Influence of high-latitude blocking and the northern stratospheric polar vortex on cold-air outbreaks under Arctic amplification of global warming - IOPscience
H simmens
Author of A Climate Vocabulary of the Future
@herbsimmens
HerbSimmens.com
Tom Goreau
“A physical explanation of the two-way vertical coupling process between the polar vortex and blocking highs, taking into account local surface conditions, remains elusive. We conclude that evidence exists for tropical preconditioning of Arctic-midlatitude climate linkages. ”
They seem to be saying that it is much more complicated than their best models can imagine!
One author, Judah Cohen, is the top expert on Arctic extreme weather events.
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H simmens
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@herbsimmens
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On Dec 31, 2024, at 8:45 AM, Tom Goreau <gor...@globalcoral.org> wrote:
Bru Pearce
Here is what Notebook LM says
Okay, here's a detailed briefing document summarizing the key themes and ideas from the provided research paper, "Influence of high-latitude blocking and the northern stratospheric polar vortex on cold-air outbreaks under Arctic amplification of global warming," with relevant quotes.
Briefing Document: Arctic Amplification, Blocking, and Cold-Air Outbreaks
1. Introduction
This document reviews the complex interplay between Arctic amplification (AA), high-latitude atmospheric blocking, and the stratospheric polar vortex (SPV) in influencing cold-air outbreaks (CAOs) in the mid-latitudes. The central question is whether the observed increase in severe winter weather, including disruptive cold spells, is coincidental with or physically linked to AA, and whether increased understanding of these relationships can better prepare society for future extremes.
Key Point: Despite the widely accepted idea that AA will moderate CAOs, recent research suggests AA may contribute to more frequent severe winter weather.
Quote: "It is widely accepted that Arctic amplification (AA)—enhanced Arctic warming relative to global warming—will increasingly moderate cold-air outbreaks (CAOs) to the midlatitudes. Yet, some recent studies also argue that AA over the last three decades to the rest of the present century may contribute to more frequent severe winter weather including disruptive cold spells."
2. Arctic Amplification (AA)
- Rapid Warming: The Arctic is warming approximately four times faster than the global average, particularly since 1980. *Quote: "Over the period 1980–2023 observed annual mean surface air temperatures in the Arctic have warmed about four times faster than the global mean; faster than predicted by climate models."
- Key Feedbacks: AA is driven by a combination of factors:
- Surface-ice albedo feedback
- Ice-ocean heat flux feedback
- Planck feedback
- Lapse-rate feedback *Changes in moisture transport and a local greenhouse effect also contribute.
- Increased latent energy transport
- Moistening Arctic: AA leads to a moistening of the central Arctic due to increased evaporation from newly ice-free ocean areas and advection of moist air, sometimes intensified by Ural blocking (UB) combined with the positive North Atlantic Oscillation (NAO).
Key Point: AA is a complex phenomenon driven by multiple interacting feedback mechanisms and atmospheric dynamics that impact mid-latitudes in complex ways.
3. Cold-Air Outbreaks (CAOs)
- Recent Severe Events: Despite AA, recent years have witnessed a number of historic and severe CAOs in the US and Eurasia, which is seemingly at odds with anticipated warming. *Quote: "Despite this Arctic amplification (AA), a surprising number of historic cold-air outbreaks (CAOs) have occurred in the United States (US) and Eurasia in recent years, the frequency of which may even be increasing regionally during the period of AA"
- Socioeconomic Impacts: CAOs result in significant economic losses, travel disruptions, energy issues, and fatalities. *Quote: "Severe CAOs cause socioeconomic impacts including economic losses, travel and energy disruptions, and fatalities"
4. High-Latitude Blocking
- Definition: Atmospheric blocking refers to quasi-stationary, persistent modifications of the jet stream flow, typically lasting 1-3 weeks. Quote: "An atmospheric block is a quasi-stationary, persistent modification of the jet-stream flow that occurs at mid and high latitudes that typically lasts for one to a few weeks"
- Link to Extremes: Blocking events are associated with persistent weather conditions, often leading to extreme weather such as CAOs. *Quote: "Blocking events are associated with persistent weather conditions in the vicinity of the block that frequently leads to extreme weather events in midlatitudes, including winter CAOs"
- Uncertain Causality: The physical causes and climate change responses to blocking aren't fully understood, but they can act as conduits between AA and mid-latitude jet stream changes. Quote: "The physical causes of blocking, and consequently how blocking responds to and influences climate change, are not well understood"
- Regional Blocking: Specific blocking regions (Greenland, North Pacific, Barents/Kara Seas) may serve as crucial linkages between the Arctic and mid-latitudes.
