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    • Arctic
    • Antarctic
    • Arctic Warming & Arctic Amplification.

    Click on the title of a paper you are interested in to go straight to the full paper. You may also wish to check out the Climate Change research papers.

    Warm Arctic, Cold Continents? It Sounds Counterintuitive, but Research Suggests it’s a Thing
    Published 22 Nov 2020. Easy to read overview of the impact of Arctic Warming.
    By any measure, the Arctic has changed profoundly in the last 40 years, warming three times as fast as the global average, and losing half its summer sea ice, as well as billions of tons of land-based glacier ice. And even though the Arctic only encompasses about 6 percent of the Earth's surface area, the warming there has kicked off climate chain reactions that are disrupting weather and climate patterns across the mid-latitudes of the Northern Hemisphere, including most major North American and European cities and agricultural areas.

    A Theory for Polar Amplification from a General Circulation Perspective
    2014 paper. Abstract:
    Records of the past climates show a wide range of values of the equator-­‐to-­‐pole temperature gradient,with an apparent universal relationship between the temperature gradient and the global-­‐mean temperature: relative to a reference climate, if the global-­mean temperature is higher (lower), the greatest warming (cooling) occurs at the polar regions. This phenomenon is known as polar amplification. Understanding this equator-­‐to-­‐pole temperature gradient is fundamental to climate and general circulation, yet there is no established theory from a perspective of the general circulation. Here, a general-­‐circulation-­‐based theory for polar amplification is presented. Recognizing the fact that most of the available potential energy (APE) in the atmosphere is untapped, this theory invokes that La-­‐Niña-­‐like tropical heating can help tap APE and warm the Arctic by exciting poleward and upward propagating Rossby waves.

    An observational analysis: Tropical relative to Arctic influence on mid-latitude weather in the era of Arctic amplification
    2016 paper. Abstract:
    The tropics, in general, and El Niño/Southern Oscillation (ENSO) in particular are almost exclusively relied upon for seasonal forecasting. Much less considered and certainly more controversial is the idea that Arctic variability is influencing mid-latitude weather. However, since the late 1980s and early 1990s,the Arctic has undergone the most rapid warming observed globally, referred to as Arctic amplification (AA),which has coincided with an observed increase in extreme weather. Analysis of observed trends in hemispheric circulation over the period of AA more closely resembles variability associated with Arctic boundary forcings than with tropical forcing. Furthermore, analysis of intra seasonal temperature variability shows that the cooling in mid-latitude winter temperatures has been accompanied by an increase in temperature variability and not a decrease, popularly referred to as“weather whiplash.”

    Arctic Change and possible influence on mid-latitude climate and weather (White Paper)
    2018 paper. No abstract but this paper details the findings of a 2017 workshop.

    Arctic sea ice reduction and European cold winters in CMIP5 climate change experiments
    2012 paper. Abstract:
    European winter climate and its possible relationship with the Arctic sea ice reduction in the recent past and future as simulated by the models of the Climate Model Intercomparison Project phase 5 (CMIP5) is investigated, with focus on the cold winters. While Europe will warm overall in the future, we find that episodes of cold months will continue to occur and there remains substantial probability for the occurrence of cold winters in Europe linked with sea ice reduction in the Barents and Kara Sea sector. A pattern of cold‐European warm‐Arctic anomaly is typical for the cold events in the future, which is associated with the negative phase of the Arctic Oscillation. These patterns, however, differ from the corresponding patterns in the historical period, and underline the connection between European cold winter events and Arctic sea ice reduction.

    Atmospheric response to changes in Arctic sea ice thickness
    2006 paper. Abstract:
    Experiments with an atmospheric GCM are used to determine the effect of anomalous Arctic sea ice thickness on the atmospheric circulation. Ice thickness data are taken from a hind-cast simulation with an ocean-sea ice model under NCAR/NCEP forcing. Ice conditions from 1964–1966 and 1994–1996 represent extreme cases of largest and smallest ice volume, respectively, during the last 50 years.The atmospheric response to the 1990s thinning of Arctic sea ice comprises a reduction in sea level pressure in the central Arctic and over the Nordic Seas. High pressure anomalies evolve over the subtropical North Atlantic and over the sub-polar North Pacific. Similar signals occur at500 hPa. Realistic sea ice thickness changes can induce atmospheric signals that are of similar magnitude as those due to changes in sea ice cover.

