of the North Pacific and North Atlantic, where the land-sea contrast and SST gradients are strongest. The 141-year trends in jet latitude and speed show differences on a regional basis. The North Atlantic has significant increasing jet latitude trends in all seasons, up to 3° in winter. Eurasia has significant increasing trends in winter and summer, however, no increase is seen across the North Pacific or North America. Jet speed shows significant increases evident in winter (up to 4.7ms -1 ), spring and autumn over the North Atlantic, Eurasia and North America however, over the North Pacific no increase is observed. Long term trends are generally overlaid by multidecadal variability, particularly evident in the North Pacific, where 20-year variability in jet latitude and jet speed are seen, associated with the Pacific Decadal Oscillation which explains 50% of the winter variance in jet latitude since 1940. Northern hemisphere jet variability and trends differ on a regional basis (North Atlantic, North Pacific, Eurasia and America) on seasonal to decadal timescales, indicating different mechanisms are influencing the jet latitude and speed. It is important that the differing regional trends and mechanisms are incorporated into climate models and predictions.

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.

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