- For example, the early December 2022 Greenland blocking event coincided with a weakening SPV and intensifying Ural ridge.
- Variable Trends: Trends in blocking frequency and intensity vary depending on the metrics and time periods studied, highlighting the need for a multi-metric approach.
5. Nonlinear Theory of Blocking
- Nonlinear Multi-scale Interaction (NMI) Model: This theory views blocking as an Arctic/mid-latitude "weather bridge" involving the interaction of synoptic-scale eddies, blocking dipoles, and background zonal flow.
- Meridional Potential Vorticity Gradient (PVy): Blocking lifetime is significantly influenced by PVy, which is the north-south gradient of atmospheric features. Quote: "According to NMI theory, the lifetime of blocking is mainly determined by the meridional background potential vorticity gradient (PVy)."
- A weaker PVy results in longer-lasting, more intense blocking, favouring cold extremes.
- PVy is influenced not only by Arctic conditions, but also midlatitude conditions. Quote: "The magnitude of PVy does not only depend on the value of PVN over the Arctic, but also on the value of PVS over northern midlatitudes."
- Positive Feedback: A positive feedback exists between Barents-Kara Sea (BKS) warming/sea ice decline and Ural blocking:
- BKS warming reduces PVy, maintaining the block and potentially leading to more severe CAOs in Eurasia. Quote: "The PVy theory based on the NMI model reveals a positive feedback between UB and BKS warming or sea-ice decline. The background BKS warming or sea-ice decline can reduce PVy, maintaining UB and increasing its quasi-stationarity, which can result in severe and persistent CAOs over Eurasia and the further intensification (reduction) of BKS warming (sea ice)."
- Key Point: Nonlinear internal atmospheric dynamics, the occurrence and location of blocking, and the sub-seasonal duration of events are all important factors in the NMI theory.
6. The Stratospheric Polar Vortex (SPV)
- Role: The SPV is a mass of cold, cyclonically rotating air in the stratosphere (15-50 km altitude). Its disruptions are linked to mid-latitude winter weather. *Quote: "When the SPV is in an extreme state, being anomalously weak or strong or shifted over continents, this leads to the modulation of large-scale tropospheric circulation patterns, and thereby winter weather in the midlatitudes."
- Types of Disruption: The review details various types of SPV disruption:
- Displacements: The SPV centre shifts away from the North Pole, either towards North America or Eurasia. Can lead to CAOs over North America.
- Stretching: The SPV elongates, with asymmetric warming over the North Pacific. These are often forced by amplified tropospheric wavenumber 2 and can result in CAOs in Canada and the US.
- Wave reflection off a reflective layer limits polar stratospheric warming.
- Splits: The SPV separates into two vortices. Often associated with Sudden Stratospheric Warmings (SSWs).
- Sudden Stratospheric Warmings (SSWs):
- SSWs are characterized by rapid increases in stratospheric temperature and abrupt decreases in zonal winds. They are linked to negative phase NAO and colder weather in Eurasia.
- SSWs can be categorised into multiple types depending on the shape of the vortices: displacement, or split. Different types of SSWs have differing surface impacts. *DD-type SSWs have opposite surface temperature responses before and after the event.
- DS-type SSWs have more prominent temperature response in mid-latitudes. *SS-type SSWs tend to result in colder than normal weather in both Eurasia and North America.
- The pre-existing tropospheric state, such as Ural blocking, is a precursor to SSWs.
- New Metric for SPV Disruption: A novel metric, using 50-10 hPa thickness anomaly fields (rather than 100 hPa height), is proposed to isolate stratospheric changes from tropospheric influences when identifying SPV disruptions. This revealed that a strong, pole-centred SPV has become more common recently, which is opposite to the trend suggested by the traditional 100 hPa height metric, suggesting the traditional approach may be influenced by tropospheric changes. Quote: "We propose and demonstrate a new metric to identify SPV disruptions that isolates stratospheric behaviour rather than conflating anomalies in both the stratosphere and troposphere."
- Precursor Conditions:
- High pressure over the Ural region can trigger wave propagation that leads to SPV disruption. *The Aleutian low is also an important link between El Nino Southern Oscillation (ENSO) and the SPV.