    Changing state of Arctic sea ice across all seasons
    2018 paper. Abstract:
    The decline in the floating sea ice cover in the Arctic is one of the most striking manifestations of climate change. In this review, we examine this ongoing loss of Arctic sea ice across all seasons. Our analysis is based on satellite retrievals, atmospheric reanalysis, climate-model simulations and a literature review. We find that relative to the 1981–2010 reference period, recent anomalies in spring and winter sea ice coverage have been more significant than any observed drop in summer sea ice extent (SIE) throughout the satellite period. For example, the SIE in May and November 2016 was almost four standard deviations below the reference SIE in these months. Decadal ice loss during winter months has accelerated from −2.4 %/decade from 1979 to 1999 to −3.4%/decade from 2000 onwards. We also examine regional ice loss and find that for any given region, the seasonal ice loss is larger the closer that region is to the seasonal outer edge of the ice cover. Finally, across all months, we identify a robust linear relationship between pan-Arctic SIE and total anthropogenic CO2 emissions. The annual cycle of Arctic sea ice loss per ton of CO2 emissions ranges from slightly above 1 m2 throughout winter to more than 3 m2 throughout summer. Based on a linear extrapolation of these trends, we find the Arctic Ocean will become sea-ice free throughout August and September for an additional 800 ± 300 Gt of CO2 emissions, while it becomes ice free from July to October for an additional 1400 ± 300 Gt of CO2 emissions.

    Cold winter extremes in northern continents linked to Arctic sea ice loss
    2013 paper. Abstract:
    The satellite record since 1979 shows downward trends in Arctic sea ice extent in all months,which are smallest in winter and largest in September. Previous studies have linked changes in winter atmospheric circulation, anomalously cold extremes and large snowfalls in mid-latitudes to rapid decline of Arctic sea ice in the preceding autumn. Using observation analyses, we show that the winter atmospheric circulation change and cold extremes are also associated with winter sea ice reduction through an apparently distinct mechanism from those related to autumn sea ice loss. Associated with winter sea ice reduction, a high-pressure anomaly prevails over the subarctic, which in part results from fewer cyclones owing to a weakened gradient in sea surface temperature and lower baroclinicity over sparse sea ice. The results suggest that the winter atmospheric circulation at high northern latitudes associated with Arctic sea ice loss, especially in the winter, favors the occurrence of cold winter extremes at middle latitudes of the northern continents.

    Consistency and discrepancy in the atmospheric response to Arctic sea-ice loss across climate models
    2018 paper. Abstract:
    The decline of Arctic sea ice is an integral part of anthropogenic climate change. Sea-ice loss is already having a significant impact on Arctic communities and ecosystems. Its role as a cause of climate changes outside of the Arctic has also attracted much scientific interest. Evidence is mounting that Arctic sea-ice loss can affect weather and climate throughout the Northern Hemisphere. The remote impacts of Arctic sea-ice loss can only be properly represented using models that simulate interactions among the ocean, sea ice, land and atmosphere. A synthesis of six such experiments with different models shows consistent hemispheric-wide atmospheric warming, strongest in the mid-to-high-latitude lower troposphere; an intensification of the wintertime Aleutian Low and, in most cases, the Siberian High; a weakening of the Icelandic Low; and a reduction in strength and southward shift of the mid-latitude westerly winds in winter. The atmospheric circulation response seems to be sensitive to the magnitude and geographic pattern of sea-ice loss and, in some cases, to the background climate state. However, it is unclear whether current-generation climate models respond too weakly to sea-ice change. We advocate for coordinated experiments that use different models and observational constraints to quantify the climate response to Arctic sea-ice loss.

    Continental heat anomalies and the extreme melting of the Greenland ice surface in 2012 and 1889
    2014 paper. Abstract:
    Recent decades have seen increased melting of the Greenland ice sheet. On 11 July 2012,nearly the entire surface of the ice sheet melted; such rare events last occurred in 1889 and, prior to that,during the Medieval Climate Anomaly. Studies of the 2012 event associated the presence of a thin, warm elevated liquid cloud layer with surface temperatures rising above the melting point at Summit Station, some3212m above sea level. Here we explore other potential factors in July 2012 associated with this unusual melting. These include (1) warm air originating from a record North American heat wave, (2) transitions in the Arctic Oscillation, (3) transport of water vapor via an Atmospheric River over the Atlantic to Greenland, and(4) the presence of warm ocean waters south of Greenland. For the 1889 episode, the Twentieth Century Reanalysis and historical records showed similar factors at work. However, markers of biomass burning were evident in ice cores from 1889 which may reflect another possible factor in these rare events. We suggest that extreme Greenland summer melt episodes, such as those recorded recently and in the late Holocene, could have involved a similar combination of slow climate processes, including prolonged North American droughts/heat waves and North Atlantic warm oceanic temperature anomalies, together with fast processes,such as excursions of the Arctic Oscillation, and transport of warm, humid air in Atmospheric Rivers to Greenland. It is the fast processes that underlie the rarity of such events and influence their predictability