- Stratosphere-Troposphere Oscillation (STO):
- The STO is a newly identified phenomenon, a zonal-asymmetric mode, involving the SPV displacing westwards on the intraseasonal time scale (10-60 days).
- The STO is linked to an oscillating phenomena with a deep structure from the troposphere to the stratosphere
- The mechanism involves vertical and horizontal Rossby wave propagation. *This phenomenon unifies previous studies into one stratosphere-troposphere coupling framework.
7. Role of the Tropics
- Tropical Variability: Modes like the Quasi-Biennial Oscillation (QBO), Madden-Julian Oscillation (MJO), and El Niño Southern Oscillation (ENSO) can influence NH climate through teleconnections. Quote: "The QBO, Madden–Julian Oscillation (MJO) and ENSO are well-known modes of tropical atmosphere and oceanic variability that may have teleconnections with NH climate"
- QBO: The QBO influences both tropospheric and stratospheric circulation, with a weaker SPV observed during QBO easterly phase (QBOE) winters.
- QBOE conditions can interact with Barents-Kara sea turbulent heat fluxes to create specific atmospheric circulation conditions.
- MJO: The MJO can influence large-scale flow in higher latitudes, including the Euro-Atlantic region. Quote: "An active MJO in certain phases influences large-scale flow in higher latitudes, such as the Euro-Atlantic."
- ENSO: La Niña conditions with AA can weaken or shift UB, promoting CAOs over East Asia during early winter.
- The weakened PVy during the winter of 2022/23 was amplified by anomalous Arctic warming and tropical Pacific cooling.
Key Point: Tropical modes interact to modulate mid-latitude responses, so they must not be assessed in isolation.
8. Large-Ensemble Climate Model Simulations
- Need for Large Ensembles: Large-ensemble simulations are crucial for separating forced responses to AA from internal variability. Quote: "For any individual model in PAMIP and other modelling experiments, the ensemble size (typically between 100 and 500) may not be sufficiently large to fully separate forced response from internal variability"
- Model Discrepancies: Significant inter-model differences exist, particularly regarding stratospheric responses to Arctic sea-ice loss.
- Responses to sea-ice loss vary among models.
- Quantifying Internal Variability: Very large-ensemble simulations can robustly quantify internal atmospheric variability. It is important to have larger ensembles (>=400) to reliably estimate responses to AA and extreme events. Quote: "The uncertainty in the forced response to projected Arctic sea-ice loss arising from internal variability has been extensively studied in recent very large-ensemble climate simulations"
9. Conclusions and Recommendations
- Key Linkages: Blocking, SPV disruptions, and tropical modes play crucial roles in connecting AA and mid-latitude CAOs.
- Improved Understanding: A comprehensive understanding requires consideration of both large and synoptic drivers, and local factors.
- Metric for SPV Disruption: Using stratospheric thickness anomalies allows for better characterisation of SPV disruptions.
- PVy: The PVy theory provides a robust perspective for linking large-scale and synoptic events, including AA, ENSO, and SPV disruptions.
- It also highlights how Arctic warming can lead to more persistent blocking.
- Future Research:Investigate the relative importance of large- and synoptic-scale drivers, and local factors in determining the severity of CAOs.
- Further research should focus on how changes in tropospheric precursor patterns impact the stratosphere.
- The relative contributions of different tropical drivers should be assessed.
Quote: "Research should investigate the relative importance of both large- and synoptic-scale drivers and local factors (orography, snow/ice cover, clouds, surface energy budget, ABL structure) that determine the local severity of extreme CAOs."
10. Schematic Overview The document includes a summary figure (Figure 13) that provides a schematic overview of the complex interplay between the Arctic, mid-latitudes and the various drivers of change, such as high-latitude blocking, sea-ice concentration and the SPV.
This briefing document highlights that the linkages between Arctic Amplification, high latitude atmospheric dynamics and mid-latitude weather is complex. Whilst AA may moderate the frequency of cold-air outbreaks, the evidence suggests that changes in the strength and behaviour of the polar vortex, combined with atmospheric blocking and other factors, may actually be increasing the frequency and intensity of disruptive cold spells. This further demonstrates that there are a number of factors at play, and that an integrated approach is required to properly investigate these phenomena.