    Divergent consensuses on Arctic amplification influence on mid-latitude severe winter weather
    2019 paper. Abstract:
    The Arctic has warmed more than twice as fast as the global average since the late twentieth century, a phenomenon known as Arctic amplification (AA). Recently, there have been considerable advances in understanding the physical contributions to AA, and progress has been made in understanding the mechanisms that link it to mid-latitude weather variability. Observational studies overwhelmingly support that AA is contributing to winter continental cooling. Although some model experiments support the observational evidence, most modelling results show little connection between AA and severe mid-latitude weather or suggest the export of excess heating from the Arctic to lower latitudes. Divergent conclusions between model and observational studies, and even intra-model studies, continue to obfuscate a clear understanding of how AA is influencing mid-latitude weather.

    Links Between Barents‐Kara Sea Ice and the Extratropical Atmospheric Circulation Explained by Internal Variability and Tropical Forcing
    2016 paper. Abstract:
    The recent accelerated Arctic sea ice decline has been proposed as a possible forcing factor for midlatitude circulation changes, which can be projected onto the Arctic Oscillation (AO) and/or North Atlantic Oscillation (NAO) mode. However, the timing and physical mechanisms linking AO responses to the Arctic sea ice forcing are not entirely understood. In this study, the authors suggest a connection between November sea ice extent in the Barents and Kara Seas and the following winter’s atmospheric circulation in terms of the fast sea ice retreat and the subsequent modification of local air–sea heat fluxes. In particular, the dynamical processes that link November sea ice in the Barents and Kara Seas with the development of AO anomalies in February is explored. In response to the lower-tropospheric warming associated with the initial thermal effect of the sea ice loss, the large-scale atmospheric circulation goes through a series of dynamical adjustment processes: The decelerated zonal-mean zonal wind anomalies propagate gradually from the subarctic to midlatitudes in about one month. The equivalent barotropic AO dipole pattern develops in January because of wave–mean flow interaction and firmly establishes itself in February following the weakening and warming of the stratospheric polar vortex. This connection between sea ice loss and the AO mode is robust on time scales ranging from interannual to decadal. Therefore, the recent winter AO weakening and the corresponding midlatitude climate change may be partly associated with the early winter sea ice loss in the Barents and Kara Seas.

    Evidence for a wavier jet stream in response to rapid Arctic warming
    2014 paper. Abstract:
    New metrics and evidence are presented that support a linkage between rapid Arctic warming, relative to Northern hemisphere mid-latitudes, and more frequent high-amplitude (wavy) jet-stream configurations that favor persistent weather patterns. We find robust relationships among seasonal and regional patterns of weaker poleward thickness gradients, weaker zonal upper-level winds, and a more meridional flow direction. These results suggest that as the Arctic continues to warm faster than else-where in response to rising greenhouse-gas concentrations, the frequency of extreme weather events caused by persistent jet-stream patterns will increase.

    Evidence linking Arctic amplification to extreme weather in mid-latitudes
    2012 paper. Abstract:
    Arctic amplification (AA)–the observed enhanced warming in high northern latitudes relative to the northern hemisphere–is evident in lower-tropospheric temperatures and in 1000-to-500 hPa thicknesses. Daily fields of 500 hPa heights from the National Centers for Environmental Prediction Reanalysis are analyzed over N. America and the N. Atlantic to assess changes in north-south (Rossby) wave characteristics associated with AA and the relaxation of pole-ward thickness gradients. Two effects are identified that each contribute to a slower eastward progression of Rossby waves in the upper-level flow: 1) weakened zonal winds,and 2) increased wave amplitude. These effects are particularly evident in autumn and winter consistent with sea-ice loss, but are also apparent in summer, possibly related to earlier snow melt on high-latitude land. Slower progression of upper-level waves would cause associated weather pat-terns in mid-latitudes to be more persistent, which may lead to an increased probability of extreme weather events that result from prolonged conditions, such as drought, flooding,cold spells, and heat waves.

    Extreme weather in Europe linked to less sea ice and warming in the Barents Sea
    2018 paper. No abstract available.

    Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics
    2018 paper. Abstract:
    The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss.

    Global and Arctic climate sensitivity enhanced by changes in North Pacific heat flux
    2018 paper. Abstract:
    Arctic amplification is a consequence of surface albedo, cloud, and temperature feedbacks, as well as poleward oceanic and atmospheric heat transport. However, the relative impact of changes in sea surface temperature (SST) patterns and ocean heat flux sourced from different regions on Arctic temperatures are not well constrained. We modify ocean-to-atmosphere heat fluxes in the North Pacific and North Atlantic in a climate model to determine the sensitivity of Arctic temperatures to zonal heterogeneities in northern hemisphere SST patterns. Both positive and negative ocean heat flux perturbations from the North Pacific result in greater global and Arctic surface air temperature anomalies than equivalent magnitude perturbations from the North Atlantic; a response we primarily attribute to greater moisture flux from the subpolar extratropics to Arctic. Enhanced poleward latent heat and moisture transport drive sea-ice retreat and low-cloud formation in the Arctic, amplifying Arctic surface warming through the ice-albedo feedback and infrared warming effect of low clouds. Our results imply that global climate sensitivity may be dependent on patterns of ocean heat flux in the northern hemisphere.

    Impact of declining Arctic sea ice on winter snowfall
    2012 paper. Abstract:
    While the Arctic region has been warming strongly in recent decades, anomalously large snowfall in recent winters has affected large parts of North America, Europe, and east Asia. Here we demonstrate that the decrease in autumn Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circu-lation that have some resemblance to the negative phase of the winter Arctic oscillation. However, the atmospheric circulation change linked to the reduction of sea ice shows much broader meridional meanders in midlatitudes and clearly different interannual variability than the classical Arctic oscillation. This circulation change results in more frequent episodes of blocking patterns that lead to increased cold surges over large parts of northern continents. Moreover, the increase in atmospheric water vapor content in the Arctic region during late autumn and winter driven locally by the reduction of sea ice provides enhanced moisture sources,supporting increased heavy snowfall in Europe during early winter and the northeastern and midwestern United States during winter. We conclude that the recent decline of Arctic sea ice has played a critical role in recent cold and snowy winters.

    Increased Arctic influence on the midlatitude flow during Scandinavian Blocking episodes
    2019 paper. Abstract:
    Recent studies have suggested that Arctic teleconnections affect the weather of the midlatitudes on time-scales relevant for medium-range weather forecasting. In this study, we use several numerical experimentation approaches with a state-of-the-art global operational numerical weather prediction system to investigate this idea further. Focusing on boreal winter, we investigate whether the influence of the Arctic on midlatitude weather, and the impact of the current Arctic observing system on the skill of medium-range weather forecasts in the midlatitudes is more pronounced in certain flow regimes. Using so-called Observing System Experiments, we demonstrate that removing in situ or satellite observations from the data assimilation system, used to create the initial conditions for the forecasts, deteriorates midlatitude synoptic forecast skill in the medium-range, particularly over northern Asia. This deterioration is largest during Scandinavian Blocking episodes, during which: (a) error growth is enhanced in the European-Arctic, as a result of increased baroclinicity in the region, and (b) high-amplitude planetary waves allow errors to propagate from the Arctic into midlatitudes. The important role played by Scandinavian Blocking, in modulating the influence of the Arctic on midlatitudes, is also corroborated in relaxation experiments, and through a diagnostic analysis of the ERA5 reanalysis and reforecasts.

    Investigating Possible Arctic–Midlatitude Teleconnections in a Linear Framework
    2016 paper. Abstract:
    There is an ongoing debate over whether accelerated Arctic warming [Arctic amplification (AA)] is altering the large-scale circulation responsible for the anomalous weather experienced by midlatitude regions in recent years. Among the proposed mechanisms is the idea that local processes associated with sea ice loss heat the lower troposphere at high latitudes, thus weakening the equator-to-pole temperature gradient and driving changes in quasi-stationary waves, the midlatitude jets, and storm tracks. It is further hypothesized that these circulation changes are conducive to persistent weather patterns. Because of the short observational record and large atmospheric internal variability, it is difficult to identify robust relationships and infer causality.Here, a simplified, linear, steady-state model is used to investigate the direct response of the midlatitude atmospheric circulation to thermal forcing in the Arctic. The results suggest that there is a weak midlatitude circulation response to an idealized, but representative, Arctic heating perturbation. Further, the stationary wave responses are shown to be well within the bounds of internal variability. A midlatitude response is excited if the idealized heating penetrates up to the tropopause. Such deep, persistent heating is not ob-served on average during the AA period but does suggest a pathway for Arctic–midlatitude linkages under specific conditions. This study adds to the growing body of work suggesting that warming in the lower troposphere associated with Arctic amplification is not currently a direct driver of anomalous midlatitudecirculation changes.