Bru
Pearce
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Michael MacCracken
Hi Herb--The first paragraph of the Synthesis at the end of the article is like a plain language summary. It says:
7. Synthesis including future research priorities
Our research findings lead to important scientific and societal implications. The need is growing for early predictions of atmospheric circulation regimes likely to produce extreme weather across diverse socio-economic sectors that can significantly benefit from advanced warnings. An improved understanding of Arctic-midlatitude climate linkages benefits subseasonal-to-seasonal (S2S) weather predictions, covering outlooks for weeks up to 2 months, which are increasingly vital for weather-dependent planning (e.g. White et al 2021). Even if CAOs become less frequent and/or less intense overall, their impacts can be more significant as society under continued global warming becomes increasingly less prepared as CAOs penetrate into regions ill-equipped to respond. Given the potential high impact on large populations, further research is essential to improve understanding of climate-change-related teleconnections and their two-way interactions on the atmospheric dynamics responsible for the onset of CAOs. There is a need to look systematically and mechanistically at multiple cases of suspected Arctic/midlatitude weather connections, especially with the ongoing occurrence of extreme CAOs, such as during January 2024 in northern Europe (Rantanen et al 2024) and February 2021 in the south-central US.
------End
of quoted section
Basically, this indicates to me that they are seeking to help in making progress in monthly to seasonal forecasts, and searching for correlations and linkages. If you look at their Figure 13 it think you will see that there are a lot of potential linkages to be examined. Reading further in the Synthesis (I've not read the article), it looks to me as if they have a ways to go and the article is mainly a summary of what is being looked at with respect linkages.
Best,
Mike
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rob...@rtulip.net
Thanks Herb, good summary on the polar vortex, except for leaving out the potential for higher albedo to mitigate the crisis.
When I read the obligatory statement of genuflection to the decarbonising gods, it offered a subtle ray of hope. It says “Researchers also underscore the need for urgent action to address the climate crisis, and mitigate and adapt to the consequences of increasingly extreme weather.” This offers progress toward recognition of the centrality of SRM, which is likely the only “urgent action” that can “mitigate consequences of extreme weather”, with some slower assistance from GHG removal. Cutting emissions impacts weather on far too slow a timescale to be relevant.
This gets walked back in Jennifer Francis’s quote, where she argues a simple logical fallacy. She says “To reverse these trends, and better protect our communities and our planet, we must take bold and rapid action now to reduce the burning of fossil fuels and the build-up of heat-trapping gases in the atmosphere.” That does not follow. Decarbonisation cannot reverse the polar vortex instability as Dr Francis asserts it can. That looks more like a political than a scientific claim. To “reduce the build-up” means to slow the GHG increase, which can obviously do nothing to “reverse” the jetstream going haywire. It almost looks as though such statements are enforced by dogmatists, who have little concern about precise meaning as long as scientists toe the line.
Regards
Robert Tulip
From: planetary-...@googlegroups.com <planetary-...@googlegroups.com> On Behalf Of H simmens
Sent: Wednesday, 1 January 2025 2:43 AM
To: Tom Goreau <gor...@globalcoral.org>
Cc: healthy-planet-action-coalition <healthy-planet-...@googlegroups.com>; Planetary Restoration <planetary-...@googlegroups.com>
Subject: Re: [prag] Influence of high-latitude blocking and the northern stratospheric polar vortex on cold-air outbreaks under Arctic amplification of global warming - IOPscience
Thanks Tom!
I wrote to Jennifer Francis and she responded with this article from Woodwell.
Herb
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Herb Simmens
Author of A Climate Vocabulary of the Future
“A SciencePoem and an Inspiration.” Kim Stanley Robinson
@herbsimmens
HerbSimmens.com
On Dec 31, 2024, at 8:45 AM, Tom Goreau <gor...@globalcoral.org> wrote:
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Bruce Melton -- Austin, Texas
I would like to offer some anecdotal experience and results of findings on polar vortex excursions impacts to the natural world from my filmwork and study:
The Synthesis below discusses needs to inform the public and
built culture about increasing cold extremes where warming has
lulled us into complacency. As important if not more, are effects
on the natural world. Though this work is mainly a motivator for
human adaptation strategies, the effects of polar vortex excursion
on the natural world are major, and unfortunately adaptation
strategies are few. Thus, the reason for climate restoration.
Warmer than normal weather does not allow many species to form
protective antifreeze or other cold-enduring behaviors so as to
endure the rigors of winter. In a warmer climate when normal cold
or even colder than normal conditions descend, ecologies are
impacted in a far greater way than during our old climate when
they were able to slowly develop the freeze-proofing their
evolution allowed. The results are extreme degradation and
mortality. Critically, drought stress, that is generally
long-lived in long-lived species, compounds the effects of this
extreme temperature change from above normal for long periods to
colder than normal.