    Nonlinear response of mid-latitude weather to the changing Arctic
    2016 paper. Abstract:
    Are continuing changes in the Arctic influencing wind patterns and the occurrence of extreme weather events in northern mid-latitudes? The chaotic nature of atmospheric circulation precludes easy answers. The topic is a major science challenge, as continued Arctic temperature increases are an inevitable aspect of anthropogenic climate change. We propose a perspective that rejects simple cause-and-effect pathways and notes diagnostic challenges in interpreting atmospheric dynamics. We present a way forward based on understanding multiple processes that lead to uncertainties in Arctic and mid-latitude weather and climate linkages. We emphasize community coordination for both scientific progress and communication to a broader public.

    On the atmospheric response experiment to a Blue Arctic Ocean: Climate Response to Blue Arctic Ocean
    2016 paper. Abstract:
    We demonstrated atmospheric responses to a reduction in Arctic sea ice via simulations in which Arctic sea ice decreased stepwise from the present-day range to an ice-free range. In all cases, the tropospheric response exhibited a negative Arctic Oscillation (AO)-like pattern. An intensification of the climatological planetary-scale wave due to the present-day sea ice reduction on the Atlantic side of the Arctic Ocean induced stratospheric polar vortex weakening and the subsequent negative AO. Conversely, strong Arctic warming due to ice-free conditions across the entire Arctic Ocean induced a weakening of the tropospheric Westerlies corresponding to a negative AO without troposphere–stratosphere coupling, for which the planetary-scale wave response to a surface heat source extending to the Pacific side of the Arctic Ocean was responsible. Because the resultant negative AO-like response was accompanied by secondary circulation in the meridional plane, atmospheric heat transport into the Arctic increased, accelerating the Arctic amplification.

    Recent Arctic amplification and extreme mid-latitude weather
    2014 paper. Abstract:
    The Arctic cryosphere is an integral part of Earth's climate system and has undergone unprecedented changes within the past few decades. Rapid warming and sea-ice loss has had significant impacts locally, particularly in late summer and early autumn. September sea ice has declined at a rate of 12.4% per decade since 1979 (ref.1), so that by summer 2012, nearly half of the areal coverage had disappeared. This decrease in ice extent has been accompanied by an approximately 1.8 m (40%) decrease in mean winter ice thickness since 1980 (ref.2) and a 75–80% loss in volume 3 . Though sea-ice loss has received most of the research and media attention, snow cover in spring and summer has decreased at an even greater rate than sea ice. June snow cover alone has decreased at nearly double the rate of September sea ice 4 . The decrease in spring snow cover has contributed to both the rise in warm season surface temperatures over the Northern Hemisphere extratropical landmasses and the decrease in summer Arctic sea ice 5 . The combined rapid loss of sea ice and snow cover in the spring and summer has played a role in amplifying Arctic warming. However, snow cover and sea-ice trends diverge in the autumn and winter with sea ice decreasing in all months while snow cover has exhibited a neutral to positive trend in autumn and winter

    Seasonal and Regional Manifestation of Arctic Sea Ice Loss
    2018 paper. Abstract:
    The Arctic Ocean is currently on a fast track toward seasonally ice-free conditions. Although most attention has been on the accelerating summer sea ice decline, large changes are also occurring in winter. This study assesses past, present, and possible future change in regional Northern Hemisphere sea ice extent throughout the year by examining sea ice concentration based on observations back to 1950, including the satellite record since 1979. At present, summer sea ice variability and change dominate in the perennial ice-covered Beaufort, Chukchi, East Siberian, Laptev, and Kara Seas, with the East Siberian Sea explaining the largest fraction of September ice loss (22%). Winter variability and change occur in the seasonally ice-covered seas farther south: the Barents Sea, Sea of Okhotsk, Greenland Sea, and Baffin Bay, with the Barents Sea carrying the largest fraction of loss in March (27%). The distinct regions of summer and winter sea ice variability and loss have generally been consistent since 1950, but appear at present to be in transformation as a result of the rapid ice loss in all seasons. As regions become seasonally ice free, future ice loss will be dominated by winter. The Kara Sea appears as the first currently perennial ice-covered sea to become ice free in September. Remaining on currently observed trends, the Arctic shelf seas are estimated to become seasonally ice free in the 2020s, and the seasonally ice-covered seas farther south to become ice free year-round from the 2050s.