I have witnessed this not only on my home turf in Central Texas, but in the Chihuahuan and Sonoran Deserts. In Texas, Winter Storm Uri in 2021 - the one that almost exploded the grid in Texas, created significant species mortality even in what we have previously understood as our most resilient species like live oaks and junipers. In the Chihuahuan and Sonoran Deserts, what has been most obvious is mortality of thorny species with the exception of saguaro degradation in the Sonoran.
This degradation of saguaro was observed in and around the
Sonoran Desert National Monument west of Tuscon and south of
Phoenix. This degradation took the form of frostbite on saguaros
where baseball to basketball-sized scars sometimes a foot deep
into the flesh of a saguaro, were seen in very large numbers in
individuals with about half of individuals impacted. Because
saguaros are vascular, where their entire trunk conveys fluids up
and down, mass mortality was not evident, but very significant
damage was observed, certainly resulting widespread stress that is
long-lived. Interestingly, it was the lower elevation saguaros
that were impacted and at higher elevation in both the Saguaro
National Parks on either side of Tuscon, very little saguaro
damage was seen. Probably, colder temperature at higher elevations
allowed greater formation of cold resistance, where at lower
elevations in the Sonoran Desert National Monument this
resistance was lacking. See a photojournal that includes saguaro
frostbite here - https://climatediscovery.org/summer-filmwork-photo-tour-saguaros-sequoias-yosemite-and-the-paradise-fire-september-9-2019/
The stresses caused by these temperature swings beyond the evolutionary boundaries of species linger, and they linger longer in long-lived species. Stress beyond what was encountered in the evolution of these species not only contributes to further damage or mortality from repeated cold extremes in a warmer world, but it contributes to drought and insect degradation and mortality. An example is the bark beetle outbreak on Ocotillo and increased mortality in creosote bush, both resident in both deserts. And, these are just the macro-species degradation and mortality that are readily observable.
The effects are quite likely occurring across all ecologists on
Earth as species world-wide have this ability to create greater
freeze protection as cold normally increases into the depths of
winter. An example is bark beetle attacks across the West I have
been observing and studying since the mid-2000s, where
overwintering bark beetles too, become acclimated to cold
temperatures as winter progressed in our old climate.
Specifically, the most aggressive and meaningful dendroctonus
ponderosae, the mountain pine bark beetle that is responsible for
a very significant majority of the 100 million acres of beetle
kill across the west since the late 1990s, can be killed by 20
below (F) temperatures early in the cold season, but can endure
40 below temperatures (in our old climate) because of cold
acclimatization in the depths of winter. Due to the almost
complete lack of temperatures this cold in our warmed climate,
bark beetles most years overwinter in far larger numbers than in
our old climate, leading to outbreaks that kill landscape scale
forest instead of the kill observed in our old climate of only ten
percent of the mortality we have seen since the turn of the
century. In the case of bark beetles then, polar vortex excursions
are a good thing that reduce the overwintering population, if they
are cold enough which is one of those things discussed in this
work that remains a bit undecided.
The meaning of all this goes far beyond effects to the built
environment and its occupants in that gross species mortality in
ecologies quickly flips those ecologies from sequestration of
carbon to emissions. We are seeing this now across the planet
where on average, our forests are no longer sequestering but
emitting, because of multiple mortality factors that have created
on average, a global forest mortality double the normal rate. In
general, when mortality in a forest doubles, over time its age is
halved, halving carbon storage. In the North American West,
mortality ranges from twice to quadruple normal in findings.
In our filming this past year, where we began work on the Eastern US, forest species mortality was surprisingly high, far greater than indicated by findings that take time for data collection and publication. Examples are of the near complete loss of Frazer fir in the high altitudes of Appalachia from balsam woolly adelgid, and ash from emerald ash borer regionwide, plus very substantial loss of red pine from upper Appalachia through New England from red pine scale and hemlock from hemlock woolly adelgid. All of these mortality agents are non-native in the East versus natives in the West, but mortality is still mortality and findings should soon show that forest mortality across most of the Eastern US is also far above a doubling. Polar vortex excursion are but one stress agent in our natural world, but they combine or cascade, as so many effects do, to create impacts far greater than those from the individual stressors.
Yippee yo ki yay.
B
Director, Climate Change Now Initiative, 501c3
President, Melton Engineering Services Austin
8103 Kirkham Drive
Austin, Texas 78736
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