    The Effect of QBO Phase on the Atmospheric Response to Projected Arctic Sea Ice Loss in Early Winter
    2019 paper. Abstract:
    Recent modeling studies have shown an important role for stratosphere‐troposphere coupling in the large‐scale atmospheric response to Arctic sea ice loss. Evidence is growing that the Quasi‐biennial Oscillation (QBO) can contribute to or even mitigate teleconnections from surface forcing. Here, the influence of QBO phase on the atmospheric response to projected Arctic sea ice loss is examined using an atmospheric general circulation model with a well‐resolved stratosphere and a QBO prescribed from observations. The role of the QBO is determined by compositing seasons with easterly phase (QBO‐E) separately from seasons with westerly phase (QBO‐W). In response to the sea ice forcing in early winter, the polar vortex during QBO‐E weakens with strong stratosphere‐troposphere wave‐1 coupling and a negative Northern Annular Mode‐type response. At the surface, this results in more severe Siberian cold spells. For QBO‐W, the polar vortex strengthens in response to the sea ice forcing.

    The influence of Arctic amplification on mid-latitude summer circulation
    2018 paper. Abstract:
    Accelerated warming in the Arctic, as compared to the rest of the globe, might have profound impacts on mid-latitude weather. Most studies analyzing Arctic links to mid-latitude weather focused on winter, yet recent summers have seen strong reductions in sea-ice extent and snow cover, a weakened equator-to-pole thermal gradient and associated weakening of the mid-latitude circulation. We review the scientific evidence behind three leading hypotheses on the influence of Arctic changes on mid-latitude summer weather: Weakened storm tracks,shifted jet streams, and amplified quasi-stationary waves. We show that interactions between Arctic teleconnections and other remote and regional feedback processes could lead to more persistent hot-dry extremes in the mid-latitudes. The exact nature of these non-linear interactions is not well quantified but they provide potential high-impact risks for society.

    The stratospheric pathway for Arctic impacts on mid-latitude climate
    2016 paper. Abstract:
    Recent evidence from both observations and model simulations suggests that an Arctic sea ice reduction tends to cause a negative Arctic Oscillation (AO) phase with severe winter weather in the Northern Hemisphere, which is often preceded by weakening of the stratospheric polar vortex. Although this evidence hints at a stratospheric involvement in the Arctic‐midlatitude climate linkage, the exact role of the stratosphere remains elusive. Here we show that tropospheric AO response to the Arctic sea ice reduction largely disappears when suppressing the stratospheric wave mean flow interactions in numerical experiments. The results confirm a crucial role of the stratosphere in the sea ice impacts on the midlatitudes by coupling between the stratospheric polar vortex and planetary‐scale waves. Those results and consistency with observation‐based evidence suggest that a recent Arctic sea ice loss is linked to midlatitudes extreme weather events associated with the negative AO phase.

    Understanding the Causes and Consequences of Polar Amplification
    2017 paper. Abstract:
    The Arctic is warming twice as fast as the global average temperature. How these rapid changes will affect the Arctic region is critical to understand, though the significance of this understanding extends beyond the region since changes in the Arctic are increasingly understood to interact with the climate system of the Earth as a whole via atmospheric circulation and ocean currents. In particular, as climate change continues understanding how changes in the Arctic will affect weather and climate of the northern continents is a critical and timely question. Improved understanding of the mechanisms of teleconnection in these systems will shed light on how the Earth’s climate system works as it departs further from the norms of the 20th century. The ability to model these changes has the potential to better describe future climate and its ecological and societal impacts as the century unfolds. To make progress, it is imperative to consider the larger context of the causes and consequences of polar amplification in the global climate system, and examine connections between the faster pace of warming in the polar regions compared to lower latitudes.

    Arctic Amplification and Extreme Weather: Controversy Lingers
    Published Nov 2020.
    No abstract but the report looks at whether Arctic Amplification Causes Mid-Latitude Cooling. Includes charts with long-term trends of 2m temps, AO and NAO.


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